Research On Modeling And Influencing Factors Of Electromagnetic Interference In Motor Drive System Based On Analytic Method

The inverter motor drive system is widely used in electric vehicles and other fields because of the advantages of cleaning and efficient.However,with the integration and high-frequency application of internal power converters,electromagnetic Interference(EMI)has become an important issue that needs to be solved in the application of motor-driven system engineering.In addition to the parasitic parameters,the system EMI is also affected by operating parameters such as torque and speed.However,the modeling method that relies on the test on power to establish interference sources can only reflect the conduction interference level under specific operating parameters.In order to grasp the impact of operating parameters on system conduction interference,it is necessary to incorporate them into the EMI high-frequency model of the motor drive system to carry out systemic analysis and research.This article uses an permanent magnet synchronous motor drive system for electric vehicles as the research object to model and analyze the influencing factors of electromagnetic interference during the operation of the system.The main work of this article is as follows:(1)An analytical modeling method of interference sources considering the modulation mode of the inverter is studied.According to the system modulation strategy,the transmission functions between the operating parameters.Based on this,the analytical model of the system control circuit is established.Combining it with the transient parameters of the switch tube and the steady-state model,the transient response voltage of the junction capacitance is obtained by simulation to replace the measured interference source.Therefore,the disturbance source model of the motor drive system with the operating parameters as input variables is established.(2)A coupling path analysis method taking switch state vector as the core is developed.The impedance of the power converter load in the model is adjusted according to the switching state,and the corresponding coupling topology is constructed to characterize the change of the loop impedance.The transient interference voltage waveform under each switching state can be obtained by simulation,and the equivalent EMI spectrum of the system can be obtained according to the law of energy conservation.Finally,the analytical model of the electromagnetic interference of the motor drive system is established.The experimental platform is set up to verify the the model through the comparison of experimental tests.(3)Using the established analytical model of electromagnetic interference of the motor drive system,the influence of operating parameters on the system conducted interference is analyzed according to the changes of the high-order harmonic amplitude of the interference source and the impedance of the coupling loop.It is deduced that increasing the output torque will periodically reduce the amplitude of the high-order harmonic components.And it is found that the extreme value of the carrier ratio will increase the peak value of the high-order harmonic or interfere with the noise floor.This article focuses on the impact of operating parameters on the level of conduction interference of the motor drive system.The new modeling and analysis method of electromagnetic interference of the motor drive system is proposed.The established model can reflect the EMI level of the system under different operating parameters,support the comparative study among various control methods,and provide theoretical support for the design of the motor drive system control strategy and the evaluation of the EMI level.