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      Online First

      • DU Wei, LUO Xianjue, WANG Xiuli, ZHANG Qiwen, LI Xue

        Available online:April 01, 2020  DOI: 10.7500/AEPS20190528010

        Abstract:The research shows that the reliability of power system of offshore oilfield group has a significant impact on the oil production. Considering that this kind of power grid is an independent power grid including generation, transmission and distribution systems at the same time, and load shedding measures are different from those of onshore power grid when fault occurs, the traditional reliability evaluation model and algorithm cannot be used directly. A reliability evaluation method is proposed for offshore oilfield power system based on the system-wide reliability evaluation theory and an index system is set up for the system-wide reliability. During the state sampling, the whole power system sampling can be divided into generation and transmission system sampling and distribution system sampling according to the system-wide reliability evaluation theory, and the comprehensive evaluation method can be established. In the state evaluation of generation and transmission system, the load curtailment model based on priority trip is constructed considering the characteristics of offshore power grid and its load equipment. In the state evaluation of distribution system, the effects of cascading failure are taken into consideration. Finally, experiments are conducted on a practical example of a certain offshore oilfield power system. The system-wide indices are obtained and the influences of the four kinds of failure are analyzed to prove the correctness and effectiveness of the proposed method.

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      • NIU Dongxiao, JI Huizheng

        Available online:April 01, 2020  DOI: 10.7500/AEPS20191224003

        Abstract:Short-term wind power forecasting is one of basic supports of dispatching operation of wind power, and the physical prediction methodology is one of the basic methods for short-term wind power forecasting, which is still the main prediction method in Europe, America and other countries. Therefore, it is important to analyze the error sources of the physical prediction method to improve the prediction accuracy of wind power. In view of the error source problem of the wind power physical prediction method, and on the basis of decomposing the key links of physical prediction model, a scheme of detecting errors in physical model, the geostrophic drag law, the conversion model between numerical weather prediction (NWP) and power is designed by using the principle of single variable. Through a derivation to the physical process, an error source analysis method for wind power physical prediction model is proposed. Furthermore, the quantitative results of prediction errors in each part of the physical prediction method are obtained. Finally, an actual case is used to test and the results show that the proposed error source analysis method can obtain quantitative analysis results of error sources, and the analysis results are consistent with the actual, which verifies the accuracy of the method.

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      • Tu Jing-Zhe, ZHANG Jian, LIU Mingsong, PAN Yan, XI Gongwei, YI Jun

        Available online:April 01, 2020  DOI: 10.7500/AEPS20190609005

        Abstract:Under the background of centralized access of large-capacity HVDC and high-ratio renewable energy, the problem of transient overvoltage has severely constrained the transmission capacity of HVDC and wind generation, so it is quite necessary to conduct further studies on mechanism and impact factors of transient overvoltage under large disturbance considering dynamic characteristic of wind generators. In this paper, study was conducted through both theoretical derivation and simulation analysis. Firstly, the theoretical equations calculating transient voltage magnitude of converter station and wind generator side after AC/DC contingency were derived. Then, the mechanism and main factors of transient overvoltage caused by AC/DC contingency were analyzed. Finally, the impact of different wind generator active/reactive power characteristics during low-voltage-ride-through (LVRT) on transient overvoltage was analyzed combined with simulation. All the conclusions were verified through simulation of practical case systems. The study results reflected that the wind generator LVRT characteristic makes the wind farm be another ‘reactive power source’ resulting transient overvoltage besides the converter station, and the severer of the transient overvoltage will be caused by the smaller of the wind generator active power output and the larger of the wind generator reactive power output.

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      • CHEN Boda, LIN Kaidong, SU Jieying, ZHANG Yongjun, YANG Yin

        Available online:April 01, 2020  DOI: 10.7500/AEPS20190820001

        Abstract:Considering the uncertainty of renewable energy and electricity, gas and heat load, this paper discusses the island partition of integrated energy micro-grid and establishes a robust island partition model based on continuous operation of island. This model uses energy conversion and storage equipment of integrated energy micro-grid as scheduling resources, and targets to optimize islanding partition scheme after fault occurrence. In this model, the shortest notification time constraint against the blackout is taken as the target penalty term, so that a certain response time is reserved for the load to the greatest extent. Meanwhile, it avoids repeated access and removal to island load caused by source power and load fluctuation. The robust discrete optimization model transforms uncertain constraints into certain constraints, therefore, a mixed integer linear programming model is constructed. This uses global robust tuning coefficient to improve the conservativeness of robust optimization. The economy and operability of the islanding scheme are well balanced to meet different decision-making needs. Finally, the example verifies the effectiveness of proposed model and solutions.

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      • WANG Dongyue, GU Huaiguang, WEI Shurong, WU Rui, FU Yang

        Available online:April 01, 2020  DOI: 10.7500/AEPS20190913001

        Abstract:The stator winding inter-turn short-circuit fault is a common fault form of the doubly-fed induction generator (DFIG) and the occurrence probability is up to 30%, which directly threatens the safe operation of the generator. When a generator is operated in a complex and variable environment, it is often difficult to diagnosis inter-turn short-circuit fault accurately by a single fault feature, which can easily lead to misjudgments and missed diagnosis. Therefore, a new fault diagnosis method for stator winding inter-turn short circuit fault is proposed in this paper based on electrical and mechanical signal fusion: the joint diagnosis of negative sequence current difference and 2f component of stator radial vibration signal. Firstly, support vector machine is used to calculate the probability of the inter-turn short circuit fault under the single fault feature, and then the probability is taken as the basic probability assignment of D-S evidence theory. The final diagnosis result is obtained relying on the evidence combination rule. The experimental results indicate that compared with the fault diagnosis method based on single fault feature, this method can diagnose the inter-turn short circuit faults in stator winding more effectively and identify the number of short-circuit turns reliably, so as to improve the accuracy of fault diagnosis, and can be applied to the other fields requiring higher fault identification accuracy, such as offshore wind power.

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      • JIN Xin, XUE Yongduan, PENG Zhenhua, YANG Fan, XU Bingyin

        Available online:April 01, 2020  DOI: 10.7500/AEPS20190319001

        Abstract:Most distribution terminals are difficult to obtain zero-sequence voltage or three-phase voltage signals. So the application of transient power direction method in fault location, multi-level protection and demarcation of single-phase grounding fault in resonant grounding system is limited. In this paper, the relationship of the initial phase angle with different components of zero-sequence current of fault points on upstream and downstream, under single-phase grounding fault in resonant grounding system, is analyzed. The component could be power frequency component, transient main resonance component and decaying DC component. It is found that the power frequency component of zero-sequence current can be used as the polarization phasor of the zero-sequence voltage, to further identify the fault direction using zero-sequence current only. The fault direction is positive, when the phase of power frequency component is within (-45°,75°) and the phase of transient main resonant component is within (-30°,30°), or the phase of power frequency component is within (135°,255°) and the phase of transient main resonant component is within (150°,210°), or the ratio of the amplitudes of decaying DC component to power frequency component is greater than the preset threshold. Otherwise, the fault direction is opposite. Both the simulation and the field fault data verify the correctness.

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      • CAO Na, ZHAO Xu, YU Qun

        Available online:April 01, 2020  DOI: 10.7500/AEPS20190527005

        Abstract:Transient energy flow method is a new method for locating oscillation sources. Firstly, according to the calculation formula of transient energy flow, combined with the shafting model, the grid-side converter model of doubly-fed wind turbine and the third-order simplified model of doubly-fed induction motor, the transient energy flow for doubly-fed wind turbine is deduced and the energy flow power is defined as an index of the energy flow direction. Secondly, the frequency characteristics of the doubly-fed wind turbine are analyzed after the forced sources are added. Finally, based on the PSCAD/EMTDC electromagnetic transient simulation platform, a single-machine infinite system with forced oscillation sources and a grid connection system of several wind turbines via series compensated line are built for time domain simulation. Transient energy flow and energy flow power are calculated using the collected data. The validity of the transient energy flow method for locating the forced oscillation sources of doubly-fed wind turbine is verified.

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      • PANG Lei, HAN Bei, WANG Keyou, LI Guojie, WANG Chunning

        Available online:April 01, 2020  DOI: 10.7500/AEPS20190909004

        Abstract:Droop coefficients of inverters for distributed generators in AD/DC hybrid microgrid can have great influences on feasibility region of power flow in island operation mode. While traditional droop coefficients are determined by capacity and frequency of inverters and voltage regulation range, which not gives full consideration to the above influence. To fill the gap, a calculation model of power flow in AC/DC hybrid microgrid considering control modes of inverter is firstly established. Then a fast calculation method of feasibility region of power flow in parameter space is proposed, the impact of droop coefficients on feasibility region of power flow is further considered. The optimal values of droop coefficients are suggested by overall considering both load stability margin and small-signal stability factors. Finally, an improved 12-node AC/DC hybrid microgrid is simulated to verify the effectiveness and applicability of the proposed method. Results show that the voltage stability margin is significantly increased compared with traditional methods.

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      • LIU Liang, SU Sheng, CAO Yijia, KUANG Wenkai, CAI Ye, ZHANG Heng

        Available online:April 01, 2020  DOI: 10.7500/AEPS20190704004

        Abstract:Cyber-attack against the global navigation satellite system has become a real threat with the intensification of attack in cyber space. The slow sustained satellite time synchronization attack can bypass the anomaly detection mechanism of existing satellite clock and trick the timed device to output an incorrect clock signal, and cause serious damage via operation mechanism of the power system. A Kalman filtering based protection method of sustained satellite time synchronization attack is proposed. Firstly, a Kalman filtering based satellite timing model considering sustained malicious interference is developed. Then, clock bias of time synchronism device in malicious attack is optimized by energy functional regularization. Finally, the clock bias is compensated according to the constructed compensation model to achieve precise time synchronization in attack. Simulation result shows that this method can effectively prevent the impact of slow sustained satellite time synchronization attacks on the time synchronism system.

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      • QI Bing, YE Xin, LI Bin, LIU Lin, CHENG Ziyun, XI Peifeng

        Available online:April 01, 2020  DOI: 10.7500/AEPS20190610006

        Abstract:With the rapid development of the smart grid and the Energy Internet, the services carried by the electric power communication network (EPCN) are becoming more diverse. In order to improve the utilization of EPCN resources, reduce the network risk, and ensure the reliable transmission of power services, this paper proposes a differential protection strategy of link fault (DLFDP) for distinguishing quality of protection (QoP) of power business. Firstly, based on the characteristics of power communication service flow, the failure risk of the link is analyzed, and the business risk in EPCN is modeled. Secondly, based on the importance of the business and the risk of the link, three types of protection models based on QoP are proposed. Considering the impact of load balancing, the services in the network are channeled to the links with lower risk, and the services are allocated for high importance. Based on the independent redundant path, the multiplexed P-cycle protects the high-risk link to simultaneously reduce the network blocking rate and risk. The simulation results show that the DLFDP algorithm can effectively utilize network resources, reduce service risk and link risk in the network, and reduce the network blocking rate.

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      • HOU Hui, YU Shiwen, XIAO Xiang, HUANG Yong, GENG Hao, YU Jufang

        Available online:March 24, 2020  DOI: 10.7500/AEPS20191113002

        Abstract:Risk assessment and visualization of power system under typhoon disasters has scientific significance and engineering application value for disaster prevention and mitigation of power systems. In order to predict high-risk areas and optimize the emergency material allocation and risk-based dispatch of power flow, the data layer, knowledge extraction layer and visualization layer are used to construct the risk assessment system for power transmission towers under typhoon disasters. Firstly, based on equipment operation information, meteorological information and geographic information, a spatial multi-source heterogeneous information database is built. Then, based on parameter optimization, six machine learning algorithms are used to establish intelligent models for tower damage risk prediction, and a relative optimal model is selected through index comparison. At the same time, a combined model based on goodness of fit method with unequal weight is proposed. The tower damage risk in a Chinese coastal city under the typhoon “Mujigae” is assessed and visualized with dimension of 1 km×1 km. The relative optimal model is compared with the combined model in detail. The results show that both relative optimal model and combined model can identify the most severely damaged area, but the combined model has better prediction with the same risk threshold, which verifies the feasibility and rationality of the proposed method. Finally, the model universality and the influence of sample magnitude on prediction effect are analyzed.

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      • ZHANG Yufan, AI Qian, LI Zhaoyu, XIAO Fei, RAO Yuze

        Available online:March 24, 2020  DOI: 10.7500/AEPS20190624003

        Abstract:With the development of grid cyber-physical system, part of data processing task gradually sinks to the edge side near end users. To provide dependable data source and detect anomaly consumption behavior, electricity theft detection is one of important functions of edge data center. In our electricity theft detection framework, the features are extracted by the discriminator of deep convolutional generative adversarial networks (DCGAN) and used to train L2-regularized linear support vector machine (L2SVM) in edge data center. The results show that DCGAN has good convergence performance. The features of normal and abnormal data can be easily separate and the proposed feature extraction method is more efficient than the method based on principal component analysis (PCA). Compared with support vector machine (SVM), the proposed method can achieve higher accuracy and have lower computation complexity and therefore is suitable for an edge data center.

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      • ZHANG Jing, DAI Pan, WU Tianjing, YU Haiyu, LI Bin, QI Bing

        Available online:March 24, 2020  DOI: 10.7500/AEPS20191012006

        Abstract:The strong and smart grid is the material base for State Grid Corporation of China (SGCC) to achieve high quality development of power grid. With the change of internal and external situation, the existing smart grid technical standard system has been unable to meet the needs of standardization work in the new era. Optimization and improvement of the standard system must be carried out. The research status of standard system for smart grid is sort out by domestic enterprises, alliances, international standard organization and major foreign countries. A new hierarchical architecture and conceptual model of smart grid standard system are designed in accordance with the principles of inheritance, innovation and practicability. The overall framework of the new smart grid standard system is constructed, the requirement analyses of standardization are conducted in eight professional directions including integration and planning, smart power generation, Ultra high voltage(UHV) power transmission and transformation, smart power distribution, smart power utilization, dispatching control and electricity trading, information and communication, common supporting technologies. Finally, the key action plan of various professional directions is put forward according to the principle of importance, urgency and relevance.

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      • LI Zhenkun, WANG Fashun, GUO Weiyi, MI Yang, JI Liang

        Available online:March 24, 2020  DOI: 10.7500/AEPS20190418008

        Abstract:In recent years, due to the influence of extreme weather, the rate of large-scale blackouts in distribution networks has been raised, and the resilient distribution network that can resist natural disasters and reduce the impact of power failure accidents has attracted people’s attention. In order to better evaluate the resilience of distribution network to extreme disasters, a method for evaluating the resilience of smart distribution network is proposed. Firstly, a fault model in extreme weather is established to quantify the influence of extreme weather on the distribution network. Secondly, in view of the randomness of extreme weather, Monte Carlo simulation of extreme weather scenarios is adopted and K-means clustering algorithm is applied for scenarios reduction. Time-varying failure rate of each branch of distribution network can be obtained according to the vulnerability curve. Considering the uncertainty of load and renewable energy, Latin hypercube sampling is adopted to extract load, renewable energy and distribution network fault scenarios to evaluate the resilience of distribution network. Then, in order to fully and accurately reflect the resilience of distribution network with distribution generator, the distribution network is divided into two stages of disaster prevention and reductionwhen suffering from natural disaster. Based on this, index system of resilience evaluation is constructed contains defense time of distribution network, coefficient of resilience recovery, coverage rate of island sustainable time and mean interruption time of critical load. Finally, the simulation evaluation of the resilience of an actual distribution system with two feeders is carried out, and the influence of power line type, photovoltaic permeability rate and tie lines on the resilience of the distribution network is considered, which verifies the effectiveness of the proposed evaluation method.

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      • SHU Hongchun, LIU Jialu, TIAN Xincui

        Available online:March 24, 2020  DOI: 10.7500/AEPS20190522001

        Abstract:The complex topology of the radial distribution network makes the faulty branch difficult to identify. Based on the definition of the topological backbone, this paper uses the PCA-SVM model to extract the curve cluster characteristics of the fault current traveling wave, and divides the fault section and defines it as a cut set. The ranging function is constructed by the relationship between the forward and reverse voltage traveling waves, and the distribution characteristics along the traveling wave are extracted, and the invalid mutation points are filtered according to the relationship between the amplitude, polarity, time window and line length of the mutation point, and the effective mutation point is identified. . For the extra mutation points that cannot be filtered out, the “post-test simulation” combined with the fault branch discriminant is further filtered to identify the effective mutation points and achieve accurate fault location of the radiation distribution network. The simulation software is used to simulate the faults of different branches. The results show that this method can accurately locate the fault points.

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      • XU Haibo, FANG Yongjie, CUI Xiaodan

        Available online:March 24, 2020  DOI: 10.7500/AEPS20190920006

        Abstract:DC commutation Failure brings significant changes to the fault characteristics of the AC grid near the inverter station. The influence of DC commutation failure on the RMS current of the AC fault line at the inverter station is analyzed theoretically, the deficiency of traditional criteria used in stability control devices is pointed out. Based on the real-time digital simulation platform (RTDS), the inadaptable scenarios described in the theoretical analysis are verified. By analyzing By analyzing the AC equivalent network after the DC system short circuit, new criteria for identifying fault-induced tripping based on current sequence component and interphase cosine voltage are proposed. RTDS simulation results show the validity and reliability of the new criteria.

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      • PENG Liuyang, SUN Yuanzhang, XU Jian, LIAO Siyang, YANG Li

        Available online:March 24, 2020  DOI: 10.7500/AEPS20190706003

        Abstract:When the large-scale intermittent generation sources including wind and photovoltaic generation connects to the power system, in order to cope with their uncertainty, the economic dispatch model for power system needs to be built based on the uncertainty modeling. The accuracy of modeling will directly affect the accuracy of the dispatching results. However, when considering the complex uncertainty of both load and intermittent generation sources such as wind and photovoltaic generation, it is particularly difficult to accurately model the overall uncertainty of the system. In view of this problem, the deep deterministic policy gradient (DDPG) algorithm in the deep reinforcement learning is introduced. The work of uncertainty modeling is avoided. Instead, the uncertainty is adapted by the DDPG algorithm relied on the mechanism of interacting with the environment and improving the strategy based on feedbacks. In order to guarantee the applicability of the algorithm, the generalization method for the DDPG model is proposed. Aiming at the stability problem of the algorithm, two mechanisms are designed, including perception-learning ratio adjustment and experience replay improvement. The result of example shows that the dynamic economic dispatch problem of power systems with any scenario can be solved by the proposed method based on adapting the system uncertainty.

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      • ZHANG Yikang, ZHAO Jinquan, LIU Ziwen, WU Haiwei, WANG Zhicheng

        Available online:March 20, 2020  DOI: 10.7500/AEPS20191018003

        Abstract:The construction of economic operation region (EOR) is the first step to realize automatic cruise function for bulk power grid dispatching. EOR is defined as the set of all optimal security-constrained day-ahead generation and transmission scheduling with various preferences for scheduling objectives. Then, this paper develops a centralized multi-objective model of day-ahead generation and transmission scheduling for inter-regional interconnected bulk power grid via HVDC tie-line, to minimize power generation cost, carbon emission and pollutant emission. The multi-objective optimization problem is transformed into a series of single-objective optimization problems by using the normal boundary intersection (NBI) method. And a decomposition-coordination model for sending and receiving power grids based on synchronous alternating direction method of multipliers (SADMM) is constructed for each single-objective optimization problem to realize distributed solution. Finally, a uniformly distributed Pareto frontier is obtained, which is the EOR. A two-area interconnected test system via HVDC tie-line modified from IEEE 39-bus system is utilized to verify the effectiveness of this method.

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      • LIU Xiaoou, GE Shaoyun

        Available online:March 18, 2020  DOI: 10.7500/AEPS20190523002

        Abstract:Firstly, considering the different energy levels of multi-energy, the regional integrated energy system (RIES) is divided into five parts: energy supply, energy conversion, energy transmission, energy storage and energy demand, and an expression of energy utilization efficiency (EUE) for evaluation of RIES is proposed. Then, through the theoretical analysis of EUE related factors, penetration of renewable energy, efficiency of energy conversion equipment and capacity allocation structure, demand structure of cool/ heat/ electricity load in five parts of RIES are the core elements, which affect the EUE of RIES. Finally, a case study of demonstration district in China is given to show that the energy efficiency expression can accurately reflect the characteristics of multi-energy complementary coupling and gradient utilization of RIES. By analyzing the EUE of RIES, the importance and method of reasonably allocating energy conversion equipment and optimizing the demand structure of cool/heat/electricity load are demonstrated, which is consistent with the theoretical analysis. The validity of the proposed EUE of RIES is illustrated.

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      • WANG Hao, YANG Dongsheng, ZHOU Bowen, GAO Xiaoting, PANG Yongheng

        Available online:March 18, 2020  DOI: 10.7500/AEPS20191124003

        Abstract:In view of the fault characteristics of multi-terminal HVDC (MTDC) transmission lines, such as rapid rising speed, large peak value of fault current and difficulty in fault location, a fault diagnosis method for MTDC system with both rapidity and accuracy is proposed. Firstly, the amplitude and frequency characteristics of fault signal waveforms of MTDC transmission line faults are analyzed. The extraction methods for fault amplitude and frequency features of MTDC transmission line faults are studied separatedly based on amplitude variation characteristics of signal waveforms and wavelet packet analysis.Then, the fault diagnosis method of MTDC transmission system based on amplitude-frequency characteristics is formed. Secondly, the parallel convolutional neural network (P-CNN) with fault classification and fault location branch is constructed, and the training method of P-CNN based on transfer learning is proposed. Finally, the simulation verifies that the fault diagnosis method of MTDC system based on P-CNN meet the fast requirements, and the parallel structure is more accurate and expandable than other artificial intelligence fault diagnosis methods.

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      • CHEN Shuyu, LIU Wenhua, ZHAO Xianghua, MA Huiyuan, YU Xijuan

        Available online:March 18, 2020  DOI: 10.7500/AEPS20190823004

        Abstract:To address the issue of state of charge (SOC) unbalance in cascaded battery energy storage system, this paper analyzes the boundary conditions of over-modulation with unity power factor for balancing control strategy when SOC is extremely imbalanced and proposes a novel balancing control strategy of SOC in phase with injection of reactive power. By superimposing the active and reactive voltage components to each H-bridge modulation signal and redistributing active power and reactive power, this strategy can ensure that the batteries with extreme SOC mainly exchange active power, while other batteries mainly exchange reactive power. Therefore, it can effectively reduce the modulation ratio of the batteries with extreme SOC, while slightly increase the modulation ratio of other batteries, and avoid over-modulation. Compared with the balancing control strategy with unity power factor, this strategy can fully coordinate the modulation ratio of each module by controlling the power factor angle and expand application scope of balancing control with bigger difference between SOC of each battery. The simulation results verify the correctness and effectiveness of the proposed control strategy.

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      • SUN Jun, JIANG Tianlong, WANG Yangming, SUN Dan, YE Shankun, DUAN Hui

        Available online:March 18, 2020  DOI: 10.7500/AEPS20190708005

        Abstract:When the grid voltage is unbalanced, since the control bandwidth of the virtual synchronous generator (VSG) is limited, it has almost no control effect over the double-frequency fluctuation component of the power caused by the negative sequence voltage of the grid. Therefore, the long-term voltage imbalance will cause problems such as stator and rotor current distortion, power and torque oscillation, which seriously affect the power quality and operation performance of the doubly-fed induction generator (DFIG) system. In order to solve these problems, this paper proposes a method to quantitatively control the double-frequency pulsation of the electromagnetic torque and reactive power of DFIG by using the second-order generalized integrator (SOGI).This method enables the DFIG VSG control system achieving three control objectives under unbalanced grid conditions, namely balanced and sinusoidal stator current, sinusoidal stator current and constant active power, sinusoidal stator current and constant reactive power and electromagnetic torque. At the same time, each control target can be flexibly switched according to the real-time requirements of the power grid, which improves the control performance of the DFIG VSG system. Finally, the effectiveness of the proposed strategy is verified by simulation results.

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      • CAI Hui, QIAO Shisu, YUAN Jian, CHEN Hanqi, LI Jing, PAN Yizhou

        Available online:March 16, 2020  DOI: 10.7500/AEPS20190528006

        Abstract:Aiming at the problem that the state evaluation technology of intelligent electricity meter needs to be perfected, this paper establishes a new dynamic evaluation model of low-voltage intelligent electricity meter based on information fusion theory. While analyzing the reliability of the low-voltage intelligent electricity meter, the four state factors, namely abnormal measurement, full event, overload rate of the electricity meter and abnormal clock battery are comprehensively considered, and the entropy method is adopted to calculate the weight of each index in real-time. In addition, the dynamic state evaluation of the low-voltage intelligent electricity meter is made based on the regional influence factors. Based on Weibull distribution theory, a sub-evaluation model of reliability for electricity meter is developed, a sub-evaluation model of measurement anomaly and full event is established by using Bayesian formula, and the Thiel index is introduced to evaluate area influential factors. The evaluation model is verified by the actual operation data, and the results show that the developed model is reasonable and feasible, and can effectively evaluate the intelligent electricity meter.

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      • DONG Hongzhao, FANG Yaxiu, FU Fengjie

        Available online:March 16, 2020  DOI: 10.7500/AEPS20190523010

        Abstract:Existing studies on waiting time of charging stations often neglect the time-varying differences in charging requirements for different vehicles. A prediction method of charging waiting time distribution for electric vehicles (EVs) in Internet of Things (IOT) perception environment is proposed to comprehensively explore the time-varying law of charging waiting time. Firstly, on the basis of determining the quantity distribution of vehicles arriving at the charging stations and the charging duration distribution, the M/G/n queuing model is used to simulate the queuing system at charging stations and solve the distribution function of charging waiting time for EVs. Secondly, the utility function for user to select charging stations is established, the Multi-logit model is used to predict the charging demand in each charging station. Furthermore, the average arrival rate, service time and variation coefficient are updated according to the predicted value of charging demand and the real-time data of network-connected charging stations, and the short-time prediction of EVs charging waiting time is realized with the distribution function of charging waiting time. Finally, taking a certain area of a city as an example, the accuracy of this distribution is verified, and the influence of charging waiting time distribution and reliability on charging stations is analyzed, which provides a decision basis for reducing queuing congestion and balancing power system load.

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      • WU Xi, WANG Mengting, WANG Liang, TAO Jiagui, CHEN Xuan, XU Xiaoyi

        Available online:March 12, 2020  DOI: 10.7500/AEPS20190416005

        Abstract:The unified power flow controller (UPFC) can effectively solve a series of problems caused by unbalanced power flow distribution, which has received extensive attention in recent years. In order to further explore the control potential of UPFC and enhance the safety of power grids, this paper proposes an N-1 security constrained optimal power flow model considering control modes of UPFC. Firstly, the equivalent power injection model considering the double-circuit structure of UPFC is established. Secondly, combined with the actual example of 500 kV power grid in southern Suzhou of China, the effect of UPFC control mode on static security is analyzed. The necessity of considering UPFC control mode in the process of power flow optimization is also indicated. Finally, the optimization model of the system aiming at minimizing static security margin is constructed. In the optimization process, the effect of UPFC control modes on the power flow distribution after the N-1 fault is fully taken into account to make the optimal selection of both system operation parameters and control modes of UPFC. The results of the simulation case of the power grid in southern Suzhou of China show that the proposed power flow optimization method can fully exploit the static control potential of UPFC and significantly improve the static security of the system.

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      • LIU Hao, BI Tianshu, XU Quan, CUI Shijie, SHI Bonian, XUE Ancheng

        Available online:March 12, 2020  DOI: 10.7500/AEPS20190814002

        Abstract:With the increasing penetration of distributed renewable energies, more and more electronics devices are brought into smart distribution networks. However, the observation problem of distribution networks is becoming more severe. Therefore, synchrophasor measurement units for distribution network (D-PMU) is of great significance. In this paper, based on former researches, five aspects of synchrophasor measurement of distribution network are introduced in-cluding the sychophasor measurement method with high accuracy under high noises and step changes, the synchroni-zation technology with weak commutation, the information security technology, the development, and the testing technology and platform of D-PMU. The general prospects of the research is outlined. Then, the framework of D-PMU, phasor measurement methods for D-PMU and its calibration are proposed.

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      • LI Jinliang, LIU Huaidong, WANG Ruizhuo, YAN Shuzhen, CUI Liyao

        Available online:March 12, 2020  DOI: 10.7500/AEPS20190805008

        Abstract:According to the characteristics of various types of energy utilization and wide range of input and output indexes in the comprehensive energy system, a comprehensive efficiency evaluation model based on cross-super-efficiency CCR model was established by introducing the mature comprehensive evaluation theory in operational research. The evaluation model is based on relative efficiency. Firstly, each index value was calculated according to the economic dispatch results of each integrated energy system. Secondly, the index value was substituted into the evaluation model to calculate the cross-super-efficiency of integrated energy system and then the comprehensive efficiency could be compared. Through an example of a small-scale Park, the paper analyzed the differences and reasons of the comprehensive efficiency of the park in summer and winter, and verified the correctness and rationality of the comprehensive efficiency evaluation model. The influence of installed capacity of fan and heat pump on the comprehensive efficiency of integrated energy system was further analyzed and the optimal capacity allocation was determined. Compared with the evaluation results of the super-efficiency CCR model, the cross-super-efficiency CCR model is more reasonable and effective.

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      • XIE Nan, XU Qifeng, TAN Qiao

        Available online:March 12, 2020  DOI: 10.7500/AEPS20190508005

        Abstract:The measurement results of the optical voltage transducer based on the nonlinear demodulation mode are related to the optical power, and the half-wave voltage limits its voltage measurement range. To fix these issues, this paper proposes a linear optical voltage sensor based on Newton’s ring sub-wavelength grating. Compared with the radial analyzer grating, the TM mode transmittance of the Newton ring grating are evenly distributed in the radial direction. It converts the electro-optic phase delay into the synchronous rotation of the spot image. The four-quadrant detector is used to locate the spot image for real-time linear measurement of the voltage signal. The experimental results show that the measurement result of the optical voltage transformer is independent of the optical power, and the measurement range of the electro-optic phase delay can reach ±80 degrees, and the accuracy level is 0.2 level under laboratory conditions. The next step will be to study the effect of temperature and vibration on the measurement accuracy of the transducer.

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      • WANG Wenrui, QU Kaiping, YU Tao, LAN Chaofan, LIU Jianing

        Available online:March 12, 2020  DOI: 10.7500/AEPS20190601002

        Abstract:Existing robust interval dispatching models for wind power often aims to minimize the generation cost for base state and maximize the accommodation of wind power, which are difficult to consider the optimization of generation cost in the actual dispatching process. To solve the above problem, this paper proposes a method to simultaneously optimize allowable interval of wind power and expected generation cost of units. Based on the three-point estimation method of Nataf inverse transformation, the proposed method guarantees the maximization of allowable interval for wind power, and takes the expected value of generation cost coping with the wind power fluctuations as the economic objective to reflect the minimization of actual generation cost. In order to improve the capacity of wind power accommodation, the proposed method takes the wind power undertaking coefficient of the unit as a variable and relaxes the introduced nonlinear term. For the non-convexity introduced by the expected power generation cost as the objective, a convexity-concave process is adopted for iterative processing to ensure the accuracy of the method. Finally, the Monte Carlo simulation on modified IEEE 118-bus system is carried out by using the corrected model to verify the validity of the proposed method.

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      • DU Hui, LIN Tao, CHEN Rusi, LI Shuitian, DING li, XU Xialing

        Available online:March 12, 2020  DOI: 10.7500/AEPS20190709007

        Abstract:Active power steady-state security region (APSSR) represents feasible region for injection power under the given power grid structure. Application of APSSR is conducive to online security assessment and preventive control. With increasing broad application of flexible alternative current transmission devices such as thyristor controlled series compensations (TCSCs) and unified power flow controllers (UPFCs), power grid structure parameters is becoming continuously adjustable and the power flow distribution is further complex. Efficiency of existing APSSR construction method is limited by iteratively high-dimensional parametric matrix inversion. Method proposed in this paper transfers influence of TCSCs on the power flow distribution into modifying the injected power of nodes, thus APSSR with TCSCs equivalent reactance parameters can be constructed. Formula of branch APSSR with single TCSC equivalent reactance parameters is deduce on this basis, and further extend to an explicit expression of branch APSSR with multiple TCSCs. Based on numerical simulations with different grid distribution and quantity of accessed TCSCs, the effectiveness of the proposed method and superiority in computational efficiency are verified. Finally, one of feasible method of APSSR application in prevention control and structural parameter optimization is exemplified.

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      • YANG Jiaqi, YU Jie, TIAN Hongjie, WANG Siyu, TENG Xianliang, DING Qia

        Available online:March 12, 2020  DOI: 10.7500/AEPS20190423009

        Abstract:The new energy unit has the characteristics of flexible control and rapid response. Technically, it has the ability to participate in power system frequency regulation. If it is regarded as a frequency regulation resource, it will be beneficial to relieve system pressure. In this paper, the ancillary service market mechanism of new energy participating in frequency regulation is proposed. The performance index of frequency regulation is evaluated with the accuracy probability index, the risk loss of frequency regulation is calculated quantitatively, and the market clearing model considering the risk of frequency regulation of new energy is established. In the actual scheduling process, considering the deviation between the accuracy of real-time frequency regulation of new energy units and the historical data, a real-time frequency regulation scheduling model based on model predictive control is constructed.The market mechanism and scheduling strategy proposed in this paper not only make full use of new energy as frequency regulation resource, but also effectively control the uncertainty risk of output of new energy.Simulation examples show the effectiveness of the model and algorithm.

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      • YU Hongru, SU Jianhui, WANG Yiding, WANG Haining, SHI Yong

        Available online:March 12, 2020  DOI: 10.7500/AEPS20191029006

        Abstract:The small-signal model of grid-connected inverter is an important tool for judging system stability and parameter design. The complete state equation of the grid-connected inverter will be accompanied by more redundant information. It is convenient to tune and debug system parameters by adopting appropriate reduced-order model. However, some of the existing typical reduced-order models have narrow applicability, low accuracy under specific conditions or loss of generality with the change of parameters. Firstly, this paper develops a general power-loop model based on the concepts of equivalent inertia constant and equivalent damping coefficient. Through single-side Fourier analysis, it is pointed out that the traditional third-order model is only suitable for the analysis of the systems with large inertia and high damping. Through the analysis of output impedance of grid-connected inverter, it is pointed out that the accuracy of the electromagnetic fifth-order model is sensitive to the control parameters. In order to solve the accuracy problem of reduced-order model, a model order-reduction method based on time constant is proposed by using the characteristics of natural separation of time scale of inverters. The proposed method is simple and effective. And a simple reduced-order model of the inverter is derived. The obtained model has high accuracy and wide application. Finally, the correctness of the theoretical analysis and the effectiveness of the order-reduction method and the reduced-order model are verified by comparative experiments.

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      • TANG Wei, LI Tianrui, ZHANG Lu, CAI Yongxiang, ZHANG Bo, WANG Zhaoqi

        Available online:March 12, 2020  DOI: 10.7500/AEPS20190609004

        Abstract:The unbalanced connection of large-scale residential photovoltaic (PV) power integrated into low-voltage distribution network (LVDN) will bring problems such as voltage violations, power losses and three-phase imbalance. In order to solve the problem that the accommodation control technology is not suitable to the three-phase four-wire low-voltage distribution system, a coordinated control method considering PV and energy storage system (ESS) is proposed based on three-phase four-wire optimal power flow (OPF). The network topology of LVDN is established by using three-phase four-wire node admittance, where the amplitudes and phase angles of voltage and current are considered. Multi-period coordinated control model of three-phase four-wire lines for active power of energy storage elements and reactive power of PV inverters is developed by overall considering the minimum of both power loss and three-phase imbalance. The difficulty of solving three-phase four-wire model is reduced through complex variable decomposition and model convexity, and the global optimal solution can be got by CPLEX method package. Simulation results show that the proposed OPF based control method can effectively mitigate the voltage violation in conditions of large-scale PV and load unbalanced connection, meanwhile the network power loss is reduced and the degree of three-phase imbalance is also optimized.

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      • WANG Tao, PENG Guorong, HU Junxuan, YANG Tao, LONG Xi, Jiazhu XU

        Available online:March 11, 2020  DOI: 10.7500/AEPS20190808006

        Abstract:A integrated filtering method for 12-pulse rectifier based on harmonic magnetic potential balance (HMPB-IPF) is proposed. The topology, mathematical model and filtering principle of HMPB-IPF are explained in detail. In this method, a back-to-back converter is connected to the tap of star and delta windings on the secondary side of transformer of 12-pulse rectifier. The specific harmonic current components are injected into each winding tap through the back-to-back converter. By using the magnetic potential balance between these harmonic components generated by back-to-back converter and the harmonic components generated by the load side of 12-pulse rectifier, the specific harmonic current components on the grid side of 12-pulse rectifier can be eliminated well. The proportional-integral (PI) + proportional-resonant (PR) controller is adopted to realize error-free tracking of the specific harmonic components. The proposed method can improve the voltage and current adaptability of the filter converter, so the cost of voltage matching transformer can be saved effectively and the capacity potential of filter converter can be used fully. Finally, the correctness of the proposed filtering method is verified by simulation and experiment.

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      • LIU Wenxia, LI Zhengzhou, YANG Yue, YI Fang, WANG Yao

        Available online:March 10, 2020  DOI: 10.7500/AEPS20190731013

        Abstract:This paper presents a method of equipment optimal configuration for an integrated energy system (IES) considering the uncertainties of integrated demand response (IDR). Firstly, in order to improve energy efficiency, the basic structure of IES considering IDR is constructed based on a combined cooling heating and power (CCHP) system. Then, the aleatory and epistemic uncertainty of IDR is analyzed by the evidence theory, and the load curve under a certain price scheme is optimized by using a credible level constraint. On this basis, a bi-level collaborative planning model considering the optimal configuration and operation strategy of the equipment in IES is established, wherein the upper level conducts the equipment selection and capacity allocation with the goal of minimizing the total planning cost, and the lower level optimizes the equipment output with the lowest operation cost as the objective. By comparing the total cost of all tariff schemes, the optimal tariff and equipment allocation scheme can be obtained. Finally, the proposed approach is illustrated on an example and the results demonstrate that the optimal allocation results considering the uncertainties of IDR are more resistant to risks. Meanwhile, evidence theory can be used to achieve the unification of probability theory and interval theory.

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      • JIA Ke, CHEN Jinfeng, WANG Hechun, YANG Bin, ZHAO Guankun, BI Tianshu

        Available online:March 05, 2020  DOI: 10.7500/AEPS20190710006

        Abstract:When the grid fault by a large transition resistance is cleared, the direct current transformer (DCT) is difficult to automatically switch back to its original control because the DC voltage fails to drop to the minimum threshold voltage. Based on the analysis of the relationship between transition resistance and the DC voltage fluctuation, a coordination control strategy based on the feedforward compensation of grid voltage incremental is proposed. By detecting the incremental value of the grid voltage, the value of DC voltage fluctuation increases by correcting the reference DC voltage value of inverter outer control loop. In this case, the DCT can switch back to the maximum power tracking (MPPT) control in time by monitoring the amplitude of the DC voltage without requiring communications. The PSCAD simulation results show that the DCT can reliably and quickly switch the control strategy after the large transition resistance fault in the AC grid is cleared, which effectively improves the utilization of photovoltaic (PV) resources.

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      • LI Zhaowei, FANG Yongjie, LI Wei, LIU Fusuo, XU Guang, WANG Caixia

        Available online:March 05, 2020  DOI: 10.7500/AEPS20191101007

        Abstract:With the continuous increase of UHVDC and renewable energy generation in the grid, the system frequency security situation based on traditional synchronous generators is becoming more and more serious. Electrochemical energy storage is a potential control resource which attracts growing attention in power system. Based on the frequency defense system of China"s power grid, the fast power regulation characteristics of battery storage is used to enhance it and the roles it plays in the triple defense lines of frequency are analyzed. According to the control target of grid frequency in different scenarios, the configuration principle of electrochemical energy storage under frequency security constraint are discussed. And the future research directions in this field are proposed. #$NLKeywords: Electrochemical Energy Storage; Fault Defense System; Frequency Security; emergency control; Frequency adjustment

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      • LI Lixing, MIAO Shihong, TU Qingyu, LI Yaowang, LI Chao, DUAN Simo

        Available online:March 05, 2020  DOI: 10.7500/AEPS20190430016

        Abstract:As the penetration rate of wind power in the power system continues to increase, its uncertainty poses a great challenge to the safe and economic operation of the power system. In order to obtain accurate wind power uncertainty model and help operators to achieve stable and economic operation of the system, this paper proposes a conditional probability distribution modelling method of wind power forecast error considering the heteroskedasticity effect. Firstly, the dependence of wind power forecast error and various factors is analyzed. Based on the results and the dynamic Copula theory, a dynamic dependence model of wind power forecast error is established. Then, based on the temporal features displayed by the edge distribution, combined with the autoregressive integrated moving average (ARIMA) model and the generalized autoregressive conditional heteroskedasticity (GARCH) model, this paper develops a time-varying edge distribution model with consideration of heteroskedasticity effect. Finally, the two models are combined to give the forecast error distribution of wind power conditions at different fluctuation levels, and the verification is performed in the uncertain unit combination model, which proves the validity of the model.

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      • QI Ning, CHENG Lin, TIAN Liting, GUO Jianbo, HUANG Renle, WANG Cunping

        Available online:March 05, 2020  DOI: 10.7500/AEPS20191030003

        Abstract:First of all, this paper analyzes the demand of current distribution network planning, and establishes the important role of bringing the flexible load resources into planning. Furthermore, the classification methods and results of flexible load are proposed from three aspects, i.e. energy interaction mode, scheduling response mode, user and equipment type. Then, aiming at the influence of access of flexible load on the distribution network planning, the adaptability and shortcomings of the existing planning methods are analyzed from four aspects, including load forecasting, power balance, planning optimization and planning evaluation, and corresponding improvement ideas and suggestions are put forward. Finally, the new key technologies such as flexible load modeling, big data mining and application are summarized, and the future development of distribution network construction is summarized and prospected.

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      • WENG Hanli, JIA Yongbo, LI Zhenxing, HUANG Jingguang, LIN Xiangning, LIU Lei

        Available online:March 04, 2020  DOI: 10.7500/AEPS20190612003

        Abstract:Under the influence of fault current, the current transformers(CT) on both sides of the transformer differential protection are prone to saturate. This will cause the waveform distortions of the transformed currents and severely impact the correct operation of the transformer differential protection. Aiming at the malfunction of transformer differential protection caused by CT saturation, the phase relationship characteristics between the currents on both sides of the transformer under different fault types are comparatively analyzed. A novel criterion for transformer differential protection is proposed to identify various faults accompanied by the CT saturation, which is based on the two-dimensional reconstruction of currents on both sides and their reconstructed characteristics tracks. The results of simulation and experimental tests indicate that the proposed criterion has high reliability and sensitivity, as well as the ability of anti-saturation of CT.

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      • CHEN Zhe, WANG Luyu, GUO Chuangxin, MA Guang, ZHANG Jinjiang

        Available online:March 04, 2020  DOI: 10.7500/AEPS20190813001

        Abstract:To deal with the problem of system operation and reserve scheduling caused by multiple kinds of uncertainty, a two-stage robust optimization model of multiple reserve resources is proposed, which considers the wind power reserve capacity and demand response. On the one hand, to make full use of the wind farm and demand reserve capacity and improve the flexibility of system operation, the reserve provided by the two resources is modeled respectively. On the other hand, based on the robust optimization model, multiple reserve resources are co-optimized to ensure the reliable operation of the power grid under the worst operating conditions, thus improving the robustness of the power systems. The two-stage robust optimization problem is solved by the state-of-the-art column and constraint generation algorithm (C&CG). Simulation results on the modified IEEE RTS-79 test system verify the effectiveness of the proposed model and algorithm. The results show that the co-optimization of multiple reserve resources can improve the operational flexibility of power systems and promote wind power consumption. At the same time, by adjusting the uncertainty set of the robust model, the balance between the robustness and economic efficiency of the system can be achieved.

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      • WANG Ying, WANG Huan, ZHANG Shu

        Available online:March 04, 2020  DOI: 10.7500/AEPS20190809004

        Abstract:It is important to accurately identify voltage sag sources for sag responsibility allocation and mitigation decision-making. This paper proposes a recognition method of voltage sag sources based on the optimized extreme learning machine (ELM). The time-domain features are directly extracted from the voltage sag waveforms, and the time-frequency domain features (include energy entropy and singular entropy) are extracted by S-transform. Then the feature vectors are built based on the time-domain and time-frequency domain features. The feature vectors make up for the shortcomings that the existing methods only use time-frequency transform to extract features and may lose the important information only existing in the time-domain and affect the recognition accuracy. The genetic algorithm is used to optimize the input weight and hidden layer bias of the ELM. The optimized ELM model is proposed to solve the problem of the pattern recognition, whose model is complex and time-consuming. The validity of the proposed feature vectors and optimized ELM model are verified by the simulated data and the measured data. Compared with other methods, it is proved that the proposed model is simple and fast in training and classification, and has higher recognition accuracy. It is suitable for edge calculation, so as to identify the voltage sag sources accurately and fast.

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      • LI Chao, YAN Yunsong, XIONG Jun, TANG Fan, LI Mingying, LI Peng

        Available online:March 02, 2020  DOI: 10.7500/AEPS20190719002

        Abstract:Abstract: After Chongqing-Hubei back-to-back operation, the main problem of asynchronous operation of southwest power grid has become its own frequency problem, and the existing stability control system can only solve local prob-lems, so it is necessary to construct AC/DC coordinated control system of southwest power grid. The design of AC/DC coordinated control system for southwest power grid is analyzed in terms of processing means, coordination mode and construction mode.The overall architecture of the system is described in detail, and the principles of construction are introduced in the aspects of site configuration and communication design. The function and function of AC/DC coor-dinated control system are described in detail from the aspects of fortification principle and control strategy of AC/DC coordinated control system. Moreover, the AC/DC coordinated control system is applied to the actual southwest power grid, and detailed test verification is carried out at the same time. Key words: Asynchronous power grid; existing security control measures; frequency problem; AC / DC coordinated control system; frequency coordinated control

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      • QI Bing, LIU Sifang, LI Bin, SUN Yi, JING Dongsheng, CHENG Ziyun

        Available online:March 02, 2020  DOI: 10.7500/AEPS20190702006

        Abstract:Based on the composition of power communication network, the importance of the network-borne service and its importance degree is analyzed. Then the technique for order preference by similarity to an ideal solution (TOPSIS) method for evaluating the importance of the business is proposed. The widely existed shared risk problem in the network is analyzed, and the risk balanced model is established. In the proposed shared risk link group (SRLG) and risk balanced routing optimization algorithm for power communication network, the average service risk, risk balancing degree, block-risk comprehensive index and SRLG remaining bandwidth capacity ratio are introduced to optimize the routing path and performance. The simulation is carried out in the cable routing topology of a city in Jiangsu Province to verify the effectiveness of the proposed algorithm. The simulation results show that without increasing the blocking risk of the network, the proposed algorithm effectively reduces the average network service risk, improves the risk balancing degree of the working path, reduces the remaining bandwidth capacity ratio of SRLG and lowers the failure risk of shared links.

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      • ZHAO Wenguang, ZHANG Xing, LI Yanjun, GAO Shuai

        Available online:February 27, 2020  DOI: 10.7500/AEPS20190801002

        Abstract:When the Buck/Boost bi-directional topology is used as energy storage ports of power routers, the energy storage port exists grid-connection startup inrush current and the bus voltage has fluctuation in off-grid mode. Aiming at the problem, an optimal grid-connection/off-grid control strategy is proposed for energy storage port, which combines voltage feedforward of energy storage port and load power feedforward control. The feedforward of voltage on the energy storage side can effectively restrain the inrush current of energy storage port during grid-connection startup, and eliminate the impact of voltage fluctuation of energy storage side on bus voltage. The communication unit is fast controlled by power router based on Ethernet control automation technology (EtherCAT) to feeds forward the load power, which can restrain bus voltage fluctuation caused by load disturbance in off-grid mode and reduce the cost of current sampling. The theoretical analysis and experimental results show that the proposed method can effectively improve the performance of power router.

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      • ZHU Xiaorong, LIU Yawei

        Available online:February 27, 2020  DOI: 10.7500/AEPS20190626009

        Abstract:In order to maximize the power generation efficiency of photovoltaic power plants and reduce the maintenance costs, this paper proposes a maintenance strategy based on component-system classification optimization method. Firstly, considering the failure rate of each component in the photovoltaic power plant, the state transition matrix for each component is determined and states of each component are predicted using Markov chain method. In the component-level optimization stage, by considering the direct maintenance costs , maintenance downtime losses, and fault risk losses, the most optimal maintenance time and near-optimal maintenance time for each component are determine and a maintenance strategy set for each component is obtained. In the system-level optimization stage, the time thresholds for the combination maintenance of components are calculated based on the economic dependence and structural dependence between components,and the optimal maintenance strategy of the system is determined according to the time thresholds. Finally, the validity of the proposed method is verified through case studies. Results show that the proposed maintenance strategy can significantly reduce maintenance costs and system downtime losses.

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      • LIAN Zikuan, YAO Li, LIU Shengyuan, YU Yuntao, TANG Xiaoqi, YANG Li, LIN Zhenzhi

        Available online:February 26, 2020  DOI: 10.7500/AEPS20190621001

        Abstract:The accurate phase and meter box information of single-phase users in low-voltage courts have great influences on the checking of user-transformer relationships and the treatment and analysis of line losses. At present, the correction of topological documents mainly relies on the on-site checking by electrical engineers, which spends a lot of manpower and material resources and is with low efficiency. Therefore, it is necessary to study a more efficient method of checking the topological documents of the low-voltage courts. Given this background, a phase and meter box identification method based on voltage measurement data of smart meters is proposed, which is helpful for topology identification and correction of low-voltage courts. Firstly, the t-distributed stochastic neighbor embedding (t-SNE) technology is adopted to reduce the dimension of original load data, so as to solve the redundancy problems caused by excessively high dimension of original load characteristics of users. Then, the balanced iterative reducing and clustering using hierarchies (BIRCH) method is used to cluster the dimension-reduced load data, so as to identify the phase and meter box information of single-phase users. Finally, case studies for actual low-voltage court in Haining, China, are performed to verify the correctness of the proposed method, and the results show that the proposed model is feasible and effective.

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      • XU Jian, LIAO Siyang, WEI Congying, YUAN Jiaxin, YANG Jun, JIA Yuqiao, FU Haobo, XIE Boyu, YUAN Zhiyong

        Available online:February 26, 2020  DOI: 10.7500/AEPS20190829003

        Abstract:With the large-scale distributed generations, electric vehicles and other power electronic devices access to the distribution network, new challenges are brought to both control flexibility and control time scale. The micro synchronous phasor measurement unit (D-PMU) can make it possible for online monitoring and real-time control in the distribution network with distributed generators. Based on the wide area measurement information, the fast coordinated control of source-network-load in distribution network can significantly improve the economy and the utilization of renewable energy. This paper presents the technical content needs to be studied in the area of the source-grid-load coordinate control technology in distribution network, conceives the overall framework and technical route and prospects the key technical difficulties in the research from the aspects of distributed generation and load power prediction and controllability modeling, source-load cooperative control, island smooth switching and stability control.

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      • CHEN Lijuan, QIN Meng, GU Shaoping, QIAN Kejun, XU Xiaohui

        Available online:February 25, 2020  DOI: 10.7500/AEPS20190730003

        Abstract:Considering the loss cost of power batteries, a multi-time scale optimal scheduling strategy of electric buses participating in vehicle-to-grid (V2G) is proposed. Firstly, based on the principle of engineering economics, a loss model of power battery is established. In order to optimize both the battery loss cost and the charging-discharging plan of charging station, an iterative method is adopted to minimize the daily operating cost of the bus company in upper layer of day-ahead stage. Based on results optimized in upper layer, the charging-discharging plan of charging station is further optimized to minimize the peak-to-valley difference of distribution network. In the intraday stage, the output power of photovoltaic (PV) and the base load power of distribution network are rolling updated, the day-ahead plan is revised in order to minimize the daily operating cost of bus company and the deviation between day-ahead plan and intraday plan. Finally, from the perspectives of bus company and power grid, three strategies of disordered charging, orderly charging and participating in V2G are compared and analyzed to verify the superiority of electric bus participating in V2G. The changing trend of the operating cost of bus company with different V2G compensation coefficients is reflected by sensitivity analysis.

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      • LIU Yindi, ZENG Xiangjun, LUO Yiping, ZHANG Shiyong, WEI Milan

        Available online:February 25, 2020  DOI: 10.7500/AEPS20190427001

        Abstract:To solve the problem of various transform series for traditional wind power system, this paper proposes a hybrid topology of high voltage direct current (HVDC) wind power system based on multi-phase permanent magnet synchronous generator (MPPMSG). The multiple sets of windings of the generator are separately connected to unipolar converters, which connects in series on the DC side and transfers into high voltage to connect the HVDC transmission line. One set of windings injects reactive power into the generator to improve the generator speed regulation and steady-state performance. On the on-shore substation, the line commutated converter (LCC) based on thyristors is applied because of its advantage to block the short-circuit current when the DC transmission line is shorted. In order to solve the multi-winding coupling problem, a feedback decoupling control strategy is adopted for MPPMSG. According to the analysis of short-circuit characteristics for generator, a fault ride-through strategy is proposed combined with the short-circuit current limitation method, which can deal with the short-circuit fault of DC transmission line effectively. Finally, the switching-circuit simulation model of the hybrid wind power system is built in PSCAD/EMTDC, and the effectiveness of the proposed control strategy is verified.

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      • LIN Guoying, LU Shixiang, GUO Kunjian, GAO Ciwei, FENG Xiaofeng

        Available online:February 21, 2020  DOI: 10.7500/AEPS20190613004

        Abstract:A Stackelberg game model between a single grid company and multiple users is constructed for the demand response. The grid company selects the appropriate time period to formulate the demand response subsidy strategy based on the predicted load duration curve of the next year. The transmission and distribution construction costs are decreased by reducing the peak load, thereby improving the overall revenue of transmission and distribution. Users choose the change in electricity consumption based on the subsidy price set by the grid company for the time period to obtain additional profits. Moreover, the existence of the Stackelberg game model and the method for solving the model are analyzed, and the process of solving the game equilibrium solution is presented. Case study shows that the grid company can declares subsidized price during peak load period based on the proposed model. Both grid company and users can benefit from demand response. In addition, the impact of the unit cost of avoidable transmission and distribution capacity on profits of the grid company is analyzed.

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      • LI Zeyu, GUO Chuangxin, ZHU Chengzhi

        Available online:February 21, 2020  DOI: 10.7500/AEPS20190203002

        Abstract:In this paper, Back propagation neural networks (Back Propagation Neural Network, BPNN) were used to establish prediction models of the wind turbine (WT) condition parameters. In order to improve the prediction accuracy, the genetic algorithm (GA) was used to optimize the initial weights and threshold values of the BPNN models. T-location scale (TLS) distribution was used to characterize the distribution characteristics of condition parameter prediction errors under different wind speed intervals. Moment Estimation was used to calculate the TLS parameters. Error abnormal index (EAI) was defined to quantify the abnormal level of prediction errors, which has been verified to be an indicator of the WT anomalies. The proposed method has been used for real 1.5 MW WTs with doubly fed induction generators. The results show that the proposed method was effective in WT anomaly identification.

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      • ZHANG An’an, FENG Yating, LIN Dong, LI Qian, WU Jianzhong

        Available online:February 21, 2020  DOI: 10.7500/AEPS20190908003

        Abstract:Because of the low energy utilization rate caused by the single utilization mode of natural gas pressure energy and the difficulty of cold energy utilization in the pressure regulating stations, this paper proposes an integrated scheme of pressure energy generation and cold energy comprehensive utilization of natural gas high-pressure pipe network. Considering the instability of energy supply caused by the geographical characteristics of the pressure regulating station, a micro integrated energy network structure was constructed. It combined natural gas pressure energy with various energy sources such as electricity, gas, cold and heat, to realize multi-energy coupling and complementation. Then, an integrated gas-electricity demand response model was established by introducing two types of responses: price-based demand response and incentive-based demand response. The former created a demand response model of electricity load and gas load based on price elasticity matrix, while the latter carries out peak regulation of the natural gas pipeline network using the subsidy. Considering the energy consumption cost, operation and maintenance cost, environmental cost, and demand response of the micro integrated energy network, an optimal dispatching model for integrated natural gas-electricity demand response of the micro energy network was proposed. And the optimal dispatching results of electricity-gas-cold energy of the micro energy network in different cases were calculated and analyzed. The feasibility and effectiveness of the proposed integration scheme and the natural gas-electricity demand response model were also verified.

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      • LIU Wenxia, HAN Hui

        Available online:February 21, 2020  DOI: 10.7500/AEPS20190710002

        Abstract:With access of renewable energy and application of voltage control system, distribution network relies more heavily on cyber system to realize active control,thus cyber failure will inevitably affect distribution network. In order to evaluate the influence that cyber failure exert on the voltage of distribution network, a cyber system validity model with the consider of various cyber failure factors is firstly established in this paper. Secondly, distribution index and probability index are introduced. Then this study presents an analysis method of voltage fluctuation considering different failures, finally it calculates index with sequential Monte Carlo Simulation method. The test system verifies the feasibility of the model, and discusses the influence of different failure factors on indexes,providing technical support for the planning and operation of cyber physical distribution system.

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      • YAN Longchuan, CHEN Zhiyu, YU Xuehao, LYU Qiang, ZHU Jing, ZHAO Ziyan

        Available online:February 21, 2020  DOI: 10.7500/AEPS20190312005

        Abstract:With the intrinsic shortcomings of power systems, such as large scale, numerous micro-grids, fuzzy network boundaries, and complex operating environment, the security threats of traditional urban power grids are becoming increasingly acute. In order to meet the development needs of new urbanization, and make up for the shortage of online updating of encryption keys of power equipment, this paper studies the practical technology and core service characteristics of power quantum secret communication. A new generation of power quantum secure communication framework with high-security level protection is proposed to improve security level of power information transmission. The performance test of the proposed scheme is based on the actual urban power grid line and test environment. The results show that the proposed method can meet the operational needs of the power service. Moreover, it can effectively improve the security protection capability of the power grid.

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      • LI Cunbin, JI Liyan, ZHAO Defu, LI Xiaopeng

        Available online:February 17, 2020  DOI: 10.7500/AEPS20190226004

        Abstract:With the deep integration of cyber-physical system, power system presents the development trend that structure is complicated and external hazard factors are easy to occur. Based on the analysis of the current research of power system disaster, this paper proposes the theory of power system catastrophic process —“disaster pregnancy -disaster transmission-disaster reporting-disaster prevention” for the catastrophe evolution and prevention of power system. Firstly, the hazard factors and disaster-generation mechanism of power system and their coupling relationship are analyzed based on the big data-driven. Secondly, the pregnancy, evolution, critical state, emergence and transmission mechanism of hazard factors are studied. Thirdly, based on the Internet of Things(IoT) real-time monitoring technology for external hazard factors, the assessment and early warning mechanism of hazard factors and disasters are studied. Then, based on situational awareness technology, active disaster prevention and control strategies are analyzed from the aspects of disaster prevention and control strategy database construction, perception prediction of the catastrophic development trend, intelligent decision-making of prevention and control strategies, and sensitivity evaluation. Finally, a big data analysis framework for power system disaster prevention and control is proposed.

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      • XIA Bingqing, SHEN Danfeng, ZHENG Xiang, HUA Wen, WU Hao, SONG Yonghua

        Available online:February 17, 2020  DOI: 10.7500/AEPS20190903005

        Abstract:There are many parameters in power systems which affect the stability of mid-long term voltage stability, we proposed a quasi-steady-state modeling based polynomial approximation for the approximation of mid-long term voltage stability trajectory. Through this method, the effect of parameters on mid-long term voltage stability can be accurately analyzed. Polynomial approximation is the idea of approximating a continuous function with polynomial, this paper proposes a polynomial approximation method for power system mid-long term dynamics based on traditional Galerkin method. The proposed method constructs a polynomial approximation expression that can explicitly describe the approximate relationship between system state and control parameters by performing polynomial approximation on the continuous dynamic process and discrete dynamic process of the system respectively. Because the proposed method retains the nonlinear characteristics of the system, its approximation accuracy is relatively high and its accuracy increases with the increase of the degree of the selected polynomial basis function, Finally, the Nordic 74-bus system is taken as an example to compare the difference of the accuracy and calculation time between the proposed method and the traditional method, proving that the method can provide more accuracy analysis results in the study of mid-long term stability problems.

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      • WANG Can, DU Chuan, XU Jiexiong

        Available online:February 16, 2020  DOI: 10.7500/AEPS20191021006

        Abstract:With the development of DC power transmission and distribution system, in order to better meet the requirements of DC system fault suppression and fault current removal, DC circuit breaker can be used to solve the problems of speed, stability and economy in DC fault removal. This paper discusses the development status of dc circuit breaker, and summarizes the DC circuit breaker cut-off topology proposed at home and abroad in recent years.On this basis, the mechanical, Z source structure,combined, cascade module, device combination DC circuit breaker topology and DC circuit breaker test circuit are discussed in detail.The topology principle, advantages and main problems of each aspect are discussed, the literature in the same field is compared. Finally, the possible future development direction and related problems of DC circuit breaker are put forward.

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      • YANG Yulian, QI Linhai, WANG Hong, SU Linping, XU Yonghai

        Available online:February 16, 2020  DOI: 10.7500/AEPS20190605007

        Abstract:Traditional data missing reconstruction technology mostly relies on mathematical statistics method and prior knowledge combined with mechanism analysis to construct mathematical models. However, measurement data in distribution network has high dimensional, time-varying, non-linear characteristics, high complexity, difficult characterization, and it is difficult to ensure high-precision reconstruction. In this paper, an unsupervised generation antagonism training method is proposed to extract data features independently and reconstruct missing data with dual semantic perception constraints. Among them, the reconstructed model based on two-dimensional convolution and the two-dimensional gray image training of measurement data enhance the generalization ability and stability of the model. This method does not need prior knowledge distribution hypothesis and explicit physical modeling, and can effectively improve the accuracy of reconstructed data while guaranteeing maximum feature extraction. Finally, the validity of this method in reconstructing missing data is verified by the measured data. National Natural Science Foundation of China (No. 51277069) and State Grid Corporation of China (No. 52094018001C).

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      • CHENG Xin, XU Liang, ZHOU Shucan, LIU Zhengchao, LIN Yong, GONG Xianfu

        Available online:February 16, 2020  DOI: 10.7500/AEPS20190717008

        Abstract:The integration of large-scale new energy to the power grid makes the uncertainty caused by power supply higher than the uncertainty of load demand. The probabilistic power flow of power system makes the management of operation department even more difficult. To solve this problem, this paper proposes an energy storage configuration method based on trajectory sensitivity analysis based on guaranteed rate of new energy output. Firstly, an over-limit equation of probabilistic power flow for tested components is set up according to the uncertainty of new energy output. Secondly, an analysis model of trajectory sensitivity for probabilistic power flow is built by setting the guaranteed rate of new energy output as a parameter. Thirdly, a configuration strategy of energy storage is proposed to make the probabilistic power flow not exceed limit. In the meanwhile, power and energy requirements of energy storage are calculated for component-related nodes which have low trajectory sensitivities. Finally, the proposed method is simulated and verified on a practical power system in a area of South China.

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      • WU Hangfei, YANG Xiaodong, ZHANG Youbing, YANG Yu, PAN Hongwu, HUANG Xiaoming

        Available online:February 14, 2020  DOI: 10.7500/AEPS20190521001

        Abstract:This paper proposes an automatic demand response strategy based on event-driven mechanism, considering the diversity and richness of residential loads and great challenges brought by random electricity consumption behaviors to residential multi-microgrid system. The operational statuses of residential microgrids are divided into different events by using event-driven mechanism. The residential load is guided to fulfil consumption optimization considering price incentive and schedulable potential with the event-driven signal, so as to achieve automatic demand response. On this basis, the concept of energy level is introduced to the energy sharing model. By calculating the energy levels of each sub-microgrid in multi-microgrid system, the interactive power among microgrids is determined. The decoupling between inter-network and intra-network can decrease the complexity of energy sharing strategy. The numerical simulation results of a residential multi-microgrid system show that the proposed algorithm can effectively reduce operating cost of residential multi-microgrid system and improve optimization efficiency.

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      • Li Dongdong, Duan Weiyi, Lin Shunfu, Zhou Bo, Yao Yin

        Available online:February 08, 2020  DOI: 10.7500/AEPS20190726003

        Abstract:With the rapid growth of the amount of Electric Vehicles (EV), the demand for battery charging and discharging is also increasing correspondingly, but the growth rate of infrastructure construction is still relatively slow. The current situation is there is more EVs than charging piles. This has led to the problem of unbalanced distribution of charging piles. Based on this problem and combined with the real-time market demand, a user-guided EV-charging pile matching strategy is proposed. Firstly, an allocation function is established from the energy aggregator"s viewpoint and generate the information of available charging piles. Secondly, an optimization function is established from the user"s viewpoint to determine the geographical range of available charging piles. Finally, considering real-time electricity prices, EV users are encouraged to select appropriate charging piles for charging and discharging battery within the selected geographical range and effectively participate in power dispatch by updating subsidy fees. The Simulation results show that under the market requirements, the EV-charging pile matching strategy considers the two-way willingness of users and aggregators, and provides a decision basis for the rational distribution of charging piles.

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      • HUANG Wei, LIU Siqi, YE bo

        Available online:February 07, 2020  DOI: 10.7500/AEPS20190521003

        Abstract:A two-level model of station-network cooperative optimization of integrated energy system for park is established. The upper-level model is an improved p-median model, and the decision variables are the location and capacity of energy stations and network layout. Considering the demand response characteristics of electric and heat loads, the lower model coordinates the interruptible load with the energy station supported by the power-heat-gas multi-energy flow. The greedy-variable neighborhood-cobweb (GVNC) algorithm is used to solve the model, which can improve the computational efficiency and obtain the global optimal solution. Second-order cone relaxation (SOCR) is used to transform the non-linear programming problem into a second-order cone programming (SOCP) problem which is easy to solve. Convex-concave procedure (CCP) is used to solve the problem of accuracy recovery after relaxation. The example shows that considering the influence of source-load interaction, the operation cost of the system can be effectively reduced, and the planned capacity of the energy station can be more economical and reasonable.

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      • WU Wenchuan, ZHANG Boming, SUN Hongbin, WANG Bin, YANG Yue, LIU Haotian, Lin Chenhui, WANG Siyuan

        Available online:February 05, 2020  DOI: 10.7500/AEPS20191030001

        Abstract:The traditional centralized control system in an active distribution network (ADN) would meet the problems of control agility, system reliability, mass communication and information privacy. This paper proposed a novel architecture of the energy management and operation regulation system for AND. Three are thee control levels in this hierarchical control system, including distribution controller for renewable energy resource cluster, optimization of the distribution networks incorporated with multi-clusters and coordination operation of integrated transmission & distribution networks. The paper mainly introduces the characteristics of the proposed system and some key technologies about cluster control, multi-level coordination optimization: (1) network analysis technology for ADN; (2) distributed cluster control technology; (3) active power and reactive coordination optimization technology for distribution network considering uncertainty; (4) distributed coordination and dispatching technology for integrated transmission and distribution networks. Finally, a pilot project is briefly described, and future researches are proposed.

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      • YANG Dongfeng, JIANG Chao, CAI Guowei, HUANG Nantian, LIU Xiaojun, HUANG Zheng

        Available online:February 03, 2020  DOI: 10.7500/AEPS20190731014

        Abstract:With the development trend of the increasingly close electricity-heat connection and the maturity of AC/DC microgrid, a bi-level optimal configuration model considering electricity/heat coupling for AC/DC hybrid microgrid is proposed. This model takes the annual investment cost, annual CO2 emission and transmission loss as the optimization objectives with giving consideration of the electric/heat power balance, self-government and other operational constraints as well. The upper layer is the capacity planning model of each device in the microgrid, and the lower layer determines the operation strategy of each device in the microgrid. Through the joint optimization of the upper and lower levels, the capacity configuration of each device in the microgrid is studied. By comparing different planning scenarios, the influence of electricity/heat coupling system on optimization objectives is analyzed. Through equipment power output and power balance curve of typical days, the energy supply reliability of AC/DC microgrid with electricity/heat coupling system is illustrated. Finally, the rationality and effectiveness of the model are verified.

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      • LI Xiaohua, LIANG Zipeng, FENG Jiawei, ZHANG Shaofan, CAO Jie, DING Xiaobing

        Available online:February 03, 2020  DOI: 10.7500/AEPS20190310003

        Abstract:The DC transmission projects in China have long transmission distance and large span, and the crossing between AC lines and DC lines is increasing day by day. The power grid presents new fault type, that is touching fault for AC/DC transmission lines. There is lack of fault characteristics for touching fault and their influence on relay protection. Theoretical analysis on characteristics of touching fault for AC/DC transmission lines is made. AC/DC model is developed based on PSCAD/EMTDC simulation platform of detailed DC project. The characteristic quantities and key factors caused by touching fault are investigated, and potential challenges of which on operating characteristic of AC/DC protection are analyzed. Simulation results show that the fundamental frequency component introduced by touching fault can reduce the action rate of traveling wave protection for DC lines, there is a action dead zone in protection range between traveling wave protection and touching protection for AC/DC lines, and the sensitivity of AC distance protection is lower. This work is supported by National Natural Science Foundation of China (No. 51777079) and National Natural Science Foundation of China-State Grid Joint Fund for Smart Grid (No. U1766213).

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      • LI Zhen, SHENG Wanxing, DU Songhuai, LI Penghua, WANG Jianhua

        Available online:January 16, 2020  DOI: 10.7500/AEPS20190812008

        Abstract:Supplying power for loads and realizing the connection of distributed generators (DGs) are the essential functions of the flexible distribution equipment (FDE). Consequently, the control of AC port in FDE is intensely crucial. Aiming at the AC port voltage control of FDE, the three-phase voltage is controlled independently based on the virtual synchronous generator (VSG) control, and its dynamic performance is improved by cascaded quasi proportional-resonant (PR) voltage outer-loop and current inner-loop. Furthermore, the influence of AC port output current of FDE on the voltage is analyzed in detail by taking single-phase voltage as an example. And the current feedforward control strategy is proposed to ensure the AC port voltage stability while loads vary and DG access. The output impedance of AC port is obtained by the impedance modeling method, and the stability of FDE is analyzed by generalized Nyquist stability criterion when AC port supplies power for loads and realizes DG connection. Finally, the correctness and effectiveness of the proposed control strategy are verified by simulation and experiment.

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      • ZU Guoqiang, XIAO Jun, MU Yunfei, ZHU Xiaohui, YAO Ying, JI Dalong

        Available online:November 19, 2019  DOI: 10.7500/AEPS20190617001

        Abstract:The China urban power grid is evolving to smart distribution grid, of which the operating circumstance will be more complicated. Security region is a new method for the distribution system operating. This paper studies the smart distribution system security region (DSSR) from the view of user load, taking two main elements into account, which are distributed generation (DG) and demand response (DR). Firstly, it analyzes and formulates the characteristics of security operating for distribution systems with DG and DR then the DSSR with DG and DR is modeled. It observes the DSSR 2D sections on case grids and studies the mechanism of DG and DR on DSSR, based on which the guidance for the distribution system planning and operating is proposed. The DSSR in this paper is consistent with the usual practice of dispatchers and could be a useful tool of the security monitoring and analysis for urban power grids, in which the user load service is more important than the service of DG and DR.

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      • WANG Shouxiang, GUO Luyang, CHEN Haiwen, DENG Xinyu

        Available online:October 21, 2019  DOI: 10.7500/AEPS20190625010

        Abstract:Aiming at the limitation of using single equipment features for load identification, we proposed a non-invasive load identification algorithm based on feature fusion and deep learning. Firstly, The V-I trajectory image features and power numerical features are extracted by analyzing the high frequency sampling data of the equipment. Then the fusion of V-I track image features and power numerical features is realized by using the advanced feature extraction ability of ANN. Finally, the BP neural network is trained to identify equipment by using fusion feature as the new feature of the equipment. We used PLAID data set to verify the identification performance of the algorithm, and compared the performance of different classification algorithms for feature fusion and load identification ability. The results show that the proposed algorithm makes use of the complementarity of different features, overcomes the disadvantage that V-I track features cannot reflect the power of the equipment, and improves the load identification ability of V-I track features. In embedded devices, the computing speed of proposed algorithms can reach the millisecond level.

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      Volume 44,2020 Issue 6

        >Views
      • LIU Qiuhua, YUAN Hao, YANG Zhenglin, FAN Haifeng, XU Chunlei

        2020,44(6):1-8, DOI: 10.7500/AEPS20191108007

        Abstract:The method of quantifying ancillary services as corresponding green certificates can motivate the enthusiasm of ancillary service providers, which is conducive to the consumption of renewable energy. After analyzing the additional increase of ancillary service caused by connecting renewable energy, the unfairness of current cost allocation way for ancillary service is pointed out. Then, based on the deviation theory of predicted power generation curve, a green certificate calculation method for compensating the ancillary service by transferring the deviation between predicted and actual power generation curves into the numbers of green certificates. Furthermore, a quantitative allocation method of green certificate for frequency regulation ancillary service is designed. The effects and possible problems of compensation method are discussed.

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      • >Basic Research
      • ZHANG Zhimei, HUANG Shaowei, MEI Shengwei, ZHANG Xuemin, JIANG Yefeng

        2020,44(6):9-16, DOI: 10.7500/AEPS20190626005

        Abstract:The vulnerability assessment of branch lines in power grid is an important step in the subsequent analysis and prevention of cascading outages. Existing vulnerability indices have problems including unclear physical meaning, lacking consideration of the impact of multiple outages on vulnerability and so on. To address the issues, this paper constructs a cooperative game framework of branch lines in power grid. According to the game result, the loss caused by a fault chain is properly distributed to each branch line as their vulnerabilities. The indices can reflect the contribution of the fault on branch lines to the power grid loss caused by the outage accidents, and its physical meaning is clear. To solve the problem of the non-superposition of the loss of mutiple fault chains, the corresponding multi-objective optimal programming is transformed into a two-stage optimization model with collective rationality and individual rationality. The two-stage optimization model uses genetic algorithm and linear programming, respectively. The case study of IEEE 39-bus system verifies the validity of the proposed index.

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      • LI Baoqin, WU Junyong, SHAO Meiyang, ZHANG Ruoyu, HAO Liangliang

        2020,44(6):17-26, DOI: 10.7500/AEPS20190528009

        Abstract:In order to further improve the prediction accuracy of transient stability for power system and give more refined evaluation results, the deep learning is combined with the transient stability of power system. A refined evaluation model of transient stability for power system based on ensemble deep belief network (DBN) with different structures is proposed based on the characteristics of the generator power angle "trajectory cluster" after fault removal. The base classifier DBN of the model can effectively utilize the feature extraction ability of the deep architecture and fully exploit the nonlinear mapping relationship between the input features and the evaluation results of transient stability. Experimental results on the New England 10-machine 39-node system show that this method is not only superior to the shallow learning framework, but also superior to the partial deep learning model. In addition, the ensemble DBN algorithm not only has higher prediction accuracy, but also can effectively evaluate the stability margin and instability level of the system. It shows strong robustness when some information of phasor measurement unit (PMU) is missing and contains noise.

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      • MA Rui, LIU Zhenlei, HE Pingping, YU Haifeng

        2020,44(6):27-36, DOI: 10.7500/AEPS20190217002

        Abstract:In view of the fact that the traditional continuous power flow method is difficult to adapt to the AC/DC interconnected systems with access of large-scale wind power, this paper proposes a probabilistic continuous power flow calculation method for AC/DC systems with wind power. Based on the frequency regulation characteristics of conventional units and the static characteristics of voltage and frequency of loads, the randomness of wind power output, the DC control mode and the frequency fluctuation deviation constraints are taken into account. Then this paper establishes the probabilistic continuous power flow equation of AC/DC systems with wind power considering the frequency regulation of power sources and static characteristics of voltage and frequency of loads. Based on the Jacobian matrix of the modified equation, the load margin sensitivity index reflecting the frequency fluctuation, wind power output and control mode is derived. The power flow solution and load margin in multiple scenarios of N and N-1 states are obtained by combining Monte Carlo method and predictor-corrector method. The correctness and validity of the proposed method are verified by simulation results of the modified IEEE 39-bus system.

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      • XIE Jiping, ZHANG Wen, YANG Hao

        2020,44(6):37-44, DOI: 10.7500/AEPS20190403005

        Abstract:Compared with the conventional single-layer connection mode of ultra-high voltage direct current (UHVDC) system, the hierarchical connection mode improves the ability of AC system in acceptance and provides voltage support for multi-infeed UHVDC systems from the aspect of grid structure, and it makes power flow distribution and control more flexible and reasonable. In order to make full use of the fast power adjustment capability of UHVDC systems in the hierarchical connection mode, and avoid or reduce the economic loss caused by the load shedding during the medium- and long-term voltage instability process, this paper proposes a coordinated control method for AC/DC power systems with hierarchical connection mode of UHVDC systems. Firstly, based on the quasi-steady model of UHVDC system in the hierarchical connection mode, this paper deduces the analytical expressions of the sensitivities of converter bus voltages with different control modes of UHVDC systems to the inverter transmission power of UHVDC systems in hierarchical connection mode. Secondly, the voltage trajectory prediction model of AC/DC power systems is established based on the derived sensitivities. Finally, considering modulations of the DC current and the extinguishing angles of high and low ends of the inverter, a receding horizon optimization model of coordinated voltage control is constructed based on the predicted trajectory. The hierarchical DC injection power and the voltage control means of AC system are coordinately controlled. The simulation analysis of the planning system of Shandong power grid shows that the proposed method can effectively coordinate the distribution of DC transmission power in AC power grid, which enhances the system voltage stability and reduces the load shedding loss.

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      • ZHANG Yanke, LIU Yuan, JI Changming, ZHANG Jiaxin

        2020,44(6):45-51, DOI: 10.7500/AEPS20190411007

        Abstract:In order to reduce the impact of time-lag of water flow in the process of short-term generation optimization dispatch of cascade hydropower reservoirs, the mapping function between outflow of upstream reservoir, local inflow, water level and inflow of downstream reservoir is quantized based on the principle of linear space. Secondly, the artificial neural network, K-means and Relief methods in data mining are comprehensively applied to solve the mapping relationship. A short-term generation optimization dispatch model of cascade hydropower reservoirs considering time-lags of water flow is established. Finally, the analysis of case in the application of short-term generation optimization dispatch of Jinguan power package in Yalong River of China shows that, the established model could improve the accuracy of short-term generation dispatching plan.

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      • ZHU Yongqiang, ZHANG Quan, LIU Kang, WANG Zhi, WANG Fuyuan

        2020,44(6):52-58, DOI: 10.7500/AEPS20190227008

        Abstract:In order to solve the power fluctuation caused by the change of micro-source output, loads and charging and discharging power of energy storage devices because of state of charge in hybrid AC/DC microgrid, a segmented coordination control strategy for hybrid microgrid is proposed. Aiming at the hybrid microgrid in the islanded state, the typical topology of the hybrid microgrid and the power relations in different operation modes are analyzed. The characteristic quantity which can represent the whole operation state of hybrid microgrid is obtained by the standardization method. According to the variation of the characteristic quantity, the control strategy is divided into segments. Then the working principle of each section control is analyzed in detail and the coordinated control of the converters in different control segments is studied. Aiming at the possible power oscillation in microgrid and frequent switching of operation modes for interlinking converter (ILC), the action criterion is compensated. Finally, a simulation model is established in PSCAD/EMTDC. The simulation results show that all converters can respond quickly in different operation conditions to ensure the stable operation of the system.

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      • LI Man, WANG Bing, QU Linan, TANG Zhen, YAN Song, XU Qiang

        2020,44(6):59-66, DOI: 10.7500/AEPS20190603011

        Abstract:Traditional control strategy of high voltage ride through (HVRT) for photovoltaic (PV) grid-connected inverter (GCI) improves reactive power output at the cost of reducing active power, which is difficult to achieve a balance between grid-side current and DC bus voltage. And it suppresses the transient impact caused by sudden voltage and current changes after the fault removal. Based on the analysis on the transient power characteristics of high voltage, an HVRT control strategy that maintains active power output and adjusts the reference value of reactive current is proposed. Firstly, a small-signal model is used to analyze the transient power characteristics of HVRT, which reveals that the key of suppressing voltage recovery is the constant active power and reactive redundancy on grid side. Secondly, a method for estimating the reference value of reactive current is proposed according to the voltage surge amplitude. On this basis, by combining with active current control, the control capacity of the GCI with three different voltage surge amplitudes is discussed, and the control strategies of HVRT are given respectively. Finally, the simulation and experiments verify the effectiveness of the proposed control strategies.

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      • REN Yongfeng, XUE Yu, YUN Pingping, HAN Junfei, JIA Weiqing

        2020,44(6):67-74, DOI: 10.7500/AEPS20190201001

        Abstract:In the renewable energy power system dominated by high proportion of wind power, configuring energy storage system (ESS) is an effective solution to suppress wind power fluctuations, achieve peak load shaving and improve wind power dispatchability. A multi-objective hybrid optimization simulation model for joint wind power and energy storage operation is designed, which integrates the impact of output level of the large-scale energy storage and the future output of wind power on the current energy storage operation. Markov prediction model is adopted to forecast the future output of wind power, and particle swarm optimization algorithm is used to optimize the grid-connected power of wind power and energy storage system in real time, then the optimal operation strategy of ESS can be obtained. The typical wind power data from a hundred-megawatt wind farm are used for simulation. Simulation results show that the proposed method has good smoothing performance, which avoids excessive charging and discharging of ESS and prevents it from entering dead zone, and further improves the reliability and the economy of the integrated system of wind power and energy storage.

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      • NIAN Heng, ZHU Maowei, XU Yunyang, CHEN Liang, ZHU Qiongfeng, LI Qing

        2020,44(6):75-83, DOI: 10.7500/AEPS20190804005

        Abstract:The output harmonics and switching losses can be significantly reduced with the application of modular multilevel converter (MMC) in high voltage DC transmission system, while it also brings prominent stability problems. Impedance-based stability analysis method can be applied to analyze the stability problems when MMC system operates. In the existing studies, the sequence impedance model of MMC is derived, which is decoupled into a positive-sequence impedance and a negative-sequence impedance, and the system stability can be determined by single-in-single-out stability criterion. However, MMC exhibits significant frequency coupling characteristic in the low frequency band, making the positive-sequence impedance and negative-sequence impedance no longer decoupled, therefore the single-in-single-out stability criterion cannot accurately determine the system stability. In this paper, the frequency coupling mechanism of MMC is revealed by analyzing the interaction between perturbation and steady-state harmonics. Furthermore, the frequency coupling model of MMC with AC voltage control is derived based on harmonic transfer matrices. Based on the derived model, the influence of frequency coupling characteristic on system stability judgment and the main factor influencing frequency coupling characteristic are analyzed. Finally,the simulation results based on MATLAB/Simulink simulation system validate the correctness of the frequency coupling model and stability analysis results.

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      • MA Wenzhong, ZHOU Guanyu, SUN Peng, SAILIJIANG Gulipali, ZHANG Zi’ang, DONG Lei

        2020,44(6):84-90, DOI: 10.7500/AEPS20190411002

        Abstract:DC circuit breaker (DCCB) is a key device for clearing DC faults in voltage source converter based multi-terminal DC (VSC-MTDC) system. Most DCCB systems require to connect DC reactor in series to limit the rising rate of the fault current, but large-capacity DCCB connecting DC reactor in series could decrease the damping of DC system and reduce the stability of multi-terminal DC system. In this paper, a small-signal mathematical model for VSC-MTDC system with DC breakers is constructed and modal analysis is performed to illustrate the main factors which could affect the system stability. To solve the stability problem caused by the circuit breaker system, a damping controller based on H hybrid sensitivity theory is designed to improve the weak damping characteristics of the system. Finally, with a four-terminal VSC-MTDC model implemented in MATLAB/Simulink, time-domain simulation and eigenvalue analysis results show that the proposed approach can efficiently suppress the DC system oscillations and improve the system stability. Compared with other traditional damping controllers, it is more applicable in scenarios with strong disturbances and uncertainties.

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      • ZHANG Xueyin, XU Yonghai, XU Shaobo, XIAO Xiangning

        2020,44(6):91-97, DOI: 10.7500/AEPS20190328001

        Abstract:Medium-voltage multilevel converters usually adopt modular structures. They can be used in AC/DC distribution networks. As a result of the relatively low voltage in distribution networks, the number of converter sub-modules is small. Therefore, the carrier phase shift pulse width modulation (CPS-PWM) is usually adopted to increase the equivalent switching frequency. The modeling of CPS-PWM is one of the fundamentals of converter system modeling. The modulation stage is nonlinear, and thus, only the fundamental frequency component is usually considered. The existing fundamental approximation model of CPS-PWM is based on equivalent switching frequency, hence the low time delay and large errors exist when asymmetric regular sampling is adopted. In this work, the following three forms of fundamental approximation models of CPS-PWM are established, i.e. zero order holder (ZOH) delay approximation, ZOH no approximation, and delay Padé approximation. These models are developed by combining the outputs of sub-models on the basis of a sub-module. The proposed models reflect the frequency characteristics of CPS-PWM more accurately than the traditional one. A simulation study verifies the correctness of the theoretical analysis.

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      • HU Jingzhe, WANG Xu, JIANG Chuanwen, CONG Hao

        2020,44(6):98-105, DOI: 10.7500/AEPS20190611005

        Abstract:Considering the environmental demands of residents in the hard-hit areas of carbon emissions, an allocation scheme of comprehensive index carbon emission rights based on equilibrium of regional carbon emission is proposed. The allocation of carbon quota is obtained by entropy method with the indicators of the benchmark scheme and the regional carbon emissions of the plant. In order to study the impact of carbon price on carbon emissions in power system, a three-stage optimal tiered carbon price model is established. The first stage is unit commitment problem in normal conditions. The second stage is to find the worst fault scenarios. The third stage is the solution model of the optimal stepped carbon price. The model is solved by the column and constraint generation(C&CG) algorithm and dichotomy. Case study shows that when the emission task is small, tiered carbon price could control carbon emissions with less carbon trading cost. Carbon emission right allocation scheme based on comprehensive indicators has a significant effect on balancing regional carbon emissions differences.

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      • XIE Min, HU Xintong, LIU Mingbo

        2020,44(6):106-112, DOI: 10.7500/AEPS20190304008

        Abstract:Iterative bidding mechanism can promote power generators to quote electricity price economically and rationally and organize production. It can also give purchasers the ability to negotiate, and promote the coordinated and efficient operation of the power market. However, current iterative bidding methods mainly settle accounts according to the quoted price or the uniform marginal clearing price, but seldom according to the locational marginal price of nodes. There may be also too many iterations to be applied. Therefore, an iterative bidding model for power market based on analytical target cascading theory is proposed. Power generators and independent system operators are regarded as different stakeholders, and their objectives are optimizing the production efficiency and minimizing the cost of purchasing electricity, respectively. Coupling and parallel solution of the two optimized models are realized by connecting through generation power. Considering the influence of network constraints, the model can effectively motivate generators to report their real costs and is conducive to the optimal allocation of social resources. Examples of IEEE 39-bus system and IEEE 118-bus system show that analytical target cascading can be applied to the iterative bidding mechanism of fully competitive power generation market, and the convergence and computational efficiency can meet the requirements.

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      • GONG Jinxia, LIU Yanmin

        2020,44(6):113-120, DOI: 10.7500/AEPS20190321010

        Abstract:Applying the new generation of artificial intelligence in smart grid and Energy Internet, to achieve high proportion renewable energy access to the power grid in a timely and effective manner, the deep deterministic policy gradient (DDPG) algorithm based on deep learning is applied in the optimized operation of active distribution network (ADN). Firstly, DDPG return function of optimization model for ADN with multiple microgrids is constructed, which can minimize the total node voltage deviation and line loss of ADN. The proposed function can also minimize the variation of the power regulation of microgrid to reduce the impact on operation of the microgrid, and maintain the balance of tie-line power blance to reduce the impact on the distribution network. Secondly, DDPG sample data processing, design of return function, model training and learning process of optimization control for ADN are analyzed. Finally, the effectiveness of the algorithm is verified by the improved IEEE 14-bus example simulation.

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      • >Application Research
      • ZHAO Yitong, WANG Huifang, HE Benteng, XU Weina

        2020,44(6):121-128, DOI: 10.7500/AEPS20190507001

        Abstract:In order to improve the economy of the investment and operation of user-side battery energy storage and reduce the cost of users’ power consumption, a rolling optimization method of configuration and operation scheduling for user-side battery energy storage is proposed. Firstly, the benefit of users after installing energy storage and the constraints of energy storage operation are analyzed. Then the configuration optimization model of energy storage, the optimization model of energy storage before month and the rolling optimization model for intra-day operation are constructed and solved by CPLEX solver. Performance constraints of energy storage are added to the model, which can effectively reduce the number of transitions between charging and discharging states and prolong the life of energy storage. In the pre-month optimization, a predicted monthly demand defense value is determined. In the intra-day rolling optimization, a subsection optimization model of daily operation for energy storage and a renewal model of monthly demand defense value are constructed. The daily load data and monthly demand defense value are updated in real time, and the rolling optimization is carried out to continuously correct the impact of load forecasting error. Finally, an industrial user is simulated to verify the validity of the proposed optimization model.

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      • WU Yongbin, WANG Su’e, XIONG Liansong, ZHANG Donghui, XU Zhao

        2020,44(6):129-137, DOI: 10.7500/AEPS20190308009

        Abstract:The grid-connected power generation system integrated with photovoltaic (PV) and energy storage systems (ESSs) is taken as the research object, and multiple time scales are used in the modeling ideas. Focusing on the main time scale affecting the dynamic characteristics of system frequency—the DC voltage time scale, this paper develops a dynamic model of DC voltage time scale for the analysis of the system inertia and damping characteristics. On the basis of this model, the electric torque analysis method is used to analyze the main factors and their action laws on the inertia effect, damping capacity and synchronization characteristics from the physical mechanism level. The research results show that the dynamic characteristics of the system are determined by its control parameters, structural parameters and steady-state operation point parameters. The inertia effect and synchronization characteristics of the system are respectively affected by the proportional controller and integral controller in the DC bus voltage control loop. The damping capacity of the system is mainly affected by the frequency droop control in the energy storage device. The system dynamic characteristics will not be affected by the PV converter operating in the maximum power point tracking (MPPT) mode. In addition, the system dynamic characteristics are also affected by the structural parameters (such as line impedance and DC bus capacitance), the steady-state operation point parameters (such as the AC/DC bus voltage level of the system) and the steady-state operation power (power angle). Finally, the correctness of the above analysis is verified by the simulation and experiment results.

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      • CAO Zeyu, SUN Yichao, DING Nanmu, WANG Qi, JIANG Chen, LIU Yanan

        2020,44(6):138-145, DOI: 10.7500/AEPS20190610002

        Abstract:At present, the grid-connection process of most new-type synchronous condensers in China is achieved in the idle speed mode, which is uncontrollable and irreversible. Therefore, the improvement of the grid-connection success rate of the grid-connection process is the key to minimize the corresponding economic cost. Considering the complete idle speed process of the new-type synchronous condenser and the main loss during the process, this paper analyzes the change rule of frequency difference and phase angle difference between the synchronous condenser and the power grid. Then the influence of the phase angle difference between the synchronous condenser and the power grid on the grid-connection success rate at the start of idle speed is obtained. Based on the analysis of the influence of the condenser speed on the initial position of grid-connection success area, the adjustment method of the speed at the idle speed point is proposed, which is able to improve the grid-connection success rate with satisfaction of the strict grid-connection requirements. Finally, the example results validate the feasibility of the proposed idle speed point setting method, and the complete iteration times and the final idle speed point are predicted accurately by statistics, while the required information during the setting process is significantly reduced.

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      • ZHANG Xueguang, ZHANG Yage, FANG Ran, CHEN Lie, XU Dianguo

        2020,44(6):146-154, DOI: 10.7500/AEPS20190216002

        Abstract:A compensation control strategy for doubly-fed induction generator (DFIG) based wind turbine is proposed based on disturbance compensation of grid voltage, which can solve the stability problem of grid-connected in weak grid. Firstly, a unified impedance model of DFIG based wind turbine is established in the synchronous reference frame including rotor side converter (RSC) and grid side converter (GSC). Then, based on the established impedance model, the transfer relationship between the voltage disturbance at point of common coupling and the controller output is analyzed, the voltage disturbance compensation is introduced into the current loop of RSC and GSC respectively to improve the converter control. The generalized Nyquist criterion (GNC) proves that the proposed method can effectively improve the grid-connected stability of DFIG based wind turbine in weak grid. Theoretical analysis shows that the compensation control of RSC and GSC based on the voltage disturbance compensation at point of common coupling can improve the impedance characteristics of DFIG so as to improve their stability under weak grid condition. Finally, the effectiveness of the proposed compensation control method is verified by simulation analysis.

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      • SUN Yuwei, WU Chengjie, FU Chao, ZHANG Shuai, GAO Zhen

        2020,44(6):155-163, DOI: 10.7500/AEPS20190513001

        Abstract:Power electronic transformers (PETs) are the key equipment in AC/DC hybrid distribution network. In order to improve the operation efficiency of cascaded PET under the condition of light-load, this paper proposes an efficiency optimization strategy based on active unbalanced power control, which utilizes the unbalanced characteristics of hybrid pulse width modulation (HPWM) technology. By analyzing the power losses of both cascaded H-bridge converter with HPWM and isolated bidirectional DC/DC converter, the operation efficiency model of cascaded PET is established. Based on the efficiency model, the feasibility for improving the overall efficiency of PET through unbalanced power distribution of each module is analyzed. The power stable operation range of each unit with HPWM is derived, and the active unbalanced power control strategy suitable for system efficiency optimization under the condition of light-load is proposed. Finally, the validation of the proposed strategy in comparison with the traditional power balanced control is confirmed by experiments, and the results show that the proposed unbalanced power control can reduce the power loss under the condition of light-load and improve the overall efficiency of PET.

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      • LIU Shuo, SU Jianhui, LAI Jidong, ZHANG Jian, WANG Haining

        2020,44(6):164-170, DOI: 10.7500/AEPS20190408002

        Abstract:The calculation of voltage gain-frequency characteristic is vital in the design of LLC resonant converter. The LLC converter have various operation modes due to the existence of nonlinearity in the rectifier part of the converter. And the voltage gain-frequency characteristic is closely related to operation modes. The PO mode is a discontinuous conduction mode (DCM), which is beneficial to reduce switching losses of the converter. However, the voltage gain-frequency characteristic of converter in the PO mode is hard to be solved because it involves complex computations. On the basis of subinterval analysis method, this paper analyzes the operation characteristics in the PO mode of LLC resonant converter, and deduces a simplified and high-accuracy calculation formula of voltage gain. In addition, the parsing and concise expressions of power boundary conditions both in DCM mode and PO mode are provided according to the nonlinear characteristic in the rectifier part of the converter. Finally, a simulation model and an experimental prototype of LLC converter are developed. The simulation and experiment results verify the validity of the deduced voltage gain formula and power boundary condition.

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      • WANG Yibo, CAI Guowei, LIU Chuang, GUO Dongbo, WANG Peng, ZHU Bingda

        2020,44(6):171-177, DOI: 10.7500/AEPS20190409006

        Abstract:Dynamic voltage restorer (DVR) is a power electronic device connected in series with source and load, which is used to rapidly compensate voltage fluctuation in the power system. However, due to the energy storage equipment, the conventional DVR based on voltage source inverters (VSIs) has some shortcomings. And the DVR based on direct AC/AC conversion with pulse width modulation (PWM) has the shortages of commutation problem and voltage balance of flying capacitor. Therefore, this paper proposes a single-phase DVR based on bipolar direct AC/AC conversion. The AC/AC converter topology with PWM used in the proposed DVR has the characteristics of common grounding between the input and output ports. In addition, the proposed DVR can achieve bipolar voltage regulation with a simple control strategy and effectively solve the commutation problem during operation. In order to verify the engineering value of the proposed DVR, a 1 kW experimental platform has been built to verify its rationality and effectiveness on the basis of theoretical analysis.

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      • ZHOU Bohao, LI Fengting, YIN Chunya, ZHANG Zengqiang

        2020,44(6):178-185, DOI: 10.7500/AEPS20190630005

        Abstract:In order to solve the difficulties in the accurate prediction of DC current during fault transient period, a DC line transient mathematical model with flat wave reactor is presented. Considering the change of overlap angle during transient period, a prediction method of DC current variation is proposed for the accurate prediction of DC current variation. And a commutation failure prediction criterion based on DC current variation during commutation is constructed to realize the prediction of the first commutation failure. Meanwhile, a control strategy which can effectively prevent the first commutation failure is proposed. The DC system model of CIGRE high voltage direct current (HVDC) benchmark model is built based on PSCAD/EMTDC simulation platform. The simulation results of different fault situations reveal that the proposed method and control strategy are effective.

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      • >Egineering Application
      • CHEN Yiping, LI Chongtao, YANG Ruopu, ZHANG Yong, TANG Zhuoyao

        2020,44(6):186-193, DOI: 10.7500/AEPS20190729004

        Abstract:Some frequency oscillations occurred near the governor dead band in the test of asynchronous interconnection in Yunnan in China. To analyze this issue, a piecewise linear system model considering governor dead band is established. The effect of governor dead band on frequency stability is clarified through steady-state and dynamic behavior analysis. Research results show that the system may have no equilibrium point with step-response dead band and it will cause frequency oscillations near the dead band. Meanwhile, the stability of piecewise linear system is determined by the eigenvalue of the linear system corresponding to each frequency range, and the negative damping effect can also cause system frequency instability. Different frequency oscillations in the test are simulated by both the simplified system model and the actual model of Yunnan power grid.

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      • XIAO Bai, LIANG Xuefeng, JIANG Zhuo, NIU Xiangzhi, NIU Qiang, LI Jiefu

        2020,44(6):194-199, DOI: 10.7500/AEPS20190521008

        Abstract:Aiming at the problem that the spatial load forecasting accuracy is reduced due to the random fluctuation in the measured cellular load data, a method for ascertaining the reasonable maximum value of cellular load by using complementary ensemble empirical mode decomposition and runs test technique is proposed. The method decomposes each class Ⅰ cellular load sequence by complementary ensemble empirical mode decomposition technique. Each class Ⅰ cell obtains a set of intrinsic mode functions. Random test of each intrinsic mode function is carried out by using runs test technique, and the criterion for identifying the high-frequency component is established. The high-frequency intrinsic mode function that characterizes the random fluctuation of the cellular load is removed, and the remaining intrinsic mode functions that characterize the regularity and trend of the cellular load are reconstructed to obtain the main component, and the maximum value is taken as the reasonable maximum value of the class Ⅰcellular load. Finally, the reasonable maximum value is used to predict the space load based on class Ⅰ cells and class Ⅱ cells. The engineering example shows that the method is correct and effective.

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      Display Method: |
      • XIN Yaozhong, SHI Junjie, ZHOU Jingyang, GAO Zonghe, TAO Hongzhu, SHANG Xuewei, ZHAI Mingyu, GUO Jiancheng, YANG Shengchun, NAN Guilin, LIU Jinbo

        2015,39(1):2-8, DOI: 10.7500/AEPS20141008024

        Abstract:Firstly, the development history of power grid dispatching automation systems in China is reviewed. The architecture of smart grid dispatching and control systems is described. Then the main technical breakthroughs of smart grid dispatching and control systems are summarized, including improvement of the observability and controllability of ultra large power grids, the coordinated ability of control centers, the early warning ability of on-line dynamic security of ultra large power grids, the economic operation efficiency of ultra large power grids, the ability for power grids to accommodate new energy generation, and the ability of the control centers of power grids to withstand major natural calamities and group cyber-attacks. Finally, further research areas of smart grid dispatching and control systems are outlined.

      • WANG Xifan, WANG Biyang, WANG Xiuli, SHAO Chengcheng

        2014,38(17):4-13, DOI: 10.7500/AEPS20140324013

        Abstract:Offshore wind energy is a promising solution to the environment and energy crisis thanks to its excellent performance of production.It would be further developed with the support from low-carbon economy.This paper summarizes the configuration of offshore wind power systems and surveys their optimal planning methods.Methods of offshore wind farm siting,common topologies of collecting systems and different transmission schemes are reviewed,while reliability evaluation is discussed in detail.Based on this,modeling approaches and algorithms for optimal planning of offshore wind power systems are briefly treated.Finally,some suggestions for potential research directions of optimal planning of offshore wind power systems are made.

      • XUE Yusheng, LAI Yening

        2016,40(1):1-8, DOI: 10.7500/AEPS20151208005

        Abstract:The macro energy thinking which regards electricity as a hub between energy production and consumption, can promote “clean energy substitution” of the upstream primary energy and “electricity substitution” of the downstream end-use energy, in order to support the sustainable development of energy. Meanwhile the big data thinking regards various data resources as fundamental elements of production rather than simple process objects. The integration of these thinking will make the big data on power become the foundation of an extensively interconnected, openly interactive and highly intelligent macro energy system. Key elements of this integration include the acquirement, transmission and storage of wide-area power data with different timescales, the data from related domains, as well as the fast and in-depth knowledge extraction from the multi-source heterogeneous data and its applications. As the first part of a series of paper, this paper summarizes unique features of big data based on the deduction of the basic concept, data structures and essential characteristics of big data. For the comprehensive energy network, a knowledge extraction platform is constructed by integrating the causal data (based on mathematical models), the statistic data (with non-causal relationship) and the gambling data (of human participants). More case studies will be proposed in the subsequent paper, which will show the contributions of big data thinking to enhance the economy and reliability of macro energy systems. This work is supported by National Natural Science Foundation of China (No. 61533010), NSFC-EPSRC Collaborative Project (No. 513111025-2013), China-Thailand Cooperation Fund Project (No. 5151101161), and State Grid Corporation of China.

      • WEI Zhinong, YU Shuang, SUN Guoqiang, SUN Yonghui, WANG Dan

        2013,37(21):196-202, DOI: 10.7500/AEPS20130513006

        Abstract:The virtual power plant(VPP),which has received much attention of the developed countries in Europe,is an effective management form of grid connection of distributed energy resources as well as an important component part of the smart grid.In the past ten or more years,the European Union/European countries have carried out many research and pilot projects on VPP.These projects not only have different emphases,but also constitute an integral system.Focusing on VFCPP,Power Matcher VPP,FENIX,EDISON and WEB2ENERGY projects,a description is made of European VPP-related research projects prior to their summation.The major problems of VPP which still need to be addressed are proposed.

      • 程时杰

        2013,37(1):3-8, DOI: 10.7500/AEPS201209150

        Abstract:An analysis is made of the role energy storage technology will play in the development and reform of power systems.A comprehensive survey is made of such aspects as the basic principles,technical performance,development status,main problems,and key bottlenecks needing solution.Evaluation indices for large-scale application of energy storage technology are presented.On this basis,the development and application prospects of multiple energy storage technologies are analyzed and a roadmap is provided.

      • YU Yixin, LIU Yanli

        2015,39(2):1-5, DOI: 10.7500/AEPS20141204007

        Abstract:Barrier exists in every stage of developing a smart grid,from fundamental science and engineering technology research to development,demonstration and operation.Figuring out the critical barrier will be helpful to clarifying how to maximize smart grid's potential,thus providing comprehensive social and economic benefits to the nation.This paper identifies eleven key challenging issues of the smart grid and emphasizes that metrology and standardization are the priority important areas,interdisciplinary cooperative research is the inevitable choice for developing the smart grid,while legal framework and supervision,market design and management reform are the basic guarantees of successfully implementing the smart grid and obtaining the deserved benefits.

      • CHEN Xu, ZHANG Yongjun, HUANG Xiangmin

        2016,40(1):143-151, DOI: 10.7500/AEPS20150330005

        Abstract:In order to adapt to the access of high penetration and large-scale distributed generators (DGs), the active distribution network (ADN) has become the research trend of current and future smart grids. The influences of DG access, demand-side management and topology changes on the voltage distribution and voltage stability of distribution network in the AND background are reviewed. The reactive power and voltage control method of ADN are summarized from the perspective of centralized and decentralized control. According to an analysis of the current research status, some of the problems and shortcomings of research on reactive power and voltage control method of AND influenced by various factors are briefly treated. Some problems in research on the AND reactive power and voltage control method are pointed out. This work is supported by National Natural Science Foundation of China (No. 51377060).

      • ZHAO Junhua, DONG Zhaoyang, WEN Fushuan, XUE Yusheng

        2017,41(4):1-11, DOI: 10.7500/AEPS20160813002

        Abstract:The comprehensive energy system, which can coordinate multiple types of energy and be characterized by a deep integration of “cyber-physical-social” systems, is emerging. There is therefore an urgent need to conduct in-depth study on data science and big data mining for energy systems. This paper presents an initial discussion on data science and its applications in comprehensive energy systems. The fundamentals of data science, in particular the importance of the statistical learning theory and data quality, are discussed first. The new progresses in big data mining, such as deep learning, transfer learning and cross domain data fusion, are introduced then. Finally, a brief review is given on the applications of data mining techniques in energy systems; some research problems in energy system data mining, which require further attentions in future, are also discussed. This work is supported by National Basic Research Program of China(973 Program)(No. 2013CB228202), National Natural Science Foundation of China(No. 51477151)and Specialized Research Fund for the Doctoral Program of Higher Education of China(No. 20120101110112).

      • QIN Wenping, WANG Peng, HAN Xiaoqing, LIU Zhijuan

        2014,38(1):28-33, DOI: 10.7500/AEPS20130529009

        Abstract:Reactive power plays an important role in power system reliability as it is closely related to system voltage stability and voltage collapse.However,the reactive power related reliability issues are seldom emphasized in conventional power reliability evaluation.This paper studies the power system reliability from the perspective of active and reactive power,respectively.Active and reactive power inadequacy and the associated voltage perturbation due to system failure are considered in reliability evaluation of power systems.A three-stage load shedding technique for past contingencies are implemented to determine the influence of active and reactive power on system reliability and to find an optimal way to relieve network violation.

      • JU Ping, LIU Yongfei, XUE Yusheng, LI Hongyu, SUN Lixia, ZHOU Haiqiang

        2017,41(1):1-8, DOI: 10.7500/AEPS20160530011

        Abstract:Randomness exists extensively in nature, engineering and social systems, the power system not excepted. Randomness has gradually taken into consideration in power system analysis since the 1970s, with emphasis on analysis of steady-state random problems while research on power system dynamics is still based on the deterministic theory. In recent years, with increasing integration of typical sets of stochastic sources into power systems, such as the large-scale renewable power generation and electric vehicles, the influence of randomness on power system dynamics can no longer be neglected. For this reason, a research framework is proposed for stochastic dynamics of power system focusing on dynamic problems under the action of randomness, including stochastic dynamic modelling, stochastic dynamic responses, stochastic stability, stochastic dynamic security and stochastic optimum control of power system. Some suggestions are given for the research.

      • XIA Yan, LI Gengyin

        2017,41(13):22-29, DOI: 10.7500/AEPS20161123004

        Abstract:The establishment of distribution market needs to rely on the friendly interaction between various resources and power grid in the distribution network. Hence their demand for guidance by a scientific incentive mechanism. To this end, a mode is proposed for encouraging distribution side users interacting with the grid. According to the principle of incentive compatibility, a reasonable and effective price mechanism is suggested to clarify the contribution of flexible users to capacity saving. Relying on the transmission day-ahead market, the participation of users in distribution day-ahead interaction is designed including architecture, process and settlement. Based on the idea of decentralized decision-making, the interactive model of users' self-response and multi-round game of distribution network is simulated. The numerical example shows that, with the proposed mechanism, the costs and benefits arising from interaction can be fairly shared to deeply inspire user interaction with the distribution system, promote effective assets utilization of the grid, and achieve cooperation and mutual benefit as a win-win situation between distribution network and microgrids.

      • DONG Zhaoyang, ZHAO Junhua, WEN Fushuan, XUE Yusheng

        2014,38(15):1-11, DOI: 10.7500/AEPS20140613007

        Abstract:The traditional way of economic and social development,characterized by centralized utilization of fossil fuel energy,is gradually changing.On the other hand,the third industrial revolution is now rising.As the core technology of the third industrial revolution,the Energy Internet aims at facilitating large-scale utilization and sharing of renewable energy by integrating renewable energy and internet technologies.It will enhance the merging of electricity,transportation and natural gas networks,change the way of energy utilization,and finally achieve the goal of promoting sustainable economic and social development.Given this background,an overview of the Energy Internet is first provided,and a basic research framework developed.A definition of the Energy Internet is then suggested,followed by its basic architecture and main components.Several main research challenges to the Energy Internet,such as the wide-area coordination and control of distributed devices,the integration of the power system with the transportation system and natural gas network,as well as the cyber physical modeling and security,are next discussed in more details.

      • LU Zhigang1 , XIE Xiaowei2 , LI Xueping1

        2012,36(7):86-91, DOI:

        Abstract:In order to determine the optimal break point sets(OBPSs) for protection coordination in multi-loop network, four indices are introduced as the judgment criterion of OBPSs, the math model looking for OBPSs is developed. Then, based on the principle of bacterial colony chemotaxis algorithm, a new method of determining OBPSs is presented. Comparing with the existing method, the proposed method can find the optimal minimum break point set. An example analysis proves that this method is valid and applicable.

      • WANG Yelei, ZHAO Junhua, WEN Fushuan, XUE Yusheng

        2015,39(21):1-10, DOI: 10.7500/AEPS20150623001

        Abstract:The emergence and development of the power-to-gas (P2G) technique have made the bidirectional energy flow between power and natural gas systems possible. P2G represents a key technique in the emerging energy internet, and promotes the integration of multi-energy systems. By transforming electricity to gas, existing gas storage facilities can be used to mitigate the volatility of renewable energy generation. The modeling of future complex multi-energy systems with P2G functions is presented based on the “energy hub” framework, and a coordinated optimization model presented. A game-theory-based method is next proposed to attain market equilibrium in a multi-energy system. A 4-bus sample multi-energy system and a simplified Victoria gas-electricity combined network system in Australia are adopted for demonstrating the effectiveness of the presented optimization model and solving algorithm. This work is supported by National Basic Research Program of China (973 Program) (No. 2013CB228202) and National Natural Science Foundation of China (No. 51361130153, No. 51361130152).

      • GAO Hui,LI Huailiang,ZHAI Changguo,CHEN Liangliang

        2013,37(1):186-190, DOI: 10.7500/AEPS201207057

        Abstract:In order to improve the energy efficiency of electric vehicle(EV)power battery and increase the start-up power of EV,a maglev flywheel battery energy storage system with the active suspension controlled at five degrees of freedom is designed for EV.The system suspension control principle is expounded,and the radial single freedom transfer function of the maglev flywheel is established by referring to a digital proportion-integral-differential(PID)control algorithm.The frequency spectrum characteristic of the transfer function and the flywheel rotor trajectory curve are simulated,and the30000r/min rotation experiment on the maglev flywheel battery prototype is realized.The experiment results show that the maglev flywheel rotor is capable of high speed steady spin,and with good energy storing ability.The maglev flywheel battery energy storage system will assist the EV power battery work,improve the battery charge and discharge properties and prolong the service life of the motive power battery.

      • YANG Ting, ZHAO Liyuan, WANG Chengshan

        2019,43(1):2-14, DOI: 10.7500/AEPS20180706005

        Abstract:In order to promote the energy production and consumption revolution and build a clean, low-carbon, secure and efficient energy system, it is necessary to develop a new generation of power system and integrated energy system which are more intelligent. Artificial intelligence is one of the most disruptive technologies in the world, which has strong processing ability in computational intelligence, perceptual intelligence and cognitive intelligence. The application of artificial intelligence in power system and integrated energy system will change the traditional utilization mode of energy and promote the further intellectualization of the system. The contents of this review are as follows: the summary of artificial intelligence, the demand for artificial intelligence in power system and integrated energy system, and the various applications of artificial intelligence in the energy field. Finally, the paper presents the future challenges and opportunities faced by the energy field in the era of artificial intelligence.

      • LI Peng, HUANG He, WU Xiaochen, HUANG Mei, YANG Yinguo, LI Ling

        2014,38(1):127-133, DOI: 10.7500/AEPS20130712005

        Abstract:Security and stability standards of power grids are the basic norm of power system planning and operation."Security and stability guide of power systems" is China's reliability standard which has been in use since 1980s.The guide defines several levels of contingency according to the severity,and requires different defense plans.It has played an important role in security and stability during the period of rapid development of power grids.In 2011,the Central Government of China promulgated"Regulations on accident investigation and handling of electricity safety emergency",which makes new requirements on grids and power companies from the perspective of load loss.Electricity utilities in China should review their security and reliability standards at present.The paper describes the security and stability standards carried out by the major Western developed countries,compares them with Chinese standards,and makes some useful suggestions for the next version of China's reliability standards.

      • XU Hongqiang, YAO Jianguo, NAN Guilin, YU Yijun, YANG Shengchun, ZHAI Mingyu

        2018,42(1):1-7, DOI: 10.7500/AEPS20170518001

        Abstract:With the construction of ultra-high voltage(UHV)AC/DC interconnected power grid, the advancement of new energy and the deepening of electricity market reform, significant changes have taken place in the operation of power grid in China, which makes higher requirements on the dispatching and control functions. Based on the integrated distribution and concentration deployment scheme of application functions, this paper gives an overview of the new features of the application function, i. e. , global, rapid and accurate, analyzes the technological support to realize such application functions, and points out the urgency of promotion basic work such as power grid model, operation data and management rules.