Onboard battery charger for plug-in electric vehicles with constant current / constant voltage control and active power decoupling

Abstract

This paper presents a single-phase onboard battery charger (OBC) with constant current/constant voltage control and active power decoupling for plug-in electric automobiles. The onboard battery charger has three modes: grid-to-vehicle (G2V), which charges the high voltage batteries from the grid; vehicle-to-grid (V2G), which the high voltage (HV) batteries deliver a portion of the stored energy back to the grid; and High voltage to low voltage (H2L) mode, which charges the low voltage (LV) or auxiliary battery from the high voltage (HV) batteries. An active power decoupling function is implemented using the LV battery charging circuit. The LV battery charging circuit acts as an active filter to minimize low-frequency power ripple at the DC link in G2V and V2G modes, and as a converter to store energy into the auxiliary battery in H2L mode. Both HV and LV batteries are controlled by Constant current/constant voltage control method for charging to avoid overheating and the float voltage limited to avoid over-charging. LCL filter is adopted to improve the total harmonic distortion (THD) and power factor (PF). The onboard battery charger system's validity has been confirmed by simulation results.