Comparação do controle do inversor trifásico conectado à rede com filtro LCL considerando o amortecimento passivo e ativo

Distributed generation systems must fulfill standards specifications of current harmonics injected to the grid. In order to satisfy these grid requirements, passive filters are connected between inverter and grid. This work compares the characteristic response of the traditional inductive (L) filter with the inductive-capacitive-inductive (LCL) filter. It is shown that increasing the inductance L leads to a good ripple current suppression around the inverter switching frequency. The LCL filter provides better harmonic attenuation and reduces the filter size. The main drawback is the LCL filter impedance, which is characterized by a typical resonance peak, which must be damped to avoid instability. Passive or active techniques can be used to damp the LCL resonance. To address this issue, this dissertation presents a comparison of current control for PV grid-tied inverters with L filter and LCL filter and also discuss the use of active and passive damping for different regions of resonance frequency. From the mathematical models, a design methodology of the controllers was developed and the dynamic behavior of the system operating in closed loop was investigated. To validate the studies developed during this work, experimental results are presented using a three-phase 5kW experimental platform. The main components and their functions are discussed in this work. Experimental results are given to support the theoretical analysis and to illustrate the performance of grid-connected PV inverter system. It is shown that the resonant frequency of the system, and sampling frequency can be associated in order to calculate a critical frequency, below which is essential to perform the damping of the LCL filter. Also, the experimental results show that the active buffer per virtual resistor, although with a simple development, is effective to damp the resonance of the LCL filter and allow the system to operate stable within predetermined parameters.

Transformadores. Funcionamento em paralelo na rede elétrica

O crescimento do consumo de energia elétrica verificado nos últimos anos e o aparecimento e evolução dos sistemas de produção de energia por fontes de energia renováveis, como a eólica e fotovoltaica, levam a que sejam necessários ajustes no sistema de forma a comportar estas variações no trânsito de potências. Assim, pode ser necessário instalar transformadores em paralelo para comportar o aumento da potência consumida num determinado local. Este artigo aborda a utilização dos transformadores nos Sistemas Elétricos de Energia e explica as condições necessárias para o correto funcionamento de transformadores em paralelo.

Controlo de conversores de eletrónica de potência para integração com SMES na melhoria da qualidade de energia elétrica

Dissertação para obtenção do Grau de Mestre em Engenharia Eletrotécnica e de Computadores

Bullying escolar: da midiatização à invisibilidade. A (im)potência institucional diante do sofrimento ou das possibilidades de inclusão nas interações entre crianças

O presente artigo é o recorte de um estudo produzido numa escola pública portuguesa, com três turmas: pré-escola, 1º e 3º ano. Aborda crítica e propositivamente o contexto socializador institucional, com especial atenção a prática de bullying entre pares. O Material levantado através de grupos focais com crianças, observações do cotidiano escolar e, entrevistas à educadora, professores, assistente e auxiliares, revela o bullying enquanto fenômeno ativo nas três turmas. Entretanto, o discurso adulto, docente e da equipe técnica, exceção do que observa um professor, é coeso na referencia a um ambiente escolar livre dessa forma de violência. As narrativas infantis reconhecem-nas e, inicialmente as circunscrevem aos pares de etnia cigana, posteriormente, e nos desdobramentos da dialogicidade estabelecida, tratam de um protagonismo alargado para além de fatores étnicos, e, na primeira pessoa. Os dados gerados indicam haver relações entre um modelo escolar centrado no trabalho individual e no mérito acadêmico com os papeis sociais de cada criança. Baixo desempenho acadêmico e desinvestimento docente estão presentes no perfil das crianças vitimadas. Nos recreios, tempos e espaços preferidos pelas crianças, o que não representa menor investimento ou valor às ações e compromissos implicados no exercício do ofício de aluno, atos de bullying são facilmente perceptíveis. Órfãos do olhar curioso e interessado nas culturas infantis, produzidas no brincar, são um campo previsível de violências entre os pares. Também permitem observar um núcleo comum às crianças diretamente envolvidas com o bullying: vítimas e agressores enfrentam dificuldades para participar, com pleno envolvimento lúdico, de jogos e de brincadeiras. Perceber a criança real, nas suas especificidades, competências e direito de participação é um desafio posto a escola, não só para fazer frente às diversas formas de violência, mas especialmente para promover uma socialização inclusiva, de bem estar e de respeito ao que é próprio da infância.

Análise do Efeito Goos-Hanchen e Não-reciprocidade do fluxo de potência em antiferromagnéticos

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

Um novo sistema de refrigeração com controle de temperatura, compressor aberto, máquina de indução trifásica com velocidade variável e correção ativa do fator de potência do estágio de entrada

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Programa computacional para análise do faturamento do consumo de energia elétrica através do k-hiperbolóide de carga e potência em empresas frigoríficas abatedoras de bovinos

Pós-graduação em Agronomia (Energia na Agricultura) - FCA

Fluxo de potência ótimo em sistemas multimercados através de um algorítmo evolutivo multiobjetivo

Pós-graduação em Engenharia Elétrica - FEIS

Teorias de potência conservativa e instantânea: análise comparativa

Pós-graduação em Engenharia Elétrica - FEB

Análise do acabamento superficial e da potência consumida na usinagem de fresamento frontal e cilíndrico tangencial da madeira de eucalipto

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Autonomic hardware manager: uma arquitetura de hardware autonômico usando a solução de repositório ativo de componentes

This Thesis main objective is to implement a supporting architecture to Autonomic Hardware systems, capable of manage the hardware running in reconfigurable devices. The proposed architecture implements manipulation, generation and communication functionalities, using the Context Oriented Active Repository approach. The solution consists in a Hardware-Software based architecture called "Autonomic Hardware Manager (AHM)" that contains an Active Repository of Hardware Components. Using the repository the architecture will be able to manage the connected systems at run time allowing the implementation of autonomic features such as self-management, self-optimization, self-description and self-configuration. The proposed architecture also contains a meta-model that allows the representation of the Operating Context for hardware systems. This meta-model will be used as basis to the context sensing modules, that are needed in the Active Repository architecture. In order to demonstrate the proposed architecture functionalities, experiments were proposed and implemented in order to proof the Thesis hypothesis and achieved objectives. Three experiments were planned and implemented: the Hardware Reconfigurable Filter, that consists of an application that implements Digital Filters using reconfigurable hardware; the Autonomic Image Segmentation Filter, that shows the project and implementation of an image processing autonomic application; finally, the Autonomic Autopilot application that consist of an auto pilot to unmanned aerial vehicles. In this work, the applications architectures were organized in modules, according their functionalities. Some modules were implemented using HDL and synthesized in hardware. Other modules were implemented kept in software. After that, applications were integrated to the AHM to allow their adaptation to different Operating Context, making them autonomic.

Topologia de gerador de distúrbios elétricos baseada em conversores de potência

Electrical disturbances such as voltage sags, interruptions and voltage unbalances might cause serious problems for the end-user and for the companies of generation and transmission of energy. Few years ago, those companies have been using methods and equipments of protection to avoid the disturbances’ presence or to mitigate their effects on the power system. Disturbances generators are used to analyse the behavior of electrical and electronic equipments affected by disturbances. The analysis of those failures allows the development of appropriated protection equipments. In this paper, the development of a disturbances generator based on power converters is presented. The disturbance generator developed is able to generate some symmetrical disturbances, such as: voltage sags, voltage swells and harmonic distortion. The control strategy used in the disturbance generator is based on discrete and repetitive control. The steps of the design of the control and of the filter used for reducing harmonic in the output, are detailed in the text. Are presented the obtained results on computational simulations and the obtained results on laboratory tests.

Corpo, força e potência: Nietzsche e Spinoza no pensamento de Deleuze

This dissertation aims at showing the importance of the Nietzsche s and Spinoza s philosophy in Deleuze thought, about body, force, and potency concepts. The search starts from Deleuze texts around two authors of his inspiration, reaching understand in the plan of immanence of the relationship between concepts and the way life as ethics and political affirmation. The first goal is the concept of rhizome; propose by Deleuze in what manner to walk the ways traced by philosophers and at the same time to create self ways. The second chapter examines the body in Nietzsche as force s relations. Find to show the genesis of the force in its determination as relative quantity strong or weak, and as absolute quality active or reactive; and for other side the genesis of the force from two poles of the will to power affirmation or negation, examining the consequences for life and thought. In the third chapter explained the definitions of body in Spinoza. The body, in Spinoza, defines itself complex relation of movement and repose, velocity and slowness and by it s to affect and be affecter s power. Find to show understanding the mediums for to amplify the power of to exist or the potency of to act, in what manner ethics of to live. The fourth chapter makes one parallel between the war and the thought in the constitution of socials body and collectives agenciamientos, for understand in the fifth chapter the body as war s machine of the thought, from the relationship between nomad way life and war s machine showed in Tractate of Nomadologia. Wait like this to show the importance of the ethics and political thought than affirm the existence in the world through active force from that body s power.

Projeto, implementação e análise de um conversor CC-CC de alto ganho e alto rendimento para aplicações fotovoltaicas

In recent years the photovoltaic generation has had greater insertion in the energy mix of the most developed countries, growing at annual rates of over 30%. The pressure for the reduction of pollutant emissions, diversification of the energy mix and the drop in prices are the main factors driving this growth. Grid tied systems plays an important role in alleviating the energy crisis and diversification of energy sources. Among the grid tied systems, building integrated photovoltaic systems suffers from partial shading of the photovoltaic modules and consequently the energy yield is reduced. In such cases, classical forms of modules connection do not produce good results and new techniques have been developed to increase the amount of energy produced by a set of modules. In the parallel connection technique of photovoltaic modules, a high voltage gain DC-DC converter is required, which is relatively complex to build with high efficiency. The current-fed isolated converters explored in this work have some desirable characteristics for this type of application, such as: low input current ripple and input voltage ripple, high voltage gain, galvanic isolation, feature high power capacity and it achieve soft switching in a wide operating range. This study presents contributions to the study of a high gain and high efficiency DC-DC converter for use in a parallel system of photovoltaic generation, being possible the use in a microinverter or with central inverter. The main contributions of this work are: analysis of the active clamping circuit operation proposing that the clamp capacitor connection must be done on the negative node of the power supply to reduce the input current ripple and thus reduce the filter requirements; use of a voltage doubler in the output rectifier to reduce the number of components and to extend the gain of the converter; detailed study of the converter components in order to raise the efficiency; obtaining the AC equivalent model and control system design. As a result, a DC-DC converter with high gain, high efficiency and without electrolytic capacitors in the power stage was developed. In the final part of this work the DC-DC converter operation connected to an inverter is presented. Besides, the DC bus controller is designed and are implemented two maximum power point tracking algorithms. Experimental results of full system operation connected to an emulator and subsequently to a real photovoltaic module are also given.

Arquitetura híbrida com DSP e FPGA para implementação de controladores de filtros ativos de potência

The presence of non-linear loads at a point in the distribution system may deform voltage waveform due to the consumption of non-sinusoidal currents. The use of active power filters allows significant reduction of the harmonic content in the supply current. However, the processing of digital control structures for these filters may require high performance hardware, particularly for reference currents calculation. This work describes the development of hardware structures with high processing capability for application in active power filters. In this sense, it considers an architecture that allows parallel processing using programmable logic devices. The developed structure uses a hybrid model using a DSP and an FPGA. The DSP is used for the acquisition of current and voltage signals, calculation of fundamental current related controllers and PWM generation. The FPGA is used for intensive signal processing, such as the harmonic compensators. In this way, from the experimental analysis, significant reductions of the processing time are achieved when compared to traditional approaches using only DSP. The experimental results validate the designed structure and these results are compared with other ones from architectures reported in the literature.