Research On Low Speed Sensorless Control Strategies For Spmsm

Permanent magnet synchronous motor(PMSM)has been widely used in industrial and civil motor drive systems because of its high power density and high efficiency.High performance vector control requires the real-time position of rotor to realize the decoupling of motor flux and torque.The traditional solution is to install position sensor on the shaft,but in some industrial transmiss ion applications,it is not suitable to install position sensor,and the use of sensor also has the problem of poor economy,so the sensorless drive control technology is becomi ng increasingly attractive.The initial-position-detection technology and low-speed operation control technology of SPMSM are studied.Firstly,the rotor-initial-position-detection strategy of SPMSM without injecting high voltage short pulse signal is studied.The trad itional method of rotor position detection is to acquire the rotor position information by compound signal injection method in static state,and to detect the rotor position information by high frequency voltage signal injection method.Then,based on the saturation nonlinear characteristics of stator core,the polarity information of rotor pole is extracted by pulse voltage signal injection method,and the final rotor position estimation value is obtained.However,in the phase of pole identification,due to the pulse voltage signal injection,it will produce large vibration and noise,and also will cause the rotor position to shift,reducing the starting performance.Therefore,this paper studies an initial position detection strategy based on the high-frequency square-wave voltage signal injection method.The rotor position information and the polarity of the rotor pole can be extracted by the high frequency signal injection method.By using this method,the initial position of the rotor and the polarity of the magnetic pole can be accurately determined.In order to realize the low speed operation of SPMSM,a sensorless control strategy based on high-frequency square-wave signal injection method is studied.The high-frequency square-wave signal injected into the observed d-axis can effectively avoid the torque ripple caused by the rotating signal injection method in the q-axis component of the rotor,and improve the steady-state performance of the system.The research method extracts the position error signal from the measurement shafting which lags 45 ° behind the observation shafting,constructs the relationship between the high frequency current of the measurement shafting and the position error,designs the normalization method of the position error suitable for the measurement shafting,and adjusts the position error t o zero by combining with the PI position observer.The simulation and experimental results show that the tracking of the rotor position can be realized.In order to solve the problem of position error,a method of position observation error compensation based on disturbance observation method is studied.Based on the analysis of the non-ideal factors in the actual motor drive system,the cross-coupling magnetic saturation effect,current sampling error and their effects on the performance of the drive system are modeled and studied.Starting from the extraction of position error,the secondary compensation is added to the initially extracted position observation error to reduce the secondary pulsation error.In addition,the phase and amplitude self-tuning strategy of the compensation based on the disturbance observation method is studied to realize the automatic optimization of the optimal compensation value.Based on the research and simulation analysis,the control algorithm is realized on the general inverter platform.A 7.5k W surface mounted PMSM loading platform was built.And the initial position identification method and high frequency square wave voltage injection method were used to verify the effectivenes of the method.