DE102014117916A1 - Method for monitoring a wind turbine, acceleration sensor for a rotor blade, and rotor blade with acceleration sensor - Google Patents

Abstract

It is described a method for monitoring a wind turbine. The method includes measuring acceleration with a fiber optic acceleration sensor in a rotor blade of the wind turbine, wherein the acceleration sensor is less than 10 wt% of metal or contains less than 20 grams of metal.

Description

TECHNICAL AREA

 Embodiments of the present invention relate generally to a control and / or regulation or monitoring of the operation of wind turbines and the components used for this purpose, such as acceleration sensors and / or the corresponding components of a wind turbine. In particular, embodiments relate to a fiber optic acceleration sensor. This may be for methods for monitoring a torsional instability of a rotor blade of a wind turbine, methods for individual pitch control of rotor blades of a wind turbine, method for controlling and / or regulating a wind turbine with an acceleration sensor, in particular for tower release warning, and method for monitoring a wind turbine with a fiber optic Acceleration sensor can be used. Further, embodiments relate to a profile for a trailing edge of a rotor blade of a wind turbine, a rotor blade of a wind turbine, a rotor of a wind turbine, and a wind turbine.

STATE OF THE ART

 Wind turbines are subject to a complex control, which may be necessary, for example, by changing operating conditions. Due to the conditions associated with the operation of a wind turbine, for example, temperature fluctuations, weather and weather conditions, but also in particular greatly changing wind conditions, as well as the variety of legally required safety measures, the monitoring and necessary for monitoring sensors are subject to a variety of boundary conditions.

 For example, torsional instability of the rotor blades may occur during operation. Here, the rotor blade rotates about a substantially along the radius extending torsion axis, and may optionally lead to a vibration or oscillation about the torsion axis, the so-called flutter. To control the operation of a wind turbine, it is important to detect or monitor a torsional instability. In particular, when flapping critical operating conditions can be achieved, with appropriate countermeasures must be taken.

 Furthermore, it is desirable to improve wind turbines nowadays to provide an individual pitch control in order to ensure optimized operation according to the external conditions. For this purpose, an improved detection of the forces acting on the wind turbine forces and the operating state is desirable.

 Also, the detection or measurement of the so-called tower clearance of a rotor blade (the blade clearance), i. the minimum distance of a rotor blade to the tower, is an important parameter for safe operation. For this purpose, an improved detection of the forces acting on the wind turbine forces and the operating state is desirable.

 In the monitoring of operating conditions of wind turbines, a plurality of sensors is used. For example, strain measurements for measuring the bending of a rotor blade, acceleration measurements for measuring an acceleration of a rotor blade, or other quantities can be measured. A group of sensors that appear promising for future applications are fiber optic sensors. It is therefore desirable to further improve measurements for monitoring a wind turbine with fiber optic sensors.

 In general, therefore, it is desirable to provide improvements in control and monitoring, in the sensors for a rotor blade of a wind turbine, in rotor blades for wind turbines, and in wind turbines themselves.

SUMMARY OF THE INVENTION

 According to one embodiment, a method for monitoring a wind turbine is provided. The method includes measuring acceleration with a fiber optic acceleration sensor in a rotor blade of the wind turbine, wherein the acceleration sensor is less than 10 wt% of metal or contains less than 20 grams of metal.

 According to one embodiment, a rotor blade of a wind turbine is provided. The rotor blade includes a fiber optic acceleration sensor, wherein the acceleration sensor is less than 10% by weight of metal or contains less than 20 g of metal.

In one embodiment, a fiber optic acceleration sensor is provided. The fiber optic acceleration sensor includes a light guide having a light exit surface; a membrane; a mass associated with the membrane; an optical resonator formed between the light exit surface and the diaphragm; and a mirror provided in the beam path between the light exit surface and the diaphragm, wherein the Mirror is formed at an angle of 30 ° to 60 ° relative to an optical axis of the light guide.

BRIEF DESCRIPTION OF THE DRAWINGS

 Embodiments are illustrated in the drawings and explained in more detail in the following description. In the drawings show:

1 shows schematically a rotor blade of a wind turbine with an acceleration sensor according to embodiments described herein;

2 schematically shows a part of a wind turbine with rotor blades and acceleration sensors according to embodiments described herein;

3 schematically shows a light guide with a fiber Bragg grating for use in acceleration sensors according to embodiments described herein;

4 schematically shows an embodiment of an acceleration sensor according to embodiments described herein or for use in embodiments described herein;

5 schematically shows a rotor of a wind turbine with rotor blades and acceleration sensors according to embodiments described herein or for use in embodiments described herein;

6 schematically shows a measurement setup for a fiber optic acceleration sensor according to embodiments described herein or for methods of monitoring and / or control and / or regulation according to embodiments described herein;

7 schematically shows a measurement setup for a fiber optic acceleration sensors according to embodiments described herein or for methods of monitoring and / or control and / or regulation according to embodiments described herein;

7A shows the influence of the measurement with an anti-aliasing filter according to embodiments described herein;

8A and 8B schematically show acceleration sensors for use in embodiments described herein;

9A and 9B schematically show a fiber optic acceleration sensor according to embodiments described herein or for use in embodiments described herein;

10 shows schematically a rotor blade of a wind turbine with an acceleration sensor according to embodiments described herein;

11 schematically shows a rotor blade of a wind turbine with an acceleration sensor according to embodiments described herein or for use in embodiments described herein, wherein a profile for a rotor blade according to embodiments described herein is provided;

11A shows a profile for a rotor blade according to embodiments of the present invention;

12 . 13A and 13B schematically show a part of a rotor blade of a wind turbine with an acceleration sensor according to embodiments described herein or for use in embodiments described herein;

14 schematically shows another part of a rotor blade of a wind turbine with a connection of an acceleration sensor according to embodiments described herein or for use in embodiments described herein;

15 schematically shows a part of a rotor blade of a wind turbine with an acceleration sensor according to embodiments described herein or for use in embodiments described herein; and

16 to 20 show flowcharts of methods for monitoring and / or control and / or regulation of wind turbines according to embodiments described herein.

 In the drawings, like reference characters designate like or functionally identical components or steps.

WAYS FOR CARRYING OUT THE INVENTION

 In the following, more detailed reference will be made to various embodiments of the invention, one or more examples of which are illustrated in the drawings.

1A shows a rotor blade 100 a wind turbine. The rotor blade 100 has an axis 101 along its longitudinal extent. The length 105 of the rotor blade extends from the blade flange 102 to the blade tip 104 , According to embodiments described here is located in an axial or radial region, that is, a region along the axis 101 , an acceleration sensor 110 wherein the acceleration sensor is provided at a radial position in the range of the outer 70% of the radius of a rotor blade of the wind turbine.

Sensors are in practice so far near the blade flange 102 been installed. Typically, sensors have in practice been mounted in the inner 20% of the radius of a rotor blade. This positioning has been an often required prerequisite, since a lightning strike is a serious hazard for wind turbines or wind turbines. On the one hand, a lightning strike can take place directly in electronic components and / or cables or signal cables for electronic components. On the other hand, even with a derivative of a lightning strike via a lightning arrester, ie a controlled derivation to a ground potential, damage caused by the currents generated by induction in cables or signal cables. In lightning strikes, this can lead to the destruction of components of a wind turbine. On the other hand, lightning strikes can lead to greater material fatigue. This can, for example, significantly increase maintenance costs. For example, one to four lightning strikes per year can be expected in a rotor blade.

 This positioning of sensors near the blade flange is in practice a constraint or assumption that opposes embodiments of the present invention. Sensors, in particular acceleration sensors, can provide improved methods for measuring operating states of a wind turbine in the case of radial positioning, which is provided in the range of the outer 70% of the radius of the rotor blade contrary to common practice.

 According to typical embodiments, positioning of an acceleration sensor along the radius of a rotor blade can be provided as follows. In the case of rotor blades which can be walked on up to approximately 50% to 60% of the radius (the blade flange corresponds approximately to 0% of the radius), at least one acceleration sensor can be provided at a radial position in the outer 70% of the radius of the rotor blade become. In rotor blades, which have a much lower walk-in area, the advantage of mounting on a walk-in position can alternatively be given up. In such a case, mounting of an acceleration sensor near the blade tip, for example in a range of 30% to 95% of the radius (0% corresponds to the flange on the blade root) may be provided.

2 shows a wind turbine 200 , The wind turbine 200 includes a tower 40 and a gondola 42 , At the gondola 42 the rotor is attached. The rotor includes a hub 44 at the rotor blades 100 are attached. According to typical embodiments, the rotor has at least 2 rotor blades, in particular 3 rotor blades. During operation of the wind power plant or the wind turbine rotates the rotor, ie the hub with the rotor blades about an axis. In this case, a generator is driven to generate electricity. As in 2 is at least one acceleration sensor 110 in a rotor blade 100 made available. The acceleration sensor is connected to a signal line with an evaluation unit 114 connected. The evaluation unit 114 provides a signal to a controller and / or controller 50 the wind turbine 200 ,

According to some embodiments that may be combined with other embodiments, the acceleration sensor is one 110 to a fiber optic acceleration sensor, in particular a fiber optic acceleration sensor. For fiber optic acceleration sensors, an optical signal is transmitted by means of a light guide 112 , For example, an optical fiber, to the evaluation unit 114 transfer. In a fiber optic acceleration sensor, the sensor element itself can be provided outside of an optical fiber. An example is in detail in relation to 9A and 9B described. Alternatively, in a fiber optic acceleration sensor, the actual sensor element may be provided within an optical fiber, for example in the form of a fiber Bragg grating. This is in detail in terms of the 3 and 4 described.

In 2 is through the arrows 201 a twist of a rotor blade 100 illustrated. For example, this torsion can be along an axis 101 exist. In case of unwanted oscillations around the axis 101 one speaks of flapping the rotor blade 110 , The flapping of the rotor blade 110 can lead to dangerous operating conditions. It is therefore desirable to provide improved methods for monitoring torsional instability of a wind turbine rotor blade. According to embodiments described herein, acceleration is measured with an acceleration sensor, wherein the acceleration sensor is provided at a radial position in the range of the outer 70% of the radius of the rotor blade. The signal of the acceleration sensor, ie the acceleration signal or the acceleration is evaluated in order to generate a warning signal. The warning signal may be a signal for detecting a torsional instability, in particular, flutter, and / or a signal for detecting a torsion-bending coupling. In the present disclosure, the term torsional bending coupling is used. Alternatively, the term bending-torsion coupling can be used. The evaluation of the acceleration signal can in this case in the evaluation 114 or in the control and / or regulation 50 respectively.

 In contrast to so-called "edgewise vibrations" in rotor blades, i. lateral vibrations, which can arise, for example, by dynamic stall effects, the torsional or torsional vibrations are not detectable in the nacelle or, the leaf root or, the leaf flange. In the "edgewise vibrations", the rotor blades are poorly damped in this direction, and it can cause a stimulation by dynamic stall effects. For torsional instabilities, a measurement is made in the blade tip. For example, the torsional instability may occur locally. For example, only the tip of the rotor blade can swing. Each rotor blade may separately have an individual torsional instability. Therefore, according to some embodiments that may be combined with other embodiments, an acceleration sensor is provided in each rotor blade. The sensor is provided in the blade tip, i. in the last 30% of the radius of the rotor blade, since a torsional instability only in the rotor blade tip. According to embodiments described here, in particular solutions for the repair, attachment or replacement of the acceleration sensors are made available, wherein in the relevant area of the rotor blade for mounting the acceleration sensor of the rotor blade is not accessible.

 During the design of a rotor blade, the problem of torsional instability is difficult to exclude, since this problem may not occur in the test. It can be reduced or excluded by embodiments described here accordingly design risks in large rotor blades or such rotor blades with a structurally provided torsional bending coupling. According to typical embodiments, the methods for monitoring torsional instability are also provided in rotor blades that use torsional bending coupling for passive power control. The torsional instability is a problem that occurs in particular for larger leaves, for example with a length of about 40 m or more, or in modern rotor blades, which have a certain ratio of torsional stiffness to the excitation frequencies.

 According to typical embodiments that may be combined with other embodiments, the acceleration sensor is provided in the outer 50% of the radius of the rotor blade. Additionally or alternatively, the acceleration sensor may have a distance from the torsion axis of at least 10 cm. Furthermore, it is favorable if the acceleration sensor provides at least one acceleration with a directional component perpendicular to the chord of the rotor blade or perpendicular to the blade surface. A measured acceleration direction may thus be tangential with respect to the traction axis. By the arrangement and orientation of the acceleration sensor, an improved detection of a dynamic torsion, for example, an oscillation about a torsion axis can be provided.

 The radial position provided in accordance with embodiments in the area of the outer 70% of the radius of the rotor blade, in particular the outer 50% of the radius of the rotor blade, in particular the outer 70 to 95% of the radius of the rotor blade, generates an improved signal of the acceleration sensor. This allows a more reliable detection or monitoring of a torsional instability, for example, flutter.

According to some embodiments described herein which may be combined with other embodiments, fiber optic acceleration sensors in which a signal is optically transmitted via a light pipe 112 is transmitted, a hitherto considered unfavorable in practice radial position, since the transmission by means of a light guide or an optical fiber brings a reduced risk of lightning damage with it. Consequently, an existing prejudice of the mounting of sensors in the vicinity of the blade flange is thereby overcome. This can be achieved, in particular, by the use of metal-free acceleration sensors or substantially metal-free acceleration sensors, as described in relation to FIGS 9A and 9B be explained more. However, fiber-optic acceleration sensors can also be provided in such a way that they allow mounting in a radially outer region of a rotor blade without ignoring the risk of lightning damage.

3 shows a sensor integrated in an optical waveguide or a fiber optic sensor 310 which is a fiber Bragg grating 306 having. Although in 3 only a single fiber Bragg grating 306 1, it is to be understood that the present invention is not limited to data acquisition from a single fiber Bragg grating 306 is limited, but that along a light guide 112 , a transmission fiber, a sensor fiber and an optical fiber, respectively, a plurality of fiber Bragg gratings 306 can be arranged.

3 thus shows only a portion of an optical waveguide, which as a sensor fiber, optical fiber or optical fiber 112 is formed, this sensor fiber is sensitive to fiber elongation (see arrow 308 ). It should be noted that the term "optical" or "light" is intended to indicate a wavelength range in the electromagnetic spectrum, which may extend from the ultraviolet spectral range over the visible spectral range to the infrared spectral range. A center wavelength of the fiber Bragg grating 306 , ie a so-called Bragg wavelength λB, is obtained by the following equation: λB = 2 · nk · Λ.

Here, nk is the effective refractive index of the fundamental mode of the core of the optical fiber and Λ the spatial grating period (modulation period) of the fiber Bragg grating 306 ,

A spectral width, which is given by a half width of the reflection response, depends on the extent of the fiber Bragg grating 306 along the sensor fiber. The light propagation within the sensor fiber or the light guide 112 is thus due to the effect of the fiber Bragg grating 306 For example, depending on forces, moments and mechanical stresses and temperatures at which the sensor fiber, ie the optical fiber and in particular the fiber Bragg grating 306 be charged within the sensor fiber.

As in 3 shown, electromagnetic radiation occurs 14 or primary light from the left into the optical fiber or the light guide 112 one part being the electromagnetic radiation 14 as a transmitted light 16 with one compared to the electromagnetic radiation 14 changed wavelength course emerges. Further, it is possible to reflect reflected light 15 at the input end of the fiber (ie at the end, at which also the electromagnetic radiation 14 is irradiated), the reflected light 15 also has a modified wavelength distribution. The optical signal used for detection and evaluation can be provided according to the embodiments described herein by the reflected light, by the transmitted light, as well as a combination of the two.

In a case where the electromagnetic radiation 14 or the primary light is irradiated in a wide spectral range, results in the transmitted light 16 at the location of the Bragg wavelength, a transmission minimum. In the reflected light arises at this point a reflection maximum. A detection and evaluation of the intensities of the transmission minimum or of the reflection maximum, or of intensities in corresponding wavelength ranges, generates a signal which, with regard to the change in length of the optical fiber or of the light guide 112 can be evaluated and thus provides information on forces or accelerations.

4 shows a device 110 for detecting an acceleration. The device includes a mass 402 attached to a lever arm 406 is attached. The lever arm 406 has a fixed point 422 so that a movement of the lever arm and the mass by arrow 423 is shown is possible. Furthermore, an optical fiber or a light guide 112 with a fiber Bragg grating 306 on the lever arm 406 attached. Here is the sensor fiber with a fastener 412 on the lever arm 406 attached. According to typical embodiments, the fastening element may be a splice or a clamping device. The crowd 402 is at a first lever position with the lever arm 406 connected and the optical fiber is at a second lever position with the lever arm 406 connected. A movement of the mass or lever arm, indicated by arrow 423 is shown, leads to a change in length of the optical fiber or the optical fiber 112 by arrow 308 is shown, or a force impact on the optical fiber. This produces the fiber Bragg grating 306 a dependent on the elongation or change in length changed wavelength characteristic of the optical signal such as the reflected light 15 in that by reflection of the primary light or the electromagnetic radiation 14 is produced.

 In conventional acceleration sensors, the mass is typically limited by a spring mechanism to the design in one or more spatial directions. In the simplest case, the mass can only move in one direction. In this direction, a sensor fiber is attached to the mass, which expands as the mass accelerates. In such an arrangement, the maximum elongation and thus the sensitivity of the fiber is given by the weight of the mass and the stiffness of the fiber. In this case, in order to increase the sensitivity of such a sensor, only the mass can be increased. For sensitive sensors, this can lead to masses of up to several 100 g in weight. Another disadvantage of such an arrangement is that in this case the resonance frequency f of the fiber-mass system has a dependence f root (k / m), which consequently decreases with increasing mass. Here, k is the spring stiffness of the fiber-mass system. Since the minimum spring stiffness is limited by the stiffness of the fiber, only a limited range can be configured.

By using a lever arm, this limitation of the area to be configured can be canceled or reduced. As already in 4 can be seen, by changing the mounting position of the optical fiber along the lever arm 406 , ie a change in the second lever position at which the optical fiber or the light guide 112 is attached, a change in the sensitivity of the device for detecting an acceleration can be provided. The sensitivity can thus be changed without the mass 402 to change and thus influence the resonance frequency.

Thus, embodiments allow according to 4 to break the connection between stiffness of the fiber, sensitivity, as well as resonance frequency. By using a mechanical lever, the ratio of deflection of the fiber and necessary force is arbitrarily configurable. Furthermore, the use of a lever arm allows an increased force on the fiber even with a small mass or a constant mass.

The by arrow 423 Movement shown is a movement of the lever arm 406 or the mass 402 in the paper plane of 4 , Typically, the fixed point 422 be designed such that a movement takes place only in one plane. However, according to further embodiments, a movement can also take place in two levels or even three levels. In such an embodiment with a plurality of planes of motion, further optical fibers can each have a fiber Bragg grating 306 with the lever arm 406 be connected, so that detection of acceleration in several directions in space can be done. However, according to typical embodiments, an apparatus for multi-dimensionally detecting acceleration is described with reference to FIG 8B described executed.

5 shows a rotor 500 a wind turbine. The rotor 500 has a hub 44 and attached rotor blades 100 , In at least one of the rotor blades 100 is an acceleration sensor 110 made available. The signal of the acceleration sensor 110 is over a light guide 112 to a distributor 510 directed. The distributor 510 may be, for example, a field distributor to which several signals from different sensors are provided.

According to some embodiments which may be combined with other embodiments, the distributor or field distributor may be attached to the blade bulkhead of the rotor blade. The distributor can be designed for connecting and disconnecting a signal cable of a sensor. Furthermore, a sensor cable can be provided for connection and disconnection from the field distributor to the measuring device or to the evaluation unit. In accordance with some embodiments that may be combined with other embodiments, the distributor is 510 provided on the leaf bulkhead or in the leaf root.

The area of the leaf root is through the dividing line 502 illustrated. Typically, the blade root extends from a blade flange 102 with which the rotor blade 100 at the hub 44 is fixed, radially, ie along the longitudinal extent of the rotor blade, over a length of 1 m to 3 m.

As in 5 may be a light guide according to some embodiments 512 or an optical fiber from the distributor 510 to the evaluation unit 114 be guided. For example, the light guide 512 along a spring or a spiral 513 or by a spring or a spiral 513 or a corresponding mechanical element are guided, so that upon rotation of the rotor blade 100 around its longitudinal axis, ie when pitching the rotor blade, the light guide is not damaged. The mechanical guidance of the light guide 512 along a spiral or through a spiral 513 allows a twist of the light guide, so that when pitching the rotor blade of the light guide is not damaged

A majority of the embodiments described in the figures show an acceleration sensor in each case one of the rotor blades. According to further embodiments which can be combined with other embodiments, a measurement of the acceleration at a plurality of positions of a rotor blade, in particular at a plurality of radial positions in the region of the outer 70% of the radius of the rotor blade, can be performed. For this purpose, a plurality of acceleration sensors may be provided at the respective radial position. By measuring at several radial positions, on the one hand, the measurement accuracy can be increased. Additionally or alternatively, signals for detecting a torsional instability, in particular flutter, and / or signals for instability warning in a torsional bending coupling for different operating conditions at different radial positions can be detected more easily and / or reliably. For example, control and / or regulation of a wind turbine may be triggered by generating a warning signal at at least one radial position or generating it at a predetermined number of radial positions. According to still further embodiments that may be combined with other embodiments, one or more acceleration sensors may also be combined with at least one other sensor. The at least one further sensor may be selected from one or more sensors from the group consisting of: a Strain sensor, a temperature sensor, a pressure sensor, a sound level sensor, and an inclinometer (to measure the position of the rotation of the rotor).

 In particular, for the generation of signals for flutter warning or torsional instability warning, a sensor for measuring a pressure fluctuation (for example, a sound pressure) can be provided on the rotor blade. In this way, for example, noises that may typically occur when a rotor blade flutters can be detected and used for the generation of warning signals.

 In addition, the measurement of the temperature on the rotor blade for evaluating the signals of the acceleration sensor (s) is advantageous, since the temperature influences the sheet properties, such as the natural frequency. A correlation of the sheet properties with the signals of the acceleration sensor (s) leads to a more precise evaluation in the generation of warning signals or the measurements of the acceleration sensor (s). For example, the measurement of temperature may be made, such as with a temperature sensor, in an acceleration sensor or in an optical fiber.

 According to further embodiments, which may be combined with other embodiments described herein, a strain sensor for measuring a static bending moment, in particular a static torsional moment, may be provided. Thus, in generating a flutter warning signal and / or a signal for instability warning in a torsional-bending coupling, a dynamic signal of the acceleration sensor may be combined with a static signal of the strain sensor. For example, a strain sensor can be provided in the area of the blade root. For a combined measurement, an orientation of a strain sensor in a range of 30 ° to 60 °, in particular 45 °, relative to the torsion axis may be advantageous.

In a control and / or regulation 50 a wind turbine 200 as they are in 2 is shown, the signal for flutter warning and / or the signal for instability warning in a torsional bending coupling can be used for the control and / or regulation of the wind turbine. The control and / or regulation may in particular consist of a pitch control of a rotor blade, an adaptation of a generator characteristic of the wind turbine, an emergency shutdown of the wind turbine, or a combination of two or more of these measures.

6 FIG. 12 shows a typical acceleration detection system with an acceleration detection device according to the embodiments described herein. FIG. The system contains one or more acceleration sensors 110 , The system has a source 602 for electromagnetic radiation, for example a primary light source. The source serves to provide optical radiation with which at least one fiber-optic sensor element of an acceleration sensor can be irradiated. For this purpose, an optical transmission fiber or a light guide 603 between the primary light source 602 and a first fiber coupler 604 provided. The fiber coupler couples the primary light into the optical fiber or the optical fiber 112 The source 602 For example, a broadband light source, a laser, a light emitting diode (LED), an SLD (superluminescent diode), an Amplified Spontaneous Emission (ASE) light source, or a Semiconductor Optical Amplifier (SOA). For embodiments described herein, multiple sources of the same or different types (see above) may also be used.

The fiber optic sensor element, such as a fiber Bragg grating (FBG) or an optical resonator, is integrated into a sensor fiber or optically coupled to the sensor fiber. The light reflected by the fiber optic sensor elements is in turn transmitted via the fiber coupler 604 which passes the light over the transmission fiber 605 a beam splitter 606 passes. The beam splitter 606 divides the reflected light for detection by means of a first detector 607 and a second detector 608 , This is done on the second detector 608 detected signal first with an optical edge filter 609 filtered.

Through the edge filter 609 For example, a shift in the Bragg wavelength at the FBG or a wavelength change through the optical resonator can be detected. In general, a measuring system, as in 6 is shown without the beam splitter 606 or the detector 607 be made available. The detector 607 however, allows normalization of the measurement signal of the acceleration sensor with respect to other intensity fluctuations, such as variations in the intensity of the source 602 , Fluctuations due to reflections at interfaces between individual light guides, or other intensity fluctuations. This standardization improves the measuring accuracy and reduces the dependence of measuring systems on the length of the optical fibers provided between the evaluation unit and the fiber-optic sensor.

In particular, when using multiple FBGs, additional optical Filtering devices (not shown) are used for the filtering of the optical signal or secondary light. An optical filter device 609 or additional optical filter means may comprise an optical filter selected from the group consisting of a thin film filter, a fiber Bragg grating, an LPG, an Arrayed Waveguide Grating (AWG), an Echelle grating, a Grid arrangement, a prism, an interferometer, and any combination thereof.

 Another aspect of wind turbine monitoring that may be combined with other embodiments and aspects described herein, but that is also provided independently of other embodiments, aspects, and details, is an improved method of monitoring a wind turbine with a fiber optic acceleration sensor. According to such aspect or embodiment, a method of monitoring a wind turbine is provided. The method of monitoring a wind turbine includes measuring an acceleration with a fiber optic acceleration sensor, wherein the acceleration sensor is provided at a radial position in the area of the outer 70% of the radius of a rotor blade of the wind turbine and filtering an acceleration signal of the fiber optic acceleration sensor with an analog Low-pass filter or an analog anti-aliasing filter.

7 shows an evaluation unit 114 wherein a signal of a fiber Bragg grating 306 is guided over an optical fiber to the evaluation. In 7 is still a light source 602 represented, which can optionally be provided in the evaluation unit. The light source 602 but can also be independent or outside of the evaluation unit 114 be made available. The optical signal of the fiber optic acceleration sensor 110 is converted into an electrical signal with a detector. The conversion from an optical signal to an electrical signal is indicated by the symbol 702 in 7 shown. The electrical signal comes with an analogue anti-aliasing filter 710 filtered. Following analogue filtering with an analog anti-aliasing filter or low-pass filter, the signal is passed through an analog-to-digital converter 704 digitized.

 According to some embodiments, which may be combined with other embodiments, the anti-aliasing filter may have a cut-off frequency of 1 kHz or less, in particular of 500 Hz or less, more particularly of 100 Hz or less. According to embodiments described herein, such filtering takes place prior to digitization. Furthermore, no spectral splitting of the signals takes place for the embodiments described here, an optical digitization already being carried out with a spectrometer and a multichannel detector.

 According to embodiments described herein, analog low pass filtering occurs prior to digitizing a signal of a fiber optic acceleration sensor. According to embodiments described herein which may be combined with other embodiments, the low-pass filter may also be referred to as an analog anti-aliasing filter. In this case, the Nyquist frequency is taken into account in the context of a sampling theorem, and a low-pass filtering with signal portions smaller than the Nyquist frequency by means of the analog low-pass filter or analog anti-aliasing filter is made available.

 By the embodiments described herein with a fiber optic acceleration sensor and analog low-pass filtering, an improved measurement of acceleration for monitoring a wind turbine can be provided.

7 further shows a digital evaluation unit 706 which may include, for example, a CPU, memory, and other digital computing elements. The aspect of improved measurement with fiber optic acceleration sensors on wind turbines by the use of an analog anti-aliasing filter can be used with other embodiments, in particular with regard to the positioning of the acceleration sensors, the use of the signals for flutter warning or torsional instability warning, for pitch Regulation; for warning in relation to the tower clearance of a rotor blade, the mounting of acceleration sensors or optical fibers, fiber optic acceleration sensors which are improved for use in wind turbines by a reduced metal content.

According to further embodiments, the improved measurement with fiber-optic acceleration sensors with an analog low-pass filtering prior to digitization can be further advantageously designed to provide a digital evaluation in the digital evaluation unit 706 to the Stochastic Subspace Identification (SSI). In this case, eigenvalues of the rotor blade, wherein the eigenvalues in particular may include the attenuations and the frequencies, ie the natural frequencies, of a rotor blade can be calculated. The eigenvalues can be used in particular for the detection of ice formation on a rotor blade. This allows more reliable detection of ice formation on a rotor blade. Other conditions, such as material fatigue, can by means of Eigenvalues are determined. According to some embodiments that may be combined with other embodiments described herein, the detection of ice formation described herein may also be provided in a standing and / or spinning wind turbine. According to some embodiments which may be combined with other embodiments described herein, detection of ice formation on the rotor blade may be provided by means of eigenvalues, in particular by detecting a change in the eigenvalues. In particular, a change in the eigenvalues can be detected by ice formation on the rotor blade. For example, a method may include detecting a change in the eigenvalues, particularly by ice formation on the rotor blade.

 According to embodiments described herein, a standing or spinning wind turbine is a wind turbine with no load turning of the rotor. For example, the wind turbine can rotate freely without turning on the generator with zurückppitchten rotor blades. For example, this state may be described by a rotation frequency of the rotor of 0.1 Hz or less.

 According to further embodiments, the measurement may be combined with a fiber optic acceleration sensor with a temperature measurement. The temperature affects the properties of the rotor blade. Thus, the temperature measurement in the detection of ice formation and / or evaluation of the eigenvalues can be consulted. For example, the eigenvalues typically have a functional dependence on temperature. A deviation or change in the eigenvalues can thus be determined relative to the expected eigenvalue at a predetermined temperature. According to still further embodiments that may be combined with embodiments described herein, consideration of a size selected from the group consisting of rotor position, temperature, pitch angle, yaw acceleration, and rotor rotation rate may be provided in the evaluation ,

As for 7 1, a method for monitoring a wind turbine by means of a fiber optic acceleration sensor can be improved by using an analog low-pass filter or an analog anti-aliasing filter. According to respective embodiments, a rotor wind turbine can be provided. The rotor includes at least one rotor blade. A fiber optic acceleration sensor is provided at a radial position in the area of the outer 70% of the radius of the rotor blade. An analog low-pass filter or anti-aliasing filter is designed to filter the acceleration signal of the fiber-optic acceleration sensor, in particular for analog filtering of an electrical signal generated from the fiber-optic acceleration signal. For example, the rotor includes an evaluation unit 114 in a hub 44 is provided. The evaluation unit 114 may include a converter for converting the optical signal into an electrical signal. For example, a photodiode, photomultiplier (PM), or other opto-electronic detector may be used as the transducer. The evaluation unit also contains an anti-aliasing filter 710 which is connected, for example, to the output of the converter or the opto-electronic detector. The evaluation content may further include an analog-to-digital converter 704 include that with the output of the anti-aliasing filter 710 connected is. The evaluation unit 114 In addition, a digital evaluation unit 706 included, which is set up to evaluate the digitized signals. Further embodiments of the rotor or of the rotor blades can be provided according to the embodiments described here with respect to the fiber-optic acceleration sensors, the positioning of fiber-optical acceleration sensors, and / or the signal transmission with optical fibers.

7A shows different acceleration signals for further explanation of the embodiments described here. The upper graph ( 730 ) in 7A a real acceleration in a rotor blade or a reference signal, which was determined for experimental purposes with a reference sensor. The Power Spectral Density (PSD) is plotted against the frequency to, for example, find the eigenvalues described here. The middle graph ( 731 ) shows the acceleration signal of a fiber optic acceleration sensor, wherein the acceleration signal corresponds to the reference signal. The middle graph was generated without the sequence of opto-electronic conversion of the acceleration signal of the fiber optic acceleration sensor and filtering of the opto-electronically converted acceleration signal with an analog anti-aliasing filter. The lower graph in 7A shows the acceleration signal of a fiber optic acceleration sensor, wherein the acceleration signal corresponds to the reference signal. The lower graph was generated with the sequence of opto-electronic conversion of the acceleration signal of the fiber optic acceleration sensor and filtering of the opto-electronically converted acceleration signal with an analog anti-aliasing filter. It can be clearly seen that for the lower graph ( 732 ) an improved detection of eigenvalues especially in a frequency range of 0.3 Hz to 20 Hz compared to the middle graph ( 731 ) exists. According to here As a result, an improved measurement of optical acceleration signals can be achieved. According to further embodiments that may be combined with embodiments described herein, filtering the opto-electronically-converted acceleration signal with an analog anti-aliasing filter may have a cutoff frequency of 10 Hz to 40 Hz, more preferably 15 Hz to 25 Hz.

 According to embodiments described herein, acceleration can be optically measured in a rotor blade. Here, an anti-aliasing filtering is performed, in particular an analog anti-aliasing filter. In contrast to other conventional means of optical signal detection by means of spectrometer or reading by means of a scanning laser, an acceleration in a rotor blade can be optically measured according to embodiments described here. An aliasing effect is prevented, in contrast to a smoothing of the measured values, whereby the smoothing of the measured values merely produces a better control signal. Anti-aliasing filtering is performed analogously in the embodiments described herein, i. For example, a conversion of the optical acceleration signal into an analog electrical measurement signal is used before analogue anti-aliasing filtering is provided. The analog electrical measurement signal is analogue low-pass filtered, with at least half the Nyquist frequency is used as a limit.

 According to other embodiments described herein, the signal filtered with an analog anti-aliasing filter is evaluated by SSI (Stochastic Subspace Identification). Hereby, ice accumulation and / or other frequency-dependent properties of rotor blades, for example aging, damage, etc., can be detected.

 According to other embodiments described herein, a method of ice detection may be provided. The method includes measuring an acceleration with a fiber optic acceleration sensor, opto-electronically converting an acceleration signal of the optical acceleration sensor, filtering the opto-electronically converted acceleration signal with an analog anti-aliasing filter, evaluating the filtered acceleration signal using Stochastic Subspace Identification for calculation of eigenvalues of the rotor blade, and detecting ice formation on the rotor blade using the eigenvalues. For example, one or more eigenvalues may be compensated for with at least one measured quantity from the group consisting of: a temperature at a rotor blade of the wind turbine, a wind speed, a power of the wind turbine, a rotation rate of a rotor of the wind turbine, and a pitch angle of a rotor blade , Compensation may be performed, for example, by the following calibration procedures.

 For example, acceleration in a rotor blade is measured with a fiber optic acceleration sensor described herein. This can be done in a first time interval, for example a short time interval of e.g. 5-30 minutes. Furthermore, one or more of the parameters to be compensated can be measured. These parameters may be: a blade temperature, a pitch angle, a wind speed, a wind turbine power (e.g., the power delivered or delivered to the grid), and / or a rotation rate of the rotor. In particular, the temperature of the rotor blade can be measured as an influencing variable on the eigenvalues of the rotor blade. The eigenvalues of the rotor blade can be determined from the acceleration data by means of SSI in the first time interval. The eigenvalues with associated parameter set from one or more of the parameters to be compensated can be stored. The above-described measurement with the determination of the eigenvalues can be repeated several times until a data set is obtained which represents part or all of the parameter space during operation of the respective wind turbine. This second period may, for example, extend over several weeks. After determining values in a part of the parameter space, the behavior of the eigenvalues above the parameter space can be determined, for example by applying a suitable model (linear model, Taylor approximation, lookup table). The coefficients of the compensation model or the lookup table can be stored in a computing unit on the wind turbine. It is thus possible to calibrate the eigenvalues as a function of one or more parameters.

According to further embodiments, after the calibration, a measurement can be carried out with compensated or calibrated parameters. The eigenvalues of a rotor blade can be determined by means of an acceleration measurement, for example with a fiber optic acceleration sensor. These can be converted with the help of the calibration model or the parameters, which are determined during the acceleration measurement, can be used for a compensation of the eigenvalues. Based on the compensated eigenvalues, a deviation of the compensated eigenvalues can be determined. For example, the output of a warning signal can be made available by means of one or more threshold values. Alternatively, multiple thresholds within the Parameter space are provided so that the output of a warning signal based on the eigenvalues in the parameter space is done, ie without prior conversion of the eigenvalues.

 Another aspect or embodiment, independently of other embodiments but also provided in combination with other embodiments, is monitoring of a wind turbine with a fiber optic strain sensor. The method of monitoring a wind turbine includes measuring strain with a fiber optic strain sensor. A digitized signal of the strain sensor is subjected, for example, to a digital evaluation in a digital evaluation unit, using an evaluation by means of Stochastic Subspace Identification (SSI). Here, too, eigenvalues of the rotor blade, the eigenvalues in particular the attenuations and the frequencies, i. the natural frequencies of a rotor blade can be calculated. The eigenvalues can be used in particular for the detection of ice formation on a rotor blade. This also allows a more reliable detection of ice formation on a rotor blade. Other states, such as material fatigue, can also be determined by means of the eigenvalues.

 If appropriate, the eigenvalues thus calculated may also be combined with or compared with the eigenvalues from a fiber-optic acceleration sensor in order to obtain redundancy with regard to the information of ice formation. According to further embodiments, the measurement may be combined with a fiber optic strain sensor with a temperature measurement. The temperature affects the properties of the rotor blade. Thus, the temperature measurement in the detection of ice formation and / or for the evaluation of the eigenvalues can be consulted. This can be done for example by a calibration described here. According to still further embodiments that may be combined with embodiments described herein, consideration of a size selected from the group consisting of rotor position, temperature, pitch angle, yaw acceleration, and rotor rotation rate may be provided in the evaluation ,

The acceleration sensor 110 in the 8A and 8B is explained in more detail, includes a test mass whose acceleration is measured in the sensor. According to typical embodiments, strain sensors used and / or acceleration sensors used may be fiber optic sensors. Here, the strain or the acceleration of the test mass is optically measured by fiber Bragg gratings in a fiber. By using these sensors, the measurement accuracy described above can be provided. Furthermore, these sensors offer advantageous properties for use in wind turbines.

The acceleration sensors used in the arrangement and method described herein 110 will be regarding now 8A and 8B described. 8A shows an acceleration sensor 110 being a test mass 812 on an optical fiber 822 is appropriate. A housing 802 is designed such that when accelerating the mass 812 an elongation, ie a relative change in length (extension or shortening) of the optical fiber 822 entry. By stretching the fiber 822 becomes the fiber Bragg grating 824 changed. This leads to an altered reflection or transmission of the fiber Bragg grating with respect to the reflected or transported wavelengths. This change can be used as a measure of the elongation of the fiber and thus indirectly as a measure of the acceleration of the test mass 812 be used. In 8B is an acceleration sensor 110 shown. This arrangement combines 3 of the in 8A 3, wherein the rotation of the sensors in illustration is to represent a three-dimensional arrangement, so that 3 acceleration values are measured in a coordinate system, such as a Cartesian coordinate system.

The use of the sensors 110 or their arrangement to each other and the interaction of the evaluation 114 for monitoring a condition of a rotor blade will be described with reference to FIGS 2 and 5 explained in more detail. 2 shows a part of a wind turbine 200 , On a tower 40 is a gondola 42 arranged. At a rotor hub 44 are rotor blades 100 arranged so that the rotor (with the rotor hub and the rotor blades) in one through the line 852 rotated level shown. Typically, this plane is inclined relative to the vertical. 5 shows a front view of the rotor blades 100 and the rotor hub 44 in the direction of the axis of rotation, where coordinates x and y in the sheet-fixed coordination system, the gravitational force or gravitational acceleration g, and the sensor 110 are shown.

During a rotation of the rotor of the wind turbine, the acceleration sensor measures 110 Among other things, the gravitational acceleration. This gravitational acceleration is in the coordinate system according to 5 Measured in the y direction and in the x direction. Due to the inclination of the rotor, the in 2 is shown in the coordinate system in 5 also in the z-direction, the gravitational acceleration to a certain extent be superimposed on a signal. The measurement signal, which is typically in the in 5 marked y-direction is measured, is superimposed on the gravitational signal. By cleaning up the measurement signal from the gravitational signal, a cleaned signal is obtained.

The controls and / or controls of modern wind turbines typically include a so-called pitch control, wherein the rotor blade is rotated about a longitudinal axis of the rotor blade. As a result, in a leaf-fixed coordination system, the in 5 illustrated y-direction during rotation of the rotor blade 100 around the longitudinal axis of the rotor blade. When looking at the from an accelerometer 110 measured acceleration, which includes the influence of gravitational acceleration on a test mass, it is necessary for improved evaluation of the signals of a consideration of the various coordinate systems. First, there is a sheet-fixed coordinate system. When the rotor blade rotates about the longitudinal axis of the rotor blade, the coordinate system and the sensor rotate 110 , In addition, there exists a coordinate system fixed with respect to the rotor hub 44 is. It is a rotating coordinate system that can be used independently of a pitch control. Furthermore, there is a fixed coordinate system fixed with respect to the wind turbine 200 and thus is fixed in relation to the gravitational force or gravitational acceleration.

 According to typical embodiments, to correct the signal (s) of the acceleration sensor and / or the strain sensors, i. a signal in the x-, y- and z-direction in the sheet-fixed coordinate system, a transformation carried out in the stationary coordinate system, taking into account the rotation of the rotor, the pitch angle of the rotor blade and the inclination of the rotor. In the fixed coordinate system, the signal can be corrected for gravitational acceleration. Subsequently, a back transformation into the coordinate system, which is fixed with respect to the rotor hub, can be performed. In this coordinate system, which is fixed with respect to the rotor hub, typically an acceleration is determined substantially parallel to the wind direction or substantially parallel to the axis of rotation of the rotor.

 According to some embodiments described herein, an acceleration sensor is provided in the outer 70% of the radius of a rotor blade, in particular in a range of 60 to 90% of the radius of the rotor blade. In this case, for example, by the use of a fiber-optic acceleration sensor, such as a fiber-optic acceleration sensor, carried an optical signal transmission. The optical signal transmission reduces the risk of lightning damage. By the optical signal transmission, a previously existing in practice limitation, sensors as close to the blade flange to be made available.

 The reduction in the risk of lightning or lightning damage can be further reduced by providing a metal-free or substantially metal-free acceleration sensor. According to one embodiment, a method for monitoring a wind turbine is provided. The method includes measuring an acceleration with a fiber optic acceleration sensor, wherein the acceleration sensors are provided at a radial position in the outer 70% radius of the rotor blade, the acceleration sensors being less than 10% by weight of metal or less than Contains 20 g of metal.

 According to another embodiment, a rotor blade of a wind turbine is provided. The rotor blade includes a fiber optic acceleration sensor, wherein the fiber optic acceleration sensor is provided at a radial position in the range of the outer 70% of the radius of the rotor blade, and wherein the acceleration sensor is less than 10 wt .-% of metal or less than 20 g Contains metal. For example, an optical fiber may be routed from the fiber optic acceleration sensor to a radial rotor blade position where the rotor blade is passable. According to still further embodiments that may be combined with other embodiments, the fiber optic acceleration sensors may have a maximum extension of 10 mm in a cross section perpendicular to an extension of the light pipe.

 According to embodiments described herein, acceleration sensors may be provided with sufficient metal or metal-free acceleration sensors. Thus, in addition to existing ideas of wireless signal transmission, i. a signal transmission without electrical cables in a rotor blade, metal-free acceleration sensors are provided, which provide a reduced risk of lightning or lightning strike. A lightning-proof design or design with a reduced risk of lightning damage can meet the high reliability and service life requirements of wind turbines.

For example, for an advantageous attachment in the blade tip small dimensions and / or masses of the sensor may be advantageous. For the fiber optic measurement by means of fiber Bragg gratings but relatively large masses are necessary because the fiber is relatively stiff. This can be a Membrane sensor using Fabry Perot interferometer lead to even further improvements.

 In addition to fiber-optic acceleration sensors, which can also be provided essentially metal-free, since the actual sensor system is provided by a fiber Bragg grating, according to one embodiment a fiber-optic acceleration sensor can be provided as follows. The fiber optic acceleration sensor includes a light guide or optical fiber having a light exit surface. Further, the fiber optic acceleration sensor includes a diaphragm and a mass in communication with the diaphragm. Here, the mass can be provided either in addition to the mass of the membrane available or the membrane can be designed with a suitable sufficiently large mass. The fiber optic acceleration sensor includes an optical resonator formed between the light exit surface and the diaphragm. For example, the resonator may be a Fabry-Perot resonator. Further, the fiber optic acceleration sensor includes a mirror provided in the beam path between the light exit surface and the diaphragm, the mirror being formed at an angle of 30 ° to 60 ° relative to an optical axis of the optical fiber. For example, the mirror may be formed at an angle of 45 °.

The 9A and 9B show a fiber optic accelerometer 910 , A primary optical signal is transmitted via a light guide 112 the acceleration sensor 910 fed. For example, the optical fiber may be connected to a substrate 912 get connected. The substrate 912 may consist of a non-metallic material. On the substrate 912 or on the substrate 912 is a membrane 914 educated. That from the light guide 112 Exiting primary optical signal is transmitted through a mirror 916 in the direction of the membrane 912 directed. According to typical embodiments that may be combined with other embodiments, the mirror 916 be provided as a surface formed in the substrate. For example, the substrate may be made of a material that reflects in a predetermined wavelength range, typically the wavelength range of the primary optical signal. The mirror may have an angle in the range of 30 ° to 60 °, for example an angle of 45 °, relative to the axis of the light guide.

The primary optical signal is as indicated by the arrow 901 indicated by the mirror 916 deflected and directed to the membrane. At the diaphragm a reflection of the primary optical signal takes place. The reflected light is like the arrow 903 represented back into the optical fiber or the optical fiber 112 coupled. Thus, between the light exit surface for the exit of the primary optical signal and the diaphragm becomes an optical resonator 930 educated. It should be noted that in general the light exit surface of the primary optical signal is equal to the light entrance surface for the reflected secondary signal. The optical resonator can thus be designed as a Fabry-Perot resonator. For a fiber optic acceleration sensor according to embodiments described herein, a mass 922 on the membrane 914 be made available. Alternatively, the mass of the membrane itself may serve as ground for the detection of acceleration. At an acceleration, the membrane 914 through the inertia of the mass 922 deflected. This leads to an optically measurable signal in the optical resonator 930 , According to embodiments described herein, the fiber optic acceleration sensor is configured to provide acceleration with a directional component for measuring which is a direction component perpendicular to the axis of the fiber or optical fiber 112 is. Due to the directional component perpendicular to the axis of the light guide 112 , can the fiber optic acceleration sensors 912 be used for methods for monitoring rotor blades, or be installed in rotor blades of wind turbines or wind turbines, to allow monitoring.

Embodiments described herein which may be combined with other embodiments include a fiber optic acceleration sensor, eg, an extrinsic fiber optic acceleration sensor having an optical sensor provided by or adjacent the fiber, for example, an optical resonator intrinsic fiber optic accelerometer with a sensor provided within the fiber, provided at a radial position of the outer 70% of the radius of the rotor blade. This corresponds in some cases to a radial region of the rotor blade on which it is not possible to commit the rotor blade in the finished state. Thus, according to further embodiments, the radial position of the acceleration sensors described here can also be described by a radial position, at which the rotor blade in the finished state is not accessible. In particular, the acceleration sensors in the outer 50% of the radius of the rotor blade or the outer 60 to 90% of the radius of the rotor blade can be provided. Due to the substantially metal-free design of the fiber-optic acceleration sensor, the risk of lightning strike can be reduced sufficiently to use an acceleration sensor at such a radial position in practice. By the outside displaced radial position of the acceleration sensor, a sensitivity of the acceleration sensor can be achieved, which allows a variety of monitoring, state determinations, and control options and / or control options.

The in the 9A and 9B The components of the extrinsic fiber-optic acceleration sensor shown can consist of the following materials according to exemplary embodiments. The light guide 112 For example, a glass fiber, an optical fiber, or an optical fiber may be used, and materials such as optical polymers, polymethyl methacrylate, polycarbonate, quartz glass, ethylene tetrafluoroethylene, which may be doped, may be used. The substrate 912 or the mirror configured therein 916 can be made of silicon, for example. The membrane can be made of a plastic or a semiconductor which is suitable to be formed as a thin membrane. The crowd 922 can be provided from any non-metallic material, in particular materials with a high density are suitable. Due to a high density, the dimension of the mass can be reduced.

To a fiber optic acceleration sensor, such as in the 9A and 9B is shown particularly simple to provide on a rotor blade, in particular in an outer radial region, it is advantageous if the fiber-optic acceleration sensors in a cross section perpendicular to the light guide 112 in 9A respectively. 9B has a small dimensions. For example, a maximum dimension in a cross section perpendicular to the axis of the optical fiber 112 10 mm or less. By the design, how you in relation to the 9A and 9B is shown, such dimensioning can be easily realized.

The in the 9A and 9B described fiber optic acceleration sensor 910 can be formed by a further modification to an independent further aspect, which can be applied in particular in methods for monitoring rotor blades of wind turbines and in rotor blades of wind turbines. At a decrease or a loss of mass 922 can the membrane 914 Both are used for measuring a static pressure as well as for measuring a sound pressure level. For the measurement of a static pressure is the range of the optical resonator 930 separated from the ambient pressure, so that when the ambient pressure changes, a movement of the membrane takes place. For the measurement of a sound pressure level, the membrane is designed to perform at a corresponding sound pressure, a movement, in particular an oscillating movement, which is transmitted via the optical resonator in an optical signal. Here, it is particularly favorable for use in rotor blades of wind turbines or for the methods for monitoring wind turbines, which is the sound pressure in a direction perpendicular to the longitudinal extent of the light guide 112 is measured.

According to embodiments described herein, different methods of monitoring and / or controlling wind turbines are provided. Furthermore, according to embodiments described here, improved acceleration sensors, in particular intrinsic or extrinsic fiber-optic acceleration sensors, are provided. Here are intrinsic fiber optic acceleration sensors, sensors with a provided within the fiber sensor unit, such as a fiber Bragg grating. Extrinsic fiber optic acceleration sensors have an optical sensor provided by the fiber or on the fiber. Thus, extrinsic fiber optic acceleration sensors can also be detected by means of an optical fiber and an optical sensor, i. a non-electrical sensor, measure acceleration without electrical components. In this case, acceleration sensors can be provided, for example, at a radial position in the area of the outer 70% of the radius of the rotor blade, in particular in the area of the outer 50% of the radius of the rotor blade, for example in the range of 60% to 95% of the radius, where 0% corresponds to the flange on the blade root. Further embodiments for mounting, positioning and guiding the acceleration signals from the acceleration sensor to the blade root are described below. These embodiments for mounting, positioning and guiding the acceleration signals from the acceleration sensor to the blade root can be used advantageously for all embodiments described here.

10 shows a rotor blade 100 , The rotor blade extends along its length 105 , which corresponds to the radius of the rotor blade, from the blade flange 102 to the blade tip. An acceleration sensor 110 is at a radial position in the area 107 made available. The acceleration sensor may be, for example, a fiber optic acceleration sensor 110 be. A signal line from the acceleration sensor 110 to the blade root is guided along the trailing edge of the rotor blade. For example, the signal line may be an optical fiber 112 be. According to embodiments described herein, the signal line may be within of the rotor blade along the trailing edge, for example in a newly produced rotor blade, or outside the rotor blade along the trailing edge, for example in a profile attached to the trailing edge.

Embodiments of the present invention make it possible to use, retrofit and retrofit acceleration sensors, in particular fiber-optic acceleration sensors or fiber-optical acceleration sensors, near the blade tip, ie in radially outer regions described here in which a rotor blade is not accessible, and / or to take appropriate maintenance measures in the event of repair , Thus, in accordance with the present disclosure, a detailed technical teaching of the design and / or the method for measuring the acceleration in the radially outer regions of a rotor blade described here results. This technical teaching relates on the one hand to the assembly, the guidance of optical fibers, redundant use of components, and / or retrofitting of corresponding sensors, on the other - alternatively or additionally - on the other hand to a data acquisition by means of an analog anti-aliasing filter or an SSI evaluation of the acceleration sensors described here. Thus, in addition to the purely theoretical use of such sensors in radially outer regions of a rotor blade, a technical teaching is made available which allows a practical use of fiber optic acceleration sensors in a radial region of a rotor blade on which the rotor blade is not accessible (for example outer 70%, especially the outer 50%, continue to allow in particular the outer 30% of the radius). Thus, embodiments described herein allow for good use of measurement signals through the described anti-aliasing filters. In addition, alternatively or additionally, the corresponding components can also be technically made available in such a way that the improved control strategies or measurement strategies also have a sufficiently long service life of, for example, more than 20 Years can be made available. Embodiments allow, for example, repair and replacement possibilities, without which the use of acceleration sensors is impractical.

In the area of the blade root is illustrated by the dotted line that according to embodiments described here in a cable laying on the trailing edge of the rotor blade, a puncture is provided in the interior of the rotor blade at a radial position at which the rotor blade is accessible. This may be near the leaf root or at the leaf root. However, it can also be in another radial region of the rotor blade, on which the rotor blade can be walked on.

In the production of new rotor blades may be within the production of a laying of the signal cable, such as the light guide 112 , be made inside the rotor blade, in particular in the rear of the rotor blade. Furthermore, the sensor can also be mounted inside the rotor blade. In particular, the sensor can be provided in a separate chamber. This allows protection against loose glue residue and other contaminants. However, a signal cable such as a light guide can also be guided along the trailing edge, wherein a puncture into the interior of the rotor blade preferably takes place in a walk-on area of the rotor blade. This position of the puncture allows simplified maintenance. For example, in a repair case of an acceleration sensor, the signal line or the optical fiber may be disconnected from a connector that may be provided near the puncture. A signal line provided as a substitute, for example a replacement optical fiber, or an acceleration sensor provided as a substitute can be laid outside in such a case. The original signal line or the original sensor can be abandoned here.

According to further embodiments that can be combined with other embodiments, when retrofitting a sensor, for example for ice detection, the light guide 112 also outside laid. For a retrofitting of a sensor and / or for a subsequent attachment of a light guide, a separate profile can be provided according to embodiments described herein. 11 shows another rotor blade 100 , Here is a profile at the trailing edge of the rotor blade 150 provided so that the light guide 112 can be guided in the profile. According to embodiments described herein which can be combined with other embodiments, the profile has a fixing device for the light guide 112 or a corresponding signal cable, in particular an optical signal cable.

The profile 150 may be, for example, a pultruded profile. The profile may be further adapted to the trailing edge of a rotor blade. It has, for example, a longitudinal extent which corresponds to at least 10% or at least 30% of the radius of the rotor blade. Furthermore, the profile can be provided by segmented elements. For example, multiple segmented elements may extend along at least 10% or at least 30% of the radius of the rotor blade. According to some embodiments that may be combined with other embodiments, the profile may have a constant geometry along its length. It can also be one Geometry, which is designed for different rear edge thicknesses. Furthermore, the profile may optionally be configured to effect aerodynamic improvements of the rotor blade.

As in 11A shown, the profile can 150 at the rear edge 109 the rotor blade are provided. For example, the profile with a fastener 151 be attached to the trailing edge. The profile can by means of an adhesive 152 be provided at the trailing edge. According to some embodiments, the light guide 112 be provided in the adhesive, for example embedded. The light guide 112 runs along the trailing edge 109 of the rotor blade in the profile 150 ,

According to further embodiments, the profile may be an empty channel 153 in order to provide a replacement light guide during maintenance or repair. According to yet further alternative or additional embodiments, the profile 150 a structure 157 for aerodynamic flow control. This can be a gurney flap, for example. The structure 157 is in 11A shown in dashed lines.

12 shows a further optional embodiment that can be combined with other embodiments. Here has the profile 150 at the trailing edge of the rotor blade 100 can be provided, another fastening device for an acceleration sensor 110 , The acceleration sensor 110 can in the profile 150 be made available. This allows a particularly simple retrofitting of an acceleration sensor and the corresponding optical signal transmission in the retrofittable profile at the trailing edge of the rotor blade.

According to one aspect described herein, a profile for the trailing edge of a rotor blade of a wind turbine is provided. The profile includes at least one fastening device for a light guide. Typically, the profile is configured to extend along at least 10% or at least 30% of the radius of the rotor blade. According to further embodiments, which may be combined with other embodiments, the at least one fastening device may be one or more splices. For example, a light guide can be glued into the profile. According to further embodiments, a clamping device for a light guide or an empty channel can be provided as fastening device, through which a light guide can be passed.

According to yet further embodiments, which may be combined with other embodiments described herein, the profile may include a further attachment device for an acceleration sensor. The further fastening device can be provided as a clamping device, thread or screw, and / or by one or more splices. In particular, clamping devices, threads or screws are preferably formed from a non-metallic material. By a profile according to embodiments described here, retrofitting for a rotor blade with an acceleration sensor and a corresponding optical signal transmission can be made particularly easy. Furthermore, the use of non-metallic materials can reduce the risk of lightning or lightning strikes.

13A shows another embodiment that may be combined with other embodiments described herein. The acceleration sensor 110 is in a chamber 162 made available. The light guide 112 is at the trailing edge of the rotor blade 100 guided. The light guide 112 will be in the profile 150 guided along the trailing edge in the direction of the blade root and the blade flange. As another additional option as you in 13B can be shown in an area of transition between the rotor blade 100 and the profile 150 a plug connection 172 to provide. This allows easy replacement of the light guide 112 if it should be changed during maintenance.

With regard to retrofitting, maintenance or replacement of components, it should be noted that fiber-optic acceleration sensors, in particular fiber-optic acceleration sensors, have relatively low maintenance requirements or are relatively robust. For use on wind turbines, however, it should be considered that the operating conditions are extreme due to large temperature fluctuations and / or large accelerations acting on the components, in particular also possibly existing vibrations. Thus, when used in wind turbines, a redundancy of components or the simplified possibility for the exchange of components, in particular advantageous.

14 illustrates the laying of cables, for example the laying of the light guide 112 in a radial region of the rotor blade facing the blade root. These details, configurations, and embodiments of cable routing may be combined with other embodiments. The light guide 112 is along the trailing edge of the rotor blade 100 guided. This can be made possible for example in a profile as described above. A puncture into the interior of the rotor blade is provided. In particular, the radial Position of the puncture be set so that the rotor blade is accessible at the radial position of the puncture. According to further optional embodiments, in the region of the puncture, for example, directly at the puncture or near the puncture in the interior of the rotor blade, another plug connection 174 to provide. A light guide or an optical fiber leads from the connector 174 to a plug 176 at a distributor 510 , for example, a field distributor. Another light guide 512 leads from the distributor 510 to the evaluation unit 114 , For example, the evaluation unit 114 be provided in the hub of the rotor. According to typical embodiments, as may be combined with other embodiments, the light guide may 512 so along a spiral (spring) or by a spiral 513 be guided, which is a rotation of the rotor blade 100 around its longitudinal axis, for example when pitching, not to damage the light guide 512 leads. For a better overview, the light guide 512 in 14 Dashed lines marked by the spring or spiral. An improved discharge of the light guide can be given by the fact that, according to embodiments that can be combined with other embodiments, the light guide parallel to the spiral 513 is guided (symbolized by the dashed line or not explicitly shown).

15 shows by way of example a further embodiment for the use of an acceleration sensor 110 in a rotor blade 100 , The acceleration sensor 110 is in an area near the blade tip 104 made available. Furthermore, inside the rotor blade 100 two light guides led in the direction of the blade root or in the direction of the blade flange. In another chamber 164 , which can be opened during maintenance work, there is a first plug connection 178 and another plug 179 , By using two optical fibers a redundancy can be provided. In case of failure of a light guide, the chamber 164 to be opened and the plug connection 178 the acceleration sensor 110 be solved in order to subsequently the acceleration sensor 110 to the plug 179 to stick. As by the alternatively or additionally provided second acceleration sensor 110 (shown in phantom), additional or alternative redundancy may also be provided with respect to the acceleration sensor. In addition or as an alternative, the failure of an acceleration sensor can be remedied by changing over.

According to still further embodiments, which can be combined with other embodiments, for a repair of a light guide, a light guide laid inside can be abandoned and replaced by a light guide provided in a profile. Furthermore, it is possible to abandon a light guide provided in a profile as part of a repair and to mount another light guide with a further profile on the first profile. According to still further embodiments, an empty channel may be provided both within a rotor blade and / or within a profile. In an empty channel, a light guide can be introduced later. This can be particularly advantageous with a plug connection 174 as you in 14 is shown combined.

The use of an empty channel in a profile or in the interior of a rotor blade may also be advantageous with embodiments of acceleration sensors which, as described above, have a small maximum dimension in a cross section perpendicular to the optical fiber axis. For fiber-optic acceleration sensors with small dimensions in cross-section perpendicular to the optical fiber axis, a replacement optical fiber may optionally be introduced into the empty channel with a replacement acceleration sensor.

According to embodiments described herein, a plurality of uses of acceleration sensors, in particular fiber optic acceleration sensors, such as fiber optic acceleration sensors, described in wind turbines, embodiments by the radial positioning, the structure of fiber optic acceleration sensors, as well as the attachment of acceleration sensors and / or attachment of optical fibers are provided.

According to one embodiment, a method for monitoring a torsional instability of a rotor blade of a wind turbine is provided. A corresponding flow chart is in 16 shown. An acceleration is measured with an acceleration sensor (see reference numeral 962 ), wherein the acceleration sensor is provided at a radial position in the range of the outer 70% of the radius of the rotor blade. Furthermore, the acceleration for generating a signal for flutter warning and / or a signal for instability warning in a torsional bending coupling is evaluated (see reference numeral 964 ). The existence of a torsional instability is recorded or monitored in order to be able to undertake appropriate measures in the regulation of the wind power plant.

According to another embodiment, a method for monitoring a wind turbine is provided. A corresponding flow chart is in 17 shown. A Acceleration is measured with a fiber optic acceleration sensor (see reference numeral 972 ), wherein the acceleration sensor is provided at a radial position in the range of the outer 70% of the radius of a rotor blade of the wind turbine. Further, the acceleration signal of the fiber optic acceleration sensor is filtered with an analog anti-aliasing filter (see reference numeral 974 ).

According to yet another embodiment, a method for monitoring a wind turbine is provided. A corresponding flow chart is in 18 shown. An acceleration is measured with a fiber optic acceleration sensor (see reference numeral 982 ), wherein the acceleration sensor is provided at a radial position in the range of the outer 70% of the radius of the rotor blade, wherein the acceleration sensor is less than 10 wt .-% of metal or contains less than 20 g of metal.

According to yet another embodiment, a method for individual pitch control of rotor blades of a wind turbine is provided. A corresponding flow chart is in 19 shown. The method involves measuring (see reference numeral 992 ) acceleration with an acceleration sensor, wherein the acceleration sensor is provided in a first rotor blade, for example at a position in the region of the outer 70% of the radius. Furthermore, the method includes a pitching (see reference numeral 994 ) of the first rotor blade of the wind turbine by means of the measured acceleration, wherein the pitching takes place in the context of an individual pitch control. The method further includes a high-pass filtering of a signal of the acceleration sensor for determining a time-variable variable, wherein the pitching of the first rotor blade of the wind turbine takes place by means of the time-variable variable.

According to the embodiments described here, a time-variable, high-pass filtered variable is determined from the acceleration signal, which variable is used directly for the individual pitch control. Complex evaluation methods or complicated measuring methods of a plurality of different sizes can be omitted hereby. For a controller, only time-varying, high-pass-filtered quantities are used. These can be determined particularly easily from the acceleration signals in accordance with embodiments described here. These time-variable sizes have the advantage that they are more stable even when using fiber-optic acceleration signals, which may be subject to drift, need calibration or the sensors for the measurement are technically simple. Among other things, complicated integration steps, etc. can be dispensed with here. According to some embodiments that may be combined with other embodiments described herein, the high pass filtering may be performed by forming a time derivative, by high pass filtering, and / or by a Fourier transform. It should be noted here that a time derivative, in particular when selecting suitable coefficients, corresponds to a high-pass filtering or a suppression of changes with low frequencies relative to signal changes with high frequencies. A high-pass signal can thus be regarded as a differentiator, or a time differentiation can be regarded as a high-pass. Thus, for example, the high pass filtering may have a cutoff frequency for signal portions having frequencies greater than the rotational frequency of the rotor. The cut-off frequency may be from 0.3 to 0.5 Hz, in particular wherein the high-pass filtering has a suppression of a signal of 0.2 Hz relative to a signal of 0.6 of at least a factor of 5.

In particular, when combined with a fiber optic acceleration sensor, the method may further include opto-electronically converting the signal of the fiber optic acceleration sensor and filtering the opto-electronically converted acceleration signal with an analog anti-aliasing filter. Thus, a signal is used for the individual pitch control, which is on the one hand high-pass filtered and has also been subjected to analog anti-aliasing filtering. Further time-variable quantities are thus not required for an individual pitch control, even if these could optionally be added to a controlled variable. According to typical embodiments that may be combined with other embodiments described herein, filtering the opto-electronically-converted acceleration signal with the analog anti-aliasing filter may have a cutoff frequency of 10 Hz to 40 Hz, more preferably 15 Hz to 25 Hz.

Methods for individual pitch control are known based on a plurality of different control or measured variables. By using acceleration sensors in a rotor blade, wherein the acceleration sensor is provided at a radial position in the area of the outer 70% of the radius, an acceleration sensor can be used with a signal which is most suitable for individual pitch control. When using the signal of an acceleration sensor, which is provided in a radially outer region of the rotor blade, the sensitivity of the acceleration sensors in this radial region, a improved pitch control can be achieved. In this case, by measuring an acceleration in each case one rotor blade, an individual pitch control can be carried out for each rotor blade.

According to embodiments described here, an individual pitch control is understood to mean a control in which each rotor blade has its own drive for pitch control. For example, shows 5 one drive each 570 that with a control 50 the wind turbine is connected, so that each one drive 570 the rotor blade about an axis 501 can rotate to vary the angle of attack of the rotor blade, ie to pitch the rotor blade. With the individual pitch control every drive can 570 get its own signal for the pitch control, which need not necessarily be identical to the signals of the other drives for the other rotor blades. It is obvious that even with an individual pitch control all rotor blades can be controlled with an identical pitch signal. An individual pitch control, however, is characterized by the fact that it allows deviations between rotor blades in the pitch control.

An individual pitch control can be provided in particular in embodiments in which an acceleration sensor is located in the outer 50% of the radius of the rotor blade, more particularly in a range of 60% to 90% of the radius rotor blade. As in 5 is shown in a rotor blade 101 accelerometer 110 made available. For example, the acceleration sensor may be a fiber optic acceleration sensor or a fiber optic acceleration sensor. The optical signal is transmitted via a light guide 112 to an evaluation unit 114 guided. For example, the optical signal can be sent via a distributor 510 to the evaluation unit 114 be guided. The evaluation unit 114 is with the controller 50 connected to the wind turbine. Based on the signals of the acceleration sensors 110 can be an individual control of the drives 570 for each of the rotor blades 100 to provide. A time-varying quantity determined directly from the acceleration signal is used. A determination of the time-variable quantity directly from the acceleration signal is to be understood as a waiver of integration steps etc. or as a reduction of integration steps, etc.

According to further embodiments, in particular a plurality of acceleration sensors can be used on a rotor blade at a plurality of radial positions.

With regard to the individual pitch control with acceleration sensors, according to one embodiment of a wind turbine is provided. The wind turbine includes a first rotor blade mounted on a hub, a first drive for rotating the first rotor blade for pitch control of the first rotor blade, at least one second rotor blade mounted on the hub, at least one second driver for rotation of the second rotor blade for a pitch control of the second rotor blade, wherein the second drive is controllable independently of the first drive, and a controller for driving at least the first drive. The wind turbine further includes an acceleration sensor, wherein the acceleration sensor is provided at a radial position in the area of the outer 70% of the radius of the first rotor blade, and a measurement signal line for guiding the measurement signal of the acceleration sensor to the controller, wherein the controller and is configured to control a pitching of the first rotor blade by means of a determined time-variable variable.

In such embodiments of wind power plants, the acceleration sensor may be provided in particular in the outer 50% of the radius of the rotor blade, and in particular in a range of 60% to 90% of the radius of the rotor blade. In this case, it is particularly advantageous if the acceleration sensor consists of less than 10% by weight of metal or contains less than 20 g of metal. Such an acceleration sensor may in particular be the fiber-optic acceleration sensor according to one of the embodiments described in relation to FIGS 9A and 9B are described. Furthermore, the acceleration sensor or a light guide for signal transmission of the signal of the acceleration sensor according to one of the embodiments can be provided, as they are with regard to 10 to 15 are described.

According to yet another embodiment, a method for controlling and / or regulating a wind turbine is provided. A corresponding flow chart is in 20 shown. An acceleration is measured with an acceleration sensor (see reference numeral 997 ), wherein the acceleration sensor is provided at a radial position in the range of the outer 70% of the radius of the rotor blade. Furthermore, the acceleration becomes Generation of a signal for blade clearance warning, ie a perception in case of lack of tower clearance of a rotor blade, evaluated (see reference numeral 999 ).

Another aspect of the acceleration sensors described herein at a radial position in the range of the outer 70% of the radius of a rotor blade of a wind turbine relates to the generation of a signal for blade clearance warning or tower release warning. To explain the Turmfreigangs can on 2 Be referred. During the rotation of the rotor, the rotor blades move 100 in a substantially vertically downwardly directed position on the tower 40 past. The minimum distance between the rotor blade, in particular the rotor blade tip 104 , and the tower 40 is called a blade clearance or tower clearance. When falling below a critical value, it is necessary or advantageous to provide a warning signal, since a collision of the rotor blade with the tower can lead to destruction of the wind turbine and / or serious accidents.

According to embodiments described herein, an acceleration sensor may be used to generate a tower release warning signal, particularly when it is provided in the outer 50% of the radius of the rotor blade, more particularly in a range of 60 to 90% of the radius of the rotor blade. In methods for controlling and / or regulating a wind power plant according to these embodiments, the signal of the acceleration is evaluated to generate a signal for blade clearance warning or tower clearance warning. In this case, the signal of the acceleration sensor can in particular be integrated over time, for example integrated twice over time. In addition, by means of a coordinate transformation as in relation to the 8A and 8B is described, whereby gravitational accelerations and other effects can be calculated out, a dynamic load or a dynamic position of the rotor blade, for example, the rotor blade tip, are calculated. It is particularly advantageous if acceleration sensors are provided at a plurality of radial positions in a rotor blade.

According to further embodiments, which can be combined with the embodiments described here, the dynamic load determined with at least one acceleration sensor or the position calculated with at least one acceleration sensor based on the dynamic behavior of the rotor blade can be combined with a static load or a static bending moment , For this purpose, a signal of a strain sensor, which is provided for example in the blade root, can be used. For example, a strain sensor, for example a fiber optic strain sensor, may measure strain in at least one direction along the radius of the rotor blade. By combining a dynamic load and a static load, an improved signal can be provided for warning in case of insufficient tower clearance of a rotor blade.

According to further embodiments, which may be combined with other embodiments described herein, the signal may be used to alert if there is insufficient tower clearance of a rotor blade to control the wind turbine. In this case, in particular, the regulation may consist in a pitch regulation of at least one rotor blade, an adaptation of a generator dividing line of the wind turbine and / or an emergency shutdown of a wind turbine.

With respect to the examples and embodiments described herein, a plurality of embodiments may be described. A first embodiment includes a method for detecting a torsional instability of a rotor blade of a wind turbine. The method includes measuring acceleration with a fiber optic acceleration sensor, wherein the acceleration sensor is provided at a radial position in the range of the outer 70% of the radius of the rotor blade; and evaluating the acceleration to generate a signal for detecting a torsional instability, in particular flutter, and / or a signal for detecting a torsional-bending coupling. According to a second embodiment, a method according to the first embodiment is provided, wherein the signal is guided with an optical fiber to the blade root of the rotor blade, in particular wherein the signal with a light guide, which extends along the trailing edge of the rotor blade is guided. According to a third embodiment, a method for detecting torsional instability of a rotor blade of a wind turbine is provided. The method includes measuring acceleration with a fiber optic acceleration sensor, wherein the acceleration sensor is provided at a radial position in the range of the outer 70% of the radius of the rotor blade, and wherein the signal with an optical fiber to the blade root of the rotor blade, in particular along a trailing edge of the rotor blade extends, is guided; and evaluating the acceleration to generate a signal for detecting a torsional instability, in particular flutter, and / or a signal for detecting a torsional-bending coupling. According to a fourth embodiment, a method according to one of the embodiments 2 to 3 is provided, wherein the light guide is guided in the region of the blade root via a spiral which allows a torsion of the light guide. According to a fifth embodiment, a method according to any one of embodiments 2 to 4 is provided, wherein the light guide is provided on a profile provided at a trailing edge of the rotor blade. According to a sixth Embodiment, a method according to Embodiment 5 is provided, wherein the profile is a pultruded profile and / or wherein the profile causes aerodynamic influence of the rotor blade. According to a seventh embodiment, a method according to one of the embodiments 2 to 6 is provided, wherein the optical fiber is guided from outside into the interior of the rotor blade at a radial position at which the rotor blade is accessible. According to an eighth embodiment, there is provided a method according to Embodiment 7, wherein the optical fiber is connected to a male connector when guided from outside to inside or inside substantially at the radial position. According to a ninth embodiment, a method according to any one of embodiments 5 to 8 is provided, wherein the profile extends along at least 10% or at least 30% of the radius of the rotor blade, in particular wherein one or more segments of the profile along at least 10% or extend at least 30% of the radius of the rotor blade. According to a tenth embodiment, there is provided a method according to any one of Embodiments 5 to 9, wherein the acceleration sensor is provided within the profile or at the trailing edge. According to an eleventh embodiment, there is provided a method according to any one of Embodiments 1 to 10, wherein the acceleration sensor is provided in the outer 50% of the radius of the rotor blade and / or wherein the acceleration sensor is spaced from a torsion axis of 10 cm or more Has. According to a twelfth embodiment, a method according to any of embodiments 1 to 11 is provided, wherein the measured acceleration has a directional component perpendicular to the chord of the rotor blade. According to a 13th embodiment, there is provided a method according to any one of Embodiments 1 to 12, further comprising measuring a sound pressure level on the rotor blade. According to a 14th embodiment, a method according to one of the embodiments 1 to 13, further comprising measuring a temperature, in particular in the acceleration sensor and / or in the light guide is included. According to a 15th embodiment, a method according to one of the embodiments 1 to 14, further comprising at least one strain sensor for measuring a static bending moment, in particular a static torsion, wherein the strain is measured in at least one direction tangential to the torsion axis. According to a 16th embodiment, a method according to any one of embodiments 1 to 15 is provided, wherein the signal for flutter warning and / or a signal for instability warning is used in a torsional bending coupling to a control of the wind turbine, in particular wherein the control in a pitch control of the rotor blade, in an adjustment of a generator characteristic, and / or a shutdown of the wind turbine. According to a 17th embodiment, there is provided a method according to embodiments 1 to 16, wherein the rotor blade includes means for passive load or power control monitored by the detected torsion signal. According to an 18th embodiment, a profile for the trailing edge of a rotor blade of a wind turbine is provided. The profile includes at least a first attachment device for a light pipe, in particular wherein the profile is configured to extend along at least 10% or at least 30% of the radius of the rotor blade, more particularly wherein one or more segments of the profile along at least 10% or extend at least 30% of the radius of the rotor blade. According to a 19th embodiment, the profile according to embodiment 18 is provided, wherein the fastening device comprises one or more splices and / or one or more clamping devices. According to the 21st embodiment, the profile according to one of the embodiments 18 to 19 is provided, the profile further including a further attachment device for an acceleration sensor. According to a 21st embodiment, the profile is provided according to one of the embodiments 18 to 20, wherein the profile further includes a second fastening device for a further optical fiber, in particular wherein the further fastening device is an empty channel includes.

According to a second 20th embodiment, a method for monitoring a wind turbine is provided. The method includes measuring acceleration with a fiber optic acceleration sensor in a rotor blade of the wind turbine; opto-electronic conversion of an acceleration signal of the fiber optic acceleration sensor; and filtering the opto-electronically-converted acceleration signal with an analog anti-aliasing filter. According to a 21st embodiment, a method according to embodiment 20 is provided, wherein the fiber optic acceleration sensor is provided at a radial position in the area of the outer 70% of the radius of the rotor blade, in particular in the area of the outer 50% of the radius of the rotor blade , According to a 22nd embodiment, a method is provided according to one of the embodiments 20 to 21, wherein a signal of the fiber optic acceleration sensor is guided with a light guide to the hub, in particular wherein the light guide is guided in the region of the blade root via a spiral which causes a torsion of the light guide allowed. According to a 23rd embodiment, a method according to embodiment 22 is provided, wherein a Distributor, in particular provided on a blade bulkhead distributor, a plug connection with the light guide provides. According to a twenty-fourth embodiment, there is provided a method according to any of embodiments 22 to 23, wherein the light guide is provided at the trailing edge of the rotor blade, in particular wherein the light guide is provided at a profile provided at a trailing edge of the rotor blade is. According to a 25th embodiment, a method according to embodiment 24 is provided, wherein the profile is a pultruded profile and / or wherein the profile causes aerodynamic manipulation of the rotor blade. According to a 26th embodiment, a method according to one of embodiments 24 to 25, wherein the profile extends along at least 10% or at least 30% of the radius of the rotor blade, in particular wherein one or more segments of the profile along at least 10% or at least 30th % of the radius of the rotor blade. According to a 27th embodiment, a method according to any one of Embodiments 24 to 26 is provided, wherein the acceleration sensor is provided within the profile. According to a 28th embodiment, a method according to one of the embodiments 22 to 27 is provided, wherein the optical waveguide is guided from the outside into the interior of the rotor blade at a radial position at which the rotor blade can be walked on. According to a 29th embodiment, a method according to one of the embodiments 20 to 28, wherein the method further comprises evaluating the acceleration signal using Stochastic Subspace Identification for calculating eigenvalues of the rotor blade. According to the 30th embodiment, a method according to Embodiment 29 is provided, the method further comprising detecting ice formation on the rotor blade by means of the eigenvalues. According to a 31st embodiment, a method according to any one of Embodiments 20 to 30 is provided, the method further comprising measuring a sound pressure level on the rotor blade. According to a thirty-second embodiment, there is provided a method according to any one of Embodiments 1 to 31, wherein the acceleration is measured in a stationary or non-rotating wind turbine. According to a 33rd embodiment, there is provided a method of ice detection on a wind turbine, the method comprising: measuring acceleration with a fiber optic acceleration sensor in a rotor blade of the wind turbine; opto-electronic conversion of an acceleration signal of the fiber optic acceleration sensor; filtering the opto-electronically-converted acceleration signal with an analog anti-aliasing filter; evaluating the filtered acceleration signal using Stochastic Subspace Identification to compute rotor blade eigenvalues; and detecting ice formation on the rotor blade using the eigenvalues. According to a 34th embodiment, a method according to embodiment 33 is provided, the method further comprising: compensating the eigenvalues with at least one measured quantity from the group consisting of: a temperature at the rotor blade of the wind turbine, a wind speed, a power of the Wind turbine, a rotation rate of a rotor of the wind turbine, and a pitch angle of the rotor blade. According to a 35th embodiment, a rotor of a wind turbine is provided. The rotor includes a fiber optic acceleration sensor in a rotor blade of the wind turbine; an opto-electronic converter for changing an acceleration signal of the fiber optic acceleration sensor; and an analog anti-aliasing filter configured to filter the opto-electronically-converted acceleration signal. According to a 36th embodiment, a rotor according to embodiment 35 is provided, wherein the fiber optic acceleration sensor is provided at a radial position in the region of the outer 70% of the radius of the rotor blade, in particular in the region of the outer 50% of the radius of the rotor blade , and wherein a light guide is guided by the fiber optic acceleration sensor to a radial rotor blade position at which the rotor blade is accessible. According to a 37th embodiment, a rotor according to any one of Embodiments 35 to 36 is provided, wherein the acceleration sensor has a maximum extension of 10 mm in a cross section perpendicular to an axis of the optical fiber.

According to a 38th embodiment, a method for individual pitch control of rotor blades of a wind turbine is provided. The method includes measuring acceleration with an acceleration sensor in a rotor blade of the wind turbine; a high-pass filtering of a signal of the acceleration sensor for determining a time-variable variable, and pitching of the first rotor blade of the wind turbine by means of the time-variable variable, wherein the pitching takes place in the context of an individual pitch control. According to a 39th embodiment, a method according to embodiment 38 is provided, wherein the acceleration sensor is provided at a radial position in the area of the outer 70% of the radius of a first rotor blade, in particular wherein the acceleration sensor in the outer 50% of the radius of the Rotor blade, further provided in particular in a range of 60% to 90% of the radius of the rotor blade. According to a 40th embodiment, a method according to any one of embodiments 38 to 39 is provided, wherein the High pass filtering is performed by forming a time derivative, by high-pass filtering, and / or by means of a Fourier transform. According to a 41st embodiment, a method according to any of embodiments 38 to 40, wherein the high-pass filtering has a cut-off frequency of 0.3 to 0.5 Hz, in particular wherein the high-pass filtering is a suppression of a signal of 0.2 Hz relative to a signal of Has 0.6 of at least a factor of 5. According to a 42nd embodiment, a method according to any one of Embodiments 38 to 41 is provided, wherein the acceleration sensor is a fiber-optic acceleration sensor; and wherein the method further includes: opto-electronically converting the signal of the fiber optic acceleration sensor; and filtering the opto-electronically-converted acceleration signal with an analog anti-aliasing filter. According to a 43rd embodiment, a method according to embodiment 42 is provided, wherein the filtering of the opto-electronically converted acceleration signal with the analog anti-aliasing filter has a cut-off frequency of 10 Hz to 40 Hz, in particular from 15 Hz to 25 Hz , According to a 44th embodiment, a method according to one of the embodiments 42 to 43 is provided, wherein the signal is guided with an optical fiber to the hub, in particular wherein the optical fiber is guided in the region of the blade root via a spiral which allows a torsion of the optical fiber , According to a 45th embodiment, a method according to embodiment 44 is provided, wherein the light guide is provided at the trailing edge of the rotor blade, in particular wherein the light guide is provided at a profile provided at a trailing edge of the rotor blade. According to a 46th embodiment, a method according to embodiment 45 is provided, wherein the profile is a pultruded profile and / or wherein the profile causes an aerodynamic influence of the rotor blade. According to a 47th embodiment, a method according to any one of embodiments 45 to 46 is provided, wherein the profile extends along at least 30% of the radius of the rotor blade, in particular wherein one or more segments of the profile extend along at least 30% of the radius of the rotor blade extend. According to a 48th embodiment, a method according to any of embodiments 45 to 47 is provided, wherein the acceleration sensor is provided within the profile. According to a 49th embodiment, a method according to one of the embodiments 44 to 48 is provided, wherein the light guide is guided from outside into the interior of the rotor blade at a radial position at which the rotor blade is passable. According to a 50th embodiment, a wind turbine is provided. The wind turbine includes a first rotor blade mounted on a hub; a first drive for rotating the first rotor blade for pitch control of the first rotor blade; at least a second rotor blade mounted on the hub; at least one second drive for rotating the second rotor blade for a pitch control of the second rotor blade, wherein the second drive is controllable independently of the first drive; a controller for driving at least the first drive; a first acceleration sensor in the first rotor blade of the wind turbine; Means for high pass filtering a signal of the first acceleration sensor to determine a time variable variable; and a controller, wherein the controller is configured to control pitching of the first rotor blade using the time-varying amount. According to a 51th embodiment, a wind turbine according to embodiment 50 is provided, wherein the acceleration sensor is provided at a radial position in the range of the outer 70% of the radius of a first rotor blade, in particular wherein the first acceleration sensor in the outer 50% of the radius of the rotor blade, further provided in particular in a range of 60% to 90% of the radius of the rotor blade. According to a 52nd embodiment, the wind turbine according to one of the embodiments 50 to 51, wherein the acceleration sensor to less than 10 wt .-% of metal or contains less than 20 g of metal. According to a 53rd embodiment, the wind turbine according to one of the embodiments 50 to 52 is provided, wherein the wind turbine further includes: a light guide, wherein the acceleration sensor is a fiber optic acceleration sensor and the light guide is guided from the acceleration sensor to a radial rotor blade position, on the the rotor blade is accessible. According to a 54th embodiment, a wind turbine according to Embodiment 53 is provided, wherein the acceleration sensor has a maximum extension of 10 mm in a cross section perpendicular to an axis of the optical fiber. According to a 55th embodiment, there is provided a wind turbine according to any one of embodiments 53 to 54, wherein the light guide is provided at the trailing edge of the rotor blade, in particular wherein the light guide is provided at a profile provided at a trailing edge of the rotor blade is. According to a 56th embodiment, a wind turbine according to embodiment 55 is provided, wherein the profile is a pultruded profile and / or wherein the profile is configured to effect aerodynamic manipulation of the rotor blade. According to a 57th embodiment, a wind turbine according to embodiments 55 to 56 is provided, wherein the profile extends along at least 30% of the radius of the rotor blade, in particular wherein one or more segments of the profile extend along at least 30% of the radius of the rotor blade. According to a 58th embodiment, a wind turbine according to any of embodiments 55 to 57 is provided, wherein the first acceleration sensor is provided within the profile.

Although the present invention has been described above by means of typical embodiments, it is not limited thereto, but modifiable in many ways. Also, the invention is not limited to the applications mentioned.

Claims (15)

 A method of monitoring a wind turbine, comprising: Measuring an acceleration with a fiber optic acceleration sensor in a rotor blade of the wind turbine, wherein the acceleration sensor is less than 10 wt .-% of metal or contains less than 20 g of metal.  Method according to claim 1, wherein the acceleration sensor is available at a radial position in the region of the outer 70% of the radius of the rotor blade, in particular in the outer 50% of the radius of the rotor blade, in particular in a range of 60% to 90% of the radius of the rotor blade is placed.  Method according to one of claims 1 to 2, wherein the acceleration sensor is a fiber optic acceleration sensor and wherein the signal is guided with an optical fiber to the hub, in particular wherein the optical fiber is guided in the region of the blade root via a spiral which allows a torsion of the optical fiber.  A method according to claim 3, wherein a distributor, in particular a distributor provided on a sheet bulkhead, provides a plug-in connection with the light guide.  Method according to one of claims 3 to 4, wherein the light guide is provided at the trailing edge of the rotor blade, in particular wherein the light guide is provided at a provided at a trailing edge of the rotor blade profile.  A method according to claim 5, wherein the profile is a pultruded profile and / or wherein the profile causes aerodynamic influence of the rotor blade.  Method according to one of claims 5 to 6, wherein the profile extends along at least 10% or at least 30% of the radius of the rotor blade, in particular wherein one or more segments of the profile extend along at least 10% or at least 30% of the radius of the rotor blade.  Method according to one of claims 5 to 7, wherein the acceleration sensor is provided within the profile.  Method according to one of claims 3 to 8, wherein the light guide at a radial position at which the rotor blade is accessible, is guided from the outside into the interior of the rotor blade.  A method according to any one of claims 1 to 9, wherein the acceleration measured with a fiber optic acceleration sensor is evaluated to generate a tower release warning signal.  A rotor blade of a wind turbine, comprising: a fiber optic acceleration sensor, wherein the acceleration sensor is less than 10% by weight of metal or contains less than 20 g of metal.  The rotor blade according to claim 11, wherein the fiber optic acceleration sensor is provided at a radial position in the area of the outer 70% of the radius of the rotor blade, in particular in the area of the outer 50% of the radius of the rotor blade, and wherein a light guide from the fiber optic acceleration sensor to is guided to a radial rotor blade position at which the rotor blade is accessible.  The rotor blade according to claim 12, wherein the acceleration sensor has a maximum extension of 10 mm in a cross section perpendicular to an axis of the optical fiber.  A fiber optic acceleration sensor comprising: a light guide having a light exit surface; a membrane; a mass associated with the membrane; an optical resonator formed between the light exit surface and the diaphragm; and a mirror provided in the beam path between the light exit surface and the diaphragm, the mirror being formed at an angle of 30 ° to 60 ° relative to an optical axis of the light guide.  The rotor blade according to any one of claims 11 to 13, wherein the fiber optic acceleration sensor is a fiber optic acceleration sensor according to claim 14.

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