基于辅助子模块的MMC输出电流谐波优化控制方法  

Harmonic Optimization Control Method of MMC Output Current Based on Auxiliary Sub-module

作　　者：荣飞[1] 孙宗卿 徐爽 潘烙 RONG Fei;SUN Zongqing;XU Shuang;PAN Luo(College of Electrical and Information Engineering,Hunan University,Changsha 410082,China)

机构地区：[1]湖南大学电气与信息工程学院,长沙410082

出　　处：《高压电器》2023年第5期154-162,共9页High Voltage Apparatus

基　　金：国家自然科学基金(51977070)。

摘　　要：基于半桥结构的模块化多电平变流器(modular multilevel converter,MMC)因其具有功率大、电压等级高等特点,在柔性直流输电系统中被广泛应用。与载波移相调制(carrier phase shift modulation,CPS-PWM)相比,最近电平逼近调制(nearest level modulation,NLM)具有控制简单,开关频率低的显著优势。但在输出电平较少时,NLM调制输出电流谐波畸变率较大。因此,文中在传统MMC的每个桥臂中串入1个全桥子模块,控制该全桥子模块的电容电压为半桥子模块的1/2,以增加MMC输出电平数。对NLM调制策略进行改进,改进后的调制策略可以实现半桥和全桥子模块的平衡控制,并在此基础上,提出了一种降低子模块开关频率的方法。最后,在MATLAB/Simulink中搭建了详细的仿真模型,仿真结果验证了文中MMC拓扑和改进NLM调制策略的有效性。Modular multilevel converter(MMC)based on half bridge structure is used widely in flexible DC transmission system(VSC-HVDC)due to its such features as high power and high voltage level.Compared with carrier phase shift modulation(CPS-PWM),the nearest level modulation(NLM)has the advantages of simple control and low switching frequency.However,in case of less output level,the harmonic distortion rate of NLM modulation output current is large.Therefore,a full bridge sub-module is connected in series in each bridge arm of traditional MMC in this paper,the capacitive voltage controlling the full bridge sub-module is 1/2 that of half bidge sub-module in order to increase the output levels of MMC.The NLM modulation strategy is improved and the improved modulation strategy can achieve the balance control of half bridge and full bridge sub-modules.On this basis,a method to reduce the switching frequency of sub modules is proposed.Finally,a detailed simulation model is set up in MATLAB/Simulink.The effectiveness of MMC topology and improved NLM modulation strategy are verified by the simulation result.

关 键 词：模块化多电平变流器 最近电平逼近调制 电容电压平衡 开关频率 

分 类 号：TM46[电气工程—电器]