A Single-phase Integrated Battery Charger for EV Based on Dual Three-phase Motor

This paper presents a new solution of single-phase integrated battery charger using dual inner permanent magnet synchronous motor (IPMSM) and dual inverter. Several topologies of previous integrated battery charger are based on the modification of motor windings or converter by using mechanical switches or by adding extra device in order to operate in charging and driving modes. This solution is not viable since it reduces the system performance and lifetime, and increase weight/volume and cost for those requiring extra non-integrated elements. In this proposed system, the charger circuit is constructed directly by connecting the positive side of single-phase grid to one input terminal of PMSM and joining the negative side to one input terminal of another PMSM without the utilization of switch or extra device. The rotor shaft of these two motor are connected to each other via torque coupler. In charging, the dual motor acts as grid harmonic filter and dual inverter performs as a single-phase parallel rectifier. During charging, these two IPMSMs develop torque fluctuation having the same amplitude but being in opposite direction, resulting in the total mechanical torque to be zero at torque coupler. In this charging mode, the system performs under unity power (UPF) with total harmonic distortion (THD) of grid current below 5%. The system topology and control algorithm are presented in this paper. Simulation and experimental results are provided to verify the theoretical analysis.