Performance Improvement of SiC Based Electric Vehicle Charger with an Advanced PWM Method

This paper presents a Silicon Carbide based electric vehicle (EV) onboard charger featuring low switching losses. EV onboard chargers are required to have very high efficiency because of limited space. Most onboard EV chargers deploy a front-end AC-DC converter followed by a DC-DC converter that interfaces the EV battery to the AC grid. In this work, all SiC devices with a switching frequency of 100 kHz are used. A Dual Active Bridge (DAB) is used as a DC-DC stage that meets the requirement of galvanic isolation. A low loss modulation method called 240°-Clamped Pulse Width Modulation (240CPWM) is deployed in the AC-DC stage that yields very high efficiency even at high switching frequency. The total power loss breakdown along with controller design is detailed. Simulation results for 43 kW AC Level 2 onboard EV charger show that 240CPWM improves the combined efficiency of the AC-DC stage followed by the DC-DC stage to 96.7% as compared to 95.7% for conventional space vector PWM (CSVPWM).