Four-branch star hybrid power filter for three-phase four-wire systems

This paper presents a new concept for filtering current harmonics in three-phase four-wire networks. The four-branch star (FBS) filtering topology presented in this work is characterized by a particular layout consisting of single-phase inductances and capacitors. Via this layout, a power filter, with two different and simultaneous resonance frequencies and sequences, is achieved -one frequency for positive-/negative-sequence and another one for zero-sequence components. This filter topology can work either as a passive filter or as a hybrid filter. The paper analyzes the proposed topology and derives fundamental concepts about the control of the resulting hybrid power filter. From this analysis, a specific implementation of a three-phase four-wire hybrid power filter is presented as an illustrative application of the filtering topology. An extensive evaluation using simulation and experimental results is conducted in order to verify and validate the good performance of the proposed four-branch star passive/hybrid power filter.