An Integrated Electrolytic Capacitorless Onboard Charger for Electric Vehicles

Abstract

In this paper, an integrated electrolytic capacitorless onboard charger is proposed for electric vehicles, which consists of a phase-shift full-bridge (PSFB) DC/DC converter cascaded by a three-phase four-leg (TPFL) DC/AC converter that realizes both vehicle-to-grid (V2G) and traction operation. An active snubber is connected to the DC link to suppress the voltage spike induced by current mismatch between the two converters and reduce power loss in comparison with passive snubber. By phase shifting the primary H-bridge of PSFB, the DC link voltage is high-frequency pulsating owing to the absence of electrolytic capacitance, which provides ZVS condition for secondary H-bridge and TPFL. To utilize the zero portion of DC link voltage, finite-set model-predictive-control (FS-MPC) and switch-table direct-torque-control (ST-DTC) are adopted to regulate TPFL in V2G operation mode and traction operation mode, respectively. For comparison, a conventional topology with DC link electrolytic capacitor is also studied. Simulation and experiment are conducted to verify the effectiveness of the proposed integrated onboard charger and compare the conversion efficiency with conventional onboard charger.