Single-phase and three-phase compatible isolated on-board charging system

Abstract

Aiming at the problem caused by the fact that traditional on-board charging systems (OBC) usually use a single form of AC input, this research suggests a suitable isolated OBC for single-phase and three-phase power sources. It adopts a two-stage structure. The front stage can switch between different input modes. Using a single-phase AC input mode, the front stage is a totem pole bridgeless cascade Boost circuit for power factor correction (PFC). It can be switched to a three-phase six-switch PFC circuit in a three-phase AC input mode. A full-bridge LLC resonant converter serves as the rear stage. The system adopts a double closed-loop control strategy and a mixed control mode that consists of pulse width modulation (PWM) and pulse frequency modulation (PFM). In either the single-phase or three-phase AC input mode, the front stage PFC circuit can output a 700 V DC bus voltage, and keep the input current and input voltage in phase. It is possible to achieve soft switching in the rear stage resonant converter, and to output a wide range of voltage to charge the power battery. According to a theoretical analysis, a system simulation model is built and an experimental prototype of the OBC is produced. The accuracies of the simulation and the theoretical analysis are confirmed by experimental findings.