Sensorless direct torque control of a fractional-slot concentrated winding interior permanent magnet synchronous machine using extended rotor flux model

This paper presents the sensorless direct torque control based on the extended rotor flux concept of 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 high-power 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. In this paper, the sensorless direct torque control scheme that uses an extended rotor flux model was applied to a prototype FSCW IPM machine. By using extended rotor flux model, the flux and rotor positions can be obtained without any speed adaptation. The speed adaptation is not required because the model uses both the rotating and stationary reference frames simultaneously. Thus, unlike speed adaptive observers, the extended rotor flux observer is immune to speed estimation errors. Because of this, the extended rotor flux models can provide significantly improved performance at very low speed. The experiment results, presented in this paper, will confirm the effectiveness of the method in a FSCW IPM synchronous machine.