Research On Restart Strategy Of High Speed Permanent Magnet Synchronous Motor Drives

With the advantages of high power density and high energy efficiency ratio,permanent magnet synchronous motors have achieved wide applications in fans,compressors,pumps,flywheel energy storage,high speed centrifuges and other fields.Conventional PMSM achieves motor vector control by obtaining the motor rotor position and speed through position sensors.However,the installation of position sensors increases the system size and complexity.They cannot meet the high reliability requirements under specific industrial conditions due to the high cost and low reliability,which prompts the vigorous development of position sensorless control technology.Flying restart is a difficult point in the sensorless control of permanent magnet synchronous motors.The observation of motor rotor speed and position under idling condition is needed by using flying restart method,and restart the motor using the sensorless control method on this basis.This paper presents an in-depth study on the method of flying restart of PMSM position sensorless control,the main research contents are as follows:This paper proposes a three-time short-circuit current method suitable for highspeed permanent magnet synchronous motors with flying restart.The method extends the injection vector interval by injecting a zero-voltage vector three times.Based on the first two short-circuit current vector phase angle changes,all possibilities of the third short-circuit current vector phase angle are inferred.The measured third shortcircuit current vector phase angle is compared with the inferred result,and then the actual rotation angle and direction of the current vector during the second and the third vector intervals.Compared with the two-time short-circuit current method,it solves the problem of low observation accuracy caused by the short interval of zero voltage vector and cannot be applied to high-speed permanent magnet synchronous motors.Simulation experiments show that this method can be used for high speed permanentmagnet synchronous motor flying restart.Based on the open-loop V/f control,this paper proposes a V/f control method that can be used for coasting start.Firstly,by analyzing the small signal model of the openloop V/f control PMSM,it is concluded that the V/f control is unstable at high speed due to the undamped rotor of the PMSM.To solve this problem,The stator voltage frequency is dynamically compensated using a sliding mode observer to observe the real-time speed,and the system damping is increased.Simultaneously,combined with the surface-mounted PMSM id=0 control method,the reactive power is used to obtain the d-axis current and achieve dynamic regulation of the voltage amplitude.The simulation results show that the method combined with the three-time short-circuit current method can realize the flying restart.The simulation results show that the method combined with the three-time short-circuit current method can realize the flying restart.The paper builds a PMSM flying restart experiment platform,and the three-time short-circuit current method and the V/f control method with stable loop proposed in the article are carried out.The experimental results show that the rotor position and speed accuracy observed by the three-time short-circuit current methods are higher than those of the two-time short-circuit current methods.The PMSM flying restart can be realized in combination with the V/f starting method with a stable loop.