Study On Full-speed Range Sensorless Control Of PMSM

The rotor position and speed signals are needed to realize closed loop control in permanent magnet synchronous motor vector control and direct torque control systems. Usually the rotor position and speed signal is obtained through mechanical sensors. The use of mechanical sensors increases the system volume, at the same time, reduces the operational reliability of the system. Sensorless control technology of permanent magnet synchronous motor is a good way to overcome the mechanical sensor faults. However, existing sensorless control technology has limitations in the range of speed. The composite control method which combines sensorless control technology suitable for different speed ranges is an effective way to achieve the full-speed range sensorless control of PMSM. In this paper, a detailed study of full-speed range sensorless control of permanent magnet synchronous motor is done.Mathematical model of the three-phase static coordinate system of PMSM is deduced in detail. Coordinate transformation is introduced, and then the Mathematical model of the two-phase rotating coordinate system of PMSM is obtained. On this basis, permanent magnet synchronous motor vector control program is discussed.The basic principles of the kalman filter and extended Kalman filter was discussed in detail. The operation was taken to linearize and discretize the mathematical model of permanent magnet synchronous motor, and then the rotor position and speed observer based on EKF was designed to achieve high-speed range sensorless control.To achieve low-speed sensorless control of permanent magnet synchronous motor, high-frequency signal injection method was used. Meanwhile, EKF was introduced into the filtering aspects of the high-frequency signal injection method. This method avoided the phase lag of traditional filter. On the basis of analysis the principle of the rotating high frequency signal injection method and pulsating high frequency signal injection method, the viewpoint that stator currents under the two different high frequency signal incentive have a unified model was proposed. The EKF filter design of the two high-frequency signal injection method was also been unified with the help of stator current unified model.The EKF method used in high-speed range and the high-frequency signal inject+EKF method used in low-speed range were combined to complete the full-speed range sensorless control of permanent magnet synchronous motor. Thereinto, the weighted method was used to guarantee smooth transition between low speed range and medium and high speed range. At the end of the article. Adopting presented composite control method, PMSM simulation was built. Experiment results show that presented compound control method is able to reliably estimate rotor position and speed in the full-speed range.