Charging method for the second battery in dual inverter drive systems for electric vehicles

A dual inverter with an open-end winding motor configuration is an attractive method to supply a higher voltage to a motor for electric vehicle (EV) applications. A topology utilizing two isolated dc sources is considered to reap the advantages of reliability and high voltage. Although this design may require two battery chargers, in this study, the use of only one charger to a main battery was considered. The central issue is to charge the secondary battery from the main battery via the motor, whether it is at a standstill or running. The inverter voltage margin remaining after motor torque production determines the charging capacity. The unity power factor operation is shown to be useful to maximize the charging power. Simulations and experiments are presented that show the validity of the proposed scheme.