Permanent magnet synchronous motor(PMSM) is widely used in industrial applications due to high efficiency, high power ratio, and easy maintenance. Position and speed detectors requied in the motor increase the drive cost, and reduce the application range.
This paper presents the position sensorless vector control of a PMSM in the field weakening region. The position sensorless algorithm using an instant reactive power of the PMSM is proposed. An instant reactive power can be obtained from the vector product of rotor currents and back emf of the PMSM. Back emf includes the information of rotor speed. So the estimated speed can be yielded from the voltage equation of the PMSM.
