WO2009033472A2

WO2009033472A2 - Wind turbine and method for operating a wind turbine

Info

Publication number: WO2009033472A2
Application number: PCT/DE2008/001519
Authority: WO
Inventors: Edwin Becker; Johann Lösl
Original assignee: Prüftechnik Dieter Busch AG
Priority date: 2007-09-14
Filing date: 2008-09-11
Publication date: 2009-03-19
Also published as: DE102008023109A1; DE112008003090A5; WO2009033472A3

Abstract

The invention relates to a wind turbine comprising a rotor (10) having a hub (12) and at least two blades (14) that have respective liquid tanks (34) or that are firmly connected to at least one liquid tank each, an imbalance sensor (30, 52), a control unit (44) for continuously detecting an imbalance of the rotor from the signal of the imbalance sensor, at least one liquid reservoir (42), and a transfer system (36, 38, 40, 46, 48, 50), suitably controlled by the control unit, for transferring liquid between the liquid reservoir or the liquid reservoirs and the liquid tanks when the rotor rotates depending on the detected imbalance to continuously minimize the imbalance of the rotor.

Description

Wind energy plant and method for operating a wind energy plant

The present invention relates to a wind turbine and a method for operating a wind turbine.

Wind turbines typically include a rotor with a hub and three rotor blades mounted in horizontal alignment in a nacelle, one of which

Rotor driven generator houses and rotatably mounted on a tower. In the

Usually, the rotor blades are adjustably mounted on the rotor hub to control the angle of attack of each individual rotor blade separately. In the current research is even considered, too

Parts of the rotor blade to be adjusted separately. By such an adjustment of the angle of attack (also called pitch angle), the speed of the rotor can be controlled.

Wind turbines are generally susceptible to vibration, in particular due to imbalances of the rotor. The imbalances occurring essentially have the following causes: on the one hand, mass imbalances, in particular due to unequal rotor blade masses or unequal mass distributions in the individual rotor blade, hub unbalance, eccentricities of the complete rotor, ice accumulation on the rotor blades, water penetration into the interior of the rotor blades, and on the other aerodynamic imbalances, especially due From blade angle errors, unequal rotor blade profile shapes, rotor blade damage, oblique flow of the rotor and location-based suggestions from the outside, eg turret buildup and the fact that wind speed usually depends on altitude above ground so that one and the same rotor blade is subject to different aerodynamic forces, depending on whether it is straight down or up. Such imbalances lead to increased wear of the wind turbine. Minimizing the imbalance of the rotor is therefore desirable.

To determine the mass imbalance of the rotor, i. the balancing quality of the rotor, usually test weights, which are typically lead belt or steel plates, attached by means of tension straps on the rotor blades, then from the comparison of vibration measurements without or with the test weights the balancing quality of the rotor (im

State without test weights) is determined. A disadvantage of using this type of

Test weights is the relatively complex assembly and disassembly of the test weights. An overview of the vibration problem in wind turbines can be found, for example, in the magazine telediagnose.com, issue no. 12, at www.telediagnose.com/telediagnose/index.html. In DE 102 19 664 Al a wind turbine is described in which sensor elements are provided for determining mechanical loads of the rotor on the rotor blades and on the rotor shaft in order to adjust the rotor blades on the basis of the determined mechanical loads. The sensors provided on the rotor shaft serve to detect pitching and yawing moments. Furthermore, the rotor blades may be provided with ballast tanks for pumping water from a storage tank provided in the hub into the ballast tanks or discharging water from the ballast tanks into the storage tank to minimize any possible rotor imbalance by re-trimming. While the filling of the ballast tanks is also possible during operation, the rotor must be stopped in the appropriate position to discharge a ballast tank.

From DE 10 2004 014 992 Al a wind energy plant is known, in which an unbalance sensor is provided for determining the imbalance of the rotor and the rotor blades are provided with adjustable in the axial direction Auswuchtgewichten, which are adjusted according to the determined imbalance to the imbalance of the rotor to minimize.

In US 5,140,856 a wind turbine is described in which at the bearing of the rotor shaft, a piezoelectric sensor is provided which can measure vibrations in the range of 1 Hz to detect Rotorunwuchten.

GB 2 319 812 A discloses an aircraft turbine in which the blades are provided with chambers into which liquid can be selectively introduced from a hoop-like ring via valve-controlled supply lines, wherein the ring co-rotates and from a stationary line via a stationary line Reservoir is filled with liquid. The selective filling of the chambers with liquid serves to compensate for an imbalance caused by damage or loss of one of the turbine blades, wherein the occurrence of an imbalance is detected by means of a vibration sensor arranged on the turbine housing.

In WO 01/98745 A1 an aircraft propeller is described in which the propeller shaft is provided with liquid reservoirs between which liquid can be selectively pumped back and forth to balance the system, with imbalances being detected by detecting vibrations. In WO 2006/054828 A1, EP 0 732 574 A2 and EP 0 325 521 Bl, centrifuges with balancing chambers are described, which can be filled selectively with liquid for balancing the centrifuge.

It is an object of the present invention to provide a wind turbine with a rotor in which imbalances can be minimized at any time as effectively as possible. It is a further object of the invention to provide a corresponding method for operating such a wind energy plant.

These objects are achieved by a wind turbine according to claim 1 and a method according to claim 27. In the solution according to the invention is advantageous in that the rotor imbalance is continuously detected during operation of the wind turbine and liquid depending on the detected imbalance in the operation of the Rotor is transferred into or out of the liquid tank in or on the rotor blades, the imbalance of the rotor can be continuously minimized and so the wear of the wind turbine can be reduced.

It is also an object of the present invention to provide a method for operating such a wind turbine, wherein the balancing quality of the rotor can be determined in a simple manner.

This object is achieved by a method according to claim 29. It is advantageous that the use of externally attached to the rotor blades liquid tanks in comparison to the use of lead belts or steel plates simplified assembly and disassembly of test weights for determining the balancing quality of the rotor can be achieved. Thus, especially during disassembly, the liquid can be drained from the tanks safely and thus the dismantling can be simplified and accelerated. By attaching the liquid tanks externally to the rotor blades, the constructive additional expenditure associated with the solution proposed with integrated tanks in DE 102 19 664 A1 can be avoided.

Preferably, the rotor imbalance is detected by means of a vibration sensor arranged on the hub main bearing, which is preferably an accelerometer, or by means of a two-axis inclinometer, which detects the inclination of the wind turbine and can be arranged in the nacelle or at the top of the tower. Preferred embodiments of the invention will become apparent from the dependent claims.

In the following the invention will be described by way of example with reference to the accompanying drawings. Showing:

Fig. 1 is a schematic example of a wind turbine according to the invention;

Fig. 2 is a block diagram of the essential components of the wind turbine of Fig. 1;

3 shows a schematic view of an alternative embodiment of the liquid tank of a wind turbine according to the invention in longitudinal section; and

Fig. 4 is a view like Fig. 3, wherein a further alternative embodiment of the liquid tank is shown.

FIG. 1 shows a schematic example of a wind energy plant according to the invention. In this case, a rotor 10 is provided with a hub 12 for three rotor blades 14 (only two of which are shown in FIG. 1). The rotor 10 is mounted in a horizontal orientation in a nacelle 16 which accommodates a generator 18 which is driven by the rotor shaft 20 via a gearbox 22. The nacelle 16 is rotatably mounted on a tower 24 about a vertical axis. The nacelle further includes a sensor 26 for wind speed and wind direction. In addition, a sensor 28 for detecting the rotational speed of the rotor 10 is provided. At the hub main bearing, a vibration sensor 30 is provided as the unbalance sensor, which is preferably designed as a piezo sensor and which is capable of vibrations at very low frequencies, i. in the range of 0.1 to 5 Hz. Basically come as unbalance sensors all suitable for measuring imbalances sensors in question, in particular force measuring devices, such as load cells, and strain gauges.

The rotor blades 14 are each adjustable by means of a blade adjustment 32 about its longitudinal axis with respect to the hub 12 in order to realize a pitch adjustment of the rotor blades 14 in the usual way. Preferably, each rotor blade 14 is adjusted individually.

In each rotor blade 14 at least one liquid tank 34 is provided, which via lines

36 is connected to a manifold assembly 38. The manifold assembly 38 is connected to a

Pump 40 in communication, which in turn is connected to a liquid reservoir 42. The manifold assembly 38, the pump 40 and the liquid reservoir 42 are in the hub 12 fixed with respect to the hub 12 and rotate accordingly in the operation of the rotor 10 with. Further, a control unit 44 is provided to control the pump 40 and the manifold assembly 38, respectively. The liquid may be, for example, water, if necessary with the addition of antifreeze, for example glycol.

2, a block diagram of the components of FIG. 1 is shown.

The signal of the vibration sensor 30 is supplied to the control unit 44 in order to continuously determine the unbalance of the rotor 10 from the vibration signal, wherein the rotor speed detected by the speed sensor 28 is preferably taken into account in order to sort the vibration signal at the corresponding speed range and to be able to evaluate the speed. The measurement period for the vibration measurement by means of the vibration sensor 30 is typically in the range of minutes and is preferably at least one minute. Further, the control device 44 preferably has an input for the blade adjustment 32 and an input for the wind sensor 26. From the determined rotor imbalance, possibly taking into account the blade adjustment 32 and the signals of the wind sensor 26, the controller 44 generates a control signal for the of the Pump 40 and the distributor 38 formed liquid transfer assembly to selectively transfer liquid between the liquid reservoir 42 and the liquid tank 34 in response to the detected unbalance to continuously minimize the imbalance of the rotor 10.

The pitch adjustment 32 takes into account as input signals, inter alia, the signals of the wind sensor 26 and the speed sensor 28 and an output signal of the control unit 44, which is representative of the detected rotor imbalance. In this way, the blade adjustment 32 of the speed control and can also assist in the compensation of imbalances of the rotor 10. In this case, a smoothing of the dynamics of the blade adjustment is made possible by the described pumping of liquid into or out of the tanks 34.

The electrical supply to the co-rotating pump 40 is preferably via a slip ring (not shown).

In the embodiment of the tanks 34 shown in Fig. 1, the supply / discharge line 36 is respectively connected to the rotor hub 12 far end of the tank 34, whereby when rotating the rotor 10 not only the possibility of liquid supply to the tanks 34, but also the possibility of liquid discharge from the tanks 34 is ensured at all times, because due to the centrifugal force always liquid at the rotor hub 12 far end of the tank 34 is present, even if the tank 34 contains little liquid and air is in the system. Basically, in such an embodiment, the tank 34 may be formed with rigid walls or bag-like with flexible walls.

In principle, one single tank 34 or even several such tanks can be provided per rotor blade 14. Likewise, instead of a single storage reservoir 42, a plurality of such reservoirs may also be provided. Furthermore, instead of a pump 40 provided in common for all tanks 34, a separate fluid pump may also be provided, for example for each of the rotor blades 14 or for each of the tanks 34. The manifold assembly 38 may take the form of a block, as shown in FIG. be realized as a three-way valve, also by separately controlled valves in each of the supply lines / leads 36.

In Fig. 3 is a modification of the liquid tank 34 is shown, wherein a two-chamber system is shown with a pressurized air from a compressed air source 46 to be acted upon via a line 48 balloon-like bag 50 in the tank 34; In this case, the liquid level in the tank 34 is controllable by the pressure in the compressed air bag 50. The outer walls of the tank 34 may be rigid. With such an embodiment, u.U. even dispensed with a liquid pump, since when filling the tank 34 due to the centrifugal liquid would flow on lowering the air pressure in the bag 50 by itself and when draining the tank 34 by increasing the air pressure in the bag 50 liquid from the tank 34 could be pressed. In the embodiment shown in FIG. 3, the fluid tube 36 is shown as being connected at the near-end of the tank 34.

In Fig. 4 an alternative embodiment of the tank 34 is shown, wherein the tank 34 is formed as a two-chamber bag, which has a flexible outer skin, which surrounds the compressed air bag 50 and applies in the liquid-filled state to the inner wall of the rotor blade 14.

According to a modification of the previously described embodiments, the liquid tanks 34 are not arranged in the interior of the leaves 14, but they are on the

Outside of the blades 14 mounted, e.g. in the form of fluid bags, by means of

Tension straps are attached to the respective sheet. This solution is especially as Retrofit already existing wind turbines of interest, since an arrangement of the tanks inside the sheets already in the construction of the wind turbine must be considered.

Such a design with liquid tanks to be mounted on the outside of the rotor blades is not only for the continuous automatic described so far

It is also suitable for minimizing the total imbalance of the rotor, but it is also particularly suitable for a discontinuous determination of mass imbalance, i. the balancing quality (residual imbalance) of the rotor, in existing wind turbines, optionally followed by a discontinuous minimization of certain residual imbalance suitable. Such a discontinuous determination or minimization of the residual imbalance is usually of

Service technicians made at certain intervals.

In this case, the rotor blades must be provided on the outside in each case with at least one liquid tank, wherein temporary imbalance conditions are generated by means of liquid in the liquid tank, and wherein by means of an arranged on the hub main bearing unbalance sensor measuring signals are detected in a frequency range of 0.1 to 5 Hz to off To determine the balancing quality of the rotor the temporary unbalance states of the rotor. By varying the total amount of liquid attached to the respective rotor blade, different temporary unbalance states can thus be generated in a simple manner, which are required for determining the mass imbalance of the rotor.

In this case, the mass imbalance can be minimized by means of suitable test masses in the form of liquid in the tanks, the tanks then remain with the determined optimum level on the rotor blades and the rotor is operated in this state. For this purpose, the balancing quality is determined in each case for different temporary unbalance states of the rotor produced by means of liquid in the liquid tank, and that of the temporary unbalance states with the lowest balancing quality is selected for the operation of the wind energy plant.

As already mentioned, the process, i. Determining the balancing quality or minimizing the balancing quality at regular intervals, eg. B once a year, be repeated.

Advantageously, the liquid tanks are filled in the mounted on the leaves state by means of a transfer arrangement from a liquid reservoir with liquid. The Liquid reservoir can be provided in the nacelle or on the ground, for example as a tank in a truck, wherein the transfer arrangement expediently corresponding lines, eg in the form of a tube. The imbalance sensor can be part of a hand-held device that the service technician carries with him.

The liquid tanks are preferably liquid sacks which are fastened to the respective rotor blade by means of tension straps.

According to a modification of the previously described embodiments, the detection of the imbalance of the rotor 10 instead of means of the hub main bearing 21 arranged vibration sensor 30 by means of a biaxial inclinometer 52 for determining the inclination of the wind turbine can be determined. It is preferably an inclinometer that can be read out electrically or electronically so that its signals can be processed by the control device 44. A rotor imbalance inevitably causes a corresponding periodic change in the inclination of the wind turbine during operation of the system, so that can be deduced from the measurement of the inclination of the wind turbine by means of the inclinometer 52 on the rotor imbalance. The inclinometer 52 may be disposed on the nacelle 12 or on the top of the tower 24. Preferably, the inclinometer 52 is MEMS-based.

Basically, a combination of vibration measurement and inclination measurement is conceivable for detecting the rotor imbalance.

Claims

claims

Wind turbine with a rotor (10) having a hub (12) and at least two blades (14), each having at least one liquid tank (34) or fixed to at least one liquid tank, an unbalance sensor (30, 52), a Control unit (44) for continuously detecting an imbalance of the rotor from the signal of the imbalance sensor, at least one liquid reservoir (42), and a controlled by the control unit transfer arrangement (36, 38, 40, 46, 48, 50) for transferring liquid between the liquid reservoir or the liquid reservoir and the liquid tanks with a rotating rotor in response to the detected unbalance to continuously minimize the imbalance of the rotor.

2. Wind turbine according to claim 1, further provided with an arrangement (32) for adjusting the angle of attack of each rotor blade (14), wherein the control unit (44) is adapted to the transfer arrangement (36, 38, 40, 46, 48, 50 ) depending on the angle of attack of each rotor blade.

3. Wind turbine according to claim 2, characterized in that the arrangement (32) for adjusting the angle of attack of each rotor blade (14) is designed to operate in dependence on the detected by means of the control unit (44) unbalance.

4. Wind turbine according to one of the preceding claims, characterized in that an arrangement (28) for detecting the rotor speed is provided to take into account the rotor speed when detecting the rotor imbalance from the signal of the imbalance sensor (30, 52).

5. Wind turbine according to one of the preceding claims, characterized in that the at least one liquid reservoir (42) fixed with respect. The rotor hub (12) is formed in or on the rotor hub.

6. Wind energy plant according to one of the preceding claims, characterized in that the transfer arrangement (36, 38, 40, 46, 48, 50) has at least one liquid pump (40).

7. Wind turbine according to one of the preceding claims, characterized in that for each rotor blade (14) has its own liquid pump (40) is provided.

8. Wind energy plant according to one of claims 1 to 6, characterized in that for each liquid tank (34) its own liquid pump (40) is provided.

9. Wind energy plant according to one of claims 1 to 6, characterized in that a common liquid pump (40) is provided, which is connected downstream of a distribution valve arrangement (38).

10. Wind turbine according to one of the preceding claims, characterized in that the liquid pump (s) (40) fixed with respect to. The rotor hub (12) is arranged in or on the rotor hub or are.

11. Wind turbine according to one of the preceding claims, characterized in that a slip ring for the electrical supply of the liquid pump (s) (40) is provided.

12. Wind turbine according to one of the preceding claims, characterized in that the transfer arrangement (36, 38, 40, 46, 48, 50) has a gas filled with controllable pressure bag (50) in each liquid tank (34).

13. Wind energy plant according to claim 12, characterized in that each liquid tank (34) is rigid-walled, wherein the liquid level in the liquid tank by the pressure in the gas-filled bag (50) is controllable.

14. Wind turbine according to claim 12, characterized in that each liquid tank (34) has a flexible outer skin, which surrounds the gas-filled bag (50).

15. Wind energy plant according to one of the preceding claims, characterized in that each liquid tank (34) at its rotor hub (12) far end is provided with a liquid with the reservoir (42) or one of the liquid reservoir in communication liquid connection (36).

16. Wind turbine according to one of the preceding claims, characterized in that the control arrangement (44) is formed to the transfer arrangement (36, 38, 40, 46, 48, 50) in dependence on the rotor speed, the wind speed and / or the wind direction to control.

17. Wind energy plant according to one of the preceding claims, characterized in that the unbalance sensor (30) is arranged on the hub main bearing (21).

18. Wind turbine according to claim 17, characterized in that it is the unbalance sensor is a vibration sensor (30), in particular a piezoelectric sensor.

19. Wind turbine according to one of claims 1 to 16, characterized in that it is the unbalance sensor is a biaxial inclinometer (52) for determining the inclination of the wind turbine.

20. Wind turbine according to claim 19, characterized in that the inclinometer (52) is arranged on the nacelle (12) or on the upper part of the tower (24).

21. Wind turbine according to claim 19 or 20, characterized in that the inclinometer is electrically or electronically readable.

22. Wind energy plant according to one of claims 19 to 21, characterized in that the inclinometer (52) is formed on a MEMS basis.

23. Wind energy plant according to one of claims 1 to 18, characterized in that the unbalance sensor (30, 52) operates in a frequency range of 0.1 to 5 Hz.

24. Wind energy installation according to one of the preceding claims, characterized in that the liquid tanks (34) are each arranged in the interior of the respective blade (14).

25. Wind turbine according to one of claims 1 to 23, characterized in that the liquid tanks (34) are each mounted on the outside of the respective sheet (14).

26. Wind turbine according to claim 25, characterized in that it is the liquid tanks to liquid bags, which are fastened by means of tension straps on the respective sheet.

27. A method for operating a wind turbine with a rotor (10) having a hub (12) and at least two blades (14), each having at least one liquid tank (34) or fixed to at least one liquid tank, an imbalance sensor (30, 52), at least one liquid reservoir (42), and a transfer arrangement (36, 38, 40, 46, 48, 50), wherein by means of the unbalance sensor measuring signals are detected and continuously an imbalance of the rotor is determined and wherein with rotating rotor means the transfer assembly liquid is transferred between the liquid reservoir and the liquid reservoir and the liquid tank to continuously minimize the imbalance of the rotor.

28. The method according to claim 27, characterized in that the imbalance measurement period for continuously detecting the rotor imbalance is at least one minute in each case.

29. A method for operating a wind energy plant with a rotor (10) having a hub (12) and at least two blades (14), wherein at least one fluid tank is attached to the outside of the blades, an imbalance sensor (30, 52) is arranged, Temporary imbalance conditions are generated by means of liquid in the liquid tank, and by means of the unbalance sensor measuring signals are detected in order to determine the balancing quality of the rotor from the temporary imbalance states of the rotor.

30. The method according to claim 29, characterized in that the liquid tanks are mounted in the attached state to the leaves by means of a transfer arrangement from a liquid reservoir with liquid.

31. Method according to claim 29, wherein the balancing quality is determined for different temporary unbalance states of the rotor produced by means of liquid in the liquid tanks, and the one of the temporary unbalance states with the lowest balancing quality is selected for the operation of the wind energy plant.

32. The method according to any one of claims 27 to 31, characterized in that the unbalance sensor (30) for vibration measurement at the hub main bearing (21) is arranged.

33. The method according to any one of claims 27 to 31, characterized in that the unbalance sensor (52) is arranged as a biaxial inclinometer (52) for determining the inclination of the wind turbine at the top of the tower or on the nacelle of the wind turbine.

34. The method according to any one of claims 27 to 32, characterized in that the unbalance sensor (30) operates in a frequency range of 0.1 to 5 Hz.