Sensorless detection methods of Permanent Magnet Synchronous Motor (PMSM) are mainly divided into two categories:

A: Based on the fundamental wave model response method high frequency signal injection method. However, no matter which method is adopted, it can meet the Angle speed detection of PMSM in the full speed range. The former detection method is sensitive to the parameter changes of the motor has poor robustness. When the motor is in depth adjustment, this detection method will fail due to too low speed. The latter detection method can be detected at low speed even zero speed, but its dynamic performance is limited, tracking failure will occur when the motor suddenly increases decreases the load, the speed changes greatly. Therefore, the two detection methods are usually combined to achieve the detection of the permanent magnet synchronous motor in the full speed range, including zero speed.