一种具有故障阻断能力的改进混合型半桥MMC

Modified hybrid half bridge MMC with fault blocking capability

为克服半桥模块化多电平换流器(MMC)直流侧短路后无法阻断故障电流这一缺点,提出一种具有故障阻断能力的改进混合型半桥MMC,依靠改进半桥子模块的故障阻断能力配合相应辅助电路实现故障电流转移与阻断。分析了直流双极短路故障下改进混合型半桥MMC故障阻断的动态过程,设计了关键器件的参数选择方法,并对比了该拓扑的经济性,与传统半桥MMC相比,改进混合型半桥MMC无需增加开关器件使用,仅增加晶闸管、二极管和1个机械开关,且通态损耗很低。最后,搭建双端51电平改进混合型半桥MMC直流输电模型对所提拓扑的故障阻断能力进行验证,仿真结果表明,所提改进混合型半桥MMC拓扑能够在几十ms内清除直流故障,具有良好的实用性和经济性。

In order to overcome the shortcoming of traditional half bridge MMC(Modular Multi-level Converter)that cannot block fault current after DC side short circuit,a MH-HB-MMC(Modified Hybrid Half Bridge MMC)with fault blocking capability is proposed,which relies on the fault blocking capability of the M-HBSM(Modified Half Bridge Sub Module)and the corresponding auxiliary circuit to realize fault current transfer and blocking.The dynamic process of MH-HB-MMC fault blocking under the condition of DC bipolar short circuit is analyzed,the parameter selection method of key device is designed,and the economy of the topology is compared.Compared with the traditional half bridge MMC,MH-HB-MMC does not need to add switching devices,but only adds some thyristors,diodes and a mechanical switch,and the on-state loss is very low.Finally,the bipolar 51-level MB-HB-MMC DC transmission model is built to verify the fault blocking ability of the proposed topology.The simulative results show that the proposed MB-HB-MMC topology can clear DC fault within tens of ms,which has good practicability and economy.