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Load Frequency Control of Interconnected Hydro-Thermal System with Conventional Controllers and Expert Controllers  [cached]
Krishan Arora,Baljinder Singh
Buletin Teknik Elektro dan Informatika , 2012,
Abstract: Load-frequency control (LFC) is a part of the Automatic Generation Control (AGC) in power systems, the aim of which is to maintain the system frequency and tie line flow at their scheduled values during normal period in an interconnected system. This research paper is devoted to explore the interconnection of the load frequency control of hydro power system and the thermal system. The thermal system is comprised with governor dead band, generation rate constraint and boiler dynamics where as the hydro system is comprised with generation rate constraint. The conventional PID controller does not have adequate control performance with the consideration of nonlinearities and boiler dynamics. To overcome this drawback, Genetic Algorithm helps in solving optimization problems by exploitation of random search. The aim of the proposed expert controller is to restore the frequency to its nominal value in the smallest possible time whenever there is any change in the load demand etc.
Automatic Generation Control for Interconnected Hydro-thermal System with the help of Conventional Controllers
Vikram Kumar Kamboj,Krishan Arora,Preeti Khurana
International Journal of Electrical and Computer Engineering , 2012, DOI: 10.11591/ijece.v2i4.305
Abstract: The Problem of Automatic Generation Control of large interconnected multi-area system is necessitated by the importance of maintenance of frequency and tie-line flows at their scheduled values. Disturbance in any part of the power system network has its effect on the frequency and tie-line power flows of the entire network. Thus, It is the responsibility of the Power system engineers to ensure that adequate power is delivered to the load reliably and economically so that nominal condition will be re-established. This Research paper aims to represents how nominal value can be achieved by close loop control of real and reactive powers generated in the controllable source of the system with the help of conventional controllers.
Application of artificial intelligence in load frequency control of interconnected power system
S Prakash, SK Sinha
International Journal of Engineering, Science and Technology , 2011,
Abstract: This paper presents the use of artificial intelligence to study the load frequency control of interconnected power system. In the proposed scheme, a control methodology is developed using Artificial Neural Network (ANN) and Fuzzy Logic controller (FLC) for interconnected hydro-thermal power system. The control strategies guarantees that the steady state error of frequencies and inadvertent interchange of tie-lines power are maintained in a given tolerance limitations. The performances of the controllers are simulated using MATLAB/SIMULINK package. A comparison of Fuzzy controller and ANN controller based approaches shows the superiority of proposed ANN based approach over Fuzzy one for different loading conditions (1% and 2% step load variations). The simulation results also tabulated as a comparative performance in view of settling time and peak over shoot.
Passivity and passivation of interconnected time-delay models of reheat power systems  [PDF]
Magdi S. Mahmoud,Abdulla Ismail
Mathematical Problems in Engineering , 2006, DOI: 10.1155/mpe/2006/90416
Abstract: This paper investigates the problems of delay-dependent passivity and passivation of a class of linear interconnected time-delay systems with particular emphasis on multiarea reheat power systems. This class contains state delay in the dynamics and observation at the subsystem (local) level. A new state transformation is developed to exhibit the delay dependence in the system dynamics and a less conservative passivity-bounding inequality is incorporated. Through the analytical development, it is established that the passivity condition can be cast in a linear matrix inequality (LMI) format at the subsystem level thereby facilitating decentralized passivity analysis. For state-feedback passivation, it is proven that it is indifferent to use instantaneous or delayed decentralized state feedback. The case of dynamic output-feedback passivation is also treated. The analytical developments are simulated to a typical multiarea power system and the ensuing results show satisfactory performance.
performance evaluation of evolutionary designed conventional AGC controllers for interconnected electric power system studies in a deregulated market environment
Y Karnavas, K Dedousis
International Journal of Engineering, Science and Technology , 2010,
Abstract: Electric power industry is currently in transition from vertically integrated utilities to an industry that will incorporate competitive companies. This increases the complexity of the load frequency issue and calls for more insight and research. In this context, the tuning of a multi-area automatic generation control (AGC) system after deregulation and furthermore, the effect of reheat turbines dynamics in the power system performance, are not yet discussed in depth and are studied in this work. The effect of bilateral contracts on the dynamics of the system is taken into account and the concept of DISCO participation matrix for these bilateral contracts is simulated. Genetic algorithms are adopted in order to obtain the optimal parameters of the load-frequency controllers as well as of the frequency biases of thermal systems with reheat turbines. Also, since the optimum parameter values of the classical AGC have been obtained in the literature by minimizing the popular integral of the squared errors criterion (ISE) only, an effort is made in this study to show that this criterion does not give always the best system performance especially in a deregulated environment. In this work, we investigate the optimum adjustment of the load frequency controllers using a set of performance indices which are various functions of error and time. In this way, someone can observe the various performances that such a kind of power system might have when a different performance index is used. It should be noted that to the extent of the authors' knowledge, this kind of optimization has not been done yet in the literature. The performances of the tuned two–area AGC system are obtained using appropriate Matlab/Simulink models. Finally, it is envisaged that the synthesis procedure highlighted in this paper could be of practical significance for tuning conventional AGC controllers for an interconnected thermal-electric power system in a deregulated environment.
Power System Restoration Index for Load Frequency Control Assessment Using Artificial Bee Colony Algorithm in a Two-Area Reheat Interconnected Power System Co-ordinated with SMES Units  [PDF]
R . Jayanthi,I.A.Chidambaram
International Journal of Soft Computing & Engineering , 2012,
Abstract: This paper proposes evaluation of Restoration Indices for the Load-Frequency Control assessment of a Two-Area Two Unit Interconnected Power System (TATURIPS) coordinated with Superconducting Magnetic Energy Storage (SMES) units. As Proportional Integral (PI) type controller is still widely used for the solution of the Load Frequency Control (LFC) problem, in this paper also PI controllers are used. The optimal gain tuning of PI controllers for various case studies for the LFC problem is proposed and obtained using Artificial Bee Colony (ABC) algorithm. These controllers are designed and implemented in a TATURIPS coordinated without and with SMES units. The system was simulated and the frequency deviations, tie-line power deviation, control input deviations and additional mechanical power generation required for step load disturbance of 0.01 p.u.MW and 0.04 p.u.MW without and with outage condition in area-1 are presented. The simulation results and the evaluation of the Restoration Indices shows that the TATURIPS coordinated with SMES units ensures a better transient and steady state response and improved Restoration Indices than that of TATURIPS without SMES Units.
Synthesis of Decentralized Variable Gain Robust Controllers for Large-Scale Interconnected Systems with Structured Uncertainties  [PDF]
Shunya Nagai,Hidetoshi Oya
Journal of Control Science and Engineering , 2014, DOI: 10.1155/2014/848465
Abstract: In this paper, we propose a decentralized variable gain robust controller which achieves not only robust stability but also satisfactory transient behavior for a class of uncertain large-scale interconnected systems. For the uncertain large-scale interconnected system, the uncertainties and the interactions satisfy the matching condition. The proposed decentralized robust controller consists of a fixed feedback gain controller and a variable gain one determined by a parameter adjustment law. In this paper, we show that sufficient conditions for the existence of the proposed decentralized variable gain robust controller are given in terms of LMIs. Finally, a simple numerical example is included. 1. Introduction To design control systems, it is necessary to derive a mathematical model for controlled systems. However, there always exist some gaps between the mathematical model and the controlled system; that is, uncertainties between actual systems and mathematical models are unavoidable. Hence for dynamical systems with uncertainties, so-called robust controller design methods have been well studied in the past thirty years, and there are a large number of studies for linear uncertain dynamical systems (e.g., see [1, 2] and references therein). In particular for uncertain linear systems, several quadratic stabilizing controllers and one have been suggested (e.g., [3–5]), and a connection between control and quadratic stabilization has also been established [6]. In addition, several design methods of variable gain controllers for uncertain continuous-time systems have been shown (e.g., [7–9]). These robust controllers are composed of a fixed gain controller and a variable gain one, and variable gain controllers are tuned by updating laws. Especially, in Oya and Hagino [8] the error signal between the desired trajectory and the actual response is introduced and the variable gain controller is determined so as to reduce the effect of uncertainties. On the other hand, the decentralized control for large-scale interconnected systems has been widely studied, because large-scale interconnected systems can be seen in such diverse fields as economic systems, electrical systems, and so on. A large number of results in decentralized control systems can be seen in ?iljak [10]. A framework for the design of decentralized robust model reference adaptive control for interconnected time-delay systems has been considered in the work of Hua et al. [11] and decentralized fault tolerant control problem has also been studied [12]. Additionally, there are many existing results
L. ShanmukhaRao,N. Venkata Ramana
International Journal of Advances in Engineering and Technology , 2012,
Abstract: This paper presents analysis on Improvement of dynamic performance of a three-area Hydro-thermal system interconnected with AC tie-line parallel with HVDC link when subjected to parametric uncertainties when compared to a three-area Hydro-thermal system interconnected with AC tie-line. In this paper three areas consists of one Hydro and one thermal power plant are considered.AC-Tie line parallel with HVDC link is used as a system interconnection between all the three areas. Open transmission access and the evolution of more socialized companies for generation, transmission and distribution affects the formulation of Automatic Generation Control (AGC) problem. So, the traditional three area system is modified and taken into the account the effect of bilateral contracts on the dynamics.
An Investigation of ANN based PID Controllers using Three- Area Load Frequency Control in Interconnected Power System
V.Shanmuga Sundaram ,,Dr. T.Jayabharathi
International Journal of Engineering Science and Technology , 2011,
Abstract: The LFC problem, which is the major requirement in parallel operation of several interconnected systems, is one of very important subjects in power system studies. In this study, the power systems with threeareas connected through tie-lines are considered. The perturbation of frequencies at the areas and resulting tieline power flows arise due to unpredictable load variations that cause mismatch between the generated and demanded powers. The objective of LFC is to minimize the transient deviations and to provide zero steady state errors of these variables in a very short time. Variation in load frequency is an index for normal operation of power systems. When load Perturbation takes place anywhere in any area of the system, it will affect the frequency at other areas also. To control load frequency of power systems various controllers are used in different areas, but due to non-linearity's in the system components and alternators, these controllers cannot control the frequency quickly and efficiently. The simple neural networks can alleviate this difficulty. This paper deals with various controllers like proportional integral (PI), Proportional Integral Derivative (PID) andANN (Artificial neural network) tuned PID controller for three area load frequency control.The performance of the PID type controller with fixed gain, Conventional integral controller (PI) and ANN based PID (ANN-PID) controller have been compared through MATLAB Simulation results. Comparison of performance responses of integral controller & PID controller show that the ANN- PID controller has quite satisfactory generalization capability, feasibility and reliability, as well as accuracy in three area system. The qualitative and quantitative comparison have been carried out for Integral,PID and ANN- PID controllers. The superiority of the performance of ANN over integral and PID controller is highlighted.
Hybrid GA-SA Based Optimal AGC of a Multi-Area Interconnected Power System
Ibraheem,Omveer Singh
International Journal of Electrical and Power Engineering , 2012, DOI: 10.3923/ijepe.2010.78.84
Abstract: The Automatic Generation Control (AGC) of interconnected power systems has been considered as one of the most challenging problems for about the last four decades. Following the pioneering research of Elgerd and Fosha in 1970, a heap of research are appeared from time to time on optimal AGC of power systems considering various structural as well as technical aspects of power systems. This study is an attempt to propose a design of optimal AGC gains of a multi-area power system. The design of optimal AGC gains is based on Genetic Algorithm (GA) and Simulated Annealing (SA). It is a synergetic combination of GA and SA through a penalty function. The penalty function is derived based on the transient response specifications of dynamic response of the interconnected power system. A multi-area interconnected power system model is considered for the investigations. The power system model consists of three identical control areas consisting of reheat thermal plants. The investigations have been carried out with the designed Automatic Generation Controllers (AGC) based on GA-SA considering 2% load perturbation in one of the areas. The system dynamic responses obtained for various system states are compared with those achieved using optimal controllers derived using Linear Quadratic Regulator (LQR) theory. The simulation results show that the proposed GA-SA based optimal load frequency controllers are superior in all respects in comparison to the optimal AGC based on LQR theory.
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