混合型MMC启动策略及全桥子模块数目配置研究

Start-up Control Strategies of Hybrid MMC and Configuration of FBSM

模块化多电平换流器(Modular Multilevel Converter,MMC)是柔性直流输电的研究热点。由半桥子模块(Half-bridge Sub-module,HBSM)和全桥子模块(Full-bridge Sub-module,FBSM)组成的混合型MMC非常适用于大容量架空线输电系统。考虑到混合型MMC的拓扑结构特点,首先提出了一种分段式启动控制策略;然后分别对两种最常见的直流故障(单极接地短路和双极短路)的故障机理进行分析,并结合故障机理提出两种子模块的数目配比方案;最后在PSCAD/EMTDC仿真环境中建立了401电平,±320 k V,1 000 MW的混合型MMC模型,对论文所提出的启动策略和直流故障穿进行仿真分析,结果证明了所提出控制策略的有效性。

Modular Multilevel Converter（ MMC） is one of the research focuses of flexible HVDC. The hybrid modular multilevel converter（ MMC） is composed of half-bridge sub-module（ HBSM） and full-bridge sub-modules（ FBSM）,which is a good candidate for the overhead line（ OHL） HVDC transmission with high capacity. In consideration of the topological structure of the hybrid MMC,a three-stage start-up control strategy is proposed at first. Then,the fault mechanisms of the single pole-to-ground and the pole-to-pole short circuits on DC-side are analyzed respectively. Furthermore,critical configuration of HBSM and FBSM of hybrid MMC are designed to block the DC-side fault currents reliably. Finally,a benchmarked hybrid MMC-HVDC model in 401-level, ± 320 k V,1 000 MW is established in PSCAD/EMTDC,then the proposed strategies and DC fault blocking are analyzed. The results show that the proposed approaches are valid.