Transient performance of an active filter under harmonic power variations

In this paper the authors discuss the transient performance of a DSP-based power active filter, when subjected to sudden changes on both the instantaneous reactive power and oscillating active power demanded by a three-phase AC/DC rectifier, whose firing angle moved transiently from one value to another. A voltage source AC/DC inverter fed, either by a constant DC source, or by a previously charged DC capacitor, acts as a main compensator device for the active filter, whose transient performance was investigated under the action of these two types of DC voltage sources. Digital simulation and laboratory tests demonstrated that under the action of a constant DC source, the DSP-based active filter performed complete harmonic current suppression, and instantaneous reactive and oscillating active power compensation, under all circumstances of firing angle variations. When the active filter is supplied by a DC capacitor, a partial compensation is achieved, that improves when the amount of instantaneous reactive power becomes larger than the instantaneous oscillating active power