Systems and methods for improved extreme load control of wind turbine rotor blades

Abstract

The invention relates to a method for reducing extreme loads acting on at least one rotor blade of a wind turbine, comprising calculating, via a processor, a flap bending moment of the rotor blade(s). Furthermore, the method comprises calculating, via the processor, a edgewise bending moment of the rotor blade(s). The method further comprises calculating, via the processor, an average load envelope of a root bending moment of the rotor blade(s) as a function of the flap bending moment and the edgewise bending moment of the rotor blade(s). Moreover, the method comprises calculating, via the processor, a total load envelope of the root bending moment of the rotor blade(s) as a function of the average load envelope of the root bending moment of the rotor blade(s) and a future load estimate. Thus, the method further comprises implementing, via the processor, a control action when the total load envelope is above a certain threshold.

Description

Technical Field

[0001] This topic generally relates to wind turbines, and more specifically to a system and method for improving extreme load control of wind turbine components such as rotor blades. Background Technology

[0002] Wind power is recognized as one of the cleanest and most environmentally friendly energy sources available today, and wind turbines are receiving increasing attention in this regard. A modern wind turbine typically includes a tower, generator, gearbox, nacelle, and one or more rotor blades. The rotor blades are the primary components used to convert wind energy into electrical energy. The blades typically have an airfoil-like cross-sectional profile, such that during operation, airflow across the blade creates a pressure difference between its two sides. Therefore, lift, directed from the pressure side towards the suction side, acts on the blade. This lift generates torque on the main rotor shaft, which is connected to the generator for power generation.

[0003] The amount of power that can be generated by a wind turbine is typically limited by the structural constraints (i.e., design loads) of the individual turbine components. For example, the blade root of a wind turbine may experience loads associated with average loads due to turbine operation and dynamic fluctuations due to environmental conditions (e.g., blade root resultant torque). These loads can damage turbine components, ultimately leading to turbine failure. Fluctuating loads may vary day-to-day or seasonally and may be based on wind speed, wind crests, wind turbulence, wind shear, changes in wind direction, air density, yaw shift, updrafts, or similar factors. Specifically, for example, the load experienced by a wind turbine may vary with wind speed.

[0004] Therefore, it is essential to ensure that the load acting on the wind turbine does not exceed the design load. Consequently, many wind turbines employ one or more sensors configured to measure the load acting on the individual turbine components. While sensors can provide the desired information, new sensor systems can be expensive and complex to install. Furthermore, sensors may provide incorrect information and are prone to failure.

[0005] Additionally, wind turbines utilize control systems configured to estimate the loads acting on the wind turbine based on its thrust. The terms "thrust," "thrust value," "thrust parameter," or similar terms used herein are intended to encompass the forces acting on the wind turbine due to wind. Thrust arises from pressure changes as the wind passes through and decelerates from the turbine. This control strategy estimates the loads acting on the wind turbine by determining the estimated thrust using multiple turbine operating conditions (e.g., pitch angle, power output, generator speed, and air density). The operating conditions are inputs to the algorithm and include a series of equations, one or more aerodynamic performance plots, and one or more lookup tables (LUTs). For example, an LUT may represent the wind turbine thrust. The + / - standard deviation of the estimated thrust, as well as the operating maximum thrust and thrust limit, can also be calculated. Thus, the wind turbine can be controlled based on the difference between the maximum thrust and the thrust limit.

[0006] In view of the foregoing, the art is constantly seeking new and improved systems for controlling extreme loads on wind turbine components such as rotor blades to solve the aforementioned problems. Summary of the Invention

[0007] Aspects and advantages of the invention will be set forth in part in the description which follows, or may be apparent from the description, or may be understood by practicing the invention.

[0008] On one hand, this disclosure relates to a method for reducing loads (such as extreme loads) acting on at least one rotor blade of a wind turbine. The method includes calculating, via a processor, the flapping (flapwise or blade-beating direction) bending moment of (one or more) rotor blades. Furthermore, the method includes calculating, via a processor, the edgewise (edgewise or blade-edge direction) bending moment of (one or more) rotor blades. The method also includes calculating, via a processor, an average load envelope of the root bending moment of (one or more) rotor blades based on the flapping and edgewise bending moments of (one or more) rotor blades. Additionally, the method includes calculating, via a processor, a total load envelope of the root bending moment of (one or more) rotor blades based on the average load envelope of the root bending moment of (one or more) rotor blades and a future load estimate. Therefore, the method also includes implementing a control action via a processor when the total load envelope exceeds a certain threshold.

[0009] In one embodiment, calculating the flapping moment may include calculating the flapping moment based on the equivalent thrust acting on the rotor of the wind turbine and the total length of (one or more) rotor blades. Furthermore, in one embodiment, the method may include calculating the equivalent thrust acting on the rotor based on the thrust, rotor radius, and one or more processor variables, said one or more processor variables including at least one of hub load sensor measurements, dq coordinate torque, or the aerodynamic location where the thrust is applied on (one or more) rotor blades.

[0010] In another embodiment, calculating the shimmy moment may include calculating the shimmy moment based on two or more of the following parameters: the mass of one or more rotor blades, the acceleration due to gravity, the position of the center of gravity of one or more rotor blades, the hub connection distance, the low-speed shaft mechanical torque, the rotor radius, the partial derivative of rotor rotation with respect to time, and the rotor inertia.

[0011] In another embodiment, calculating the average load envelope of the blade root moment based on the flapping moment and the swaying moment may include summing the squares of the flapping moment and the swaying moment and calculating the square root of the sum of squares.

[0012] In another embodiment, the method may include filtering the average load envelope of the blade root moment via at least one filter. More specifically, in one embodiment, filtering the average load envelope of the blade root moment via at least one filter may include filtering the average load envelope of the blade root moment via two notch filters. For example, in one embodiment, the two notch filters may be characterized by a transfer function that includes the gain attenuation, damping factor, and target frequency of the notch filters.

[0013] In yet another embodiment, the method may include predicting a future load estimate of the blade root moment by calculating a future load envelope of the blade root moment based on one or more partial derivatives of the thrust with respect to wind speed and rotor speed, the effective length of one or more rotor blades(s), and travel time, wherein the travel time is equal to the shortest time required for an extreme blade root moment event on any one or more rotor blades(s) of the wind turbine to travel down to the plane of the blade to ensure that subsequent one or more rotor blades(s) are unaffected, and the effective blade length corresponds to the location where the application of aerodynamic thrust produces a given blade root moment.

[0014] In several embodiments, the method may further include calculating the travel time based on the distance traveled by the windward rotor of the wind turbine after any rotor blade has experienced an extreme root moment event and an estimated wind speed.

[0015] In another embodiment, calculating the total load envelope of the leaf root moment based on the average load envelope and the future load estimate may include adding the average load envelope and the future load estimate together.

[0016] In a particular embodiment, the method may further include calculating the aerodynamic thrust that generates a given blade root moment at the effective blade length, and determining the distance between the aerodynamic thrust and a corresponding threshold. Therefore, in such an embodiment, the method may include determining control actions based on the distance between the aerodynamic thrust and the corresponding threshold, and hysteresis.

[0017] In some embodiments, as an example, control actions may include pitching one or more rotor blades of a wind turbine. More specifically, in one embodiment, pitching one or more rotor blades may include pitching multiple rotor blades of a wind turbine together, pitching each of the multiple rotor blades individually, pitching each of the multiple rotor blades periodically, pitching each of the multiple rotor blades minutely, or at least a combination thereof.

[0018] On the other hand, this disclosure relates to a system for reducing loads (such as extreme loads) acting on the rotor blades of a wind turbine. The system includes a controller having at least one processor configured to perform a plurality of operations. The plurality of operations may include, but are not limited to, calculating the flapping moment of the rotor blades, calculating the flaring moment of the rotor blades, calculating the average load envelope of the blade root moment based on the flapping moment and flaring moment, filtering the average load envelope of the blade root moment via at least one filter, calculating the total load envelope of the rotor root moment based on the average load envelope of the blade root moment and a future load estimate, and performing a control action when the total load envelope exceeds a certain threshold. It should be further understood that the system may include any of the additional features described herein.

[0019] These and other features, aspects, and advantages of the invention will become more readily 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. Attached Figure Description

[0020] The complete and open disclosure of the invention (including its best mode) to those skilled in the art is set forth in the description with reference to the accompanying drawings, in which:

[0021] Figure 1 A perspective view showing one embodiment of a wind turbine according to the present disclosure;

[0022] Figure 2 A simplified interior view of one embodiment of the nacelle of a wind turbine according to the present disclosure is shown;

[0023] Figure 3 A schematic diagram illustrating one embodiment of a controller according to the present disclosure is shown;

[0024] Figure 4 A perspective view of an embodiment of a wind turbine according to the present disclosure is shown, particularly illustrating various axes of rotation and the corresponding forces and moments acting on the wind turbine;

[0025] Figure 5 A flowchart illustrating an embodiment of a method for reducing extreme loads acting on the rotor blades of a wind turbine according to the present disclosure;

[0026] Figure 6 The estimates shown are based on this disclosure. M z B1 , M z B2 and M z B3 and its corresponding envelope M z B env And estimated M y B1 , M y B2 and M y B3 and its corresponding envelope M y B env A diagram of one embodiment;

[0027] Figure 7 Showing according to this disclosure MrB1 , MrB2 and MrB3 and the corresponding primitive envelope An example of an equivalent diagram;

[0028] Figure 8 A graph illustrating one embodiment of the MrB envelope power spectral density according to this disclosure is shown;

[0029] Figure 9 A schematic diagram illustrating an embodiment of the MrB envelope filtered via two notch filters according to this disclosure is shown.

[0030] Figure 10A graph illustrating one embodiment of the estimated MrB envelope according to this disclosure is shown, particularly showing the original MrB envelope compared to the filtered MrB envelope;

[0031] Figure 11 A schematic diagram of one embodiment of the rotor of a wind turbine according to the present disclosure is shown, with particular emphasis on the travel distance D. tvl ;

[0032] Figure 12 A schematic diagram of one embodiment of a rotor blade is shown, which is represented as being driven by thrust. FzAero A cantilever beam excited at the tip, and specifically showing the effective blade length. ;

[0033] Figure 13 A graph illustrating one embodiment of travel time (y-axis) versus time (x-axis) according to this disclosure is shown, particularly illustrating constrained travel time; and

[0034] Figure 14 A diagram illustrating one embodiment of the functional behavior of envelope-based MrB control according to this disclosure is shown. Detailed Implementation

[0035] Reference will now be made in detail to embodiments of the invention, one or more of which are illustrated in the accompanying drawings. Each example is provided by way of illustrative purposes and not by way of limitation. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made to the invention without departing from the scope or spirit of the invention. For example, a feature shown or described as part of one embodiment may be used in combination with another embodiment to produce yet another embodiment. Therefore, it is intended that the invention cover such modifications and variations that fall within the scope of the appended claims and their equivalents.

[0036] In general, this disclosure relates to improved systems and methods for improved extreme load control of wind turbine components, such as rotor blades. More specifically, the method aims to utilize an envelope-based blade root moment control algorithm. Such a control strategy comprises multiple sub-elements, including but not limited to the extraction of the blade root moment load envelope, a state machine, and control actions. Therefore, the blade root moment envelope extraction described herein provides a framework for detecting the instantaneous envelope of the blade root moment for each rotor blade to determine the blade root moment load envelope that can be used in envelope-based control of wind turbines. The envelope detection algorithm includes at least the extraction of the original blade root moment envelope, a filtering process for removing unwanted frequency components from the original blade root moment envelope, and computation for predicting or leading the envelope components to provide a preview capability for the algorithm.

[0037] Now see Figure 1This figure shows a perspective view of one embodiment of a wind turbine 10 that can implement the control technology according to the present disclosure. 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 outward 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 apart around the hub 20 to facilitate rotation of the rotor 18 so that kinetic energy from the wind can be converted into usable mechanical energy, and subsequently into electrical energy. For example, the hub 20 may be rotatably coupled to a generator 24 located within the nacelle 16. Figure 2 This allows for the generation of electrical energy.

[0038] 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 outside the wind turbine. Furthermore, 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 perform corrective actions. Thus, the controller 26 may include a computer or other suitable processing unit. Therefore, in several embodiments, the controller 26 may include suitable computer-readable instructions that, when implemented, configure the controller 26 to perform various functions, such as receiving, transmitting, and / or executing wind turbine control signals. Thus, the controller 26 may be generally configured to control various operating modes (e.g., start-up or shutdown sequence), derate the wind turbine, and / or control various components of the wind turbine 10, as will be described in more detail below.

[0039] Now see Figure 2 , showing Figure 1 The diagram shows a simplified internal view of one embodiment of the nacelle 16 of the wind turbine 10. As shown, a generator 24 may be coupled to a rotor 18 to generate electricity from the rotational energy produced by the rotor 18. For example, as shown in the illustrated embodiment, the rotor 18 may include a rotor shaft 34 coupled to a hub 20 to rotate therewith. The rotor shaft 34 may then 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 the 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.

[0040] Each rotor blade 22 may also include a pitch adjustment mechanism 32 configured to rotate each rotor blade 22 about its pitch axis 28. Furthermore, 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 an embodiment, the pitch drive motor 40 may be coupled to the pitch drive gearbox 42 to impart mechanical force to it. Similarly, the pitch drive gearbox 42 may be coupled to the pitch drive pinion 44 to rotate with it. The pitch drive pinion 44 may then be rotatably engaged with a pitch bearing 46 connected 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 an embodiment, rotation of the pitch drive motor 40 drives the pitch drive gearbox 42 and the pitch drive pinion 44, thereby 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 (one or more) yaw drive mechanism 66 is configured to change the angle of the nacelle 16 relative to the wind (e.g., by engaging the yaw bearing 68 of the wind turbine 10).

[0041] Still referencing Figure 2The wind turbine 10 may also include one or more sensors 48, 50 for measuring various operating parameters that may be required for various blade moments, as described in more detail below. 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, speed, acceleration, and / or power output); sensors for measuring unbalanced loads in the rotor (e.g., a main shaft bending sensor); and / or various wind sensors 50 for measuring various wind parameters (e.g., wind speed, wind crest, wind turbulence, wind shear, wind direction change, air density, or similar conditions). Furthermore, the sensors may be located near the ground of the wind turbine, on the nacelle, or on the weather mast of the wind turbine. It should also be understood that any other number or type of sensors may be employed and in any location. For example, the sensor may be a micro inertial measurement unit (MIMU), strain gauge, accelerometer, pressure sensor, angle of attack sensor, vibration sensor, proximity sensor, light detection and ranging (LIDAR) sensor, camera system, fiber optic system, anemometer, wind vane, sound detection and ranging (SODAR) sensor, infrared laser, radiometer, pitot tube, anemometer, other optical sensor, and / or any other suitable sensor. It should be recognized that the term "monitoring" and its variations, as used herein, indicate that various sensors can be configured to provide direct or indirect measurements of the parameter being monitored. Thus, for example, a sensor may be used to generate a signal about the parameter being monitored, which can then be used by controller 26 to determine the actual parameter.

[0042] Now see Figure 3 This diagram illustrates a block diagram of one embodiment of various components of the controller 26 according to the present disclosure. As shown, the controller 26 may include one or more processors 58 and associated memory devices 60 configured to perform various computer-executable functions (e.g., performing methods, steps, calculations, etc., and storing related data, as disclosed herein). Additionally, the controller 26 may include a communication module 62 to facilitate communication between the controller 26 and various components of the wind turbine 10. Furthermore, the communication module 62 may include a sensor interface 64 (e.g., one or more analog-to-digital converters) to allow signals transmitted from sensors 48, 50 to be converted into signals that can be understood and processed by the processor 58. It should be appreciated that sensors 48, 50 may be communicatively coupled to the communication module 62 using any suitable means. For example, as Figure 3 As shown, sensors 48 and 50 are connected to sensor interface 64 via a wired connection. However, in other embodiments, sensors 48 and 50 may be connected to sensor interface 64 via a wireless connection, such as by using any suitable wireless communication protocol known in the art.

[0043] As used herein, the term "processor" refers not only to integrated circuits included in a computer as understood in the art, but also to controllers, microcontrollers, microcomputers, programmable logic controllers (PLCs), application-specific integrated circuits (ASICs), and other programmable circuits. Furthermore, the memory device(s) 60 may generally include one or more 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, optical disc read-only memory (CD-ROM), magneto-optical discs (MOD), digital versatile discs (DVDs), and / or other suitable memory elements). Such a memory device(s) 60 may be generally configured to store suitable computer-readable instructions that, when implemented by the processor 58, configure the controller 26 to perform various functions, including but not limited to determining one or more current wind turbine parameters of the wind turbine 10 based on multiple operational data, determining maximum wind turbine parameters, transmitting suitable control signals to implement control actions to reduce the load acting on the wind turbine, and various other suitable computer-implemented functions.

[0044] like Figure 4 The diagram shows an exploded view of one embodiment of a wind turbine 10, specifically illustrating the various axes of rotation and the corresponding forces and moments acting on the wind turbine 10. The peak load of the wind turbine 10 can vary between turbines, but generally corresponds to at least one of the following: blade root resultant moment (e.g., MrB, which includes pitch and hub load M). xB M yb and M zb ), spindle load (e.g., M) yr M zr ), main bearing load (e.g., M) xr M yr ), yaw drive load (e.g., M) xk ), yaw bolt / bearing / flange load (e.g., M) yk M zk ) or 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 load experienced by the wind turbine 10, and Figure 4 The loads shown are provided for illustrative purposes only. The calculations of such forces and moments are described further in this paper.

[0045] Now see Figure 5This document illustrates a flowchart of a method 100 for reducing extreme loads acting on components of a wind turbine according to an embodiment of the present disclosure. In one embodiment, the component may include, for example, one or more of a rotor blade 22, a pitch bearing 46, or a hub 20 of a wind turbine 10. Method 100 is described herein as being implemented, for example, using the wind turbine 10 described above. However, it should be recognized that the disclosed method 100 can be implemented using any other suitable wind turbine now known in the art or developed thereafter. Furthermore, although Figure 5 The steps are illustrated in a specific order for illustrative and descriptive purposes, but the methods described herein are not limited to any particular order or arrangement. Those skilled in the art using the disclosure provided herein will recognize that the various steps of the methods can be omitted, rearranged, combined, and / or modified in various ways.

[0046] As shown at (102), method 100 includes calculating the flapping moment (e.g., MyB) of one or more rotor blades 22 via processor(s) 58. env For example, in one embodiment, processor(s) 58 may, for example, use the following equation (1), based on the equivalent thrust acting on rotor 18 (e.g., F r The total length of the rotor blades 22 and (one or more) is (e.g., Rr-P HubCO To calculate the flapping moment of (one or more) rotor blades 22:

[0047] Equation (1)

[0048] in P OPAeroLoc It is the aerodynamic location where force Fr is applied to one or more rotor blades 22.

[0049] Rr It is the rotor radius, and

[0050] P HubCo It is the length of the hub connection.

[0051] Furthermore, in one embodiment, method 100 may include calculating the equivalent thrust acting on rotor 18 based on thrust, rotor radius, and one or more processor variables. F rMore specifically, in one embodiment, the processor variables may include hub load sensor measurements, dq coordinate torque, or the aerodynamic location where thrust is applied to one or more rotor blades 22. Therefore, in such an embodiment, the processor 58 is configured to calculate the equivalent thrust using the following equation (2). F r :

[0052] Equation (2)

[0053] in FzAero It is thrust, and

[0054] D LessGravity and The D and Q torques from the processor 58 are typically determined via one or more sensors.

[0055] See also Figure 5 As shown at (104), method 100 further includes calculating the swaying moment (MzB) of one or more rotor blades 22 via processor (one or more) 58. env More specifically, in one embodiment, processor(s) 58 is configured to calculate the shimming moment of rotor(s) 22 based on two or more of the following parameters: the mass of rotor(s) 22, acceleration due to gravity, position of the center of gravity of rotor(s) 22, hub connection distance, low-speed shaft mechanical torque, rotor radius, partial derivative of rotor rotation with respect to time, and rotor inertia. Therefore, in a particular embodiment, processor(s) 58 is configured to calculate the shimming moment of rotor(s) 22 using the following equation (3):

[0056] Equation (3)

[0057] in P BladeMass It is the quality of the blades.

[0058] SG It is acceleration caused by gravity.

[0059] P CMloc It is the position of the center of gravity of (one or more) rotor blades 22.

[0060] LSSMechTrq It is the mechanical torque of the low-speed shaft.

[0061] dWr It is the partial derivative of the rotor rotation with respect to time, and

[0062] PJr It is rotor inertia.

[0063] As shown at (106), method 100 further includes calculating the average load envelope of the root moments of the rotor blades 22 based on the flapping moments and shimmy moments of the rotor blades 22 via processors 58. More specifically, in one embodiment, processors 58 are configured to calculate the average load envelope by adding the squares of the flapping moments and shimmy moments and calculating the square root of the sum of squares, as shown in equation (4) below.

[0064] Equation (4)

[0065] See in particular Figure 6 and 7 , Figure 6 The estimate for three rotor blades is shown. MzB1 , MzB2 and MzB3 202, 204, 206 and their envelope MyB env Example chart 200 of 208. Furthermore, as shown in the figure, this chart illustrates the estimated... MyB1 , MyB2 and MyB3 210, 212, 214 and their corresponding envelopes MxB env 216. Figure 7 Show MrB1 , MrB2 and MrB3 302, 304, 306 and their corresponding original envelopes The equivalent diagram of 308 is 300.

[0066] To better understand the frequency content carried by the original MrB envelope (e.g., ... Figure 7 As shown in the diagram, spectral density analysis can be performed. For example, as... Figure 8 As shown, in one embodiment, the envelope 402 of the original MrB estimate is dominated by the 3P component, with smaller peaks at 6P and 9P. These higher harmonics may become less significant (or more significant) in the presence (or absence) of wind misalignment. Conversely, the MrB estimate 404 for a single blade is largely dominated by the 1P and blade flare frequency components. This frequency shift generally occurs because the envelope carries the average frequency content of the three rotor blades. In this case, the 1P frequency shifts with respect to the number of blades, i.e., shifts to 3P. This is called "clustering" and is likely a typical phenomenon in envelope extraction.

[0067] Given these results, the envelope-based MrB control of this disclosure should be less sensitive to variations in the (at least) 3P and (additionally) 6P harmonics in order to improve the controller response to MrB excitation driven by rotor rotation. Furthermore, given the typically finite frequency bandwidth of pitch systems, extending this frequency rejection to harmonics above 6P offers no significant benefit. Therefore, the mitigation of the 3P and 6P harmonics is achieved by filtering the average load envelope of the blade root moment via at least one filter. More specifically, in one embodiment, as... Figure 9 As shown, processor 58 can filter the average load envelope of the blade root moment via one or more notch filters (such as two notch filters 500, 502). For example, in one embodiment, notch filters 500, 502 can be characterized by the transfer function of the following equation (5):

[0068] Equation (5)

[0069] in g It's gain attenuation.

[0070] d It is the damping factor, and

[0071] It is the target frequency of (one or more) filters 500, 502.

[0072] In some embodiments, for both 3P and 6P notch filters, the attenuation level g It can be set to 0.25 (i.e., only retain...). (25% of the original frequency content), and d It can be set to 0.707. Both parameters can be selected to provide optimal decay and minimum delay. Furthermore, such parameters can be turbine-specific or not. Figure 10 Figure 500 illustrates an example of a filtered envelope, where the original MrB envelope is labeled 502, and the envelope after applying two notch filters at 3P and 6P is labeled 504. The individual rotor blades... MrB1 , MrB2 and MrB3 They are labeled as 506, 508, and 510 respectively.

[0073] See again Figure 5As shown at (108), method 100 further includes predicting a future load estimate of the root moment of the rotor blades 22 via processor(s) 58. For example, in one embodiment, processor(s) 58 may calculate the future load envelope of the root moment based on one or more partial derivatives of the thrust with respect to wind speed and rotor speed, the effective length of the rotor blade, and the travel time, where the travel time is equal to the shortest time required for an extreme root moment event on any rotor blade of the wind turbine to travel downhill to the blade plane to ensure that subsequent rotor blades are unaffected, and the effective blade length corresponds to the location where the application of aerodynamic thrust produces a given root moment.

[0074] Therefore, predictive or anticipatory capabilities can be added to the envelope before proceeding to the control algorithm described herein. For example, in such an embodiment, using knowledge available from the partial derivatives of thrust with respect to wind speed and rotor speed, processor(s)58 can use the following equation (6) to calculate the travel distance T. tvl :

[0075] Equation (6)

[0076] in D tvl It is the distance traveled by the wind towards the rotor 18 after any one of the rotor blades 22 experiences an extreme MrB event, and

[0077] That's the estimated wind speed.

[0078] More precisely, such as Figure 11 As shown, the distance traveled D tvl Generally speaking, this refers to the effective blade length. The distance between the next two adjacent blades 22 can be calculated using the following equation (7):

[0079] Equation (7)

[0080] Furthermore, assuming that (one or more) rotor blades 22 are cantilever beams excited at the tip by thrust FzAero, static beam theory shows that the effective blade length is one-quarter of the total blade length, as expressed by equation (8):

[0081] Equation (8)

[0082] in It is the total blade length, and

[0083] L bldIt is the length of one of the rotor blades 22.

[0084] Therefore, in such an embodiment, the effective blade length is the location where the application of aerodynamic thrust produces a given MrB blade root torque. Figure 12 A schematic diagram illustrating one embodiment of the concept is shown.

[0085] Therefore, as described in this article, the travel time T tvl Generally speaking, this refers to the shortest time required for an extreme MrB event on any one or more rotor blades 22 to travel downstream in the rotor plane to ensure that subsequent blades 22 22 are not affected. Such a travel time can also be equal to the minimum time before the pitch commanded by the control algorithm described herein begins to decay to a small pitch. This travel time ensures that the extreme MrB event is far enough downstream to avoid affecting subsequent blades, due to the distance from the blade that caused the extreme event. D tvl .

[0086] Given the inverse relationship between the estimated wind speed and travel time, and the fact that processor(s)58 does not operate until the wind turbine 10 engages, T tvl It reaches its maximum value at the cut-in wind speed. However, the envelope-based MrB control algorithm is most likely to work near the nominal wind speed. Therefore, in one embodiment, as Figure 13 As shown in Figure 600, the upper limit of the travel time can be set to the rated wind speed 602 of the wind turbine 10.

[0087] Given travel time T tvl Effective blade length The MrB envelope prediction term can be calculated using the following equation (9) by estimating the partial derivatives of the thrust with respect to both wind speed and rotational speed:

[0088] Equation (9)

[0089] therefore, The forecast term is configured to be equal to the future forecast thrust. T tvl The amount of adjustment to the MrB envelope allows (one or more) processors 58 to arrive and reduce the load in the near future.

[0090] Return to reference Figure 5As shown at (110), method 100 further includes calculating, via one or more processors 58, the total load envelope of the blade root bending moment of one or more rotor blades 22 based on the average load envelope and future load estimates (e.g., For example, in one embodiment, processor(s) 58 may be configured to calculate the total load envelope of the leaf root moment by adding the average load envelope and the future load estimate. Therefore, processor 58 may use the following equation (10) to calculate the complete MrB envelope, including the prediction term:

[0091] Equation (10)

[0092] Therefore, please refer to Figure 5 As shown at (112), method 100 includes when the total load envelope ( When the value exceeds a certain threshold, a control action is performed via processor(s) 58. For example, in a particular embodiment, the control action may include pitching(s) rotor blade(s) 22. More specifically, in such an embodiment, pitching(s) rotor blade(s) 22 may include pitching a plurality of rotor blades 22 of the wind turbine 10 together, pitching each of the plurality of rotor blades 22 individually, pitching each of the plurality of rotor blades 22 periodically, pitching each of the plurality of rotor blades 22 minutely, or a combination thereof.

[0093] In a particular embodiment, the method 100 may further include calculating the aerodynamic thrust that generates a given blade root moment at the effective blade length, and determining the distance between the aerodynamic thrust and a corresponding threshold. Therefore, in such an embodiment, the method may include determining control actions based on the distance between the aerodynamic thrust and the corresponding threshold, and hysteresis.

[0094] For example, in a particular embodiment, given Load envelope, effective blade length as described in this article Estimated blade root bending moment for tip-to-tower clearance control (e.g., ), activation threshold (e.g., ) and hysteresis (e.g., One or more processors 58 can use equations (11)-(14) to calculate the following equivalent thrust parameters:

[0095] Equation (11)

[0096] Equation (12)

[0097] These are the so-called equivalent thrust, and are used by one or more processors 58 to calculate the pitch required to alleviate MrB loads exceeding a certain threshold. More specifically, in one embodiment, the thrust(s) described herein are... When the thrust is applied, a root torque is generated, and therefore must be calculated. Similarly, the threshold is also represented by the equivalent thrust to assess overshoot and hysteresis conditions.

[0098] Then, the distance between such equivalent thrust and the corresponding threshold, as well as the size of the hysteresis band, can be calculated using the following equations (13)-(14):

[0099] Equation (13)

[0100] Equation (14)

[0101] Therefore, the control algorithm of one or more processors can take different actions based on the magnitude of these distances between the actual torque and the threshold. In some embodiments, a state machine implementation can be used to determine appropriate control actions, where the state is defined based on the instantaneous value of the MrB envelope relative to the threshold and the hysteresis. For example, in one embodiment, as... Figure 14 As shown in the diagram, a graph of envelope-based MrB control is illustrated according to this disclosure. More precisely, Figure 14 This demonstrates how envelope-based MrB control operates and displays... and The performance relative to the MrB envelope compared to the threshold.

[0102] As shown in the figure, when the MrB envelope exceeds the threshold, the algorithm becomes effective when it enters state 3. Here, This is limited to an additional common pitch signal equal to the load exceedance, calculated using the derivative of thrust with respect to pitch. Furthermore, this function can be temporarily disabled when the algorithm is in state 3 to prevent it from reducing the effectiveness of the envelope-based MrB control strategy in mitigating extreme blade root loads.

[0103] Once the MrB envelope enters the hysteresis loop (or falls below the threshold, assuming the hysteresis is 0), the algorithm can switch to state 2, and the timer can begin to increment (this timer is reset in all other states). If the envelope is within the hysteresis loop and the timer remains within the following travel time... T tvl In this state, one or more processors 58 may remain in that state. Then, additional conditions are only allowed to enter state 2 if the algorithm was in state 3 or exactly in state 2 prior to this state. Furthermore, as shown in the illustrated embodiment, in state 2, Keep it constant.

[0104] Once the MrB envelope is below the hysteresis loop, the travel time has elapsed, and the previous state was 2 or 1, the algorithm can exit state 2 and enter state 1. It begins to decay towards a small pitch, and the algorithm remains in state 1 until... Within a certain degree (such as 0.05 degrees) of a very small pitch, the algorithm becomes ineffective. ), and enter state 0, and remain in that state until the condition for entering state 3 is met.

[0105] The MrB envelope control algorithm also allows for limiting via one or more parameters defined by one or more processors 58. The saturation level. This represents the maximum pitch angle that the algorithm can request to prevent extreme MrB from exceeding design limits under extreme load conditions.

[0106] Various aspects and embodiments of the present invention are defined by the following numbered clauses:

[0107] Clause 1. A method for reducing the load acting on at least one rotor blade of a wind turbine, the method comprising:

[0108] The wagging moment of at least one rotor blade is calculated via a processor;

[0109] The processor calculates the shimmy bending moment of at least one rotor blade;

[0110] The average load envelope of the root moment of at least one rotor blade is calculated by the processor based on the flapping moment and swaying moment of at least one rotor blade.

[0111] The total load envelope of the root bending moment of at least one rotor blade is calculated by the processor based on the average load envelope of the root bending moment of at least one rotor blade and the future load estimate; and

[0112] When the total load envelope exceeds a certain threshold, the processor will implement control actions.

[0113] Clause 2. The method of claim 1, wherein calculating the flapping moment further comprises: calculating the flapping moment based on the equivalent thrust acting on the rotor of the wind turbine and the total length of at least one rotor blade.

[0114] Clause 3. The method of claim 2, further comprising: calculating an equivalent thrust acting on the rotor based on thrust, rotor radius, and one or more processor variables, said one or more processor variables including at least one of hub load sensor measurements, dq coordinate torque, or the aerodynamic location where the thrust is applied to at least one rotor blade.

[0115] Clause 4. The method according to any one of the preceding claims, wherein calculating the shimmy moment further comprises calculating the shimmy moment based on two or more of the following parameters: the mass of at least one rotor blade, the acceleration due to gravity, the position of the center of gravity of at least one rotor blade, the hub connection distance, the low-speed shaft mechanical torque, the rotor radius, the partial derivative of rotor rotation with respect to time, and the rotor inertia.

[0116] Clause 5. The method according to any one of the preceding claims, wherein calculating the average load envelope of the blade root moment based on the flapping moment and the swaying moment further comprises summing the squares of the flapping moment and the swaying moment, and calculating the square root of the sum of squares.

[0117] Clause 6. The method according to any one of the preceding claims further includes filtering the average load envelope of the leaf root moment via at least one filter.

[0118] Clause 7. The method of claim 6, wherein filtering the average load envelope of the blade root moment via at least one filter further comprises: filtering the average load envelope of the blade root moment via two notch filters.

[0119] Clause 8. The method of claim 7, wherein the two notch filters are characterized by transfer functions, the transfer functions including the gain attenuation, damping factor, and target frequency of the notch filters.

[0120] Clause 9. The method according to any one of the preceding claims further comprises predicting a future load estimate of the blade root moment by calculating a future load envelope of the blade root moment based on one or more partial derivatives of the thrust with respect to wind speed and rotor speed, the effective length of at least one rotor blade, and travel time, wherein the travel time is equal to the shortest time required for an extreme blade root moment event on any rotor blade of the wind turbine to travel downhill to the blade plane to ensure that subsequent rotor blades are unaffected, and the effective blade length corresponds to the location where the application of aerodynamic thrust produces a given blade root moment.

[0121] Clause 10. The method of claim 9, further comprising calculating the travel time based on the distance traveled by the windward rotor of the wind turbine after any rotor blade has experienced an extreme root moment event in at least one rotor blade and an estimated wind speed.

[0122] Clause 11. The method according to any one of the preceding claims, wherein calculating the total load envelope of the leaf root moment based on the average load envelope and the future load estimate further comprises adding the average load envelope and the future load estimate.

[0123] Clause 12. The method of claim 9, further comprising:

[0124] Calculate the aerodynamic thrust that produces a given blade root bending moment at the effective blade length; and

[0125] Determine the distance between the aerodynamic thrust and the corresponding threshold.

[0126] Clause 13. The method of claim 12, further comprising determining the control action based on the distance between the aerodynamic thrust and a corresponding threshold and hysteresis.

[0127] Clause 14. The method according to any one of the preceding claims, wherein the control action comprises pitching one or more rotor blades of a wind turbine.

[0128] Clause 15. The method of claim 14, wherein pitching one or more rotor blades further comprises pitching a plurality of rotor blades of a wind turbine together, pitching each of the plurality of rotor blades independently, pitching each of the plurality of rotor blades periodically, pitching each of the plurality of rotor blades micro-pitch, or at least one combination thereof.

[0129] Clause 16. A system for reducing the load acting on at least one rotor blade of a wind turbine, the system comprising:

[0130] A controller including at least one processor, the processor being configured to perform a plurality of operations, the plurality of operations including:

[0131] Calculate the wagging moment of at least one rotor blade;

[0132] Calculate the swaying bending moment of at least one rotor blade;

[0133] Calculate the average load envelope of the root moment of at least one rotor blade based on the flapping moment and swaying moment of at least one rotor blade.

[0134] The average load envelope of the blade root bending moment is filtered by at least one filter;

[0135] The total load envelope of the root bending moment of at least one rotor blade is calculated based on the average load envelope of the root bending moment of at least one rotor blade and the future load estimate; and when the total load envelope is higher than a certain threshold, a control action is implemented.

[0136] Clause 17. The system of claim 16, wherein calculating the flapping moment further comprises: calculating the flapping moment based on the equivalent thrust acting on the rotor of the wind turbine and the total length of at least one rotor blade.

[0137] Clause 18. The system of claim 16, wherein calculating the shimmy moment further comprises calculating the shimmy moment based on two or more of the following parameters: the mass of at least one rotor blade, the acceleration due to gravity, the position of the center of gravity of at least one rotor blade, the hub connection distance, the low-speed shaft mechanical torque, the rotor radius, the partial derivative of rotor rotation with respect to time, and the rotor inertia.

[0138] Clause 19. The system of claim 16, wherein filtering the average load envelope of the blade root moment via at least one filter further comprises: filtering the average load envelope of the blade root moment via two notch filters.

[0139] Clause 20. The system of claim 16, wherein the control action comprises pitching one or more blades of the wind turbine, wherein pitching one or more rotor blades further comprises pitching a plurality of rotor blades of the wind turbine together, pitching each of the plurality of rotor blades independently, pitching each of the plurality of rotor blades periodically, pitching each of the plurality of rotor blades minutely, or at least one combination thereof.

[0140] 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 apparatus or system, and performing any incorporated methods. The scope of the invention is defined by the claims, but may include other examples that may occur to those skilled in the art. Such other embodiments are intended to be within the scope of the claims if they include structural elements that are not different from the written language of the claims, or if they include equivalent structural elements that are not substantially different from the written language of the claims.

Claims

1. A method for reducing the load acting on at least one rotor blade of a wind turbine, the method comprising: The waving moment of the at least one rotor blade is calculated by the processor; The processor calculates the shimmy bending moment of the at least one rotor blade; The processor calculates the average load envelope of the root moment of the at least one rotor blade based on the flapping moment and oscillation moment of the at least one rotor blade. The processor calculates the total load envelope of the root bending moment of the at least one rotor blade based on the average load envelope of the root bending moment of the at least one rotor blade and the future load estimate. as well as When the total load envelope exceeds a certain threshold, a control action is performed via the processor; The method further includes predicting a future load estimate of the blade root moment by calculating a future load envelope of the blade root moment based on one or more partial derivatives of the thrust with respect to wind speed and rotor speed, the effective length of the at least one rotor blade, and a travel time equal to the shortest time required for an extreme blade root moment event on any rotor blade of the wind turbine to travel downhill to the blade plane to ensure that subsequent rotor blades are unaffected, and the effective blade length corresponding to the location where the application of aerodynamic thrust produces a given blade root moment.

2. The method according to claim 1, characterized in that, The calculation of the flapping moment further includes: calculating the flapping moment based on the equivalent thrust acting on the rotor of the wind turbine and the total length of the at least one rotor blade.

3. The method according to claim 2, characterized in that, The method further includes: calculating an equivalent thrust acting on the rotor based on thrust, rotor radius, and one or more processor variables, the one or more processor variables including at least one of hub load sensor measurements, dq coordinate torque, or the aerodynamic position where the thrust is applied on at least one rotor blade.

4. The method according to claim 1, characterized in that, Calculating the sway moment further includes calculating the sway moment based on two or more of the following parameters: the mass of the at least one rotor blade, the acceleration due to gravity, the position of the center of gravity of the at least one rotor blade, the hub connection distance, the low-speed shaft mechanical torque, the rotor radius, the partial derivative of rotor rotation with respect to time, and the rotor inertia.

5. The method according to claim 1, characterized in that, Calculating the average load envelope of the blade root moment based on the flapping moment and the swaying moment further includes summing the squares of the flapping moment and the swaying moment, and calculating the square root of the sum.

6. The method according to claim 1, characterized in that, The method further includes filtering the average load envelope of the leaf root bending moment via at least one filter.

7. The method according to claim 6, characterized in that, Filtering the average load envelope of the blade root moment via the at least one filter further includes filtering the average load envelope of the blade root moment via two notch filters.

8. The method according to claim 7, characterized in that, The two notch filters are characterized by transfer functions, which include the gain attenuation, damping factor, and target frequency of the notch filters.

9. The method according to claim 1, characterized in that, The method further includes calculating the travel time based on the distance traveled by the wind towards the rotor of the wind turbine after any of the at least one rotor blades has experienced the extreme root moment event and the estimated wind speed.

10. The method according to claim 1, characterized in that, Calculating the total load envelope of the leaf root moment based on the average load envelope and the future load estimate further includes adding the average load envelope and the future load estimate.

11. The method according to claim 1, characterized in that, The method further includes: Calculate the aerodynamic thrust that produces the given blade root bending moment at the effective blade length; and Determine the distance between the aerodynamic thrust and the corresponding threshold.

12. The method according to claim 11, characterized in that, The method further includes determining the control action based on the distance and hysteresis between the aerodynamic thrust and the corresponding threshold.

13. The method according to claim 1, characterized in that, The control action includes pitching one or more rotor blades of the wind turbine.

14. The method according to claim 13, characterized in that, Pitching the one or more rotor blades further includes pitching multiple rotor blades of the wind turbine together, pitching each of the multiple rotor blades independently, pitching each of the multiple rotor blades periodically, pitching each of the multiple rotor blades micro-pitch, or at least one combination thereof.

15. A system for reducing the load acting on at least one rotor blade of a wind turbine, the system comprising: A controller including at least one processor, the processor being configured to perform a plurality of operations, the plurality of operations including: Calculate the waving moment of the at least one rotor blade; Calculate the swaying bending moment of the at least one rotor blade; The average load envelope of the root bending moment of the at least one rotor blade is calculated based on the flapping bending moment and swaying bending moment of the at least one rotor blade. The average load envelope of the blade root bending moment is filtered by at least one filter; The total load envelope of the root bending moment of the at least one rotor blade is calculated based on the average load envelope of the root bending moment of the at least one rotor blade and the future load estimate. When the total load envelope exceeds a certain threshold, a control action is performed. The future load estimate of the blade root moment is predicted by calculating the future load envelope of the blade root moment based on one or more partial derivatives of the thrust with respect to wind speed and rotor speed, the effective length of the at least one rotor blade, and the travel time, wherein the travel time is equal to the shortest time required for an extreme blade root moment event on any rotor blade of the wind turbine to travel downhill to the blade plane to ensure that subsequent rotor blades are not affected, and the effective blade length corresponds to the location where the application of aerodynamic thrust produces a given blade root moment.

16. The system according to claim 15, characterized in that, The calculation of the flapping moment further includes: calculating the flapping moment based on the equivalent thrust acting on the rotor of the wind turbine and the total length of the at least one rotor blade.

17. The system according to claim 15, characterized in that, Calculating the sway moment further includes calculating the sway moment based on two or more of the following parameters: the mass of the at least one rotor blade, the acceleration due to gravity, the position of the center of gravity of the at least one rotor blade, the hub connection distance, the low-speed shaft mechanical torque, the rotor radius, the partial derivative of rotor rotation with respect to time, and the rotor inertia.

18. The system according to claim 15, characterized in that, Filtering the average load envelope of the blade root moment via the at least one filter further includes filtering the average load envelope of the blade root moment via two notch filters.

19. The system according to claim 15, characterized in that, The control action includes pitching one or more blades of the wind turbine, wherein pitching the one or more rotor blades 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, pitching each of the plurality of rotor blades periodically, pitching each of the plurality of rotor blades minutely, or a combination thereof.

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