An improved control method for MMC capacitor voltage balancing
ZHENG Lianqing
XU Jiangtao
MA Shiqiang
Abstract：The capacitor voltage sorting algorithm is a simple and effective method for equalizing MMC(Modular Multilevel Converter) capacitor voltages.However,the traditional sort algorithm leads to the submodules switched repeatedly.The high switching frequency increases the system loss.Therefore,an improved method is proposed,which can reduce the switching frequency by controlling the sorting frequency.The sorting frequency is the minimum for equalizing voltages that is calculated by the capacitor voltage difference and arm current.So the submodule voltages can be equalized at a low switching frequency.Finally,a MMC simulation model is built in Simulink to compare the two methods before and after the improvement.The simulation resuits show that the improved sorting method can effectively reduce the switching frequency,which the reduction is up to 70％.
Keywords：modular multilevel convertervoltages balancingvariable-frequency sortswitching frequency
Publication Date：2017-01-01
Online Publishing Date：2025-08-15(First online date of this platform, not the publication date of the document)
Pages：6( 112-116,122 )