基于3次谐波注入的MMC冗余容错控制策略

Fault-tolerant Method of Modular Multilevel Converter Based on Third Harmonic Injection

针对模块化多电平换流器(MMC)在子模块(SM)故障时存在冗余度不足的情况,提出了一种基于3次谐波注入的MMC冗余容错运行策略。在不继续增加冗余SM的前提下,以维持输出线电压不变为基本思路,通过在桥臂电压调制波中注入3次谐波降低其调制比,等效地增大MMC冗余度,实现MMC在SM深度故障时的容错运行。与基频零序分量注入的方法进行对比,分析了所提方法的优势。在Matlab/Simulink上进行了仿真和实验验证。结果表明,所提控制策略能使MMC在冗余备份不足的情况下继续正常工作,有效避免了停机隐患。

In order to fully implement the functionalities of modular multilevel converter（MMC）, its fault-tolerant op- eration without redundant sub-modules（SMs） is comprehensively investigated.To avoid completely shut down the MMC system under SMs fault, a novel fault-tolerant method based on third harmonic injection is put forward to ensure the line voltage remain constant.Without additional redundant SMs, the method realizes normal function of MMC by inject- ing the third harmonic into the modulation voltage to reduce modulation ratio.Compare with the zero-sequence voltage injection method, there are lots of advantages.The simulation model of the system by Matlab/Simulink and experimen- tation are realized.The results show that the proposed strategy can enhance the fault ride-through capability of MMC system, ensuring the reliable operation of the system.