Research On Electromagnetic Safety And Shielding Technology Of Resonant Wireless Power Transmission System

As a new power transmission method,wireless power transmission technology is more convenient and flexible than the traditional plug-in type.It is not easy to be affected by the weather and causes leakage,no wear,stronger operability,and broad application prospects.And green power supply provides a new method.However,with the continuous development of wireless power transmission technology,people began to pay attention to the issue of electromagnetic radiation for human safety.Therefore,this thesis mainly studies the influence of electromagnetic radiation on the surrounding human body when the wireless power transmission system is working,and then studies the shielding technology for electromagnetic radiation that exceeds the prescribed limits,and simulates the material,shape,thickness and position of the shielding device.Find a better shielding method,so that the electromagnetic radiation of the system to the human body is reduced below the safety limit.The research contents of this thesis include:(1)The mathematical model of wireless power transmission system is established by using coupled mode theory and circuit theory respectively,and the expression of system transmission efficiency is derived.The analysis method of electromagnetic environment and the coupling mechanism between resonance system and human body are analyzed to provide theoretical basis for the later research.Add shielding device to the system,and use ANSYS Maxwell finite element simulation software to compare the structural parameters and magnetic field distribution of the two models before and after shielding.The results show that the addition of shielding devices can enhance the magnetic field strength in the coupling area and limit magnetic leakage.At the same time,it is concluded that the material,position and shape of the shielding device will affect the structural parameters of the system and the distribution of the electromagnetic field.(2)Based on the wireless power transmission system without the addition of shielding devices,the electromagnetic safety of the human body around the resonance coil is studied.Use 3DS Max 3D modeling software to build a human body model containing the main organs(brain,heart,lung,liver,kidney,stomach).After importing ANSYS Maxwell software,simulate the human body and the resonance coil at different distances,different positions,and different states electromagnetic safety situation under the current situation,and compared with the ICNIRP guidelines anddomestic derived guidelines.The results show that when the distance between the human body and the coil is 20 cm,the magnetic induction intensity of the human body standing around the coil(front-facing,back-facing,side-facing coil)and lying on the coil directly above the coil exceeds the limit value stipulated in ICNIRP guidelines and domestic derived guidelines.(3)The shielding technology is researched on the part that exceeds the limit,and the materials,thickness and placement of the shielding device are studied respectively to determine the optimal size and optimal position of the shielding device.The simulation results show that although the shielding devices under different materials can reduce the magnetic induction of various organs of the human body,they do not reduce it to below the safety limit.On the basis of saving the amount of shielding materials,when using 4mm thick ferrite shielding,the magnetic induction intensity of each organ lying directly above the coil can be reduced to below the safety limit.When the vertical shield is added on the basis of the horizontal ferrite shield,the leakage magnetic field on the side of the coil can be reduced,and the magnetic induction intensity of the organs standing around the coil can be reduced below the safety limit.