Research On Safety Issues Of Electrical-Field Coupled Wireless Power Transfer System

Electrical-field Coupled Power Transfer(ECPT)technology makes use of high frequency electric field to transfer power from a source to loads wirelessly.Due to the advantages of design flexibilities,low electromagnetic radiation and no eddy current losses,ECPT technology has been applied in many field such as electric vehicle,under water detection,biomedical implants.However,the plate voltage of ECPT system needs to be amplified to transfer power effectively.In some high-power application fields,the plate voltage may reach several thousand volts,this makes the safety issues of ECPT technology a matter of great concern.On one side,the high plate voltage will cause the induced voltage on the metal conductor placed around the coupling plates,on the other side,strong electric field radiation excited from coupling plates will threaten human health.In order to solve the issues of electrostatic induced voltage and electric field radiation generated by the coupling plates,circuit theory,electromagnetic theory and power electronics technology are cohesively applied.This paper aims to ensure the safety of ECPT system,and the main research contents as follows:(1)Establishment of equivalent circuit for electric shock.By comparing and analyzing the inverter circuits and resonant networks used in ECPT system,this paper takes the full bridge series resonant ECPT system as the research object.In order to analyze the issues of electrostatic induced voltage,an equivalent capacitor model of the metallic conductor and the coupling plate is established.Besides,a human body impedance model is introduced to construct the equivalent circuit of electric shock.On this basis,by analyzing the voltage characteristics of different plates,the shock voltage is derived when human touch the conductor placed above different coupling plates.(2)Multi-constraint parameters design method.In addition to meeting the security constraints,the actual ECPT system still needs to achieve the desired transmission power and efficiency.In order to satisfy the above conditions,the parameters design method of multi-constraint conditions is presented.(3)Electric field radiation around coupling plates.The Finite Difference Method(FDM)is used to calculate the electric field around four plates.The results show that the plates at the power transmitting side emit a stronger electric field than receiving side.(4)Modeling of stacked coupling mechanism and analyzing of electric field shielding effectiveness.For reducing the electric field radiation around the coupling plates,a stacked coupling mechanism is proposed to make the low voltage plates shield the electric field excited from high voltage plates.In the end,this paper designed Matlab/Simulink and Maxwell simulation models and built an experimental setup to validate the correctness of the conductor induced voltage formulas,parameters design method and stacked coupling mechanism.