Submitted by Haroudo Xavier Filho (haroudo.xavierfo@ufpe.br) on 2016-03-01T13:09:14Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Silva Filho, Luis Rodrigues da.pdf: 5874183 bytes, checksum: 60b4246d84e077fb2131d50faca19bd3 (MD5) / Made available in DSpace on 2016-03-01T13:09:14Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Silva Filho, Luis Rodrigues da.pdf: 5874183 bytes, checksum: 60b4246d84e077fb2131d50faca19bd3 (MD5) Previous issue date: 2015-01-30 / CAPES / Atualmente, um grande número de computadores e outras cargas elétricas sensíveis ligadas à rede elétrica são diretamente afetados por problemas de qualidade de energia. Uma das questões mais importantes está relacionada com as correntes harmônicas geradas pelo aumento do número de cargas não-lineares conectadas ao sistema elétrico, tais como retificadores a diodo e tiristores. Como consequência, estes harmônicos podem causar distorções na tensão, perdas adicionais no sistema de energia e mau funcionamento de equipamentos eletrônicos sensíveis. A literatura apresenta diferentes topologias de filtros híbridos de potência visando a compensação harmônica de corrente. Este trabalho apresenta o estado da arte de algumas topologias, realizando uma análise comparativa entre elas. Em comum, todas as topologias possuem um reduzido número de chaves. Adicionalmente, é apresentada uma nova topologia chamada six-switch two-leg hybrid power filter, que além de apresentar um número reduzido de chaves quando comparada a outras topologias com dupla compensação, é capaz de fornecer compensação total, mesmo para cargas com um alto conteúdo harmônico. Os resultados experimentais são apresentados para um protótipo, a fim de demonstrar que o desempenho de compensação harmônica da proposta cumpre a norma IEEE 519. / Nowadays, a large number of computers and other sensitive electrical loads connected to the power grid are directly affected by power quality problems. One of the most important issues is related to current harmonics generated by the increasing number of nonlinear loads connected to the power grid, such as diode and thyristor front-end rectifiers. As consequence, these harmonics can cause voltage distortions, additional losses in the power system and malfunction of sensitive electronic equipment. The literature presents several hybrid power filters topologies, aiming current harmonic compensation. This work presents some state of - art topologies with reduced number of switches and performs a comparative analysis among them. Additionally, a six-switch two-leg hybrid power filter topology, that presents a reduced number of switches when compared with dual topologies, is proposed. The solution is capable of providing fully compensation even for loads with high harmonic content. Experimental results, obtaneid by a prototype, are presented in order to demonstrate that the harmonic compensation performance meets the IEEE 519 standard.

Orientadores: José Roberto de França Arruda, Philippe Herzog / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-16T06:12:24Z (GMT). No. of bitstreams: 1 Pasqual_AlexanderMattioli_D.pdf: 10340586 bytes, checksum: 74b86a8897be1f1c00e3c13b018e73bb (MD5) Previous issue date: 2010 / Resumo: O controle angular da radiação sonora pode ser obtido utilizando um arranjo compacto de alto-falantes independentemente programáveis operando na mesma faixa de frequência. Geralmente, os alto-falantes são dispostos sobre uma estrutura de formato esférico seguindo a geometria de um sólido de Platão a fim de se obter uma configuração altamente simétrica. Recentemente, protótipos de arranjos esféricos compactos de alto-falantes vêm sendo desenvolvidos e aplicados a medições em acústica de salas, performances de música eletroacústica e síntese de padrões de diretividade de fontes acústicas tais como instrumentos musicais. Contudo, muitos aspectos referentes a seu controle, projeto e comportamento eletromecânico, bem como à sua habilidade em proporcionar uma experiência sonora mais realista que sistemas de áudio convencionais, permanecem não esclarecidos. Este trabalho contempla a análise e síntese de campos sonoros através de um arranjo esférico compacto de alto-falantes e pretende contribuir para o esclarecimento de alguns aspectos supracitados. Propõe-se uma estratégia de controle baseada nos modos de radiação acústica do arranjo esférico, a qual apresenta várias vantagens sobre a estratégia usual fundada nos harmônicos esféricos. Uma análise teórica e experimental do comportamento eletromecânico de arranjos compactos de alto-falantes também é apresentada, na qual o acoplamento acústico entre os alto-falantes no interior da estrutura esférica é considerado. Além disso, os sinais ótimos dos alto-falantes correspondentes a um dado padrão de diretividade são calculados utilizando duas funções custo distintas, revelando que o realismo do padrão sintetizado pode ser significativamente ampliado desprezando-se a fase da diretividade alvo. Finalmente, os modelos teóricos propostos são validados por medições de impedância elétrica, velocidade dos diafragmas dos alto-falantes e padrões de diretividade / Abstract: Angular control of the sound radiation can be achieved by using a compact array of independently programmable loudspeakers operating at the same frequency range. The drivers are usually distributed over a sphere-like frame according to a Platonic solid geometry to obtain a highly symmetrical configuration. Prototypes of compact spherical loudspeaker arrays have been recently developed and applied in room acoustics measurements, electroacoustic music performance and synthesis of directivity patterns of acoustical sources such as musical instruments. However, many aspects concerning their control, design, electromechanical behavior and ability to provide a more realistic sound experience than conventional audio systems remain unclear. This work concerns the analysis and synthesis of sound fields by a compact spherical loudspeaker array and aims to contribute to clarifying some aspects mentioned above. A control strategy based on the acoustic radiation modes of the spherical array is proposed, which presents several advantages over the usual strategy based on the spherical harmonics. A theoretical and experimental analysis of the electromechanical behavior of compact loudspeaker arrays is also presented, in which the acoustic coupling between drivers inside the array frame is taken into account. In addition, optimumdriver signals corresponding to a given target directivity pattern are derived using two different cost functions, indicating that the realism of the synthesized pattern may be significantly increased by neglecting the phase of the target directivity pattern. Finally, the proposed theoretical models are validated through measurements of electrical impedance, loudspeaker diaphragm velocity and directivity patterns / Doutorado / Mecanica dos Sólidos e Projeto Mecanico / Doutor em Engenharia Mecânica

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Este trabalho apresenta o estudo, análise e a implementação de três topologias de condicionadores ativos de energia elétrica, utilizados para a melhoria da qualidade da energia em sistemas elétricos trifásicos a quatro fios. Estes condicionadores de qualidade de energia podem trabalhar tanto como um condicionador unificado de qualidade de energia (UPQC), bem como uma fonte de alimentação ininterrupta (UPS), permitindo: (i) a supressão das correntes harmônicas da carga; (ii) a compensação de energia reativa da carga; (iii) compensação dos desequilíbrios das correntes de carga; (iv) a compensação de desequilíbrios de tensão da rede; (v) supressão das tensões harmônicas da rede elétrica; (vi) a regulação das tensões de saída (tensões de carga); e (vii) fornecimento de energia ininterrupta para as cargas críticas (sistema UPS). Dentre as três topologias de UPQC/UPS estudadas, uma delas é proposta neste trabalho com o intuito de reduzir a tensão no barramento CC. Além disso, todas as topologias em estudo são constituídas por dois conversores PWM, nos quais é adotada uma estratégia de controle dual. Desse modo, o conversor colocado em paralelo com a carga, funciona como uma fonte de tensão senoidal, enquanto que o conversor colocado em série entre a rede elétrica e a carga, é controlado para operar como uma fonte de corrente senoidal. Tanto os controladores de tensão, quanto os de corrente são implementados no referencial síncrono dq0. Além disso, a técnica de modulação vetorial espacial tridimensional (3-D-SVM) é empregada nos conversores. Testes experimentais são apresentados para validar o desenvolvimento teórico e verificar o bom desempenho estático e dinâmico dos condicionadores ativos de energia elétrica, operando como UPQC, bem como sistema UPS. / This work presents the study, analysis and implementation of three topologies of active power conditioners, which are used to improve the power quality in three-phase four-wire systems. These power quality conditioner can work as unified power quality conditioner (UPQC), as well as an uninterruptible power supply (UPS) system allowing: (i) suppression of load harmonic currents; (ii) compensation of load reactive power; (iii) load unbalances compensation; (iv) utility voltage unbalances compensation; (v) utility voltage harmonics suppression; (vi) regulation of the output voltages (load voltages); and (vii) uninterruptible power for critical loads when working as UPS system. Among the three topologies of UPQC/UPS studied, one of them is proposed in this work in order to reduce the DC-bus voltage. Besides, all the topologies are comprised of two PWM converters, where a dual control strategy is adopted. The first converter, which is placed in parallel with the load, operates as a sinusoidal voltage source, while the second, which is placed in series between the utility grid and the load, is controlled to operate as a sinusoidal current source. Both the voltage and current controllers are implemented into the synchronous rotating reference frame (dq0-axes). In addition, the series and parallel converters use the three-dimensional space vector modulation (3-D-SVM) technique. The experimental tests are presented to validate the theoretical development and to verify the effective static and dynamic performance of the proposed active power conditioners, operating as UPQC and UPS.

Orientador: Pedro José Catuogno / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Matemática Estatística e Computação Científica / Made available in DSpace on 2018-08-23T19:39:42Z (GMT). No. of bitstreams: 1 Neves_EduardodeAmorim_D.pdf: 2575933 bytes, checksum: c52665fabd4cb103ecdff3106990155e (MD5) Previous issue date: 2013 / Resumo: Esta tese está dividida em duas partes. Na primeira parte, faremos uma abordagem probabilística para a teoria de aplicações L-harmônicas em variedades diferenciáveis, passaremos para esse contexto os Teoremas de Liouville, Picard, Elworthy e Dirichlet. Na segunda parte do trabalho, o objetivo é generalizar e caracterizar o conceito de difusão, martingale e movimento Browniano em variedades que estejam munidas por uma família de métricas e conexões que variam diferenciavelmente com o tempo / Abstract: This thesis is divided into two parts. In the first part, we will make a probabilistic approach to the theory of L-harmonic applications on manifolds; we generalize to this context Theorems of Liouville, Picard, Elworthy and Dirichlet. In the second part of the work, the goal is to generalize and characterize the concept of diffusion, martingale and Brownian motion on manifolds that are provided by a family of metrics and connections which depends smoothly on time / Doutorado / Matematica / Doutor em Matemática

The connection of high penetrations of new low carbon technologies such as PV and electric vehicles onto the distribution network is expected to cause power quality problems and the thermal capacity of feeder cables may be exceeded. Replacement of existing infrastructure is costly and so feeder cables are likely to be operated close to their hosting capacity. Network operators therefore require accurate simulation models so that new connection requests are not unnecessarily constrained. This work has reviewed recent studies and found a wide range of assumptions and approximations that are used in network models. A number of these have been investigated further, focussing on methods to specify the impedances of the cable, the impacts of harmonics, the time resolution used to model demand and generation, and assumptions regarding the connectivity of the neutral and ground conductors. The calculation of cable impedances is key to the accuracy of network models but only limited data is available from design standards or manufacturers. Several techniques have been compared in this work to provide guidance on the level of detail that should be included in the impedance model. Network modelling results with accurate impedances are shown to differ from those using published data. The demand data time resolution has been shown to affect estimates of copper losses in network cables. Using analytical methods and simulations, the relationship between errors in the loss estimates and the time resolution has been demonstrated and a method proposed such that the accuracy of loss estimates can be improved. For networks with grounded neutral conductors, accurate modelling requires the resistance of grounding electrodes to be taken into account. Existing methods either make approximations to the equivalent circuit or suffer from convergence problems. A new method has been proposed which resolves these difficulties and allows realistic scenarios with both grounded and ungrounded nodes to be modelled. In addition to the development of models, the voltages and currents in a section of LV feeder cable have been measured. The results provide a validation of the impedance calculations and also highlight practical difficulties associated with comparing simulation models with real measurement results.

En studie om medveten memorering av harmonik inom klassiskt pianospel. Arbetet bygger på observationer av en tolv veckors lång instuderingsprocess, sett i relation till ett urval av tidigare litteratur och forskning inom området. Studien har i syfte att ge en djupare bild och förståelse av memoreringens påverkan vid konsertsituationen samt vilka fördelar respektive nackdelar det kan finnas med medveten memorering av harmonik. För att uppnå syftet tar studien utgångspunkt i tre frågeställningar. Frågeställningarna berör medveten memorering av harmonik som metod att instudera ett stycke, vilka fördelar och nackdelar det kan få samt om det kan hjälpa en musicerande att känna sig tryggare på scen. Som blivande lärare hoppas jag att detta dels ska hjälpa mig vid egna uppspel men också att jag ska kunna förmedla en bra memoreringsmetod till de elever som jag kommer att möta under min tid som lärare. / A study about conscious memorization of harmony in classical piano playing. The study is based on observations of a twelve week period and on chosen literature from previous research in this field. The purpose of the study is to get a deeper knowledge and understanding in how memorizing can effect the results at a performance and also what other benefits and disadvantages there could be. The study has as a starting point three questions. These questions are about memorization of harmonics as a method to learn a music piece, the benefits and disadvantages with conscious memorization and also if a pianist can feel safer on stage after consciously memorizing harmony. As a future teacher I hope this study will help me with my own performances and also the pupils that I will teach and meet during my professional work as a musicteacher.

Power quality has become one of major concerns in the power industry. It can be described as the reliability of the electric power to maintain continuity operation of end-use equipment. Power quality problems are defined as deviation of voltage or current waveforms from the ideal value. The expansion plan of wind power generation has raised concern regarding how it influences the voltage and current signals. The variability nature of wind energy and the requirements of wind power generation increase the potential problems such as frequency and harmonic distortions. In order to analyze and mitigate problems in wind power generation, it is important to monitor power quality in wind farm. Therefore, the more accurate and reliable parameter estimation methods suitable for wind power generation are needed. Three parameter estimation methods are proposed in this thesis to estimate the unknown parameters, i.e. amplitude and phase angle of fundamental and harmonic components, DC component and system frequency, during the dynamic change in wind farm. In the first method, a self-tuning procedure is introduced to least square method to increase the immunity of the algorithm to noise. In the second method, nonrecursive Newton Type Algorithm is utilised to estimate the unknown parameters by obtaining the left pseudoinverse of Jacobian matrix. In the last technique, unscented transformation is used to replace the linearization procedure to obtain mean and covariance which will be used in Kalman filter method. All of the proposed methods have been tested rigorously using computer simulated data and have shown their capability to track the unknown parameters under extreme distortions. The performances of proposed methods have also been compared using real recorded data from several wind farms in Europe and have demonstrated high correlation. This comparison has verified that UKF requires the shortest processing time and STLS requires the longest.