METHOD FOR MEASURING IMBALANCES IN WIND TURBINE ROTORS

Abstract

The invention relates to the use of laser beams for measuring rotors, in particular wind turbines, for determining an imbalance or defining the absolute setting angle and/or measuring a half-profile of a rotor blade, and a method for determining a torsion of the rotor blade as a deviation between two pitch angles. In contrast to the solution in EP 2582970A1, the invention enables the determining of the absolute pitch angle of a rotor blade during operation, without it being necessary to obtain information relating to the rotor blade or reference points with a Known position relative to the pitch axis, in particular using measuring devices that are mobile and/or positioned on the ground. It is also possible to contactlessly detect imbalances.

Claims

1. A method for determining and/or or measuring, in particular independently, an imbalance, in particular at least a static imbalance and/or or an eccentric moment of inertia of a rotor rotating around a rotor axis and comprising at least two rotor blades, wherein the sweep of the at least two rotor blades through at least one measurement section during the rotation of the rotor around the rotor axis is detected by contactless and time-resolved measurement.

2. The method for determining or measuring according to claim 1, comprising the determining of time spans between the sweep of the measurement section by different, in particular successive, rotor blades.

3. The method for determining or measuring according to claim 2, comprising the comparing of time spans, in particular the determining of differences between the time spans, between the sweep of, in particular, respective successive rotor blades.

4. The method for determining or measuring according to claim 2, comprising normalization of the time spans with respect to the rotational speed which is determined by data of the contactless and time-resolved measurement.

5. The method for determining and/or measuring according to claim 1, comprising the associating of the time spans or normalized time spans between the sweeps of, in particular successive, rotor blades with respect to the rotor blade sweeping through the at least one measurement section after the respective time span.

6. The method for determining or measuring according to claim 1, wherein the measurement section has been and/or is arranged so that, within one or more segments of a circle around the rotor axis, the measurement section is swept by the at least two rotor blades, which extend in an angular range of +/20, in particular around the vertical.

7. A method for determining, in particular independently, a setting angle, in particular an absolute pitch angle, or for measuring a half-profile of a rotor blade of a rotor rotating around a rotor axis, wherein, by contactless distance measuring on at least two measurement sections which are not parallel to the rotor axis and which are oriented so that the at least two measurement sections are swept at least also simultaneously by a rotor blade, at least during the sweep of the rotor blade through the at least two measurement sections, on each measurement section, at least twenty distance measurement values, in particular in each case at least twenty measurement points on the rotor blade, are detected, wherein in particular the angles between the measurement sections and the horizontal are measured, and wherein in each case at least a first and a second connection line, in particular at least ten connection lines, are determined between at least two interpolation points which are each given by a measurement point or a point on an interpolation of the measurement points of a measurement line, wherein the at least two interpolation points, in particular the interpolation points of each of the connection lines, lie at least on two different measurement lines, and wherein the measurement lines in each case are given by connecting the measurement points at which the measurement values of a respective measurement section on the rotor blade were obtained, wherein, between the sweep of the interpolation points of a connection line, through the measurement sections, there is a maximum temporal spacing of s or a maximum temporal spacing in which the rotor is rotated maximally by 0.5 around the rotor axis.

8. The method according to claim 7, wherein the at least two measurement sections are oriented so that they are located within a common plane which is arranged in particular parallel to the rotor axis and/or at an angle of less than +/20 with respect to the rotor axis and/or is arranged vertically.

9. The method according to claim 7, wherein, from the measurement, values at the measurement points, in particular based on the connection lines, a half-profile is calculated, which is in particular perpendicular to an edge, in particular trailing edge, of the rotor blade or perpendicular to the first or second connection line or parallel to a plane perpendicular to the rotor axis.

10. The method according to claim 7, wherein the method is carried out using the angles between the measurement sections and the horizontal.

11. The method according to claim 7 for the interpolation of an assumed rotor blade surface or rotor blade partial surface by connecting multiple connection lines and in particular generation of a half-profile as section through the assumed rotor blade surface.

12. The method to claim 11, wherein the pitch angle is determined as angle between a plane perpendicular to the rotor axis and a line which extends parallel to the linking line from the leading edge to the trailing edge of the rotor blade or to the calculated half-profiles or which extends perpendicularly to an edge, in particular a trailing edge of the rotor blade or perpendicularly to at least one of the first or second connection line, wherein the line in particular intersects the first and a second connection line or extends perpendicularly thereto, wherein the interpolation points between which the first connection line extends have a maximum temporal spacing of s, in particular maximally s and/or a maximum temporal spacing in which the rotor is rotated by maximally 1, in particular 0.5 around the rotor axis, from the leading edge of the rotor blade, and the measurement points between which the second connection line extends have a maximum temporal spacing of s, in particular of maximally s or a maximum temporal spacing in which the rotor is rotated maximally by 1, in particular 0.5 around the rotor axis, from the trailing edge of the rotor blade.

13. A method according to claim 12, utilized to determine, in particular independently, a torsion of the rotor blade as a deviation between two pitch angles, wherein the pitch angles are each defined as angles between a plane perpendicular to the rotor axis and in each case a different line, wherein the first line used for determining the first pitch angle lies between interpolation points of a first and a second measurement line, and the second line used for determining the second pitch angle lies between interpolation points of a third measurement line and the second measurement line or of the third measurement line and a fourth measurement line, wherein, with respect to the horizontal, the inclination angle of the measurement section of the first measurement line is smaller than that of the second measurement line, which is smaller than that of the third measurement line, or, with respect to the horizontal, the inclination angle of the measurement section of the first measurement line is smaller than that of the second measurement line, which is smaller than that of the third measurement line, which is smaller than that of the fourth measurement line.

14. A method for determining, in particular independently, a torsion of a rotor blade of a rotor rotating around a rotor axis, wherein, by contactless distance measurement on at least two measurement sections which are not parallel to the rotor axis and which are oriented so that the at least two measurement sections are at least also simultaneously swept by a rotor blade, at least during the sweep of the rotor blade through the measurement sections on each measurement section, at least twenty distance measurement values, in particular in each case at least twenty measurement points on the rotor blade, are detected, wherein the angles between the measurement sections and the horizontal are measured, and wherein at least a first and a second connection line, in particular at least ten connection lines are determined in each case between at least two interpolation points which are given in each case by a measurement point or point on an interpolation of the measurement points of a measurement line, wherein the interpolation points, in particular the interpolation points of each connection line, lie at least on two different measurement lines, and wherein the measurement lines in each case are given by connecting the measurement points at which the measurement values of a respective measurement section on the rotor blade were obtained, wherein, between the sweep of the interpolation points of a connection line through the measurement sections, there is a maximum temporal spacing of s or a maximum temporal spacing in which the rotor is rotated maximally by 0.5 around the rotor axis, as angles between two lines which in each case extend parallel to the linking line from a leading edge to a trailing edge of the rotor blade or which extend perpendicularly to an edge, in particular trailing edge, of the rotor blade or perpendicularly to at least a first or a second connection line and which extend in particular in planes that are parallel to one another, wherein the line in particular intersects the first and a second connection line or extends perpendicularly thereto, wherein the interpolation points between which the first connection line extends have a maximum temporal spacing of s, in particular of maximally s or a maximum temporal spacing in which the rotor is rotated maximally by 1, in particular 0.5 around the rotor axis, from the leading edge of the rotor blade, and the measurement points between which the second connection line extends have a maximum temporal spacing of s, in particular of maximally s or a maximum temporal spacing in which the rotor is rotated maximally by 1, in particular 0.5 around the rotor axis, from the trailing edge of the rotor blade, are defined, wherein the first line lies between interpolation points of a first measurement line and a second measurement line, and the second line lies between interpolation points of a third measurement line and the second measurement line or of the third measurement line and a fourth measurement line, wherein, with respect to the horizontal, the inclination angle of the measurement section of the first measurement line is smaller than that of the second measurement line, which is smaller than that of the third measurement line, or, with respect to the horizontal, the inclination angle of the measurement section of the first measurement line is smaller than that of the second measurement line, which is smaller than that of the third measurement line, which is smaller than that of the fourth measurement line.

15. The method for determining or measuring according to claim 1, using a mobile measuring device which comprises devices for the contactless distance measurement along measurement sections, wherein the implementation is in particular independent of stationary reference points and/or independent of additional measurement instruments, in particular additional sensors, in particular those with direct contact or known arrangement with respect to the rotor and/or independent of additional information with regard to the design, in particular the geometry of the rotor blades and/or arrangement of the measurement sections and/or measuring device relative to the rotor.

16. The method for determining or measuring according to claim 7, using a mobile measuring device which comprises devices for the contactless distance measurement along, measurement sections, wherein the implementation is in particular independent of stationary reference points and/or independent of additional measurement instruments, in particular additional sensors, in particular those with direct contact or known arrangement with respect to the rotor and/or independent of additional information with regard to the design, in particular the geometry of the rotor blades and/or arrangement of the measurement sections and/or measuring device relative to the rotor.

17. The method for determining or measuring according to claim 14, using a mobile measuring device which comprises devices for the contactless distance measurement along measurement sections, wherein the implementation is in particular independent of stationary reference points and/or independent of additional measurement instruments, in particular additional sensors, in particular those with direct contact or known arrangement with respect to the rotor and/or independent of additional information with regard to the design, in particular the geometry of the rotor blades or arrangement of the measurement sections or measuring device relative to the rotor.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0076] Additional advantages and possible embodiments will be explained purely as examples and in a non-limiting manner in reference to the following figures. The figures show:

[0077] FIG. 1: a side view of a wind turbine with a measurement section directed onto its rotor,

[0078] FIG. 2: a representation of the time-resolved distance measurement values measured on the measurement section from FIG. 1,

[0079] FIG. 3: a side view of the wind turbine from FIG. 1 with two measurement sections directed onto its rotor,

[0080] FIG. 4: a side view onto the rotor from FIG. 3,

[0081] FIG. 5: a front view onto the rotor from FIG. 4,

[0082] FIG. 6: a representation of two slanted half-profiles with connection lines,

[0083] FIG. 7 a representation of two slanted half-profiles with connection lines and a half-profile perpendicular to the rotor blade longitudinal direction and

[0084] FIG. 8 a representation of two slanted half-profiles and a half-profile perpendicular to the longitudinal axis of the rotor blade as well as two measurement sections.

DETAILED DESCRIPTION

[0085] FIG. 1 shows a side view of a wind turbine 1 with a rotor 3 with a hub 4 and three rotor blades 2 of which only two are shown in this representation. A laser beam of a laser distance measuring device is oriented along a measurement section 5 onto the rotor.

[0086] FIG. 2 shows a time-resolved representation of the measurement values of the laser distance measuring device from FIG. 1. A time axis 7 on which the distance measurement values 8 are plotted is represented, Three rotor blade sweeps through the measurement section 5 can be seen as deflections of the measurement values downward. At the end of the deflections, in each case a half-profile of the respective rotor blade can also be seen. Between the sweeps of the rotor blades, time spans between the rotor blade sweeps are drawn as double arrows.

[0087] By comparing the time spans, in particular the differences and/or ratios thereof, imbalances can be detected. Here, the ratio of the time spans associated with the individual rotor blades is used as a measure of the relative weights of the rotor blade, in that they are associated with the rotor blade sweeping through the measurement section after the time span.

[0088] FIG. 3 shows the wind turbine from FIG. 1 in a side view. On two measurement sections 9, 10 with different angles with respect to the horizontal, laser distance measuring devices are directed onto the rotor.

[0089] FIG. 4 shows the rotor from FIG. 3 in the side view from FIG. 3. The position of the half-profiles 11, 12 detected by the laser distance measurement on the measurement sections 9, 10 are drawn with dashed lines. One can see that the profiles are not oriented perpendicularly with respect to the rotor longitudinal axis but instead are oriented at a slant relative to said rotor longitudinal axis.

[0090] FIG. 5 shows the rotor from FIG. 4 in a front view onto the rotor. The position of the half-profiles detected by the laser distance measurement on the measurement sections 9, 10 is drawn with dashed lines.

[0091] FIG. 6 shows the measurement lines of the measurements of the two measurement sections 9, 10. They represent half-profiles 11, 12. Interpolation points 13 are drawn on them. Between the interpolation points 13, connection lines 14 are drawn. Here, the interpolation points 13 of a connection line 14 are arranged or selected so that there is a very small temporal difference, in particular of less than 5 ms, between their sweep through the measurement section.

[0092] FIG. 7 shows the measurement lines 11, 12 from FIG. 6. By means of the connection lines, the rotor blade surface 16 has been partially reconstructed. The lines between the interpolation points 13 here illustrate the reconstructed rotor blade partial surface. Also shown is a calculated half-profile 15 perpendicular to the rotor blade longitudinal axis and parallel to the linking lines 17 which in this case also represent lines 18. This was determined by means of the connection lines and a section through them, perpendicular to the rotor blade longitudinal axis. Alternatively, based on the angle between the horizontal and the measurement sections, on the connection lines, corresponding points can be calculated, which are perpendicular to a plane which is perpendicular to the rotor blade longitudinal axis and in which a line (18) is in particular perpendicular to the trailing edge.

[0093] FIG. 8 illustrates this situation again. Shown are two measurement sections 9, 10 and two slanted half-profiles 11, 12 formed by measurement lines and detected on the measurement sections. Also shown between the slanted half-profiles 11, 12 is a half-profile perpendicular to the rotor blade longitudinal axis, which was calculated from the slanted half-profiles. The additional dashed lines which represent a slanted section of a cuboid are only provided to illustrate the three-dimensionality.

LIST OF REFERENCE NUMERALS

[0094] 1 Wind turbine [0095] 2 Rotor blade [0096] 3 Rotor [0097] 4 Hub [0098] 5 Measurement section [0099] 6 Time span [0100] 7 Time axis [0101] 8 Distance measurement value [0102] 9 First measurement section [0103] 10 Second measurement section [0104] 11 First slanted half-profile [0105] 12 Second slanted half-profile [0106] 13 Interpolation point [0107] 14 Connection line [0108] 15 Half-profile perpendicular to the rotor blade longitudinal axis [0109] 16 Reconstituted rotor blade partial surface [0110] 17 Linking line [0111] 18 Line