柔性直流输电系统交流侧线路继电保护适应性研究

基于模块化多电平换流器的柔性直流输电（MMC-HVDC）系统运行控制特性与常规直流输电（LCC-HVDC）差别较大，其对交流侧继电保护的影响也不同于LCC-HVDC。基于MMC换流站控制器的动态响应特性，推导了交流电网故障下MMC逆变站交流侧短路电流表达式，分析了逆变站输出短路电流幅值、相位特性与MMC控制方式之间的关系；在此基础上，提出了基于MMC控制方式的等效矢量分析方法，直观刻画了保护电气量之间的相位关系。通过推导故障电气量及保护动作方程，分析了逆变站在不同控制方式下纵联电流差动保护、距离保护和零序电流保护的动作特性，明确了MMC对交流侧继电保护的影响范围，所得结论为MMC-HVDC交流侧线路保护的配置及整定提供了参考依据，通过PSCAD/EMTDC仿真验证了理论分析的有效性。

Adaptability of MMC-HVDC System on Relay Protection of AC Transmission Lines

The operating principles of MMC-HVDC transmission system are different from that of LCC-HVDC， and its effect on AC side relay protection is different from that of LCC-HVDC. Based on the dynamic response characteristics of MMC，the expression of AC short-circuit current on MMC converter station side is derived，the relationship among current amplitude， phase characteristics and MMC control methods are analyzed. Furthermore， equivalent vector analysis method based on MMC is proposed， and the phase relationship among the electrical quantities is intuitively described. Through the derived fault electrical quantity and the protective action equation，the operation features of current differential protection， distance protection and zero-sequence current protection under different control method are analyzed， the influence scope of MMC on AC side relay protection is clarified，the conclusions provide references for the configuration and setting of MMC-HVDC AC side protection. The simulation on PSCAD/EMTDC are presented to verify the validity of theoretical analysis.