الفهرس 
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Abstract
Power quality is a very important issue due to its impact on electricity suppliers, equipment manufactures and customers. One of the major problems dealt in this thesis is the voltage sag/swell and its severe impacts on sensitive equipments.
The main goal of this research work is the assessment of voltage deviations to determine the affected area and monitoring this area to determine the minimum number and location of monitors that detect the voltage sag/swell. In addition, a suitable device is utilized to mitigate the voltage deviations problem in power systems.
The evaluation of voltage deviations starts with the correct assessment and monitoring for this voltage. The method of fault positions is used to assess the voltage sag performance of an existing power system. Several parameters that affect the sag performance results such as fault impedance, number of fault positions on each line and the values of pre-fault voltages are studied and analyzed.
A proposed method based on modified monitor reach area (MMRA) technique is introduced to determine the optimal number and location of monitors, so that every fault is detected at least a given number of power quality monitors. The formulation of optimization problem is extended for application in large power networks by adapting the modeling approach for the sag monitor placement problem. The objective function is proposed to be used with this algorithm to find the optimal number and location of monitors that detect the voltage deviations.
The results of the monitoring program are then used to perform voltage sag estimation, adjusting the stochastic assessment and extending monitoring results to non-monitored buses. The proposed method thereafter is used to determine the optimal monitor placement for voltage sag/swell. A simulation test results are obtained and analyzed using MATLAB/SIMULINK model for IEEE 30-bus test system.
Finally, a proposed algorithm is presented to mitigate the effect of voltage deviations using dynamic voltage restorer (DVR) and distributed static synchronous compensator (D-STATCOM) for balanced and unbalanced conditions. The modeling and simulation of DVR and D-STATCOM using MATLAB/SIMULINK has been presented and applied to IEEE 30-bus test system. The simulation results show that the DVR has a capability of compensating voltage sag/swell quickly and provides excellent voltage regulation with reduced rating as compared to D-STATCOM.