I. Introduction
Switched reluctance motor (SRM) [1], [2] has several advantages as compared to other competing machines including, but not limited to low cost, fault-tolerance, a wide range of speed and ability to operate under harsh environment [3]. Their rotor construction is robust and simple as well which makes SRMs a serious contender for propulsion systems in HEVs and plug-in HEVs [4]. However, during the period of current commutation among various phases, there would be a large amount of energy transfer between the dc bus and the machine. A simple way to restrain this undesirable ripple power is to apply a relatively large capacitor in the dc bus of the motor driver, which acts as a buffer and balances the difference of the instantaneous power. Unfortunately, the theoretical lifetime of electrolytic capacitances is much shorter than the lifetime of semiconductors and other passive components [5], [6]. In addition, the cost, size, and thermal management of electrolytic capacitor form a major part of the overall system. Thus, the electrolytic capacitor is an obstacle to the overall long-term reliability and commercial viability of the SRM drives [7].