High-grade control of switched reluctance machines

This paper formulates the objectives associated with high-grade torque control of switched reluctance motors (SRMs). Low torque ripple is a natural outcome of high bandwidth torque control. Smooth torque operation is only uniquely defined together with a secondary objective, such as maximum efficiency, maximum torque-speed capability, maximum power factor, etc., as the SRM does not enjoy the inherent distribution between phases that characterizes AC drives. By introduction of the flux-angle parameter, operation at any point between maximum torque-current ratio and maximum torque-flux ratio is possible. A systematic approach to waveform design is developed and is evaluated using both simulation and experimental testing of a SRM servo-drive system. This approach, which can be regarded as a functional equivalent of AC vector control, starts from machine parameters and gives smooth torque operation with maximized torque-speed range and/or efficiency. Excellent dynamic performance is obtained for speed and position control, together with optimized low torque ripple operation.