Method for detecting damage of wind turbine blade and wind turbine

Patent metadata

Field	Value
Publication number	US-10167853-B2
Application number	US-201514809916-A
Country	US
Kind code	B2
Filing date	Jul 27, 2015
Priority date	Feb 24, 2015
Publication date	Jan 1, 2019
Grant date	Jan 1, 2019

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

The invention claimed is:

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 attached to each wind turbine blade and including a diffraction grating having a refractive index which is repetitively varied in a longitudinal direction of the diffraction grating;
a light detection step of detecting reflected light from the diffraction grating;
an obtaining step of obtaining, from a periodic temporal change of a wavelength of the reflected light received in the light detection step due to rotation of the wind turbine rotor, a wavelength variation index representing a temporal variation component of the wavelength in the periodic temporal change; 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,
wherein the wavelength variation index is a difference between a local maximum of the wavelength and a local minimum of the wavelength appearing in each rotation period of the wind turbine rotor.

2. The method for detecting damage of a wind turbine blade according to claim 1 , wherein in the obtaining step, after a first extremal value that is one of the local maximum value or the local minimum value appears, determination of a second extremal value which is next to the first extremal value is suspended from a time point until an end of a time period t which satisfies a relation of 0.1 T≤t≤0.5 T where T is the rotation period of the wind turbine rotor.

3. 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.

4. 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.

5. 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.

6. The method for detecting damage of a wind turbine blade according to claim 5 , 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 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, and
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.

7. 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.

8. 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.

9. The method for detecting damage of a wind turbine blade according to claim 8 ,
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.

10. A wind turbine comprising:
a wind turbine rotor having at least one wind turbine blade;
an optical fiber sensor being attached to each wind turbine blade and including a diffraction grating having a refractive index which is repetitively varied in a longitudinal direction of the diffraction grating;
a light source/signal processing unit connected to the optical fiber sensor and including: a light source for generating light which is input into the optical fiber sensor; and a light detector for detecting reflected light from the diffraction grating; and
an index calculator for calculating, from a periodic temporal change of a wavelength of the reflected light detected by the light detector due to rotation of the wind turbine rotor, a difference between a local maximum of the wavelength and a local minimum of the wavelength appearing in each rotation period of the wind turbine rotor as a wavelength variation index representing a temporal variation component of the wavelength in the periodic temporal change, the wavelength variation index being used for determination of presence or absence of a damage of the wind turbine blade.

11. The wind turbine according to claim 10 , wherein the index calculator 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

• F05B2270/326

  Rotor angle · CPC title

• Y02E10/721

  Cross-Sectional Technologies · mapped topic

• F05B2270/803

  Sampling thereof · CPC title

• G01M11/085

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

• F05B2270/804

  Optical devices · CPC title