• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 187
  • 61
  • 42
  • 31
  • 20
  • 14
  • 14
  • 7
  • 4
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • Tagged with
  • 415
  • 415
  • 206
  • 122
  • 119
  • 100
  • 100
  • 99
  • 97
  • 78
  • 66
  • 62
  • 60
  • 59
  • 55
  • 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.
331

Estrat?gia de conversor para interliga??o de sistemas de gera??o e?lica ? rede el?trica

Arrais Junior, Ernano 11 July 2014 (has links)
Made available in DSpace on 2014-12-17T14:56:19Z (GMT). No. of bitstreams: 1 ErnanoAJ_DISSERT.pdf: 1903927 bytes, checksum: 0bb4c95cc8f08d85b6af9c71ab44494b (MD5) Previous issue date: 2014-07-11 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / Currently, there are several power converter topologies applied to wind power generation. The converters allow the use of wind turbines operating at variable speed, enabling better use of wind forces. The high performance of the converters is being increasingly demanded, mainly because of the increase in the power generation capacity by wind turbines, which gave rise to various converter topologies, such as parallel or multilevel converters. The use of converters allow effective control of the power injected into the grid, either partially, for the case using partial converter, or total control for the case of using full converter. The back-to-back converter is one of the most used topologies in the market today, due to its simple structure, with few components, contributing to robust and reliable performance. In this work, is presented the implementation of a wind cogeneration system using a permanent magnet synchronous generator (PMSG) associated with a back-to-back power converter is proposed, in order to inject active power in an electric power system. The control strategy of the active power delivered to the grid by cogeneration is based on the philosophy of indirect control / Existem diversas topologias de conversores de pot?ncia aplicadas a sistemas de gera??o de energia e?lica. Os conversores permitem a gera??o de energia com turbinas e?licas em condi??es de velocidade vari?vel do vento, possibilitando um aproveitamento de forma mais eficaz das for?as do vento. A utiliza??o dos conversores possibilita o controle efetivo da pot?ncia injetada na rede, seja de maneira parcial, no caso de utiliza??o de conversores parciais, ou controle total, no caso de utiliza??o de conversores completos. O alto desempenho dos conversores vem sendo cada vez mais necess?rio, principalmente quando se busca a eleva??o da capacidade de gera??o de pot?ncia por parte das turbinas e?licas, o que fez surgir diversas novas topologias de conversores, sejam conversores paralelos ou multin?veis. O conversor na configura??o back-to-back ? um dos mais utilizados no mercado atualmente, devido ? sua estrutura simples, com poucos componentes, contribuindo assim para um desempenho robusto e confi?vel. Neste trabalho, apresenta-se a implementa??o de um sistema de cogera??o e?lica utilizando um gerador s?ncrono a ?m? permanente (PMSG) associado a um conversor de pot?ncia na topologia back-to-back, de maneira a injetar pot?ncia ativa em um sistema el?trico de pot?ncia. A estrat?gia do controle da pot?ncia ativa fornecida pela cogera??o ? rede el?trica ? baseada na filosofia do controle indireto
332

Transformação dq não senoidal para máquinas síncronas com imã permanente no rotor / Non-sinusoidal dq transformation for rotor permanent magnet synchronous machines

José Roberto Boffino de Almeida Monteiro 19 December 2002 (has links)
O presente trabalho apresenta uma transformação dq não senoidal e sua aplicação em máquinas síncronas com ímã permanente na superfície do rotor (MSIP) e forma de onda de FEM não senoidal. O modelo resultante da aplicação dessa transformação permite o controle direto do torque eletromagnético, permitindo reduzir as ondulações do torque produzido nesse tipo de máquina. A redução dessas ondulações em MSIPs não senoidais possibilita que esse tipo de máquina seja empregado em aplicações onde somente MSIPs senoidais, que possuem custo mais elevado, poderiam ser usadas. Simulações e resultados práticos, obtidos pela implementação do sistema de controle vetorial não senoidal desenvolvido, são apresentados no trabalho. Pelos resultados obtidos, pode-se verificar que o método proposto é eficaz na redução das ondulações do torque eletromagnético em MSIPs não senoidais. / This work presents a non-sinusoidal dq transformation and its application in permanent- magnet synchronous machines (PMSM) with a non-sinusoidal back-EMF waveform. The resulting model of the application of such transformation permits direct control of machine electromagnetic torque, which achieves the reduction of torque ripple. The reduction of torque ripple in non-sinusoidal PMSMs makes possible the use of this kind of PMSM instead of sinusoidal PMSMs, which are more expensive. Simulation and practical results, obtained by the implementation of such non-sinusoidal vectorial control system, are shown in this work. Those results show that the method presented is efficacious in the torque ripple reduction in non-sinusoidal PM synchronous machines.
333

CONTROLE DE POTÊNCIA EM MICRORREDES CA ISOLADAS COM AEROGERADORES E BANCOS DE BATERIAS DISTRIBUÍDOS / POWER CONTROL IN ISOLATED CA MICROGRIDS WITH TURBINES AND DISTRIBUTED BATTERY BANKS

Matos, José Gomes de 31 March 2014 (has links)
Made available in DSpace on 2016-08-17T16:54:34Z (GMT). No. of bitstreams: 1 Tese Jose Gomes de Matos.pdf: 8310310 bytes, checksum: b4d88d65be5edbb4f214f9dd09ed8f3b (MD5) Previous issue date: 2014-03-31 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / This work proposes a new strategy to control the generated power in an alternating current autonomous microgrid that has distributed generators and battery banks. There are no restrictions regarding the type of generator to be connected, however in this particular study the effectiveness of the proposed strategy is analyzed by considering that the power source is a wind turbine coupled to a permanent magnet synchronous generator. The microgrid analyzed consists of at least one bidirectional electronic converter powered by a battery bank, which has the function of forming the microgrid; an electronic converter connected to a wind turbine generator, which operates as a power supplier to the microgrid; loads, and other peripheral systems of control and maneuver. The main objective of the proposed strategy is to maintain the terminal voltages of battery banks under control and below its upper limit, even when momentarily the power demanded by the loads connected to the microgrid is less than the power sources generation capacity. The proposed strategy controls the terminal voltage of the battery banks, controlling the power output that comes from the generators. This is done without the use of dump loads or any physical communication between the electronic converters connected to the battery banks and the electronic converters connected to the generators. A modified droop control technique, based on the grid frequency, is used to inform to the power generator electronic converters on the amount of energy they need to generate in order to maintain the state of charge of the battery banks below their limits. The work also presents the methodology to design and tuning the controllers of the associated variables of the generation system. This includes the voltage and frequency grid, the active and reactive power generated by the generators, the DC bus voltages in all electronic power converters and the terminal voltage of the battery banks. All controllers are designed in the discrete domain. A strategy to decouple the effects of the input disturbances is incorporated, into each controller. Special attention is given to the grid voltage controller due the fact that the effect of the load current disturbance is very significant for the grid power quality. Issues x related to the operation of the wind turbine on its maximum power point are also addressed in the control of the power electronic converter connected to the generator. The control strategy proposed in this study is validated through experimental results obtained using a microgrid prototype of 15 kW rated power. / Este trabalho propõe uma nova estratégia para controle da potência gerada em uma microrrede isolada, que opera em corrente alternada e que dispõe de geradores e bancos de baterias distribuídos ao longo da mesma. Embora não haja restrições quanto ao tipo de gerador a ser conectado à microrrede, neste estudo a aplicabilidade da estratégia proposta é analisada considerando a fonte de potência como sendo uma turbina eólica acoplada a um gerador síncrono a imãs permanentes. A microrrede estudada é composta de um conversor eletrônico bidirecional, alimentado por um banco de baterias, que tem a função de formar a microrrede; um conversor eletrônico ligado ao gerador da turbina eólica e que funciona como alimentador da microrrede; além das cargas e demais sistemas periféricos de controle e manobra. O principal objetivo dessa estratégia é controlar a tensão terminal dos bancos de baterias abaixo de um determinado valor limite, mesmo quando momentaneamente a potência demandada pela carga conectada à microrrede seja inferior à capacidade de geração das fontes de potência. A estratégia proposta controla a tensão dos bancos de baterias, controlando a energia gerada que vem dos geradores. Isto é feito sem a utilização de carga auxiliar para consumir o excesso de energia e sem comunicação física entre os conversores eletrônicos dos bancos de baterias e os conversores eletrônicos conectados aos geradores. Uma técnica de controle droop modificada, com base na frequência da microrrede, é usada para informar aos conversores dos geradores sobre a quantidade de energia que eles estão liberados para gerar, a fim de manter a tensão dos bancos de baterias abaixo dos seus valores limites. O trabalho ainda apresenta as sistemáticas de projeto e sintonia dos controladores das variáveis associadas com o sistema de geração. Isso compreende o controle da tensão e da frequência da microrrede, o controle das tensões nos barramentos de corrente contínua de todos os conversores eletrônicos de potência e o controle da tensão terminal dos bancos de baterias. Todos os controladores são projetados no domínio discreto. Uma estratégia de desacoplamento dos efeitos das entradas de perturbações é incorporada a cada controlador. Nesse enfoque, é dada atenção especial ao controlador de tensão da microrrede, cujo efeito da viii perturbação da corrente da carga é muito significativo para a qualidade de energia do sistema de geração. As questões relativas à maximização do aproveitamento energético das fontes renováveis são contempladas no controle do conversor da turbina eólica. A estratégia de controle proposta neste trabalho é validada a partir de resultados experimentais obtidos com um protótipo de microrrede de potência nominal 15 kw.
334

Estratégias de acionamento e controle em máquinas CA de ímã permanente com fluxo não senoidal / Control strategies for permanent magnet AC machines with non-sinusoidal flux

José Roberto Boffino de Almeida Monteiro 29 August 1997 (has links)
O objetivo desse trabalho é o estudo e a análise do desempenho de máquinas brushless com ímã permanente no rotor, com fluxo de entreferro não senoidal. São consideradas máquinas brushless com ímã permanente na superfície do rotor. Três modelos matemáticos são considerados: o modelo por fase de estator, o modelo vetorial e o modelo velocidade-tensão de segunda ordem. Máquinas com diferentes tipos de enrolamento de estator são comparadas, incluindo as máquinas síncronas com ímã permanente no rotor (com a densidade dos enrolamentos distribuída de forma senoidal no estator). Os resultados para o torque eletromagnético das máquinas foram obtidos considerando-se dois tipos de acionamentos em malha aberta: um acionamento de seis pulsos e um acionamento senoidal. Por fim, um método de controle é apresentado para máquinas não senoidais. As ondulações no torque e o desempenho das máquinas não senoidais. As ondulações no torque e o desempenho das máquinas não senoidais, utilizando controle vetorial, são comparados aos das máquinas senoidais. / The aim of this work is to analyse the torque performance of brushless machines with non-sinusoidal distributed magnetic fluxes. The machine type considered is a surface mount permanent magnet brushless machine. Three mathematical models for the machine are considered: the per stator phase, the vectorial and the linear second order speed-voltage models. Machines with different stator windings are compared including the permanent magnet synchronous machines with sinusoidal distributed stator windings. The torque outputs of these machines are obtained considering two kinds of open loop driving systems: one with a six-pulse waveform and other with a sinusoidal waveform. Finally, a vectorial control is proposed for the non-sinusoidal machines. The torque ripple as well the overall performance of non-sinusoidal machines with vectorial control is compared to that of sinusoidal machines.
335

Controlador preditivo aplicado na regulação das correntes de um motor CC de ímãs permanentes sem escovas de baixa indutância

Valle, Rodolfo Lacerda 02 February 2017 (has links)
Submitted by Renata Lopes (renatasil82@gmail.com) on 2017-04-18T15:37:21Z No. of bitstreams: 1 rodolfolacerdavalle.pdf: 15632691 bytes, checksum: 70a89dc2e4e38eb468aa2013be66ab1f (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2017-04-19T11:31:54Z (GMT) No. of bitstreams: 1 rodolfolacerdavalle.pdf: 15632691 bytes, checksum: 70a89dc2e4e38eb468aa2013be66ab1f (MD5) / Made available in DSpace on 2017-04-19T11:31:54Z (GMT). No. of bitstreams: 1 rodolfolacerdavalle.pdf: 15632691 bytes, checksum: 70a89dc2e4e38eb468aa2013be66ab1f (MD5) Previous issue date: 2017-02-02 / Esta tese apresenta as etapas de projeto e de implementação de um controlador digital preditivo para regular as correntes de um motor CC de ímãs permanentes sem escovas (do inglês, Permanent Magnets Brushless DC motor) (BLDC) de baixa indutância, trifásico a três fios. Estes tipos de motores são usualmente acionados por conversores eletrônicos de potência com múltiplos estágios, comutados em altas frequências, ou usam filtros adicionais para limitar as ondulações de corrente. As formas de onda da força contra eletromotriz induzida e das correntes retangulares dificulta o projeto e sintonia de controladores lineares. A complexidade desta tarefa aumenta quando se considera a ampla faixa de velocidade de operação do motor. Controladores digitais preditivos são facilmente implementados em processadores digitais de sinais, tendo sido usados com sucesso para regular correntes de diferentes tipos de conversores eletrônicos de potência. Três estratégias de comutação (bipolar, unipolar síncrona e unipolar) são usadas para obter três controladores PWM preditivos para regular as correntes retangulares do motor BLDC, sem a necessidade de filtros ou conversores adicionais. O fato das correntes fluírem por apenas duas das fases do motor em cada intervalo de π/3 rad permite operar o inversor fonte de tensão trifásico (Voltage Source Inverter) (VSI) como um conversor CC-CC em ponte completa. Esta característica simplifica o algoritmo de controle sendo necessário apenas um controlador para as correntes trifásicas. Parcelas para compensar o erro em regime permanente devido ao tempo morto, queda de tensão nos interruptores e atrasos de amostragem e de disparo dos interruptores são incorporadas à lei de controle modificada. Resultados experimentais e de simulação para um motor BLDC trifásico de 5 kW/48 V são apresentados para demonstrar a viabilidade da proposta. O algoritmo de controle do sistema de acionamento do motor BLDC foi implementado usando o controlador digital de sinais TMS320F28335. / This thesis presents the design and implementation steps of a digital predictive controller to regulate a low–inductance, three–phase, three–wire permanent magnet brushless DC (BLDC) motor currents. These types of motors are usually driven by multi-stage converters, switched at high frequencies, or use additional inductances to limit the current ripple. The motor’s trapezoidal back electromotive force and rectangular currents waveforms make the design and the tuning process of linear controllers difficult. This task complexity increases when a wide speed range is considered. Digital predictive controllers are easily implemented using digital signal processors (DSP), as successfully used for different types of power electronic converters currents regulation. Three switching strategies (bipolar, synchronous unipolar e unipolar) are used to obtain three PWM predictive controllers to regulate the rectangular currents of a brushless DC motor, without the need for any additional filters or converter. Due the fact that the currents flow only between two phases of the motor at every π/3 rad period makes possible to operate the three-phase voltage source inverter as a full-bridge DC–DC converter. This feature simplify the control algorithm which requires only one controller to synthesize the three-phase currents. A methodology to eliminate the steady-state error due to blanking time, switches voltage drop, sampling delay and pulse driver delay were incorporated in the modified predictive control law. Experimental and simulation results using a 5 kW/48 V three–phase BLDC motor are presented to demonstrate the feasibility of this proposal. The control algorithm was implemented in a digital signal controller TMS320F28335.
336

Acionamento de um motor síncrono de ímãs permanentes sem escovas visando aplicação em veículos elétricos

Valle, Rodolfo Lacerda 07 March 2013 (has links)
Submitted by Renata Lopes (renatasil82@gmail.com) on 2017-04-24T18:25:05Z No. of bitstreams: 1 rodolfolacerdavalle.pdf: 17326163 bytes, checksum: b5bfc03806c064bdf98c9890ed322936 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2017-04-25T12:14:13Z (GMT) No. of bitstreams: 1 rodolfolacerdavalle.pdf: 17326163 bytes, checksum: b5bfc03806c064bdf98c9890ed322936 (MD5) / Made available in DSpace on 2017-04-25T12:14:13Z (GMT). No. of bitstreams: 1 rodolfolacerdavalle.pdf: 17326163 bytes, checksum: b5bfc03806c064bdf98c9890ed322936 (MD5) Previous issue date: 2013-03-07 / Esta dissertação apresenta as etapas de desenvolvimento de um sistema de acionamento de um motor CC de ímãs permanentes sem escovas para aplicação em veículos elétricos de pequeno porte. O motor é acionado por um inversor fonte de tensão trifásico (VSI, Voltage Source Inverter) baseado em interruptores IGBT (Insulated Gate Bipolar Transistor). Os sinais de comutação dos interruptores são gerados por uma estratégia de modulação vetorial. Sinais gerados por três sensores de efeito Hall são usados para detectar a posição angular do rotor. O motor é controlado a partir de duas malhas. Uma malha externa controla a velocidade enquanto a malha interna controla as correntes de fase do motor. O desempenho de dois tipos de controladores foram investigados para o controle das correntes sintetizadas pelo VSI: (i) controlador proporcional– integral no sistema de coordenadas síncrono e (ii) controlador proporcional–integral com integradores em múltiplos sistemas de coordenadas rotativas. Além das malhas de controle, o sistema de acionamento foi projetado com uma estratégia de desacoplamento das correntes de controle e uma ação preditiva para compensar o efeito das tensões contra–eletromotriz trapezoidais geradas por fase pelo motor. Um protótipo experimental do sistema de 5 kW foi montado em laboratório. Os algoritmos de controle do motor e do VSI, juntamente com o algoritmo de deteção de posição do rotor foi implementado em um controlador digital de sinais TMS320F28335. Resultados experimentais são apresentados, discutidos e utilizados para validar as estratégias de controle. / This dissertation presents the development of a permanent magnet brushless DC motor drive (PMBLDC) for small electric vehicles applications. A three–phase voltage source inverter (VSI) based on IGBT (insulated gate bipolar transistor) is used to drive the electric motor. The semiconductor switches are controlled by space vector modulation (SVM). Signals from three Hall effect sensors are used to detect the rotor angular position. Two closed–loops are used to control the PMBLDC motor. The outer loop controls the rotor velocity while the inner loop controls the motor phase currents. Two types of controllers were investigated to synthesize the currents: (i) proportional– integral controller in synchronous reference frame and (ii) proportional–integral controller with multiple rotating synchronous reference frame integrators. Besides the current control loops, the drive system was designed considering the decoupling of the synthesized phase currents and a feed-forward electromotive force waveform compensation. An experimental prototype of 5 kW was built in laboratory. The motor and VSI control algorithms and the algorithm used to detect the rotor position were implemented in a TMS320F28335, digital signal controller. Experimental results are presented, discussed along with the validation of the control strategy.
337

Modélisation et caractérisation thermique de machines électriques synchrones à aimants permanents / Thermal modelling of permanent magnet synchronous machine

Guedia Guemo, Gilles Romuald 27 February 2014 (has links)
Les machines électriques synchrones à aimants permanents sont susceptibles de rencontrer un disfonctionnement suite à un échauffement non maîtrisé. L’objectif de cette étude est de développer un modèle thermique générique et prédictif pouvant simuler diverses situations d’intérêts: régime permanent, régime transitoire, mode dégradé, entrefer immergé, haute vitesse. Pour cela, la méthode nodale est utilisée pour développer le modèle thermique générique. En parallèle, un banc d’essai et un prototype sont conçus pour valider le modèle. L’étude de sensibilité des résultats du modèle à certains paramètres montrent que certains coefficients de convection, certaines conductances de contact et la conductivité thermique radiale du bobinage ont une influence considérable sur les résultats du modèle. Cependant ces paramètres sont mal connus, car ils sont issus des formules empiriques ou des abaques. Grâce au prototype et au modèle développé, ces paramètres sont identifiés. Trois méthodes d’identification sont testées pour aboutir à une stratégie d’identification: les algorithmes génétiques, la méthode de Gauss-Newton et la méthode de Levenberg-Marquardt. Plusieurs essais sont effectués sur le prototype instrumenté. La mesure des températures à des lieux précis du prototype permet d’identifier les paramètres mal connus et de valider le modèle. / Permanent magnet synchronous machines are likely to break down due to poorly controlled heating. The goal of this study was to develop a generic and predictive thermal model to calculate the temperature of machines during the design phase simulating temperatures at various states. These states include: steady state, transient state, fault mode, axial circulating of a cooling fluid in the air-gap and high speed. The lumped parameter method was used to develop this generic thermal model. Meanwhile, a test bench and a prototype instrumented with thermocouples were manufactured to validate the model at the same time. Sensitivity studies of the results of the model to some parameters demonstrated that some convective coefficients, contact conductances and the thermal conductivity of the winding in the radial direction influenced the model. However, these parameters are poorly known, because empirical formulas or abacus are used to calculate them. Using, the prototype and the developed model, these parameters were identified. Three methods of identification were tested in order to find a strategy for the identification: the genetic algorithms method, the Gauss-Newton method and the Levenberg-Marquardt method. Many tests were done on the prototype. The measure of the temperatures on the specific place allows to identify these parameters and to validate the model.
338

Développement d’un indicateur d’évaluation d’impacts de la consommation des ressources : cas d'application à une extraction des matériaux versus un recyclage / Development of a new resource consumption impact assessment indicator : applied to extraction of materials versus recycling.

Adibi, Naeem 01 December 2016 (has links)
L’augmentation de la consommation de ressources suscite des préoccupations quant à leur disponibilité. Ces dernières années, les organisations nationales et internationales ont défini l’approvisionnement durable des ressources et la mise en place d’une économie circulaire comme des objectifs centraux de leurs stratégies à court et long termes.Dans ce contexte, différentes approches méthodologiques relevant de l’Analyse du Cycle de Vie (ACV) sont utilisées pour caractériser l'impact de l'épuisement des ressources. Les approches actuelles fournissent néanmoins des visions partielles, car dépendantes de données disponibles limitées, et ne reflètent pas les défis de la société en lien avec cette question des ressources.La méthode et les facteurs nouvellement développés fournissent une vision plus exhaustive de la disponibilité des ressources et peuvent être utilisés dans des analyses du cycle de vie ou dans des approches d'économie circulaire. Ce travail fut produit en partenariat avec le cd2e et le pôle de compétitivité Team². Il a également été réalisé en collaboration avec le bureau d’études et d’expertise en ACV, Cycleco. / Increase in resource demand raises concerns over their availability. In the recent years, national and international institutions have targeted sustainable resource supply and new economy models (e.g. circular economy, etc.) as a goal of their short- and long-term strategies. In this context, different methodological approaches under Life Cycle Assessment (LCA) framework are used to address the impact of resource depletion. However, they provide partial visions, based on limited available data, and do not reflect society challenges related to the resources. The newly developed factors and the LCIA method provide a more exhaustive vision through the availability of resources and may be used in Life Cycle Assessment or circular economy approaches. This work is done in partnership with the cd2e and Team2 cluster. It is also carried out in collaboration with CYCLeco Life Cycle Assessment Experts.
339

Optimisation du dimensionnement d’une chaîne de conversion électrique directe incluant un système de lissage de production par supercondensateurs : application au houlogénérateur SEAREV / Sizing optimization of a direct electrical conversion chain including a supercapacitor-based power output smoothing system : application to the SEAREV wave energy converter

Aubry, Judicaël 03 November 2011 (has links)
Le travail présenté dans cette thèse porte sur l'étude du dimensionnement d'une chaine de conversion électrique en entrainement direct d'un système direct de récupération de l'énergie des vagues (searev). Cette chaine de conversion est composée d'une génératrice synchrone à aimants permanents solidaire d'un volant pendulaire, d'un convertisseur électronique composé de deux ponts triphasés à modulation de largeur d'impulsion, l'un contrôlant la génératrice, l'autre permettant d'injecter l'énergie électrique au réseau. En complément, un système de stockage de l'énergie (batterie de supercondensateurs) est destiné au lissage de la puissance produite. Le dimensionnement de tous ces éléments constitutifs nécessite une approche d'optimisation sur cycle, dans un contexte de fort couplage multi-physique notamment entre les parties hydrodynamique et électromécanique. Dans un premier temps, l'ensemble génératrice-convertisseur, dont le rôle est d'amortir le mouvement d'un volant pendulaire interne, est optimisé en vue de minimiser le coût de production de l'énergie (coût du kWh sur la durée d'usage). Cette optimisation sur cycle est réalisée en couplage fort avec le système houlogénérateur grâce à la prise en compte conjointe de variables d'optimisation relatives à l'ensemble convertisseur-machine mais aussi à la loi d'amortissement du volant pendulaire. L'intégration d'une stratégie de défluxage, intéressante pour assurer un fonctionnement en écrêtage de la puissance, permet, dès l'étape de dimensionnement, de traiter l'interaction convertisseur-machine. Dans un second temps, la capacité énergétique du système de stockage de l'énergie fait l'objet d'une optimisation en vue de la minimisation de son coût économique sur cycle de vie. Pour ce faire, nous définissons des critères de qualité de l'énergie injectée au réseau, dont un lié au flicker, et nous comparons des stratégies de gestion de l'état de charge tout en tenant compte du vieillissement en cyclage des supercondensateurs dû à la tension et à leur température. Dans un troisième temps, à partir de données d'états de mer sur une année entière, nous proposons des dimensionnements de chaines de conversion électrique qui présentent les meilleurs compromis en termes d'énergie totale récupérée et de coût d'investissement. / The work presented in this thesis sets forth the study of the sizing of a direct-drive electrical conversion chain for a direct wave energy converter (SEAREV). This electrical chain is made up of a permanent magnet synchronous generator attached to a pendular wheel and a power-electronic converter made up of two three-phase pulse width modulation bridge, one controlling the generator, the other allowing injecting electrical energy into the grid. In addition, an energy storage system (bank of supercapacitors) is intended to smooth the power output. The sizing of all these components needs an operating cycle optimization approach, in a system context with strong multi-physics coupling, more particularly between hydrodynamical and electromechanical parts. At first, the generator-converter set, whose role is to damp the pendular movement of an internal wheel, is optimized with a view to minimize the cost of energy (kWh production cost). This optimization, based on torque-speed operating profiles, is carried out considering a strong coupling with the wave energy converter thanks to the consideration as design variables, some relatives to the generator-converter sizing but also some relatives to the damping law of the pendular wheel. In addition, the consideration of a flux-weakening strategy, interesting to ensure a constant power operation (levelling), allows, as soon as the sizing step, to deal with the generator-converter interaction. In a second step, the rated energy capacity of the energy storage system is being optimized with a view of the minimization of its economical life-cycle cost. To do this, we define quality criteria of the power output, including one related to the flicker, and we compare three energy managment rules while taking into account the power cycling aging of the supercapacitors due to the voltage and their temperature. In a third step, from yearly sea-states data, we provide sizings of the direct-drive electrical conversion chain that are the best trades-offs in terms of total electrical produced energy and economical investment cost.
340

Aberration Corrector for an Exclusively Low-Voltage Electron Microscopy / Aberration Corrector for an Exclusively Low-Voltage Electron Microscopy

Bačovský, Jaromír January 2021 (has links)
Současný vývoj v oblasti nízkovoltové elektronové mikrokospie vede ke zlepšování prostorového rozlišení cestou korekce elektronově-optických vad. V posledních letech se implementace korektorů u konvenčních elektronových mikroskopů (50-200 kV) stává standardem. Nicméně zabudování korektoru do malého stolního prozařovacího mikroskopu pracujícího s nízkým urychlovacím napětím je stále výzva. Velmi vhodným řešením korekce otvorové vady u takovýchto přístrojů se zdá být koncept hexapólového korektoru založeného na bázi permantních magnetů umožňující zachovat minimální rozměry stolního transmisního mikroskopu. Přednosti a potenciál Roseho hexapólového korektoru vzhledem k použití v nízkovoltových systémech jsou předmětem kritické analýzy obsažené v této práci, včetně zásadního příspěvku tohoto korektoru k celkové chromatické vadě přístroje. Chromatická vada zůstává, navzdory veškeré snaze o její minimalizaci, zcela zásadním aspektem při návrhu korektoru. Koncept představený v rámci této dizertační práce je určen především pro skenovací prozařovací transmisní mód z důvodu omezení nárůstu chromatické vady způsobeného průchodem elektronového svazku preparátem. V práci lze také nalézt podrobný popis navržených kompenzačních systémů korektoru určených k precisnímu seřízení optické soustavy.

Page generated in 0.0541 seconds