Research On Common Mode Harmonic Prediction Of Permanent Magnet Synchronous Motor Drive System

As the size of the device in the permanent magnet synchronous motor drive system becomes smaller and smaller,the parasitic effect in the system becomes more and more serious,and the switching speed of the switching device in the system becomes faster and faster,resulting in a large number of high-frequency common mode in the system.Harmonics,these harmonics will not only affect the normal operation of the motor,but also cause serious electromagnetic interference to the electronic equipment around the motor drive system.Therefore,reducing common-mode harmonics in the motor drive system has become a hot spot of current research.Accurate prediction of common-mode harmonics is the basis for reducing common-mode harmonics.However,existing models and analysis methods are not accurate enough to predict common-mode harmonics.To solve the above problems,this paper uses the laboratory 3kW permanent-magnet synchronous motor drive system,as the object of the study is to establish an impedance network prediction model and a harmonic numerical analysis and prediction model as targets,and propose two accurate methods for predicting common mode harmonics.On the one hand,this paper proposes a numerical model for predicting the accuracy of common-mode harmonics.By analyzing the working states of the rectifier and inverter,the time domain and frequency domain expressions of the harmonic voltage generated by the switching devices in the system are obtained.The comparison with the experiment shows that this model is feasible for predicting common mode harmonics.Accuracy and accuracy;In addition,this paper also established a simulation model of voltage pulse spike oscillation in motor drive system,and through simulation and experimental comparison,it shows that the simulation model can accurately predict the pulse spike oscillation in common-mode harmonics and give A detailed analysis of common-mode harmonic sources.On the other hand,this paper proposes an impedance model for predicting common-mode harmonics of high-frequency motors and transmission lines and validates them experimentally.Aiming at the shortcomings of the impedance model in the existing motor modeling,such as the poor accuracy of the differential mode impedance and the unreasonable circuit parameters,a high-frequency model of the motor with 4Hz~10MHz high-precision three-phase differential mode and common mode was proposed.The model’s three-phase differential mode,common-mode impedance and measured impedance are compared to prove the accuracy of the model;a high-frequency model of the transmission line is obtained by the vector-fitting algorithm,compared to the traditional sub-band equivalent circuit method.The method has significantly improved the efficiency of the specific parameters of the circuit,and compared the impedance of the transmission line measured by the model and the experiment,and proved the accuracy of the model;the system was predicted by establishing the high frequency model of the entire motor drive system in Matlab/Simulink.In the common mode harmonics,the experimentally measured common mode harmonics are compared with the simulation results.It is proved that the model has high accuracy for the prediction of common mode harmonics and the model is more practical and can be applied to all kinds of Switching devices and control algorithms.The research results show that the common mode harmonics of the motor drive system can be accurately predicted by establishing the state of the switching device and the LCR oscillation of the analysis system.The system high-frequency impedance model and control model can also be established in Simulink for prediction.The above two common mode harmonic prediction methods have important significance for improving the electromagnetic compatibility of the motor drive system.