Design-Oriented Analysis and Experimental Validation of a Three-Phase Single-Stage Soft-Switching AC–DC Converter

This article presents a nonmodular three-phase single-stage isolated AC–DC converter with a series resonant tank for unidirectional electric-vehicle battery charging that achieves power factor correction and wide-range soft switching using a variable switching frequency. The proposed converter reduces the active-device count and avoids secondary-side active-bridge control while maintaining high-frequency isolation and soft-switching capability. The proposed topology combines a three-phase bridge front end, grid-side inductors, and a high-frequency three-phase transformer with diode rectification, enabling compact implementation with reduced component count. Closed-form analytical expressions are derived for the input-current ripple, rectified current, transferred power, and zero-voltage switching (ZVS) boundary, providing design-oriented relationships that directly link circuit parameters to achievable power transfer, power quality, and soft-switching margin. These expressions provide practical design guidance for selecting the DC-link voltage, grid-side inductance, resonant components, and switching-frequency range. A 1.5 kW prototype was implemented to validate the analysis and demonstrate both constant-current and constant-voltage (CC/CV) charging capability using the same power stage. Experimental results confirm near-unity power factor with low total harmonic distortion of 3.24%, and sustained ZVS over the designed CC/CV envelope.