Design Of LLC Resonant Electric Vehicle On-board Charger

On-board charger of electric vehicle is a power electronic device that is fixedly installed inside the electric vehicle,converting the AC voltage of the power grid into the DC voltage that meets the charging requirements of the on-board battery.The on-board charger circuit structure and control strategy were studied,and an LLC resonant electric vehicle on-board charger has been designed in this thesis.On the basis of working principle of on-board charger studied,a two-stage on-board charger scheme composed of AC-DC converter and DC-DC converter has been designed.A circuit model of Boost-APFC converter and LLC half-bridge resonant converter has been established and simulated,and the feasibility of the scheme has been verified.In order to improve the power factor of the device,an AC-DC converter hardware circuit using Boost-APFC has been designed,and the input AC voltage was converted into the DC bus voltage.A hardware circuit of the DC-DC converter based on LLC half-bridge resonant has been designed,and the DC bus voltage from the front-stage converter was converted into the DC voltage required by the battery.The designed on-board charger mainly includes two-stage power conversion circuit,isolating drive circuit,charging voltage and charging current detection circuit.The design method of circuit parameters has been determined,and the design steps of APFC boost inductor and magnetically integrated transformer have been presented.The two-stage charging PI control algorithm,namely the constant current charging initially and the constant voltage charging subsequently,has been designed.The complementary timing control program of LLC half-bridge resonant converter,the frequency decreasing soft start program and the charging control program of the on-board charger have been written.The prototype of on-board charger based on DSP has been achieved and experimented in the laboratory,and the collected experimental waveforms and tested experimental datas have been analyzed.The experimental result shows that the designed LLC resonant electric vehicle on-board charger can effectively charge the on-board battery.