Research And Design Of Single-phase And Three-phase Compatible Isolated On-board Charger

Global energy shortages and pollution have worsened in recent years.To solve the energy and environment problems caused by fuel vehicles,electric vehicles are becoming the first choice for the development of the automobile industry.On-board charger is a key component of electric vehicles.Electric vehicles draw energy from the AC network through the on-board charger,and charge the power battery after electric energy conversion.Traditional on-board chargers usually use single-phase AC input,charging time is long and output power is low.To meet the requirements of AC input of different specifications and to be suitable for different power occasions,a single-phase and three-phase compatible input on-board charger is designed.In order to facilitate the overall optimization design of the on-board charger circuit,the single-phase and three-phase compatible on-board charger structure proposed in this paper is composed of two isolated circuits.Based on the three-phase six-switch Power Factor Correction(PFC)circuit,by switching on and off,the front stage is transformed into a cascade topology of a totem-pole PFC circuit and a boost circuit.In the single-phase or three-phase input condition,the front-stage PFC circuit can uniformly output 700 V DC bus voltage.The rear stage is a full-bridge LLC resonant converter,which can obtain a wide range of output voltages to charge the power battery.For the front-stage PFC circuit,the circuit working principle under single-phase and three-phase input conditions are analyzed and modeled respectively.According to the design indexes of the on-board charger,the input inductance and DC bus capacitance of the compatible components are designed,and the optimal value is determined to realize the requirements of the same circuit working at different input voltages.According to the established model and the calculated main parameters,the transfer function of the PFC circuit under each working condition is derived.The double closed-loop control strategy is adopted to realize the input current and input voltage in the same phase and the stable output of DC bus voltage.Focusing on the full-bridge LLC resonant converter,an equivalent model of the circuit is developed by fundamental analysis,the voltage gain function is derived.and the resonant parameters are designed so that the circuit can realize soft switching.The simulation model of the whole machine circuit is created using MATLAB software and the results confirm the feasibility of the system.Based on the analysis of the main parameters and control strategy of the system,an experimental prototype of the single-phase and three-phase compatible on-board charger is produced.Experimental results showed that the prototype could perform the proposed functions,confirming the correctness of the theoretical analysis and topology design.