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This paper introduces a new dynamic wide‐area cooperative protection based on cooperative control of distributed multi‐agent systems and graph theoretical methods. For power system cooperative protection, a new voting method is designed that manages each agent's cooperation according to each protection area. Cooperative protection areas work together and make a wide area of cooperative protection for the specific protection scheme. As the power system configuration varies, the voting management and the wide‐area cooperative protection dynamically change. The proposed protection method decisions are collective, while a centralized master does not exist, and local information is used. A fault detection code and a wide‐area fault detection code are presented for fault detection. The suggested dynamic wide‐area cooperative protection scheme is tested on an IEEE 39‐bus test system. The proposed protection performance is studied as backup protection for distance relays during normal, stable power swings, unstable power swings, and load encroachment conditions. [ABSTRACT FROM AUTHOR]

The Automatic Voltage Regulator (AVR) system is one of the important systems in power grids. Proportional - Integral (PI) controller is usually used in industries to control the AVR system. However, to increase the flexibility or improving the performance of the PI controller, fractional order PID (FOPID) or combined PID and fuzzy controllers can be used. A new method for the control of AVR has been proposed in this paper. For this purpose, a Fuzzy-PID controller with optimized membership functions has been employed. Input membership functions along with gains of Fuzzy-PID controller have been optimized with imperialist competitive algorithm (ICA) to control the AVR system. Optimizations have been done with various fitness functions. To compare, simulations have been carried out by optimized fractional order PID (FOPID) controller, too. Results of simulations have illustrated that the proposed controller has better performance compared to the FOPID controller according to settling time, overshoot, fitness function and the maximum of control signal values in all cases in such a way that the minimum improvement of overshoot, settling time, the maximum value of control signal, and fitness function value have improved 59%, 33%, 65%, and 3%, respectively. Moreover, to verify the robustness of the proposed controller to system uncertainties, simulations have been carried out by changing the parameters of the system. Results of simulations have shown the perfect performance of the proposed controller. [ABSTRACT FROM AUTHOR]

New approach based on structured singular value ([mu]-synthesis) was proposed for the robust decentralized unified power flow controller (UPFC) design. To achieve decentralization, using the Schauder fixed point theorem the synthesis and analysis of multi-input multi-output (MIMO) control system translated into a set of equivalent multi-input single-output (MISO) control system. Power systems similar to other industrial plants contain different kinds of uncertainties which should be considered in controller design procedure. For this reason, the idea of [mu]-synthesis technique being used for designing of UPFC controllers. The proposed [mu]-based controller had a decentralized scheme and advantage of a decentralized controller design reduction in the controller complexity and suitability for practical implementation. The effectiveness of the proposed control strategy evaluated under operating conditions on damping of low frequency oscillations in comparison with the classical controller to demonstrate its robust performance through nonlinear time simulation and some performance indices. Key words: Unified power flow controller, decentralized control, [mu]-synthesis, Flexible Ac Transmission Systems (FACTS), robust control, structured singular value, INTRODUCTION In recent years, the fast progress in the field of power electronics has opened new opportunities for the power industry via utilization of the controllable FACTS devices such as [...]

Load Frequency Control (LFC) is one the most important issues in electrical power system design/operation and is becoming much more significant recently with increasing size, changing structure and complexity in interconnected power systems. In practice LFC systems use simple Proportional-Integral (PI) or Integral (I) controllers. However, since the PI or I control parameters are usually tuned based on classical or trial-and-error approaches, they are incapable of obtaining good dynamic performance for various load changes scenarios in multi-area power system. For this reason, in this study the PI and I control parameters are tuned based on Hybrid Particle Swarm Optimization (HPSO) algorithm method for LFC control in two-area power system. Because HPSO is an optimization method, therefore, in the uncertainty area of controller parameters, finds the best parameters for controller and obtained controller is an optimal controller. A two-area power system example is given to illustrate proposed methods. To show effectiveness of proposed method and compare the performance of optimized PI and I type controllers, several time-domain simulation for various load changes scenarios are presented. Simulation results emphasis on the better performance of optimized PI controller in compared to optimized I controller in LFC. Key words: Load Frequency Control (LFC), Hybrid Particle Swarm Optimization (HPSO), decentralized control, deregulated power systems, INTRODUCTION Large-scale power systems are normally composed of interconnected subsystems or control areas. The connection between the control areas is done using tie lines. Each area has its own generator [...]

An industrial plant, such a power system, always contains parametric uncertainties. In the design of a controller the uncertainties have to be considered. Otherwise, if the real plant differs from the assumed plant model, a controller, designed based on classical controller design approaches, may not ensure the stability of the overall system. In this paper design of robust control for the UPFC controllers including power-flow and DC voltage regulator, using a [H.sub.[infinity]] loop-shaping design via a normalized coprime factorization approach, where loop-shape refers to magnitude of the loop transfer function L = GK as function of frequency is presented. As an example, we have designed a case for the system to compare the proposed method with a conventional method (classical P-I controller). AS the results of the linear and nonlinear simulations, the validity of the proposed method has been confirmed. Keywords: Unified Power Flow Controller (UPFC); Flexible AC Transmission Systems (FACTS); power system oscillation; [H.sub.[infinity]] loop-shaping, INTRODUCTION The Flexible AC Transmission Systems (FACTS) based on power electronics offer an opportunity to enhance controllability, stability, and power transfer capability of AC transmission systems . The Unified Power [...]

This paper presents the application of hybrid particle swarm optimization technique to find optimal location of unified power flow controller to achieve optimal power flow. Objective function in the OPF, that is to be minimized, are the overall cost functions, which include the total active and reactive production cost function of the generators and installation cost of UPFCs. The OPF constraints are generators, transmission lines and UPFCs limits. We propose HPSO algorithm to consider the objective function and all equality and inequality constraints. Simulations are performed on 4 bus test system and modified IEEE 14 bus system for optimal location of UPFC and the results obtained are encouraging and will be useful in electrical restructuring. Keywords: Deregulated Power System, Hybrid Particle Swarm Optimization, Optimal Location, Optimal Power Flow, Unified Power Flow Controller, INTRODUCTION Nowadays, actual power systems are facing new challenges due to deregulation and restructuring of the electricity markets. Hence, in order to be able to obtain a high operational efficiency [...]

The Load Frequency Control problem has been a major subject in electrical power system design/operation and is becoming more significant recently with increasing size, changing structure and complexity in interconnected power systems. In practice LFC systems use simple proportional-integral controllers. However, since the PI control parameters are usually tuned based on classical or trial-and-error approaches, they are incapable of obtaining good dynamic performance for a wide range of operation conditions and various load changes scenarios in multi-area power system. For this problem, in this paper quantitative feedback theory method is used for LFC control in multi-area power system with system parametric uncertainties. The system parametric uncertainties are obtained by changing parameters by 40% simultaneously from their typical values. A two-area power system example with a wide range of parametric uncertainties is given to illustrate proposed method. To show effectiveness of proposed method, a classical I type controller optimized by genetic algorithm is designed for LFC for comparison with QFT. The validity of the proposed method was confirmed by comparing it results with those of traditional methods (I controller optimized by genetic algorithm) has been confirmed. Key words: Load Frequency Control, robust control, quantitative feedback theory, and decentralized control deregulated power system, INTRODUCTION For large-scale power systems, which normally consist of interconnected control area, Load Frequency Control (LFC) is important to keep the system frequency and the inter-area tie power as close [...]

In a deregulated electricity market, it may always not be possible to dispatch all of the contracted power transactions due to congestion of the transmission corridors. The ongoing power system restructuring requires an opening of unused potentials of transmission system due to environmental, right-of-way and cost problems which are major hurdles for power transmission network expansion. Flexible ac transmission systems devices can be an alternative to reduce the flows in heavily loaded lines, resulting in an increased loadability, low system loss, improved stability of the network, reduced cost of production and fulfilled contractual requirement by controlling the power flows in the network. A method to determine the optimal location of thyristor controlled series compensators has been suggested in this paper based on real power performance index and reduction of total system reactive power loss. Keywords: Congestion, Optimal Location, Deregulated Power System, INTRODUCTION In a competitive electricity market, congestion occurs when the transmission network is unable to accommodate all of the desired transactions due to a violation of system operating limits. Congestion [...]