COMPARISON OF CONTROL STRATEGIES TO MINIMIZE THE TORQUE RIPPLE OF A SWITCHED RELUCTANCE MACHINE

The Switched Reluctance Machine (SRM) presents simple structure with p assive rotor without windings nor any magnets. That enables applicatio ns in mass production (low production and material costs) or in harsh environments (high temperature...). Unfortunately, its polyphase torqu e is naturally pulsed because of the highly nonlinear electromagnetic characteristics and because the phases have to be successively commuta ted in order to maintain a continuous rotation. A torque control assoc iated with an appropriate strategy for the phase commutation is thus s ought in order to reduce the torque ripple. Initially, the limits of t he classical linear control (Proportional Integral controller) are det ermined. Then, the performances of the PI controller are improved by m eans of electromotive forces compensation. Nevertheless, the torque ri pple remains significant. In order to compensate for SRM nonlinearitie s, we propose a nonlinear torque control associated with a suitable co mmutation strategy. This control has been simulated and experimentally tested. Its performances have been compared with the PI-obtained perf ormances. Very promising results have been obtained at low and medium speeds. However, even with this nonlinear torque control, torque rippl e still remains in the presence of voltage saturation. This is precise ly why we are presenting herein an original method, which enables comp ensating for the effects of the feeding-voltage saturation.