MMC系统级拓扑及其直流故障电流阻断能力研究

MMC System Topology and Its DC Fault Current Blocking Capability

由于直流断路器成本较为昂贵,尚处于试验阶段,具备直流故障电流阻断能力的MMC拓扑才是实现输配电网可控性,提高MMC运行可靠性的关键。文中在分析传统半桥型模块化多电平换流器(half bridge sub module based modular multilevel converter,HBSM-MMC)直流侧故障机理的基础上,对具有直流故障电流阻断能力MMC相关研究进行综述。分析了桥臂优化MMC的拓扑结构及直流故障抑制能力,包括子模块混合型MMC及二极管阻断型MMC;分析了单相优化MMC拓扑结构及直流故障电流阻断能力,包括桥臂交替导通MMC和混合级联型MMC。仅从理论角度来说,具备直流故障电流阻断能力的MMC拓扑结构研究已经较为成熟,但混合子模块优化控制、改进子模块封装、串联子模块和开关器件的协调配合、器件冷却等工程实现诸多问题还有待进一步研究。

Because of high cost and immaturity of DC circuit breaker, the modular multilevel converter （MMC） topology with DC fault current blocking capability plays an important role in realizing the control- lability of power grid and improving the operation reliability of MMC. In this paper, based on the analysis of DC-side fault mechanism of the traditional half bridge MMC, the researches on MMC are reviewed. The topology and the DC fault current suppression capability of the MMC with optimized bridge are analyzed, including the submodule hybrid MMC and the diode blocking type MMC. The topology and the DC fault current blocking capability of the single-phase optimized MMC are discussed, including the bridge arm al- ternately conducting type MMC and the hybrid cascaded MMC. It is concluded that the theoretical re- searches on the MMC topology with DC fault current blocking capability have become mature, but the en- gineering implementation topics, such as optimum control of hybrid submodule, improvement of submodule packaging, coordination of serial module and switching device, and device cooling, need further study.