CN100398813C - Method of controlling wind turbine aerodynamic loads - Google Patents

Abstract

The present invention relates to a method of controlling the aerodynamic load of a wind turbine's blades individually in such a way that the dynamic aerodynamic loads on the turbine are reduced and power production is optimised. In general the present invention will improve the overall stability of the turbine leading to reduce fatigue loads, reduced extreme loads during operation and reduced risk of blade-tower interaction. In particular preferred embodiment of the invention, flow properties are measured locally on the different blades or in front of the blades and from these measurements the pitch angle settings are changed, in other ways changing the aerodynamic properties, for the blades through a control unit.

Description

Method of controlling wind turbine aerodynamic loads

field

The present invention relates to a method for independently controlling the aerodynamic loads of wind turbine blades in such a way that the dynamic aerodynamic loads on the turbine are reduced and the power output is optimized. In summary, the invention will improve the overall stability of the turbine to reduce fatigue loads, reduce extreme loads during operation and reduce the risk of blade tower interaction. In a preferred embodiment of the invention, the flow properties are measured on different blades or locally in front of the blade, and based on these measurements the helix angle setting is changed, the aerodynamic performance of the blade is otherwise changed by the control unit.

Another aspect of the invention relates to particular flow measurement methods, methods of designing control systems and methods of how to change the aerodynamic performance of a blade.

Background technique

The dimensions of current wind turbines are such that the wind is in most cases not evenly distributed over the entire rotor area. These differences in wind speed, caused by turbulence, wind shear, yaw error handling, tower shadow and wake effects, etc., produce varying aerodynamic forces on the blades during rotation, causing severe fatigue loads on the turbine, in some cases also cause extreme loads.

The conventional control method for pitch-regulated turbines is to control the common pitch (ie all blades turned to the same angle at the same time) setting of all blades to provide an optimum yet well-defined power output of the turbine. From US patent 4,339,666 it is known that the pitch angle is controlled in such a way that the maximum load on the rotor and generator is below the maximum allowable value. This patent describes the use of mean wind speed and turbulence as the main control parameters. However, its disadvantage is that it does not take into account the change of wind speed in the rotor area.

From patent WO0133075 it is known a method how to control the helix angle of a wind turbine based on the measurement of the mechanical load of the turbine, with independent pitches to compensate uneven wind loads. However, the disadvantage is that, due to the large aerodynamic damping of the blades, the mechanical loads are sometimes measured after the wind disturbance has occurred.

US Patent 6 361 275 patents a wind turbine that uses independent pitches to effectively shed loads. The patent mainly focuses on measuring the effect of loading on the blade or hub using strain gauges or similar. In conjunction with the load measurement, the measurement of the local wind speed and direction on the blade is mentioned. However, due to the emphasis on load measurement performance, it does not describe how to use these different flow sensors. The aerodynamic sensor is placed on the trailing edge of the blade and the only way to change the aerodynamic load is by adjusting the pitch of the blade or part of the blade.

Description of the invention

It is an object of a preferred embodiment of the present invention to overcome the aforementioned drawbacks by providing a method of controlling the operation of a wind turbine based on measurements of local aerodynamic flow parameters on or in front of the blades. In a particularly preferred embodiment of the invention flow parameters are measured and utilized. The method preferably also includes means and means for calculating load shedding independent helix angle settings as a superimposed signal of the power-dependent common helix angle setting.

According to a preferred embodiment of the present invention there is provided a method of independently controlling the operating conditions of each blade of a wind turbine preferably comprising at least two blades. The method preferably includes the steps of determining at least one aerodynamic flow property in the vicinity of each blade, and determining one or more operating conditions for each blade, such as pitch angle, flap deflection angle, etc., based on the determined flow property.

In a particularly preferred embodiment of the invention, the operating condition for a given blade is the helix angle, and wherein said helix angle includes a component determined based on the angle of attack of the blade and a component determined based on the velocity of the relative blade. The invention also includes a wind turbine suitable for carrying out the method according to the invention.

Preferred embodiments of the present invention will be described below in conjunction with the accompanying drawings, wherein

Figure 1 schematically represents a rotor of a wind turbine;

Figures 2-5 show different embodiments of blades according to a preferred embodiment of the invention equipped with flow measuring devices. In Figures 5a and 5b, PS denotes a pressure sensor and is represented by a thick black line;

Figure 6 shows a blade according to a preferred embodiment of the invention, in which TEF denotes a trailing edge flap;

Figure 7 schematically represents a regulating system according to a preferred embodiment of the invention for controlling the aerodynamic load of a wind turbine;

Figure 8 shows the angle of attack and wingwise blade bending moment measured on a Tellus T-1995. A good correlation can be seen. From Madsen 1991; Header text: RISO NATIONAL LABORATORY, DENMARK; Oct.31, 1990; 12:50; File: D\t132bi\t32ix1 Points averaged 15; Records: 2500-2999;

Figure 9 schematically represents the relationship between the angle of attack and the lift and drag respectively;

Figure 10 shows schematically the relationship between angle of attack and lift, and in particular the non-linear part of the relationship;

Figure 11 schematically shows a blade whose radian can be changed;

Figure 12 shows schematically a blade with a movable trailing edge, denoted in the figure by MTE;

Figure 13 shows the ratio of the optimum cyclic pitch amplitude θ _cyc to the in-plane wind velocity V _x plotted as a function of the out-of-plane wind velocity V _y ;

Figure 14 represents the ratio of the optimum cyclic pitch amplitude θ _cyc to the in-plane wind velocity _Vx , plotted as a function of the square ratio of rotational speed to nominal rotational speed;

Figure 15 represents the ratio of the optimum cyclic pitch amplitude θ _cyc to the in-plane wind velocity _Vx , plotted as a function of the common helix angle;

Figure 16 shows the notation used here;

Figure 17 shows a uniform inflow of 20 m/s with a particularly negative wind shear. Common pitch adjustment. From top: wind speed at the hub and at the bottom of the rotor, blade 1 helix angle and average, blade 1 angle of attack and average, blade 1 in-plane relative velocity and average, blade 1 lap at the root wing moment and yaw moment at the top of the tower;

Figure 18 shows a uniform inflow of 20 m/s with a particularly negative wind shear. Independent pitch adjustment. From top: wind speed at the hub and at the bottom of the rotor, blade 1 helix angle and average, blade 1 angle of attack and average, blade 1 in-plane relative velocity and average, blade 1 lap at the root wing moment and yaw moment at the top of the tower;

Figure 19 shows a common pitch adjustment of 30 degrees yaw error and 7 m/s. From top: wind speed and direction at hub, helix angle, flap moment of blade 1 at root, tower top tilt moment and tower top yaw moment;

Figure 20 shows 30° yaw error and 7m/s independent pitch adjustment. From top: wind speed and direction at hub, helix angle, flap moment of blade 1 at root, tower top tilt moment and tower top yaw moment;

Figure 21 shows a yaw error of 30 degrees and a common pitch adjustment of 25 m/s. From top: wind speed and direction at hub, helix angle, flap moment of blade 1 at root, tower top tilt moment and tower top yaw moment;

Figure 22 shows 30 degrees yaw error and 25m/s independent pitch adjustment. From top: wind speed and direction at hub, helix angle, flap moment of blade 1 at root, tower top tilt moment and tower top yaw moment;

Figure 23 shows the 1HZ equivalent load for the selected sensor; and

Fig. 24 shows electric power average values. A small difference can be seen between wind speeds of 10 and 16 m/s.

This new load shedding regulation strategy is preferably based on the measurement of the inflow parameters angle of attack and relative velocity. It is quite evident that there is a very strong correlation between changes in the inflow parameters and the blade load response, see eg Madsen-1991, Fig. 8, and if the inflow is known, measures can be taken to mitigate subsequent load increases.

Currently, the most immediate performance to be measured is considered to be the local relative wind speed and angle of attack of a single blade within a representative distance from the hub. This can be done using a tachometer (see figure 2) mounted at 3/4 to 5/6 of the blade radius (see figure 1). The benefit of this system is that both speed and angle of attack are measured and can be measured in front of the blade. The system is preferably designed to be robust and easy to maintain. Another way to measure wind speed and angle of attack in front of the blade is to use a tube with a pressure measurement device. On the same principle as the tachometer, this embodiment is designed for a robust and easy-to-maintain example, see Figure 3.

A third method of measuring speed and angle of attack is to use a sonic anemometer placed in front of the blade, see Figure 4. When using such a system, consideration should be given to the temperature range in which the system will be used.

A fourth way to measure speed and angle of attack is by measuring the local pressure distribution on the blade profile, see Figures 5a, 5b.

A fifth way to measure the angle of attack is to use a movable trailing edge flap, see Figure 6.

According to the general principles of the invention, the method preferably uses the measured aerodynamic parameters to control the blade angle of attack in such a way that the dynamic load is relieved and the power output of the turbine is kept unchanged or even slightly increased. Therefore, the invention is preferably based on aerodynamic properties only and therefore the method preferably does not use direct measurements such as mechanical loads.

In general, due to the direct relationship between angle of attack and aerodynamic lift, the difference in aerodynamic lift of the rotor blades is greatly reduced if the three blades have the same angle of attack. One way of doing this, according to a preferred embodiment of the present invention, is to minimize the error between the instantaneous angle of attack of the blades and the average angle of attack of all blades. This can be done using a proportional-total regulator such as that shown in FIG. 7 . In addition to the angle of attack, the local velocity on the blade also affects aerodynamics. However, since changes in the helix angle do not affect speed changes, this measurement signal requires the application of another control system. Proportional helix angle adjustment based on the difference between the local velocity and the average blade velocity is a suitable method.

One advantage of the control system described above is that when operated correctly, the power output of the turbine is not affected. The power output controller controls the common pitch setting of the blades, and the invention provides a load-relieved superimposed pitch signal. Since the angle of attack is preferably adjusted such that the common helix angle can also be optimized, more power is generated. The reason for this is that the local aerodynamic distribution has an optimum angle of attack where lift is high and drag is low. At low wind speeds, if optimum power output is required, the common pitch setting can be controlled by the average angle of attack adjustment.

Since the relationship between lift, drag and angle of attack is highly non-linear in the range of maximum lift, the above load shedding control section is believed to result in better power output performance when the blade angle of attack is more stable and thus has a higher lift average.

Several methods of constructing inflow-based regulators have been investigated. One of the most promising approaches is to separate actions based on angle-of-attack measurements from actions based on relative velocity. This is basically based on the assumption that if the local angle of attack is kept the same on all three blades, the loads will be the same. However, this is only valid if no skew inflows (yaw error, pitch, rotor inclination, etc.) occur, since such a load position produces a significant change in the relative velocity and thus a varying load on the rotor. Skewed inflows can be compensated by relative velocity based actions, since the flow in the rotor face produces 1P varying relative velocities. If the helix angle changes in-phase with a change in relative velocity, the load will be reduced - the difficulty is changing the pitch with the smallest possible phase delay and the correct magnitude of movement. For blade no. i, the pitch notation from the angle of attack part is denoted θ _δi,a and the pitch notation from the relative velocity part is denoted θ _δi,b . Also, it is very important to ensure that movements from relative speeds do not affect the angle of attack regulator. This will be described later.

Action based on angle of attack measurement

"If the angle of attack of all three blades remains the same, the load will be the same" is the basic idea of this regulation section. This is a very effective method of load mitigation, eliminating loads arising from wind shear or low frequency turbulence in the direction of the wind. It can be done by using a PI regulator, controlling the helix angle based on the error between the angle of attack of a single blade and the average angle of attack, see Figure 7. By using a small means of error between the angle of attack on a single blade and the average value of all blades a system is created that does not conflict with the common pitch adjuster. Common pitch adjusters control the average, while individual pitch adjusters minimize differences in blade angle of attack. Clearly, measurements and actions can be done with as little phase delay as possible.

Actions based on relative speed measurements

Compared to the measured angle of attack, it seems that using a PI-based regulator unit for the relative speed part is not feasible, since the speed change is hardly affected by the pitch angle change. Hence the need to use a model-based regulator. Based on simulations, it is clear that the helix angle needs to vary within phases with the relative velocity. The key is to determine the appropriate pitch variable range, because this is different from relying on at least the magnitude of wind speed and relative in-plane velocity.

The particular relative wind speed regulator used in this analysis is based on the calculation of the in-plane wind speed and rotor _Vx .

V _x =V _rel cos(α+θ) (1)

θ _δi,b = (V _x −V _{x, ave} )K(ω, θ _col ) (2)

where (V _x −V _x,ave ) is the error between the relative in-plane velocity on a single blade and the average in-plane relative velocity of the three blades, and K(ω,θ _col ) is the gain function. The gain function is essentially a function of wind speed, but is stronger at high wind speeds using a common helix angle. The gain function is based on calculations for skewed inflows and turbines equipped with cyclic pitch regulators, since this regulation is well suited to compensate for such inflows, see Caselitz-1997 and Bossanyi-2003. Using these calculations the optimum magnitude was found. The gain function was determined by plotting the results in FIG. 13 . The same results have been plotted in Figures 14 and 15 as a function of rotor speed and pitch angle, leading to the gain function of equation (3). A specific characteristic of a nonlinear gain function is to have a signal gain variation. The helix angle should change in phase with relative velocity at low wind speeds and in antiphase at high wind speeds above rated.

$\mathrm{<span\; class="notranslate">\; K</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&omega;</span>}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; col</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\left\{\begin{array}{cc}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="0"\; label="K"\; filenames="C20048000745100212.png,C20048000745100221.png"\; state="\{\{state\}\}">K</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; (</span>\frac{{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; ref</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; )</span><span\; class="notranslate">\; ,</span>& \mathrm{<span\; class="notranslate">\; \&omega;</span>}<span\; class="notranslate">\; <</span>\mathrm{<span\; class="notranslate">\; 0</span>}<span\; class="notranslate">\; .</span>\mathrm{<span\; class="notranslate">\; 95</span>}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; ref</span>}}<span\; class="notranslate">\; ^</span>{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; col</span>}}<span\; class="notranslate">\; \&le;</span>{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}\\ \mathrm{<span\; class="notranslate">\; 0</span>}<span\; class="notranslate">\; ,</span>& \mathrm{<span\; class="notranslate">\; \&omega;</span>}<span\; class="notranslate">\; \&Greater\; Equal;</span>\mathrm{<span\; class="notranslate">\; 0.95</span>}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; ref</span>}}<span\; class="notranslate">\; ^</span>{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; col</span>}}<span\; class="notranslate">\; \&le;</span>\mathrm{<span\; class="notranslate">\; \&theta;</span>}\\ \mathrm{<span\; class="notranslate">\; \&beta;</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; col</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; )</span>& {\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; col</span>}}<span\; class="notranslate">\; ></span>{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}\end{array}\right.<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

where α and β are the slopes of the curves in Figures 14 and 15, _K0 is the gain at ω= _ωref in Figure 15, _θ0 is the helix angle for zero gain (about 9° in Figure 15), and _θcol is the common helix angle, ω is the rotor rotational speed and ω _ref is the rated rotor rotational speed.

How to avoid interference between two flow regulators

When the turbine operates with a deflected inflow, the in-plane relative velocity _Vx changes. This change can cause a change in the angle of attack, which then leads to an incorrect pitch angle adjustment by the angle of attack controller. Therefore this definite change in angle of attack caused by _Vx changes needs to be eliminated as well as changes in pitch angle caused by relative speed regulators.

The variation in angle of attack according to V _x is roughly

in

where B is the number of leaves. The modified input for the angle of attack regulator is

See Figure 16 for an explanation of terms.

Since the angle of attack is measured, it is also possible to optimize the common helix angle, resulting in more power. The reason for this is that the local aerodynamic distribution has an optimum angle of attack where lift is high and drag is low. At low wind speeds, if optimum power output is required, the common helix setting can be controlled by the average angle of attack measurement, see Figure 9.

Since the relationship between lift, drag and angle of attack is highly non-linear in the region of maximum lift, the above load shedding control part is considered to achieve better power output performance when the blade angle of attack is more stable and thus has higher lift Average values, see Figure 10.

Methods of Controlling Aerodynamic Performance

The basic method of controlling the aerodynamic lift and drag of a blade is by varying the helix angle of the individual blades, as described above. Methods for independently varying the helix angle can be found in, for example, EP 1 241 350A1, US-5,011,373, EP 0 359 624 B1.

The second way to vary the aerodynamic loads is through active control of the blade profile curvature, see Figure 11.

A third method of altering the aerodynamic distribution is through flaps or ailerons, see Figure 12.

load comparison

Control systems were compared with the code HAWC by aeroelastic simulations, see Petersen-1997, Larsen-2001. Several types of simulations were carried out, starting with basic simulations in defined wind domains to understand the performance of the different controllers, and ending with simulations in random turbulence that the turbine would actually encounter. The turbines used in the simulations have a rated nominal power of 2-MW.

Shear and Yaw Error Manipulation

Different control methods are simulated at a large number of locations, both with and without natural turbulence. However, to illustrate the fundamental performance of the different systems, no-turbulence simulations in defined wind domains are shown in Figures 17 to 22 . This particular negative wind shear is similar to positive but with an increased wind speed, 50% higher at the hub than at the bottom of the rotor. In all turbulent-free simulations, the rotor helix angle was set to 0, since this is roughly consistent with the yaw error distribution.

The performance of the turbine with common pitch regulation can be seen in FIG. 17 . Large loads are seen on blade flap moments and tower top yaw moments. The performance of a turbine with an independent pitch system can be seen in Figure 18. Blade flap moments and tower top yaw moments are reduced, and the difference in angle of attack from the average of the three blades is also reduced. The helix angle varies non-sinusoidally, which is the main reason for the very low yaw moment.

A simulation of the turbine in yaw error operation can be seen in FIGS. 19 to 22 . Compared to common pitch systems, independent pitch systems produce load relief on blade flap moments, tower tip tilt moments, and tower tip yaw moments.

Fatigue load calculation

Comparing the loads of different control methods (common, cyclic and independent), the fatigue load range based on IEC61400-1, level 1B is calculated. Load conditions are normal output conditions with ±10% yaw error and wind speeds ranging from 4m/s to 24m/s. Wind conditions for turbine class 1B V _ave =10.0 m/s, I ₁₅ =0.16, a=3). The roughness length is 0.2m, which is consistent with the wind shear specified in IEC61400. Turbulent flow was simulated with the Mann model, see Mann-1998.

To summarize the overall fatigue load mitigation for wind turbines, equivalent loads for selected load sensors are provided in Fig. 23 and Table 1. The limit load at the time of operation is shown in Table 2.

The effect of power output is shown in Figure 24. The 20-year output increased by 0.6% for independent pitches compared to common pitch adjustments.

Table 1: Comparison of 20-year fatigue loads, n = 10 ⁷ - Index

sensor m common independent Blade flaps at the hub 12 1.0 0.72 Blade pitch adjustment 12 1.0 1.01 drive torque 5 1.0 1.00 Shaft bending at hub 5 1.0 0.91 The top of the tower is inclined 5 1.0 0.69 Top Yaw 5 1.0 0.65 The bottom of the tower is inclined 5 1.0 0.78 tower top side 5 1.0 0.59

Table 2: Comparison of extreme loads in operation - index

sensor common independent Blade flaps at the hub 1.0 0.86 Blade pitch adjustment 1.0 0.94 drive torque 1.0 0.79 Shaft bending at hub 1.0 0.98 The top of the tower is inclined 1.0 1.03 Top Yaw 1.0 0.68 The bottom of the tower is inclined 1.0 0.70 tower top side 1.0 0.64

references

Madsen-1991: H.A.Madsen. Aerodynamics and Structural Dynamics of a Horizontal Axis Wind Turbine. Risφ-M-2902, Risoe, National Laboratory, February 1991.

J.Petschenka，M.Reichardtand

Reduction of fatigue loads on wind energy converters by advancedcontrol methods.Proceedings of the international conference held in Dublin Castle，Ireland.IWEA 1997Caselitz-1997: P. Caselitz, W. Kleinkauf, T.

J. Petschenka, M. Reichardtand

Reduction of fatigue loads on wind energy converters by advanced control methods. Proceedings of the international conference held in Dublin Castle, Ireland. IWEA 1997

Bossanyi-2003: E.A. Bossanyi. Individual Blade Pitch Control for Load Reduction. Wind Energy, 6: 119-128.2003

Petersen-1996: JT Petersen, The Aeroelastic Code HawC-Model and Comparisons. ^28th IEA Experts Meeting: 'State of the Art of Aeroelastic Codes'. DTU, Lyngby, 1996

Larsen-2001: T.J.Larsen.Description of the DLL Regulation Interface inHAWC.Ris-R-1290(en), Risoe, National Laboratory, September 2001.

Mann-1998: J. Mann. Wind Field Stimulation. Prob. Engng. Mech, Elsevier Science, vol 13 (no4): pp 269-283, 1998

Claims (12)

1. an independent control comprises the method for each operational condition of wind turbine of at least two blades, described method comprises step, near each blade, determine at least a Aerodynamic Flows performance, and determine the operating conditions that one or more comprise helix angle for each blade based on the mobile performance of determining

Wherein said helix angle comprises composition of determining based on blade incidence and the composition of determining based on the wind speed of relative blade,

And wherein the composition of determining based on the angle of attack is determined according to the error between the mean angle of attack of the instant angle of attack of blade and all blades.

2. according to the process of claim 1 wherein that the skew inflow condition of the variation by considering to cause the projection of relative velocity on the rotor plane revises the error between the instant angle of attack and the mean angle of attack.

3. according to the method for claim 1 or 2, wherein determine by the difference homophase of relative velocity based on the composition that relative velocity is determined.

4. according to the method for claim 1 or 2, wherein the composition of determining based on relative velocity is determined the error between the speed in the centre plane of relative velocity and all blades in the face of the single blade that work multiplies each other by a gain function.

5. according to the method for claim 1 or 2, wherein this at least one mobile performance comprises the instant angle of attack.

6. according to the method for claim 1 or 2, wherein this at least one mobile performance comprises instant local wind speed.

7. according to the method for claim 1 or 2, wherein this at least one mobile performance is by local measurement.

8. according to the method for claim 1 or 2, wherein these at least two blades can be fixed in hub along the mode that its longitudinal axis independently rotates with each blade, and one or more operating conditions that wherein should determine comprise that the individual pitch angle of each blade and this method comprise each blade is set in individual pitch angle that their are determined.

9. according to the method for claim 1 or 2, wherein each blade has movably wing flap or aileron, and the operating conditions of determining comprises the setting of wing flap movably or aileron.

10. according to the method for claim 5, wherein determine the instant angle of attack by velocity measuring instrument, trailing edge flap hinge, sound wave recording anemometer, the pressure measurement of blade surface, laser Doppler anemometer.

11., wherein measure local wind speed by the pressure measurement that utilizes velocity measuring instrument, sound wave recording anemometer, laser Doppler anemometer, blade surface according to claim 6 method.

12. according to the method for claim 1 or 2, comprise or further comprise one or more following steps,

Write down the air pressure on each blade

Write down the air pressure on each trailing edge

Write down the air pressure on each blade inlet edge

The record mechanical load;

The pressure of record supporting structure

Near or the contiguous wind speed of locating of record wind turbine

The record auxiliary data

Send record data/definite mobile performance to analytical equipment, and/or

The data of analyzing stored in storage device.

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