Sensorless Control Research And Design For Permanent Magnet Synchronous Motor

With the wide application of permanent magnet synchronous motor in the field of AC drive, vector control of permanent magnet synchronous motor without position sensor has become a research focus, and various control algorithms have been proposed. A sensorless method based on full order state observer and phase locked loop for measuring back electromotive force has good performance in medium and high speed operation. In this paper, the basic principle of vector control is introduced, the operation principle of the full order state observer for estimating the rotor position is studied,the stability of the observer is analyzed, and the I/F speed open loop-current closed loop starting method is studied in detail. The experimental results show that this sensorless control algorithm has good running performance.In this sensorless algorithm, because the rotor position angle has the phase difference and the phase current has the amplitude difference when the motor is switched from the I/F to the state observer, cause the problem of phase current mutation and electromagnetic torque is not stable. In order to solve this problem, this paper proposes a new method of smooth transition allow the I/F generation position angle and the state observer estimates position angle gradually tend to the same and reduce the amplitude of the phase current, finally realize the smooth transition. The proposed algorithm is simple and easy to implement, and the effectiveness of this method is verified by experiments.In the last part of this paper, the problem of restart in rotation condition of sensorless permanent magnet synchronous motor control is studied. For the medium or high speed restart, the "one-time short-circuit method" have been proposed based on analysis of the existing research. For the low speed restart, by using zero input full order state observer, the open loop method combined with the I/F and the direct entry speed closed loop method are proposed. Finally, all the methods are verified by experiments, and the results show that these methods have good restart performance and reliability.