桥臂复用型模块化多电平换流器的拓扑及控制研究

Research on Topology and Control of Arm Multiplexing Modular Multilevel Converter

针对模块化多电平换流器(modular multilevel converter,MMC)的轻型化需求,提出一种具备子模块高利用率的桥臂复用型模块化多电平换流器(arm multiplexing MMC,AM-MMC)。通过将相单元划分为上桥臂、复用桥臂和下桥臂,并利用桥臂切换开关对桥臂进行复用,AM-MMC可有效提高子模块利用率、降低子模块装配数量。为了避免桥臂切换开关的动态均压问题,设计确保AM-MMC在上、下桥臂复用模式之间平稳切换的模式切换策略。此外,根据AM-MMC拓扑特点,设计最近电平逼近调制和分段脉宽调制策略,以满足其在高压直流输电和中低压直流配用电领域的调制需求。基于Matlab/Simulink的仿真结果和物理实验结果表明,AM-MMC能够顺利完成交直电压变换与能量传输,且运行效果良好。与常规MMC相比,所提AM-MMC的子模块利用率提升至66.7%,子模块装配数量降低25%,有效实现了轻型化目标。

For the light weight requirement of modular multilevel converter(MMC),an arm multiplexing MMC(AM-MMC)with high utilization of submodules was proposed.By dividing phase unit into upper,multiplexed and lower arms,and multiplexing arms via arm switches,AM-MMC could effectively improve the utilization of submodules and reduce the quantity.In order to avoid the challenge of dynamic voltage equalization for arm switches,a mode switching strategy which could ensure smooth switching between upper and lower arm multiplexing modes of AM-MMC was designed.In addition,based on the topology features of AM-MMC,nearest level modulation and sectionalized PWM modulation strategies were designed to satisfy its application in HVDC as well as medium and low voltage DC distribution.Simulation results based on Matlab/Simulink and experiment results reveal that AM-MMC can achieve AC-DC voltage conversion and energy transmission successfully,and possesses excellent operating performance.Compared with the conventional MMC,the submodule utilization of the proposed AM-MMC increase to 66.7%while the quantity decrease by 25%,so the target of light weight is realized effectively.