Research On Bidirectional On-board Charging System Based On Three-phase Interleaved CLLLC Resonant Converter

Under the dual pressure of the energy crisis and environmental pollution,new energy vehicles represented by electric vehicles have developed rapidly.At the same time,energy transfer technology between vehicles and the power grid has gradually become a research hotspot.The traditional on-board charging system can only realize the unidirectional transmission of electric energy from the grid to the power battery.With the increase of applications,the electric energy in the power battery of electric vehicles needs to be released and used in reverse.Therefore,the research on the related technologies of the bidirectional on-board charging system of electric vehicles will inject new power into the development of electric vehicles.Based on the characteristics analysis of the bidirectional on-board charging system of electric vehicles,the bidirectional totem-pole converter and the three-phase interleaved CLLLC resonant converter are used as the front-stage and rear-stage topology of the bidirectional on-board charging system.The working principle and characteristics of the front-stage bidirectional totem-pole converter are analyzed by the voltage state of the power grid.The single-phase equivalent circuit model of the rear-stage three-phase interleaved CLLLC resonant converter is derived by the first harmonic analysis method,and the voltage gain,impedance characteristics,and conditions of realizing zero-voltage switching(ZVS)are analyzed according to the single-phase equivalent circuit.According to the design indicators of the bidirectional on-board charging system,the parameters and magnetic components of the input inductance,DC bus capacitance,and resonant network are calculated and selected.The control strategy of the bidirectional on-board charging system is studied,and the parameters of the voltage loop and current loop controller are derived by establishing the small signal circuit model of the front-stage bidirectional totem pole converter so that the input current and voltage remain in phase.The rear-stage three-phase interleaved CLLLC resonant converter adopts frequency conversion control,which can realize constant voltage and constant current output according to the charging needs of electric vehicles.The simulation model of the bidirectional vehicle charging system is built by using MATLAB/Simulink software.In forward charging mode,the power flows from AC side to DC side;in reverse inverting mode,the power flows from DC side to AC side and outputs 220 V AC power.According to the main circuit parameters,a3.3k W prototype was prototyped,and the experimental results verified the correctness of the design of the bidirectional vehicle charging system.