In modern era, the tradition of non-linear loads in Electrical power system has sparked the research in power quality (PQ) concern like voltage flicker, voltage sag and swell, harmonics, etc., Among all the other concerns, one of the the majority significant of PQ problem is Harmonics .Active Power Filter (APF) is one of most challenging filter for the mitigation of harmonics. The heart of the Active power Filter is the controller part. In this study, a wide-ranging review of various controllers have been projected,Which mitigate harmonics, reactive power and unbalanced load currents originating from load side, and also the advantages and disadvantages of presented techniques are presented. The study also helps the researchers to select the optimum control strategies and power circuit configuration for APF applications.