MMC-UPFC不同接地设计的故障特性及对本体保护配置影响

摘要

根据MMC-UPFC示范工程的实际需要,提出3种可行的交流侧接地方式:仅并联变阀侧中性点经大电阻接地、仅串联变阀侧中性点经大电阻接地及仅并联变阀侧中性点经小电阻接地.结合示范工程系统参数与实时数字仿真(RTDS)实验,详细分析了不同接地方式对故障特性与保护配置的影响,重点讨论接地点位置对串联变网侧单相接地故障及对应保护配置影响,以及接地电阻阻值对阀侧短引线单相接地故障、换流器桥臂单相接地故障及相应保护配置影响.最终得出仅并联变阀侧中性点经大电阻接地为较优的MMC-UPFC接地方案.%According to the actual demands of a pilot MMC(Modular Multilevel Converter)-UPFC Unified Power Flow Controller) project,three AC-side grounding modes are proposed:grounding via large resistance only for the valve-side neutral-point of parallel transformer;grounding via large resistance only for the valve-side neutral-point of series transformer;and grounding via small resistance only for the valve-side neutral-point of parallel transformer.Combined with the system parameters of that pilot project and the RTDS real-time digital simulation,the impact of grounding mode on the fault characteristics and protection scheme is analyzed in detail.The impact of grounding position on the single-phase grounding fault at the grid side of series transformer and the corresponding protection scheme as well as the impact of grounding resistance on the single-phase grounding fault of valve-side AC bus or converter bridge-arm and the corresponding protection scheme are emphasized.It is concluded that,grounding via large resistance only for the valve-side neutral-point of parallel transformer is the best grounding design for MMC-UPFC.