Four-quadrant instantaneous torque control of switched reluctance machine at low speed based on co-energy control

An instantaneous torque control scheme of switched reluctance machines for four-quadrant operation at low speed based on co-energy considerations is presented. The co-energy is estimated online with a co-energy estimator, which only requires easily obtainable parameters such as the machine terminal quantities and the machine characteristics at low current. By regulating the co-energy while tracking a one-dimensional co-energy profile, the torque contribution of each phase of the switched reluctance machine can be controlled and optimised. Thus, the requirement of pre-measured data is reduced when compared to current-profiling methods. The closed-loop control system is analysed and then designed based on internal model control. The excitation sequence and torque sharing function for four-quadrant operation to produce smooth torque output are also presented. The operation limits of the scheme are examined. Computer simulation and experimental results confirm that the proposed scheme can be exploited to reduce the high-frequency torque ripples significantly.