Wind turbine control based on noise emission measurement by pressure sensors on rotor blades

Description

TECHNICAL FIELD

[0001] The application is in the field of wind turbine technology. In particular, the present application discloses systems and methods for measuring with sensors for improved prediction and evaluation of wind flows in wind energy generation systems. TECHNICAL BACKGROUND

[0002] Wind turbines are exposed to winds with varying characteristics, which strike the rotor blades from different directions and with varying strengths. Under these varying wind conditions, the wind turbines convert kinetic energy extracted from the wind into electrical energy and feed it into a power grid. When converting wind energy into electrical energy, the wind turbines are operated at different operating points depending on the wind conditions and a predetermined electrical power to be fed in. Each operating point is determined in particular by a blade pitch angle and a set generator torque.

[0003] An operating point is set as ideally as possible to enable efficient operation while ensuring a long service life and, increasingly, maintaining low operating noise. Efficient means, in particular, generating the highest possible energy from the available wind. Operating noise, which is primarily caused by turbulence on the rotor blades, must be minimized, especially if the wind turbine is located near residential areas, so that residents are not disturbed by the noise of the wind turbine's rotor blades.

[0004] Due to various constraints, wind turbines are therefore not operated at the physically possible power limit for most of the time.

[0005] The limitation in the generation of energy by a wind turbine is due, among other things, to limitations of the electrical grid, for example the risk of overload due to an excess of energy fed into or present in the grid, bird and bat protection, shadows, or in particular noise emissions.

[0006] Specifically, the power output of wind turbines is limited by noise emissions. More precisely, the limitation is achieved by controlling the wind turbine based on the initially measured noise emissions under its respective operating conditions. In many cases, the turbine is shut down unnecessarily early because the control system is designed rather conservatively to avoid exceeding the threshold values. Furthermore, wind direction and noise propagation are not taken into account, resulting in further unnecessary restrictions.

[0007] There are various approaches to optimizing wind turbine noise emissions. This primarily involves optimizing operating points to minimize noise emissions. For this purpose, operating points with minimal emissions are determined on test turbines and the wind turbines are controlled accordingly during operation. This essentially involves adjusting the rotor speed and pitch angle.

[0008] US20070031237A1, for example, shows a control concept for optimized sound emission based on microphones in the near field of wind turbines in an entire wind farm. This can derive a far-field sound using mathematical models. The wind farm can be optimized accordingly based on the actual measurements from the microphones. However, this measurement does not refer to the direct sound generator, namely the rotor or rotor blade. The sound emission is measured only in the vicinity of the sound generator, and conclusions are drawn from this.

[0009] US 2017 / 191464 A1 is another relevant prior art document.

[0010] Until now, noise emission compliance has been achieved through a control system based on a prior determination of the maximum noise emission. The potential for static or dynamic optimization of wind turbines during operation has not been utilized.

[0011] It is therefore advantageous to provide a device and a method that avoids the aforementioned disadvantages and enables better detection of noise emissions from rotor blades of wind turbines and allows optimized operation of a wind turbine, in which shutdown, i.e. the worst case scenario during operation, advantageously only occurs in exceptional cases, when unavoidable. SUMMARY

[0012] In a first aspect according to claim 1, a measuring device for determining sound emissions from one or more rotor blades of a wind turbine is disclosed. The measuring device has at least one sensor, preferably at least two sensors, which are adapted to detect vibrations on one or more rotor blades and provide a result as a signal. The at least one sensor is mounted flush with the surface of the rotor blades.

[0013] In a further aspect according to claim 6 of the present application, a rotor blade of a wind turbine with a measuring device according to one or more aspects of the application is disclosed, wherein the measuring device is designed to transmit measured and analyzed data to a control device.

[0014] A further aspect according to claim 8 discloses a method for determining sound emissions at one or more partial surfaces of a rotor blade surface of a wind turbine (WTG). The method can include, among other things, determining vibrations at one or more partial surfaces of the rotor blade surfaces. It can further include evaluating the vibrations determined at the one or more partial surfaces and subsequently analyzing which frequency range generates sound waves and acts as a sound source on the rotor blade surface. Furthermore, the intensity of one of the calculated or determined sound sources can be compared with predetermined values, and, if necessary, the method can subsequently initiate appropriate measures at the WTG.

[0015] In yet another aspect according to claim 11 of the application, a wind turbine with a measuring device according to aspects of the application is disclosed. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In the figures illustrating the revelation shows: Fig. 1a: a rotor blade, according to one or more embodiments, with embedded sensors in a side view; Fig. 1b: a rotor of a wind turbine according to one or more embodiments; Fig. 2: a rotor with sound emission sources on blade surfaces and influence on residential buildings; and Fig. 3: a flowchart of one or more embodiments of the method. DESCRIPTION OF THE EMBODIMENTS

[0017] Until now, noise sources were not measured directly on the rotor blade. Local measurement provides a much more detailed picture of the noise sources for control purposes aimed at suppressing noise emissions and their propagation. Furthermore, knowledge of the noise sources allows for the development of more intelligent control concepts for noise reduction.

[0018] The localization of sound sources can also facilitate maintenance and elimination of the sound source through repair measures, as the search is much easier.

[0019] In a first aspect, a measuring device for determining noise emissions from one or more rotor blades of a wind turbine is disclosed. The measuring device ( Fig. 1a) can contain at least one sensor 120 adapted to detect vibrations on one or more rotor blades 110 and provide a result as an electronically processable signal 125; wherein the at least one sensor 120 is mounted flush with a surface of the rotor blade(s) 110. Preferably, at least two sensors, preferably pressure sensors, are installed in a rotor blade. Since the sensors are inexpensive and reliable due to their design, more than two sensors can preferably be installed in the rotor blades, which increases the measurement accuracy. Fig. 1b shows a rotor 115 with three rotor blades 115. Pressure sensors 120 are embedded at the tips of each rotor blade.

[0020] By using pressure sensors on the blade surface of wind turbines, the sound sources can be measured locally. Typically, pressure sensors covering relevant frequency ranges are installed near the trailing edge and the blade tip, as these are the dominant sound sources of a wind turbine. Alternatively, microphones can be used. The microphones can be arranged in addition to the pressure sensors or instead of them. The processing circuits and devices are designed to also work with the signals emitted by the microphones.

[0021] In a further embodiment, a measuring device according to further aspects of the application is disclosed. In particular, the sensor for the measuring device can be a fiber optic pressure sensor.

[0022] Due to the exposed location of the pressure sensors on the rotor blades, they are exposed to extreme environmental conditions and loads. Fiber optic pressure sensors can be advantageously used in this case. Fiber optic pressure sensors are known as such and are disclosed, for example, in DE 10 2014 210 949 A1.

[0023] These fiber optic sensors have the additional advantage that they are inherently electromagnetically compatible, allow long signal transmission paths without interference from, for example, electromagnetic fields, are very lightweight, do not corrode, and are highly robust against other environmental influences such as humidity, temperature, and overpressure.

[0024] The fiber optic pressure sensor can preferably be installed flush with the surface of the rotor blade in order to have as little influence as possible on the aerodynamics and aeroacoustics of the rotor blade.

[0025] In a further embodiment, a measuring device is disclosed, wherein the at least one sensor can be mounted on a blade tip and / or on a blade trailing edge. Advantageously, pressure sensors covering the relevant frequency range can be installed near the blade trailing edge and the blade tip. The dominant sound sources of a wind turbine are preferably located in these areas.

[0026] In another aspect of the application, a measuring device according to one or more further aspects of the application is disclosed, wherein the measuring device may include a data processing device. The data processing device may be adapted to analyze the sensor signal for vibrations. The data processing device may have an input for receiving optical data. Preferably, the data from the optical sensors is transmitted to the data processing device via optical conductors.

[0027] In a further embodiment of the measuring device according to one or more further aspects of the disclosure, the data processing device can be adapted to determine sound emissions at the rotor blade surface. The data processing device of the measuring device can thus include a computer-aided analysis unit. This analysis unit can be designed to evaluate the data received from the sensors using various algorithms and to analyze them for specific frequencies.

[0028] A further embodiment according to one or more aspects of the application relates to a measuring device, wherein the data processing device can be further adapted to determine a point or location of the sound emissions on the rotor blade surface. Advantageously, the data processing device of the measuring device can be adapted so that the data from various sensors (more than one sensor) can be used to determine where on the blade sources of sound emissions may be located.

[0029] According to a further aspect of the application, the data processing device in the measuring device can be further adapted to determine a far-field of the sound emissions at a predetermined distance from the wind turbine. The behavior of the sound propagation at a corresponding distance, e.g., when the wind turbines are located near residential units, can thus be determined.

[0030] Inclusion of wind direction, wind speed and wind turbine azimuth provides a sound emission rose around the wind turbine.

[0031] By measuring, for example, precise measurements of sound sources using sensors and / or microphones, the wind turbine's noise emissions can be regulated rather than simply controlled. This offers great potential for the operation of wind turbines and entire farms, since, especially in densely populated areas, power curtailment and thus a reduction in the AEP can be achieved primarily through noise restrictions.

[0032] Fig. 2shows a wind turbine with noise sources 210 located on the rotor blades. These can be caused, for example, by damage to the blade surface or simply by partial vibrations of surface areas. A rotor blade as such is not a rigid structure, but can have vibration modes at different locations. Residential building 230 is located in a far field and is hit by sound waves 240. If it is calculated that the far field of sound at building 230 is too high (there are legal requirements that wind turbines must meet), appropriate measures are initiated to counteract the noise.

[0033] For example, the wind turbine tower can be rotated far enough out of the wind 220 that a calculated far-field of sound no longer reaches the residential building, or at least only in a weakened form. A similar effect can be achieved by adjusting the angle of the rotor blades. Reducing the speed of the turbine's rotor can also be considered as a measure to reduce noise emissions. For this purpose, a load on the generator can be adjusted accordingly.

[0034] At the same time, it can be ensured that this corrective measure is only implemented to the extent that the turbine still generates as much wind energy as possible. Thus, this application enables the optimization of each individual turbine.

[0035] In addition, systems can be monitored even more effectively, and immediate remedial measures can be initiated in the event of stochastically occurring strong noise sources, such as damage. For example, a sudden change in noise emissions under otherwise identical or similar ambient conditions could indicate a defect in the turbine's blades or the turbine itself.

[0036] A further aspect of the present application relates to a rotor blade of a wind turbine having a measuring device according to one of the preceding aspects. The measuring device can advantageously be designed to transmit measured and analyzed data to a control device. Such a control device does not necessarily have to be present in the wind turbine itself, but can also be arranged externally. The measurement data can be transmitted from the measuring device to the control device using known data transmission methods.

[0037] For example, a wind turbine equipped with a measuring device according to the invention can transmit the measured values ​​to directly adjacent turbines that do not have a corresponding measuring device. Advantageously, the data is only transmitted to turbines, preferably of the same or similar design, which can be assumed to produce similar noise emissions under similar wind or operating conditions.

[0038] The goal is for each rotor to have its own sensor array and thus its own measuring device. This allows each individual wind turbine to be controlled completely independently of other systems.

[0039] A further aspect of the present application discloses a rotor blade of a wind turbine having a measuring device according to one or more aspects, wherein the control device 140 of the measuring device can be designed to control an angular adjustment of the rotor blade and to change parameters of the wind turbine, for example a pitch angle of the blade, until predetermined requirements regarding sound emission are met or are met again.

[0040] In the rotor blade, see Fig. 1aThe signal 125 from the sensors 120, which are flush with the rotor blade surface, is preferably transmitted via optical (fiber) cable to the evaluation unit and analyzed using algorithms. The results are transmitted to the control device 140, which can then control actuators such as 150 (blade pitch) or 160 (rotor direction). The control device 140 can also be capable of shutting down the turbine if the noise emission requirements cannot be met otherwise.

[0041] In another aspect of the application, see Fig. 3 A method for determining sound emissions at one or more partial surfaces of a rotor blade surface of a wind turbine is disclosed.

[0042] The method may include, among other things: a determination 310 of vibrations on one or more partial surfaces of the rotor blade surfaces. An evaluation 320 of the vibrations determined on the one or more partial surfaces and a subsequent analysis 330 may be performed to determine whether a specific vibration / frequency range generates sound waves and acts as a sound source on the rotor blade surface.

[0043] A comparison 340 of the intensity of a detected sound source with predetermined values ​​can be performed. If predetermined values ​​regarding the intensity of sound radiation are exceeded, appropriate measures can be initiated at the wind turbine, such as adjusting the rotor blade angle or turning the rotor out of the wind.

[0044] In a further embodiment, a method for determining noise emissions according to one or more of the aforementioned aspects is disclosed, wherein measures that can be taken can be, for example, an adjustment of the angles of the rotor blades or a shutdown of the wind turbine.

[0045] The goal is to avoid shutting down the system and thus preventing a loss of energy production. Therefore, shutting down the system is only an option if optimizations of noise emissions from the rotor blades or the wind turbine itself are unsuccessful and permanent, predetermined limits are exceeded.

[0046] In another aspect of the application, the method for determining noise emissions according to one or more of the aforementioned aspects can be carried out continuously in order to achieve permanent noise optimization of the wind turbine. Thus, once a particularly low-noise operating position of the turbine is reached, e.g., by changing the blade angle, the data supplied by the sensors continues to be analyzed and evaluated. If it is determined over time that the sound radiation from the wind turbine is deteriorating, i.e., that specified maximum values ​​are exceeded, measures are taken to reduce the noise, for example, by adjusting the blade angle again.

[0047] Only if control measures do not result in an improvement in noise emissions, for example if there is damage to the system, e.g. to the rotor blades, and limit values ​​are exceeded on a permanent basis, will the wind turbine in question be shut down.

[0048] The advantage is that the measuring device according to the invention allows individual systems to be examined without affecting the yield of other systems, as was previously the case with a general measurement using, for example, microphones in the far field of the systems.

[0049] A further aspect of the present application discloses a wind turbine with a measuring device according to one or more of the aforementioned aspects and embodiments.

[0050] In yet another aspect, according to further aspects of the invention, the wind turbine can contain a computer program product that can be loaded into a memory of a digital computing device and includes software code sections with which steps according to one or more of the remaining aspects can be carried out when the computer program product is running on the computing device. Furthermore, a computer program product is proposed that can be loaded directly into a memory, for example a digital memory of a digital computing device. In addition to one or more memories, a computing device can contain a CPU, signal inputs and signal outputs, as well as other elements typical of a computing device. A computing device can be part of an evaluation unit, or the evaluation unit can be part of a computing device.A computer program product may include software code portions that at least partially execute the steps of the methods of the embodiments described herein when the computer program product is running on the computing device. Any embodiments of the method may be executed by a computer program product.

[0051] The present disclosure discloses a measuring device that can determine acoustic emissions from rotor blades in the near and far fields. Fiber optic pressure sensors are used, which are preferably installed flush with the blade surface.

[0052] The presented measuring device and method offers various advantages for wind turbines:

[0053] The control of the wind turbine can be adjusted to the actual permitted maximum limit with regard to noise emissions by measuring the radiated noise.

[0054] The sound emission can be measured using local pressure measurements (aerodynamics and aeroacoustics) on the rotor blades in the extreme near field, rather than using remote microphones. This allows for more precise measurements and the basis for further calculations, as the sound sources on the rotor blades can be directly identified.

[0055] The measuring device according to the invention enables high-resolution detection of noise sources on a single rotor blade and even segments of the rotor blade, thus enabling optimized control concepts for noise reduction and far-field dissipation. In other words, optimized values ​​can be determined that allow the wind turbine to meet legal requirements regarding noise protection while simultaneously ensuring optimized power output to the power grid. Because this occurs continuously, optimization can be achieved even with changing parameters.

[0056] Furthermore, the measuring device according to the invention can enable the detection of unexpected noise sources caused, for example, by erosion and structural damage, and thus improve the monitoring of the condition of rotor blades.

[0057] Although the present invention has been described above using typical embodiments, it is not limited thereto but can be modified in a variety of ways. Nor is the invention limited to the aforementioned possible applications.

Claims

1. A measuring device for determining sound emissions on one or more partial surfaces on one or more rotor blades (110) of a wind turbine, comprising: at least one pressure sensor and / or a microphone (120) on at least one of the rotor blades (110); wherein the at least one pressure sensor and / or the microphone (120) is mounted flush with a surface of the rotor blades (110); a data processing device (130) which is configured to analyze the signal of the at least one pressure sensor and / or microphone (120) for sound emissions; characterized in that the data processing device (130) is further configured to determine a far field of the sound emissions at a predetermined distance from the wind turbine while taking wind direction, wind speed, and the azimuth of the wind turbine into account.

2. The measuring device according to claim 1, wherein the at least one pressure sensor and / or microphone (120) is configured to detect sound emission at one or more of the rotor blades (110) .

3. The measuring device according to claim 1 or 2, wherein the pressure sensor (120) is a fiber optic pressure sensor.

4. The measuring device according to any one of the preceding claims, wherein the at least one pressure sensor and / or microphone (120) is attached to a blade tip and / or to a blade trailing edge.

5. The measuring device according to any one of the preceding claims, wherein the data processing device (130) is configured to determine sound emissions at the rotor blade surface.

6. A rotor blade of a wind turbine with a measuring device according to any one of the preceding claims, wherein the measuring device is designed to transmit measured and analyzed data to a control device (140).

7. A rotor blade of a wind turbine with a measuring device according to any one of the preceding claims, wherein the control device is designed to control an angle adjustment of the rotor blade (110) and to change a pitch angle of the rotor blade (110) or to change an angle of the rotor (125) relative to incident wind until predetermined requirements with regard to sound emission are met.

8. A method for determining sound emissions on one or more partial surfaces of a rotor blade surface of a wind turbine with a measuring device according to any one of claims 1 to 6, comprising: determining (310) sound emission at one or more partial surfaces of the rotor blade surfaces by means of at least one pressure sensor and / or microphone; evaluating (320) the sound emission determined at the one or more partial surfaces; determining one or more setpoints for operating parameters based on the evaluated sound emission; and controlling the wind turbine on the basis of one or more setpoints.

9. The method for determining noise emissions according to claim 8, wherein measures can be an adjustment of the rotor blades (110), a reduction in the speed of the rotor, or a shutdown of the wind turbine.

10. The method for determining noise emissions according to any one of claims 8 or 9, wherein the method steps are carried out continuously in order to achieve permanent noise optimization of the wind turbine.

11. A wind turbine with a measuring device according to the preceding claims.

12. The wind turbine according to claim 11, further comprising: a computer program product which can be loaded into a memory of a digital computing device and comprises software code portions that carry out the steps according to any one of claims 8 to 10 when the computer program product is running on the computing device.