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基于主动限流控制的直流配电网保护及故障隔离方案
作者:
作者单位:

1.新能源电力系统国家重点实验室(华北电力大学),北京市 102206;2.斯特拉斯克莱德大学电气与电子工程学院,格拉斯哥G1 1XW,英国

作者简介:

郑涛(1975—),男,博士,教授,博士生导师,主要研究方向:电力系统保护与控制。E-mail: zhengtao_sf@126.com
吴琼(1995—),男,通信作者,硕士研究生,主要研究方向:柔性直流配电网保护与控制。E-mail: ncepuwuqiong@163.com
吕文轩(1996—),男,硕士研究生,主要研究方向:柔性直流配电网保护与控制。E-mail: ncepulwx@163.com

通讯作者:

基金项目:

国家重点研发计划智能电网技术与装备重点专项资助项目(2016YFB0900600);国家电网公司科技项目(521104180002)。


Protection and Fault Isolation Scheme Based on Active Current-limiting Control for DC Distribution Network
Author:
Affiliation:

1.State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources;(North China Electric Power University), Beijing 102206, China;2.Department of Electronic and Electrical Engineering, University of Strathclyde, Glasgow G1 1XW, UK

Fund Project:

This work is supported by Key Project of Smart Grid Technology and Equipment of National Key R&D Program of China (No. 2016YFB0900600)and State Grid Corporation of China (No. 521104180002).

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    摘要:

    柔性直流配电网中直流故障易引起系统过流,严重威胁电网的安全运行。基于全桥子模块的模块化多电平换流器(FBSM-MMC)的柔性直流配电网大多利用MMC闭锁来切断故障电流,但其闭锁会导致整个直流配电网的短时停电,降低供电的可靠性,迄今尚无有效的解决方案。对此,文中提出一种基于FBSM-MMC主动限流控制的柔性直流配电网保护及故障隔离方案,共包含3个阶段:故障发生后首先利用MMC主动限流控制将换流器输出直流电流限制在1.2倍额定电流附近(阶段1),进而根据各条线路两端直流电流是否具有同步性过零特征实现故障线路的识别(阶段2),在此基础上,进一步提出基于直流断路器与快速机械开关协同配合的故障隔离方案(阶段3)。通过断开故障关联的直流断路器,并控制相应换流站的输出直流电流降低为0,使得故障线路上的机械开关亦能快速开断,从而实现故障隔离。最后,在PSCAD/EMTDC中搭建了四端柔性直流配电网模型,通过大量仿真验证了所提保护及故障隔离方案的可行性。

    Abstract:

    DC faults in flexible DC distribution network could easily lead to overcurrent, which seriously threatens the safe operation of power grid. Modular multilevel converter (MMC) blocking is mostly used to cut off the fault current in FBSM-MMC based distribution network, but the blocking will cause power outage of the whole network for a moment, which reduces the reliability of the power supply. To solve the problem, a protection and fault isolation scheme based on active current-limiting control of FBSM-MMC for flexible DC distribution network is proposed, which consists of three stages. After a short-circuit fault occurs, the output DC current of the inverter will be limited to 1.2 times of the rated current by the control of MMC (stage 1). The faulty line is identified according to the synchronous zero-crossing characteristic at both ends of each line (stage 2). A fault isolation scheme which contains the cooperation of DC circuit breakers and high-speed switches is proposed (stage 3). By disconnecting the DC breaker associated with the fault and controlling the output DC current of the corresponding converter station to be reduced to 0, the mechanical switch on the fault line can also be quickly turned off, thereby achieving fault isolation. Finally, a four-terminal flexible DC distribution network model is built in PSCAD/EMTDC, and the feasibility of the proposed protection and fault isolation scheme are verified through a large number of simulations.

    表 1 Table 1
    图1 柔性直流配电网拓扑结构Fig.1 Topology of flexible DC distribution network
    图2 FBSM-MMC结构示意图Fig.2 Schematic diagram of FBSM-MMC structure
    图3 不同故障点处线路L1故障电流流向Fig.3 Flow direction of fault current with different fault locations on line L1
    图4 保护及故障隔离方案流程图Fig.4 Flow chart of protection and fault isolation scheme
    图5 f1处故障时L1~L4线路电流波形Fig.5 Fault current waveforms of L1~L4 when a fault occurs at f1
    图 MMC控制结构图Fig. Structure of MMC control
    图 CCSC控制原理图Fig. Principle of CCSC control
    图 MMC子模块电压参考值计算逻辑图Fig. Calculation of the reference value of MMC sub-module voltage
    图 MMC主动限流控制策略示意图Fig. Diagram of the current limited control strategy of MMC
    图 F1处故障下故障电流示意图Fig. Fault current when a fault occur at F1
    图 增加电流偏差量后区内故障示意图Fig. Diagram of in-zone fault when ΔI added
    图 线路L1两端保护装置动作示意图Fig. The action of protection device at both ends of line L1
    图 换流站控制切换示意图Fig. Switching of the converter’s control
    图 主动限流控制投入前后换流站输出直流电流Fig. DC current of MMC output idc1 with and without MMC current limited control
    图 CB1处电流i12波形Fig. Fault current of i12
    图 换流站T2中换流站输出直流电流iMMC2及CB2处电流i24波形Fig. Fault current of iMMC2 and i24
    图 开关S2处电流i21波形Fig. Fault current of i21
    图 线路L1首端(0%)处双极短路故障电流波形Fig. Current waveform of the bipolar short-circuit fault at the beginning (0%) of line L1
    图 线路L1中点(50%)处双极短路故障电流波形Fig. Current waveform of the bipolar short-circuit fault at the middle (50%) of line L1
    图 线路L1末端(100%)处双极短路故障电流波形Fig. Current waveform of the bipolar short-circuit fault at the end (100%) of line L1
    图 线路L1中点单极接地故障电流波形Fig. Current waveform of the single-pole grounded fault at the middle of line L1
    图 线路L2中点单极接地故障电流波形Fig. Current waveform of the single-pole grounded fault at the middle of line L2
    图 线路L3中点单极接地故障电流波形Fig. Current waveform of the single-pole grounded fault at the middle of line L3
    图 线路L4中点单极接地故障电流波形Fig. Current waveform of the single-pole grounded fault at the middle of line L4
    图 线路L1中点双极短路故障电流波形Fig. Current waveform of the bipolar short-circuit fault at the middle of line L1
    图 线路L2中点双极短路故障电流波形Fig. Current waveform of the bipolar short-circuit fault at the middle of line L2
    图 线路L3中点双极短路故障电流波形Fig. Current waveform of the bipolar short-circuit fault at the middle of line L3
    图 线路L4中点双极短路故障电流波形Fig. Current waveform of the bipolar short-circuit fault at the middle of line L4
    图 过渡电阻分别为10Ω、20Ω、50Ω时的双极短路故障电流波形Fig. Current waveform of bipolar short-circuit fault with 10Ω, 20Ω, and 50Ω transition resistances
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引用本文

郑涛,吴琼,吕文轩,等.基于主动限流控制的直流配电网保护及故障隔离方案[J].电力系统自动化,2020,44(5):114-121. DOI:10.7500/AEPS20191114003.
ZHENG Tao,WU Qiong,LYU Wenxuan,et al.Protection and Fault Isolation Scheme Based on Active Current-limiting Control for DC Distribution Network[J].Automation of Electric Power Systems,2020,44(5):114-121. DOI:10.7500/AEPS20191114003.

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  • 收稿日期:2019-11-14
  • 最后修改日期:2019-12-08
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  • 在线发布日期: 2020-03-08
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