Study of On-board Bidirectional AC/DC Converter Based on Non-differential Beat + PFM Frequency Control

With the increasing scarcity of traditional energy sources and the worsening of environmental pollution, electric vehicles are beginning to connect to the power grid on a large scale, and the requirements for on-board AC/DC chargers have been developed in the direction of high-efficiency, high-power density, and bi-directional charging and discharging. Aiming at the problems of low efficiency and insufficient system dynamic response performance of the current on-board AC/DC charger in realizing the bidirectional energy transmission from the vehicle network, a topology using staggered-parallel totem pole PFC in the front stage and CLLC resonant converter in the back stage is proposed. Based on the topology, the shortcomings of the traditional proportional-integral controller in current tracking control are analyzed, and a composite control strategy of differential beat-free control + PFM inverter control is proposed. This control strategy uses the front stage current inner loop with no differential beat current prediction control and the back stage with PFM inverter control, which can realize the full range of soft switching and accelerate the dynamic response of the system while improving the efficiency.