An advanced multi-level converter for four-phase SRM drive

As generally recognized, the driving performance of SRM at higher speed will be degraded due to the effects of back electromagnetic force (EMF). In this paper, a multi-level converter is proposed to have an enhanced performance at a high speed range. The converter boosts voltage during phase excitation for a four-phase switched reluctance motor(SRM). By using one additional capacitor and switch, an extra controllable boosted voltage can be produced during the rise and fall periods of a motor phase current. Then this active boosted voltage can reduce the effect of EMF at high speeds. The operation and analysis of proposed converter are given for each operation mode. And effect of the boost capacitor voltage on the current waveform is studied. The attractive features of the proposed converter are as follows: obtaining boosted voltage to improve performance of SRM with same numbers of switch and diode as asymmetric converter, having higher control flexibility and capability of boosting voltage compared with passive boosting converters, possessing lower cost and simpler control in comparison with existing active boosting converters. The performances of the proposed circuit are verified by the simulation and experiment results.