Direct torque control for sensor-less switched reluctance motor drives

Abstract

This paper presents a novel control method for sensorless Switched Reluctance Motor (SRM) drives. The sensorless control is based on Direct Torque Control (DTC) with Direct Flux Compensation (DFC) for SRM drives. The use of DTC, implemented in AC drives with a varying degree of success, has yet been reported in SRMs because the SRM is intrinsically driven by 'switched' currents and is not conducive to voltage vector. This explains why DTC, which invariably embodies the concept of voltage vector, has not yet been reported for SRM drives, despite their well,known advantages such as simple and robust structure, wide torque-speed range and maintenance-free. Here we propose a novel way to utilise the SRMs in a fashion similar to that of a 'voltage vector' motor by modification of the motor windings and/or the driving method. The paper then derives and explains the algorithm to be employed in this new DTC scheme in SRM drives and concludes by highlighting the important consequence of the elimination of use of magnetisation curves in the control of sensorless SRMs by a 'voltage vector' operation. Initial simulation results are presented.