Abstract: With the rapid use of power electronic converters which are considered as non-linear loads have problems of drawing non-sinusoidal currents and reactive power from source which in turn pollutes the power quality. This paper presents the power quality problems and methods for its correction where two control strategies (p - q instantaneous power theory and d - q synchronous reference frame theory) for extracting reference currents for shunt active power filters (SAPF) have been evaluated and their performances have been compared under distorted supply and non-linear load conditions. These theories are used to implement the control algorithm of a shunt active filter which compensates harmonic currents. This paper implements the three phase three wire shunt active power filter to suppress current harmonics. The SAPF performance is validated using MATLAB/Simulink model showing comparisons for the two algorithms.