Conversor CC/CA de alta freqüência baseado em inversores ressonantes com comutação seqüencial para excitação de uma tocha indutiva a plasma térmico

This work describes the study, the analysis, the project methodology and the constructive details of a high frequency DC/AC resonant series converter using sequential commutation techniques for the excitation of an inductive coupled thermal plasma torch. The aim of this thesis is to show the new modulation technique potentialities and to present a technological option for the high-frequency electronic power converters development. The resonant converter operates at 50 kW output power under a 400 kHz frequency and it is constituted by inverter cells using ultra-fast IGBT devices. In order to minimize the turn-off losses, the inverter cells operates in a ZVS mode referred by a modified PLL loop that maintains this condition stable, despite the load variations. The sequential pulse gating command strategy used it allows to operate the IGBT devices on its maximum power limits using the derating and destressing current scheme, as well as it propitiates a frequency multiplication of the inverters set. The output converter is connected to a series resonant circuit constituted by the applicator ICTP torch, a compensation capacitor and an impedance matching RF transformer. At the final, are presented the experimental results and the many tests achieved in laboratory as form to validate the proposed new technique

Controle Adaptativo Robusto para Filtros Ativos de Potência Paralelo

Conventional control strategies used in shunt active power filters (SAPF) employs real-time instantaneous harmonic detection schemes which is usually implements with digital filters. This increase the number of current sensors on the filter structure which results in high costs. Furthermore, these detection schemes introduce time delays which can deteriorate the harmonic compensation performance. Differently from the conventional control schemes, this paper proposes a non-standard control strategy which indirectly regulates the phase currents of the power mains. The reference currents of system are generated by the dc-link voltage controller and is based on the active power balance of SAPF system. The reference currents are aligned to the phase angle of the power mains voltage vector which is obtained by using a dq phase locked loop (PLL) system. The current control strategy is implemented by an adaptive pole placement control strategy integrated to a variable structure control scheme (VS-APPC). In the VS-APPC, the internal model principle (IMP) of reference currents is used for achieving the zero steady state tracking error of the power system currents. This forces the phase current of the system mains to be sinusoidal with low harmonics content. Moreover, the current controllers are implemented on the stationary reference frame to avoid transformations to the mains voltage vector reference coordinates. This proposed current control strategy enhance the performance of SAPF with fast transient response and robustness to parametric uncertainties. Experimental results are showing for determining the effectiveness of SAPF proposed control system

Comparação entre modelos equivalentes de aerogeradores síncronos utilizando o programa ATP

At present, the electricity generation through wind energy has an importance growing in the world, with the existence of very large plans for future wind power installation worldwide. Thus, the increasing the electricity generation through wind power requires, more and more, analysis of studies of interaction between wind parks and electric power systems. This paper has as purposes to implement equivalent models for synchronous wind generators to represent a wind park in ATP program and to check behavior of the models through simulations. Simulations with applications of faults were achieved to evaluate the behavior of voltages of system for each equivalent model, through comparisons between the results of models proposed, to verify if the differences obtained allows the adoption of the simplest model

Desenvolvimento e avaliação de controladores preditivos baseados em modelos biliares

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

Técnica de controle adaptativo robusto aplicada a filtros ativos de potência e paralelo

The Methods for compensation of harmonic currents and voltages have been widely used since these methods allow to reduce to acceptable levels the harmonic distortion in the voltages or currents in a power system, and also compensate reactive. The reduction of harmonics and reactive contributes to the reduction of losses in transmission lines and electrical machinery, increasing the power factor, reduce the occurrence of overvoltage and overcurrent. The active power filter is the most efficient method for compensation of harmonic currents and voltages. The active power filter is necessary to use current and voltage controllers loop. Conventionally, the current and voltage control loop of active filter has been done by proportional controllers integrative. This work, investigated the use of a robust adaptive control technique on the shunt active power filter current and voltage control loop to increase robustness and improve the performance of active filter to compensate for harmonics. The proposed control scheme is based on a combination of techniques for adaptive control pole placement and variable structure. The advantages of the proposed method over conventional ones are: lower total harmonic distortion, more flexibility, adaptability and robustness to the system. Moreover, the proposed control scheme improves the performance and improves the transient of active filter. The validation of the proposed technique was verified initially by a simulation program implemented in C++ language and then experimental results were obtained using a prototype three-phase active filter of 1 kVA

Estratégia de controle robusto para filtro ativo paralelo sem detecção de harmônicos de correntes

Conventional control strategies used in shunt active power filters (SAPF) employs real-time instantaneous harmonic detection schemes which is usually implements with digital filters. This increase the number of current sensors on the filter structure which results in high costs. Furthermore, these detection schemes introduce time delays which can deteriorate the harmonic compensation performance. Differently from the conventional control schemes, this paper proposes a non-standard control strategy which indirectly regulates the phase currents of the power mains. The reference currents of system are generated by the dc-link voltage controller and is based on the active power balance of SAPF system. The reference currents are aligned to the phase angle of the power mains voltage vector which is obtained by using a dq phase locked loop (PLL) system. The current control strategy is implemented by an adaptive pole placement control strategy integrated to a variable structure control scheme (VS¡APPC). In the VS¡APPC, the internal model principle (IMP) of reference currents is used for achieving the zero steady state tracking error of the power system currents. This forces the phase current of the system mains to be sinusoidal with low harmonics content. Moreover, the current controllers are implemented on the stationary reference frame to avoid transformations to the mains voltage vector reference coordinates. This proposed current control strategy enhance the performance of SAPF with fast transient response and robustness to parametric uncertainties. Experimental results are showing for determining the effectiveness of SAPF proposed control system

Estudo e implementação de um controlador preditivo generalizado bilinear compensado adaptativo

The present work presents the study and implementation of an adaptive bilinear compensated generalized predictive controller. This work uses conventional techniques of predictive control and includes techniques of adaptive control for better results. In order to solve control problems frequently found in the chemical industry, bilinear models are considered to represent the dynamics of the studied systems. Bilinear models are simpler than general nonlinear model, however it can to represent the intrinsic not-linearities of industrial processes. The linearization of the model, by the approach to time step quasilinear , is used to allow the application of the equations of the generalized predictive controller (GPC). Such linearization, however, generates an error of prediction, which is minimized through a compensation term. The term in study is implemented in an adaptive form, due to the nonlinear relationship between the input signal and the prediction error.Simulation results show the efficiency of adaptive predictive bilinear controller in comparison with the conventional.

Estabilizador de sistema de potência para máquinas síncronas de polos salientes utilizando a transformada Wavelet

The power system stabilizers are used to suppress low-frequency electromechanical oscillations and improve the synchronous generator stability limits. This master thesis proposes a wavelet-based power system stabilizer, composed of a new methodology for extraction and compensation of electromechanical oscillations in electrical power systems based on the scaling coefficient energy of the maximal overlap discrete wavelet transform in order to reduce the effects of delay and attenuation of conventional power system stabilizers. Moreover, the wavelet coefficient energy is used for electric oscillation detection and triggering the power system stabilizer only in fault situations. The performance of the proposed power system stabilizer was assessed with experimental results and comparison with the conventional power system stabilizer. Furthermore, the effects of the mother wavelet were also evaluated in this work

Estratégia de controle robusto para interconexão de sistemas PV trifásicos à rede elétrica

Atualmente há uma grande preocupação em relação a substituição das fontes não renováveis pelas fontes renováveis na geração de energia elétrica. Isto ocorre devido a limitação do modelo tradicional e da crescente demanda. Com o desenvolvimento dos conversores de potência e a eficácia dos esquemas de controle, as fontes renováveis têm sido interligadas na rede elétrica, em um modelo de geração distribuída. Neste sentido, este trabalho apresenta uma estratégia de controle não convencional, com a utilização de um controlador robusto, para a interconexão de sistemas fotovoltaicos com à rede elétrica trifásica. A compensação da qualidade de energia no ponto de acoplamento comum (PAC) é realizada pela estratégia proposta. As técnicas tradicionais utilizam detecção de harmônicos, já neste trabalho o controle das correntes é feita de uma forma indireta sem a necessidade desta detecção. Na estratégia indireta é de grande importância que o controle da tensão do barramento CC seja efetuado de uma forma que não haja grandes flutuações, e que a banda passante do controlador em regime permanente seja baixa para que as correntes da rede não tenham um alto THD. Por este motivo é utilizado um controlador em modo dual DSM-PI, que durante o transitório se comporta como um controlador em modo deslizante SM-PI, e em regime se comporta como um PI convencional. A corrente é alinhada ao ângulo de fase do vetor tensão da rede elétrica, obtido a partir do uso de um PLL. Esta aproximação permite regular o fluxo de potência ativa, juntamente com a compensação dos harmônicos e também promover a correção do fator de potência no ponto de acoplamento comum. Para o controle das correntes é usado um controlador dupla sequencia, que utiliza o princípio do modelo interno. Resultados de simulação são apresentados para demonstrar a eficácia do sistema de controle proposto

Utilização da lógica difusa no controle inteligente de sistemas eletro-hidráulicos

Electro-hydraulic servo-systems are widely employed in industrial applications such as robotic manipulators, active suspensions, precision machine tools and aerospace systems. They provide many advantages over electric motors, including high force to weight ratio, fast response time and compact size. However, precise control of electro-hydraulic systems, due to their inherent nonlinear characteristics, cannot be easily obtained with conventional linear controllers. Most flow control valves can also exhibit some hard nonlinearities such as deadzone due to valve spool overlap on the passage´s orifice of the fluid. This work describes the development of a nonlinear controller based on the feedback linearization method and including a fuzzy compensation scheme for an electro-hydraulic actuated system with unknown dead-band. Numerical results are presented in order to demonstrate the control system performance

Controle inteligente de sistemas eletroidráulicos utilizando redes neurais artificiais

This work describes the development of a nonlinear control strategy for an electro-hydraulic actuated system. The system to be controlled is represented by a third order ordinary differential equation subject to a dead-zone input. The control strategy is based on a nonlinear control scheme, combined with an artificial intelligence algorithm, namely, the method of feedback linearization and an artificial neural network. It is shown that, when such a hard nonlinearity and modeling inaccuracies are considered, the nonlinear technique alone is not enough to ensure a good performance of the controller. Therefore, a compensation strategy based on artificial neural networks, which have been notoriously used in systems that require the simulation of the process of human inference, is used. The multilayer perceptron network and the radial basis functions network as well are adopted and mathematically implemented within the control law. On this basis, the compensation ability considering both networks is compared. Furthermore, the application of new intelligent control strategies for nonlinear and uncertain mechanical systems are proposed, showing that the combination of a nonlinear control methodology and artificial neural networks improves the overall control system performance. Numerical results are presented to demonstrate the efficacy of the proposed control system

Exercícios respiratórios para asma: revisão sistemática com metanálise

Introdução: A asma se tornou um problema de saúde pública devido aos seus grandes custos em cuidados de saúde. Os exercícios respiratórios constituem uma intervenção não farmacológica de baixo custo e baixo risco que vem sendo utilizada por fisioterapeutas em diferentes países no tratamento de pacientes asmáticos. Objetivo: Avaliar a eficácia dos exercícios respiratórios no tratamento de pacientes adultos com asma nos seguintes desfechos: qualidade de vida, sintomas da asma, número de exacerbações agudas, episódios de hospitalização, mensurações fisiológicas (função pulmonar e capacidade funcional), número de consultas médicas, número de faltas no trabalho devido a exacerbações da doença, avaliação subjetiva do paciente em relação à intervenção. Método: Revisão sistemática de estudos controlados randomizados com metanálise realizada em parceria com a Colaboração Cochrane. As seguintes bases de dados foram consultadas: the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE, CINAHL, AMED, e PsycINFO, além de busca manual em revistas da área e em resumos de congressos. Os seguintes termos foram utilizados: (breath*) and (exercise* or retrain* or train* or re-educat* or educat* or physiotherap* or "physical therap*" or "respiratory therapy" or buteyko ). As listas de referências dos estudos selecionados e registros de ensaios clínicos também foram consultados. A seleção dos estudos e a avaliação do risco de viés dos estudos incluídos foram realizadas de maneira independente por dois revisores. O software Review Manager foi utilizado para análise dos dados, no qual o modelo de efeito fixo foi utilizado. As variáveis contínuas foram expressas como diferença de média ponderada com um intervalo de confiança de 95%. A heterogeneidade dos resultados dos estudos incluídos foi realizada por meio da análise dos Forest plots. O teste qui-quadrado (Chi2) com um P valor de 0.10 foi utilizado para indicar significância estatística. O Índice de heterogeneidade (I2) foi implementado com um valor acima de 50% como um nível substancial de heterogeneidade. Resultados: 13 estudos envolvendo 906 pacientes estão atualmente incluídos na revisão. Os seguintes desfechos foram mensurados pelos estudos incluídos: qualidade de vida, sintomas da asma, número de exacerbações agudas e função pulmonar. Os estudos relataram uma melhora na qualidade de vida, sintomas da asma e número de exacerbações agudas. Seis dos onze estudos que avaliaram função pulmonar mostraram uma diferença significativa favorável aos exercícios respiratórios. Não houve relato de efeitos adversos. Devido à heterogeneidade substancial encontrada entre os estudos, metanálise foi possível apenas para sintomas da asma, a qual incluiu dois estudos e mostrou uma diferença significativa favorável aos exercícios respiratórios. A avaliação do risco de viés foi prejudicada devido ao relato incompleto de aspectos metodológicos pela maioria dos estudos incluídos. Conclusão: Embora os resultados encontrados pelos estudos incluídos demonstraram individualmente que os exercícios respiratórios podem ser importantes no tratamento da asma, não há evidência conclusiva nesta revisão para suportar ou refutar a eficácia desta intervenção no tratamento de pacientes asmáticos. Este fato foi devido às diferenças metodológicas entre os estudos incluídos e à ausência de relato de aspectos metodológicos por parte da maioria dos estudos incluídos. Não há dados disponíveis em relação aos efeitos dos exercícios respiratórios nos seguintes desfechos: episódios de hospitalização, número de consultas médicas, número de faltas no trabalho devido a exacerbações da doença, e avaliação subjetiva do paciente em relação à intervenção

Modelo de programação matemática para controle do crescimento da vegetação sob redes de distribuição de energia elétrica

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

A inclusão escolar da subjetividade do professor à constituição de um lugar de aluno

The move to include students with special needs (NEE) in the schools presents a paradigm that raises continual discussion about how to implement this proposal. Considering that learning is built from the weaving of socially constructed knowledge and the field of knowledge concerning subjectivity, this research explores the difficulties that occur with the later in the process of inclusion in the schools. Admittedly, the promise implicit in the school does not guarantee that the student learn, but the envisioning of this learning, when the student s educator discredits him, is such that the person is then not taken on as an actual student, being excluded from the transmission of knowledge, even within the school. The project implemented at the Instituto Educacional Casa Escola IECE, for the last three years, shows us that the possibility and sustainability of this envisioning is intimately linked to the subjectivity of the educator, as well as how one relates to the institutional culture. We question then, how this perspective is formed in the educator this perspective capable of denying the offer of a place as student, allowing him to advance while learning. With this in mind, we explore the paradoxical elements present in the paradigm of inclusion, as well as analyzing theoretically, through the body of conceptual psychoanalysis, the process of subjective constitution. We intend to bring to light how this process coincides with the construction of the educator s perspective of exemption from teaching the special needs students. We question, through the formative functions of subjective structuring (The Mirror Stage and the Oedipus Complex), how to form a perspective capable of promoting inclusion of special needs students in educators. Finally, we show how it is possible to bring to light, with the concepts of the I ideal and the ideal I, the subjective difficulties in the practicing instructor

Síntese e caracterização de materiais nanoporosos para pirólise catalítica de óleos pesados

The present work reports the study of nanoporous structures, aiming at their use in research directed to the current demand of the petroleum industry to value heavy oil. Initially, two ways were chosen for the synthesis of porous structures from the molecular sieves of type Si-MCM-41. In the first way, the structure MCM-41 is precursory for heteroatom substitutes of silicon, generating catalyst of the type Al-MCM-41 from two different methods of incorporation of the metal. This variation of the incorporation method of Aluminum in the structure of Si-MCM-41 was carried out through the conventional procedure, where the aluminum source was incorporated to the gel of synthesis, and the procedure post-synthesis, where the Aluminum source was incorporated in catalyst after the synthesis of Si-MCM-41. In the second way, the MCM-41 acts as a support for growth of nanocrystals of zeolite embedded in their mesoporous, resulting in hybrid MCM-41/ZSM-5 catalyst. A comparative analysis was carried through characterizations by XRD, FTIR, measures of acidity through n-butylamine adsorption for TGA, SEM-XRF and N2 adsorption. Also crystalline aluminosilicate with zeolitic structure MFI of type ZSM-5 was synthesized without using organic templates. Methodologies to the preparation of these materials are related by literature using conventionally reactants that supply oxides of necessary silicon and aluminum, as well as a template agent, and in some cases co-template. The search for new routes of preparation for the ZSM-5 aimed at, above all, the optimization of the same as for the time and the temperature of synthesis, and mainly the elimination of the use of organic templates, that are material of high cost and generally very toxic. The current study is based on the use of the H2O and Na+ cations playing the role of structural template and charge compensation in the structure. Characterizations by XRD, FTIR, SEM-XRF and N2 adsorption were also conducted for this material in order to compare the samples of ZSM-5 synthesized in the absence of template and those used industrially and synthesized using structuring