Permanent Magnet Synchronous Motor System Without Position Sensor With Speed Re-throwing Control

Permanent Magnet Synchronous Motors(PMSM)are widely used in electric vehicles,rail transportation due to their high power density and high reliability.In the sensorless control system of PMSM,when the main power supply is over-voltage and over-current,the protection mechanism in the control system will automatically cut off the power supply of the main power supply to the motor inverter,so that the motor will slow down under the load.When the main power supply is restored,if the PMSM is still in the rotating state,the accurate rotor position information must be obtained before the inverter outputs the driving pulse.Otherwise,the output voltage of the inverter will not match the amplitude and phase of the motor back EMF,resulting in a large strike current.Therefore,how to obtain the rotor position information becomes very important.This paper introduces the research status of rotating restart of the PMSM in free-running,and summarizes the existing control methods.In the control of rotating restart at low speed,the rotor position information can only be detected after the main power supply is restored.When the power-off time of the main power supply is more than half a cycle,the polarity judgment must be performed again after the rotor position is obtained by the inductance method,so as to reduce the speed of rotating restart of the PMSM in free-running.In order to solve the above problems,this paper proposes a restarting control method of ultra-high frequency(UHF)sinusoidal signal injection.After the main power is cut off,the UHF sinusoidal signal is coupled to the stator winding through the high-frequency signal injection module,and the UHF sinusoidal signal in the stator winding is extracted by the high-frequency signal detection module.The relationship of stator winding inductance can be obtained by processing the extracted UHF sinusoidal signal.According to the relationship between stator winding inductance and rotor position,rotor position information can be obtained.Compared with the traditional control of rotating restart at low speed,the proposed method can replace the traditional high-frequency signal injection method to continuously detect the rotor position during the main power failure,avoiding the loss of rotor polarity.When the main power supply is restored,the current rotor position information is assigned to the PLL as the initial value,so that the rotor position output by the PLL converges to the actual rotor position quickly,so as to control the permanent magnet synchronous motor to return to normal operation immediately.In order to verify the feasibility and superiority of the proposed method,the experimental platform of the control system is built,and the experimental verification under different working conditions is carried out on the experimental platform.The experimental results show that the proposed method can continuously detect the rotor position and avoiding the loss of rotor polarity after the main power supply is cut off,and that the PMSM can be quickly restarted after the mains power supply is restored.