Method and system for optimizing power output of a wind turbine with yaw offset

Abstract

A system comprising a wind turbine (1) and a first control device for controlling the wind turbine (1) is described. The first control device is configured to: acquire a yaw offset (γ) of the wind turbine (1), the yaw offset (γ) being the difference between the actual yaw angle and the wind direction at the wind turbine (1); and determine, based on the yaw offset (γ), at least one of a target pitch angle (β) of the blades (6) and a target torque (TCtrl) of the generator (5) to optimize the power output from the wind turbine (1). A wind farm including this system and a method for controlling the wind turbine (1) are also described.

Description

Technical Field

[0001] This invention relates to a system comprising a wind turbine and a first control device for controlling the wind turbine based on yaw misalignment. The invention also relates to a wind farm including this system, wherein a plurality of adjacent wind turbines are provided, and to a method for controlling the wind turbines. Background Technology

[0002] In conventional wind farms, wake steering strategies are implemented by adjusting the wake effect between wind turbines to increase the annual power generation (AEP) of the wind farm. For example, an upstream wind turbine is set to a yaw state, i.e., with yaw offset, where the axis of rotation of the hub is not perfectly aligned with the wind direction, so that the wake generated by the upstream wind turbine is deflected away from the downstream wind turbine. By minimizing the wake effect, the power output of the wind farm is increased. The yaw condition can therefore represent the desired yaw offset of the corresponding wind turbine in order to operate the wind farm controller under optimal conditions. If all the wind turbines in the wind farm are properly aligned with the wind direction, there will be no yaw offset, but the overall performance of the wind farm controller will be degraded due to the wake effect. Wake steering strategies require the wind turbine generators (WTGs) to operate correctly under yaw conditions, where the wind turbines are not necessarily aligned with the wind direction.

[0003] In conventional control, the wind turbine is not subjected to any offset and is regulated based on the aerodynamic characteristics and other properties of the wind turbine, such as mechanical and electrical efficiency, rotor size, etc. Specifically, the target pitch angle β is selected from a lookup table in open-loop control because the angle (i.e., the target pitch angle β) that provides the maximum power coefficient cp for a given inlet wind speed U and a given rotor speed (=hub rotation speed) ωrot is determined as a function of the wind speed U and the rotor speed ωrot. The target torque TCtrl of the generator is also determined as a function of the rotor speed ωrot and other characteristics of the wind turbine.

[0004] Based on both pitch and torque control laws, the operating point of a wind turbine converges to the optimum, provided all assumptions are met. The controller aims to perform as optimally as possible at rated power. Conventional controllers are tuned based on a model of a wind turbine aligned with the wind direction, and are designed for the optimal operating point under normal operation. However, if some wind turbines (e.g., in a wind farm) have a (desired) yaw offset, for example, to avoid wake effects, the wind turbine will not operate at the optimal operating point. Wind turbines can also experience (desired) yaw offsets for reasons other than avoiding wake effects. Summary of the Invention

[0005] The object of this invention is to provide a system including a wind turbine and a first control device for controlling the wind turbine, which can increase annual power generation (AEP). A further object of this invention is to provide a wind farm including this system, wherein a plurality of adjacent wind turbines are provided, and a method for controlling the wind turbines, which can increase annual power generation (AEP).

[0006] This objective is achieved by means of the subject matter according to the independent claims. The invention is further developed as set forth in the dependent claims.

[0007] According to a first aspect of the invention, a system includes a wind turbine and a first control device. The wind turbine includes: a tower; a nacelle rotatably mounted relative to the tower about a yaw axis such that the nacelle is oriented at an actual yaw angle; a hub mounted to be rotatable relative to the nacelle about a rotation axis; at least one blade mounted to the hub; and a generator disposed in the nacelle and including an electromagnetic rotor connected to the hub, wherein the generator is configured to convert rotational energy from the electromagnetic rotor into electrical energy. The first control device is configured to: acquire a yaw offset of the wind turbine, the yaw offset being the difference between the actual yaw angle and the wind direction at the wind turbine; and determine, based on the yaw offset, at least one of a target blade pitch angle and a target generator torque to optimize power output from the wind turbine.

[0008] Advantageously, WTG operates optimally under yaw conditions with minimal energy loss, making wind turbine control more efficient under wake-turn conditions and achieving higher wind farm energy output. This improved WTG control will enhance wind farm performance with better and more efficient operation, at virtually no additional cost. For example, the first control unit can be upgraded or retrofitted into existing wind turbines or wind farms.

[0009] In one embodiment, the first control device is configured to determine at least one of the target blade pitch angle and the target generator torque by calculating the target blade pitch angle as a function of the incoming wind speed, the rotor speed of the hub, and the yaw offset, and by calculating the target torque as a function of the rotor speed and the yaw offset.

[0010] Compared to conventional control that ignores any yaw offset compensation, this invention takes into account the changes in aerodynamic behavior during hub offset operations. This optimizes the efficiency of the wind turbine. Because the aerodynamic behavior of the hub differs from that during normal alignment operations, the pitch angle can be controlled in an open-loop manner by taking yaw offset into account.

[0011] In one embodiment, the first control device is configured to determine at least one of the target blade pitch angle and the target generator torque by considering a lookup table, in which the relationship between the incoming wind speed, the rotor speed at the hub and the yaw offset, and / or the relationship between the target torque and the rotor speed and the yaw offset is stored.

[0012] In one embodiment, the first control device is integrated into the wind turbine or a remote control device. Preferably, the remote control device is wirelessly connected to the wind turbine.

[0013] In one embodiment, the first control device is configured to determine at least one of the target pitch angle of the blade and the target torque of the generator, such that a tip-speed ratio is set at which the power coefficient of the wind turbine becomes optimal for a given yaw offset.

[0014] According to a second aspect of the invention, a wind farm is provided. The wind farm includes a system in which a plurality of adjacent wind turbines are provided. The wind farm includes a second control device configured to determine the respective actual yaw angles of the plurality of adjacent wind turbines based on wake conditions between the plurality of adjacent wind turbines.

[0015] In one embodiment, the second control device is configured to determine the corresponding actual yaw angles of the multiple adjacent wind turbines based on the wake conditions between the multiple adjacent wind turbines, so that the total power output of the wind farm becomes optimal.

[0016] In one embodiment, the first control device and the second control device are integrated into a single unit or separate control devices.

[0017] According to a third aspect of the invention, a method for controlling a wind turbine is provided. The wind turbine includes: a tower; a nacelle rotatably mounted relative to the tower about a yaw axis such that the nacelle is oriented at an actual yaw angle; a hub mounted to be rotatable relative to the nacelle about a rotation axis; at least one blade mounted to the hub; and a generator disposed in the nacelle and including an electromagnetic rotor connected to the hub, wherein the generator is configured to convert rotational energy from the electromagnetic rotor into electrical energy. The method includes the steps of: obtaining a yaw offset of the wind turbine, the yaw offset being the difference between the actual yaw angle and the wind direction at the wind turbine; and determining, based on the yaw offset, at least one of a target blade pitch angle and a target generator torque to optimize power output from the wind turbine.

[0018] In one embodiment, at least one of the target blade pitch angle and the target generator torque is determined by calculating the target blade pitch angle as a function of the incoming wind speed, the rotor speed at the hub, and the yaw offset, and by calculating the target torque as a function of the rotor speed and the yaw offset.

[0019] In one embodiment, at least one of the target blade pitch angle and the target generator torque is determined by considering a lookup table, which stores the relationship between the incoming wind speed, the rotor speed at the hub, and the yaw offset, as well as the relationship between the target torque and the rotor speed and the yaw offset.

[0020] In one embodiment, at least one of the target blade pitch angle and the target generator torque is determined such that a tip speed ratio is set at which the power coefficient of the wind turbine becomes optimal for a given yaw offset.

[0021] In one embodiment, a plurality of adjacent wind turbines are provided, and the corresponding actual yaw angles of the plurality of adjacent wind turbines are controlled based on the wake conditions between the plurality of adjacent wind turbines.

[0022] In one embodiment, the actual yaw angles of multiple adjacent wind turbines are controlled based on the wake conditions between them, so that the total power output of the wind farm is optimized.

[0023] 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 device type claims, while others have been described with reference to method type claims. However, those skilled in the art will understand from the above and below description that, unless otherwise indicated, any combination of features related to different subjects, in particular any combination of features between device type claims and method type claims, is also considered to be disclosed in this application, except for any combination of features belonging to one type of subject matter. Attached Figure Description

[0024] The above and other aspects of the invention will be apparent from the examples of the embodiments described below, and will be explained with reference to these examples. The invention will now be described in more detail with reference to examples of embodiments, but the invention is not limited to these examples.

[0025] Figure 1 This shows a wind turbine and its different components;

[0026] Figure 2 A schematic configuration of a wind turbine generator system (WTG system) according to an embodiment is shown; and

[0027] Figure 3 The operating points according to an embodiment relative to the prior art are shown on a graph of the aerodynamic power coefficient cp versus the tip speed ratio λ. Detailed Implementation

[0028] The illustrations in the accompanying drawings are schematic. Note that similar or identical elements are given the same reference numerals in different drawings.

[0029] Figure 1 A 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 about a yaw axis 10 by means of a yaw bearing.

[0030] The wind turbine 1 also includes three rotor blades 6 (two of which are in...) Figure 1 The hub 4 (shown in the diagram) is rotatably mounted relative to the nacelle 3 via the main bearing 7. The hub 4 is rotatably mounted about the rotor rotation axis 8.

[0031] The wind turbine 1 further includes a generator 5. The generator 5 includes an electromagnetic rotor connecting the generator 5 to the hub 4. If the hub 4 is directly connected to the generator 5, the wind turbine 1 is referred to as a gearless direct-drive wind turbine. This generator 5 is referred to as a direct-drive generator 5. Alternatively, the hub 4 can also be connected to the generator 5 via a gearbox 9 (see...). Figure 2 This type of wind turbine 1 is called a geared wind turbine. This invention applies to both types of wind turbines 1.

[0032] Generator 5 is housed within engine compartment 3. Generator 5 is arranged and prepared to convert the rotational energy from hub 4 into electrical energy in the form of AC power.

[0033] The operation of the wind turbine 1 is controlled by a first control device (not shown). The first control device may be integrated into the wind turbine 1 or a remote control device. For example, the first control device, as a remote control device, may be configured to control multiple adjacent wind turbines 1 of the wind farm. The remote control device is preferably wirelessly connected to the wind turbines 1 of the wind farm.

[0034] Figure 2A schematic configuration of a wind turbine generator system (WTG) according to an embodiment is shown. Wind-driven blades 6 and a hub 4, with a wind speed U, are connected to the electromagnetic rotor of a generator 5 via a gearbox 9. The hub 4 rotates at a rotor speed ωrot. The blades 6 are adjusted to have a (preferably common) target pitch angle β, which is the orientation of the blades 6 about the longitudinal axis of the respective blades 6. Wind drives the hub 4 to rotate via aerodynamic power Pwareo and aerodynamic torque Taero. A first control unit determines the setpoint of the target torque TCtrl of the generator 5. The mechanical efficiency of the system consisting of the blades 6, hub 4, and gearbox 9 is indicated by the reference numeral ηmech.

[0035] The first control device is configured to acquire the yaw offset γ of the wind turbine 1, which is the difference between the actual yaw angle of the nacelle 3 and hub 4 and the wind direction at the wind turbine 1. The first control device may be configured to directly measure the wind direction or receive information about the wind direction from a remote device (e.g., from a second control device used to control multiple wind turbines 1 in a wind farm).

[0036] The first control device is further configured to determine at least one of the target pitch angle β of the blade 6 and the target torque TCtrl of the generator 5 based on the yaw offset γ, in order to optimize the power output from the wind turbine 1. For example, the first control device may be configured to determine at least one of the target pitch angle β of the blade 6 and the target torque TCtrl of the generator 5 based on the yaw offset γ, in order to maximize the power output from the wind turbine 1. The power output of the wind turbine 1 is the amount of electrical energy output per unit time. In detail, the first control device is configured to determine at least one of the target pitch angle β of the blade 6 and the target torque TCtrl of the generator 5 by: calculating the target pitch angle β of the blade 6 as a function of the incoming wind speed U, the rotor speed ωrot of the hub 4, and the yaw offset γ; and calculating the target torque TCtrl as a function of the rotor speed ωrot and the yaw offset γ. For example, the target torque TCtrl may be calculated as follows: TCtrl = f(ωrot) × X(γ).

[0037] Preferably, the first control device can be configured to determine at least one of the target pitch angle β of the blade 6 and the target torque TCtrl of the generator 5 by considering a lookup table, wherein the lookup table stores the relationship between the incoming wind speed U, the rotor speed ωrot of the hub 4 and the yaw offset γ and / or the relationship between the target torque TCtrl and the rotor speed ωrot and the yaw offset γ.

[0038] Figure 3Operating points 21 and 210 according to embodiments relative to the prior art are shown on graphs 20 and 200, respectively, representing the aerodynamic power coefficient cp relative to the tip speed ratio (TSR) λ. The tip speed ratio λ is the ratio between the tangential velocity at the tip of blade 6 and the actual wind speed U. Two graphs 20 and 200 are plotted for a given yaw offset γ. Reference numeral 200 indicates a prior art graph on which operating point 210 is set without considering yaw offset γ. Reference numeral 20 indicates a graph according to an embodiment of the present invention on which operating point 21 is set considering yaw offset γ. Figure 3 As can be seen, the operating point 21 of the present invention is the optimal operating point, while the operating point 210 of the prior art is the suboptimal operating point 21. In other words, the first control device is configured to determine at least one of the target pitch angle β of the blade 6 and the target torque TCtrl of the generator 5, such that the tip speed ratio λ is set at which the power coefficient cp of the wind turbine 1 becomes optimal at a given yaw offset γ.

[0039] If the control algorithm does not consider the yaw offset γ, wind turbine 1 will converge to a suboptimal operating point 210. However, by considering the yaw offset γ, the efficiency loss is eliminated and the wind turbine performance is optimized.

[0040] exist Figure 3 In the prior art, the curves 200 and 210 of the aerodynamic power coefficient cp versus the tip speed ratio λ are the same for the prior art and the present invention; however, the curves 200 and 210 of the aerodynamic power coefficient cp versus the tip speed ratio λ of the prior art and the present invention may be different from each other.

[0041] This invention is particularly useful in controlling wind farms that provide multiple adjacent wind turbines 1. Typically, wind turbine 1 generates a wake effect on adjacent downstream wind turbines 1, which can impair the output power of the adjacent downstream wind turbines 1 and thus the efficiency of the entire wind farm. To avoid this efficiency loss, a second control device (not shown) is provided that minimizes the efficiency loss by minimizing the wake effect. This is achieved by setting a yaw offset γ for a specific wind turbine 1 to deflect the wake from other wind turbines 1. The term yaw offset γ here refers to the expected difference between the wind direction at wind turbine 1 and the adjusted actual (and desired) yaw angle. On the one hand, the specific wind turbine 1 will have reduced output power, but on the other hand, the wake effect on other wind turbines 1 is minimized, which in turn improves the overall efficiency of the entire wind farm.

[0042] Therefore, the second control device is configured to determine the corresponding actual yaw angles of the multiple adjacent wind turbines 1 based on the wake conditions between them, preferably so that the total power output of the wind farm becomes optimal. For example, the total power output of the wind farm is maximized.

[0043] The first and second control devices can be integrated into one unit or can be separate control devices.

[0044] It should be noted that the term "comprising" does not exclude other elements or steps, and "a" (or "an") does not exclude multiple. Furthermore, elements described in connection with different embodiments may be combined. It should also be noted that reference numerals in the claims should not be construed as limiting the scope of the claims.

Claims

1. A system comprising a wind turbine (1) and a first control device, wherein: The wind turbine (1) includes: Tower (2); The nacelle (3) is mounted to be able to rotate relative to the tower (2) about the yaw axis (10), such that the nacelle (3) is oriented at the actual yaw angle; The hub (4) is mounted so as to be able to rotate about the axis of rotation (8) relative to the nacelle (3); At least one blade (6) is mounted to the hub (4); and A generator (5), arranged in the nacelle (3) and comprising an electromagnetic rotor connected to the hub (4), wherein the generator (5) is configured to convert rotational energy from the electromagnetic rotor into electrical energy; and The first control device is configured as follows: Obtain the yaw offset γ of the wind turbine (1), whereby the yaw offset γ is the difference between the actual yaw angle and the wind direction at the wind turbine (1); and The target pitch angle β of the blade (6) is determined by calculating the target pitch angle β of the blade (6) as a function of the incoming wind speed U, the rotor speed ωrot of the hub (4) and the yaw offset γ, in order to optimize the power output from the wind turbine (1), or the target torque TCtrl of the generator (5) is calculated based on the yaw offset γ in order to optimize the power output from the wind turbine (1).

2. The system according to claim 1, wherein, The first control device is configured to determine the target torque TCtrl of the generator (5) by calculating the target torque TCtrl as a function of the rotor speed ωrot and the yaw offset γ.

3. The system according to claim 2, wherein, The first control device is configured to determine at least one of the target pitch angle β of the blade (6) and the target torque TCtrl of the generator (5) by considering a lookup table, wherein the lookup table stores the relationship between the incoming wind speed U, the rotor speed ωrot of the hub (4) and the yaw offset γ and / or the relationship between the target torque TCtrl and the rotor speed ωrot and the yaw offset γ.

4. The system according to any one of claims 1 to 3, wherein, The first control device is integrated into the wind turbine (1) or into a remote control device.

5. The system according to any one of claims 1 to 3, wherein, The first control device is configured to determine at least one of the target pitch angle β of the blade (6) and the target torque TCtrl of the generator (5) such that the tip speed ratio λ is set such that the power coefficient cp of the wind turbine (1) becomes optimal at a given yaw offset γ.

6. A wind farm comprising the system according to any one of claims 1 to 5, wherein, A plurality of adjacent wind turbines (1) are provided, and the wind farm includes a second control device configured to determine the respective actual yaw angles of the plurality of adjacent wind turbines (1) based on the wake conditions between the plurality of adjacent wind turbines (1).

7. The wind farm according to claim 6, wherein, The second control device is configured to determine the corresponding actual yaw angle of the plurality of adjacent wind turbines (1) based on the wake conditions between the plurality of adjacent wind turbines (1) so that the total power output of the wind farm becomes optimal.

8. The wind farm according to any one of claims 6 and 7, wherein, The first control device and the second control device are either integrated into a single unit or separate control devices.

9. A method for controlling a wind turbine (1), the wind turbine (1) comprising: Tower (2); nacelle (3), which is mounted to be able to rotate relative to the tower (2) about the yaw axis (10) such that the nacelle (3) is oriented at the actual yaw angle; A hub (4) mounted to be rotatable about a rotation axis (8) relative to the nacelle (3); at least one blade (6) mounted to the hub (4); and a generator (5) disposed in the nacelle (3) and including an electromagnetic rotor connected to the hub (4), wherein the generator (5) is configured to convert rotational energy from the electromagnetic rotor into electrical energy; The method includes the following steps: Obtain the yaw offset γ of the wind turbine (1), where the yaw offset γ is the difference between the actual yaw angle and the wind direction at the wind turbine (1); as well as The target pitch angle β of the blade (6) is determined by calculating the target pitch angle β of the blade (6) as a function of the incoming wind speed U, the rotor speed ωrot of the hub (4) and the yaw offset γ, in order to optimize the power output from the wind turbine (1), or the target torque TCtrl of the generator (5) is calculated based on the yaw offset γ in order to optimize the power output from the wind turbine (1).

10. The method according to claim 9, wherein, The target torque TCtrl of the generator (5) is determined by calculating the target torque TCtrl as a function of the rotor speed ωrot and the yaw offset γ.

11. The method according to claim 10, wherein, At least one of the target pitch angle β of the blade (6) and the target torque TCtrl of the generator (5) is determined by considering a lookup table, which stores the relationship between the incoming wind speed U, the rotor speed ωrot of the hub (4) and the yaw offset γ, as well as the relationship between the target torque TCtrl and the rotor speed ωrot and the yaw offset γ.

12. The method according to any one of claims 9 to 11, wherein, Determine at least one of the target pitch angle β of the blade (6) and the target torque TCtrl of the generator (5) such that the tip speed ratio λ is set such that the power coefficient cp of the wind turbine (1) becomes optimal at a given yaw offset γ.

13. The method according to any one of claims 9 to 11, wherein, A plurality of adjacent wind turbines (1) are provided, and the corresponding actual yaw angles of the plurality of adjacent wind turbines (1) are controlled based on the wake conditions between the plurality of adjacent wind turbines (1).

14. The method according to claim 13, wherein, The actual yaw angles of the multiple adjacent wind turbines (1) are controlled based on the wake conditions between the multiple adjacent wind turbines (1) to optimize the total power output of the wind farm, wherein the multiple adjacent wind turbines (1) are provided in the wind farm.

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