| Name: | Description: | Size: | Format: | |
|---|---|---|---|---|
| 13.92 MB | Adobe PDF |
Authors
Advisor(s)
Abstract(s)
No presente trabalho de Doutoramento procura-se contribuir para a investigação e desenvolvimento
de geradores lineares de relutância variável comutados de topologia tubular com
aplicação em sistemas de absorção pontual para a conversão de energia das ondas.
É feito o enquadramento de Portugal na exploração do recurso energético das ondas e é
apresentada a teoria linear, que permite a descrição do comportamento hidrodinâmico de uma
onda regular. São apresentados os métodos estatísticos para a análise de mares irregulares.
Os métodos referidos são posteriormente aplicados a um conjunto de observações de estados
marítimos para a caracterização energética de quatro locais na costa Portuguesa.
É descrito o funcionamento do dispositivo de absorção pontual, é definido o modelo matemático
que rege o seu comportamento e são apresentadas as expressões analíticas que permitem
o dimensionamento dos elementos mecânicos considerados no presente estudo.
São identificados os vários tipos de configurações estruturais adoptados em máquinas lineares
de relutância variável e mencionados os conversores electrónicos de potência típicos para o
seu controlo. É feita a descrição dos princípios de conversão energética de máquinas lineares de
relutância variável e são indicados os materiais normalmente adoptados para a sua construção.
Para o gerador linear pretendido, são propostos quatro modelos estruturais de topologia tubular
como possíveis opções. Cada modelo é caracterizado por três fases eléctricas e apresenta
duas configurações distintas, em função da localização dos enrolamentos de fase. É proposta
uma metodologia de projecto para cada modelo estrutural que tem por base a aplicação de métodos
de optimização no dimensionamento de um gerador com capacidade de desenvolver uma
dada força axial. Duas versões de projecto são consideradas. O projecto analítico, que envolve
a solução de expressões analíticas para caracterização electromagnética de cada gerador e o
projecto numérico, que utiliza o método de elementos finitos, por intermédio de um software
comercial, para avaliar as grandezas electromagnéticas de cada modelo estrutural.
É formulado o modelo matemático do gerador linear em estudo e é descrita a estratégia de
controlo adoptada para o seu funcionamento em dispositivos de absorção pontual. O controlo
por histerese é adaptado às condições de geração variável impostas pelas ondas com o objectivo
de melhorar o desempenho de conversão do dispositivo de absorção pontual.
O método do Enxame de Partículas e o método do Complexo de Box são propostos para a
realização dos processos de optimização necessários ao projecto e análise do sistema de geração
considerado neste trabalho. É feita a formulação dos problemas a optimizar e são expostos os
algoritmos referentes a cada método.
Com base nos resultados fornecidos pela análise estatística aplicada às condições marítimas
de quatro locais da costa Portuguesa, são estabelecidos dois casos de estudo para o dimensionamento
e análise do sistema de conversão. O Caso 1 é relativo às condições marítimas com maior
probabilidade de ocorrência e o Caso 2 ao estado marítimo com maior densidade de energia.
Dos quatro locais avaliados é seleccionado o local mais apropriado para a instalação do dispositivo
de absorção pontual. De acordo com as condições marítimas deste local são dimensionados
oito geradores para cada caso de estudo. O gerador com maior capacidade de geração eléctrica
é eleito, para cada caso, como unidade de extracção de potência do dispositivo de absorção
pontual.
O sistema conversor de energia das ondas é avaliado para situações de carga imposta por
uma onda regular. São calculadas as forças hidrodinâmicas exercidas no sistema e são determinados
os parâmetros óptimos de controlo para diferentes cenários de operação. Em cada caso de estudo, é avaliado o desempenho do sistema com a estratégia de controlo proposta.
Todo o processo de cálculo computacional é implementado em linguagem própria do software
Matlab®. As forças hidrodinâmicas são calculadas pelo software Nemoh e a análise de
elementos finitos é executada com o software MagNet®.
The present work aims to contribute to the research and development of tubular linear switched reluctance generators with application in point absorber devices for ocean wave energy conversion. The Portuguese status, in the ocean wave energy resource exploration, is evaluated. The linear wave theory is presented in order describe the hydrodynamic behavior of a regular ocean wave. Statistical methods are presented for the evaluation of irregular seas. These are applied to a data set of sea state observations to perform the energy resource assessment of four sites in the Portuguese coast. The point absorber operation is described. Its mathematical model is presented as well as the analytical expressions for the design of the mechanical elements considered in this work. The structural configurations used in linear switched reluctance machines are identified and the electronic power converters, commonly used for their control, are briefly described. The electromagnetic conversion principles of linear switched reluctance machines are explained and the usual materials, chosen for their construction, are specified. Four structural models with tubular topology are proposed for the pretended linear generator. Each model has three electric phases and may adopt two distinct configurations according to the location of the coils. A design methodology based on optimization procedure is established to each model in order to obtain a generator with the ability to develop a specified axial force. Two design versions are considered. The analytical design, that comprises the solution of the analytical expressions for the electromagnetic characterization of each generator and the numerical project, that applies the finite element method, using a dedicated commercial software, to evaluate the electromagnetic entities of each structural model. A mathematical model is formulated for the linear generator under evaluation and the control strategy adopted for its operation, in point absorber devices, is described. The hysteresis control is adapted to the variable generation conditions, imposed by the ocean waves, to improve the conversion efficiency of the point absorber device. The Particle Swarm Optimization method and the Box Complex method are proposed to solve the optimization processes related with the design and analysis of the energy conversion system addressed in this work. The optimization problems are formulated and the algorithms referred to each method are exposed. Based on the results obtained by the statistical analysis, applied to the maritime conditions of four sites in the Portuguese coast, two case studies are established for the design and analysis of the conversion system. Case 1 is addressed to the maritime conditions with the highest probability of occurrence and Case 2 to the sea state characterized with the highest energy density. The most suitable site is selected for the installation of the conversion system. According to the respective sea state conditions, eight generators are designed for each case study. The generator with more generation capabilities is chosen, for each case study, as the power take-off system of the point absorber device. The ocean wave conversion system is evaluated for loads induced by a regular wave. The hydrodynamic forces exerted on the system are computed and the optimal control parameters are determined for different operation scenarios. For each case study the conversion efficiency of the system for the proposed control strategy is evaluated. The main computational procedures are implemented in the software Matlab®. The hydrodynamic loads are computed by using the software Nemoh and the finite element analysis is performed within the software MagNet®.
The present work aims to contribute to the research and development of tubular linear switched reluctance generators with application in point absorber devices for ocean wave energy conversion. The Portuguese status, in the ocean wave energy resource exploration, is evaluated. The linear wave theory is presented in order describe the hydrodynamic behavior of a regular ocean wave. Statistical methods are presented for the evaluation of irregular seas. These are applied to a data set of sea state observations to perform the energy resource assessment of four sites in the Portuguese coast. The point absorber operation is described. Its mathematical model is presented as well as the analytical expressions for the design of the mechanical elements considered in this work. The structural configurations used in linear switched reluctance machines are identified and the electronic power converters, commonly used for their control, are briefly described. The electromagnetic conversion principles of linear switched reluctance machines are explained and the usual materials, chosen for their construction, are specified. Four structural models with tubular topology are proposed for the pretended linear generator. Each model has three electric phases and may adopt two distinct configurations according to the location of the coils. A design methodology based on optimization procedure is established to each model in order to obtain a generator with the ability to develop a specified axial force. Two design versions are considered. The analytical design, that comprises the solution of the analytical expressions for the electromagnetic characterization of each generator and the numerical project, that applies the finite element method, using a dedicated commercial software, to evaluate the electromagnetic entities of each structural model. A mathematical model is formulated for the linear generator under evaluation and the control strategy adopted for its operation, in point absorber devices, is described. The hysteresis control is adapted to the variable generation conditions, imposed by the ocean waves, to improve the conversion efficiency of the point absorber device. The Particle Swarm Optimization method and the Box Complex method are proposed to solve the optimization processes related with the design and analysis of the energy conversion system addressed in this work. The optimization problems are formulated and the algorithms referred to each method are exposed. Based on the results obtained by the statistical analysis, applied to the maritime conditions of four sites in the Portuguese coast, two case studies are established for the design and analysis of the conversion system. Case 1 is addressed to the maritime conditions with the highest probability of occurrence and Case 2 to the sea state characterized with the highest energy density. The most suitable site is selected for the installation of the conversion system. According to the respective sea state conditions, eight generators are designed for each case study. The generator with more generation capabilities is chosen, for each case study, as the power take-off system of the point absorber device. The ocean wave conversion system is evaluated for loads induced by a regular wave. The hydrodynamic forces exerted on the system are computed and the optimal control parameters are determined for different operation scenarios. For each case study the conversion efficiency of the system for the proposed control strategy is evaluated. The main computational procedures are implemented in the software Matlab®. The hydrodynamic loads are computed by using the software Nemoh and the finite element analysis is performed within the software MagNet®.
Description
Keywords
Energia das ondas Gerador linear de relutância variável Energias renováveis