Flux and torque control of switched reluctance machines

The theory and implementation of a flux-linkage controller applied to a swi tched reluctance machine drive are described. Analysis of the simplified di screte time load model shows that a simple flux-linkage controller can prod uce a 'dead-beat' system response. Comparison of the response from a discre te time PID current controller, hysteresis current controller and the new f lux-linkage controller, show that the flux controller has a much improved r esponse. The experimental controller is used to control an IGBT converter, driving a commercial 7.5kW switched reluctance motor. A method of constant torque operation is introduced. This takes account of limitations imposed b y the finite DC-link voltage and rotor speed when calculating the reference values. The method is based on 'flux ramps', where the ramps are chosen to give constant shaft torque, and remain within the capabilities of the powe r converter. Correct selection of the flux ramps allows constant torque ope ration to be achieved over a wide speed and torque range. Measured results for the experimental drive demonstrate the low torque ripple achieved for m otoring and generating operation over a range of speed and torque values.