Closed-Loop Control Method and Implementation of Selective Harmonic Type Active Power Filters

Because the higher harmonic currents can be damped by the impedance of the power line, the selective harmonic type active power filter (SH-APF), which shunted on the load side, concentrates on compensating lower harmonic currents and than can improve the effectiveness and precision of the compensation. In this paper, we analyze the key points of the system implementation, such as the harmonic current detection method, the closed-loop control methods of compensating currents and DC voltage, and the compensation of the time delays which are introduced by the harmonic detection unit and the control loops. The construction of the controller is introduced. The results of simulation and experiment of SH-APF are given and the several performances are compared with conventional one which detects and compensates all harmonic currents.