A Dual‐Voltage 400‐/800‐V Compatible DC Charging System for Electric Vehicles

ABSTRACT This paper addresses the demand for electric vehicle DC charging systems compatible with both 400‐ and 800‐V platforms by designing a cascaded AC/DC converter. The front stage employs a Vienna rectifier, characterized by high efficiency and low harmonic distortion. It provides high‐quality DC power while reducing interference to the grid and equipment. The rear stage is reconfigured based on the conventional LLC resonant converter, featuring series‐connected primary windings and series/parallel output terminals. Switching between 400‐ and 800‐V charging modes is achieved by controlling the switching of relays on the secondary side. Based on the operating characteristics of the Vienna rectifier, midpoint potential balancing control and a computationally efficient two‐level Space Vector Pulse Width Modulation (SVPWM) strategy are adopted. The rear stage utilizes dual‐loop constant voltage/constant current control. Combined with hardware parameter optimization, this effectively enhances the current‐sharing performance of the series/parallel structure. A 3.3‐kW experimental prototype was fabricated and subjected to static and dynamic tests. The experimental results demonstrate that the system can stably output the rated voltages of 400 and 800 V. The startup process is free from overshoot, and the system exhibits excellent dynamic response characteristics under rapid load changes.