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.