Systems and methods for improving extreme load control of wind turbine components

Abstract

A method for reducing extreme loads acting on components of a wind turbine includes measuring a plurality of operating parameters of the wind turbine via one or more sensors. Additionally, the method includes predicting at least one blade moment of at least one rotor blade of the wind turbine based on the plurality of operating parameters. The method further includes predicting the load and associated load angle of at least one rotor blade based on the at least one blade moment. Additionally, the method includes predicting the pitch angle of at least one rotor blade of the wind turbine. Further, the method includes generating a load envelope for the component, which includes at least one load value with respect to the pitch angle and the load angle. Accordingly, the method includes implementing a control action when the load is outside the load envelope.

Description

Technical Field

[0001] The present subject matter generally relates to wind turbines, and more particularly to a system and method for improving the control of extreme loads on wind turbine components such as rotor blades, pitch bearings, and hubs. Background Art

[0002] Wind power is considered to be one of the cleanest and most environmentally friendly energy sources currently available, and wind turbines have received increased attention in this regard. Modern wind turbines typically include a tower, a generator, a gearbox, a nacelle, and one or more rotor blades. The rotor blades are the main elements that convert wind energy into electrical energy. The blades typically have an airfoil cross-sectional profile such that during operation, air flows over the blade creating a pressure differential between its two sides. Thus, a lift force acting from the pressure side towards the suction side acts on the blade. The lift force generates a torque on the main rotor shaft, which is connected to a generator for electricity generation.

[0003] The amount of power that can be generated by a wind turbine is typically limited by the structural limitations (i.e., design loads) of the individual wind turbine components. For example, the blade root of a wind turbine can experience loads related to the average load due to turbine operation and the dynamic fluctuating loads due to environmental conditions (e.g., blade root resultant moment). Such loads can damage turbine components, ultimately leading to turbine component failure. The fluctuating loads can change daily or seasonally and can be based on wind speed, wind peaks, wind turbulence, wind shear, changes in wind direction, air density, yaw misalignment, upwind, or the like. In particular, for example, the loads experienced by a wind turbine can vary with wind speed.

[0004] Thus, it is necessary to ensure that the loads acting on a wind turbine do not exceed the design loads. Accordingly, many wind turbines employ one or more sensors configured to measure the loads acting on the individual wind turbine components. While sensors can provide the desired information, installing a new sensor system can be complex and expensive. In addition, sensors can provide incorrect information and are prone to failure.

[0005] Additionally, a wind turbine uses a control system configured to estimate the loads acting on the wind turbine based on the wind turbine thrust. As used herein, the terms "thrust", "thrust value", "thrust parameter", or the like are intended to include the forces acting on the wind turbine due to the wind. The thrust results from a change in pressure as the wind passes over and decelerates across the wind turbine. Such control strategies estimate the loads acting on the wind turbine by determining an estimated thrust using multiple turbine operating conditions such as, for example, pitch angle, power output, generator speed, and air density. The operating conditions are inputs to the algorithm, which includes a series of equations, one or more aerodynamic performance maps, and one or more look-up tables (LUTs). For example, the LUT may represent the wind turbine thrust. The + / − standard deviation of the estimated thrust can also be calculated, as well as the operational maximum thrust and thrust limits. Thus, the wind turbine can be controlled based on the difference between the maximum thrust and the thrust limits.

[0006] However, such existing control devices are tuned to minimize the resultant blade root moment regardless of the load direction and pitch angle, and thus are always targeted at the worst-case scenario. Therefore, such control operates conservatively with additional pitch travel and also sacrifices annual energy production in the process.

[0007] In view of the foregoing, there is a continuing need in the art for new and improved systems for controlling extreme loads on wind turbine components such as rotor blades, pitch bearings, and hubs to address the above problems. Summary of the Invention

[0008] Aspects and advantages of the invention will be set forth in part in the following description, or may be apparent from the description, or may be learned by practice of the invention.

[0009] In one aspect, the subject matter relates to a method for reducing extreme loads acting on components of a wind turbine. The method includes measuring, via one or more sensors, a plurality of operating parameters of the wind turbine. Additionally, the method includes predicting, via a processor, at least one blade moment of at least one rotor blade of the wind turbine based on the plurality of operating parameters. The method further includes predicting, via the processor, a load (e.g., such as a resultant blade root moment) and an associated load angle of at least one rotor blade of the wind turbine based on the at least one blade moment. Additionally, the method includes predicting, via the processor, a pitch angle of at least one rotor blade of the wind turbine. Further, the method includes generating, via the processor, a load envelope for the component, which includes at least one load value with respect to the pitch angle and the load angle. Thus, the method includes implementing a control action via a controller when the load is outside the load envelope.

[0010] In an embodiment, the component may include, for example, a rotor blade, a pitch bearing, or a hub of a wind turbine. In another embodiment, the plurality of operating parameters of the wind turbine may include any one or combination of the following: rotor position, thrust, load, power, speed, torque, blade weight, gravity, pitch angle, point moment, overhang moment, bearing lubrication schedule, rotor azimuth angle, and / or yaw moment.

[0011] In other embodiments, predicting the blade moment of a rotor blade of a wind turbine may include calculating the blade moment of the edge direction of the rotor blade based on a plurality of operating parameters and an estimated state of the wind turbine. Additionally, predicting the blade moment of a rotor blade of a wind turbine may include calculating the blade pendulum moment of the rotor blade based on the rotor position, blade weight, and torque.

[0012] In several embodiments, predicting the load and associated load angle based on the blade moment may include calculating the load and associated load angle based on the edge direction blade moment of the rotor blade and the blade pendulum moment of the rotor blade. In such embodiments, calculating the load and associated load angle based on the edge direction blade moment of the rotor blade and the blade pendulum moment of the rotor blade may include calculating the associated load angle by dividing the blade pendulum moment of the rotor blade by the edge direction blade moment of the rotor blade, and calculating the load based on the associated load angle.

[0013] In a particular embodiment, predicting the pitch angle of a rotor blade of a wind turbine may include calculating the pitch angle of the rotor blade of the wind turbine based on one or more controller commands.

[0014] In other embodiments, implementing a control action when the load is outside the load envelope may include pitching the rotor blade. In such embodiments, pitching one or more rotor blades may include pitching the plurality of rotor blades of the wind turbine together, pitching each of the plurality of rotor blades independently, and / or pitching each of the plurality of rotor blades periodically.

[0015] In another aspect, the present disclosure relates to a system for reducing extreme loads acting on a component of a wind turbine. The system includes one or more sensors configured to measure a plurality of operating parameters of the wind turbine and a controller configured with the one or more sensors. The controller includes a processor configured to perform a variety of operations, including but not limited to predicting at least one blade moment of at least one rotor blade of the wind turbine based on the plurality of operating parameters, predicting the load and associated load angle of the rotor blade based on the blade moment, the load corresponding to the resultant root moment of the rotor blade, predicting the pitch angle of the wind turbine rotor blade, generating a load envelope for the component, which includes at least one load value regarding the pitch angle and the load angle, and implementing a control action when the load is outside the load envelope.

[0016] Technical solution 1. A method for reducing extreme loads acting on a wind turbine component, the method comprising:

[0017] Measuring a plurality of operating parameters of the wind turbine via one or more sensors;

[0018] Predicting at least one blade moment of at least one rotor blade of the wind turbine via a processor based on the plurality of operating parameters; predicting the load and the associated load angle of the at least one rotor blade via the processor according to the at least one blade moment; predicting the pitch angle of at least one rotor blade of the wind turbine via the processor;

[0019] Generating, via the processor, a load envelope for the component, the load envelope including at least one load value with respect to the pitch angle and the load angle; and

[0020] Implementing a control action via a controller when the load is outside the load envelope.

[0021] Technical solution 2. The method according to technical solution 1, wherein the component comprises at least one of a rotor blade, a pitch bearing or a hub of the wind turbine.

[0022] Technical solution 3. The method according to technical solution 1, wherein the plurality of operating parameters of the wind turbine comprises at least one of the following: rotor position, thrust, load, power, speed, torque, blade weight, gravity, pitch angle, point dynamic moment, overhang moment, bearing lubrication plan, rotor azimuth angle, or yaw moment.

[0023] Technical solution 4. The method according to technical solution 3, wherein predicting at least one blade moment of a rotor blade of the wind turbine further comprises:

[0024] Calculating an edge-direction blade moment of the rotor blade according to the plurality of operating parameters and the estimated state of the wind turbine.

[0025] Technical solution 5. The method according to technical solution 4, wherein predicting at least one blade moment of a rotor blade of the wind turbine further comprises:

[0026] Calculating a blade sway moment of the rotor blade according to the rotor position, the blade weight and the torque.

[0027] Technical solution 6. The method according to technical solution 5, wherein predicting the load and the associated load angle according to the at least one blade moment further comprises:

[0028] Calculate the load and the associated load angle based on the edgewise blade moment of the rotor blade and the flapwise blade moment of the rotor blade.

[0029] Aspect 7. The method according to Aspect 6, wherein calculating the load and the associated load angle based on the edgewise blade moment of the rotor blade and the flapwise blade moment of the rotor blade further comprises:

[0030] Calculating the associated load angle by dividing the flapwise blade moment of the rotor blade by the edgewise blade moment of the rotor blade; and

[0031] Calculating the load based on the associated load angle.

[0032] Aspect 8. The method according to Aspect 1, wherein predicting the pitch angle of at least one rotor blade of the wind turbine further comprises calculating the pitch angle of at least one rotor blade of the wind turbine based on one or more controller commands.

[0033] Aspect 9. The method according to Aspect 1, wherein the load on the at least one rotor blade comprises the resultant moment at the blade root.

[0034] Aspect 10. The method according to Aspect 1, wherein implementing the control action when the load is outside the load envelope further comprises pitching the at least one rotor blade.

[0035] Aspect 11. The method according to Aspect 10, wherein pitching the at least one rotor blade further comprises at least one of the following: pitching the plurality of rotor blades of the wind turbine together, pitching each of the plurality of rotor blades independently, or pitching each of the plurality of rotor blades periodically.

[0036] Aspect 12. A system for reducing extreme loads acting on components of a wind turbine, the system comprising:

[0037] One or more sensors configured to measure a plurality of operating parameters of the wind turbine;

[0038] A controller configured with the one or more sensors, the controller comprising a processor configured to perform a plurality of operations, the plurality of operations comprising:

[0039] Predicting at least one blade moment of at least one rotor blade of the wind turbine based on the plurality of operating parameters;

[0040] Predicting the load and associated load angle of the at least one rotor blade based on the at least one blade moment, the load corresponding to the resultant blade root moment of the at least one rotor blade;

[0041] Predicting the pitch angle of at least one rotor blade of the wind turbine;

[0042] Generating a load envelope for the component, including at least one load value with respect to the pitch angle and the load angle; and

[0043] Implementing a control action when the load is outside the load envelope.

[0044] Aspect 13. The system according to aspect 12, wherein the component includes at least one of a rotor blade, a pitch bearing, or a hub of the wind turbine.

[0045] Aspect 14. The system according to aspect 12, wherein the plurality of operating parameters of the wind turbine include at least one of the following: rotor position, thrust, load, power, speed, torque, blade weight, gravity, pitch angle, point dynamic moment, overhang moment, bearing lubrication schedule, rotor azimuth angle, or yaw moment.

[0046] Aspect 15. The system according to aspect 14, wherein predicting at least one blade moment of a rotor blade of the wind turbine further includes:

[0047] Calculating the edgewise blade moment of the rotor blade based on the plurality of operating parameters and estimated states of the wind turbine; and

[0048] Calculating the blade flapping moment of the rotor blade based on the rotor position, the blade weight, and the torque.

[0049] Aspect 16. The system according to aspect 15, wherein predicting the load and the associated load angle based on the at least one blade moment further includes:

[0050] Calculating the load and the associated load angle based on the edgewise blade moment of the rotor blade and the blade flapping moment of the rotor blade.

[0051] Aspect 17. The system according to aspect 16, wherein calculating the load and the associated load angle based on the edgewise blade moment of the rotor blade and the blade flapping moment of the rotor blade further includes:

[0052] Calculating the associated load angle by dividing the blade flapping moment of the rotor blade by the edgewise blade moment of the rotor blade; and

[0053] Calculate the load based on the associated load angle.

[0054] Aspect 18. The system according to Aspect 12, wherein predicting a pitch angle of at least one rotor blade of the wind turbine further comprises calculating the pitch angle of at least one rotor blade of the wind turbine based on one or more controller commands.

[0055] Aspect 19. The system according to Aspect 12, wherein the one or more sensors comprise proximity sensors.

[0056] Aspect 20. The system according to Aspect 12, wherein implementing the control action when the load is outside the load envelope further comprises pitching the at least one rotor blade, and pitching the at least one rotor blade further comprises at least one of the following: pitching a plurality of rotor blades of the wind turbine together, pitching each of the plurality of rotor blades independently, or pitching each of the plurality of rotor blades periodically.

[0057] These and other features, aspects, and advantages of the present invention will become better understood with reference to the following description and the appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] A complete and enabling disclosure of the present invention, including its best mode, for a person of ordinary skill in the art is set forth in the specification with reference to the drawings, in which:

[0059] Figure 1 A perspective view of an embodiment of a wind turbine according to the present disclosure is shown;

[0060] Figure 2 A simplified internal view of an embodiment of a nacelle of a wind turbine according to the present disclosure is shown;

[0061] Figure 3 A schematic diagram of an embodiment of a controller according to the present disclosure is shown;

[0062] Figure 4 A flowchart of an embodiment of a method for reducing extreme loads acting on components of a wind turbine according to the present disclosure is shown;

[0063] Figure 5 A perspective view of an embodiment of a wind turbine according to the present disclosure is shown, particularly showing various axes of rotation and the corresponding forces and moments acting on the wind turbine;

[0064] Figure 6A A graph showing an embodiment of the blade resultant moment (MrB) (y-axis) versus the load angle (x-axis) from a time series near the rated wind speed with the RIC always on, according to the present disclosure;

[0065] Figure 6B A graph showing an embodiment of the blade resultant moment (MrB) (y-axis) versus the load angle (x-axis) from a time series near the rated wind speed with the RIC not on, according to the present disclosure; and

[0066] Figure 7 A schematic diagram showing an embodiment of a system for reducing extreme loads acting on components of a wind turbine, according to the present disclosure. DETAILED DESCRIPTION

[0067] Reference will now be made in detail to embodiments of the invention, one or more examples of which are illustrated in the figures. Each example is provided by way of explanation of the invention, and not as a limitation of the invention. Indeed, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. For example, features shown or described as part of one embodiment can be used with another embodiment to yield yet another embodiment. Accordingly, it is intended that the present invention cover such modifications and variations as fall within the scope of the appended claims and their equivalents.

[0068] Generally, the present disclosure relates to improved systems and methods for improving extreme load control of wind turbine components such as rotor blades, pitch bearings, and hubs. More particularly, the method is intended to use extreme component envelopes at each load angle and pitch angle. For example, unbalanced load measurements, thrust estimates, rotor position, and pitch angle predictions are used to predict load magnitude and load angle. The predicted load magnitude is compared with the load envelope to determine the necessary control measures. Thus, the present disclosure limits unnecessary pitching and energy losses associated with the control of a single extreme load.

[0069] In a particular embodiment, for example, load envelopes of the load angle and blade pitch angle are used to determine the margin on certain wind turbine components. The data is used in a controller to determine how close the wind turbine is operating to the stress limit. The controller uses proximity sensor information and estimated states to predict edgewise blade loads. Similarly, torque can be predicted based on rotor position, stored weight data, and rotor torque. The combined information is used to predict the load angle and magnitude. The pitch angle can also be predicted based on controller commands. This information can then be used for comparison with the envelope information. Then, when an overshoot is predicted, the controller uses this information to reduce the load.

[0070] Now refer toFigure 1 , a perspective view of an embodiment of a wind turbine 10 in which control techniques according to the present disclosure may be implemented is shown. As shown, the wind turbine 10 generally includes a tower 12 extending from a support surface 14, a nacelle 16 mounted on the tower 12, and a rotor 18 coupled to the nacelle 16. The rotor 18 includes a rotatable hub 20 and at least one rotor blade 22 coupled to and extending outwardly from the hub 20. For example, in the illustrated embodiment, the rotor 18 includes three rotor blades 22. However, in alternative embodiments, the rotor 18 may include more or fewer than three rotor blades 22. Each rotor blade 22 may be spaced about the hub 20 to facilitate rotation of the rotor 18 such that kinetic energy can be converted from wind into useful mechanical energy and then into electrical energy. For example, the hub 20 may be rotatably coupled to a generator 24( Figure 2 ) positioned within the nacelle 16 to permit generation of electrical energy.

[0071] The wind turbine 10 may also include a wind turbine controller 26 centralized within the nacelle 16. However, in other embodiments, the controller 26 may be located within any other component of the wind turbine 10 or at a location external to the wind turbine. Additionally, the controller 26 may be communicatively coupled to any number of components of the wind turbine 10 to control the operation of such components and / or to implement corrective actions. Thus, the controller 26 may include a computer or other suitable processing unit. Accordingly, in several embodiments, the controller 26 may include suitable computer-readable instructions that, when implemented, cause the controller 26 to be configured to perform various different functions, such as receiving, transmitting, and / or executing wind turbine control signals. Thus, as will be discussed in more detail below, the controller 26 may generally be configured to control various operating modes (e.g., startup or shutdown sequences), derate the wind turbine, and / or control various components of the wind turbine 10.

[0072] Now referring to Figure 2 , a simplified internal view of an embodiment of the nacelle 16 of the wind turbine 10 shown in Figure 1 is shown. As shown, the generator 24 may be coupled to the rotor 18 for generating electrical power from the rotational energy generated by the rotor 18. For example, as shown in the illustrated embodiment, the rotor 18 may include a rotor shaft 34 that is coupled to the hub 20 for rotation therewith. The rotor shaft 34 may in turn be rotatably coupled to a generator shaft 36 of the generator 24 via a gearbox 38. As generally understood, the rotor shaft 34 may provide a low-speed high-torque input to the gearbox 38 in response to rotation of the rotor blades 22 and the hub 20. The gearbox 38 may then be configured to convert the low-speed high-torque input into a high-speed low-torque output to drive the generator shaft 36 and thus the generator 24.

[0073] Each rotor blade 22 may also include a pitch adjustment mechanism 32 configured to rotate each rotor blade 22 about its pitch axis 28. Additionally, each pitch adjustment mechanism 32 may include a pitch drive motor 40 (e.g., any suitable electric, hydraulic, or pneumatic motor), a pitch drive gearbox 42, and a pitch drive pinion 44. In such embodiments, the pitch drive motor 40 may be coupled to the pitch drive gearbox 42 such that the pitch drive motor 40 imparts mechanical force to the pitch drive gearbox 42. Similarly, the pitch drive gearbox 42 may be coupled to the pitch drive pinion 44 for rotation therewith. The pitch drive pinion 44 may in turn be in rotational engagement with a pitch bearing 46 coupled between the hub 20 and the corresponding rotor blade 22 such that rotation of the pitch drive pinion 44 causes rotation of the pitch bearing 46. Thus, in such embodiments, rotation of the pitch drive motor 40 drives the pitch drive gearbox 42 and the pitch drive pinion 44, causing the pitch bearing 46 and the rotor blade 22 to rotate about the pitch axis 28. Similarly, the wind turbine 10 may include one or more yaw drive mechanisms 66 communicatively coupled to the controller 26, wherein each yaw drive mechanism 66 is configured to change the angle of the nacelle 16 relative to the wind (e.g., by engaging a yaw bearing 68 of the wind turbine 10).

[0074] Still referring to Figure 2, the wind turbine 10 may also include one or more sensors 48, 50 for measuring various operating parameters (described in more detail below) that may be required for various blade moments. For example, in various embodiments, the sensors may include blade sensors 48 for measuring the pitch angle of one of the rotor blades 22 or for measuring the load acting on one of the rotor blades 22; generator sensors (not shown) for monitoring the generator 24 (e.g., torque, rotational speed, acceleration, and / or power output); sensors for measuring rotor unbalance loads (e.g., main shaft bending sensors); and / or various wind sensors 50 for measuring various wind parameters (such as wind speed, wind peaks, wind turbulence, wind shear, changes in wind direction, air density, or the like). Additionally, the sensors may be located near the ground of the wind turbine, on the nacelle, or on the meteorological mast of the wind turbine. It should also be understood that any other number or type of sensors may be used and in any location. For example, the sensors may be micro-inertial measurement units (MIMUs), strain gauges, accelerometers, pressure sensors, angle-of-attack sensors, vibration sensors, proximity sensors, light detection and ranging (LIDAR) sensors, camera systems, fiber optic systems, anemometers, wind vanes, sound detection and ranging (SODAR) sensors, infrared lasers, radiometers, pitot tubes, radiosondes, other optical sensors, and / or any other suitable sensors. It should be appreciated that as used herein, the term "monitoring" and its variants indicate that the various sensors may be configured to provide either direct measurements of the monitored parameters or indirect measurements of such parameters. Thus, for example, the sensors may be used to generate signals regarding the monitored parameters, which may then be used by the controller 26 to determine the actual parameters.

[0075] Now referring to Figure 3 , a block diagram of an embodiment showing various components of the controller 26 in accordance with the present disclosure is shown. As shown, the controller 26 may include one or more processors 58 and associated memory devices 60, which are configured to perform a variety of computer-implemented functions (e.g., execute methods, steps, calculations, etc. as disclosed herein and store related data). Additionally, the controller 26 may also include a communication module 62 to facilitate communication between the controller 26 and the various components of the wind turbine 10. Further, the communication module 62 may include a sensor interface 64 (e.g., one or more analog-to-digital converters) to allow signals transmitted from the sensors 48, 50 to be converted into signals that can be understood and processed by the processor 58. It should be understood that the sensors 48, 50 may be communicatively coupled to the communication module 62 using any suitable device. For example, as Figure 3 shown, the sensors 48, 50 are coupled to the sensor interface 64 via a wired connection. However, in other embodiments, the sensors 48, 50 may be coupled to the sensor interface 64 via a wireless connection, such as by using any suitable wireless communication protocol known in the art.

[0076] As used herein, the term "processor" refers not only to integrated circuits conventionally considered to be included in a computer in the art, but also to controllers, microcontrollers, microcomputers, programmable logic controllers (PLCs), application specific integrated circuits, and other programmable circuits. Additionally, the memory device 60 may generally include memory elements including, but not limited to: computer-readable media (e.g., random access memory (RAM)), computer-readable non-volatile media (e.g., flash memory), floppy disks, compact disk-read only memory (CD-ROM), magneto-optical disk (MOD), digital versatile disk (DVD), and / or other suitable memory elements. Such memory devices 60 may generally be configured to store suitable computer-readable instructions that, when implemented by the processor 58, cause the controller 26 to be configured to perform various functions including, but not limited to, determining one or more current wind turbine parameters of the wind turbine 10 based on a plurality of operating data, determining maximum wind turbine parameters, transmitting suitable control signals to implement control actions to reduce loads acting on the wind turbine, and various other suitable computer-implemented functions.

[0077] Now referring to Figure 4 , a flowchart of a method 100 for reducing extreme loads acting on components of a wind turbine in accordance with an embodiment of the present disclosure is shown. In an embodiment, for example, the component may include, for example, one of the rotor blades 22, the pitch bearing 46, or the hub 20 of the wind turbine 10. The method 100 is described herein as being implemented, for example, using the wind turbine 10 described above. However, it should be understood that the disclosed method 100 may be implemented using any other suitable wind turbine now known or later developed in the art. Additionally, although Figure 4 the steps are depicted in a particular order for purposes of illustration and discussion, the methods described herein are not limited to any particular order or arrangement. Using the disclosures provided herein, those skilled in the art will appreciate that the various steps of the methods may be omitted, rearranged, combined, and / or altered in various ways.

[0078] As shown at (102), the method 100 includes measuring a plurality of operating parameters of the wind turbine 10 via one or more sensors. For example, in one embodiment, the sensors 48, 50 are configured to measure or otherwise monitor various operating parameters of the wind turbine 10. More particularly, as mentioned, the operating parameters may include one or a combination of the following: rotor position, thrust, load, power, speed, torque, blade weight, gravity, pitch angle, point dynamic moment, overhang moment, bearing lubrication schedule, rotor azimuth angle, and / or yaw moment.

[0079] Thus, as shown at (104), method 100 includes predicting, via processor 58, at least one blade moment of rotor blade 22 of wind turbine 10 based on a plurality of operating parameters. For example, as Figure 5 shown, a exploded view of one embodiment of wind turbine 10 is shown, particularly showing various axes of rotation and corresponding forces and moments acting on wind turbine 10. The peak load of wind turbine 10 can vary between turbines, but generally, typically corresponds to at least one of the following: the resultant blade root moment (e.g., M rB , which includes the pitch and hub loads M xB , M yb and M zb ), the main shaft load (e.g., M yr , M zr ), the main bearing load (e.g., M xr , M yr ), the yaw drive load (e.g., M xk ), the yaw bolt / bearing / flange load (e.g., M yk , M zk ) or the tower bending load (e.g., M xt , M yt and M zt ). It should be understood that the peak load as described herein may also include any additional loads experienced by wind turbine 10, and the loads shown in Figure 5 are provided for illustrative purposes only.

[0080] Thus, in a particular embodiment, processor 58 may be configured to calculate the edgewise blade moment (M yB ) of rotor blade 22 according to the operating parameters and estimated state of wind turbine 10. Additionally, processor 58 may be configured to predict and calculate the blade flapping moment (M zB ) of rotor blade 22 according to the rotor position, blade weight, and torque.

[0081] Returning to Figure 4 , as shown at (106), method 100 includes predicting, via processor 58, a load (e.g., such as the resultant blade root moment, M rB ) and an associated load angle of rotor blade 22 according to the blade moment described herein. For example, in several embodiments, processor 58 may be configured to calculate the load and the associated load angle according to the edgewise blade moment and the blade flapping moment of rotor blade 22. More particularly, in such embodiments, processor 58 may be configured to calculate the associated load angle by dividing the blade flapping moment of rotor blade 22 by the edgewise blade moment of rotor blade 22, and calculate the load according to the associated load angle.

[0082] As shown at (108), method 100 includes predicting the pitch angle of rotor blade 22 of wind turbine 10 via processor 58. In a particular embodiment, for example, processor 58 is configured to predict the pitch angle of the rotor blade of the wind turbine by calculating the pitch angle of the rotor blade of the wind turbine according to one or more controller commands.

[0083] As shown at (110), method 100 includes generating, via processor 58, a load envelope for a component, the load envelope including one or more load values of pitch angle and load angle. For example, Figure 6A and Figure 6B respectively show examples of load envelopes according to the present disclosure.

[0084] Returning to Figure 4 , as shown at (112), method 100 includes implementing a control action via controller 26 when the load is outside the load envelope. For example, in a particular embodiment, the control action may include pitching rotor blade 22. More particularly, in such an embodiment, pitching one or more rotor blades 22 may include pitching the plurality of rotor blades 22 of wind turbine 10 together, pitching each of the plurality of rotor blades 22 independently, and / or pitching each of the plurality of rotor blades 22 periodically.

[0085] With respect to Figure 6A and Figure 6B the advantages of the present disclosure can be better understood. More particularly, as shown, FIGS. 200, 300 show blade resultant moment (MrB) (y-axis) versus load angle (x-axis) from a time series near rated wind speed according to the present disclosure. Figure 6A FIG. 200 of Figure 6B shows a scenario where RIC is always on, while Figure 6A and Figure 6B FIG. 300 of

[0086] It should also be understood that control actions as described herein may include any suitable commands or constraints of the controller 26. For example, in several embodiments, the control actions may include temporarily derating or ramping up a wind turbine to prevent excessive loads on one or more wind turbine components. Ramping up a wind turbine (such as by ramping up torque) may temporarily slow down the speed of the wind turbine and act as a brake to help reduce or prevent loads. Derating a wind turbine may include speed derating, torque derating, or a combination of both. Additionally, as mentioned, a wind turbine 10 may be derated by pitching one or more rotor blades 22 about their pitch axes 28. More particularly, the controller 26 may generally control each pitch adjustment mechanism 32 to vary the pitch angle of each rotor blade 22 between 0 degrees (i.e., the power position of the rotor blade 22) and 90 degrees (i.e., the feather position of the rotor blade 22). Thus, in one embodiment, the controller 26 may command a new pitch setpoint (e.g., from 0 degrees to 5 degrees), while in another embodiment, the controller 26 may specify a new pitch constraint (e.g., a constraint to ensure that subsequent pitch commands are at least 5 degrees).

[0087] In yet another embodiment, a wind turbine 10 may be temporarily derated by modifying the torque demand on the generator 24. Generally, the torque demand may be varied using any suitable methods, processes, structures, and / or means known in the art. For example, in one embodiment, the torque demand on the generator 24 may be controlled using the controller 26 by transmitting a suitable control signal / command to the generator 24 to modulate the magnetic flux generated within the generator 24.

[0088] A wind turbine 10 may also be temporarily derated by yawing the nacelle 22 to change the angle of the nacelle 16 relative to the wind direction. In additional embodiments, the controller 26 may be configured to actuate one or more mechanical brakes to reduce the rotational speed of the rotor blades 22 and thereby reduce component loads. In yet additional embodiments, the controller 26 may be configured to perform any suitable control actions known in the art. Additionally, the controller 26 may implement a combination of two or more control actions.

[0089] Referring now to FIG. 6, there is shown a schematic flow diagram of a particular embodiment of a system 400 for reducing extreme loads acting on components of a wind turbine in accordance with the present disclosure. As shown, the system 400 may include a controller 402 that receives D and Q torques 404, rotor azimuth angle 406, and gravity load 408. The controller 402 may then determine MyB and MzB torques 410, 412 based on the received inputs. As shown at 414, the controller 402 may use the MyB torque 410 and the MzB torque 412 to determine the MrB load. Additionally, as shown at 416, the controller 402 may also use the MyB and MzB torques 410, 412 to determine the load angle. As shown at 418, the controller 402 may also predict the pitch angle. Thus, as shown at 420, the controller 402 may determine the MrB threshold / envelope based on the load angle and the pitch angle. The MrB load 414 and the MrB threshold / envelope 420 may then be used to determine pitch actions (e.g., collective / independent / periodic).

[0090] Various aspects and embodiments of the present invention are defined by the following numbered clauses:

[0091] Clause 1. A method for reducing extreme loads acting on components of a wind turbine, the method comprising:

[0092] Measuring a plurality of operating parameters of a wind turbine via one or more sensors;

[0093] Predicting, via a processor, at least one blade torque of at least one rotor blade of the wind turbine based on the plurality of operating parameters;

[0094] Predicting, via a processor, a load and an associated load angle of at least one rotor blade of the wind turbine based on the at least one blade torque;

[0095] Predicting, via a processor, a pitch angle of at least one rotor blade of the wind turbine;

[0096] Generating, via a processor, a load envelope for a component, the load envelope including at least one load value with respect to the pitch angle and the load angle; and

[0097] Implementing a control action via a controller when the load is outside the load envelope.

[0098] Clause 2. The method of clause 1, wherein the component includes at least one of a rotor blade, a pitch bearing, or a hub of the wind turbine.

[0099] Clause 3. The method of any of the preceding clauses, wherein the plurality of operating parameters of the wind turbine includes at least one of: rotor position, thrust, load, power, speed, torque, blade weight, gravity, pitch angle, point dynamic torque, overhang torque, bearing lubrication schedule, rotor azimuth angle, or yaw torque.

[0100] Clause 4. The method of any of the preceding clauses, wherein predicting at least one blade moment of a rotor blade of a wind turbine further comprises:

[0101] Calculating an edgewise blade moment of the rotor blade based on a plurality of operating parameters and an estimated state of the wind turbine.

[0102] Clause 5. The method of any of the preceding clauses, wherein predicting at least one blade moment of a rotor blade of a wind turbine further comprises:

[0103] Calculating a blade flapping moment of the rotor blade based on the rotor position, the blade weight, and the torque.

[0104] Clause 6. The method of any of the preceding clauses, wherein predicting a load and an associated load angle based on at least one blade moment further comprises:

[0105] Calculating the load and the associated load angle based on the edgewise blade moment of the rotor blade and the blade flapping moment of the rotor blade.

[0106] Clause 7. The method of any of the preceding clauses, wherein calculating the load and the associated load angle based on the edgewise blade moment of the rotor blade and the blade flapping moment of the rotor blade further comprises:

[0107] Calculating the associated load angle by dividing the blade flapping moment of the rotor blade by the edgewise blade moment of the rotor blade; and

[0108] Calculating the load based on the associated load angle.

[0109] Clause 8. The method of any of the preceding clauses, wherein predicting a pitch angle of at least one rotor blade of a wind turbine further comprises calculating the pitch angle of at least one rotor blade of the wind turbine based on one or more controller commands.

[0110] Clause 9. The method of any of the preceding clauses, wherein the load on at least one rotor blade comprises a resultant blade root moment.

[0111] Clause 10. The method of any of the preceding clauses, wherein implementing a control action when the load is outside the load envelope further comprises pitching at least one rotor blade.

[0112] Clause 11. The method of any of the preceding clauses, wherein pitching at least one rotor blade further comprises at least one of: pitching a plurality of rotor blades of the wind turbine together, pitching each of the plurality of rotor blades independently, or pitching each of the plurality of rotor blades periodically.

[0113] Clause 12. A system for reducing extreme loads acting on components of a wind turbine, the system comprising:

[0114] One or more sensors configured to measure a plurality of operating parameters of the wind turbine;

[0115] A controller configured with the one or more sensors, the controller including a processor configured to perform a plurality of operations, the plurality of operations including:

[0116] Predicting at least one blade moment of at least one rotor blade of the wind turbine based on the plurality of operating parameters;

[0117] Predicting the load and associated load angle of at least one rotor blade based on at least one blade moment, the load corresponding to the resultant blade root moment of at least one rotor blade;

[0118] Predicting the pitch angle of at least one rotor blade of the wind turbine;

[0119] Generating a load envelope for the component, the load envelope including at least one load value with respect to the pitch angle and the load angle; and

[0120] Implementing a control action when the load is outside the load envelope.

[0121] Clause 13. The system of Clause 12, wherein the component includes at least one of a rotor blade, a pitch bearing, or a hub of the wind turbine.

[0122] Clause 14. The system of Clauses 12 - 13, wherein the plurality of operating parameters of the wind turbine includes at least one of: rotor position, thrust, load, power, speed, torque, blade weight, gravity, pitch angle, point dynamic moment, overhang moment, bearing lubrication schedule, rotor azimuth angle, or yaw moment.

[0123] Clause 15. The system of Clauses 12 - 14, wherein predicting at least one blade moment of a rotor blade of the wind turbine further includes:

[0124] Calculating an edge - direction blade moment of the rotor blade based on the plurality of operating parameters and the estimated state of the wind turbine; and

[0125] Calculating a blade flapping moment of the rotor blade based on the rotor position, blade weight, and torque.

[0126] Clause 16. The system of Clauses 12 - 15, wherein predicting the load and associated load angle based on at least one blade moment further includes:

[0127] Calculating the load and associated load angle based on the edge - direction blade moment of the rotor blade and the blade flapping moment of the rotor blade.

[0128] Clause 17. The system of Clauses 12 - 16, wherein calculating the load and the associated load angle based on the blade moment and the blade pitching moment of the rotor blade in the edge direction of the rotor blade further includes:

[0129] Calculating the associated load angle by dividing the blade pitching moment of the rotor blade by the blade moment of the rotor blade in the edge direction; and

[0130] Calculating the load based on the associated load angle.

[0131] Clause 18. The system of Clauses 12 - 17, wherein predicting the pitch angle of at least one rotor blade of a wind turbine further includes calculating the pitch angle of at least one rotor blade of the wind turbine based on one or more controller commands.

[0132] Clause 19. The system of Clauses 12 - 18, wherein one or more sensors include proximity sensors.

[0133] Clause 20. The system of Clauses 12 - 19, wherein implementing a control action when the load is outside the load envelope further includes pitching at least one rotor blade, and pitching at least one rotor blade further includes at least one of the following: pitching a plurality of rotor blades of the wind turbine together, pitching each of the plurality of rotor blades independently, or pitching each of the plurality of rotor blades periodically.

[0134] This written description uses examples to disclose the invention (including the best mode), and also enables any person skilled in the art to practice the invention, including making and using any device or system and performing any combined method. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. If such other examples include structural elements that are not different from the literal language of the claims, or if they include equivalent structural elements with non - substantial differences from the literal language of the claims, such other examples are intended to be within the scope of the claims.

Claims

1. A method for reducing extreme loads acting on components of a wind turbine, the wind turbine having at least one rotor blade, the method comprising: Measuring, via one or more sensors at the at least one rotor blade, a plurality of operating parameters of the wind turbine; Calculating, via a processor, an edgewise blade moment and a flapwise blade moment of the at least one rotor blade based on the plurality of operating parameters of the wind turbine; Predicting, via the processor, a load and an associated load angle of the at least one rotor blade based on the edgewise blade moment and the flapwise blade moment of the at least one rotor blade, wherein the load of the at least one rotor blade includes a resultant root moment; Predicting, via the processor, a pitch angle of at least one rotor blade of the wind turbine; Generating, via the processor, a load envelope for the component, the load envelope including at least one load value with respect to the pitch angle and the load angle; And Implementing, via a controller, a control action when the load is outside the load envelope, the control action including pitching the at least one rotor blade.

2. The method according to claim 1, wherein The component includes at least one of a rotor blade, a pitch bearing, or a hub of the wind turbine.

3. The method according to claim 1, characterized in that The plurality of operating parameters of the wind turbine includes at least one of the following: rotor position, thrust, load, power, speed, torque, blade weight, gravity, pitch angle, point moment, overhang moment, bearing lubrication schedule, rotor azimuth, or yaw moment.

4. The method according to claim 3, wherein Further comprising calculating the edgewise blade moment of the at least one rotor blade based on the plurality of operating parameters and an estimated state of the wind turbine.

5. The method according to claim 4, characterized in that, Further comprising calculating the flapwise blade moment of the at least one rotor blade based on the rotor position, the blade weight, and the torque.

6. The method according to claim 5, wherein Predicting the load and the associated load angle of the at least one rotor blade based on the edgewise blade moment and the flapwise blade moment of the at least one rotor blade further comprises: Calculating the associated load angle by dividing the flapwise blade moment of the rotor blade by the edgewise blade moment of the rotor blade; and Calculating the load based on the associated load angle.

7. The method according to claim 1, wherein Predicting the pitch angle of at least one rotor blade of the wind turbine further comprises calculating the pitch angle of at least one rotor blade of the wind turbine based on one or more controller commands.

8. The method according to claim 1, wherein Pitching the at least one rotor blade further comprises at least one of the following: pitching the plurality of rotor blades of the wind turbine together, pitching each of the plurality of rotor blades independently, or pitching each of the plurality of rotor blades periodically.

9. A system for reducing extreme loads acting on components of a wind turbine, the wind turbine having at least one rotor blade, the system comprising: One or more sensors at the at least one rotor blade, the one or more sensors configured to measure a plurality of operating parameters of the wind turbine, wherein the plurality of operating parameters includes at least one of the following: rotor position, blade weight, and torque; A controller, the controller being configured with the one or more sensors, the controller including a processor configured to perform a plurality of operations, the plurality of operations including: Calculating an edgewise blade moment of the at least one rotor blade based on a plurality of operating parameters of the wind turbine; Calculating an edgewise blade moment and a blade flap moment of the at least one rotor blade based on a rotor position, blade weight, and torque of at least one rotor of the wind turbine; Predicting a load and an associated load angle of the at least one rotor blade based on the edgewise blade moment and the blade flap moment of the at least one rotor blade, the load corresponding to a resultant root moment of the at least one rotor blade; Predicting at least one load value of a pitch angle of at least one rotor blade of the wind turbine; Generating a load envelope for the component, the load envelope including at least one load value with respect to the pitch angle and the load angle; and Implementing a control action when the load is outside the load envelope, the control action including pitching the at least one rotor blade.

10. The system according to claim 9, characterized in that The component includes at least one of a rotor blade, a pitch bearing, or a hub of the wind turbine.

11. The system according to claim 9, wherein The plurality of operating parameters of the wind turbine further includes at least one of the following: thrust, load, power, speed, gravity, pitch angle, point moment, overhang moment, bearing lubrication schedule, rotor azimuth, or yaw moment.

12. The system according to claim 9, wherein The plurality of operations further includes calculating the edgewise blade moment of the at least one rotor blade based on the plurality of operating parameters and an estimated state of the wind turbine.

13. The system according to claim 12, wherein Predicting the load and the associated load angle of the at least one rotor blade based on the edgewise blade moment and the blade flap moment of the at least one rotor blade further includes: Calculating the associated load angle by dividing the blade flap moment of the rotor blade by the edgewise blade moment of the rotor blade; and Calculating the load based on the associated load angle.

14. The system according to claim 9, wherein Predicting the pitch angle of at least one rotor blade of the wind turbine further includes calculating the pitch angle of at least one rotor blade of the wind turbine based on one or more controller commands.

15. The system according to claim 9, characterized in that, The one or more sensors include proximity sensors.

16. The system according to claim 9, wherein Implementing the control action when the load is outside the load envelope further includes at least one of the following: pitching a plurality of rotor blades of the wind turbine together, pitching each of the plurality of rotor blades independently, or pitching each of the plurality of rotor blades periodically.

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