Active source current filtering to minimize the DC-link capacitor in switched reluctance drives

Switched reluctance machines receive increased attention from the automotive industry because of their cost efficiency. However, the independent phase excitation and the resulting current reversal demand comparatively large dc-link capacitors to meet the requirements regarding the ripple on the dc-link voltage and current. This paper validates the effects of the usage of a dc-dc boost converter to reduce the size of the dc-link capacitor by actively filtering the source current. The active filter is compared with the state-of-the-art topology and a passive filter. The investigations show that the active filter is able to reduce the dc-link capacitance by 80%. The dc-dc converter also provides the feature of adjusting the inverter dc-link voltage level independently from the battery voltage level. The positive effect of this additional degree of freedom on the machine efficiency is investigated and due to this feature the total efficiency of the electrical drive train remains nearly unchanged despite the extra losses in the dc-dc converter. All presented results are based on detailed simulations and experimentally validated with a 20 kW switched reluctance generator.