Modeling and Control of an Integrated Battery Charger With Split-Phase Machine

Abstract

The battery charging technology is a rapidly developing area in the electric vehicle (EV) industry. The nonavailability of charging stations, longer battery charging times, and range-anxiety are main concerns for EV users. A fast, light, and efficient on-board charger is the need of the hour. Integrated battery chargers (IBC) are a viable solution since it uses the driving circuit (motor and inverter) already present in the EV for charging the battery. IBC using split-phase machine and three-legged inverter is an interesting topology. It has the advantage of using the existing three-phase machine and three-legged inverter. Also, this topology generates zero instantaneous torque while charging the battery. Due to motor winding reconfiguration during charging, even when the grid supply is balanced, the grid currents were found to be highly unbalanced. In this article, a mathematical model of the IBC using a split-phase machine in stationary and rotating reference frame is developed and presented for the first time. Mathematical proof for zero instantaneous torque production while charging the battery is presented. The effects of mutual inductance, $L_{dq}$ along with $L_d$ and $L_q$ , are presented in the rotating reference frame model of the IBC. This is found to make the system unbalanced, and the grid currents represented the in rotating reference frame are found to contain second harmonic components along with the expected dc terms. Using the mathematical model, new feedforward terms have been developed, and used in the control loop with proportional integral controller (PI) and proportional resonant controllers to mitigate grid current harmonics. Exhaustive simulation and experimental results are included for the proposed system.