Le Carbure de Silicium (SiC) va permettre de repousser les limites des convertisseurs dans trois directions : tenue en tension élevée, haute température de fonctionnement et forte vitesse de commutation. Aujourd’hui, les premiers modules MOSFET SiC sont disponibles sur le marché et semblent prometteurs. L’objectif de ces travaux de thèse consiste plus particulièrement à mettre en œuvre des montages permettant de caractériser ces premiers modules de puissance MOSFET SiC en vue de les utiliser dans les convertisseurs ferroviaires. Le premier chapitre est consacré à l’état de l’art d’une chaîne de traction de Tramway. C’est ce type de chaîne de traction sur lequel se concentrent les études des premières implantations de composants en SiC. Le deuxième chapitre présente un état de l’art des composants semi-conducteurs de puissance en SiC. Il rappelle tout d’abord les propriétés du matériau et détaille ensuite différentes structures de composants en SiC. Le troisième chapitre concerne les modélisations et les simulations de modules de puissance MOSFET SiC au sein d’une cellule de commutation. Les phases de commutation de ces composants sont étudiées en détail, les influences de différents paramètres sont mises en évidence et des simulations multi-physiques permettent de concevoir les bancs d’essais nécessaires à la caractérisation. Le quatrième chapitre présente les résultats des caractérisations statiques et dynamiques de modules de puissance MOSFET SiC. Ces résultats d’essai sont comparés à des modules IGBT Si de même calibre. Le cinquième chapitre est consacré à la mise en œuvre d’un banc d’essai utilisant la « méthode d’opposition ». Celui-ci permet de comparer les modules IGBT Si et les MOSFET SiC en fonctionnement onduleur grâce à des mesures électriques et calorimétriques. Le sixième et dernier chapitre présente des conclusions et donne des perspectives d’utilisation des composants MOSFET SiC dans les convertisseurs ferroviaires. Différents projets visant à utiliser des MOSFET SiC sur des applications ferroviaires y sont présentés. / Silicon Carbide (SiC) technology is pushing the limits of switching devices in three directions: higher blocking voltage, higher operating temperature and higher switching speed. Nowadays, samples of Silicon Carbide (SiC) MOSFET modules are available on the market and seem promising. The aim of the thesis is to characterize these first power modules thanks to dedicated test beds in order to use them in railway converters. The first chapter focuses on the state of the art of Tramway traction chain. It is this type of traction chain which is the target application of these SiC components. The second chapter presents a state of the art of the SiC devices. First, we recall the material properties and then we detail different structures of SiC components. The third chapter concerns modelling and simulations of SiC MOSFET power modules within a commutation cell. The switching phases of these components are studied in detail and the influences of various parameters are highlighted. Multi-physicals simulations allow designing test benches necessary for the characterization. The fourth chapter presents the results of static and dynamic characterizations of SiC MOSFET power modules. The test results are compared with Silicon IGBT modules of the same rating. The fifth chapter is dedicated to the achievement of a test bench based on the "opposition method". This test bench allows comparing Si IGBT and SiC MOSFET modules in a voltage source inverter (VSI) operation by using electrical and calorimetric measurement methods. The sixth and last chapter presents conclusions and provides outlook for SiC MOSFET components in railway converters. Different projects targeting to use SiC MOSFET on railway applications are presented.

International Telemetering Conference Proceedings / October 25-28, 1999 / Riviera Hotel and Convention Center, Las Vegas, Nevada / Compiling a PCM data frame with super commutation poses problems of maintaining constant sample intervals for the parameters whilst keeping within channel bandwidth limitations. Add an extra requirement of using variable word lengths to optimise the use of available bit rate and the problem becomes more challenging. The available telemetry or tape recorder channel bandwidth rather than the capabilities of the data acquisition system normally govern the amount of data that can be acquired by the aircraft instrumentation system. The amount of data demanded usually expands to fill all available bandwidth and the bit rates are operated at the maximum for the particular channel. The use of variable word lengths can, in some circumstances, increase the utilisation of a channel bandwidth. In order to visualise if a particular requirement can be accommodated within a given data structure a method of sketching PCM data frames containing a wide mixture of sample rates using an intermediate matrix has been devised. The method is described in three stages. 1. Compiling a simple PCM frame. 2. Sketching the intermediate matrix to assist in visualising super commutation limits. 3. Mixing variable word lengths and super commutation in the same PCM format. The method is not guaranteed to be the most efficient but does give a relatively simple, non mathematical, way to visualise if the required sample rates can be accommodated in a given data structure. If the requirement will not fit into the data structure then the method allows the impact of the necessary changes to the structure to be rapidly assessed. The paper includes comments on the relevant characteristics needed in the aircraft data acquisition system. These include variable word lengths, frame lengths, incremental bit rates and coherency of multiple data bus word parameters

ITC/USA 2011 Conference Proceedings / The Forty-Seventh Annual International Telemetering Conference and Technical Exhibition / October 24-27, 2011 / Bally's Las Vegas, Las Vegas, Nevada / The Spectrum Efficient Technology Science and Technology (SET S&T) Program is sponsoring the development of the Dynamic Commutation and Decommutation System (DCDS), which optimizes telemetry data transmission in real time. The goal of DCDS is to improve spectrum efficiency - not through improving RF techniques but rather through changing and optimizing contents of the telemetry stream during system test. By allowing the addition of new parameters to the telemetered stream at any point during system test, DCDS removes the need to transmit measured data unless it is actually needed on the ground. When compared to serial streaming telemetry, real time re-formatting of the telemetry stream does require additional processing onboard the test article. DCDS leverages advances in microprocessor technology to perform this processing while meeting size, weight, and power constraints of the test environment. Performance gains of the system have been achieved by significant multi-threading of the application, allowing it to run on modern multi-core processors. Two other enhancing technologies incorporated into DCDS are the Java programming language and lossless compression.

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Compared to conventional AC-circuit breakers, a DC-breaker has to act fast and force the current down to zero. Many different DC-breaker topologies are available, and this thesis is focused on the hybrid DC-breaker comprising a mechanical switch and high power semiconductors. The main part of this thesis is focused on the current commutations in the hybrid DC-breaker. The two current commutations: from the mechanical switch to the semiconductor branch, and from the semiconductor to the metal oxide varistor, have completely different characteristics. When the mechanical switch opens, the metallic contacts separate and an electric arc is formed. As the voltage across the arc is higher than the voltage across the semiconductors, the current is pushed over to the semiconductor branch. The undesired stray inductance in the loop limits the current derivative and slows down the commutation. As the contacts keep separating, the arc voltage increases and eventually all current is conducted by the semiconductor and the arc ceases. For a hybrid DC-breaker, the worst case is a solid ground fault, as the fast rising current results in high current levels and makes the commutation from the mechanical switch to the semiconductor both difficult and slow. However, the fast rise of the current can be used to enhance the commutation by using coupled inductors in the two parallel branches. When the fault current rises in the semiconductor branch, the mutual coupling of the inductors causes the current in the mechanical switch to decrease and helps the commutation. The result is that the commutation time decreases with decreasing fault impedance, and makes the solid ground fault easier to handle. The commutation from the semiconductor to the metal oxide varistor is controlled by the turn-off of the semiconductor. When the semiconductor is turned off, it pulls the current down to zero with a rather constant current derivative regardless of the surrounding circuit and the system current is taken over by the metal oxide varistor. Hence, any inductance in the commutation loop will result in an over-voltage proportional to this inductance on top of the varistor voltage. By connecting a smaller metal oxide varistor, as a snubber, close to the semiconductor, the over-voltage can be controlled and the commutation from the snubber to the metal oxide varistor will be driven by the voltage difference between the two varistors. It is shown that for a 12 kV DC-system, a possible design of the mechanical switch in the hybrid DC-breaker comprises two contact gaps in series and opens with a velocity of 11 m/s. It has been experimentally verified that when starting the commutation at 4 kA, the commutation takes less than 700 us and is over before the switch has opened 1 mm. The thesis also contains proposed designs for an 80 kV DC-breaker that can be used as a modular solution for higher system voltages. For this higher voltage, the design will be a choice of the combination between the number of contact gaps in series and the opening velocity of the mechanical switch. / Till skillnad från konventionella brytare i växelspänningssystem behöver en brytare för likström (DC) reagera fortare och tvinga ner strömmen. Det finns många olika topologier för hur man kan designa en DC-brytare, men denna avhandling fokuserar på en hybridbrytare som består av en mekanisk kontakt och halvledarkomponenter. Huvuddelen av denna avhandling fokuserar på kommuteringen av strömmar mellan hybridbrytarens grenar. Brytförloppet består av två kommuteringar: från den mekaniska kontakten till halvledarna och från halvledarna till en metalloxidvaristor och dessa två kommuteringar har helt olika karakteristik. När den mekaniska kontakten öppnar bildas en ljusbåde. Eftersom ljusbågsspänningen är högre än spänningsfallet över halvledarna, flyttas strömmen över till halvledargrenen. Den oönskade induktansen som finns i kretsen kommer begränsa kommuteringen och förlänga tiden det tar att flytta strömmen från den mekaniska kontakten till halvledarna. Tack vare att den mekaniska kontakten öppnar med hög hastighet förlängs ljusbågen och ljusbågsspänningen fortsätter att öka tills all ström flyttats över till halvledarna och ljusbågen slocknar. För hybridbrytaren är ett solitt jordfel det värsta felfallet eftersom den snabbt ökande felströmmen leder till en svårare och mer utdragen kommutering till halvledarna. Den höga strömderivatan kan dock utnyttjas genom att installera två kopplade spolar i serie med den mekaniska kontakten och halvledarna. När strömmen ökar i halvledargrenen skapar den kopplade induktansen en motspänning som leder till en minskad ström genom den mekaniska kontakten och snabbar på kommuteringen. Resultatet är att kommuteringstiden blir kortare ju snabbare felströmmen växer. Kommuteringen från halvledarna till varistorn styrs av halvledarkomponenternas karakteristik. När halvledaren stänger av tvingas strömmen ner med en näst intill konstant derivata oberoende av komponenterna i kretsen och strömmen tas över av varistorn. Den oönskade induktansen i kretsen kommer då ge upphov till en överspänning proportionell till induktansen som ökar kraven på halvledaren. Genom att installera en liten varistor nära halvledaren kan överspänningen kontrolleras och kommuteringen kommer istället drivas av spänningsskillnaden mellan de två varistorerna. För ett 12 kV likströmssystem är en möjlig design av den mekaniska kontakten att ha två kontaktgap i serie och en öppningshastighet på 11 m/s. Experiment har verifierat att om kommuteringen startar vid 4 kA tar den midre än 700 us och är avslutad innan kontakten öppnats 1 mm. Avhandlingen innehåller även förslag på hur en 80 kV brytare kan designas för att användas som en modul i system med högre spänning. I det fallet är designen en avvägning mellan antalet kontakter i serie och öppningshastigheten på kontakten. / <p>QC 20170519</p>

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

La demande en applications gourmandes en bande passante, comme la vidéo interactive et le multimédia, s’est encore accrue rendant l’attribution de la bande passante particulièrement problématique. Ainsi, bien que le multiplexage par répartition en longueur d'onde du réseau optique passif (WDM-PON) est considéré comme un candidat prometteur pour réaliser les réseaux d'accès optiques, de nouvelles générations de systèmes hauts débits plus adaptés apparaissent grâce à la gestion d’une bande passante dédiée pour chaque abonné et de façon générale, une gestion de bande passante plus flexible. La première moitié de cette thèse porte sur trois technologies dans un WDM-PON : un système de recouvrement de multidiffusion, un système de protection automatique de commutation et de diode laser accordable Fabry-Pérot (FP-LD) en régime auto-amorcé. Dans la seconde moitié de la thèse, on étudie un réseau optique WDM distribué, utilisé pour un environnement informatique virtuel reliant des ressources informatiques largement distribuées afin de supporter des applications de calcul scientifique, d'ingénierie ou commerciale distribués à grande échelle. Ce système est ainsi appelé "grille" des systèmes optiques. Les applications de réseaux peuvent aller du simple transfert d'un grand ensemble de données à l'exécution complexe d'un ensemble de tâches interdépendantes. Cependant, dans un tel système impliquant de nombreuses ressources informatiques hétérogènes ainsi que des ressources réseau, les imperfections paraissent inévitables. Cette thèse aborde également en conséquence la question de la maximisation de la disponibilité des applications réseau en temps réel (grille de systèmes optiques) grâce à des techniques de planification des ressources et leurs tolérances face aux pannes. / The bandwidth-intensive applications, such as interactive video and multimedia services, have further increased the demand of bandwidth. Thus wavelength division multiplexing passive optical network (WDM-PON) is viewed as a promising candidate to realize the next generation optical access networks due to its dedicated bandwidth for each subscriber and more flexible bandwidth management. The first half of this thesis will cover three technologies in a WDM-PON, including multicast overlay scheme, automatic protection switching scheme and tunable Fabry-Pérot laser diode (FP-LD) self-seeding scheme. In the second half of the thesis, WDM optical network is utilized as a virtual computing environment, which connects widely distributed computing resources to support large-scale scientific, engineering or commercial computing applications. It is so called “optical Grid” systems. Grid applications may range from the simple transfer of a large data set to the complex execution of a collection of interdependent tasks. However, for such a system involving many heterogeneous computing and network resources, faults seem to be inevitable. This thesis will also address the issue of maximizing grid application availability in real-time optical Grid systems through resource-fault-tolerant scheduling techniques.

Title: Instantons and Unitarily Inequivalent Quantum Vacua Author: Roman Derco Department: Institute of Particle and Nuclear Physics Supervisor: doc. Alfredo Iorio, Ph.D., Institute of Particle and Nuclear Physics Abstract: In the presented thesis we investigate the relationship between the topologically distinct instantonic vacua and the unitarily inequivalent vacua of the quantum field theory. We focus on quantum mechanical exam- ples, where instantons appear but the complications due to quantum gauge field theory are absent. A model for quantum dissipation and the theory of one particle escaping from a metastable minimum were compared, what led to some observations. A double well system was build from harmonic oscillators and an interaction term to get closer to the quantum dissipation model, where inequivalent representations are involved. We identified the particularly simple model of a quantum particle constrained on a circle to be the ideal toy model for spotting the relation among unitarily inequivalent vacua and topologically distinct vacua we were seeking for. 1

Dans l'aéronautique, l'alimentation d'un système embarqué contribue largement à augmenter le coût récurrent, l'efficacité globale et le volume de l'équipement. De plus, les alimentations sont installées dans un environnement sévère avec une large plage de tension d'entrée et un milieu confiné. Dans ces conditions, les pertes du convertisseur influent fortement sur le volume et le poids du système qui doit s'efforcer de limiter les échauffements. Ainsi, la réduction des pertes du convertisseur est l'un des leviers les plus efficaces pour augmenter la densité de puissance des convertisseurs. Parmi les techniques connues, la commutation douce peut être une solution pour réduire les pertes du convertisseur tout en augmentant sa fréquence de découpage. La sélection d'une topologie à commutation douce se fait selon 3 critères; un faible nombre de composants, une fonction de transfert et des commutations douces qui couvrent toute la plage de fonctionnement. En prenant tout cela en considération, la meilleure candidate semble être la topologie Flyback active-clamp. Avec seulement une capacité et un transistor supplémentaires, cette topologie possède une fonction abaisseuse et élévatrice et réalise des commutations en ZVS au primaire.Un travail technologique doit également être réalisé afin d'améliorer davantage l'efficacité du convertisseur. Les technologies qui ont été sélectionnées sont les transistors GaN pour leurs performances en commutation et le transformateur planar pour son intégration dans le PCB. Par ailleurs, une intégration verticale du convertisseur qui est à présent sur deux cartes superposées, une pour les fonctions BF et l'autre pour les fonctions HF, a permis de minimiser l'empreinte du convertisseur.Les technologies émergentes vont faire un important saut technologique, en particulier dans les systèmes où l'alimentation représente une part significative de l'équipement. Le succès des transistors GaN met clairement en lumière que l'électronique de puissance devient plus performante. Dans ce contexte, réduire les éléments parasites est une priorité. En se projetant dans le futur, l'intérêt porté aux alimentations intégrées va accélérer le développement des techniques de packaging telles que l'enfouissement des composants dans le PCB et les modules sur céramique / The power supply system in an onboard aeronautical application represents an important contribution to the recurring cost, global efficiency and the volume of the system. Moreover, power supplies are installed in a harsh environment with a wide input voltage range and a confined area. In these conditions, power supply losses impact the converter volume and weight to prevent the system from overheating. Therefore, a gain in efficiency is the main purposes, since it has a significant impact on the reduction of weight and volume of the equipment.Soft-switching is a reasonable technique to increase the switching frequency and limit the power losses. The selection of the topology should take into account 3 considerations: a low number of components, an efficient control, which allows to cover the wide input voltage range and a soft-switching validity over a large input voltage range. Regarding all the considerations, the Flyback active-Clamp topology seems to be the best candidate which has a step-up and down transfer function and ZVS at the primary with only ones additional capacitor and transistor.A technological work is also done to further increase the power supply efficiency. The technologies which have been selected are the GaN transistors for its good switching performances and a planar transformer for its integration into the PCB. Also, the vertical integration of the converter which is actually on two stackable boards, one for the low frequency functions and the other one for the high frequency functions, minimizes the footprint of the converter. The new technologies will make a huge technological leap, especially in the systems where the power supply represents a significant proportion of the equipment. The success of GaN transistor highlights that the power electronics is currently driving by the performance and reducing the parasitic elements is becoming the priority. Looking forward into the future, the interest in 3D packaging and PCB integration will grow rapidly to provide a fully embedded power supply

Este trabalho tem como principal objetivo apresentar uma investigação e uma metodologia de projeto, até o presente momento inédita, de uma topologia de um conversor ca-cc trifásico de comutação forçada. Através da análise desenvolvida neste trabalho, determina-se um modelo matemático do conversor ca-cc para os quatro modos que determinam o processo da comutação nesse circuito. Esse modelo resulta em sistemas de equações fundamentais na forma de equações diferenciais, que são resolvidos com a finalidade de determinar o comportamento do circuito do conversor durante o processo de comutação e de obter uma metodologia de projeto. Com o objetivo de validar a investigação e o método de projeto foi implementada simulação computacional, no programa Simmon, dos intervalos de comutação do conversor ca-cc de comutação forçada. Essa estrutura, que durante a sua operação emprega tanto a comutação forçada como a natural, quando comparada com os conversores de comutação natural apresenta várias vantagens, como um alto fator de potência e a eliminação dos harmônicos de baixa ordem na linha ca (utilização da comutação forçada com a técnica de modulação por largura de pulso PWM), como mostra vátios trabalhos publicados, que estão desctitos na parte de referências bibliográficas deste texto. / The main objective of this work is to present an investigation and a design method, which up to now is not available in the literature, of a three-phase force commutated ac-dc convetier. From the analysis developed in this work one obtains the mathematical model of the ac-dc converter for its four modes of commutation, which determine the commutation process in the converter circuit. The fundamental equations, which have been written in the form of differential equations, are solved to determine the behaviour of the converter circuit during commutation, and also to obtain a design method. To validate the analysis and the design procedure, computer simulation of the commutation intervals of the ac-dc converter was implemented using the program Simnon. The three-phase ac-dc converter, which uses both forced and line commutation, when compared with the conventional line commutated converter, presents several advantages as a high power factor and the elimination of lower harmonics of the ac line (utilization of the forced commutation and the pulse width modulation strategy), as it is shown in several published works, which can be found in the references of this work.