Comparison between Two Types of Current Control Techniques Applied to Shunt Active Power Filters and Development of a Novel Fuzzy Logic Controller to Improve SAPF Performance

In this paper two types of current control techniques, namely, direct and indirect current control techniques are employed to a three phase shunt active power filter for the compensation of the harmonics in the current caused by the non-linear loads. The difference between these two types of current control technique is in the number of current sensors used. In direct current control technique both load and filter currents are sensed whereas indirect current control technique is based up on sensing source side current only. For both the schemes a simple PI-controller is used to obtain reference current templates. Also, a novel fuzzy logic based controller is developed to replace the conventional PIcontroller. The advantages of fuzzy controllers over conventional controllers are that they do not require an accurate mathematical model, they can work with imprecise inputs, can handle non-linearity and they are more robust. Various simulations are presented for direct and indirect current control techniques along with PI-controller and Fuzzy Logic Controller under both steady state and transient conditions. Keywords— shunt active power filter, harmonics, direct current control technique, indirect current control technique, fuzzy logic controller, dc-link voltage List of Symbols isa ∗ , isb ∗ , isc ∗ Three phase reference source currents is t , il t , if(t) Instantaneous value of source, load and filter current vs t ,Vm(t) Instantaneous and peak value of source voltage Rs , Ls Source resistance and inductance Rf , Lf Filter resistance and inductance isp , isl Peak value of reference current and loss current Vdc ,Vdcref Actual and reference value of DC capacitor voltage pl(t) Instantaneous load power pf t ,pr t ,ph (t) Instantaneous fundamental(real), reactive and harmonic power cosφ1 Displacement factor