不平衡交流电网模块化多电平变流器特性分析及环流抑制方法  

Characteristic Analysis and a Circulating Current Control Method in Modular Multilevel Converters under Unbalanced Grid Conditions

作　　者：李金科[1] 金新民[1] 吴学智[1] 荆龙[1] 武文 王帅 王小星 

机构地区：[1]北京交通大学国家能源主动配电网技术研发中心,北京市海淀区100044 [2]北京电动车辆协同创新中心,北京市海淀区100044

出　　处：《中国电机工程学报》2017年第12期3535-3544,共10页Proceedings of the CSEE

基　　金：北京市科技计划项目(Z161100000716003)~~

摘　　要：高压直流输电系统中的模块化多电平变流器的安全稳定运行是当前的研究热点。当交流侧出现不平衡时,通常需要对环流及直流侧脉动分别进行控制。因此,针对不平衡交流电网的情况,首先利用桥臂瞬时功率方程分析直流侧波动状态;其次,再通过不平衡下的调制函数及子模块端口电压方程,推导出整个桥臂模块电压波动表达式及环流表达式。分析得到正、负、零序2倍频波动分量贯穿桥臂,以此提出一种无需正负序分离和坐标变换的分相控制的环流抑制策略,以同时消除桥臂环流及直流电流的脉动。最终,通过傅里叶分析对不平衡下的系统特性进行了验证,并利用Matlab及实验平台对所提出的控制策略进行了仿真和实验验证。Safe and stable operation of modular multilevel converters （MMCs） used in high voltage direct current systems （HVDC） is concerned. The circulating current and DC power fluctuation need to be controlled respectively under unbalanced grid conditions. Firstly, the DC power fluctuation of the whole bridge was analyzed by instantaneous power equations under unbalanced voltage conditions. The capacitor fluctuation and circulating current components were analyzed by the modulation function and submodule port voltage equations. Due to the double line frequency components of positive, negative and zero sequences flowing the whole bridge, thus, a circulating current suppression strategy of individual phase control based on theoretical analysis was proposed. The separate control of positive and negative sequence components and the coordinate transformation were avoided by this method. It can not only suppress the circulating current, but also eliminate the DC current ripples. Finally, the system characteristics under unbalanced grids was analyzed and verified by the Fourier analysis, the control strategy was tested by utilizing the Matlab simulation and experiment platform.

关 键 词：模块化多电平变流器 不平衡电网电压 系统特性 环流抑制 

分 类 号：TM46[电气工程—电器]