An Investigation on Torque Control Strategies for Switched Reluctance Motor

The torque ripple is owing to inherent non-linear characteristics of switched reluctance motor (SRM). It leads to the noise and vibration that limits the adoption of SRM in industrial and automotive applications. Numerous control strategies found in literature to cut down the torque ripple of SRM. This research focuses on an extensive survey on direct and indirect torque control algorithms. Direct torque control algorithms consists of direct instantaneous torque control (DITC) which is implemented with hysteresis and PWM based controller. While, indirect torque control is implemented by instantaneous torque control (ITC) and average torque control (ATC). It is observed from the survey that, in hysteresis based DITC, hysteresis band is designed to limit torque ripple which increases the switching losses due to high switching frequencies whereas, PWM based algorithms have constant switching frequencies but limited to low speed operating range. It also observed from study that, ITC is suitable for lower operating speed if back-EMF is less than dc link voltage and ATC is appropriate for complete operating speed range. Finally, critical comparison in terms of operating range, switching frequency, torque per ampere ratio and current control of these algorithms are presented. Outcome of this study helps the researcher in making the judicious choice for selection of appropriate algorithm for mitigation of torque ripple of SRM employed in various applications.