A new hybrid sensorless method using a back EMF estimator and a current model of permanent magnet synchronous motor

This paper presents a sensorless method which combined a back-EMF estimator and a current model of PMSM. Sensorless method using the back-EMF estimator, because of its position estimation method, the lowest controllable speed is limited despite of the correct back-EMF estimation. On the other hands, the current model based sensorless method has the benefit that robust control for large load torque. However, the correctness of the estimated back-EMF is determined by a back-EMF coefficient which is varied by load torque and speed. For these problems, this paper proposes the hybrid sensorless method that the back-EMF estimator for precise back-EMF estimating, and the current model of PMSM for robust control and extend the controllable speed region. This method offers not only non-necessary back-EMF coefficient which should be varied, but also wide speed operating region in no specific transition method.