Most of the modern wind turbines are based on doubly fed induction generators (DFIG), with a back to back power converter connecting the rotor to the network. It is known that voltage dips at the stator terminals can cause overcurrents in the rotor windings, which could threaten the converter integrity. In order to protect the converter, several strategies have been proposed in technical literature, requiring in some cases the converter deactivation, which disables the control that the converter has over the power transference between the generator and the system. This last is not a desirable behavior since it can put on risk the voltage stability of the electric system. It is the aim of this dissertation to introduce and compare five of those protection strategies, through the computational simulation of their performance in case of balanced voltage dips. In order to achieve this, the electromagnetic dynamic model of the DFIG was theoretically developed, as well as the models of the strategies of interest. Subsequently, the computational model of the system was assembled in the software Matlabs Simulink to finally perform the desired simulations and its corresponding analysis. / A maioria das turbinas eólicas modernas é baseada em geradores de indução duplamente alimentados (GIDE), com um back to back conversor de energia que liga o rotor para a rede. Sabe-se que as quedas de tensão nos terminais do estator podem causar sobrecorrentes nos enrolamentos do rotor, que podem ameaçar a integridade do conversor. A fim de proteger o conversor, várias estratégias têm sido propostas na literatura técnica, exigindo, em alguns casos, a desativação do conversor, o qual desativa o controlo do conversor, que possui ao longo da transferência de energia entre o gerador e o sistema. Este último não é um comportamento desejável, uma vez que pode colocar em risco a estabilidade de tensão do sistema elétrico. É o objetivo desta dissertação apresentar e comparar cinco dessas estratégias de proteção, através da simulação computacional de seu desempenho em caso de quedas de tensão equilibrada. A fim de alcançar este objetivo, o modelo dinâmico eletromagnética do DFIG teoricamente foi desenvolvido, bem como os modelos das estratégias de interesse. Subsequentemente, o modelo computacional do sistema foi montado no software Simulink do Matlab para finalmente executar as simulações desejadas e sua análise correspondente.

Para acompanhar o atual crescimento de demanda energética mundial, novas topologias de geradores estão sendo pesquisadas, estando nesse nicho o Gerador a Relutância Chaveado. Para seu correto funcionamento é necessário que técnicas de controle sejam empregadas para garantir níveis estáveis de tensão gerada mediante variações de velocidade e/ou carga. Portanto, o objetivo deste trabalho é apresentar uma metodologia de um controlador fuzzy da tensão gerada para a máquina em questão. Uma simulação em Matlab Simulink é apresentada para um sistema de geração de energia utilizando um gerador a relutância chaveado integrada com a malha de controle fuzzy. Resultados da dinâmica do funcionamento do controlador fuzzy são apresentados. O Controlador fuzzy proposto apresentou bom desempenho ao manter a tensão gerada em níveis desejáveis frente a distúrbios de carga e de variação de velocidade no eixo do gerador. Trata-se de um controlador robusto e versátil que garante estabilidade de tensão gerada mesmo com a operação do sistema com velocidade variável e/ou variação de carga. / Due to the growing demand of electric power energy, the engineering has to evolve by producing new efficient techniques and low cost equipment. Therefore, new electric power generator topologies have been studied, mainly switched reluctance generators due to their simple structure, reliability and low cost of fabrication. In order for a good operation of a switched reluctance generator, control techniques have to be applied to guarantee stable voltage levels under variable speed and load conditions. Hence, the objective of this work is to present a methodology based on fuzzy voltage controller for switched reluctance machine. Simulations are achieved in Matlab/Simulink for a power energy generation system using a switched reluctance generator with a fuzzy control loop. Results of the dynamic response of such controller are presented. The fuzzy controller could obtain good performance maintaining voltage levels in desired range. Therefore, the proposed controller showed to be robust, versatile and guarantee the voltage stability under speed and load variations.

Made available in DSpace on 2017-07-10T15:14:20Z (GMT). No. of bitstreams: 1 DissertacaoFelipePSilva.pdf: 1750362 bytes, checksum: d5954e3ba25ab6d54527f7566b0d47ac (MD5) Previous issue date: 2015-03-11 / The swine farming is an important Brazilian agricultural business. The activity held in confinement generates a large volume of wastewater that may be treated by anaerobic digestion. To use the biogas generated in the process, it is necessary better knowledge through the variables involved. The objective of this study was the evaluation of biogas production parameters, power generation, generator set performance in biogas conversion into electricity and the avoided cost of electricity from of the farm. Biogas parameters were monitored as methane content, digester production, and the engine consumption in generation of electricity. Monitoring was realized with the use of instruments and storage of information in a database. The results indicated an average daily production of 443 m3.dia-1, with an average of 0.10 m3 of biogas per pig and 68% of methane content. The average electricity generation was 324,5 kWh.dia-1, and efficiency of the generator set was 17% with a power of 70 kW and an average of 6,5 hours of daily operation. The avoided cost by self-consumption of electricity generated was R$ 13,718.20, and during the monitoring 70.5 MWh of electricity was generated, of which 26.6 MWh were exported to the distribution network. / A suinocultura é uma importante atividade no negócio agropecuário brasileiro. A atividade realizada em confinamento gera um grande volume de efluentes que pode ser tratado por meio da digestão anaeróbia. Para aproveitamento do biogás gerado neste processo, é necessário um melhor conhecimento através das variáveis envolvidas. O objetivo deste estudo foi a avaliação dos parâmetros de produção de biogás, geração de energia elétrica, desempenho do grupo gerador na conversão de biogás em energia elétrica e o custo evitado de energia elétrica da propriedade rural. Foram monitorados parâmetros de concentração, produção e consumo biogás; e geração de energia elétrica O monitoramento foi realizado com a utilização de instrumentos e posterior armazenamento das informações em banco de dados. Os resultados encontrados indicaram uma produção diária média de 443 m3, com uma média de 0,10 m3 de biogás por suíno e uma concentração média de 68% de metano. A geração de energia elétrica média foi de 324,5 kWh.dia-1, e a eficiência do grupo gerador foi de 17% com uma potência média ativa de 70 kW e operação diária de 6,5 horas. O custo evitado pelo autoconsumo da energia elétrica na propriedade gerada foi de R$ 13.718,20, e durante o período monitorado houve uma geração total de energia elétrica de 70,5 MWh, dos quais 26,6 MWh foram exportados para a rede de distribuição da concessionária local.

In the face of the internationally tightened requirements and regulations for CO2 emissions from the transportation sector, waste heat recovery using a thermoelectric generator (TEG) has become the most significant research interest. A vehicular TEG, converting otherwise wasted thermal energy from engines to electricity directly for use in the vehicle systems, is a promising approach for vehicle original equipment manufacturers (OEMs) to reduce fuel consumption and lower CO2 emissions. This thesis aims to explore the main challenges to be faced in the commercialization of TEGs. Based on a review of the literature, four research gaps have been identified, which are respectively: * Translating the material improvements into TEG Performance, * Transient behaviors of vehicular TEGs under driving cycles, * Fuel saving percentage and cost-benefit estimation of TEG, * Bidirectional characteristic of TEM and bifunctional vehicular TEG. To directly address these research gaps, a quasi-static TEM model, a dynamic TEG model, a semi-empirical vehicular TEG model, and a dual-model TEM model have been respectively developed and validated through experiments on both TEM test rigs and TEG engine test benches. These developed models are used as tools to investigate the performance of TEG, parameters sensitivity, and integration effects. Model-based TEG control, TEG cost benefit ratio and feasibility of a bifunctional TEG are also explored based on the developed models. The simulation results show that TEG power generation is highly sensitive to the heat transfer coefficient of hot side heat exchanger and thermal contact resistance. The TEG installation position is identified as the most important integration effect. It has been found by the simulation result that the fuel saving with TEG installed upstream of the three-way catalyst (TWC) is 50% higher than the fuel saving with TEG installed downstream of the TWC. The fuel saving percentage for a skutterudite vehicular TEG, which can generate around 400-600W in constant speed 120km/h, is 0.5-3.6% depending on the integration position in the exhaust line. A 3-minute faster warm-up effect of engine oil can be obtained when the bifunctional TEG works in engine warm-up mode with electrical current applied.

This diploma thesis deals with creation of several random number generators. The data from these prototypes are then compared according to various aspects and statistical methods. The reader is familiar with the basic concepts, the existing random number generators and the technologies used.

Processos K começaram a ser estudados nos anos 50 como uma fonte de contraexemplos e de comportamento patológico. Recentemente descobriu-se que eles são um limite de escalas para modelos de armadilha, fato que voltou a trazer certa atenção para eles. Nesse trabalho vamos adotar uma abordagem construtiva, usando-a para mostrar a propriedade forte de Markov e calcular as taxas de transição e o gerador infinitesimal. / K processes were studied in the 50\'s as a source of counter examples and of pathological behaviour. It is now know that they are a scaling limit for trap models, which led attention back to them. In this work, we will adopt a constructive approach, using it to show the strong Markov propriety, calculate the transition rates and the infinitesimal generator.

Este trabalho descreve o desenvolvimento e a construção de um gerador de pulsos de 8 canais, com interface para controle externo por microcomputador. O gerador possui 16 passos programáveis definindo a largura do pulso entre 200 ns e 10 segundos. Permite também a repetição automática de um intervalo selecionado. O microcomputador tem controle total do gerador de pulsos, incluindo programação de memórias e execução e interrupção de sequências de pulsos. Este gerador foi construído para ser usado em experiências de Ressonância Magnética Nuclear Pulsada, no controle de portas de RF e sistema de detecção / This work describes the development and construction of a 8 channel pulse generator with interface for external microcomputer control. The generator has 16 programmable steps defining pulse widths between 200 nsec and 10 seconds, with 100 nsec resolution. Automatic repeat of a selected step range is also provided. The microcomputer has full control of the pulse generator including programing of memories, execution and interruption of pulse sequences. The generator was built to be used in Pulsed Nuclear Magnetic Resonance experiments to control the high Power RF gate and the detection system

This thesis seeks to extend the PDG methodology by developing a generalized formal method for nesting PDGs in an interconnected system. A procedure for decomposing an individual PDG into reusable modules will be defined and a software architecture will be presented which takes advantage of these reusable modules. This method breaks the PDG structure into discrete elements known as PDG objects, PDG modules and PDG services. Each of these elements forms a distinct unit of reuse and each can be seen as a "little" PDG. Two different industrial implementations of this method are presented. These examples show that it is possible to share PDG services amongst multiple PDGs and provide a mechanism to create a PDG for a complicated system.

Decisions Support Systems (DSSs) are used to enhance decision maker speed and effectiveness. However, without a view of an entire system, any decision may have unanticipated effects such as sub-optimal outcomes. The purpose of this research is to show that with a system-level analysis, more informed decisions can be made that take into account a larger system or greater number of dimensions or objectives. This research also explores the benefits of using a DSS over analysis of unprocessed data and the effectiveness of integrating a product design generator (PDG) with a business DSS, creating a system DSS, where system-level effects can be analyzed. These are connected using software which allows them to be interactive, and dynamically updating. After this DSS was developed a variation was also made and decision makers evaluated these tools to identify how they performed in comparison to each other. In one variation, aspects of the tool were split up, guiding the decision maker through the analysis while the other did not. Using survey questions and recording decision makers' actions, it was found that decision makers are significantly faster and came to better conclusions when using the DSS over unprocessed data. However, it was also seen that the difference between the two variants of the System DSS tests was insignificant. This suggests that the limits in potential interactions in the one variant of a system DSS did not substantially reduce the ability of a decision maker to explore and make good design decisions. Overall this research showed that having a system-level tool is better than the unprocessed data, and that more extreme differences in a DSS are required for improved comparisons to establish which visualizations and elements are most effective in a System DSS. Future effort should be made to completely isolate different portions of the System DSS and see how well users are able to make decisions with it compared to the full system analysis.

Une utilisation intelligente de l’espace Hertzien sera nécessaire pour permettre aunombre croissant d’objets sans-fil connectés de communiquer dans le même espace de propagation.Ces travaux de thèse proposent une architecture d’émetteur radiofréquence flexible, faiblecoût et faible consommation, en rupture avec les techniques conventionnelles. Cet émetteur estfondé sur un encodage de la dérivée du signal à générer, ce qui permet de réduire le coût énergétiquede la conversion de l’information. Un convertisseur numérique analogique compatibleavec cette architecture est présenté et ses performances sont évaluées dans le cadre de la générationde signaux radiofréquence. Les résultats de mesures obtenus avec un prototype réalisé entechnologie CMOS 65 nm apporte la preuve du concept. / The increasing density of wireless devices and the associated communication flowssharing the same air interface will require a smart and agile use of frequency resources. Thisthesis proposes a flexible, low cost and low power disruptive transmitter architecture. It usesa differentiating coding scheme which leverages a mathematical and technological reduction ofthe energy cost of information conversion. The design of a DAC suited to this architecture isdeveloped and its performances are assessed toward RF signal generation. The measurementsof a demonstrator designed in 65 nm CMOS technology bring a proof of concept.