Research On Electromagnetic Enviroment Safety Of Electric Vehicle Wireless Charging

With the increase of energy crisis and environmental pollution,electric vehicles(EV)have been developed rapidly due to their advantages of zero emissions and low pollution.At present,there are two main charging methods for EV:one is the charging pile method,and the other is wireless charging.Compared with the former,EV wireless charging has the advantages of high safety,flexibility and reliability,which has been widely concerned.The technology of EV wireless charging is based on the principle of electromagnetic induction,so the magnetic field radiation generated during the charging process may be harm to the people in vehicle and the pedestrians around vehicle,and at the same time affect the electromagnetic compatibility of EV.For this reason,it is necessary to study on electromagnetic environment safety of EV wireless charging.The specific contents are as follows:(1)Based on the basic principle of electric vehicle wireless charging system,the transmission performance of four basic compensation topologies for EV wireless charging system were analyzed by using circuit analysis method.Summarizing the advantages and disadvantages of four basic compensation topologies,the topology that transmitting coil adopts inductor-capacitor-capacitor(LCC)compensation method and the receiving coil adopts the compensation method of series capacitor was selected.And the parameters of each component were designed to make its output power as high as 23 kW and transmission efficiency over 95%.(2)In the magnetic field modeling,the finite element software ANSYS Maxwell was used to model and analyze various scenarios of EV static wireless charging.It included the situations that the receiving coil is installed in different positions of the vehicle chassis,and the transmitting coil and the receiving coil are offset.In general,during the EV static wireless charging,people outside the vehicle are more affected by magnetic field radiation than drivers inside the vehicle.When the receiving coil is installed in the middle of the vehicle chassis,since the driver’s position is closer to the center of the resonance coil,the magnetic field strength and magnetic flux density of the driver’s feet have exceeded the safety limit.Compared to the alignment situation,when the transmitting coil and receiving coil are offset by 75 mm,the leakage magnetic field in the space is increased,the magnetic field radiation is more serious,and the system output power is reduced by about 17.7%.(3)Dynamic wireless charging system of EV model was established,the magnetic field radiation to the driver and the change of the magnetic field strength on the vehicle were analyzed.During the dynamic wireless charging process,the maximum value of the driver’s magnetic field strength and magnetic flux density far exceed the specified safety limit.Compared with the moment when the transmitting coil and the receiving coil are perfect alignment,when the receiving coil is in the middle of the two transmitting coils,the influence of magnetic field radiation is greater,so electromagnetic protection measures should be taken for the driver and members in the vehicle.The magnetic field strength is the largest at the chassis of the vehicle,therefore,electromagnetic sensitive components should avoid to be placed near the chassis of the vehicle.