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Vertical Axis Wind Turbines: Electrical System and Experimental Results
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The wind power research at the division of Electricity at Uppsala University is aimed towards increased understanding of vertical axis wind turbines. The considered type of wind turbine is an H-rotor with a directly driven synchronous generator operating at variable speed. The experimental work presented in this thesis comprises investigation of three vertical axis wind turbines of different design and size. The electrical, control and measurement systems for the first 12 kW wind turbine have been designed and implemented. The second was a 10 kW wind turbine adapted to a telecom application. Both the 12 kW and the 10 kW were operated against dump loads. The third turbine was a 200 kW grid-connected wind turbine, where control and measurement systems have been implemented.

Experimental results have shown that an all-electric control, substituting mechanical systems such as blade-pitch, is possible for this type of turbine. By controlling the rectified generator voltage, the rotational speed of the turbine is also controlled. An electrical start-up system has been built and verified. The power coefficient has been measured and the stall behaviour of this type of turbine has been examined. An optimum tip speed ratio control has been implemented and tested, with promising results. Use of the turbine to estimate the wind speed has been demonstrated. This has been used to get a faster regulation of the turbine compared to if an anemometer had been used.  

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2012. , 77 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 981
Keyword [en]
VAWT, H-rotor, start-up, all-electric control, Power Coefficient, stall, tip speed ratio, Renewable energy, Measurement systems, PM-generator
National Category
Energy Systems Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:uu:diva-182438ISBN: 978-91-554-8496-5 (print)OAI: oai:DiVA.org:uu-182438DiVA: diva2:559793
Public defence
2012-11-30, Room 2001, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 13:00 (English)
Opponent
Supervisors
Available from: 2012-11-07 Created: 2012-10-10 Last updated: 2013-01-23Bibliographically approved
List of papers
1. Experimental results from a 12 kW vertical axis wind turbine with a direct driven PM synchronous generator
Open this publication in new window or tab >>Experimental results from a 12 kW vertical axis wind turbine with a direct driven PM synchronous generator
2007 (English)Conference paper, Published paper (Other academic)
Abstract [en]

Experimental results from a three bladed vertical axis wind turbine with a direct driven PM synchronous generatorare presented. The H-rotor turbine, independent of wind direction, does not require any yaw mechanism.Furthermore, the variable speed, stall regulated turbine does not require pitch mechanism. The specifically designeddirectly driven generator eliminates the need for a gearbox. All electrical equipment, including generator, are placedon the ground. This reduces the weight that has to be supported by the structure and simplifies maintenance. Thus, theoverall strength of this concept is simplicity.The H-rotor has five meter long blades that are tapered at the tips. The aerodynamic torque is transferred to thegenerator via a 5.4 meter long drive shaft supported by a tower. A universal joint connects the drive shaft to thegenerator shaft, cancelling any transverse bending moments from the turbine on the generator. The generator acts as amotor to start up the turbine using a separate auxiliary winding. The turbine has a swept area of 30 m2 and is rated at12 kW in 12 m/s winds for 127 rpm.The turbine has been placed on a site where the wind resources have been extensively documented. The wind datarecord is more then ten years and includes data from various heights giving an accurate wind mapping of the area.The experimental aerodynamic power curve in turbulent wind conditions is presented. Considering the highlyturbulent wind conditions and the small size of the wind turbine these results are encouraging.

National Category
Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-97453 (URN)
Conference
EWEC 2007 - European Wind Energy Conference & Exhibition, Milan, Italy, May. 7-10, 2007
Available from: 2008-09-05 Created: 2008-09-05 Last updated: 2016-04-08Bibliographically approved
2. Progress of control system and measurement techniques for a 12 kW vertical axis wind turbine
Open this publication in new window or tab >>Progress of control system and measurement techniques for a 12 kW vertical axis wind turbine
Show others...
2008 (English)Conference paper, Published paper (Refereed)
National Category
Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-97454 (URN)
Conference
??
Available from: 2008-09-05 Created: 2008-09-05 Last updated: 2016-04-12Bibliographically approved
3. Power coefficient measurement on a 12 kW straight bladed vertical axis wind turbine
Open this publication in new window or tab >>Power coefficient measurement on a 12 kW straight bladed vertical axis wind turbine
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2011 (English)In: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 36, no 11, 3050-3053 p.Article in journal (Refereed) Published
Abstract [en]

A 12 kW vertical axis H-rotor type wind turbine has been designed and constructed at Uppsala University. A measurement campaign has been performed to collect data to calculate the power coefficient using the method of bins. The measurement was performed at different constant rotational speeds on the turbine during varying wind speeds to observe the power coefficients dependence on tip speed ratio. The power coefficient peaked at 0.29 for a tip speed ratio equal to 3.3.

Keyword
VAWT, H-rotor, Experimental, Measured, Cp
National Category
Engineering and Technology
Research subject
Engineering Science with specialization in Science of Electricity
Identifiers
urn:nbn:se:uu:diva-156579 (URN)10.1016/j.renene.2011.03.031 (DOI)000292441400035 ()
Available from: 2011-08-07 Created: 2011-08-04 Last updated: 2017-12-08Bibliographically approved
4. Electrical Starter System for an H-Rotor Type VAWT with PM-Generator and Auxiliary Winding
Open this publication in new window or tab >>Electrical Starter System for an H-Rotor Type VAWT with PM-Generator and Auxiliary Winding
2011 (English)In: Wind Engineering: The International Journal of Wind Power, ISSN 0309-524X, E-ISSN 2048-402X, Vol. 35, no 1, 85-92 p.Article in journal (Refereed) Published
Abstract [en]

In order to operate a modern wind turbine an effective start procedure is required. This article presents an electrical start for a VAWT which is shown to have advantages over an aerodynamic start. An electrical starter for a 12 kW VAWT has been designed and built. The starter is based on a six-step modulated inverter that is feedback-controlled by the rotor position. The inverter is connected to an auxiliary winding in the generator to separate the starter electronics from the main system. The system has been simulated and experimentally verified in the wind turbine setup.

Place, publisher, year, edition, pages
Multi Science Publishing, 2011
National Category
Engineering and Technology
Research subject
Engineering Science with specialization in Science of Electricity
Identifiers
urn:nbn:se:uu:diva-164210 (URN)10.1260/0309-524X.35.1.85 (DOI)
Available from: 2011-12-16 Created: 2011-12-16 Last updated: 2017-12-08Bibliographically approved
5. Adapting a VAWT with PM generator to telecom applications
Open this publication in new window or tab >>Adapting a VAWT with PM generator to telecom applications
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2010 (English)In: European Wind Energy Conference & Exhibition, Warsaw, Poland, 2010Conference paper, Published paper (Refereed)
Place, publisher, year, edition, pages
Warsaw, Poland: , 2010
National Category
Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-142522 (URN)
Conference
European Wind Energy Conference & Exhibition
Available from: 2011-01-14 Created: 2011-01-14 Last updated: 2017-01-25Bibliographically approved
6. Laboratory verification of system for grid connection of a 12 kW variable speed wind turbine with a permanent magnet synchronous generator
Open this publication in new window or tab >>Laboratory verification of system for grid connection of a 12 kW variable speed wind turbine with a permanent magnet synchronous generator
2012 (English)In: EWEA 2012 Annual Event, Copenhagen, Denmark, 2012, 2012Conference paper, Poster (with or without abstract) (Refereed)
Abstract [en]

In this paper the first laboratory tests of the gridconnection system, connected to a resistiveload, for a vertical axis wind turbine (VAWT)with a permanent magnet generator arepresented. The system is based on a taptransformertopology with a voltage sourceinverter and an LCL-filter. The use of a taptransformer topology eliminates the need for aDC-DC converter to handle the variations inDC voltage. The harmonic content of thecurrents from experiments and simulationsperformed in Simulink using different taps onthe transformer are presented. The simulatedcurrents, fed to the resistive load, have a totalharmonic distortion (THD) of 0.5% to 0.9% forthe different taps. The experimental systemhas a current THD ranging from 1.8% to 2.8%.The difference is expected to be due tounbalances, delays and dead times in theexperimental set-up as the major THDcontribution is from harmonic orders below 11.The results show that an LCL filter can bedesigned to meet the demands on powerquality for grid connection of the system withall the taps of the tap transformer inaccordance with IEEE 519-1992.

Keyword
VAWT, Tap transformer, LCL-filter, voltage source inverter
National Category
Energy Systems Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Engineering Science with specialization in Science of Electricity
Identifiers
urn:nbn:se:uu:diva-182434 (URN)
Conference
EWEA 2012 Annual Event, Copenhagen, Denmark, 2012
Available from: 2012-10-10 Created: 2012-10-10 Last updated: 2016-10-06
7. Electric control substituting pitch control for large wind turbines
Open this publication in new window or tab >>Electric control substituting pitch control for large wind turbines
(English)Article in journal (Other academic) Submitted
Keyword
VAWT, Electrical, Control, Stall-regulation, Novel System
National Category
Energy Systems Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:uu:diva-182436 (URN)
Available from: 2012-10-10 Created: 2012-10-10 Last updated: 2013-01-23Bibliographically approved
8. Tip Speed ratio control of a 200 kW VAWT with synchronous generator and variable DC voltage
Open this publication in new window or tab >>Tip Speed ratio control of a 200 kW VAWT with synchronous generator and variable DC voltage
2013 (English)In: Energy Science & Engineering, ISSN 2050-0505, Vol. 1, no 3, 135-143 p.Article in journal (Refereed) Published
Abstract [en]

A novel control method for a fixed-pitch variable speed wind turbine is introduced and experimental results are presented. The measured absorbed power and rotational speed, together with a look-up table for the aerodynamic efficiency, are used to estimate the wind speed reaching the turbine as well as the tip speed ratio. Thereby, the control is independent on wind speed measurements and the wind turbine itself is used as an anemometer. Tip speed ratio control is implemented by comparing the estimated tip speed ratio to a reference value and adjusting the DC voltage level accordingly. Tip speed ratio control benefits from that the aerodynamic efficiency hardly varies with changing tip speed ratio when close to its optimum value. Experimental results from a 200 kW vertical axis wind turbine are presented. The voltage from the permanent magnet generator is passively rectified and the alternating DC voltage is then inverted, filtered, transformed, and grid connected. The estimated wind speed is compared with the measured wind speed. The absorbed power when tip speed ratio control has been implemented is shown. It is concluded that the presented control method works and some future improvements are discussed.

Keyword
control method, wind turbine, variable speed, H-rotor, experiments
National Category
Energy Systems Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:uu:diva-182437 (URN)10.1002/ese3.23 (DOI)000209695200004 ()
Available from: 2012-10-10 Created: 2012-10-10 Last updated: 2016-12-01Bibliographically approved

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Citation style
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Output format
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