Active Filter Technique for the Attenuation of AC Ripple in DC Power Plants and Distribution

Low-pass passive filters used in power converters attenuate low frequency ripple in a very inefficient way. The purpose of this paper is to show how small power active filters can effectively suppress low frequency ripple levels in large power systems. Switchmode power converters with high switching frequency and high gain voltage feedback control have been used as active filters. Three different devices are described - a dc/dc, ac/dc and dc/ac converter. In all three cases an impressive reduction of low frequency ripple level has been achieved.