7,354 research outputs found
Mixed Integer Linear Programming Models for Network Reconfiguration and Resource Optimization in Power Distribution Networks
No full textThis chapter deals with two typical optimization problems relevant to the operation of power distribution systems. The first aims at finding the minimum power loss configuration of the network. The second is the so-called Voltage/Var Optimization problem (VVO), i.e. the definition of the most efficient operating condition of voltage control apparatus and reactive power resources. The chapter describes the various parts of the proposed mixed integer linear programming (MILP) model of problems, such as the objective function, and the implementation of the radiality constraint. Both the objective function and the maximum line current constraints require the evaluation of the square value of the real and imaginary parts of each line current phasor. Piecewise linear functions (PLFs) are adopted for the MILP representation of these square values. Also the bus voltage constraints require a PLF representation of the square value of the real and imaginary parts of each bus voltage phasor
An automatic system to locate phase-to-ground faults in medium voltage cable networks based on the wavelet analysis of high-frequency signals
No full textThe paper presents a microcontroller-based automatic system that applies the continuous wavelet analysis to the measured fault-originated electromagnetic transients in order to locate phase-to-ground faults in power distribution networks composed by coaxial cables. The paper describes the numerical procedure conceived to: (i) detect the presence of fault-originated transients superimposed to steady-state voltage waveforms, (ii) identify the faulted phase-conductor and (iii) identify the part of the fault transient that can be used to build a specific mother wavelet so to improve the fault location accuracy. The paper also describes the implementation of the procedure into an embedded microcontroller as well as its experimental validation carried out by means of analog real-time generated fault waveforms obtained from EMTP simulations. © 2011 IEEE.DESLDepartment of Electrical Engineering, University of Bologna, Bologna, Italy, Conference code: 86744, Export Date: 25 April 2012, Source: Scopus, Art. No.: 6019280, doi: 10.1109/PTC.2011.6019280, Language of Original Document: English, Correspondence Address: Paolone, M.; Department of Electrical Engineering, University of Bologna, Bologna, Italy; email: [email protected], References: Radial distribution test feeders (1991) IEEE Trans. Power Syst., 6 (3), pp. 975-985. , IEEE Distribution Planning Working Group, Aug; (1998) CIRED WG03 Fault Management, , Fault Management in Electrical Distribution Systems; (2004) IEEE Guide for Determining Fault Location on AC Transmission and Distribution Lines, , IEEE Std C37.114; Sachdev, M.S., Agarwal, R., TECHNIQUE FOR ESTIMATING TRANSMISSION LINE FAULT LOCATIONS FROM DIGITAL IMPEDANCE RELAY MEASUREMENTS. (1988) IEEE Transactions on Power Delivery, 3 (1), pp. 121-129. , DOI 10.1109/61.4237; Srinivasan, K., St-Jacques, A., New fault location algorithm for radial transmission lines with loads (1989) IEEE Transactions on Power Delivery, 4 (3), pp. 1676-1682. , DOI 10.1109/61.32658; Girgis, A.A., Hart, D.G., Peterson, W.L., A new fault location technique for two- and three-terminal lines (1992) IEEE Trans. on PWRD, 7 (1), pp. 98-107. , Jan; Magnago, F.H., Abur, A., Fault location using wavelets (1998) IEEE Trans. on PWRD, 13 (4), pp. 1475-1480. , Oct; Magnago, F.H., Abur, A., A new fault location technique for radial distribution systems based on high frequency signals (1999) Proc. IEEE-Power Eng. Soc. Summer Meeting, 1, pp. 426-431. , Jul. 18-22; Izykowski, J., Rosolowski, E., Saha, M.M., Locating faults in power transmission lines under availability of complete measurements at one end (2004) IEE Proc. Gener. Transm. Distrib., 151 (2), pp. 268-273. , Mar; Borghetti, A., Corsi, S., Nucci, C.A., Paolone, M., Peretto, L., Tinarelli, R., On the use of continuous-wavelet transform for fault location in distribution power systems (2006) International Journal of Electrical Power and Energy Systems, 28 (9 SPEC. ISS.), pp. 608-617. , DOI 10.1016/j.ijepes.2006.03.001, PII S0142061506000792; Borghetti, A., Bosetti, M., Di Silvestro, M., Nucci, C.A., Paolone, M., Continuous-Wavelet Transform for Fault Location in Distribution Power Networks: Definition of Mother Wavelets Inferred from Fault Originated Transients (2008) IEEE Trans. on PWRS, 23 (2), pp. 380-388. , May; Borghetti, A., Bosetti, M., Nucci, C.A., Paolone, M., Abur, A., Integrated Use of Time-Frequency Wave-let Decompositions for Fault Location in Distribution Networks: Theory and Experimental Validation (2010) IEEE Trans. on PWRD, 25 (4), pp. 3139-3146. , Oct; Strang, G., Nguyen, T., (1996) Wavelets and Filter Banks, , Wellesley Cambridge Press; Mahseredjian, J., Lefebvre, S., Do, X.-D., A new method for time-domain modelling of nonlinear circuits in large linear networks Proc. of 11th Power Systems Computation Conference PSCC, August 1993; Mahseredjian, J., Dennetiere, S., Dube, L., Khodabakhchian, B., Gerin-Lajoie, L., On a new approach for the simulation of transients in power systems (2007) Electric Power Systems Research, 77 (11), pp. 1514-1520. , DOI 10.1016/j.epsr.2006.08.027, PII S0378779606002094; Greenwood, A., (1991) Electrical Transients in Power Systems, , John Wiley and Sons, New York; Clarke, E., (1943) Circuit Analysis of AC Power Systems 1, , John Wiley & Sons, New York; Peretto, L., Rinaldi, P., Sasdelli, R., Tinarelli, R., Fioravanti, A., Implementation and Characterization of a System for the Evaluation of the Starting Instant of Lightning-Induced Transients (2007) IEEE Trans. on Instrumentation and Measurement, 56 (5), pp. 1955-1960. , Oct; Yamabuki, K., Borghetti, A., Napolitano, F., Nucci, C.A., Paolone, M., Peretto, L., Tinarelli, R., Vitale, R., A Distributed Measurement System for Correlating Faults to Lightning in Distribution Networks Proc. of the International Symposium on High Voltage Engineering (ISH), Ljubljana, Slovenia, Aug. 27-31, 2007; Kunt, M., (1980) Traitement Numérique des Signaux, Traité D'électricité, 20. , EPFL, Switzerland; Grandke, T., INTERPOLATION ALGORITHMS FOR DISCRETE FOURIER TRANSFORMS OF WEIGHTED SIGNALS. (1983) IEEE Transactions on Instrumentation and Measurement, IM-32 (2), pp. 350-355; Graps, A., An introduction to wavelets (1995) IEEE Computational Science and Engineering, 2 (2), pp. 50-61; De Boor, C.A., (1978) A Practical Guide to Splines, , Springer-Verlag; Lobos, T., Sikorski, T., Schegner, P., Joint time-frequency representation of non-stationary signals in electrical power engineering Proc. of the 15th Power Systems Computation Conference (PSCC'05), Liege, Belgium, 22-26 August 2005, , paper fp 97; Borghetti, A., Morched, A.S., Napolitano, F., Nucci, C.A., Paolone, M., Lightning-Induced Overvoltages Transferred Through Distribution Power Transformers (2009) IEEE Trans. on PWRD, 24 (1), pp. 360-372. , Jan; Marti, L., Simulation of transients in underground cables with frequency-dependent modal transformation matrices (1988) IEEE Trans. on PWRD, 3 (3), pp. 1099-1110. , July; Dommel, H.W., Digital computer solution of Electromagnetic Transients in single and multiphase networks (1969) IEEE Transactions on PAS, 88, pp. 388-399. , April, Sponsors: IEEE; IEEE Power and Energy Society (PES
Simulation of the Volt/Var Control in Distribution Feeders by Means of a Networked Multiagent System
Get PDFThe adoption of networked multiagent systems (MAS) has been recently proposed for the solution of the volt/var control (VVC) problem in distribution feeders. However, constraints and limitations due to the communication network, to the dynamic behavior of power system components and regulators, as well as to the measurement uncertainties of the adopted sensors need to be specifically analyzed for the design of the MAS. For this purpose, a cosimulation platform has been built by the integration of two simulation tools: 1) the electromagnetic transient program EMTP-rv; and 2) the communication network simulator Riverbed-OPNET Modeler. This paper presents the modeling and simulation of an asynchronous leaderless MAS-based approach that coordinates the reactive power outputs of a set of power compensators equipped with phasor measurement units via a shared band-limited packet-switched digital communication network. The effects of communication network latency and packet loss on the VVC performances are analyzed for two unbalanced IEEE Test feeders equipped with on-load tap changer transformers. The paper compares the results obtained by using a transmission control protocol (TCP) and a user datagram protocol (UDP), for different levels of background traffic (BT) and different packet discard ratios (PDRs) in the communication links
Filmare l'opera senza filmare il canto: la "Carmen" di Francesco Rosi
No full textIl presente saggio si concentra sul rapporto tra melodramma e film, analizzare un caso specifico di messa in video di un’opera: Carmen di Francesco Rosi (1984). Il saggio inizia discutendo il rapporto tra due linguaggi (filmico e operistico), tradizionalemente considerati antitetici; indaga poi il film-opera di Rosi, collocandolo nella storia della fortuna cinematografica dell’opera di Bizet, e soffermandosi sull’analisi di alcune sequenze particolarmente significative per comprendere l’operazione compiuta da Rosi (innanzitutto il Duetto Micaela-Don José del I Atto)
Volt/var optimization of unbalanced distribution feeders via mixed integer linear programming
Get PDFThe paper presents a Mixed Integer Linear Programming (MILP) model for the solution of the three-phase volt/var optimization (VVO) of medium voltage unbalanced distribution feeders. The VVO of a distribution feeder is aimed at calculating the most efficient operating conditions by means of the scheduling of transformers equipped with an on-load tap changer and distributed reactive power resources (such as embedded generators and switchable capacitors banks). The proposed model allows the representation of feeders composed by three-phase, two-phase, and single-phase lines, by transformers with different winding connections, by unbalanced wye- and delta-connected loads, by three-phase and single phase capacitor banks and embedded generators. The accuracy of the results is verified by using IEEE test feeders
OP3
No full textMILP instances (in LP format) of the paper
Alberto Borghetti
Using mixed integer programming for the volt/var optimization in distribution feeders
Electric Power Systems Research
Volume 98, May 2013, Pages 39-50
https://doi.org/10.1016/j.epsr.2013.01.003
originally available at http://www.lisep.ing.unibo.it/op3.zip
EVIDENCIAÇÃO DE INFORMAÇÕES NO SETOR PÚBLICO – UM ESTUDO COMPARATIVO DO IMPACTO DA APLICAÇÃO DAS NBCASP
No full textO presente estudo trata da influência das novas normas contábeis para as entidades do setor público na evidenciação de informações de situação patrimonial. O seu objetivo é identificar se houve melhoraria na evidenciação de informações de situação patrimonial. Nesse sentido, apresentou-se a importância do conceito de accountability para o controle, o papel da evidenciação contábil como o seu pressuposto, além do processo de mudanças pelo qual as normas de contabilidade pública passaram nos últimos anos. Definido o Estado de Santa Catarina como ente objeto da análise, coletaram-se dados de demonstrações contábeis dos últimos três exercícios disponíveis e procedeu-se à tabulação e comparação das informações. Os resultados encontrados evidenciaram que das seis demonstrações previstas pela NBC T 16.6, três passaram por modificações e uma delas foi publicada pela primeira vez. No que diz respeito às duas outras demonstrações, verificou-se que uma delas é facultativa, e não é elaborada pelo ente, e que o Balanço Orçamentário ainda não se adequou à nova legislação. Constatou-se, portanto, que apesar do cumprimento parcial das disposições, houve indicadores de aumento da capacidade informacional dos relatórios contábeis
Synchrophasors-based Distributed Secondary Voltage/VAR Control via Cellular Network
Get PDFThe impact of the increasing connection of distributed generation to medium voltage (MV) feeders, with particular reference to photovoltaic (PV) units, justifies the investigation on secondary voltage/VAR control (VVC) schemes able to improve the utilization of available control resources and to reduce reactive power flows. The paper deals with a secondary VVC scheme based on a distributed multi-agent approach that requires only the estimation of the reactive power flows between the buses where the PV units with reactive power control capability are connected. Phasor Measurement Units (PMUs) are used to get the relevant information. In general, distributed control approaches are expected to work adequately even by using communication infrastructures with lower performances than those required by centralized approaches. The paper addresses such an issue by the analysis of the distributed VVC performance when a shared cellular network is used for the cooperative adjustment of PV inverters reactive power outputs and of tap positions of transformers equipped with on-load tap changers. The analysis is carried out by using a specifically developed ICT (Information and Communications Technology)- power co-simulation platform. It is shown that the VVC scheme has adequate performances also in the presence of significant levels of background traffic and data loss
Using mixed integer programming for the volt/var optimization in distribution feeders
No full textOne of the functions that characterize modern management systems of electric power distribution networks is the periodical short-term optimization of the operating conditions. Such a function is typically designated as volt/var optimization (VVO). The usual objective is the minimization of network loss or demand. The main constraints are the maximum current values in lines or transformers and a few percentage point deviation of bus voltages from the rated value. VVO exploits the availability of two-way communication and the possibility to control transformer load tap changers, switchable capacitor banks, and reactive outputs of specific embedded generators (being active outputs often fixed by market decisions or by energy resource characteristics). The use of mixed integer linear programming (MILP) appears to have been less explored than other approaches for the solution of VVO problems. This paper presents a MILP model that includes the approximate representation of the main characteristics and constraints of short-term distribution system operation. The quality of the results obtained for different test feeders in various operating conditions and the corresponding performances of the solver appear promising for online applications
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