Converter rating reduction in Hybrid Active Power Filters (HAPF)

This paper presents a new topology of Hybrid Active Power Filters (HAPF). HAPFs are composed of both passive and active elements and are an attractive solution to mitigate harmonic pollution. They are less expensive than Active Power Filters (APF), and at the same time do not have the drawbacks associated with Passive Power Filters (PPF). Among various topologies proposed for HAPF, the one with series combination of active and passive elements in parallel with the load is more common. In this configuration, some fundamental current flows in the active part without any contribution in harmonic compensation. This fundamental current in turn increases the current rating of the active part. In this paper, a new topology is proposed in which the fundamental current through the active part is eliminated. This is accomplished by introducing another branch which generates a fundamental current equal to the main branch. By using the MMF balancing feature of a three-winding transformer, the equal fundamental current in two branches cancel out each other, leading to zero fundamental current in the tertiary winding where the active part (i.e. converter) is connected. Theoretical analysis is presented which explains the operation of proposed topology. Simulation and experimental results are presented to validate theoretical results.