Performance Investigation of Fractional PI Controller in Shunt Active Filter for a Three Phase Four Wire System

Abstract

Sources of harmonic distortions in the power system are nonlinear loads. Since advancement in properties of semiconductor devices, semiconductor devices are widely used. These devices are showing nonlinear property in the system and causes different power quality problems. Especially in three phase four wire system nonlinear loads or unbalanced load causes flow of zero sequence current through neutral wire. These zero sequence current components are the multiple of third order harmonics. To eliminate these harmonics various technologies has been used including passive filters, zigzag transformers, active filters etc. active filters can be used in different topologies such as series active power filter, shunt active filter etc.. In this work shunt active power filter has been used to eliminate the harmonics from the system. For three phase four wire system shunt active power filters compensates not only active and reactive power, but also compensates zero sequence power of the system. The PI controllers are generally used in shunt active filters as control elements. To obtain accurate output result, tuning of PI parameters (proportionality constant Kp, integral constant Ki) are required. While fractional order PI controller are used recently as this type of controller shows better result than conventional PI controller. In fractional PI controller one more constant called as fractional constant λ is also used for tuning.