Cost-Effective and High-Power-Density Nonisolated Bidirectional On-Board Charger

Abstract

This article presents a nonisolated, single-stage, bidirectional on-board charger (OBC) for electric vehicles based on a differential Y-rectifier with one phase-inductor per phase, enabling seamless operation on single- and three-phase grids. A straightforward, unchanged modulation, and current-control strategy is retained across 1ϕ/3ϕ operation, yielding mode-invariant device stresses and efficiency, and supporting equal rated power in both configurations. The topology features a markedly reduced component count and a common reference coincident with the high voltage (HV) battery, simplifying gate-drive and sensing circuitry, and lowering isolation requirements in the control path. In addition, the converter integrates a buck-type power pulsation buffer (PPB) that compensates the 2·f_ac ripple otherwise imposed on the battery, thereby allowing a compact energy buffer and high power density. Grid-compliant operation is ensured under U_batt>Û_ac (practically ∼400 V), targeting modern 800 V battery platforms. The proposed converter is tested by means of a hardware prototype rated at 11 kW that operates over 85–256 V_rms, 40–65 Hz, with battery voltages ≥ 400 V (tested up to 850 V). The design achieves 10.2 kW/L power density and peak efficiencies > 97%, with PF ≥ 0.99 and THDi ≤ 5%. Experimental results validate operation in both grid configurations and confirm invariant device rms/peak stresses, identical control, and equivalent efficiency between 1ϕ and 3ϕ operation, establishing a cost-effective, high-power-density alternative to two-stage OBCs.