Method for detecting damage of wind turbine blade and wind turbine

Patent metadata

Field	Value
Publication number	US-2016245262-A1
Application number	US-201514809916-A
Country	US
Kind code	A1
Filing date	Jul 27, 2015
Priority date	Feb 24, 2015
Publication date	Aug 25, 2016
Grant date	—

Abstract

A method for detecting damage of a wind turbine blade of a wind turbine rotor having at least one wind turbine blade comprises: a light incident step of allowing light to enter an optical fiber sensor being mounted on each of the wind turbine blade and having a diffraction grating part having a refractive index which is periodically varied in a longitudinal direction of the diffraction grating part; a light detection step of detecting reflected light from the diffraction grating part; an obtaining step of obtaining, from a temporal change of a wavelength of the reflected light received in the light receiving step, a wavelength variation index representing a variation amount of the wavelength; and a damage determination step of determining presence or absence of a damage of the wind turbine blade on the basis of the wavelength variation index calculated in the obtaining step.

First claim

1 . A method for detecting damage of a wind turbine blade of a wind turbine rotor having at least one wind turbine blade, comprising:
a light incident step of allowing light to enter an optical fiber sensor being mounted on each of the wind turbine blade and having a diffraction grating part having a refractive index which is periodically varied in a longitudinal direction of the diffraction grating part; a light detection step of detecting reflected light from the diffraction grating part; an obtaining step of obtaining, from a temporal change of a wavelength of the reflected light received in the light receiving step, a wavelength variation index representing a variation amount of the wavelength; and a damage determination step of determining presence or absence of a damage of the wind turbine blade on the basis of the wavelength variation index calculated in the obtaining step.

2 . The method for detecting damage of a wind turbine blade according to claim 1 , wherein in the obtaining step, a difference between a local maximum and a local minimum of the temporal change is calculated as the wavelength variation index.

3 . The method for detecting damage of a wind turbine blade according to claim 2 , wherein the difference between the local maximum and the local minimum which repeatedly alternately appear corresponding to a rotation period of the wind turbine rotor is calculated as the wavelength variation index.

4 . The method for detecting damage of a wind turbine blade according to claim 2 , wherein in the obtaining step, determination of a second extremal value which is next to the first extremal value is suspended from a time point when a first extremal value appears until an end of a time period t which satisfies a relation of 0.1 T≦t≦0.5 T where T is a rotation period of the wind turbine rotor.

5 . The method for detecting damage of a wind turbine blade according to claim 1 , wherein in the obtaining step, a standard deviation of the wavelength within a time period of a prescribed length is calculated as the wavelength variation index.

6 . The method for detecting damage of a wind turbine blade according to claim 1 , wherein in the damage determination step, presence of the damage of the wind turbine blade is determined if a magnitude or change rate of the wavelength variation index falls outside a prescribed range.

7 . The method for detecting damage of a wind turbine blade according to claim 1 , further comprising:
a time average calculation step of calculating an average of the wavelength variation index calculated in the obtaining step within a time period of not less than a rotation period of the wind turbine rotor, wherein in the damage determination step, presence of the damage of the wind turbine blade is determined on the basis of the average calculated in the time average calculation step.

8 . The method for detecting damage of a wind turbine blade according to claim 7 , further comprising:
a data validity determination step of determining whether the wavelength variation index calculated in the obtaining step is a valid data or an invalid data, wherein in the time average calculation step, the average is calculated by using only the wavelength variation index determined as a valid data in the data validity determination step.

9 . The method for detecting damage of a wind turbine blade according to claim 8 , wherein in the data validity determination step, the wavelength variation index is determined as an invalid data if a value of the wavelength represents an abnormality of the optical fiber sensor or if the wavelength variation index calculated in the obtaining step is obtained from a difference between a local maximum of the wavelength and a local minimum greater than the local maximum.

10 . The method for detecting damage of a wind turbine blade according to claim 1 , wherein in the damage determination step, the damage of the wind turbine is determined by using, among the wavelength, only the wavelength obtained when a wind velocity falls within a prescribed range of wind velocity.

11 . The method for detecting damage of a wind turbine blade according to claim 1 ,
wherein the wind turbine rotor has a plurality of wind turbine blades, wherein the method further comprises a difference calculation step of calculating a difference between the wavelength variation index of a detection target wind turbine blade among the plurality of the wind turbine blades and a reference value which reflects the wavelength variation index of at least one comparison target wind turbine blade among the other wind turbine blades, and wherein in the damage determination step, a damage of the detection target wind turbine blade is determined on the basis of a temporal change in the difference calculated in the difference calculation step.

12 . The method for detecting damage of a wind turbine blade according to claim 11 ,
wherein the wind turbine rotor has at least three wind turbine blades, wherein the difference as to each of the wind turbine blades is calculated by repeating the difference calculation step by regarding the each of the wind turbine blades as the detection target wind turbine blade, and wherein in the damage determination step, which wind turbine blade has the damage is determined on the basis of the difference as to each of the wind turbine blades.

13 . A wind turbine comprising:
a wind turbine rotor having at least one wind turbine blade; an optical fiber sensor being mounted on each of the wind turbine blade and having a diffraction grating part having a refractive index which is periodically varied in a longitudinal direction of the diffraction grating part; a light incident part for allowing light to enter the optical fiber sensor; a light detection part for detecting reflected light from the diffraction grating part; and a damage determination part for detecting a damage of the wind turbine blade; wherein the damage determination part is configured to obtain, from a temporal change of a wavelength of the reflected light detected by the light detection part, a wavelength variation index representing a variation amount of the wavelength, and to determine presence or absence of a damage of the wind turbine blade on the basis of the wavelength variation index.

14 . A wind turbine according to claim 13 , wherein the damage determination part is configured to calculate, as the wavelength variation index, a difference between a local maximum and a local minimum of the temporal change.

15 . A wind turbine according to claim 13 , wherein the damage determination part is configured to calculate, as the wavelength variation index, a standard deviation of the wavelength within a time period of a prescribed length.

Assignees

• Mitsubishi Heavy Ind Ltd

Inventors

• Ide Kazunari
• Takita Katsuhiko
• Kuroiwa Takao
• Baba Mitsuya
• Nishino Hiroshi
• Koyanagi Takuya

Classifications

• G01M11/085

  the optical fiber being on or near the surface of the DUT · CPC title

• F03D17/00 Primary

  Monitoring or testing of wind motors, e.g. diagnostics (testing during commissioning of wind motors F03D13/30) · CPC title

• F05B2270/326

  Rotor angle · CPC title

• Y02E10/72

  Wind turbines with rotation axis in wind direction · CPC title

• F05B2270/803

  Sampling thereof · CPC title