A Novel Three Phase Unbalance Detection and Compensation method of Active Power Filter

With the rapid development of power electronics technology, active power filter (APF) device has become one of the main methods to compensate unbalanced nonlinear load and improve power quality. Quickly and accurately calculating the compensate current for unbalance load is the key of the APF performance. Based on instantaneous reactive power theory, this paper first analyzes the defects of ip-iq detection algorithm in application of unbalanced three-phase four-wire power distribution system. And then proposes a improved three-phase unbalanced current compensation method based on positive sequence extractor of fundamental wave. By comparison with ip-iq detection algorithm in Matlab/Simulink tools, this method has the advantages of fast response, small mutation and accurate extraction of compensate current. The result also shows this method is more suitable for three-phase voltage distortion and unbalanced heavy load application environments.