Submitted by Renata Lopes (renatasil82@gmail.com) on 2017-04-24T15:04:21Z No. of bitstreams: 1 luizfernandoalvesguedes.pdf: 8533376 bytes, checksum: 1fb75359e16225fb5b36b42d374e4b7a (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2017-04-24T16:59:50Z (GMT) No. of bitstreams: 1 luizfernandoalvesguedes.pdf: 8533376 bytes, checksum: 1fb75359e16225fb5b36b42d374e4b7a (MD5) / Made available in DSpace on 2017-04-24T16:59:50Z (GMT). No. of bitstreams: 1 luizfernandoalvesguedes.pdf: 8533376 bytes, checksum: 1fb75359e16225fb5b36b42d374e4b7a (MD5) Previous issue date: 2012-12-17 / Este trabalho tem o objetivo de estudar, projetar, simular e obter resultados experimentais, a partir de um conversor flyback operando no modo descontínuo (DCM), para acionar uma luminária de diodos emissores de luz (LEDs). Além disso, deseja-se que o conversor possua elevado fator de potência, alta eficiência, baixa distorção harmônica da corrente de entrada, vida útil elevada (através da possibilidade de substituir de capacitores eletrolíticos por capacitores de filme metálico) e baixo custo. Inicialmente, o trabalho apresenta um breve estudo da iluminação a LEDs, o modelo elétrico simplificado dos LEDs, bem como uma revisão de alguns conversores aplicados ao acionamento deste tipo de fonte luminosa. Em seguida é analisada a operação do conversor flyback em modo DCM alimentado a partir da retificação (em ponte) da tensão da rede elétrica. Além do estudo teórico, a simulação do conversor é apresentada de modo a validar o projeto do conversor e servir de base de comparação com os resultados experimentais. O projeto do transformador (indutores acoplados) do conversor flyback tem destaque especial neste trabalho, pois, este elemento é fundamental para elevar a eficiência do conversor. Portanto, parte deste trabalho é dedicada ao estudo de perdas do transformador. Isto é feito através de uma adaptação de técnicas consagradas nesta área por meio de uma compilação didática visando a repetitividade do estudo. A partir do estudo teórico sobre as perdas no transformador, programas elaborados no MATLAB e no MICROSOFT EXCEL auxiliam o projeto do elemento magnético do conversor flyback. Estes dois programas, visam facilitar o exaustivo equacionamento das perdas e auxiliam no desenvolvimento de um projeto com elevada eficiência do transformador flyback elevando, consequentemente, a eficiência global do conversor. Empregando os programas elaborados, o projeto é calculado e resultados experimentais são obtidos a partir de medições realizadas em um protótipo em escala. Estes resultados são analisados e comparados com os resultados teóricos e de simulação. Ao final, é realizada uma análise simplificada do custo dos componentes do conversor e também são apresentadas as principais conclusões deste trabalho. / This work aims to study, design, simulate and obtain experimental results from a flyback converter operating in discontinuous mode (DCM), to trigger a fixture of light emitting diodes (LEDs). Furthermore, it is desired that the converter has high power factor, high efficiency, low harmonic distortion of input current, high life (through the possibility of replacing the electrolytic capacitors for metal film capacitors) and low cost. Initially, the paper presents a brief study of lighting LEDs, LEDs for simplified electrical model, as well as a review of some converters used to drive this type of light source. Then it analyzed the operation of the flyback converter in DCM mode fed from the rectification (bridged) the utility voltage. Besides the theoretical study, the simulation of the converter is presented in order to validate the design of the converter as a basis for comparison with experimental results. The transformer design (coupled inductors) flyback converter has special emphasis in this work, because this element is essential to raise the efficiency of the converter. So part of this work is devoted to the study of transformer losses. This is done by an adaptation of standard techniques in this area via a teaching order to build repeatability study. From the theoretical study on the losses in the transformer, programs developed in MATLAB and MICROSOFT EXCEL aid the design of the magnetic element of the flyback converter. These two programs are designed to facilitate the comprehensive equating of losses and assist in developing a project with high efficiency flyback transformer raising therefore the overall efficiency of the converter. Employing the programs drawn up, the project is calculated and experimental results are obtained from measurements performed on a prototype scale. These results are analyzed and compared with the theoretical results and simulation. At the end we provide a simplified analysis of the cost of the converter components and also presents the main conclusions of this work.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / This Master Thesis presents a new analysis, modeling and design guideline for an Insulated Power Factor Corrected Single-Stage Converter. First, the operating principle is presented which provides a better understanding of the converter. So, based on this new analysis, the two operation modes description and the new steady-state gain of the converter are provided. A new control strategy for the input current control-loop is also proposed which provides an improvement of the total harmonic distortion (THD). The conditions to reset the magnetic flux for the high frequency transformer (HFT) into a switching period and the mitigation of the reactive energy are provided. At the sequence, the transfer functions that describe the dynamic behavior of the output voltage and the input current due to perturbations on duty-cycle and input voltage are derived. These dynamic models are derived based on the averaged equivalent circuit (AEC) obtained by modeling an equivalent DC-DC converter. Finally, the design guideline and experimental results for validation of the mathematical analysis and numerical simulation confirmation are provided. / Esta Dissertação de Mestrado apresenta uma nova análise, modelagem e metodologia de projeto de um conversor CA-CC isolado com um único estágio e correção do fator de potência. Inicialmente, é apresentado o princípio de operação do conversor em estudo propiciando um melhor entendimento do funcionamento do mesmo. Assim, baseada na nova análise, são apresentados os dois modos de operação do conversor e o novo ganho estático resultante. Também é proposta uma nova estratégia de controle para a corrente de entrada do conversor proporcionando uma redução na distorção harmônica total (DHT). Também serão estabelecidas as condições necessárias para a desmagnetização do núcleo do transformador de alta freqüência (TAF) em um período de chaveamento e a minimização de reativos circulantes. Posteriormente, são obtidas as funções de transferências que descrevem o comportamento dinâmico da tensão de saída e da corrente de entrada para perturbações na variável de controle ou na tensão de entrada. Esses modelos dinâmicos serão derivados do circuito médio equivalente (CME) obtido através da modelagem do conversor em estudo operando como um conversor CC-CC equivalente. Por fim, são apresentadas uma metodologia de projeto e os resultados experimentais para a validação da análise matemática e confirmação dos resultados obtidos através de simulações numéricas.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / This work aims to develop a family of electronic converters with electrical isolation to supply a group of power light emitting diodes, applied to street lighting systems. The converters have high power factor and still meets the IEC61000-3-2, for lighting equipment. The integration between the power stages is realized to decrease the number of active semiconductors in the topologies. The topologies are modeled, considering the electrical model of light emitting diodes, and controllers are proposed to turns possible the reduction of the capacitances values in the analyzed topologies. This reduction aims to turns possible the replacement of the electrolytic capacitors for film capacitors, with higher lifetime. The implemented topology is a converter with 70 W of power, supplying 32 power LEDs with 700 mA. The experimental results prove the design methodology, presenting the desired characteristics, like high power factor (0.962), agreement with the standard IEC 61000-3-2 and high efficiency (88%). / Este trabalho visa o desenvolvimento de uma família de conversores eletrônicos com isolação elétrica para o acionamento de um conjunto de diodos emissores de luz de potência, aplicados à iluminação pública. Estes sistemas devem possuir elevado fator de potência e ainda estar de acordo com a norma IEC 61000-3-2, para equipamentos de iluminação. É realizada a integração entre os estágios de potência, de tal forma a reduzir o número de semicondutores ativos das topologias. As topologias são modeladas, considerando o modelo elétrico dos diodos emissores de luz, e é proposto o uso de controladores, visando possibilitar a redução dos valores de capacitâncias das topologias analisadas. Esta redução possibilita a substituição de capacitores eletrolíticos por capacitores de filme, com maior vida útil. Um protótipo para 70 W foi implementado, alimentando 32 LEDs de potência com 700 mA, foram utilizados os conversores Boost-Flyback, Buck-Flyback e Buck-Boost Flyback, além disso o conversor Flyback foi implementado visando a comparação entre conversores integrados e de estágio único. Os resultados experimentais comprovam a metodologia de projeto, apresentando as características desejadas, como elevado fator de potência (0,962), concordância com a norma IEC 6100-3-2 e rendimento de 88%.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / This master thesis presents the analysis and design of an electronic drive system for fluorescent induction lamps. This lighting technology, despite being patented since the 60s, is not widely diffused in the market context. However, it is an extremely attractive alternative due to long lifetime and high luminous efficiency. The analysis circuit consists of a power factor correction associated with a power control stage, which provides the lamp ignition and current limitation. An integration methodology is applied in order to reduce the number of active semiconductor switches. The resulting topology, called here SEPIC half-bridge, presents a shared switch able to act, both in the pre-regulator stage, as well as for the power control stage. The number of elements reduction also occurs by magnetic integration. In this case, the pre-regulator inductors are distributed in a single core. For electronic system flexibility, it was inserted the dimming capability, where the low frequency modulation technique was evaluated. This technique is suitable for high power variation rates and provides a stable operation. The topology is controlled by a feedback system ensuring a satisfactory response of the system when subjected to disturbances, in addition to ensuring the correct power to the lamp. The electronic ballast designed behavior was evaluated experimentally. In this situation, there was obtained a low input current distortion associated with a high power factor. The lamp power variation range was 70% (30 W to 100 W), with an average efficiency around 82%. / Neste trabalho de mestrado, apresenta-se a análise e o projeto de um sistema eletrônico de acionamento para lâmpadas fluorescentes de indução. Esta tecnologia de iluminação, apesar de ser patenteada desde a década de 60, ainda é pouco difundida em âmbito comercial. Entretanto, é uma alternativa extremamente atraente devido a longa vida útil e a elevada eficiência luminosa. O circuito analisado consiste de um estágio de pré-regulação do fator de potência associado a um estágio de controle de potência, capaz de prover as necessidades de partida e limitar a corrente aplicada à lâmpada. Para estes estágios, visando a redução do número de semicondutores ativos, é aplicada a metodologia de integração de interruptores. A topologia resultante, chamada de SEPIC half-bridge, apresenta um interruptor compartilhado, capaz de atuar tanto para o pré-regulador, quanto para o controle de potência. A redução do número de elementos se dá também pela integração de magnéticos. Nesta situação, os indutores do pré-regulador são distribuídos em um único núcleo. Buscando a flexibilidade do sistema eletrônico, neste foi inserido a capacidade de variação da intensidade luminosa, onde a técnica de modulação de baixa frequência foi avaliada. Tal técnica é apropriada para elevados índices de variação de potência, além de proporcionar uma operação estável do circuito. A topologia é controlada por um sistema de retroalimentação, capaz de garantir uma resposta satisfatória do sistema quando submetido a distúrbios, além de garantir a potência processada pela lâmpada. O comportamento do reator eletrônico projetado foi avaliado experimentalmente. Nesta situação, obteve-se uma baixa distorção da corrente de entrada e elevado fator de potência. A faixa de variação de potência foi de 70% (100 W à 30 W), com um rendimento médio de 82%.

Dans le cadre de cette thèse, nous nous sommes intéressés à l’étude de l’apport d’une aide assistée par ordinateur au diagnostic de certaines maladies dégénératives du cerveau, en explorant les images de tomographie par émission de positons, par des techniques de traitement d’image et d’analyse statistique.Nous nous sommes intéressés à la représentation corticale des 116 régions anatomiques, en associant à chacune d’elles un vecteur d’attribut issu du calcul des 4 premiers moments des intensités de voxels, et en y incluant par ailleurs l’entropie. Sur la base de l’aire de courbes ROC, nous avons établi qualitativement la pertinence de chacune des régions anatomiques, en fonction du nombre de paramètres du vecteur d’attribut qui lui était associé, pour séparer le groupe des sujets sains de celui des sujets atteints de la maladie d’Alzheimer. Dans notre étude nous avons proposé une nouvelle approche de sélection de régions les plus pertinentes, nommée "combination matrix", en se basant sur un système combinatoire. Chaque région est caractérisée par les différentes combinaisons de son vecteur d’attribut. L’introduction des régions les plus pertinentes(en terme de pouvoir de séparation des sujets) dans le classificateur supervisé SVM nous a permis d’obtenir, malgré la réduction de dimension opérée, un taux de classification meilleur que celui obtenu en utilisant l’ensemble des régions. / Our research focuses on presenting a novel computer-aided diagnosis technique for brain Positrons Emission Tomography (PET) images. It processes and analyzes quantitatively these images, in order to better characterize and extract meaningful information for medical diagnosis. Our contribution is to present a new method of classifying brain 18 FDG PET images. Brain images are first segmented into 116 Regions Of Interest (ROI) using an atlas. After computing some statistical features (mean, standarddeviation, skewness, kurtosis and entropy) on these regions’ histogram, we defined a Separation Power Factor (SPF) associated to each region. This factor quantifies the ability of each region to separate neurodegenerative diseases like Alzheimer disease from Healthy Control (HC) brain images. A novel region-based approach is developed to classify brain 18FDG-PET images. The motivation of this work is to identify the best regional features for separating HC from AD patients, in order to reduce the number of features required to achieve an acceptable classification result while reducing computational time required for the classification task.

This thesis contributes to the state of the art in integrated design of insect-scale piezoelectric actuated flapping wing vehicles through the development of novel theoretical models for flapping wing aerodynamics and piezoelectric actuator dynamics, and integration of these models into a closed form design process. A comprehensive literature review of available engineered designs of miniature rotary and flapping wing vehicles is provided. A novel taxonomy based on wing and actuator kinematics is proposed as an effective means of classifying the large variation of vehicle configurations currently under development. The most successful insect-scale vehicles developed to date have used piezoelectric actuation, system resonance for motion amplification, and passive wing pitching. A novel analytical treatment is proposed to quantify induced power losses in normal hover that accounts for the effects of non uniform downwash, wake periodicity and effective flapping disc area. Two different quasi-steady aerodynamic modelling approaches are undertaken, one based on blade element analysis and one based on lifting line theory. Both approaches are explicitly linked to the underlying flow physics and, unlike a number of competing approaches, do not require empirical data. Models have been successfully validated against experimental and numerical data from the literature. These models have allowed improved insight into the role of the wing leading-edge vortex in lift augmentation and quantification of the comparative contributions of induced and profile drag for insect-like wings in hover. Theoretical aerodynamic analysis has been used to identify a theoretical solution for the optimum planform for a flapping wing in terms of chord and twist as a function of span. It is shown that an untwisted elliptical planform minimises profile power, whereas a more highly tapered design such as that found on a hummingbird minimises induced power. Aero-optimum wing kinematics for hovering are also assessed. It is shown that for efficient flight the flapping velocity should be constant whereas for maximum effectiveness the flapping velocity should be sinusoidal. For both cases, the wing pitching at stroke reversal should be as rapid as possible. A dynamic electromechanical model of piezoelectric bending actuators has been developed and validated against data obtained from experiments undertaken as part of this thesis. An expression for the electromechanical coupling factor (EMCF) is extracted from the analytical model and is used to understand the influence of actuator design variables on actuator performance. It is found that the variation in EMCF with design variables is similar for both static and dynamic operation, however for light damping the dynamic EMCF will typically be an order of magnitude greater than for static operation. Theoretical contributions to aerodynamic and electromechanical modelling are integrated into a low order design method for propulsion system sizing. The method is unique in that aside from mass fraction estimation, the underlying models are fully physics based. The transparency of the design method provides the designer with clear insight into effects of changing core design variables such as the maximum flapping amplitude, wing mass, transmission ratio, piezoelectric characteristics on the overall design solution. Whilst the wing mass is only around 10% of the actuator mass, the effective wing mass is 16 times the effective actuator mass for a typical transmission ratio of 10 and hence the wing mass dominates the inertial contribution to the system dynamics. For optimum aerodynamic effectiveness and efficiency it is important to achieve high flapping amplitudes, however this is typically limited by the maximum allowable field strength of the piezoelectric material used in the actuator.

With the increasing demand for fast, cheaper, and efficient power converters come the need for a single-stage power factor correction (PFC) converter. Various single-stage PFC converter proposed in the literature has the drawback of high DC bus voltage at the input side and together with the shift to wide bandgap switches like GaN drives the converter cost higher. However, an interleaved topology with high-frequency isolation was proposed in this research work due to the drastic reduction in the DC bus voltage and extremely low input current ripple thereby making the need for an EMI filter circuit optional.   Meanwhile, this research work focuses on adapting the proposed topology for a high voltage low current application (EV charger - 400V, 7KW) and low voltage high current application (telecom power supply - 58V,  58A) owing to cost benefits. However, all single-stage PFC are faced with the drawback of second-order (100Hz) output harmonic ripple. Therefore, the design and simulation presented a huge peak to peak ripple of about 50V/3A and 26V/26A for the EV charger and telecom power supply case, respectively. This created the need for the design of a ripple cancellation circuit as the research required a peak to peak ripple of 8V and 200mV for the EV - charger and telecom power supply, respectively.   A novel output passive ripple cancellation technique was developed for the EV charger case due to the ease it offers in terms of control, circuit complexity and extremely low THDi when compared with the active cancellation approach. The ripple circuit reduced the 50V ripple to 431mV with the use of a total of 2.2mF capacitance at the output stage.   Despite designing the passive technique, an active ripple cancellation circuit was designed using a buck converter circuit for the telecom power supply. The active approach was chosen because the passive has a slow response and incurs more loss at a high current level. Adding the active ripple cancellation circuit led to a quasi-single stage LLC PFC converter topology. A novel duty-ratio feedforward control was added to synchronize the PFC control of the input side with the buck topology ripple cancellation circuit. The addition of the ripple circuit with the feedforward control offered a peak to peak ripple of 6.7mV and a reduced resonant inductor current by half.   After analysis, an extremely low THDi of 0.47%, PF of 99.99% and a peak efficiency of 97.1% was obtained for the EV charger case. The telecom power supply offered a THDi of 2.3%, PF of 99.96% with a peak efficiency of 95%.

Thesis is devoted to a problem of Power Factor Correction on the low voltage level. It has still its own difficulties despite the fact that topic moved through long development. The main goal of this work is to offer reader variable procedure considering design process. It is based on use of measured data of network analyzer Meg30. The design algorithm has to share a maximum of eventual influencing factors. Therefore the body of master thesis goes through detailed analysis of Power Factor Correction.

This master thesis investigates the possibilities for performance improvements of synchronous machines with unidirectional application.The literature review part presents theories and applications of asymmetrical machine. Four categories regarding asymmetrical machine, namely mixed pole, saturation mitigation, pole shifting and asymmetrical pole shaping, are summarized. It is shown that asymmetrical concept offers characteristic improvement in one or both rotational directions. A field winding synchronous model was used in FEM simulation (FLUX 2D). Armature reaction effecton this machine is investigated. It is found that armature reaction has different effects with varying current angle.Two ideas regarding asymmetrical pole shaping are investigated. First of all, pole shoe cutting idea is investigated. It leads to increased airgap length and less output torque. Secondly, progressive airgap idea shows reduced armature reaction effect and improved power factor, but higher torque ripple.Furthermore, an improved idea is suggested to reduce the torque ripple. Performance improvement by assisted permanent magnet is also studied. Four ideas of this field are investigated. It is found that permanent magnet can be used to reduce saturation, improve power factor and output torque. The reasons for limited improvements are analyzed.

Grid connection of wave energy is one of the crucial remaining areas of development towards the commercialization of this renewable energy technology. One of the major challenges with the grid connection of the wave energy technology is power variability. The rapidly changing voltage and power production from very high peaks to lows, increases the complexity for the wave farm developers to reach an agreement with the grid owners to satisfy the grid compliance. Correspondingly, electrical network designs of the offshore wind sector also differ on some key features which includes the power variability, cable lengths, power ratings, connection layouts, sea depths and transmission distances. These differences present new challenges to engineers in adapting technology and knowhow from the wind industry wherever applicable; whereas in parts of the network where power ratings are <2 MW, new designs need to be derived. Hence, power system dynamic modelling of variable emerging wave energy puts a great field of research. CorPower Ocean AB is in the process of developing a 300-kW point absorber type Wave Energy Converter (WEC) that is a commercial fullscale prototype. In this regard, the thesis will discuss the topics of optimization of offshore wave energy electrical networks for farms primarily focused on a 10 MW rating. The modelling for RMS simulation, network efficiency, voltage profile and power quality analysis has been simulated on DIgSILENT PowerFactory. Grid connection compliance for voltage levels, voltage flicker and power factor has been evaluated against local site regulations and parameters for optimal efficiency and better power quality with respect to grid connection is discussed. The impact of grid impedance angle and the wave front incidence angle on the rating of wave farm being connected is also evaluated. The study leads to an optimized electrical layout of a wave farm which can tackle problems such as voltage flicker and varying power. The study also leads to the understanding of better layout for the point absorber with least transmission losses. This study can also be generalized for bigger wave farms in the future which will reduce the complexity and time for wave farms engineers while planning.