Apparatus and method for controlling operation of a wind turbine to reduce yaw misalignment induced loads

Abstract

An apparatus and a method of controlling operation of a wind turbine (1) are described. The wind turbine (1) comprises a rotor (4) with a plurality of rotor blades (6), the rotor (4) being mounted to a nacelle (3) for rotation about a rotation axis (8), and the nacelle (3) being mounted to a tower (3) for rotation about a yaw axis (9), such that the rotation axis (8) is also rotatable about the yaw axis (9). The method comprises the steps of determining a wind direction, acquiring a yaw angle of the nacelle (3) and the rotation axis (8), determining an angular misalignment between the wind direction and the yaw angle of the rotation axis (8), the angular misalignment being measured in a plane perpendicular to the yaw axis (9), and performing a stall operation in case the angular misalignment exceeds a predetermined threshold.

Description

Technical Field

[0001] This invention relates to apparatus and methods for controlling the operation of a wind turbine to reduce the load during yaw misalignment. Background Technology

[0002] A conventional wind turbine consists of a nacelle and a tower, with the nacelle rotatably mounted on top of the tower. The axis of rotation of the nacelle about the tower is called the yaw axis. In cases of high yaw misalignment (i.e., misalignment between the nacelle's yaw position and the wind direction), cyclic loads can occur at multiple structural components. These loads are caused by the yaw misalignment between the nacelle's yaw position and the wind direction, and these loads can be amplified by a certain pitch angle, i.e., the rotation angle of the blades about their longitudinal axis. Therefore, in these situations, shutting down or reducing the wind turbine will actually increase the load, as the pitch angle typically increases during such shutdowns or reductions.

[0003] The results indicate that conventional mitigation strategies (i.e., shutting down or reducing wind turbine operations) are not adequately effective unless the wind turbines can be stopped at a very early stage, resulting in some false alarms and reduced availability.

[0004] To date, this problem has been addressed by either reducing the maximum wind speed at which the turbine operates or by increasing the capacity of blades, towers, or other structural components to meet load levels. However, these existing solutions are relatively expensive and assume that these components can be designed to stable load levels. Furthermore, these loads often exhibit large fluctuations, making them difficult to manage in all situations. Summary of the Invention

[0005] There may be a need for devices and methods to control the operation of wind turbines in order to efficiently reduce the load during yaw misalignment. This need can be met by the subject matter described in the independent claim. The invention is further improved as set forth in the dependent claims.

[0006] According to a first aspect of the invention, a method for controlling the operation of a wind turbine is provided. The wind turbine includes a rotor having a plurality of rotor blades, the rotor being mounted to a nacelle for rotation about a rotation axis, and the nacelle being mounted to a tower for rotation about a yaw axis, such that the rotation axis also rotates about the yaw axis. The method includes the steps of: determining a wind direction; acquiring a yaw angle between the nacelle and the rotation axis; determining an angular misalignment between the wind direction and the yaw angle of the rotation axis, the angular misalignment being measured in a plane perpendicular to the yaw axis; and performing a stall operation if the angular misalignment exceeds a predetermined threshold.

[0007] Advantageously, when the predetermined threshold is exceeded, the aerodynamic efficiency of the blades (which causes high loads) is reduced by stalling the blades. As a result, this stall operation reduces the load caused by yaw misalignment.

[0008] In one embodiment, the method further includes the step of determining a wind speed, wherein the predetermined threshold is a function of the wind speed. Preferably, the higher the wind speed, the smaller the predetermined threshold. The threshold may be stored in a lookup table.

[0009] In one embodiment, each blade is configured to pitch about the blade's pitch axis by a pitch angle, wherein the stall operation includes setting the pitch angle to exceed a predetermined stall pitch angle.

[0010] In one embodiment, each blade includes at least one stall adjustment member configured to alter the aerodynamic characteristics of the blade, wherein the stall operation includes setting the stall adjustment member in a state that degrades the aerodynamic efficiency of the blade.

[0011] According to a second aspect of the invention, a control device for controlling the operation of a wind turbine is provided. The wind turbine includes a rotor having a plurality of rotor blades, the rotor being mounted to a nacelle for rotation about a rotation axis, and the nacelle being mounted to a tower for rotation about a yaw axis, such that the rotation axis can also rotate about the yaw axis. The control device includes: a wind direction determining device configured to determine a wind direction; an acquisition device configured to acquire a yaw angle of the nacelle and the rotation axis; an angle misalignment determining device configured to determine an angle misalignment between the wind direction and the yaw angle of the rotation axis, the angle misalignment being measured in a plane perpendicular to the yaw axis; and a stall operation device configured to induce stall operation if the angle misalignment exceeds a predetermined threshold.

[0012] In one embodiment, the control device further includes a wind speed determining device configured to determine a wind speed, wherein the predetermined threshold is a function of the wind speed. Preferably, the higher the wind speed, the smaller the predetermined threshold.

[0013] In one embodiment, each blade is configured to pitch about its pitch axis by a pitch angle, wherein the stall operating device is configured to set the pitch angle to exceed a predetermined stall pitch angle. This embodiment can be implemented without complex modifications to existing wind turbines that are typically already equipped with pitch systems.

[0014] In one embodiment, each blade includes at least one stall adjustment member configured to alter the blade's aerodynamic characteristics, wherein the stall actuation device is configured to place the stall adjustment member in a state that degrades the blade's aerodynamic efficiency. Advantageously, this measure can be implemented in existing stall adjustment systems without complex modifications. For example, existing stall adjustment flaps can be used, which degrade aerodynamic efficiency to stall the blade. As another advantage, the operation of the stall adjustment member is generally faster than that of the pitch control system mentioned above.

[0015] According to a third aspect of the invention, a wind turbine includes the aforementioned control device.

[0016] It should be noted that embodiments of the invention have been described with reference to different subjects. In particular, some embodiments have been described with reference to claims of the device type, while others have been described with reference to claims of the method type. However, those skilled in the art will understand from the above and below description that, unless otherwise stated, any combination of features related to different subjects, in particular any combination of features of device type claims and features of method type claims, is also considered to utilize the disclosure of this application, except for any combination of features belonging to one type of subject matter. Attached Figure Description

[0017] The aspects defined above, as well as other aspects of the invention, will be apparent by way of examples of embodiments described below, and will be explained with reference to these examples. The invention will be described in more detail below with reference to examples of embodiments, but the invention is not limited to these examples.

[0018] Figure 1 The wind turbine and its various components are shown.

[0019] Figure 2 A block diagram illustrating a method for controlling the operation of a wind turbine according to an embodiment is shown; and

[0020] Figure 3 An example of a blade with a trim stall member is shown. Detailed Implementation

[0021] The illustrations in the accompanying drawings are schematic. It should be noted that similar or identical elements are labeled with the same reference numerals in different drawings.

[0022] Figure 1A wind turbine 1 is shown. The wind turbine 1 includes a nacelle 3 and a tower 2. The nacelle 3 is mounted on top of the tower 2. The nacelle 3 is mounted so that it can rotate relative to the tower 2 by means of a yaw bearing (not shown). The axis of rotation of the nacelle 3 relative to the tower 2 is referred to as the yaw axis 9.

[0023] The wind turbine 1 also includes three rotor blades 6 ( Figure 1 The rotor 4 depicts two rotor blades 6. Each blade 6 is configured to pitch about its pitch axis. The pitch axis of the blade 6 is typically the longitudinal axis of the blade 6. This pitch is typically actuated by a pitch actuator, such as a hydraulic pitch actuator. The rotor 4 is mounted so as to be rotatable relative to the nacelle 3 by means of a main bearing 7. The rotor 4 is mounted so as to be rotatable about a rotation axis 8. The rotation axis 8 is typically orthogonal (perpendicular) to the yaw axis 9.

[0024] Furthermore, the wind turbine 1 also includes a generator 5. The generator 5 further includes a rotor 10 that connects the generator 5 to the rotor 4. Since the rotor 4 is directly connected to the generator 5, the wind turbine 1 is referred to as a direct-drive wind turbine without a transmission. Such a generator 5 is called a direct-drive generator 5. Alternatively, the rotor 4 can also be connected to the generator 5 via a gearbox. This type of wind turbine 1 is called a geared wind turbine. This invention is applicable to both types of wind turbines 1.

[0025] The generator 5 is housed within the engine compartment 3. The generator 5 is arranged and prepared to convert the rotational energy from the rotor 4 into electrical energy in the form of alternating current.

[0026] Figure 2 A block diagram illustrating a method for controlling the operation of a wind turbine 1 according to an embodiment is shown. The method includes a step S1 of determining the wind direction, which can be performed by a wind direction determining device. This wind direction determining device can be a wind direction detection device. However, the wind direction can also be estimated indirectly based on parameters other than wind direction. Wind speed and wind direction can also be transmitted from another wind turbine in the field, such as a wind farm. The determined wind direction can refer to any predetermined reference direction where the wind direction is defined as zero degrees.

[0027] The method includes step S2 of obtaining the yaw angle of the nacelle 3 and the rotation axis 8. The yaw angle of the nacelle 3 and the rotation axis 8 may refer to any predetermined reference orientation in which the yaw angle is defined as zero degrees. Preferably, the reference orientation in which the yaw angle is zero degrees coincides with a reference direction in which the wind direction is also zero degrees.

[0028] The method includes step S3, which determines the angular misalignment between the wind direction and the yaw angle of the rotation axis 8, the angular misalignment being measured in a plane perpendicular to the yaw axis 9. The method includes step S4, which checks whether the determined angular misalignment exceeds a threshold. The method includes step S5, which performs a stall operation if the angular misalignment exceeds a predetermined threshold.

[0029] exist Figure 2 In one embodiment, the method further includes a step S6 of determining wind speed. Wind speed can be detected by a wind speed detection device, or it can be indirectly estimated based on other parameters besides wind speed. Wind speed and direction can also be transmitted from another wind turbine in the field, such as a wind farm. The method includes a step S7, wherein a predetermined threshold γ [degrees] is determined as a function of wind speed v [m / s]. The threshold γ and wind speed v can be stored in a lookup table.

[0030] exist Figure 2 In one embodiment, a threshold γ as a function of wind speed v is plotted in a graph of region A with lower wind speed and region B with higher wind speed. The threshold γ in region A is greater than the threshold γ in region B. This graph reflects a pattern where the higher the wind speed v, the smaller the predetermined threshold γ. In a preferred embodiment, the function reflected by this graph can be stored in a lookup table.

[0031] The stall operation can be achieved by modifying the pitch angle of blade 6. Specifically, performing the stall operation may include setting the pitch angle of blade 6 to exceed a predetermined stall pitch angle at which stall occurs at blade 6. If an existing wind turbine is equipped with such a pitch system, no hardware modification is required to implement the invention. However, the stall operation can be achieved by any other means.

[0032] Figure 3 An example of a blade 6 with an active stall adjustment member 17 is shown, which is typically driven by a hydraulic stall adjustment actuator. The stall adjustment member 17 may also be driven by a pneumatic system. The stall adjustment member 17 is configured to alter the aerodynamic characteristics of the blade 6. Performing the stall operation may include setting the stall adjustment member 17 in a state that degrades the aerodynamic efficiency of the blade 6, causing a stall at the blade 6. For example, this state may correspond to the maximum extension position of the stall adjustment member 17. In this embodiment, existing stall adjustment systems can be used, where the active stall adjustment member 17 or an active additional member on the blade 6 reduces the aerodynamic efficiency of the blade 6, thereby reducing the load caused by yaw misalignment. If an existing wind turbine is equipped with such a stall adjustment member 17, no hardware modification is required to implement the invention.

[0033] The above method can be implemented in a control device (not shown) configured to control the operation of the wind turbine 1. The control device includes: a wind direction determining device configured to determine the wind direction; an acquisition device configured to acquire the yaw angle of the nacelle 3 and the rotation axis 8; an angle misalignment determining device configured to determine the angle misalignment between the wind direction and the yaw angle of the rotation axis 8, the angle misalignment being measured in a plane perpendicular to the yaw axis 9; and a stall operation device configured to induce stall operation if the angle misalignment exceeds a predetermined threshold.

[0034] The control device may further include a wind speed determining device configured to determine a wind speed, wherein the predetermined threshold is a function of the wind speed. Preferably, the higher the wind speed, the smaller the predetermined threshold.

[0035] In a simplified implementation, each blade 6 may be configured to pitch about the pitch axis of the blade 6 by a pitch angle, wherein the stall operating device is configured to set the pitch angle to exceed a predetermined stall pitch angle.

[0036] exist Figure 3 In one embodiment, each blade 6 includes at least one stall adjustment member 17 configured to alter the aerodynamic characteristics of the blade 6, wherein the stall actuation device is configured to set the stall adjustment member 17 in a state that degrades the aerodynamic efficiency of the blade 6.

[0037] In a modified embodiment, any other means or measures may be used to perform the stall operation.

[0038] It should be noted that the term "comprising" does not exclude other elements or steps, and the wording "a," "an," or "a kind" does not exclude multiple. Furthermore, elements described in different embodiments may be combined. It should also be noted that the reference numerals in the claims should not be construed as limiting the scope of the claims.

Claims

1. A method for controlling the operation of a wind turbine (1), said wind turbine (1) comprising a rotor (4) having a plurality of rotor blades (6), wherein, Each blade (6) is configured to pitch about the pitch axis of the blade (6) by a pitch angle, wherein stall occurs at the blade (6) when the pitch angle exceeds a predetermined stall angle, the rotor (4) is mounted to the nacelle (3) to rotate about the rotation axis (8), and the nacelle (3) is mounted to the tower (2) to rotate about the yaw axis (9), such that the rotation axis (8) can also rotate about the yaw axis (9), the method comprising the following steps: Determine the wind direction; Obtain the yaw angle of the cabin (3) and the rotation axis (8); Determine the angular misalignment between the wind direction and the yaw angle of the rotation axis (8), the angular misalignment being measured in a plane perpendicular to the yaw axis (9); and If the angular misalignment exceeds a predetermined threshold, a stall operation is performed by at least one of the following: a) Setting the pitch angle to exceed the predetermined stall pitch angle; and b) Each blade (6) includes at least one stall adjustment member (17) configured to alter the aerodynamic characteristics of the blade (6), wherein the stall operation includes setting the stall adjustment member (17) in a state that degrades the aerodynamic efficiency of the blade (6).

2. The method according to claim 1, further comprising: Determine the wind speed, wherein the predetermined threshold is a function of the wind speed.

3. The method according to claim 2, wherein The higher the wind speed, the lower the predetermined threshold.

4. A control device for controlling the operation of a wind turbine (1), the wind turbine (1) comprising a rotor (4) having a plurality of rotor blades (6), wherein, Each blade (6) is configured to pitch at a pitch angle about the pitch axis of the blade (6), wherein stall occurs at the blade (6) when the pitch angle exceeds a predetermined stall angle, the rotor (4) is mounted to the nacelle (3) to rotate about the rotation axis (8), and the nacelle (3) is mounted to the tower (3) to rotate about the yaw axis (9), such that the rotation axis (8) can also rotate about the yaw axis (9), the control device comprising: A wind direction determining device, configured to determine the wind direction; Acquisition device configured to acquire the yaw angle of the cabin (3) and the rotation axis (8); An angular misalignment determination device configured to determine the angular misalignment between the wind direction and the yaw angle of the rotation axis (8), the angular misalignment being measured in a plane perpendicular to the yaw axis (9); and A stall control device configured to induce stall operation by at least one of the following when the angular misalignment exceeds a predetermined threshold: a) The stall operating device is configured to set the pitch angle to exceed the predetermined stall pitch angle; and b) Each blade (6) includes at least one stall adjustment member (17) configured to change the aerodynamic characteristics of the blade (6), wherein the stall operation device is configured to set the stall adjustment member (17) in a state that degrades the aerodynamic efficiency of the blade (6).

5. The control device according to claim 4, further comprising: A wind speed determining device configured to determine a wind speed, wherein the predetermined threshold is a function of the wind speed.

6. The control device according to claim 5, wherein... The higher the wind speed, the lower the predetermined threshold.

7. A wind turbine (1) comprising a control device according to any one of claims 4 to 6.

Images