Dissertations / Theses on the topic 'Transient Analysis of Control Systems'
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Parsi-Feraidoonian, Raiomand. "Application of catastrophe theory to transient stability analysis of multimachine power systems." Thesis, University of British Columbia, 1990. http://hdl.handle.net/2429/29723.
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Transient stability analysis is an important part of power planning and operation. For large power systems, such analysis is very time consuming and expensive. Therefore, an online
transient stability assessment will be required as these large power systems are operated close to their maximum limits. In this thesis swallowtail catastrophe is used to determine the transient stability regions. The bifurcation set represents the transient stability region in terms of power system transient parameters bounded by the transient stability limits. The system modelling is generalized in such, that the analysis could handle either one or any number of critical machines. This generalized model is then tested on a three-machine as well as a seven-machine system. The results of the stability analysis done with the generalized method is compared with the time solution and the results were satisfactory. The transient stability regions determined are valid for any changes in loading conditions and fault location. This method is a good candidate for on-line assessment of transient stability of power systems.Applied Science, Faculty of
Electrical and Computer Engineering, Department of
Graduate
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Mu, Cheng. "Robust active vibration control of flexible rotor-bearing systems under steady and transient conditions." Thesis, University of Bath, 1994. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.387119.
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Todeschini, Grazia. "Wind Energy Conversion Systems based on DFIG Technology used as Active Filters: Steady-State and Transient Analysis." Digital WPI, 2010. https://digitalcommons.wpi.edu/etd-dissertations/97.
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This thesis deals with the performance of a Wind Energy Conversion System operating as a power generator and Active Filter simultaneously. As a power generator, the Wind Energy Conversion System converts wind energy into electric energy; as an Active Filter, it sinks the harmonic currents injected by Non-Linear Loads connected at the same feeder. Three control systems are developed to ensure the described operation; a specific study regarding the compensation of the triplen harmonics is carried out; Doubly-Fed Induction Generator derating is defined; and an engineering economic analysis is performed to determine the profitability of the proposed operation. The Wind Energy Conversion System performance as generator and Active Filter has been studied for steady-state analysis, fast transients and low transients. It is concluded that the proposed control systems allow operating the Wind Energy Conversion System as power generator and harmonic compensator both during steady state and transient operation; the described operation causes power loss increase and voltage distortion that determine the choice of the component and require system derating.
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Granzotto, Desiree Grenier. "Modelagem e projeto de um sistema de controle aplicado ao escoamento bifasico de oleo viscoso e agua em padrão anular." [s.n.], 2008. http://repositorio.unicamp.br/jspui/handle/REPOSIP/265674.
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Orientador: Antonio Carlos BannwartDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica e Instituto de Geociencias
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Resumo: As grandes reservas mundiais de óleo pesado e os elevados preços do barril de petróleo tornam essencial o desenvolvimento de tecnologias de elevação e transporte desses óleos. O óleo pesado, com suas características desfavoráveis de alta viscosidade (100 - 10000 cP) e de densidade (abaixo de 20° API), necessita de métodos específicos que viabilizem sua movimentação em dutos a altas vazões. Para isto, um dos métodos mais simples e que não requer utilização de calor ou diluentes é oferecido pelo escoamento anular óleo-água (core-flow). Entre as questões ainda não resolvidas sobre esse escoamento está o controle do escoamento bifásico, de modo a se obter uma operação segura com a razão água-óleo adequada. Neste trabalho é apresentada uma modelagem do escoamento anular de óleo viscoso e água em regimes permanente e transiente no interior de um duto horizontal. Das possíveis estratégias de controle, optou-se, por simplicidade, pelo controle da vazão de água a uma dada vazão de óleo (desejada para a linha), através da atuação na rotação da bomba d'água. A modelagem permanente da perda de carga em escoamento anular foi ajustada aos dados experimentais colhidos em uma linha de aço de 2,5 polegadas de diâmetro nominal e comprimento 30 m, para diversas combinações de vazões de óleo e água, devido a certa aderência do óleo na parede do duto. A modelagem transiente satisfaz o critério clássico de estabilidade de Ledinegg. Esses resultados possibilitaram projetar e testar um sistema de controle para a vazão de água em duas versões: proporcional-integral (PI) e fuzzy. As comparações permitiram concluir pelo melhor desempenho do controlador fuzzy, por suas características e robustez
Abstract: The significant heavy oil reserves worldwide and the presently high crude oil prices make it essential the development of technologies for heavy oil production and transportation. Heavy oils, with their inherent features of high viscosity (100-10,000 cP) and density (below 22°API) require specific techniques for pipe flow at high flow rates. For this purpose, one of the simplest methods, which does not require use of heat or diluents, is provided by oil-water annular flow (core-flow). Among the still unsolved issues regarding core-flow is the two-phase flow control, in order to obtain a safe operation of the line at the lowest possible water-oil ratio. In this work a model of the viscous oil-water annular flow in a horizontal pipe for both steady and unsteady regimes is presented. From the possible strategies, the water flow rate control for a given oil flow rate was selected for simplicity. Due to the observation of some oil adherence to the wall, the steady state flow model was adjusted to experimental data collected in a 2.5 inches, 30 meters long steel pipe at several combinations of oil and water flow rates. On the other hand the transient model is shown to satisfy the well-known Ledinegg stability criterion. These features made it possible to design and testing a control system for the water flow rate in two different versions: proportional-integral (PI) and fuzzy. Comparisons indicate that the fuzzy controller performs better due to its features and robustness
Mestrado
Explotação
Mestre em Ciências e Engenharia de Petróleo
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Zheng, Wei. "Control strategies enabling seamless switching to islanded operation." Thesis, University of Manchester, 2018. https://www.research.manchester.ac.uk/portal/en/theses/control-strategies-enabling-seamless-switching-to-islanded-operation(bbd0b08b-0a72-4c45-99de-c3b98f908058).html.
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Significant penetration of distributed generation (DG) and the increasing automation level available for distribution networks have opened an option of splitting a network into subsystems and operating each as an "autonomous island". This is particularly important when a major contingency occurs. However, there are issues and challenges that must be addressed before islanded operation becomes viable, among which, ensuring seamless switching of a distribution subsystem from grid-connected to islanded mode is critically important. Unless the subsystem is a predesigned microgrid, it is highly possible that the subsystem load demand will exceed the generation capacity of island DGs. Therefore, an appropriate load shedding scheme must be implemented to ensure the islanded subsystem is power balanced. In this thesis, a switching control strategy is designed to deliver seamless islanding switching. This strategy comprises a multiple-DG coordination method and a single-step load shedding scheme. Mathematical studies and time-domain simulations that investigate the transients observed during the islanding switching process are both conducted, and together, they are used to address the transient stability issues of an islanded subsystem. This thesis focuses on a distribution subsystem consisting of a mix of synchronous and inverter-based DGs and a combination of static and dynamic loads. DG modelling and control is first introduced, and based on that, various types of method to achieve multiple-DG coordination, including an innovative multiple-master strategy, are investigated. The widely accepted master-slave strategy is used to coordinate DGs when the subsystem is islanded. The strategy demands a single dispatchable and controllable DG, such as a synchronous generator, to be the master, whilst requires the others, such as intermittent renewable-based DGs, to be the slaves. Dynamic load modelling is another critical part of this thesis. The transient stability of dynamic loads after major disturbances is investigated and then used to design the stability-oriented load shedding priority. The single-step load shedding scheme calculates the load shedding amount based on the power flow at the point of common coupling (PCC) and the spinning reserve available in the island. This scheme is activated by the tripping event of the PCC circuit breaker between the grid and the island, and then priorities the load to be shed according to the priority predetermined from the stability perspective. Mathematical analysis is first conducted on a simple subsystem to investigate the impact of DG settings on the islanding transients. A full-scale subsystem is also simulated in PSCAD/EMTDC and used to verify the effectiveness of the switching control strategy. In time-domain simulations, the subsystem is islanded following either a routine switching event or a permanent grid fault. Various factors that may affect the transient performance are analysed, such as the severity of the fault, the DG penetration level, the fault clearance time and the switching control delay. This thesis concludes that based on the proposed switching control strategy, the concept of seamless switching from grid-connected to islanded operation is technically viable.
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Stott, Iain Michael. "Modelling transient population dynamics and their role in ecology and evolution." Thesis, University of Exeter, 2012. http://hdl.handle.net/10036/3733.
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Population projection matrix (PPM) models are a central tool in ecology and evolution. They are widely used for devising population management practises for conservation, pest control, and harvesting. They are frequently employed in comparative analyses that seek to explain demographic patterns in natural populations. They are also a key tool in calculating measures of fitness for evolutionary studies. Yet, demographic analyses using projection matrices have, in some ways, failed to keep up with prevailing ecological paradigms. A common focus on long-term and equilibrium dynamics when analysing projection matrix models fits better with the outmoded view of ecosystems as stable and immutable. The more current view of ecosystems as dynamic and subject to constant extrinsic disturbances has bred new theoretical advances in the study of short-term "transient" dynamics. Transient dynamics can be very different to long-term trends, and given that ecological studies are often conducted over short timescales, they may be more relevant to research. This thesis focuses on the study of transient dynamics using population projection matrix models. The first section presents theoretical, methodological and computational advances in the study of transient dynamics. These are designed to enhance the predictive power of models, whilst keeping data requirements to a minimum, and borrow from the fields of engineering and systems control. Case studies in this section provide support for consideration of transient dynamics in population management. The second section applies some of these new methods to answer pertinent questions surrounding the ecology and evolution of transient dynamics in plants. Results show that transient dynamics exhibit patterns according to life form and phylogenetic history. Evidence suggests that this can be linked to the stage-structuring of life cycles, which opens up the possibility for new avenues of research considering the evolution of transient dynamics in nature.
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Llamas, Armando. "Assessment of direct methods in power system transient stability analysis for on-line applications." Diss., Virginia Polytechnic Institute and State University, 1992. http://hdl.handle.net/10919/49933.
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The advent of synchronized phasor measurements allows the problem of real time prediction of instability and control to be considered. The use of direct methods for these on-line applications is assessed.
The classical representation of a power system allows the use of two reference frames: Center of angle and one machine as reference. Formulae allowing transition between the two reference frames are derived. It is shown that the transient energy in both formulations is the same, and that line resistances do not dampen system oscillations.
Examples illustrating the mathematical characterization of the region of attraction, exit point, closest u.e.p. and controlling u.e.p. methods are presented.
Half-dimensional systems (reduced-order systems) are discussed. The general expression for the gradient system which accounts for transfer conductances is derived without making use of the infinite bus assumption. Examples illustrating the following items are presented: a) Effect of the linear ray approximation on the potential energy (inability to accurately locate
the u.e.p.’s); b) Comparison of Kakimoto’s and Athay’s approach for PEBS crossing detection; c) BCU method and; d) One·parameter transversality condition.
It is illustrated that if the assumption of the one-parameter transversality condition is not
satisfied, the PEBS and BCU methods may give incorrect results for multi-swing stability. A
procedure to determine if the u.e.p. found by the BCU method lies on the stability boundary of
the original system is given. This procedure improves the BCU method for off~line applications
when there is time for a hybrid approach (direct and conventional), but it does not improve
it for on-line applications due to the following: a) It is time consuming and b) If it finds that
the u.e.p. does not belong to the stability boundary it provides no information concerning the
stability/instability of the system.
lPh. D.
incomplete_metadata
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Bu, Siqi. "Probabilistic small-signal stability analysis and improved transient stability control strategy of grid-connected doubly fed induction generators in large-scale power systems." Thesis, Queen's University Belfast, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.580121.
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Growing numbers of large-scale wind farms have been recently established and connected to conventional power grid. With the rising level of penetration, the impact of wind power sources on the grid has extended from simple power quality problems to power grid security and stability, frequency and peak regulation, and economic dispatch issues. Therefore, it has significant theoretical and practical values to comprehensively investigate the effect of grid-connected wind power sources on the power system stability. In order to study the influence of considerable stochastic characteristic of wind power generation, probabilistic analysis of power system small-signal stability has been implemented. An analytical method of probabilistic analysis based on Gram-Charlier expansion is proposed to deal with the stochastic uncertainty and spatial correlation of multiple grid-connected wind power sources. Results of probabilistic stability analysis of the example power system demonstrate that the stochastic fluctuation of wind power generation certainly affects small-signal stability of the power system especially in a stressed load condition. Probabilistic stability changes significantly with the variation of wind power penetration level. Focusing on the examination of mechanism of terminal voltage dip during the grid fault, this thesis then develops an improved flux magnitude and angle control (IFMAC) strategy to enhance the grid fault ride-through (FRT) capability of grid-connected doubly fed induction generators (DFIGs). It is indicated by analysis that the significant increase of DFIG power angle stimulated by grid faults during the transient is the essential reason of DFIG voltage dip. IF MAC scheme is proposed with the aim to control the DFIG power angle. The theoretical analysis has also illustrated that the surrounding power system may benefit prominently in terms of transient stability margin by applying the proposed control strategy. Simulation results of the example system have validated the effectiveness and robustness of IF MAC controller in different operating conditions.
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Wahlström, Johan. "Control of EGR and VGT for emission control and pumping work minimization in diesel engines." Licentiate thesis, Linköping University, Linköping University, Vehicular Systems, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-7508.
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Legislators steadily increase the demands on lowered emissions from heavy duty vehicles. To meet these demands it is necessary to integrate technologies like Exhaust Gas Recirculation (EGR) and Variable Geometry Turbochargers (VGT) together with advanced control systems. A control structure with PID controllers and selectors is proposed and investigated for coordinated control of EGR valve and VGT position in heavy duty diesel engines. Main control goals are to fulfill the legislated emission levels, to reduce the fuel consumption, and to fulfill safe operation of the turbocharger. These goals are achieved through regulation of normalized oxygen/fuel ratio and intake manifold EGR-fraction. These are chosen as main performance variables since they are strongly coupled to the emissions, compared to manifold pressure or air mass flow, which makes it easy to adjust set-points depending on e.g. measured emissions during an emission calibration process. In addition a mechanism for fuel efficient operation is incorporated in the structure, this is achieved by minimizing the pumping work. To design a successful control structure, a mean value model of a diesel engine is developed and validated. The intended applications of the model are system analysis, simulation, and development of model-based control systems. Model equations and tuning methods for the model parameters are described for each subsystem in the model. Static and dynamic validations of the entire model show mean relative errors that are less than 12%. Based on a system analysis of the model, a key characteristic behind the control structure is that oxygen/fuel ratio is controlled by the EGR-valve and EGR-fraction by the VGT-position, in order to handle a sign reversal in the system from VGT to oxygen/fuel ratio. For efficient calibration an automatic controller tuning method is developed. The controller objectives are captured in a cost function, that is evaluated utilizing a method choosing representative transients. The performance is evaluated on the European Transient Cycle. It is demonstrated how the weights in the cost function influence behavior, and that the tuning method is important in order to improve the control performance compared to if only a standard method is used. It is also demonstrated that the controller structure performs well regarding all control objectives. In combination with its efficient tuning, the controller structure thus fulfills all requirements for successful application.
Report code: LiU-TEK-LIC-2006:52.
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Beak, Byungho, and Byungho Beak. "Systematic Analysis and Integrated Optimization of Traffic Signal Control Systems in a Connected Vehicle Environment." Diss., The University of Arizona, 2017. http://hdl.handle.net/10150/626304.
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Traffic signal control systems have been tremendously improved since the first colored traffic signal light was installed in London in December 1868. There are many different types of traffic signal control systems that can be categorized into three major control types: fixed-time, actuated, and adaptive. Choosing a proper traffic signal system is very important since there exists no perfect signal control strategy that fits every traffic network. One example is traffic signal coordination, which is the most widely used traffic signal control system. It is believed that performance measures, such as travel times, vehicle delay, and number of stops, can be enhanced by synchronizing traffic signals over a corridor. However, it is not always true that the coordination will have the same benefits for all the traffic in the network. Most of the research on coordination has focused only on strengthening the major movement along the coordinated routes without considering system-wide impacts on other traffic.
Therefore, before implementing a signal control system to a specific traffic network, a thorough investigation should be conducted to see how the control strategy may impact the entire network in terms of the objectives of each type of traffic control system. This dissertation first considers two different kinds of systematic performance analyses for traffic signal control systems. Then, it presents two types of signal control strategies that account for current issues in coordination and priority control systems, respectively.
First, quantitative analysis of smooth progression for traffic flow is investigated using connected vehicle technology. Many studies have been conducted to measure the quality of progression, but none has directly considered smooth progression as the significant factor of coordination, despite the fact that the definition of coordination states that the goal is to have smooth traffic flow. None of the existing studies concentrated on measuring a continuous smooth driving pattern for each vehicle in terms of speed. In order to quantify the smoothness, this dissertation conducts an analysis of the speed variation of vehicles traveling along a corridor. A new measure is introduced and evaluated for different kinds of traffic control systems. The measure can be used to evaluate how smoothly vehicles flow along a corridor based on the frequency content of vehicle speed. To better understand the impact of vehicle mode, a multi-modal analysis is conducted using the new measure.
Second, a multi-modal system-wide evaluation of traffic signal systems is conducted. This analysis is performed for traffic signal coordination, which is compared with fully actuated control in terms of a systematic assessment. Many optimization models for coordination focus mainly on the objective of the coordinated route and do not account for the impacts on side street movements or other system-wide impacts. In addition, multi-modality is not considered in most optimized coordination plans. Thus, a systematic investigation of traffic signal coordination is conducted to analyze the benefits and impacts on the entire system. The vehicle time spent in the system is measured as the basis of the analysis. The first analysis evaluates the effect of coordination on each route based on a single vehicle mode (regular passenger vehicles). The second analysis reveals that how multi-modality affects the performance of the entire system.
Third, in order to address traffic demand fluctuation and traffic pattern changes during coordination periods, this dissertation presents an adaptive optimization algorithm that integrates coordination with adaptive signal control using data from connected vehicles. Through the algorithm, the coordination plan can be updated to accommodate the traffic demand variation and remain optimal over the coordination period. The optimization framework consists of two levels: intersection and corridor. The intersection level handles phase allocation in real time based on connected vehicle trajectory data, while the corridor level deals with the offsets optimization. The corridor level optimization focuses on the performance of the vehicle movement along the coordinated phase, while at the intersection level, all movements are considered to create the optimal signal plan. The two levels of optimizations apply different objective functions and modeling methodologies. The objective function at the intersection level is to minimize individual vehicle delay for both coordinated and non-coordinated phases using dynamic programming (DP). At the corridor level, a mixed integer linear programming (MILP) is formulated to minimize platoon delay for the coordinated phase.
Lastly, a peer priority control strategy, which is a methodology that enhances the multi modal intelligent traffic signal system (MMITSS) priority control model, is presented based on peer-to-peer (P2P) and dedicated short range communication (DSRC) in a connected vehicle environment. The peer priority control strategy makes it possible for a signal controller to have a flexible long-term plan for prioritized vehicles. They can benefit from the long-term plan within a secured flexible region and it can prevent the near-term priority actions from having a negative impact on other traffic by providing more flexibility for phase actuation. The strategy can be applied to all different modes of vehicles such as transit, freight, and emergency vehicles. Consideration for far side bus stops is included for transit vehicles.
The research that is presented in this dissertation is constructed based on Standard DSRC messages from connected vehicles such as Basic Safety Messages (BSMs), Signal Phasing and Timing Messages (SPaTs), Signal Request Messages (SRMs), and MAP Messages, defined by Society of Automotive Engineers (SAE) (SAE International 2016).
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Salomonsson, Daniel. "Modeling, Control and Protection of Low-Voltage DC Microgrids." Doctoral thesis, Stockholm : Elektriska energisystem, Electric Power Systems, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4666.
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Yakout, Ahmed Hassan. "Transient frequency control options for future power systems." Thesis, University of Strathclyde, 2010. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=13223.
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Townsend, Philip. "Asymptotic and transient behaviour of nonlinear control systems." Thesis, University of Bath, 2007. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.486479.
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In this thesis, the problem of controlling both transient and asymptotic behaviour of solutions of functional differential equations is addressed. The work begins, in Chapter 1, with an introduction to basic control theory principles that will be used throughout. This is followed by the introduction of a class of nonlinear operators in Chapter 2 and the development of suitable existence theories for the associated system classes of functional differential equations and inclusions in Chapter 3. A discussion is provided, in Chapter 2, describing diverse phenomena, such as delays and hysteresis, that can be incorporated in the class of operators. Chapters 4-7 cover four areas of research. Chapter 4 examines the asymptotic and transient behaviour of nonlinearly-perturbed linear systems of known relative degree; a continuous feedback strategy is adopted and an approximate tracking result is presented. In Chapter 5 the class of systems considered is expanded to a large class of nonlinear systems and a continuous feedback strategy is implemented in order to achieve approximate tracking. In Chapters 6 and 7 attention is restricted to systems <;>f relative degree one, but this limitation is compensated for by targeting an exact asymptotic tracking result. The first investigation, in Chapter 6, involves a potentially discontinuous feedback controller applied to a class of nonlinear systems, with comparisons made to an internal model approach. Asymptotic tracking and approximate tracking are developed in unison within a framework of functional differential inclusions. Finally, in Chapter 7, a continuous controller is applied to single-input, single-output, nonlinear systems with input hysteresis.
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Jiang, Haibo. "Robust control strategies for the transient control of interconnected power systems." Diss., Georgia Institute of Technology, 1994. http://hdl.handle.net/1853/15728.
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Lee, Chien-Hsing. "Wavelet-based transient analysis." Diss., Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/14713.
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Stamoulis, George D. "Transient analysis of some open queueing systems." Thesis, Massachusetts Institute of Technology, 1988. http://hdl.handle.net/1721.1/14602.
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Zhu, Tao. "Extended cluster weighted modeling methods for transient recognition control." Diss., Montana State University, 2006. http://etd.lib.montana.edu/etd/2006/zhu/ZhuT0806.pdf.
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Shen, Li. "Model integration and control interaction analysis of AC/VSC HVDC system." Thesis, University of Manchester, 2015. https://www.research.manchester.ac.uk/portal/en/theses/model-integration-and-control-interaction-analysis-of-acvsc-hvdc-system(2d4bcb21-a97f-4c7f-b413-1a2a54086145).html.
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The development of voltage source converter (VSC) based high voltage direct current (HVDC) transmission has progressed rapidly worldwide over the past few years. The UK transmission system is going through a radical change in the energy landscape which requires a number of VSC HVDC installations to connect large Round 3 windfarms and for interconnections to other countries. For bulk power long distance transmission, VSC HVDC technology offers flexibility and controllability in power flow, which can benefit and strengthen the conventional AC system. However, the associated uncertainties and potential problems need to be identified and addressed. To carry out this research, integrated mathematical dynamic AC/DC system models are developed in this thesis for small disturbance stability analysis. The fidelity of this research is further increased by developing a dynamic equivalent representative Great Britain (GB) like system, which is presented as a step-by-step procedure with the intention of providing a road map for turning a steady-state load flow model into a dynamic equivalent. This thesis aims at filling some of the gaps in research regarding the integration of VSC HVDC technology into conventional AC systems. The main outcome of this research is a systematic assessment of the effects of VSC controls on the stability of the connected AC system. The analysis is carried out for a number of aspects which mainly orbit around AC/DC system stability issues, as well as the control interactions between VSC HVDC and AC system components. The identified problems and interactions can mainly be summarized into three areas: (1) the effect of VSC HVDC controls on the AC system electromechanical oscillations, (2) the potential control interactions between VSC HVDC and flexible alternating current transmission systems (FACTS) and (3) the active power support capability of VSC HVDC for improving AC system stability. The effect of VSC controls on the AC system dynamics is assessed with a parametric sensitivity analysis to highlight the trade-offs between candidate VSC HVDC outer control schemes. A combination of analysis techniques including relative gain array (RGA) and modal analysis, is then applied to give an assessment of the interactions – within the plant model and the outer controllers – between a static synchronous compensator (STATCOM) and a VSC HVDC link operating in the same AC system. Finally, a specific case study is used to analyse the capability of VSC HVDC for providing active power support to the connected AC system through a proposed frequency droop active power control strategy.
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Hoagland, Steven. "TRANSIENT-BASED RISK ANALYSIS OF WATER DISTRIBUTION SYSTEMS." UKnowledge, 2016. http://uknowledge.uky.edu/ce_etds/39.
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Water distribution system utilities must be able to maintain a system’s assets (i.e., pumps, tanks, water mains, etc.) in good working condition in order to provide adequate water quantity and quality to its customers. Various asset management approaches are employed by utilities in order to make optimal decisions regarding the renewal of system components. Part of a good asset management approach is performing a comprehensive risk analysis which consists of considering all potential ways in which the system may fail, the likelihood failure of for each scenario, and the consequences of said failure. This study investigates a water distribution system’s risk of failure due to both acute transient events (e.g., pump trip) and standard pressure fluctuations due to daily system operations. Such an analysis may be useful in optimal decision making such as asset monitoring, scheduling of condition assessments or system renewal projects, policy implementation, and investment priorities in order to keep the utility’s total costs at a minimum. It may also be useful as a precautionary measure to help prevent catastrophic failures such as large main blowouts for which the utility would incur substantial costs, both direct and indirect.
As part of this thesis, a database of water distribution system models is used to analyze the effects of an acute transient event for different system configurations. The database was created at the University of Kentucky and has been made available to the research community to test newly developed algorithms for various studies including optimal system operations and optimal system design.
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Cvetkovic, Milos. "Power-Electronics-Enabled Transient Stabilization of Power Systems." Research Showcase @ CMU, 2013. http://repository.cmu.edu/dissertations/344.
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Transient stability of electric energy grids is defined as the ability of the power system to remain in synchronism during large disturbances. If the grid is not equipped with controllers capable of transiently stabilizing system dynamics, large disturbances could cause protection to trigger disconnecting the equipment and leading further to cascading system-wide blackouts. Today’s practice of tuning controllers generally does not guarantee a transiently stable response because it does not use a model for representing system-wide dynamic interactions. To overcome this problem, in this thesis we propose a new systems modeling and control design for provable transient stabilization of power systems against a given set of disturbances. Of particular interest are fast power-electronically-controlled Flexible Alternating Current Transmission System (FACTS) devices which have become a new major option for achieving transient stabilization. The first major contribution of this thesis is a framework for modeling of general interconnected power systems for very fast transient stabilization using FACTS devices. We recognize that a dynamic model for transient stabilization of power systems has to capture fast electromagnetic dynamics of the transmission grid and FACTS, in addition to the commonly-modeled generator dynamics. To meet this need, a nonlinear dynamic model of general interconnected electric power systems is derived using time-varying phasors associated with states of all dynamic components. The second major contribution of this thesis is a two-level approach to modeling and control which exploits the unique network structure and enables preserving only relevant dynamics in the nonlinear system model. This approach is fundamentally based on separating: a) internal dynamics model for ensuring stable local response of components; b) system-level model in terms of interaction variables for ensuring stability of the system when the components are interconnected. The two levels can be controlled separately which minimizes the need for communication between controllers. Both distributed and cooperative ectropy-based controllers are proposed to control the interaction-level of system dynamics. Proof of concept simulations are presented to illustrate and compare the promising performance of the derived controllers. Some of the most advanced FACTS industry installations are modeled and further generalized using our approach.
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Grimm, Alexander Rudolf. "Parametric Dynamical Systems: Transient Analysis and Data Driven Modeling." Diss., Virginia Tech, 2018. http://hdl.handle.net/10919/83840.
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Dynamical systems are a commonly used and studied tool for simulation, optimization and design. In many applications such as inverse problem, optimal control, shape optimization and uncertainty quantification, those systems typically depend on a parameter. The need for high fidelity in the modeling stage leads to large-scale parametric dynamical systems. Since these models need to be simulated for a variety of parameter values, the computational burden they incur becomes increasingly difficult. To address these issues, parametric reduced models have encountered increased popularity in recent years.
We are interested in constructing parametric reduced models that represent the full-order system accurately over a range of parameters. First, we define a global joint error mea- sure in the frequency and parameter domain to assess the accuracy of the reduced model. Then, by assuming a rational form for the reduced model with poles both in the frequency and parameter domain, we derive necessary conditions for an optimal parametric reduced model in this joint error measure. Similar to the nonparametric case, Hermite interpolation conditions at the reflected images of the poles characterize the optimal parametric approxi- mant. This result extends the well-known interpolatory H2 optimality conditions by Meier and Luenberger to the parametric case. We also develop a numerical algorithm to construct locally optimal reduced models. The theory and algorithm are data-driven, in the sense that only function evaluations of the parametric transfer function are required, not access to the internal dynamics of the full model.
While this first framework operates on the continuous function level, assuming repeated transfer function evaluations are available, in some cases merely frequency samples might be given without an option to re-evaluate the transfer function at desired points; in other words, the function samples in parameter and frequency are fixed. In this case, we construct a parametric reduced model that minimizes a discretized least-squares error in the finite set of measurements. Towards this goal, we extend Vector Fitting (VF) to the parametric case, solving a global least-squares problem in both frequency and parameter. The output of this approach might lead to a moderate size reduced model. In this case, we perform a post- processing step to reduce the output of the parametric VF approach using H2 optimal model
reduction for a special parametrization. The final model inherits the parametric dependence of the intermediate model, but is of smaller order.
A special case of a parameter in a dynamical system is a delay in the model equation, e.g., arising from a feedback loop, reaction time, delayed response and various other physical phenomena. Modeling such a delay comes with several challenges for the mathematical formulation, analysis, and solution. We address the issue of transient behavior for scalar delay equations. Besides the choice of an appropriate measure, we analyze the impact of the coefficients of the delay equation on the finite time growth, which can be arbitrary large purely by the influence of the delay.Ph. D.
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WENG, CHIYUAN. "Transient Stability Analysis of Power Systems with Energy Storage." Case Western Reserve University School of Graduate Studies / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=case1348453228.
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Chen, Fei. "Cooperative Control of Leader-follower Multi-agent Systems under Transient Constraints." Licentiate thesis, KTH, Reglerteknik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-283583.
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Significant research has been devoted to the problem of distributed consensus or formation control of multi-agent systems in the last decades. These distributed control strategies are designed for all agents and sometimes it may be redundant and costly since the desired tasks may be fulfilled by steering part of the agents through the appropriately designed local control strategy while the other agents can just follow some standard distributed control protocol. Therefore, the leader-follower framework is considered in this thesis, which is meant in the sense that a group of agents with external inputs are selected as leaders in order to drive the group of followers in a way that the entire system can achieve consensus or target formation within certain transient bounds. The followers are only guided through their dynamic couplings with the steered leaders and without any additional control effort. The first part of the thesis deals with consensus or formation control for leader-follower multi-agent systems in a distributed manner using a prescribed performance strategy. Both the first and second-order cases are treated. Under the assumption of tree graphs, a distributed control law is proposed for the first-order case when the decay rate of the performance functions is within a sufficient bound. Then, two classes of tree graphs that can have additional followers are investigated. For the second-order case, we propose a distributed control law based on a backstepping approach for the group of leaders to steer the entire system achieving the target formation within the prescribed performance bounds. In the second part, we further discuss the results for general graphs with cycles, which are extended based on the previous results of tree graphs. The extension of general graphs with cycles has more practical applications and offers a complete theory for undirected graphs. In the last part of the thesis, we derive necessary and sufficient conditions for the leader-follower graph topology in order to achieve the desired formation while satisfying the prescribed performance transient bounds. The results developed in this thesis are further verified by several simulation examples.QC 20201008
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Anderson, Sharon Lee. "Reduced order power system models for transient stability studies." Thesis, This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-09052009-040743/.
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Cheung, Siu-pan. "Direct transient stability margin assessment of power system with excitation control and SVC control /." Hong Kong : University of Hong Kong, 1996. http://sunzi.lib.hku.hk/hkuto/record.jsp?B1753706X.
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張小彬 and Siu-pan Cheung. "Direct transient stability margin assessment of power system with excitation control and SVC control." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1996. http://hub.hku.hk/bib/B31212979.
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Zadehkhost, Sajjad. "Efficient algorithms to expedite transient stability analysis of power systems." Thesis, University of British Columbia, 2015. http://hdl.handle.net/2429/52816.
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With rapid increase in complexity of modern power systems, there is a strong need for better computational tools to ensure the reliable operation of electrical grids. These tools need to be accurate, computationally efficient, and capable of using advanced measurement devices. In this context, transient stability assessment (TSA) is an important study that determines system’s dynamic security margins following a major disturbance. The TSA consists of a set of differential-algebraic equations (DAEs), which are typically solved using time-domain simulation (TDS) approach. While being very accurate, the TDS requires significant computational resources when applied to practical power systems. This problem becomes more significant in transient stability monitoring (TSM), wherein the computational performance of the TDS is typically the bottleneck. This research is to investigate available challenges in the TSM applications and develop new algorithms to help realizing a practical monitoring tool for transient stability studies. The thesis focuses on three research thrusts: i) dynamic reduction of power system to reduce problem size; ii) advanced computation approaches to expedite the TDS method; iii) integration of PMU measurements into the TSM. Initially, a new adaptive aggregation algorithm for dynamic reduction is proposed, wherein parameters of generators and structure of transmission network are considered to aggregate coherent generators and create a reduced-order system. Also, a new criterion is defined to monitor validity of the constructed reduced system. It is shown that the proposed technique is more accurate than traditional aggregation methods. To expedite the TDS approach, this thesis presents two new integration techniques, which are called Multi-Decomposition Approach (MDA) and Successive Linearization and Integration Technique (SLIT). In these methods, the nonlinear DAEs are decomposed into a series of linear subsystems, which participate in approximating actual solution. It is demonstrated that sequential and parallel versions of the MDA and SLIT are faster than state-of-the-art integration techniques. Finally, a dynamic state estimator based on Extended Kalman Filter is developed to convert the PMU measurements into a set of state variables suitable for transient stability studies. Computer studies show that the proposed framework provides accurate results in highly disturbed power systems with fairly low PMU sampling rates.Applied Science, Faculty of
Electrical and Computer Engineering, Department of
Graduate
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Mihirig, Ali Mohamed. "Transient stability analysis of multimachine power systems by catastrophe theory." Thesis, University of British Columbia, 1987. http://hdl.handle.net/2429/29022.
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Transient stability analysis is an important part of power system planning and operation. For large power systems, such analysis is very demanding in computation time. On-line transient stability assessment will be necessary for secure and reliable operation of power systems in the near future because systems are operated close to their maximum limits.
In the last two decades, a vast amount of research work has been done in the area of fast transient stability assessment by direct methods. The major difficulties associated with direct methods are the limitations in the power system model, determination of transient stability regions and adaptation to changes in operating conditions. In this thesis catastrophe theory is used to determine the transient stability regions. Taylor series expansion is used to find the energy balance equation in terms of clearing time and system transient parameters. The energy function is then put in the form of a catastrophe manifold from which the bifurcation set is extracted. The bifurcation set represents the transient stability region in terms of the power system transient parameters bounded by the transient stability limits. The transient stability regions determined are valid for any changes in loading conditions and fault location. The transient stability problem is dealt with in the two dimensions of transient stability limits and critical clearing times. Transient stability limits are given by the bifurcation set and the critical clearing times are calculated from the catastrophe manifold equation. The method achieves a breakthrough in the modelling problem because the effects of exciter response, flux decay and systems damping can all be included in the transient stability analysis. Numerical examples of one-machine infinite-bus and multi-machine power systems show very good agreement with the time solution in the practical range of first swing stability analysis. The method presented fulfills all requirements for on-line assessment of transient stability of power systems.Applied Science, Faculty of
Electrical and Computer Engineering, Department of
Graduate
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Pullinger, Michael. "Evaluating hydraulic transient analysis techniques in pumped-storage hydropower systems." Thesis, Pullinger, Michael (2011) Evaluating hydraulic transient analysis techniques in pumped-storage hydropower systems. Masters by Coursework thesis, Murdoch University, 2011. https://researchrepository.murdoch.edu.au/id/eprint/5819/.
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Hydropower is the most widely adopted form of renewable energy in the world today, accounting for approximately 16% of global energy production [1]. With increasing demand for electricity, and concern about reducing fossil fuel consumption, hydropower is likely to continue to play a key role in global energy production. The interest in pumped-storage systems is increasing, due to their ability to regulate power grids, increase the efficiency of thermal power (coal and nuclear), and maximise the penetration of renewable energy such as wind and solar. Since pumped-storage systems must respond quickly to load variations, transient flow phenomena are frequent. In the design of hydropower systems, transient effects are an important consideration, as rapid flow variations can lead to potentially catastrophic increases in pressure (water-hammer). Numerical techniques for hydraulic transient analysis appear to be well understood, but the hydraulic characteristics of reversible pump-turbines can create difficulties depending on the software used for the analysis. The “S” shape of the machine characteristic in the turbine runaway region is a cause of instability in real machines and a potential cause of numerical instability in incorrectly designed or unsuitable software packages. The commercial hydraulic analysis software package SIMSEN-Hydro was used to evaluate hydraulic transients in two systems. Project A is a 25.5 MW run of river system utilising three Francis turbines. Hydraulic transients in the system were successfully modelled, and the results showed good agreement with load rejection data measured on site during commissioning of the project. Project B is a 1333 MW pumped-storage system utilising four reversible Francis pump-turbines. The machine curves include the characteristic “S” shape in the runaway region of the turbine zone. Using SIMSEN-Hydro, the transients in the system were modelled, utilising the machine characteristics. Results were similar to those obtained during preliminary design of the system. By undertaking a sensitivity analysis for Project B, the effect of modifying input parameters on the simulation results was highlighted. The choice of pipe friction factor, surge tank throttling coefficient and generator inertia all had a notable effect on the results of the analysis. While the range of pressure wave-speeds that were examined did not have a significant effect on the results, this may differ for other systems. Based on these results, it seems important that sensitivity analysis be included on all transient analysis projects, unless the modelling inputs are all known with a reasonable level of accuracy.
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Goodman, Mark Stephen. "Transient air/fuel ratio control of spark ignition engines using neural networks." Thesis, University of Nottingham, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.319923.
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Martínez, Sanz Inmaculada. "Control of AC/DC systems for improved transient stability and frequency support provision." Thesis, Imperial College London, 2014. http://hdl.handle.net/10044/1/25956.
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In this thesis, control of future AC/DC systems for improved system dynamic performance is studied. The objective is to determine mechanisms for providing AC network services (e.g. frequency support, damping, etc.) through coordinated control of HVDC power converters and FACTS devices while considering increased levels of wind generation. In particular, this work addresses some of the concerns associated with the stability of the future Great Britain (GB) transmission network as it evolves to support low carbon generation scenarios and the use of DC grids to integrate offshore renewable resources and form a sub-sea interconnection across Europe. The contributions of this thesis are in two main areas: emergency control for power system stabilization and exchange of frequency support across a DC grid. Fast control of FACTS devices and HVDC links can be exercised as a post-fault corrective action to maintain system stability without the need of constraining pre-fault transfer levels. This work employs a model predictive control (MPC) scheme that relies on system wide-area measurements to preserve the system stability after critical contingencies. MPC can explicitly account for system constraints and changing operating conditions and is therefore suited for on-line applications and power electronic actuators with limited short-term overload capability. The effectiveness of the proposed approach is demonstrated using time domain simulations on representative equivalent models of the future GB transmission network. A detailed analysis of the dynamic behaviour and stability issues associated with the GB transmission grid have also been presented. In the DC grid context, this thesis investigates the provision of frequency services considering frequency droop loops in the control of the converters. The interaction between onshore AC systems and a DC grid is analyzed through an extended steady-state formulation. A methodology for providing frequency response from offshore wind farms connected through a DC grid is also proposed. The performance of this scheme is illustrated both analytically and also through simulation results.
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Wang, Chen. "Transient performance simulation of gas turbine engine integrated with fuel and control systems." Thesis, Cranfield University, 2016. http://dspace.lib.cranfield.ac.uk/handle/1826/9881.
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Two new methods for the simulation of gas turbine fuel systems, one based on an inter-component volume (ICV) method, and the other based on the iterative Newton Raphson (NR) method, have been developed in this study. They are able to simulate the performance behaviour of each of the hydraulic components such as pumps, valves, metering unit of a fuel system, using physics-based models, which potentially offer more accurate results compared with those using transfer functions. A transient performance simulation system has been set up for gas turbine engines based on an inter-component volume (ICV). A proportional- integral (PI) control strategy is used for the simulation of engine control systems. An integrated engine and its control and hydraulic fuel systems has been set up to investigate their coupling effect during engine transient processes. The developed simulation methods and the systems have been applied to a model turbojet and a model turboshaft gas turbine engine to demonstrate the effectiveness of both two methods. The comparison between the results of engines with and without the ICV method simulated fuel system models shows that the delay of the engine transient response due to the inclusion of the fuel system components and introduced inter-component volumes is noticeable, although relatively small. The comparison of two developed methods applied to engine fuel system simulation demonstrate that both methods introduce delay effect to the engine transient response but the NR method is ahead than the ICV method due to the omission of inter-component volumes on engine fuel system simulation. The developed simulation methods are generic and can be applied to the performance simulation of any other gas turbines and their control and fuel systems. A sensitivity analysis of fuel system key parameters that may affect the engine transient behaviours has also been achieved and represented in this thesis. Three sets of fuel system key parameters have been introduced to investigate their sensitivities, which are, the volumes introduced for ICV method applied to fuel system simulation; the time constants introduced into those first order lags tosimulate the valve movements delay and fuel spray delay effect; and the fuel system key performance and structural parameters.
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Roberts, Lewis George Wilson. "Parametric analysis of transient stability in power systems using classical models." Thesis, University of Bristol, 2016. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.702145.
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This thesis aims to strengthen the bridge between mathematical and practical research into the transient stability of power systems. Literature that exploits the mathematical parallels between models for transient dynamics in power systems and the phenomenon of synchronisation in complex networks is explored. However, it is contended that research at the intersection of complex systems and power system stability can limit its applications to practical issues in power engineering. This thesis focuses on the measurement of transient stability in power systems in terms of a traditional stability metric for short-circuit faults on a power network, the critical clearing time (CCT). The CCT provides an upper bound on the duration of a short circuit on a power network before it is removed - cleared - by the action of protection mechanisms to isolate the faulted circuit such that the system will regain synchrony once the fault is cleared. Approaches that use energetic methods for assessing the transient stability of a power system are extended by developing metrics that can measure stability trends for different scenarios in a power system via the numerical continuation of equilibrium configurations under the variation of system parameters. An analytical CCT (ACCT) approximation is derived from this energetic framework in order to capture trends in stability with respect to a system parameter. The performance of the ACCT is compared to more accurate computations of CCT that use slower numerical simulation techniques. Attention is given to how well the ACCT approximation can capture stability trends under variation of key network design parameters such as load admittance and generator inertia. It is found for a two-machine infinite bus (TMIB) system that load parameter values that can improve stability can be identified using the ACCT. Also, the general dependence of a fault's CCT on the inertia of a generator in a TMIB power system is identifiable using the ACCT. For power systems with stationary generator inertia values, a method to provide a contingency analysis of fault locations is proposed. The method ranks the locations of short-circuit faults by their CCT; the more severe a fault the shorter its CCT. It is found in a TMIB system that the ACCT can identify the general location of severe faults under different inertia scenarios. It is shown that in larger power systems, energetic methods can be used to accurately identify the locations of faults with short CCTs. These results, together with relevant literature are used to suggest possible strategies to monitor transient stability within modern power systems.
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Kittel, Tim. "Transient Analysis of Complex Dynamical Systems in the Context of Sustainability." Doctoral thesis, Humboldt-Universität zu Berlin, 2018. http://dx.doi.org/10.18452/18928.
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Ein wichtiger Aspekt der Analyse von dynamischen Systemen ist die Transiente einer Trajektorie.
Im Kontext der Nachhaltigkeitsforschung bearbeite ich diesbezüglich zwei Fragen: (i) ”Wie kann
man die Zeit zum Erreichen des Attraktors quantifizieren?“ und (ii) ”Kann man es verhindern,
bestimmte Grenzen zu überschreiben und somit sicher zu bleiben?“
Bzgl. (i) analysiere ich mehrere Probleme, welche bei der Quantifizierung solcher transienter
Zeiten auftreten, und definiere vier Bedingungen, die eine Antwort auf Frage (i) erfüllen soll.
Weiterhin führe ich zwei Metriken, Area under Distance Curve und Regularized Reaching Time,
ein, die verschiedene Aspekte der transienten Dynamik einfangen.
Frage (ii) bezieht sich auf Systeme mit sowohl erwünschten und unerwünschten Zuständen
als auch Möglichkeiten zur Beeinflussung. Ich stelle ”Topology of Sustainable Management“
als ein Werkzeug zur Analyse solcher Modelle vor. Diese baut auf ”Viabilitätstheorie“ auf, um
den dazugehörigen Saint-Pierre Algorithmus (SPA) verwenden zu können. Ich erweitere den
Algorithmus zur Schätzung von ”implicitly-defined Capure Basins“ und löse zwei substanzielle
Probleme, welche häufig bei der Anwendung von SPA vorkommen. Zur Demonstration verwende
ich ein Beispielmodell, das auf Klimawandel, Wirtschaftsleistung und die Transformation des
Energiesystems fokussiert.
Danach nutze ich funktionale Klimanetzwerke, um zu analysieren, wie sich die transien-
te Phase nach großen Klimastörungen – die El Niño- und La Niña-Phasen von ENSO und
die drei größten Vulkaneruptionen seit 1950 – die Telekonnektionsstruktur der globalen Oberflächentemperatur auswirkt. Die Resultate bestätigen den globalen Einfluss von ENSO durch
das Zusammenbrechen der modularen Struktur des global SAT-Feldes. Dies zeigt die Emergenz
starker Telekonnektionen. Weiterhin habe ich deutlich, qualitative Unterschiede zwischen diesen
global Klimaextremsituationen identifizieren können.An important feature of dynamical systems is the transient phase of a trajectory that I approach with two question: (i) “How can we properly quantify the time to reach a system’s attractor?” and (ii) “Can we avoid transgressing certain boundaries and stay safe (& just)?” In particular, I consider these questions in the context of sustainability science. Concerning (i), I analyze several problems that come up when quantifying such transient times and define four conditions that a metric answering question (i) should fulfill. Further, I introduce two metrics, Area under Distance Curve and Regularized Reaching Time, capturing two complementary aspects of the transient dynamics. Question (ii) concerns with systems having distinctions of the state space in desirable and undesirable, e.g. defined by “planetary boundaries”, and some sort of influencing/managing it. I present Topology of Sustainable Management as a tool to analyze such models. It is built on concepts from viability theory (VT) in order to use the Saint-Pierre algorithm (SPA). I extend the SPA to compute so-called implicitly defined capture basins and solve two substantial problems repeatedly occuring when using the SPA. For Demonstration, I use a three-dimensional model focusing on climate change, economic output and energy transformation. Finally, I use functional climate networks to analyze how the transient phase after major climate perturbations – the El Niño and La Niña phases of ENSO and three largest recent volcanic eruptions – influence the teleconnectivity structure of the surface area temperature field (SAT). The results confirm the existence of global effects of ENSO by breaking down the modular structure of the global SAT field, and I have identified distinct qualitative differences between theses two global climate extreme situation.
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Landschoot, Timothy P. "Suppression of the transient response in linear time-invariant systems /." Online version of thesis, 1994. http://hdl.handle.net/1850/11794.
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Akhurst, Timothy John. "Symbolic control analysis of cellular systems." Thesis, Stellenbosch : University of Stellenbosch, 2011. http://hdl.handle.net/10019.1/6627.
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Thesis (PhD (Biochemistry))--University of Stellenbosch, 2011.ENGLISH ABSTRACT: Metabolic Control Analysis (MCA) provides a powerful quantitative framework for understanding and explaining the control and regulation within a cellular system. MCA allows the global control of a steady-state system to be quantified in terms of control coeficients, which we can express in terms of the local properties referred to as elasticity coeficients. MCA relates elasticities to control coeficients through a matrix inversion, thus allowing scientists to predict and quantify how the kinetics of the individual enzymes affect the systemic behaviour of cellular systems. Traditionally we solved this problem numerically, while we used algebraic and symbolic control analysis techniques less frequently. By using symbolic algebraic computation we present a general implementation of the symbolic matrix inversion of MCA, known as SymCA, which requires only the description of any allosteric modifier interactions and the stoichiometry of a cellular system. The algebraic expressions generated allow an in-depth analysis of the distribution of the control within a system and also of the parameters which exhibit the greatest effect on this control distribution. This also applies when the exact values for the elasticities or control coeficients are unknown. We have demonstrated that by quantifying the control patterns, referred to as `routes of regulation', inherent in all control coeficient expressions, we can gain insight into how perturbations are propagated through a cellular system and which regulatory pathways are favoured under changing conditions.
AFRIKAANSE OPSOMMING: Metaboliese Kontrole-Analise (MKA) bied 'n kragtige kwantitatiewe raamwerk om die beheer en regulering binne sellulere sisteme te verstaan en te verduidelik. 'n Sleutelaspek van MKA is dat die globale beheer van 'n sisteem met 'n bestendige toestand gekwantifiseer kan word in terme van kontrole-koefisente en dat hierdie koefisente uitgedruk kan word in terme van die sisteem se lokale eienskappe, genaamd elastisiteitskoefisente. Deur van matriksinversie gebruik te maak kan MKA die verband tussen elastisiteitskoefisente en kontrole-koefisente aflei wat mens in staat stel om te sien hoe die kinetika van die individuele ensiemreaksies die sisteemgedrag op sellulere vlak beinvloed. Die probleem word tradisioneel hoofsaaklik op numeriese wyse bereken terwyl die gebruik van algebraiese en simboliese kontrole-analise minder gereeld gebruik word. In hierdie proefskrif verskaf ons, deur van simboliese algebraiese metodes gebruik te maak, 'n generiese implementasie van die simboliese matriksinversie van MKA, genaamd SymCA, wat slegs 'n beskrywing van 'n sellulere sisteem se allosetriese interaksies en die stoichiometrie benodig. Die algebraiese uitdrukkings sodanig gegenereer stel mens in staat om 'n in-diepte analise te doen om vas te stel waar die beheer binne 'n sisteem le, asook watter parameters die grootste effek op die kontrole-verspreiding het. Dit geld selfs in die geval waar die presiese waardes van die elastisiteitskoefisente of kontrole-koefisente onbekend is. Hierdie proefskrif demonstreer hoe die kwantifisering van kontrole-patrone, ook gesien as 'roetes van regulering', wat inherent is aan kontrole-koefisent vergelykings, mens in staat stel om te sien hoe perturbasies in 'n sellulere sisteem voortplant en watter regulatoriese paaie bevoordeel word onder veranderde kondisies.
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Cade, Iain Stuart. "A wavelet based approach to the transient control of rotor/active magnetic bearing systems." Thesis, University of Bath, 2006. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.426295.
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Ozcaldiran, Kadri. "Control of descriptor systems." Diss., Georgia Institute of Technology, 1985. http://hdl.handle.net/1853/13531.
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Almér, Stefan. "Control and Analysis of Pulse-Modulated Systems." Doctoral thesis, KTH, Optimeringslära och systemteori, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4713.
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The thesis consists of an introduction and four appended papers. In the introduction we give an overview of pulse-modulated systems and provide a few examples of such systems. Furthermore, we introduce the so-called dynamic phasor model which is used as a basis for analysis in two of the appended papers. We also introduce the harmonic transfer function and finally we provide a summary of the appended papers. The first paper considers stability analysis of a class of pulse-width modulated systems based on a discrete time model. The systems considered typically have periodic solutions. Stability of a periodic solution is equivalent to stability of a fixed point of a discrete time model of the system dynamics. Conditions for global and local exponential stability of the discrete time model are derived using quadratic and piecewise quadratic Lyapunov functions. A griding procedure is used to develop a systematic method to search for the Lyapunov functions. The second paper considers the dynamic phasor model as a tool for stability analysis of a general class of pulse-modulated systems. The analysis covers both linear time periodic systems and systems where the pulse modulation is controlled by feedback. The dynamic phasor model provides an $\textbf{L}_2$-equivalent description of the system dynamics in terms of an infinite dimensional dynamic system. The infinite dimensional phasor system is approximated via a skew truncation. The truncated system is used to derive a systematic method to compute time periodic quadratic Lyapunov functions. The third paper considers the dynamic phasor model as a tool for harmonic analysis of a class of pulse-width modulated systems. The analysis covers both linear time periodic systems and non-periodic systems where the switching is controlled by feedback. As in the second paper of the thesis, we represent the switching system using the L_2-equivalent infinite dimensional system provided by the phasor model. It is shown that there is a connection between the dynamic phasor model and the harmonic transfer function of a linear time periodic system and this connection is used to extend the notion of harmonic transfer function to describe periodic solutions of non-periodic systems. The infinite dimensional phasor system is approximated via a square truncation. We assume that the response of the truncated system to a periodic disturbance is also periodic and we consider the corresponding harmonic balance equations. An approximate solution of these equations is stated in terms of a harmonic transfer function which is analogous to the harmonic transfer function of a linear time periodic system. The aforementioned assumption is proved to hold for small disturbances by proving the existence of a solution to a fixed point equation. The proof implies that for small disturbances, the approximation is good. Finally, the fourth paper considers control synthesis for switched mode DC-DC converters. The synthesis is based on a sampled data model of the system dynamics. The sampled data model gives an exact description of the converter state at the switching instances, but also includes a lifted signal which represents the inter-sampling behavior. Within the sampled data framework we consider H-infinity control design to achieve robustness to disturbances and load variations. The suggested controller is applied to two benchmark examples; a step-down and a step-up converter. Performance is verified in both simulations and in experiments.QC 20100628
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Taylor, Andrew. "Performance analysis of cross-directional control systems." Thesis, University of Oxford, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.534187.
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Almér, Stefan. "Control and analysis of pulse-modulated systems /." Stockholm : Optimization and Systems Theory, Department of Mathematics, Royal Institute of Technology, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4713.
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Huang, Shan. "Analysis and control of marine cable systems." Thesis, University of Strathclyde, 1992. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=21240.
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The thesis deals with systems consisting of marine cables and subsea units. Such systems have wide applications in offshore subsea operations. After a general introduction, the thesis sets out to analyse both the static and dynamic behaviours of the system under various environmental and operational conditions. It endeavours to pursue a fundamental approach in order to reveal the basic characteristics of the system, in addition to developing numerical algorithms for predicting performance. The analysis of behaviour of marine cables consists of the following parts: Statics A semi-analytic approach is developed to predict the equilibrium configurations of marine cables. One-dimensional dynamics Using a coordinate transformation, the method can predict the unsteady dynamic behaviour of systems where the length of cable varies. Two-dimensional dynamics The methodology adopted in the one-dimension analysis is extended to a more general case. Three-dimensional dynamics An alternative approach based upon a lumped mass model is developed. Mathematical analysis reveals many interesting characteristics of the model. By applying modern control theory, a novel heave compensation mechanism is developed for marine systems of cables and subsea units. This mechanism involves an actively controlled winch system. A framework of optimal stochastic control is outlined for integrating all the elements of surface supported subsea operations. The thesis presents a variety of numerical examples in domenstrating the validity of the approaches adopted, along with discussions. Further developments are also recommended.
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Liu, Yang. "Analysis and control of underactuated mechanical systems." Thesis, Staffordshire University, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.522385.
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Shukla, Himanshu. "Nonlinear Analysis and Control of Aeroelastic Systems." Diss., Virginia Tech, 2016. http://hdl.handle.net/10919/71468.
Full textAbstract:
Presence of nonlinearities may lead to limit cycle oscillations (LCOs) in aeroelastic systems.
LCOs can result in fatigue in wings leading to catastrophic failures. Existence of LCOs for
velocities less than the linear flutter velocity has been observed during flight and wind tunnel
tests, making such subcritical behavior highly undesirable. The objective of this dissertation
is to investigate the existence of subcritical LCOs in aeroelastic systems and develop state
feedback controllers to suppress them. The research results are demonstrated on a two degree
of freedom airfoil section model with stiffness nonlinearity.
Three different approaches are developed and discussed. The first approach uses a feedback
linearization controller employing the aeroelastic modal coordinates. The use of modal coordinates results in a system which is linearly decoupled making it possible to avoid cancellation
of any linear terms when compared to existing feedback linearization controllers which use
the physical coordinates. The state and control costs of the developed controller are compared to the costs of the traditional feedback linearization controllers. Second approach
involves the use of nonlinear normal modes (NNMs) as a tool to predict LCO amplitudes
of the aeroelastic system. NNM dynamics along with harmonic balance method are used
to generate analytical estimates of LCO amplitude and its sensitivities with respect to the
introduced control parameters. A multiobjective optimization problem is solved to generate optimal control parameters which minimize the LCO amplitude and the control cost.
The third approach uses a nonlinear state feedback control input obtained as the solution
of a multiobjective optimization problem which minimizes the difference between the LCO
commencement velocity and the linear flutter velocity. The estimates of LCO commencement velocity and its sensitivities are obtained using numerical continuation methods and
harmonic balance methods. It is shown that the developed optimal controller eliminates any
existing subcritical LCOs by converting them to supercritical LCOs.Ph. D.
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Gonzalez-Torres, Juan Carlos. "Transient stability of high voltage AC-DC electric transmission systems." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLS041.
Full textAbstract:
Les nouvelles politiques adoptées par les autorités nationales ont encouragé pendant les dernières années l'intégration à grande échelle des systèmes d'énergie renouvelable (RES). L'intégration à grande échelle des RES aura inévitablement des conséquences sur le réseau de transport d'électricité tel qu'il est conçu aujourd'hui, car le transport de l'électricité massif sur de longues distances pourrait amener les réseaux de transport à fonctionner près de leurs limites, réduisant ainsi leurs marges de sécurité. Des systèmes de transport d’électricité plus complexes seront donc nécessaires.Dans ce scénario, les systèmes de transmission à Courant Continu Haute Tension (HVDC) constituent la solution la plus intéressante pour le renforcement et l'amélioration des réseaux à Courant Alternatif (AC) existants, non seulement en utilisant des configurations point à point, mais aussi dans des configurations multi-terminales. L'introduction des systèmes HVDC aboutira à terme à un réseau électrique hybride haute tension AC/DC, qui doit être analysé comme un système unique afin de mieux comprendre les interactions entre le réseau AC et le réseau DC.Cette thèse porte sur l'analyse de la stabilité transitoire des systèmes de transmission électrique hybrides AC/DC. Plus particulièrement, deux questions ont été abordées: Quel est l'impact d'un défaut du réseau DC sur la stabilité transitoire du réseau AC? Comment est-il possible de se servir des systèmes de transmission DC en tant qu'actionneurs afin d'améliorer la stabilité transitoire AC ?Dans la première partie de ce travail, les modèles mathématiques du réseau hybride AC/DC sont décrits ainsi que les outils nécessaires à l'analyse du système en tenant compte de sa nature non linéaire. Ensuite, une analyse approfondie de la stabilité transitoire du réseau électrique dans le cas particulier d'un court-circuit dans le réseau DC et l'exécution des stratégies de protection correspondantes sont effectuées. En complément, des indicateurs de stabilité et des outils pour dimensionner les futurs réseaux de la MTDC afin de respecter les contraintes des stratégies de protection existantes sont proposés.La deuxième partie de la thèse porte sur les propositions de commande pour la modulation des références de puissance des systèmes de transmission HVDC dans le but d'améliorer la stabilité transitoire du système AC connecté à ce réseau DC. Tout d'abord, nous axons notre étude sur le contrôle non linéaire des liaisons HVDC point à point dans des liaisons hybrides AC/DC. La compensation rapide des perturbations de puissance, l'injection de puissance d'amortissement et l'injection de puissance de synchronisation sont identifiées comme des mécanismes par lesquels les systèmes HVDC peuvent améliorer les marges de stabilité des réseaux AC.Enfin, une stratégie de contrôle pour l'amélioration de la stabilité transitoire par injection de puissance active dans par un réseau MTDC est proposée. Grâce à la communication entre les stations, la commande décentralisée proposée injecte la puissance d'amortissement et de synchronisation entre chaque paire de convertisseurs en utilisant uniquement des mesures au niveau des convertisseurs. L'implémentation proposée permet d'utiliser au maximum la capacité disponible des convertisseurs en gérant les limites de puissance d'une manière décentraliséeThe new policy frameworks adopted by national authorities has encouraged the large scale-integration of Renewable Energy Systems (RES) into bulk power systems. The large-scale integration of RES will have consequences on the electricity transmission system as it is conceived today, since the transmission of bulk power over long distances could lead the existing transmission systems to work close to their limits, thus decreasing their dynamic security margins. Therefore more complex transmissions systems are needed.Under this scenario, HVDC transmission systems raise as the most attractive solution for the reinforcement and improvement of existing AC networks, not only using point-to-point configurations, but also in a Multi-Terminal configuration. The introduction of HVDC transmission systems will eventually result in a hybrid high voltage AC/DC power system, which requires to be analyzed as a unique system in order to understand the interactions between the AC network and the DC grid.This thesis addresses the transient stability analysis of hybrid AC/DC electric transmission systems. More in particular, two questions sought to be investigated: What is the impact of a DC contingency on AC transient stability? How can we take advantage of the of DC transmission systems as control inputs in order to enhance AC transient stability?In the first part of this work, the mathematical models of the hybrid AC/DC grid are described as well as the necessary tools for the analysis of the system taking into account its nonlinear nature. Then, a thorough analysis of transient stability of the power system in the particular case of a DC fault and the execution of the corresponding protection strategies is done. As a complement, stability indicators and tools for sizing future MTDC grids in order to respect the constraints of existing protection strategies are proposed.The second part of the thesis addresses the control proposals for the modulation of power references of the HVDC transmission systems with the purpose of transient stability enhancement of the surrounding AC system. Firstly, we focus our study in the nonlinear control of point-to-point HVDC links in hybrid corridors. Fast power compensation, injection of damping power and injection of synchronizing power are identified as the mechanisms through which HVDC systems can improve stability margins.Finally, a control strategy for transient stability enhancement via active power injections of an MTDC grid is proposed. Using communication between the stations, the proposed decentralized control injects damping and synchronizing power between each pair of converters using only measurements at the converters level. The proposed implementation allows to fully use the available headroom of the converters by dealing with power limits in a decentralized way
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Gruenwald, Benjamin Charles. "Toward Verifiable Adaptive Control Systems: High-Performance and Robust Architectures." Scholar Commons, 2018. https://scholarcommons.usf.edu/etd/7676.
Full textAbstract:
In this dissertation, new model reference adaptive control architectures are presented with stability, performance, and robustness considerations, to address challenges related to the verification of adaptive control systems.
The challenges associated with the transient performance of adaptive control systems is first addressed using two new approaches that improve the transient performance. Specifically, the first approach is predicated on a novel controller architecture, which involves added terms in the update law entitled artificial basis functions. These terms are constructed through a gradient optimization procedure to minimize the system error between an uncertain dynamical system and a given reference model during the learning phase of an adaptive controller. The second approach is an extension of the first one and minimizes the effect of the system uncertainties more directly in the transient phase. In addition, this approach uses a varying gain to enforce performance bounds on the system error and is further generalized to adaptive control laws with nonlinear reference models.
Another challenge in adaptive control systems is to achieve system stability and a prescribed level performance in the presence of actuator dynamics. It is well-known that if the actuator dynamics do not have sufficiently high bandwidth, their presence cannot be practically neglected in the design since they limit the achievable stability of adaptive control laws. Another major contribution of this dissertation is to address this challenge. In particular, first a linear matrix inequalities-based hedging approach is proposed, where this approach modifies the ideal reference model dynamics to allow for correct adaptation that is not affected by the presence of actuator dynamics. The stability limits of this approach are computed using linear matrix inequalities revealing the fundamental stability interplay between the parameters of the actuator dynamics and the allowable system uncertainties. In addition, these computations are used to provide a depiction of the feasible region of the actuator parameters such that the robustness to variation in the parameters is addressed. Furthermore, the convergence properties of the modified reference model to the ideal reference model are analyzed. Generalizations and applications of the proposed approach are then provided. Finally, to improve upon this linear matrix inequalities-based hedging approach a new adaptive control architecture using expanded reference models is proposed. It is shown that the expanded reference model trajectories more closely follow the trajectories of the ideal reference model as compared to the hedging approach and through the augmentation of a command governor architecture, asymptotic convergence to the ideal reference model can be guaranteed. To provide additional robustness against possible uncertainties in the actuator bandwidths an estimation of the actuator bandwidths is incorporated.
Lastly, the challenge presented by the unknown physical interconnection of large-scale modular systems is addressed. First a decentralized adaptive architecture is proposed in an active-passive modular framework. Specifically, this architecture is based on a set-theoretic model reference adaptive control approach that allows for command following of the active module in the presence of module-level system uncertainties and unknown physical interconnections between both active and passive modules. The key feature of this framework allows the system error trajectories of the active modules to be contained within apriori, user-defined compact sets, thereby enforcing strict performance guarantees. This architecture is then extended such that performance guarantees are enforced on not only the actuated portion (active module) of the interconnected dynamics but also the unactuated portion (passive module).
For each proposed adaptive control architecture, a system theoretic approach is included to analyze the closed-loop stability properties using tools from Lyapunov stability, linear matrix inequalities, and matrix mathematics. Finally, illustrative numerical examples are included to elucidate the proposed approaches.
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Bagheri, Shervin. "Stability analysis and control design of spatially developing flows." Licentiate thesis, KTH, Mechanics, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4769.
Full textAbstract:
Methods in hydrodynamic stability, systems and control theory are applied to spatially developing flows, where the flow is not required to vary slowly in the streamwise direction. A substantial part of the thesis presents a theoretical framework for the stability analysis, input-output behavior, model reduction and control design for fluid dynamical systems using examples on the linear complex Ginzburg-Landau equation. The framework is then applied to high dimensional systems arising from the discretized Navier–Stokes equations. In particular, global stability analysis of the three-dimensional jet in cross flow and control design of two-dimensional disturbances in the flat-plate boundary layer are performed. Finally, a parametric study of the passive control of two-dimensional disturbances in a flat-plate boundary layer using streamwise streaks is presented.
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Wu, Xiaohe. "OPTIMAL UPFC CONTROL AND OPERATIONS FOR POWER SYSTEMS." Doctoral diss., University of Central Florida, 2004. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/4462.
Full textAbstract:
The content of this dissertation consists of three parts. In the first part, optimal control strategies are developed for Unified Power Flow Controller (UPFC) following the clearance of fault conditions. UPFC is one of the most versatile Flexible AC Transmission devices (FACTs) that have been implemented thus far. The optimal control scheme is composed of two parts. The first is an optimal stabilization control, which is an open-loop 'Bang' type of control. The second is an suboptimal damping control, which consists of segments of 'Bang' type control with switching functions the same as those of a corresponding approximate linear system. Simulation results show that the proposed control strategy is very effective in maintaining stability and damping out transient oscillations following the clearance of the fault. In the second part, a new power market structure is proposed. The new structure is based on a two-level optimization formulation of themarket. It is shown that the proposed market structure can easily find the optimal solutions for the market while taking factors such as demand elasticity into account. In the last part, a mathematical programming problem is formulated to obtain the maximum value of the loadibility factor, while the power system is constrained by steady-state dynamic security constraints. Aniterative solution procedure is proposed for the problem, and the solution gives a slightly conservative estimate of the loadibility limit for the generation and transmission system.Ph.D.
Department of Electrical and Computer Engineering
Engineering and Computer Science
Electrical and Computer Engineering
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Li, Tianya. "Electromechanical wave propagation phenomenon and its control implications in power systems." Thesis, Queensland University of Technology, 2016. https://eprints.qut.edu.au/95962/1/Tianya_Li_Thesis.pdf.
Full textAbstract:
This thesis investigates advanced control methods and strategies to enhance the transient stability of a power system which is affected by the electromechanical wave propagation phenomenon. The characteristics of the travelling wave phenomenon and its impact on system separation during first swing are investigated in detail. This thesis identifies four innovative control implications for power system stability and proposes an improved method to enhance power system transient stability. By designing better control of existing equipment, this research achieves increased maximum power transfer under contingencies in a cost efficient and readily implemented way.
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Wang, Bo. "Analysis and implementation of time-delay systems and networked control systems." Thesis, University of South Wales, 2008. https://pure.southwales.ac.uk/en/studentthesis/analysis-and-implementation-of-timedelay-systems-and-networked-control-systems(f54e4378-db9b-443d-b505-88b4af5bb72a).html.
Full textAbstract:
Systems with delays frequently appear in engineering. The presence of delays makes system analysis and control design much more complicated. Networked control systems where the delays are often random are typical cases of such systems. For one particular category of time-delays systems, integral processes with dead time (IPDTs), the control limits that a PI controller can achieve are discussed in this thesis. These limits include the region of the control parameters to guarantee the system stability, the control parameters to achieve the given gain and/or phase margins (GPMs), the constraint on achievable gain and phase margins, the performance of set point tracking and disturbance rejection. Three types of PI controllers, namely typical PI controller, single tuning-parameter PI controller and PI controller under two-degree-of-freedom (2-DOF) structure, are studied. In control schemes of the modified Smith predictor (MSP) where the controller usually includes a distributed delay, the system implementation is not trivial because of the inherent hidden unstable poles. This thesis provides an estimation of the minimal number of implementation steps for the distributed delay in linear control laws. This is obtained by solving an inequality with respect to the number of implementation steps. A coarse estimation is given as the initial value to solve the inequality using bisection algorithms. A minimization process as well as some other techniques are also introduced to further improve the estimation. In networked control systems, the network-transmission delay and data dropout are combinedly represented by a network-induced delay. By designing a data pre processing mechanism, the network-induced delay can be assigned. Such delay as signment is applied to networked predictive control schemes, which alleviates systemstability limits on the network-induced delay. Two stability criteria are given for the closed-loop system with random network-induced delay, and a resulting implementation algorithm is also provided. The control and implementation of a magnetic levitation system over the network is studied in this thesis. Firstly, a test-rig which is suitable to implement control over a network is set up. Feedback linearization and direct local linearization methods for the nonlinear MagLev system are presented. In order to improve the control performance, a networked predictive method is employed, where the system model is identified in real-time. Local control and networked control are implemented on this test-rig, including networked predictive control. Model predictive control demonstrates a clear performance advantage over the networked control strategies which does not incorporate compensation for the network-induced delay. In order to quickly implement networked control systems (NCSs) by simulation or practical application, a MATLAB/Simulink based NCS toolbox is developed. This toolbox incorporates basic parts of a general NCS, that is, network simulation, network interface, plant interface and typical control schemes. With the NCS toolbox, users can focus on the study of new control schemes.