Control system and method for stabilizing YAW moments in a wind turbine

Abstract

A method for stabilizing yaw moments in a wind turbine, comprising obtaining at least one wind measurement comprising at least one wind direction measurement, determining a yaw drift Δ Ψ and an expected yaw actuation angle ΨT, obtaining a saturation range, modifying the saturation range, determining a yaw actuation angle Ψ which is a function of the yaw drift Δ Ψ, applying the modified saturation range on the yaw actuation angle Ψ, and performing a yaw actuation of the rotor on the wind turbine based on the saturated yaw actuation angle Ψs. A control system for stabilizing yaw moments in a wind turbine comprising a first unit, configured to obtain wind measurements, a second unit, in data communication with the first unit, and an actuating unit, in data communication with the second unit, and in engagement with a rotor of a wind turbine.

Description

CONTROL SYSTEM AND METHOD FOR STABILIZING YAW MOMENTS IN A WIND TURBINEFIELD OF INVENTION

[0001] The present disclosure concerns a control system and method for stabilizing and / or mitigating yaw moments in a wind turbine.BACKGROUND

[0002] Yaw moments on wind turbines refer to the rotational forces acting around the vertical axis of the turbine, which dictate the orientation of the nacelle relative to the wind direction. They arise from aerodynamic forces on the blades and nacelle, as well as from external factors such as wind shear, turbulence, and directional shifts in wind flow.

[0003] Minimization of these moments through an optimal alignment of the turbine with incoming wind maximizes energy capture while minimizing mechanical stress. Proper management of yaw moments can contribute towards balancing energy efficiency with structural integrity, as excessive or poorly controlled yaw forces can lead to increased wear on components like the yaw drive and bearings.

[0004] In floating wind turbines, aerodynamic yaw moments will try to rotate the platform, creating an angle between the incoming wind and the rotor’s normal vector (yaw angle). This misalignment may further reduce power production and increase mechanical loads.

[0005] Most wind turbines have a tilt angle, denoted as ϑ in Figure 1, which prevents blade-tower collisions. This tilt angle may create uneven loading across the rotor, generating a moment in the tower. In floating wind turbines, moments from tilt angles may be counter-balanced by the mooring system at each corner of the floating platform.

[0006] EP 2159415 B1 discloses a method and an apparatus for adjusting a yaw angle (106) of a wind turbine (100) comprising a rotor having a plurality of rotor blades (101 ) and a hub (104). The method is adapted for adjusting the yaw angle (106) from an actual yaw angle to a desired yaw angle and comprises the steps of measuring a wind direction (105) at the location of the wind turbine (100), measuring the yaw angle (106)of the wind turbine (100) and / or a wind direction relative to the nacelle orientation, calculating a pitch angle (108) of at least one rotor blade (101) as a function of the measured wind direction (105) and the measured yaw angle and / or a wind direction relative to the nacelle orientation, and adjusting the pitch angle (108) of the rotor blades (101) according to the calculated pitch angle (108) such that a yaw momentum (107) is generated for changing the yaw angle (106) from the actual yaw angle to the desired yaw angle.

[0007] WO 2022167180 A1 discloses a system comprising a wind turbine (1) and a first control device for controlling the wind turbine (1). The first control device is configured to acquire a yaw misalignment (y) of the wind turbine (1), which yaw misalignment (y) is a difference between the actual yaw angle and a wind direction at the wind turbine (1); and to determine at least one of a target pitch angle ([3) of the blade (6) and a target torque (TCtrl) of the generator (5) based on the yaw misalignment (y) to optimize a power output from the wind turbine (1). It is further described a wind farm comprising the system, and a method of controlling a wind turbine (1).

[0008] EP 3273055 B1 discloses methods, apparatus, systems and articles of manufacture to provide wind turbine 100 control and compensate for wind induction effects 320. An example method includes receiving wind speed data from a Light Detecting and Ranging (LIDAR) sensor 148. The example method includes receiving operating data 520 indicative of wind turbine 100 operation. The example method includes determining an a priori induction correction for wind turbine 100 operating conditions with respect to the LIDAR wind speed data based on the operating data. The example method includes estimating a wind signal from the LIDAR sensor 148 that is adjusted by the correction. The example method includes generating a control signal for a wind turbine based on the adjusted LIDAR estimated wind signal 670.

[0009] However, the prior art relies heavily on indirect methods such as pitch angle adjustments, torque modifications, or induction corrections for minimizing yaw angles.

[0010] Another potential issue is the increased mechanical stress on turbine components, particularly rotor blades and pitch mechanisms, due to continuous adjustments aimed at compensating for yaw misalignment or optimizing other parameters.SUMMARY OF INVENTION

[0011] According to a first aspect of the present disclosure, it is provided a method for stabilizing yaw moments in a wind turbine. The method comprises obtaining at least one wind direction measurement comprising at least one wind direction measurement. The method further comprises determining a yaw drift ip and an expected yaw actuation angle ipT. The method further comprises obtaining a saturation range, the saturation range having a first saturation limit and a second saturation limit. The method further comprises modifying the saturation range, thereby obtaining a modified saturation range. The method further comprises determining a yaw actuation angle ip which is a function of the yaw drift ip. The method further comprises applying the modified saturation range on the yaw actuation angle ip, thereby obtaining a saturated yaw actuation angle ips. The method further comprises performing a yaw actuation of the rotor on the wind turbine based on the saturated yaw actuation angle ips.

[0012] The obtaining at least one wind measurement may further comprise at least one wind speed measurement.

[0013] The method may further comprise filtering the at least one wind measurement, using a filtering unit, thereby obtaining at least one filtered wind measurement.

[0014] The at least one wind measurement may be obtained using LIDAR.

[0015] The method may further comprise determining an angular rate pT.

[0016] The method may further comprise calculating a mean yaw value ψ̄ based on the yaw drift.

[0017] Determining a yaw actuation angle ip may further comprise being a function of the time rate of variation of the expected angle pT. Determining a yaw actuation angle ip may further comprise being a function of the mean yaw value ip.

[0018] The method may further comprise calculating a pitch actuation angle. The calculating a pitch actuation angle may be based on a yaw actuation angle ip. The calculating a pitch actuation angle may be based on one or more of the yaw actuation angle ip, the expected yaw actuation angle ipT, or the saturated yaw actuation angle ^s-

[0019] The method may further comprise performing a pitch actuation based on the calculated pitch actuation angle.

[0020] According to a second aspect of the present disclosure, it is provided a non-transitory computer-readable medium comprising instructions that, when executed byone or more processors, perform the method according to the first aspect of the present disclosure.

[0021] According to a third aspect of the present disclosure, it is provided a control system for stabilizing yaw moments in a wind turbine. The control system comprises a first unit, configured to obtain at least one wind measurement. The at least one wind measurement may comprise at least one wind speed measurement. The at least one wind measurement may comprise at least one wind direction measurement. The control system further comprises a second unit, in data communication with the first unit, configured to determine a yaw drift i and an expected yaw actuation angle iT, obtain a saturation range, the saturation range having a first saturation limit and a second saturation limit, modify the saturation range, thereby obtaining a modified saturation range, determine a yaw actuation angle ψ which is a function of the yaw drift Δψ; and apply the modified saturation range on the yaw actuation angle ψ, thereby obtaining a saturated yaw actuation angle is. The control unit further comprises an actuating unit, in data communication with the second unit, and in engagement with a rotor of a wind turbine, configured to perform a yaw actuation on the rotor of the wind turbine based on the saturated yaw actuation angle ψs.

[0022] The control system may further comprise a filtering unit for filtering the at least one wind measurement.

[0023] The first unit may comprise a LIDAR.

[0024] The control system may further comprise a pitch actuation unit in engagement with the rotor, the pitch actuation unit being configured to perform a pitch actuation on the rotor of the wind turbine based on a calculated pitch actuation angle. The pitch actuation unit may be in data communication with the first unit. The pitch actuation unit may be in data communication with the second unit.

[0025] The control system may further comprise the non-transitory computer-readable medium according to the second aspect of the disclosure.

[0026] According to a fourth aspect of the present disclosure, it is provided a use of a control system, in offshore wind turbines, floating wind turbines, single-point moored floating wind turbines, bottom-fixed wind turbines, or onshore wind turbines.

[0027] The control system and method can be applied to horizontal-axis turbines, whether floating, bottom-fixed, or onshore.

[0028] According to a fifth aspect of the present disclosure, it is provided a use of a control system for yaw actuation or load alleviation.

[0029] The control system and method mitigate the yaw angle - thereby increasing power output, reducing loads, and extending operational life.

[0030] The controller and method may be useful for overall load reduction, as they can be used to reduce moments from other angles, such as tilt angles, conning angles, or pitch of the platform.

[0031] In floating wind turbines, this moment is counter-balanced by the mooring system at each corner of the floating platform. However, generic floating wind turbines and onshore wind turbines could also benefit from the load reduction.

[0032] Moreover, the method and system offer stability to the wind turbine and prevents the wind turbine from diverging.BRIEF DESCRIPTION OF DRAWINGS

[0033] Embodiments of the invention will now be described, by way of example only, and with reference to the accompanying drawings, in which:

[0034] Figure 1 illustrates an exemplary wind turbine with denoted angles in relation to an incoming wind,

[0035] Figure 2 illustrates an exemplary way of Individual Pitch Actuation (IPC) actuation for a wind turbine with three blades,

[0036] Figure 3 illustrates the yaw drift as a function of time presented for three distinct exemplary scenarios,

[0037] Figure 4 illustrates an exemplary diagram of a method for stabilizing yaw moments in a wind turbine,

[0038] Figure 5 illustrates an exemplary graph made from values of a look-up table providing a relationship between expected yaw angles as a function of the wind speed, V,

[0039] Figure 6 illustrates the yaw actuation angle i of an exemplary system as a function of time,

[0040] Figure 7 illustrates an exemplary rotor angle as a function of time for two different wind speeds, V=20 m / s and V=9 m / s,

[0041] Figure 8 illustrates the yaw drift i as a function of time for three exemplary systems, and

[0042] Figure 9 illustrates an exemplary schematic of a control system for stabilizing yaw moments in a wind turbine.

[0043] All illustrations of the drawings are for the purpose of describing selected versions of the present invention and are not intended to limit the scope of the present invention.DETAILED DESCRIPTION

[0044] The present disclosure alleviates the above problems with the method and control system described below.

[0045] The yaw drift i refers to a signal coming from wind speed and wind direction measurements. The yaw drift i is then defined as the angle between the mean wind direction and the normal vector of the rotor plane.

[0046] It is common for wind turbines to employ individual pitch controllers (IPCs) to control the pitch of the blades. An exemplary way of IPC actuation for a wind turbine with three blades is shown in Figure 2. The inverse multi-blade coordinate (IMBC) transformation is based on Bossanyi, E. A. (2003), Individual Blade Pitch Control for Load Reduction. Wind Energ., 6: 119-128. https: / / doi.org / 10.1002 / we.76. The IMBC transformation is used to alleviate the issue of the controller output and the blades being in different frames; the controller on the non-rotatory frame, while the blades on the rotatory frame.

[0047] The IPC system, if provided for a wind turbine, may actuate continuously and mitigate instantaneous effects of fluctuations of Δψ. The IPC may also be calibrated to reduce loads on the rotor and structure. The signal i may come from Lidar measurements. The method and control system described below is not limited to a system which employs individual pitch control, but it may be used complementary or independently.

[0048] One of the effects of the method and system is shown in Figure 3, where the yaw drift as a function of time is presented for three distinct scenarios. The continuous line 31 provides the yaw drift of a system which only uses an IPC. The dashed line 32 provides the yaw drift of a system which uses both an IPC and a device for obtaining wind direction and wind speed measurements. In this example, that device is a light detection and ranging (lidar) device. The dotted line 33 represents the yaw drift of a system where yaw action is provided in addition to the IPC and the device for obtaining wind direction and wind speed measurements.

[0049] The system on which the yaw actuation was performed, that of dotted line 33 in Figure 3, provides a smaller yaw drift angle compared to the cases where yaw actuation was not used.

[0050] The method 400 for stabilizing yaw moments in a wind turbine is shown in Figure 4. The method comprises obtaining at least one wind measurement. The at least one wind measurement comprises at least one wind direction measurement. Preferably, the at least one wind measurement comprises at least one wind speed measurement. The wind direction and / or wind speed measurements may be Lidar measurements.

[0051] The method 400 may further comprise the optional step of filtering 401 A the obtained at least one wind measurement. In this way, at least one filtered wind measurements are obtained. The at least one filtered wind measurements may be at least one filtered wind direction and / or filtered wind speed measurements. The filtering may be achieved through the use of a low-pass filter. The filtering may be applied to avoid high fluctuations on the measurements. The low-pass filter may allow low-frequency signals to pass through while attenuating high-frequency signals. Its purpose may be manyfold, such as reducing noise, smoothing data, and highlighting longer-term trends in a signal, improving the accuracy and stability of measurements.

[0052] The method 400 further comprises determining 402 a yaw drift i and an expected yaw actuation angle iT. The expected yaw actuation angle iTmay be based on the wind direction and / or wind speed measurements. The determination of the expected yaw actuation angle iTmay be achieved by referring to a look-up table. The look-up table may provide a relationship between expected yaw angles as a function of the wind speed, V.

[0053] An exemplary graph made from values of a look-up table is shown in Figure 5. The exemplary graph and look-up table may be constructed by creating a model whereconstant wind V is applied to the wind turbine, while only using the yaw control system, until the system reaches steady state with i = 0. The angle of the yaw actuation found at this condition is iT(V). The effect of this term is a reduction of the root mean squared yaw error AI / J.

[0054] Alternatively, a table may be constructed such that it could provide a yaw angle that leads to minimum loads at a given wind speed. In this way, load alleviation may be achieved.

[0055] Another possibility is a table with yaw angles that leads to a combined optimized yaw angle value, where it is achieved minimum load while reducing the yaw error.

[0056] The method 400 further comprises obtaining 403 a saturation range. The saturation range has a first saturation limit and a second saturation limit. The first saturation limit and second saturation limit may refer to an upper and lower saturation limit, respectively, defining the saturation range. This saturation range may be written conventionally throughout this disclosure as [first limit, second limit],

[0057] An exemplary way of obtaining a saturation range is shown in Figure 6, where the yaw actuation angle i of a system as a function of time is presented. To produce this graph, simulations similar to those presented in connection with Figure 5 are executed. These simulations consider the yaw system alone, and parameters of the system are evaluated at different wind speeds and different limits [first limit, second limit]. These parameters may include yaw drift, yaw moment, fatigue, rotor angle, platform yaw angle, or other parameters of interest that could be affected by the yaw actuation angle i. The yaw actuation itself could be a parameter to measure the stability of the system: if the yaw actuation fluctuates a lot between the saturated values and do not find a steady value, it is an indication of instability. Stable systems should converge to some yaw angle, as indicated in Figure 6. When the system stabilizes, the values of [first limit, second limit] are selected. By looking at the graph in this case for example, [first limit, second limit] = [-7, 7] deg. The graph is for illustrative purposes; in practice, the first limit and second limit may be determined by analyzing the minimum and maximum values produced during the simulation.

[0058] The method 400 further comprises modifying 404 the saturation range, thereby obtaining a modified saturation range. The modification may be achieved by adding the first saturation limit and the second saturation limit to the expected yaw actuation angle iT.

[0059] The method 400 further comprises determining 405 a yaw actuation angle i which is a function of the yaw drift AI / J. The yaw actuation angle i may be the yaw drift i value multiplied by a weight parameter a, plus optionally an angle value c, such that:

[0060] I / J = a • i + c (Equation 1 )

[0061] In the case where a = 1 and c = 0, the yaw actuation angle i is equal to the yaw drift AI / J.

[0062] The method 400 further comprises applying 406 the modified saturation range on the yaw actuation angle i, thereby obtaining a saturated yaw actuation angle is.

[0063] The step of applying the saturation range contributes towards keeping the system stable. The saturation range may be the modified saturation range, which comprises a modified first limit and / or a modified second limit. Figure 7 illustrates the effects of the modification in saturation limits, where the rotor angle as a function of time for two different wind speeds, V=20 m / s and V=9 m / s, is illustrated. The dashed line 73 represents the wind direction, while the dotted line 71 represents a system where saturation limits are applied. For the system where the saturation limits are applied, it is evident that the rotor angle stabilizes around the wind direction. The continuous line 72 represents a system where no saturation is applied. The rotor angle in this case oscillates with a significantly higher amplitude compared to the system where saturation limits were applied. The amplitude of this oscillation even diverges under certain parameters, leading to an increase in deviation between the rotor angle and the wind direction. This shows that when no limits are applied to the yaw control the system becomes unstable, and it diverges.

[0064] The method 400 further comprises performing 407 a yaw actuation of the rotor on the wind turbine based on the saturated yaw actuation angle is. The saturation range, and therefore the saturation limits [first limit, second limit] are shifted around the angle iT(V), which is the expected yaw actuation angle iTat the current wind speed. This contributes to the system quickly reaching the expected steady state actuation angle. Therefore, this change in saturation limits may be applicable to single point moored floating wind turbines, but it may also be applied to quicker lead to yaw angles in systems looking for load alleviation, for example.

[0065] The method may further comprise determining 404A an angular rateT. The angular rate ipTmay be used in the determination 405 of the yaw actuation angle i.Determining a yaw actuation angle ip may further comprise being a function of the time rate of variation of the expected angle ipT. The time rate of variation of the expected angle pTmay be multiplied by a time step between actuations. The yaw actuation angle ip may for example be the yaw drift Aip value multiplied by a weight parameter a, plus the time rate of variation of the expected angle pTmultiplied by a time step between actuations DT, and a weight parameter w, plus optionally an angle value c, such that:

[0066] ip = a • Aip + w • ṗT• DT + c (Equation 2)

[0067] In the scenario where a = 1, w = 1 and c = 0, Equation 2 can be written as

[0068] ip = Aip + ipT• DT (Equation 3)

[0069] Regarding the time step between actuations DT, in an exemplary case, 100 s may be used, but it can vary depending on the application. The choice of DT being equal to 100 s means that yaw actuations in such a system occur every 100 s.

[0070] The method 400 may further comprise calculating a mean yaw value ψ̄ based on the yaw drift. Determining a yaw actuation angle ip may further comprise being a function of the mean yaw value ip. The yaw actuation angle ip may be the yaw drift Aip value multiplied by a weight parameter a, plus the mean yaw value ip multiplied by a weight parameter / , plus optionally an angle value c, such that

[0071] ip = a - Aip +y - ip + c (Equation 4)

[0072] In the scenario where a = 1, y = 1 and c = 0, Equation 4 can be written as:

[0073] ip = Aip + ip (Equation 5)

[0074] The incorporation of the mean yaw value ip may be used to improve the calculation of the yaw drift Aip. Figure 8 shows an illustration of the effect of that incorporation on the yaw drift Aip. The continuous line 81 shows the yaw drift of a system over time where the mean yaw value ip is not taken into account. The dotted line shows the yaw drift of a system over time, where the mean yaw value ip is incorporated into the calculation of the yaw actuation angle ip. The dashed line 83 shows the yaw drift of a system over time, where the mean yaw value ip is incorporated into the calculation of the yaw actuation angle ip where, in addition, information regarding the wind direction and wind speed are included. In this example, the wind direction and wind speed are provided by a lidar.

[0075] Determining a yaw actuation angle ip may further be a function of the time rate of variation of the expected angle ipTand the mean yaw value ip. As described above,the time rate of variation of the expected angle ipTmay be multiplied by a time step DT between actuations. The yaw actuation angle ip may be the yaw drift ip value multiplied by a weight parameter a, plus the time rate of variation of the expected angle ipTmultiplied by a time step between actuations and a weight parameter w, plus mean yaw value ip multiplied by a weight parameter γ, plus optionally an angle value c, such that

[0076] ψ = a · Δψ + w · ψ̇T· DT + γ · ψ̄ + c (Equation 6)

[0077] In the scenario where a = 1, w = 1, y = 1 and c = 0, Equation 6 can be written as:

[0078] ψ = Δψ + ψ̇T· DT + ψ̄ (Equation 7)

[0079] The method 400 may further comprise calculating 408 a pitch actuation angle. The calculating 408 a pitch actuation angle may be based on a yaw actuation angle ip. The calculating 408 a pitch actuation angle may be based on one or more of actuation angle ip, the expected yaw actuation angle ipT, or the saturated yaw actuation angle Ps-

[0080] The method 400 may further comprise performing 409 a pitch actuation based on the calculated pitch actuation angle. Regarding the pitch actuation angle, each blade may have its own pitch angle. Alternatively, the pitch actuation angle may be the sum of a collective angle, i.e. a mean pitch actuation angle, plus one part that comes from a common amplitude, considering a trigonometric component to translate this amplitude into a proper component for each blade.

[0081] A non-transitory computer-readable medium comprising instructions that, when executed by one or more processors, perform the method 400.

[0082] A control system 90 for stabilization of yaw moments in a wind turbine is shown in Figure 9. The control system comprises a first unit 91. The first unit 91 is configured to obtain at least one wind measurement. The at least one wind measurement may comprise at least one wind direction measurement. The at least one wind measurement may comprise at least one wind speed measurement. The first unit 91 may comprise a lidar. The lidar may be used for obtaining the at least one wind measurement, i.e. the at least one wind direction and / or at least one wind speed measurement.

[0083] The control system 90 further comprises a second unit 92. The second unit 92 is in data communication with the first unit.

[0084] The second unit 92 is configured to determine a yaw drift ip and an expected actuation angle ipT. This can be achieved by the wind direction and wind speed measurements received from the first unit 91.

[0085] The second unit 92 is further configured to obtain a saturation range, the saturation range having a first saturation limit and a second saturation limit.

[0086] The second unit 92 is further configured to modify the saturation range. A modified saturation range can therefore be obtained. An exemplary modification of the saturation range may for example be the addition of the first saturation limit and the second saturation limit to the expected yaw actuation angle. The second unit 92 is further configured to determine a yaw actuation angle ψ which is a function of the yaw drift Δψ.

[0087] Furthermore, the second unit 92 is configured to apply the modified saturation range on the yaw actuation angle ψ, thereby obtaining a saturated yaw actuation angle ψs.

[0088] The control system 90 further comprises an actuating unit, in data communication with the second unit, and in engagement with the rotor of a wind turbine. The actuating unit 93 is configured to perform a yaw actuation on the rotor of the wind turbine based on the saturated yaw actuation angle ips.

[0089] The control system 90, may further comprise a filtering unit 95 for filtering the wind direction and wind speed measurements.

[0090] The control system 90 may further comprise a pitch actuation unit 94 in engagement with the rotor. The pitch actuation unit 94 may be in data communication with the first unit 91. Alternatively, the pitch actuation unit 94 may be in data communication with the second unit 92. The pitch actuation unit 94 is configured to perform a pitch actuation on the rotor of the wind turbine based on a calculated pitch actuation angle. The person skilled in the art will understand that the pitch actuation unit 94 is an alternative formulation for the IPC and may be used interchangeably throughout this disclosure.

[0091] Achieving data communication between the pitch actuation unit 94 and the second unit 92 may provide the possibility for improved pitch actuation for the pitch actuation unit 94 system based on data from the second unit 92. This allows for a yaw actuation angle to be used to determine a pitch actuation angle. A yaw actuation anglemay be the yaw actuation angle ψ, the expected yaw actuation angle ψT, or the saturated yaw actuation angle ψs.

[0092] Regarding the pitch actuation angle, each blade may have its own pitch angle. Alternatively, the pitch actuation angle may be the sum of a collective angle, i.e. a mean pitch actuation angle, plus one part that comes from a common amplitude, considering a trigonometric component to translate this amplitude into a proper component for each blade.

[0093] Having a controller with the possibility of both calculating a pitch actuation angle and a yaw actuation angle may be beneficial for a wind turbine system to reach and maintain stability, as the two different types of actuations may assist each other. In this way, the system may achieve stability quicker and maintain said stability for longer.

[0094] The rotor may therefore receive an additional control actuation, that of individual pitch of the blades. The individual pitch of the blades actuates all the time and mitigates instantaneous effects of fluctuations of Δψ. It can be calibrated to reduce loads on the rotor and structure. The control system 90 described above is not limited for use in connection with wind turbines which are equipped with IPCs.

[0095] In one example, the control system 90 comprises the non-transitory computer readable medium comprising instructions that, when executed by one or more processors, perform the method 400.

[0096] The control system 90 may be used in the fields of offshore wind turbines, floating wind turbines, single-point moored floating wind turbines, bottom-fixed wind turbines, or onshore wind turbines.

[0097] The control system may be used for yaw actuation or load alleviation.

[0098] Having described example embodiments of the invention it will be apparent to those skilled in the art that other embodiments incorporating the concepts may be used. These and other non-limiting examples illustrated above are intended by way of example only and the actual scope of the invention is to be determined from the appended claims.

[0099] The skilled person will also understand that any use of “or” throughout the statements of invention or description herein encompasses use of “or”, “and / or”, and “and”. For example, the term "or" within the discourse is construed to encompass both "and" and "and / or" owing to its inherent inclusivity. Within linguistic reasoning, "or"denotes an inclusive disjunction, allowing for the consideration of scenarios wherein either one condition holds true, the other condition holds true, or both conditions hold true concurrently. This interpretation inherently incorporates the conjunction "and", permitting the acknowledgment of scenarios wherein multiple conditions coexist. Additionally, the term "and / or" explicitly acknowledges the possibility of either condition being singularly true or both conditions being true simultaneously, thus aligning with the broader meaning of "or" within the context of this disclosure. Consequently, "or" functions as a flexible connector within the statements of invention, accommodating both exclusive and inclusive interpretations to suit the nuanced requirements of embodiments described herein.

Claims

PATENT CLAIMS1. A method for stabilizing yaw moments in a wind turbine, the method comprising:obtaining at least one wind measurement comprising at least one wind direction measurement;determining a yaw drift Δψ and an expected yaw actuation angle ψT; obtaining a saturation range, the saturation range having a first saturation limit and a second saturation limit;modifying the saturation range, thereby obtaining a modified saturation range; determining a yaw actuation angle ψ which is a function of the yaw drift Δψ; applying the modified saturation range on the yaw actuation angle ψ, thereby obtaining a saturated yaw actuation angle ψs; andperforming a yaw actuation of the rotor on the wind turbine based on the saturated yaw actuation angle ψs.

2. The method according to claim 1, wherein obtaining at least one wind measurement further comprises at least one wind speed measurement.

3. The method according to claim 1 or claim 2, further comprising filtering the at least one wind measurement, using a filtering unit, thereby obtaining at least one filtered wind measurement.

4. The method according to any one of claims 1 - 3, wherein the at least one wind measurement is obtained using LIDAR.

5. The method according to any one of claims 1 - 4, further comprising:determining an angular rate ψ̇T.

6. The method according to any one of claims 1 - 5, further comprising: calculating a mean yaw value ψ̄ based on the yaw drift.

7. The method according to claim 5, wherein determining a yaw actuation angle ψ further comprises being a function of the time rate of variation of the expected angle ψ̇T.

8. The method according to claim 6 or claim 7, wherein determining a yaw actuation angle ψ further comprises being a function of the mean yaw value ψ̄.

9. The method according to any one of the preceding claims, further comprising:calculating a pitch actuation angle based on a yaw actuation angle ψ.

10. The method according to any one of claims 1 - 8, further comprising:calculating a pitch actuation angle based on one or more of the yaw actuation angle ψ, the expected yaw actuation angle ψT, or the saturated yaw actuation angle ψs.

11. The method according to claim 9 or claim 10, further comprising:performing a pitch actuation based on the calculated pitch actuation angle.

12. A non-transitory computer-readable medium comprising instructions that, when executed by one or more processors, perform the method according to any one of claims 1 - 11.

13. A control system for stabilizing yaw moments in a wind turbine, comprising: a first unit, configured to obtain at least one wind measurement;a second unit, in data communication with the first unit, configured to:determine a yaw drift Δψ and an expected yaw actuation angle ψT; obtain a saturation range, the saturation range having a first saturation limit and a second saturation limit;modify the saturation range, thereby obtaining a modified saturation range;determine a yaw actuation angle ψ which is a function of the yaw drift Δψ; andapply the modified saturation range on the yaw actuation angle ψ, thereby obtaining a saturated yaw actuation angleandan actuating unit, in data communication with the second unit, and in engagement with a rotor of a wind turbine, configured to perform a yaw actuation on the rotor of the wind turbine based on the saturated yaw actuation angle ψs.

14. The control system according to claim 13, further comprising a filtering unit for filtering the at least one wind measurement.

15. The control system according to claim 13 or claim 14, wherein the first unit comprises a LIDAR.

16. The control system according to any one of claims 13 - 15, further comprising a pitch actuation unit in engagement with the rotor, the pitch actuation unit being configured to perform a pitch actuation on the rotor of the wind turbine based on a calculated pitch actuation angle.

17. The control system according to claim 16, wherein the pitch actuation unit is in data communication with the first unit.

18. The control system according to claim 16 or claim 17, wherein the pitch actuation unit is in data communication with the second unit.

19. The control system of any of claims 13 to 18, comprising the non-transitory computer-readable medium of claim 12.

20. Use of the control system according to any one of claims 13 - 19, in offshore wind turbines, floating wind turbines, single-point moored floating wind turbines, bottom-fixed wind turbines, or onshore wind turbines.

21. Use of the control system according to any one of claims 13 - 19, for yaw actuation or load alleviation.

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