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Experimental Results of a Load-Controlled Vertical Axis Marine Current Energy Converter
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity. (Marine Current Power)
2015 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis investigates the load control of a marine current energy converter using a vertical axis turbine mounted on a permanent magnet synchronous generator. The purpose of this thesis is to show the work done in the so far relatively uncharted territory of control systems for hydro kinetic energy conversion. The work is in its early stage and is meant to serve as a guide forfuture development of the control system.

An experimental power station has been deployed and the first results are presented.

A comparison between three load control methods has been made; a fixedAC load, a fixed pulse width modulated DC load and a DC bus voltage control of a DC load. Experimental results show that the DC bus voltage control reduces the variation of rotational speed with a factor of 3.5. For all three cases, the tip speed ratio of the turbine can be kept close to the expected optimal tip speed ratio. However, for all three cases the average extracted power was significantly lower than the average power available in the turbine times the estimated maximum power coefficient. A maximum power point tracking system, with or without water velocity measurement, should increase the average extracted power.

A simulation model has been validated using experimental data. The simulated system consists of the electrical system and a hydrodynamic vortex model for the turbine. Experiments of no load operation were conducted to calibrate the drag losses of the turbine. Simulations were able to predict the behaviour in a step response for a change in tip speed ratio when the turbine was operated close to optimal tip speed ratio. The start position of the turbine was varied in the simulation to view the influence on the step response from a changed turbine position relative to the direction of the water flow.

Place, publisher, year, edition, pages
Uppsala: Uppsala universitet, 2015. , p. 53
Series
UURIE / Uppsala University, Department of Engineering Sciences, ISSN 0349-8352 ; 345-15L
Keywords [en]
Marine Current; Vertical Axis; Load Control;
National Category
Engineering and Technology
Research subject
Engineering Science with specialization in Science of Electricity
Identifiers
URN: urn:nbn:se:uu:diva-268867OAI: oai:DiVA.org:uu-268867DiVA, id: diva2:881408
Presentation
2015-12-16, Å4101, Lägerhyddsvägen 1, Ångströmlaboratoriet, Uppsala, 09:15 (English)
Opponent
Supervisors
Funder
StandUpÅForsk (Ångpanneföreningen's Foundation for Research and Development)Vattenfall ABSwedish Research CouncilSwedish Energy Agency
Note

Funders: J Gust Richert, Bixia Miljöfond

Available from: 2015-12-10 Created: 2015-12-10 Last updated: 2018-10-25Bibliographically approved
List of papers
1. The Söderfors Project: Experimental Hydrokinetic Power Station Deployment and First Results
Open this publication in new window or tab >>The Söderfors Project: Experimental Hydrokinetic Power Station Deployment and First Results
Show others...
2013 (English)Conference paper, Published paper (Refereed)
Abstract [en]

The Division of Electricity at Uppsala University recently deployed an experimental hydrokinetic power station for in-stream experiments at a site in a river. This paper briefly describes the deployment process and reports some initial results from measurements made at the test site.

Keywords
Marine Current Power, Renewable energy, Söderfors, Strömkraft, Förnybar energi, Söderfors
National Category
Engineering and Technology
Research subject
Engineering Science with specialization in Science of Electricity
Identifiers
urn:nbn:se:uu:diva-209220 (URN)
Conference
10th European Wave and Tidal Energy Conference (EWTEC), 2-5 september, 2013, Aalborg, Denmark
Projects
Marine Current Power
Funder
StandUpSwedish Research Council, 621-2009-4946
Available from: 2013-10-15 Created: 2013-10-15 Last updated: 2018-10-25Bibliographically approved
2. Experimental Results of a DC Bus Voltage Level Control for a Load-Controlled Marine Current Energy Converter
Open this publication in new window or tab >>Experimental Results of a DC Bus Voltage Level Control for a Load-Controlled Marine Current Energy Converter
2015 (English)In: Energies, ISSN 1996-1073, E-ISSN 1996-1073, Vol. 8, no 5, p. 4572-4586Article in journal (Refereed) Published
Abstract [en]

This paper investigates three load control methods for a  marine current energy converter using a vertical axis current  turbine (VACT) mounted on a permanent magnet synchronous generator  (PMSG). The three cases are; a fixed AC load, a fixed pulse width  modulated (PWM) DC load and DC bus voltage control of a DC  load. Experimental results show that the DC bus voltage control  reduces the variations of rotational speed by a factor of 3.5 at the cost  of slightly increased losses in the generator and transmission lines.  For all three cases, the tip speed ratio   can be kept close to  the expected    . The power coefficient is estimated to be  0.36 at    ; however, for all three cases, the average  extracted power was about  \%. A maximum power point  tracking (MPPT) system, with or without water velocity measurement,  could increase the average extracted power.

Keywords
Load Control, Vertical axis turbine, permanent magnet generator
National Category
Engineering and Technology
Research subject
Engineering Science with specialization in Science of Electricity
Identifiers
urn:nbn:se:uu:diva-244939 (URN)10.3390/en8054572 (DOI)000356879600064 ()
Funder
StandUpÅForsk (Ångpanneföreningen's Foundation for Research and Development)Swedish Research CouncilSwedish Energy AgencyVattenfall AB
Note

Funders: J Gust Richert, Bixia Miljöfond

Available from: 2015-02-23 Created: 2015-02-23 Last updated: 2017-12-04Bibliographically approved
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In thesis
1. Studies of a Vertical Axis Turbine for Marine Current Energy Conversion: Electrical system and turbine performance
Open this publication in new window or tab >>Studies of a Vertical Axis Turbine for Marine Current Energy Conversion: Electrical system and turbine performance
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Ocean energy is a field of growing interest when it comes to renewable energy thanks to its high density of energy per unit area, and to the high predictability. Conversion of hydrokinetic energy, found in marine currents, is the utilization of the energy in free-flowing water for conversion to electric energy. This thesis presents experimental data from a test site with a marine current converter.

The converter system features a vertical axis turbine directly connected to a permanent magnet synchronous generator placed on the riverbed. The converter is controlled by an electrical system. The focus of the work is to evaluate power control methods and turbine performance.  

Results of a simple voltage control system is presented and compared with operation without control. The turbine type in the converter system is not self-starting. The startup power and energy has been investigated through experiments. The converter system has been connected to the local electric utility grid and the first experimental results are presented.  

The performance of the turbine for a range of water speeds is investigated. The range of experiments are limited by the water velocity at the experimental site. To address the issue, a simulation model coupling the electrical system and hydrodynamic model into one has been validated. One factor affecting the turbine's power capture is the angle of the blade pitch relative to the water flow. The influence of blade pitch on turbine performance is studied with experiments and two 3D simulation models.

The possibilities of powering a desalination plant using marine current converters is discussed. Water speed data from outside the east coast of South Africa has been used for a case study. The study investigates how many people can early be supplied with freshwater using the converter system at the experimental site as a model. 

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2018. p. 77
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1739
National Category
Engineering and Technology
Research subject
Engineering Science with specialization in Science of Electricity
Identifiers
urn:nbn:se:uu:diva-363256 (URN)978-91-513-0491-5 (ISBN)
Public defence
2018-12-13, 80101, Ångströmslaboratoriet, Lägerhyddsvägen 1, Uppsala, 09:15 (English)
Opponent
Supervisors
Available from: 2018-11-21 Created: 2018-10-25 Last updated: 2018-11-30

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