Switching technique for minimisation of DC-link capacitance in switched reluctance machine drives

A switched reluctance (SR) machine drive has many advantages over other competing drive technologies in terms of reliability and fault tolerance, which make it particularly attractive for safety critical applications in more electric aircraft technologies. However, an SR machine drive requires a large DC-link capacitor to buffer the de-fluxing magnetic energy during a phase commutation period and to filter out AC harmonic currents from contaminating the DC supply. This study describes a switching technique for minimisation of the DC-link capacitance in SR machine drives and presents experimental results from a laboratory demonstrator. The proposed switching method aims to maintain a constant average DC-link current over a switching cycle, thus eliminating commutation-induced low-frequency current harmonics. Consequently, the DC-link capacitance can be minimised. The effectiveness of the proposed technique is assessed through filter design and demonstrated by experiments with a dSPACE control platform.