Research On The Influence Of Voltage Sags On Performance Of Variable-Frequency Adjustable-Speed Permanent Magnet Synchronous Motor

As a kind of adjustable speed motor, PMSM is very sensitive to voltage sags, especially when the driving process is strict with the speed and torque of motor. In this paper, the principle of the variable-frequency drives(VFDs) and mathematical model of PMSM is briefly illustrated. The influence mechanism of voltage sag on variable-frequency adjustable-speed PMSM is analyzed. The simulation model is built by using MATLAB/Simulink, and simulation research on the influence of the basic characteristic of voltage sag on PMSM is conducted. An experimental research platform is developed. Three domestic and foreign brands of variable-frequency drives are selected as the driving equipment of PMSM, and the speed drop and the stator impact current of PMSM driven by different VFDs are researched. The simulation and experimental results show that the smaller the magnitude of voltage sags, the greater the influence on the motor speed. With the increase of the duration of sags, the decrease of the motor speed is in an increasing trend during sags, and the peak value of the stator current is in a downtrend during the voltage recovery. The effects on the operating performance of motor driven by different variable-frequency drives are significantly obvious. The motor speed decreases by a maximum of 30 percent of the rated speed, and the stator impact current exceeds the rated current by three times, which brought great challenges to the operation stability of motor.