Güç sistem kararlayıcıları ve uygulamaları

Abstract

frequency oscillations successfully compared to delta-P-omega type. But in delta-P- omega type, PSS could damp them perfectly. It can be noted from these simulations that, power system stabilizers, especially dclta-P-omega types, can damp the low frequency oscillations in power systems successfully. XV

POWER SYSTEM STABILIZERS AND THEIR APPLICATIONS SUMMARY KEYWORDS : Power systems, power system control, excitation control, small signal stability, power system slahili/crs In recent years, electric power systems, worldwide, have grown markedly in size and complexity. In order to maximize efficiency of generation and distribution of electric power, the interconnections between individual utilities have increased and the generators have been required to operate at maximum limits for extensive periods of time. In addition, the most economic sites for generation plants are often remote from load centers like metropolitan cities, industrial centers, etc. Power must be transmitted over long distances. The majority of power system interconnections are made through AC transmission lines and the interconnected systems, there may be thousands of synchronous generator in service to supply the load. Because of the many generators in service, controllability and reliability problem occurred in interconnected power systems. The reliability of the interconnected system is enhanced by virtue of the capability of transferring power readily from one area to others within the large systems. For improving the controllability and reliability, modern control techniques and equipments are used in power systems. Excitation system and control, primary system control, automatic voltage regulators (AVR), governors and power system stabilizers (PSS) are important control equipments of generating systems. In interconnected power systems, some electromechanical oscillations may occur. These oscillations appear in turbine-generator shaft, and as a result angular speed changes. These oscillations are called `low frequency oscillations'. A synchronous generator and its controllers have dynamic non-linear characteristics. For analysis of this system, linearized dynamic equations have to be known. In this thesis, excitation system control is studied using PSS. Computer aided simulations are made. One machine-infinite bus system is used in the simulations. Chapter one is introductory. Basic power system components are introduced and stability concepts are classified in chapter two. In chapter three, linear models and state equations of power system components are given. These state equations are used in simulations. In chapter four, models, types, and linear state equations of PSS are given. At the end of this chapter, linear state equations of the whole system with ten state variables are obtained. In chapter five, results of the simulations are illustrated. PSS's types simulated are delta-omega and delta-P-omega. In delta-omega type, PSS could not damp low xivfrequency oscillations successfully compared to delta-P-omega type. But in delta-P- omega type, PSS could damp them perfectly. It can be noted from these simulations that, power system stabilizers, especially dclta-P-omega types, can damp the low frequency oscillations in power systems successfully. XV