Generalized Proportional-Integral control for voltage-sag compensation in Dynamic Voltage Restorers

The Dynamic Voltage Restorer (DVR) is a custom power device used to protect sensitive loads in power distribution systems from the most frequent voltage disturbances, such as sags, swells, imbalances and harmonics. This paper presents a control strategy for voltage-sag compensation in DVR systems which offers an accurate tracking of the voltage compensation reference and a very fast transient response. The proposed control scheme is based on the technique known as Generalized Proportional-Integral (GPI) control. This type of control is closely related to the use of the classical compensation network controllers and consists in the estimation of certain state variables by means of integral reconstructors avoiding the use of derivative operators. Furthermore, the control scheme is completed by adding a feedforward term in which an approximation of the inverse dynamics of the system is used to improve and quicken the transient response. The paper includes a brief theoretical introduction to GPI control design and simulation results to corroborate the suitability of the GPI controller for voltage-sag compensation in DVR systems.