基于改进算法的MMC电容电压平衡策略  

MMC Capacitor Voltage Balance Strategy Based on Improved Algorithm

作　　者：吕习超 胡付有 王荣超 李晓霞 曾子安 樊友平[2] LYU Xi-chao;HU Fu-you;WANG Rong-chao;LI Xiao-xia;ZENG Zi-an;FAN You-ping(Liuzhou Bureau of China Souther Power Grid Co.,Ltd.,EHV Transmission Company,Liuzhou 545000,China;School of Electrical Engineering and Automation,Wuhan University,Wuhan 430072,China)

机构地区：[1]中国南方电网有限责任公司超高压输电公司柳州局,广西柳州545000 [2]武汉大学电气与自动化学院,武汉430072

出　　处：《电力学报》2021年第6期491-497,共7页Journal of Electric Power

基　　金：“南方电网乌东德电站送电广东、广西特高压多端柔性直流示范工程”项目研究成果。

摘　　要：基于电压源型换流器的高压直流输电采用全控器件IGBT,又称为柔性直流输电,其中模块化多电平换流器(modular multilevel converter,MMC)技术具有开关频率低、谐波少、方便拓展等特点,现已成为学者广泛关注的热点,对其子模块均压控制则是该技术的关键。通过对MMC结构进行深入分析,提出了一种改进的电容电压平衡方法。该方法首先确定电压参考值和允许的最大电压波动范围,然后对比子模块电容电压与电压参考值的大小,最后在充放电过程中根据线路运行需求分区投入MMC子模块,对电压进行补偿或削减,从而保证电容电压的稳定,使输出波形恒定。在此过程中,因减少了MMC子模块随着电流波动而产生的反复投切排序的过程,大大减小了电力电子器件的损耗,降低了运行成本。与常规电容电压控制排序法相比,所提方法减少了电容电压的比较次数,可以大大降低IGBT器件的开关频率,同时也能在线路功率发生突变时,快速平衡电容电压。最后在PSCAD中搭建了仿真模型,验证了所提出方法的准确性。HVDC transmission based on voltage source converters adopts fully-controlled device IGBT,also known as flexible direct current transmission.Among them,modular multilevel converter(MMC)technology has the characteristics of low switching frequency,less harmonics,and convenient expansion,which is becoming the hotspot of scholars’wide attention.The pressure equalization control for the sub-modules is the key of MMC technology.An improved capacitor voltage balance method through an in-depth analysis of the MMCstructure was proposed.This method firstly determines the voltage reference value and the maximum allowable voltage fluctuation range,and then compared the capacitance voltage of the sub-module with the voltage refer⁃ence value.At last,during the charging and discharging process,the MMC sub-modules were put into divisions according to the line operation requirements,and the voltage was compensated or reduced.To ensure the stabili⁃ty of the capacitor voltage and make the output waveform constant.In this process,because the repeated switch⁃ing and sequencing process of MMC sub-modules with current fluctuations was reduced,the loss of power elec⁃tronic devices is greatly reduced,and the operating cost is reduced.Compared with the conventional capacitor voltage control sequencing method,the number of comparisons of capacitor voltage was reduced in the proposed method,and the switching frequency of IGBT devices could be greatly reduced.At the same time,it could quick⁃ly balance the capacitor voltage when the line power changes suddenly.Finally,a simulation model was built in PSCAD to verify the accuracy of the proposed method.

关 键 词：高压直流输电 模块化多电平换流器(MMC) PSCAD 电容电压控制 

分 类 号：TM561[电气工程—电器]