Research On Optimization Of Wireless Charing Magnetic Coupling Mechanism And System Control Strategy For Electric Vehicle

As a new type of renewable energy vehicle,electric vehicles have gradually replaced fuel vehicles into people's lives because of their advantages of cleanliness and nonpollution.However,the charging problem of EV batteries has become the main technical bottleneck restricting their further development.Nowadays,most electric vehicles still use the traditional wired charging mode.The factors such as slow charging and short supply of charging piles are putting forward higher requirements for charging technology of electric vehicles.Wireless charging technology is a new charging technology based on radio power transmission technology,which has the advantages of safety,flexibility and efficiency.However,its charging efficiency and stability still need further study.In view of the shortcomings of wireless charging technology in charging efficiency and transmission stability,on the one hand,this paper optimizes the magnetic coupling mechanism of wireless charging system to improve transmission coupling coefficient and transmission efficiency;on the other hand,frequency conversion control method is used to track the maximum transmission efficiency of wireless charging system to improve the stability of the system when transmission conditions change.Firstly,the radio power transmission system is equivalent to a two-port network with mutual inductance components,and the compensation capacitance of the original side and the secondary side in the resonant state is derived from the point of view of the input impedance of the system,and the main topology is determined.The mechanism of frequency splitting and the effect of equivalent load and coupling coefficient on transmission characteristics are analyzed from a mathematical point of view.Then,the core structure of DD coil is optimized by means of finite element simulation software ANSOFT.Firstly,the expression of coupling coefficient of DD magnetic coupling mechanism is deduced,and the coupling coefficient is analyzed and optimized.After that,four core structures with different areas are simulated to verify the optimization effect.In order to reduce the weight of the magnetic core,the strip core structure is proposed to replace the flat core structure,and the simulation is carried out.Finally,the relationship between the coupling coefficients of round square coils and DD coils and the shape coefficients of coils is compared.Subsequently,in order to solve the problem that the power transmission characteristic curve changes with the transmission state at any time in the process of wireless charging,a frequency tracking control method is proposed.Compared with the perturbation method,the simulation results show that the parameters of particle swarm optimization are better than the perturbation method.When the coupling coefficient mutates,it can accurately track the optimal operating point of the system.Finally,a wireless charging experiment system is built and tested.Firstly,the optimization experiment of the magnetic coupling mechanism is carried out.The experiment shows that the optimized magnetic coupling mechanism in this paper improves the transmission efficiency of the system on the basis of retaining the advantage of anti-offset of DD coil.Secondly,the experiment of wireless charging frequency control is carried out.The experimental results show that the proposed control method can make the wireless charging system quickly and accurately find the new optimal operating point after the transmission state changes.