Four-Leg Soft-Switched Active Rectifier for Non-Isolated EV Chargers

A four-leg active rectifier that could be implemented as a grid interface power-factor correcting (PFC) component of a two-stage non-isolated on-board electric vehicle (EV) charger is proposed in this paper. The analyzed converter leverages existing three-phase topology by extending it to work also in a four-wire configuration, allowing to control the current in the neutral conductor. The control algorithm is performed in a dqδσ reference frame, which is generated through the introduction of a modified Clarke-Park transformation that exploits the differential and common mode signal decomposition to decouple the neutral current control and the regulation of the common mode voltage. Moreover, a discrete Variable Frequency Critical Soft Switching (VFCSS) technique is used to increase the efficiency of the converter by maintaining soft-switching operation. The proposed topology and control scheme are verified through a simulated model in PLECS. Simulation results have been reported for both balanced and unbalanced three-phase scenarios, showing that the fourth leg can be controlled to generate different current set-points in order to adapt to the three-phase currents.