A Hybrid Modular Multilevel Converter with Multiple Common-Mode Voltages Injection Control for Electric Vehicle Applications

The modular multilevel converter (MMC) for electric vehicle applications has been studied in recent years, for its advantages such as high modularity, fault tolerant ability and capability of multi-function (motor drive, cell equalizer and on-board charger) integration. However, during the operation of MMC, specific ac harmonics will be introduced in battery cell currents, reducing battery lifetime. A multiple common-mode voltages injection control method, increasing the frequency of the 2nd order current harmonic and allowing the filtering through smaller filters, is proposed in this paper, to mitigate the negative influence of current harmonics on battery lifetime. To eliminate the effect of injected common-mode components on the ac side, a hybrid MMC topology is also proposed. Simulation results verify the validity of the proposed method and topology.