The Mitigation Of Electromagnetic Interference And Magnetic Field Distribution Of Coupling Structure In Wireless Charging System Of Electric Vehicle

The electromagnetic emission interference(EMI)was researched based on wireless charging system(WCS)in electric vehicles.The conducted emission(150 k Hz-108MHz)and radiated emission(150 k Hz-108MHz)from power cables and low frequency magnetic emission from coupling coils(1Hz-400 k Hz)were included.The relevant circuit models and simulation models were built to predict the effects of conducted emission or radiated emission or low frequency magnetic emission.The test platforms were built to verify the correctness of simulation results and mitigation strategies proposed.The detailed work has been given below:Firstly,an equivalent circuit model in a 3.7k W power level and 85 k Hz operation frequency was built based on standard SAE J2954,including electrical model of rectification,invertor,compensation,resonance coils and controller.The circuit model was verified by the results in Matlab/Simulink.Secondly,the researches about conducted EMI from power cables of primary side refered to standard GB/T 18655.An equivalent circuit with high-frequency parasitic parameters for WCS was built based on measurement results to obtain the characteristics of conducted emission from WCS.The transfer functions of(differential mode)DM interference and(common mode)CM interference were established.Using transfer functions to determine the dominated interference mode responsible for EMI was proposed.From the comparison of simulation results between CM or DM and CM+DM interference,it can be seen that the CM interference is the dominated interference mode,which causes the conducted EMI in WCS in EVs.A strategy of giving priority to the dominated interference mode was designed for designing the CM interference filter.Conclusively,the conducted voltage experiment was performed to verify the mitigation conducted emission strategy.Thirdly,the radiated EMI from power cables of the second side was researched refer to standard GB/T 18655.The radiated noises were exacted in CST DESIGN workshop,and the radiated equivalent model was built in CST CABLE workshop.The electrical field and radiated characteristic was obtained before and after using the filter proposed in the Chapter3.Meanwhile,the method were verified by simulation and experiments.Fourthly,the low frequency magnetic radiation from resonance coils was researched,refer to standard SAE J2954 and JASO TP 13002.An equivalent coupling coils model and whole vehicle model were setup in Maxwell.The characteristic of magnetic field,self-inductance and mutual inductance,coupling coefficient,currents of coils,and current phase relative to maximum magnetic strength were analyzed with the change of offset distance.A test for measuring the magnetic field was setup.Fifthly,a complete WCS was setup to achieve the charging function.A conducted EMI experiment was built in anechoic chamber,the conducted voltage with filter and without field were obtained and compared.While the WCS is working,the magnetic field was measured by magnetic-field probe.All of those experiments and tests were aimed to verify the electromagnetic EMI from WCS and prove the correctness and effectiveness of novel strategies.