MMC-HVDC的新型交流故障穿越策略

A New AC Fault Ride-through Strategy of MMC-HVDC

通常柔性直流输电(MMC-HVDC)系统在满功率调制下,开关管的过流裕度较小,容易在整流站交流故障恢复时刻发生桥臂过流现象。深入分析了柔直系统中的环流特性,推导出环流幅值和相位关系,以及环流对桥臂电流中有功和无功分量电流的影响。指出MMC固有的环流可减小桥臂有功电流的峰值,并基于此提出了在交流故障期间不使能环流抑制的新型交流故障穿越策略。新策略增加了交流故障穿越的成功率,简单可靠,易于实现,最后通过实时数字仿真(RTDS)试验平台验证所提策略的正确性。

Generally the IGBT has a less over-current margin when modular multilevel converter HVDC(MMC-HVDC)is used under full power modulation,bridge arm overflow is easy to occur at the AC fault recovery of the rectifier station.The characteristics of the circulating current in the MMC-HVDC were analyzed deeply,and the relationship between the amplitude and phase of the circulating current was deduced.The influence of the circulating current on the active and reactive component currents in the bridge arm current was also discussed.A new strategy of AC fault crossing without circulating current suppression during AC fault period was proposed,basing on the inherent circulation of MMC which can reduce the peak value of active current.The new strategy not only increases the success rate of AC fault crossing,but also is simple,reliable and easy to implement.Finally,the correctness of the proposed strategy was verified through the real time digital simulator(RTDS)test platform.