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- Eriksson, Mikael, 1976-
(author)
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Modelling and Experimental Verification of Direct Drive Wave Energy Conversion : Buoy-Generator Dynamics
- 2007
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Doctoral thesis (other academic/artistic)abstract
- This thesis is focused on development of models and modelling of a wave energy converter in operation. Through the thesis linear potential wave theory has been used to describe the wave-buoy interaction. The differences lie in the generator models, in the simplest model the generator is a mechanical damper characterized by a damping factor. In the most advanced generator model the magnetic fields is calculated the by a FE-method, which gives detailed description of the electric properties and the effect it has on the buoy dynamics. Moreover, an equivalent circuit description of the generator has been tested. It has the same accuracy as the field based model but with a strongly enhanced CPU time. All models are verified against full scale experiments. The models are intended to be used for design of the next generation wave energy converters. Further, the developed models have also been used to study what effect buoy geometry and generator damping have on the ability to energy absorption. In the spring 2006 a full scale wave energy converter was installed at the west coast of Sweden. It was in operation and collected data during three months. During that period the load resistance was varied in order to study the effect on the energy absorption. These collected data was then used in the verification of the developed models. In the year 2002 a wave energy project started at Uppsala University; this work is a part of that larger project which intendeds to develop a viable wave energy conversion concept.
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| 2. |
- Leijon, Mats, et al.
(author)
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An electrical approach to wave energy conversion
- 2006
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In: Renewable energy. - : Elsevier BV. - 0960-1481 .- 1879-0682. ; :31, s. 1309-1319
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Journal article (peer-reviewed)abstract
- Motions in nature, for example ocean waves, can play a significant role in tomorrow's electricity production, but the constructions require adaptations to its media. Engineers planning hydropower plants have always taken natural conditions, such as fall height, speed of flow, and geometry, as basic design parameters and constraints in the design. The present paper describes a novel approach for electric power conversion of the vast ocean wave energy. The suggested linear electric energy converter is adapted to the natural wave motion using straightforward technology. Extensive simulations of the wave energy concept are presented, along with results from the experimental setup of a multisided permanent magnet linear generator. The prototype is designed through systematic electromagnetic field calculations. The experimental results are used for the verification of measurements in the design process of future full-scale direct wave energy converters. The present paper, describes the energy conversion concept from a system perspective, and also discusses the economical and some environmental considerations for the project.
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| 3. |
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| 4. |
- Lundin, Urban, 1972-, et al.
(author)
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Method for modeling time-dependent nonuniform rotor/stator configurations in electrical machines
- 2009
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In: IEEE transactions on magnetics. - USA : IEEE. - 0018-9464 .- 1941-0069. ; 45:7, s. 2976-2980
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Journal article (peer-reviewed)abstract
- Nonuniform air gaps in electrical machines cause problems with forces and noise. There are a number of analytical and numerical methods to calculate the response due to nonuniform air gaps. In this paper, we present an efficient method based on an effective air gap permeability. Our unified method enables all nonuniform rotor-stator configurations to be simulated. We provide some results from simulations of static and dynamic eccentricity as well as irregularity.
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| 5. |
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| 6. |
- Thorburn, Karin, et al.
(author)
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Time stepping finite element analysis of variable speed synchronous generator with rectifier
- 2006
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In: Applied Energy. - : Elsevier BV. - 0306-2619 .- 1872-9118. ; 83:4, s. 371-386
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Journal article (peer-reviewed)abstract
- Several applications for renewable energy conversion make use of variable speed generators. A conversion from variable frequency to grid frequency is therefore essential. One part of the converter is a rectifier. A rectifier model is presented, which is integrated in a time stepping finite element simulation environment where the generator and circuit equations are solved simultaneously. The model handles bidirectional alternator speeds as the application is a linear generator for ocean wave energy conversion. The rectifier model is extended with a load model, consisting of R, L and E, and simulations show what impact the rectifier has on the generator’s behaviour.
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