A new hybrid parallel active filter

This paper presents a new parallel hybrid active filter topology which can reduce the VA rating of the active power filter (APF) greatly. Based on the conventional topology of the hybrid parallel filter, the basic idea of the new topology is to add a small inductor in parallel with APF controlled as a harmonic current source, in order to force the fundamental reactive current to flow through the additional inductor, instead of flowing through APF. Three different control methods and a formula estimating VA rating of APF are proposed for the new topology. Experimental results obtained from a 30 kVA prototype exhibit excellent performance of the new hybrid filter. The required rating of the active filter is approximately only 1% of the harmonic-producing load.