具有直流故障阻断能力的逆阻型混合子模块拓扑

柔性直流输电系统发生直流侧双极短路故障是目前存在较为严重的问题。为了实现故障清除,在半桥型模块化多电平换流器(Half-bridgemodularmultilevelconverter,HBSM-MMC)的基础上,基于逆阻型绝缘栅双晶体管(Reverse-blocking insulated gate double transistor, RB-IGBT)设计了具有故障阻断能力的逆阻型混合子模块拓扑结构(Reverse-blocking hybrid submodule, RBHSM)。然后在此基础上,分析了RBHSM的故障电流阻断机理,推导了故障电流解析表达式。在故障闭锁阶段,子模块中所有电容均串入回路,始终提供2U_C的反电动势实现故障电流阻断。最后,以该子模块拓扑为例,在PSCAD/EMTDC软件中搭建RBHSM-MMC仿真模型,验证了所提子模块拓扑的正确性。仿真结果表明,所提出的新型子模块拓扑结构能够迅速实现故障电流的阻断,且在故障阻断过程中始终提供2U_C的反电动势。

An improved RB-hybrid SM with DC fault blocking capability

The occurrence of DC-side bipolar short-circuit faults in flexible DC transmission systems is currently a serious problem. In order to achieve fault clearing, based on the half-bridge modular multilevel converter (half-bridge modular multilevel converter, HBSM-MMC) and the reverse blocking type insulated gate double transistor (reverse-blocking insulated gate double transistor, RB-IGBT), an improved reverse-blocking hybrid sub-module topology with fault blocking capability is designed (reverse-blocking hybrid submodule, RBHSM), referred to as RBHSM. Then, on this basis, the fault current blocking mechanism of RBHSM is analyzed, and the analytical expression of fault current is derived. In the fault blocking phase, all capacitors in the sub-module are connected into the loop, and 2UC back electromotive force (EMF) is always provided to achieve fault current blocking. Finally, taking the sub-module topology as an example, an RBHSM-MMC simulation model is built in PSCAD/EMTDC software to verify the correctness of the proposed sub-module topology. The simulation results show that the novel sub-module topology proposed in this paper can quickly block the fault current and provide 2UC back EMF in the fault blocking process. This work is supported by National Natural Science Foundation of China (No. 5170070473) and the Fundamental Research Funds for the Central Universities (No. 106112017CDJXY150101).