Balancing of Wind Turbine Parts

Abstract

A wind of the type having a tower and a nacelle with a rotor rotatably connected to the nacelle for rotating about a rotor axis and having a plurality of equally spaced blades has the rotor balanced by firstly taking a measurement of torsional vibration and then by using photographic techniques to analyze dynamic imbalance caused by differences in the angle of attack of the blades. The torsional vibration is detected using two sensors at positions mirrored exactly in distance to the left and right of the rotor axis and detecting vibration in the axial direction. The angle of attack is measured by analyzing images of the tip of the blade where, during the analysis, distortion in angles at different locations in the image are corrected, in dependence upon a prior analysis of an image taken by the camera relative to a known image.

Description

[0001]This application claims the benefit of priority under 35 USC 119(e) of Provisional Application 61 / 440,500 filed Feb. 8, 2011.[0002]This invention relates to a method of aerodynamic balancing a rotor of a wind turbine of the type comprising a tower and a nacelle mounted to the top of the tower, the rotor being rotatably connected to the nacelle for rotating about a rotor axis and having a plurality of equally spaced blades around the axis.BACKGROUND OF THE INVENTION[0003]Wind turbines in HAWT design (horizontal axis) consist of four main parts as a structure, the base, the tower, the nacelle and the rotor with one or more blades.[0004]The blades are mounted at fixed angularly spaced positions around the axis. The turbine includes a wind detection system which analyses the wind speed and direction repeatedly so as to repeatedly adjust the angle of the nacelle around a vertical axis of the tower, that is the angle of the rotor axis relative to the wind direction, and to adjust th...

AI Technical Summary

Benefits of technology

[0034]Preferably the use of the two axial sensors in the axial direction and at the mirrored or exactly symmetrical distance from the axis eliminates all axial vibration by subtracting both axial signals and doubling the torsional signal at the same time.

[0054]The present disclosure as set out hereinafter provides a method to achieve sufficient measurements of angles for the purpose described with minimized errors caused by lens distortion and trapezoidal distortion. To minimize systematic errors the procedure describes ways to establish which blade should be selected as the first blade to be analyzed.

[0070]Furthermore the practice has shown in the past that rearrangements of heavier parts as well as exchange (e.g. lighter generator) can easily shift this center and lead to misleading readings on torsional vibration evaluation.

Problems solved by technology

Turbines if out of balance will cause significant vibration in the tower and can if sufficient rapidly deteriorate the structure or individual components to a position where it cannot be repaired or leave the turbine in an unsafe condition to operate in.

Several attempts have been made to measure the angles remote from the ground with simple photograph based measurements but are not satisfactory.

In most cases no suitable procedures were taken to verify measurements.

In other cases vibration measurements have revealed results inconsistent with the measurements taken.

When followed, the described methods in that patent application are unsatisfactory in that the measurements taken will include errors which up to now have not been determined so that this method has not lead to a satisfactory solution.

Furthermore, the methods are of limited practical value and may provide a serious risk to the safe operation of a wind turbine when used as the base of further decision making.

If the analysis of the aerodynamic related moments and the mass moments is based on faulty data, it is very possible that any adjustments made actually create a deteriorating situation so that the amount of vibration worsens.

Typically the evaluation of torsions vibration modes is made with two lateral sensors; but this is not suitable or reliable if the center of the torsional movement is not accurately determined.

The arrangement of the nacelle mass, the hub and rotor mass as well as all other components mounted on the tower causes a situation where the center for torsional movement is not identical with the center of the tower so that this manner of measuring balance is inaccurate and can lead to faulty conclusions.

Furthermore it is known that rearrangements of heavier parts in the wind turbine as well as exchange of parts, for example the use of a lighter generator, can easily shift this center and lead to misleading readings on torsional vibration evaluation.

Up to now therefore balancing of turbines of this type has been ineffective and in some cases has lead to a situation where the results are confusing or even worsen the situation.

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