METHOD OF ADJUSTING AT LEAST ONE ROTOR BLADE OF A WIND TURBINE AND A SYSTEM AND A WIND TURBINE FOR CARRYING OUT THE METHOD

Abstract

A method of adjusting at least one rotor blade of a wind turbine which includes the steps of receiving a command for adjustment of the rotor blade at an adjustment speed, ascertaining a current moment of inertia of the rotor blade and acceleration of the rotor blade until reaching the adjustment speed, wherein the acceleration until reaching the adjustment speed is limited in dependence on the ascertained moment of inertia. A system and a wind turbine.

Claims

1. A method of adjusting a rotor blade of a wind turbine, the method comprising: receiving a command for adjusting the rotor blade to an adjustment speed, determining a current moment of inertia of the rotor blade, and accelerating the rotor blade until reaching the adjustment speed, wherein the accelerating is limited in dependence on the current moment of inertia.

2. The method as claimed in claim 1 comprising determining a current deflection of the rotor blade, and wherein determining the current moment of inertia is determine in dependence on the determined current deflection of the rotor blade.

3. The method as claimed in claim 2 comprising determining a current wind speed, and wherein the current deflection and/or the current moment of inertia of the rotor blade is determined in dependence on the determined current wind speed.

4. The method as claimed in claim 3 wherein the current wind speed is determined by a measured wind speed or by a continuously determined wind speed mean value.

5. The method as claimed in claim 4 wherein the measured wind speed is measured by an anemometer or a lidar system.

6. The method as claimed in claim 4 wherein the continuously determined wind speed mean value is a 3-second mean value or a 10-second mean value that is retrieved.

7. The method as claimed in claim 2 wherein the current moment of inertia or the current deflection is determined in dependence on a current pitch angle of the rotor blade and/or a current rotary speed of a rotor coupled to the rotor blade and/or a current electrical power of a wind turbine generator of the wind turbine.

8. The method as claimed in claim 2 wherein determining the current deflection of the rotor blade is performed by one or more sensors.

9. The method as claimed in claim 8 wherein the one or more sensors include at least one of a strain gauge, an optical sensor, a laser sensor, or a camera on the rotor blade.

10. The method as claimed in claim 1 wherein receiving the command for adjusting the rotor blade comprises receiving a commend for adjusting first and second rotor blades, wherein adjusting the first rotor blade comprises accelerating the first rotor blade and after an expiration of a predetermined period of time or after the occurrence of a predefined event, accelerating the second rotor blade.

11. The method as claimed in claim 10 wherein the predetermined period of time is less than 250 milliseconds.

12. The method as claimed in claim 10 wherein the predetermined period of time is less than 100 milliseconds.

13. The method as claimed in claim 1 wherein receiving the command for adjusting the rotor blade comprises receiving a command for adjusting first and second rotor blades, and further comprising: determining a current first moment of inertia for the first rotor blade and a current second moment of inertia for the second rotor blade, and the acceleration of the first rotor blade until reaching the adjustment speed is limited in dependence on the ascertained first moment of inertia and the acceleration of the second rotor blade until reaching the adjusting speed is limited in dependence on the ascertained second moment of inertia.

14. The method as claimed in claim 1 wherein to determine the moment of inertia an association is stored, wherein in the association at least one moment of inertia is associated with each deflection or each of a plurality of states of the wind turbine, wherein the association is previously determined by a simulation or by test series and is stored in a memory.

15. The method as claimed in claim 1 further comprising establishing a maximum acceleration value, and wherein the acceleration of the rotor blade is effected in such a way that the maximum acceleration value is not exceeded independently of the determined moment of inertia.

16. The method as claimed in claim 1 wherein receiving the command comprises receiving the command for adjusting three rotor blades of a wind turbine, and wherein a threshold value for limitation of the accelerations for each of the rotor blades is respectively identical as a result of division of a product from a presetting of a predefined maximum power and a level of efficiency of the pitch motors used for the adjustment by a total of the determined moments of inertia for all three rotor blades.

17. The method as claimed in claim 1 comprising activating an extreme load avoidance function by a wind turbine controller prior to receiving the command for adjusting the rotor blade.

18. A system adapted to carry out the method as claimed in claim 1.

19. A wind turbine comprising: a system configured to: receive a command for adjusting a rotor blade to an adjustment speed, determine a current moment of inertia of the rotor blade, and accelerate the rotor blade until the adjustment speed is reached, wherein the accelerating is limited in dependence on the current moment of inertia, a power supply, a rotor blade, a pitch drive coupled to the rotor blade, and a controller, wherein the power supply is configured to supply the pitch drive of the rotor blade, and wherein the controller is configured to determine acceleration of the rotor blade in such a way that a maximum power is not exceeded.

20. The wind turbine as claimed in claim 19, wherein the maximum power is predefined or is provided by the power supply.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0029] Further configurations will be apparent from the embodiments by way of example described in greater detail with reference to the Figures in which:

[0030] FIG. 1 shows a wind turbine,

[0031] FIG. 2 shows a system for adjustment of the rotor blades, and

[0032] FIG. 3 shows the steps in an embodiment of the method.

DETAILED DESCRIPTION

[0033] FIG. 1 shows a diagrammatic view of a wind turbine according to the invention. The wind turbine 100 has a tower 102 and a nacelle 104 on the tower 102. Provided on the nacelle 104 is an aerodynamic rotor 106 having three rotor blades 108 and a spinner 110 which can also be referred to as the rotor blade hub. In operation of the wind turbine 100 the aerodynamic rotor 106 is caused to rotate by the wind and thus also rotates an electrodynamic rotor or rotor member of a wind turbine generator coupled directly or indirectly to the aerodynamic rotor 106. The electric wind turbine generator is arranged in the nacelle 104 and generates electrical power. The pitch angles of the rotor blades 108, which can also be referred to as rotor blade attack angles or briefly angles of attack can be altered by pitch motors which can also be referred to as adjustment drives at the rotor blade roots of the respective rotor blades 108.

[0034] FIG. 2 shows a diagrammatic view of a nacelle 104 of a wind turbine with individual components of a system 10 according to an embodiment in order to carry out an embodiment of the method of adjusting at least one rotor blade 108 of a wind turbine 100.

[0035] Arranged in the nacelle 104 is a power supply 12 which supplies power to further components 14 (not shown) of the wind turbine. A controller 16 for adjustment of the rotor blades is also shown. The controller 16 can also be referred to as a pitch controller. The controller 16 is connected to a power electronic system 18 to which power is fed by the power supply. By actuation of the power electronic system 18 with an actuation signal 19 one or more adjusting drives 20 are supplied with power corresponding to the actuation signal 19 in order to rotate the rotor blades 108 which are also shown in FIG. 2 about a longitudinal axis 22, that is to say to adjust the pitch angles thereof. In dependence on the actuation signal 19, for example when a low level of acceleration or adjustment speed, that is to say a speed of rotation, of the rotor blade 108 is desired the power circuit 18 is actuated in such a way that only a comparatively low amount of power is passed to the motors 20 from the power supply 12. In a situation involving high desired levels of acceleration or adjustment speeds the power electronic system 18 is in comparison actuated in such a way that comparatively more power is fed to the motors 20 from the power supply 12.

[0036] For that purpose the controller 16 for control of the pitch motors 20 receives a command 24 for adjustment of the rotor blades 108 from a wind turbine control system 26. The wind turbine control system 26 is connected to a large number of further components 14 in order to set, provide for closed-loop control of and monitor operating states of the components 14 with the wind turbine control system 26. Monitoring also includes monitoring the operating state itself and also environmental influences acting on the wind turbine 100.

[0037] If in dependence on a current operating state and for example changing environmental influences like for example the occurrence of severe squalls, an extreme load is detected, namely a loading on the wind turbine reaches an avoidable degree of wear or even a threat of damage then for example a command 24 is sent to the controller 16 for adjustment of the rotor blades 108. In that case preferably also a desired adjustment speed 28 is preset with the command 24, which is selected to be comparatively high in relation to an adjustment speed 28 which is wanted in normal operation of the wind turbine 100, for example to avoid damage or a high level of wear. Then a current moment of inertia of the rotor blade 108 or all rotor blades 108 is ascertained in the controller 16 for actuation of the pitch motors 20. As the rotor blade 108 is substantially dependent on a deflection 29 from a rest position 31 which can also be referred to as warpage of the rotor blade 108, strain gauges 30 are provided in the rotor blade 108, with which warpage and thus a deflection 29 of the rotor blade 108 can be directly detected. Therefore the controller 16 ascertains a current moment of inertia of the rotor blade 108 on the basis of the deflection 29 measured with the strain gauges 30.

[0038] Alternatively or additionally it is also possible to measure a wind speed 32 which prevails in the region of an anemometer and that can be taken into consideration as the current wind speed 33 in determining the moment of inertia. The controller 16 then controls the power electronic system 18 in dependence on the ascertained moment of inertia and the adjustment speed in such a way that the rotor blade 108 is accelerated until reaching the adjustment speed, in which respect the level of acceleration remains below a threshold value of an acceleration which was determined in dependence on the moment of inertia. The acceleration is thus limited in dependence on the ascertained moment of inertia. That ensures that the power supply 12 can provide sufficient power for powering the components 14, even if power has to be delivered for acceleration of the pitch motors 20, as the power for the pitch motors 20 is suitably limited.

[0039] FIG. 3 shows the steps in the method according to an embodiment for adjusting at least one rotor blade of a wind turbine. In a step 40 a command for adjustment of the rotor blade 108 at an adjustment speed 28 is received. Thereupon warpage or deflection 29 of the rotor blade 108 is determined in a step 42. Alternatively in step 46 a current wind speed 33 is determined in the region of the wind turbine 100 or the rotor blade 108. That can be effected as in FIG. 2 by direct recording of the wind speed 33 from an anemometer 34, in which case in the present embodiment a 10-second mean value 47 stored in a wind turbine control system 26 is retrieved in step 44.

[0040] Furthermore in a step 48 in both alternatives of different preceding steps a rotary speed 49 of the rotor 106 of the wind turbine 100 is determined in the step 48 while in a step 50 in addition the pitch angle 51 of at least one of the rotor blades 108 is also determined. Thereupon the moment of inertia 53 of the rotor blade or blades 108 is determined in a step 52 from all the detected values, namely either the deflection 29, the rotary speed 49 of the rotor 106 and the pitch angle 51 or the wind speed 33, the rotary speed 49 and the rotor blade angle 51. Preferably that involves using an association 54, on the basis of which the moment of inertia 53 is afforded from the previously ascertained values. Then in a step 55 the power electronic system 18 is so actuated that in step 56 the rotor blade or blades 108 is or are accelerated until reaching the adjustment speed with the pitch motors 20. In step 57 directly after the beginning of acceleration, a check is made to ascertain that the power electronic system 18 is actuated in such a way that acceleration until reaching the adjustment speed 28 is limited in dependence on the ascertained moment of inertia 53. For that purpose a threshold value 59 is preferably determined in parallel from the moment of inertia 53 in a step 58, in which respect the threshold value 59 may not be exceeded by the acceleration.

[0041] Then in step 60 the predetermined adjustment speed 28 is reached so that an acceleration is reduced to 0 and the rotor blade 108 is adjusted until reaching a position which is also preset with the command, namely a target pitch angle.

[0042] The various embodiments described above can be combined to provide further embodiments. These and other changes can be made to the embodiments in light of the above-detailed description. In general, in the following claims, the terms used should not be construed to limit the claims to the specific embodiments disclosed in the specification and the claims, but should be construed to include all possible embodiments along with the full scope of equivalents to which such claims are entitled. Accordingly, the claims are not limited by the disclosure.