Model reference adaptive control design for a shunt active power filter system

In this paper, model reference adaptive control (MRAC) is proposed for a single-phase shunt active power filter (APF) to improve line power factor and to reduce line current harmonics. The proposed active power filter controller forces the supply current to be sinusoidal with low current harmonics and in phase with the line voltage. The advantages of using MRAC over conventional proportionalintegral (PI) control are more flexibility, adaptive and robustness; moreover, MRAC can self-tune the controller gains to assure the system stability. Since the APF is a bilinear system, it is hard to design the controller. This paper will solve the stability problem when linearization method is used to approach the nonlinearity of the system. Besides, using Lyapunov's stability theory and Barbalat's Lemma, an adaptive law is designed to guarantee asymptotic output tracking for the system. To verify the proposed APF system, a digital signal controller is adopted to implement the algorithm of MRAC and an 1-kVA laboratory prototype is built to test the feasibility.