Дисертації з теми "Load Flow Methods"
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Joubert, Adriaan Wolfgang. "Parallel methods for systems of nonlinear equations applied to load flow analysis." Thesis, Queen Mary, University of London, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.362721.
Повний текст джерелаTrussell, Larry V. "Segflow: a new object-oriented load flow which uses trace methods and affiliation objects." Diss., Virginia Tech, 1994. http://hdl.handle.net/10919/40082.
Повний текст джерелаBorquez, Caballero Rodrigo Edgardo. "Calculating the Distance to the Saddle-Node Bifurcation Set." Thesis, KTH, Elektriska energisystem, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-119236.
Повний текст джерелаGupta, Nitin. "HOLOMORPHIC EMBEDDED LOAD-FLOW METHOD'S APPLICATION ON THREE-PHASE DISTRIBUTION SYSTEM WITH UNBALANCED WYE-CONNECTED LOADS." Cleveland State University / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=csu1624146858767491.
Повний текст джерелаGarbelini, Enio. "Proposição de uma técnica de parametrização geométrica para o fluxo de carga continuado /." Ilha Solteira : [s.n.], 2008. http://hdl.handle.net/11449/100326.
Повний текст джерелаBanca: Carlos Roberto Minussi
Banca: Francisco Villarreal Alvarado
Banca: Vivaldo Fernando da Costa
Banca: Walmir de Freitas Filho
Resumo: O fluxo de carga convencional é considerado inadequado para a obtenção do ponto de máximo carregamento devido a singularidade da matriz Jacobiana. Os métodos da continuação são ferramentas eficientes para a solução deste tipo de problema, e diferentes parametrizações são utilizadas para evitar a singularidade da matriz. Neste trabalho apresentase uma técnica de parametrização geométrica que possibilita o traçado completo das curvas PV sem os problemas de mal condicionamento. A técnica proposta associa a robustez com a simplicidade e a facilidade de compreensão. A singularidade da matriz Jacobiana é eliminada pela adição da equação de uma reta que passa por um ponto no plano formado pelas variáveis perdas de potência ativa totais e o fator de carregamento, dois parâmetros físicos de fácil compreensão. A técnica, aplicada aos sistemas do IEEE (14, 30, 57, 118 e 300 barras) e ao sistema brasileiro sul-sudeste (638 e 787 barras), mostra que as características do fluxo de carga não só são preservadas, mas também melhoradas. Diversos testes são realizados para proporcionar a comparação do desempenho do esquema de parametrização proposto para o método do fluxo de carga continuado.
Abstract: The conventional Newton's method has been considered inadequate to obtain the maximum loading point of power systems due to the Jacobian matrix singularity. Continuation methods are efficient tools for solving this kind of problem, and different parameterizations are used to avoid the matrix singularity. This paper presents a new geometric parameterization scheme that allows the complete tracing of the PV curves without ill-conditioning problems. The proposed technique associates the robustness to the simplicity and easy understanding. The Jacobian matrix singularity is overcome by the addition of a line equation, which passes through a point in the plane, determined by the real power losses and loading factor variables, two parameters with clear physical meaning. The application of this new technique to the IEEE systems (14, 30, 57, 118 and 300 buses) and to the Brazilian systems south-southeast (638 and 787 buses) shows that the characteristics of the conventional Newton's method are not only preserved but also improved. Several tests are carried out to compare the performance of the proposed parameterization scheme for the continuation power flow method.
Doutor
Guedes, Renato Braga de Lima. "Cálculo das soluções de baixa tensão das equações de fluxo de carga através de sistemas dinâmicos auxiliares e função energia estendida com modelo ZIP para análise de colapso de tensão." Universidade de São Paulo, 2004. http://www.teses.usp.br/teses/disponiveis/18/18133/tde-19052017-154844/.
Повний текст джерелаThis work may be divided into two distinct parts. Both of them are new contributions to stability analysis of power systems. In the first part it is proposed a new method to calculate the critical load flow low voltage solutions, and it is the main part of this work. Meanwhile, the last two chapters of this work presents a proposed extended energy function that consider the common load ZIP models. It allows the analysis of angle and voltage stability for power systems subjected to large disturbances. This work proposes a method to calculate the low voltage solutions (LVS) of the load flow equations of an electrical power system. The proposed method identifies the LVS involved in the saddle-node bifurcation leading the power system to a voltage collapse. This solution is known as the critical low voltage solution. In order to perform the proposed calculation, an auxiliary dynamical gradient system is used. It is shown that the equilibrium points of that associated auxiliary dynamical gradient system are the solutions of the load flow equations. In such manner, the paper proposes identifying the critical LVS calculating the equilibrium points of an auxiliary dynamical gradient system. The proposed method was tested on the Stagg 5-bus, on the IEEE 39-bus and on IEEE 118-bus test systems, and the results are presented at the end of the text.
Bodin, Hristina. "Wastewater treatment in constructed wetlands : Effects of vegetation, hydraulics and data analysis methods." Doctoral thesis, Linköpings universitet, Biologi, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-91402.
Повний текст джерелаKonstruerade våtmarker representerar ett koncept för möjligheten att nå en hållbar vattenresurshantering genom att agera som ”filter” mellan föroreningskälla och viktiga vattenresurser såsom sjöar och hav. Mycket kunskap saknas däremot om hur man konstruerar våtmarker med en optimal och pålitlig vattenreningskapacitet. Den här avhandlingen undersöker därför hur vegetation och vattnets väg genom våtmarken (hydrauliken) påverkar avloppsvattenrening i våtmarker. Dessutom undersöktes hur valet av dataanalysmetod av insamlad data påverkar resultaten. Studier genomfördes i Kenya och Sverige i experimentvåtmarker (ca. 40-60 m2) och inkluderadedatainsamling av vattenkvalité, hydraulik (spårämnesexperiment) samt biomassa och fosfor i biomassan av två olika våtmarksväxter. Dessutom genomfördes datorsimuleringar. Resultaten från Kenya visade att växtskörd och efterföljande näringsupptag av nyskördade växter var viktig för att uppnå låga utgående koncentrationer av fosfor och ammonium i en tropisk våtmark, speciellt under torrsäsongen. Däremot var en välutvecklad och tät vegetation viktig för reningen av partiklar. Fosfor i grön växtbiomassa representerade cirka 1/3 av våtmarkernas totala fosforrening, vilket påvisade potentialen i att genom skörd ta bort fosfor från avloppsvatten m.h.a. konstruerade våtmarker. Resultaten pekade också på att skörden bör vara art-specifik för att uppnå en hög fosforrening och generellt bra vattenreningsresultat. Dock visade olika beräkningsmetoder att vattenbalansen i en tropisk våtmark markant kan påverka vattenreningsresultaten. Resultaten från spårämnesexperimenten demonstrerade att den effektiva våtmarksvolymen för vattenrening blev mindre vid hög täthet av övervattensväxter. Detta pekade på att regelbunden växtskörd var viktig för att uppnå god vattenrening i våtmarker. Experiment med spårämnet litium visade att man kan få felaktiga resultat p.g.a. att en del spårämne fasthålls på botten i våtmarken om denna har mycket övervattensväxter. Därför bör spridningen av spårämnet i sådana våtmarker underlättas m.h.a. en spridningsbarriär nära inloppsröret. Simuleringar visade också att valet av dataanalysmetod av spårämnesdata starkt kan påverka resultaten och därmed också vår tolkning av en våtmarks hydraulik och reningskapacitet. Den effektiva volymen kunde vara 50% högre och reningseffekten 13% högre beroende på vilken metod som användes. Likaså kan valet av dataanalysmetod ha bidragit till överskattade och orealistiska effektiva volymer (över 100%) i artiklar publicerade de senaste 25 åren. Genom att fokusera mer på valet av dataanalysmetod och t.ex. jämföra resultaten från två olika metoder kan man minimera risken för bristfälliga resultat och därmed felaktiga slutsatser om en våtmarks vattenreningskapacitet.
Oke, Oluwabukola A. "Enhanced unscented transform method for probabilistic load flow studies." Thesis, University of Nottingham, 2013. http://eprints.nottingham.ac.uk/14040/.
Повний текст джерелаEllis, Mikle Val. "The ladder load-flow method extended to distribution networks." Diss., Virginia Tech, 1994. http://hdl.handle.net/10919/39138.
Повний текст джерелаPh. D.
CASTRO, ANDRE MILHORANCE DE. "PROBABILISTIC LOAD FLOW VIA MONTE CARLO SIMULATION AND CROSS-ENTROPY METHOD." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2017. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=36794@1.
Повний текст джерелаCONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
Em planejamento e operação de sistemas de energia elétrica, é necessário realizar diversas avaliações utilizando o algoritmo de fluxo de potência, para obter e monitorar o ponto de operação da rede em estudo. Em sua utilização determinística, devem ser especificados valores de geração e níveis de carga por barra, bem como considerar uma configuração especifica da rede elétrica. Existe, porém, uma restrição evidente em se trabalhar com algoritmo de fluxo de potência determinístico: não há qualquer percepção do impacto gerado por incertezas nas variáveis de entrada que o algoritmo utiliza. O algoritmo de fluxo de potência probabilístico (FPP) visa extrapolar as limitações impostas pelo uso da ferramenta convencional determinística, permitindo a consideração das incertezas de entrada. Obtém-se maior sensibilidade na avaliação dos resultados, visto que possíveis regiões de operação são mais claramente examinadas. Consequentemente, estima-se o risco do sistema funcionar fora de suas condições operativas nominais. Essa dissertação propõe uma metodologia baseada na simulação Monte Carlo (SMC) utilizando técnicas de amostragem por importância via o método de entropia cruzada. Índices de risco para eventos selecionados (e.g., sobrecargas em equipamentos de transmissão) são avaliados, mantendo-se a precisão e flexibilidade permitidas pela SMC convencional, porém em tempo computacional muito reduzido. Ao contrário das técnicas analíticas concebidas para solução do FPP, que visam primordialmente à elaboração de curvas de densidade de probabilidade para as variáveis de saída (fluxos, etc.) e sempre necessitam ter a precisão obtida comparada à SMC, o método proposto avalia somente as áreas das caudas dessas densidades, obtendo resultados com maior exatidão nas regiões de interesse do ponto de vista do risco operativo. O método proposto é aplicado nos sistemas IEEE 14 barras, IEEE RTS e IEEE 118 barras, sendo os resultados obtidos amplamente discutidos. Em todos os casos, há claros ganhos de desempenho computacional, mantendo-se a precisão, quando comparados à SMC convencional. As possíveis aplicações do método e suas derivações futuras também fazem parte da dissertação.
In planning and operation of electric energy systems, it is necessary to perform several evaluations using the power flow algorithm to obtain and monitor the operating point of the network under study. Bearing in mind its deterministic use, generation values and load levels per bus must be specified, as well as a specific configuration of the power network. There is, however, an obvious constraint in running a deterministic power flow tool: there is no perception of the impact produced by uncertainties on the input variables used by the conventional algorithm. The probabilistic power flow (PLF) algorithm aims to solve the limitations imposed by the use of the deterministic conventional tool, allowing the consideration of input uncertainties. Superior sensitivity is obtained in the evaluation of results, as possible regions of operation are more clearly examined. Consequently, the risk of the system operating outside its nominal conditions is duly estimated. This dissertation proposes a methodology based on Monte Carlo simulation (MCS) using importance sampling techniques via the cross-entropy method. Risk indices for selected events (e.g., overloads on transmission equipment) are evaluated, keeping the same accuracy and flexibility tolerable by the conventional MCS, but in much less computational time. Unlike the FPP solution obtained by analytical techniques, which primarily aim at assessing probability density curves for the output variables (flows, etc.) and always need to have the accuracy compared to MCS, the proposed method evaluates only the tail areas of these densities, obtaining results with greater accuracy in the regions of interest from the operational risk point of view. The proposed method is applied to IEEE 14, IEEE RTS and IEEE 118 bus systems, and the results are widely discussed. In all cases, there are clear gains in computational performance, maintaining accuracy when compared to conventional SMC. The possible applications of the method and future developments are also part of the dissertation.
Chen, Ying Chih. "Visualizing Load Path in Perforated Shear Walls." Scholar Commons, 2018. https://scholarcommons.usf.edu/etd/7609.
Повний текст джерелаSelim, Asif. "An investigation of the use of Broyden's method of load flow analysis." Ohio : Ohio University, 1994. http://www.ohiolink.edu/etd/view.cgi?ohiou1178734278.
Повний текст джерелаFan, Li 1958. "Solution of the ill-conditioned load flow problem by the tensor method." Thesis, McGill University, 1989. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=62002.
Повний текст джерелаPonrajah, Ranendra Anthony. "The minimum cost optimal power flow problem solved via the restart homotopy continuation method /." Thesis, McGill University, 1987. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=75455.
Повний текст джерелаThe pertinent steps of the first phase are as follows: (1) Create a sub-problem of the complete optimal power flow problem by relaxing boundary limits on all functional variables, namely voltages at load buses, line flows and reactive generations. (2) Parameterize a subset of the whole set of controls which comprises initially of tap-changers, phase-shifters, shunt controllers, and the voltages at generation buses. (3) Optimize the resulting problem.
The solution in step (3) is used as an initial starting point in a continuation process, designed to track this solution to the optimal solution of the sub-problem defined in step (1). The tracking is accomplished via a predictor-corrector path following algorithm embodying certain special features, such that the solution accuracy can be improved to any desired degree through a flexible restart feature developed in this study. Within the tracking process only a subset (identified in step 2 above) of the whole set of controls require specific monitoring for break-points. This feature greatly reduces the computational burden. Termination of the first phase marks an operating point in which all controls are strictly feasible.
If, following the termination of the first phase, functional variables previously ignored prove to be within their respective bounds, the solution to the sub-problem becomes the solution to the complete optimal power flow problem. However, should functional variables violate their bounds the second phase of the algorithm is invoked, which in essence creates a new sub-problem by changing the roles of the control and violated dependent variables, such that the newly modified sub-problem maintains the same basic structure as its predecessor.
Phase I is invoked again at this juncture to solve the modified sub-problem. This process is repeated in cycles until the Kuhn-Tucker optimality conditions are satisfied. Simulations suggest that convergence is usually achieved within two or three Phase I/II cycles.
This being a method unique to the minimum cost optimal power flow problem, numerous examples (up to 118 buses) have been tested and compared against the commercial code MINOS. The newly proposed algorithm appears to be faster and more reliable.
Davis, Richard. "An efficient Non-iterative probabilistic load flow analysis method comparison and worked example." Thesis, Davis, Richard (2016) An efficient Non-iterative probabilistic load flow analysis method comparison and worked example. Masters by Coursework thesis, Murdoch University, 2016. https://researchrepository.murdoch.edu.au/id/eprint/35852/.
Повний текст джерелаGarbelini, Enio [UNESP]. "Proposição de uma técnica de parametrização geométrica para o fluxo de carga continuado." Universidade Estadual Paulista (UNESP), 2008. http://hdl.handle.net/11449/100326.
Повний текст джерелаCoordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
O fluxo de carga convencional é considerado inadequado para a obtenção do ponto de máximo carregamento devido a singularidade da matriz Jacobiana. Os métodos da continuação são ferramentas eficientes para a solução deste tipo de problema, e diferentes parametrizações são utilizadas para evitar a singularidade da matriz. Neste trabalho apresentase uma técnica de parametrização geométrica que possibilita o traçado completo das curvas PV sem os problemas de mal condicionamento. A técnica proposta associa a robustez com a simplicidade e a facilidade de compreensão. A singularidade da matriz Jacobiana é eliminada pela adição da equação de uma reta que passa por um ponto no plano formado pelas variáveis perdas de potência ativa totais e o fator de carregamento, dois parâmetros físicos de fácil compreensão. A técnica, aplicada aos sistemas do IEEE (14, 30, 57, 118 e 300 barras) e ao sistema brasileiro sul-sudeste (638 e 787 barras), mostra que as características do fluxo de carga não só são preservadas, mas também melhoradas. Diversos testes são realizados para proporcionar a comparação do desempenho do esquema de parametrização proposto para o método do fluxo de carga continuado.
The conventional Newton’s method has been considered inadequate to obtain the maximum loading point of power systems due to the Jacobian matrix singularity. Continuation methods are efficient tools for solving this kind of problem, and different parameterizations are used to avoid the matrix singularity. This paper presents a new geometric parameterization scheme that allows the complete tracing of the PV curves without ill-conditioning problems. The proposed technique associates the robustness to the simplicity and easy understanding. The Jacobian matrix singularity is overcome by the addition of a line equation, which passes through a point in the plane, determined by the real power losses and loading factor variables, two parameters with clear physical meaning. The application of this new technique to the IEEE systems (14, 30, 57, 118 and 300 buses) and to the Brazilian systems south-southeast (638 and 787 buses) shows that the characteristics of the conventional Newton’s method are not only preserved but also improved. Several tests are carried out to compare the performance of the proposed parameterization scheme for the continuation power flow method.
Wallace, Ian Patrick. "Improved computational approaches to classical electric energy problems." Thesis, University of Edinburgh, 2017. http://hdl.handle.net/1842/28922.
Повний текст джерелаLiu, Xin. "Numerical Modelling of Shallow Water Flows over Mobile Beds." Thesis, Université d'Ottawa / University of Ottawa, 2016. http://hdl.handle.net/10393/35131.
Повний текст джерелаBonini, Neto Alfredo [UNESP]. "Proposição de uma técnica de parametrização geométrica para o fluxo de carga continuado baseado nas variáveis tensão e fator de carregamento." Universidade Estadual Paulista (UNESP), 2006. http://hdl.handle.net/11449/87242.
Повний текст джерелаCoordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Este trabalho apresenta um novo esquema de parametrização geométrico para o fluxo de carga continuado que possibilita o traçado completo das curvas P-V, e o cálculo do ponto de máximo carregamento de sistemas de potência, sem os problemas de mau-condicionamento. O objetivo é o de apresentar de uma forma clara e didática, os passos envolvidos no desenvolvimento de uma técnica de parametrização geométrica a partir da observação das trajetórias de solução do fluxo de carga. A técnica associa robustez com facilidade de compreensão. A singularidade da matriz Jacobiana é eliminada pela adição da equação de uma reta que passa por um ponto no plano formado nas variáveis magnitude da tensão nodal e o fator de carregamento, dois parâmetros físicos de fácil compreensão. O uso desta técnica amplia o grupo das variáveis de tensão que podem ser usadas como parâmetro de continuação. Os resultados obtidos com a nova metodologia para os sistemas testes do IEEE (14, 30, 57, 118 e 300 barras), mostram que as características do método convencional são melhoradas e a região de convergência ao redor da singularidade é ampliada. Vários testes são apresentados com intuito de prover um completo entendimento do método proposto e possibilitar comparação e a avaliação do desempenho do esquema de parametrização proposto.
This work presents a new geometrical parameterization scheme to the continuation power flow that allows the complete tracing of P-V curves and the computation of the maximum loading point of a power system, without ill-conditioning problems. The objective is to present in a clear and didactic way, the steps involved in the development of a geometrical parameterization technique from the observation of the behavior of power flow solutions path. The technique associates robustness with simplicity and easy interpretation. The Jacobian matrix singularity is overcome by the addition of a line equation which passes through a point in the plane determined by variables bus voltage magnitude and the loading factor, two physical parameter of easy understanding. The use of this technique enlarges the group of voltage variables that can be used as continuation parameter. The results obtained with the new methodology for the IEEE systems (14, 30, 57, 118 and 300 buses), show that the characteristics of the conventional method are improved and the region of convergence around the singular solution is enlarged. Many tests are also presented in intention to provide the complete understanding of the proposed method and to allow the comparison and assessment of the performance of the proposed parameterization scheme.
Pajic, Slobodan. "Sequential quadratic programming-based contingency constrained optimal power flow." Link to electronic thesis, 2003. http://www.wpi.edu/Pubs/ETD/Available/etd-0430103-152758.
Повний текст джерелаSanjab, Anibal Jean. "Statistical Analysis of Electric Energy Markets with Large-Scale Renewable Generation Using Point Estimate Methods." Thesis, Virginia Tech, 2014. http://hdl.handle.net/10919/74356.
Повний текст джерелаMaster of Science
Rämmal, Hans. "Studies of flow duct acoustics with applications to turbocharged engines." Doctoral thesis, KTH, MWL Marcus Wallenberg Laboratoriet, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-10590.
Повний текст джерелаQC 20100809
Bonini, Neto Alfredo. "Proposição de uma técnica de parametrização geométrica para o fluxo de carga continuado baseado nas variáveis tensão e fator de carregamento /." Ilha Solteira : [s.n.], 2006. http://hdl.handle.net/11449/87242.
Повний текст джерелаBanca: Francisco Villarreal Alvarado
Banca: Eduardo Nobuhiro Asada
Resumo: Este trabalho apresenta um novo esquema de parametrização geométrico para o fluxo de carga continuado que possibilita o traçado completo das curvas P-V, e o cálculo do ponto de máximo carregamento de sistemas de potência, sem os problemas de mau-condicionamento. O objetivo é o de apresentar de uma forma clara e didática, os passos envolvidos no desenvolvimento de uma técnica de parametrização geométrica a partir da observação das trajetórias de solução do fluxo de carga. A técnica associa robustez com facilidade de compreensão. A singularidade da matriz Jacobiana é eliminada pela adição da equação de uma reta que passa por um ponto no plano formado nas variáveis magnitude da tensão nodal e o fator de carregamento, dois parâmetros físicos de fácil compreensão. O uso desta técnica amplia o grupo das variáveis de tensão que podem ser usadas como parâmetro de continuação. Os resultados obtidos com a nova metodologia para os sistemas testes do IEEE (14, 30, 57, 118 e 300 barras), mostram que as características do método convencional são melhoradas e a região de convergência ao redor da singularidade é ampliada. Vários testes são apresentados com intuito de prover um completo entendimento do método proposto e possibilitar comparação e a avaliação do desempenho do esquema de parametrização proposto.
Abstract: This work presents a new geometrical parameterization scheme to the continuation power flow that allows the complete tracing of P-V curves and the computation of the maximum loading point of a power system, without ill-conditioning problems. The objective is to present in a clear and didactic way, the steps involved in the development of a geometrical parameterization technique from the observation of the behavior of power flow solutions path. The technique associates robustness with simplicity and easy interpretation. The Jacobian matrix singularity is overcome by the addition of a line equation which passes through a point in the plane determined by variables bus voltage magnitude and the loading factor, two physical parameter of easy understanding. The use of this technique enlarges the group of voltage variables that can be used as continuation parameter. The results obtained with the new methodology for the IEEE systems (14, 30, 57, 118 and 300 buses), show that the characteristics of the conventional method are improved and the region of convergence around the singular solution is enlarged. Many tests are also presented in intention to provide the complete understanding of the proposed method and to allow the comparison and assessment of the performance of the proposed parameterization scheme.
Mestre
Magalhães, Elisabete de Mello. "Aplicação do método de Newton desacoplado para o fluxo de carga continuado /." Ilha Solteira : [s.n.], 2010. http://hdl.handle.net/11449/87114.
Повний текст джерелаBanca: Anna Diva Plasencia Lotufo
Banca: Edmárcio Antonio Belati
Resumo: Este trabalho apresenta o método de Newton desacoplado para o fluxo de carga continuado. O método foi melhorado por uma técnica de parametrização geométrica possibilitando assim o traçado completo das curvas P-V, e o cálculo do ponto de máximo carregamento de sistemas elétricos de potência, sem os problemas de mau condicionamento. O objetivo é o de apresentar de forma didática os passos envolvidos no processo de melhoria do método de Newton Desacoplado a partir da observação das trajetórias de solução do fluxo de carga. A técnica de parametrização geométrica que consiste na adição de uma equação de reta que passa por um ponto no plano formado pelas variáveis: tensão nodal de uma barra k qualquer e o fator de carregamento eliminam os problemas de singularidades das matrizes envolvidas no processo e ampliam o grupo das variáveis de tensão que podem ser usadas como parâmetro da continuação. Os resultados obtidos com a nova metodologia para o sistema teste do IEEE (14, 30, 57, 118 e 300 barras) e também para os sistemas reais de grande porte, o 638 barras do sistema Sul-Sudeste brasileiro e do sistema de 904 barras do sudoeste Americano, mostram que as características do método convencional são melhoradas na região do ponto de máximo carregamento e que a região de convergência ao redor da singularidade é sensivelmente aumentada. São apresentados vários testes com a finalidade de prover um completo entendimento do funcionamento do método proposto e também avaliar seu desempenho
Abstract: This work presents the decoupled Newton method for continuation power flow. The method was improved by using a geometric parameterization technique that allows the complete tracing of P-V curves, and the computation of maximum loading point of a power system, without ill-conditioning problems. The goal is to present in a clear and didactic way the steps involved in the development of the improved decoupled Newton method obtained from the observation of the geometrical behavior of power flow solutions. The geometric parameterization technique that consists of the addition of a line equation, which passes through a point in the plane determined by the bus voltage magnitude and loading factor variables, can eliminate the ill-conditioning problems of matrices used by the method and can enlarge the set of voltage variables that can be used as continuation parameter to P-V curve tracing. The method is applied to the IEEE systems (14, 30, 57, 118 and 300 buses) and two large real systems: the south-southeast Brazilian system (638 buses) and the 904-bus southwestern American system. The results show that the best characteristics of the conventional decoupled Newton's method are improved in the vicinity of the maximum loading point and therefore the region of convergence around it is enlarged. Several tests are presented with the purpose of providing a complete understanding of the behavior of the proposed method and also to evaluate its performance
Mestre
Carvalho, Marcus Rodrigo. "Estudo de técnicas eficientes para a resolução do problema de fluxo de potência para sistemas de distribuição radial." Universidade de São Paulo, 2006. http://www.teses.usp.br/teses/disponiveis/18/18133/tde-27072006-164213/.
Повний текст джерелаThis work describes an approach on primal-dual logarithmic barrier method (PDLBM) associate to the method of Newton modified for the resolution of the problem of power flow for radial distribution systems. Also a comparative study with two classic techniques of solution of the flow problem was carried through power for nets of radial distribution. They are the methods: Backward/Forward Sweep and the method considered for M. Baran and F. Wu, that is based on the technique of Newton-Raphson. This method uses modified Jacobiana matrix that takes care of the radial characteristic of the distribution systems. In the comparative tests all will be considered the parameters of the system. The solution algorithms will be analyzed in its properties of convergence and will be carried through a robustness test. The results of the tests carried through in 4 systems (4, 10, 34 and 70 bus) and the comparative test between the methods evidence the best methodology in the solution of the problem of power flow for radial systems
Magalhães, Elisabete de Mello [UNESP]. "Aplicação do método de Newton desacoplado para o fluxo de carga continuado." Universidade Estadual Paulista (UNESP), 2010. http://hdl.handle.net/11449/87114.
Повний текст джерелаCoordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Este trabalho apresenta o método de Newton desacoplado para o fluxo de carga continuado. O método foi melhorado por uma técnica de parametrização geométrica possibilitando assim o traçado completo das curvas P-V, e o cálculo do ponto de máximo carregamento de sistemas elétricos de potência, sem os problemas de mau condicionamento. O objetivo é o de apresentar de forma didática os passos envolvidos no processo de melhoria do método de Newton Desacoplado a partir da observação das trajetórias de solução do fluxo de carga. A técnica de parametrização geométrica que consiste na adição de uma equação de reta que passa por um ponto no plano formado pelas variáveis: tensão nodal de uma barra k qualquer e o fator de carregamento eliminam os problemas de singularidades das matrizes envolvidas no processo e ampliam o grupo das variáveis de tensão que podem ser usadas como parâmetro da continuação. Os resultados obtidos com a nova metodologia para o sistema teste do IEEE (14, 30, 57, 118 e 300 barras) e também para os sistemas reais de grande porte, o 638 barras do sistema Sul-Sudeste brasileiro e do sistema de 904 barras do sudoeste Americano, mostram que as características do método convencional são melhoradas na região do ponto de máximo carregamento e que a região de convergência ao redor da singularidade é sensivelmente aumentada. São apresentados vários testes com a finalidade de prover um completo entendimento do funcionamento do método proposto e também avaliar seu desempenho
This work presents the decoupled Newton method for continuation power flow. The method was improved by using a geometric parameterization technique that allows the complete tracing of P-V curves, and the computation of maximum loading point of a power system, without ill-conditioning problems. The goal is to present in a clear and didactic way the steps involved in the development of the improved decoupled Newton method obtained from the observation of the geometrical behavior of power flow solutions. The geometric parameterization technique that consists of the addition of a line equation, which passes through a point in the plane determined by the bus voltage magnitude and loading factor variables, can eliminate the ill-conditioning problems of matrices used by the method and can enlarge the set of voltage variables that can be used as continuation parameter to P-V curve tracing. The method is applied to the IEEE systems (14, 30, 57, 118 and 300 buses) and two large real systems: the south-southeast Brazilian system (638 buses) and the 904-bus southwestern American system. The results show that the best characteristics of the conventional decoupled Newton’s method are improved in the vicinity of the maximum loading point and therefore the region of convergence around it is enlarged. Several tests are presented with the purpose of providing a complete understanding of the behavior of the proposed method and also to evaluate its performance
Matarucco, Rogério Rocha [UNESP]. "Método da continuação aplicado na análise de contingência de linhas de transmissão." Universidade Estadual Paulista (UNESP), 2010. http://hdl.handle.net/11449/100314.
Повний текст джерелаCoordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Este trabalho apresenta dois métodos para a análise estática de contingências em Sistemas Elétricos de Potência utilizando o Método da Continuação. No primeiro método a margem de carregamento pós-contingência é obtida a partir do ponto de máximo carregamento do caso base. A magnitude de tensão de uma barra qualquer é usada como parâmetro na etapa de parametrização do fluxo de carga continuado. O ramo selecionado para avaliação da contingência é parametrizado por um fator de escalonamento que possibilita a remoção gradual do ramo e assegura a convergência nos casos em que o método diverge para a retirada total da linha de transmissão. Em geral, para a maioria das contingências analisadas são necessárias poucas iterações para a determinação do ponto de máximo carregamento pós-contingência. Mostra-se que o método pode ser usado como uma técnica alternativa para a averiguação e até mesmo para a obtenção da lista de contingências críticas fornecida pela função de análise de segurança de sistemas elétricos. No outro método, o qual obtém o ponto de máximo carregamento de pós-contingência a partir do caso base, as variáveis ângulo de fase e magnitude de tensão de uma barra k qualquer, e a perda total de potência ativa, são propostas como parâmetros para a etapa de parametrização do fluxo de carga continuado utilizado na averiguação da lista de contingências críticas fornecida pela função de análise de segurança de sistemas elétricos. Nos casos em que há divergência do fluxo de carga, o método proposto possibilita confirmar se esta ocorre devido à deficiência numérica do método em si ou a inexistência de um ponto de operação factível de pós-contingência. O uso da perda total de potência ativa como parâmetro traz como vantagem a possibilidade da determinação de pontos além do ponto de singularidade sem a necessidade...
This work presents two methods for static contingency analysis of electric power systems by using Continuation Methods. In the first the post-contingency loading margin is obtained from the base case maximum loading point. The voltage magnitude of any bus can be used as a parameter in the parameterization step of the proposed continuation power flow. The branch selected for contingency evaluation is parameterized by a scaling factor which allows its the gradual removal and assures the continuation power flow convergence for the cases where the method would diverge for the complete transmission line removal. In general, for most of the analyzed contingencies little iterations are necessary for the determination of the post-contingency maximum loading point. It is shown that the method can be used as an alternative technique to verify and even to obtain the list of critical contingencies supplied by the electric power systems security analysis function. In the other method, which obtains the maximum loading point from the base case, new parameters, namely the voltage magnitudes, phase angles and the total power losses, for evaluating the effects of branch outages. The approach can be used as a verification tool after a list of critical contingencies had been ranked according to their severities by the contingency selection functions. It is then possible to find whether the non-convergence of a power flow is due to a numerical problem or to an infeasible operating situation. The mains advantage of using the total real power losses as a parameter is that it is not necessary to change parameters during the solutions tracing until beyond the simple limit point, where the original Jacobian is singular. The proposed methods facilitate the development and the implementation of continuation methods for contingencies analysis
Matarucco, Rogério Rocha. "Método da continuação aplicado na análise de contingência de linhas de transmissão /." Ilha Solteira : [s.n.], 2010. http://hdl.handle.net/11449/100314.
Повний текст джерелаBanca: Percival Bueno de Araujo
Banca: Carlos Roberto Minussi
Banca: Geraldo Roberto Martins da Costa
Banca: Luiz Carlos Pereira da Silva
Resumo: Este trabalho apresenta dois métodos para a análise estática de contingências em Sistemas Elétricos de Potência utilizando o Método da Continuação. No primeiro método a margem de carregamento pós-contingência é obtida a partir do ponto de máximo carregamento do caso base. A magnitude de tensão de uma barra qualquer é usada como parâmetro na etapa de parametrização do fluxo de carga continuado. O ramo selecionado para avaliação da contingência é parametrizado por um fator de escalonamento que possibilita a remoção gradual do ramo e assegura a convergência nos casos em que o método diverge para a retirada total da linha de transmissão. Em geral, para a maioria das contingências analisadas são necessárias poucas iterações para a determinação do ponto de máximo carregamento pós-contingência. Mostra-se que o método pode ser usado como uma técnica alternativa para a averiguação e até mesmo para a obtenção da lista de contingências críticas fornecida pela função de análise de segurança de sistemas elétricos. No outro método, o qual obtém o ponto de máximo carregamento de pós-contingência a partir do caso base, as variáveis ângulo de fase e magnitude de tensão de uma barra k qualquer, e a perda total de potência ativa, são propostas como parâmetros para a etapa de parametrização do fluxo de carga continuado utilizado na averiguação da lista de contingências críticas fornecida pela função de análise de segurança de sistemas elétricos. Nos casos em que há divergência do fluxo de carga, o método proposto possibilita confirmar se esta ocorre devido à deficiência numérica do método em si ou a inexistência de um ponto de operação factível de pós-contingência. O uso da perda total de potência ativa como parâmetro traz como vantagem a possibilidade da determinação de pontos além do ponto de singularidade sem a necessidade...(Resumo completo, clicar acesso eletrônico abaixo)
Abstract: This work presents two methods for static contingency analysis of electric power systems by using Continuation Methods. In the first the post-contingency loading margin is obtained from the base case maximum loading point. The voltage magnitude of any bus can be used as a parameter in the parameterization step of the proposed continuation power flow. The branch selected for contingency evaluation is parameterized by a scaling factor which allows its the gradual removal and assures the continuation power flow convergence for the cases where the method would diverge for the complete transmission line removal. In general, for most of the analyzed contingencies little iterations are necessary for the determination of the post-contingency maximum loading point. It is shown that the method can be used as an alternative technique to verify and even to obtain the list of critical contingencies supplied by the electric power systems security analysis function. In the other method, which obtains the maximum loading point from the base case, new parameters, namely the voltage magnitudes, phase angles and the total power losses, for evaluating the effects of branch outages. The approach can be used as a verification tool after a list of critical contingencies had been ranked according to their severities by the contingency selection functions. It is then possible to find whether the non-convergence of a power flow is due to a numerical problem or to an infeasible operating situation. The mains advantage of using the total real power losses as a parameter is that it is not necessary to change parameters during the solutions tracing until beyond the simple limit point, where the original Jacobian is singular. The proposed methods facilitate the development and the implementation of continuation methods for contingencies analysis
Doutor
Biehl, Scheila Valechenski. "Uma nova abordagem para resolução de problemas de fluxo de carga com variáveis discretas." Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/18/18154/tde-14052012-103104/.
Повний текст джерелаThis work presents a new approach to the load flow problem in electrical power systems and develops a methodology for its resolution. The proposed model is simultaneously composed by nonlinear equations and inequations which represent the load and operational restrictions of the system, where a set of complementarity constraints model the relationship between voltage and reactive power generation in controled buses. It is also proposed a new technique to obtaining a discrete solution for the transformer taps, allowing their discrete adjustment. The method developed treats the mixed system of equations and inequations of the load flow problem as a nonlinear feasibility problem and converts it in a nonlinear least squares problem, which is solved by minimizing a sequence of linearized subproblems, whitin a trust region. To obtain approximate solutions at every iteration, we use the Steihaug conjugate gradient method, combining trust region and multidimensional filters techniques to analyse the quality of the provided solution. Numerical results using 14, 30, 57, 118 and 300-bus IEEE power systems, and a real brazilian equivalent system CESP 53-bus, indicate the flexibility and robustness of the proposed method.
Zebiri, Boubakr. "Étude numérique des interactions onde de choc / couche limite dans les tuyères propulsives Shock-induced flow separation in an overexpanded supersonic planar nozzle A parallel high-order compressible flows solver with domain decomposition method in the generalized curvilinear coordinates system Analysis of shock-wave unsteadiness in conical supersonic nozzles." Thesis, Normandie, 2020. http://www.theses.fr/2020NORMIR06.
Повний текст джерелаThe need for a better understanding of the driving mechanism for the observed low-frequency unsteadiness in an over-expanded nozzle flows was discussed. The unsteady character of the shock wave/boundary layer remains an important practical challenge for the nozzle flow problems. Additionally, for a given incoming turbulent boundary layer, this kind of flow usually exhibits higher low-frequency shock motions which are less coupled from the timescales of the incoming turbulence. This may be good from an experimenter’s point of view, because of the difficulties in measuring higher frequencies, but it is more challenging from a computational point of view due to the need to obtain long time series to resolve low-frequency movements. In excellent agreement with the experimental findings, a very-long LES simulation run was carried out to demonstrate the existence of energetic broadband low-frequency motions near the separation point. Particular efforts were done in order to avoid any upstream low-frequency forcing, and it was explicitly demonstrated that the observed low-frequency shock oscillations were not connected with the inflow turbulence generation, ruling out the possibility of a numerical artefact. Different methods of spectral analysis and dynamic mode decomposition have been used to show that the timescales involved in such a mechanism are about two orders of magnitude larger than the time scales involved in the turbulence of the boundary layer, which is consistent with the observed low-frequency motions. Furthermore, those timescales were shown to be strongly modulated by the amount of reversed flow inside the separation bubble. This scenario can, in principle, explain both the low-frequency unsteadiness and its broadband nature
Fidler, Tomáš. "Zatížení střechy vzdušným proudem vrtulníku při montážních pracích." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2013. http://www.nusl.cz/ntk/nusl-226473.
Повний текст джерелаLoureiro, Pedro da Cruz. "Controle de tensão e harmônicos por compensador estático de reativos com ajuste de parâmetros via redes neurais artificiais." Universidade Federal de Juiz de Fora, 2012. https://repositorio.ufjf.br/jspui/handle/ufjf/1785.
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CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
Neste trabalho é proposta a aplicação de redes neurais artificiais para ajuste de parâmetros de um compensador estático de reativos, para controle de tensão e harmônicos. Devido à intensa produção de correntes harmônicas e possíveis afundamentos de tensão em instalações industriais como o forno a arco, é necessário um sistema de controle eficiente e robusto. Além disso, os sistemas elétricos de potência se encontram em um cenário com a presença cada vez maior de geração distribuída, cargas não-lineares e forte tendência à operação no contexto das smartgrids e microgrids. Sendo assim, o suporte de reativos deve ser adequado a esses sistemas, podendo atuar de forma rápida, precisa e confiável. Uma possível solução é a utilização de um compensador estático de reativos (CER) com função adicional de filtragem no ponto onde se deseja controlar a tensão e a distorção harmônica. Entretanto, para o correto funcionamento, é necessário um sistema preciso para o ajuste dos parâmetros do CER, ou seja, determinar os ângulos de disparo dos tiristores e o número de bancos de capacitores a serem ligados. Neste trabalho é proposta uma estratégia de controle via redes neurais artificiais, treinadas para o reconhecimento de padrões de operação em regime permanente e definição da configuração do CER, conferindo inteligência ao equipamento. Os desenvolvimentos propostos foram implementados no ambiente MatLab®. A validação do método é feita através de simulações em sistemas-teste, presentes na literatura técnica, utilizando o fluxo de potência pelo método de injeção de correntes trifásico harmônico. Os resultados obtidos mostram as vantagens da utilização da estratégia proposta.
In this work, an artificial neural network-based static var compensator tuning is proposed for voltage and harmonic distortion control. Due to intense harmonic current injection and possible voltage sags produced by industrial facilities such as arc furnaces, an efficient robust control system is needed. Besides, electrical power systems face a new scenario with high penetration of distributed generation and non-linear loads and increased smart grid and microgrid trends. Therefore, the available reactive power sources must be able to provide system control in order to operate the system in a fast, accurate and reliable way. The application of a static var compensator (SVC) with additional filtering function at the controlled node is a possible solution. However, a precise SVC parameters tuning is needed, in order to make the system to work properly. In this work, a control strategy based on artificial neural networks is proposed. The neural networks are trained to recognize steadystate operating patterns and give the SVC adjustment. The proposed technique was implemented in the MatLab® environment. The methodology is validated by simulations in test-systems available in technical literature, using the three-phase harmonic current injection method power flow. Results show the advantages of the proposed methodology.
Ben, Mladenović. "Компаративна анализа ерозије земљишта у Хомољу и Звижду". Phd thesis, Univerzitet u Novom Sadu, Prirodno-matematički fakultet u Novom Sadu, 2013. https://www.cris.uns.ac.rs/record.jsf?recordId=83645&source=NDLTD&language=en.
Повний текст джерелаErozija zemljišta je jedan od najkompleksnijih problema i ujedno jedan od najpodmuklijih čovekovih neprijatelja. Erozivni procesi postepeno razaraju i uništavaju zemljište, odnose hranljive supstrate i remete vodni režim. Oni dovode stanovništvo mnogih, često prostranih oblasti u bedu, siromaštvo i migraciju. Zbog toga, mnoge privredne grane moraju biti uvučene u borbu protiv erozije zemljišta i njenih strahovitih posledica. Erozija je veoma složena dinamička pojava, koja zavisi od niza faktora čije je diferenciranje vrlo teško. Ispitivanje i utvrđivanje intenziteta vodne erozije spada u grupu problema koji se ne mogu sveobuhvatno rešiti. Veoma je teško, skoro nemoguće, izdvojiti sve faktore, a potom multiplicirati sve te faktore u svim postojećim kombinacijama. Ovim radom sagledano je stanje erozije zemljišta u slivu Mlave i Peka, odnosno Homolju i Zviždu, sa više aspekata i utvrđen niz pojava kao što su: koncentracija rastvorenih mineralnih materija, procentualno učešće makroelemenata u ukupnoj mineralizaciji, odnos mineralizacije prema proticaju, ukupan godišnji pronos rastvorenih mineralnih materija, odnos specifične električne provodljivosti i ukupne mineralizacije, iznos hemijske evakuacije, iznos hemijski rastvorenih mineralnih materija koje potiču od stenskog komleksa u slivu, uticaj geološkog sastava na ukupnu mineralizaciju vode, njenu strukturu i specifičnu hemijsku eroziju, koncentracija suspendovanog nanosa po profilima, odnos suspendovanog nanosa prema proticaju, ukupan godišnji pronos suspendovanog nanosa kao i specifična erozija, uticaj sezonskih faktora na koncentraciju silta i iznos mehaničke erozije, uticaj geološkog sastava na ukupan pronos suspendovanog nanosa, merenje vučenog nanosa, odnos hemijske i mehaničke erozije. Homolje i Zvižd najvećim delom pripadaju brdsko – planinskom području koje se odlikuje vodotokovima sa relativno velikim uzdužnim padovima, gde su uglovi nagiba od 10 do 40. u Homolju i Zviždu sve vodotokove karakterišu vrlo velike razlike između ekstremno velikih i malih voda, pa na nekim vodotokovima odnos maksimalnih i minimalnih proticaja dostiže vrednost i hiljadu. Ovakav odnos između malih i velikih voda pogoduje razvoju erozivnih procesa i razaranju zemljišta. Erozija u slivu koja počinje pluvijalnom erozijom, a nastavlja se denudacijom, dovodi do snižavanja topografske površine i erodiranja zemljišta. Taloženjem nanosa na dnu rečnog korita ono se izdiže, što dovodi do smanjivanja ovlaženog profila. Velike poplavne vode zbog toga ne mogu da proteknu tako oplićalim rečnim koritom, pa zbog toga dolazi do njihovog izlivanja, što se manifestuje poplavama. Bez zemljišta ostaju gornji delovi sliva, a poplavama, usled taloženja vučenog i suspendovanog nanosa na dnu rečnog korita, bivaju izloženi donji delovi rečnih tokova. Ovakav negativan trend uočen je i u Homolju i u Zviždu koji su poslednjih godina sve češće ugroženi poplavnim vodama koje pričinjavaju velike štete kako poljoprivrednom zemljištu tako i naseljima u slivovima Mlave i Peka. S obzirom na činjenicu da u Homolju i Zviždu postoji veliki broj bujičnih tokova koji nose ogromne količine nanosa, realno je očekivanje da će se taj nanos akumulirati u srednjem i donjem delu slivova Mlave i Peka. Izbor hidrotehničkog metoda za istraživanje obima i intenziteta erozije u Homolju i Zviždu, kao i korišćenje metode profesora S. Gavrilovića u analizi bujičnih tokova je pokušaj preciznijeg utvrđivanja kvantiteta ovog procesa koji poslednjih godina ima uzlazni trend. Ostvarenje postavljenih zadataka utvrđenom metodologijom i postignuće zadatih ciljeva pruža odgovor na pitanje koliki je intenzitet i obim procesa erozije u Homolju i Zviždu na godišnjem nivou, po godišnjim dobima i mesecima. Utvrđen je stepen delovanja fizičko – geografskih faktora koji imaju uticaj na proces erozije, ukazano je na obim i vrstu primene antierozivnih mera, naročito u slivovima bujičnih tokova. Sagledavanjem intenziteta i obima erozije u Homolju i Zviždu, odnosno slivovima Mlave i Peka, uspešnije će biti rešeni vodoprivredni problemi koji ovde postoje.
The abstract has been processed with OCR optical text recognition technology.Soil erosion is one of the most complex problems and at the same time one of the most insidious of human enemies. Erosion processes gradually destroy the land, carry away nutritional substrates and disrupt the water regime. They drive many people, often from large areas, to misery and poverty, and cause migration. Therefore, many industries have to be included into the fight against soil erosion and its terrible consequences. Erosion is a very complex and dynamic phenomenon that relies on many factors which are hard to define. Differentiating and determining the intensity of water erosion are among the problems that cannot be comprehensively solved. It is very difficult, almost impossible, to extract all the factors and then multiply all these factors in every possible combination. This paper looks at the situation with soil erosion in the water basins of the rivers Mlava and Pek respectively, that is, in the areas of Homolje and Zvižd, from various aspects, and identifies a series of phenomena such as concentration of dissolved minerals, percentage of macroelements in the total mineralization, the relationship of mineralization to the flow, the total annual transport of dissolved minerals, the ratio of the specific electrical conductivity and total mineralization, the amount of chemical evacuation, the amount of chemically dissolved minerals that come from the rock complex in the basin, the impact of geological composition on the total mineralization of water, its structure and specific chemical erosion, suspended sediment concentration by profiles, the effect of suspended sediment on the flow, the total annual transport of suspended sediment as well as the specific erosion, the impact of seasonal factors on the concentration of silt and the amount of mechanical erosion, the impact of geological composition on the total transport of suspended sediment, bed load measurement, the ratio of chemical and mechanical erosion. Homolje and Zvižd are mostly hilly and mountainous areas characterized by water streams with relatively large vertical drops where the pitch angles may vary from 10° to 40°. In Homolje and Zvižd all the waterways are characterized by very large differences between extremely high and low water, reaching the value of a thousand in some points. This kind of a ratio between high and low waters favors the development of erosion processes and the destruction of land. Erosion in a basin starts with a pluvial erosion and continues with denudation, causing the lowering of the topographic surface and soil erosion. When the sediment deposits at the bottom of the river bed, the bed rises, leading to a reduction of the humidified profile. Therefore great floodwater cannot pass through such a shallow riverbed, which leads to its discharge and causes a flood. The upper parts of the basin lose land, and the lower parts of the basin become exposed to floods due to the deposition of bed load and suspended sediment at the bottom of the riverbed. This negative trend has been observed both in Homolje and Zviždi which in recent years have become increasingly threatened by flood waters which cause great damage to agricultural land and settlements in the basins of the rivers Mlava and Pek. Considering the fact that Homolje and Zvižd there is a large number of torrential streams that carry huge amounts of sediment, it is reasonable to expect the sediment to accumulate in the middle and lower parts of the basins of Mlava and Pek. The selection of the hydrotechnical method to explore the scope and intensity of erosion in Homolje and Zvižd, and the use of Professor S. Gavrilović’s method in the analysis of torrential flows is an attempt to determine more precisely the quantity of this process with an increasing trend in recent years. Fulfillment of tasks and achievement of objectives through suggested methodology and achievement of objectives provides the answer to the question of intensity and extent of erosion in Homolje and Zvižd on an annual basis, according to seasons and months. The paper has determined the degree of impact of physical and geographic factors on the erosion process, and has pointed to the scope and type of application anti-erosion measures, especially in watersheds with torrential flows. If we manage to comprehend the intensity and extent of erosion in Homolje and Zvižd, that is, in the basins of Mlava and Pek, we will be able to solve the existing water management problems more successfully.
TSENG, HUAN YAO, and 曾煥堯. "Comparisons of fast Decoupled load flow methods." Thesis, 1995. http://ndltd.ncl.edu.tw/handle/69580018787460267372.
Повний текст джерела國立中山大學
電機工程研究所
83
Due to higher efficiency and lower memory requirement in solving load flow problems , fast decoupled load flow has been adopted to solve many power system problems that reuqire higher speed in the computation of steady state load flow sloutions. However ,the fast decoupled load flow method is not without deficiencies , for power networks with high R/X ratios , long and/or short transmission lines and larges shunt capacitance due to network reduction , the fast decoupled load flow suffers slower convergence rate and in many cases , it fails to converge. In order to be able to handle these cases , several researchers have proposed many useful methods for improving the convergence characteristics . In this thesis , many of these modified methods are implemented and compared and compared . Suggestions on suitable methods for certain problems are given .
Su, Rui-Zhen, and 蘇瑞珍. "River Water Quality Risk Analysis for Design Flow Q75 and Varied Waste Load Allocation Methods." Thesis, 1998. http://ndltd.ncl.edu.tw/handle/10286001539010640953.
Повний текст джерелаZhang, Rui. "Advanced methods for power system security operations." Thesis, 2014. http://hdl.handle.net/1959.13/1048178.
Повний текст джерелаThe fundamental role of an electrical power system is to deliver the requested electricity to customers in a secure and economical manner. In general, to realize the proper functionality of a modern power system, efforts should be devoted to operation and planning stages. This research focuses on the operation stage of power systems. Specifically, advanced methods are developed for three essential problems in power system security operation studies: 1) short-term load forecasting (STLF), 2) security-constrained optimal power flow (SCOPF), and 3) dynamic security assessment (DSA). Where the STLF is the basis for system operation, SCOPF aims to economically dispatch the system while satisfying the security constraints, and DSA focuses on the dynamic security issue of the power system. This research is carried out in a logic way to address the three problems. In the area of STLF, a model based on extreme learning machine (ELM) technique is first developed for the Australian National Electricity Market (NEM). The model is an ensemble of a series of strategically arranged individual ELMs. Compared with some existing methods, it is much faster in model training and can provide more accurate load forecasting results. After this, a composite k-nearest neighbor (kNN) model is developed to deal with the situation that limited temperature input is available. The model uses only the minimum and maximum temperature forecasts as the model input and can provide reasonably accurate load forecast results. At last, a hybrid model for time-varying reactive power load forecasting is developed. This model is among the first in filling the gap between the need for accurate reactive load forecast and current industrial practices which are mainly using a fixed power factor to derive the reactive load. The developed hybrid load forecasting model has been practically applied in a real-world distribution network in U.S. In the area of SCOPF, research efforts are firstly devoted to the corrective security-constrained optimal power flow (CSCOPF) problem. In contrast to traditional OPF models, the CSCOPF considers the use of corrective control (CC) actions to regain the system security in the post-contingency state, and is able to provide the same security level with more economical generator dispatching solutions over the conventional OPF models. This research develops a hybrid computational strategy to solve the much more complex CSCOPF problems. Besides of this, this research proposes a preventive-corrective SCOPF (PCSCOPF) model and corresponding solution method. The PCSCOPF aims to optimally coordinate the preventive control (PC) and CC against the probable contingencies during system operations. In the area of DSA, this research applies the intelligent system (IS) strategy which has been identified in recent years as a promising approach for much faster DSA. First, a comprehensive review and systematic classification of existing methods is conducted. Subsequently, for pre-disturbance DSA, a systematic study on feature selection stage is conducted, and two alternative algorithms are introduced to this area. Then, an IS model for on-line voltage stability margin (VSM) prediction is developed. It employs system loading direction as the input and is much faster in model training and more accurate. After this, a novel IS for post-disturbance transient stability assessment (TSA) is proposed. The proposed IS can be fully integrated in the wide-area protection and control (WAPaC) systems. Compared with existing models, it is radically superior as it is self-adaptive in making the right TSA decision at an appropriate earlier time, hence allowing more time to take the remedial control actions against the instability. The developed methods have been numerically validated on a number of benchmark test systems, and shown satisfactory performance. They can be practically applied for enhanced security operation of modern power systems.
Lin, Guan-You, and 林冠佑. "The Impact of Different Media-Rich Learning Methods on Flow Experience and Cognitive Load—Game-based Learning versus Non-game-based Learning." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/3qgbj5.
Повний текст джерела國立臺灣師範大學
科技應用與人力資源發展學系
101
The purpose of this study was to investigate the impact of different media-rich learning methods on flow experience and cognitive load as well as the correlation between flow experience and cognitive load. The research subjects were first-year students of a general curriculum in a university. A total of 103 students participated in this experiment, 50 of them assigned to the experimental group (game-based learning) and while the remaining 53 to the control group (non-game-based learning). The main findings were as follows: 1. Students engaged in game-based learning had significantly better flow experiences than those engaged in non-game-based learning. 2. No significant difference in intrinsic cognitive load was observed between the two groups. 3. Compared to the control group, students engaged in game-based learning had significantly lower extraneous cognitive load and higher germane cognitive load. 4. Flow experience was significantly negatively related to intrinsic cognitive load and extraneous cognitive load but significantly positively related to germane cognitive load.
Yu, Ti-Hsuan, and 於迪萱. "Taguchi method based probabilistic optimal load flow analysis." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/25308033942236058139.
Повний текст джерела國立中央大學
電機工程學系
104
As the penetration of distributed generation goes up rapidly, the traditional power system is faced with challenges. One of the most severe problems for renewable energy is the fluctuation of the output power. If the output power of distributed generators could not be consumed by local loads, inverse load flow may occur. As a result, developing three-phase unbalanced load flow algorithms for distribution system considering distributed generation seem to be particularly important. By means of day-ahead scheduling, operators could take it as a reference to make an optimal decision. This thesis proposes a novel probabilistic load flow method that is based on Taguchi’s orthogonal arrays from Taguchi method. The proposed method only needs to sample probabilistic variables through orthogonal arrays and utilize few deterministic load flows to obtain the mean and standard deviation of bus voltages. An optimal experiment is also achieved through main effects from Taguchi’s method with the largest deviation from the nominal line-flow result. This thesis also presents a more practical model for distributed generators. To proof the well-behavior of this model, some abnormal operation scenarios are demonstrated. When over-voltage or low-voltage situation occurs caused by excess output power from wind turbine and PV, the model will acquire a voltage set point from optimal algorithm in order to absorb or generate reactive power to improve voltage profile considering the deviation of demands and output power from renewable energies. The simulation results were compared with results attained by Monte Carlo simulation (MCS) and point estimate method (PEM). A 25-bus Penghu system, an IEEE 118-bus system and a modified 12-bus feeder in Taiwan are used as test systems. The results show that the proposed method attains both accurate means and standard deviations of bus voltages and line flows and is time-saving.
Muhammed, Elssodani Abdelhadi. "HIGH VOLTAGE AC-DC LOAD FLOW IN ELECTRICAL POWER NETWORKS." Thesis, 2014. http://hdl.handle.net/10222/50521.
Повний текст джерелаChen, Chung-Hong, and 陳俊宏. "A TOPOLOGY-FREE METHOD FOR LOAD FLOW ANALYSIS IN GENERAL POWER SYSTEM." Thesis, 1994. http://ndltd.ncl.edu.tw/handle/58630011670183213744.
Повний текст джерела國立成功大學
電機工程研究所
82
In this thesis, a so-called ''topology-free method'''' for the power flow analysis in power systems is presented. Without solving the specific networks of the power systems , the fundamental and harmonic power flow solutions can be obtained simultaneously. Using the concept of ''topology- free method'''', two possible applications for the power flow analysis in power systems are demonstrated in both the transmission system and the distribution system. In the first application, the power distribution in various loads and transmission systems will be evaluated from the total system dissipations and the power factors of the various loads. In the second application, the power distribution in distribution systems will be evaluated from the total complex power supplied from the sources and the power factors of the loads partitioned in a ''binary- tree'''' structure. The proposed method offers some new idea for power flow evaluation in power systems. Examples using Taiwan Power( Taipower) system will be used to demonstrate the application of the new approach in power flow analysis.
Chu, Shou-Yung, and 朱守勇. "A Modified Forward and Backward Sweep Method for Radial Distribution Load Flow Analysis." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/44501508379022743394.
Повний текст джерела國立中正大學
電機工程所
96
Load flow analysis is the most fundamental work for power system operation and planning. In transmission systems, the network is always treated as balanced. Then, the load flow problem for transmission system can be dealt by single-phase method. However, the distribution power system is unbalanced inherently because of unsymmetrical network and unbalanced loads. In such situation, the conventional load flow methods for transmission systems are not suitable for distribution systems. In addition, high R/X ratio and radial structure are also to restrict the use of single-phase load flow approaches. Therefore, the three-phase approaches are required for distribution system load flow studies. The thesis proposes an improved forward/backward sweep algorithm for three-phase load flow analysis of radial distribution systems. In the backward sweep, the KCL and KVL are used to calculate each line current and the upstream bus voltage of each line or a transformer branch. Then, linear proportion principle for finding the real and imaginary ratios on each line section and bus index for fast mapping the terminal bus at each branch are exploited in the forward sweep to update the voltage at each junction or each terminal bus. The procedure stops after the mismatch of the calculated and the specified voltages at the substation is less than the predefined convergence tolerance. In the proposed method, the distribution component models including overhead lines, underground cables, different connecting type transformers, spot loads, distributed loads, capacitor banks and cogenerator are in consideration. The proposed solution algorithm has been described in details and tested by IEEE benchmark distribution systems with default system data, different system loadings, different power factors and different R/X ratios at different system loadings. Results show that the algorithm is accurate and computationally efficient in comparing with conventional forward/backward sweep method and ladder iteration method.
TENDEROVÁ, Renata. "Analýza obnovy vozového parku výrobního podniku." Master's thesis, 2011. http://www.nusl.cz/ntk/nusl-71065.
Повний текст джерелаSantosh, Kumar A. "Voltage Stability Analysis of Unbalanced Power Systems." Thesis, 2016. http://hdl.handle.net/2005/3065.
Повний текст джерела