Onboard Battery Chargers for Plug-in Electric Vehicles With Dual Functional Circuit for Low-Voltage Battery Charging and Active Power Decoupling

Abstract

This paper proposes a single-phase onboard battery charger (OBC) for plug-in electric vehicles, where the low-voltage (LV) battery charging circuit is utilized for an active power decoupling function. The OBC is operated in three different modes by sharing the transformer, switches, and capacitors. For a grid-to-vehicle mode or a vehicle-to-grid mode, the LV battery charging circuit serves as an active filter to eliminate the low-frequency power ripple at the DC link. Thus, the small film capacitors can be employed instead of large capacitors at the DC link. For the third operating mode, where the LV battery is charged from the HV battery, the isolation is provided by the dual active bridge (DAB) DC-DC converter. Since some components in the proposed OBC are used in common, the size and cost of the OBC can be reduced significantly. The simulation and experimental results have verified the validity of the proposed system.