Improvement of voltage unbalance and voltage sag in radial distribution systems using DG

Most of the dispersed generation systems (DGS) have smaller installation capacity and have to be connected to the distribution network to supply electric power into the utility as well as local loads. When the DG is interconnected in parallel with the utility distribution system, some operating conflicts might arise that affect the system power quality. This paper investigate the effect of DG on the distribution network, with more focusing on power quality issues especially voltage quality issues like voltage sag and voltage unbalance. To confirm this subject, simulation results are provided to reveal the effect of DG on power quality. The purpose of the simulation is to study the effect of different sizes of synchronous DG on voltage regulation, voltage sag and voltage unbalance in two cases: without local load and with RL local load. The simulation is performed using MATLAB/SIMULINK.