Using Two Multivariate Methodsfor Line Congestion Study inTransmission Systems Under Uncertainty

Deladreue, S.; Brouaye, F.; Bastard, P; Peligry, L.

Author Affiliations: Supelec, France; EDF-R&D Service Etudesde Reseaux, France.

Abstract: Two multivariate methods (correlation analysis and prin-cipal components analysis) are used to forecast which lines may be si-multaneously congested. These statistical methods are applied to adatabase that takes into account transmission planning uncertaintiessuch as localization of new independent power producers and new eli-gible customers (i.e., customers who can choose their energy supplier),and level of international exchanges. To face the very large number ofpossible configurations, a design of experiment is used to create the da-tabase. A complete active/reactive power flow program is used to simu-late the power system. The results show the relevance of the proposedmethods as applied to a 21-bus power system test case. Knowing whichlines will be simultaneously congested may help the system operator tomake decisions in short-term operation (congestion management) aswell as in long-term planning (grid reinforcement).

Keywords: Correlation analysis, line congestion, open electricitymarket, power flow, power system planning, principal component anal-ysis, uncertainty.

Preprint Order Number: PE-181PRS (08-2002)Discussion Deadline: January 2003

General Model for RepresentingVariable-Speed Wind Turbines inPower System Dynamics Simulations

Slootweg, J.G.; De Haan, S.WH.; Polinder, H.; Kling, WL.

Author Affiliations: Delft University of Technology, TheNetherlands.

Abstract: A tendency to erect ever more wind turbines can be ob-served in order to reduce the environmental consequences of electricpower generation. As a result of this, in the near future wind turbinesmay start to influence the behavior of electric power systems by inter-acting with conventional generation and loads. Therefore, wind turbinemodels that can be integrated into power system simulation softwareare needed. A model that can be used to represent all types of vari-able-speed wind turbines in power system dynamics simulations is pre-sented. The modeling approach is commented upon, and models of thesubsystems of which a variable speed wind turbine consists are dis-cussed. Some results obtained after incorporation of the model inPSS/E, a widely used power system dynamics simulation softwarepackage, are presented and compared with measurements.

Keywords: Variable-speed wind turbine, modeling, simulation,power system dynamics, grid integration, PSS/E.

Preprint Order Number: PE-233PRS (08-2002)Discussion Deadline: January 2003

A New Preconditioned ConjugateGradient Power Flow

Dag, H.; Semlyen, A.

Author Affiliations: Istanbul Technical University, Turkey; Uni-versity of Toronto, Canada.

Abstract: A new solution methodology for the constant matrix, de-coupled power flow problem is presented in this paper. The proposedmethod uses the conjugate gradient method instead of the traditional di-rect solution ofAx = b for updating the power flow variables. The con-jugate gradient method is accelerated with an approximate inversematrix preconditioner obtained from a linear combination of ma-trix-valued Chebyshev polynomials. The new method has been testedon several systems of different sizes. In terms of speed, the method iscomparable to the fast decoupled load flow in serial environments, but

it is more amenable to parallel and vector processing since it containsonly matrix-vector multiplications.

Keywords: Chebyshev polynomials, conjugate gradient method,decoupled load flow, iterative methods, preconditioner.

Preprint Order Number: PE-270PRS (08-2002)Discussion Deadline: January 2003

Reliability Worth Assessment of High-Tech Industry

Yin, S.A.; Chang, R.F.; Lu, C.N.

Author Affiliations: National Sun Yat-Sen University, Taiwan;Kao Yuan Institute of Technology, Taiwan.

Abstract: This paper introduces a new approach to customer inter-ruption cost evaluation that recognizes the dispersed nature of the costdata. The proposed method is designated as the possibility distributionapproach and provides a realistic and effective assessment of the lossesincurred by high-tech industry electrical users due to power failures.Fuzzy linear regression models are used to describe the distribution anddispersed behaviors of interruption costs. Bootstrap technique is usedto generate a sampling distribution of small samples so that confidenceintervals of interruption costs of different high-tech sectors can be ob-tained. Using the obtained cost models, interruption costs and reliabil-ity worth of high-tech industries that require higher reliability andpremium power service, can be properly assessed.

Keywords: Interruption costs, reliability worth, fuzzy regression.Preprint Order Number: PE-424PRS (08-2002)Discussion Deadline: January 2003

Using DEA To Measure the Relative Efficiencyof the Service Center and Improve OperationEfficiency Through ReorganizationChien, C.F.; Lo, F.Y; Lin, J.T.

Author Affiliations: National Tsing Hua University, Taiwan; Tai-wan Power Company, Taiwan.

Abstract: Data envelopment analysis (DEA) has become a practi-cable approach to evaluate the relative efficiencies of decision-makingunits in various contexts. A DEA study was conducted to measure therelative efficiencies of 17 service centers of the NAN-TOU electricitydistribution district of Taiwan Power Company (TPC). Altematives forreorganizing the service centers via efficiency measurement wereinvestigated. The results showed that the proposed reorganization alter-natives have better efficiency scores. Based on DEA evaluations, weprovide specific directions for the inefficient service centers to improvetheir operation efficiencies and thus maintain the competitive advan-tage of TPC in facing power market liberalization.

Keywords: Data envelopment analysis (DEA), relative efficiency,reorganization, power systems, Taiwan Power Company (TPC).

Preprint Order Number: PE-509PRS (08-2002)Discussion Deadline: January 2003

Var Compensation by SequentialQuadratic ProgranuningPerez Abril, I.; Gonzalez Quintero, J.A.

Author Affiliations: Central University of Las Villas, Cuba.Abstract: This paper presents an application of the sequential qua-

dratic programming method to find the optimal sizing of shunt capaci-tors and/or passive filters for maximizing the net present value resultingfrom energy loss reduction while taking investment cost into accountand complying with IEEE Standard 519. The proposed methodologyallows the simultaneous solving for fixed and switched var compensa-tors by considering a characteristic load variation curve for each linearand nonlinear load.

Keywords: Power system harmonics, optimization methods.Preprint Order Number: PE-521PRS (08-2002)Discussion Deadline: January 2003

IEEE Power Engineering Review, November 200256