CONTROLLING AN OFFSHORE WIND TURBINE USING ACTIVE ADD-ONS

Abstract

It is described a method of controlling an offshore wind turbine (50) installed on a floating platform (12) and having at least one rotor blade (6) comprising at least one adaptable flow regulating device (9) configured to adapt/modulate an air flow exposed profile, the method comprising: receiving a load related signal (3, 14) indicative of a load due to a movement of the floating platform (12); and controlling the adaptable flow regulating device (9) based on the load related signal (3, 14).

Claims

1-12. (canceled)

13. A method of controlling an offshore wind turbine installed on a floating platform and having at least one rotor blade comprising at least one adaptable flow regulating device configured to adapt/modulate an air flow exposed profile, wherein the at least one rotor blade is adjustable regarding a pitch angle using a pitching system, the method comprising: receiving a load related signal indicative of a load due to a movement of the floating platform; filtering the load related signal to obtain a filtered load related signal; controlling the at least one adaptable flow regulating device based on the filtered load related signal such as to counteract or dampen at least one load which is due to the movement of the floating platform; receiving a wind turbine operation related signal; filtering the wind turbine operation related signal to obtain a filtered wind turbine operation related signal; and controlling the pitching system based on the filtered wind turbine operation related signal.

14. The method according to claim 13, wherein the load related signal comprises information regarding at least one of: a translational and/or rotational velocity of the floating platform and/or a nacelle of the wind turbine and/or a rotor of the wind turbine; a translational and/or rotational acceleration of the floating platform and/or the nacelle and/or a rotor of the wind turbine; a load on at least one mooring line connecting the floating platform to the sea ground; an interface moment between a wind turbine tower and a base foundation at the floating platform; at least one load experienced on any component of the floating platform and/or of the wind turbine.

15. The method according to claim 13, wherein the filtering the received load related signal comprises using a first band-pass filter to obtain the filtered load related signal, and/or wherein filtering the received wind turbine operation related signal comprises using a second band-pass filter to obtain the filtered wind turbine operation related signal.

16. The method according to claim 13, wherein the filtered load related signal is utilized to dampen wind-excited motions of the floating offshore platform, wherein oscillations not due to motions of the floating offshore platform are disregarded.

17. The method according to claim 13, wherein the filtered load related signal is utilized to dampen sea wave-excited motions, wherein oscillations not due to motions of the floating offshore platform are disregarded.

18. The method according to claim 16, wherein the method is configured to dampen an oscillating frequency between 0.04 Hz and 0.25 Hz, or between 0.1 Hz and 0.5 Hz, wherein a first order wave-induced motions ranges in a frequency interval between 0.04 Hz and 0.25 Hz.

19. The method according to claim 13, wherein controlling the adaptable flow regulating device is performed using a first controller, receiving the filtered load related signal and outputting a flow regulating device control signal to an actuator.

20. The method according to claim 13, wherein the at least one adaptable flow regulating device comprises a plurality of adaptable flow regulating device portions affecting different regions of the at least one rotor blade, the plurality of adaptable flow regulating device portions being arranged at different positions along a longitudinal axis of the at least one rotor blade; wherein controlling the at least one adaptable flow regulating device based on the load related signal comprises controlling at least one adaptable flow regulating device portion independently from other adaptable flow regulating device portions based on the load related signal.

21. The method according to claim 13, wherein the controlling the at least one adaptable flow regulating device is such as to achieve at least one of: aerodynamic damping and/or counteracting of at least one acceleration and/or oscillation and/or rolling motion of the platform and/or a nacelle; mitigating at least one load; mitigating floating platform fore-aft and/or side-side rotational and/or translational acceleration; selectively decreasing load on certain blade sections; and changing pressure distribution around and/or across an airfoil of the at least one rotor blade.

22. The method according to claim 13, the method further comprising: controlling the at least one adaptable flow regulating device further based on the wind turbine operation related signal, at least based on information regarding rotor speed and/or wind speed, such that as to avoid exceeding a pitch system capability.

23. The method according to claim 13, wherein the wind turbine operation related signal is indicative of at least one of: a rotational speed of a rotor at which the rotor blade is mounted; a blade pitch angle; a wind speed; a tower-foundation moment; a blade root moment; translational and/or rotational velocity of the wind turbine and/or the nacelle and/or the rotor; and translational and/or rotational acceleration of the wind turbine and/or a nacelle and/or a rotor.

24. The method according to claim 13, wherein controlling the pitch system is performed using a second controller, receiving the filtered wind turbine operation related signal and outputting a pitch system control signal.

25. The method according to claim 13, wherein the at least one adaptable flow regulating device comprises at least one of: at least one surface member changeable in position and/or orientation relative to a main airfoil of the at least one rotor blade, configured to retract or extend a leading edge and/or a trailing edge; an adaptable spoiler, having a plurality of spoiler portions arranged at a suction surface of the at least one rotor blade, close to or at the trailing edge of the at least one rotor blade; an adaptable flap installed close to or at a blade tip end; an airfoil morphing system; an aileron; an inflatable bag configured to change position and/or orientation of a surface member upon inflation or deflation; and a pneumatic system arranged to selectively inflate or deflate the inflatable bag.

26. An arrangement for controlling an offshore wind turbine installed at a floating platform and having at least one rotor blade comprising at least one adaptable flow regulating device configured to adapt/modulate an air flow exposed profile, the arrangement comprising: a controller configured to carry out a method according to claim 13.

27. An offshore wind turbine system, comprising: an offshore floating platform; a wind turbine installed at the offshore floating platform and having at least one rotor blade comprising at least one adaptable flow regulating device configured to adapt/modulate an air flow exposed profile; and an arrangement according to claim 26, communicatively coupled to the flow regulating device.

Description

BRIEF DESCRIPTION

[0060] Some of the embodiments will be described in detail, with reference to the following figures, wherein like designations denote like members, wherein:

[0061] FIG. 1 schematically illustrates an arrangement for controlling an offshore wind turbine according to an embodiment of the present invention;

[0062] FIG. 2 schematically illustrates a rotor blade which may be comprised in an offshore wind turbine system according to an embodiment of the present invention; and

[0063] FIG. 3 schematically illustrates an offshore wind turbine system according to an embodiment of the present invention.

DETAILED DESCRIPTION

[0064] The arrangement 1 for controlling an offshore wind turbine installed at a floating platform (an example is illustrated in FIG. 3 described below) schematically illustrated in FIG. 1 comprises a controller 2 which is adapted to receive a load-related signal 3 indicative of a load due to a movement of the floating platform. The controller 2 is further configured to control an adaptable flow-regulating device which is present at a rotor blade, based on the load-related signal 3. Therefore, the arrangement 1 outputs the flow-regulating device control signal 4 to an actuator system 5 which is configured to modify or modulate an airflow exposed profile of the rotor blade.

[0065] FIG. 2 schematically illustrates a rotor blade 6 which may be comprised in an offshore wind turbine as controlled according to embodiments of the present invention. The rotor blade 6 illustrated in FIG. 2 is illustrated in a side-view having its longitudinal axis 7 oriented horizontally. The rotor blade 6 comprises an outer surface 8 which is airflow exposed during normal operation. The rotor blade 6 comprises an adaptable flow-regulating device 9 comprising plural adaptable flow-regulating device portions 9a, 9b, 9c, 9d, 9e. The adaptable flow-regulating device portions 9a, 9b, 9c, 9d, 9e are arranged along the longitudinal axis 7 of the rotor blade 6. The adaptable flow-regulating device 9 may for example be configured as an adaptable segmented spoiler, wherein the adaptable flow-regulating device portions 9a, . . . , 9e are attached to a suction surface 8 of the rotor blade. The rotor blade 6 may comprise one or more other types of flow-regulating devices.

[0066] The actuator system 5 controlled by the controller 2 outputs drive signals 10 or actuating influence (such as hydraulic action) to the adaptable flow-regulating device portions 9a, . . . 9e, as is schematically illustrated in FIG. 2. Thereby, the individual flow-regulating device portions 9a, . . . 9e may independently be controlled by control or drive signals or actuating influence 10. The flow-regulating device portions 9a, . . . 9e each comprise at least one surface member exposed to an airflow during normal operation of the wind turbine 50.

[0067] The rotor blade 6 further comprises a pitch actuator 11 which is configured to rotate the rotor blade 7 around its longitudinal axis 7. Thereby, the pitch angle of the rotor blade 6 may be adjusted.

[0068] FIG. 3 schematically illustrates an offshore wind turbine system 60 according to an embodiment of the present invention, comprising an offshore floating platform 12 and further comprising a wind turbine 50 installed at the offshore floating platform 12. The wind turbine 50 has a rotor 52 (harboured in nacelle 51) at least one rotor blade 6 comprising at least one adaptable flow-regulating device 9, such as an adaptable flow-regulating device 9, as is illustrated in FIG. 1. The wind turbine 50 or the offshore wind turbine system 60 further comprises an arrangement 1 for controlling the offshore wind turbine 50 having the at least one rotor blade 6 which comprises at least one adaptable flow-regulating device 9. Symbolized by the arrow 10 the actuator 5 actuates the different portions of the adaptable flow-regulating device 9. The platform 12 is floating on sea surface 37 and is connected to a sea ground 33 using mooring lines 35. Due to wave motion or wind, the offshore platform 12 undergoes motions as represented by the arrow 31. Those kinds of motions may lead to loads on components of the wind turbine which may be damped or mitigated by appropriately controlling the adaptable flow-regulating device 9.

[0069] The controller 2 of the arrangement 1 illustrated in FIG. 1 comprises a first controller 13 which is provided for controlling the adaptable flow-regulating device, for example illustrated in FIGS. 2 and 3. The first controller 13 may also be referred to as active add-on controller. The first controller 13 receives a filtered load-related signal 14 which is obtained by a first bandpass filter 15. The filtered load-related signal 14 evolves by filtering the filter input signal 16 by the first filter 15. The filter 15 may be a bandpass filter, damping or attenuating frequencies of oscillations which are not intended to be damped or reduced by the add-on controller 13.

[0070] The input signal 16 may correspond or may be equal to the load-related signal 3 or may be the sum of the load-related signal 3 and a further signal 17 which may relate to wind turbine operation related signal 18. The load-related signal 3 is obtained from measurement or estimation block 19 providing for example information regarding 6-DOF platform velocity and/or acceleration and/or mooring line loads and/or interface moment between the tower 39 and a foundation 41 at the platform 12.

[0071] The wind turbine operation related signal 18 may comprise information regarding rotational speed of a rotor of the wind turbine and/or blade pitch angle and/or wind speed and/or tower-bottom moment and/or blade-root moment and/or 6-DOF rotor-nacelle arrangement velocity and/or accelerations, as obtained, measured or estimated in block 43.

[0072] The controller 2 comprises beside the first controller 13 a second controller 20 which receives a filtered wind turbine operation related signal 21 and outputs a pitch system control signal 22. The second controller 20 is also referred to as pitch controller. The filtered wind turbine operation related signal 21 is obtained by filtering a filter input signal 23 by a second filter 24 which may be a bandpass filter. The second filter 24 may attenuate or reduce oscillations in one or more particular frequency ranges, for example frequency ranges related to movements of the offshore platform due to sea waves or wind. The filter input signal 23 for the second filter 24 may correspond or may be equal to the wind turbine operation related signal 18 or may for example be a sum of the wind turbine operation related signal 18 and further operational parameters 25 as received from the wind turbine 50.

[0073] Input (23) are a set of conventional input signals to a conventional pitch controller, like a PID controller or any generic pitch controller, not restricted to PID controller. Inputs (16) comprise of the conventional inputs (17) as well as the floater inputs (3), which are to be used by the Active-addon controller (current invention).

[0074] The pitch system control signal 22 is supplied to the pitch actuator 11 illustrated in FIGS. 1 and 2. The pitch actuator is then configured to rotate the rotor blade 6 around its longitudinal axis 7 in order to adjust a particular pitch angle.

[0075] The first controller 13 as well as the second controller 20 are configured as PID controllers. The first controller as well as the second controller comprises a proportional member 26, an integrative member 27 as well as a derivative member 28 which are connected in parallel. All of them receive the filtered input signal 14, 21, respectively. The control outputs of the proportional member 26, the integrative member 27 and the derivative member 28 are summed and provided at a controller module 29 and 30, respectively for the first controller 13 and the second controller respectively.

[0076] Controller 30 is a wind turbine pitch controller without addons. Controller 29's purpose is to target the actuation of the active add-ons on the blades based on the traditional (17) as well as the floater (3) inputs. The output of this controller (4) then determines the actuation levels of the add-ons (5).

[0077] The output of the controller module 29 of the first controller 13 represents the adaptable flow device control signal 4. The output of the controller portion 30 of the second controller 20 represents the pitch system control signal 22.

[0078] The actuator 5 may comprise a not in detail illustrated inflatable bag and/or a pneumatic system for changing the shape or inflation degree of the inflatable bag.

[0079] The term “active add-on” or “adaptable flow-regulating device” may signify any device mounted on a wind turbine rotor blade which may be configured to actively response to an input signal and change the pressure distribution around the airfoil of the rotor blade. This pressure distribution change may take effect without altering the blade pitch angle or inflow wind velocity. The active add-on may include at least one of the following: [0080] Airfoil morphing technology [0081] ailerons [0082] control surfaces, such as lifting tabs [0083] surfaces to retract/extend leading edge or trailing edge [0084] inflatable membranes.

[0085] According to embodiments of the present invention, the following control concepts are provided:

[0086] The pitch controller 20 illustrated in FIG. 1 may represent a conventional blade pitch controller. The blade pitch controller 20 may apply a collective control or an individual control of the rotor blades regarding blade pitch angle. FIG. 1 thereby, illustrates how the conventionally known blade pitch controller 20 may be integrated with the active add-on controller 13. The input signals for the pitch controller 20 comprise commonly used inputs, like rotor speed, blade pitch angle, wind speed (estimates or measured) and component loads (estimates or measurement values). These control or load signals or wind turbine operation related signals may be fed through the second filter 24 after which the signal derivatives or integral are computed. The control portion 30 may therefrom derive the actual blade pitch angle.

[0087] The platform and nacelle kinematics and platform loads are used as input to the first controller 13, i.e., the active add-on controller. Thus, the add-on controller 13 may respond to both, platform and wind turbine kinematics/loads. The first filter 15 may ensure that the PID active add-on controller responds to appropriate frequency bandwidths. These signals are fed into the control block 13 and the add-on actuators 5 then respond to these signals, namely the output signal 4 of the first controller 13.

[0088] The active add-ons 9a, 9b, . . . , 9e illustrated in FIG. 2 are arranged at the airfoil of the rotor blade 6. Each adaptable flow device portion 9a, 9b, . . . , 9e may have its own controller input signal and may respond independently of the adjacent portions. The central computing unit may be responsible for activating each add-on section 9a, 9b, . . . , 9e.

[0089] Embodiments of the present invention provide a combination of blade pitch control and active add-on control allowing them to respond to different signals and frequencies.

[0090] According to an embodiment of the present invention, the active aerodynamic add-on controller may respond to the floating platform signals and wind turbine signal. The active add-on may respond faster than the blade pitch controller. Only the parts of the blade that have activated add-ons may be affected, while the rest of the rotor blade may remain unaffected and continue to stay in a prescribed blade pitch angle. Control of blade aerodynamic response can be fine-tuned to be as minimal or aggressive as necessary, making it much more versatile than blade pitch control alone. The blade pitch controller may respond to wind turbine signals, in particular wind turbine operational parameters.

[0091] Embodiments of the present invention may allow to maintain pitch bearing design as conventional also in onshore wind turbines. Embodiments of the present invention may for example achieve to reduce the load on the blade pitch control and the blade pitch bearings. Add-ons or add-on portions may be placed on different isolated locations along the blade span. Thereby, targeted control strategies to provide localized regulation of the aerodynamic lift is enabled. The add-ons or add-on portions may be made as wide/as long as the project demands or the application demands. The response time for actuating the active add-ons may be faster than the response time of the pitching system. The blade pitch control may typically be around 3° per second, but the active add-on may response nearly instantaneously to alter the pressure distribution around an airfoil.

[0092] Embodiments of the present invention, in particular the active add-on controller, may be configured to decrease loads on floating wind turbine components and/or may be adapted for tuning the damping required in a floating system to avoid negative feedback cycles. In particular, the active add-on control system may be utilized to adopt an active damping system and it may respond to different sea-states and wind speed to mitigate damage caused by illusive and sudden rough wave events.

[0093] Although the present invention has been disclosed in the form of embodiments and variations thereon, it will be understood that numerous additional modifications and variations could be made thereto without departing from the scope of the invention.

[0094] For the sake of clarity, it is to be understood that the use of “a” or “an” throughout this application does not exclude a plurality, and “comprising” does not exclude other steps or elements.