DESIGN OF DAMPING CONTROLLER USING SSSC

Abstract

Due to various reasons such as population growth, industrialization, improvement of life style etc., the demand of electrical power is ever increasing. However, the development of new infrastructure for power generation and dispatch (transmission and distribution) is often restricted due to various economic and environmental constraints. Under this scenario, it is imperative to enhance the power transfer capability of the existing transmission corridors up to their thermal limits. Now, the power transfer limit of transmission corridor is often restricted by the stability considerations. Therefore, the power transfer capability of any transmission system can be improved by enhancing the system stability through dynamic control of various systems parameters such as line impedance, bus voltage magnitudes and angles etc. This can be achieved by using Flexible AC Transmission System (FACTS) controllers. Use of these controllers, which are essentially high speed power electronic controllers, results in enhanced utilization of the existing transmission system, Among various FACTS devices, one of the most important controllers is Static Synchronous Series Compensator (SSSC). SSSC is a series connected device, which directly or indirectly modifies the line impedance by inserting a variable voltage in series with the line, thereby controlling the power flow over the line. This provides an opportunity to relieve heavily loaded lines, enhance steady state power flow over a transmission line. Moreover, a SSSC can also enhance the power system stability significantly by dynamically changing the line impedance through a properly designed control system. Traditionally control systems are designed through mathematical analysis and synthesis technique. In mathematical analysis, it is quite difficult to obtain an accurate mathematical model of the process to be controlled; highly non-linear systems like power system. Because of the inaccurate model, it is often quite an arduous task to design a control system which would be effective over a wide range of operating conditions. Under these conditions, Fuzzy Logic Controllers (FLCs) can be*used quite effectively for controlling the process. Fuzzy logic controllers are essentially `model free' controllers, which try to control a process, based on the experience of a skilled human operator without requiring a detailed model of the process to be controlled.