A Direct Energy Control Technique for Torque Ripple and DC-link Voltage Ripple Reduction in Switched Reluctance Drive Systems

In this paper a Direct Energy Control (DEC) technique is proposed for torque ripple and DC-link voltage ripple reduction in Switched Reluctance Motor (SRM) drive systems. DC-link energy flow in a conventional SRM drive system contains high frequency switching harmonics, as well as commutation induced low frequency harmonics, which are caused by magnetization of the incoming phase and demagnetization of the outgoing phase during a commutation period. If the SRM drive is controlled to produce constant output torque, the question of how to reduce the low frequency ripple of the converter input energy is equivalent to that of how to eliminate the low frequency harmonics in the magnetic stored energy. Therefore, based on the Direct Torque Control (DTC) technique, a new control technique is proposed to control the magnetic stored energy and the instantaneous torque at the same time. The simulation results of a six-phase SRM drive system show that the proposed strategy can reduce the DC-link voltage ripple to 49.1% of that with the conventional strategy and 76.5% of that with the DTC strategy, whilst maintaining a constant output torque. In other words, the DC-link capacitor of this drive system can be half of the size of the conventional drive system when the proposed control technique is employed.