不平衡电网电压下抑制MMC子模块过电压的调制比设计方法  

Design method of modulation radio for suppressing overvoltage of MMC sub-module under unbalanced grid voltage

作　　者：王鋆鑫 杨玉坤[1] 许建中[1] WANG Yunxin;YANG Yukun;XU Jianzhong(State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources,North China Electric Power University,Beijing 102206,China)

机构地区：[1]华北电力大学新能源电力系统国家重点实验室,北京102206

出　　处：《电力自动化设备》2023年第8期141-147,共7页Electric Power Automation Equipment

基　　金：中央高校基本科研业务费专项资金资助项目(2020MS003)。

摘　　要：模块化多电平换流器(MMC)在调制比为1.414的稳态运行条件下,子模块电容电压波动的基频分量将被抑制到0;但在电网电压不平衡时基频分量会变大,导致子模块电容电压波动显著增加。为抑制电网电压不平衡时的电容电压波动,基于桥臂功率分析了稳态和电网电压不平衡条件下子模块的电压波动特性,提出了一种适用于混合型MMC的调制比设计方法,该方法以桥臂瞬时功率的基频分量为抑制目标,综合考虑了不平衡电网电压下的三相子模块电压波动特性,通过改变直流电压指令值从而改变运行调制比,避免了故障时子模块发生过电压的情况。在PSCAD中搭建混合型MMC模型,通过对3种电网电压不平衡工况进行仿真分析,验证了所提方法的有效性。Under the steady-state condition of modular multilevel converter(MMC)with the modulation radio of 1.414,the fundamental-frequency component of sub-module capacitor voltage fluctuation can be suppressed to zero.However,when the grid voltage is unbalanced,the fundamental-frequency component may increase,resulting in a significant increase in the sub-module capacitor voltage fluctuations.In order to suppress the capacitor voltage fluctuations when the grid voltage is unbalanced,the voltage fluctuation characteristics of sub-modules under steady-state and unbalanced grid voltage conditions are analyzed based on the arm po-wer,and the modulation radio design method suitable for hybrid MMC is proposed.It takes the fundamental-frequency component of the instantaneous arm power as the suppression target,the voltage fluctuation cha-racteristics of the three-phase sub-modules under unbalanced grid voltage are comprehensively considered,and the operation modulation radio is changed by changing the DC voltage reference to avoid sub-module overvoltage during faults.The hybrid MMC model is built in PSCAD,and the effectiveness of the proposed method is verified by simulation analysis of three types of grid voltage unbalanced conditions.

关 键 词：混合型MMC 不平衡电网电压 电容电压波动 调制比 

分 类 号：TM46[电气工程—电器]