功率开关故障情况下MMC型电力电子变压器的故障穿越运行策略

Fault Ride-Through Strategy for MMC Based Power Electronic Transformer Considering Power Switches Failures

基于模块化多电平结构的电力电子变压器输入级、隔离级和输出级均包含大量的IGBT和续流二极管。针对各层级IGBT和续流二极管在开路故障和短路故障下的电路拓扑和故障特性进行了分析,根据电力电子变压器各层级的特点,设计了相应的冗余方案以实现故障穿越:输入级采用子模块热备用冗余;隔离级首先对双有源桥进行了改进,通过在其串联电容侧并联半桥模块以便于单级双有源桥的切除,以此为基础为隔离级配置了热备用的冗余;输出级逆变器采用桥臂冗余。最后,通过仿真验证了所提故障穿越运行策略的有效性。

The input stage,isolation stage and output stage of modular multilevel converter（ MMC） based power electronic transformer contain a large number of IGBTs and freewheeling diodes. The circuit topologies and fault characteristics of IGBTs and freewheeling diodes under open-circuit and short-circuit faults are analyzed. According to the characteristics of each stage of power electronic transformer,the corresponding redundancy methods are designed to help the system to achieve fault ride-through. The input stage adopts sub-module spinning reserve redundancy. The dual active bridge of isolation stage is improved to be used for the isolation of the single stage double active bridge by means of parallel half bridge module in the series capacitors,on this basis,spinning reserve redundancy is configured for the isolation stage. The output stage inverter adopts bridge leg redundancy. Finally,the effectiveness of the proposed fault ride-through strategy is verified though simulation.