Abstract
Modular multilevel converters with embedded battery cells are suitable candidates to improve the energy conversion efficiency of battery electric vehicles. In this new topology, the series connection of the battery cells is obtained by means of H-bridge modules, allowing the highest flexibility for the discharge and recharge of each individual battery cell. This objective can be achieved in practice only when a suitable control algorithm is designed to control at the same time the generation of the desired output voltages and the state of charge of cells. This paper discusses some aspects of the balancing algorithm of the battery cells including the cross-balancing between the converter's arms and the design of the control loop for symmetric three-phase output voltages. Simulations results applied to a city car confirm the theoretical considerations and illustrate the main features of the proposed control algorithm.