Research On Negative Effects Of SiC-based Inverter Fed Motor Drive System

With the development of modern power electronics technology,the requirements for motor drivers in aviation,aerospace and other fields are becoming higher and higher,and it is hoped that the drivers will have higher switching frequency,efficiency and reliability.Compared with Si devices,new power devices made of silicon carbide(SiC)have faster switching speeds and lower switching losses.They play an increasingly important role in motor drive systems.However,it cannot be ignored that SiC MOSFETs also cause unavoidable negative effects on the system,which are mainly manifested in bridge arm crosstalk,gate-source voltage oscillation,motor-end overvoltage and electromagnetic interference caused by cable-driven motors,which seriously affect the motor’s safe and stable operation,so it is particularly important to analyze and study the negative effects and suppression strategies of motor systems powered by SiC-based inverters.In order to study the characteristics of the motor system at high-frequency switching frequency,the paper first establishes a high-frequency lumped parameter model of the permanent magnet synchronous motor and a high-frequency distributed parameter model of the cable.According to the actual parameters of the motor,the finite element electromagnetic field simulation software is used to obtain the resistance,high frequency inductance and parasitic capacitance parameters of the motor,thereby obtaining the high frequency circuit model of the motor.Based on the transmission line principle,the mechanism of the overvoltage at the motor end caused by the inverter driving the motor through a long-line cable is studied.The characteristic impedance of the motor does not match the characteristic impedance of the cable,resulting in voltage reflection.Analyze the propagation and reflection process of the voltage waveform in the cable to obtain the influencing factors of overvoltage.The simulation compares the effects of overvoltage,switching time,switching frequency and cable length caused by SiC and Si devices on the amplitude of overvoltage.The suppression strategies of the parallel RC filter at the motor end and the parallel RLC filter at the inverter end are studied respectively.The filter parameters and filter losses are designed and calculated,and verified by simulation.This paper analyzes the mechanism of conducted electromagnetic interference of SiC-based inverter fed motor system.The noise source of conducted electromagnetic interference is the inverter’s high-frequency voltage pulse waveform.Deduce the envelope function of the common-mode voltage spectrum,compare and analyze the effects of the rise time,off time,and switching frequency of the Si and SiC-based devices on the low,medium and high frequency bands of the common-mode electromagnetic interference spectrum,and verify the influence of various factors on the pulse voltage spectrum through simulation law.In order to reduce the conducted common mode electromagnetic interference of the SiC-based inverter fed motor system,active zero state pulse-width modulation(AZSPWM),random frequency pulse-width modulation(RFPWM)and hardware filter are used to suppress the common mode voltage of the system,and the filter is combined with the control strategy to suppress common mode voltage amplitude and motor overvoltage.Build a simulation model of SiC-based inverter fed permanent magnet synchronous motor system to verify the feasibility of the scheme.