WO2016091254A1

WO2016091254A1 - Method for the reduction of aerodynamic imbalances of wind turbines

Info

Publication number: WO2016091254A1
Application number: PCT/DE2015/100527
Authority: WO
Inventors: Mathias Hillmann; Thomas Rische; Erik Miersch; Sirko Bartholomay; Burkhard Cerbe
Original assignee: Cp.Max Rotortechnik Gmbh & Co.Kg
Priority date: 2014-12-09
Filing date: 2015-12-09
Publication date: 2016-06-16
Also published as: DE112015005527A5

Abstract

The invention relates to a method for reducing the aerodynamic imbalance of a wind turbine when the rotor rotates, wherein, in the context of an oscillation measurement in the original state, an original axial oscillation of a rotor (2) is determined with an oscillation amplitude â_ur,ax and a phase angle φ_υr,ax, whereupon by adjusting a blade setting angle of at least one rotor blade (7) an aerodynamic imbalance is caused in terms of location and size with a resulting total blade pitch angle change α_pitch,test and a resulting phase angle φ(α_pitch,test); subsequently, a single oscillation measurement is carried out again in the test state for determining an axial oscillation with an oscillation amplitude â_test,ax and a phase angle φtest,ax > which allow the determination of an axial balancing pointer with the amount ẑ_tarier,ax and phase change Δφ and a tare value tarn while taking into account the original axial oscillation, followed by the determination of a necessary blade pitch angle change α_pitch,korr and a phase angle φ_korr, on which the blade pitch angle change α_pitch,korr has to be made, in order to correct the original aerodynamic imbalance, including a vectorial allocation of the blade pitch angle change α_pitch,korr to at least one rotor blade (7).

Description

Method for reducing aerodynamic imbalances of

Wind turbines

The invention relates to a method for reducing aerodynamic imbalances of wind turbines. Wind turbines, also referred to as wind power converters or wind turbines, are available in various designs, in particular concerning the design of the rotor. The rotor is crucial for the mechanical efficiency of the wind turbine. The present invention is a design of a known wind turbine with horizontal rotor axis, in particular with three-blade rotor. However, an application of the present invention can also be made for designs with more rotor blades or even two leaves. The rotor blades of modern wind turbines have aerodynamically carefully optimized wings, which not only maximize the efficiency and thus the energy yield, but at the same time minimize the noise. The wings consist of perpendicular to the blade axis arranged profiles, which are each rotated by a twisting angle.

In particular, the invention relates to wind power plants which have an adjustment mechanism of the rotor blades about their respective longitudinal axis (pitch mechanism). Such a rotor blade is constantly adjusted in operation by the plant control to an optimum pitch angle to ensure the necessary torque. An important investigation, which is the basis for the correct setting in operation, is the measurement of the blade pitch. Here, the pitch angle of 0 ° is specified at standstill of the system control. The angle measured in this state will be referred to as the blade pitch. If this angle deviates from the manufacturer's specification, this is called an absolute error of the blade pitch angle. If the blade pitch angles of the individual rotor blades differ from one another, this is a relative error or a deviation in the synchronous position.

The state of the art is to set the rotor blades of a wind turbine as optimally as possible synchronously: By a correspondingly optimal synchronous position of the rotor blades of a wind turbine with respect to the zero degree Blateinstellwinkel the occurrence of an axial unbalance vibration is prevented. So far, rotor blades are adjusted by means of a marking scale in the flange area. In some cases, the setting of the rotor blades is also measured separately (usually photometrically or by means of a laser method). According to the guideline of Germanischer Lloyd (2010), the synchronicity of the three rotor blades of a wind turbine must be in the range of +/- 0.3 ° (total 0.6 °). It is believed that this accuracy is sufficient to prevent the occurrence of significant aerodynamic imbalances. However, this method is based on the assumption that the deviation of the zero grade blade angle adjustment is the dominant cause for aerodynamic imbalances.

The theoretical maximum of the achievable power is the Betz power factor. This value is 59.3%. Wind turbines that meet the state of the art, already achieve values of about 50%, so that the physically possible is largely exhausted. The further optimization aims u.a. It is to largely eliminate inhomogeneities in circulation, ie mass-related or even aerodynamic imbalances of the rotor. It is therefore an effort of the experts to recognize, to take exclusively influence on the rotor, to bring the rotor blades in an optimal position and thus to achieve the vibration-free concentricity with maximum energy yield. The low-vibration concentricity of the rotor requires both low aerodynamic imbalances, ie axial and radial vibrations, as well as low mass-related (usually radial) imbalances.

The mass imbalance is determined by the well-known, cross-disciplinary expertise by a series of measurements, consisting of a primitive course and a test run with mounted on the rotor, known in place and size test mass. The result is the size and location of a required balance weight.

Mass imbalances lead in particular to a radial oscillation, ie perpendicular to the rotor axis. Aerodynamic imbalances, caused by different pitch angles of the rotor blades, twisting errors, profile deviations, pitch errors, defective flow elements or damage to the blade surface, lead to axial, torsional but also to lateral (radial) excitations of the gondola tower vibrations. Mass or aerodynamic imbalances can lead to increased wear of all components of a wind turbine. In addition, incorrectly adjusted blade angles can ultimately lead to losses in the production of electrical energy. While the mass imbalance is therefore well manageable in practice, the aerodynamic imbalance, the cause of which are different contributions of the individual blades to the torque of the rotor, still causes problems and must be reduced by matching the individual powers of the rotor blades to each other.

To achieve this goal at least partially have already tried the solutions according to the publications DE 100 32 314 C1 and DE 10 2008 013 392 A1. Both solutions are looking for a way to the best possible synchronous position of the individual rotor blades to each other in the hope that they then take over the same proportions of torque. While DE 100 32 314 C1 determines the position of the leaves by means of a distance measurement by means of laser distance measurement from the tower, this is done according to the document DE 10 2008 013 392 A1 by measuring the distance from the nacelle, the trailing edge of the vane being measured and thus closed at an angular position becomes.

However, such a determination presupposes a perfect equality with exactly matching aerodynamic properties. This is hardly to be expected since, in particular, very long rotor blades have slight differences in twisting and / or curvature due to unavoidable tolerances in the production process. These are already sufficient to have different aerodynamic properties. Thus, a satisfactory result can not be achieved in the manner described above.

This deficiency is able to partially solve the solution shown in document DE 196 28 073 C1. There, the contribution of the individual sheet to the torque is determined by the power output by the generator, which varies over the revolution of the rotor. It is a time-resolved power measurement. By adjusting the rotor blades by means of random adjustment and checking the result can be achieved that the differences between the individual sheets are minimized in terms of their performance.

With this measure, axial vibrations are detected and eliminated, as well as related radial vibrations are reduced. An actual detection of axial or radial vibrations is - despite the high cost of the empirical method - not possible. These can thus not be excluded in such a way. Consequently, by a solution according to DE 196 28 073 C1 no satisfactory results in the Elimination of vibrations in the rotor can be achieved, even if a mass imbalance was previously remedied in a conventional manner. A remaining aerodynamic imbalance can neither be specifically detected nor successfully eliminated.

Other methods are also based on photometric analysis of leaf position or on laser measurement. A photometric analysis is used in the method according to document WO 2009/129 617 A1. This method provides that the blade angles are determined by analyzing prominent points on the blade surface.

Laser methods go have been described, for example, in the previously mentioned documents DE 10 2008 013 392 B4 and DE 100 32 314 C1. These methods are based on measuring the tracking of all three blades and then calculating the respective blade angles from the measured data.

Surveying tower-nacelle oscillations in practice, however, has shown that the correction of blade angles based solely on an optical process is not always sufficient to reduce aerodynamic imbalances. In particular, in the case of rotors with a very large diameter, moreover, it has been shown that the mere adjustment of the rotor blades to the measured values of one of the optical methods described above gives insufficient results.

At the same time, the use of a method that measures only the tower-gondola vibration and does not visually control the blade angles, may result in a low-vibration rotor, but in underachievement of the equipment due to blade pitch errors of one or more rotor blades. This results from the fact that the manufacturer specified blade angle adjustment is not controlled in such an approach. Thus, only the synchronous position, but not a correct setting of the absolute Blateinstellwinkel would be guaranteed.

According to the present state of the art, it is indeed possible to free the rotor of a wind turbine in the axial and radial directions from imbalances. However, it is possible under certain circumstances, for example, in case of errors in the twisting of the leaves or other geometrical deviations, that the known methods are not sufficient to adjust the rotor with low vibration. Under these conditions an extension of the procedures would be necessary, for which however the state of the art offers neither practical suggestions nor suitable suggestions for a finding of a solution. Various documents, such as. For example, US 8 360 722 B2 and US 2009 0 035 136 A1, determine the vibrations directly on the bending of the shaft or the power at the generator. These procedures are inaccurate or require considerable effort to achieve reasonable accuracy. The document US 2012 0 183 399 A1 proposes to carry out an initial measurement and then to adjust a rotor blade, which leads to a defined aerodynamic imbalance, and to determine the result obtained by the adjustment by means of a test measurement. Adjustment and test measurement are performed at least twice in order to be able to determine empirically from the results in a numerical method or according to a table of values, how an adjustment of the rotor blades must ultimately be carried out in order to reduce the aerodynamic imbalance. This process is inaccurate and at the same time complex, because to achieve an adequate accuracy in the reduction of the aerodynamic unbalance, a multiplicity of measuring cycles becomes necessary.

Existing methods are at least very expensive in order to achieve a higher accuracy.

Object of the present invention is therefore to provide a method by which the absolute pitch adjustment and the synchronous position of the rotor blades of a wind turbine optimizes and at the same time vibrations in the radial and axial directions can be minimized. The object is also to offer a particularly simple and quickly feasible method for reducing aerodynamic imbalance.

The object is achieved by a method for reducing an aerodynamic imbalance of a wind turbine.

In fact, it has surprisingly been found that significant aerodynamic imbalances occur even in the case of wind power plants with very large rotor diameters even with very small deviations in synchrony (<0.1 °) (see exemplary embodiment). This is due to the fact that low fault tolerances in production, ie, for example, deviations in the twist course or the geometry (thickness, etc.) lead to aerodynamic imbalances. Therefore, examining the zero grade blade pitch angle at only one radial position (blade flange or optical method) is often not sufficient for large diameter wind turbines. To remedy this problem, the inventive test pitch method has been developed.

As part of a vibration measurement in the original state, an initial axial vibration of a rotor of the wind turbine is determined, the original axial vibration has a vibration amplitude ä _X and a phase angle φ _υΓιβχ at rotational frequency (1 P). 1 P means the first order of a Order spectrum, related to the rotor speed. An order analysis in the present case is to be understood as the analysis of the vibrations of rotating machinery. In contrast to the frequency analysis, the energy content of the vibration is not plotted against the frequency but above the order. The order is a multiple of the speed. For example, a motor turns at 3000 revolutions per minute, which corresponds to a mains frequency of 50 hertz for a two-pole AC or three-phase motor. The first order is then at 50 Hz, the second order at 100 Hz, the third at 150 Hz, etc. The determined oscillation amplitude of the axial oscillation of a rotor of the wind turbine is thus a 1 P oscillation amplitude for _X.

The vibration measurement is performed with the rotor rotating, preferably at a constant speed.

After the vibration measurement in the original state, an aerodynamic imbalance defined with regard to location and size is produced by adjusting a blade pitch angle of at least one rotor blade resulting in a total _{blade pitch change} a _pitchi test and resulting phase angle φ (apitcn, test) as a test condition. Only then is a single new vibration measurement, now in the test state, to determine an axial vibration with vibration amplitude ä _{test ax} and phase angle (p _{test X} at rotational frequency (1 P), taking into account the original axial vibration determination of an axial tare with magnitude z _iarieoax and phase change Δφ and a tara value tarn The tare value tara represents the relationship between the At the same time, this represents the great advantage of the method according to the invention in that surprisingly high accuracy is achieved in minimizing the axial oscillation. At the same time the effort for this is very low, since only a vibration measurement in the original state and a vibration measurement in the test state are needed. This is made possible by employing a method for determining a necessary blade _{pitch change pitch: corr} and a phase angle (p _com according to the following method step This determination is made in an analytical method in contrast to the numerical methods known from the prior art As a result, no further measurements are necessary for determining values for the numerical calculation and the effort for the adjustment is greatly reduced, the availability of the wind energy plant is increased.

The subsequent method step is thus the determination of a necessary blade _{pitch change} a _pit ch, corr and a phase angle (p _corr at which the blade _{pitch change} a _{pitch: corr} is to be corrected to correct the original aerodynamic imbalance, including a vectorial mapping of the blade _pitch angle change a _pit The result of this method, contrary to the prior art, is not necessarily the same zero-degree setting angle of the rotor blades, but, under certain circumstances, a small deviation between the blades, which is determined mathematically by the aforementioned analytical method has been.

As soon as the determined correction values on the rotor blade or on the rotor blades are set, when the determined blade pitch change a _pit ch, corr is situated between two rotor blades, the aerodynamic imbalance is eliminated. This can optionally be confirmed by a control measurement.

In addition to a correction point lying outside of the rotor blade, the adjustment of a plurality of rotor blades can also be advantageous if an optimization with regard to efficiency and concentricity can thereby be achieved. Thus, for example, an equally good result can be achieved in the concentricity by either one or more blades are adjusted. Now you can decide between the variants based on the better efficiency. For example, promises the adjustment of two rotor blades better efficiency than the adjustment from only one rotor blade, the first variant is chosen. It may be necessary to test both variants in practice and to check the result.

The procedure for eliminating an axial aerodynamic imbalance is therefore summarized as follows:

Measurement of the original unbalance vector with oscillation amplitude and phase angle axial: {ä _{ur ax} , cp _ur , ax}

Setting a specific angle value for test pitch measurement on a rotor blade (0.1 to 2.0 ° recommended): a ₀ °, pitch, test

after adjustment: measurement of a test vector with altered blade angle on at least one blade with oscillation amplitude and phase angle axially:

vectorial determination of the tare pointer with amplitude and phase angle axial:

° " ^z {tarier, ax> ^ taricr, ax}

Tar Utest Uur

° ^z tarier, ax ^- { ^a test, ax> Ψίεεί, Βχ} ^- { ^a ur, ax> ΨΙΙΓ, ΒΧ}

• Determination of the tare value:

, ^ O-.pitch.test

o tara = -

· Determination of required blade _{pitch change} : a _{pitch korr} = tara * _{aur ax}

• phase angle change (location where the blade pitch change must be made) Δφ = cp (a ₀ °, pitch, test) + <(a _U r, axAarier, ax)

• Since the location of the sheet pitch change is not necessarily at the position of a sheet, the sheet pitch change must be converted to the adjacent sheets: a a a

For a better understanding of the vectors and formula symbols, reference is made to FIG. 2 and the setting and measured values shown there.

Further advantages accrue from an embodiment of the method according to the invention in which prior to the oscillation measurement in the original state an analysis of blade angle settings of all rotor blades, followed by correction of the blade angle settings, with the result of the synchronous position of the rotor blades to each other and the set absolute blade pitch of all Rotor blades. This can be assumed in the subsequent minimization of the aerodynamic imbalance of an optimal blade angle position, which deviates only by a minimum of the aerodynamic optimal position by the necessary adjustment in the context of reducing the imbalance.

A further embodiment of the method additionally provides a documenting vibration measurement before the vibration measurement in the original state and the correction of the blade angle settings.

The corrected blade position usually results in an optimal efficiency of the rotor, so that the wind, the maximum amount of energy can be removed. But at least there is a clearly defined blade angle adjustment of all rotor blades after the correction of the blade angle adjustment. From this defined blade angle setting should be assumed to compensate for any remaining aerodynamic imbalances, in order to deviate as little as possible from the optimal setting and thus have to accept the smallest possible loss of efficiency due to necessary corrections of the blade position.

The analysis of the actual leaf position in all alternative methods requiring such an analysis is preferably carried out by a photometric analysis on the one hand or a distance measurement between at least one point on each rotor blade and a fixed point on the wind turbine or in the vicinity thereof. In the photometric analysis, the rotor blade is photographically recorded at a standstill, preferably with the tip down, while a profile marked at a certain point or prominent points are imaged. By comparing the recordings thus obtained with a desired position known as optimal, an approximately existing correction requirement with respect to the desired setting angle can be determined and the correction subsequently made.

Another possible type of analysis is the distance measurement between at least one point on each rotor blade and a fixed point on the wind turbine, such as the tower or the nacelle or any other suitable fixed point in the vicinity of the wind turbine. The distance measurement itself is carried out a known manner with a measuring beam, such as by means of ultrasound or, more preferably, laser beam. The sheet passing the measuring beam is scanned in its profile and the result is recorded for comparison. Besides Further suitable types of analysis of the actual leaf position according to the invention are provided.

As an alternative to the documentary vibration measurement and the analysis of the blade angle settings of all rotor blades for their correction, it is provided according to a further embodiment of the method according to the invention, without prior correction of the blade angle settings aerodynamic imbalance defined by location and size by adjusting a blade pitch of at least one rotor blade resulting in Gesamtblatteinstellwinkeländerung _{p / icii} test and resulting phase angles (p (a _{pITCH test)} cause. This adjustment is based on an analysis of the blade angle settings of all rotor blades, with changes of at least one blade angle setting which test a Gesamtblatteinstellwinkeländerung a _pitchi and a resultant phase angle <p (a _P uch Thus, the upstream documenting vibration measurement is unnecessary and also eliminates the correction of the blade angle settings of all rotor blades lt - but without sacrificing an optimal correction of the aerodynamic imbalance. Since, according to this variant of the method, there is also clarity about the blade angle adjustment of each rotor blade, this can be taken into account in the correction of the aerodynamic imbalance and the blade position can be corrected so that existing misalignments are simultaneously corrected towards an absolute blade angle adjustment.

It is achieved with the aforementioned method variants that before the vibration measurement in the original state, an analysis of blade angle settings of all rotor blades and then either a correction of the blade pitch takes place. This is done in such a way that the setting for all rotor blades has the same blade pitch or an adjustment of a blade pitch on at least one rotor blade for generating a defined aerodynamic imbalance in the vibration measurement in the test state, wherein selection of the blade to be adjusted and adjustment of its blade pitch to a Approximation to that adjustment of the rotor blades leads, in which all rotor blades have the same blade pitch. Also when adjusting the blade angle to correct the aerodynamic imbalance, this aspect is given appropriate attention. As an alternative to a determination of a necessary change in the blade _pitch α _ρΛο ^ _οπ by a measuring method, it is also provided according to the invention that in an alternative _{embodiment of the} method according to the invention the Gesamtblatteinstellwinkeländerung _{pitch: test} without application of an optical method in particular, but solely on the basis of a manual estimation based method is determined. This has the advantage that neither measuring devices must be used, nor can corresponding measuring errors have an adverse effect on the result of the entire method. In addition, the procedure is simplified and the working time is shortened.

Preferably, in the vibration measurement in the original state and the vibration measurement in the test state, an axial vibration is determined. Such a measurement is simple and feasible with cost-effective measurement technology. Alternatively, and particularly preferably, the vibration measurement in the original state and / or the vibration measurement in the test state are performed as a combined vibration measurement, wherein at least one radial and one axial vibration are determined. As a result, it can be determined whether there is additionally a mass-related imbalance after correction of the aerodynamic imbalance. This would then have to be determined and eliminated in a conventional way. This is preferably done by attaching a test mass to remedy after calculating the location and size of the imbalance by a balancing mass.

First, however, it is about the determination of the axial vibration, wherein preferably in the determination of the axial tare and the tare value tara the axial component from the combined vibration measurement flows.

It is necessary to perform the vibration measurement with rotating rotor, which preferably rotates at a constant speed.

It is also advantageous, during a final vibration measurement in the final state to determine a remaining radial vibration, which is subsequently eliminated after determining the location and size of the causative mass imbalance by means of at least one balancing mass. This serves to comprehensively optimize the smooth running of the rotor, regardless of the specific cause, since mass imbalances by considering the radial vibrations be determined and also this radial vibration is significantly influenced by an aerodynamic imbalance.

It is also favorable if at least one radial oscillation amplitude and one radial oscillation phase angle as well as an axial oscillation amplitude and an axial oscillation phase angle can be determined within the scope of the combined oscillation measurement. Then a complete picture of the vibration conditions on the rotor is obtained and a detailed assessment of the situation becomes possible. In any case, with these values, the imbalance or the respective prevailing vibration state can be completely described and, if it is the test measurement, the necessary countermeasures can be defined.

In the context of the method described above, the method according to the invention is carried out as an on-site maintenance or repair. In systems that can adjust the zero degree pitch angle but software side or control side, this method is in a particularly advantageous manner but also independently of the software or control of the wind turbine possible. The prerequisite for the automated variant of the method according to the invention described below is thus that the blade pitch (zero degree angle or offset) of the system via the controller is automatically adjustable and not manually-mechanically by service teams on site.

Furthermore, can be counteracted by the integration of the method according to the invention in the system control the normal wear on the elements of the Blattverstellmechanismus. This wear results in the problem of durability of the described exact setting, as change with increasing wear and parameters. By repeating the procedure at regular intervals, a permanent solution is thus available to eliminate or reduce aerodynamic imbalances of wind turbines.

The setting for the low-vibration state can be used as a starting point to correct ground imbalances. On the other hand, this state is the optimal starting point for optimizing performance. In an iterative process, the blade angles can then be adjusted in the total offset and the resulting power curve thereby optimized. Based on the implementation of the method according to the invention by a maintenance expert, the method according to the invention for the removal of aerodynamic imbalances is to be integrated automatically into the control of a system.

In addition, it is also provided within the scope of the invention to carry out mass balancing by measuring a tower damping or a phase difference between oscillation amplitude and position of the imbalance (static moment).

The method according to the invention in the automated method variant is characterized by the following sequence:

1. Wind energy plant measures during operation or in load-free operation (generator-free) automatically by suitable sensors, the axial gondola vibration (Urmessung).

2. The system adjusted by their adjusting devices during operation, or in a short stop or in the spinning mode, at least one blade pitch (zero-degree angle or offset) by a predetermined amount. This amount is at least so large that a changed vibration property can be determined.

3. The wind turbine measures again in the same operating state as under 1. the axial gondola vibrations (test measurement). 4. From the result of the original run and the test run, a taring pointer and tare value are determined, which makes it possible to determine the position (phase angle) of the blade pitch change and its amount. This must be set to run the plant low vibration. 5. The phase amount of 4. can be between two sheets and the pitch angle change can then be divided mathematically into two sheets. (The calculation in section 4 and 5 corresponds to the calculation according to the manual procedure.) 6. The blade angles can be adjusted in total by the plant control to achieve the optimum power generation. This can be done by iterative adjustment and in each case measurement of the power curve. As far as the process corresponds to the manual process, but using or setting up appropriate sensors and actuators of the wind turbine, which at least detect vibrations and allows adjustment of at least the leaf position of all leaves. Furthermore, by implementing an emergency stop, automatically triggered by system control or manually, the tower damping can be determined. This allows determination of the position of the mass imbalance (static moment) after measuring the radial oscillation amplitude. This method is automated according to the invention in a suitable manner, preferably integrated into the plant control.

With increased vibration amplitude, which can be determined with knowledge of the static torque of the rotor, a service team can be ordered for balancing. This is then the knowledge of the introduced mass and position, radially and in the circumferential direction (phase), before, if according to the invention, an automated measurement was carried out. In addition, various automatic balancing methods (eg, weight transfer by liquid tanks) are known from the prior art, which can be controlled in the sense of the automated method according to the invention. Further details, features and advantages of the invention will become apparent from the following description of exemplary embodiments with reference to the accompanying drawings. Show it:

Fig. 1: schematic representation of axial, radial and torsional Turmanregulation; Presentation and state of the art in the removal of imbalances;

2 shows a schematic phasor diagram showing settings and measured values with their symbols as well as their relationship to one another;

3 is a schematic representation of a graph of a nominal power curve and power curves for absolute blade pitch errors;

4 shows a schematic representation of a diagram of a power curve of a wind energy plant before and after the blade angle correction; and 5 shows a schematic representation of a method sequence of an embodiment of the method according to the invention.

Mass imbalances lead in particular to a radial oscillation, ie perpendicular to the rotor axis, as shown in FIG. 1. As is customary in the industry, mass imbalances, unless otherwise defined by the manufacturer, are based on a permissible deviation of 0.5% from the mean static moment of the rotor blade set. Aerodynamic imbalances, caused by different angles of rotation of the rotor blades, twisting errors, profile deviation, pitch errors, defective flow elements or damage to the blade surface, lead to axial, torsional but also to lateral (radial) excitations of the gondola tower vibrations, as also shown in FIG ,

The determination of axial and radial gondola tower vibrations with acceleration sensors and subsequent Fourier analysis is known in the prior art. In addition, some providers measure the torsional gondola tower vibrations. The elimination of mass-induced vibrations by introducing a defined reversible static moment and thus the inference to the Urunwucht is carried out in practice and is thus known.

Various procedures are used to prepare for the correction of aerodynamic imbalances. By way of example, a photometric method may be mentioned which is based on the marking of a specific radius position, photography thereof and the evaluation of the acquired images by means of a special CAD software. It is also possible to use another photometric method in which prominent points on the leaf surface are analyzed. The limit value for the optimal adjustment of rotor blades to each other should not exceed ± 0.3 °, as specified by Germanischer Lloyd (see Germanischer Lloyd, Rules and Guidelines Industrial Services, Guideline for the Certification of Wind Turbines, 2010.).

2 shows a schematic phasor diagram with representation of setting and measured values as well as their relationship to one another. Here the given formula symbols mean: • Oscillation amplitude and phase angle axial: ä _{ur ax} , ⁽ p _ur , _a x

• Vibration amplitude and phase angle radial: ä _{ur rad} , <p _U r, rad

• Absolute blade pitch of a wind turbine with three blades: a ₀ =, α-120 °. ^a 120 °

· After adjustment: oscillation amplitude and phase angle axial: ä _{test ax} ,

⁽ Ptest.ax

• after adjustment: vibration amplitude and phase angle radial: _{test wheel} , testxad

• amplitude and phase angle tare pointer axial: z _tarierAX , ⁽ p _t arier, ax

· Ratio of the tare pointer to the blade pitch change

• Tare value: tara = ^{Acc (} - ^<Ptest [tara] = -

ctarian, ax TlTl / S

• Aa corresponds here to a

• determination of required blade _{pitch change} - result: a _{pitch korr} = tara * aur, ax

· Phase angle change (place where the blade _{pitch change has} to be made) Αφ = <pa ₀ ° _{pitch test} ) + <{ _ur , ax '^ tare, ax)

Since the location of the sheet pitch change is not necessarily at the position of a sheet, the sheet pitch change must be converted to the sheets: <Xo °, corr> -120 °, corr> 120 °, corr

3 shows a schematic representation of a graph of a nominal power curve 30 and power curves 31, 32 for absolute blade pitch errors. The effects on the output power of a wind turbine can be seen, which occur depending on the wind speed and the direction of the misalignment. For example, with an adjustment to "stall" (power curve 31, dotted line) at each wind speed, there is a drop in power compared to the rated power, which even increases at higher wind speeds. Point line) especially power losses at lower wind speeds.

4 shows a schematic representation of a diagram of a power curve of a wind energy plant before and after the blade angle correction. Here are, similar to in Fig. 3, the effects of misalignments of the rotor blade recognizable, but here by specifying concrete angular positions. Dashed line 33 shows a blade angle of 0.8 ° after stall (before correction), dotted line 34 a blade angle of 0.0 ° (after correction).

Furthermore, two exemplary embodiments for carrying out the method according to the invention on a wind energy plant with a three-wing rotor are explained below, in which the determination and elimination of an actual error is shown.

5 shows a schematic illustration of a method sequence of an embodiment of the method according to the invention corresponding to the sequence of the method steps of the following exemplary embodiment.

The goal is to minimize the radial and axial tower-gondola vibration of a wind turbine as well as to set the absolute blade angles to optimize the power curve.

Step I (reference numeral 11): A measurement of the rotor vibrations 20 is carried out during operation of the wind energy plant. The following results (amplitudes) are determined:

axial vibration 40.0 mm / s ²

radial vibration 28.0 mm / s ²

Step II (reference numeral 12): First, the measurement of the blade angle position takes place according to a known method. As a reference profile, the profile along the rotor blade is selected, at which the torsion angle is 0 °. The optimum setting angle at this profile cut would be 0.00 °. (Alternatively, any other radial position with a known corresponding twist angle could be selected.) The following results are obtained:

Sheet I angle + 0.10 °

Sheet II angle + 0,60 °

Sheet III angle -0,30 ° Step III (reference 13): All three blades are adjusted to the nominal optimum angle (0.00 °).

Sheet I angle 0.00 °

Sheet II angle 0.00 °

Sheet III angle 0.00 °

Step IV (Reference 14): A measurement of the rotor vibrations 21 during operation of the wind turbine is again carried out. The following results (amplitudes) are determined:

axial vibration 48.0 mm / s ²

radial vibration 36.0 mm / s ²

Step V (reference numeral 15): From the two vibration measurements carried out, the angle correction values are determined by observing the vibration vectors at which a minimum of the axial vibrations occurs:

Sheet I correction angle + 0.10 °

Sheet II correction angle 0.00 °

Sheet III correction angle + 0,30 °

Step VI (reference 16): The rotor blades are adjusted with the determined correction angles.

Step VII (Reference 17): For optional validation of the new setting, a third measurement of the rotor vibrations 22 is made during operation of the wind turbine. The following results (amplitudes) are determined:

axial vibration 2.4 mm / s ²

radial vibration 3, 1 mm / s ²

Embodiment 2:

At another wind turbine, the power curve before and after the blade angle correction is considered.

Step I: There is a measurement of the blade pitch:

Leaf I angle - 0.69 °

Sheet II angle - 0.95 °

Sheet III angle - 0,90 ° Step II: The rotor vibrations are measured at rated speed:

axial vibration amplitude 9.43 mm / s ²

radial vibration amplitude 1 1, 80 mm / s ²

Step II I: The blade pitch of the 3 rotor blades are adjusted to the nominal target angle:

Sheet I angle 0.00 °

Sheet II angle 0.00 °

Sheet III angle 0.00 °

Step IV: A new measurement of the rotor vibrations is carried out:

axial vibration amplitude 22.82 mm / s ²

radial vibration amplitude of 17.16 mm / s ²

Step V: From the measured values, the required correction of the blade pitch angle is determined using the described method in order to achieve a low axial vibration level:

Sheet I angle - 0.05 °

Sheet II angle - 0.00 °

Sheet III angle + 0.22 °

Step VI: A final measurement of the rotor vibrations is carried out: axial vibration amplitude 1, 53 mm / s ²

radial vibration amplitude of 8.30 mm / s ²

Evaluation of Exemplary Embodiment 2: At the wind energy plant, an absolute angle of the rotor blades lying on average by 0.85 ° in the direction of the stall was first determined. The correction of the blade pitch led to a change in the power curve, which now follows the course of the desired power curve. In addition, a slight deviation from the blade angle setpoint is set to achieve a low vibration level of the plant. LIST OF REFERENCE NUMBERS

1 wind energy plant

2 rotor

3 gondola

4 axial nacelle turbo-excitation

5 radial tower excitation

6 torsional gondola tower excitation

7 rotor blade

8 tower

1 1 step I

12 step II

13 step III

14 step IV

15 step V

16 step VI

17 step VII

20 rotor vibrations axial, radial (original state)

21 rotor vibrations axial, radial (after blade adjustment)

22 rotor vibrations axial, radial (after blade correction)

30 rated power curve

31 Power curve Blade angle too far to barn

32 power curve blade angle too far to flag

33 power curve blade angle 0.8 ° after stall (before correction)

34 power curve blade angle 0.0 ° (after correction)

Claims

claims

1. A method for reducing an aerodynamic imbalance of a wind turbine with rotating rotor, characterized in that in the context of a vibration measurement in the original state, an original axial vibration of a rotor (2) with a 1 P oscillation amplitude ä _{ur ax} and a phase angle φ _{υΓ: 3χ} determined whereupon, by adjusting a blade pitch angle on at least one rotor blade (7), an aerodynamic unbalance defined with respect to location and magnitude is produced with resulting total _pitch angle change _{pitch: test} and resulting phase angle (p (a _{pltch est} ); Determination of an axial vibration with vibration amplitude atest.ax and phase angle < _tes t, ax _> taking into account the original axial vibration, the determination of an axial tare with magnitude

and phase change Δφ and a tare value tara, followed by determining a necessary blade _{pitch change pitch: korr} and a phase angle (p _com at which the _pitch angle change _{pitch: corr} is to be corrected to correct the original aerodynamic imbalance, including a vectorial map of the _{pitch pitch change pitch : corr} on at least one of the rotor blades (7).

2. The method of claim 1, wherein the determination of the axial tare with amplitude and phase angle axially according to the equations

"" { ^Z tarier, ax> Ψ 'tare, ax}

Tar Utest Uur

" ^z tare, ax ^- { ^a test, ax> εεεί, Βχ} ^- { ^a ur, ax> ΨΙΙΓ, ΒΧ}

he follows,

the determination of the tare value tara according to the equation

, ^ O-.pitch.test

^■ tara = -r ^

ztarier, ax

he follows;

the determination of the necessary blade _{pitch change pitch: corr} and the phase angle (p _corr , at which the blade _{pitch change} a _pit ch, corr is to be made, according to the equations

" ^a pitch, corr ⁼ tara * a _{ur ax}

he follows.

3. The method of claim 1 or 2, wherein prior to the vibration measurement in the original state, an analysis of blade angle settings of all rotor blades (7) and then a correction of Blakeinstellwinkel done in such a way that the setting for all rotor blades (7) has the same Blateinstellwinkel.

4. The method of claim 1 or 2, wherein prior to the vibration measurement in the original state, an analysis of blade angle settings of all rotor blades (7) and then an adjustment of a blade pitch on at least one rotor blade (7) for generating a defined aerodynamic imbalance, wherein selection of the rotor blade ( 7) and its adjustment leads to an approach to that setting of the rotor blades (7), in which all the rotor blades (7) have the same blade pitch.

5. The method according to claim 1, wherein the analysis of the blade angle adjustment is made by a photometric analysis or by a distance measurement between at least one point on each rotor blade and a tower or nacelle of the wind turbine or a fixed point in an environment of the wind turbine is made.

6. The method according to any one of the preceding claims, according to which the Gesamtblatteinstellwinkeländerung a _{pitch: test is} between 0.1 ° and 90 °.

7. The method of claim 6, _wherein the Gesamtblatteinstellwinkeländerung _{pitch: test} between 0, 1 ° and 2 °.

8. The method according to any one of the preceding claims, wherein at least one radial and one axial 1 P vibration amplitude and phase are determined in the vibration measurement in the original state and / or in the vibration measurement in the test state.

9. The method according to any one of the preceding claims, wherein the vibration measurement is carried out at a constant speed of the rotor (2).

10. The method according to any one of the preceding claims, wherein during a final vibration measurement in the final state, a residual radial vibration is determined, which is subsequently eliminated by determining the location and size of the causative mass imbalance by means of at least one balancing mass.

11. The method according to claim 1, wherein the measurements, at least one vibration measurement using sensors, and adjustments, at least of the blade angle, are made automatically by a control device of the wind energy plant based on the measured values of the sensors and using control devices.

12. The method of claim 11, wherein the reduction of an aerodynamic imbalance of a wind turbine with rotating rotor is characterized by the following sequence

a) the wind turbine measures in the context of the original measurement during operation or in no-load operation automatically by sensors, the axial gondola vibration;

b) the wind turbine adjusts via adjusting devices during operation or during a short stop or in spinning mode at least one blade pitch by a predetermined amount, which is at least sized so that a changed vibration characteristic can be determined;

c) the wind turbine measures in the context of the test measurement again in the same operating condition as under a) the axial gondola vibrations;

d) from the result of the Urmessung and the test measurement a Tarierzeiger and a tare value are determined, which make it possible to determine the phase angle of Blätterninstellwinkeländerung and its amount according to claim 2, wherein the amount must be adjusted at least one rotor blade to the wind turbine low vibration to run; e) the phase amount according to letter d) can be between two sheets and the pitch angle change can then be mathematically divided according to claim 2 into two sheets;

f) the blade angles are adjusted in total by the plant controller in order to achieve optimal power generation, which can be done by iterative adjustment and respective measurement of the power curve.