Nonrotating Beams Isospectral to Tapered Rotating Beams

In this paper, we seek to find nonrotating beams that are isospectral to a given tapered rotating beam. Isospectral structures have identical natural frequencies. We assume the mass and stiffness distributions of the tapered rotating beam to be polynomial functions of span. Such polynomial variations of mass and stiffness are typical of helicopter and wind turbine blades. We use the Barcilon-Gottlieb transformation to convert the fourth-order governing equations of the rotating and the nonrotating beams, from the (x, Y) frame of reference to a hypothetical (z, U) frame of reference. If the coefficients of both the equations in the (z, U) frame match with each other, then the nonrotating beam is isospectral to the given rotating beam. The conditions on matching the coefficients lead to a pair of coupled differential equations. Wesolve these coupled differential equations numerically using the fourth-order Runge-Kutta scheme. We also verify that the frequencies (given in the literature) of standard tapered rotating beams are the frequencies (obtained using the finite-element analysis) of the isospectral nonrotating beams. Finally, we present an example of beams having a rectangular cross-section to show the application of our analysis. Since experimental determination of rotating beam frequencies is a difficult task, experiments can be easily conducted on these isospectral nonrotating beams to calculate the frequencies of the rotating beam.

Modelo de canal para caracterizar la señal dispersada por un parque eólico en la banda UHF e influencia sobre la calidad de servicio de DVB-T

288 p. : il.

Diseño de un aerogenerador de muy baja potencia para la alimentación de sistemas eléctricos aislados

[ES]En este Proyecto se desarrolla el diseño y la optimización de un aerogenerador de muy pequeña potencia enfocado a alimentar sistemas eléctricos aislados; concretamente, un sistema de iluminación. Se analizan todos los componentes del sistema aerogenerador, comparando las diversas alternativas posibles y eligiendo soluciones sencillas, baratas y eficientes para cada uno de ellos. Asimismo, se lleva a cabo un primer dimensionamiento de los mismos. El esfuerzo de diseño se ha centrado en las palas, por considerarse el componente más crítico y menos normalizado. Se han estudiado herramientas para su análisis detallado y su optimización desde el punto de vista aerodinámico, y éstas han sido implementadas en Matlab. Esto ha permitido generar un diseño óptimo ajustado a las necesidades del sistema. Asimismo, se han realizado las correspondientes tareas de planificación, analizado los múltiples beneficios de tipo técnico, económico, social y ambiental que la ejecución del presente Proyecto reportará, haciendo una programación completa del mismo y un análisis de los costes que supondrá.

Proyecto de un parque eólico para la alimentación de las bombas de la central hidráulica de Belesar (Lugo).

[ES]El proyecto consiste en el estudio de las necesidades energéticas de las bombas de una central hidráulica y la construcción de un parque eólico para satisfacer dichas necesidades. Para ello será necesario llevar a cabo un estudio del área y así encontrar el lugar más adecuado para ubicar los aerogeneradores, teniendo en cuenta la frecuencia, velocidad y dirección de los vientos predominantes del lugar. Después habrá que estudiar el mercado y elegir el aerogenerador adecuado para las condiciones del lugar y del viento, atendiendo también a otras cuestiones de relevancia. Se estudiará, además, la posibilidad de inyectar un posible exceso de electricidad a la red general. Una vez hecho esto, habrá que calcular el coste del proyecto.

Estudio del abastecimiento energético del municipio de Abadín mediante un sistema eólico.

[ES]Este trabajo tiene como objetivo satisfacer la demanda de energía del municipio de Abadín, situado en la provincia de Lugo, aprovechando los recursos eólicos de la zona. Para ello será necesario un análisis de la demanda total de la población y de las condiciones del viento en la zona. Después se elegirá el emplazamiento donde las condiciones de viento sean adecuadas para instalar el sistema eólico. Conocidos estos datos, se elegirá un aerogenerador y se calculará la potencia que proporciona en función de sus características. Por último, se concluirá si el sistema eólico diseñado cubre las necesidades energéticas del municipio o no.

Otimização de torre de aço para aerogerador eólico.

Diversas formas de geração de energia vêm sendo desenvolvidas com o objetivo de oferecer alternativas ecologicamente corretas. Neste contexto, a energia eólica vem se destacando na região Nordeste do Brasil, devido ao grande potencial dos ventos da região. As torres, que representam parcela significativa do custo total do sistema, tendem a crescer buscando ventos mais fortes e permitindo assim a utilização de aerogeradores com maior capacidade de geração de energia. Este trabalho tem como objetivo formular um modelo de otimização de torres tubulares de aço, para aerogeradores eólicos. Busca-se minimizar o volume total (custo, indiretamente), tendo como variáveis de projeto as espessuras da parede da torre. São impostas restrições relativas à frequência natural e ao comportamento estrutural (tensão e deslocamento máximo de acordo com recomendações da norma Europeia). A estrutura da torre é modelada com base no Método dos Elementos Finitos e o carregamento atuante na estrutura inclui os pesos da torre, do conjunto de equipamentos instalados no topo (aerogerador), e o efeito estático da ação do vento sobre a torre. Para verificação das tensões, deslocamentos e frequências naturais, foram utilizados elementos finitos de casca disponíveis na biblioteca do programa de análise ANSYS. Os modelos de otimização foram também implementados no modulo de otimização do programa ANSYS (design optimization), que utiliza técnicas matemáticas em um processo iterativo computadorizado até que um projeto considerado ótimo seja alcançado. Nas aplicações foram usados os métodos de aproximação por subproblemas e o método de primeira ordem. Os resultados obtidos revelam que torres para aerogeradores merecem atenção especial, em relação à concepção do projeto estrutural, sendo que seu desempenho deve ser verificado através de metodologias completas que englobem além das análises clássicas (estáticas e dinâmicas), incluam também as análises de otimização.

Modeling seabird group size: implications for ecological impact assessments

The purpose of this project is to model seabird flock size data to provide recommendations to the Bureau of Ocean and Energy Management for offshore wind turbine placement. Our hypothesis is that ecological characteristics influence which statistical distribution will provide the best fit to seabird flock size data. To test this, seabird species can be grouped based on shared ecological traits, such as foraging mechanism or diet.

The experiment to evaluate the AC loss of 2G HTS windings in the application of rotating electric machines

This paper presents the design of an AC loss experiment using nitrogen boil-off method. This experiment is aimed at exploring the AC loss of HTS double race-track coils which will be installed on the rotor of a wind turbine generator. The operating environment is simulated by designing a cryostat with rotating magnetic field windings. Apart from the fact that the alternating magnetic field causes most of AC loss on the HTS coils, we also believe that the DC background field would be another important factor causing AC loss if the HTS coil is experiencing by both alternating magnetic field in the perpendicular direction and DC background field in the parallel direction. In order to perform the boil-off measurement, we present the method to estimate the heat leakage in the cryostat which might cause errors to the measurement. © 2011 IEEE.

Design and testing of a 250 kW medium-speed Brushless DFIG

This paper presents the design and testing of a 250 kW medium-speed Brushless Doubly-Fed Induction Generator (Brushless DFIG), and its associated power electronics and control systems. The experimental tests confirm the design, and show the system's steady-state and dynamic performance. The medium-speed Brushless DFIG in combination with a simplified two-stage gearbox promises a low-cost low-maintenance and reliable drive train for wind turbine applications.

Trailing edge noise theory for rotating blades in uniform flow

This paper presents a new formulation for trailing edge noise radiation from rotating blades based on an analytical solution of the convective wave equation. It accounts for distributed loading and the effect of mean flow and spanwise wavenumber. A commonly used theory due to Schlinker and Amiet (1981) predicts trailing edge noise radiation from rotating blades. However, different versions of the theory exist; it is not known which version is the correct one and what the range of validity of the theory is. This paper addresses both questions by deriving Schlinker and Amiet's theory in a simple way and by comparing it to the new formulation, using model blade elements representative of a wind turbine, a cooling fan and an aircraft propeller. The correct form of Schlinker and Amiet's theory (1981) is identified. It is valid at high enough frequency, i.e. for a Helmholtz number relative to chord greater than one and a rotational frequency much smaller than the angular frequency of the noise sources.

Design and testing of a medium-speed 250 kW Brushless DFIG

This paper presents the design and testing of a 250 kW medium-speed Brushless Doubly-Fed Generator (Brushless DFIG), and its associated power electronics and control systems. The experimental tests confirm the design, and show the system's steady-state and dynamic performance. The medium-speed Brushless DFIG in combination with a simplified twostage gearbox promises a low-cost low-maintenance and reliable drive train for wind turbine applications.

Experimental LVRT performance of a 250 kW brushless DFIG

Nowadays, all new wind turbine generators have to meet strict grid codes, especially riding through certain grid faults, such as a low voltage caused by grid short circuits. The Low-Voltage Ride Through (LVRT) capability has become a key issue in assessing the performance of wind turbine generators. The mediumspeed Brushless DFIG in combination with a simplified two-stage gearbox shows commercial promise as a replacement for conventional DFIGs due to its lower cost and higher reliability. Furthermore, the Brushless DFIG has significantly improved LVRT performance when compared with the DFIG due to its inherent design characteristics. In this paper, the authors propose a control strategy for the Brushless DFIG to improve its LVRT performance. The controller has been implemented on a prototype 250 kW Brushless DFIG and test results show that LVRT is possible without a need for any external protective hardware such as a crowbar.

Performance analysis and testing of a 250 kW medium-speed brushless doubly-fed induction generator

This study presents the performance analysis and testing of a 250 kW medium-speed brushless doubly-fed induction generator (DFIG), and its associated power electronics and control systems. The experimental tests confirm the design, and showthe system's steady-state and dynamic performance and grid low-voltage ride- through capability. The medium-speed brushless DFIG in combination with a simplified two-stage gearbox promises a low-cost low-maintenance and reliable drivetrain for wind turbine applications. © The Institution of Engineering and Technology 2013.

A novel modeling approach for design studies of brushless doubly fed induction generator based on magnetic equivalent circuit

Brushless doubly fed induction generator (BDFIG) has substantial benefits, which make it an attractive alternative as a wind turbine generator. However, it suffers from lower efficiency and larger dimensions in comparison to DFIG. Hence, optimizing the BDFIG structure is necessary for enhancing its situation commercially. In previous studies, a simple model has been used in BDFIG design procedure that is insufficiently accurate. Furthermore, magnetic saturation and iron loss are not considered because of difficulties in determination of flux density distributions. The aim of this paper is to establish an accurate yet computationally fast model suitable for BDFIG design studies. The proposed approach combines three equivalent circuits including electric, magnetic and thermal models. Utilizing electric equivalent circuit makes it possible to apply static form of magnetic equivalent circuit, because the elapsed time to reach steady-state results in the dynamic form is too long for using in population-based design studies. The operating characteristics, which are necessary for evaluating the objective function and constraints values of the optimization problem, can be calculated using the presented approach considering iron loss, saturation, and geometrical details. The simulation results of a D-180 prototype BDFIG are compared with measured data in order to validate the developed model. © 1986-2012 IEEE.

Design and performance analysis of a 6 MW medium-speed Brushless DFIG

The paper presents the design and performance analysis of a 6 MW medium-speed Brushless Doubly-Fed Induction Generation (Brushless DFIG) for a wind turbine drivetrain. Two machines with different frame sizes have been designed to show the flexibility of the design procedure. The mediumspeed Brushless DFIG in combination with a two stage gearbox offers a low-cost, low-maintenance and reliable drivetrain for wind turbine applications.