Dissertations / Theses on the topic 'Grids'
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Wolter, Martin. "Grid state identification of distribution grids." Aachen Shaker, 2008. http://d-nb.info/990522008/04.
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Tysell, Lars. "Hybrid Grid Generation for Viscous Flow Computations Around Complex Geometries." Doctoral thesis, KTH, Mekanik, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-11934.
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A set of algorithms building a program package for the generation of twoandthree-dimensional unstructured/hybrid grids around complex geometrieshas been developed. The unstructured part of the grid generator is based on the advancing frontalgorithm. Tetrahedra of variable size, as well as directionally stretched tetrahedracan be generated by specification of a proper background grid, initiallygenerated by a Delaunay algorithm. A marching layer prismatic grid generation algorithm has been developedfor the generation of grids for viscous flows. The algorithm is able to handleregions of narrow gaps, as well as concave regions. The body surface is describedby a triangular unstructured surface grid. The subsequent grid layers in theprismatic grid are marched away from the body by an algebraic procedurecombined with an optimization procedure, resulting in a semi-structured gridof prismatic cells. Adaptive computations using remeshing have been done with use of a gradientsensor. Several key-variables can be monitored simultaneously. The sensorindicates that only the key-variables with the largest gradients give a substantialcontribution to the sensor. The sensor gives directionally stretched grids. An algorithm for the surface definition of curved surfaces using a biharmonicequation has been developed. This representation of the surface canbe used both for projection of the new surface nodes in h-refinement, and theinitial generation of the surface grid. For unsteady flows an algorithm has been developed for the deformationof hybrid grids, based on the solution of the biharmonic equation for the deformationfield. The main advantage of the grid deformation algorithm is that itcan handle large deformations. It also produces a smooth deformation distributionfor cells which are very skewed or stretched. This is necessary in orderto handle the very thin cells in the prismatic layers. The algorithms have been applied to complex three-dimensional geometries,and the influence of the grid quality on the accuracy for a finite volumeflow solver has been studied for some simpler generic geometries.QC 20100812
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SANTOS, MARCELO NERY DOS. "GRIDFS: SERVER FOR GRIDS AND HETEROGENEOUS DISTRIBUTED ENVIRONMENTS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2006. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=9212@1.
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COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIORFINANCIADORA DE ESTUDOS E PROJETOS
FUNDO SETORIAL PARA DESENV. TECNOLÓGICO DAS TELECOMUNICAÇÕES
A computação em grade permite o uso de recursos computacionais distribuídos em várias redes para a execução de tarefas que requerem um alto poder computacional. Uma infra-estrutura para grades pode ser utilizada para auxiliar na execução dessas tarefas e pode coordenar o controle das atividades envolvidas na execução, como a disponibilização dos arquivos de dados para as tarefas em execução nos nós da grade. O GridFS é um sistema para o compartilhamento de arquivos em grades e ambientes distribuídos heterogêneos. Ao disponibilizar um servidor em diversas máquinas, é possível construir uma federação integrando os diversos sistemas de arquivos locais e abrindo possibilidades de armazenamento na ordem de terabytes. O sistema proposto foi modelado e desenvolvido levando em consideração diversos aspectos como escalabilidade, interoperabilidade e desempenho. O GridFS agrega algumas características dos sistemas de compartilhamento de arquivos atualmente em uso pela comunidade, isto é, o sistema oferece uma API para acesso remoto aos dados, disponibiliza a opção de cópia de arquivos entre diferentes servidores e fornece algumas funções especiais para os ambientes de computação em grade, como uma estimativa do tempo de transferência entre os diversos nós. Além de definir as características e os aspectos de implementação do sistema, esta dissertação apresenta alguns resultados experimentais para a transferência de arquivos na rede e, como forma de avaliação, discutimos a integração do GridFS ao emph {framework} CSBase, utilizado no desenvolvimento de sistemas para computação em grade.
Grid computing allows the use of distributed networks resources for tasks requiring a high processing power. A Grid infra-structure may help in the execution of these tasks and is able to coordinate their related activities, possibly regarding the provision of data files for the tasks executing in the grid nodes. GridFS is a system that enables data sharing in grid and heterogeneous distributed environments. By deploying servers over several nodes, it is possible to build a federated system integrating all local file systems and leveraging possibilities for tera-scale sized data storage. The proposed system was modeled and developed considering several aspects such as scalability, interoperability and performance. GridFS combines some characteristics from diverse file management systems, that is, GridFS provides an API for remote data access, copy operations allowing file transfers between servers, and some special features for grid environments. Apart from defining system characteristics and implementation aspects, this dissertation shows some experimental results about the service scalability and performance, and, as an evaluation, discusses the integration of GridFS with CSBase, a framework used to develop systems for grid computing.
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Wolter, Martin [Verfasser]. "Grid State Identification of Distribution Grids / Martin Wolter." Aachen : Shaker, 2008. http://d-nb.info/1161303480/34.
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Liu, Qing. "Control of grid-tied inverters for nano-grids." Doctoral thesis, Università degli studi di Padova, 2019. http://hdl.handle.net/11577/3422338.
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In recent times, with the development of renewables, the concept of micro-grid emerged, representing a novel bottom up power distribution organization. The micro-grid can integrate the nearby distributed, and mostly renewable, energy sources, the storage devices and the loads into the grid, with increased efficiency, flexibility and reliability, showing significant economical and environmental benefits. The micro-grid concept can be further scaled down to the range of a single house or small building, and differentiated by a new terminology, nano-grid. The proposal of the nano-grid concept is aimed at simplifying the application scenarios, so that a hierarchical bottom-up power distribution network can be established, where the nano-grid plays the lowest-end role. It can not only operate autonomously, feeding the typical household appliances from the available renewable sources; thanks to the modular smart grid architecture, it can also be conveniently interconnected to other similar units, operating in parallel and harmoniously energizing a larger region in a city, a small-island or a village. In addition, the nano-grid also has the possibility of self-integrating into the utility grid, exchanging power with the mains when needed, thanks to a specifically designed grid interface converter. Referring to the latter, a variety of requirements are defined by applicable standards, in terms of load power quality, grid support functionalities, abnormal condition ride-through and protection means.
The realization of the above functionalities is heavily dependent on the control of the grid interfacing inverter hosted within the nano-grid, about which numerous solutions have been proposed in the existing literature. However, few of them can realize all the functionalities simultaneously in a single controller. The target of this dissertation is therefore proposing, analyzing and testing a high-quality, multi-functional control scheme for grid-tied inverters.
This goal is reached in three steps: i) a deep literature review, ii) the identification, study and realization of the multi-functional inverter controller, and iii) the implementation of further, higher level functionalities, like the grid-supporting and parallel operation capabilities.
Accordingly, the study is initiated from step i), with an overview of existing control strategies and key functionalities of grid-tied inverters. The comprehensive review of a research topic is, in any case, very advantageous to define the state of the art solutions and to evaluate the margins for improvement in the existing technology. In this research case, it allowed to understand that a triple-loop controller structure is the most suitable to achieve high-performance control of the nano-grid electrical system and the most promising as to the capability of implementing multiple interface and protection functionalities jointly. In the second step ii), a large-bandwidth triple-loop controller is proposed, whose implementation is the first contribution of this dissertation. The peculiarity of the proposed controller is the large-bandwidth control of the injected grid current, which brings in many beneficial features. Leveraging on this controller organization, multiple functionalities are later implemented by means of a superimposed flexible mode-transition manager and an auto-tuner, altogether forming a high quality, multi-functional control scheme for grid-tied inverters. This represents the second contribution delivered by this dissertation. Finally, in step iii), the extended scenario of multiple parallel-connected grid-tied inverters is discussed, targeting the realization of distributed grid-supporting functionalities in grid-tied mode and the automatic balanced power sharing in parallel-islanded mode. The final implemented control scheme provides a feasible solution for the forthcoming smart nano-grids and represents the third contribution of this research activity.
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Eld, Jonas, and Jens Melin. "Test Grids for Reliability analysis : Analysing interruptions and developing test grids based on Mälarenergi Elnät distribution grid." Thesis, Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-35925.
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The purpose of this degree project is to examine power outages that has occurred during the years 2009 and 2016 on Mälarenergi Elnät distribution grid. Interruptions that has occurred on 10 kV voltage level and on overhead lines or underground cable was examined. The examined interruptions are based on the DARWin data from Mälarenergi Elnät. The examined interruptions resulted in four different test grids. Test grid A are overhead line grid in rural area, test grid B are mixed grid in rural area, test grid C are underground cable grid in semi urban area and test grid D are underground cable grid in urban area. Test grid C and D which have the highest customer density were then used for reliability analysis. The reliability analysis was performed using Microsoft Excel. The main focus for the reliability analysis were the impact of different sectioning times. Another focus for the reliability analysis was introducing breakers at key-points in test grid C. The primarily cause of interruptions on overhead line grids are weather related events and on underground cable grids it is digging and fabrication or material errors. It is concluded that with quicker sectioning times, the reliability of the grid increases linearly. The introduction of breakers at key-points in the grid results in increased reliability.
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Lu, Kai. "Decentralized load balancing in heterogeneous computational grids." Thesis, The University of Sydney, 2007. http://hdl.handle.net/2123/9382.
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With the rapid development of high-speed wide-area networks and powerful yet low-cost computational resources, grid computing has emerged as an attractive computing paradigm. The space limitations of conventional distributed systems can thus be overcome, to fully exploit the resources of under-utilised computing resources in every region around the world for distributed jobs. Workload and resource management are key grid services at the service level of grid software infrastructure, where issues of load balancing represent a common concern for most grid infrastructure developers. Although these are established research areas in parallel and distributed computing, grid computing environments present a number of new challenges, including large-scale computing resources, heterogeneous computing power, the autonomy of organisations hosting the resources, uneven job-arrival pattern among grid sites, considerable job transfer costs, and considerable communication overhead involved in capturing the load information of sites. This dissertation focuses on designing solutions for load balancing in computational grids that can cater for the unique characteristics of grid computing environments. To explore the solution space, we conducted a survey for load balancing solutions, which enabled discussion and comparison of existing approaches, and the delimiting and exploration of the apportion of solution space. A system model was developed to study the load-balancing problems in computational grid environments. In particular, we developed three decentralised algorithms for job dispatching and load balancing—using only partial information: the desirability-aware load balancing algorithm (DA), the performance-driven desirability-aware load-balancing algorithm (P-DA), and the performance-driven region-based load-balancing algorithm (P-RB). All three are scalable, dynamic, decentralised and sender-initiated. We conducted extensive simulation studies to analyse the performance of our load-balancing algorithms. Simulation results showed that the algorithms significantly outperform preexisting decentralised algorithms that are relevant to this research.
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Bertetti, Odilia. "Benchmarking of Smart Grid Conceptsin Low-Voltage Distribution Grids." Thesis, KTH, Kraft- och värmeteknologi, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-217979.
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Mia, Gredelj. "DC micro-grids." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for elkraftteknikk, 2014. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-27249.
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The conventional electrical system in place today sees our electrical devices powered by AC mains. But as renewable technologies such as solar photovoltaic and wind power become more prevalent at a household level, DC micro-grids could be a cheaper and more efficient alternative. New lighting devices (LED) can reduce the electricity consumption substantially. Two alternatives are envisioned in this paper: A stand-alone alternative in which there is no grid connection, that would require local storage (battery), and a grid-connection alternative. After reviewing and investigating relevant literature for this topic and writing theoretical part of thesis there were the fallowing tasks. One typical four member family household was described and hourly load curves for one year period, with typical summer and winter days, were made for this case. Next task that was completed was generating yearly energy production from solar panels, which the observed household contains, in INSEL software. With having those previously mentioned data, combined with necessary information about prices of all necessary components and prices from Croatian power system, it was possible to make feasibility and cost analysis where the two previously mentioned alternatives were investigated. With changing some parameters in that economical analysis several scenarios were observed. At the end conclusions were made about which one of those two options is more profitable and under what conditions. Also, suggestions were made for further work on this topic. This assignment is realized as a part of the collaborative project “Sustainable Energy and Environment in Western Balkans” that aims to develop and establish five new internationally recognized MSc study programs for the field of “Sustainable Energy and Environment”, one at each of the five collaborating universities in three different WB countries. The project is funded through the Norwegian Programme in Higher Education, Research and Development in the Western Balkans, Programme 3: Energy Sector (HERD Energy) for the period 2011-2014.
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Landberg, Gustav, and Kim Elfström. "Realising Smart Grids." Thesis, Uppsala universitet, Institutionen för teknikvetenskaper, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-278959.
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The smart grid is a popular and well-debated topic in the energy industry right now. The concept itself has a variety of definitions, both followers and opponents have their opinions. The smart grid has been a discussed on both the national and international market. In Sweden, the smart grid has received increased interest and numerous stakeholders. This applies both among politicians with organizations such as The Smart Grid Council, but also at energy producers Vattenfall and giant engineering companies like ABB. What happens in the future is still uncertain but there is reason to believe that the Swedish grid is becoming smarter, at least with respect to all the attention it gets. The purpose of this paper has been to examine the realization of a smart grid in Sweden, by examining possible incentives and barriers. As mentioned, the concept of smart grids is widely debated and relatively undefined. Therefore the work started by utilizing a definition which had to be well established, accepted and correlated with the authors' approach and aim. The chosen definition comes from the European Commission (2010) and reads: “A Smart Grid is an electricity network that can cost efficiently integrate the behaviour and actions of all users connected to it – generators, consumers and those that do both – in order to ensure economically efficient, sustainable power system with low losses and high levels of quality and security of supply and safety” A theoretical framework was developed in order to obtain facts, information, and serve as tools for future analyses. For example, the authors selected The evolution of large technological systems by Thomas Hughes (1987), which describes large technological systems and how they develop in society. Further Marx’s ”Das Kapital” (1867) and several earlier research regarding smart grids were also selected and used for the analyses. Potential stakeholders and key-actors were pointed out and examined to get a picture of the current situation regarding the smart grid in Sweden. Three main areas of key-actors were chosen: academia, business, and political/governmental organizations. Nine qualitative interviews were conducted with actors who were considered to have good insight and influence in the area. The collected material and information was analyzed by the following aspects: financial, technological, sociological, and environmental. The following results were found through the interviews: Almost all interviewed key-actors pointed out the economic factor as the decisive aspect for a Swedish smart grid realization in Sweden. At present, it was not considered to be sufficient economic incentives. It was pointed out that the electricity in Sweden is very cheap and therefore customers are not interested in paying more for it, especially not big ones like major industries. The uncertainty about who will pay for the necessary renovations of the existing power grid was also pointed out. Many of the interviewed actors saw great potential in the political guidelines and regulations. They considered that more stringent requirements and rules that favours a smarter and greener electricity, would lead the development towards a smart grid. The technical aspect of a smart grid was not considered to be an obstacle. On the contrary, most of the technology was considered already available. A summative finding was that the majority of actors did not believe in a revolution of the smart grid in the near future. They rather saw it as an evolutionary process that may emerge. Several findings correlate well with the theoretical framework. For instance, Beise & Rennings (2004) confirms the importance of political regulations. Their view on the smart grid as an evolution that will adapt little by little follows the arguments ii that Hughes describes. The value-aspect of the smart grid and the fact that is not considered to be enough today, at least not in an economical way, follows Marx’s theory of value from 1867. The smart grid development fitted well into Leonard- Barton’s (1998) aspect of mutual adaption, which points out that both the users and the technology have to be changed in order to achieve success. The conclusion was drawn that most of the actors are in favour of a smart grid, but they did not see that there will be a "smart revolution" in the next few years given the current financial barriers.
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Rose, Robert W. "Defending electrical power grids." Thesis, Monterey, Calif. : Naval Postgraduate School, 2007. http://bosun.nps.edu/uhtbin/hyperion.exe/07Mar%5FRose.pdf.
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Thesis (M.S. in Operations Research)--Naval Postgraduate School, March 2007.Thesis Advisor(s): Javier Salmeron. "March 2007." Includes bibliographical references (p. 51-52). Also available in print.
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Mitsos, Ioannis. "Double-layer tensegrity grids." Thesis, University of Cambridge, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.648489.
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Alvarez, Rogelio E. "Interdicting electrical power grids." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2004. http://library.nps.navy.mil/uhtbin/hyperion/04Mar%5FAlvarez.pdf.
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Thesis (M.S. in Operations Research)--Naval Postgraduate School, March 2004.Thesis advisor(s): Javier Salmeron, R. Kevin Wood. Includes bibliographical references (p. 69-70). Also available online.
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Zaenker, Tobias. "Hypermaps : Beyond occupancy grids." Thesis, Luleå tekniska universitet, Institutionen för system- och rymdteknik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-75858.
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Intelligent and autonomous robotic applications often require robots to have more information about their environment than provided by traditional occupancy maps. An example are semantic maps, which provide qualitative descriptions of the environment. While research in the area of semantic mapping has been performed, most robotic frameworks still offer only occupancy maps. In this thesis, a framework is developed to handle multi-layered 2D maps in ROS. The framework offers occupancy and semantic layers, but can be extended with new layer types in the future. Furthermore, an algorithm to automatically generate semantic maps from RGB-D images is presented. Software tests were performed to check if the framework fulfills all set requirements. It was shown that the requirements are accomplished. Furthermore, the semantic mapping algorithm was evaluated with different configurations in two test environments, a laboratory and a floor. While the object shapes of the generated semantic maps were not always accurate and some false detections occurred, most objects were successfully detected and placed on the semantic map. Possible ways to improve the accuracy of the mapping in the future are discussed.
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Majwi, Milambo. "Micro-grids with distributed generators in an edge-of-main grid scenario." Thesis, Majwi, Milambo (2009) Micro-grids with distributed generators in an edge-of-main grid scenario. Other thesis, Murdoch University, 2009. https://researchrepository.murdoch.edu.au/id/eprint/3225/.
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This thesis investigates the dynamic behaviour and transients of a sub-system when operating in two scenarios: Grid-connected mode, and islanding mode. The sub-system consists of two distributed generators (DGs). One DG is modeled using a rotating synchronous machine fitted with a governor to represent a diesel generator, while the other is modeled using a DC voltage source and a converter to represent a photovoltaic (PV) energy source. The distribution network also consists of a grid connected source known as the main grid. During normal operation, the supply of electricity to the connected loads is shared among the three energy sources, the DGs supplying about 80 percent of the loads and the rest are supplied by the main grid. When the main grid is disconnected from the network, supply to the connected loads is shared by the two DGs. The PV energy source system is equipped with real and reactive power control mechanisms that minimize islanding transients and maintain angle stability and voltage quality of the network. The study includes examples of micro-grid transient analysis carried out in the past. This is followed by the study of how transient analysis can be carried out in PowerFactory software.
The simulation studies show that the electronic power control system in a PV generator is capable of maintaining the angle stability of a micro grid in response to transient conditions. These transients may result from changes in power demands from connected loads or severe islanding events. The diesel generator through the use of a governor responds to supply the required power to the system when the PV has reached its maximum supply limits. The diesel generator acts as a back-up to the PV supply.
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Rui, Han [Verfasser]. "Target-oriented Planning for Electric Distribution Grids with Smart Grid Metrics / Han Rui." Aachen : Shaker, 2017. http://d-nb.info/113817730X/34.
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Haselbacher, Andreas C. "A grid-transparent numerical method for compressible viscous flows on mixed unstructured grids." Thesis, Loughborough University, 1999. https://dspace.lboro.ac.uk/2134/7257.
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The goal of the present work is the development of a numerical method for compressible viscous flows on mixed unstructured grids. The discretisation is based on a vertex-centred finite-volume method. The concept of grid transparency is developed as a framework for the discretisation on mixed unstructured grids. A grid-transparent method does not require information on the cell types. For this reason, the numerical method developed in the present work can be applied to triangular, quadrilateral, and mixed grids without modification. The inviscid fluxes are discretised using the approximate Riemann solver of Roe. A limited linear-reconstruction method leads to monotonic capturing of shock waves and second-order accuracy in smooth regions of the flow. The discretisation of the viscous fluxes on triangular and quadrilateral grids is first studied by reference to Laplace's equation. A variety of schemes are evaluated against several criteria. The chosen discretisation is then extended to the viscous fluxes in the Navier-Stokes equations. A careful study of the various terms allows a form to be developed which may be regarded as a thin-shear-layer approximation. In contrast to previous implementations, however, the present approximation does not require knowledge of normal and tangential coordinate directions near solid surfaces. The effects of turbulence are modelled through the eddy-viscosity hypothesis and the one-equation model of Spalart and Allmaras. The discrete equations are marched to the steady-state solution by an explicit Runge-Kutta method with local time-stepping. The turbulence-model equation is solved by a point-implicit method. To accelerate the convergence rate, an agglomeration multigrid method is employed. In contrast to previous implementations, the governing equations are entirely rediscretised on the coarse grid levels. The solution method is applied to various inviscid, laminar, and turbulent flows. The performance of the multigrid method is compared for triangular and quadrilateral grids. Care is taken to assess numerical errors through grid-refinement studies or comparisons with analytical solutions or experimental data. The main contributions of the present work are the careful development of a solution method for compressible viscous flows on mixed unstructured grids and the comparison of the impact of triangular, quadrilateral, and mixed grids on convergence rates and solution quality.
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Legry, Martin. "Control of distributed energy resources for primary response of grid-interactive micro-grids." Thesis, Lille 1, 2019. http://www.theses.fr/2019LIL1I099.
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Ces travaux portent sur la commande d’un micro-réseau interactif pour fournir des services système à un réseau électrique faible, et plus particulièrement une réponse primaire en fréquence et en tension au point d’interconnection (PCC). Le premier objectif de cette thèse est de superviser un micro-réseau afin d’assurer un fonctionnement stable tout en respectant les objectifs économiques définis par un optimiseur externe.Dans un second temps, une nouvelle méthodologie en trois étapes a été mise au point. Premièrement, pour fournir les services auxiliaires au PCC, il est nécessaire d’estimer et de coordonner les flexibilités des différents équipements tels que les générateurs d’énergie distribués, les énergies renouvelables, les stockages, etc. Un algorithme d’optimisation est proposé pour l’agrégation de ces flexibilités afin de déterminer les flux de puissance active et réactive maximum que le micro-réseau peut fournir. La deuxième étape détermine le comportement possible du micro-réseau à son PCC. Enfin, deux nouveaux algorithmes de contrôle ont été développés pour assurer un comportement de type statisme au PCC.Une première solution, basée sur un superviseur centralisé et la commande prédictive, assure un ajustement en temps réel des points de consigne. La seconde est une solution distribuée qui détermine de nouvelles lois de contrôle locales primaires pour les différents actionneurs. L’efficacité des deux architectures de contrôle a été validée par simulation sur un modèle de micro-réseau de référenceThis work focuses on the control of a grid-interactive micro-grid to provide ancillary services to a weak power system, and more particularly a primary frequency and voltage response at the point of common coupling (PCC). The first objective of this thesis is to supervise a micro-grid in order to ensure stable operation while enforcing the economic objectives defined by an external optimizer.Then, a novel three-step methodology has been developed. First, to provide the ancillary services at the PCC, it is necessary to estimate and coordinate the flexibility of heterogeneous equipment such as distributed generators, renewables, storages, etc. An optimization algorithm is proposed for the aggregation of these flexibilities to deduce the maximum active and reactive power flows that the micro-grid can provide. The second step determines the possible behavior of the micro-grid at its PCC. Finally, two new control algorithms have been developed to ensure a droop-like behavior at the PCC. A first solution, based on a centralized Model Predictive Control based supervisor, ensures a real-time adjustment of the set-points. The second one is a distributed solution that determines new primary local control laws for DERs. The effectiveness of the two control architectures has been validated by simulation with a benchmark micro-grid model
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Rocha, Mário. "The embedding of complete bipartite graphs onto grids with a minimum grid cutwidth." CSUSB ScholarWorks, 2003. https://scholarworks.lib.csusb.edu/etd-project/2311.
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Osika, Oleg. "Stability of micro-grids and inverter-dominated grids with high share of decentralised sources." Kassel : Kassel Univ. Press, 2005. http://deposit.d-nb.de/cgi-bin/dokserv?idn=982006888.
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Grădinaru, Vasile Catrinel. "Whitney elements on sparse grids." [S.l. : s.n.], 2002. http://deposit.ddb.de/cgi-bin/dokserv?idn=964889897.
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Liu, Chen. "Multilevel halftoning over hexagonal grids." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file 0.85 Mb., 47 p, 2006. http://wwwlib.umi.com/dissertations/fullcit/1435813.
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Hægland, Håkon. "Streamline tracing on irregular grids." Bergen : [H. Hægland] ; [Universitetet i Bergen], 2003. http://www.uib.no/people/fcihh/thesis/thesis.pdf.
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Thesis (M.S.)--Universitetet i Bergen, 2003Hovedoppgave i matematikk - Universitetet i Bergen, 2003 II Title from document title page. Includes bibliographical references. Available in PDF format via the World Wide Web.
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Zheng, Yun. "Aerodynamic computation on unstructured-grids." Thesis, Durham University, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.398570.
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Ballette, Marco. "Load distribution in mobile grids." Thesis, University of Essex, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.433544.
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Nassar, Jad. "Ubiquitous networks for Smart Grids." Thesis, Lille 1, 2018. http://www.theses.fr/2018LIL1I053/document.
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Les Smart Grids visent à transformer le réseau électrique actuel en un réseau "plus intelligent" où la production énergétique est décentralisée et automatisée, facilitant l'intégration des sources d'énergie renouvelables. Cette évolution est rendue possible grâce à l'utilisation d'un réseau de communication pour les multiples échanges de données hétérogènes des Smart Grids. L'objectif de cette thèse est de proposer un paradigme de communication efficace en termes de qualité de service pour les Smart Grids basé sur les réseaux de capteurs.Dans un premier temps, on s’intéresse au protocole standard RPL. Nous proposons une évolution de celui-ci à travers une nouvelle fonction objectif. Celle-ci tire parti de l’hétérogénéité matérielle des nœuds et des liens pour introduire la qualité de service. Cela permet à RPL de satisfaire les multiples et différentes exigences en termes de fiabilité, de latence et de priorité dans l'acheminement des données. Nos résultats montrent que notre approche permet bien la différentiation du trafic tout en réduisant la latence du routage et en économisant l'énergie.Nous proposons également d'améliorer l'utilisation du réseau de capteurs en y introduisant l’auto-organisation et la réduction des données. Le but est alors de prédire la valeur des données mesurées plutôt que de les transmettre.Une autre approche explorée est d'agréger les différents messages transitant sur le réseau tout en considérant leurs différentes exigences de qualité de service. Ces deux approches permettent ainsi de réduire la consommation d'énergie tout en respectant les exigences des différentes applications des Smart GridsSmart Grids aim to transform the current electric grid into a "smarter" network where energy production is decentralized and automated, which facilitates the integration of renewable energy resources. This evolution is made possible thanks to the use of a communication network for the multiple heterogeneous data exchanges of the Smart Grids. Hence, the aim of this thesis is to propose an efficient communication paradigm in terms of quality of service for Smart Grids based on wireless sensor networks.First, we study data routing in Smart Grids with the RPL standard. Nevertheless, RPL is not suitable for Smart Grid applications in terms of quality of service. Therefore, we propose an objective function for RPL that takes different features of both nodes and links into consideration. Results show that our approach improves network performance compared to existing solutions in terms of packet delivery ratio, network lifetime, latency and traffic differentiation.Then, we also propose a more efficient data collection by introducing self-organization and data reduction for these wireless sensors. The goal is to predict the value of the measured data rather than transmitting them. Another explored approach is to aggregate the different messages sent across the network while considering their different requirements in terms of quality of service.These two approaches reduce the energy consumption while respecting the requirements of the different applications of the Smart Grids
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Palma, David João Nunes. "Design of future distribution grids." Master's thesis, Faculdade de Ciências e Tecnologia, 2013. http://hdl.handle.net/10362/11110.
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Dissertação para obtenção do Grau de Mestre em
Engenharia Electrotécnica e de ComputadoresThis work presents the concept of voltage control in power distribution systems with distributed generation and electric vehicles penetration. The impact of DG and EV in the voltage supply is investigated. DG provides more power into the system, which can cause the inversion of the load flow and an increase in the voltage supply when the demand is low. EVs on the other hand are additional load in distribution systems, increasing power demand and voltage drop. Both might be a cause of voltage problems in the power supply, when no voltage control is applied. Devices such as the tap-changer transformer or the voltage regulator which were not essential in the past are now important solutions to solve voltage variation issues. In this work, several different solutions for voltage control are analyzed, both technically and economically. Overall, the results show that different strategies have different outcomes, and some solutions provide better voltage control than others. In order to have a proper solution for a system, when choosing a control strategy, it is necessary to always take into account the cable ampacity, the technical limits of each device and the costs associated with it.
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Molnar, Grant Steven. "The Arithmetic of Modular Grids." BYU ScholarsArchive, 2018. https://scholarsarchive.byu.edu/etd/6990.
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Let Mk(∞) (Gamma, nu) denote the space of weight k weakly holomorphic weight modular forms with poles only at the cusp (∞), and let widehat Mk(∞) (Gamma, nu) subseteq Mk(∞) (Gamma, nu) denote the space of weight k weakly holomorphic modular forms in Mk(∞) (Gamma, nu) which vanish at every cusp other than (∞). We construct canonical bases for these spaces in terms of Maass--Poincaré series, and show that the coefficients of these bases satisfy Zagier duality.
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Busuladzic, Ishak, and Marcus Tjäder. "Performance Indicators for Smart Grids : An analysis of indicators that measure and evaluate smart grids." Thesis, Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-48902.
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Sweden has developed ambitious goals regarding energy and climate politics. One major goal is to change the entire electricity production from fossil fuels to sustainable energy sources, this will contribute to Sweden being one of the first countries in the world with non-fossil fuel in the electricity sector. To manage this, major changes need to be implemented and difficulties on the existing grid will occur with the expansion of digitalization, electrification and urbanization. By using smart grids, it is possible to deal with these problems and change the existing electricity grid to use more distributed power generation, contributing to flexibility, stability and controllability. The goal with smart grids is to have a sustainable electricity grid with low losses, security of supply, environmental-friendly generation and also have choices and affordable electricity for customers. The purpose of this project is to identify and evaluate several indicators for a smart grid, how they relate and are affected when different scenarios with different technologies are implemented in a test system. Smart grid indicators are quantified metrics that measure the smartness of an electrical grid. There are five scenarios where all are based on possible changes in the society and electricity consumption, these scenarios are; Scenario A – Solar power integration, Scenario B – Energy storage integration, Scenario C – Electric vehicles integration, Scenario D – Demand response and Scenario E – Solar power, Energy storage, Electric vehicles and Demand response integration. A model is implemented in MATLAB and with Monte Carlo simulations expected values, standard deviation and confidence interval were gained. Four selected indicators (Efficiency, capacity factor, load factor and relative utilization) was then analyzed. The results show that progress on indicators related to all smart grid characteristics is needed for the successful development of a smart grid. In scenario C, all four selected indicators improved. This shows that these indicators could be useful for promoting the integration of electric vehicles in an electricity grid. In Scenario A, solar power integration contributed to all indicators deteriorate, this means that, technical solutions that can stabilize the grid are necessary to implement when integrating photovoltaic systems. The load factor is a good indicator for evaluating smart grids. This indicator can incentivize for an even load and minimize the peak loads which contributes to a flexible and efficient grid. With the capacity factor, the utilization and free capacity can be measured in the grid, but it can counteract renewable energy integration if the indicator is used in regulation.
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Kraiczy, Markus [Verfasser]. "Reactive power grid adequacy studies for distribution grids with high distributed generation / Markus Kraiczy." Kassel : kassel university press c/o Universität Kassel - Universitätsbibliothek, 2021. http://d-nb.info/1232212032/34.
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Work, Dalon G. "Evaluation of Flux Correction on Three-dimensional Strand Grids with an Overset Cartesian Grid." DigitalCommons@USU, 2017. https://digitalcommons.usu.edu/etd/6425.
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Simulations of fluid flows over complex geometries are typically solved using a solution technique known as the overset meshing method. The geometry is meshed using grid types appropriate to the local geometry in a patchwork fashion, rather than meshing the entire geometry with one type of mesh. The strand-Cartesian approach is a simplification of this process. While high-order accurate solvers on Cartesian grids are simple to implement, strand grids are usually restricted to second-order accuracy, resulting in poor quality solutions. Flux correction is a high-order accurate solution method, specifically designed for use on strand grids. The flux correction method on strand grids is evaluated in conjunction with an overset Cartesian grid. Fundamental studies are considered which demonstrate the effectiveness of high-order methods in solving practical flows of interest.
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Shang, Ling. "Experiments and programming paradigms for large scale scientific computing on grids, desktop grids and private clouds." Thesis, Lille 1, 2010. http://www.theses.fr/2010LIL10095/document.
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Les grilles de calcul et les grille de PC sur Internet offrent des alternatives intéressantes pour le calcul scientifique à grande échelle, qui demande des ressources de calcul importantes. Toutefois, l’adaptation des applications pour ces systèmes est difficile à cause des facteurs nombreux tels que l'interface complexe de programmation. L'objectif de cette thèse est de trouver une solution pour faciliter le calcul scientifique à grande échelle. Pour ce faire, j’ai travaillé sur l’algorithme de Gauss Jordan et une nouvelle version d’un schéma de parallélisme. Ce schéma peut exploiter le maximum de parallélisme entre des opérations. Comme un exemple excellent, l'algorithme de Gauss Jordan est également utilisé pour évaluer des environnements expérimentaux et des outils différents. Les expérimentations avec YML, OmniRPC et XtremWeb sur les grilles et les grilles de PC montrent que YML peut être une bonne solution pour que les utilisateurs fassent du calcul scientifique à grande échelle, à cause des bonnes caractéristiques comme « l’interface d'abstraction de haut niveau», « les composants réutilisables » et «le surcoût acceptable». Pour obtenir les meilleures performances de cette plate-forme, les questions concernées, telles que la granularité des tâches, la persistance des données et le mécanisme d’ordonnancement, sont également abordés dans cette thèse. Selon les analyses faites ci-dessus et les caractéristiques communes des nuages informatiques ciblés, YML-PC, une architecture de référence basée sur les workflows pour les constructions de nuages informatiques privés scientifique est proposée. YML-PC hérite les bonnes caractéristiques présentées ci-dessus et des autres technologies clefs telles que « la persistance des données », « La prévision du temps disponible » et « l'évaluation sur des nœuds de calcul hétérogènes » pour YML-PC, qui sont également abordées dans cette thèse. Les évaluations sur l'algorithme de Gauss Jordan sont réalisées sur les grilles, les grilles de PC et les nuages informatiques privés qui sont implantés sur la plate-forme Grid5000, la plateforme de calcul de Polytech Lille en France et la plateforme de calcul de Hohai, en ChineGrid computing and Desktop Grid computing provide interesting alternatives for large scale scientific computing which needs very large scale computing resources. However gridification is hard to develop because of series of factors such as complex programming interface. The aim of this dissertation is to find a solution to make large scientific computing in an easy way. To do that, research on Gauss Jordan algorithm is made and a new parallel programming version is presented. The parallel version can achieve maximum degree parallelism between operations. Also the Gauss Jordan algorithm as an excellent example is used to evaluate different experimental environments and tools. Experiments with YML, OmniRPC and XtremWeb on Grid and Desktop Grid environments testify YML can be a good solution for end users to make large scale scientific computing for its series of good features such as higher level interface, component reuse and acceptable overhead. To get better performance of platform, related issues such as task granularity, data persistence and schedule mechanism are also discussed in this dissertation. According to analysis made above and the common features of Clouds possessed, YML-PC a reference architecture based on workflow for building scientific Private Clouds is proposed. YML-PC inherits those good features presented above and some other key technologies such as “data persistence”, “available time prediction” and “evaluation on heterogeneous computing nodes” for YML-PC are also discussed in this dissertation. Evaluations are made based on Gauss Jordan algorithm on Grids, Desktop Grids and Private Clouds which build on Grid5000, Polytech Lille platform, France and Hohai platform, China
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Osika, Oleg [Verfasser]. "Stability of micro-grids and inverter-dominated grids with high share of decentralised sources / Oleg Osika." Kassel : Kassel Univ. Press, 2005. http://d-nb.info/982006888/34.
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Schiffers, Michael. "Management dynamischer Virtueller Organisationen in Grids." Diss., lmu, 2007. http://nbn-resolving.de/urn:nbn:de:bvb:19-73526.
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Arjomandi, Human. "Nano-grids of Yeast Cytochrome C." FIU Digital Commons, 2005. http://digitalcommons.fiu.edu/etd/1312.
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One innovative thought in biomolecular electronics is the exploitation of electron transfer proteins. Using nature's self assembly techniques, proteins can build highly organized edifices with retained functional activity, and they can serve as platforms for biosensors.
In this research work, Yeast Cytochrome C (YCC) is immobilized with a help of a linker molecule, 3-Mercaptopropyltrimethoxysilane (3-MPTS) on a hydroxylated surface of a silicon substrate. Atomic Force Microscopy (AFM) is used for characterization. AFM data shows immobilization of one YCC molecule in between eight grids that are formed by the linker molecules. 3-MPTS monolayers are organized in grids that are 1.2 nm apart. Immobilization of 3-MPTS was optimized using a concentration of 5 mM in a completely dehydrated state for 30 minutes.
The functionally active grids of YCC can now be incorporated with Cytochrome C oxidase on a Platinum electrode surface for transfer of electrons in development of biosensors, such as nitrate sensor, that are small in size, cheaper, and easier to manufacture than the top-down approach of fabrication of molecular biodevices
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Globisch, G., and S. V. Nepomnyaschikh. "The hierarchical preconditioning having unstructured grids." Universitätsbibliothek Chemnitz, 1998. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-199801398.
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In this paper we present two hierarchically preconditioned methods for the fast solution of mesh equations that approximate 2D-elliptic boundary value problems on unstructured quasi uniform triangulations. Based on the fictitious space approach the original problem can be embedded into an auxiliary one, where both the hierarchical grid information and the preconditioner by decomposing functions on it are well defined. We implemented the corresponding Yserentant preconditioned conjugate gradient method as well as the BPX-preconditioned cg-iteration having optimal computational costs. Several numerical examples demonstrate the efficiency of the artificially constructed hierarchical methods which can be of importance in the industrial engineering, where often only the nodal coordinates and the element connectivity of the underlying (fine) discretization are available.
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Lastdrager, Boris. "Numerical time integration on sparse grids." [S.l. : Amsterdam : s.n.] ; Universiteit van Amsterdam [Host], 2002. http://dare.uva.nl/document/64526.
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Marshall, Gillian Fiona. "Resistive grids for robot path-planning." Thesis, University of Oxford, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.317916.
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Johnson, Anne. "Parallelising implicit methods on unstructured grids." Thesis, University of Oxford, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.320231.
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Jackson, Gary Lee II. "Parallel computing with P2P desktop grids." Thesis, University of Maryland, College Park, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=3711637.
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Tightly-coupled parallel computing is an important tool for problem solving. Structured peer-to-peer network overlays are failure-tolerant and have a low administrative burden. This work seeks to unite the two.
First, I present a completely decentralized algorithm for parallel job scheduling and load balancing in distributed peer-to-peer environments. This algorithm is useful for meta-scheduling across known clusters and scheduling on desktop grids. To accomplish this, I build on previous work to route jobs to appropriate resources then use the new algorithm to start parallel jobs and balance load across the grid. I also discuss what constitutes useful clusterings for this algorithm as well as inherent scaling limitations. Ultimately, I show that my algorithm performs comparably to one using centralized load balancing with global up-to-date information. The principal contribution of this work is that the parallel job scheduling is completely decentralized, which is not featured in previous work, and enables reliable ad hoc sharing of distributed resources to run parallel computations.
Second, I show how clusters of computers can be found dynamically by using an existing latency prediction technique coupled with a new refinement algorithm. Several latency prediction techniques are compared experimentally. One, based on a tree metric space embedding, is found to be superior to the others. Nevertheless, I show that it is not quite accurate enough. To solve this problem, I present a refinement algorithm for producing quality clusters while still maintaining bounds for the amount of information any given node must store about other nodes. I show that clusters derived this way have scheduler performance comparable to those chosen statically with global knowledge.
Lastly, I discuss previously undiscovered under-specifications in the Content Addressable Network (CAN) structured peer to peer system. In high-churn situations, the CAN allows stale information and changes to the overlay structure to create routing problems. I show solutions to these two problems, as well as discuss other issues that may also disrupt a CAN.
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Franck, Johannes [Verfasser]. "Smart Grids und Datenschutz / Johannes Franck." Frankfurt : Peter Lang GmbH, Internationaler Verlag der Wissenschaften, 2015. http://d-nb.info/1081321997/34.
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Harrysson, Mattias. "Fault Location Algorithms in Transmission Grids." Thesis, Högskolan i Halmstad, Sektionen för ekonomi och teknik (SET), 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:hh:diva-26314.
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The rapid growth of the electric power system has in recent decades resulted in an increase of the number of transmission lines and total power outage in Norway. The challenge of a fast growing electrical grid has also resulted in huge increases of overhead lines and their total length. These lines are experiencing faults due to various reasons that cause major disruptions and operating costs of the transmission system operator (TSO). Thus, it’s important that the location of faults is either known or can be estimated with reasonably high accuracy. This allows the grid owner to save money and time for inspection and repair, as well as to provide a better service due to the possibility of faster restoration of power supply and avoiding blackouts. Fault detection and classification on transmission lines are important tasks in order to protect the electrical power system. In recent years, the power system has become more complicated under competitive and deregulated environments and a fast fault location technique is needed to maintain security and supply in the grid. This thesis compares and evaluates different methods for classification of fault type and calculation of conventional one-side and two-side based fault location algorithms for distance to fault estimation. Different algorithm has been implemented, tested and verified to create a greater understanding of determinants facts that affect distance to faults algorithm’s accuracy. Implemented algorithm has been tested on the data generated from a number of simulations in Simulink for a verification process in implemented algorithms accuracy. Two types of fault cases have also been simulated and compared for known distance to fault estimation.
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Pourmahnaei, Seyed Mostafa. "The production of oriented polymeric grids." Thesis, University of Bradford, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.254399.
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Nicholson, Caitriana Mairi Macleod. "File management for HEP data grids." Thesis, University of Glasgow, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.425158.
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Townend, Paul Michael. "Topology-aware fault tolerance in grids." Thesis, University of Leeds, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.432648.
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Björk, Erik, and Viktor Åkerberg. "Data Acquisition Architecture for HVDC Grids." Thesis, KTH, Skolan för elektro- och systemteknik (EES), 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-200639.
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Babazadeh, Davood. "Distributed Control of HVDC Transmission Grids." Doctoral thesis, KTH, Elkraftteknik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-202753.
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Recent issues such as priority access of renewable resources recommended by European energy directives and increase the electricity trading among countries lead to new requirements on the operation and expansion of transmission grids. Since AC grid expansions are limited by legislative issues and long distance transmission capacity, there is a considerable attention drawn to application of HVDC transmission grids on top of, or in complement to, existing AC power systems. The secure operation of HVDC grids requires a hierarchical control system. In HVDC grids, the primary control action to deal with power or DC voltage deviations is communication-free and local. In addition to primary control, the higher supervisory control actions are needed to guarantee the optimal operation of HVDC grids. However, the implementation of supervisory control functions is linked to the arrangement of system operators; i.e. an individual HVDC operator (central structure) or sharing tasks among AC system operators (distributed structure). This thesis presents distributed control of an HVDC grid. To this end, three possible supervisory functions are investigated; coordination of power injection set-points, DC slack bus selection and network topology identification. In this thesis, all three functions are first studied for the central structure. For the distributed solution, two algorithms based on Alternating Direction Method of Multipliers (ADMM) and Auxiliary Problem Principle (APP) are adopted to solve the coordination of power injection. For distributed selection of DC slack bus, the choice of parameters for quantitative ranking of converters is important. These parameters should be calculated based on local measurements if distributed decision is desired. To this end, the short circuit capacity of connected AC grid and power margin of converters are considered. To estimate the short circuit capacity as one of the required selection parameters, the result shows that the recursive least square algorithm can be very efficiently used. Besides, it is possible to intelligently use a naturally occurring droop response in HVDC grids as a local measurement for this estimation algorithm. Regarding the network topology, a two-stage distributed algorithm is introduced to use the abstract information about the neighbouring substation topology to determine the grid connectivity.QC 20170306
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Wang, Sheng. "Control and protection of HVDC grids." Thesis, Cardiff University, 2016. http://orca.cf.ac.uk/99015/.
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The decarbonisation of Europe’s energy sector is a key driver for the development of integrated HVDC networks or DC grids. A multi-terminal HVDC grid will enable a more reliable power transfer from offshore wind farms and will facilitate the cross-border exchange of energy between different countries. However, the widespread deployment of DC grids is prevented by technical challenges, including the control and protection of DC grids. In order to close the gap, this thesis aims to contribute to three aspects (1): developing a control method for DC grids operation; (2): developing a method for optimising wind power delivery using DC grids; (3): developing a protection method for fast DC fault current interruption. The control of a DC grid demands the regulation of DC voltage and hence keeps the power into and out from the DC grid balanced. It is also important to keep the accuracy of regulating the converter DC current. In this thesis, the Autonomous Converter Control (ACC) is developed to meet this requirement. With this method, alternative droop control characteristics can be used for individual converters to share the responsibility of regulation of DC voltage while precisely controlling the converter DC current. The control algorithms of alterative droop characteristics are developed and interactions of different control characteristics are analysed. Furthermore, the potential risk of having multiple cross-over in control characteristics is uncovered. The method for designing droop characteristics is provided to avoid the multiple cross-over. The ACC is demonstrated on different simulation platforms including the PSCAD/EMTDC and a real-time hardware 4-terminal HVDC test rig. It is found that the proper use of alternative droop characteristics can achieve better current control performance. The adverse impact of having multiple cross-over in control characteristics is also studied using both simulation platforms. The effect of the control of both converters and DC power flow controllers (DC-PFCs) on DC power flow in steady state is also investigated. A method for re-dispatching control orders to optimise the wind power delivery is developed. Case studies are undertaken and it is found that both the DC line power loss and wind power curtailment can be reduced by redispatching the control orders of converters and DC-PFCs. The protection of a DC grid demands a very fast speed for fault current interruption. Conventional methods proposed for HVDC grid protection take delays of several milliseconds to discriminate a faulted circuit to healthy circuits and then allow the DC circuit breakers (DC-CBs) to open at the faulted circuits. The fault current will keep rising during Control and Protection of HVDC Grids iv the delayed time caused by fault discrimination. The Open Grid protection method is thus developed to interrupt fault current before fault discrimination. With this method, multiple DC-CBs open to interrupt the fault current based on local measurements of voltage (and current) and the DC-CBs on healthy circuits will reclose to achieve discrimination afterwards. This will reduce the delay for fault current interruption and hence the fault current can be interrupted with a much smaller magnitude. The developed Open Grid method is tested via simulation models developed in PSCAD/EMTDC. The results show that the Open Grid can detect very quickly and discriminate various faults under different fault conditions in a meshed HVDC grid.
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Bianchi, Adam, and Gabriel Nylander. "Operation and Control of HVDC Grids." Thesis, KTH, Hållbar utveckling, miljövetenskap och teknik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-229460.
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Meshed high-voltage direct current grids are becoming an increasingly important technology for integrating renewable energies into the power system. To control the grids in the best possible way, optimal converter and grid control strategies are needed. This project studies how a four-terminal high-voltage direct current grid is operated and controlled by implementing different grid and converter control strategies. The grid control strategies examined are centralized voltage control and distributed voltage control with and without deadband. Simulations are made in the software PSCAD. Different fault types on the grid are studied to investigate how the power flow and voltage level are affected. An optimal value for both the deadband width and droop constant has been identified. Moreover, the results indicate that centralized droop control is not a suitable grid control strategy, whereas distributed voltage control with and without deadband are. The fault study indicates no differences between distributed voltage control with and without deadband. The power flow and voltage levels are identical for all fault types.Högspända likströmsnät spelar en allt större roll med att integrera förnyelsebar energi i våra elnät. För att styra dessa nät på bästa möjliga sätt krävs optimala omvandlar- och nätkontrollstrategier. I detta projekt studeras hur ett fyrterminalt högspänt likströmsnät kan styras och drivas genom att implementera olika omvandlar- och nätkontrollstrategier. De nätkontrollstrategier som studerats är centraliserad spänningskontroll och distribuerad spänningskontroll med och utan ett spänningsintervall. Alla simuleringar har utförts i programmet PSCAD. Olika fel i nätet har även studerats för att undersöka hur effektflödet och spänningsnivån påverkas. Ett optimalt värde på både spänningsintervallet och droop konstanten har identifierats. Dessutom har resultat som indikerar att centraliserad spänningskontroll inte är en lämplig nätkontrollstrategi erhållits, medan distribuerad spänningskontroll med och utan spänningsintervall är det. Felsimuleringarna påvisar ingen skillnad mellan distribuerad spänningskontroll med och utan spänningsintervall. Effektflödet och spänningsnivån är identiska för alla fel.
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Omati, Marcelo Leite Viana. "Otimização em grids em N estágios." reponame:Repositório Institucional da UnB, 2012. http://repositorio.unb.br/handle/10482/12542.
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Dissertação (mestrado)—Universidade de Brasília, Departamento de Economia, 2012.Submitted by Alaíde Gonçalves dos Santos (alaide@unb.br) on 2013-03-20T12:06:51Z No. of bitstreams: 1 2012_MarceloLeiteVianaOmati.pdf: 1057393 bytes, checksum: f5d998bc29b171c3f8ad112ca2693702 (MD5)
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Esta dissertação versa sobre o tema da otimização de carteira em gestão integrada de ativos e passivos, Asset and Liability Management (ALM), voltada para as Entidades Fechadas de Previdência Complementar (EFPC). O problema de pesquisa edificou-se em fazer outra forma de otimização para determinar a melhor alocação para investimentos dos recursos garantidores de plano de benefícios. Para tanto, estabelece como objetivo geral a comparação entre duas formas de otimização com a mesma função objetivo, sujeita a um conjunto de restrições, nos diversos segmentos de investimentos das EFPC; e como objetivos específicos: a) realizar revisão histórica sobre otimização; b) conceituar e classificar as classes de ativos de uma EFPC e revisar seus os aspectos gerais; c) conceituar o ALM sob a perspectiva do gerenciamento estratégico de uma EFPC ou EAPC d)apresentar formas de otimização de funções; e e) apresentar os resultado das comparações das duas formas de otimização. Neste recorte, foi possível confirmar as vantagens da otimização em grids em n estágios sobre a programação por metas. _______________________________________________________________________________________ ABSTRACT
This dissertation deals with the issue of portfolio optimization in integrated management of assets and liabilities, Asset and Liability Management (ALM), focused on the Closed Pension Fund Entities (CVET). The research problem is built on making another form of optimization to determine the best allocation of resources for investment guarantor of benefit plan. To do so, establishes as general objective comparison between two forms of optimization with the same objective function, subject to a set of constraints, investments in various segments of CVET, and specific objectives: a) conduct historical review of optimization, b) conceptualize and classify asset classes and a CVET revise their general aspects; c) conceptualize the ALM from the perspective of strategic management of an OVET CVET or d) provide forms of optimization functions, and e) present the results of comparisons of two forms of optimization. In this cut, it was possible to confirm the benefits of optimization in grids in n stages on the goal programming (shape optimization).