Investigation of sensorless direct torque control using high frequency injection apply to a fractional-slot concentrated winding interior PMSM

This paper presents the sensorless direct torque control based on the high frequency injection method for a fractional-slot concentrated winding Interior Permanent Magnet (FSCW IPM) Synchronous Machine. Application of the concentrated winding to IPM machine is gaining attention from research community because of its advantages such as highpower density, high efficiency and wider flux-weakening capability. Sensorless direct torque control of such a machine is important for its application in high performance drive systems. High frequency injection method is based on detecting the anisotropy caused by the saliency of the machine. Since the FSCW-IPM machine produces a low saliency ratio close to unity, the high frequency injection method for position estimation will be challenging. In this paper, the sensorless direct torque control scheme that uses high frequency injection signal was applied to a prototype FSCW IPM machine. The rotor positions are estimated effectively at low speed by using high frequency injection signal. The experiment results, presented in this paper, confirm the effectiveness of the method applied to a FSCW IPM synchronous machine.