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Sensorless rotor position estimation of PMSM for low and high rotor speed

In this paper, a sensorless permanent magnet synchronous motor (PMSM) drive was presented based on calculating the back EMF using the reference stator voltages, which are the output of the d-axis current controller, which includes information about the rotor position. Sensorless control estimates the position information necessary for vector control of the motor without using position sensor or encoder. This can provide effects such as increased system reliability and cost and volume reduction. The back EMFs are calculated in a new coordinate based on the estimated speed to minimize the rotor speed estimation error. The estimated rotor position and rotor speed may fail to track the real rotor position and real rotor speed in extremely low speed since the position error can be amplified from the current controller output voltage, and this may cause the instability problems of tracking controller. So, a compensator has been added to the detector to overcome this disadvantage. In order to verify the validity of the proposed sensorless control technique, an experiment was performed on the PMSM, and the results showed fast-dynamic response, low ripples in motor’s currents, and good performance in tracking speed and power references.