Dissertations / Theses on the topic 'Solid-state transformer'

The Solid State Transformer (SST) is an emerging solution that can advantageously substitute the conventional transformer, thanks to its capabilities. Furthermore, it is a multi-functional equipment that offers: - conditioning of the power flow, whether of DC or AC form; - reduced size and weight thanks to the high frequency transformer; - good voltage regulating capabilities; - no diffusion of voltage swell or sag thanks to the DC link (if any); - power factor correction; - fast fault detection and protection; - capability to maintain the output feed for a time (hold up time) thanks to the DC link capacitors; Moreover, it offers the conventional transformer properties: - galvanic isolation between input and output; - step up/down of the input voltage; The SST capabilities make this technology an important solution to solve the current and future issues of the grid. The reduced weight and size allow getting high performances in the traction systems. The bidirectional power flow capabilities allow the connection and management of renewable energy sources (RES) with the grid and different loads, connected to AC side or, if present, to DC link.<br>Il trasformatore a stato solido (SST) è un emergente tecnologia che può sostituire i trasformatori convenzionali, apportando notevoli vantaggi grazie alle sue potenzialità e funzionalità. Tra le più importanti abbiamo: -condizionamento del flusso di potenza, sia DC che in AC; -ridotte dimensioni e peso, grazie all'uso di un trasformatore in alta frequenza; -ottima regolazione della tensione; -limita diffusione di buchi di tensione; -correzione del fattore di potenza; -hold up time funzionalità; -isolamento galvanico. Grazie a queste funzionalità questa tecnologia diventa molto importante per poter affrontare problemi, presenti e futuri, legati alla gestione della rete elettrica. La possibilità di gestire il flusso di energia e la bidirezionalità del flusso di potenza consentono di facilitare l'integrazione delle risorse rinnovabili con la rete elettrica. Inoltre, la riduzione dipeso e dimensioni consentono di ottenere alte performance in sistemi usati per la trazione.

The solid state transformer (SST) is seen as a proper replacement of the conventional iron-and-copper transformer in the future smart grid . The SST offers several benefits (e.g. enhanced power quality performance or reactive power control at both primary and secondary sides) that can be of paramount importance for the development of the smart grid . This research focuses on the development and implementation of an advanced model of a three stage bidirectional SST in Matlab/Simulink. The goal is to obtain an realistic SST model (i.e. as close to the real SST as possible) that could duplicate the performance of a real MV/LV SST. This considered design consists of three main stages: medium voltage (MV) stage, isolation stage, and low voltage (LV) stage. When the power flows from the MV side to the LV side, the input power-frequency ac voltage is converted into a MV dc voltage by the three-phase ac/dc converter, which in such case works as rectifier. The isolation stage, which includes a high-frequency transformer (HFT) and the two corresponding MV- and LV-side converters, first converts the MV-side dc voltage into a high-frequency square-wave voltage applied to the primary of the HFT; the secondary side square-wave signal is then converted to a LV dc waveform by the LV-side converter, which also works as rectifier. Finally, the output LV-side three-phase dc/ac converter, which works as inverter, provides the output power-frequency ac waveform from the LV-side dc link. Si-based semiconductor technologies can be used for MV applications using a multilelvel configuration. Recently, modular multilevel converter (MMC) topologies have attracted attention for high or medium voltage applications. These converters can provide an effective topology for the MV side of the SST; their main advantages are modularity and scalability: the desired voltage level can be easily achieved by a series connection of MMC sub-modules (SMs). In addition,a MMC topology can provide high power quality and efficiency with reduced size of passive filters. These features made the MMC option an attractive topology for the MV stage of the SST. This thesis proposes a three-stage SST configuration based on MMC technology for MV converters. * The input stage of the SST is connected to the distribution system via RL filters and its three-phase configuration uses a MMC technology. A half-bridge configuration is proposed for each SM. * The isolation stage consists of three parts: a MV single-phase MMC, the high-frequency transformer (HFT), and a single-phase LV PWM converter. * The LV side of the SST uses a three-phase four-leg PWM converter, with an RL impedance for filtering currents and a capacitor bank for filtering voltages. The converters and their controller have been implemented adn tested considering models without and with semiconductor losses, while the SST model has been tested as a stand-alone device and a compnent of a distribution system. The model has been tested under severe dynamic and unbalanced conditions. The simulation results support the choices made for any SST stage and proves that the proposed design could be a feasible choice for the future SST.<br>El Transformador de Estado Sólido ("Solid State Transformer" por sus siglas en inglés) es visto como un reemplazo adecuado del transformador convencional en las futuras redes inteligentes (smart grids ). Este nuevo dispositivo presenta una amplia gama de prestaciones (p.e. mejora de la cualidad de suministro) que pueden ser de crucial importancia para el desarrollo de las redes inteligentes. El principal objetivo de esta tesis es que desarrollar e implantar el en Matlab/Simulink un modelo realista de estado sólido trifásico y bidireccional, que pueda duplicar el comportamiento de un transformador de estado sólido de Media-Baja tensión. El diseño considerado consiste en tres etapas: etapa en media tensión (MT), etapa intermedia, etapa en baja tensión (BT). Cuando la potencia fluye del terminal en media al terminal en baja tensión, la tensión alterna en el terminal de entrada a media tensión y frecuencia de operación 50 Hz se convierte en continua a media tensión mediante un convertidor trifásico rectificador. La etapa intermedia es un puente activo dual, que incluye un transformador de alta frecuencia y los correspondientes convertidores en media y baja tensión: primero, la media tensión continua es convertida en media tensión alterna a alta frecuencia; esta tensión es reducida a baja tensión preservando la alta frecuencia mediante el transformador, finalmente, la tensión en el terminal de salida del transformador es rectificada y convertida en baja tensión continua). La entrada en la etapa de salida en BT es, por tanto, una tensión continua que es convertida en tensión alterna a frecuencia de operación 50 Hz mediante un convertidor que funciona como inversor. Puesto que el diseño del dispositivo estudiado en esta tesis es bidireccional, en caso de que la potencia tenga que fluir desde el lado de BT al lado de MT, la función de los convertidores se invierte (es decir, los rectificadores pasan a operar como inversores, los inversores pasan a operar como rectificadores) en cualquiera de las etapas. Los actuales semiconductores solo pueden ser utilizados en aplicaciones de media y alta tensión empleando convertidores multi-nivel. Durante los últimos años ha ganado popularidad la tecnología MMC (modular multilevel converter), que permite diseñar configuraciones adecuadas para el lado de MT de un transformador de estado sólido; sus principales ventajas están en modularidad y escalabilidad: el nivel de tensión adecuado se puede conseguir mediante la conexión en serie de tantos sub-módulos como sea necesario. Además con la tecnología MMC se puede obtener una alta calidad en las ondas de tensión y corriente, así como un elevado rendimiento con tamaño reducido en los filtros de entrada. Esta tesis propone un diseño trifásico bidireccional con las siguientes características: - La etapa de entrada está conectada a una red de distribución en MT mediante filtros RL y su configuración trifásica usa convertidores de tecnología MMC. - La etapa intermedia contiene tres secciones: un convertidor monofásico en configuración MMC, un transformador de MT/BT y alta frecuencia, y un convertidor monofásico en BT. - La etapa de salida en BT usa un convertidor trifásico PWM (pulse wide modulation), con un filtro RL para las corrientes y un banco de condensadores para filtrar tensiones. Los convertidores han sido implantados en Matlab/Simulink y simulados considerando modelos con y sin pérdidas en los semiconductores, mientras que el modelo completo de transformador de estado sólido ha sido analizado considerando dos configuraciones distintas del sistema a estudiar: el transformador aislado y formando parte de una red de distribución en MT. Los modelos de transformador con y sin pérdidas han sido simulados bajo ciertas condiciones de operación. Los resultados confirman que la configuración seleccionada para cada etapa del nuevo dispositivo permite obtener un diseño fiable que puede mejorar el funcionamiento de las futuras redes inteligentes.

Thesis (MScEng)--Stellenbosch University, 2011.<br>ENGLISH ABSTRACT: The Solid-State Transformer (SST) is presented as an alternative to the traditional Line-Frequency Transformer (LFT) used for voltage-level transformation in distribution grids. The LFT technology is highly matured which results in low costs and high efficiency. The SST however, introduces several advantages compared to the LFT, some of which are input unity power-factor, near perfect output-voltage regulation, frequency variation as well as harmonic filtering. The SST consists of three power-electronic converter stages: The input stage, the isolation stage and the output stage. The input and isolation stages are implemented with a multilevelconverter topology incorporating a converter-stack for each phase. Each stack consists of N converter building blocks, called cells. In this thesis the design and implementation of the main controller is presented. The main controller, together with N cell controllers, is responsible for the control of the cells within the respective stack. Three main controllers are thus implemented within the SST. Each cell consists of an Active Rectifier (AR) and a DC-DC Converter (DC-DC). The SST control design thus starts with the AR control which is subsequently expanded to Cascaded Active-Rectifier (CAR) control. Design is completed with the addition of the DC-DC control. Time domain simulations of the AR- and CAR-control are presented and discussed. Test measurements, verifying functionality of each control design-phase, are presented and discussed.<br>AFRIKAANSE OPSOMMING: Die Drywingselektroniese Transformator (DET) word voorgestel as ’n alternatief vir die Lyn Frekwensie Transformator (LFT) wat gebruik word vir spannings-vlak tranformasie op distribusie vlak. The LFT tegnologie is ver gevorderd wat ly tot hoë effektiwiteit en lae kostes. The DET bied wel voordele soos intree eenheids arbeid faktor, na aan perfecte uittree-spannings regulasie, frequensie variasie sovel as harmoniese filrteering. Die DET bestaan uit drie drywingselektroniese omsetter stadiums: Die intree-stadium, die isolasie-stadium en die uittree-stadium. The intree- en isolasie-stadiums word geïmplimenteer met ’n multivlak-omsetter topologie wat bestaan uit ’n omsetter-stapel vir elke fase. Elke stapel bestaan uit N omsetter boustene wat selle genoem word. In hierdie tesis word the ontwerp en implementasie van die hoofbeheerder voorgestel. Die hoofbeheerder, tesame met N selbeheerders, is verantwoordelik vir die beheer van elke sel in die spesifieke stapel. In die DET word daar dus drie hoofbeheerders gebruik. Elke sel bestaan uit ’n Aktiewe Gelykrigter (AG) en ’n GS-GS omsetter (GS-GS). Die DET beheerontwerp begin dus met die (AG) beheer wat daarna uitgebrei word na Kaskade Aktiewe Gelykrigter (KAG) beheer. Die beheer ontwerp word voltooi deur die byvoeging van die GSGS beheer. Tyd-gebied simulasies van die AG- en KAG-beheer word voorgelê en bespreek. Toetsmetings wat die funksionaliteit van elke beheer ontwepsfase verifeer, word voorgelê.

Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2009.<br>ENGLISH ABSTRACT: The purpose of a solid state transformer (SST) is to use power electronic converters to mimic the operation of the conventional distribution transformer. These power electronic converters are proposed to overcome the disadvantages of the conventional distribution transformer. The advantages of a SST include near perfect voltage regulation and harmonic isolation between the primary and secondary windings of the transformer. This thesis discusses the design and development of the different converters in a solid state transformer (SST). A prototype modular back-to-back converter is developed for the input and isolation stage of the SST. The isolation stage consists of a high voltage DC-DC converter, which transfers power across the isolation barrier of the SST. This stage is evaluated in the laboratory with special attention being paid to the efficiency of the converter. The second aspect that this thesis addresses is the output stage of the SST, namely a three phase inverter. The discussion of the output stage focuses on the losses occurring in the inverter. The switching device losses are calculated by means of an adapted numerical method as opposed to using conventional analytical methods. The presented numerical method is compared to the existing analytical method and the findings are discussed. A double loop control strategy is implemented for the output stage inverter. The inner current loop utilizes a predictive control strategy. The control analysis of the double loop controller is discussed and evaluated in the laboratory. All the converters that are discussed in this thesis are evaluated in the laboratory and the relevant measurements are included.<br>AFRIKAANSE OPSOMMING: Die doel van ’n drywingselektroniese transformator (DET) is om drywingselektroniese omsetters te gebruik om die werking van die konvensionele distribusietransformator na te boots. Hierdie drywingselektroniese omsetters word voorgestel ten einde die nadele van die konvensionele distribusietransformator te bowe te kom. Die voordele van ’n DET sluit in: feitlik perfekte regulering van spanning en harmoniese isolasie tussen die primˆere en sekondˆere windings van die transformator. Hierdie tesis bespreek die ontwerp en ontwikkeling van die verskillende omsetters in ’n drywingselektroniese transformator (DET). ’n Prototipe modulˆere rug-aan-rug-omsetter word ontwikkel vir die intree- en isolasiefase van die DET. Die isolasiefase bestaan uit ’n hoogspanning- GS-GS omsetter, wat drywing oor die isolasiegrens van die DET heen oordra. Hierdie omsetter word in die laboratorium ge¨evalueer met besondere aandag aan die doeltreffendheid van die omsetter. Die tweede aspek waarna in hierdie tesis gekyk word, is die uittreefase van die DET, naamlik ’n driefaseomsetter. Die bespreking van die uittreefase fokus egter op die verliese wat in die omsetter voorkom. Die verliese van die skakelaars word bereken deur middel van ’n aangepaste numeriese metode teenoor die gebruik van konvensionele analitiese metodes. Die numeriese metode wat aangebied word, word vergelyk met die bestaande analitiese metode en die bevindings word bespreek. ’n Dubbellus-beheerstrategie word vir die uittreefase-omsetter ge¨ımplementeer. Die binneste stroomlus word ge¨ımplementeer deur van ’n voorspelbare beheerstrategie gebruik te maak. Die beheeranalise van die dubbellusbeheerder word bespreek en in die laboratorium ge¨evalueer. Al die omsetters wat in hierdie tesis bespreek word, word in die laboratorium ge¨evalueer en die relevante metings word ingesluit.

Thesis (MScEng (Electrical and Electronic Engineering))--Stellenbosch University, 2011.<br>ENGLISH ABSTRACT: This thesis investigates the viability of constructing a solid-state transformer (SST) with a series-input, parallel-output connection of full-bridge, three-level ying-capacitor converters. It focusses on the active recti er front-end of the SST which is used to control the input current to be sinusoidal and in-phase with the sinusoidal input voltage. A stack of two converters are built and tested. The input current, as well as the ying capacitor voltages of the two active recti ers in the stack, are actively controlled by a nite-state model-based predictive (FS-MPC) controller. The use of multiple ying-capacitor converters poses a problem when using FS-MPC because of the large number of possible switching states to include in the prediction equations. Three FS-MPC control algorithms are proposed to attempt to overcome the problem associated with the large number of switching states. They are implemented on an FPGA digital controller. The algorithms are compared on the bases of voltage and current errors, as well as their responses to disturbances that are introduced into the system. The simulation and experimental results that are presented shows that by interleaving the control actions for the two converters, one can obtain fast and robust responses of the controlled variables. The viability of extending the interleaving control algorithm beyond two converters is also motivated.<br>AFRIKAANSE OPSOMMING: Hierdie tesis ondersoek die moontlikheid van volbrug, drievlak vlieënde-kapasitoromsetters wat gebruik word om 'n serie-intree, parallel-uittree drywingselektroniese transformator (DET) te bou. Dit fokus op die aktiewe gelykrigter van die DET wat gebruik word om die intreestroom te beheer om sinusvormig en in fase met die sinusvormige intreespanning te wees. 'n Stapel van twee omsetters word gebou en getoets. Die intreestroom, sowel as die vlieënde kapasitorspannings van die twee aktiewe gelykrigters in die stapel, word aktief beheer met behulp van 'n eindige-toestand, model-gebaseerde voorspellende beheerder (ET-MVB). Die gebruik van veelvuldige vlieënde-kapasitoromsetters bemoeilik die implementering van 'n ET-MVB-beheerder as gevolg van die groot aantal skakeltoestande wat in die voorspellende vergelykings in ag geneem moet word. Drie ET-MVB-algoritmes word voorgestel om te poog om die probleme, wat met die groot aantal skakeltoestande geassosieer word, te oorkom. Die algoritmes word in 'n FPGA digitale verwerker geïmplementeer. Die algoritmes word vergelyk op grond van hul stroom- en spanningsfoute, asook hul reaksie op steurings wat op die stelsel ingevoer word. Die simulasie en praktiese resultate toon dat, deur die beheeraksies vir die twee omsetters te laat oorvleuel, die gedrag van die beheerde veranderlikes vinniger en meer robuust is. Die moontlikheid om die oorvleuelende beheeraksies uit te brei tot meer as twee omsetters word ook gemotiveer.

Thesis (MScEng)--Stellenbosch University, 2011.<br>ENGLISH ABSTRACT: Cash can be seen as a fast moving consumer good. Approaching cash as inventory within the ATM cash management environment of a South African retail bank, provided the opportunity to apply well known industrial engineering techniques to the financial industry. This led to the application of forecasting, inventory management, operational research and simulation methods. A forecasting model is designed to address the multiple seasonalities and calendar day effects that is prevalent in the demand for cash. Special days, e.g. paydays, lead to an increase in demand for cash. The weekday on which the special day falls will also influence the demand. The multiplicative Holt-Winters method is combined with an improvised distribution method to determine the demand for cash for the region and per ATM. Reordering points are calculated and simulated to form an understanding of the effect this will have on the ATM network. Direct replenishment and the traveling salesman problem is applied and simulated to determine the difference in using one or the other. Various simulation models are build to test the operational and financial impact when certain variables are amended. It is evident that more work is required to determine the optimal combination of variable values, i.e. forecasting frequency, aggregate forecasting or individual forecasting, reorder levels, loading levels, lead times, cash swap or cash add, and the type of transportation method. Each one of these are a science in itself and cannot be seen (calculated) in isolation from the other as a change in one can affect the overall operational efficiency and costs of the ATM network. The thesis proves that significant cost savings is possible, compared to the current set-up, when applying industrial engineering techniques to a geographical ATM network within South Africa.<br>AFRIKAANSE OPSOMMING: Kontant kan gesien word as vinnig bewegende verbruikersgoedere. Deur kontant te benader as voorraad binne die ATM kontant bestuur omgewing van ’n Suid Afrikaanse kleinhandelsbank, het dit die geleentheid geskep om bekende bedryfsingenieurstegnieke toe te pas in die finansiële industrie. Dit het gelei tot die toepassing van vooruitskatting, voorraadbestuur, operasionele navorsing en simulasie metodes. ’n Vooruitskattingsmodel is ontwerp om die verskeie seisoenaliteite en kalenderdae effekte wat deel uitmaak van die vraag na kontant aan te spreek. Spesiale dae, bv. betaaldae, lei tot ’n toename in die vraag na kontant. Die weeksdag waarop die spesiale dag voorkom sal ook ’n invloed hê op die vraag. Die multiplikatiewe Holt-Winters metode is gekombineer met ’n geïmproviseerde verspreidingsmetode om die vraag na kontant vir die streek en per ATM the bepaal. Bestellingsvlakke is bereken en gesimuleer om ’n prentjie te skep van die invloed wat dit op die ATM netwerk sal hê. Direkte hervulling en die handelsreisigerprobleem is toegepas en gesimuleer om die verskille te bepaal tussen die gebruik van of die een of die ander. Veskeie simulasie modelle is gebou om die operasionele en finansiële impak te toets, wanneer sekere veranderlikes aangepas word. Dit is duidelik dat meer werk nodig is om die optimale kombinasie van veranderlike waardes te bepaal, bv. vooruitskatting frekwensie, totale vooruiskatting of individuele vooruitskatting, bestellingsvlakke, leitye, kontant omruiling of kontant byvoeging, en die tipe vervoermetode. Elkeen van hierdie is ’n wetenskap op sy eie en kan nie in isolasie gesien en bereken word nie, want ’n verandering van een se waarde kan die hele operasionele doeltreffendheid en kostes van die ATM netwerk beïnvloed.

Ce travail concerne l'étude théorique,l’analyse numérique et la validationexpérimentale d'une topologie de convertisseurd’électronique de puissance basée sur unconvertisseur multiniveau modulaire entrelacéavec transformateur moyenne fréquence.L’architecture est adaptée pour l’étage deconversion AC-DC dans les applications detransformateur d'électronique de puissance pourla connexion entre un réseau alternatif moyennetension et un réseau continu basse tension.L’entrelacement réduit les pertes par conductiondans les interrupteurs. Le transformateurmoyenne fréquence 10 kHz assure une isolationgalvanique et connecte le convertisseurmultiniveau modulaire entrelacé à unconvertisseur pont complet. Avec comme pointde départ la structure, le principe defonctionnement, la modélisation, la technique demodulation et le schéma de commande sontdiscutés. Une caractéristique du convertisseur estla génération simultanée de la tension du réseaubasse fréquence et de la tension primaire dutransformateur moyenne fréquence.L'équilibrage de la tension des condensateurs etla minimisation du courant de circulation sontcombinés dans un seul algorithme. La commanderégule le courant alternatif et la tension du buscontinu, du côté haute tension, ainsi que latension continue et le flux de puissance, du côtébasse tension. La validation expérimentale duconvertisseur est réalisée avec un prototype de720 W monophasé à l’échelle réduite. Lesrésultats démontrent la stabilité du système decommande lors d'opérations en régimepermanent et dynamiques (pas de charge,inversion du flux de puissance)<br>This work aims to present thetheoretical study, the numerical analysis and theexperimental validation of a power electronicsconverter topology based on an interleavedmodular multilevel converter with mediumfrequencytransformer. The architecture issuitable for the AC-DC stage in solid-statetransformer applications for the connectionbetween a medium-voltage AC grid and a lowvoltageDC grid. The interleaving reduces theswitch conduction losses. The 10 kHz mediumfrequencytransformer provides galvanicisolation and connects the interleaved modularmultilevel converter to a full-bridge converter.From the converter structure, the principle ofoperation, the modeling, the modulationtechnique, and the control scheme are discussed.One feature of the converter is the simultaneousgeneration of the low-frequency grid voltageand the medium-frequency transformer primaryvoltage. The capacitor voltage balancing and thecirculating currents minimization are combinedtogether in a single algorithm. The controlsystem regulates the AC current and the DC busvoltage, on the high-voltage side, and the DCvoltage and power flow, on the low voltage side.The experimental validation of the converter ismade with a scaled-down single-phase 720 Wprototype. The results demonstrate the controlsystem stability in steady-state and dynamic(load step, power flow inversion) operations

Orientador: Júlio Borges de Souza<br>Resumo: O transformador de estado sólido tem se apresentado como uma ferramenta indispensável na construção das novas redes elétricas inteligentes, uma vez que essa nova estrutura de rede altera o layout tradicional, viabilizando a conexão de fontes de energia descentralizadas. Contudo, essa conexão de sistemas de geração distribuída na rede originou a bidirecionalidade do fluxo de potência, resultando em um novo panorama para as atividades de operação e manutenção das redes para as distribuidoras de energia. A análise dos possíveis impactos técnicos gerados na rede de distribuição deve ser realizada, com o intuito de garantir um nível de qualidade energética dentro dos padrões estabelecidos pela Agência Nacional de Energia Elétrica – ANEEL. Dentre os impactos, destacam-se a elevação do nível de tensão e a alteração do fator de potência, ambos, produzidos pelo excesso de potência injetada na rede por este novo cenário de geração de energia. Nesse contexto, esta dissertação tem como principal objetivo analisar o comportamento de uma rede de distribuição genérica com penetração de geração distribuída e avaliar o perfil de tensão diante de diferentes níveis de inserção dessa geração na rede. As características de ajuste de tensão instantânea e capacidade de interação com sistemas de armazenamento que o transformador de estado sólido possui foram empregadas no auxílio da regulação dos níveis de tensão que se apresentaram fora dos padrões determinados pela resolução 794/2018 da ANEEL, qua... (Resumo completo, clicar acesso eletrônico abaixo)<br>Abstract: The solid state transformer has been presented as an essential tool in the construction of new intelligent electric grids, since this new network structure changes the traditional layout, making possible the connection of decentralized energy sources. However, this connection of distributed generation systems in the network created the bidirectionality of the power flow, resulting in a new panorama for the power distributors concerning the networks activities of operation and maintenance. The analysis of the possible technical impacts generated in the distribution network should be carried out with the purpose of guaranteeing a level of energy quality within the standards established by the National Electric Energy Agency (ANEEL). Among the impacts, we highlight the elevation of the voltage level and the change in the power factor, both produced by the excess power injected into the grid by this new energy generation scenario. In this context, the main objective of this dissertation is to analyze the behavior of a generic distribution network with distributed generation penetration and to evaluate the voltage profile before different levels of insertion of this generation in the network. The solid state transformer has instantaneous voltage adjustment characteristics and interaction capacity with storage systems, which were used to aid in the regulation of voltage levels that were out of the standards determined by ANEEL resolution 794/2018, when a high level of distributed g... (Complete abstract click electronic access below)<br>Mestre

Роботу виконано у Тернопільському національному технічному університеті імені Івана Пулюя Міністерства освіти і науки, молоді та спорту України. Захист відбувся 23 березня 2012 р. об 11.00 годині на засіданні спеціа-лізованої вченої ради К 58.052.04 у Тернопільському національному техніч-ному університеті імені Івана Пулюя (46001. Україна, м. Тернопіль, вул. Ру-ська, 56). З дисертацією можна ознайомитися у бібліотеці Тернопільського націо-нального технічного університету ім. Івана Пулюя (46001, Україна, м. Терно-піль, вул. Руська, 56).<br>У дисертації проведено дослідження високочастотних напівпровід-никових пускорегулюючих апаратів (НПРА) на базі п’єзоелектричного тран-сформатора струму (ПТ), а також розроблено методику розрахунку, яка вра-ховує як особливості самого ПТ, так і його нелінійного навантаження, яким є люмінесцентна лампа (ЛЛ) у схемах стартерного та безстартерного ввімк-нення в пусковому та робочому режимах. Розроблено та змонтовано експериментальні установки для вимірювання характеристик ПТ струму в схемах стартерного та безстартерного ввімкнення люмінесцентних ламп, за допомогою яких досліджувалися характеристики п’єзотрансформаторів струму. Розроблено схему високочастотного перетворювача, який забезпечує на-дійне функціонування ПТ в усіх можливих режимах його роботи (холостий хід, коротке замикання, режим максимального ККД); розроблено методику розрахунку конструктивних та електричних параметрів п’єзотрансформатора, що може бути рекомендована для розрахунку параметрів п’єзотрансфор-матора з нелінійним навантаженням, яким є люмінесцентна лампа. Проведено експериментальні дослідження впливу зміни параметрів на-вантаження, напруги та частоти джерела живлення, температури довкілля на параметри п’єзотрансформатора. Удосконалено математичну модель п’єзоелектричного трансформа-тора, яка базується на експериментально визначених характеристиках нелі-нійного чотириполюсника, що дозволило розробити методику розрахунку параметрів комплекту ПТ–ЛЛ у пусковому та робочому режимах.<br>В диссертации проведены исследования для создания высокочастот-ного полупроводникового пускорегулирующего аппарата (ППРА) на базе пьезоэлектрического трансформатора тока (ПТ), а также разработана мето-дика расчета, учитывающая как особенности самого ПТ, так и его нелиней-ной нагрузки, которой является люминесцентная лампа (ЛЛ) мощностью 4 ... 18 Вт в схемах стартерного и безстартерного включения в пусковом и рабо-чем режимах работы. Разработаны и смонтированы экспериментальные установки для изме-рения характеристик ПТ тока в схемах стартерного и безстартерного вклю-чения люминесцентных ламп, с помощью которых исследовались характери-стики пьезотрансформаторов тока. Разработана схема высокочастотного преобразователя, который обеспе-чивает надежное функционирование ПТ во всех возможных режимах его ра-боты (холостой ход, короткое замыкание, режим максимального КПД); раз-работана методика расчета конструктивных и электрических параметров пье-зотрансформатора, которая может быть рекомендована для расчета парамет-ров пьезотрансформатора с нелинейной нагрузкой, которой является люми-несцентная лампа. Проведены экспериментальные исследования влияния изменения пара-метров нагрузки, напряжения и частоты источника питания, температуры ок-ружающей среды на параметры пьезотрансформатора. Разработаны принципы построения ППРА для ЛЛ на основе пьезотран- сформаторов тока, которые позволяют повысить эффективность и экономич-ность электронных балластов. Усовершенствована математическая модель пьезоэлектрического транс- форматора, которая базируется на экспериментальных характеристиках не-линейного четырехполюсника, что позволило разработать методику расчета параметров комплекта ПТ-ЛЛ в пусковом и рабочем режимах работы. Впервые дано математическое обоснование возникновения нелиней-ных функциональных зависимостей параметров пьезотрансформатора, нагружен-ного люминесцентной лампой.<br>In this work the studies of high-frequency semiconductor starter devices, based on piezoelectric current transformers, were undertaken, and the method of calculation was devised, which takes into account both - properties of the piezoelectric transformer and its non-linear load (which is a fluorescent lamp) during launch and in operational modes, with and without starter arrangements. The experimental equipment for measuring the properties of piezoelectric transformer and currents it produces, in arrangement with and without a starter, was designed and constructed. The scheme for high-frequency transducer was devised, which provides reliable operation of piezoelectric transformer in all possible modes of operation (idling, short circuit, the regime of maximum efficiency); the method of calculation of structural and electrical properties of piezoelectric transformer was also developed, which could be recommended for calculating the properties of piezoelectric transformer with non-linear load (e.g. fluorescent lamp). Experimental studies of the impact the change in load, current, frequency of power source and ambient temperature has on the properties of piezoelectric transformer have been conducted. The mathematical model of piezoelectric transformer has been improved, which is based on the properties of non-linear quadripole that have been established by the experiment. This has enabled to develop the methodology for calculation of the parameters of combination of piezoelectric transformer and fluorescent lamp during launch and in operational modes.

This master thesis presents the development of an auxiliary power supply to provide energy to sensors, gate drivers, instrumentation circuits and control of a three-stage Solid State Transformer (SST). These devices require an insulated power supply of ±15V and 5V. For reason of reliability and modularity, a distributed auxiliary source is proposed. Thus, it is necessary a power supply to provide energy to the low voltage (LV) side and another to the medium voltage (MV) side. With this proposal, the auxiliary power supply does not need to have the same galvanic insulation of the SST, 25kV. However, a local power supply must operate at high voltage levels and, consequently, contain a high step-down voltage gain. Relative to LV side, the most generally used topologies as an auxiliary power supply are discussed. However, these topologies cannot be used at the MV converters, due to the high voltage stress levels involved. A study of topologies used on medium and high voltage and which enable to reach a high step-down voltage gain is realized, and two interesting topologies for this application were found. One of them uses a Flying capacitor converter connected in cascade with a Double-Ended Flyback converter. The Flying capacitor converter lowers the DC bus voltage in a controlled manner to low voltage levels. So the Double-ended Flyback converter operates in LV and provides the insulated outputs to command circuits of SST. The other topology is a unidirectional four-level NPC converter operating as Double-ended Flyback converter. For this case, a modulation strategy that allows the converter to reach a high step-down voltage gain was also proposed. These topologies were evaluated and the one which showed the best result was the four-level Double-ended Flyback converter. This converter was implemented and the experimental results prove to be effective. For the LV side, a Half-bridge LLC resonant converter as auxiliary power supply was used. This converter operates in ZVS and performs the output voltage regulation through the operating frequency variation. The experimental results of this converter are also presented.<br>Este trabalho de mestrado apresenta o desenvolvimento de fontes auxiliares para alimentar sensores, circuitos de comando, instrumentação e o controle de um Transformador de Estado Sólido (SST) de três estágios. Estes dispositivos necessitam de alimentação isolada com tensões de ±15V e 5V e por questões de confiabilidade e modularidade, propõe-se a utilização de fontes auxiliares distribuídas. Assim, emprega-se uma fonte auxiliar para alimentar o lado de média tensão (MT) e outra para alimentar o lado de baixa tensão (BT). Com essa proposta, as fontes auxiliares não necessitam ter a mesma isolação galvânica do SST, 25kV. Entretanto, uma das fontes locais deve operar em níveis de tensão elevados e, por consequência, apresentar baixo ganho estático. No lado de BT, as principais topologias normalmente utilizadas como fonte auxiliar são discutidas. No entanto, devido aos altos níveis de tensão envolvidos, estas topologias não podem ser aplicadas ao conversor que opera em MT. Um estudo sobre topologias aplicadas a média tensão e que possibilitam alcançar um baixo ganho estático é realizado, sendo que duas topologias se mostram interessantes para esta aplicação. Uma consiste na utilização de um conversor de capacitores flutuantes conectado em cascata com um conversor Double-Ended Flyback. O conversor de capacitores flutuantes rebaixa a tensão do barramento CC, de forma controlada, para baixa tensão. Assim o Double-Ended Flyback opera em BT e fornece as saídas isoladas para alimentar os circuitos de comando do SST. A outra topologia trata-se de um conversor NPC de quatro níveis unidirecional operando como conversor Double-Ended Flyback. Para este caso, também foi proposta uma estratégia de modulação que permite o conversor alcançar o baixo ganho estático. Essas topologias foram avaliadas, apresentando melhor resultado a esta aplicação o conversor Double-ended Flyback de quatro níveis, conforme será demonstrado neste trabalho. Esse conversor foi implementado e os resultados experimentais comprovam o seu funcionamento. Para a fonte do lado de BT utilizou-se um conversor Half-Bridge LLC ressonante que opera em ZVS e realiza a regulação da tensão de saída pela variação da frequência de operação. Os resultados experimentais deste conversor também são apresentados.

La méthanisation de la biomasse lignocellulosique est un des moyens les plus efficients pour la production d’énergie renouvelable. Cependant, la lignine présente dans cette biomasse est difficile à hydrolyser. Cette limite peut être surmontée grâce aux prétraitements. Parmi eux, les prétraitements peu couteux par pourritures blanches sont attrayants mais ils ont été peu appliqués pour la digestion anaérobie. La présente étude explore les prétraitements par pourritures blanches de la paille de blé afin d’en améliorer sa méthanisation. Tout d’abord, une étape de sélection a révélé l’efficacité de la souche Polyporus brumalis BRFM 985 puisque 43% de méthane supplémentaire ont été obtenus par gramme de matières volatiles par comparaison avec la paille témoin. En prenant en compte les pertes de matières occasionnées par le prétraitement, cela correspondait à 21 % d’amélioration par gramme de matière sèche initiale. De plus, il a été montré que l’addition de glucose durant le prétraitement limitait la délignification et donc la production de méthane du substrat. Puis, des échantillons prétraités furent obtenus lors d’un plan d’expérience visant à optimiser le prétraitement par P. brumalis BRFM 985 ; les paramètres du prétraitement testés étaient : la durée et la température de culture, l’humidité initiale du substrat et l’addition de métaux. Les surfaces de réponse de la production de méthane à partir de ces échantillons furent construites. La production optimale de méthane ne fut pas atteinte dans le domaine expérimental testé mais l’impact positif de l’addition de métaux fut démontré, ainsi que l’importance de choisir une durée de culture adaptée. Ensuite, l’usage de la technique de la pyrolyse-GC-MS pour évaluer l’efficacité du prétraitement fut étudié. Une estimation de la quantité de biomasse fongique avec cette méthode apparaît possible. Le ratio polysaccharides/lignine déterminé par py-GC-MS a permis de classer des échantillons prétraités selon leur biodégradabilité anaérobie. La digestion anaérobie en voie sèche (DAVS) de paille de blé prétraitée en réacteur pilote fut menée en batch avec recirculation des lixiviats. Durant le démarrage de la DAVS, un trop fort S/I mène à une accumulation d’acides gras volatils (AGV) et parfois à la défaillance de la DAVS. Néanmoins, de forts S/I permettent de traiter plus de substrat et augmentent la production de méthane par volume de réacteur. Avec la paille de blé, des S/I entre 2 et 3 (en matières volatiles) permettent un bon démarrage de la DAVS. Alors qu’un ratio AGV totaux/alcalinité inférieur à 0,6 correspond à des réacteurs stables en digestion anaérobie voie liquide ; cette limite semble mal adaptée à la DAVS. Il fut observé que la DAVS pouvait récupérer d’une phase d’acidification tant que le ratio AGV totaux/alcalinité était inférieur à 2 et que la concentration en AGV était inférieure à 10 g/L dans les lixiviats. Malgré une amélioration de la biodégradabilité et une phase de démarrage facilitée, le prétraitement fongique non optimisé ne permit pas d’améliorer la production de méthane après prise en compte des pertes de matière occasionnées par le prétraitement<br>Anaerobic digestion of lignocellulosic biomass is one of the most efficient ways to produce renewable energy. However, lignin contained in this biomass is difficult to hydrolyze. This limitation can be overcome by pretreatments. Among them, low-cost white-rot fungi pretreatments seem attractive but were scarcely applied for anaerobic digestion. The current study investigates white-rot fungi pretreatments of wheat straw to improve its methane production. Firstly, a selection step has revealed the efficiency of Polyporus brumalis BRFM 985 since 43% more methane per gram of pretreated volatile solids were obtained compared to the control straw. Taking into account the dry weight loss occurring during the pretreatment, it still corresponded to 21% more methane per gram of initial total solids. Moreover, glucose addition during the pretreatment was shown to limit delignification and thus methane production from the substrate. Secondly, pretreated samples were obtained in an experiment device aiming to optimize the pretreatment with P. brumalis BRFM 985; tested pretreatments parameters were: culture duration, temperature, initial substrate moisture content and metals addition. Response surfaces of methane production from those samples were built. Optimum methane production was not reached in the experimental domain but the positive impact of metals addition was demonstrated, so as the importance to choose adequate culture duration. Then, the use of pyrolysis-GC-MS technic to access pretreatment efficiency was studied. Estimation of fungal biomass amount on wheat straw with this method appeared possible. Polysaccharides/lignin ratio determined with py-GC-MS allowed to classify some pretreated samples according to their anaerobic degradability. Solid State Anaerobic Digestion (SSAD) of wheat straw pretreated in pilot-reactor was carried out in batch with leachate recycle. During SSAD start-up phase, too high Substrate/Inoculum (S/I) ratio leads to Volatile Fatty Acid (VFA) accumulation and sometimes to reactor failure but with high S/I more substrate can be treated and methane production per reactor volume increases. With wheat straw, S/I between 2 and 3 (Volatile Solid basis) allow a successful start-up in SSAD. Whereas Total VFA/alkalinity ratio under 0.6 corresponds to stable wet anaerobic digestion; this limit seems not well adapted to SSAD. It was observed that SSAD reactors were able to recover from acidification phase when Total VFA/alkalinity was lower than 2 and with VFA concentrations inferior to 10 g/L in leachate. Despite the improvement of biodegradability and the facilitation of start-up phase, non-optimized fungal pretreatment did not improve methane production after taking into account mass losses occurring during the pretreatment

Cette thèse est divisée en trois parties qui suivent des approches différentes. Dans la première partie, l'hydrophobicité d'acides amines, propriété bien connue, est déterminée. Un modèle thermodynamique détaillé de la topologie de polypeptides dérivés du LAH4 en fonction du pH a été développé. Ces modifications dans la topologie ont été mises en évidence par la technique de spectroscopie infrarouge de réflexion totale atténuée. (abrégée en anglais ATR-FTIR). Grâce à ces résultats et à un modèle théoretique, nous avons pu déterminer l'enthalpie nécessaire à l'insertion d'acides aminés de la phase aqueuse vers l'intérieur d'une bicouche lipidique. La seconde partie donne une vue d'ensemble (avantages et limites) de l'utilisation de RMN du deutérium sur la 2H3C-alanine. Il est en effet prouvé que cette méthode peut fournir des informations sur la structure et la dynamique des polypeptides membranaires. Bien que la RMN du deutérium ait déjà été utilisée auparavant sur des peptides marqués à l'aide de 2H3C-alanine, l'étude systematique de tels peptides par cette technique éclaire de nouveaux aspects du sujet. Dans la troisième partie, la RMN à l'état solide est appliquée à différents polypeptides et protéines d'origine naturelle. Ainsi, pour la bacteriorhodopsine et la gramicidine A, certains détails de la structure déjà connue du protéine / polypeptide ont été néanmoins élucidés. La structure du ß-peptide amyloide dans sa forme membranaire est quant à elle largement inconnue : nous avons essayé de savoir si la RMN du solide pouvait fournir de plus amples informations. Enfin, pour les protéines colicine E1 et BCL-XL , nous avons testé la validité de modèles disponibles dans la littérature. Dans le cas du domaine formant le canal de la colicine E1, une protéine marquée uniquement à une seule position a été utilisée : les spectres 15N RMN à l'état solide sont parmi les premier mesurés pour une protéine exprimée par bactérie et marquée sur une seule position<br>The thesis consists of three different sections, which follow slightly different approaches. In the first part the hydrophobicity a very basic property, of amino acids is determined. For the series of LAH4-like polypeptides a detailed thermodynamic model for the pH dependent topology of the peptides was developed. The topological changes were measured by attenuated total reflection infrared spectroscopy (ATR-FTIR). The results of the measurements and the theoretical model were used to determine the enthalpy for the insertion of some amino acid from water phase into the lipid bilayer interior. The second part gives a detailed overview of the advantages and problems of the application of deuterium NMR using 2H3C-Alanine. It is shown that the method can give valuable information of structure and dynamics of membrane polypeptides. Even thought solid-state NMR on 2H3C-Alanine labelled peptides was used before the systematic investigation of the properties of deuterium NMR on 2H3C-Alanine labelled peptides gives new and important aspects into the topic. In the third part the solid-state NMR method is applied to different natural polypeptides and proteins. For bacteriorhodopsin and gramicidine A solid-state NMR was used to investigate some details of the known structure of the protein/polypeptide. The structure of the membrane associated form of the amyloid b-peptide is widely unknown. It was tested, if solid-state NMR can provide further information of the membrane associated form of the amyloid b-peptide. For the proteins colicin E1 and BCL-XL detailed models are published and the solid-state NMR experiments are used to test these models. For the measurement of the channel-forming domain of colicin E1 a single-side labelled protein was used. The measured spectra belong to the first 15N solid-state NMR spectra of a single-side labelled protein (expressed in bacteria)

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior<br>This thesis presents a design methodology for the dual active bridge converter, that includes the influence of the nominal phase-shift angle in the behavior of the DAB converter for entire power and voltage ranges. The analysis presented focus on two important performance parameters of the DAB converter: the nonactive power and the limits of ZVS operation. The study of these two parameters results in a prior knowledge of the qualitative characteristics of the conduction and switching losses, respectively. Using this knowledge it is possible to optimize the converter operation considering the priorities of application performance. The experimental results were performed for three different projects nominal angles and three different input voltages for the whole load range, and they prove the feasibility of the proposed analysis. The analyse of the limit ZVS area took into account the switches intrinsic capacitances, and the dead time between the complementary switches. The DAB converter placed at a three-stage structure applied to solid state transformer, has voltage ripple at low frequency in their bus voltages because of the connection into the distribution network. Thus, it becomes possible to apply a low frequency burst mode modulation, without needing to oversize the bus capacitors. Three burst mode modulations are evaluated in simulation. The modulation which performed better results in simulation was implemented in practice, and the experimental results showed significant improvement in the converter´s efficiency when it is operating in light loads. Finally, a discussion of the parameters to be evaluated for the DAB converter´s design is proposed.<br>Esta tese de doutorado apresenta uma metodologia de projeto do conversor DAB, a qual inclui a influência do ângulo nominal de defasagem no comportamento do conversor DAB para toda faixa de potência e de tensão. Além disso, as análises focam em dois importantes parâmetros de desempenho do conversor DAB: a potência não ativa e os limites de operação com ZVS. O estudo destes dois parâmetros resulta em um conhecimento prévio das características qualitativas das perdas de condução e comutação, respectivamente. Através deste conhecimento é possível otimizar a operação do conversor considerando as prioridades de desempenho da aplicação. Os resultados experimentais, que comprovam as análises referentes à potência não ativa e aos limites de operação com ZVS, são realizados para três diferentes projetos de ângulos nominais e três diferentes tensões de entrada, para toda faixa de operação de carga. O estudo dos pontos de perda de ZVS considerou as capacitâncias intrínsecas dos interruptores e o tempo morto entre os interruptores complementares. O conversor DAB funcionando em uma estrutura de três estágios, aplicado a transformadores de estado sólido, apresenta ondulação de tensão em baixa frequência em seus barramentos, provinente da conexão da estrutura na rede de distribuição. Deste modo, torna-se possível a aplicação de modulações de baixa frequência do tipo burst, sem a necessidade de sobredimensionamento dos capacitores. Três modulações são realizadas e avaliadas em simulação. A modulação que apresentou melhores resultados em simulação foi implementada na prática, e os resultados experimentais mostraram melhora significativa da eficiência do conversor em baixas cargas. Por fim, uma discussão sobre as considerações a serem avaliadas nos parâmetros de projeto do conversor DAB é proposta.

Une des caractéristiques histopathologiques de la maladie d'Alzheimer (AD) est la présence de plaques amyloïdes formées par les peptides amyloïdes β (Aβ) de 40 et 42 résidus, qui sont les produits de clivage par des protéases de l'APP. Afin de comprendre le rôle des variations structurelles du TM dans le traitement de l'APP, les peptides APP_TM4K ont été étudiés dans la bicouche lipidique en utilisant l’ATR-FTIR et ssNMR. Tandis que la structure secondaire globale du peptide APP_TM4K est hélicoidale, hétérogénéité de conformation et d'orientation a été observée pour le site de clivage γ et , que peuvent avoir des implications dans le mécanisme de clivage et donc dans la production d’Aβ. Les peptides Aβ s'agrègent pour produire des fibrilles et aussi de manière transitoire d'oligomères neurotoxiques. Nous avons constaté qu'en présence de Ca2+, l’Aβ (1-40) forme de préférence des oligomères, tandis qu'en absence de Ca2+ l'Aβ (1-40) s’agrège sous forme de fibrilles. Dans les échantillons sans Ca2+, l’ATR-FTIR révèle la conversion des oligomères en feuillets β antiparallèles en la conformation caractéristique des fibrilles en feuillets β parallèles. Ces résultats nous ont amené à conclure que les Ca2+ stimulent la formation d'oligomères d'Aβ (1-40), qui sont impliqués dans l’AD. Les positions et une orientation précise de deux nouveaux médicaments puissants modulateurs de la γ-sécrétase - le benzyl-carprofen et le sulfonyl-carprofen  dans la bicouche lipidique, ont été obtenus à partir des expériences des ssNMR. Ces résultats indiquent que le mécanisme probable de modulation du clivage par la y-sécrétase est une interaction directe avec le domaine TM de l’APP<br>A histopathological characteristic of Alzheimer’s disease (AD) is the presence of amyloid plaques formed by amyloid β(A) peptides of 40 and 42 residues-long, which are the cleavage products of APP by proteases. To understand the role of structural changes in the TM domain of APP, APP_TM4K peptides were studied in the lipid bilayer using ATR-FTIR and ssNMR. While the overall secondary structure of the APP_TM4K peptide is helical, conformational and orientational heterogeneity was observed for the y- and for the -cleavage sites, which may have implications for the cleavage mechanism and therefore the production of Aβ. Starting from its monomeric form, Aβ peptides aggregate into fibrils and / or oligomers, the latter being the most neurotoxic. We found that in the presence of Ca2 +, Aβ (1-40) preferably forms oligomers, whereas in the absence of a2 + Aβ (1-40) aggregates into fibrils. In samples without Ca2 +, ATR-FTIR shows conversion from antiparallel β sheet conformation of oligomers into parallel β sheets, characteristic of fibrils. These results led us to conclude that Ca2 +stimulates the formation of oligomers of Aβ (1-40), that have been implicated in the pathogenesis of AD. Position and precise orientation of two new drugs  powerful modulators of γ-secretase  benzyl-carprofen and carprofen sulfonyl  in the lipid bilayer were obtained from neutron scattering and ssNMR experiments. These results indicate that carprofen-derivatives can directly interact with APP. Such interaction would interfere with proper APP-dimer formation, which is necessary for the sequential cleavage by β -secretase, diminishing or greatly reducing Aβ42 production

Le carbure de silicium est un matériau souvent employé comme matrice dans les composites thermostructuraux. Le précurseur classiquement utilisé pour son élaboration par dépôt/infiltration par voie gazeuse est CH3SiCl3. La thèse vise à évaluer le remplacement de ce précurseur par des précurseurs gazeux bi-sourcés de SiC où carbone et silicium sont apportés séparément.A partir du système SiHCl3/C3H8/H2, l’influence du débit total, de la température, de la pression totale et de (C/Si)gaz sont évaluées et comparées aux résultats obtenus avec le système CH3SiCl3/H2. La mesure in situ de la vitesse de dépôt permet de définir des lois cinétiques apparentes. L’analyse IRTF de la phase gazeuse indique que les évolutions des pressions partielles des différents produits stables sont corrélées avec les transitions cinétiques et les changements de composition du solide. Les simulations numériques de l’évolution de la phase gazeuse montrent une bonne corrélation avec les résultats expérimentaux et permettent de proposer des mécanismes homogènes et hétérogènes qui pourraient expliquer les écarts à la stoechiométrie du dépôt.L’étude de six précurseurs supplémentaires permet de mieux identifier le rôle des principales espèces en phase homogène et hétérogène, et notamment les précurseurs effectifs de dépôt. Enfin, l’étude de l’infiltration de matériaux poreux modèles révèle des améliorations significatives en termes d’homogénéité de vitesse de dépôt.Ainsi, des conditions propices à l’infiltration de carbure de silicium peuvent être obtenues en adaptant la réactivité de la phase gazeuse par la sélection de précurseurs initiaux et des chemins réactionnels qui en découlent<br>Silicon carbide (SiC) is material of choice for the matrix of Ceramic Matrix Composites (CMC).CH3SiCl3/H2 mixtures are currently used as gas precursor for the synthesis of the CVI-SiC matrices.The present work considers the dual-source approach with two separate carbon and silicon precursorsmolecules.In the case of SiHCl3/C3H8/H2 mixture, systematic studies of total flow rate, temperature, total pressureand C/Si ratio of initial gaseous phase are realized. Kinetics obtained with growth rate measurements and solid composition are compared with results from CH3SiCl3/H2 mixture. On the basis of the apparent reaction orders and activation energies, experimental kinetic laws are derived. Through IRTF analysis of the gas phase, the partial pressures of the different stable products are correlated with deposition kinetic and solid composition. Results obtained in gas-phase kinetic simulation show a good correlation with the experimental results and a mechanism of homogeneous decomposition is proposed. A better understanding of the role of the principal species in homogenous and heterogeneous phase is obtained through the study of six other gas systems and the roles of some effective precursors are discussed. Finally, infiltration results of porous material models with different precursor systems reveal significant improvements as homogeneity of kinetic deposit.Hence, favourable conditions to silicon carbide infiltration can be obtained by adapting the reactivity of the gas phase, with the choice of initial precursors and homogeneous chemistry associated. Asystematic study of the process evidences promising working windows for the infiltration of pure SiCin porous performs

abstract: The Solid State Transformer (SST) is an essential component in the FREEDM system. This research focuses on the modeling of the SST and the controller hardware in the loop (CHIL) implementation of the SST for the support of the FREEDM system demonstration. The energy based control strategy for a three-stage SST is analyzed and applied. A simplified average model of the three-stage SST that is suitable for simulation in real time digital simulator (RTDS) has been developed in this study. The model is also useful for general time-domain power system analysis and simulation. The proposed simplified av-erage model has been validated in MATLAB and PLECS. The accuracy of the model has been verified through comparison with the cycle-by-cycle average (CCA) model and de-tailed switching model. These models are also implemented in PSCAD, and a special strategy to implement the phase shift modulation has been proposed to enable the switching model simulation in PSCAD. The implementation of the CHIL test environment of the SST in RTDS is described in this report. The parameter setup of the model has been discussed in detail. One of the dif-ficulties is the choice of the damping factor, which is revealed in this paper. Also the grounding of the system has large impact on the RTDS simulation. Another problem is that the performance of the system is highly dependent on the switch parameters such as voltage and current ratings. Finally, the functionalities of the SST have been realized on the platform. The distributed energy storage interface power injection and reverse power flow have been validated. Some limitations are noticed and discussed through the simulation on RTDS.<br>Dissertation/Thesis<br>M.S. Electrical Engineering 2014

碩士<br>國立臺灣科技大學<br>電子工程系<br>105<br>This thesis focuses on the study and development of solid-state transformers. First, the basics of AC-AC converters is discussed. Specifically, the effect of leakage inductance on output voltage is analyzed. Hence in this thesis, a AC-AC full-bridge series resonant converter is applied to maintain output voltage. The circuit is operated close to the series resonant frequency to improve the output voltage regulation. The state analysis and basic operating principles of the proposed converter are discussed in detail. Finally, a prototype AC-AC full-bridge series resonant converter with an input/output voltage of 110 Vrms, output power 1 kW is implement and tested. The efficiency can be higher than 94.04% at full load condition. The theoretical analysis is positively agreed with the experimental results.

碩士<br>國立臺灣科技大學<br>電子工程系<br>105<br>In this thesis, a solid-state transformer is studied and implemented. The structure adopted is a high-frequency operated active-dual-bridge converter. Conventional transformers are widely applied in electric power systems for performing many functions, such as electric isolation, voltage level transformation, noise decoupling, etc. However, these conventional transformers have larger volume, heavy weight which are becoming unacceptable nowadays; therefore, newer technologies are highly expected. High-frequency operated solid-state transformers are one of solutions. By increasing the operating frequency, the volume and weight of the transformer can be reduced; on the other hand, phase-shift modulation can be used to regulate the power flow in either direction. However, the use of high-frequency operation induces unwanted high-frequency components, which claim for second-order low pass filters on both input and output sides to filter out these unwanted ingredients. Therefore, carefulness on design is required in order not to lose the objective of reducing weight and volume. A prototype circuit based on ac-ac dual-active-bridge converter has been built and tested in lab successfully. The circuit is with rated of 220 Vrms input voltage, 220 Vrms output voltage and 2 kW output power. A digital-signal processor is used to realize the control of this circuit. The measured efficiency is higher than 92% within the overall range of load conditions.

Dissertação de mestrado em Engenharia Eletrónica e de Computadores<br>O consumo de energia elétrica é essencial para o quotidiano das pessoas e empresas, sendo por isso necessário um fornecimento de energia elétrica com ótima qualidade. Posto isto, torna-se fundamental o desenvolvimento de equipamentos que assegurem uma ótima qualidade de energia elétrica. Durante os últimos 20 anos, o solid-state transformer (SST) tem sido alvo de investigação científica no sentido de substituir o transformador convencional. Face aos transformadores convencionais, o SST apresenta inúmeras vantagens, tais como, a redução do volume e peso e o facto de permitir um elevado grau de controlabilidade. Este controlo permite elevados padrões de qualidade de energia elétrica, pois controla a corrente de entrada para que tenha reduzida distorção harmónica e para que o fator de potência seja unitário. Os SSTs podem também permitir uma melhor integração das energias renováveis e de sistemas de armazenamento de energia, tal como gestão de energia nas micro-grids, sendo assim um bloco chave no desenvolvimento das smart grids. Além disso, com a introdução desta tecnologia, será possível a comunicação com os fornecedores de energia e os clientes visando estabelecer modos de operação específicos. Apesar das diversas vantagens, um SST apresenta algumas desvantagens. Atualmente, um SST não é tão eficiente como um transformador convencional, sendo também mais caro devido a utilização de diversos dispositivos eletrónicos. Em parte, o problema da eficiência é o resultado das perdas dos semicondutores utilizados (MOSFET, IGBT), sendo que com o surgimento de novos semicondutores como os SiCs (silicom carbide), verifica-se uma diminuição das perdas e um incremento da frequência de operação. Esta dissertação apresenta o desenvolvimento de um SST monofásico que permite o controlo da corrente de entrada e da tensão e frequência de saída. Consequentemente, com esta controlabilidade, é possível atingir elevados padrões de qualidade de energia elétrica. Após o estudo do estado da arte sobre conversores de eletrónica de potência e sobre estratégias de controlo, foi desenvolvido um modelo de simulação para verificar o funcionamento do SST. Posteriormente, foi desenvolvido um protótipo laboratorial e foram obtidos resultados experimentais.<br>The consumption of electric energy is essential for the daily life of people and companies, therefore a supply of electric energy with excellent quality is required. Thereby, it is fundamental to develop equipment that ensures excellent quality of electrical energy. During the last 20 years, the solid-state transformer (SST) has been the subject of scientific research to replace the conventional transformer. Compared to conventional transformers, the SST has many advantages, such as reduction of volume and weight and a high degree of controllability. This control allows high standards of electric power quality because it controls the input current so that it has reduced harmonic distortion and allows a unity power factor. SSTs enable better integration of renewable energy and energy storage systems, such as micro-grids power management, and are a key block in the development of smart grids. In addition, the introduction of this technology will enable communication with energy suppliers and customers to establish specific modes of operation. Despite the several advantages, an SST has some disadvantages. Currently, an SST is not as efficient as a conventional transformer and is also more expensive due to the use of various electronic devices. In part, the efficiency problem is the result of the losses of the used semiconductors (MOSFET, IGBTs), and with the emergence of new semiconductors such as SiCs (silicon carbides), there is a decrease in losses and an increase in the frequency of operation. This dissertation presents the development of a single-phase SST that allows the control of the input current and the output voltage and the output frequency. Consequently, with this controllability, it is possible to achieve high standards of electrical power quality. After a state-of-the-art study on power electronics converters and control strategies, a simulation model was developed to verify the functioning of the SST. Subsequently, a laboratory prototype was developed, and experimental results were obtained.<br>Este trabalho de dissertação está enquadrado no projeto de IC&DT “ESGRIDS – Enhancing Smart GRIDs for Sustainability”, financiado pela Fundação para a Ciência e Tecnologia, com a referência POCI-01-0145-FEDER-016434 (Projetos I&D em Co-Promoção). Este trabalho de dissertação está enquadrado no projeto de IC&DT “DAIPESEV – Development of Advanced Integrated Power Electronic Systems for Electric Vehicles”, financiado pela Fundação para a Ciência e Tecnologia, com a referência PTDC/EEI EEE/30382/2017.

abstract: For the solid-state transformer (SST) application, a three-stage configuration consisting of a PWM rectifier based AC/DC stage, a dual active bridge (DAB) converter based DC/DC stage and a PWM inverter based DC/AC stage offers several advantages. For single-phase SST, the instantaneous input and load power seen by the DC/DC stage varies from zero to twice the load average power at double the line frequency. Traditionally, with phase-shift control, large DAB DC link capacitors are used to handle the instantaneous power variation of the load, with the DAB converter processing only the load average power resulting in better soft-switching range and consequently high efficiency. However, the large electrolytic capacitors required adversely affect the power density and the reliability of SST. In this thesis, a PWM control is used for the DAB converter in SST, which extends the ZVS range of DAB and allows the DAB converter to handle the pulsating power while maintaining/improving efficiency. The impact of the output capacitance of switches with PWM control is discussed for practical implementation. A 40kHz, 500W DAB converter is designed and built, and the experimental results proves that the DAB converter with PWM control in SST can achieve comparable efficiency while the DC link capacitors of SST can be reduced to a value that electrolytic capacitors are not required.<br>Dissertation/Thesis<br>M.S. Electrical Engineering 2012

碩士<br>國立臺灣科技大學<br>電子工程系<br>106<br>The main purpose of this paper is to develop a solid-state transformer using an active dual-bridge converter architecture. Conventional transformers have many problems due to their operation in low-frequency voltages, such as large size and heavy weight. Therefore, new transformers need to be developed to replace them. In this paper, an AC-AC solid-state transformer with an input voltage of 300 Vrms maximum, an output voltage of 300 Vrms and an output power of 5 kW is actually completed. The power circuit mainly includes an active double-bridge converter, and the input voltage value is detected by the phase-locked loop as a reference command for the controller to stabilize the output voltage, and the transformer function is realized by the digital signal processor. Realize digital closed loop control. The experimental results show that the solid-state transformer can effectively stabilize the output voltage equal to the corresponding input voltage under different voltage input conditions, and the efficiency is above 92% under different loads.

abstract: The development of a Solid State Transformer (SST) that incorporates a DC-DC multiport converter to integrate both photovoltaic (PV) power generation and battery energy storage is presented in this dissertation. The DC-DC stage is based on a quad-active-bridge (QAB) converter which not only provides isolation for the load, but also for the PV and storage. The AC-DC stage is implemented with a pulse-width-modulated (PWM) single phase rectifier. A unified gyrator-based average model is developed for a general multi-active-bridge (MAB) converter controlled through phase-shift modulation (PSM). Expressions to determine the power rating of the MAB ports are also derived. The developed gyrator-based average model is applied to the QAB converter for faster simulations of the proposed SST during the control design process as well for deriving the state-space representation of the plant. Both linear quadratic regulator (LQR) and single-input-single-output (SISO) types of controllers are designed for the DC-DC stage. A novel technique that complements the SISO controller by taking into account the cross-coupling characteristics of the QAB converter is also presented herein. Cascaded SISO controllers are designed for the AC-DC stage. The QAB demanded power is calculated at the QAB controls and then fed into the rectifier controls in order to minimize the effect of the interaction between the two SST stages. The dynamic performance of the designed control loops based on the proposed control strategies are verified through extensive simulation of the SST average and switching models. The experimental results presented herein show that the transient responses for each control strategy match those from the simulations results thus validating them.<br>Dissertation/Thesis<br>Ph.D. Electrical Engineering 2011

碩士<br>國立成功大學<br>電機工程學系<br>106<br>As the progress of wide-bandgap (WBG) semiconductor devices and the rise of distributed energy resources (DER), medium-voltage solid-state transformer (SST) becomes more and more popular in recent years. Medium-voltage SST features high-performance and fantastic functionality. The SST proposed in this thesis is applied in 11.4 kVAC distribution system, and the DC stage of the SST is composed of 13 modules. Operating principle, steady-state analysis and components design of the converter as well as the parameter design, insulation consideration and loss optimization of the transformer, are described in detail in this thesis. Meanwhile, the simulation software SIMPLIS and COMSOL Multiphysics® are used to ensure the validity. Finally, a prototype converter with input voltage 1.52 kVDC, output voltage 380 VDC and output power 10 kW is designed and realized to verify the feasibility of the module applied in SST.

abstract: This dissertation covers three primary topics and relates them in context. High frequency transformer design, microgrid modeling and control, and converter design as it pertains to the other topics are each investigated, establishing a summary of the state-of-the-art at the intersection of the three as a baseline. The culminating work produced by the confluence of these topics is a novel modular solid-state transformer (SST) design, featuring an array of dual active bridge (DAB) converters, each of which contains an optimized high-frequency transformer, and an array of grid-forming inverters (GFI) suitable for centralized control in a microgrid environment. While no hardware was produced for this design, detailed modeling and simulation has been completed, and results are contextualized by rigorous analysis and comparison with results from published literature. The main contributions to each topic are best presented by topic area. For transformers, contributions include collation and presentation of the best-known methods of minimum loss high-frequency transformer design and analysis, descriptions of the implementation of these methods into a unified design script as well as access to an example of such a script, and the derivation and presentation of novel tools for analysis of multi-winding and multi-frequency transformers. For microgrid modeling and control, contributions include the modeling and simulation validation of the GFI and SST designs via state space modeling in a multi-scale simulation framework, as well as demonstration of stable and effective participation of these models in a centralized control scheme under phase imbalance. For converters, the SST design, analysis, and simulation are the primary contributions, though several novel derivations and analysis tools are also presented for the asymmetric half bridge and DAB.<br>Dissertation/Thesis<br>Doctoral Dissertation Electrical Engineering 2019

abstract: With the penetration of distributed renewable energy and the development of semiconductor technology, power electronic devices could be utilized to interface re- newable energy generation and the distribution power grid. However, when directly connected to the power grid, the semiconductors inside the power electronic devices could be vulnerable to the power system transient, especially to lightning strikes. The work of this research focuses on the insulation coordination of power elec- tronic devices connected directly to the power distribution system. The Solid State Transformer (SST) in Future Renewable Electric Energy Delivery and Management (FREEDM) system could be a good example for grid connected power electronic devices. Simulations were conducted in Power Systems Computer Aided Design (PSCAD) software. A simulation done to the FREEDM SST showed primary re- sults which were then compare to simulation done to the grid-connected operating Voltage Source Converter (VSC) to get more objective results. Based on the simulation results, voltage surges caused by lightning strikes could result in damage on the grid-connected electronic devices. Placing Metal Oxide Surge Arresers (MOSA, also known as Metal Oxide Surge Varistor, MOV) at the front lter could provide eective protection for those devices from power transient. Part of this research work was published as a conference paper and was presented at CIGRE US National Conference: Grid of the Future Symposium [1] and North American Power Symposium [2].<br>Dissertation/Thesis<br>Masters Thesis Engineering 2017

abstract: In recent years, wide bandgap (WBG) devices enable power converters with higher power density and higher efficiency. On the other hand, smart grid technologies are getting mature due to new battery technology and computer technology. In the near future, the two technologies will form the next generation of smart grid enabled by WBG devices. This dissertation deals with two applications: silicon carbide (SiC) device used for medium voltage level interface (7.2 kV to 240 V) and gallium nitride (GaN) device used for low voltage level interface (240 V/120 V). A 20 kW solid state transformer (SST) is designed with 6 kHz switching frequency SiC rectifier. Then three robust control design methods are proposed for each of its smart grid operation modes. In grid connected mode, a new LCL filter design method is proposed considering grid voltage THD, grid current THD and current regulation loop robust stability with respect to the grid impedance change. In grid islanded mode, µ synthesis method combined with variable structure control is used to design a robust controller for grid voltage regulation. For grid emergency mode, multivariable controller designed using H infinity synthesis method is proposed for accurate power sharing. Controller-hardware-in-the-loop (CHIL) testbed considering 7-SST system is setup with Real Time Digital Simulator (RTDS). The real TMS320F28335 DSP and Spartan 6 FPGA control board is used to interface a switching model SST in RTDS. And the proposed control methods are tested. For low voltage level application, a 3.3 kW smart grid hardware is built with 3 GaN inverters. The inverters are designed with the GaN device characterized using the proposed multi-function double pulse tester. The inverter is controlled by onboard TMS320F28379D dual core DSP with 200 kHz sampling frequency. Each inverter is tested to process 2.2 kW power with overall efficiency of 96.5 % at room temperature. The smart grid monitor system and fault interrupt devices (FID) based on Arduino Mega2560 are built and tested. The smart grid cooperates with GaN inverters through CAN bus communication. At last, the three GaN inverters smart grid achieved the function of grid connected to islanded mode smooth transition<br>Dissertation/Thesis<br>Doctoral Dissertation Electrical Engineering 2017

Dissertação de Mestrado Integrado em Engenharia Electrotécnica e de Computadores apresentada à Faculdade de Ciências e Tecnologia<br>Nos últimos anos, tem havido um aumento de veículos elétricos devido a uma questão ambiental e a um interesse nesta nova tecnologia. Esta dissertação propõe uma arquitetura de conversão de energia com a implementação de um posto de carregamento rápido para baterias, como as dos veículos elétricos. Esta arquitetura é baseada nos Transformadores de Eletrónica de Potência (TEP). Inicialmente, irá ser realizado o estado de arte, e, através da literatura analisada relativamente aos TEP’s, serão escolhidas as soluções mais adequadas para esta arquitetura. Após escolhida a ideia para o caso de estudo, e, posteriormente, a verificação do estudo elétrico e matemático, este sistema será simulado de modo a consolidar o sistema teórico. Nestas simulações, irá se avaliar os diferentes modos de carregamento das baterias, carregamento em modo tensão constante, carregamento em modo corrente constante e carregamento em modo corrente constante e tensão constante. Também se irá escolher o melhor método e mais eficaz de carregamento das baterias. Verificar-se-á a fiabilidade deste sistema, fazendo-se simulações com desequilíbrios no modelo, como por exemplo, carregar o sistema com as baterias em desiquilíbrio, ou seja, cada bateria tem um estado de carga diferente das outras, e causar uma falha num IGBT de uma das pontes do conversor DC-DC unidirecional isolado ou do retificador multinível, a duas configurações são utilizadas em alguns modelos do transformador eletrónico de potência. Por fim, irão ser tiradas conclusões e serão dadas recomendações de trablhos futuros para melhoramento desta dissertação.<br>In recent years, there has been an increase in electric vehicles due to an environmentalissue and an interest in this new technology.This dissertation proposes an architecture of energy conversion with the implementation of a fast charging station for batteries, such as those of electric vehicles.This architecture is based on the Power Electronic Transformers (PET). Initially, the state of art will be realized, and, through the analyzed literature regarding the PET's, will be chosen the most appropriate solutions for this architecture.After choosing the idea for the case study, and later the verification of the electrical and mathematical study, this system will be simulated to consolidate the theoretical system.In these simulations, we will evaluate the different modes of charging the batteries, charging in constant voltage mode, charging in constant current mode and charging in constant current mode and constant voltage. You will also choose the best and most effective method of charging the batteries. The reliability of this system will be verified by simulations with imbalances in the model, such as loading the system with unbalanced batteries, ie each battery has a different state of charge than others, and cause an IGBT to fail from one of the isolated single-way DC-DC converter or multi-level rectifier, two configurations are used on some models of the power transformer. Finally, conclusions will be drawn and future work recommendations will be given to improve this dissertation.

abstract: A robust, fast and accurate protection system based on pilot protection concept was developed previously and a few alterations in that algorithm were made to make it faster and more reliable and then was applied to smart distribution grids to verify the results for it. The new 10 sample window method was adapted into the pilot protection program and its performance for the test bed system operation was tabulated. Following that the system comparison between the hardware results for the same algorithm and the simulation results were compared. The development of the dual slope percentage differential method, its comparison with the 10 sample average window pilot protection system and the effects of CT saturation on the pilot protection system are also shown in this thesis. The implementation of the 10 sample average window pilot protection system is done to multiple distribution grids like Green Hub v4.3, IEEE 34, LSSS loop and modified LSSS loop. Case studies of these multi-terminal model are presented, and the results are also shown in this thesis. The result obtained shows that the new algorithm for the previously proposed protection system successfully identifies fault on the test bed and the results for both hardware and software simulations match and the response time is approximately less than quarter of a cycle which is fast as compared to the present commercial protection system and satisfies the FREEDM system requirement.<br>Dissertation/Thesis<br>M.S. Electrical Engineering 2014

abstract: This thesis provides a cost to benefit assessment of the proposed next generation distribution system, the Future Renewable Electric Energy Distribution Management (FREEDM) system. In this thesis, a probabilistic study is conducted to determine the payback period for an investment made in the FREEDM distribution system. The stochastic study will help in performing a detailed analysis in estimating the probability density function and statistics associated with the payback period. This thesis also identifies several parameters associated with the FREEDM system, which are used in the cost benefit study to evaluate the investment and several direct and indirect benefits. Different topologies are selected to represent the FREEDM test bed. Considering the cost of high speed fault isolation devices, the topology design is selected based on the minimum number of fault isolation devices constrained by enhanced reliability. A case study is also performed to assess the economic impact of energy storage devices in the solid state transformers so that the fault isolation devices may be replaced by conventional circuit breakers. A reliability study is conducted on the FREEDM distribution system to examine the customer centric reliability index, System Average Interruption Frequency Index (SAIFI). It is observed that the SAIFI was close to 0.125 for the FREEDM distribution system. In addition, a comparison study is performed based on the SAIFI for a representative U.S. distribution system and the FREEDM distribution system. The payback period is also determined by adopting a theoretical approach and the results are compared with the Monte Carlo simulation outcomes to understand the variation in the payback period. It is observed that the payback period is close to 60 years but if an annual rebate is considered, the payback period reduces to 20 years. This shows that the FREEDM system has a significant potential which cannot be overlooked. Several direct and indirect benefits arising from the FREEDM system have also been discussed in this thesis.<br>Dissertation/Thesis<br>Masters Thesis Electrical Engineering 2016