Avec le remplacement des réseaux hydrauliques et pneumatiques à bord des aéronefs par des réseaux électriques, le nombre d'équipements embarqués pour assurer un bon fonctionnement augmentera. Le passage à un avion entièrement électrique permettrait de réduire les couts de production et fonctionnement, assurerait une meilleure fiabilité des systèmes, et réduirait l'impact écologique de la circulation d'un tel appareil. En effet, un tel avion serait plus léger qu'un avion actuel. Pour s'assurer de cela, il est nécessaire de réduire la masse des équipements embarqués servant à la gestion, la mise en forme, la distribution d'énergie électrique. Le dimensionnement et l'optimisation de la masse des équipements embarqués est donc une problématique fondamentale dans le développement de l'avion plus électrique. Cette masse est majoritairement fixée par les systèmes de refroidissement lorsque l'on considère des systèmes de conversion d'énergie. Parmi l'ensemble des systèmes de refroidissement disponibles et dédiés au refroidissement des convertisseurs statiques, deux grandes technologies ont été sélectionnées, dans l'objectif d'en produire des modèles dédiés à des routines d'optimisation. Les dissipateurs à ailettes droites en convection forcée, ainsi que les systèmes associant dissipateurs à ailettes et caloducs seront modélisés au cours de ces travaux de thèse. Des modèles analytiques de ces systèmes de refroidissement seront proposés, dans l'optique de pouvoir optimiser au mieux leur masse tout en assurant un bon fonctionnement thermique. Même si de nombreuses méthodes de dimensionnement et d'optimisation dédiées aux systèmes de refroidissement existent, notre choix de modélisation s'est porté sur une représentation analytique. En effet, ce type de modélisation est déduit d'une résolution exacte de l'équation de la chaleur pour représenter des configurations géométriques et thermiques simples. Les configurations sélectionnées correspondent à des configurations simples à modéliser analytiquement. L'avantage de tels modèles réside dans le fait que le comportement thermique de systèmes de refroidissement, i.e de la température de la source de chaleur à l'ambiant, est une fonction des paramètres géométriques, des matériaux et des conditions environnementales des systèmes de refroidissement. Ce sont donc des modèles très rapides d'exécution qui donnent une solution exacte du comportement thermique des dissipateurs modélisés. Ils présentent donc un réel intérêt dans l'optique d'optimiser la masse de ces systèmes. / The replacement of hydraulic and pneumatic network embedded in aircraft by electrical network will increase the number of embedded systems to ensure the effective functioning of the aircraft. The development of an electrical aircraft will allow the reduction of production and functioning costs. It will also help ensure a better reliability of systems and will reduce the ecological impact of the aircraft circulation. This kind of plane would be lighter than a usual one. To be sure of this, it is necessary to reduce weight of embedded equipment's dedicated to management, conversion and distribution of electrical energy. The sizing and the optimization of embedded equipment's weight is a critical issue in the development of more electrical aircraft. This weight is mostly defined by heat transfer systems, when we consider the sizing of energy conversion system A lot of heat transfer system exists and are dedicated to the cooling of power converters. We selected two of these heat transfer system, in order to produce models of them. These models will be used in optimization routines. Plate fin heat sink in forced convection, and system assembly, combining heat pipe and plate fin heat sink, will be modelled during this thesis. Analytical models of these heat transfer systems will be developed, to optimize their weight and ensure a good cooling of electrical systems. Even if lots of dimensioning and optimization methods exists, dedicated to heat transfer systems, we choose to use analytical modelling. This kind of models gives an exact solution to the heat equation, to describe simple geometric and thermic configurations. Selected heat transfer systems can be simply described. The main advantage of these models is that it represents the thermal behavior of the system as a function of its geometrical parameters, materials and environmental conditions. Execution of these models is very fast and gives a precise solution of the thermal parameters of the described configuration. There is then a real interest to use this type of models to optimize weight of heat transfer systems, and then power converter.

Submitted by Geandra Rodrigues (geandrar@gmail.com) on 2018-01-08T12:01:24Z No. of bitstreams: 1 guilhermemárciosoares.pdf: 24810934 bytes, checksum: d538ec8cfbd6bb9363a5aa07343bda48 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2018-01-22T18:36:09Z (GMT) No. of bitstreams: 1 guilhermemárciosoares.pdf: 24810934 bytes, checksum: d538ec8cfbd6bb9363a5aa07343bda48 (MD5) / Made available in DSpace on 2018-01-22T18:36:10Z (GMT). No. of bitstreams: 1 guilhermemárciosoares.pdf: 24810934 bytes, checksum: d538ec8cfbd6bb9363a5aa07343bda48 (MD5) Previous issue date: 2017-11-18 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Este documento apresenta uma nova técnica para a minimização da ondulação de baixa frequência, típica de conversores para o acionamento de LEDs alimentados a partir da rede elétrica. Esta estratégia baseia-se na modulação em baixa frequência da razão cíclica do conversor de modo que a ondulação de corrente possa ser reduzida e, consequentemente, as capacitâncias de filtragem do conversor possam ser minimizadas. Esta técnica foi desenvolvida para a aplicação em conversores de malha única, como é o caso de conversores de estágio único ou mesmo dois estágios integrados. A modulação da razão cíclica é projetada de maneira que o comportamento de baixa frequência das principais variáveis do conversor seja alterado, permitindo uma redução da ondulação da corrente de saída ao custo de um incremento cotrolado no conteúdo harmônico da corrente de entrada. Duas possíveis metodologias para a implementação da técnica proposta são discutidas ao longo do trabalho. A primeira envolve a injeção de harmônicas específicas no sinal da razão cíclica do conversor através de ramos adicionais na estrutura de controle. Esta abordagem foi aplicada para projetar um controlador de LEDs baseado em um conversor flyback e também em uma topologia integrada baseada na conexão cascata de dois conversores Buck-boost. Este estudo inicial foi expandido para outros conversores e uma análise generalizada acerca da influência da modulação da razão cíclica no comportamento de controladores de LED alimentados a partir da rede elétrica é apresentada. A segunda metodologia para a implementação da compensação ativa da ondulação de baixa frequência do conversor é baseada na otimização de um controlador proporcional-integral a fim de que tal elemento influencie não só no comportamento dinâmico do circuito, mas também na característica de baixa frequência do conversor. Por fim são discutidas as principais contribuições da tese e algumas propostas para trabalhos futuros são apresentadas / This document presents a novel approach for low-frequency output current ripple minimization in off-line light-emitting diode (LED) drivers. This strategy is based on the large-signal modulation of the duty-cycle so that the output ripple can be reduced and, consequently, the required filtering capacitances of the converter can be somehow decreased. This technique is devised to be used on converters in which a single control loop is employed, such as off-line single-stage or integrated converters. The duty-cycle modulation is used to change the shape of the main waveforms of the converter, especially the input and output currents. This allows for a reduction of the output current peak-to-peak ripple while the harmonic content of the input current is increased but kept within the limits imposed by the IEC standard. Two methodologies for implementing the proposed technique are discussed along the text. The first one is related to the injection of harmonic components to the duty cycle signal by means of additional branches inserted in the conventional control structure. This approach was applied to design an off-line flyback-based LED driver and also a circuit based on the Integrated Double Buck-boost converter. This first study was expanded to other topologies and a generalized analysis regarding the impact of the duty cycle modulation on off-line converters is then presented. The second methodology for implementing the ripple compensation is based on the optimization of a proportional-integral controller so that this element is designed to influence not only in the dynamic behavior of the circuit, but also in its low-frequency characteristic. Finally, the main contributions of this work are discussed and the proposals for future works are presented.