无联结变压器MMC-MVDC配电网零序电压抑制策略

介绍了基于模块化多电平换流器（modular multilevel converter, MMC）的中压直流配电网采用无联结变压器接入的技术方案，针对单相故障零序电压导致直流波动和非故障站电压畸变，分析了单相接地故障零序电压产生及传导机理，并设计了相应的零序电压抑制控制器（zero sequence voltage suppressing controller, ZSVSC），抑制直流正负极电压中含有的零序电压，实现了非故障站交流电压对称稳定运行。在PSCAD/EMTDC仿真平台搭建了含ZSVSC的两端基于模块化多电平换流器的中压直流（modular multilevel converters medium voltage direct current ,MMC-MVDC）配电网仿真模型，仿真结果表明所设计控制器在不影响已有正负序控制策略的基础上，有效抑制了零序电压。

Zero-sequence Voltage-suppressing control strategy for MMC-MVDC Without Coupling Transformer

Technology scheme of AC distribution network connected by MMC-HVDC without coupling transformer is introduced. Single-phase fault will cause DC voltage fluctuation in local station and AC voltage distortion in non-faulty station. By analyzing the conduction mechanism of zero-sequence voltage when single-phase ground fault occurred, corresponding zero-sequence voltage-suppressing controller （ZSVSC） is designed. The designed ZSVSC can suppress the fluctuation of DC voltages on positive and negative poles, and realize the AC voltage at non-fault station symmetrical and stable. The MMC-MVDC simulation model with zero-sequence voltage-suppression controller is built on PSCAD / EMTDC simulation platform. Simulation results show the effectiveness of the designed ZSVSC.