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1
Zhang, Fan. "Solving Large Security-Constrained Optimal Power Flow for Power Grid Planning and Operations." Case Western Reserve University School of Graduate Studies / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=case1592567584117811.
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Chiang, Naiyuan. "Structure-exploiting interior point methods for security constrained optimal power flow problems." Thesis, University of Edinburgh, 2013. http://hdl.handle.net/1842/8281.
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The aim of this research is to demonstrate some more efficient approaches to solve the n-1 security constrained optimal power flow (SCOPF) problems by using structure-exploiting primal-dual interior point methods (IPM). Firstly, we consider a DC-SCOPF model, which is a linearized version of AC-SCOPF. One new reformulation of the DC-SCOPF model is suggested, in which most matrices that need to be factorized are constant. Consequently, most numerical factorizations and a large number of back-solve operations only need to be performed once throughout the entire IPM process. In the framework of the structure-exploiting IPM implementation, one of the major computational efforts consists of forming the Schur complement matrix, which is very computationally expensive if no further measure is applied. One remedy is to apply a preconditioned iterative method to solve the corresponding linear systems which appear in assembling the Schur complement matrix. We suggest two main schemes to pick a good and robust preconditioner for SCOPF problems based on combining different “active” contingency scenarios. The numerical results show that our new approaches are much faster than the default structure-exploiting method in OOPS, and also that it requires less memory. The second part of this thesis goes to the standard AC-SCOPF problem, which is a nonlinear and nonconvex optimization problem. We present a new contingency generation algorithm: it starts with solving the basic OPF problem, which is a much smaller problem of the same structure, and then generates contingency scenarios dynamically when needed. Some theoretical analysis of this algorithm is shown for the linear case, while the numerical results are exciting, as this new algorithm works for both AC and DC cases. It can find all the active scenarios and significantly reduce the number of scenarios one needs to contain in the model. As a result, it speeds up the solving process and may require less IPM iterations. Also, some heuristic algorithms are designed and presented to predict the active contingencies for the standard AC-SCOPF, based on the use of AC-OPF or DC-SCOPF. We test our heuristic algorithms on the modified IEEE 24-bus system, and also present their corresponding numerical results in the thesis.
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Zhang, Shouming. "Security optimised optimal power flow." Thesis, Brunel University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.320858.
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Bahrami, Shahab. "Algorithm design for optimal power flow, security-constrained unit commitment, and demand response in energy systems." Thesis, University of British Columbia, 2017. http://hdl.handle.net/2429/62754.
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Energy management is of prime importance for power system operators to enhance the use of the existing and new facilities, while maintaining a high level of reliability. In this thesis, we develop analytical models and efficient algorithms for energy management programs in transmission and distribution networks. First, we study the optimal power flow (OPF) in ac-dc grids, which is a non-convex optimization problem. We use convex relaxation techniques and transform the problem into a semidefinite program (SDP). We derive the sufficient conditions for zero relaxation gap and design an algorithm to obtain the global optimal solution. Subsequently, we study the security-constrained unit commitment (SCUC) problem in ac-dc grids with generation and load uncertainty. We introduce the concept of conditional value-at risk to limit the net power supply shortage. The SCUC is a nonlinear mixed-integer optimization problem. We use ℓ₁-norm approximation and convex relaxation techniques to transform the problem into an SDP. We develop an algorithm to determine a near-optimal solution. Next, we target the role of end-users in energy management activities. We study demand response programs for residential users and data centers. For residential users, we capture their coupled decision making in a demand response program with real-time pricing as a partially observable stochastic game. To make the problem tractable, we approximate the optimal scheduling policy of the residential users by the Markov perfect equilibrium (MPE) of a fully observable stochastic game with incomplete information. We develop an online load scheduling learning algorithm to determine the users’ MPE policy. Last but not least, we focus on the demand response program for data centers in deregulated electricity markets, where each data center can choose a utility company from multiple available suppliers. We model the data centers’ coupled decisions of utility company choices and workload scheduling as a many-to-one matching game with externalities. We characterize the stable outcome of the game, where no data center has an incentive to unilaterally change its strategy. We develop a distributed algorithm that is guaranteed to converge to a stable outcome.Applied Science, Faculty of
Electrical and Computer Engineering, Department of
Graduate
5
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.
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Mohammadi, Javad. "Distributed Computational Methods for Energy Management in Smart Grids." Research Showcase @ CMU, 2016. http://repository.cmu.edu/dissertations/710.
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It is expected that the grid of the future differs from the current system by the increased integration of distributed generation, distributed storage, demand response, power electronics, and communications and sensing technologies. The consequence is that the physical structure of the system becomes significantly more distributed. The existing centralized control structure is not suitable any more to operate such a highly distributed system. This thesis is dedicated to providing a promising solution to a class of energy management problems in power systems with a high penetration of distributed resources. This class includes optimal dispatch problems such as optimal power flow, security constrained optimal dispatch, optimal power flow control and coordinated plug-in electric vehicles charging. Our fully distributed algorithm not only handles the computational complexity of the problem, but also provides a more practical solution for these problems in the emerging smart grid environment. This distributed framework is based on iteratively solving in a distributed fashion the first order optimality conditions associated with the optimization formulations. A multi-agent viewpoint of the power system is adopted, in which at each iteration, every network agent updates a few local variables through simple computations, and exchanges information with neighboring agents. Our proposed distributed solution is based on the consensus+innovations framework, in which the consensus term enforces agreement among agents while the innovations updates ensure that local constraints are satisfied.
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Macfie, Peter. "Large-scale security constrained optimal reactive power flow for operational loss management on the GB electricity transmission network." Thesis, Brunel University, 2010. http://bura.brunel.ac.uk/handle/2438/5073.
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The transmission of power across the GB transmission system, as operated by National Grid, results in inevitable loss of electrical power. Operationally these power losses cannot be eliminated, but they can be reduced by adjustment of the system voltage profile. At present the minimisation of active power losses relies upon a lengthy manually based iterative adjustment process. Therefore the system operator requires the development of advanced optimisation tools to cope with the challenges faced over the next decade, such as achieving the stringent greenhouse gas emission targets laid down by the UK government, while continue to provide an economical, secure and efficient service. To meet these challenges the research presented in this thesis has developed optimisation techniques that can assist control centre engineers by automatically setting up voltage studies that are low loss and low cost. The proposed voltage optimisation techniques have been shown to produce solutions that are secured against 800 credible contingency cases. A prototype voltage optimisation tool has been deployed, which required the development of a series of novel approaches to extend the functionality of an existing optimisation program. This research has lead to the development of novel methods for handling multi-objectives, contradictory shunt switching configurations and selecting all credible contingencies. Studies indicate that a theoretical loss saving of 1.9% is achievable, equivalent to an annual emissions saving of approximately 64,000 tonnes of carbon dioxide. A novel security constrained mixed integer non-linear optimisation technique has also been developed. The proposed method has been shown to be superior to several conventional methods on a wide range of IEEE standard network models and also on a range of large-scale GB network models. The proposed method manages to further reduce active power losses and also satisfies all security constraints.
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Hamon, Camille. "Probabilistic security management for power system operations with large amounts of wind power." Doctoral thesis, KTH, Elektriska energisystem, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-166398.
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Power systems are critical infrastructures for the society. They are therefore planned and operated to provide a reliable eletricity delivery. The set of tools and methods to do so are gathered under security management and are designed to ensure that all operating constraints are fulfilled at all times. During the past decade, raising awareness about issues such as climate change, depletion of fossil fuels and energy security has triggered large investments in wind power. The limited predictability of wind power, in the form of forecast errors, pose a number of challenges for integrating wind power in power systems. This limited predictability increases the uncertainty already existing in power systems in the form of random occurrences of contingencies and load forecast errors. It is widely acknowledged that this added uncertainty due to wind power and other variable renewable energy sources will require new tools for security management as the penetration levels of these energy sources become significant. In this thesis, a set of tools for security management under uncertainty is developed. The key novelty in the proposed tools is that they build upon probabilistic descriptions, in terms of distribution functions, of the uncertainty. By considering the distribution functions of the uncertainty, the proposed tools can consider all possible future operating conditions captured in the probabilistic forecasts, as well as the likeliness of these operating conditions. By contrast, today's tools are based on the deterministic N-1 criterion that only considers one future operating condition and disregards its likelihood. Given a list of contingencies selected by the system operator and probabilitistic forecasts for the load and wind power, an operating risk is defined in this thesis as the sum of the probabilities of the pre- and post-contingency violations of the operating constraints, weighted by the probability of occurrence of the contingencies. For security assessment, this thesis proposes efficient Monte-Carlo methods to estimate the operating risk. Importance sampling is used to substantially reduce the computational time. In addition, sample-free analytical approximations are developed to quickly estimate the operating risk. For security enhancement, the analytical approximations are further embedded in an optimization problem that aims at obtaining the cheapest generation re-dispatch that ensures that the operating risk remains below a certain threshold. The proposed tools build upon approximations, developed in this thesis, of the stable feasible domain where all operating constraints are fulfilled.QC 20150508
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Pajic, Slobodan. "Power System State Estimation and Contingency Constrained Optimal Power Flow - A Numerically Robust Implementation." Digital WPI, 2007. https://digitalcommons.wpi.edu/etd-dissertations/240.
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The research conducted in this dissertation is divided into two main parts. The first part provides further improvements in power system state estimation and the second part implements Contingency Constrained Optimal Power Flow (CCOPF) in a stochastic multiple contingency framework. As a real-time application in modern power systems, the existing Newton-QR state estimation algorithms are too slow and too fragile numerically. This dissertation presents a new and more robust method that is based on trust region techniques. A faster method was found among the class of Krylov subspace iterative methods, a robust implementation of the conjugate gradient method, called the LSQR method. Both algorithms have been tested against the widely used Newton-QR state estimator on the standard IEEE test networks. The trust region method-based state estimator was found to be very reliable under severe conditions (bad data, topological and parameter errors). This enhanced reliability justifies the additional time and computational effort required for its execution. The numerical simulations indicate that the iterative Newton-LSQR method is competitive in robustness with classical direct Newton-QR. The gain in computational efficiency has not come at the cost of solution reliability. The second part of the dissertation combines Sequential Quadratic Programming (SQP)-based CCOPF with Monte Carlo importance sampling to estimate the operating cost of multiple contingencies. We also developed an LP-based formulation for the CCOPF that can efficiently calculate Locational Marginal Prices (LMPs) under multiple contingencies. Based on Monte Carlo importance sampling idea, the proposed algorithm can stochastically assess the impact of multiple contingencies on LMP-congestion prices.
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Zhang, Wang. "Optimisation and Integration of Variable Renewable Energy Sources in Electricity Networks." Thesis, The University of Sydney, 2017. http://hdl.handle.net/2123/16858.
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The growing penetration of renewable energy sources (RESs) into the electricity power grid is profitable from a sustainable point of view and provides economic benefit for long-term operation. Nevertheless, balancing production and consumption is and will always be a crucial requirement for power system operation. However, the trend towards increasing RESs penetration has raised concerns about the stability, reliability and security of future electricity grids. The clearest observation in this regard is the intermittent nature of RESs. Moreover, the location of renewable generation tends to be heavily defined by meteorological and geographical conditions, which makes the generation sites distant from load centres. These facts make the analysis of electricity grid operation under both dynamic and the steady state more difficult, posing challenges in effectively integrating variable RESs into electricity networks. The thesis reports on studies that were conducted to design efficient tools and algorithms for system operators, especially transmission system operators for reliable short-term system operation that accounts for intermittency and security requirements. Initially, the impact of renewable generation on the steady state is studied in the operation stage. Then, based on the first study, more sophisticated modeling on the electricity network are investigated in the third and fourth chapters. Extending the previous studies, the fourth chapter explores the potential of using multiple microgrids to support the main grid’s security control. Finally, the questions regarding the computational efficiency and convergence analysis are addressed in chapter 5 and a DSM model in a real-time pricing environment is introduced. This model presents an alternative way of using flexibility on the demand side to compensate for the uncertainties on the generation side.
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Kreikebaum, Frank Karl. "Control of transmission system power flows." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/50392.
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Power flow (PF) control can increase the utilization of the transmission system and connect lower cost generation with load. While PF controllers have demonstrated the ability to realize dynamic PF control for more than 25 years, PF control has been sparsely implemented.
This research re-examines PF control in light of the recent development of fractionally-rated PF controllers and the incremental power flow (IPF) control concept. IPF control is the transfer of an incremental quantity of power from a specified source bus to specified destination bus along a specified path without influencing power flows on circuits outside of the path.
The objectives of the research are to develop power system operation and planning methods compatible with IPF control, test the technical viability of IPF control, develop transmission planning frameworks leveraging PF and IPF control, develop power system operation and planning tools compatible with PF control, and quantify the impacts of PF and IPF control on multi-decade transmission planning.
The results suggest that planning and operation of the power system are feasible with PF controllers and may lead to cost savings. The proposed planning frameworks may incent transmission investment and be compatible with the existing transmission planning process. If the results of the planning tool demonstration scale to the national level, the annual savings in electricity expenditures would be $13 billion per year (2010$). The proposed incremental packetized energy concept may facilitate a reduction in the environmental impact of energy consumption and lead to additional cost savings.
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Anthony, Ikenna O., Geev Mokryani, Rana H. A. Zubo, and O. A. Ezechukwu. "Distribution Network Reconfiguration Considering Security-Constraint and Multi-DG Configurations." IEEE, 2020. http://hdl.handle.net/10454/18492.
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YesThis paper proposes a novel method for distribution network reconfiguration considering security-constraints and multi-configuration of renewable distributed generators (DG). The objective of the proposed method is to minimize the total operational cost using security constrained optimal power flow (SCOPF). The impact of multi-configuration of renewable DGs in a meshed network is investigated. In this work, lines were added to the radial distribution network to analyse the network power flow in different network configurations. The added lines were connected to the closest generator bus which offered least operating cost. A 16-bus UK generic distribution system (UKGDS) was used to model the efficiency of the proposed method. The obtained results in multi-DG configuration ensure the security of the network in N-1 contingency criteria.
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Karimishad, Amir. "Transient stability-constrained load dispatch, ancillary services allocation and transient stability assessment procedures for secure power system operation." University of Western Australia. Energy Systems Centre, 2008. http://theses.library.uwa.edu.au/adt-WU2009.0028.
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[Truncated abstract] The present thesis is devoted to the development of new methods for transient stability-constrained optimal power flow, probabilistic transient stability assessment and security-constrained ancillary services allocation. The key objective of the thesis is to develop novel dispatch and assessment methods for power systems operation in the new environment of electricity markets to ensure power systems security, particularly transient stability. A new method for economic dispatch together with nodal price calculations which includes transient stability constraints and, at the same time, optimises the reference inputs to the Flexible AC Transmission System (FACTS) devices for maintaining power systems transient stability and reducing nodal prices is developed. The method draws on the sensitivity analysis of time-domain transient stability simulation results to derive a set of linearised stability constraints expressed in terms of generator active powers and FACTS devices input references. '...' The low computing time requirement of the two-point estimate method allows online applications, and the use of detailed power systems dynamic model for time-domain simulation which offers high accuracy. The two-point estimate method is integrated in a straightforward manner with the existing transient stability analysis tools. The integrated software facility has potential applications in control rooms to assist the system operator in decision making process based on instability risks. The software system when implemented on a cluster of processors also makes it feasible to re-assess online transient stability for any change in system configuration arising from switching control. The method proposed has been tested on a representative power system and validated using the Monte Carlo simulation. In conjunction with the energy market, by which forecasted load demand is met by generator dispatch, ancillary services are required in relation to control for secure system operation and power quality. The final part of the thesis has a focus on the key aspect of allocating these ancillary services, subject to an important constraint that the dispatch of the ancillary services will not impair the system security achieved in the load dispatch. With this focus and requirement, the thesis develops a new dispatch formulation in which the network security constraints are represented in the optimal determination of generator active power schedule and allocation of ancillary services. Contingencies considered include power demand variations at individual load nodes from the values specified for the current dispatch calculation. The required changes in generator active powers to meet the new load demands are represented by additional control variables in the new dispatch formulation which augment those variables in the traditional OPF dispatch calculation. Based on the Lagrange function which includes the extended set of security constraints, the formulation derives the optimality condition to be satisfied by the dispatch solution, together with the marginal prices for individual ancillary service providers and LMPs. The effects of the security constraints are investigated and discussed. Case studies for representative power systems are presented to verify the new dispatch calculation procedure.
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Nair, Nirmal-Kumar. "Incorporating voltage security into the planning, operation and monitoring of restructured electric energy markets." Texas A&M University, 2004. http://hdl.handle.net/1969.1/3199.
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As open access market principles are applied to power systems, significant changes
are happening in their planning, operation and control. In the emerging marketplace,
systems are operating under higher loading conditions as markets focus greater attention
to operating costs than stability and security margins. Since operating stability is a basic
requirement for any power system, there is need for newer tools to ensure stability and
security margins being strictly enforced in the competitive marketplace. This dissertation
investigates issues associated with incorporating voltage security into the unbundled
operating environment of electricity markets. It includes addressing voltage security in
the monitoring, operational and planning horizons of restructured power system.
This dissertation presents a new decomposition procedure to estimate voltage
security usage by transactions. The procedure follows physical law and uses an index
that can be monitored knowing the state of the system. The expression derived is based
on composite market coordination models that have both PoolCo and OpCo transactions,
in a shared stressed transmission grid. Our procedure is able to equitably distinguish the
impacts of individual transactions on voltage stability, at load buses, in a simple and fast
manner.
This dissertation formulates a new voltage stability constrained optimal power flow
(VSCOPF) using a simple voltage security index. In modern planning, composite power
system reliability analysis that encompasses both adequacy and security issues is being
developed. We have illustrated the applicability of our VSCOPF into composite
reliability analysis.
This dissertation also delves into the various applications of voltage security index.
Increasingly, FACT devices are being used in restructured markets to mitigate a variety
of operational problems. Their control effects on voltage security would be
demonstrated using our VSCOPF procedure. Further, this dissertation investigates the
application of steady state voltage stability index to detect potential dynamic voltage
collapse.
Finally, this dissertation examines developments in representation, standardization,
communication and exchange of power system data. Power system data is the key input
to all analytical engines for system operation, monitoring and control. Data exchange
and dissemination could impact voltage security evaluation and therefore needs to be
critically examined.
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Nasri, Amin. "On the Dynamics and Statics of Power System Operation : Optimal Utilization of FACTS Devicesand Management of Wind Power Uncertainty." Doctoral thesis, KTH, Elektriska energisystem, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-154576.
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Nowadays, power systems are dealing with some new challenges raisedby the major changes that have been taken place since 80’s, e.g., deregu-lation in electricity markets, significant increase of electricity demands andmore recently large-scale integration of renewable energy resources such aswind power. Therefore, system operators must make some adjustments toaccommodate these changes into the future of power systems.One of the main challenges is maintaining the system stability since theextra stress caused by the above changes reduces the stability margin, andmay lead to rise of many undesirable phenomena. The other important chal-lenge is to cope with uncertainty and variability of renewable energy sourceswhich make power systems to become more stochastic in nature, and lesscontrollable.Flexible AC Transmission Systems (FACTS) have emerged as a solutionto help power systems with these new challenges. This thesis aims to ap-propriately utilize such devices in order to increase the transmission capacityand flexibility, improve the dynamic behavior of power systems and integratemore renewable energy into the system. To this end, the most appropriatelocations and settings of these controllable devices need to be determined.This thesis mainly looks at (i) rotor angle stability, i.e., small signal andtransient stability (ii) system operation under wind uncertainty. In the firstpart of this thesis, trajectory sensitivity analysis is used to determine themost suitable placement of FACTS devices for improving rotor angle sta-bility, while in the second part, optimal settings of such devices are foundto maximize the level of wind power integration. As a general conclusion,it was demonstrated that FACTS devices, installed in proper locations andtuned appropriately, are effective means to enhance the system stability andto handle wind uncertainty.The last objective of this thesis work is to propose an efficient solutionapproach based on Benders’ decomposition to solve a network-constrained acunit commitment problem in a wind-integrated power system. The numericalresults show validity, accuracy and efficiency of the proposed approach.The Doctoral Degrees issued upon completion of the programme are issued by Comillas Pontifical University, Delft University of Technology and KTH Royal Institute of Technology. The invested degrees are official in Spain, the Netherlands and Sweden, respectively.QC 20141028
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Damazo, Graciliano Antonio. "Modelo de máximo carregamento com fator de potência da demanda ajustável e restrição de segurança /." Bauru, 2020. http://hdl.handle.net/11449/192373.
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Orientador: Edméa Cássia BaptistaResumo: O problema de maximização da margem de carregamento operacional tem por finalidade determinar a maior demanda de carga em um sistema elétrico de potência que satisfaça todas as restrições operacionais do sistema e de equipamentos. Em linhas gerais, conhecer com precisão a máxima demanda de potência ativa e reativa suportada pelo sistema elétrico de potência para que o mesmo opere em condições satisfatórias é uma informação importante para a operação e planejamento do sistema. Muitos trabalhos, da literatura, formulam o problema de máximo carregamento através de um modelo de otimização contínuo, e mais recentemente, alguns trabalhos apresentam modelos que também passaram a levar em consideração o fator de potência da demanda das barras de carga. Neste trabalho propõe-se um modelo para o problema de máximo carregamento baseado no fator de potência de demanda ajustável e levando em consideração restrições de segurança. O problema de maximização da margem de carregamento operacional será formulado como um problema de programação não linear, não convexo de grande porte com variáveis contínuas e visa maximizar o somatório de potências ativas demandadas pelas barras de carga, respeitando um fator de potência mínimo pré-estabelecidos e restrições de segurança pós-contingência. Destaca-se que uma contribuição do trabalho é que o modelo encontre para o sistema um ponto de operação factível na presença de contingências pré-definidas, além disso, respeita os limites físicos e operacionai... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: The problem of maximizing the operating load margin aims to determine the highest load demand in an electrical power system that satisfies all operational constraints of the system and equipment. In general, knowing precisely the maximum demand for active and reactive power supported by the electrical power system, in order that it operates in satisfactory conditions, is an important information for the operation and planning of the system. Many works in the literature formulate the problem of maximum loading through a continuous optimization model, and more recently, some works present models that also started to take into account the power factor of the load bars demand. This work proposes a model for the maximum load problem based on the adjustable demand power factor, taking into account security constraints. The problem of maximizing the operating load margin will be formulated as a non-linear, non-convex large programming problem with continuous variables and aims to maximize the sum of active powers demanded by the load bars, respecting an established minimum power factor and post-contingency security constraints. It is important to highlight that the model also ensures that the system finds a feasible operating point, even in the presence of predefined contingencies, besides; it respects the physical and operational limits provided for in the traditional Optimal Power Flow. The proposed model was tested for the IEEE 14, 30, 118 bus systems, simulated on the GAMS platf... (Complete abstract click electronic access below)
Doutor
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Kasmaei, Mahdi Pourakbari. "Despacho ótimo de potências ativa e reativa de sistema elétricos multi-áreas considerando restrições físicas, econômicas e ambientais = Envronmentally constrained active-reactive optimal power flow-a compromising strategy for economic-emission dispatch and a multi-area paradigm /." Ilha Solteira, 2015. http://hdl.handle.net/11449/126414.
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Orientador: José Roberto Sanches MantovaniBanca: Ruben Augusto Romero Lazaro
Banca: Antonio Padilha Feltrin
Banca: Elizete de Andrade Amorim
Banca: Roberto Chouhy Leborgne
Resumo: Nos estudos de planejamento da operação de sistemas de energia elétrica a formulação e solução dos problemas de despacho econômico-ambiental e multi-área são considerados dois problemas de otimização desafiadores. Neste trabalho propõem-se dois novos modelos matemáticos que visam contribuir e contornar algumas desvantagens dos modelos existentes na literatura para os problemas de fluxo de potência ótimo ativo-reativo econômico- ambiental (FPOAREA), e uma formulação integrada para problema multi-área (FPOAREA- MA). No FPOAREA propõe-se uma formulação eficaz para obter um compromisso adequado entre os custos de geração e de emissão, através de um paradigma baseado em normalização inequívoca (PBNI). Ao contrário dos métodos comumente utilizados, que são principalmente aplicáveis a problemas de FPO simples (despacho econômico, despacho econômico com restrições de segurança, etc.), na abordagem PBNI, ao invés de usar um custo do controle da poluição com base na potência máxima (CCPBPM), utiliza-se um custo de controle adaptativo da poluição (CCAP), que representa o custo de controle baseado na topologia atual de operação da rede. A principal contribuição desse paradigma é utiliza a teoria da normalização para o FPO econômico-orientado, o FPO ambiental-orientado, e até mesmo para o fator CCAP. No modelo proposto para o FPOAREA-MA em vez de usar metodologias de decomposição descritas na literatura que têm várias desvantagens e problemas de coordenação, uma formulação integrada que considera as restrições ambientais é proposta. Esta formulação integrada foi desenvolvida com base nos conceitos de modelos centralizados e descentralizados. Este modelo pode ser facilmente resolvido através de solvers comerciais e a sua resposta é precisa, e os resultados obtidos podem ser usados em mercados de eletricidade, planejamento de linhas de interconexões entre sistemas vizinhos, etc. Para mostrar...
Abstract: In a power system, the economic and emission dispatch and multi-area-based problems are considered as the two most challenging optimization problems. This work presents two novel mathematical models to address some drawbacks of the existing models in the domain of the aforementioned problems, including an economic and emission active- reactive optimal power flow (AROPF), and an integrated formulation for multi-area environmentally-constrained AROPF. In order to obtain an effective formulation to make an appropriate compromise between cost and emission, an unequivocal normalization-based paradigm (UNBP) is presented that solves the dynamic economic and emission AROPF problems. Unlike the commonly used methods, which are mostly applicable to simple OPF problems (economic dispatch, security-constrained economic dispatch, etc.), in the UNBP approach, rather than using a maximum output-based pollution control cost (MOPCC), an adaptive pollution control cost (APCC) is employed, which is a topology-based control cost is used. The main contribution of this paradigm is to make use of the normalization theory for the economic- oriented OPF, the environment-oriented OPF, and even for the APCC factor. In addition, in this work a multi-area active-reactive optimal power flow (MA- AROPF) is proposed. In the MA-AROPF model, instead of using decomposition methodologies that have several disadvantages and shortcomings, an integrated formulation that considers the environmental constraints is proposed. This integrated formulation has been created based on the concepts of centralized and decentralized models. This model can be easily solved via commercial solvers and because of its precise answer, it can be used in electricity markets, tie line planning, etc. In order to show the easy implementable characteristic of the MA-AROPF, it is applied on a tie line planning problem. In this work, in order to obtain optimal tie lines, the planning is performed under ...
Doutor
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Kasmaei, Mahdi Pourakbari [UNESP]. "Despacho ótimo de potências ativa e reativa de sistema elétricos multi-áreas considerando restrições físicas, econômicas e ambientais =: Envronmentally constrained active-reactive optimal power flow-a compromising strategy for economic-emission dispatch and a multi-area paradigm." Universidade Estadual Paulista (UNESP), 2015. http://hdl.handle.net/11449/126414.
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000842739.pdf: 2853860 bytes, checksum: e865f5bbf60a5ebbea741caed7414898 (MD5)Nos estudos de planejamento da operação de sistemas de energia elétrica a formulação e solução dos problemas de despacho econômico-ambiental e multi-área são considerados dois problemas de otimização desafiadores. Neste trabalho propõem-se dois novos modelos matemáticos que visam contribuir e contornar algumas desvantagens dos modelos existentes na literatura para os problemas de fluxo de potência ótimo ativo-reativo econômico- ambiental (FPOAREA), e uma formulação integrada para problema multi-área (FPOAREA- MA). No FPOAREA propõe-se uma formulação eficaz para obter um compromisso adequado entre os custos de geração e de emissão, através de um paradigma baseado em normalização inequívoca (PBNI). Ao contrário dos métodos comumente utilizados, que são principalmente aplicáveis a problemas de FPO simples (despacho econômico, despacho econômico com restrições de segurança, etc.), na abordagem PBNI, ao invés de usar um custo do controle da poluição com base na potência máxima (CCPBPM), utiliza-se um custo de controle adaptativo da poluição (CCAP), que representa o custo de controle baseado na topologia atual de operação da rede. A principal contribuição desse paradigma é utiliza a teoria da normalização para o FPO econômico-orientado, o FPO ambiental-orientado, e até mesmo para o fator CCAP. No modelo proposto para o FPOAREA-MA em vez de usar metodologias de decomposição descritas na literatura que têm várias desvantagens e problemas de coordenação, uma formulação integrada que considera as restrições ambientais é proposta. Esta formulação integrada foi desenvolvida com base nos conceitos de modelos centralizados e descentralizados. Este modelo pode ser facilmente resolvido através de solvers comerciais e a sua resposta é precisa, e os resultados obtidos podem ser usados em mercados de eletricidade, planejamento de linhas de interconexões entre sistemas vizinhos, etc. Para mostrar...
In a power system, the economic and emission dispatch and multi-area-based problems are considered as the two most challenging optimization problems. This work presents two novel mathematical models to address some drawbacks of the existing models in the domain of the aforementioned problems, including an economic and emission active- reactive optimal power flow (AROPF), and an integrated formulation for multi-area environmentally-constrained AROPF. In order to obtain an effective formulation to make an appropriate compromise between cost and emission, an unequivocal normalization-based paradigm (UNBP) is presented that solves the dynamic economic and emission AROPF problems. Unlike the commonly used methods, which are mostly applicable to simple OPF problems (economic dispatch, security-constrained economic dispatch, etc.), in the UNBP approach, rather than using a maximum output-based pollution control cost (MOPCC), an adaptive pollution control cost (APCC) is employed, which is a topology-based control cost is used. The main contribution of this paradigm is to make use of the normalization theory for the economic- oriented OPF, the environment-oriented OPF, and even for the APCC factor. In addition, in this work a multi-area active-reactive optimal power flow (MA- AROPF) is proposed. In the MA-AROPF model, instead of using decomposition methodologies that have several disadvantages and shortcomings, an integrated formulation that considers the environmental constraints is proposed. This integrated formulation has been created based on the concepts of centralized and decentralized models. This model can be easily solved via commercial solvers and because of its precise answer, it can be used in electricity markets, tie line planning, etc. In order to show the easy implementable characteristic of the MA-AROPF, it is applied on a tie line planning problem. In this work, in order to obtain optimal tie lines, the planning is performed under ...
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Almeida, Thiago Resende de. "Representação da variação da frequência em estudos de segurança de tensão de sistemas elétricos de potência." Universidade Federal de Juiz de Fora, 2013. https://repositorio.ufjf.br/jspui/handle/ufjf/990.
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CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
O principal objetivo deste trabalho é avaliar a influência da variação dos parâmetros da rede elétrica em função da frequência do sistema em estudos relacionados à avaliação da segurança de tensão de Sistemas Elétricos de Potência (SEP). Neste sentido, é proposta uma alteração na formulação denominada Fluxo de Potência com Regulação Primária. Tal formulação representa uma modelagem alternativa do problema de Fluxo de Potência, onde a frequência do sistema pode ser estimada com precisão satisfatória. É importante destacar que a metodologia proposta neste trabalho mantém a formulação full Newton do problema. A partir deste contexto são consideradas as variações dos parâmetros da rede, tais como shunts de barra, shunts de linha e o modelo de Linhas de Transmissão e Transformadores, tornando estes parâmetros dependentes com os desvios de frequência do sistema. É também realizada uma avaliação das cargas tipo motor de indução. Assim como os parâmetros da rede, os parâmetros do motor de indução são modificados de acordo com os desvios de frequência do sistema. Em seguida são desenvolvidos estudos de avaliação da segurança de tensão a partir do desenvolvimento e implementação de um Fluxo de Potência Continuado modificado e de uma formulação alternativa do problema de Fluxo de Potência Ótimo (FPO). A partir dessas ferramentas é possível avaliar a variação da frequência do sistema em função do aumento do seu carregamento. Também são feitas análises a partir dos autovalores da matriz Jacobiana do método proposto. Finalmente são utilizados cinco sistemas de pequeno e médio portes para a validação da metodologia proposta. Além de dois sistemas tutoriais de pequeno porte, é utilizado o sistema 16 Barras, que é um sistema criado a partir de dados reais e condições operativas encontradas no Sistema Interligado Nacional (SIN), os sistemas New England e IEEE-118 Barras, que são sistemas testes normalmente utilizados na literatura. O programa ANATEM, desenvolvido pelo CEPEL, é utilizado de forma a validar os desenvolvimentos realizados neste trabalho.
The main objective of this work is to evaluate the influence of varying the network parameters depending on the system frequency in studies related to the voltage security assessment of Electric Power Systems. In this sense, it is proposed a modification in the formulation of the called Governor Power Flow. Such formulation represents an alternative modeling of the power flow problem, where the system frequency can be estimated with satisfactory accuracy. It is important to highlight that in this work the proposed methodology retains full Newton formulation of the problem. From this context it is considered variations of the network parameters, such as shunt devices (capacitors and reactors) and equivalent models of transmission lines and transformers, making them dependent parameters with frequency system. It is also studied the induction motor modeling. As the network parameters, the parameters of the induction motor are modified according to the deviation of system frequency. Then voltage security assessment studies are carried out through the development and implementation of a Modified Continuation Power Flow and an Optimal Power Flow. Using these tools it is possible to evaluate the system frequency variation due to the increase of the system loading. Analyzes are also made using the eigenvalues of the Jacobian matrix associated with the proposed methodology. Finally six systems of small and medium scale are used in validation process of the proposed methodology. In addition to two tutorials small systems are used a 16 buses test system, which is created from real data and operating conditions found in the Interconnected Brazilian System, the well know New England system and the IEEE-118 buses test systems, which are systems commonly used in the literature. The ANATEM program, developed by CEPEL, is used to validate the developments made in this work.
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Salehi, Pour Mehr Vahid. "Development and Verification of Control and Protection Strategies in Hybrid AC/DC Power Systems for Smart Grid Applications." FIU Digital Commons, 2012. http://digitalcommons.fiu.edu/etd/804.
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Modern power networks incorporate communications and information technology infrastructure into the electrical power system to create a smart grid in terms of control and operation. The smart grid enables real-time communication and control between consumers and utility companies allowing suppliers to optimize energy usage based on price preference and system technical issues. The smart grid design aims to provide overall power system monitoring, create protection and control strategies to maintain system performance, stability and security.
This dissertation contributed to the development of a unique and novel smart grid test-bed laboratory with integrated monitoring, protection and control systems. This test-bed was used as a platform to test the smart grid operational ideas developed here. The implementation of this system in the real-time software creates an environment for studying, implementing and verifying novel control and protection schemes developed in this dissertation. Phasor measurement techniques were developed using the available Data Acquisition (DAQ) devices in order to monitor all points in the power system in real time. This provides a practical view of system parameter changes, system abnormal conditions and its stability and security information system. These developments provide valuable measurements for technical power system operators in the energy control centers. Phasor Measurement technology is an excellent solution for improving system planning, operation and energy trading in addition to enabling advanced applications in Wide Area Monitoring, Protection and Control (WAMPAC).
Moreover, a virtual protection system was developed and implemented in the smart grid laboratory with integrated functionality for wide area applications. Experiments and procedures were developed in the system in order to detect the system abnormal conditions and apply proper remedies to heal the system.
A design for DC microgrid was developed to integrate it to the AC system with appropriate control capability. This system represents realistic hybrid AC/DC microgrids connectivity to the AC side to study the use of such architecture in system operation to help remedy system abnormal conditions.
In addition, this dissertation explored the challenges and feasibility of the implementation of real-time system analysis features in order to monitor the system security and stability measures. These indices are measured experimentally during the operation of the developed hybrid AC/DC microgrids. Furthermore, a real-time optimal power flow system was implemented to optimally manage the power sharing between AC generators and DC side resources.
A study relating to real-time energy management algorithm in hybrid microgrids was performed to evaluate the effects of using energy storage resources and their use in mitigating heavy load impacts on system stability and operational security.
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Costa, Marina Teixeira [UNESP]. "Solução do problema de fluxo de potência ótimo com restrição de segurança e controles discretos utilizando o método primal-dual barreira logarítmica." Universidade Estadual Paulista (UNESP), 2016. http://hdl.handle.net/11449/148774.
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
O problema de Fluxo de Potência Ótimo determina a melhor condição de operação de um sistema elétrico de potência. Há diferentes classes de problemas de Fluxo de Potência Ótimo de acordo com os tipos de funções a serem otimizadas, e os conjuntos de controles e de restrições utilizados. Dentre elas, dá-se destaque ao problema de Fluxo de Potência Ótimo com Restrição de Segurança, o qual é uma importante ferramenta para os Operadores dos Sistemas de Transmissão, tanto para o planejamento operacional, quanto para a precificação da energia. Seu objetivo é minimizar os custos operacionais de geração de energia levando em consideração as restrições decorrentes da operação do sistema sob um conjunto de contingências. Ele é formulado como um problema de otimização não linear, não-convexo de grande porte, com variáveis contínuas e discretas. Neste trabalho investiga-se este problema em relação à sua formulação, dificuldades computacionais e método de solução. Para um tratamento do problema mais próximo à realidade adotam-se alguns controles como variáveis discretas, ou seja, os taps dos transformadores. Estes são tratados através de um método que penaliza a função objetivo quando as variáveis discretas assumem valores não discretos. Desta forma, o problema não linear discreto é transformado em um problema contínuo e o método Primal-Dual Barreira Logarítmica é utilizado em sua resolução. Testes computacionais são apresentados com o problema de Fluxo de Potência Ótimo com Restrição de Segurança associado ao sistema teste IEEE 14 barras em três etapas de teste. Os resultados obtidos e as comparações realizadas comprovam a eficiência do método de resolução escolhido
The Optimum Power Flow problem determines the best operating condition of an electric power system. There are different classes of Optimal Power Flow problems according to the types of functions to be optimized, and the sets of controls and constraints used. Among them, the problem of Optimal Power Flow with Security Constraint is highlighted, which is an important tool for the Transmission System operators, both for operational planning and for energy pricing. Its objective is to minimize the operational costs of power generation taking into account the constraints arising from the operation of the system under a set of contingencies. It is formulated as a nonlinear, nonconvex large optimization problem, of continuous and discrete variables. In this work, the problem in relation to its formulation, computational difficulties and solution method is investigated. For a treatment of the problem closest to the reality, some controls such as discrete variables, i.e. the taps of the transformers, are used. These are treated by a method that penalizes the objective function when the discrete variables assume non-discrete values. Thus, the discrete nonlinear problem is transformed into a continuous problem and the Primal-Dual Logarithmic Barrier method is used in its resolution. Computational tests are performed with the optimal power flow problem with security constraint associated with the test system of IEEE 14 bars in three test stages. The obtained results and the realized comparisons prove the efficiency of the chosen resolution method.
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Freire, Rene Cruz. "Otimização natural multiobjetivo como ferramenta para desvio mínimo de pontos de operação considerando restrições de segurança." Niterói, 2017. https://app.uff.br/riuff/handle/1/3927.
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
Um dos temas de alta relevância para a sociedade atual é a qualidade do suprimento de energia elétrica, que deve ser ininterrupto, seguro e econômico. Para tal, é primordial que o sistema de potência esteja preparado para um possível defeito de algum equipamento da rede, mantendo a operação dentro dos patamares seguros, evitando os blecautes e todas as suas consequências para a sociedade. Isso pode ser feito através do redespacho das unidades geradoras, de modo a encontrar um ponto de operação que concilie segurança e economicidade, dois objetivos conflitantes, enquanto busca se afastar o mínimo possível do ponto de operação previamente estabelecido, via planejamento eletroenergético, para o sistema de potência em questão. Trata-se de uma abordagem multiobjetiva do Fluxo de Potência Ótimo com Restrições de Segurança (FPORS) que pode ser solucionada com uma abordagem de Computação Evolucionária (CE) com viés multiobjetivo. Neste trabalho, foram implementadas e comparadas duas meta-heurísticas evolutivas multiobjetivo: Nondominated Sorting Genetic Algorithm II (NSGA-II) e o Multi-objective Evolutionary Particle Swarm Optimization (MOEPSO). Os resultados dessas heurísticas também foram comparados com a abordagem mono-objetivo do mesmo problema. Os algoritmos foram implementados no MATLAB® e testados em um sistema-teste que simula as condições do Sistema Interligado Nacional (SIN). As heurísticas multiobjetivo foram comparadas através da metodologia de análise da Fronteira de Pareto (FP), onde é analisado qual método concilia melhor os objetivos de economia e segurança. Na primeira análise o NSGA-II saiu-se melhor, entretanto após a implementação de melhorias no algoritmo, o MOEPSO mostrou desempenho superior na segunda análise. Nas duas análises, o viés multiobjetivo mostrou-se superior ao mono-objetivo, na comparação através do critério de agregação de objetivos. Em relação ao tempo de simulação de cada método, o MOEPSO foi superior na primeira análise, já na segunda análise foi implementado um refinamento baseado no Fluxo de Potência Linearizado no FPORS, que baixou o tempo de simulação das duas heurísticas multiobjetivas em comparação com a primeira análise, e o MOEPSO teve o menor tempo de simulação. Na comparação com o viés mono-objetivo, apenas o NSGA-II teve tempo médio de simulação maior que o método mono-objetivo na primeira análise. Na segunda análise, todas as heurísticas multiobjetivo possuíam tempo de simulação menores que o método mono-objetivo.
One of the topics of high relevance to the today’s society is the quality of electric power supply, which must be uninterrupted, safe and economical. To this end, it is essential that the power system be prepared for a possible defect of some equipment from the network while maintaining operation within safe levels, avoiding blackouts and all its consequences for society. This can be done by redispatch of generating units, in order to find an operation point which conciliate security and economy, two conflicting objectives, while seeking to depart as little as possible of the operation point previously established in the energy planning for the power system in question. This is a multi-objective approach to Security Constrained Optimal Power Flow (SCOPF) that can be solved with an approach of Evolutionary Computation with multi-objective bias. In this work we were implemented and compared two multi-objective evolutionary meta-heuristics: Nondominated Sorting Genetic Algorithm II (NSGA-II) and Multi-objective Evolutionary Particle Swarm Optimization (MOEPSO). The results of these heuristics were also compared with mono-objective approach to the same problem. The algorithms were implemented in MATLAB® and tested in a test-case that simulates the conditions of the Brazilian Sistema Interligado Nacional (National Interconnected System). The multi-objective heuristics were compared using the analysis methodology of the Pareto Frontier, where is analyzed which method is better to conciliate the economy and security objectives. In the first analysis the NSGA-II fared better, but after the implementation of improvements in the algorithm, the MOEPSO showed superior performance in the second analisys. In both analyzes, the multi-objective bias was superior to the mono-objective bias, in the comparison through objectives aggregation criteria. Concerning the simulation time of each method, the MOEPSO was superior in the first analysis, but in the second analysis was implemented a refinement based on DC Load Flow, which lowered the simulation time of the two multi-objective heuristics compared with the first analysis, and the MOEPSO had the shortest time simulation. Compared to the mono-objective bias, only the NSGA-II had an average time simulation greater than the mono-objective method in the first analysis. In the second analysis, all multi-objectives heuristics had simulation time smaller than the mono-objective method.
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Altimari, Márcia Marcondes Rezende Simões. "Uma estratégia ótima para o despacho de potência ativa AC com restrição na transmissão." Universidade de São Paulo, 1999. http://www.teses.usp.br/teses/disponiveis/18/18133/tde-16112017-123038/.
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Neste trabalho realizamos um estudo do Despacho de Potência Ativa AC, o qual é uma estratégia de alocação da geração de potência entre as usinas de um sistema. Para isto, obtivemos dados teóricos, a partir de levantamento bibliográfico, que explicitaram os conceitos de Despacho Ativo. Fundamentamos, metodologicamente, nossa pesquisa no Método da Função Lagrangeana Aumentada. O sistema de equações resultantes das condições de otimalidade foram resolvidos pelo Método de Newton Modificado. Apresentamos os resultados de estudos de casos acadêmicos para a validação e verificação da eficiência da abordagem proposta. Os resultados indicaram uma coerência com as perspectivas reais de contribuição na resolução do Despacho Ótimo de Potência Ativa AC.In this work we accomplished a study of the AC Active Power Dispatch, which is a strategy of distribution of the power generation among the plants of a system. For this, we obtained theoretical data, starting from bibliographical investigation, that elucidated the concepts of Active Dispatch. We based our research in the Method of the Augmented Lagrangian Function. The equation system originated of the optimal conditions was solved for Modified Newton\'s Method. We presented the results of studies of academic cases for the validation and verification of the efficiency of the proposal approach. The results indicated a coherence with the real perspectives of contribution in the resolution of the AC Active Optimal Power Dispatch.
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Ferreira, Ellen Cristina. "Fluxo de potência ótimo multiobjetivo com restrições de segurança e variáveis discretas." Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/18/18154/tde-06072018-112756/.
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O presente trabalho visa a investigação e o desenvolvimento de estratégias de otimização contínua e discreta para problemas de Fluxo de Potência Ótimo com Restrições de Segurança (FPORS) Multiobjetivo, incorporando variáveis de controle associadas a taps de transformadores em fase, chaveamentos de bancos de capacitores e reatores shunt. Um modelo Problema de Otimização Multiobjetivo (POM) é formulado segundo a soma ponderada, cujos objetivos são a minimização de perdas ativas nas linhas de transmissão e de um termo adicional que proporciona uma maior margem de reativos ao sistema. Investiga-se a incorporação de controles associados a taps e shunts como grandezas fixas, ou variáveis contínuas e discretas, sendo neste último caso aplicadas funções auxiliares do tipo polinomial e senoidal, para fins de discretização. O problema completo é resolvido via meta-heurísticas Evolutionary Particle Swarm Optimization (EPSO) e Differential Evolutionary Particle Swarm Optimization (DEEPSO). Os algoritmos foram desenvolvidos utilizando o software MatLab R2013a, sendo a metodologia aplicada aos sistemas IEEE de 14, 30, 57, 118 e 300 barras e validada sob os prismas diversidade e qualidade das soluções geradas e complexidade computacional. Os resultados obtidos demonstram o potencial do modelo e estratégias de resolução propostas como ferramentas auxiliares ao processo de tomada de decisão em Análise de Segurança de redes elétricas, maximizando as possibilidades de ação visando a redução de emergências pós-contingência.The goal of the present work is to investigate and develop continuous and discrete optimization strategies for SCOPF problems, also taking into account control variables related to in-phase transformers, capacitor banks and shunt reactors. Multiobjective optimization model is formulated under a weighted sum criteria whose objectives are the minimization of active power losses and an additional term that yields a greater reactive support to the system. Controls associated with taps and shunts are modeled either as fixed quantities, or continuous and discrete variables, in which case auxiliary functions of polynomial and sinusoidal types are applied for discretization purposes. The complete model is solved via EPSO and DEEPSO metaheuristics. Routines coded in Matlab were applied to the IEEE 14,30, 57, 118 and 300-bus test systems, where the method was validated in terms of diversity and quality of solutions and computational complexity. The results demonstrate the robustness of the model and solution approaches and uphold it as an effective support tool for the decision-making process in Power Systems Security Analysis, maximizing preventive actions in order to avoid insecure operating conditions.
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Zhong, Yi-Shun, and 鐘義順. "A Current-Based Preventive Security-Constrained Optimal Power Flow by Particle Swarm Optimization." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/a86c53.
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碩士國立中山大學
電機工程學系研究所
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An Equivalent Current Injection（ECI）based Preventive Security- Constrained Optimal Power Flow（PSCOPF）is presented in this paper and a particle swarm optimization (PSO) algorithm is developed for solving non-convex Optimal Power Flow (OPF) problems. This thesis integrated Simulated Annealing Particle Swarm Optimization（SAPSO） and Multiple Particle Swarm Optimization（MPSO）, enabling a fast algorithm to find the global optimum. Optimal power flow is solved based on Equivalent- Current Injection（ECIOPF）algorithm. This OPF deals with both continuous and discrete control variables and is a mixed-integer optimal power flow（MIOPF）. The continuous control variables modeled are the active power output and generator-bus voltage magnitudes, while the discrete ones are the shunt capacitor devices. The feasibility of the proposed method is exhibited for a standard IEEE 30 bus system, and it is compared with other stochastic methods for the solution quality. Security Analysis is also conducted. Ranking method is used to highlight the most severe event caused by a specific fault. A preventive algorithm will make use of the contingency information, and keep the system secure to avoid violations when fault occurs. Generators will be used to adjust the line flow to the point that the trip of the most severe line would not cause a major problem.
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Avalos, Munoz Jose Rafael. "Analysis and Application of Optimization Techniques to Power System Security and Electricity Markets." Thesis, 2008. http://hdl.handle.net/10012/3692.
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Determining the maximum power system loadability, as well as preventing the system from being operated close to the stability limits is very important in power systems planning and operation. The application of optimization techniques to power systems security and electricity markets is a rather relevant research area in power engineering. The study of optimization models to determine critical operating conditions of a power system to obtain secure power dispatches in an electricity market has gained particular attention. This thesis studies and develops optimization models and techniques to detect or avoid voltage instability points in a power system in the context of a competitive electricity market.
A thorough analysis of an optimization model to determine the maximum power loadability points is first presented, demonstrating that a solution of this model corresponds to either Saddle-node Bifurcation (SNB) or Limit-induced Bifurcation (LIB) points of a power flow model. The analysis consists of showing that the transversality conditions that characterize these bifurcations can be derived from the optimality conditions at the solution of the optimization model. The study also includes a numerical comparison between the optimization and a continuation power flow method to show that these techniques converge to the same maximum loading point. It is shown that the optimization method is a very versatile technique to determine the maximum loading point, since it can be readily implemented and solved. Furthermore, this model is very flexible, as it can be reformulated to optimize different system parameters so that the loading margin is maximized.
The Optimal Power Flow (OPF) problem with voltage stability (VS) constraints is a highly nonlinear optimization problem which demands robust and efficient solution techniques. Furthermore, the proper formulation of the VS constraints plays a significant role not only from the practical point of view, but also from the market/system perspective. Thus, a novel and practical OPF-based auction model is proposed that includes a VS constraint based on the singular value decomposition (SVD) of the power flow Jacobian. The newly developed model is tested using realistic systems of up to 1211 buses to demonstrate its practical application. The results show that the proposed model better represents power system security in the OPF and yields better market signals. Furthermore, the corresponding solution technique outperforms previous approaches for the same problem. Other solution techniques for this OPF problem are also investigated. One makes use of a cutting planes (CP) technique to handle the VS constraint using a primal-dual Interior-point Method (IPM) scheme. Another tries to reformulate the OPF and VS constraint as a semidefinite programming (SDP) problem, since SDP has proven to work well for certain power system optimization problems; however, it is demonstrated that this technique cannot be used to solve this particular optimization problem.
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Arsalan, Qamar H. "Expected security cost optimal power flow using parallel and distributed computation." 2007. http://digital.library.okstate.edu/etd/umi-okstate-2584.pdf.
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Zhang, Rui. "Advanced methods for power system security operations." Thesis, 2014. http://hdl.handle.net/1959.13/1048178.
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Research Doctorate - Doctor of Philosophy (PhD)The 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.
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Foster, James Daniel. "Mixed-integer quadratically-constrained programming, piecewise-linear approximation and error analysis with applications in power flow." Thesis, 2014. http://hdl.handle.net/1959.13/1048192.
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Research Doctorate - Doctor of Philosophy (PhD)This thesis investigates of the structure and solution of quadratically constrained optimization problems incorporating models of electrical power flow through transmission networks. Approximation of the equations and inequalities describing electrical power flow play a central role. Mixed-integer nonlinear programming (MINLP) theory is applied to determining good bounds to the optimal values of power flow optimization problems. After reviewing the literature on power system planning and design methods using mixed-integer programming, we apply recently developed MINLP software tools to the problem of distributed generation design in a distribution network. We investigate the merits of three mixed-integer programming approaches for finding good designs for new generator installation, along with a method for determining lower bounds on the optimal design objective by solving a knapsack problem. We then turn our attention to a typical continuous optimization problem with power flow constraints with the objective of minimising power loss. The natural question is how to construct good approximations of the equations and inequalities describing power flow. The analytic derivation of the error in the solutions of an approximate system of equations is considered. We then give a united analysis of the special structure of certain nonconvex quadratic functions that appear within the power flow constraints. It is seen that these quadratic functions can be reduced to the symmetric paraboloid function over the real plane by a linear eigenvector-based transformation of variables. Techniques are then presented for exploiting this special paraboloid structure. A systematic study of piecewise-linear approximations to this fundamental paraboloid function is set forth through the framework of the Delaunay triangulation, an object possessing a rich theory from the area of computational geometry. We consider piecewise-linear functions which interpolate the paraboloid function at the vertices of partitions of convex regions, and propose a theory for the optimization of partition geometry. Such partition optimization is over families of partitions possessing the same topology and a fixed number of polytopes, with the objective that an optimal partition minimises the maximum separation between the paraboloid function and the piecewise-linear function generated from the partition. We finally present a novel global optimization approach to forming strong outer approximating convex programs of nonconvex power flow optimization problems. This is achieved through replacing reverse convex quadratic inequality constraints in the transformed problem with a linear mixed-integer model based on piecewise-linear functions interpolating the paraboloid function. Our approach enables the computation of lower bounds to the value of the global optimum of power flow optimization problems with convex objectives.
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Wang, Ming-Der, and 王明德. "Application of Three-phase Newton Optimal Power Flow Method to Study Security and Stability Analyses in Unbalanced Power Systems." Thesis, 1996. http://ndltd.ncl.edu.tw/handle/77884874929944366118.
Full textAbstract:
碩士中原大學
電機工程研究所
84
This thesis investigates the impact of unbalance due to the upcoming single-phase load of the High Speed Train System (HSTS) by an enhanced Newton three-phase Optimal Power Flow (TOPF) method. A voltage stability index and a new imbalance index are defined in the viewpoint of system MW loss. Three- phase series capacitor models areincluded in the new TOPF for increasing the capacity of transferred power. This helps comprehensive analysis of the security and stability in unbalanced power systems.The Taipower system including 265 buses and the HSTS load data are incorporated for illustrating the applicability of the proposed enhanced Newton TOPF. The test results cover the index variation due to the varying HSTS loads, the voltage stability curves, the comparisons of stability enhancement and the compensation of the series/ parallel capacitors, etc.
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De, Silva Jayasekara Kodithuwakku Y. Bathiya. "Determination of transient stability boundary in functional form with applications in optimal power flow and security control." 2007. http://hdl.handle.net/1993/20452.
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Tuson, Paul Matthew. "Transmission transformer tap changer optimisation while minimising system losses using security unconstrained Optimal Power Flow (OPF) techniques." Thesis, 2012. http://hdl.handle.net/10539/11632.
Full textAbstract:
This dissertation investigates the feasibility of fixed tap or reduced tap transformers on the
Eskom Transmission system, thereby reducing transformer failures and reducing the cost of
new or replacement transformers.
The main analysis uses Optimal Power Flow (OPF) techniques based on a Siemens PSS/E
software platform and a minimum system loss operating point or objective function while
reducing tap movements and maintaining prudent system limits but allowing shunt VAr
devices to freely compensate for the reduced tapping. Various years and system conditions
are analysed.Finally it is shown that replacing some Transmission transformers with fixed-tap transformers
is a more cost effective solution.
The contribution of this research is two-fold:
1. to show that there is scope for Eskom System Operations to operate its system more
efficiently in terms of system losses
2. to show that an OPF methodology is a practical technique to limit transformer tap
movements and allow optimal VAr placement while minimising system losses