基于线性自抗扰控制的MMC环流抑制策略

Circulating Current Suppressing Strategy for Modular Multilevel Converter Based on Linear Active Disturbance Rejection Control

基于模块化多电平换流器的柔性直流输电MMC-HVDC(high voltage direct current based on modular multi-level converter)技术在世界上已获得广泛运用,但换流器桥臂环流的存在影响MMC的工作特性,成为制约其发展的关键因素。提出了一种新的MMC环流抑制策略:首先设计了基于二阶广义积分器的滤波器,快速、准确地提取桥臂环流中的2次谐波分量;其次设计了基于线性自抗扰控制的环流抑制控制器CCSC(circulating currentsuppressing controller)对所提取的2次谐波分量进行抑制,与现有的PI环流抑制控制器相比,无需依赖环流精确的数学模型,并且解决了采用自抗扰控制的环流抑制控制器参数过多、整定困难的问题。最后,在PSCAD/EMT-DC仿真平台中搭建了21电平MMC-HVDC的电磁暂态仿真模型,通过仿真验证了所设计环流抑制控制器的有效性。

The technology of high voltage direct current based on modular multilevel converter（MMC-HVDC）has beenwidely used around the world. However,the working performance of MMC is affected by the existence of arm circulatingcurrent,which becomes a key factor that restricts its development. In this paper,a new circulating current suppressingstrategy for MMC is proposed. Firstly,a filter based on a second-order generalized integrator is designed,which canquickly and accurately extract the second-order harmonic components of arm circulating current. Secondly,a circulat-ing current suppressing controller（CCSC）based on linear active disturbance rejection control is designed to suppressthe extracted second-order harmonic components. Compared with the CCSC based on PI control,the designed CCSCdoes not depend on the exact mathematical model of circulating current;meanwhile,it also solves the problems of toomany design parameters associated with the CCSC based on active disturbance rejection control as well as difficult tun-ing. Finally,an electromagnetic transient simulation model of 21-level MMC-HVDC is built in PSCAD/EMTDC. Simula-tion results verify the effectiveness of the designed CCSC.