Spelling suggestions: "subject:"[een] VOLTAGE STABILITY"" "subject:"[enn] VOLTAGE STABILITY""
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[en] CONTINGENCY SCREENING AND RANKING FOR VOLTAGE SECURITY ASSESSMENT / [pt] SELEÇÃO E ORDENAÇÃO DE CONTINGÊNCIAS PARA AVALIAÇÃO DAS CONDIÇÕES DE SEGURANÇA DE TENSÃORICARDO DRUMOND DE MOURA 20 May 2003 (has links)
[pt] O uso de compensação de potência reativa, embora permita um
carregamento mais elevado do sistema elétrico, leva-o a
operar próximo de situações de colapso de tensão. Portanto,
tornou-se necessário analisar o comportamento do sistema
quanto a esse fenômeno na ocorrência de contingências.
Neste trabalho alguns métodos existentes são estudados para
verificar a capacidade de classificação das contingências
que possam afetar o sistema, e como esses métodos procedem
para ordená-las por severidade e selecionar aquelas mais
prejudiciais. Os métodos são estudados tendo como foco
principal a operação em tempo real. Este trabalho propõe um
método capaz de ordenar e selecionar uma lista de
contingências prováveis, com base em índices nodais de
avaliação das condições de segurança de tensão. Esses
índices são baseados na margem em MVA para o máximo
carregamento, indicam a região de operação na curva V x P,
Q e a importância relativa entre barras. O Índice de
Sensitividade, que indica a redução da margem de potência
diante de uma contingência, é estudado minuciosamente.
Além da análise nodal, também é proposta uma forma de
análise sistêmica, capaz de ordenar e selecionar as
contingências de acordo com as influências sobre todo
o sistema elétrico.
São apresentados resultados numéricos correspondentes ao
sistema Brasileiro Interligado Norte-Nordeste, com carga
máxima de junho de 1992. A análise da eficiência
computacional do método proposto demonstrou ser possível
sua utilização na operação em tempo real integrado à
ferramenta de avaliação da segurança de tensão, através de
uma estrutura de dados comum aos dois processos. / [en] Although the use of compensation of reactive power allows a
higher loading in the electric system, it leads it to work
closer to voltage collapse situations. Therefore it`s
necessary to assess the behavior of the system regarding to
this phenomena in the occurrence of the contingencies. In
this work some existing methods are studied to check the
capacity of ranking the contingencies that might affect the
system, and how these methods rank them by severity and
select those which are more damaging. The methods are
studied having as the main focus the real-time operation.
This work proposes a method which is able to rank and
select a list of probable contingencies, having as a basis,
nodal indexes of voltage security conditions assessment.
These indexes are based on MVA margin to the maximum
loading, indicate the region of operation on V x P,Q curve,
and the relative importance among buses. The sensitivity
index which indicates the reduction of the power margin
before a contingency, is studied in detail. Besides the
nodal analysis, it is proposed a form of a systemic
analysis which is able to rank and select the contingencies
according to their influence upon all electrical system.
Numerical results corresponding to the North-Northeast
Brazilian Interconected power system, with maximum load of
June 1992 are presented. The analysis of computational
efficiency of the proposed method showed that it`s
possible to be used in real-time operation connected to the
voltage assessment security tool, through a common
structure of data to both procedures.
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Some Aspects Of Voltage Stability Improvement In Planning And Operation Of Power SystemsVisakha, K 07 1900 (has links) (PDF)
No description available.
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Método do look ahead modificado para estudos de colapso de tensão /Martins, Luís Fabiano Barone. January 2011 (has links)
Orientador: André Christovão Pio Martins / Banca: Newton Geraldo Bretas / Banca: Andre Nunes de Souza / Resumo: 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 / Abstract: 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 / Mestre
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Analysis of the Impact of Reactive Power Control on Voltage Stability in Transmission Power GridsCabadag, Rengin Idil 16 June 2020 (has links)
Voltage stability is the ability of a power system to maintain acceptable voltages at all buses under normal and abnormal operating conditions. The scarcity of reactive power or reactive power imbalance is the main reason of voltage instabilities. The energy supply of Germany will be dominated by renewable energy sources (RES) within energy transition actions leading to a decrease in conventional power plants especially in the transmission grid. Since the conventional power plants are still main reactive power sources, key challenge in the future will be the provision of system services such as control of reactive power to maintain voltage stability in the transmission networks.
A wide range of technology that is able to provide the required dynamic reactive power compensation is already available. However, in order to find the most effective implementation, it is necessary to investigate and compare these different technologies for a voltage stable grid operation. The main challenge regarding comparative studies that incorporate reactive power compensation devices is the development and the implementation of reliable comparison strategies.
This thesis analyses the impact of reactive power on the voltage stability phenomena both in long-term and short-term time frames under various grid situations. Voltage
stability margins in the long-term time frame are quantified by gradually increasing the reactive power injection into certain buses until the voltage collapses. Voltage stability in the short-term time frame is assessed by applying grid faults and simulating the time-domain grid response. A transient voltage severity ratio (TVSR) is developed in this thesis as the main comparison metric to evaluate and compare the performance of investigated compensation devices. Additionally, TVSR and other developed comparison metrics in this thesis are used to determine the optimal settings of the controller parameters of compensation devices. As a result, the submitted thesis shows a practical and reliable approach to analyze the performance of different compensation devices under different grid situations.
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Dynamic analysis of the impact of grid connection of "La Higuera" hydropower plant to the transmission gridFelix, Isbi January 2006 (has links)
Studies regarding the development of a new hydropower plant exploiting the water resources offered by the upper Tinguiririca river, located about 150 km south-east of the capital Santiago in Chile, has been done by Pacific Hydro Ltd from Australia and Lahmeyer International from Germany. These studies have resulted in proposals to construct two Hydropower Stations, �La Higuera� and �Confluencia�. Both hydropower stations will have a total installed capacity of 300 MW. When setting up a new hydropower plant, it is important to foresee how the hydropower plant would affect the existing transmission grid in different situations during operation as well as how events in the grid may affect the La Higuera and/or Confluencia hydropower stations. In this report three kind of analysis are highlighted, which are static analysis, large signal stability and rotor angle stability. To perform these analyses a simulation tool named DigSilent is used. DigSilent is used to perform these analyses in a simulated network of the studied transmission system. These two hydropower stations as shown in the results will improve the existing transmission system by enhancing the stability margins in the presence of a fault. When performing the simulation of the existing transmission system with the newly installed hydropower plant we could see that it had a poor damping after a disturbance; this might be due to the large distance between production plants and the existing loads. This phenomenon can be alleviated if a power system stabilizer (PSS) is integrated in the hydropower plant. The final conclusion is that the integration of the two hydropower plants will improve the existing transmission system in Chile.
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Development and Analysis of Nordic32 Power System Model in PowerFactoryPeppas, Dimitris January 2008 (has links)
The present work deals with the implementation of the test system Nordic32 proposed by Cigre task force 38-02-08. This test system which consists of 32 buses is a representation of the Swedish transmission and is suitable for the simulation of transient stability and long term dynamics. This work provides a detailed description about the steps followed to create both the static part of the system for load flow calculations and the controllers that the generators are equipped with. Furthermore, the thesis closes with a basic study concerning the modal analysis and the voltage stability of the system revealing some weaknesses that need further examination.
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Stabilité du réseau électrique de distribution. Analyse du point de vue automatique d'un système complexe / Stability of a distribution electrical network. Analysis from a complex system point of viewCosson, Marjorie 19 September 2016 (has links)
Pour maintenir la tension dans des bornes admissibles, des régulations locales de puissance réactive (Q) en fonction de la tension (U) sont envisagées sur les réseaux de distribution. Ces travaux étudient l’impact de ces régulations sur la stabilité des réseaux de distribution accueillant de la production. Une étude empirique confirme le risque d’instabilité de la tension et souligne le lien avec les paramètres de la régulation. Pour aider les gestionnaires à les choisir, trois méthodes d’étude de la stabilité sont proposées. Tout d’abord, une méthode formelle fondée sur les notions d’abstraction discrète et de bisimulation est développée. Elle offre une grande précision au prix d’un effort de calcul important. Pour contournercette difficulté, un critère analytique portant sur le temps de réponse des régulations Q(U) est formulé. Ensuite, un critère valable dans tous les cas est proposé pour les codes de réseaux. Enfin, l’extension desméthodes à des cas plus complexes est discutée. / To maintain the voltage within specified limits, local control laws of distributed generators (DGs) reactive power (Q) with respect to their voltage (U) have been considered. This work studies the impact of Q(U) control laws on distribution feeders’voltage stability. An empirical study confirms the risk of voltage instability and highlights its dependence on control law parameters. To help distribution grid operators to choose these parameters, three methods assessing stability are formulated.First, a formal method based on discrete abstraction and bisimulation calculation is developed. The proposed approach yields precise results but with a high computational load. Then, to overcome this issue, an analytical criterion adapting Q(U) control laws response time with respect to grid parameters is formulated. Finally, a general criterion, valid in any cases, is established in order to be included in the grid codes. To conclude this work, extension to more complex cases is discussed.
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Architectural Solutions for Low-power, Low-voltage, and Unreliable Silicon DevicesMiller, Timothy Normand 22 June 2012 (has links)
No description available.
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Voltage Stability and Control in Autonomous Electric Power Systems with Variable FrequencyRosado, Sebastian Pedro 19 November 2007 (has links)
This work focuses on the safe and stable operation of an autonomous power system interconnecting an AC source with various types of power electronic loads. The stability of these systems is a challenge due to the inherent nonlinearity of the circuits involved. Traditionally, the stability analysis in this type of power systems has been approached by means of small-signal methodology derived from the Nyquist stability criterion. The small-signal analysis combined with physical insight and the adoption of safety margins is sufficient, in many cases, to achieve a stable operation with an acceptable system performance. Nonetheless, in many cases, the margins adopted result in conservative measures and consequent system over designs.
This work studies the system stability under large-perturbations by means of three different tools, namely parameter space mapping, energy functions, and time domain simulations. The developed parameters space mapping determines the region of the state and parameter space where the system operation is locally stable. In this way stability margins in terms of physical parameters can be established. Moreover, the boundaries of the identified stability region represent bifurcations of the system where typical nonlinear behavior appears. The second approach, based on the Lyapunov direct method, attempts to determine the region of attraction of an equilibrium point, defined by an operation condition. For this a Lyapunov function based on linear matrix inequalities was constructed and tested on a simplified autonomous system model. In Addition, the third approach simulates the system behavior on a computer using a detailed system model. The higher level of model detail allows identifying unstable behavior difficult to observe when simpler models are used.
Because the stability of the autonomous power system is strongly associated with the characteristics of the energy source, an improved voltage controller for the generator is also presented. The generator of an autonomous power system must provide a good performance under a wide variety of regimes. Under these conditions a model based controller is a good solution because it naturally adapts to the changing requirements. To this extent a controller based on the model of a variable frequency synchronous generator has been developed and tested. The results obtained show a considerable improvement performance when compared to previous practices. / Ph. D.
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[en] STATIC AND DYNAMIC SIMULATION OF VOLTAGE CONTROL BY GENERATOR AND SYNCHRONOUS COMPENSATOR / [pt] SIMULAÇÃO ESTÁTICA E DINÂMICA DO CONTROLE DE TENSÃO POR GERADOR E COMPENSADOR SÍNCRONOARMANDO GONCALVES LEITE 17 October 2008 (has links)
[pt] O tema abordado neste trabalho é a observação e análise, em
regime permanente e dinâmico, da ocorrência de um fenômeno
que já foi observado em condições reais de operação do
sistema elétrico brasileiro, que é a relação oposta entre a
tensão de excitação de geradores e compensadores síncronos
e a tensão controlada. Nessas situações, a
capacidade nominal de um gerador / compensador síncrono,
por exemplo, não seria útil para manter a tensão
controlada. Em virtude da relação oposta, um aumento na
excitação da máquina abaixaria a tensão controlada. O
controle automático continuaria agindo, abaixando ainda
mais a tensão. Este mecanismo pode levar o sistema ao
colapso. A abordagem do problema baseou-se na verificação
do comportamento do gerador / compensador como dispositivo
de controle de tensão, em regime permanente e dinâmico,
ante as diversas situações normais de um sistema elétrico,
tais como variações do valor da tensão de referência
(tensão controlada) e de carga. A análise em regime
permanente utilizou um algoritmo de fluxo de carga,
enquanto a análise em regime dinâmico utilizou a simulação
no domínio do tempo. A real existência do fenômeno foi
comprovada através de várias destas análises, mostrando
inclusive a mudança da região de operação em
algumas delas. Em outros casos, os resultados da análise em
regime permanente não coincidiram com os da análise em
regime dinâmico. / [en] The aim of this work is to investigate, in steady state and
dynamic performance, the phenomenon of the opposite
relationship, already observed at real operation conditions
of the Brazilian Electric System, between generators and
synchronous compensators excitation voltage and the
controlled one. In these situations, the generator /
synchronous compensator nominal capacity, for example,
would not be useful to keep the voltage controlled. Due the
opposite relationship, an increase in the excitation
voltage would reduce the controlled voltage. The automatic
control would keep acting and reducing more the voltage.
This mechanism can lead the system to the collapse. The
study of this problem was based in the generator /
compensator behavior as a control voltage device, in steady-
state and dynamic performance, front of several operation
situations of electric power system, like reference voltage
(controlled voltage) variation and load changing. The
steady state analysis used a load flow algorithm, while the
time domain simulation was utilized for the dynamic
performance analysis. The real existence of the phenomenon
was verified through these analyses, emphasizing the
operation region changing in some of them. In other cases,
the analyses results in the steady-state were different of
the dynamic performance results.
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