一种适用于分数电平MMC的改进分数电平调制策略

A Modified Fractional Level Modulation Strategy for Fractional Level MMC

分数电平模块化多电平换流器(fractional level modular multilevel converter,FLMMC)可有效改善少子模块MMC的电压质量,但在现有分数电平调制(fractional level modulation,FLM)策略下存在开关损耗较高问题。为降低FLMMC的开关损耗,提出了一种包含子模块能量均衡环节和子模块分类投切环节的改进FLM策略。在能量均衡环节,常规子模块和分数电平子模块均参与每次电平变化时的排序与投切,以实现两种类型子模块之间的能量均衡;在分类投切环节,常规子模块和分数电平子模块根据电平是整数或分数分别进行排序与投切,以减少功率器件的开关次数。基于Matlab/Simulink的仿真结果及物理实验结果表明,所提改进FLM策略可显著降低FLMMC的开关损耗,并获得良好的电平倍增效果。

The fractional level modular multilevel converter(FLMMC)can effectively improve the voltage quality of MMC with small quantities of submodules.However,the switching loss of FLMMC under existing fractional level mod-ulation(FLM)strategy is high.In order to reduce the switching loss of FLMMC,a modified FLM strategy including submodule energy balancing segment and submodule classification inserting segment was proposed in this paper.During the energy balancing segment,both the conventional submodule and the fractional level submodule participated in sorting and inserting at the time of each level change,so as to achieve energy balance between the two types of submodules.During the classification inserting segment,the conventional submodule and the fractional level submodule were sorted and inserted separately according to the integral level or the fractional level,so as to decrease the switching times of pow-er devices.Simulation results based on Matlab/Simulink and experimental results reveal that the proposed modified FLM strategy can significantly reduce the switching loss of FLMMC,and obtain excellent effectiveness in level multiplying.