Current waveforms distribution among electrochemical cells of Modular Multilevel Converters in Battery Electric Vehicles

Abstract

In the context of Battery Electric Vehicles, conventional Voltage Source Inverters (VSI) have been associated with several types of Battery Management System, mainly to balance the state of charge of electrochemical cells and extend their lifetime. Modular Multilevel Converters (MMC) with embedded elementary cells represent a valid alternative, thanks to the possibility of integrating the balancing functionality, ensuring a negligible harmonic content of the output currents and reducing the ringing phenomenon. On the other hand, the MMC topology exposes the cells to a different current waveform, increasing the cells losses in comparison with VSI solutions. This paper analyzes how the cells current waveforms of a MMC topology produce an unbalanced distribution of active power among the cells and evaluates their loss increase with respect to VSI configurations.