A Modular-Designed Three-Phase High-Efficiency High-Power-Density EV Battery Charger Using Dual/Triple-Phase-Shift Control

In this paper, an enhancement-mode GaN high-electron mobility transistor (HEMT)-based 7.2-kW single-phase charger was built. Connecting three such single-phase modules to the three-phase grid, respectively, generates a three-phase similar to 22-kW charger with the > 97% efficiency and > 3.3 - kW/L power density, superior to present Si-device-based chargers. In addition to GaN HEMTs with fast-switching transitions yielding high efficiency, the proposed charger employs the dc/dc stage to control the power factor and power delivery simultaneously, yielding little dc-bus capacitance and thereby high power density. To secure the soft switching for all switches within full voltage and power ranges, a variable switching frequency control with dual phase shifts was adopted at high power, and a triple phase shift was employed to improve the power factor at low power. Both control strategies accommodated the wide input range (80-260 VAC) and output range (200-450 VDC). A closed-loop control for the three-phase charger was realized to minimize the output current ripple and balance the power among three single-phase modules. Experimental results validated this design.