This paper proposes, a bidirectional battery-charger for grid-to-vehicle and vehicle-to-grid operations of electric-vehicles (EV). The DC stage of the proposed converter offers a quadratic buck-boost voltage-gain ratio, which makes it suitable for interconnecting the battery pack unit of EVs with both DC and AC grids as a home EV-charger. A high voltage-gain, low voltage and current stress of switches, high values of utilization-factors (UF) for both directions are achieved. Continuous-input current and common-electrical-ground are preserved and also, the continuous-output current of the proposed converter makes the realization of the pseudo-DC-link method possible for connecting to an AC grid. Consequently, the switching power loss in the DC-AC stage of the EV-charger is reduced, and as a result, it allows the proposed charger to run more efficiently and cooler. The operating principle, steady-state characteristics including the current, voltage stress and UF of the switches, and comparison with other state-of-the-art DC-DC bidirectional converters are carried out in detail. Finally, to verify the theoretical achievements, a 500-W laboratory prototype of the proposed EV-charger is implemented. The EV-charger exhibits the capability for AC and DC regulation and demonstrates peak efficiency of 97.8% in the forward and 97.5% in the backward direction modes of operation.

Keywords