The modular low voltage DC/DC converter for SOC balancing in electric vehicle

This paper proposes the modular low voltage DC/DC converters (MLDCs) in order to achieve state-of-charge (SOC) balancing of modularized batteries without additional balancing circuits. The MLDCs are substituted with the low voltage converter for EV, PHEV, and HEV located between the high-voltage side battery and low side battery. The MLDCs are composed of a number of modularized buck-converters and battery modules. The charge or discharge current of each battery module can be controlled individually by using the MLDCs to achieve a balanced state as well as increased utilization of the battery capacity. Also, the SOC balancing method for MLDCs is proposed to reduce the equalization time and increase utilization of the battery capacity, considering the demand of load at low-voltage side battery. The proposed system and the SOC balancing method are verified through simulation.