一种级联型电压源换流器交流侧单相接地故障特性分析

摘要

Analysis of a single-phase ground fault of aflexible DC voltage source converter(VSC)cascaded by three-phase two-level converter units is presented.The fault characteristic of cascaded VSC units of the converter is analyzed when the neutral point of the DC side of the cascaded converter is directly connected to ground.The fault current path is elaborated and the calculation formulas are derived.The influence of the fault position of the converter and the electric characteristics difference of the cascaded converter unit are analyzed.It provides the reference for the engineering design of the converter grounding and the protection strategies of converter.The validity and the feasibility of the analysis are verified on the built RTDS system of VSC cascaded by three-phase two-level converter units.%针对一种三相两电平电压源换流器(Voltage Source Converter,VSC)单元级联型柔性直流换流器交流侧单相接地故障,分析了直流侧中性点直接接地方式下换流器各级联VSC单元的故障特性,详细阐述了故障电流通路,推导了故障电流的解析方程,分析了故障点位置换流器故障特性的影响,指出了故障条件下各级联VSC单元电气量特征的差异性,为换流器接地方式及保护策略的工程设计提供依据.最后通过建立的三相两电平VSC单元级联型换流器RTDS仿真系统,验证了本文分析的正确性和有效性.