Abstract

ABSTRACT:This paper describe the modelling of the power and voltage control loop of a thermal power plant of 500MW.The problem of excitation control of power systems has been extensively studied by a number of researchers and several controller designs have been reported in the literature.The generator excitation control has been shown to be an effective means for improving the damping of machine oscillations.Based on this model the exciting controller structure has been analysed and an improved voltage control system designed. The design method is based on a statefeedback technique and pole placement.Field tests have been carried out to verify the results of the designed control algorithms. Keywords:Synchronous Generator model development,Exciter, Controller, Satiability, etc. I.INTRODUCTION An excitation controller sets an output terminal reference voltage of a synchronous machine from reactive power output from the synchronous machine and a high side reference voltage of a transformer , and controls the field current to be supplied to the field winding of the synchronous machine in response to the deviation between the reference voltage and the output terminal voltage. This makes it possible to solve a problem of a conventional excitation controller in that although it can maintain the transmission voltage on the transmission bus at a fixed value, an expensive proportional-plus-integral-plus derivative controller is needed for detecting the transmission voltage on the transmission bus, which increases the manufacturing cost of the excitation controller.Synchronous generators are exclusively used for electrical power generation. The generator is supplied with real power from a prime mover, usually a turbine, whilst the excitation current power system as a source of electrical is provided by the excitation system. A design of such an excitation system should also be satisfactory for a wide range of operating conditions as well as for fault conditions. Practical methods for nonlinear control include an open-loop inverse model of the nonlinear plant dynamics and the use of feedback loops to cancel the plant nonlinearities. The approximation of a non-linear system with a linearized model yields to the application of adaptive control, where real-time measurements of the plant inputs are used, either to derive explicitly the plant model or design a controller based on this model (indirect adaptive control), or to directly modify the controller output (direct adaptive control). Typical studies concerning applications of modern algebraic and optimal control methods in excitation controller design using linear system model.In general, excitation control systems for synchronous machines have a basic function to perform automatic voltage regulation functions so as to control a terminal voltage of the synchronous generator to be constant, with ancillary functions being an over excitation limit function and an under excitation limit function so that the operation of the synchronous machine is stable and within the critical limits. In the area of synchronous generator excitation control Kanniah, Malik, Hope et al. [2] they the use of an adaptive optimal control algorithm for two real-time control applications, an optimal excitation control of a synchronous generator (OEC) and a power system stabilizer (PSS), is described. Experimental studies on a physical model of a power system showed that the proposed optimal excitation control (OEC) and power system stabilizer (PSS) can track the controlled system by parameter identification at different operating conditions. The proposed algorithm is based on linear optimal control theory. The proposed OEC and PSS can track the controlled system very rapidly. Flynn, D. Brown and M.D et al. [3] studies have suggested a