Control device and method for controlling a wind turbine

Abstract

A control device and method for controlling a wind turbine. A control device configured to control a wind turbine (1) is described, the wind turbine (1) comprising a rotor (4) rotatable about a rotation axis (8), wherein the rotor (4) has at least one blade (6), the blade (6) comprising: at least one additional component, which is actuated by a corresponding adjustment actuator to change the aerodynamic characteristics of the blade (6); and a pitch actuator to change the pitch angle of the blade (6). The control device is configured to determine an idling mode or a self-sustaining mode of the wind turbine (1); so that if the idling mode or the self-sustaining mode is determined, the pitch actuator is controlled to set a predetermined pitch angle of the blade (6); and if the idling mode or the self-sustaining mode is determined, a target rotation speed of the rotor (4) is caused by variably controlling the adjustment actuator of the blade (6).

Description

Technical Field

[0001] The invention relates to a control device and a method for controlling a wind turbine. Background Art

[0002] When a wind turbine is not generating power to the grid, it is usually placed in idling, i.e. an idling state in which the rotor rotates at a controlled rotational speed and power is generated as a separate supply turbine (self-sustaining turbine, SST), or completely in a stopped mode (no rotor rotation). These modes are also called off-grid modes.

[0003] Generally, ensuring stable and safe wind turbines in off-grid conditions and / or in the event of a failed turbine is becoming increasingly important as offshore wind turbines will be installed further offshore where access to the wind turbines is reduced and / or very expensive due to the price of offshore repair vessels. This makes it very important that individual wind turbines can be maintained and maintained in a stable and safe off-grid condition.

[0004] EP 2 146 095 A2 discloses a method of controlling a wind turbine in which a normal pitch strategy is continuously used to control the rotation speed in conditions other than normal power generation to the grid, i.e. in off-grid conditions, in which the rotation speed is controlled for charging a pitch drive backup power source (e.g., a battery). However, changing the pitch angle in the pitch strategy may stress the system, resulting in tearing and wear of both the pitch actuator and the pitch bearing. Summary of the invention

[0005] There may be a need for a control device and method for controlling a wind turbine which enables improved control of the rotor rotation speed in idling mode or in SST mode to ensure that loads, wear, tear, power production and structural stability remain within the structural design capabilities of the wind turbine. This need is met by the subject matter according to the independent claims. The invention is further improved as set out in the dependent claims.

[0006] According to a first aspect of the invention, a control device is configured to control a wind turbine, the wind turbine comprising a rotor rotatable about a rotation axis, wherein the rotor has at least one blade, the blade comprising: at least one additional component, which is actuated by a corresponding trim actuator to change the aerodynamic characteristics of the blade; and a pitch actuator to change the pitch angle of the blade. The control device is configured to determine an idling mode or a self-sustaining mode of the wind turbine; so that if the idling mode or the self-sustaining mode is determined, the pitch actuator is controlled to set a predetermined pitch angle of the blade; and if the idling mode or the self-sustaining mode is determined, a target rotation speed of the rotor is caused by variably controlling the trim actuator of the blade.

[0007] Active blade additional components are used to ensure a stable rotational speed of the rotor and, therefore, a stable load on the turbine and a stable power production. For example, the rotational speed can be feedback controlled (under closed-loop control) by actuating the additional components of the blades. As a result, the pitch loads on the pitch actuator and the blade bearings can be reduced, making the design more robust and reducing maintenance costs.

[0008] In one embodiment, the control device is configured to maintain a predetermined pitch angle of the blade while the adjustment actuator of the blade is variably controlled. During a given blade pitch angle, only the active blade attachment member is activated. In this operation, the stress of the system is reduced, resulting in less tear and wear of both the pitch actuator and the pitch bearing.

[0009] In one embodiment, the control device is configured to select said predetermined pitch angle of the blade from a plurality of predetermined pitch angles of the blade.Thereby, fine adjustment can be achieved without excessively stressing the pitch actuator and the pitch bearing.

[0010] In one embodiment, the control device is further configured to cause a trim stall at the blades by controlling a trim actuator of the additional component. Some wind turbines are already equipped with such active additional components for causing a trim stall at the blades. Thus, the invention can be implemented in those existing wind turbines by retrofitting without expensive modifications. For example, the software of the control device can be updated, while the hardware remains essentially unchanged.

[0011] In one embodiment, the additional component is a flap or a spoiler at the rear end or at the leading edge of the blade.

[0012] According to a second aspect of the present invention, a wind turbine comprises: a tower; a rotor installed at a top of the tower to rotate about a rotation axis, wherein the rotor has at least one blade; and the control device.

[0013] According to a third aspect of the invention, a method for controlling a wind turbine is disclosed, wherein the wind turbine comprises a rotor rotatable about a rotation axis, wherein the rotor has at least one blade, the blade comprising: at least one additional component actuated by a corresponding adjustment actuator to change the aerodynamic characteristics of the blade; and a pitch actuator to change the pitch angle of the blade. The method comprises the following steps: determining an idling mode or a self-sustaining mode of the wind turbine; if the idling mode or the self-sustaining mode is determined, controlling the pitch actuator to set a predetermined pitch angle of the blade; and if the idling mode or the self-sustaining mode is determined, causing a target rotation speed of the rotor by variably controlling the adjustment actuator of the blade.

[0014] In one embodiment, the method further comprises the step of maintaining said predetermined pitch angle of the blade while the adjustment actuator of the blade is variably controlled.

[0015] In one embodiment, the method further comprises the step of selecting the predetermined pitch angle of the blade from a plurality of predetermined pitch angles of the blade. When the active additional member of the blade is in operation, the blade pitch angle may have a plurality of fixed positions so that the blade pitch angle varies discontinuously to ensure stable rotor speed, power production and load.

[0016] In one embodiment, the method further comprises the step of inducing a trim stall at the blade by controlling a trim actuator of the additional component.

[0017] In one embodiment, the target rotational speed of the rotor is determined for charging a backup battery of the wind turbine. For example, the rotor torque may be affected by the state of charge (SoC), which is the charge level of the backup battery relative to its capacity. The present invention can compensate for such changes in the rotor torque to maintain a stable rotor speed.

[0018] It should be noted that embodiments of the present invention have been described with reference to different subject matters. In particular, some embodiments have been described with reference to device-type claims, while other embodiments have been described with reference to method-type claims. However, those skilled in the art will understand from the above and the following description that, unless otherwise stated, in addition to any combination of features belonging to one type of subject matter, any combination between features related to different subject matters, in particular any combination between features of device-type claims and features of method-type claims, is also considered to be disclosed by the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The above-defined aspects of the present invention as well as further aspects will be apparent from the examples of embodiment described hereinafter and will be explained with reference to these examples of embodiment. The present invention will be described in more detail hereinafter with reference to examples of embodiment, but the present invention is not limited to these examples of embodiment.

[0020] Figure 1 An example of a wind turbine and its various elements is shown;

[0021] Figure 2 A wind turbine blade is shown with additional components; and

[0022] Figure 3 The additional component is shown in an activated position in which it is rotated to a maximum stalling effect. DETAILED DESCRIPTION

[0023] The illustrations in the drawings are schematically. It is noted that in different drawings, similar or identical elements are provided with the same reference signs.

[0024] Figure 1 An example of a wind turbine 1 is shown. The wind turbine 1 comprises a nacelle 3 and a tower 2. The nacelle 3 is mounted at the top of the tower 2. The nacelle 3 is mounted rotatable relative to the tower 2 by means of a yaw bearing (not shown). The yaw bearing may belong to an active yaw system. The axis of rotation of the nacelle 3 relative to the tower 2 is called the yaw axis.

[0025] The wind turbine 1 further comprises a rotor having three rotor blades 6 ( Figure 1 4 , a rotor (hub) 4 is depicted with two rotor blades 6 therein. These blades 6 are connected to the rotor 4 via a joint section (not shown). Each blade 6 of the wind turbine 1 comprises a pitch actuator (not shown) to change the pitch angle of the blade 6. The pitch angle generally refers to the rotation of the blade 6 about the longitudinal axis of the blade 6. The rotation speed of the rotor 4 and therefore the output power of the generator 5 depends inter alia on the pitch angle of the blade 6.

[0026] The rotor 4 is mounted rotatably relative to the nacelle 3 by means of a main bearing 7. The rotor 4 is mounted rotatably about an axis of rotation 8.

[0027] Furthermore, the wind turbine 1 comprises a generator 5. The rotor 4 is directly connected to the generator 5, so that the wind turbine 1 is called a direct-drive wind turbine without a transmission. Such a generator 5 is called a direct-drive generator 5. As an alternative, 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. The present invention is applicable to both types of wind turbines 1.

[0028] A generator 5 is housed within the nacelle 3. The generator 5 is arranged and prepared for converting rotational energy from the rotor 4 into electrical energy in the form of alternating current.

[0029] Figure 2 A wind turbine blade 6 of a wind turbine 1 is shown. Each blade 6 has at least one active additional component 17 which is actuated by a corresponding adjusting actuator (not shown) to change the aerodynamic properties of the blade 6. Figure 2 The cross section of FIG. 6 shows only one active additional component 17 ; however, additional active additional components 17 of the blade 6 may be arranged before or after this active additional component 17 .

[0030] The additional component 17 is designed as a spoiler. The spoiler 17 is arranged here near the leading edge (front edge) of the blade 6, but it can also be arranged near the trailing edge (rear edge) of the blade 6. The additional component 17 can be received in a recess 16 in the blade 6 and can be rotated about a hinge 18 by activating an adjustment actuator. Figure 2 In the figure, the spoiler 17 is shown in its normal inactive position, in which the spoiler effect and stall are not expected. This position is called the predetermined first position. The predetermined first positions of the additional components 17 of different blades 6 can be the same to ensure load symmetry when multiple additional components 17 are activated. This also reduces complexity, because one adjustment actuator (for example, a pressure supply device or an electric motor) can drive the corresponding additional components 17 on all blades 6.

[0031] Figure 3 The same additional component 17 is shown in an activated position, in which it is turned to the maximum by the adjustment actuator, so that the stall effect is maximum. This position is called the predetermined second position. The predetermined second positions of the additional components 17 of different blades 6 can be the same. This ensures that the loads are symmetrical when the additional components 17 are activated. This also reduces complexity, because one adjustment actuator (for example, a pressure supply device or an electric motor) can drive the corresponding additional components 17 on all blades 6.

[0032] According to the invention, the additional component 17 does not necessarily have to be formed as a spoiler. The additional component 17 may have any other configuration capable of changing the aerodynamic properties of the blade 6, such as a flap.

[0033] The wind turbine 1 comprises a control device (not shown) which is configured to determine an idling mode or a self-sustaining mode, i.e., an SST mode, of the wind turbine 1. The idling mode and the self-sustaining mode are also referred to as off-grid modes, in which the wind turbine 1 is not connected to the grid or substantially does not supply power to the grid. However, the wind turbine 1 itself requires energy, for example for maintaining the operation of the control device and for charging a backup battery of the wind turbine 1.

[0034] The control device is further configured to control the pitch actuator to set a predetermined pitch angle of the blade 6 if the idling mode or the self-sustaining mode is determined, and to cause a target rotation speed of the rotor 4 by variably controlling the adjustment actuator of the blade 6 if the idling mode or the self-sustaining mode is determined. Therefore, after the off-grid event is detected, the pitch angle of the blade 6 can be locked at the predetermined pitch angle (predetermined position), and the wind turbine 1 can continue to be in the idling mode or the self-sustaining mode, which is to control the rotation speed of the rotor 4 by using only the additional components 17 of the blade 6, that is, only supplying electrical energy to the wind turbine 1 itself.

[0035] The active blade additional components 17 are used to ensure a stable rotational speed of the rotor 4 and, therefore, a stable load and a stable power production on the wind turbine 1. For example, the rotational speed of the rotor 4 can be feedback controlled by the additional components 17 of the actuating blades 6 (closed loop control).

[0036] Preferably, the control device is configured to maintain a predetermined pitch angle of the blade 6 while the trim actuator of the blade 6 is variably controlled. In this operation, the stress of the system is reduced, resulting in less tear and wear of the pitch actuator and the pitch bearing.

[0037] Preferably, the control device is configured to select the predetermined pitch angle of the blade 6 from a plurality of predetermined pitch angles of the blade 6. Thereby, fine adjustment can be achieved without excessively stressing the pitch actuator and the pitch bearing.

[0038] Preferably, the control device is further configured to cause a regulating stall at the blades 6 by controlling the regulating actuators of the additional means 17. Some wind turbines 1 are already equipped with active additional means 17 for causing a regulating stall at the blades 6. Thus, the present invention can be implemented in those existing wind turbines 1 only by retrofitting and without expensive modifications. For example, the software of the control device can be updated, while the hardware is essentially maintained.

[0039] In a modified embodiment, the above-described control of the control device may be combined with an active yaw control for controlling the rotational speed of the rotor 4 .

[0040] The active yaw system of the wind turbine 1 is responsible for the orientation of the rotor 4 towards the wind, i.e. the yaw system typically aligns the rotation axis 8 with the detected wind direction in order to obtain maximum power output. The active yaw system is equipped with a yaw actuator to rotate the nacelle 3 of the wind turbine 1 against the fixed tower 2 based on a signal from a wind direction sensor or manual actuation (control system override).

[0041] In this modified embodiment, active yaw control is combined with control of the adjustment actuators of the active additional components 17 to control the rotational speed of the rotor 4 , the output power of the wind turbine 1 and / or the loads.

[0042] It should be noted that the term "comprising" does not exclude other elements or steps, and the wording "a", "an" or "an" does not exclude a plurality. Furthermore, elements described in connection with different embodiments may also be combined. It should also be noted that the reference numerals in the claims should not be interpreted as limiting the scope of the claims.

Claims

1. A control device configured to control a wind turbine (1), the wind turbine (1) comprising a rotor (4) rotatable about a rotation axis (8), wherein: The rotor (4) has at least one blade (6), the blade (6) comprising: at least one additional component (17) which is actuated by a corresponding adjustment actuator to change the aerodynamic characteristics of the blade (6); and a pitch actuator for changing the pitch angle of the blade (6); wherein The control device is configured to determining an idling mode or a self-sustaining mode of the wind turbine (1); If the idling mode or the self-sustaining mode is determined, controlling the pitch actuator to set a predetermined pitch angle of the blade (6); and If the idling mode or the self-sustaining mode is determined, a target rotational speed of the rotor (4) is caused by variably controlling the adjustment actuator of the blade (6), Therein, the control device is configured to maintain the predetermined pitch angle of the blade (6) while the adjustment actuator of the blade (6) is variably controlled.

2. The control device according to claim 1, wherein in, The control device is configured to select the predetermined pitch angle of the blade (6) from a plurality of predetermined pitch angles of the blade (6).

3. The control device according to claim 1 or 2, wherein The control device is further configured to cause a trim stall at the blade (6) by controlling the trim actuator of the additional component (17).

4. The control device according to claim 1 or 2, wherein The additional component (17) is a flap or a spoiler at the rear end or the leading edge of the blade (6).

5. A wind turbine (1), comprising: Tower (2); a rotor (4) mounted at the top of the tower (2) for rotation about an axis of rotation (8), wherein the rotor (4) has at least one blade (6); and A control device according to any one of claims 1 to 4.

6. A method of controlling a wind turbine (1), the wind turbine (1) comprising a rotor (4) rotatable about a rotation axis (8), wherein: The rotor (4) has at least one blade (6), the blade (6) comprising: at least one additional component (17) which is actuated by a corresponding adjustment actuator to change the aerodynamic characteristics of the blade (6); and a pitch actuator for changing the pitch angle of the blade (6); wherein the method comprises: determining an idling mode or a self-sustaining mode of the wind turbine (1); If the idling mode or the self-sustaining mode is determined, controlling the pitch actuator to set a predetermined pitch angle of the blade (6); and If the idling mode or the self-sustaining mode is determined, a target rotational speed of the rotor (4) is caused by variably controlling the adjustment actuator of the blade (6), The method further comprises: maintaining the predetermined pitch angle of the blade (6) while the adjustment actuator of the blade (6) is variably controlled.

7. The method according to claim 6, further comprising: The predetermined pitch angle of the blade (6) is selected from a plurality of predetermined pitch angles of the blade (6).

8. The method according to claim 6 or 7, further comprising: A trim stall is induced at the blade (6) by controlling the trim actuator of the additional component (17).

9. The method according to claim 6 or 7, wherein The target rotational speed of the rotor (4) is determined for charging a backup battery of the wind turbine (1).

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