Design and comparison of two control strategies for voltage-sag compensation using dynamic voltage restorers

Abstract

The Dynamic Voltage Restorer (DVR) is one of the most frequently used devices for voltage-sag compensation. This work explains the design procedure and comparison of two different control strategies for the compensation of balanced and imbalanced voltage sags by using a DVR. The two strategies considered are the widely-used proportional-integral (PI) controller and a new approach based on the generalized proportional-integral (GPI) controller. Both control schemes are implemented in a synchronous reference frame (SRF) and use a feedforward term to improve the time response. The simulations in PSCAD/EMTDC show the performance of both control strategies for several voltage sags and for gridfrequency deviations. The obtained results show that the SRFGPI approach is superior.