High Efficiency Bidirectional LLC+C Resonant Converter with Parallel Transformers for Solar-Charged Electric Vehicles

This paper proposes, a new power electronic challenge: the onboard charger should have high efficiency in the grid-to-vehicle (G2V) direction for normal charging power levels (i.e., 6.6 kW) and also high efficiency in the vehicle-to-grid (V2G) direction for much lower solar power levels (i.e., 6.6 kW) and also high efficiency in the vehicle-to-grid (V2G) direction for much lower solar power levels (i.e., <800 W). However, typical onboard charger topologies have low efficiency at light loads. This article proposes a novel bidirectional LLC+C converter to address this challenge. It operates as a full-bridge LLC converter in the G2V direction and a half-bridge LLCC converter with a smaller transformer in the V2G direction. Simulation results show a maximum efficiency gain of 5.1% in the V2G direction compared to the standard full bridge LLC converter.

Keywords: Battery chargers, dc–dc conversion, solar energy, vehicles, Rectifier, Inverter