Ali Feliachi

Robust load frequency control using genetic algorithms and linear matrix inequalities

In this paper, two robust decentralized control design methodologies for load frequency control (LFC) are proposed. The first one is based on H/sub /spl infin// control design using linear matrix inequalities (LMI) technique in order to obtain robustness against uncertainties. The second controller has a simpler structure, which is more appealing from an implementation point of view, and it is tuned by a proposed novel robust control design algorithm to achieve the same robust performance as the first one. More specifically, genetic algorithms (GAs) optimization is used to tune the control parameters of the proportional-integral (PI) controller subject to the H/sub /spl infin// constraints in terms of LMI. Hence, the second control design is called GALMI. Both proposed controllers are tested on a three-area power system with three scenarios of load disturbances to demonstrate their robust performances.

Dynamic and transient analysis of power distribution systems with fuel Cells-part I: fuel-cell dynamic model

The first part of this two-part-paper develops a comprehensive nonlinear dynamic model of a solid-oxide fuel cell (SOFC) that can be used for dynamic and transient stability studies. The model based on electrochemical and thermal equations, accounts for temperature dynamics and output voltage losses. The output voltage response of a stand-alone fuel-cell plant to a step load change, a fuel flow step change, and fast load variations are simulated to illustrate the dynamic behavior of SOFC for fast and slow perturbations. A method for interfacing the proposed fuel-cell models to a power system stability package is developed.

Communication delays in wide area measurement systems

This paper provides a tutorial introduction to phasor measurement units (PMU) when applied in a power system environment, provides an overview of communication alternatives for wide area measurement systems (WAMS), and computes the delay budget for each type of communication link. The goal of this study is to provide data regarding the communication delay that can be incorporated into the analysis and simulation of WAMS.

Modeling and simulation of the dynamic behavior of a polymer electrolyte membrane fuel cell

The focus of this paper is to develop a mathematical model for investigating the dynamic performance of a polymer electrolyte membrane fuel cell. The model in this work is based on physical laws having clear significance in replicating the fuel cell system and can easily be used to set up different operational strategies. Simulation results display the transient behavior of the voltage within each single cell, and also within a number of such single cells combined into a fuel cell stack system. A linear as well as a nonlinear analysis of the polymer electrolyte membrane fuel cell system has been discussed in order to present a complete and comprehensive view of this kind of modeling. Also, a comparison of the two kinds of analysis has been performed. Finally, the various characteristics of the fuel cell system are plotted in order to help us understand its dynamic behavior. Results indicate that there is a considerable amount of error in the modeling process if we use a linear model of the fuel cell. Thus, the nonlinearities present in the fuel cell system should be taken into account in order to obtain a better understanding of the dynamic behavior of the fuel cell system.

Dynamic and transient analysis of power distribution systems with fuel Cells-part II: control and stability enhancement

The objective of this paper is to analyze the dynamics of distribution systems that contain fuel cells and to enhance the stability of these systems by controlling the fuel cells. The models used in this second part of the two-part paper are the solid-oxide fuel cell (SOFC) models developed in part one. The fuel-cell control loops through the power conditioning units are first explained using a one-machine infinite bus system. Then, fuel cells are integrated into a power distribution test system, which initially contains gas turbines only. Simulation results show how a combination of fuel cells and gas turbines can help control frequency fluctuations, and supply power after islanding of the distribution system.

Stabilization of inter-area oscillation modes through excitation systems

This paper presents new analysis and design methods, based on transfer function residues to: (a) classify oscillation modes as either local or interarea; (b) determine feasibility of a given control structure such as conventional decentralized power system stabilizers (PSSs) or PSSs with remote input signals; (c) identify optimal locations for PSSs; and (d) design robust PSSs. A two-area four-generator power system is used to illustrate the proposed algorithms. >

Dynamic model of a microturbine used as a distributed generator

In this paper, a dynamic model of a microturbine, used as distributed generator, is developed. The model is suitable for transient analysis and simulation of an unbalanced three-phase power system. A microturbine unit consists of four parts: a gas turbine engine, a permanent magnet generator, a three-phase bridge AC to DC rectifier, and a power DC to AC inverter. The proposed model is built from the dynamics of each part and their interconnections. To illustrate the proposed model, an unbalanced 3-phase system that consists of a microturbine generator connected to a load is simulated using the Matlab Simulink Toolbox and power system blockset.

Optimal Decentralized Load Frequency Control

The paper presents a novel methodology for feasibility analysis and design of optimal decentralized load frequency control for multi-area interconnected electric power systems. Feasibility of the proposed decentralized control scheme is determined with a fixed mode evaluation algorithm based on eigenvalue dynamics. The eigenvalue sensitivity expressions are also used to determine decentralized feedback gains that will result in system transient performance similar to the one obtained with a centralized optimal control law. The methodology is illustrated with a two-area power system example.

Voltage Control and Active Power Management of Hybrid Fuel-Cell/Energy-Storage Power Conversion System Under Unbalanced Voltage Sag Conditions

This paper concentrates on the control of hybrid fuel-cell (FC)/energy-storage distributed generation (DG) systems under voltage sag in distribution systems. The proposed control strategy makes hybrid DG system work properly when a voltage disturbance occurs in distribution system, and it stays connected to the main grid. To distribute the power between dc power sources and stabilize the dc-link power, a Lyapunov-based neuro-fuzzy control strategy has been developed. This controller determines the supercapacitor power that should be generated according to the amount of available energy in dc-link. Also, current control strategies for the FC converter (boost) and supercapacitor converter (buck-boost converter) are designed by proportional-integral and sliding-mode control consequently. Moreover, a complementary control strategy for voltage source converter based on positive and negative symmetrical components is presented to investigate the voltage sag ride-through and voltage control capability. The hybrid system is studied under unbalance voltage sag condition. Simulation results are given to show the overall system performance including active power control and voltage sag ride-through capability of the hybrid DG system.

PAT: a power analysis toolbox for MATLAB/Simulink

A power system simulation environment in MATLAB/Simulink is presented in this paper. The developed Power Analysis Toolbox (PAT) is a very flexible and modular tool for load flow, transient and small signal analysis of electric power systems. Standard power system component models and a wide range of FACTS devices are included. Its data structure and block library have been tested to confirm its applicability to small-to medium-sized power systems. Its advantages over an existing commercial package are given.