Load Frequency Control of Interconnected Power System Using Teaching Learning Based Optimization

Load Frequency Control of Interconnected Power System Using Teaching Learning Based Optimization

Adhit Roy (Department of Electrical Engineering, Dr. B. C. Roy Engineering College, Durgapur, India), Susanta Dutta (Department of Electrical Engineering, Dr. B. C. Roy Engineering College, Durgapur, India) and Provas Kumar Roy (Department of Electrical Engineering, Dr. B. C. Roy Engineering College, Durgapur, India)
Copyright: © 2015 |Pages: 16
DOI: 10.4018/ijeoe.2015010107

Abstract

This paper presents the design and performance analysis of teaching learning based optimization (TLBO) algorithm based PID controller for load frequency control (LFC) of an interconnected power system. A two area reheat thermal system equipped with PID controllers which is widely used in literature is considered for the design and analysis purpose. The design objective is to improve the transient performance of the interconnected system. The power system dynamic performance is analyzed based on time response plots achieved with the implementation of designed optimal and sub-optimal LFC regulators in the wake of 1% load disturbance in one of the areas. The results of the TLBO optimized PID controllers on a two area reheat thermal system are compared with those of artificial bee colony (ABC) and differential evolution (DE) optimized PID controllers. The TLBO optimized controllers are found to be superior in terms of peak transient deviation, settling times, and dynamic oscillations.
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1. Introduction

The interconnected power system generation is made up of several areas. In each area, load frequency controller (LFC) monitors the system frequency and tie line flows, computes the net change in the generation required and changes the set positions of the generators within the area to keep the time average of the area control error (ACE) at a low value. The aim of LFC is to achieve zero static frequency error, distribute generation among areas so that interconnected tie line flows match a prescribed schedule and balance the total generation against the total load and tie line power exchanges. The overall aim of power system engineer is to provide a good quality of electricity to the consumer. For this reason a power system must be maintained at the desired operating level characterized by constant frequency, voltage profile and load flow configuration. As the demand deviates from its nominal value with an unpredictable small amount, the operating point of power system changes, and hence, system may experience deviations in nominal system frequency and scheduled power exchanges (Kothari & Nagrath, 2011; Kothari & Dhillon, 2010; Majhi, 2009; Ibraheem & Kothari, 2005; Elgerd & Fosha, 1970).

All conventional LFC schemes have two substantial problems (1) increasing the gain of frequency feed-back will result in LFC loop instability, i.e., frequency drop control range will be limited (2) they will be unstable if there is any load disturbance in the power system. Substitution of the conventional proportional integral (PI) controller with a new PID controller can improve the operation of LFC. In conventional studies, frequency oscillations of the system are minimized by using conventional linear controllers (Tripathy, Hope & Malik, 1982). In general, different conventional control strategies are being used for LFC. Yet, the limitations of conventional PI and PID controllers are: slow and lack of efficiency and poor handling of system nonlinearities.

The researchers in the world over trying to employ several strategies for LFC of power systems to maintain the system frequency and tie line flow at their scheduled values during normal operation and also during disturbance conditions. A critical literature review on the LFC of power systems was presented in (Saikia, Nanda & Mishra 2011) where different control techniques pertaining to LFC problem were discussed.

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