A battery lifetime improved control strategy of modular multilevel converter for electric vehicle application

The application of modular multilevel converter (MMC) in electric vehicle (EV) system is being studied in recent years as one of the emerging research topics, for its various advantages such as high modularity, fault tolerant capability, high quality output and the ability to integrate function of motor drive, on-board charger and cell equalizer. However, specific ac current harmonics introduced by operation of MMC will speed up battery degradation and are harmful to battery lifetime. In past researches on MMC in EV, there is no related study solving this problem. In this paper, an improved control method of MMC based on second order circulating current injection is proposed, mitigating the negative influence of current harmonics on battery lifetime, without increasing hardware cost. Simulation results in MATLAB/Simulink verify the effectiveness of proposed method.