Study On Electromagnetic Compatibility Of Planar Transformer In On-board Charger Of Electric Vehicle

Due to the large number of high-power electronic equipments on the vehicle,the electromagnetic environment in the electric vehicle is complex.Compared with the traditional fuel vehicle,the electromagnetic interference(EMI)problem is more serious.This dissertation mainly focuses on the EMC(Electromagnetic Compatibility,EMC)optimization design of DC/DC power converter in electric vehicle charger.The electromagnetic interference signal produced by DC/DC power converter is the main component of the electromagnetic interference source in the vehicle charging system,and it is the main problem to be overcome in the EMC test of electric vehicle.This dissertation is based on the project of "Research on Structure and Control Technology of Power Matching High Efficiency Radio Transmission System" funded by National Natural Science Foundation of China(51607052).This dissertation mainly studies the EMI suppression of the on-board charging system of electric vehicles and the optimization design of the electromagnetic compatibility of the planar transformer.The main work is as follows:(1)Based on the basic theory of EMC,the EMI sources in the system are diagnosed.Common mode interference and differential mode interference are analyzed and a linear impedance stabilization network is provided to measure the interference voltage.The main circuit topology of DC/DC power converter is isolated full bridge and its working principle is analyzed.The transmission path of EMI noise in isolated full bridge DC/DC power supply converter is analyzed.The equivalent model of common mode interference with high frequency transformer as the main coupling path is established,and the factors affecting the common mode interference intensity are analyzed.(2)To study electromagnetic interference,the main method is common mode interference suppression.The parasitic capacitance and potential distribution of different transformer outlet windings and circuit topological connection modes are calculated,and the influence of winding potential distribution on transformer electromagnetic interference is analyzed.Design of EMI filter based on interference source impedance measurement.(3)Comparing the advantages of planar transformer with traditional winding transformer,and analyzing the structural characteristics of the two transformers.The high frequency planar transformer used in DC/DC converter system is designed,and the detailed design flow of the transformer is given.The finite element analysis software Ansoft Maxwell is used to solve the transformer model.The parasitic parameters,winding potential distribution and magnetic field strength of transformer under different winding structures are obtained.The parameters and winding process of high frequency planar transformer are determined.(4)Joint simulation is carried out in Simpler simulation software,and an experimental platform of DC/DC converter system is built to test and analyze the EMI signal of the system,and to verify the feasibility of EMI suppression scheme.