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    • Key Technologies and Challenges of Low-carbon Integrated Energy System Planning for Carbon Emission Peak and Carbon Neutrality

      2022, 46(8):189-207. DOI: 10.7500/AEPS20210703002

      Abstract (626) HTML (1144) PDF 2.59 M (843) Comment (0) Favorites

      Abstract:For the carbon emission peak and carbon neutrality, deep decarbonization of the energy system is imperative. The low-carbon integrated energy system is a form of multi-energy system, which actively or passively reduces carbon emission by integrating carbon capture technologies, increasing the proportion of non-carbon energy, and fully mobilizing the flexible resources of the source-grid-load-storage. This paper reviews and prospects the key technologies of low-carbon integrated energy system planning. First, the target and path optimization methods of energy transformation are presented. Then, modeling methods of key elements in the low-carbon integrated energy system are summarized from the aspects of carbon capture and renewable energy accommodation. On this basis, according to the characteristics of different levels of low-carbon integrated energy systems, the cross-regional-level low-carbon integrated energy system planning method integrated with the carbon capture technology and high-proportional clean energy, the district-level low-carbon integrated energy system planning method considering multiple types of clean energy and flexible resources, the user-level low-carbon integrated energy system planning method considering energy consumption characteristics of users and building attributes are commented, respectively. Finally, the future development challenges of low-carbon integrated energy system planning methods at different levels are prospected.

    • Exergy Flow Mechanism and Analysis Method for Integrated Energy System

      2022, 46(12):163-173. DOI: 10.7500/AEPS20211029002

      Abstract (318) HTML (258) PDF 851.04 K (754) Comment (0) Favorites

      Abstract:An integrated energy system (IES) involves many different forms of energy, and exergy can be used as a measure of energy quality. Based on the idea of “flow”, a modeling method for the exergy flow mechanism in the IES network is proposed. First, the exergy flow analysis scope is defined based on the energy flow. The exergy flow mechanism of the heat system is analyzed. The concepts including exergy-potential and exergy-potential difference of heat system are defined. And the exergy flow mechanism model of the heat system is established. Then, the relevant laws are extended to other energy networks, and the concept of exergy-potential and exergy flow mechanism model of power systems and natural gas systems are proposed. The energy station is equivalent to an exergy loss node, and the advantage of the exergy flow mechanism model is verified through the exergy balance analysis of each link. Finally, a test system is given to intuitively show the exergy flow distribution of IES, and the exergy loss of each link is analyzed. By analyzing the overall and local exergy balance relationship, it is verified that the exergy flow mechanism model has more advantages than the traditional black-box model. The advantages of applying exergy flow theory in the high-quality energy system are discussed.

    • Flexibility of Integrated Energy System: Basic Connotation, Mathematical Model and Research Framework

      2022, 46(17):16-43. DOI: 10.7500/AEPS20220414004

      Abstract (619) HTML (649) PDF 3.16 M (1140) Comment (0) Favorites

      Abstract:Integrated energy system (IES) flexibility can serve the improvement of power system adjustability under high proportion of renewable energy. However, the mechanism of IES flexibility is complex and its connotation is rich, there is still lack of unified understanding and systematic elaboration. Firstly, the research status of power system flexibility and IES flexibility at home and abroad is comprehensively reviewed from the perspectives of flexibility-oriented planning and design, operation and regulation, market mechanism, and quantification and evaluation methods. The connection and difference between power system flexibility and IES flexibility are then summarized and analyzed. Secondly, the necessity of studying IES flexibility in the context of the high proportion of renewable energy is pointed out, and the basic connotation of IES flexibility is revealed from the perspectives of definition, basic elements, and measurement system. Thirdly, the general form of the mathematical model of IES flexibility is defined, and a specific elaboration is given with examples. Furthermore, the research framework of IES flexibility is constructed from three aspects: physical mechanism, enhancement approaches, modeling, quantification and evaluation methods. Finally, the key problems of IES flexibility research in terms of connotation, mechanism, and enhancement approaches are prospected.

    • Segmented Energy Efficiency Evaluation of Urban Integrated Energy System Based on Data Envelopment Analysis Method

      2022, 46(17):132-141. DOI: 10.7500/AEPS20211218003

      Abstract (155) HTML (143) PDF 1.86 M (824) Comment (0) Favorites

      Abstract:The multi-energy coupling characteristics of urban integrated energy systems can effectively improve the energy utilization efficiency of the system. In order to identify the weak links in the energy utilization efficiency of urban integrated energy systems in different operation scenarios, a segmented energy efficiency evaluation method of urban integrated energy systems based on data envelopment analysis (DEA) is proposed. Firstly, considering the grade differences of different forms of energy supply, the energy efficiency evaluation index system of the urban integrated energy system is constructed from the perspectives of total energy consumption, echeloned utilization of energy, and clean energy output. Then, considering the various energy flows of the system, a system energy efficiency decomposition method based on the relational network DEA model is proposed. Finally, according to the economic operation results of the urban integrated energy system, the index values in the system energy efficiency index system are obtained, and the energy efficiency evaluation results of all links of the urban integrated energy system are further calculated. The results of the example simulation show that the evaluation method can effectively compare the relative energy efficiency of urban integrated energy systems with different energy consumption needs and different operation modes, determine the key links of improving energy efficiency in different operation scenarios, and lay a foundation for the efficient carbon reduction and accurate efficiency improvement of the integrated energy system.

    • Theory and Application of High-Exergy Integrated Energy System for Energy Transition

      2022, 46(17):114-131. DOI: 10.7500/AEPS20220331003

      Abstract (496) HTML (533) PDF 4.73 M (848) Comment (0) Favorites

      Abstract:The establishment of an integrated energy system (IES) that considers both the quality and quantity of energy is one of the most important measures to promote energy transition. Traditional energy flow and energy efficiency studies focus only on the “quantity” of energy, while ignoring the “quality” of different energies, which does not fully reflect the value of energy and has limitations in application. This paper presents the concept of the high-exergy integrated energy system (HE-IES). The focus is on the enhancement of the delivery capacity of effective energy in the IES. Based on the exergy flow mechanism model of the IES and the core parameters of the system energy quality, this paper discusses the exergy flow model for power systems, natural gas systems, thermal systems, energy stations, and renewable energy. Then, the key research contents and typical mathematical models of the HE-IES in the planning, operation optimization and energy dispatching, and the trading and market-based mechanism are discussed in depth. Meanwhile, the prospects are given on the future research directions for the HE-IES.

    • Optimization and Evaluation of Urban Integrated Energy System Based on Game Equilibrium- Multidisciplinary Collaborative Theory

      2022, 46(17):102-113. DOI: 10.7500/AEPS20220115003

      Abstract (318) HTML (218) PDF 1.95 M (817) Comment (0) Favorites

      Abstract:With the continuous access of new energy, the urban integrated energy system presents the characteristics of high coupling and high freedom degree. Using the mutual transformation relationship between different forms of energy, the multi-energy flow collaborative adjustment is realized to improve the energy utilization efficiency. Taking the minimum total operation cost as the system objective function and comprehensively considering the network architecture and operation mode of the urban integrated energy system with power grid as the hub platform, the joint optimal operation model of distributed energy unit, combined cooling, heating and power system, natural gas network and urban distribution network is established. Considering the multi-energy flow control of freedom degree as the multi-energy flow flexibility evaluation index of the urban integrated energy system, the game equilibrium-multidisciplinary collaborative optimization theory is used to establish parallel sub-disciplines from different perspectives to solve the model. This method improves the consistency constraints and sub-discipline objectives on the basis of multidisciplinary collaborative optimization theory, and overcomes the problems of slow convergence and local optimization of multidisciplinary collaborative optimization theory. The feasibility and effectiveness of the proposed model and algorithm are verified by an example of connecting a 4-bus distributed energy unit and a 6-bus combined cooling, heating and power system to a 33-bus urban area distribution network, which is coupled with a 7-bus natural gas network.

    • Optimal Operation of Regional Integrated Energy System Based on Energy Supply Through Composite Energy Pipeline

      2022, 46(17):91-101. DOI: 10.7500/AEPS20220227011

      Abstract (449) HTML (207) PDF 2.53 M (791) Comment (0) Favorites

      Abstract:In the background of “carbon emission peak and carbon neutrality”, the large-scale development and utilization of low-carbon and clean energy is the only way for China’s energy transition process. Composite energy pipeline (CEP) realizes the simultaneous transmission of electric energy and liquefied natural gas (LNG) with low transmission loss, which is an important development direction of energy transmission at present. In view of the significant increase in energy intensity and coupling degree in load-concentrated areas such as central cities, a new regional integrated energy system (RIES) based on the energy supply through CEP is constructed. The system considers the cascade utilization of CEP cooling energy, realizes the multi-energy coupling and complementation of electricity, gas, cooling and heat, and improves the energy utilization rate of the system. In order to improve the economy of system operation, an optimal dispatch model considering the electricity-gas integrated demand response of the system is established with the objectives of system energy purchase cost, and operation and maintenance cost. Finally, through simulation example, the optimal dispatch results of system energy flow in different scenarios are compared and analyzed, and the feasibility and effectiveness of the proposed system and optimization model are verified.

    • Research and Prospect of Strong Coupling Pathway for Electricity-Heat Integrated Energy Network

      2022, 46(13):204-215. DOI: 10.7500/AEPS20210429008

      Abstract (167) HTML (908) PDF 832.31 K (648) Comment (0) Favorites

      Abstract:At present, the research of electricity-heat integrated energy networks is mostly based on the traditional heat network and limited to the weak coupling network composed of a small number of combined heat and power units. The energy cells driven by the 5th generation district heating and cooling (5GDHC) system can realize the high-density mesh integrated electricity-heat network through the heat pump pool and change the interactive form of the electricity-heat network. This paper discusses the great opportunities and challenges brought by the 5GDHC system to the unified modeling theory of integrated energy electricity-heat coupling network, and the broad application prospect of energy cell flexibility aggregation based on the 5GDHC system. Furthermore, the research status of the 5GDHC system, the multi-energy flow modeling theory of electricity-heat coupling network, and the flexibility aggregation method of distributed resources are summarized. Aiming at the opportunity of energy cells using the heat pump pools and the heat network thermal inertia to improve the flexibility of the power grid, the research idea of energy cell network flow theory and flexibility aggregation method driven by the 5GDHC system are proposed: the interaction mechanism and feasible region analysis of thermal dynamics from heat pump pool to distribution network and hierarchical coordinated optimization method for flexible aggregation and allocation of heterogeneous smart energy cell interconnection.

    • Review and Prospect of State Estimation for Electricity-Heat-Gas Integrated Energy System

      2022, 46(7):187-199. DOI: 10.7500/AEPS20210609003

      Abstract (402) HTML (771) PDF 754.74 K (855) Comment (0) Favorites

      Abstract:The development of integrated energy system plays a huge role in improving energy efficiency, reducing carbon emissions and increasing the permeability of renewable energy. Faced with the increasingly closely coupled integrated energy system of electricity-heat and electricity-gas interconnection, the existing energy management mode and scheduling means cannot give full play to their due advantages. Therefore, the realization of the integrated, efficient and accurate state estimation of the integrated energy system can provide reliable data support for the subsequent collaborative scheduling and safe operation. In view of this, this paper briefly summarizes the research on the state estimation of the integrated energy system in the background of carbon neutrality, and reviews the development history and difficulties of the theory of state estimation for the integrated energy system. The general idea of the research on the state estimation of the electricity-heat and electricity-gas integrated energy systems is analyzed from the three aspects of model, data and time scale. Finally, the future research directions of the integrated energy system state estimation are prospected.

    • Key Technologies for Multi-time-scale Dynamic Time-domain Simulation of Integrated Energy System

      2022, 46(10):97-110. DOI: 10.7500/AEPS20201203007

      Abstract (345) HTML (550) PDF 823.74 K (989) Comment (0) Favorites

      Abstract:In order to improve the energy efficiency, integrated energy systems (i.e. integrated electricity-heat-gas systems) attract increasing attention worldwide in recent years. Efficient and accurate multi-time-scale dynamic time-domain simulations play an essential role in the operation and control of the integrated energy system. Taking the dynamic modeling and simulation of the integrated energy system as the research object, the structure and dynamic process of integrated energy system is presented first in this paper. Then, this paper introduces the research progress achieved in the dynamic modeling and simulation technology of integrated energy system from three key points of basic model, simulation technology and numerical calculation, mainly including multi-energy coupling general modeling theory, partitioned multi-rate simulation technology, and efficient numerical calculation implementation method for heterogeneous energy networks. On this basis, the key challenges that still need to be solved in the existing research are discussed, such as dynamic modeling under variable operating conditions, multi-rate partitioning interface processing, and selection of numerical solution formats. Finally, the research directions and application scenarios of key dynamic modeling and simulation techniques for the future integrated energy system are prospected.

    • Optimal Dispatching of Integrated Energy System Considering Operation Flexibility Constraints

      2022, 46(16):84-94. DOI: 10.7500/AEPS20211010003

      Abstract (427) HTML (545) PDF 1.68 M (974) Comment (0) Favorites

      Abstract:The integrated energy system (IES) of electricity-gas-heat interconnection presents the characteristics of multiple time scales in the process of energy transmission, and the dynamic characteristics of the gas-heat network contain abundant flexible capacity. Fully tapping the potential flexibility of IES can effectively improve the consumption level of renewable energy. Thereby, an optimal dispatching model of IES considering the flexibility of sub-hourly-time-scale operation is proposed. Based on the analysis of the system operation regularity in the net load variation interval, the mathematical expression of power system flexibility demand and resources is derived. Then, the dynamic characteristics of gas network and heat network are analyzed, and the mathematical models of gas network and heat network which provide operation flexibility are established, respectively. Based on this, an optimal dispatching model of IES considering the flexibility constraints of sub-hourly-time-scale operation is constructed, and the nonlinear constraints in the model are linearized. Finally, the case studies on the modified electricity-gas-heat 24-20-16 bus system demonstrate that the dynamic characteristics of the gas-heat network can enhance the system flexibility in a short time scale and significantly improve the economy of system operation.