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On-line reactive power management in electric power systemsHawkins, Nigel Trevor January 1996 (has links)
No description available.
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Non-linear dynamics and power systemsWilson, Jonathan P. January 2000 (has links)
No description available.
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Design and implementation of a special protection scheme to prevent voltage collapse2012 March 1900 (has links)
The trend of making more profits for the owners, deregulation of the utility market and need for obtaining permission from regulatory agencies have forced electric power utilities to operate their systems close to the security limits of their generation, transmission and distribution systems. The result is that power systems are now exposed to substantial risks of experiencing voltage collapse. This phenomenon is complex and is localized in nature but has widespread adverse consequences. The worst scenario of voltage collapse is partial or total outage of the power system resulting in loss of industrial productivity of the country and major financial loss to the utility. On-line monitoring of voltage stability is, therefore becoming a vital practice that is being increasingly adopted by electric power utilities.
The phenomenon of voltage collapse has been studied for quite some time, and techniques for identifying voltage collapse situations have been suggested. Most suggested techniques examine steady-state and dynamic behaviors of the power system in off-line modes. Very few on-line protection and control schemes have been proposed and implemented. In this thesis, a new technique for preventing voltage collapse is presented.
The developed technique uses subset of measurements from local bus as well as neighbouring buses and considers not only the present state of the system but also future load and topology changes in the system. The technique improves the robustness of the local-based methods and can be implemented in on-line as well as off-line modes.
The technique monitors voltages and currents and calculates from those measurements time to voltage collapse. As the system approaches voltage collapse, control actions are implemented to relieve the system to prevent major disturbances.
The developed technique was tested by simulating a variety of operating states and generating voltage collapse situations on the IEEE 30-Bus test system. Some results from the simulation studies are reported in this thesis. The results obtained from the simulations indicates that the proposed technique is able to estimate the time to voltage collapse and can implement control actions as well as alert operators.
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Using Real Time Statistical Data To Improve Long Term Voltage Stability In Stochastic Power SystemsChevalier, Samuel 01 January 2016 (has links)
In order to optimize limited infrastructure, many power systems are frequently operated close to critical, or bifurcation, points. While operating close to such critical points can be economically advantageous, doing so increases the probability of a blackout. With the continued deployment of Phasor Measurement Units (PMUs), high sample rate data are dramatically increasing the real time observability of the power grids. Prior research has shown that the statistics of these data can provide useful information regarding network stability and associated bifurcation proximity. Currently, it is not common practice for transmission and distribution control centers to leverage the higher order statistical properties of PMU data. If grid operators have the tools to determine when these statistics warrant control action, though, then the otherwise unused statistical data present in PMU streams can be transformed into actionable information.
In order to address this problem, we present two methods that aim to gauge and improve system stability using the statistics of PMU data. The first method shows how sensitivity factors associated with the spectral analysis of the reduced power flow Jacobian can be used to weight and filter incoming PMU data. We do so by demonstrating how the derived participation factors directly
predict the relative strength of bus voltage variances throughout a system. The second method leverages an analytical solver to determine a range of "critical" bus voltage variances. The monitoring and testing of raw statistical data in a highly observable load pocket of a large system are then used to reveal when control actions are needed to mitigate the risk of voltage collapse. A simple reactive power controller is then implemented that pushes the stability of the system back to a stable operating paradigm. Full order dynamic time domain simulations are used in order to test this method on both the IEEE 39 bus system and the 2383 bus Polish system. We also compare this method to two other, more conventional, controllers. The first relies on voltage magnitude signals, and the second depends only on local control of a reactive power resource. This comparison illustrates how the use of statistical information from PMU measurements can substantially improve
the performance of voltage collapse mitigation methods.
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[en] AN ASSESSMENT OF THE VOLTAGE COLLAPSE PHENOMENON / [pt] UMA AVALIAÇÃO DO FENÔMENO DO COLAPSO DE TENSÃOANTONIO CARLOS ZAMBRONI DE SOUZA 03 August 2007 (has links)
[pt] Restrições econômicas e ecológicas têm limitado o
investimento em novas usinas e linhas de transmissão de
energia elétrica. Com os sistemas de potência trabalhando
bastante carregados, o risco da ocorrência da
instabilidade de tensão se acentua.
Neste trabalho estabeleceram-se as características
operacionais do fenômeno do colapso de tensão, e sua
similaridade e diferença em relação ao problema da
estabilidade angular.
Forma desenvolvidos métodos para avaliar um ponto de
operação do sistema quanto à proximidade da ocorrência do
fenômeno. Os resultados foram comparados.
Finalmente, foi abordado o problema da prevenção do colapso / [en] Investiments on new generators and transmission lines for
electrical power systems have been limited due to
economical and environmental constraints.
This dissertation established the operational
characteristics of the voltage collapse phenomenon, as
well as pointed out similarities and differences in
relation to the angular stability problem.
Voltage collapse assessment methods were developed and
results compared.
Finallu, the collapse prevention problem was mentioned.
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Development of intelligent systems for evaluating voltage profile and collapse under contingency operationMohammed, Mahmoud M. Jr. January 1900 (has links)
Doctor of Philosophy / Department of Electrical and Computer Engineering / Shelli K. Starrett / Monitoring and control of modern power systems have become very complex tasks due to the interconnection of power grids. These large-scale power grids confront system operators with a huge set of system inputs and control parameters. This work develops and compares intelligent systems-based algorithms which may be considered by power system operators or planners to help manage, process, and evaluate large amounts of data due to varying conditions within the system. The methods can be used to provide assistance in making operational control and planning decisions for the system in a timely manner. The effectiveness of the proposed algorithms is tested and validated on four different power systems.
First, Artificial Neural Network (ANN) models are developed and compared for two different voltage collapse indices and utilizing two different-sized sets of inputs. The ANNs monitor and evaluate the voltage profile of a system and generate intelligent conclusions regarding the status of the system from a voltage stability perspective. A feature reduction technique, based on the analysis of generated data, is used to decrease the number of inputs fed to the ANN, decreasing the number of physical quantities that need to be measured.
The major contribution of this work is the development of four different algorithms to control the VAR resources in a system. Four different objectives were also considered in this part of the work, namely: minimization of the number of control changes needed, minimization of the system power losses, minimization of the system's voltage deviations, and consideration of the computational time required. Each of the algorithms is iterative in nature and is designed to take advantage of a method of decoupling the load flow Jacobian matrix to decrease the time needed per iteration. The methods use sensitivity information derived from the load flow Jacobian and augmented with equations relating the desired control and dependent variables. The heuristic-sensitivity based method is compared to two GA-based methods using two different objective functions. In addition, a FL algorithm is added to the heuristic-sensitivity algorithm and compared to a PS-based algorithm.
The last part of this dissertation presents the use of one of the GA-based algorithms to identify the size of shunt capacitor necessary to enhance the voltage profile of a system. A method is presented for utilizing contingency cases with this algorithm to determine required capacitor size.
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Pattern Recognition of Power Systems Voltage Stability Using Real Time SimulationsBeeravolu, Nagendrakumar 17 December 2010 (has links)
The basic idea deals with detecting the voltage collapse ahead of time to provide the operators a lead time for remedial actions and for possible prevention of blackouts. To detect cases of voltage collapse, we shall create methods using pattern recognition in conjunction with real time simulation of case studies and shall develop heuristic methods for separating voltage stable cases from voltage unstable cases that result in response to system contingencies and faults. Using Real Time Simulator in Entergy-UNO Power & Energy Research Laboratory, we shall simulate several contingencies on IEEE 39-Bus Test System and compile the results in two categories of stable and unstable voltage cases. The second stage of the proposed work mainly deals with the study of different patterns of voltage using artificial neural networks. The final stage deals with the training of the controllers in order to detect stability of power system in advance.
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Predicting Voltage Abnormality Using Power System DynamicsBeeravolu, Nagendrakumar 20 December 2013 (has links)
The purpose of this dissertation is to analyze dynamic behavior of a stressed power system and to correlate the dynamic responses to a near future system voltage abnormality. It is postulated that the dynamic response of a stressed power system in a short period of time-in seconds-contains sufficient information that will allow prediction of voltage abnormality in future time-in minutes. The PSSE dynamics simulator is used to study the dynamics of the IEEE 39 Bus equivalent test system. To correlate dynamic behavior to system voltage abnormality, this research utilizes two different pattern recognition methods one being algorithmic method known as Regularized Least Square Classification (RLSC) pattern recognition and the other being a statistical method known as Classification and Regression Tree (CART). Dynamics of a stressed test system is captured by introducing numerous contingencies, by driving the system to the point of abnormal operation, and by identifying those simulated contingencies that cause system voltage abnormality.
Normal and abnormal voltage cases are simulated using the PSSE dynamics tool. The results of simulation from PSSE dynamics will be divided into two sets of training and testing set data. Each of the two sets of data includes both normal and abnormal voltage cases that are used for development and validation of a discriminator. This research uses stressed system simulation results to train two RLSC and CART pattern recognition models using the training set obtained from the dynamic simulation data. After the training phase, the trained pattern recognition algorithm will be validated using the remainder of data obtained from simulation of the stressed system. This process will determine the prominent features and parameters in the process of classification of normal and abnormal voltage cases from dynamic simulation data.
Each of the algorithmic or statistical pattern recognition methods have their advantages and disadvantages and it is the intention of this dissertation to use them only to find correlations between the dynamic behavior of a stressed system in response to severe contingencies and the outcome of the system behavior in a few minutes into the future.
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[en] MODELLING SPECIAL EQUIPMENTS OF TRANSMISSION NETWORK FOR VOLTAGE SECURITY ASSESSMENT / [pt] MODELAGEM DE EQUIPAMENTOS ESPECIAIS DA REDE DE TRANSMISSÃO PARA AVALIAÇÃO DA SEGURANÇA DE TENSÃOFAUSTO DE MARTTINS NETTO 19 May 2003 (has links)
[pt] Com o uso extremo das linhas de transmissão surgiram os problemas de estabilidade, ou mais apropriadamente, de segurança de tensão. A avaliação das condições de segurança de tensão é realizada pelo programa computacional ESTABTEN. Como os índices calculados são baseados em um ponto de operação do sistema e em um modelo linearizado das equações de fluxo de carga, assim como a função Fluxo de Carga do pacote computacional ANAREDE também o é, é importante que os modelos matemáticos do sistema, de equipamentos, de controles e de limites sejam compatíveis nos dois programas. Assim como o programa de fluxo de carga é continuamente estendido, o programa ESTABTEN deve continuar
a ter sua capacidade estendida para atender as necessidades dos estudos.Estuda-se neste trabalho a modelagem em regime permanente de alguns equipamentos especiais da rede de transmissão e sua incorporação à função de avaliação da segurança de tensão. Os equipamentos contemplados foram:
elos de corrente contínua (elo CC), compensadores estáticos de potência reativa (CER), esquemas de HVDC/CCC e linhas com compensação série controlada a tiristores (CSC). São mostrados exemplos numéricos que ilustram a necessidade de uma modelagem realista, na medida do possível. / [en] With the extreme use of the transmission lines, the voltage
stability problem, or more properly, the voltage security
problem has appeared. The voltage security condition
assessment is achieved using the computational program
ESTABTEN. The calculated indexes are based on a system
operation point and on a linear model of load flow
equations, likewise the ANAREDE load flow function. It is
important that the mathematical models of systems,
equipments, control devices and limits are compatible in
both programs. As the load flow program is continually
extended, the ESTABTEN program is to have its capability
enhanced in order to attend the study requirements.
This work is concerned with the steady-state modelling of
some special equipments of the transmission network and its
incorporation to the voltage security assessment function.
The equipments considered were: direct current link (DC
link), static VAR compensators (SVC), HVDC/CCC and lines
with series controlled compensation (TSSC).Numerical
examples are presented to illustrate the necessity of
realistic modelling.
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[en] TRANSMISSION CONGESTION ANALYSIS APPLIED ON VOLTAGE SECURITY REINFORCEMENT PROBLEM / [pt] ANÁLISE DO CONGESTIONAMENTO EM REDES DE TRANSMISSÃO APLICADA AO PROBLEMA DO REFORÇO DE SEGURANÇA DE TENSÃOFELIPE ERNESTO LAMM PEREIRA 01 October 2003 (has links)
[pt] Após a incidência de inúmeros colapsos ocorridos nos
sistemas de transmissão de energia devido ao uso extremo
das linhas de transmissão, a estabilidade, ou mais
adequadamente, a segurança de tensão tornou-se um assunto
importante ao longo dos últimos anos. Este trabalho foi
desenvolvido com o intuito de complementar um método de
reforço das condições de estabilidade de tensão. O método
consta de ações de controle para diminuir o fluxo de
potência ativa no ramo crítico do caminho de transmissão
mais carregado associado a uma barra crítica, conceitos
estes apresentados nesta dissertação. Para o propósito
citado, e considerando que o problema de estabilidade de
tensão causa restrições nos fluxos de potência na rede de
transmissão, são estudados métodos que analisam o
congestionamento dessas redes. Se destacam algoritmos que,
a partir dos fluxos de potência ativa e reativa que deixam
um gerador, ou que chegam a uma carga, determinam a
distribuição nos ramos de um sistema de transmissão, e o
algoritmo que avalia os impactos no sistema de transmissão
devido a uma determinada transação, entre barras geradoras
e/ou de cargas. São mostrados exemplos numéricos que
ilustram a possibilidade ou não da adequação destes métodos
para o problema do reforço das condições de segurança de
tensão. / [en] After a number of collapses due to the extreme use of the
transmission lines, the voltage stability, or voltage
security, became an important issue. This work was
developed in order to contribute to a voltage security
reinforcement method. The method calculates control actions
to decrease the power flowing through the critical branch
of the most loaded transmission path associated with the
critical bus (concepts present in this dissertation).
For this propose, and considering that the power flow in a
transmission network may be restricted by voltage stability
limits, transmission congestion analysis methods were
study. Two of them deal with the contribution of real and
reactive outflows of individual generator buses, and real
and reactive inflows of individual load buses, in all
network branches. Another method assess the impact of a
given power transaction on the network. Numerical examples
are presented to illustrate whether it is the possible or
not to employ the studied methods in the voltage security
reinforcement problem.
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