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Método do look ahead modificado para estudos de colapso de tensãoMartins, Luís Fabiano Barone [UNESP] 23 February 2011 (has links) (PDF)
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martins_lfb_me_bauru.pdf: 963421 bytes, checksum: 7c1f9175f040c64a63fdf8db9f7a10a1 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Neste trabalho foi feita uma análise comparativa entre diferentes escolhas dos pontos utilizados pelo método look ahead na estimação do ponto de máximo carregamento de um sistema elétrico de potência. O Fluxo de Cargo Continuado é utilizado na geração dos pontos de operação utilizados pelo método look ahead e para servir como referência na comparação entre os resultados previstos e o ponto de máximo carregamento real. Uma vez que a exatidão dessa estimativa é fortemente afetada pela escolha desses pontos, o FCC é modificado para fornecer pontos mais adequados para o bom funcionamento do método look ahead. A metodologia proposta é aplicada ao sistema IEEE de 300 barras, os resultados obtidos mostram o seu bom funcionamento / Here we did a comparative analysis between different choices of the points used by the look ahead method for estimating maximum loading point of a power system. The Continued Power Flow (CPF) is used in the generation of operating points used by the look ahead method and to serve as a reference in comparison between the predicted results and the real maximum loading point. Since the accurancy of this estimative is strongly affected by choicen of these points, the CPF is modified to provide the most appropriate for the proper functioning of the method look ahead. The proposed methodology system is applied to IEEE 300 buses, the results have shown its good functioning
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Numerical Performance of the Holomorphic Embedding MethodJanuary 2018 (has links)
abstract: Recently, a novel non-iterative power flow (PF) method known as the Holomorphic Embedding Method (HEM) was applied to the power-flow problem. Its superiority over other traditional iterative methods such as Gauss-Seidel (GS), Newton-Raphson (NR), Fast Decoupled Load Flow (FDLF) and their variants is that it is theoretically guaranteed to find the operable solution, if one exists, and will unequivocally signal if no solution exists. However, while theoretical convergence is guaranteed by Stahl’s theorem, numerical convergence is not. Numerically, the HEM may require extended precision to converge, especially for heavily-loaded and ill-conditioned power system models.
In light of the advantages and disadvantages of the HEM, this report focuses on three topics:
1. Exploring the effect of double and extended precision on the performance of HEM,
2. Investigating the performance of different embedding formulations of HEM, and
3. Estimating the saddle-node bifurcation point (SNBP) from HEM-based Thévenin-like networks using pseudo-measurements.
The HEM algorithm consists of three distinct procedures that might accumulate roundoff error and cause precision loss during the calculations: the matrix equation solution calculation, the power series inversion calculation and the Padé approximant calculation. Numerical experiments have been performed to investigate which aspect of the HEM algorithm causes the most precision loss and needs extended precision. It is shown that extended precision must be used for the entire algorithm to improve numerical performance.
A comparison of two common embedding formulations, a scalable formulation and a non-scalable formulation, is conducted and it is shown that these two formulations could have extremely different numerical properties on some power systems.
The application of HEM to the SNBP estimation using local-measurements is explored. The maximum power transfer theorem (MPTT) obtained for nonlinear Thévenin-like networks is validated with high precision. Different numerical methods based on MPTT are investigated. Numerical results show that the MPTT method works reasonably well for weak buses in the system. The roots method, as an alternative, is also studied. It is shown to be less effective than the MPTT method but the roots of the Padé approximant can be used as a research tool for determining the effects of noisy measurements on the accuracy of SNBP prediction. / Dissertation/Thesis / Masters Thesis Electrical Engineering 2018
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[en] MODELING OF VOLTAGE CONTROL FOR THE EVALUATING OF THE TRANSMISSION SYSTEM LOADING / [pt] MODELAGEM DO CONTROLE DE TENSÃO PARA A AVALIAÇÃO DO CARREGAMENTO DA REDE DE TRANSMISSÃOBERNARDO HENRIQUE TODT SEELIG 17 October 2005 (has links)
[pt] A falta de recursos e a questão ecológica tem limitado a
expansão do sistema de transmissão. Esta realidade, em
conjunto com o crescimento da carga, faz com que os
sistemas elétricos trabalhem bastante carregados. Esta
nova condição pode levar a situações de colapso de tensão.
O desenvolvimento de métodos para a avaliação do
carregamento da rede de transmissão tornou-se necessário e
imprescindível para que se possa entender o funcionamento
do sistema nestas condições e possibilitar a sua operação
de modo correto.
O carregamento da rede de transmissão pode ser avaliado
por condições nodais associadas ao máximo fluxo de
potência ativa e reativa que pode ser transmitida dos
geradores para as cargas. Estas condições nodais são
avaliadas por uma ferramenta analítica com base em modelo
matemático, simples mas poderoso, de uma direta
interpretação física do fenômeno. Índices abrangentes e
significativos são obtidos a partir da matriz Jacobiano do
sistema. Eles indicam a região de operação na curva V x P,
Q a margem em MVA para o máximo carregamento, a
importância relativa entre as barras, e uma medida de
dificuldade de transmissão.
O controle de tensão influi diretamente nas condições de
operação e portanto, deve ser incluído na modelagem do
problema. Usualmente são: controle de tensão por ajuste de
tap de LTCs e controle de tensão (local e remota) por
injeção de potência reativa. O controle é restrito pelos
limites dos taps de transformadores, limites de injeção de
potência reativa e limites de tensão.
Neste trabalho é mostrada a forma como se deve incluir os
controles e limites relacionados com a tensão, na
ferramenta analítica de avaliação do carregamento da rede
de transmissão. O índice calculado apropriadamente é nulo
no ponto de máxima transferência de potência. É mostrado
que os controles e limites de tensão do sistema podem e
devem ser representados na matriz Jacobiano do sistema
linearizado de equações que modelam o sistema, exceto os
da barra em análise, mesmo se esta tiver sua tensão
controlada. / [en] The lack of investiments and the ecological matter have
limited the expansion of the transmission system. This
reality, together with the growth of the load, makes the
electric systems to work heavy loaded. This new condition
can lead to situations of voltage collapse. The
development of methods for evaluation the loading of the
transmission network became necessary and indispensable in
understanding the performance of the system under these
conditions and in making possible the operating in a
correct way.
The transmission system loading can be evaluated by nodal
conditions associated to the maximum active and reactive
power flow that can be transmitted from generators to
loads. These nodal conditions are assessed by an analytic
tool based on a a mathematical model. Simple but powerful,
derived directly from a physical interpretation of the
phenomenon. Meaningful and comprehensive indexes are
obtained from a partition of the jacobian matrix of the
system. They indicate the operation area in the V x P, Q
curve, the margin in MVA for the maximu loading, the
relative importance among the busbars, and a measure of
transmission difficulty.
The voltage control is of paramount importance on
operating consitions and therefore should be included in
the problem modeling. Usually they are voltage control by
tap adjstment of LTCs and voltage control (local and
remote) by injection of reactive power. The control is
constrained by limits on the taps of transformers, on
reactive power injection and on voltage magnitudes.
In this work it is shown how the controls and limits
related with the voltage should be include in the
analytical tool for the evaluation of the transmission
system loading. The index calculated adequately is null in
the point of maximum power transfer, positive in the upper
half and negative in the lower half of the V x P, Q curve.
It is shown that the voltage controls and limits of the
system can and should be represented in the Jacobian
matrix of the linearised system of equations, except on
bus under analysis, even if it is a voltage controlled bus.
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[en] MODAL ANALYSIS AND CONTINUATION PAWER FLOW IN THE VOLTAGE STABILITY PROBLEM / [pt] APLICAÇÃO DOS MÉTODOS DE CONTINUAÇÃO E ANÁLISE MODAL AO PROBLEMA DA ESTABILIDADE DE TENSÃO EM SISTEMAS ELÉTRICOS DE POTÊNCIAANDRE BIANCO 25 September 2006 (has links)
[pt] A estabilidade de tensão tornou-se nos últimos anos tema
de intensa pesquisa, envolvendo principalmente a
identificação da natureza do problema e a busca de
estratégias mais favoráveis para a operação e planejamento
dos sistemas de potência. Este trabalho apresenta um
relato da evolução da análise do fenômeno sendo,
posteriormente descritos os detalhes de sua abordagem
através da teoria das bifurcações em sistemas dinâmicos
não-lineares. São caracterizados o limite de transmissão
de potência à estabilidade de tensão e a geometria das
trajetórias no espaço de estados em pontos de equilíbrio
em suas proximidades.
O estabelecimento de equivalência entre os modelos
dinâmico e estático tornou possível o emprego de métodos
baseados nas equações algébricas do fluxo de carga na
determinação do limite de estabilidade de tensão e na
avaliação do comportamento dinâmico local. Com base no
algoritmo de fluxo de carga convencional, foi desenvolvido
um programa computacional que emprega o método de
continuação parametrizado. Os métodos de continuação
permitem a obtenção do conjunto completo das soluções
reais, relacionadas por um parâmetro escalar, de um
sistema de equações. Mostra-se que a aplicação desses
métodos em conjunto com as técnicas de análise modal
resulta em uma forma eficiente para a seleção e
localização de reforços visando aumentar a capacidade
global de transmissão dos sistemas de potência. / [en] In the past few years voltage stabiity has become a
subject of intense research involving the identification
of the nature of this problem and the seek of suitable
strategies for power systems operation and planning. In
this work it is presented a report on the evolution in the
analysis of this phenomena and it is described the details
of its approach through the dynamic nonlinear systems
bifurcation theory. The power transmission limit imposed
by the voltage stability conditions is addressed and the
geometry of the trajectories in state space considering the
equilibrium points on the vicinity of this limit is deeply
studied.
The establishment of the equivalence conditions between
the dynamic and static power system models made it
possible to employ load-flow algebraic equations based
methods on both the determination of the power
transmission limit and the evaluation of local dynamic
behaviour. A load-flow based computer program which uses
the parameterized continuation method was developed. The
continuation methods are widely known for providing the
determination of whole set of a system s solutions which
are related by a scalar parameter. In the closure, it is
shown that the application of these methods, in a
complementary basis with the modal analysis techniques,
results in an efficient procedure to promote the choice
and location of devices to improve the power system global
tranmission capacity.
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Stabilita napětí v NN sítích zatížených měniči s aktivní regulací na konstantní výstup / Voltage stability in LV distribution systems loaded by converters with constant output regulationČížek, Ondřej January 2017 (has links)
This thesis contains a summary of voltage stability issues caused by appliances with constant load output. It also contains models of this appliance and outcomes of simulations done for the purpose of conformation of influence of appliances with constant output on voltage stability.
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Voltage Stability Analysis Using Simulated Synchrophasor MeasurementsAgatep, Allan 01 May 2013 (has links) (PDF)
An increase in demand for electric power has forced utility transmission systems to continuously operate under stressed conditions, which are close to instability limits. Operating power systems under such conditions along with inadequate reactive power reserves initiates a sequence of voltage instability points and can ultimately lead to a system voltage collapse. Significant research have been focused on time-synchronized measurements of power systems which can be used to frequently determine the state of a power system and can lead to a more robust protection, control and operation performance. This thesis discusses the applicability of two voltage stability synchrophasor-based indices from literature to analyze the stability of a power system. Various load flow scenarios were conducted on the BPA 10-Bus system and the IEEE 39-Bus System using PowerWorld Simulator. The two indices were analyzed and compared against each other along with other well-known methods. Results show that their performances are coherent to each other regarding to voltage stability of the system; the indices can also predict voltage collapse as well as provide insight on other locations within the system that can contribute to instability.
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Robust Non-Matrix Based Power Flow Algorithm for Solving Integrated Transmission and Distribution SystemsTbaileh, Ahmad Anan 09 November 2017 (has links)
This work presents an alternative approach to power system computations, Graph Trace Analysis (GTA), and applies GTA to the power flow problem. A novel power flow algorithm is presented, where GTA traces are used to implement a modified Gauss-Seidel algorithm coupled with a continuation method. GTA is derived from the Generic Programming Paradigm of computer science. It uses topology iterators to move through components in a model and perform calculations. Two advantages that GTA brings are the separation of system equations from component equations and the ability to distribute calculations across processors. The implementation of KVL and KCL in GTA is described. The GTA based power flow algorithm is shown to solve IEEE standard transmission models, IEEE standard distribution models, and integrated transmission and distribution models (hybrid models) constructed from modifying IEEE standard models. The GTA power flow is shown to solve a set of robustness testing circuits, and solutions are compared with other power flow algorithms. This comparison illustrates convergence characteristics of different power flow algorithms in the presence of voltage stability concerns. It is also demonstrated that the GTA power flow solves integrated transmission and distribution system models. Advantages that GTA power flow bring are the ability to solve realistic, complex circuit models that pose problems to many traditional algorithms; the ability to solve circuits that are operating far from nominal conditions; and the ability to solve transmission and distribution networks together in the same model. / PHD
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Robustness and Stability Analysis with a Heavily-Meshed Distribution NetworkKrishnan, Anaga 07 June 2019 (has links)
Power distribution systems continue to evolve to accommodate the advancements in the field of microgrids and renewable energy resources. The future grids will be highly connected and will require increased reliability of the network. To this effect, low-voltage distribution systems with meshed or networked topology can be utilized. Currently, the use of low-voltage heavily-meshed distribution systems is restricted to urban areas with high load density that require increased reliability of power. A reason for this is the high cost of construction of such systems and complex topology which creates additional challenges. The direction of power flow in such systems is not unidirectional, which makes the power flow analysis difficult. Complicated network analysis techniques are required to determine the fault currents and protection settings in the network. Due to the aforementioned reasons, there is limited work analyzing the effectiveness of existing power flow algorithms to solve complex meshed systems. In this thesis, the robustness of two power flow algorithms is compared using an index called static stability breakdown margin parameter of circuit elements. For this study, a low-voltage heavily-meshed distribution test system is also proposed. Additionally, a study is conducted to show how reliable the meshed test system is against any fault in the system. The steady-state voltage stability of the test system is observed during the event of a fault. The stability margin parameter is then used to determine the vulnerable components in the system which need to be strengthened to increase the stability and voltage profile of the system. / Master of Science / Distribution systems carry electricity from the transmission system and deliver it to the customers. Distribution systems mainly operate using two topologies for their feeders: Radial and Meshed. The majority of customers are served using radial distribution systems, as in the radial feeders power flows in one direction (i.e. from substation to the end-user). They are simple in design and operation and are constructed at a moderate cost. However, if there is a fault along the main feeder, there will be an interruption of power to the end-use customer. On the other hand, meshed distribution systems involve multiple paths of power flow between all the points in the network. If a fault occurs along the feeder, the power flow is rerouted to the other available paths. Thus, Heavily Due to their complex topology, meshed systems are expensive to construct and deploy. The power flow analysis of these systems poses many challenges. Because of these reasons, their use is mainly restricted to urban areas with high load density which require very high reliability. The future grid is becoming increasingly complex and evolving to a meshed distribution topology has its own advantages. However, as presently the use of meshed systems is sparse, the work done on evaluating the stability of these systems is minimal. As a result of which, this thesis focuses on determining the optimal power flow solvers for these complex systems, analyzing their stability under abnormal operating conditions, and suggesting methods to reinforce the vulnerabilities in the system.
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Hierarchical Decentralized Control for Enhanced Stability of Large-Scale Power SystemsShukla, Srivats 27 January 2017 (has links)
Due to the ever-increasing penetration of distributed generation units connected to the power distribution system, electric power systems, worldwide, are undergoing a paradigm shift with regards to system monitoring, operation and control. We envision that with the emergence of `active' distribution systems consisting of `prosumers' and localized energy markets, decentralized control methods in power systems are gaining a growing attention among power researchers. Traditionally, two main types of control schemes have been implemented in power systems: (a) wide-area monitoring based centralized control, and (b) local measurement based primary (machine) level control. By contrast, decentralized control schemes based on local monitoring and control of strategically-determined subsystems (or `areas') of a large-scale power system are not used. The latter control schemes offer several advantages over the former, which include more flexibility, simplicity, economy and scalability for large-scale systems. In this dissertation, we summarize our research work on hierarchical and decentralized control techniques for the enhancement in a unified manner of voltage and rotor angle stability in large-scale power systems subject to large (e.g., short circuits) and small (e.g., small load changes) disturbances. We study system robustness by calculating local stability margins. We derive decentralized control laws that guaranty global asymptotic stability by applying Lyapunov's second method for interconnected systems. Furthermore, we argue that the current centralized control structure must only play a supervisory control role at a higher (tertiary) hierarchical level by processing the decisions taken by the regional control entities regarding the stability/instability of the system. This ensures system-wide situational awareness while minimizing the communication bandwidth requirements. We also develop a multi-agent based framework for this hierarchical control scheme. Finally, we compare different communication protocols using simulation models and propose an efficient communication network design for decentralized control schemes. This work, in principle, motivates the development of fast stability analysis which, in the future, may also account for the non-linear coupling that exist between machine rotor angles and bus voltages in power system models. As a future work, we propose the use of statistical techniques like random-effects regression and saddlepoint approximation method to reliably estimate the type-I and type-II probability errors in the proposed hierarchical, decentralized control decision process. / Ph. D.
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Método da continuação aplicado na análise de contingência de linhas de transmissão /Matarucco, Rogério Rocha. January 2010 (has links)
Orientador: Dilson Amancio Alves / Banca: 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
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