Research On Compound Structure Wireless Charging Technology Of Electric Vehicle

With the introduction of the "carbon neutrality and carbon peak"-dual-carbon strategy,electric vehicles will undoubtedly be an important part of the implementation of this strategy.However,there are some problems in the charging of electric vehicles.The charging of electric vehicles requires a large number of charging stations,occupying a large amount of land area,and the safety is not high.Therefore,in recent years,wireless power transmission technology has emerged to be applied to the field of electric vehicles,which has the advantages of energy economy,environmental friendliness,and convenient charging.Because its power and load are transmitted through electromagnetic energy,it can avoid unnecessary safety hazards caused by direct connection of wires,such as unreliable insulation,aging and deformation of joints,electric sparks in contact gaps,etc.,with safe,convenient and reliable charging advantage.In the field of electric vehicles,this article applies the magnetic coupling resonance wireless power transmission technology,and conducts the following researches:First,the traditional magnetic coupling resonant wireless charging system is analyzed,its working principle and basic structure are introduced,and then the basic high-frequency inverter and loosely coupled transformer models are introduced.After analyzing and deriving the compensation capacitance and output power of four basic second-order wireless power transmission(Inductive Coupled Power Transmission,ICPT)system compensation topologies,and studying their transmission and operating characteristics,the LCL topology network is derived.The high-end topology can better and stably meet the charging characteristics of existing electric vehicles.Furthermore,a composite structure ICPT system is proposed and detailed design is carried out.The basic structure is designed,the high-frequency inverter is selected,and the composite structure topology with three variable compensation capacitors on the secondary side is proposed.The variable compensation capacitor is analyzed.It is controlled by the Magnetic Energy Regeneration Switch(MERS).The basic principle,structure and mathematical model of MERS are analyzed,and the characteristics of its equivalent capacitive reactance are analyzed.The PSIM simulation software was used to simulate and analyze MERS,and the results verified its equivalent capacitive reactance characteristics,thus showing a complete wireless charging system.Then,after analyzing the charging characteristics of the electric vehicle battery,the system operating characteristics of the LCL-composite magnetic coupling resonant ICPT circuit based on the variable compensation capacitor controlled by MERS were studied,including the constant current characteristics of the transmitter,the current amplification characteristics,Zero voltage switching characteristics,constant voltage and constant current output characteristics of the system,and maximum power output characteristics.A simulation platform was built in Matlab/Simulink.The simulation results showed that after switching the resistors,the current change rate was 0.07% in the constant current mode;and the voltage change rate was 1.45% in the constant voltage mode.In the maximum power mode,the power factor stabilizes at about0.92 after the mutual inductance coefficient changes.It shows that the system can better and flexibly meet the needs of wireless charging for electric vehicles.Finally,a set of experimental equipment was built,and the analysis of the results showed that in the constant current mode,the average rate of change of the output current at the receiving end did not exceed 1%;in the constant voltage mode,the average rate of change of the output voltage at the receiving end did not exceed 1.5%.It fully verified the correctness of the theoretical analysis and plays a vital role in the development of electric vehicles.