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  • 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.
1

[en] ACCOUNTING CO-BENEFITS IN THE REDD+ MECHANISM / [pt] CONTABILIZANDO CO-BENEFÍCIOS DO MECANISMO DE REDD+

ALEXANDRA DE SA PEREIRA MACIEL TEIXEIRA 17 May 2021 (has links)
[pt] A integração e computação de co-benefícios da preservação de ecossistemas florestais é pré-condição para o sucesso, eficiência e sustentabilidade de longo prazo de iniciativas de REDD+. Inclusive para atingir reduções de emissões em larga escala e de forma permanente, é fundamental que as iniciativas de REDD+ promovam uma ampla gama de benefícios sociais, ambientais e de governança. Com base em uma concepção holística de integridade ambiental, o presente trabalho deseja oferecer contribuições sobre a definição de co-benefícios, sua tipificação e potenciais indicadores que podem ser utilizados para integrá-los e contabilizá-los na operacionalização de iniciativas de REDD+. / [en] The integration and accounting of co-benefits of forest ecosystem preservation is a precondition for the long-term success, efficiency, and sustainability of REDD + initiatives. Even to achieve large-scale and permanent reductions of emissions, it is critical that REDD+ initiatives promote a broad range of social, environmental and governance benefits. Based on a holistic conception of environmental integrity, the present paper offers contributions on the definition of co-benefits, their typification and potential indicators that can be used for their integration and accounting in the operationalization of REDD + initiatives.
2

CONTRIBUTION METHODOLOGIQUE A LA MODELISATION POUR LE DIMENSIONNEMENT DE MOTEURS A RELUCTANCE VARIABLE

Sauvey, Christophe 08 September 2000 (has links) (PDF)
Ce travail s'intéresse à la modélisation pour le dimensionnement de moteurs à reluctance variable. Dans une première partie, on donne notre approche du problème de dimensionnement, puis on définit les trois grands types de modèles que le concepteur en électrotechnique sera amené à rencontrer. Enfin, on présente différentes méthodes de conception de moteurs à reluctance variable qui ont été mises en œuvre. Dans une seconde partie, nous présentons une méthodologie permettant d'intégrer des modèles semi analytiques dans un processus d'optimisation de type gradient : les boites de calcul. Nous présentons celles que nous avons créées, puis un exemple de leur application au dimensionnement d'un moteur à reluctance variable de type classique. On s'intéresse dans la troisième partie à la modélisation en vue du dimensionnement d'un moteur à reluctance variable à motifs. Après une présentation de la structure d'un tel moteur, on en présente un modèle analytique, puis un modèle numérique, modulaires. Enfin, on s'appuie sur la complémentarité qui existe entre ces deux modèles pour proposer une méthode de dimensionnement.
3

Amélioration de la sûreté de fonctionnement d’un actionneur électrique à réluctance variable / Improvement of the functional safety of a Switch Reluctance Actuator

Sarr, Abdoulaye 30 November 2018 (has links)
Le travail proposé dans cette thèse porte sur l’amélioration de l’efficacité énergétique et de la sûreté de fonctionnement de la Machine à Réluctance Variable (MRV). D’abord, nous avons présenté la commande de la MRV en modes moteur et générateur débitant sur bus continu. Pour le mode moteur, on cherche à réguler la vitesse de rotation et le couple, alors qu’en mode générateur, l’objectif de la commande est de maintenir constante la tension du bus malgré les fluctuations de la vitesse et de la charge. Une démarche itérative est proposée pour la maximisation du rendement global. Trois paramètres de réglage ont été choisis : L’angle d’amorçage (Ψ), l’angle de conduction (Θp) et le courant de référence des phases (Iref). L’efficacité de l’algorithme est évaluée à travers des simulations et des tests expérimentaux. Un rendement global maximal de 70% est atteint pour des vitesses et couples élevés. Ensuite, on s’est intéressé à la connexion de la Génératrice à Réluctance Variable (GRV) au réseau alternatif monophasé ou triphasé dans le cadre d’une application éolienne. La tension continue à la sortie de la GRV est convertie en une tension alternative par un convertisseur DC-AC. Le premier objectif est de maintenir la tension du bus continu à sa valeur nominale; le second est de contrôler la qualité du courant injecté dans le réseau. En monophasé, trois types de correcteur sont testés pour réguler le courant sinusoïdal (un correcteur PI, un correcteur Résonant et un correcteur Proportionnel-Résonant). En triphasé, une commande VQ dans le référentiel de Park est adoptée: La tension du bus continu est contrôlée à travers le courant id et la puissance réactive est contrôlée par le courant iq. Les résultats de simulation montrent qu’on obtient des courants quasi-sinusoïdaux avec un taux de distorsion harmonique inférieur à 1% aussi bien en monophasé qu’en triphasé. Enfin, pour améliorer la sûreté de fonctionnement de l’actionneur et réduire les coûts liés à l’utilisation de capteurs mécaniques, trois stratégies de commande sans capteur de position sont présentées. La première est basée sur la technique d’injection. La deuxième repose sur l’estimation du flux. La troisième s’appuie sur les observateurs adaptatifs. On trouve que la technique d’injection et la méthode basée sur la mesure du flux fonctionnent de façon complémentaire. La première est efficace en basses vitesses et ne dépend pas de la charge, la deuxième est performante en hautes vitesses et pour des charges élevées. L’observateur adaptatif proposé assure une convergence exponentielle de la position malgré le modèle analytique simplifié de l’inductance utilisé pour la synthèse. Son principal avantage réside dans sa robustesse aux variations paramétriques et au couple de charge qui est estimé. / The work proposed here focuses on the improvement of the energy efficiency and the safety of the Switched Reluctance Machine (SRM). First, the control of the SRM in motor and generator modes is presented. In motor mode, the speed and the torque are regulated, while in generator mode, the objective is to keep constant the DC bus voltage. An iterative optimization algorithm is proposed formaximizing the global efficiency. The analysis of the electromechanical energy conversion has shown that there is an optimal combination of the control variables - turn on angle (Ψ), conduction angle (Θp) and reference current (Iref) – to maximize the efficiency. The strategy is evaluated using intensive numerical simulations and experimental validation. Thanks to the optimization, the global efficiency reaches 70% almost from half the nominal speed to the maximum speed. Then, the Switched Reluctance Generator (SRG) is used as an AC generator for a Wind Energy Conversion (WEC) application. The produced DC power is converted into AC power by means of voltage inverter and delivered to the AC grid. The first issue of the WEC control is to maintain constant the output DC voltage despite the wind speed variations and the load uncertainty. The second issue is to control the quality of the current. In single-phase AC network, three controllers are tested to regulate the AC current (PI controller, Resonant controller, Proportional-Resonant controller). In three-phase AC network, a VQ control in Park’s frame is adopted: The DC bus voltage is controlled through the direct current and the reactive power injected into the grid is controlled through the quadrature current. Simulation results show that quasi-sinusoidal currents with a harmonic distortion rate less than 1% are obtained in both cases. Finally, we address the problem of sensorless control. In fact, the control of the SRM requires that the rotor position is known. A mechanical encoder is used generally to measure the position. The elimination of this position sensor would reduce the cost and packaging requirements of the drive. Three methods to estimate the rotor position are presented. The first one named inductance-method is an active as it is based on the pulse injection technique. The second one named flux-method is a passive one as it used the current measurement. The third one is based on the state observers for the flux, position, and velocity and load torque estimation. The simulations results have shown that the inductance-based method is efficient in low speed region and the flux-based one is more efficient in high-speed region. It is also shown that, observers are exponentially convergent even when a simple analytical modelling, that neglects saturation effect, is used to design the observer.
4

[en] MEANING OF HOMEOWNERSHIP FOR THE MIDDLE CLASS IN THE MRV DISCOURSE / [pt] SIGNIFICADOS DA CASA PRÓPRIA PARA A CLASSE MÉDIA NO DISCURSO DA CONSTRUTORA MRV

FELIPE CERQUEIRA DE LACERDA 17 October 2016 (has links)
[pt] Nos últimos anos, verificou-se notável crescimento do consumo da classe média brasileira que proporcionou a essa classe maior acesso na compra da casa própria. A aquisição da casa própria constitui um sonho de consumo desse extrato social e apresenta grande conotação simbólica. A construtora MRV, líder no segmento de imóveis para a classe média, com ênfase na oferta de imóveis com o perfil de primeiro apartamento do consumidor, destaca-se por suas estratégias de comunicação e por seu discurso publicitário. Neste contexto, o presente trabalho tem por objetivo identificar os significados que a compra da casa própria assume no discurso da construtora MRV em seus canais digitais. Para tal, analisou-se um corpus de vinte vídeos produzidos pela MRV e publicados em seu canal no YouTube entre os meses de Janeiro e Novembro de 2015. A abordagem da pesquisa foi qualitativa e exploratória, com utilização de análise textual verbal e visual do corpus, bem como de técnicas de análise de conteúdo. Os vídeos foram classificados em quatro categorias temáticas, a saber: Venda de Novos Empreendimentos, Entrega das Chaves, Histórias de vida de clientes MRV e Institucionais. O resultado do estudo apontou que no discurso analisado a casa própria assume diferentes significados, como: realização, identidade, independência, segurança e pertencimento. Com base na axiologia de valores de consumo proposta pelo semioticista J.M.Floch, tais significados revelam a prevalência de valores práticos, críticos e utópicos no discurso da construtora MRV. / [en] In recent years, there has been remarkable growth of the Brazilian middle class consumption provided to this class greater access in buying a home. The acquisition of a home is a dream of consumption of this social stratum and has great symbolic connotation. MRV construction company, leader in the real estate segment for the middle class, with an emphasis on real estate supply to the first consumer flat profile, stands out for its communication strategies and their advertising discourse. In this context, this paper aims to identify the meanings that home ownership plays in the builder MRV discourse in their digital channels. To do this, we analyzed a corpus of twenty videos produced by MRV Company and published on his YouTube channel between January and November 2015. The research approach was qualitative and exploratory, using verbal and visual textual analysis of the corpus and content analysis techniques. The videos were classified into four themes, namely: Sale of New Ventures, Delivery of the Keys, Customer Life Stories MRV and Institutional. The study results showed that in the discourse examined the house itself takes on different meanings, such as: holding, identity, independence, security and belonging. Based on the axiology of consumption values proposed by J.M.Floch semiotician such meanings reveal the prevalence of practical, critical and utopian values on the MRV discourse.
5

Controlador PI FUZZY aplicado ao controle direto de potência do gerador de relutância variável de 12/8 conectado à rede elétrica

Catata, Elmer Osman Hancco January 2016 (has links)
Orientador: Prof. Dr. José Luis Azcue Puma / Dissertação (mestrado) - Universidade Federal do ABC, Programa de Pós-Graduação em Engenharia Elétrica, 2016. / Este trabalho apresenta o controle direto de potencia do gerador de relutancia variavel de 12/8 utilizando o controlador fuzzy PI auto-ajustavel e o controle vetorial do inversor conectado à rede eletrica. Inicialmente são estudados os principios de operação da maquina e a topologia do conversor eletronico de potencia que sera utilizado para aciona-lo. Usando o software de simulaçãoMatlab/Simulink é implementado o modelo da maquina de relutancia variavel utilizando as curvas caracteristicas, de corrente e torque, que foram extraídas utilizando dados experimentais. Utilizando o modelo da maquina é projetado o controlador de velocidade para sua operação no modo motor. Tambem sera projetado o controlador de potência PI utilizando o modelo estimado do sistema de conversão de energia eólica. A partir dos ganhos do controlador PI é projetado o controlador fuzzy PI autoajustavel com o objetivo de melhorar a resposta em regime permanente da potencia controlada. A potencia gerada pelo gerador de relutancia variavel é injetada à rede eletrica, atraves do controle independente das potencias ativa e reativa, para este proposito é utilizado um conversor trifasico de dois níveis. Na parte experimental deste trabalho foi implementado o controle de corrente por histerese para maquina operando no modo motor, posteriormente foi implementado o controle de corrente e controle da tens~ao no barramento CC para a máquina operando no modo gerador. Os resultados de simulação e experimentais se mostraram coerentes validando os controladores propostos. / This work presents the direct power control of the switched reluctance generator of 12/8 using the self-tuning fuzzy PI controller and the vector control for inverter connected to the grid. Initially, the machine's operating principles and the topology of the power electronics converter used to drive this machine are studied. The model of switched reluctance machine is implemented in Matlab/Simulink simulation software using the characteristic curves of current and torque extracted using experimental data. Using the machine's model, It is designed the speed controller for its operation in motor mode. Also, the PI controller is designed for the power control loop based on the estimation of the wind energy conversion system. Using the gains of the PI controller, It is designed the self-tuning fuzzy PI controller, in order to improve the steady state response of the power control loop. The power generated by the switched reluctance generator is injected into the power grid through the independent control of active and reactive power, for this purpose is used a three-phase two level converter. In the experimental part of this work was implemented the hysteresis current control for machine operating in motor mode, also, It was implemented the current and DC bus voltage control for the machine operating in generator mode. The simulation and experimental results were proved consistent and these results validate the proposed controllers.
6

Controle de potência do gerador de relutância variável de 12/8 utilizando o controlador fuzzy pi auto-ajustável

Ccantuta Chirapo, Karlos Alexander January 2018 (has links)
Orientador: Prof. Dr. José Luis Azcue Puma / Coorientador: Prof. Dr. José Alberto Torrico Altuna / Dissertação (mestrado) - Universidade Federal do ABC, Programa de Pós-Graduação em Engenharia Elétrica, Santo André, 2018. / Este trabalho apresenta o controle de potência do gerador de relutância variável de 12/8 utilizando o controlador Fuzzy PI auto-ajustável e o controlador P+ressonante para o conversor conectado à rede elétrica. Inicialmente são estudados os princípios de operação da máquina e a topologia do conversor eletrônico de potência. Usando o software de simulação Matlab/Simulink é implementado o modelo da máquina de relutância variável utilizando as curvas características de corrente e de torque. Com o objetivo de controlar a potência gerada pela máquina e utilizando seu modelo matemático dinâmico projeta-se o controlador PI, e implementa-se o controlador Fuzzy PI auto-ajustável para atingir o mesmo objetivo. Assim, projeta-se também um controlador PI para o controle da tensão CC além de um controlador P+ressonante com o objetivo de melhorar a resposta em regime permanente da potência injetada na rede elétrica. Para este propósito é utilizado um conversor monofásico de dois níveis. Os resultados das simulações mostram o bom desempenho do sistema proposto e o controlador de potência é validado também através de resultados experimentais. / This work presents the power control of the 12/8 variable reluctance generator using Fuzzy self-tuning PI controller and the P+resonant controller for the converter connected to the electric network. Initially are studied the principles of operation of the machine and power electronic converter topology. Using the Matlab/Simulink simulation software is implemented the model of switched reluctance machine using the current and its torque characteristic curves. With the purpose of controlling the power generated by the machine and using his dynamic mathematical model is designed the PI controller, and the Fuzzy self-tuning PI controller is implemented to achieve the same objective. So, also is designed a PI controller for control of the link DC, in addition to the P+resonant controller with the objective of improving the response to its steady state of the injected power into the electric network. For this purpose it is used a single-phase two-level converter. The results of the simulations show the good performance of the proposed system and the power controller is validated by experimental results.
7

Βελτιωμένες αλγοριθμικές τεχνικές επίλυσης συστημάτων μη γραμμικών εξισώσεων

Μαλιχουτσάκη, Ελευθερία 22 December 2009 (has links)
Σε αυτή την εργασία, ασχολούμαστε με το πρόβλημα της επίλυσης συστημάτων μη γραμμικών αλγεβρικών ή/και υπερβατικών εξισώσεων και συγκεκριμένα αναφερόμαστε σε βελτιωμένες αλγοριθμικές τεχνικές επίλυσης τέτοιων συστημάτων. Μη γραμμικά συστήματα υπάρχουν σε πολλούς τομείς της επιστήμης, όπως στη Μηχανική, την Ιατρική, τη Χημεία, τη Ρομποτική, τα Οικονομικά, κ.τ.λ. Υπάρχουν πολλές μέθοδοι για την επίλυση συστημάτων μη γραμμικών εξισώσεων. Ανάμεσά τους η μέθοδος Newton είναι η πιο γνωστή μέθοδος, λόγω της τετραγωνικής της σύγκλισης όταν υπάρχει μια καλή αρχική εκτίμηση και ο Ιακωβιανός πίνακας είναι nonsingular. Η μέθοδος Newton έχει μερικά μειονεκτήματα, όπως τοπική σύγκλιση, αναγκαιότητα υπολογισμού του Ιακωβιανού πίνακα και ακριβής επίλυση του γραμμικού συστήματος σε κάθε επανάληψη. Σε αυτή τη μεταπτυχιακή διπλωματική εργασία αναλύουμε τη μέθοδο Newton και κατηγοριοποιούμε μεθόδους που συμβάλλουν στην αντιμετώπιση των μειονεκτημάτων της μεθόδου Newton, π.χ. Quasi-Newton και Inexact-Newton μεθόδους. Μερικές πιο πρόσφατες μέθοδοι που περιγράφονται σε αυτή την εργασία είναι η μέθοδος MRV και δύο νέες μέθοδοι Newton χωρίς άμεσες συναρτησιακές τιμές, κατάλληλες για προβλήματα με μη ακριβείς συναρτησιακές τιμές ή με μεγάλο υπολογιστικό κόστος. Στο τέλος αυτής της μεταπτυχιακής εργασίας, παρουσιάζουμε τις βασικές αρχές της Ανάλυσης Διαστημάτων και τη Διαστηματική μέθοδο Newton. / In this contribution, we deal with the problem of solving systems of nonlinear algebraic or/and transcendental equations and in particular we are referred to improved algorithmic techniques of such kind of systems. Nonlinear systems arise in many domains of science, such as Mechanics, Medicine, Chemistry, Robotics, Economics, etc. There are several methods for solving systems of nonlinear equations. Among them Newton's method is the most famous, because of its quadratic convergence when a good initial guess exists and the Jacobian matrix is nonsingular. Newton's method has some disadvantages, such as local convergence, necessity of computation of Jacobian matrix and the exact solution of linear system at each iteration. In this master thesis we analyze Newton's method and we categorize methods that contribute to the treatment of drawbacks of Newton's method, e.g. Quasi-Newton and Inexact-Newton methods. Some more recent methods which are described in this thesis are the MRV method and two new Newton's methods without direct function evaluations, ideal for problems with inaccurate function values or high computational cost. At the end of this master thesis, we present the basic principles of Interval Analysis and Interval Newton's method.
8

Modeling of Multiphysics Electromagnetic & Mechanical Coupling and Vibration Controls Applied to Switched Reluctance Machine / Modélisation multiphysique du couplage électromagnétique/mécanique et développement de contrôles de vibration appliqués aux machines à réluctance variable

Zhang, Man 12 September 2018 (has links)
En raison de ses avantages inhérents, tels que son faible coût, sa fiabilité élevée, sa capacité de fonctionnement à grande vitesse et en environnements difficiles, la machine à réluctance variable (MRV) est une solution attrayante pour l'industrie automobile. Cependant, la traction automobile est une application pour laquelle le comportement acoustique du groupe motopropulseur doit être particulièrement considéré, dans l'optique de ne pas dégrader le confort des passagers. Afin de rendre la MRV compétitive pour cette application automobile, le travail présenté se concentre sur plusieurs méthodes de contrôle cherchant à améliorer le comportement acoustique des MRV en réduisant les vibrations d'origine électromagnétique. Un modèle multi-physique électromagnétique / mécanique semi-analytique est proposé à partir de résultats de simulation numérique obtenus par la méthode des éléments finis. Ce modèle multiphysique est composé de modèles électromagnétiques et structurels, qui sont reliés par la composante radiale de la force électromagnétique. Deux méthodes de contrôle sont ensuite proposées. La première réduit la vibration en faisant varier l'angle de coupure du courant, la fréquence du la variation étant basée sur les propriétés mécaniques de la structure MRV. De plus, une fonction aléatoire uniformément distribuée est introduite pour éviter une composante fréquentielle locale de forte vibration. Une seconde méthode est basée sur le contrôle direct de la force (DFC), qui vise à obtenir une force radiale globale plus douce pour réduire les vibrations. Un adaptateur de courant de référence (RCA) est proposé pour limiter l'ondulation de couple introduite par le DFC, provoquée par l'absence de limitation de courant. Cette seconde méthode de réduction des vibrations appelée DFC & RCA est évaluée par des tests expérimentaux utilisant un prototype de MRV 8/6 afin de montrer sa pertinence. Une solution de partitionnement hardware/software est proposée pour implémenter cette méthode sur une carte FPGA utilisée en combinaison avec un microprocesseur. / Due to its inherent advantages Switched Reluctance Machine (SRM) are appealing to the automotive industry. However, automotive traction is a very noise sensitive application where the acoustic behavior of the power train may be the distinction between market success and market failure. To make SRM more competitive in the automotive application, this work will focus on the control strategy to improve the acoustic behavior of SRM by vibration reduction. A semi-analytical electromagnetic/structural multi-physics model is proposed based on the simulation results of numerical computation. This multi-physics model is composed by electromagnetic and structural models, which are connected by the radial force. Two control strategies are proposed. The first strategy to improve the acoustic behavior of SRM by vibration reduction. A semi-analytical electromagnetic/ structural multi-physics model is proposed based on the simulation results of numerical computation. This multi-physics model is composed by electromagnetic and structural models, which are connected by the radial force. Two control strategies are proposed. The first one reduces the vibration by varying the turn-off angle, the frequency of the variable signal is based on the mechanical property of switched reluctance machine. Besides, an uniformly distributed random function is introduced to avoid local high vibration component. Another one is based on the Direct Force Control (DFC), which aims to obtain a smoother total radial force to reduce the vibration. An reference current adapter (RCA) is proposed to limit the torque ripple introduced by the DFC, which is caused by the absence of the current limitation. The second vibration reduction strategy named DFC&RCA is evaluated by experimental tests using an 8/6 SRM prototype. A hardware/software partitioning solution is proposed to implement this method, where FPGA board is used combined with a Microprocessor.

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