Multifunctional Onboard Battery Charger for Plug-in Electric Vehicles

This paper presents a multifunctional onboard battery charger for plug-in electric vehicles (PEVs). The proposed battery charger consists of three H-bridge modules including a selective switch, a high-frequency transformer, and inductors. The first duty of the proposed charger is to charge the propulsion battery when PEV connects to the ac grid [onboard charger (OBC)]. In this case, the proposed charger plays a role in ac-to-dc converting with power factor correction. Occasionally, the propulsion battery can supply surplus energy to the grid [vehicle to grid (V2G)]. In this second task, the proposed charger acts as an inverter. The third role is to charge the auxiliary battery via the propulsion battery when PEV is in a driving state [low-voltage dc-to-dc converter (LDC)]. In this case, the proposed charger acts as a step-down converter. In conventional PEVs, the aforementioned functions are done by an OBC and an LDC separately. The proposed charger can implement the three tasks by sharing switches and inductors in an all-in-one system. Thus, the proposed approach can realize a small and light design of the EV battery charger, resulting in the improvement of fuel efficiency. After theoretical analysis, we carry out simulations and experiments using a prototype to verify the validity of the proposed approach.