Power quality is considered a pivotal issue in modern industrial and
commercial applications especially for nuclear installations. Voltage sag is a
common power quality problem. It has an impact on the sophisticated and sensitive
electronic equipment in nuclear installations. To overcome this problem, flexible
Alternating Current Transmission Systems (FACTS) are used. One of the most
efficient FACTS, namely Dynamic Voltage Restorer (DVR) is used in power
distribution networks to mitigate voltage sag. It is a series of connected power
electronic based devices that can quickly mitigate the voltage sags and restore the
load voltage to the pre-fault value. This work proposes an improvement of
conventional (d-q-0) transformation of DVR using Proportional Integral (PI)
controller to mitigate the voltage sag in distribution network. Our implementation
of the PI controller is different than the proposed work in the literature. This
allowed enhancement of the performance. Different types of faults are modeled by
using MATLAB/SIMULINK to examine the improvement of the proposed
technique over the conventional one.