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Permanent magnet synchronous motor has the advantages of simple structure, high power density, high power factor and large starting torque, which is widely used in various occasions. However, high performance permanent magnet synchronous motor control methods need to obtain accurate motor rotor speed and position information. However, high precision sensors are costly and prone to failure. Therefore, the speed sensorless control algorithm of permanent magnet synchronous motor is a hot topic for scholars. The existing speed sensorless control strategies are mainly observer methods based on the motor back EMF and algorithms based on the irrational characteristics of the motor. However, the observer method based on the motor back EMF is only suitable for the middle and high speed conditions of the motor. Although the algorithm based on the irrational characteristics of the motor can adapt to the low speed condition of the motor, it needs to continuously give additional excitation to the motor, the voltage utilization rate of the inverter is reduced, and the dynamic performance is not perfect. In this paper, the highfrequency injection method based on the irrational characteristics of the motor is used in the low speed condition, and the observer method based on the motor back electromotive force is used in the high speed condition, and the switching strategy is optimized to realize the speed sensorless control of the permanent magnet synchronous motor in a wider speed range. The simulation results show that, The composite control strategy adopted in this paper can accurately obtain the motor speed and rotor position information in a wider speed range, and the system runs well when the algorithm is switched.
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