Study on simple space-vector and one-cycle control strategy for three-phase four-leg active power filter

An active power filter (APF) is a device that is connected in parallel to and cancels the reactive and harmonic currents from a group of nonlinear loads so that the resulting total current drawn from the ac main is sinusoidal. This paper proposes a three-phase four-leg active power filter based on space-vector and one-cycle control (OCC) that has the functions of harmonic suppression, reactive power compensation, unbalanced load correction, and source neutral current limitation. It eliminates the use of any multipliers, the need of sensing load current, and the nontrivial task of calculating the harmonics, reactive and source neutral current components, as required by previously reported control method. It has the advantages of no need for reference calculation, space-vector operation, and flexible structure for three-wire or fourwire system. All analysis and results were verified by simulation based on a three-phase 6kW active power filter.