The EMC Analysis And Design Of EV Driver System

Compared with traditional cars,power electronic devices are more and more widely used in electric vehicles.Meanwhile,the electromagnetic compatibility problem generated by the EV drive system(electric vehicle drive system)during operation becomes more and more serious.The high-power DC/AC inverter in the drive system is accompanied by peak voltage and peak current at the high-speed on-off moment.When it acts on the high-frequency parasitic parameters of the components,it will generate strong electromagnetic interference,which will threat the safety of the vehicle itself.And also bring negative effect on the external environment.In view of the above problems,this paper proposes a conductive interference suppression scheme for electric vehicle electric drive system,and conducts electromagnetic immunity test.The main research contents include four aspects:(1)Based on the basic principle of electric drive system and electromagnetic compatibility theory,the main interference sources of electromagnetic interference(EMI)are analyzed.The EMI interference source is mainly derived from the high frequency interference generated by IGBT high-speed on-off.The EMI differential mode and common mode conduction interference coupling path are studied.(2)By DDM(Domain Decomposition Method),the system conduction interference is equivalent to the coupling interference problem of the system line.The ANSYS multiphysics field is used to establish the PCB microstrip line electromagnetic interference coupling model to verify the coupling mechanism of conduction interference.Based on this,the ANSOFT MAXWELL software is used to simulate the transient field and eddy current field of the EV drive system PCB microstrip line,the drive system round wire and the busbar under the high-frequency conduction electromagnetic interference coupling,Then get the conclusion that the greater the interference frequency,the smaller the skin depth.Also the smaller the effective current through the area,the greater resistive loss.And the regular conclusion that the busbar flow rate decreases due to the skin effect is obtained.Through simulation,the effect of skin effect on the performance of EV drive system under high frequency electromagnetic interference coupling can be intuitively understood.(3)Comprehensive(1)(2)Due to the influence of system conduction EMI and skin effect,the normal operation of vehicle-mounted sensitive components and even systems is seriously disturbed.Taking the sensitive component PCB of EV drive system as an example,a radio frequency immunity test method is proposed.By testing the output signal under the interference,the effectiveness and versatility of the method are verified.It is also applicable to other EV drive systems.Sensitive test of sensitive parts.Based on the resonance effect theory,an optimization design method is proposed.According to the EMS(Electromagnetic Immunity)test result,the PCB output signal fluctuation is reduced,indicating that the optimized design method can enhance the immunity of the sensitive component PCB andimprove the EV drive system anti-interference ability.(4)An optimized EMI filter based on impedance matching network is proposed to improve the ability to suppress EMI in the system.Analyze the influence of impedance mismatch on insertion loss.It is proposed to add the matching network optimized EMI filter,extract the original EMI noise signal,and clarify the insertion loss required by the EMI filter.Designed an EMI filter with P and S impedance matching networks for conducted EMI from150 kHz to 30 MHz.The experimental results show that the average attenuation of conducted electromagnetic interference is between 25dB-30 dB,and the filtering effect is better than the EMI filter without impedance matching network.It proves that the EMI filter with impedance matching network solves the source impedance and the load impedance do not match,and has a good inhibitory effect on the system conducted electromagnetic interference.