Device and method for controlling a wind turbine based on a varying component

Abstract

A control device for controlling a wind turbine (1) is described, the wind turbine including a rotor (3) and at least one blade (6) rotatably mounted to the rotor (3). The control device includes: detecting means (9) configured to detect the amount of the bending moment of the blade; and a varying element having an input part and an output part, wherein the input part is configured to receive the detected amount of the bending moment of the blade (6), and the output part is configured to output a response to a difference in the detected amount of the bending moment of the blade (6). The control device is configured to control the wind turbine (1) based on the response.

Description

Field of the Invention

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

[0002] Conventional wind turbines include a tower and a rotor mounted at the top of the tower to rotate about a rotational axis. The rotor has a plurality of blades that rotate the rotor by using wind energy. Conventional wind turbines include a control device configured to maintain a fixed rotational speed of the rotor by changing both the output power of the wind turbine and the blade pitch angle. A speed-power controller and a speed-pitch controller are the main controllers that ensure that the nominal speed of the rotor remains within acceptable limits.

[0003] In certain severe cases of gusts or sudden changes in wind direction, conventional speed control is too slow to keep the rotor speed within acceptable limits and at the same time too slow to prevent high thrust on the wind turbine, which can generate high loads on the blades and the tower. The reason for the slow control speed is the conventional controller itself, which is usually a PI controller. So far, it has been difficult to use a differentiating element in the conventional controller because the speed sensor noise is too large to use its derivative, which in turn amplifies the noise. As a result, conventional speed sensors are not suitable for derivative control.

[0004] In addition, conventional controllers are too slow for severe gust conditions. As a result, high loads may occur on many structural components of the wind turbine, such as extreme blade flap bending, extreme tower bending, and extreme tower torsion.

[0005] Ultimately, turbine shutdown may occur. When a severe gust passes through an offshore wind farm and causes overspeed due to a relatively slow PI controller, it will likely cause a large number of turbines in a single site to shut down.

[0006] So far, the load problem has been solved by improving the structural capabilities of the blades and the tower and by accepting that shutdown may occur during severe gusts. However, the effort in improving the structural capabilities increases the cost. Summary of the Invention

[0007] It is an object of the present invention to provide a control device for controlling a wind turbine, a wind turbine, and a method for controlling a wind turbine, which can reduce the loads on the blades or the tower that occur during severe gusts. This object is achieved by the subject matter of the independent claims. The present invention is further improved as set forth in the dependent claims.

[0008] According to a first aspect of the present invention, there is provided a control device for controlling a wind turbine, wherein the wind turbine includes a rotor and at least one blade rotatably mounted to the rotor. The control device includes: a detection device configured to detect the amount of bending moment of the blade; and a variation element having an input part and an output part, wherein the input part is configured to receive the detected amount of the bending moment of the blade, and the output part is configured to output a response to a difference in the detected amount of the bending moment of the blade. The control device is configured to control the wind turbine based on the response.

[0009] This difference can be a change in speed (i.e., acceleration), which allows the turbine to detect speed changes, such as a speed change in the bending moment. Alternatively, this difference can be a change in the bending moment, or a change in the bending moment can be interpreted as a change in speed. This change occurs over a predetermined time interval. In the context of the present disclosure, the term "variation element" means an element that takes into account such a change in the detected amount of the bending moment.

[0010] The variation element can be a so-called derivative element, and the response can be a step response of the so-called derivative element.

[0011] When the wind intensity increases, the blade will bend before the rotor speed increases. When the wind intensity weakens, the blade will straighten before the rotor speed decreases. Therefore, the detection of the amount of bending moment of the blade has a natural phase lead prior to the speed change. The rotor speed can be regarded as the integral of the blade deflection, and conversely, the blade deflection can be regarded as the derivative of the speed error. Since the aim is to react to changing wind conditions, the derivative (or the difference between two time instances of the bending moment, or the difference between two filtered values (with different time constants) of the bending moment) is taken from the measured value of the bending moment of the blade, which indicates whether the wind is increasing or decreasing. The derivative of this control device gives a lead in speed increase corresponding to the double derivative of the speed error, but with a lower noise level than the single derivative of the speed error.

[0012] Advantageously, due to the phase lead of the differential / variation element, it is possible to reduce the loads on the blade or the tower that occur during severe gusts with excellent response behavior, and the shutdown of the wind turbine can be avoided.

[0013] The control device and / or the variation element according to the present invention can be implemented by using software, hardware, firmware, or a combination thereof according to the embodiments described herein.

[0014] The control device and / or the varying element can be implemented in a software algorithm, in particular for calculating the response of the varying element, for example by using a predefined transfer function. The algorithm is preferably implemented in one or more computer programs, which include computer-readable instructions to be executed on the control device. Each computer program can be a set of instructions (program code) in a code module residing in the memory of the control device. Until the control device requires it, the set of computer-readable instructions can be stored in another computer memory (e.g., in a hard disk drive, or in a removable memory such as an optical disk, an external hard disk drive, a memory card, or a flash drive) or stored on another computer system and downloaded via the Internet or other network. The computer program for executing the algorithm can be written in any combination of one or more programming languages, including object-oriented programming languages such as Java, Smalltalk, C++, etc., and traditional procedural programming languages such as the "C" programming language or similar programming languages. The program code can be executed entirely on the control device of the wind turbine, partially on the control device of the wind turbine, or executed as a stand-alone software package.

[0015] A memory such as a random access memory (RAM) can be provided, in which computer-readable instructions for executing the algorithm for implementing the control device and / or the varying element of the present invention are stored. Any combination of one or more memories can be utilized as a computer-readable storage medium. The computer-readable storage medium can be, for example but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples (a non-exhaustive list) of the computer-readable storage medium can include the following: an electrical connection having one or more wires, a portable computer floppy disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing. In the context of the present invention, the computer-readable storage medium can be any tangible medium that can contain or store a program for use by or in connection with an instruction execution system, apparatus, or device.

[0016] At least one processor can be coupled to the memory and the detection device. At least one processor can be configured to execute the computer-readable instructions of the stored algorithm to implement the control device and / or the varying element of the present invention. At least one processor is an example of the control device. The processor can be a general-purpose computer, a special-purpose computer, or any other programmable data processing device, to produce a machine such that the computer-readable instructions executed via the processor of the computer or other programmable data processing device create a means for implementing the functions / actions specified in the present disclosure.

[0017] In addition, the disclosed embodiments may not be limited to any specific combination of hardware. Further, certain portions of the present invention may be implemented as "logic" that performs one or more functions. The logic may include hardware such as hardwired logic, application specific integrated circuits, field programmable gate arrays, microprocessors, or a combination of hardware and software.

[0018] In addition, unless otherwise expressly stated, the phrase "based on" as used herein is intended to mean "at least in part based on".

[0019] In one embodiment, the control device is configured to control the rotational speed of the rotor by changing the pitch angle of the blades and / or by changing the output power of the wind turbine based on the response.

[0020] In one embodiment, the control device is configured to increase the rotational speed of the rotor when the response is positive, e.g., when the bending moment increases, and / or to decrease the rotational speed of the rotor when the response is negative, e.g., when the bending moment decreases.

[0021] In one embodiment, the control device is configured to modify the speed control of the rotor by increasing the torque reference, power reference, and / or pitch reference (e.g., towards operation stop) when the response is positive, e.g., when the bending moment increases, and / or to modify the speed control of the rotor by decreasing the torque reference, power reference, and / or pitch reference (towards operation) when the response is negative, e.g., when the bending moment decreases. The torque reference, power reference, and / or pitch reference may be target values of rotor torque, wind turbine power, and the pitch angle of the blades.

[0022] First, the response behavior of the rotor speed control, which is based on, for example, conventional and relatively slow PI control, is significantly improved by directly modifying the reference variables, which can, for example, change the rotor speed with the aid of a control device that includes relatively fast changing elements. Second, since the changing elements of the bending moment of the blades are less susceptible to noise, an improved response behavior of the rotor speed control can also be achieved if the target value of the rotor speed is directly modified with the aid of the control device.

[0023] In one embodiment, the control device further includes a low-pass filter connected before the input of the changing element or after the output thereof, wherein the control device is configured to control the wind turbine based on the filtered change in the bending moment. The filter may be an adaptive band-stop filter, in particular an adaptive 3P band-stop filter, which filters out the 1P contributions in the signal, which together amount to the combined 3P interference. Several other harmonic interferences, such as 3P, 6P, and 9P interferences, may also be filtered out.

[0024] In one embodiment, the bending moment of the blade is the root moment of the blade or any other estimate of the bending moment. For example, large offshore wind turbines typically have pre-installed blade root sensors that measure the strain on the blade, which is converted into a bending moment. Advantageously, such wind turbines can be easily equipped or retrofitted with the control device according to the present invention.

[0025] In one embodiment, the wind turbine includes a plurality of blades, wherein the control device is configured to add the detected amounts of the bending moments of the blades to obtain a first sum, and input the first sum into the input portion of the varying element. For example, a wind turbine may have three blades, and each blade may have its own detection device. The three channels of these three detection devices can be combined into a single representation of the wind direction change or the wind speed change.

[0026] In one embodiment, the wind turbine includes a plurality of blades, wherein the control device is configured to control the wind turbine based on the response of the bending moment of the blade that is currently pointing upwards. The blade that is currently pointing upwards typically experiences the highest loads.

[0027] According to a second aspect of the present invention, a wind turbine includes: a tower; a rotor that is mounted at the top of the tower and rotates about a rotation axis, wherein the rotor has a plurality of blades; and the control device mentioned above.

[0028] According to a third aspect of the present invention, a method for controlling a wind turbine is provided, wherein the wind turbine includes a rotor and at least one blade rotatably mounted to the rotor. The method includes: detecting an amount of the bending moment of the blade; providing a varying element having an input portion and an output portion; inputting the detected amount of the bending moment of the blade into the input portion of the varying element; outputting a response from the output portion of the varying element; and controlling the wind turbine based on the output response.

[0029] In one embodiment, the rotational speed of the rotor is controlled based on the response by changing the pitch angle of the blade and / or by changing the output power of the wind turbine.

[0030] In one embodiment, when the response is positive, the rotational speed of the rotor increases, and / or when the response is negative, the rotational speed of the rotor decreases. For example, when the bending moment increases, the response is positive, and for example, when the bending moment decreases, the response is negative.

[0031] In the method of controlling a wind turbine, the varying element can be provided by a software algorithm. In particular, the varying element can be implemented by a software algorithm to calculate the response, for example by using a predetermined transfer function representing the response. A memory can be provided, in which computer-readable instructions for executing the algorithm of the varying element implementing the present invention are stored. A processor can be coupled to the memory and the detection means. The processor can be configured to execute the stored instructions according to the algorithm of the varying element implementing the present invention. The processor can be configured to control the wind turbine.

[0032] It should be noted that embodiments of the present 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 other embodiments have been described with reference to claims of the method type. However, those skilled in the art will learn from the foregoing and the following description that, unless otherwise stated, any combination between features related to different subjects, in particular any combination between features of device / equipment type claims and features of method type claims, is also considered to be utilized in the disclosure of the present application, in addition to any combination of features belonging to one type of subject. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The aspects of the present invention defined above, as well as additional aspects, are apparent from and will be elucidated with reference to the examples of embodiments described hereinafter. The present invention will be described in more detail hereinafter with reference to the examples of embodiments, but the present invention is not limited to the examples of these embodiments.

[0034] Figure 1 A wind turbine is shown in which a control device according to the present invention can be incorporated;

[0035] Figure 2 A timing diagram of the blade pitch angle implemented by a control device according to an embodiment of the present invention is shown as compared with the timing diagram of the blade pitch angle implemented by a conventional control device;

[0036] Figure 3 A timing diagram of the tower bending moment implemented by a control device according to an embodiment of the present invention is shown as compared with the timing diagram of the tower bending moment implemented by a conventional control device; and

[0037] Figure 4 A timing diagram of the rotor speed implemented by a control device according to an embodiment of the present invention is shown as compared with the timing diagram of the rotor speed implemented by a conventional control device. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0038] The legends in the drawings are schematic. It should be noted that in different drawings, similar or identical elements are provided with the same reference numerals.

[0039] Figure 1 Figure 1 shows a wind turbine 1. The wind turbine 1 includes a nacelle 3 and a tower 2. The nacelle 3 is mounted at the top of the tower 2. The nacelle 3 is mounted to be rotatable relative to the tower 2 by means of a yaw bearing. The axis of rotation of the nacelle 3 relative to the tower 2 is referred to as the yaw axis.

[0040] The wind turbine 1 further includes a hub 4 having three rotor blades 6 ( Figure 1 two of the rotor blades 6 are depicted therein). The hub 4 is mounted to be rotatable relative to the nacelle 3 by means of a main bearing 7. The hub 4 is mounted to be rotatable about a rotor axis of rotation 8.

[0041] In addition, the wind turbine 1 further includes a generator 5. The generator 5 in turn includes a rotor 10 that connects the generator 5 to the hub 4. The hub 4 is directly connected to the generator 5, and thus the wind turbine 1 is referred to as a gearless direct-drive wind turbine. Such a generator 5 is referred to as a direct-drive generator 5. As an alternative, the hub 4 can also be connected to the generator 5 via a gearbox. This type of wind turbine 1 is referred to as a gear-driven wind turbine. The present invention is applicable to both types of wind turbines 1.

[0042] The generator 5 is accommodated in the nacelle 3. The generator 5 is arranged and configured to convert the rotational energy from the hub 4 into electrical energy in the form of alternating current.

[0043] The wind turbine 1 includes control means (not shown) for controlling the wind turbine 1. The control means includes detection means 9 configured to detect the amount of bending moment of the blade 6. In this embodiment, the bending moment of the blade 6 is the root moment of the blade 6.

[0044] The control means further includes a varying element (not shown) having an input part and an output part, wherein the input part is configured to receive the detected amount of the bending moment of the blade 6, and the output part is configured to output a response to a differential of the detected amount of the bending moment of the blade 6. The differential can be a change in speed (i.e., acceleration), which allows the turbine to detect a change in speed, such as a change in speed of the bending moment. Alternatively, the differential can be a change in the bending moment, or the change in the bending moment can be interpreted as a change in speed. The change occurs over a predetermined time interval. The differential can also be the rate of change of the detected amount of the bending moment of the blade 6, such as the ratio between the change amount and the time interval. The varying element can also be a so-called differentiating element, and the response can be a step response of the so-called differentiating element. The control means is configured to control the wind turbine 1 based on the response.

[0045] Specifically, the control device is configured to control the rotational speed of the rotor 3 by changing the pitch angle of the blades 6 and / or by changing the output power of the wind turbine 1 based on the response. The control device is configured to increase the rotational speed of the rotor 3 when the response is positive, for example when the bending moment increases, and / or to decrease the rotational speed of the rotor 3 when the response is negative, for example when the bending moment decreases.

[0046] It is possible that the control device is configured to modify the speed control of the rotor by increasing the torque reference, power reference, and / or pitch reference (e.g., towards operation stop) when the response is positive, for example when the bending moment increases, and / or to modify the speed control of the rotor by decreasing the torque reference, power reference, and / or pitch reference (towards operation) when the response is negative, for example when the bending moment decreases. The torque reference, power reference, and / or pitch reference may be target values of the rotor torque, wind turbine power, and pitch angle of the blades.

[0047] The control device further includes a low-pass filter (not shown) connected before the input part or after the output part of the change element, wherein the control device is configured to control the wind turbine 1 based on the filtered change of the bending moment. The filter may be an adaptive band-stop filter, in particular an adaptive 3P band-stop filter, which filters the 1P contributions in the signal, and these 1P contributions add up to the combined 3P interference.

[0048] Since the wind turbine 1 includes three blades 6, the control device is configured to add three detected amounts of the bending moments of the three blades 6 to obtain a first sum and input the first sum into the input part of the change element.

[0049] Alternatively, the control device may be configured to add three responses of the three blades 6 to obtain a second sum, input the second sum into the low-pass filter, and control the wind turbine 1 based on the signal output from the low-pass filter.

[0050] Further alternatively, the control device may be configured to control the wind turbine 1 based on the response of the bending moment of the blade 6 that is currently pointing upwards.

[0051] Figure 2 A timing diagram of the blade pitch angle implemented by the control device according to an embodiment of the present invention is shown compared to the timing diagram of the blade pitch angle implemented by a conventional control device. The upper diagram represents the timing diagram of the blade pitch angle implemented by the control device according to an embodiment of the present invention, while the lower diagram represents the timing diagram of the blade pitch angle implemented by a conventional control device without any change element. The response in the upper diagram starts a few seconds earlier than that in the lower diagram and has a significant improvement in terms of the load and operation of the wind turbine 1. It can be seen that the wind turbine 1 according to an embodiment of the present invention remains in operation after this severe gust.

[0052] Figure 3 Shows a time series diagram of the tower moment achieved by a control device according to an embodiment of the present invention compared to the time series diagram of the tower moment achieved by a conventional control device. The tower moment is measured at the bottom of the tower 2. In this example, it can be seen that in the embodiment of the present invention, both the maximum positive load and the (absolute) maximum negative load at the tower bottom are reduced.

[0053] Figure 4 Shows a time series diagram of the rotor speed achieved by a control device according to an embodiment of the present invention compared to the time series diagram of the rotor speed achieved by a conventional control device. It can be seen that the wind turbine 1 according to the present invention remains on grid.

[0054] Computer simulations based on the wind turbine 1 according to the present invention have revealed the following benefits.

[0055] Secondly, by detecting gusts earlier compared to the prior art, the wind turbine 1 can pitch out earlier and thus limit the maximum speed experienced by the rotor. Instead of generating overspeed and turbine shutdown, the wind turbine 1 of the present invention can continue to operate after severe wind fronts and gusts, which results in higher grid stability by ensuring that the entire site can withstand extreme events.

[0056] The present invention can use the blade root sensor 9 to predict high rotor speed conditions where the wind turbine 1 is at risk of shutdown due to overspeed. This obtains a double derivative phase lead, but the signal quality is better than that of a single derivative (double derivatives usually contain too much noise in terms of signal quality).

[0057] It should be noted that the term "comprising" does not exclude other elements or steps, and the words "a", "an", or "one" do not exclude a plurality. In addition, elements described in connection with different embodiments may also be combined. It should also be noted that the reference signs in the claims should not be construed as limiting the scope of the claims.

Claims

1. A control device for controlling a wind turbine (1), the wind turbine comprising a rotor (3) and at least one blade (6) rotatably mounted to the rotor (3), the control device comprising: A detection device (9) configured to detect the amount of bending moment of the blade; And A varying element having an input part and an output part, wherein the input part is configured to receive the detected amount of the bending moment of the blade (6) from the detection device (9), and the output part is configured to output a response based on a difference or derivative of the detected amount of the bending moment of the blade (6); wherein The difference or derivative provides a phase lead prior to a change in rotor speed, such that the control device can react to changing wind conditions, Wherein the control device is configured to control the wind turbine (1) based on the phase lead provided by the difference or derivative, Wherein the control device is configured to modify the speed control of the rotor (3) by increasing the torque reference, power reference and / or pitch reference when the difference or derivative is positive, and / or to modify the speed control of the rotor (3) by decreasing the torque reference, the power reference and / or the pitch reference when the difference or derivative is negative.

2. The control device according to claim 1, wherein the control device is configured to control the rotational speed of the rotor (3) based on the response by changing the pitch angle of the blade (6) and / or by changing the output power of the wind turbine (1).

3. The control device according to any one of claims 1 and 2, further comprising: A low-pass filter connected before the input part or after the output part of the varying element, wherein the control device is configured to control the wind turbine (1) based on the filtered change in the bending moment.

4. The control device according to any one of claims 1 and 2, wherein the bending moment of the blade (6) is the root moment of the blade (6) or any other estimate of the bending moment.

5. The control device according to any one of claims 1 and 2, wherein the wind turbine (1) comprises a plurality of blades (6), wherein, The control device is configured to sum the detected amounts of the bending moment of the blade (6) to obtain a first sum, and input the first sum into the input part of the varying element.

6. The control device according to any one of claims 1 and 2, wherein the wind turbine (1) comprises a plurality of blades (6), wherein, The control device is configured to control the wind turbine (1) based on the response of the bending moment of the blade (6) currently pointing upwards.

7. A wind turbine (1), comprising: A tower (2); A rotor mounted at the top of the tower (2) to rotate about a rotation axis (8), wherein the rotor has a plurality of blades (6); and A control device according to any one of the preceding claims.

8. A method for controlling a wind turbine (1), the wind turbine comprising a rotor (3) and at least one blade (6) rotatably mounted to the rotor (3), the method comprising the steps of: Detect the amount of bending moment of the blade (6); Provide a varying element having an input part and an output part; Input the detected amount of the bending moment of the blade (6) into the input part of the varying element; Output a response from the output part of the varying element based on a difference or derivative of the detected amount of the bending moment, wherein the difference or derivative provides a phase lead prior to a change in rotor speed; Control the wind turbine (1) based on the phase lead; and Modify the speed control of the rotor (3) by increasing the torque reference, power reference and / or pitch reference when the difference or derivative is positive, and / or modify the speed control of the rotor (3) by decreasing the torque reference, the power reference and / or the pitch reference when the difference or derivative is negative.

9. The method according to the preceding claim, wherein the rotational speed of the rotor (3) is controlled based on the phase lead by changing the pitch angle of the blade (6) and / or by changing the output power of the wind turbine (1).

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