Adaptive repetitive controller for a three-phase Dynamic Voltage Restorer

Voltage sags and swells, voltage harmonics and voltage imbalances in power systems may affect sensitive loads causing production interruption or equipment damage. Now-a-days series voltage compensation using power electronics devices is a promising solution for these problems and the design, control and application of this type of devices have drawn much attention in the literature. Comprehensive controllers for Dynamic Voltage Restores (DVR´s) have already been proposed to tackle all those problems simultaneously, although several aspects need closer attention. This paper addresses several implementation issues for a discrete algorithm to control a three phase DVR. The controller is divided into a main one and an auxiliary one. The former is based on a state-feedback controller to achieve a fast transient response when voltage sags occur. The latter uses a repetitive controller to improve steady-state reference tracking and disturbance rejection in order to tackle harmonic and imbalance problems. This paper focuses on the repetitive-controller part. Firstly, a new method to improve the repetitive controller performance with small frequency deviations in the grid is presented. Secondly, the classical repetitive controller is modified so that the response to non-periodic disturbances is improved. Finally, the main contributions of the paper are illustrated by simulation using a test system built with SIMULINK and its PowerSim toolbox.