A Highly Efficient Wide Battery Voltage Range Dual Active Bridge-Based Single-stage Bidirectional EV Onboard Charger Without Low-Frequency Harmonics in the Charging Current

This paper introduces an on-board charger circuit capable of converting 1-phase AC to DC in a single stage. The circuit integrates a PWM 2-level voltage-sourced inverter (VSI) and a dual active bridge (DAB) converter into a unified single-stage structure with the help of a suitably crafted modulation strategy. Single-phase 1-stage topologies are known to suffer from significant double line-frequency ripple in the charging current. The proposed combined pulse-width and phase-shift modulation strategy achieves active power decoupling without any extra circuitry, eliminating the double line-frequency AC ripple in the battery charging current. This also enables the least RMS DAB current trajectory throughout the line cycle while facilitating Zero Voltage Switching (ZVS) for enhanced efficiency. The paper begins by detailing the working principle of the proposed converter, followed by an analytical examination of the modulation strategy. Simulation results indicate a peak power-stage efficiency exceeding 98 % for a 3.6k W J-phase system operating within a battery voltage range of 300V-500V. Experimental validation at 500W demonstrates efficiency levels consistent with the predicted values.