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An efficient Hopfield network to solve economic dispatch problems with transmission system representation

da Silva, I. N.; Nepomuceno, L.; Bastos, T. M.
Fonte: Elsevier B.V. Publicador: Elsevier B.V.
Tipo: Artigo de Revista Científica Formato: 733-738
ENG
Relevância na Pesquisa
36.91%
Economic dispatch (ED) problems have recently been solved by artificial neural network approaches. Systems based on artificial neural networks have high computational rates due to the use of a massive number of simple processing elements and the high degree of connectivity between these elements. The ability of neural networks to realize some complex non-linear function makes them attractive for system optimization. All ED models solved by neural approaches described in the literature fail to represent the transmission system. Therefore, such procedures may calculate dispatch policies, which do not take into account important active power constraints. Another drawback pointed out in the literature is that some of the neural approaches fail to converge efficiently toward feasible equilibrium points. A modified Hopfield approach designed to solve ED problems with transmission system representation is presented in this paper. The transmission system is represented through linear load flow equations and constraints on active power flows. The internal parameters of such modified Hopfield networks are computed using the valid-subspace technique. These parameters guarantee the network convergence to feasible equilibrium points, which represent the solution for the ED problem. Simulation results and a sensitivity analysis involving IEEE 14-bus test system are presented to illustrate efficiency of the proposed approach. (C) 2004 Elsevier Ltd. All rights reserved.

An efficient neural approach to economic load dispatch in power systems

da Silva, I. N.; Nepomuceno, L.; IEEE
Fonte: IEEE Publicador: IEEE
Tipo: Conferência ou Objeto de Conferência Formato: 1269-1274
ENG
Relevância na Pesquisa
37%
A neural approach to solve the problem defined by the economic load dispatch in power systems is presented in this paper, Systems based on artificial neural networks have high computational rates due to the use of a massive number of simple processing elements and the high degree of connectivity between these elements the ability of neural networks to realize some complex nonlinear function makes them attractive for system optimization the neural networks applyed in economic load dispatch reported in literature sometimes fail to converge towards feasible equilibrium points the internal parameters of the modified Hopfield network developed here are computed using the valid-subspace technique These parameters guarantee the network convergence to feasible quilibrium points, A solution for the economic load dispatch problem corresponds to an equilibrium point of the network. Simulation results and comparative analysis in relation to other neural approaches are presented to illustrate efficiency of the proposed approach.

An effortless hybrid method to solve economic load dispatch problem in power systems

Pourakbari-Kasmaei, M.; Rashidi-Nejad, M.
Fonte: Pergamon-Elsevier B.V. Ltd Publicador: Pergamon-Elsevier B.V. Ltd
Tipo: Artigo de Revista Científica Formato: 2854-2860
ENG
Relevância na Pesquisa
36.91%
This paper proposes a new approach and coding scheme for solving economic dispatch problems (ED) in power systems through an effortless hybrid method (EHM). This novel coding scheme can effectively prevent futile searching and also prevents obtaining infeasible solutions through the application of stochastic search methods, consequently dramatically improves search efficiency and solution quality. The dominant constraint of an economic dispatch problem is power balance. The operational constraints, such as generation limitations, ramp rate limits, prohibited operating zones (POZ), network loss are considered for practical operation. Firstly, in the EHM procedure, the output of generator is obtained with a lambda iteration method and without considering POZ and later in a genetic based algorithm this constraint is satisfied. To demonstrate its efficiency, feasibility and fastness, the EHM algorithm was applied to solve constrained ED problems of power systems with 6 and 15 units. The simulation results obtained from the EHM were compared to those achieved from previous literature in terms of solution quality and computational efficiency. Results reveal that the superiority of this method in both aspects of financial and CPU time. (C) 2011 Elsevier Ltd. All rights reserved.

An unproblematic method to solve economic and emission dispatch

Piltan, S.; Pourakbari-Kasmaei, M.; Montavani, J. R S; Rashidi-Nejad, M.
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Conferência ou Objeto de Conferência
ENG
Relevância na Pesquisa
37.06%
This paper proposes a method to determine the output of all online units with minimum total cost when the amount of emission is reasonable. A joint economic and emission dispatch is proposed in order to get a significant compromise between costs and emission such that real power supply-demand equilibrium is satisfied. In order to have a meaningful compromise between costs and emission in the problem formulation, two variables are used, weighting factor and price penalty factor. A case study comprising of a 3-unit power system is employed, where various demand is used. Results for the test system indicate the fastness and effectiveness of proposed method. © 2011 IEEE.

Optimal reactive power dispatch using stochastic chance-constrained programming

López, Julio C.; Muñoz, José I.; Contreras, Javier; Mantovani, J. R. S.
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Conferência ou Objeto de Conferência
ENG
Relevância na Pesquisa
36.91%
Deterministic Optimal Reactive Power Dispatch problem has been extensively studied, such that the demand power and the availability of shunt reactive power compensators are known and fixed. Give this background, a two-stage stochastic optimization model is first formulated under the presumption that the load demand can be modeled as specified random parameters. A second stochastic chance-constrained model is presented considering uncertainty on the demand and the equivalent availability of shunt reactive power compensators. Simulations on six-bus and 30-bus test systems are used to illustrate the validity and essential features of the proposed models. This simulations shows that the proposed models can prevent to the power system operator about of the deficit of reactive power in the power system and suggest that shunt reactive sourses must be dispatched against the unavailability of any reactive source. © 2012 IEEE.

Penalty-based nonlinear solver for optimal reactive power dispatch with discrete controls

Soler, Edilaine Martins; Asada, Eduardo N.; Da Costa, Geraldo R. M.
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 2174-2182
ENG
Relevância na Pesquisa
36.91%
The optimal reactive dispatch problem is a nonlinear programming problem containing continuous and discrete control variables. Owing to the difficulty caused by discrete variables, this problem is usually solved assuming all variables as continuous variables, therefore the original discrete variables are rounded off to the closest discrete value. This approach may provide solutions far from optimal or even unfeasible solutions. This paper presents an efficient handling of discrete variables by penalty function so that the problem becomes continuous and differentiable. Simulations with the IEEE test systems were performed showing the efficiency of the proposed approach. © 1969-2012 IEEE.

A novel straightforward compromising method for dynamic economic and emission dispatch considering valve-point effect

Pourakbari Kasmaei, M.; Rider, M. J.; Mantovani, J. R S
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Conferência ou Objeto de Conferência Formato: 335-340
ENG
Relevância na Pesquisa
37.15%
This paper proposes a straightforward compromising method to determine the output power of all committed units during the scheduling time horizon. Unlike the conventional methods that work based on a constant pollution control cost (CPCC), this method works based on the system topology such as demand, minimum cost and minimum output emission of the system. In order to have a meaningful compromise between costs and emission in economic and emission dispatch (EED) problem, a flexible pollution control cost (FPCC) is proposed. Also a dynamic economic emission dispatch (DEED) approach is considered where the ramping constraints couple the scheduling hours; the inclusion of valve-point effect makes the DEED modeling more practical. The validity and effectiveness of the unproblematic FPCC approach is verified through an IEEE 30-bus test system with 6 unit for the 6-hour scheduling horizon. © 2013 IEEE.

Investigação e aplicação de métodos primal - dual pontos interiores em problemas de despacho econômico e ambiental

Souza, Márcio Augusto da Silva
Fonte: Universidade Estadual Paulista (UNESP) Publicador: Universidade Estadual Paulista (UNESP)
Tipo: Dissertação de Mestrado Formato: 148 f. : il.
POR
Relevância na Pesquisa
27.06%
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES); Pós-graduação em Engenharia Elétrica - FEB; Este trabalho visa a investigação e implementação de métodos Primal - Dual Previsor-Corretor de Pontos Interiores com a estratégia de busca unidimensional, e a aplicação destes em problemas de Despacho Econômico e Ambiental. Objetiva-se utilizar estes métodos para determinar soluções aproximadas e consistentes dos problemas causados citados, que forneçam a solução de minimização dos custos dos combustíveis empregados na geração termoelétrica de energia, otimizando um processo de alocação da demanda de energia elétrica entre as unidades geradoras disponíveis, de tal forma que as restrições operacionais sejam atendidas e que o custo de geração é minimizado. Pretende-se também, analisar o problema de Despacho Ambiental com um objetivo único quando se acopla a este o Problema de Despacho Econômico e busca-se, simultaneamente, a minimização dos custos de geração e a redução da emissão de poluentes na natureza. Os métodos foram implementados, testados em Problemas de Despacho Econômico e Ambiental, e o seu desempenho foi comparado com outros métodos já utilizados, cujos resultados são encontrados na literatura; This work aims the investigation and implementation of Primal-Dual Predictor-Corrector interior points methods...

Despacho otimo de unidades geradoras em sistemas hidreletricos via heuristica baseada em relaxação lagrangeana e programação dinamica; Optimal dispatch of generating units in hydroelectric systems by heuristic based on langrangean relaxation and dynamic programming

Anastacio Sebastian Arce Ensina
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 27/01/2006 PT
Relevância na Pesquisa
37.06%
A Programação diária de um sistema de energia elétrica busca obter um despacho de geração para o próximo dia, que seja compatível com as metas definidas pelo Planejamento energético e que sirva como referência operativa para a operação em tempo real. Assim, a modelagem do sistema deve ser detalhada levando em consideração as características dos sistemas de geração, de transmissão, requisitos do mercado, critérios de segurança e custos associados à operação. Este trabalho apresenta um modelo de despacho ótimo de unidades geradoras hidrelétricas que adota como critério de desempenho um modelo que avalia as perdas no sistema de geração, ocasionadas pela elevação do nível de canal de fuga, pela variação do rendimento do conjunto turbina-gerador e pelo atrito do fluxo d?água nas tubulações do sistema hidráulico. Além das perdas no sistema de geração também forma parte do critério de desempenho o custo associado à partida e parada das unidades geradoras. Na formulação do problema, verifica-se a presença de variáveis inteiras, não lineares; restrições de atendimento à demanda, de meta de geração oriunda do Planejamento energético e restrições de capacidade de geração. Isto caracteriza o problema do despacho de unidades geradoras como sendo um problema de programação misto inteiro-não linear...

Despacho integrado da geração termeletrica e da produção e transmissão de gas natural; An integrated dispatch of thermoelectric power plants and natural gas system

Oderson Dias de Mello
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 01/08/2006 PT
Relevância na Pesquisa
36.77%
Esta tese apresenta um modelo de despacho para usinas termelétricas a gás natural considerando a produção e o transporte de gás. O modelo proposto associa a operação do sistema de geração termelétrica com a operação da rede de gasodutos. A metodologia utilizada para obter a solução foi aplicada a um exemplo com seis usinas termelétricas supridas por uma rede de gás natural. O modelo apresentado integra eficientemente a operação das usinas termelétricas com a operação do sistema de gasodutos; This thesis presents a dispatch model for natural gas power plants considering the production and transmission of gas. The proposed model put together the operation of the power plant system with the operation of the natural gas pipeline network. The proposed approach was applied to an example of six power plants supplied by a gas system. The proposed approach integrates the operation of power plants with the operation of natural gas transmission system

Modelo de despacho otimo com tratamento individual de unidade geradoras em usinas hidreletricas; Optimal dispach model with indivual

Glauber Renato Colnago
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 02/02/2007 PT
Relevância na Pesquisa
27.06%
Os modelos de despacho ótimo atuais em usinas hidrelétricas (UHEs) são realizados tendo em conta as eficiências das unidades geradoras (UGs) obtidos com a extrapolação dos dados de um modelo em escala reduzida das turbinas. Uma extrapolação dos dados do modelo para o protótipo realizada com grande precisão poderia ser feita se houvesse semelhança dinâmica, geométrica e cinemática entre eles. Como isto é impossível, os fabricantes de turbinas possuem relações empíricas para corrigir as eficiências medidas no modelo para refletirem melhor o desempenho do protótipo. Apesar desta correção, o desempenho real das turbinas pode ser afetado por características construtivas ou operacionais das UHEs, não levadas em conta pelos fabricantes, e pode variar com o tempo de uso de uma forma diferente para cada UG de uma UHE. Logo, as eficiências das turbinas reais não são iguais às eficiências extrapoladas do modelo em escala reduzida e, sob esta ótica, um modelo de despacho realizado com as curvas de eficiência derivadas do modelo reduzido provavelmente não otimiza a eficiência de uma UHE. Pode-se obter dados de eficiência mais precisos (atualizados) das UGs instaladas com o auxílio de métodos de medição de vazão da água nos condutos forçados das UGs. Neste trabalho foi desenvolvido um modelo de despacho ótimo em UGs de UHEs que trata individualmente as UGs...

A modified differential evolution based solution technique for economic dispatch problems

Azad, Md. Abul Kalam; Fernandes, Edite Manuela da G. P.
Fonte: AIMS Publicador: AIMS
Tipo: Artigo de Revista Científica
Publicado em //2012 ENG
Relevância na Pesquisa
37%
Economic dispatch (ED) plays one of the major roles in power generation systems. The objective of economic dispatch problem is to find the optimal combination of power dispatches from different power generating units in a given time period to minimize the total generation cost while satisfying the specified constraints. Due to valve-point loading effects the objective function becomes nondifferentiable and has many local minima in the solution space. Traditional methods may fail to reach the global solution of ED problems. Most of the existing stochastic methods try to make the solution feasible or penalize an infeasible solution with penalty function method. However, to find the appropriate penalty parameter is not an easy task. Differential evolution is a population-based heuristic approach that has been shown to be very efficient to solve global optimization problems with simple bounds. In this paper, we propose a modified differential evolution based solution technique along with a tournament selection that makes pair-wise comparison among feasible and infeasible solutions based on the degree of constraint violation for economic dispatch problems. We reformulate the nonsmooth objective function to a smooth one and add nonlinear inequality constraints to original ED problems. We consider five ED problems and compare the obtained results with existing standard deterministic NLP solvers as well as with other stochastic techniques available in literature.; Fundação para a Ciência e a Tecnologia (FCT)

An analysis of the importance of appropriate tie breaking rules in dispatch heuristics

Valente,Jorge M. S.
Fonte: Sociedade Brasileira de Pesquisa Operacional Publicador: Sociedade Brasileira de Pesquisa Operacional
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/04/2006 EN
Relevância na Pesquisa
37.06%
In this paper, we analyse the effect of using appropriate tie breaking criteria in dispatch rules. We consider four different dispatch procedures, and for each of these heuristics we compare two versions that differ only in the way ties are broken. The first version breaks ties randomly, while the second uses a criterion that incorporates problem-specific knowledge. The computational results show that using adequate tie breaking criteria improves the performance of the dispatch heuristics. The magnitude of the improvement is different for the four heuristics, and also depends on the characteristics of each specific instance. The use of problem-related knowledge for breaking ties should therefore be given some consideration in the implementation of dispatch rules.

Weekly dispatch; Weekly dispatch and county of Elgin general advertiser; Weekly dispatch, St. Thomas and county of Elgin general advertiser; Weekly dispatch, St. Thomas, Port Stanley, and county of Elgin general advertiser; Weekly dispatch, St. Thomas, Port Stanley, and county of Elgin advertiser

Canadian Library Association -- Newspaper Microfilming Project
Fonte: Canadian Library Association]; Canadian Library Association] ( [Ottawa ) Publicador: Canadian Library Association]; Canadian Library Association] ( [Ottawa )
Tipo: Artigo de Revista Científica Formato: microfilm reels : ; 35 mm.
Publicado em /1868/1855 ENGLISH
Relevância na Pesquisa
27.19%
(Statement of Responsibility) Canadian Library Association Newspaper Microfilming Project.; (Original Version) Reproduction of original: St. Thomas : P. Burke, 1861-1876. Weekly dispatch and county of Elgin general advertiser,; (Original Version) Reproduction of original: St. Thomas, [Ont.] : P. Burke, 1859?- . Weekly dispatch, St. Thomas and county of Elgin general advertiser,; (Original Version) Reproduction of original: St. Thomas [Ont.] : P. Burke, 1826-1858. Weekly dispatch, St. Thomas, Port Stanley, and county of Elgin general advertiser,; (Original Version) Reproduction of original: St. Thomas, [Ont.] : Dacres W. Hart, 1853-1856. Weekly dispatch, St. Thomas, Port Stanley, and country of Elgin advertiser,; Scattered issues missing.

Dynamic dispatch in object-oriented languages

Milton, Scott; Schmidt, Heinz
Fonte: Universidade Nacional da Austrália Publicador: Universidade Nacional da Austrália
Tipo: Working/Technical Paper Formato: 222275 bytes; 356 bytes; application/pdf; application/octet-stream
EN_AU
Relevância na Pesquisa
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Dynamic binding in object-oriented languages is perhaps the most important semantic aspect of these languages. At the same time it can contribute to inefficiency and lack of robustness because it incurs lookup overheads on function calls and hinders the compiler determining the exact type of objects held in variables or returned by functions. This may, for instance, preclude inlining of small functions or attribute offset computation at compile time. Yet attribute accesses are the most frequently executed operations. As a result, to regain lost performance, OO programmers are tempted to break the encapsulation of classes or want explicit control over dynamic dispatch, trading off extensibility. In the implementation of parallel object-oriented languages the additional complication arises that object accesses may require more expensive remote memory accesses. Lookup at the call may be inappropriate if the code has to be executed on a different processor and there perhaps has a different address. This paper summarizes dispatching as addressed in several modern object-oriented languages. We then describe and benchmark fast and exible dispatch schemes that we are currently implementing on SPARC based workstations and multi-processors. These involve elements of C++ virtual function tables and Eiffel's and Sather's ability to redefine abstract functions as attributes. Initial benchmarks seem to promise improved efficiency on a range of modern RISC based architectures.; no

Risk Limiting Dispatch with Fast Ramping Storage

Qin, Junjie; Su, Han-I; Rajagopal, Ram
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 02/12/2012
Relevância na Pesquisa
27.06%
Risk Limiting Dispatch (RLD) was proposed recently as a mechanism that utilizes information and market recourse to reduce reserve capacity requirements, emissions and achieve other system operator objectives. It induces a set of simple dispatch rules that can be easily embedded into the existing dispatch systems to provide computationally efficient and reliable decisions. Storage is emerging as an alternative to mitigate the uncertainty in the grid. This paper extends the RLD framework to incorporate fast-ramping storage. It developed a closed form threshold rule for the optimal stochastic dispatch incorporating a sequence of markets and real-time information. An efficient algorithm to evaluate the thresholds is developed based on analysis of the optimal storage operation. Simple approximations that rely on continuous-time approximations of the solution for the discrete time control problem are also studied. The benefits of storage with respect to prediction quality and storage capacity are examined, and the overall effect on dispatch is quantified. Numerical experiments illustrate the proposed procedures.; Comment: Submitted to IEEE Transactions on Automatic Control

Network Risk Limiting Dispatch: Optimal Control and Price of Uncertainty

Zhang, Baosen; Rajagopal, Ram; Tse, David
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
27.15%
Increased uncertainty due to high penetration of renewables imposes significant costs to the system operators. The added costs depend on several factors including market design, performance of renewable generation forecasting and the specific dispatch procedure. Quantifying these costs has been limited to small sample Monte Carlo approaches applied specific dispatch algorithms. The computational complexity and accuracy of these approaches has limited the understanding of tradeoffs between different factors. {In this work we consider a two-stage stochastic economic dispatch problem. Our goal is to provide an analytical quantification and an intuitive understanding of the effects of uncertainties and network congestion on the dispatch procedure and the optimal cost.} We first consider an uncongested network and calculate the risk limiting dispatch. In addition, we derive the price of uncertainty, a number that characterizes the intrinsic impact of uncertainty on the integration cost of renewables. Then we extend the results to a network where one link can become congested. Under mild conditions, we calculate price of uncertainty even in this case. We show that risk limiting dispatch is given by a set of deterministic equilibrium equations. The dispatch solution yields an important insight: congested links do not create isolated nodes...

IMPROVEMENT OF OPERATIONS OF PICKING AND DISPATCH FOR A BUSINESS IN THE MATTRESS INDUSTRY, SUPPORTED BY DISCRETE SIMULATION

CORREA ESPINAL,ALEXANDER ALBERTO; GÓMEZ MONTOYA,RODRIGO ANDRES; SÁNCHEZ ALZATE,JAMES ARIEL
Fonte: DYNA Publicador: DYNA
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2012 EN
Relevância na Pesquisa
36.77%
Warehouse management and operations of picking and dispatch in the supply chain and logistics are key factors for operational efficiency and client satisfaction. For this reason, the present article aims to develop a discrete simulation model that supports the analysis and evaluation of improvement alternatives for these operations. This model is for a medium size business in the mattress business in the city of Medellin. The business could reduce the permanency time of a mattress in the system from 4.12 h to 3.7 h and the number of mattresses attended would rise from 102 to 110 units with a confidence level of 95%. This is done via the implementation and analysis of the results of a discrete simulation model of the operations under consideration. The model allowed the mattress company to evaluate different alternatives that not only allowed analysis to improve efficiency, but also to focus on client satisfaction in warehouse management.

Attaining multiple dispatch in widespread object-oriented languages

Ortin,Francisco; Quiroga,Jose; Redondo,Jose M.; Garcia,Miguel
Fonte: DYNA Publicador: DYNA
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/08/2014 EN
Relevância na Pesquisa
37%
Multiple dispatch allows determining the actual method to be executed, depending on the dynamic types of its arguments. Although some programming languages provide multiple dispatch, most widespread object-oriented languages lack this feature. Therefore, different implementation techniques are commonly used to obtain multiple dispatch in these languages. We evaluate the existing approaches, presenting a new one based on hybrid dynamic and static typing. A qualitative evaluation is presented, considering factors such as software maintainability and readability, code size, parameter generalization, and compile-time type checking. We also perform a quantitative assessment of runtime performance and memory consumption.

A techno-economic model for optimising component sizing and energy dispatch strategy for PV-diesel-battery hybrid power systems

Hove,Tawanda; Tazvinga,Henerica
Fonte: Journal of Energy in Southern Africa Publicador: Journal of Energy in Southern Africa
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2012 EN
Relevância na Pesquisa
36.91%
This paper presents the development and application of a simple spreadsheet-based simulation model for sizing, energy performance evaluation and economic analysis of PV-diesel-battery power supply systems. The model is employed to generate a set of sizing curves that define the design space for hybrid systems using dimensionless generator component size variables, for a specified supply reliability and diesel energy dispatch strategy. The component size combination with the least unit cost of energy is selected among the many possible combinations satisfying a desired loss-of-load probability. Storage battery and diesel generator lifespan, as well as generator fuel efficiency, which depend on the operational loading stress of these components, are recognised as important variables in the economics of the system. The lifespan of the battery is premised to depend on the depth and rate of discharge of the operating cycles, while both the diesel generator lifespan and fuel efficiency are dependent on the degree and frequency of partial loading. The choice of diesel generator dispatch strategy was shown to be another important factor influencing the energy performance and economics of the system. The outputs of the model reveal several important sizing...