Active power filter using nonlinear repetitive controller

Active power filters as solutions to power quality problems have become more and more important nowadays. A nonlinear repetitive controller for current control of active power filters is proposed. The proposed method is composed of a repetitive controller and a deadband relay. Whenever the input error is above the threshold, the current control loop is driven dominantly by the deadband relay to obtain fast dynamic response. After the input error is below the threshold, the deadband relay automatically turns off and the repetitive control alone governs the current control to eliminate the steady-state error. Discussions on the design of the current and voltage control loops are also given. Simulation and experimental results verified the feasibility of the proposed method.