• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 87
  • 59
  • 26
  • 17
  • 10
  • 2
  • 1
  • 1
  • 1
  • Tagged with
  • 241
  • 241
  • 60
  • 54
  • 48
  • 39
  • 39
  • 29
  • 28
  • 24
  • 22
  • 19
  • 19
  • 19
  • 19
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
31

Stability of Impulsive Switched Systems in Two Measures

Turnbull, Benjamin Kindred January 2010 (has links)
This thesis introduces the notion of using stability analysis in terms of two measures for impulsive switched systems. Impulsive switched systems are defined in the context of hybrid system theory and the motivation for the study of these systems is presented. The motivation for studying stability in two measures is also given, along with the definitions of stability, uniform stability, and uniform asymptotic stability in one and two measures. The results presented are a sets of sufficient stability criteria for linear and nonlinear systems. For autonomous linear systems, there are criteria for stability and asymptotic stability using a particular family of choices for the two measures. There is an additional stronger set of criteria for asymptotic stability using one measure, for comparison. There is also a proposed method for finding the asymptotic stability of a non-autonomous system in one measure. The method for extending these criteria to linearized systems is also presented, along with stability criteria for such systems. The criteria for nonlinear systems cover stability, uniform stability, and uniform asymptotic stability, considering state-based and time-based switching rules in different ways. The sufficient stability criteria that were found were used to solve four instructive examples. These examples show how the criteria are applied, how they compare, and what the shortcomings are in certain situations. It was found that the method of using two measures produced stricter stability requirements than a similar method for one measure. It was still found to be a useful result that could be applied to the stability analysis of an actual impulsive switched system.
32

Stability of Impulsive Switched Systems in Two Measures

Turnbull, Benjamin Kindred January 2010 (has links)
This thesis introduces the notion of using stability analysis in terms of two measures for impulsive switched systems. Impulsive switched systems are defined in the context of hybrid system theory and the motivation for the study of these systems is presented. The motivation for studying stability in two measures is also given, along with the definitions of stability, uniform stability, and uniform asymptotic stability in one and two measures. The results presented are a sets of sufficient stability criteria for linear and nonlinear systems. For autonomous linear systems, there are criteria for stability and asymptotic stability using a particular family of choices for the two measures. There is an additional stronger set of criteria for asymptotic stability using one measure, for comparison. There is also a proposed method for finding the asymptotic stability of a non-autonomous system in one measure. The method for extending these criteria to linearized systems is also presented, along with stability criteria for such systems. The criteria for nonlinear systems cover stability, uniform stability, and uniform asymptotic stability, considering state-based and time-based switching rules in different ways. The sufficient stability criteria that were found were used to solve four instructive examples. These examples show how the criteria are applied, how they compare, and what the shortcomings are in certain situations. It was found that the method of using two measures produced stricter stability requirements than a similar method for one measure. It was still found to be a useful result that could be applied to the stability analysis of an actual impulsive switched system.
33

Hybrid Tag Recommendation in Collaborative Tagging Systems

Lipczak, Marek 15 March 2012 (has links)
The simplicity and flexibility of tagging allows users to collaboratively create large, loosely structured repositories of Web resources. One of its main drawbacks is the need for manual formulation of tags for each posted resource. This task can be eased by a tag recommendation system, the objective of which is to propose a set of tags for a given resource, user pair. Tag recommendation is an interesting and well-defined practical problem. Its main features are constant interaction with users and availability of large amounts of tagged data. Given the opportunities (e.g., rich user feedback) and limitations (e.g., real-time response) of the tag recommendation setting, we defined six requirements for a practically useful tag recommendation system. We present a conceptual design and system architecture of a hybrid tag recommendation system, which meets all these requirements. The system utilizes the strengths of various tag sources (e.g., resource content and user profiles) and the relations between concepts captured in tag co-occurrence graphs mined from collaborative actions of users. The architecture of the proposed system is based on a text indexing engine, which allows the system to deal with large datasets in real time, while constantly adapting its models to newly added posts. The effectiveness and efficiency of the system was evaluated for six datasets representing a broad range of collaborative tagging systems. The experiments confirmed the high quality of results and practical usability of the system. In a comparative study the system outperformed a state-of-the-art algorithm based on tensor factorization for the most representative datasets applicable to both methods. The experiments on the characteristics of tagging data and the performance of the system allowed us to find answers to important research questions adapted from the general area of recommender systems. We confirmed the importance of infrequently used tags in the recommendation process and proposed solutions to overcome the cold start problem in tag recommendation. We demonstrated that a parameter tuning approach makes a hybrid tag recommendation system adaptable to various datasets. We also revealed the importance of the utilization of a feedback loop in the tag recommendation process.
34

HIERARCHICAL HYBRID-MODEL BASED DESIGN, VERIFICATION, SIMULATION, AND SYNTHESIS OF MISSION CONTROL FOR AUTONOMOUS UNDERWATER VEHICLES

Bhattacharyya, Siddhartha 01 January 2005 (has links)
The objective of modeling, verification, and synthesis of hierarchical hybrid mission control for underwater vehicle is to (i) propose a hierarchical architecture for mission control for an autonomous system, (ii) develop extended hybrid state machine models for the mission control, (iii) use these models to verify for logical correctness, (iv) check the feasibility of a simulation software to model the mission executed by an autonomous underwater vehicle (AUV) (v) perform synthesis of high-level mission coordinators for coordinating lower-level mission controllers in accordance with the given mission, and (vi) suggest further design changes for improvement. The dissertation describes a hierarchical architecture in which mission level controllers based on hybrid systems theory have been, and are being developed using a hybrid systems design tool that allows graphical design, iterative redesign, and code generation for rapid deployment onto the target platform. The goal is to support current and future autonomous underwater vehicle (AUV) programs to meet evolving requirements and capabilities. While the tool facilitates rapid redesign and deployment, it is crucial to include safety and performance verification into each step of the (re)design process. To this end, the modeling of the hierarchical hybrid mission controller is formalized to facilitate the use of available tools and newly developed methods for formal verification of safety and performance specifications. A hierarchical hybrid architecture for mission control of autonomous systems with application to AUVs is proposed and a theoretical framework for the models that make up the architecture is outlined. An underwater vehicle like any other autonomous system is a hybrid system, as the dynamics of the vehicle as well as its vehicle level control is continuous whereas the mission level control is discrete, making the overall system a hybrid system i.e., one possessing both continuous and discrete states. The hybrid state machine models of the mission controller modules is derived from their implementation done using TEJA, a software for representing hybrid systems with support for auto code generation. The verification of their logical correctness properties has been done using UPPAAL, a software tool for verification of timed automata a special kind of hybrid system. A Teja to Uppaal converter, called dem2xml, has been created at Applied Reserarch Lab that converts a hybrid (timed) autonomous system description in Teja to an Uppaal system description. Verification work involved developing abstract models for the lower level vehicle controllers with which the mission controller modules interact and follow a hierarchical approach: Assuming the correctness of level-zero or vehicle controllers, we establish the correctness of level-one mission controller modules, and then the correctness of level-two modules, etc. The goal of verification is to show that any valid meaning for a mission formalized in our research verifies the safe and correct execution of actions. Simulation of the sequence of actions executed for each of the operations give a better view of the combined working of the mission coordinators and the low level controllers. So we next looked into the feasibility of simulating the operations executed during a mission. A Perl program has been developed to convert the UPPAAL files in .xml format to OpenGL graphic files. The graphic files simulate the steps involved in the execution of a sequence of operations executed by an AUV. The highest level coordinators send mission orders to be executed by the lower level controllers. So a more generalized design of the highest level controllers would help to incorporate the execution of a variety of missions for a vast field of applications. Initially, we consider manually synthesized mission coordinator modules. Later we design automated synthesis of coordinators. This method synthesizes mission coordinators which coordinate the lower level controllers for the execution of the missions ordered and can be used for any autonomous system.
35

Εξομοίωση υβριδικού συστήματος παραγωγής ενέργειας συνδεομένου σε δίκτυο υψηλής τάσης

Σφακιανάκης, Κωνσταντίνος 22 December 2009 (has links)
Στην εργασία αυτή παρουσιάζονται κάποια στοιχεία για τα ΑΠΕ και τα χαρακτηριστικά τους αλλά δίνεται περισσότερη έμφαση στο ελληνικό σύστημα παραγωγής ηλεκτρικής ενέργειας (στους σταθμούς παραγωγής είτε ιδιωτικούς είτε της ΔΕΗ) τόσο από συμβατικές όσο και από ΑΠΕ. Στη συνέχεια, αναφέρονται εκτενέστερα οι πηγές ενέργειας που θα χρησιμοποιηθούν στις εξομοιώσεις, δηλαδή η ηλιακή ενέργεια, η αιολική ενέργεια και η τεχνολογία του υδρογόνου (που περιλαμβάνει κελιά καυσίμου, ηλεκτρόλυση του νερού για την παραγωγή υδρογόνου και την αποθήκευση του τελευταίου). Η μπαταρία ως αποθηκευτική μονάδα αναπτύσσεται συνοπτικά και κατόπιν αναφέρονται τα οικονομικά στοιχεία ενός συστήματος παραγωγής ηλεκτρικής ενέργειας. Το τελευταίο θεωρητικό κομμάτι είναι αφιερωμένο στο πρόγραμμα εξομοίωσης που χρησιμοποιήθηκε, το Homer, και αναλύονται λεπτομερώς τα δεδομένα που χρησιμοποιήθηκαν καθώς και οι τεχνικές λειτουργίας του. Στο τελευταίο κομμάτι της διπλωματικής εργασίας πραγματοποιούνται οι εξομοιώσεις στο Homer για ένα υβριδικό αυτόνομο σύστημα παραγωγής ηλεκτρικής ενέργειας και παρατίθονται τα αποτελέσματα αυτών με τη βοήθεια των διαγραμμάτων που παρέχει το συγκεκριμένο πρόγραμμα. Αρχικά, παρατίθονται τα δεδομένα που χρησιμοποιήθηκαν, δηλαδή η περιοχή για την οποία έγιναν οι εξομοιώσεις με τα αιολικά και τα ηλιακά δεδομένα, τα στοιχεία που χρησιμοποιήθηκαν στις εξομοιώσεις, τα είδη των ανεμογεννητριών,των φωτοβολταϊκών πλαισίων, των κελιών καυσίμου, των ηλεκτρολυτών, των μονάδων αποθήκευσης υδρογόνου, των μπαταριών, των αντιστροφέων και των γεννητριών, καθώς και τα οικονομικά στοιχεία που θέσαμε ως δεδομένα για την πραγματοποίηση των εξομοιώσεων. Οι εξομοιώσεις που πραγματοποιήθηκαν ήταν ο συνδυασμός ανά δύο όλων των παραπάνω πηγών ενέργειας και μια με όλες μαζί (δηλαδή 6 εξομοιώσεις), με σκοπό την ανεύρεση του πιο οικονομικού συνδυασμού ενός υβριδικού αυτόνομου συστήματος παραγωγής ηλεκτρικής ενέργειας για μια περιοχή κοντά στο Ηράκλειο Κρήτης που εξετάζουμε. Οι εξομοιώσεις πραγματοποιήθηκαν τόσο με την χρήση μπαταριών όσο και χωρίς την χρήση αυτών για να διαπιστωθεί κατά πόσο οι μπαταρίες επηρεάζουν ένα αυτόνομο σύστημα. Από τα αποτελέσματα των εξομοιώσεων δεν συμπεραίνεται με ακρίβεια ποια είναι η πιο συμφέρουσα καθώς αυτό εξαρτάται από τα κριτήρια που θέτει ο κάθε επενδυτής. Αυτά είναι: • Με βάση τη χρήση ή μη των μπαταριών • Με βάση τη συνολική παραγόμενη ενέργεια • Με βάση τo συνολικό κόστος της επένδυσης • Με βάση το πλεόνασμα παραγόμενης ενέργειας • Με βάση ποια συστήματα παραγωγής ενέργειας είναι υπεύθυνα για την μόλυνση του περιβάλλοντος • Με βάση την κλίση των φ/β πλαισίων, σύμφωνα με τα αποτελέσματα της ανάλυσης ευαισθησίας Οι κυριότεροι παράγοντες για την επιλογή ενός συστήματος παραγωγής ηλεκτρικής ενέργειας είναι ο οικονομικός και η εκπομπή ρύπων. Απ' τις εξομοιώσεις συμπεραίνεται ότι η πιο οικονομική επιλογή υβριδικού συστήματος παραγωγής ηλεκτρικής ενέργειας είναι ο συνδυασμός των πηγών γεννήτριας πετρελαίου – φωτοβολταικής συστοιχίας και ο συνδυασμός των πηγών φωτοβολταικής συστοιχίας-ανεμογεννήτριας είναι η πιο φιλική επιλογή προς το περιβάλλον μιας και δεν παράγει καθόλου ρύπους. Ανάμεσα στις δύο παραπάνω επιλογές, η πιο συμφέρουσα είναι η δεύτερη μιας και ως προς οικονομικής άποψης δεν είναι ακριβή (είναι η τρίτη πιο φθηνή), ενώ ο συνδυασμός γεννήτριας πετρελαίου – φωτοβολταικής συστοιχίας παράγει αρκετά υψηλό ποσοστό ρυπών (είναι η δεύτερη). Στο τέλος, πραγματοποιήθηκαν άλλες 3 εξομοιώσεις με το συνδυασμό της τεχνολογίας του υδρογόνου με τις υπόλοιπες ανανεώσιμες πηγές ενέργειας, μια κάθε φορά και όλες μαζί στο τέλος, με τις πιθανές μελλοντικές τιμές των στοιχείων της πρώτης (προβλέψεις για το 2020). Σύμφωνα λοιπόν με τα αποτελέσματα των εξομοιώσεων χρησιμοποιώντας τις μελλοντικές τιμές για την τεχνολογία του υδρογόνου, το μέλλον ανήκει σ αυτή την τεχνολογία και ο συνδυασμός της τόσο με την αιολική όσο και με την ηλιακή είναι μια οικονομική και συνάμα αποδοτική λύση χωρίς να μολύνουμε καθόλου το περιβάλλον. / In this project is presented things about renewable energy sources and their characteristics but is given more importance in the GPS, GREEK POWER SYSTEM, (either private power stations or NATIONAL ELECTRICAL COMPANY) by conventional sources and by Renewable Energy Sources. Afterwards, it is reported, extensively, to the energy sources that is used in simulations, in other words the solar energy, the wind energy and the hydrogen technology (that includes fuel cells, electrolyze of water for hydrogen production and the storage of the last one). It is developed the battery as stocking unit and then is reported to the economic elements of a power system. The last theoretical part is dedicated to the simulation program, HOMER and is analyzed its components and its techniques. In the last part of project, is simulated autonomous power systems and is commented their results, being helped by the diagrams that HOMER exports. Initially, it is mentioned the data that were used, that is to say the area with its solar and wind data, the elements that were used in the simulations, the types of wind generators, of photovoltaic frames, of fuel cells, of electrolytes, of hydrogen storages, of batteries, of inverter and of diesel generators, as well as the economic elements of simulations. The simulations contained the combination of the above sources of energy ( 6 simulations) aiming the recovery of the most lucrative combination of hybrid autonomous power system for an area close to Heraklion of Crete that was examined. The simulations were realized with the use of batteries and without them in order to understand their influences in autonomous power systems. The results of the simulations cannot lead, precisely, to a lucrative choice about a power system, something that depends on investor’s criteria. These are: • Based on the use or not of batteries • Based on the total production of energy • Based on the excess electricity • Based on the power system responsible for the pollution of the environment • Based on the photovoltaic tilt , according to the sensitivity results The main factors το choose an electric power system are the economic and the emission of pollutants. According to simulation results, the most economic choice of hybrid system is the combination of diesel generator - photovoltaic frames and the combination of photovoltaic frames-wind generator are the friendliest choice to the environment. Between the above choices, the second one is the most aproppriate due to its low cost, while the first one produces high percentage of pollutants. Finally, we realized 3 more simulations combined the technology of hydrogen, using possible future prices of its elements (forecasts for 2020), with the renewable energy sources. According to these results, the future belongs to hydrogen technology and its combination with the solar or the wind energy can create a cheap, efficient and without pollutants choice.
36

Reachability problems for systems with linear dynamics

Chen, Shang January 2016 (has links)
This thesis deals with reachability and freeness problems for systems with linear dynamics, including hybrid systems and matrix semigroups. Hybrid systems are a type of dynamical system that exhibit both continuous and discrete dynamic behaviour. Thus they are particularly useful in modelling practical real world systems which can both flow (continuous behaviour) and jump (discrete behaviour). Decision questions for matrix semigroups have attracted a great deal of attention in both the Mathematics and Theoretical Computer Science communities. They can also be used to model applications with only discrete components. For a computational model, the reachability problem asks whether we can reach a target point starting from an initial point, which is a natural question both in theoretical study and for real-world applications. By studying this problem and its variations, we shall prove in a formal mathematical sense that many problems are intractable or even unsolvable. Thus we know when such a problem appears in other areas like Biology, Physics or Chemistry, either the problem itself needs to be simplified, or it should by studied by approximation. In this thesis we concentrate on a specific hybrid system model, called an HPCD, and its variations. The objective of studying this model is twofold: to obtain the most expressive system for which reachability is algorithmically solvable and to explore the simplest system for which it is impossible to solve. For the solvable sub-cases, we shall also study whether reachability is in some sense easy or hard by determining which complexity classes the problem belongs to, such as P, NP(-hard) and PSPACE(-hard). Some undecidable results for matrix semigroups are also shown, which both strengthen our knowledge of the structure of matrix semigroups, and lead to some undecidability results for other models.
37

Vers de nouveaux matériaux hybrides basés sur le graphène épitaxié : contrôle de la formation de défauts et leur rôle dans l’intercalation / Toward novel hybrid materials based on epitaxial graphene : controlling the formation of defects and using them for intercalation

Kimouche, Amina 20 November 2013 (has links)
Le graphène épitaxié sur des substrats métalliques est un modèle prometteur pour le développement de nouveaux systèmes hybrides, dans lesquelles les effets d'interface peuvent être exploités pour concevoir de nouvelles propriétés. L'insertion d'espèces entre le graphène et son substrat, une opération connues sous le nom d'-«intercalation», est une approche très puissante à cet égard. Avec l'aide des outils de la physique des surfaces, nous avons étudié trois systèmes graphène/métal, dont deux sont des systèmes hybrides intercalés, et l'autre est un candidat pour un tel système : (i) le graphène/Ir(111) intercalé avec un oxyde ultra-mince, (ii) graphène/Ir(111) intercalé avec des couches sub-atomiques du cobalt et (iii) de graphène sur Re(0001). Nous avons montré que certains défauts, en particulier les ridules (délamination du graphène de son substrat) et d'autres régions courbées du graphène, jouent un rôle crucial, non anticipé, dans le processus d'intercalation. Nous avons également observé que l'intercalation se déroule d'une manière nettement différente sous ultravide et à pression atmosphérique. Dans le premier système, des espèces contenant de l'oxygène entrent à l'extrémité ouverte des ridules et diffusent au long de ces ridules pour former des nano-rubans d'oxyde. Ces rubans modifient le dopage électronique du graphène, ce qui se traduit également par des changements substantiels dans la réponse optique inélastique (Raman) du graphène. Dans le second système, l'efficacité de l'intercalation est apparue dépendante de l'interaction graphène-métal, laquelle varie entre les domaines de graphène orientés différemment sur_(111). Dans ce système, les sites d'entrée pour les espèces intercalées, des régions courbées dans le graphène, ont pu être identifiés grâce à l'observation in_operando (en cours de croissance) du processus. Enfin, la croissance de graphène dans un troisième système (graphène/Re(0001)), a été étudiée afin de permettre le développement de futurs systèmes graphène/Re hybrides supraconducteurs. Dans ce système, nous avons proposé deux voies de croissance, l'une étant basé sur un processus de croissance en surface d'un monocristal massif de Re(0001), l'autre reposant sur la ségrégation en surface, activée thermiquement, du carbone dissout à haute température dans des films minces de Re sur saphir. / Epitaxial graphene grown on metal substrates is a promising platform for developing new hybrid systems, in which interface effects can be exploited to engineer novel properties. The insertion of foreign species between graphene and its substrate, referred to as “intercalation”, was shown very powerful in this respect. With the help of surface science tools, we have studied three graphene/metal systems, two of which are intercalated hybrid systems, and the other is a candidate for such a system: (i) graphene/Ir(111) intercalated with an ultrathin oxide, (ii) graphene/Ir(111) intercalated with cobalt (sub) atomic layers, and (iii) graphene on Re(0001). We found that some defects, especially wrinkles (linear delaminations of graphene from its substrate) and other curve graphene regions, play a crucial, yet unanticipated role in the intercalation process. We also found that the intercalation proceeds in a markedly different fashion under ultra-high vacuum and under atmospheric pressure. In the first system, oxygen-containing species were found to intercalate via the open end of wrinkles, to diffuse along then, and to form oxide nanoribbons along wrinkles accordingly. These ribbons modify the charge density of graphene, which also translates into substantial changes in the inelastic (Raman) optical response of graphene. In the second system, the efficiency of intercalation proved to be dependent on the graphene-metal interaction, which varies between differently oriented graphene domains on Ir(111). In this systems the entry sites for intercalated species could be identified, thanks to in operando observation of the process, as curved regions in graphene. Finally, graphene growth in a third system, graphene on Re(0001), was addressed in order to enable the future development of graphene/Re superconducting hybrids. In this system, we proposed two growth routes, one being a surface-confined process, on bulk single-crystal Re(0001), and the other being a temperature-induced segregation of carbon dissolved at high temperature in thin Re(0001) films on sapphire.
38

Ferramenta computacional para geraÃÃo distribuÃda a partir de sistemas hÃbridos renovÃveis / Computational tool to distributed generation of hybrid systems for renewable energy

Rebeca Catunda Pereira Machado 29 April 2013 (has links)
CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior / A presente dissertaÃÃo apresenta o desenvolvimento de uma ferramenta computacional de auxÃlio ao planejamento energÃtico chamada de GDHER (GeraÃÃo DistribuÃda de Sistemas HÃbridos de Energias RenovÃveis) A ferramenta pode ser utilizada sem custo uma vez que foi desenvolvido atravÃs do Calc um programa de planilha eletrÃnica semelhante ao Excel que faz parte de um pacote de vÃrios aplicativos livres da Broffice ApÃs identificar algumas limitaÃÃes dos principais softwares disponÃveis no mercado foi desenvolvida uma nova ferramenta adaptada à realidade brasileira principalmente voltada Ãs Ãreas rurais e isoladas que utiliza o portuguÃs como idioma e possui uma interface bastante amigÃvel facilitando sua compreensÃo e operaÃÃo pelo usuÃrio A ferramenta permite o usuÃrio fazer dimensionamento de algumas modalidades de geraÃÃo de energia elÃtrica a partir de tecnologias limpas como a solar fotovoltaica aerogeradores e biodigestores e atravÃs de uma anÃlise financeira esses sistemas sÃo comparados com a extensÃo da rede de energia elÃtrica permitindo que o usuÃrio obtenha um prognÃstico de viabilidade A ferramenta tambÃm permite fazer o dimensionamento e a anÃlise financeira de configuraÃÃes de sistemas hÃbridos como fotovoltaico-eÃlico fotovoltaico-biodigestor e biodigestor-eÃlico a fim de encontrar a configuraÃÃo Ãtima para o projeto Para validaÃÃo da ferramenta foi feito um estudo de caso e a partir da anÃlise financeira e anÃlise de sensibilidade a modalidade de fornecimento de energia elÃtrica mais viÃvel para os sistemas individualizados sÃo os biodigestores em seguida sÃo os mÃdulos fotovoltaicos e a rede elÃtrica e por Ãltimo sÃo os aerogeradores De acordo com a anÃlise financeira dos sistemas hÃbridos a configuraÃÃo mais lucrativo à 75% da demanda sendo atendida por biodigestores e 25% por mÃdulos fotovoltaicos Os resultados sÃo apresentados atravÃs de tabelas e grÃficos para melhor compreensÃo do usuÃrio Com todas essas caracterÃsticas a ferramenta proposta permite dimensionar sistemas com mÃxima eficiÃncia e menor custo obtendo assim sistemas mais adequados e confiÃveis tanto do ponto de vista tÃcnico como financeiro / This work presents the development of a computational tool to aid in energy planning called GDHER (Distributed Generation of Hybrid Systems for Renewable Energy) The program can be used without cost since it was developed through the Calc a program of electronic spreadsheet similar to Excel which is part of a package of several free applications of Broffice After identifying some limitations of the main software available on the market we obtained a new tool adapted to the Brazilian reality especially to rural and isolated areas which uses the portuguese as language and has an interface very user friendly facilitating the understanding and operation of the program by the user The program allows the user to do the scaling of some methods of electricity generation from clean technologies such as solar photovoltaics wind turbines and biodigesters and through a financial analysis these systems are compared with the extension of the network of electric energy allowing the user get a prognosis of viability The tool also allows the user to do the scaling and the financial analysis of some configurations of hybrid systems like photovoltaic-wind photovoltaic-digester and wind-digester in order to find the optimal configuration for the project For validation of the program it was done a case study and from the financial analysis and sensitivity analysis the modality of electric energy supply more viable for individualized systems are the digesters then are the photovoltaic modules and the electrical network and finally are the wind turbines According to the financial analysis of hybrid systems the configuration more profitable is 75% of demand being served by biodigesters and 25% by photovoltaic modules The results are presented using tables and graphs for better understanding of the user With all these features the tool allows to scale systems with maximum efficiency and lower costs thereby obtaining more appropriate and reliable systems both from the technical point of view as financial
39

Gestion, optimisation et conversion des énergies pour habitat autonome

Dahmane, Menad 24 November 2015 (has links)
Ce mémoire présente le travail de recherche qui consiste à développer et à mettre au point un dispositif capable d'alimenter en électricité un habitat isolé et le rendre autonome en utilisant des sources d'énergie renouvelable. Le système multi-sources considéré comprend une éolienne et des panneaux photovoltaïques comme sources principales, des batteries de type Lithium-Ion pour le stockage ainsi qu'un générateur Diesel comme source de secours. Dans le but d'apporter une contribution face aux problèmes de gestion d'énergie pour systèmes hybride et la commande des chaînes de conversion d'énergie renouvelable, nous proposons dans ce travail une stratégie de gestion des flux de puissances basée sur la prédiction des potentiels énergétiques sur un horizon très-court pour générer des références optimales pour assurer l'autonomie de la charge. Pour cela, nous présentons dans un premier temps, un dimensionnement des différents modules du système multi-sources ainsi que la modélisation de chacune des chaînes de conversion d'énergie. Par la suite, cette modélisation nous a permis de développer des lois de commande en utilisant les techniques LMI pour le placement de pôles dans le but d'augmenter les performances transitoires du suivi de références. L'algorithme de gestion proposé ainsi que les stratégies de commande développées pour le suivi de références et la maximisation de puissance ont été validées en simulation en utilisant des données issues de mesures réelles. Après avoir obtenu des résultats en simulation avec Matlab/Simulink, nous avons validé ces travaux expérimentalement en réalisant des tests sur la plateforme multi-sources équipée de cartes dSPACE du laboratoire / This dissertation presents a research project that consists of the development of a device that is able to supply an isolated house with electricity and to make it autonomous by using renewable energy sources. The multi-source system considered in this thesis includes a wind turbine and photovoltaic panels as main sources, Lithium-Ion batteries for storage and Diesel generator as emergency source. In order to make a contribution considering problems of energy management for hybrid systems as well as problems in controlling energy conversion chains, we are suggesting a power flow management strategy which is based on the prediction of the potential energy available on the veryshort-term. That strategy aims at generating optimal references in order to insure the electrical autonomy of the house. For this, we present firstly, a sizing and modelingof the different modules of the multi-source system. This modelling allowed us subsequently to develop a static and dynamic state feedback control strategies by using LMI techniques for pole placement in order to increase the transition performancesfor reference monitoring. The proposed management algorithm as well as the developed control strategies for tracking and maximizing power is validated in simulation using data obtained through real measurements. After having results in simulationusing Matlab/Simulink, we have validated them experimentally by conducting tests via a multi-source platform equipped with dSPACE cards of our laboratory
40

Computational Approaches to State Estimation of Periodic Signals and Control of Switched Systems

Elaghoury, Hassan January 2022 (has links)
In this thesis, two separate problems are examines. First, sinusoidal signals are quite prevalent in practical applications. For example, any machine driven by a rotary shaft will exhibit periodic behaviour. For this reason, the estimation of sinusoidal parameters is studied extensively in the literature. Often in practical applications, there are unmodeled disturbances to the system, and the incoming measurements are noisy. Thus, estimation of the parameters of a sinusoidal signal in real-time for these conditions is of interest, calling for the use of a filter-based approach such as the Extended Kalman Filter. Considering the sinusoidal signal in its complex form, a novel approach is proposed resulting in a complex-valued filter. The resulting complex Extended Kalman Filter’s performance is evaluated in various test environments and is compared to standard approaches to the estimation problem using a Discrete Fourier Transform and standard Extended Kalman Filter. Results show that the complex Extended Kalman Filter outperforms the standard approaches in some cases in both accuracy and convergence rate. Second, research on hybrid systems has seen a large growth in interest in recent years. This is largely due to the increase of natural systems where discrete mode dynamics interact with continuous state dynamics. Switched systems are a subclass of hybrid systems that restrict their definition to continuous dynamic systems that interact with dis- crete switching events. Controller synthesis for such systems is no trivial task. Given the current trend in Artificial Intelligence and Machine Learning approaches, Dynamic Programming is explored as a means to approximate optimal control policies for switched systems. Discussions of discretization of the system’s state space are presented, followed by a high-level overview of an algorithm that leverages Dynamic Programming to find the approximated optimal control policies. Finally, the algorithm is applied to several examples to demonstrate its effectiveness. / Thesis / Master of Applied Science (MASc)

Page generated in 0.0604 seconds