基于投切交换数优化的MMC均压策略OA

In the control incices of the modular multilevel converter(MMC),the voltage balancing effect of the sub-model and switching frequency of the insulated gate bipolar transistor(IGBTs)impose mutual constraints.To re-duce the switching frequency while maintaining the voltage balancing effect,in this paper a voltage balancing strat-egy based on the optimization switching number is proposed.By analyzing the variation trend of voltage balancing effect and classifying the switching actions of IGBT,it is proposed to use the current arm current value to calculate the the switching number between inserted modules and removed modules.When arm current value is less than the set value and voltage balancing effect of SMs can be achieved in accordnce with modulation variation,the switching number is set to zero.Otherwise the threshold of voltage balancing effect is corrected in accordance with real-time arm current value,and the switching numbers are calculated based on the corrected voltage threshold,the direction of arm current,the corrected number of inserted modules and the sorting results of the submodule voltages.Finally,the trigger pulses are refreshed based on the corrected number of inserted modules and the switching number.This strategy can ensure the stability of voltage balancing at different power levels and,at the same time,reduce effec-tively switching frequency.The effectiveness of the proposed strategy is verified by constructing a simulation plat-form based on RTLAB real-time simulation system.