DK201570134A1 - Dynamic range control for wind turbine damping system - Google Patents

Abstract

Embodiments herein include disposing a dynamic range controller between a damping system and a physical control system - e.g., a blade pitch control system or a power control system. The range controller can determine whether a control signal outputted by the damping system exceeds the saturation limits of the physical control system, and if so, scale the control signal to generate an adjusted control signal which is then provided to the physical control system. In addition to ensuring the control signal remains within the saturation limits, in one embodiment, the dynamic range controller scales the control signal without introducing harmonic distortions into the adjusted control signal.

Description

DYNAMIC RANGE CONTROL FOR WIND TURBINE DAMPING SYSTEM BACKGROUND Field of the Invention

Embodiments presented in this disclosure generally relate to wind turbine tower damping systems. More specifically, embodiments disclosed herein generate control signals for reducing oscillations in the wind turbine without introducing harmonic distortions into the control signals.

Description of the Related Art

Oscillations and vibrations in a tower of a wind turbine may fatigue the wind turbine. Tower oscillations may arise each time a rotor blade passes the tower and generates wind that pushes against the tower. Another source for tower oscillations is wind turbulence which may cause periodic or instantaneous movements in the wind turbine tower. If left unchecked, these oscillations can have a detrimental effect on the lifespan of the wind turbine.

One way of compensating for tower oscillations is to design the tower with these oscillations in mind. For example, tower oscillations may be reduced by making the tower stiffen designing the blades to mitigate oscillations, reducing the weight of the nacelle and rotor, etc. But these design measures often conflict with other desired qualities of the wind turbine such as low cost and high efficiency. As such, some turbines include a tower damping system that is used to actively counter tower oscillations and vibrations detected in the turbine.

SUMMARY

One embodiment of the present disclosure is a method and a computer program product of operating a wind turbine. The method and computer program product include receiving a control signal from a wind turbine damping system and estimating an envelope of the control signal. The method and computer program product include determining a compression value based on the envelope and a saturation threshold of a control system in the wind turbine and scaling the control signal based on the compression value to generate an adjusted control signal.

Another embodiment described herein is a wind turbine controller that includes a processor, a control system, a wind turbine damping system configured to generate a control signal for reducing oscillations in a wind turbine, and a dynamic range controller. The dynamic range controller is configured to estimate an envelope of the control signal using the processor and determine a compression value based on the envelope and a saturation threshold of the control system. The dynamic range controller is configured to scale the control signal based on the compression value to generate an adjusted output signal and provide the adjusted control signal to the control system.

Another embodiment described herein is a wind turbine controller that includes a processor, a control system, a wind turbine damping system configured to generate a control signal for reducing oscillations in a wind turbine, and a dynamic range controller. The dynamic range controller is configured to scale the control signal according to a saturation limit associated with the control system to generate a scaled control signal, where scaling the control signal does not introduce harmonic distortion into the scaled control signal. The range controller is also configured to provide the scaled control signal to the control system in order to reduce oscillations in the wind turbine.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the present disclosure can be understood in detail, a more particular description of the disclosure, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this disclosure and are therefore not to be considered limiting of its scope, for the disclosure may admit to other equally effective embodiments.

Figure 1 illustrates a diagrammatic view of a wind turbine, according to an embodiment described herein.

Figure 2 illustrates a diagrammatic view of the components internal to the nacelle and tower of a wind turbine, according to an embodiment described herein.

Figure 3 illustrates a wind turbine controller for operating a wind turbine, according to an embodiment described herein.

Figure 4 is a block diagram of a dynamic range controller for controlling the output of a tower damping system, according to an embodiment described herein.

Figure 5 is a graph illustrating various signals in the dynamic range controller, according to an embodiment described herein.

Figure 6 is a graph illustrating gain values generated by the range controller, according to an embodiment described herein.

Figure 7 is a graph illustrating control signals with and without harmonic distortion, according to an embodiment described herein.

Figure 8 is a method for scaling a control signal received from a tower damping system without introducing harmonic distortion, according to an embodiment described herein.

To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements disclosed in one embodiment may be beneficially utilized on other embodiments without specific recitation.

DESCRIPTION OF EXAMPLE EMBODIMENTS

OVERVIEW

Embodiments herein describe using a tower damping system to actively counter oscillations {or vibrations) in a wind turbine. As described above, if left uncheck, these oscillations can cause structural harm to the tower or other components In the turbine and reduce the lifespan of the wind turbine. Examples of a tower damping system include a side-side tower damping (SSTD) system, which reduces tower oscillations in the left and right directions when facing a rotor plane, and a fore-aft tower damping (FATD) system, which reduces tower oscillations in the forward and backward directions when facing the rotor plane. These damping systems generate control signals that are then provided to other physical control systems in the turbine (e.g., blade pitch controllers or power controllers) which then use the control signals to reduce oscillations in the turbine.

However, the wind turbine damping systems may generate control signals that exceed the saturation limit of the physical control systems (e.g., a maximum or minimum voltage or current value). Instead of directly providing the control signals to the physical control systems, the embodiments herein include disposing a dynamic range controller between a damping system and a physical control system. The range controller can determine whether the control signal exceeds the saturation limits, and if so, scale the control signal to generate an adjusted control signal which is then provided to the physical control system. In addition to ensuring the control signal remains within the saturation limits, in one embodiment, the dynamic range controller scales the control signal without introducing harmonic distortions into the adjusted control signal.

EXAMPLE EMBODIMENTS

Figure 1 illustrates a diagrammatic view of a horizontal-axis wind turbine generator 100. The wind turbine generator 100 typically comprises a tower 102 and a wind turbine nacelle 104 located at the top of the tower 102. A wind turbine rotor 106 may be connected with the nacelle 104 through a low speed shaft extending out of the nacelle 104. The wind turbine rotor 106 comprises three rotor blades 108 mounted on a common hub 110 which rotate in a rotor plane, but may comprise any suitable number of blades, such as one, two, four, five, or more blades. The blade 108 (or airfoil) typically has an aerodynamic shape with a leading edge 112 for facing into the wind, a trailing edge 114 at the opposite end of a chord for the blade 108, a tip 116, and a root 118 for attaching to the hub 110 in any suitable manner.

For some embodiments, the blades 108 may be connected to the hub 110 using pitch bearings 120 such that each blade 108 may be rotated around its longitudinal axis to adjust the blade’s pitch. The pitch angle of a blade 108 relative to the rotor plane may be controlled by linear actuators or stepper motors, for example, connected between the hub 110 and the biade 108.

Figure 2 illustrates a diagrammatic view of typical components internal to the nacelle 104 and tower 102 of a wind turbine generator 100. When the wind 200 pushes on the blades 108, the rotor 106 spins and rotates a low-speed shaft 202. Gears in a gearbox 204 mechanically convert the low rotational speed of the low-speed shaft 202 into a relatively high rotational speed of a high-speed shaft 208 suitable for generating electricity using a generator 206.

A controller 210 may sense the rotational speed of one or both of the shafts 202, 208. If the controller decides that the shaft(s) are rotating too fast, the controller may signal a braking system 212 to slow the rotation of the shafts, which slows the rotation of the rotor 106 - i.e., reduces the revolutions per minute (RPM). The braking system 212 may prevent damage to the components of the wind turbine generator 100. The controller 210 may also receive inputs from an anemometer 214 (providing wind speed) and/or a wind vane 216 (providing wind direction). Based on information received, the controller 210 may send a control signal to one or more of the blades 108 in an effort to adjust the pitch 218 of the blades. By adjusting the pitch 218 of the blades with respect to the wind direction, the rotational speed of the rotor (and therefore, the shafts 202, 208) may be increased or decreased. Based on the wind direction, for example, the controller 210 may send a control signal to an assembly comprising a yaw motor 220 and a yaw drive 222 to rotate the nacelle 104 with respect to the tower 102, such that the rotor 106 may be positioned to face more (or, in certain circumstances, less) upwind.

Figure 3 illustrates a controller 210 for operating a wind turbine, according to an embodiment described herein. Controller 210 includes a processor 305 and memory 310. Processor 305 represents one or more processing elements that each may include one or more processing cores. Memory 310 may include volatile memory, non-volatile memory, or a combination of both. Furthermore, controller 210 may be located on the turbine 100 as shown in Figure 2 or may located remotely of the turbine (e,g., as part of a supervisory control and data acquisition (SGADA) system).

Memory 310 includes a tower damping system module 315, range controller module 320, pitch controller module 325, and power controller module 330. Although these modules are shown as software applications in memory 310, in other embodiments, the modules may include hardware components or a combination of both software and hardware. The tower damping system module 315 may include a SSTD or FATD for damping tower oscillations during operation of the wind turbine. The embodiments herein are not limited to any particular technique for damping the side-to-side or fore-aft oscillations of the tower. In one embodiment, the tower damping system module 315 uses wind speed, torque/force measurements, and/or tower accelerations to output a control signal for reducing the tower oscillations. The control signal may be sent to either the pitch controller module 325 or the power controller module 330 which use the control signal to reduce oscillations in the turbine. In other embodiments, the tower damping system module 315 may output multiple control signals that are sent to different control systems that work together to reduce the turbine oscillations.

The pitch controller module 325 controls the pitch angle of the blades attached to the rotor. By controlling the pitch, module 325 determines how much energy is harvested from the wind. Moreover, by adjusting the pitch using the control signal provided by the tower damping system module 315, the pitch controller module 325 can reduce tower oscillations.

The power controller module 330 controls the output power generated by the wind turbine. To do so, the power controller module 330 may be coupled to a power converter or generator in the wind turbine. The power controller module 330 may set the voltage of the output power as well as its frequency, in one embodiment, the control signal generated by the tower damping system module 315 is provided to the power controller module 330. By controlling the output power of the wind turbine, the power controller module 330 can change the load on the rotor and reduce tower oscillations. Although Figure 3 illustrates pitch controller module 325 and power controller module 330 as suitable candidates for receiving the control signal outputted by the tower damping system, the embodiments herein are not limited to such. That is, the tower damping system module 315 may generate control signals for other types of physical control systems such as a rotor braking system or a specialized damping system (e.g., a pendulum hanging within the tower) for reducing oscillations in the turbine.

The range controller module 320 (also referred to as a dynamic range controller (DRC)) is communicatively coupled between the tower damping system module 315 and either the pitch controller module 325 or power controller module 330 (depending on which module 325, 330 receives the control signal generated by tower damping system module 315). The range controller module 320 scales the control signal according to a saturation limit associated with the controller that ultimately receives the control signal - i.e., the pitch or power controller module 325, 330. Stated differently, the range controller module 320 may attenuate the control signal so that the signal does not exceed the saturation limit of the pitch or power controller module 325, 330. For example, the pitch or power controller module 325, 330 may only be able to process signals within a certain input range (e.g., a certain voltage range) defined by one or more saturation limits. If the pitch or power controller module 325, 330 receive contro! signals that exceed these saturation limits, the control signals may harm the controllers or cause the controller to behave abnormally or unpredictably. Thus, before being fed into one of the controllers 325, 330, the range controller module 320 may adjust a characteristic of the control signal provided by the tower damping system such as reducing a voltage swing, changing or filtering a frequency component or range, reshaping the signal, and the like to ensure the control signal falls within the saturation limits, in one embodiment, when altering the characteristic of the control signal, the range controller module 320 may do so without introducing harmonic distortion into the signal. That is, the range controller module 320 adjusts the control signal to be within the saturation limits without adding in noise at harmonic frequencies corresponding to the frequency range (or bandwidth) of the unadjusted control signal.

Although the embodiments herein disclose using the range controller module 320 with tower damping system module 315, the range controller module 320 may be used in other wind turbine damping system besides tower damping systems. For example, the range controller module 320 may be used in any damping system that reduces oscillations in the wind turbine such as harmonic oscillations in the blades, nacelle, and the like.

Figure 4 is a block diagram of a range controller module 320 for controlling the output of the tower damping system, according to an embodiment described herein. In one embodiment, the range controller module 320 adjusts a control signal received from the tower damping system to be within saturation limits of a controlled system (e.g., a pitch controller or power controller) without introducing harmonic distortion into the control signal. To do so, the range controller module 320 includes an envelope estimator 405, a compressor 410, a gain factor filter 420, and a multiplier 425 which each may be implemented using software, hardware, or a combination of both. As shown by arrow 400, the range controller module 320 receives the control signal from the tower damping system at the input of the envelope estimator 405. The control signal may be a pitch actuator signal for changing the pitch angle on the blades, or the signal may be a desired power setting for controlling the output power of the turbine.

Figure 5 is a graph 500 illustrating various signals in the range controller module 320, according to an embodiment described herein. The dotted line labeled 505 illustrates an example of a control signal that may be inputted into the envelope estimator 405 shown in Figure 4. Although the input signal 505 is sinusoidal, this is not a requirement. Moreover, the sinusoidal signal may be a combination of multiple different frequency signals. During the interval between five to ten seconds, the tower damping system increases the magnitude (e.g., degree or radians if the pitch control system is used to dampen oscillations or power if the power generation system is used) of the input signal 505 in response to detecting a tower oscillation. Around 6 or 7 seconds, the input signal 505 generated by the tower damping system exceeds a saturation threshold 520. As mentioned above, if the input signal 505 was directly fed into the pitch or power controller rather than first being adjusted by the range controller, this signal would exceed the controller’s saturation limit (represented by threshold 520) and may cause the corresponding system to behave abnormally or unpredictably. Although graph 500 illustrates only a positive threshold 520, there may be a negative saturation threshold as well.

Returning to Figure 4, the envelope estimator 405 generates an envelope of the control signal provided by the tower damping system. For example, the envelope 510 in graph 500 illustrates the corresponding envelope for the input signal 505. This envelope 510 follows the maximum peaks of the input signal 505, but may follow its minimum peaks as well. The embodiments in this disclosure are not limited to any particular technique for calculating the envelope of a signal, and thus, any technique that can perform the functions described herein may be used. As the envelope is calculated, the envelope estimator 405 outputs this signal to the compressor 410 as shown by arrow 430. The compressor 410 includes a saturation threshold 415 which, in one example, corresponds to the threshold 520 shown in graph 500. Using threshold 415, the compressor 410 calculates a compression value (e.g., a gain) used to scale the control signal provided by the tower damping system.

Figure 6 is a graph 600 illustrating gain values generated based on the input signal 505 and envelope 510 shown in Figure 5, according to an embodiment described herein. In one embodiment, the compressor 410 compares the envelope 510 to the saturation threshold 520. As shown by dotted line 605 which represents the output of the compressor 410, the gain is unity so long as the envelope 510 remains beiow the saturation threshoid 520. However, when the envelope 510 outputted by the envelope estimator 405 crosses the threshold 520. the compressor 410 begins to reduce the gain, in this embodiment, the change in the gain represented by signal 605 corresponds to the change in the envelope 510. As the envelope 510 becomes wider (i.e., increases), the gain value decreases (assuming the envelope 510 exceeds the threshold 520). For example, between the time the envelope 510 crosses the saturation threshoid 520 and approximately 11 seconds, the width of envelope 510 increases thereby causing the compressor 410 to decrease the gain 605, However, once the envelope 510 stabilizes, the gain 605 also stabilizes - i.e., remains constant. At approximately 45 seconds, the envelope 510 begins to decrease thereby causing the compressor 410 to increase the gain signal 605, Around the time the envelope 510 falls beiow the saturation threshoid 520, the compressor 410 outputs a gain signal 605 at unity. In this manner, the compressor 410 uses the saturation threshold 415 and the envelope generated by the estimator 405 to output a compression value (e.g., gain signal 605) for scaling the input signal.

As shown by arrow 435 in Figure 4, the compressor 410 transmits the compression value to the gain factor filter 420. As shown in Figure 6, the gain signal 605 outputted by the compressor 410 may include undulations made from high-frequency signals. To smooth the gain signal 605, the gain factor filter 420 filters out the high-frequency signal and outputs the filtered gain signal 610. In one embodiment, the gain factor filter 420 includes a low-pass filter that permits the low-frequency signals in the gain signal 605 to pass but removes the high-frequency signals, thereby generating the filtered gain signal 610 (also referred to as a filter compression value).

The output of the gain factor filter 420 (e.g., the filtered gain signal 610) is provided to multiplier 425 which multiplies the output of the filter 420 with the control signal received from the tower damping system. When the filter compression value is at unity, then the output of the multiplier 425 as shown by arrow 445 is the original control signal - i.e., the control signal is unaltered by the range controller module 320. However, when the compression value is less than one, the multiplier 425 scales the control signal to output an adjusted control signal. In one embodiment, the multiplier 425 uses the compression value to attenuate the control signal such that the output of the range controller module 320 does not exceed the saturation threshold 415. For example, Figure 5 illustrates an adjusted control signal 515 outputted by the range controller module 320 that has a maximum voltage that is below the threshold 520. That is, although the input signal 505 (e.g., a control signal) provided by the tower damping system exceeds threshold 520, after being scaled by the range controller module 320, the adjusted control signal 515 remains at or below the threshold 520. In this manner, the range controller module 320 outputs the adjusted control signal 515 that is within the saturation limits of the pitch or power controller (e.g., has a maximum voltage less than the threshold 520).

Moreover, the range controller module 320 scales the control signal without introducing harmonic distortion into the adjusted control signal by using the range controller 320. Alternatively, if the control signal (e.g., input signal 505) was clipped at the threshold 520, the resulting control signal would appear more like a square wave in the time period extending from about 7 seconds to 47 seconds when the magnitude of the control signal exceeds the threshold 520. However, clipping the input signal adds high-frequency noise into the control signal - i.e., harmonic distortion. Clipping the sinusoidal input signal 515 into square wave can be described as adding an infinite series of odd harmonics of the frequency of the original sinusoidal control signal.

Figure 7 is a graph 700 illustrating control signals with and without harmonic distortion, according to an embodiment described herein. Graph 700 illustrates the frequency response of three signals: the input signal 505 shown in Figure 5 (i.e.. the control signal received from the tower damping signal), the output signal 515 (i.e., the adjusted control signal outputted from the range controller module 320), and an output signal 705 when the input signal 505 is ciipped for exceeding the threshold 520. In this example, the frequency response is measured when the input signal 505 exceeds the threshold 520 (e.g., within the range of 7-47 seconds). As shown, the input signal 505 is primarily centered at 1 Hz. Because the range controller module 320 does not introduce harmonic distortion, the output signal 515 is also centered at 1 Hz. In contrast, hard clipping the input signal 505 results in signal 705 which includes frequencies at the odd harmonics of the original frequency - i.e., 3Hz, 5Hz, 7Hz, 9Hz, etc. Adding these odd harmonics to the control signal can cause problems in the downstream systems. For example, if signal 705 is transmitted to the power controller, the result may cause the power to flicker in the grid or cause a failure of the turbine’s electrical system, if signal 705 is transmitted to the pitch controller, the controller may overload due to large pitch acceleration levels. That is, the odd harmonics cause much faster pitch accelerations than the original control signal outputted by the tower damping system. These unnecessary accelerations may cause added wear and tear on the wind turbine. Moreover, the change in pitch caused by the odd harmonics may excite other turbine structural modes and cause additional vibrations in the turbine - e.g., edgewise vibrations - which may reduce the turbine’s lifespan.

The present disclosure is not limited to the specific range controller module 320 shown in Figure 4. Instead, any dynamic range controller that adjusts a control signal to be within a threshold without introducing harmonic distortion is contemplated by this disclosure.

Figure 8 is a method 800 for scaling a control signal received from a tower damping system without introducing harmonic distortion, according to an embodiment described herein. At block 805, the range controller receives a control signal from the tower damping system. In some examples, the control signal is a sinusoidal signal that controls a physical system in the wind turbine such as the pitch of the blades or the generated power. However, the control signal may exceed a saturation threshold corresponding to the physical system. For instance, the physical system may require the control signal to be within a certain voltage or current range, if the control signal were to exceed that range, the control signal may harm the physical system or cause the physical system to behave unpredictably. To prevent this, the range controller scales the control signal to prevent the signal from exceeding the saturation threshold.

At block 810, the range controller estimates an envelope of the output control signal, in one embodiment, the envelope tracks the maximum (and minimum) extremes of the control signal. For example, the range controller may generate an envelope that contains the voltage or current fluctuations of the control signal, in this manner, the envelope bounds the control signal into a certain range.

At block 815, the range controller determines a compression value based on the envelope and a saturation threshold. By comparing the envelope estimated at block 810 to the threshold, the range controller can determine whether the control signal is below or above the saturation threshold, if below the saturation threshold, the range controller may output a gain of unity (i.e., no change in gain). However, if the envelope exceeds the threshold (i.e., the control signal is fluctuating such that the maximum or minimum extreme of the signal exceeds the threshold), the range controller generates a gain for attenuating the control signal, in one embodiment, the compression value varies according to the width of the envelope. For example, as the envelope gets wider (e.g., the maximum of the control signal increases), the compression value may decrease (e.g., a value less than one). Once the envelope stabilizes, the compression value may remain constant. Conversely, when the envelope decreases in width, the range controller increases the compression value until the envelope is below the saturation threshold and the gain is at unity.

At block 820, the range controller scales the output control signal based on the compression value to generate an adjusted control signal. In one embodiment, the range controller multiplies the control signal by the compression value to result in the adjusted control signal. For example, if the compression value is less than one, the adjusted control signal is an attenuated version of the original control signal. By doing so, the range controller ensures that the adjusted controi signal remains at or below the saturation threshold. The range controller provides the adjusted controi signal to the physical system (e.g., a pitch control system or power generation system) to reduce or dampen oscillations in the tower. Advantageously, the adjusted control signal is within the saturation limits of the physical system. Moreover, using method 800, the range controller scales the output signal without introducing harmonic distortions in the adjusted control signal.

in the preceding, reference was made to embodiments presented in this disclosure. However, the scope of the present disclosure is not limited to specific described embodiments. Instead, any combination of the features and elements, whether related to different embodiments or not, is contemplated to implement and practice contemplated embodiments. Furthermore, although embodiments disclosed herein may achieve advantages over other possible solutions or over the prior art, whether or not a particular advantage is achieved by a given embodiment is not limiting of the scope of the present disclosure. Thus, the aspects, features, embodiments and advantages herein are merely illustrative and are not considered elements or limitations of the appended claims except where explicitly recited in a claim(s). Likewise, reference to “the invention” shall not be construed as a generalization of any inventive subject matter disclosed herein and shall not be considered to be an element or limitation of the appended claims except where explicitly recited in a claim(s).

As will be appreciated by one skilled in the art, the embodiments disclosed herein may be embodied as a system, method or computer program product. Accordingly, aspects may take the form of an entirely hardware embodiment, an entirely software embodiment (including firmware, resident software, micro-code, etc.) or an embodiment combining software and hardware aspects that may all generally be referred to herein as a “circuit,” “module” or “system.” Furthermore, aspects may take the form of a computer program product embodied in one or more computer readable medium(s) having computer readable program code embodied thereon.

The present invention may be a system, a method, and/or a computer program product. The computer program product may include a computer readable storage medium (or media) having computer readable program instructions thereon for causing a processor to carry out aspects of the present invention.

Any combination of one or more computer readable mediurn(s) may be utilized. The computer readable medium may be a computer-readable signal medium or a computer-readable storage medium. A computer readable storage medium may 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 would include the following: an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), an optica! fiber, a portable compact disc read-only memory (CD-ROM), an optica! storage device, a magnetic storage device, or any suitable combination of the foregoing. In the context of this document, a computer readable storage medium is any tangible medium that can contain, or store a program for use by or in connection with an instruction execution system, apparatus or device.

A computer readable signal medium may include a propagated data signal with computer readable program code embodied therein, for example, in baseband or as part of a carrier wave. Such a propagated signal may take any of a variety of forms, including, but not limited to, electro-magnetic, optical, or any suitable combination thereof. A computer readable signal medium may be any computer readable medium that is not a computer readable storage medium and that can communicate, propagate, or transport a program for use by or in connection with an instruction execution system, apparatus, or device.

Program code embodied on a computer readable medium may be transmitted using any appropriate medium, including but not limited to wireless, wireline, optica! fiber cable, RF, etc., or any suitable combination of the foregoing.

Computer program code for carrying out operations for aspects of the present disclosure may be written in any combination of one or more programming languages, including an object oriented programming language such as Java, Smalltalk, C++ or the like and conventional procedural programming languages, such as the "C" programming language or similar programming languages. The program code may execute entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer or entirely on the remote computer or server. In the latter scenario, the remote computer may be connected to the user's computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or the connection may be made to an external computer (for example, through the internet using an Internet Service Provider).

Aspects of the present disclosure are described above with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to embodiments presented in this disclosure. It will be understood that each block of the flowchart illustrations and/or block diagrams, and combinations of blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks.

These computer program instructions may also be stored in a computer readable medium that can direct a computer, other programmable data processing apparatus, or other devices to function in a particular manner, such that the instructions stored in the computer readable medium produce an article of manufacture including instructions which implement the function/act specified in the flowchart and/or block diagram block or blocks.

The computer program instructions may also be loaded onto a computer, other programmable data processing apparatus, or other devices to cause a series of operational steps to be performed on the computer, other programmable apparatus or other devices to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide processes for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks.

The flowchart and block diagrams in the Figures illustrate the architecture, functionality and operation of possible implementations of systems, methods and computer program products according to various embodiments. In this regard, each block in the flowchart or block diagrams may represent a module, segment or portion of code, which comprises one or more executable instructions for implementing the specified logical function(s). It should also be noted that, in some alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved, it will also be noted that each block of the block diagrams and/or flowchart illustration, and combinations of blocks in the biock diagrams and/or flowchart illustration, can be implemented by special purpose hardware-based systems that perform the specified functions or acts, or combinations of special purpose hardware and computer instructions.

In view of the foregoing, the scope of the present disclosure is determined by the claims that follow.

Claims (14)

1. A method of operating a wind turbine, the method comprising: receiving a control signal from a wind turbine damping system; estimating an envelope of the control signal; determining a compression value based on the envelope and a saturation threshold of a control system in the wind turbine; and scaling the control signal based on the compression value to generate an adjusted control signal.

2. The method of claim 1, further comprising: transmitting the adjusted control signal to the control system which is configured to use the adjusted control signal to reduce oscillations in the wind turbine.

3. The method of any of the preceding claims, wherein the saturation threshold is equal to or less than a saturation limit of input signals being received by the control system.

4. The method of claim 1, wherein the adjusted control signal comprises a sinusoidal signal, and wherein scaling the control signal is performed in a manner such that harmonic distortion are not introduced into the adjusted control signal.

5. The method of claim 1, further comprising: filtering the compression value using a low pass filter before scaling the control signal.

6. The method of claim 1, wherein the compression value defines a gain to be applied when scaling the control signal to generate the adjusted control signal.

7. A wind turbine controller, comprising: a processor; a control system; a wind turbine damping system configured to generate a control signal for reducing oscillations in a wind turbine; and a dynamic range controller configured to: estimate an envelope of the control signal using the processor, determine a compression value based on the envelope and a saturation threshold of the control system, scale the control signal based on the compression value to generate an adjusted output signal, and provide the adjusted control signal to the control system.

8. The wind turbine controller of claim 7, wherein the control system is configured to use the adjusted control signal to reduce oscillations in the wind turbine.

9. The wind turbine controller of claim 7, wherein the saturation threshold is equal to or less than a saturation limit of input signals being received by the control system.

10. The wind turbine controller of claim 7. wherein the adjusted control signal comprises a sinusoidal signal, and wherein scaling the control signal does not introduce harmonic distortion into the adjusted control signal.

11. The wind turbine controller of claim 7. wherein the dynamic range controller is configured to: filter the compression vaiue using a low pass filter before scaling the control signal.

12. The wind turbine controller of claim 7, wherein the compression vaiue defines a gain to be applied when scaling the control signal to generate the adjusted control signal.

13. A non-transitory computer-readable storage medium storing computer-readable program code which, when executed on a processor, performs an operation, the operation comprising: receiving a control signal from a wind turbine damping system of a wind turbine; estimating an envelope of the control signal; determining a compression value based on the envelope and a saturation threshold of a control system in the wind turbine; and scaling the control signal based on the compression value to generate an adjusted control signal.

14. A wind turbine controller, comprising: a processor; a control system; a wind turbine damping system configured to generate a control signal for reducing oscillations in a wind turbine; and a dynamic range controller configured to: scale the control signal according to a saturation limit associated with the control system to generate a scaled control signal, wherein scaling the control signal does not introduce harmonic distortion into the scaled control signal, and provide the scaled control signal to the control system in order to reduce oscillations in the wind turbine.