半桥–全桥子模块混合型桥臂复用MMC的拓扑及故障穿越策略研究

Research on Topology and Fault Ride-through Strategy of Hybrid Arm Multiplexing MMC Composed of HBSMs and FBSMs

为了实现模块化多电平换流器(modularmultilevel converter,MMC)的轻型化并使其具备直流短路电流阻断能力,文中针对桥臂复用型MMC(armmultiplexingMMC,AM-MMC)独特的桥臂结构,提出两种由半桥子模块(half bridgesubmodule,HBSM)和全桥子模块(fullbridge submodule,FBSM)构成的混合型AM-MMC(hybrid AM-MMC,HAM-MMC):FHF型和HFH型HAM-MMC。以直流双极短路故障为例,文中对两种HAM-MMC的故障特性进行研究,推导故障电流表达式,分析FBSM装配比例,并提出相应的故障穿越策略。与HBSM和FBSM按1:1比例构成的常规混合型MMC相比,所提两种HAM-MMC均具备器件成本优势,且HFH型HAM-MMC可将FBSM的装配量降低50%。基于Matlab/Simulink的仿真结果表明,FHF型和HFH型HAM-MMC均可顺利完成交直电压变换与能量传输,且在直流短路故障发生后能够快速清除故障电流并阻断交流侧馈流。在推进换流站轻型化的同时,所提HAM-MMC可有效降低为实现直流故障穿越而带来的附加投资。

For the light weight target of modular multilevel converter(MMC)and to equip it with the ability of blocking DC short-circuit current,two hybrid arm multiplexing MMCs(HAM-MMC)named FHF-HAM and HFH-HAM composed of half bridge submodules(HBSM)and full bridge submodules(FBSM)were proposed,aiming at the unique arm structure of AM-MMC.Taking DC bipolar short-circuit fault as an example,fault characteristics of the two HAM-MMCs were studied,fault current expressions were derived,assembly proportion of FBSM was analyzed,and relative fault ride-through strategies were proposed.Compared with the conventional hybrid MMC composed of HBSMs and FBSMs in equal proportion,the two HAM-MMCs both possess device cost advantage,and the FHF-HAM can reduce the quantity of FBSMs by 50%.Simulation results based on Matlab/Simulink reveal that HFH-HAM and FHF-HAM can not only successfully achieve AC-DC voltage conversion and energy transmission,but also clear fault current quickly and block AC feeding current after the DC short-circuit fault.At the same time as promoting the light weight of MMC,the proposed HAM-MMCs can effectively reduce the additional investment for DC fault ride-through.