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MMC-HVDC电网输电线路双极短路故障电流的实用计算
作者:
作者单位:

1.北京交通大学电气工程学院,北京市 100044;2.南京南瑞继保电气有限公司,江苏省南京市 211102

作者简介:

郝亮亮(1985—),男,通信作者,博士,副教授,博士生导师,主要研究方向:电力系统主设备故障分析及保护、直流输电控制与保护、励磁控制。E-mail: llhao@bjtu.edu.cn
李伟杰(1995—),男,硕士研究生,主要研究方向:柔性直流输电系统短路电流计算。E-mail: lwj950813@163.com
王卓雅(1995—),女,博士研究生,主要研究方向:柔性直流输电。E-mail: 19117028@bjtu.edu.cn

通讯作者:

基金项目:

国家重点研发计划资助项目(2018YFB0904600)。


Practical Calculation for Bipolar Short-circuit Fault Current of Transmission Line in MMC-HVDC Grid
Author:
Affiliation:

1.School of Electrical Engineering, Beijing Jiaotong University, Beijing 100044, China;2.NR Electric Co., Ltd., Nanjing 211102, China

Fund Project:

This work is supported by National Key R&D Program of China (No. 2018YFB0904600).

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    摘要:

    基于模块化多电平换流器的高压直流电网作为支撑高比例可再生能源接纳的有效手段,已经成为电网发展的重要方向。双极短路故障是输电线路发生的最严重故障,目前一般通过在 s域内列写直流系统状态方程,然后再基于拉氏反变换求解故障电流,亟待提出短路电流的工程实用计算方法。为此,以张北柔性直流电网为研究对象,首先分析了输电线路双极短路的故障特性及耦合机理。在此基础上,将故障线路靠近阀侧的两端分别看作二端口,分析了故障电流与二端口两侧电压的关系。其次,基于正、负极线路二端口电压变化不大的思想,将环形直流电网简化为两端网络或开式网络,得到故障线路电流的实用计算方法,不再需要求解高阶的拉氏反变换而直接得到故障电流。最后,通过与电磁暂态仿真结果的对比,验证了实用计算方法的可行性与高效性。

    Abstract:

    As an effective means to support the adoption of high proportion of renewable energy, modular multilevel converter based high-voltage direct current (MMC-HVDC) has become an important development direction of power grid. The bipolar fault is the most serious fault in transmission lines. At present, state equations of DC system are usually written in s-domain, and then fault currents are solved based on the inverse Laplace transformation. A practical engineering calculation method for fault current is needed urgently. Zhangbei MMC-HVDC grid of China is taken as the research object, the fault characteristics and coupling mechanism for bipolar fault of transmission line are analyzed firstly. On this basis, the two ends of the fault lines near the valve side are regarded as two ports respectively, and the relationship between the fault currents and the voltages of the two ports are analyzed. Secondly, based on the idea that the voltage of the two ports of the positive and negative lines does not change too much, the annular MMC-HVDC grid is simplified to a two-terminal network or an open network. The practical calculation method of fault line current is obtained to calculate fault current directly, while it is no longer necessary to solve the high-order inverse Laplace transformation. Finally, the feasibility and efficiency of the practical calculation method are verified by comparing with the electromagnetic transient simulation results.

    表 1 Table 1
    表 3 Table 3
    表 2 Table 2
    图1 中国张北柔性直流电网的基本结构Fig.1 Basic structure of Zhangbei MMC-HVDC grid of China
    图2 故障后电流特性Fig.2 Current characteristics after fault occurs
    图3 换流器闭锁前换流站等值电路Fig.3 Equivalent circuit of MMC before being blocked
    图4 换流站并联等效电路图Fig.4 Equivalent circuit of parallel converter stations
    图5 故障线路的二端口等值Fig.5 Two-terminal equivalent of fault line
    图6 两端网络和原环网中仿真结果对比Fig.6 Comparison of simulation results between two-terminal system and original topology
    图7 两端等效电路及其故障电流解析值Fig.7 Equivalent circuit of two-terminal system and its analytic value of fault currents
    图8 由不同非故障线路拆分的3种等效拓扑Fig.8 Three equivalent topologies after removing different non-faulted lines
    图 移除金属回线后的拓扑结构Fig. Topology after removing non-fault terminal
    图 康保站提供故障电流路径Fig. Fault current paths of Kangbao station
    图 故障后直流电网拓扑及电流故障分量分布Fig. Topology of DC grid and distribution of current fault components after fault
    图 并联的换流站中子模块电容对故障点的放电路径重合导致的耦合作用示意图Fig. Schematic diagram of coupling effect caused by the coincidence of discharge paths of capacitors in parallel converter stations to the fault point
    图 故障线路及其两端换流站组成的两端网络Fig. Two-terminal system composed by fault line and its both side MMCs
    图 直流电网中不同位置故障Fig. Different fault locations in DC grid
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引用本文

郝亮亮,李伟杰,王卓雅,等.MMC-HVDC电网输电线路双极短路故障电流的实用计算[J].电力系统自动化,2020,44(5):68-76. DOI:10.7500/AEPS20190729015.
HAO Liangliang,LI Weijie,WANG Zhuoya,et al.Practical Calculation for Bipolar Short-circuit Fault Current of Transmission Line in MMC-HVDC Grid[J].Automation of Electric Power Systems,2020,44(5):68-76. DOI:10.7500/AEPS20190729015.

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  • 收稿日期:2019-07-29
  • 最后修改日期:2019-10-17
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  • 在线发布日期: 2020-03-08
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