This chapter presents about one of the power quality improvement issues such a current harmonic compensation in a shunt active power filter as power quality issues distort the system. The control theory employed here is PI–hysteresis controller-based instantaneous PQ current theory. Simulation is done in MATLAB for a three-phase shunt active power filter, and the results of load current, filter current, and source current have been verified before and after compensation. An FFT analysis is done to evaluate the total harmonic distortion.