Method of Identifying a Wind Distribution Pattern Over the Rotor Plane and a Wind Turbine Thereof

Abstract

The invention relates to a method of identifying a wind distribution pattern over a rotor plane and a wind turbine thereof. At least one operating parameter of the wind turbine and a rotational position of the rotor are measured over a time period. A first wind turbine blade passing signal is extracted from the measured operating parameter and a second wind turbine blade passing signal is generated from the rotational position. The first and second wind turbine blade passing signals are then analysed to determine the characteristics of the actual wind turbine blade passing signal in the rotor plane. These characteristics are afterwards compared to the characteristics of a plurality of known wind distribution patterns, and a unique relationship between the characteristics of the wind turbine blade passing signal and the wind distribution pattern is used to identify a distinctive wind distribution pattern.

Claims

1-13. (canceled)

14. A method of identifying a wind distribution pattern over a rotor plane of a wind turbine, the wind turbine comprising a rotor rotary arranged relative to a nacelle, the nacelle is arranged on top of a wind turbine tower, the rotor comprises at least two wind turbine blades mounted to a rotatable hub, wherein the at least two wind turbine blades define the rotor plane, the wind turbine further comprising an angular sensor configured to measure a rotational position, at least a second sensor configured to measure at least one operating parameter, and a control system electrically connected to the angular sensor and the at least second sensor, wherein the method comprises the steps of: measuring at least one operating parameter, measuring a rotational position of the rotor, determining a wind distribution over the rotor plane, e.g. in at least a horizontal direction or a vertical direction, by determining at least one wind turbine blade passing signal based on said at least one operating parameter or said rotational position and calculating the characteristics, e.g. an amplitude or a phase, of said one wind turbine blade passing signal, comparing said wind distribution to a plurality of predetermined wind distribution patterns, and identifying a match between the wind distribution and one of said plurality of predetermined wind distribution patterns by applying a pattern recognition algorithm to the calculated characteristics of the wind turbine blade passing signal.

15. The method according to claim 14, wherein each of the predetermined wind distribution patterns is defined by a unique relationship between said each wind distribution pattern and predetermined characteristics of the wind turbine blade passing signal, wherein said step of comparing said wind distribution to a plurality of predetermined wind distribution patterns comprises comparing the calculated characteristic to said predetermined characteristics.

16. The method according to claim 14, wherein the at least one operating parameter or the rotational position of the rotor is measured over a predetermined time period.

17. The method according to claim 14, wherein the method further comprises the step of updating the predetermined wind distribution patterns.

18. The method according to claim 14, wherein said step of calculating the characteristics of said one wind turbine blade passing signal comprises calculating an amplitude and a phase, the amplitude and the phase being indicative of the wind turbine blade passing signal of the rotor plane.

19. The method according to claim 14, wherein said at least one operating parameter is selected from a generator torque signal, a rotor torque signal, a vibration signal, or a blade bending moment signal.

20. The method according to claim 14, wherein said method further comprises at least one step of: operating the wind turbine in a load protective mode, wherein the configuration of the wind turbine in said load protective mode is selected according to the identified wind distribution pattern, or storing the wind distribution in a database, e.g. transmitting said stored wind distribution to a remote control system or monitoring unit, or both.

21. A wind turbine comprising: a rotor rotary arranged relative to a nacelle, the rotor comprises at least two wind turbine blades mounted to a rotatable hub, wherein the at least two wind turbine blades define a rotor plane, the nacelle being arranged on top of a wind turbine tower, an angular sensor configured to measure a rotational position of the rotor, at least a second sensor configured to measure at least one operating parameter of the wind turbine, a control system electrically connected to the angular sensor and the at least second sensor, wherein the control system is configured to determine a wind distribution over the rotor plane, e.g. in at least a horizontal direction or a vertical direction, wherein the control system is configured to determine at least one wind turbine blade passing signal from said at least one operating parameter or said rotational position, and to calculate the characteristics, e.g. at least an amplitude or a phase, of said one wind turbine blade passing signal, and to compare said wind distribution to a plurality of predetermined wind distribution patterns and the control system being configured with a pattern recognition algorithm configured to apply the calculated characteristics of the wind turbine blade passing signal to identify a match between the wind distribution and one of said plurality of predetermined wind distribution patterns.

22. The wind turbine according to claim 21, wherein each of the predetermined wind distribution patterns is defined by a unique relationship between said each wind distribution pattern and predetermined characteristics of the wind turbine blade passing signal, wherein the control system is configured to compare the calculated characteristic to said predetermined characteristics for identifying a match.

23. The wind turbine according to claim 21, wherein said control system is configured to operate the wind turbine in a normal operation mode and in at least one load protective mode, wherein the control system in the at least one load protective mode is configured to apply a protective action to the wind turbine based on the identified wind distribution pattern.

Description

DESCRIPTION OF THE DRAWING

[0070] The invention is described by example only and with reference to the drawings, wherein:

[0071] FIG. 1 shows an exemplary embodiment of a wind turbine,

[0072] FIG. 2 shows an exemplary graph of the measured operating parameter,

[0073] FIG. 3 shows a first wind turbine blade passing signal extracted from the measured operating parameter,

[0074] FIG. 4 shows an exemplary graph of the measured rotational position,

[0075] FIG. 5 shows an exemplary graph of the phase error between the actual wind turbine blade passing signal, the rotational position, and a second wind turbine blade passing signal, and

[0076] FIG. 6a-c show the unique relationships between the characteristics of the wind turbine blade passing signal and three distinctive wind distribution patterns.

[0077] In the following text, the figures will be described one by one, and the different parts and positions seen in the figures will be numbered with the same numbers in the different figures. Not all parts and positions indicated in a specific figure will necessarily be discussed together with that figure.

POSITION NUMBER LIST

[0078] 1. Wind turbine [0079] 2. Tower [0080] 3. Nacelle [0081] 4. Rotor [0082] 5. Hub [0083] 6. Wind turbine blades [0084] 7. Control system [0085] 8. Sensor units [0086] 9. Operating parameter [0087] 10. First wind turbine blade passing signal [0088] 11. Rotational position [0089] 12. Second wind turbine blade passing signal [0090] 13. Actual wind turbine blade passing signal [0091] 14. First wind distribution pattern [0092] 15. Second wind distribution pattern [0093] 16. Third wind distribution pattern

DETAILED DESCRIPTION OF THE INVENTION

[0094] FIG. 1 shows an exemplary embodiment of a wind turbine 1 in the form of a variable speed wind turbine. The wind turbine 1 comprises a wind turbine tower 2 provided on a foundation. A nacelle 3 is arranged on top of the wind turbine tower 2 and configured to yaw relative to the wind turbine tower 2 via a yaw system (not shown). A rotor 4 comprising a hub 5 and at least two wind turbine blades 6 is rotatably arranged relative to the nacelle 3, wherein the wind turbine blades 6 are mounted to the hub 5. The wind turbine 1 is here shown with three wind turbine blades 6. The hub 5 is connected to a drive train arranged in the nacelle 3 via a drive shaft, wherein the drive train comprising at least a generator for producing an electrical power output.

[0095] The wind turbine 1 further comprises a control system 7 in the form of a local control system connected to a plurality of sensor units 8. The control system 7 is configured to operate the wind turbine 1 in a normal operation mode and in at least one load protective mode. The sensor units 8 include an angular sensor configured to measure a rotational position of the rotor 4 and at least an operating sensor configured to measure an operating parameter of the wind turbine 1.

[0096] FIG. 2 shows an exemplary graph of the measured operating parameter 9 of a clockwise rotating rotor 4. The operating parameter is here measured as a generator speed signal using a suitable generator speed sensor. The x-axis indicates the measured time in milliseconds [ms] while the y-axis indicates the measured number of revolutions of the generator in rounds per minute [rpm].

[0097] FIG. 3 shows a first wind turbine blade passing signal 10, 10′ extracted from the measured operating parameter 9. The wind turbine blade passing signal is here measured as a 3P signal of the wind turbine 1 and is processed in the time and frequency domains respectively. The x-axis indicates the measured time in milliseconds [ms] and in hertz [Hz] respectively while the y-axis indicates the relative amplitude of the signal. The amplitude is here shown in [rpm], but can also be measured in radians per second [rad/s].

[0098] The first wind turbine blade passing signal is here extracted by having applied a Kalman filter algorithm to the operating sensor signal, i.e. the measured operating parameter 9. This extracted signal 10 is further transformed into the frequency domain by applying a FFT-algorithm. This frequency transformed signal 10′ is then analysed to determine the relative amplitude of the actual wind turbine blade passing signal.

[0099] FIG. 4 shows an exemplary graph of the measured rotational position 11. The rotational position is here measured as an angular signal using a suitable angular sensor. The x-axis indicates the measured time in milliseconds [ms] while the y-axis indicates the angular position of the rotor 4 in degrees. The measured angular positions are here shown in multiples of 360 degrees, i.e. the angular position is rest to zero each time the angular position passes 360 degrees.

[0100] FIG. 5 shows an exemplary graph of the phase error between the actual wind turbine blade passing signal, the rotational position 11 and a second wind turbine blade passing signal 12. The x-axis indicates the measured time in milliseconds [ms] while the y-axis indicates the relative angular position of the rotor 4 in degrees.

[0101] The rotation speed 11 signal is here processed in the time domain by multiplying it with the number of wind turbine blades 6 to generate the second wind turbine blade passing signal 12. This second wind turbine blade passing signal 12 is then analysed using a Hilbert transformation algorithm to determine a phase error in relation to the first wind turbine blade passing signal 10. This phase error is then used to determine the phase of the actual wind turbine blade passing signal 13.

[0102] FIG. 6a-c show the unique relationships between the characteristics of the actual wind turbine blade passing signal 13 and three distinctive wind distribution patterns 14, 15, 16. In the upper diagram, the x-axis indicates the width of the rotor plane defined by the rotor 4 in metres [m] while the y-axis indicates the height of this rotor plane in metres [m]. The reference point {0m, 0m} indicates the rotational axis or y-axis of the wind turbine 1. The wind speed is here measured in metres per second [m/s]. In the lower diagram, the radius indicates the relative amplitude of the actual wind turbine blade passing signal 13 while the radial extending lines indicate the phase of the actual wind turbine blade passing signal 13.

[0103] FIG. 6a shows the unique relationship between a first distinctive wind distribution pattern 14 and the corresponding characteristics, e.g. the amplitude and phase, of the actual wind turbine blade passing signal 13′. The first distinctive wind distribution pattern 14 is here shown as vertical wind shears extending in an upwards direction, i.e. parallel to the longitudinal direction of the wind turbine tower 2 and with the highest wind speeds at the uppermost part of the rotor plane.

[0104] FIG. 6b shows the unique relationship between a second distinctive wind distribution pattern 15 and the corresponding characteristics, e.g. the amplitude and phase, of the actual wind turbine blade passing signal 13″. The second distinctive wind distribution pattern 15 is here shown as vertical wind shears in opposite direction, i.e. parallel to the longitudinal direction of the wind turbine tower 2 and with the highest wind speeds at the lowermost part of the rotor plane.

[0105] FIG. 6c shows the unique relationship between a third distinctive wind distribution pattern 16 and the corresponding characteristics, e.g. the amplitude and phase, of the actual wind turbine blade passing signal 13′″. The third distinctive wind distribution pattern 16 is here shown as a combination of horizontal wind shears, i.e. perpendicular to the longitudinal direction of the wind turbine tower 2, and vertical wind shears, e.g. with the highest wind speeds at the lower-left part of the rotor plane.

[0106] When the characteristics of the actual wind turbine blade passing signal 13 are determined, they are then compared to a plurality of stored distinctive wind distribution patterns stored in a database in order to identify a match. Each distinctive wind distribution pattern is defined by distinctive characteristics of the actual wind turbine blade passing signal 13 as shown in FIG. 6a, FIG. 6b, and FIG. 6c. This enables the control system 7 to identify and recognise the distinctive wind distribution patterns acting on the rotor plane by simply analysing the wind turbine blade passing signal generated in the wind turbine 1.