An incorporation method of sensorless algorithms: Signal injection and back EMF based methods

This paper considers the smooth transition method between the signal injection and the back-EMF based sensorless algorithm for an interior(salient) permanent-magnet synchronous machines(IPMSMs). For the starting algorithm, signal injection techniques are used in the zero-speed and low-speed regions, and the back-electromotive force (EMF) based sensorless technique is used for higher speeds. A phase-locked loop (PLL) type position and speed estimator is considered in both the signal injection and the back-EMF based sensorless. Particular focus is put on the transition method in transition region, i.e., the speed region where the estimator switches between signal injection and the back-EMF based sensorless technique. In order to achieve the smooth transition, two PLL type estimators are combined with a transition function based on the estimated speed. The proposed smooth transition method for sensorless control is simple and easy to implement. Several experimental drive tests are demonstrated and the experimental results show the effectiveness of the proposed method.