Comparison of methods for back EMF estimation at low speed for PMSM drive

The paper presents a comparison of methods of the back EMFs estimation for the permanent magnets synchronous motor in a case of position estimation at the low speed range. These methods are based on the following structures for back EMF estimation: observer for model of the electrical part of the motor, the observer for the modified correction function and estimation based on the simplified model. Obtained in this way the instantaneous values of the back EMFs, depending on the method of obtaining them, are characterized by different quality and accuracy of the estimated shaft position.