DELAYLESS METHOD TO GENERATE CURRENT REFERENCE FOR ACTIVE-FILTERS

Active power filters are used to eliminate ac harmonic currents by inj ecting equal but opposite compensating currents, Successful control of active filters requires, among other things, an accurate current refe rence. In this paper, we introduce a multistage adaptive filtering sys tem which generates the current reference delaylessly and accurately. Our filter structure combines a low-pass prefilter and an adaptive pre dictive filter, making it possible to extract the sinusoidal active cu rrent from the distorted waveform without harmful phase shift, even wh en the frequency and amplitude alter simultaneously. Although active f ilters are typically used to compensate for the supply harmonics, wher e the fundamental frequency remains almost constant, we will show that our filter structure can also be applied in applications where the fr equency alters rapidly.