A Hybrid Particle Swarm Optimizationfor Distribution State Estimation

Naka, S.; Genji, T.; Yura, T.; Fukuyama,Y

Author Affiliations: Kansai Electric Power Co., Japan; Fuji Elec-tric Co., Japan.

Abstract: This paper proposes a hybrid particle swarm optimiza-tion for a practical distribution state estimation. The proposed methodconsiders nonlinear characteristics of the practical equipment and ac-tual limited measurements in distribution systems. The method can es-timate load and distributed generation output values at each node byminimizing the difference between measured and calculated voltagesand currents. The feasibility of the proposed method is demonstratedand compared with an original particle swarm optimization basedmethod on practical distribution system models. Effectiveness of theconstriction factor approach of particle swarm optimization is also in-vestigated. The results indicate the applicability of the proposed stateestimation method to the practical distribution systems.

Keywords: Distributed generation, distribution state estimation,hybrid particle swarm optimization, modern heuristic method, voltageregulator.

Preprint Order Number: PE-079PRS (08-2002)Discussion Deadline: January 2003

A Probabilistic Methodology forDistribution Substation Location

Khodr, H.M.; Melian, J.A.; Quiroz, A.J.; Picado, D.C.; Yusta,J.M.; Urdaneta, Aj.

Author Affiliations: Universidad Simon Bolivar, Venezuela;AES-Venezuela; Universidad de Zaragoza, Spain.

Abstract: A probabilistic methodology is presented, conceived toassist electric system planning engineers in the selection of the distribu-tion substation locations, taking into account the hourly load changes orthe daily load cycle. The hourly load centers for each of the differenthourly load scenarios are calculated deterministically. These locationpoints, properly weighted according to their correspondent load magni-tude, are used to calculate the best fit probability distribution. This dis-tribution is used to determine the maximum likelihood perimeter of thearea where the substation should preferably be located. Results are pre-sented and discussed for the application of the methodology to a realcase, assuming three different bivariate probability distributions: theGaussian distribution, a bivariate version of Freund's exponential dis-tribution, and the Weibull probability distribution.

Keywords Power distribution planning, substations, probability.Preprint Order Number: PE-094PRS (08-2002)Discussion Deadline: January 2003

Human Factors Aspects of PowerSystem Voltage Contour Visualizations

Overbye, T.J.; Wiegmann, D.A.; Rich, A.M.; Sun, Y

Author Affiliations: University of Illinois at Urbana-Champaign, USA.Abstract: This paper presents experimental results associated with

human-factors aspects of utilizing color contours to visualize electricpower system bus voltage magnitude information. Participants were di-vided into three groups: the first group saw only one-line numeric data,the second only one-line contour data, while the third saw both. Thepurpose of the experiment was to determine how quickly participantscould both acknowledge low voltage violations and perform correctivecontrol actions. Results indicated the contour-only visualization re-sulted in the quickest voltage violation acknowledgments, while the nu-meric-data-only visualization resulted in the quickest solution times.Testing was done using a modified version of the IEEE 1 18 bus system.

Keywords Power system operations and planning, voltage visual-ization, contouring, human factors.

Preprint Order Number: PE-106PRS (08-2002)Discussion Deadline: January 2003

Use of ARMA Block Processingfor Estimating Stationary Low-FrequencyElectromechanical Modes of Power Systems

Wies, R.W; Pierre, J.W; Trudnowski, D.J.

Author Affiliations: University of Alaska at Fairbanks, USA; Uni-versity of Wyoming, USA; Montana Tech, USA.

Abstract: Accurate knowledge of low-frequency electromechani-cal modes in power systems gives vital information about the stabilityof the system. Current techniques for estimating electromechanicalmodes are computationally intensive and rely on complex system mod-els. This research complements model-based approaches and uses mea-surement-based techniques. This paper discusses the development ofan auto-regressive moving average (ARMA) block processing tech-nique to estimate these low-frequency electromechanical modes frommeasured ambient power system data without requiring a disturbance.This technique is applied to simulated data containing a stationarylow-frequency mode generated from a 19-machine test model. The fre-quency and damping factor of the estimated modes are compared withthe actual modes for various block sizes. This technique is also appliedto 35-minute blocks of actual ambient power system data before and af-ter a disturbance and compared to results from Prony analysis on theringdown from the disturbance.

Keywords Estimation, Interconnected power systems, power sys-tem modeling, power system monitoring, power system transients,power system state estimation, power system stability, power systemcontrol, signal analysis, signal sampling.

Preprint Order Number: PE-41 1PRS (08-2002)Discussion Deadline: January 2003

Hydrothermal Market Simulator UsingGame Theory: Assessment of Market Power

Villar, J.; Rudnick, H.

Author Affiliations: Pontificia Universidad Cat6lica de Chile.Abstract: The aim of this work is to build a model able to simulate a

hydrothermal electric power market based on simple bids to a powerexchange. The model studies the behavior of different market agents ina short-term horizon and delivers information about spot prices, use ofwater, and other relevant variables. Initially, a thermoelectric market issimulated through a static model based on Cournot concepts. The addi-tion of hydroelectric power stations and time dependencies is madelater, using a dynamic programming algorithm to build a dynamicmodel. In each stage and state of the dynamic programming, aNash-Cournot equilibrium is determined to assess the behavior of thethermoelectric power stations (static model). Different strategies thatfirms can follow and the consequences of each one of them are ana-lyzed. Market power mitigation effects of physical and financial bilat-eral contracts are also investigated. A case study with data on theChilean power system is presented and analyzed.

Keywords Power sector deregulation, electric market, marketpower, Cournot, oligopoly, game theory.

Preprint Order Number: PE-169PRS (08-2002)Discussion Deadline: January 2003

A Hybrid Method for Observability AnalysisUsing a Reduced Network Graph Theory

Korres, G.N.; Katsikas, PJ.

Author Affiliations: National Technical University of Athens,Greece.

Abstract: This paper presents a hybrid topological-numerical ap-proach for observability analysis in power system state estimation. Bypartitioning the network in observable areas, a reduced network isformed, where each area is represented by a supernode and each line be-tween areas as a branch. We select as areas the flow islands, being themaximal connected components of flow measured branches. Onlyboundary nodes and injections at flow islands are retained for numerical

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processing. Observability testing and identification of maximal observ-able islands are accomplished by numerical processing on the echelonform of a rectangular test matrix, which is based on the reduced networkgraph properties. The method uses a noniterative scheme to select a mini-mal set of nonredundant pseudo measurements which make anunobservable network barely observable. The existing numerical meth-ods are based on the number of zero pivots obtained during the triangularfactorization of the gain matrix. Due to round-off errors, the zero pivotsmay be misclassified. In the proposed method, the non-zero values of theprocessed test matrix are +1 or -1, resulting in better numerical condi-tioning and accurate detection of zero pivots. The test matrix is generallysparser than the reduced network gain matrix. As a consequence, the pro-posed method is faster either for observability testing or multiple mea-surement placement. Several test results are presented.

Keywords Observability analysis, reduced model, supemodes, ob-servable islands, rank deficiency, graph theory.

Preprint Order Number: PE-172PRS (08-2002)Discussion Deadline: January 2003

Power System Dynamic Performance

Computing Dominant Poles of PowerSystem Multivariable Transfer Functions

Martins, N.; Quintao, P

Author Affiliations: CEPEL, Brazil; Fundacao Padre LeonelFrance, Brazil.

Abstract: This paper describes a numerical linear algebra algo-rithm to compute the dominant poies of multiinput/multioutput(MIMO) high-order transfer functions. The results presented are re-lated to the study of electromechanical oscillations in large electricpower systems, but the algorithm is completely general. The computeddominant poles may then be used to build modal equivalents for MIMOtransfer functions of large linear systems, among other applications.

Keywords: Small-signal stability, oscillations, transfer function,dominant poles, transfer function residues, modal analysis, dynamicequivalent, model reduction, multivariable systems, large-scale sys-tems, eigenvalue, numerical linear algebra.

Preprint Order Number: PE-409PRS (08-2002)Discussion Deadline: January 2003

PAT: A Power AnalysisToolbox for MATLAB/SimulinkSchoder, K.; Hasanovic, A.; Feliachi, A.; Hasanovic, A.

Author Affiliations: West Virginia University, USA; AmericanElectric Power, USA.

Abstract: A power system simulation environment inMATLAB/Simulink is presented in this paper. The developed PowerAnalysis Toolbox (PAT) is a very flexible and modular tool for loadflow, transient and small signal analysis of electric power systems.Standard power system component models and a wide range ofFACTSdevices are included. Its data structure and block library have beentested to confirm its applicability to small- to medium-sized power sys-tems. Its advantages over an existing commercial package are given.

Keywords: PAT, simulation, transient stability, Simulink.Preprint Order Number: PE-522PRS (08-2002)Discussion Deadline: January 2003

Modeling Combined-Cycle Power Plantfor Simulation of Frequency Excursions

Kunitomi, K; Kurita, A.; Tada, Y; Ihara, S.; Price, WW;Richardson, L.M.; Smith, G.R.

Author Affiliations: Tokyo Electric Power Co., Japan; GE PowerSystems, USA.

Abstract: The maximum continuous power output of a com-bined-cycle power plant depends on the system frequency and the am-bient temperature. The temperature control of a gas turbine limits theexhaust temperature by reducing the fuel flow as the air flow decreaseswith the shaft speed. A simple model of a combined-cycle power plantis derived from a detailed design model for an example plant. Themodel is suitable for long-term simulation of power system dynamicperformance involving abnormal frequency conditions.

Keywords Gas turbines, dynamic modeling, combined-cyclepower plants.

Preprint Order Number: PE-107PRS (08-2002)Discussion Deadline: January 2003

Power System Operations

Application of Fuzzy Logic for Reactive PowerCompensation of Radial Distribution Feeders

Mekhamer, S.F.; Soliman, S.A.; Moustafa, M.A.; El-Hawary, M.E.

Author Affiliations: Ain Shams University, Egypt; Dalhousie Uni-versity, Canada.

Abstract: A new algorithm determines the exact optimal solution forcapacitor allocation in radial distribution feeders. Results of previouswork using fuzzy and heuristic strategies, on this feeder, are comparedwith the exact reference solution. The effect of varying some parametersin the membership functions to get better results is discussed. Also, theeffect of selection of parameters that should be used in the fuzzy model-ing is investigated. The advantages of the fuzzy and heuristic methodspresented are combined in a new fuzzy-heuristic idea. This combinedtechnique is verified, by the application to test feeders, to give better re-sults. Different fuzzy decision-making forms are applied to the fuzzymodeling problem. A recommendation is made for the most efficientway to get a solution equal or very close to the optimal.

Keywords: Capacitor placement, fuzzy set theory, fuzzy deci-sion-making, radial distribution feeder.

Preprint Order Number: PE-412PRS (08-2002)Discussion Deadline: January 2003

Determination of Power System CoherentBus Groups by Novel Sensitivity-BasedMethod for Voltage Stability Assessment

Aumuller, C.; Saha, TK.

Author Affiliations: University of Queensland, Australia.Abstract: This paper presents a method that is used to determine

the coherent bus groups of a system with similar reactive reserve bas-ins. The differences between this proposed method and another widelyaccepted voltage stability analysis method are highlighted, and resultsobtained from the proposed method are discussed. This method is moreefficient and requires comparatively less VQ curve computations. Defi-nitions are proposed for the categorization of buses by the cause of theirloading limitation. Results obtained from the test systems support themethod's validity and the validity of the bus categories proposed. Bydetermining the reactive reserve margin, it is possible to determinewhich generators will have an impact on the maximum permissibleloading of a bus and which will not. This information is particularlyuseful for performing voltage stability analysis.

Keywords Coherent bus groups, voltage stability, sensitivity analysis.Preprint Order Number: PE-654PRS (08-2002)

IEEE Power Engineering Review, November 200258