Research On MCR-WPT And Its Application In Wireless Charging Of Electric Vehicles

Electrical energy is transmitted from a power source to the load through electromagnetic effect or energy exchange without any electrical contact.This technology is called wireless power transmission(WPT).The application of WPT technology in electric vehicles has the advantages of flexibility,convenience and low maintenance cost,and there is no operation of plugging and unplugging wires,which may not cause electric shock,fire and so on caused by arcing.This technology can be safely used in harsh environments,and is more in line with the future development direction of electric vehicles.The research development trends and working principles of several mainstream WPT technologies is summarized in this paper.The magnetically coupled resonant WPT(MCR-WPT)technology is discussed in detail,and the research status and existing problems of this technology in wireless charging of electric vehicles are presented.The transmission characteristics of the system are analyzed based on the circuit theory and the coupled mode theory model.Among them,the influence of coil parameters on the transmission performance of the system can be analyzed by the circuit theory model.The simulation analysis is carried out in MATLAB software,and the parameters of the transmitting/receiving resonant coil are designed according to the simulation results.A two-dimensional coil model and a three-dimensional system model are established in Maxwell electromagnetic field simulation software based on the model simulation analysis results.Focusing on the influence of skin effect and proximity effect on transmission performance,modeling,and simulation of the electromagnetic field behavior is carried out to optimize the resonant coil structure.In order to reduce the effect of the skin effect and the proximity effect,a copper tube having a thickness of 1 mm is used for coil winding.The car can be charged without stopping by dynamic wireless charging technology.During the vehicle moving,the position of the receiving coil relative to the transmitting coil is horizontally displaced,which will cause the mutual inductance between the coils changed,and the energy transmission of the system affected.To solve this problem,the relationship between mutual inductance and horizontal lateral displacement distance is analyzed.The structural block diagram of the dynamic wireless charging system for electric vehicles is designed.In order to make the system transmit energy stably,the functions and design process of power factor correction circuit,high-frequency inverter topology circuit and power conversion circuit in the system are calculated and explained in detail.Finally,the WPT system is simulated by Simulink.The simulation results show that the designed circuit has certain feasibility.Based on the previous theory and simulation analysis results,a wireless power transmission experimental platform with a transmission power of 500 W is built.Based on this platform,the transmission performance of the system is analyzed when the resonant coils moved at different distances and different horizontal lateral displacements.The experimental results show that when the transmission distance is within the range of 0.2m-0.3m at the working frequency of 13.56 MHz,the system has the advantages of higher transmission power and transmission efficiency,which proves that the coil parameters designed and analyzed in this paper can be stable and work normally.Finally,the wireless battery charging of the battery car is attempted,which provides some reference for the design and application of the wireless charging system of the electric vehicle based on the magnetically coupling resonant wireless power transmission technology.