Sensorless drive of SMPM motor by high frequency signal injection

This paper represents a new sensorless control scheme of surface mounted permanent magnet (SMPM) motors. To estimate the rotor position of the SMPM motor, a high frequency voltage signal is injected and the resultant injected frequency current signal is used. In the SMPM motor, due to the flux of the permanent magnet, the stator core around the q-axis winding is saturated. This saturation effect makes some magnetic saliency of the SMPM motor. In this paper, to estimate the rotor position using this magnetic saliency, the high frequency model of the SMPM motor is developed and the high frequency impedance characteristics are analyzed experimentally under various conditions. The proposed sensorless control scheme makes it possible to drive the SMPM motor at low and zero speed operation even under heavy load conditions. The experimental results verify the performance of the proposed sensorless algorithm.