一种适用于架空线柔性直流输电的增强型四电平子模块拓扑

摘要

架空线柔性直流输电技术在高压直流断路器尚未达到大规模商业化应用阶段,采用具有直流故障自清除能力的换流器拓扑具有重要的工程意义.基于改进型子模块的模块化多电平直流输电技术,提出了一种具有直流故障自清除能力的增强型四电平子模块(enhanced four level sub-module,EFLSM),可以独立控制每个电容的投切状态,任意输出3电平到0电平之间的4种电平,与现有的全桥子模块以及箝位双子模块相比,子模块在保证直流故障自清除能力的基础上,每个电容所平摊的半导体器件数有所下降,换流器损耗已接近传统的半桥子模块型模块化多电平换流器的水平.最后,应用电力系统计算机辅助设计和电磁暂态模拟程序软件(power system computer aided design and electric magnetic transient in DC system,PSCAD/EMTDC)搭建时域仿真模型进行仿真计算,验证所提拓扑的有效性.%Voltage source converter based high voltage direct current (VSC-HVDC) technology has not been massively and commercially applied in high voltage DC breakers,it has very important engineering meanings to use converter topology with DC fault self-cleaning capability.In allusion to modular multi-level converter based high voltage DC (MMC-HVDC) technology based on improved sub-module,a kind of enhanced four-level sub-module (EFLSM) with DC fault self-cleaning capability is presented which is able to independently control switching state of each capacitor and output four level among three level and zero level at random.Compared with current full-bridge sub-module and clamped double sub-module,this sub-module can ensure DC self-cleaning capability as well as reduce semiconductor apparatus shared by each capacitor,in addition,converter loss has been close to that of the level of traditional half-bridge sub-modular multi-level converter.In PSCAD/EMTDC,a time-domain simulation model is established to verify validity of the proposed topology.