الفهرس 
INTRODUCTION AND PREVIOUS WORKOnly 14 pages are availabe for public view
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Abstract
The demand for a new control policy to improve dynamic performance of large interconnected power systems is becoming very essential. Among all recently developed control approaches, the fuzzy logic control policy has the potential of being the most suitable and promising and provides a simplified, feasible solution for large interconnected system problems. In this thesis, a systematic approach is presented for the implementation of adaptive fuzzy logic power system stabilizers to standard and multimachine power systems. The main idea of fuzzy logic technique, is to retain some state variables as inputs to the adaptive fuzzy logic power system stabilizer in order to get deffuzzfied signal at its output. For power system, the speed deviation, the acceleration, the terminal voltage deviation and the change in terminal voltage deviation are considered as inputs to the adaptive fuzzy logic power system stabilizer. The output of the adaptive fuzzy logic power system stabilizer is the control signal injected to the summing point of the excitation system at all operating conditions; steady state and transient. The inputs are to be interpreted into a number of linguistic variables to relate the input and output fuzzy sets. Then, it is necessary to transform the fuzzy set obtained into numerical form, using an appropriate defuzzification technique. Two adaptive fuzzy logic controllers for power system are proposed in this study; which are: two inputs adaptive fuzzy logic power system stabilizer and four inputs adaptive fuzzy logic power system stabilizer. Tuning of the fuzzy logic controllers is online and based on modifying the controller inputs in order to match the instantaneous power system fluctuations. A new proposed performance measure is used to adjust the scaling factors. Other tuning techniques such as fuzzy set representing the meaning of linguistic values and the if-then rules are also used. The feasibility of using such adaptive fuzzy logic controllers to damp electromechanical oscillations is confirmed through time simulations of power system responses, subjected to the most expected disturbances. It is proved that both two inputs adaptive fuzzy logic power system stabilizer and four inputs adaptive fuzzy logic power system stabilizer contribute effectively to electromechanical oscillations damping. They are found to be more superior than conventional power system stabilizer and conventionally known self-tuning controllers. It is proved that application of such recent fuzzy controls to multimachine power system can contribute in using AVR’s with less ratings and prices than with conventional controllers for the same oscillations damping conditions. Also, application of the scaling factors routine has resulted in adapting the proposed control algorithm effectively at all normal and abnormal system, operating conditions, as well as it provides the desired regulation. In the case of multimachine power systems, since only local measurements are required by the fuzzy logic controllers on each generating unit, the proposed controller is of decentralized output feedback form and easy for practical implementation.