模块化多电平换流器改进型子模块拓扑仿真研究

Simulating research of improved topologies of modular multilevel converter

针对模块化多电平换流器高压应用和高电平输出时子模块数量过多问题,研究了堆叠式两电平和多电平输出子模块拓扑特点。在总结不同改进类型子模块拓扑特点基础上,定性比较了各种拓扑在直流侧短路故障时所具有的故障电流抑制能力差异性。针对串联双子模块拓扑,设计了基于全控和半控整流方式的混合充电策略。以改进型拓扑为例,在PSCAD/EMTDC中搭建了两端有源MMC-HVDC系统,对不同子模块拓扑的直流侧故障抑制特性以及串联双子模块拓扑启动策略的有效性进行了分析验证。

Firstly, for the large number of sub module（SM） caused by high voltage applications and high level output of modular multilevel converter（MMC）, cascaded two levels（CTL） and multi-level output SM topologies are studied. Secondly, the characteristics of different types of improved SM topologies are summarized and qualitative comparison of their different DC link fault blocking capability is conducted. Then a hybrid self-startup strategy based on full controlled and half controlled rectifier is designed for the serial connected double sub module topology. Lastly, MMC-HVDC with two active terminals in the PSCAD/EMTDC software is built based on these improved topologies, and DC link fault suppressing characteristics of different SM topologies and the startup strategy are analyzed and verified.