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Power smoothing in an offshore wave energy converter array
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(English)Manuscript (preprint) (Other (popular science, discussion, etc.))
URN: urn:nbn:se:uu:diva-112955OAI: oai:DiVA.org:uu-112955DiVA: diva2:289135
Available from: 2010-01-22 Created: 2010-01-22 Last updated: 2010-01-25
In thesis
1. Ocean Wave Energy: Underwater Substation System for Wave Energy Converters
Open this publication in new window or tab >>Ocean Wave Energy: Underwater Substation System for Wave Energy Converters
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis deals with a system for operation of directly driven offshore wave energy converters. The work that has been carried out includes laboratory testing of a permanent magnet linear generator, wave energy converter mechanical design and offshore testing, and finally design, implementation, and offshore testing of an underwater collector substation. Long-term testing of a single point absorber, which was installed in March 2006, has been performed in real ocean waves in linear and in non-linear damping mode. The two different damping modes were realized by, first, a resistive load, and second, a rectifier with voltage smoothing capacitors and a resistive load in the DC-link. The loads are placed on land about 2 km east of the Lysekil wave energy research site, where the offshore experiments have been conducted. In the spring of 2009, another two wave energy converter prototypes were installed. Records of array operation were taken with two and three devices in the array. With two units, non-linear damping was used, and with three units, linear damping was employed. The point absorbers in the array are connected to the underwater substation, which is based on a 3 m3 pressure vessel standing on the seabed. In the substation, rectification of the frequency and amplitude modulated voltages from the linear generators is made. The DC voltage is smoothened by capacitors and inverted to 50 Hz electrical frequency, transformed and finally transmitted to the on-shore measuring station. Results show that the absorption is heavily dependent on the damping. It has also been shown that by increasing the damping, the standard deviation of electrical power can be reduced. The standard deviation of electrical power is reduced by array operation compared to single unit operation. Ongoing and future work include the construction and installation of a second underwater substation, which will connect the first substation and seven new WECs.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2010. 114 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 711
wave energy, wave power, wave energy converter, direct-drive, permanent magnet linear generator, point absorber, array, farm, park, offshore, marine, substation, electrical transmission system
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Engineering Science with specialization in Science of Electricity
urn:nbn:se:uu:diva-112915 (URN)978-91-554-7713-4 (ISBN)
Public defence
2010-03-05, Ångströmlaboratoriet, Polhemsalen, Lägerhyddsvägen 1, Uppsala, 13:00 (English)
Available from: 2010-02-12 Created: 2010-01-22 Last updated: 2013-07-31Bibliographically approved

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