Showing papers by "Vestas published in 2006"
TL;DR: In this article, a more extended evaluation is reported using a scanning lidar next to a meteorological mast with calibrated anemometers at the Riso wind test site in Hovsore on the windy northwest coast of Denmark.
Abstract: Initial assessments of a wind lidar have shown the technology to have significant potential for wind field measurements in the wind energy industry. A more extended evaluation is now reported using a scanning lidar next to a meteorological mast with calibrated anemometers at the Riso wind test site in Hovsore on the windy northwest coast of Denmark. Results are presented of wind speed comparisons at heights up to 100 m above ground level showing excellent correlation between the lidar and the cup anemometers. Copyright © 2006 John Wiley & Sons, Ltd.
193 citations
TL;DR: In this paper, two experimental methods for estimating the modal damping of a wind turbine during operation are presented, based on the assumption that a turbine mode can be excited by a harmonic force at its natural frequency, whereby the decaying response after the end of excitation gives an estimate of the damping.
Abstract: The theory and results of two experimental methods for estimating the modal damping of a wind turbine during operation are presented. Estimations of the aeroelastic damping of the operational turbine modes (including the effects of the aerodynamic forces) give a quantitative view of the stability characteristics of the turbine. In the first method the estimation of modal damping is based on the assumption that a turbine mode can be excited by a harmonic force at its natural frequency, whereby the decaying response after the end of excitation gives an estimate of the damping. Simulations and experiments show that turbine vibrations related to the first two tower bending modes can be excited by blade pitch and generator torque variations. However, the excited turbine vibrations are not pure modal vibrations and the estimated damping is therefore not the actual modal damping. The second method is based on stochastic subspace identification, where a linear model of the turbine is estimated alone from measured response signals by assuming that the ambient excitation from turbulence is random in time and space. Although the assumption is not satisfied, this operational modal analysis method can handle the deterministic excitation, and the modal frequencies and damping of the first tower and first edgewise whirling modes are extracted. Copyright © 2006 John Wiley & Sons, Ltd.
151 citations
TL;DR: A new current programmed control technique is presented, which is an extension of the conventional CPC method, that enables the variable output dc voltage, and is therefore suitable in a pulse amplitude modulated (PAM) motor drive or as a universal input-power supply.
Abstract: This paper presents a new current programmed control (CPC) technique for a cascaded two-switch buck-boost converter suitable as a low-cost power factor correction (PFC) rectifier in a variable speed motor drive. This new CPC technique, which is an extension of the conventional CPC method, enables the variable output dc voltage, and is therefore suitable in a pulse amplitude modulated (PAM) motor drive or as a universal input-power supply. The CPC method is very simple and requires only a constant-current reference without any changes in the transition between boost and buck operating mode, and the line current is practically unaffected by the topology-mode shift. Simulations and experimental results verify the presented control technique. Compliance with IEC-61000-3-2 class A is achieved. The experimental setup is based on a commercial CPC integrated circuit (IC) for dc-dc converters. This new control technique enables a simple low-cost control circuit for the two-switch buck-boost converter, which complies with IEC-61000-3-2, and the PFC circuit has inherent in-rush and overcurrent protection.
113 citations
Patent•
09 Jun 2006TL;DR: In this paper, a wind turbine blade is characterized as having at least one joint area of the turbulence generating strips and a surface of the blade is completely or partially covered by sealing means.
Abstract: The invention relates to a wind turbine blade comprising one or more turbulence generating strips, where the strips are placed on a surface of the blade. The blade is characterized in that at least one joint area of the turbulence generating strips and the surface of the blade are completely or partially covered by sealing means. The invention further relates to a pitch controlled wind turbine comprising at least two pitch controlled wind turbine blades and pitch controlling means for pitching the blades. The pitch controlled wind turbine is characterized in that the blades comprises one or more turbulence generating strips, wherein at least one joint area of the turbulence generating strips and a surface of the blades are completely or partially covered by sealing means.
104 citations
Patent•
16 Mar 2006TL;DR: In this paper, a method for reducing fatigue loads in the components of a wind turbine subjected to asymmetrical loading of its rotor is proposed, comprising the steps of: repeatedly collecting and storing load data of the rotor, determining a load distribution function for the rotor from said stored data, deriving a plurality of periodic functions from said load distribution functions, determining actions for the wind turbine control means for reducing the fatigue load of the turbine components from said derived plurality of frequent functions, and implementing of said determined actions on the wind turbines control means.
Abstract: The invention relates to a method for reducing fatigue loads in the components of a wind turbine subjected to asymmetrical loading of its rotor, comprising the steps of: repeatedly collecting and storing load data of the rotor, determining a load distribution function for the rotor from said stored data, deriving a plurality of periodic functions from said load distribution function, determining actions for the wind turbine control means for reducing the fatigue load of the wind turbine components from said derived plurality of periodic functions, and implementing of said determined actions on the wind turbine control means. The invention also relates to a control system as well as a wind turbine and wind park.
62 citations
Patent•
22 Feb 2006TL;DR: In this paper, a method for manufacturing a wind turbine blade or a section of a turbine blade is described, which comprises the steps of, establishing a first part (8) comprising a first turbine blade part (9) in a first fixating unit (10), establishing a second part (11), comprising a second turbine part (12), in a second fixed unit (13), and positioning the first turbine part in contact with, or in close proximity of, the second turbine piece (14).
Abstract: The invention relates to a method for manufacturing a wind turbine blade (5) or a section of a wind turbine blade (5). The method comprises the steps of, establishing a first part (8) comprising a first wind turbine blade part (9) in a first fixating unit (10), establishing a second part (11) comprising a second wind turbine blade part (12) in a second fixating unit (13), and positioning the first part (8) in contact with, or in close proximity of, the second part (11). After this a pressure below atmospheric pressure is established, forcing the first wind turbine blade part (9) and the second wind turbine blade part (12) against each other. The invention further relates to a wind turbine blade manufacturing facility, wind turbine blades (5) as well as uses hereof.
28 citations
Patent•
13 Feb 2006TL;DR: In this article, a fixture to be connected to an end of a large member, such as wind turbine blade and wind turbine tower sections, is provided, which allows for a high degree of flexibility with regard to size of the end and arrangement of holes in the flange of the member.
Abstract: A fixture to be connected to an end of a large member, such as wind turbine blade and wind turbine tower sections is provided. The fixture allows for a high degree of flexibility with regard to size of the end and arrangement of holes in the flange of the member.
26 citations
TL;DR: Based on a large Danish survey of companies in tradable goods and services sectors, the authors presents the results of offshoring and its impact on jobs, adding new perspectives to the globalization debate.
Abstract: Based on a large Danish survey of companies in tradable goods and services sectors, this working paper presents the results of offshoring and its impact on jobs, adding new perspectives to the globalization debate. Globalization entails a cross-border flow of jobs, but contrary to the mainstream media portrayal of globalization, it is not a one-way but a two-way street. In 2002-05 more jobs were created as a result of offshoring of activities into eastern Denmark from companies outside Denmark (i.e., inshored to Denmark) than were eliminated due to offshoring from companies in the Danish region. Overall, the employment effects of both offshoring and inshoring were found to be limited to less than 1 percent of all jobs either lost to offshoring or gained via inshoring. For Denmark, the worries in purely numerical terms regarding the employment effects of globalization seem overly alarmist. However, the trends revealed in the study do pose challenges for low-skilled workers - the group most negatively affected - and for highly skilled specialists, who face pressure to constantly upgrade their skills. Policy implications can be drawn in view of our results to ensure that labor markets are able to meet the demands of globalizing firms.
25 citations
Patent•
23 Jan 2006TL;DR: In this article, a bearing for a wind turbine comprising bearing rings with raceways, and at least one row of bearing balls or rollers positioned between said raceways is described.
Abstract: The invention relates to a bearing for a wind turbine comprising bearing rings with raceways, and at least one row of bearing balls or rollers positioned between said raceways. At least one of said raceways comprises one or more indentation areas in relation to a standard shape of the raceways. The invention also relates to a wind turbine and methods for manufacturing a bearing.
20 citations
Patent•
09 Oct 2006TL;DR: In this article, an earthing system for a wind turbine connected to a utility grid was proposed. But the earthing wire embedded in the wind turbine foundation was not included in the design.
Abstract: The invention relates to an earthing system for a wind turbine connected to a utility grid. The wind turbine comprises at least one electric system such as low or high voltage power systems and cables (16), at least one control system such as a SCADA system and control cables (18), and/or at least one safety system such as a lightning protection system, wherein a connection to an electrically earth potential is established from one defined place (12) within the wind turbine for said systems. In another embodiment, a wind turbine comprises at least two electric systems such as a lightning protection system and a low or high voltage power system, an electrically earth potential established by at least one foundation earthing (8) including at least one earthing wire embedded partly or totally in the wind turbine foundation (6), and at least one electric conducting means (9) extending radial from said wind turbine (1) into the ground, wherein a connection to said electrically earth potential is established from one defined place within the wind turbine (1) for said systems. Even further the invention relates to an earthing system for a wind turbine park.
15 citations
Patent•
20 Feb 2006TL;DR: In this article, the authors described a wind turbine tower consisting of at least two adjacent metal tower plates, which are connected by one or more fish joints, and described a method for assembling the tower.
Abstract: The invention relates to a wind turbine tower (2) comprising at least two adjacent metal tower plates (7). The wind turbine tower (2) is characterized in that, the tower plates (7) are connected by one or more fish joints (16). The invention further relates to a wind turbine (1) and a method for assembling a wind turbine tower (2).
Patent•
17 Jan 2006TL;DR: In this article, a wind turbine tower elevator was designed for use in wind turbine towers, enabling both vertically and horizontally movement of the elevator and maintaining a constant distance to the inside surface of the turbine tower.
Abstract: The invention relates to a wind turbine tower elevator (22) for use in a wind turbine tower (2). The elevator (22) comprises means for enabling both vertically and horizontally movement of the elevator and is characterized in that the elevator (22) comprise means for making an elevator basket (23) of the elevator (22) maintaining a constant distance to the inside surface of the wind turbine tower (2).
Patent•
27 Apr 2006Patent•
17 Jan 2006TL;DR: In this article, a wind turbine tower comprising at least two annular tower rings placed vertically on top of each other is characterized. And a method for assembling a wind-turbine tower is described.
Abstract: The invention relates to a wind turbine tower comprising at least two annular tower rings placed vertically on top of each other. The wind turbine tower is characterized in that, a first tower ring overlaps at least a further tower ring of the at least two tower rings. The invention further relates to a wind turbine, a wind turbine tower elevator for use in a wind turbine tower and a method for assembling a wind turbine tower.