Recently it has been focused on the behavior of the of distribution networks especially from power quality side because of disturbances caused by the non-linear loads, Increase in the number of electronic devices and growth of renewable energy sources. Power quality measures the efficiency of electric power transmitted from generation to the industrial, domestic and commercial consumers. At least 50% of power quality problems are of voltage quality type. In a power system voltage sags and voltage distortion introduced by harmonics are considered to be the most severe affecting power quality, because of both utilities and consumers are affected by these disturbances. These problems could be solved by: design equipment's and electrical systems to prevent electrical disturbances from causing equipment's or systems to malfunction, Analyze the symptoms of a power quality problems to determine its causes and solutions, study the medium that is transmitting the electrical disturbance and eliminate or reduce the effect of that medium. Treat the symptoms of the power quality problems by using the power conditioning device and custom power device. The presents work considers the power quality problems such as, sags, swells, harmonics, voltage interruptions and transients. A techniques which are of two categories power conditioning devices and custom power devices are investigated and the results showed that the second method is the most efficient and effective method to solve the power quality problems and protect the sensitive loads from power disturbances. The modeling and simulation of a power distribution network is achieved using MATLABL/Simulink. Three phase fault and double line to ground fault are created with the proposed system, and the faults are initiated at a duration of 0.8 sec till 0.95 sec. Comparison the power quality problems with and without custom power device are presented with the help of Dynamic Voltage Restorer (DVR).

Power quality is a problem that leads to financial issues. Many surveys have been shown that poor power quality causes large economic losses to industrial sectors and large amount of power is wasted due to power quality problems like sags, swells, harmonics, flickers etc. The present work considers, the modeling and simulation of a dynamic voltage restorer (DVR), which is achieved using MATLAB/Simulink. Faults are created with the proposed systems, and the disturbances are initiated at a duration of 0.8 sec till 0.95 sec. Comparison of the performances of the Fuzzy neural and Fuzzy logic based DVR are presented. Results are showed that Fuzzy logic controller is able to restore the load voltage to the nominal value in both linear and non linear loads quickly and efficiently. But when the 2 nd and 3 rd harmonics are superimposed on the voltage sag and voltage swell by the application of 3-ph programmable source, the fuzzy logic controller fails to restore and reduce the harmonic content to an acceptable values which is according to IEEE standard 3% for the individual voltage and 5% for the three phase voltage. While the Fuzzy neural controller has been very powerful and efficient to restore the load voltage to the pre-sag value and make it smooth under different cases of faults and nonlinear load conditions and keep the harmonics within the permissible limits in all cases.