Method for wind turbine operation in response to grid disturbance

Abstract

A method of operating at least one adaptable airflow regulation system (13) of at least one rotor blade (15) of a wind turbine (1) connected to a utility grid (6) is described, the method comprising: receiving information (10) about a grid disturbance; adapting the airflow regulation system (13) based on the information (10) while the wind turbine (1) remains connected to the utility grid (6), in particular during the duration of the disturbance.

Description

Technical Field

[0001] This invention relates to a method and apparatus for operating at least one adjustable airflow conditioning system for at least one rotor blade of a wind turbine connected to a public power grid in the event of grid disturbances. Furthermore, this invention relates to a wind turbine including the apparatus. Background Technology

[0002] Wind turbines can be connected to the utility grid along with multiple other wind turbines, for example, via a point of common coupling and wind farm transformers. During normal operation, the utility grid may have a nominal voltage and nominal frequency. For example, in the event of a fault in one or more components of the utility grid, the grid may experience disturbances such as voltage drops, which may even fall to zero volts.

[0003] Today, grid specifications for wind power integration may require wind turbines to remain connected during grid faults, even when grid voltage drops to zero. Furthermore, wind turbines may need to inject reactive current proportional to the voltage drop. In particular, wind turbines may need to comply with standard IEC 61400-1, which defines load conditions for grid disturbances, especially grid dips (DLC 2.1).

[0004] A grid fault can be a grid dip detected during wind turbine operation. A grid dip can cause the wind turbine's output power to drop rapidly to zero. This also includes the rapid removal of mechanical torque from the generator, resulting in a step change in load, which can trigger high-load cycles in the structure and drive the rotor toward overspeed. The equilibrium point (the turbine's operating point) just before the grid dip depends on the rotor's ability to transmit mechanical torque to the electrical system to balance the rotational speed. Whenever counter-torque from the generator is suddenly removed (e.g., in the event of a grid voltage dip), excess torque can affect the rotor's acceleration. This can involve dangerous situations and risks of damage to wind turbine components.

[0005] Conventionally, control methods may involve pitching the wind turbine blades, i.e., changing the pitch angle of the wind turbine blades, in order to reduce the risk of the rotor accelerating beyond a rotational speed threshold. Specifically, the control system may spend a period of time pitching to limit input power and stop acceleration.

[0006] Some power grid specifications also require that power production be restored to near pre-fault levels shortly after the grid returns to normal operating conditions, with little or no oscillations in power production following a grid failure. Therefore, the mechanical torque from the generator is rapidly re-established (i.e., meaning increased to pre-fault values), and the control system must now pitch the rotor blades to accommodate the re-established torque from the rotor.

[0007] Typically, in the event of a voltage drop, the pitch angle of at least one rotor blade may have already changed. Therefore, the requirements for grid fault ride-through (GFRT) may have already been met. Normally, wind turbine blades begin pitch control upwind as early as possible to avoid rotor overspeed. The so-called pitch kick function, when triggered, introduces a rapid change in the pitch angle in the positive direction, meaning an increase in the pitch angle.

[0008] However, it has been observed that pitching the blades in the event of a voltage drop does not provide reliable and safe operation in all situations. Furthermore, it may have been observed that pitching, particularly on large turbines, is too slow to adjust the drive torque, resulting in undesirable variations in rotor speed. When torque is re-established, the variation can be either above the nominal speed (overspeed is a serious example of speed variation) or below the nominal speed. The latter is problematic because speeds below the nominal value reduce the turbine's electrical production capacity.

[0009] Furthermore, applying pitch control to the rotor blades during significant grid disturbances can negatively impact the lifespan of the pitch control equipment. Additionally, pitch control of the rotor blades may not be fast enough to adequately prevent rotor overspeed.

[0010] Therefore, a method and corresponding apparatus may be needed to ensure the safe and reliable operation of wind turbines in the event of grid disturbances, particularly grid voltage dips. Furthermore, a method and apparatus for operating wind turbines may be needed, wherein response time can be improved in the event of grid voltage dips. Summary of the Invention

[0011] This need can be met through the subject matter of this invention.

[0012] According to one embodiment of the present invention, a method is provided for operating at least one adjustable airflow conditioning system (also referred to as an auxiliary device, such as a lift conditioning device, for example including an aerodynamically active surface that is positionally and / or orientationably variable relative to the outer airfoil of the blade) of at least one rotor blade of a wind turbine connected to a public power grid, the method comprising: receiving information about a power grid disturbance; and adjusting the airflow conditioning system based on the information while the wind turbine remains connected to the public power grid, particularly during the duration of the disturbance, wherein controlling the airflow conditioning system includes: moving the position and / or orientation of at least one aerodynamically active surface of the airflow conditioning system relative to the airfoil portion of the rotor blade.

[0013] This method can be implemented in part in software and / or hardware. It can be performed, for example, by a software module of a wind turbine controller. The adaptable airflow control system may include one or more components arranged at or near the airfoil portion of the rotor blades. The airflow control system may, for example, include a spoiler, which may specifically include several segments arranged along the longitudinal direction of the rotor blades, for example, on the suction side of the rotor blade airfoil. Furthermore, alternatively or additionally, the airflow control system may include one or more flaps, for example, mounted near or at the trailing edge of the rotor blades.

[0014] Airflow control systems are adaptable in a sense because their aerodynamic properties, particularly the airfoil portion integrated with the rotor blades, are variable. For example, due to the specific adaptability of the airflow control system, the lift or thrust experienced by the rotor blades when wind impacts them and when the blades rotate can be variable. Therefore, the airflow control system can be configured in one or more different states. For example, when the airflow control system comprises multiple sections, those individual sections can be individually controlled to be in an off or on state, including, for example, changing the position and / or orientation of at least one movable surface portion relative to the rotor blade airfoil. In other embodiments, adaptation can be continuous, whereby at least one movable surface portion can continuously change its orientation and / or position relative to the rotor blade airfoil. The airflow control system may also be referred to as an active attachment.

[0015] To adapt the airflow conditioning system, it means setting it to different states, for example, by utilizing a pneumatic system. In one embodiment, the airflow conditioning system may include a spoiler that can be positioned on the suction side of the rotor blades. The airflow conditioning system may also include one or more vortex generators, such as those positioned in the streamline behind the spoiler when viewed from the leading edge. The one or more spoilers can be activated using a pressure hose placed under a moving surface (e.g., a flap), which can raise the moving surface above the blade surface when air is pushed into the hose. When the one or more spoilers are activated, for example, tilted upwards to protrude from the rotor blade airfoil, a rapid reduction in blade load (and aerodynamic lift) can be achieved by inducing at least a local stall in the airflow across the rotor blades.

[0016] By adjusting the airflow control system (e.g., setting it to one or more different states), the lift generated by the combination of the rotor blade airfoil and the adjusted airflow control system can be altered. Consequently, when lift decreases, the aerodynamic torque exerted by the wind on the rotor blades also decreases. Therefore, the rotor acceleration also decreases, particularly reducing torque that existed prior to, for example, grid disturbances by 10% to 70%.

[0017] An airflow control system may, for example, include sending appropriate control signals to a pneumatic system that, upon receiving the signal, can generate aerodynamic pressure to inflate (or deflate), for example, a hose, which moves a movable surface portion during inflation or deflation (e.g., in the case of a spoiler). When the airflow control system comprises several sections, different individual control signals can be supplied to each section of the airflow control system. For example, different sections can be controlled in different ways. One or more sections can be opened (including tilting the corresponding movable surface outward), and one or more other sections can be closed. This control can reduce lift due to aerodynamics or airflow.

[0018] The received information may include information received from a public grid operator, and / or information about the electrical properties of the grid received from the public grid operator or from a measurement system. Furthermore, the received information may involve or include receiving measurements of the public grid voltage. The method may also involve or include detecting grid disturbances, for example, by evaluating measurements of the public grid voltage. Grid disturbances may, for example, include voltage drops in the public grid voltage between 10% and 100% of the nominal public grid voltage. If the public grid voltage drop exceeds a specific applied threshold, only an adaptive airflow control system may be implemented.

[0019] Grid disturbances can be any type of disturbance that may require unloading the rotor blades, i.e., reducing the aerodynamic lift of the rotor blades or reducing the aerodynamic torque generated by the impinging winds on the rotor blades. Grid disturbances can last, for example, from 0.1 s to 10 s, particularly from 1 s to 5 s. Throughout the entire length of the grid disturbance, for example, over a time span of up to 10 s, the wind turbine can remain connected to the public grid. During grid disturbances, particularly during voltage dips, the wind turbine output power can be regulated to zero. Furthermore, the generator torque, which counteracts the aerodynamic torque exerted by the rotor during normal operation, can also be regulated to essentially zero.

[0020] The airflow conditioning system can be adjusted in one direction to reduce the lift of the rotor blades, and thus also reduce the aerodynamic torque. This reduces the rotor's acceleration. Additional or alternative measures can be employed to reduce rotor blade lift, such as changing the pitch angle of (or similar) rotor blades. However, these measures may only be applied in the second stage and may not be as fast as adapting the airflow conditioning system. Therefore, a reliable method is provided to respond to grid voltage dips and any grid disturbances that typically require a reduction in rotor blade lift.

[0021] The greatest advantage of the active device is that it can reduce (e.g., during grid voltage dips) and rebuild (e.g., after grid disturbances have ended) the drive torque much faster than pitch control.

[0022] The position and / or orientation of at least one aerodynamically movable surface of the airflow control system relative to the airfoil portion of the rotor blades can be achieved by appropriately controlling a pneumatic system (e.g., a piezoelectric system or a combination thereof) or a hydraulic system, depending on the application and specific implementation of the airflow control device or system. For example, moving the orientation of the aerodynamically movable surface to an open state (e.g., partially or fully turned off) may, for example, cause localized airflow stall. Setting the movable surface to a closed state can establish an airflow across the movable surface, which can be shaped according to the normal airfoil surface shape of the rotor blades.

[0023] According to an embodiment of the invention, the grid disturbance includes a grid voltage drop, particularly a grid voltage drop over a duration between 0.1 seconds and 10 seconds, particularly a grid voltage drop between 0% and 50% of the nominal grid voltage, wherein the adaptive airflow regulation system is executed only when the grid voltage drop exceeds a threshold.

[0024] Grid voltage drops can occur at very high rates, such as from the nominal grid voltage to 0V in, for example, between 0.1 seconds and 10 milliseconds. Neither the pitch control nor any active device (such as an auxiliary device) can react so quickly; that is, the system response may always be lagging, and the rotor speed will increase. However, the faster the response provided by operating the auxiliary device, the less the rotor speed increases. Active devices (such as auxiliary devices) can be faster than the pitch control, thus reducing speed variations.

[0025] The duration of a grid disturbance can refer to a time range from the point in time when the voltage drops to when the grid voltage recovers to, for example, at least 90% or 100% of the nominal grid voltage. If the grid disturbance lasts longer than, for example, 30 seconds, further measures may be taken or implemented, such as pitching the rotor blades and / or braking the rotor and / or disconnecting the wind turbine from the grid.

[0026] According to an embodiment of the present invention, the greater the voltage drop in the power grid, the greater the reduction in the aerodynamic lift and / or aerodynamic torque of the rotor blades.

[0027] When there is only a relatively small voltage drop, such as 10% or 20% below the nominal grid voltage, the generator's reverse torque does not need to be reduced to zero, but can be maintained at a small value.

[0028] For example, a 20% drop in grid voltage can reduce the maximum power output to the grid by 30%. At the onset of a fault (before the speed changes), this also means a 30% reduction in torque. (As speed increases, but power remains constant, torque drops further).

[0029] In this scenario, it's not necessary to reduce aerodynamic lift to the maximum extent possible; a slight reduction is sufficient to avoid rotor overspeed due to excessive acceleration. The airflow adjustment system can be tailored, for example, so that the reduction in aerodynamic lift is at least substantially proportional to the magnitude of the grid voltage drop. Therefore, a individually customized response can be provided for different voltage drops, thereby improving wind turbine operation.

[0030] According to an embodiment of the invention, the adaptive airflow control system includes reducing the aerodynamic lift of the rotor blades and / or the aerodynamic torque acting on the rotor with blades, particularly by reducing the lift or torque by 10% and 70%, respectively, before disturbance, particularly within a time span between 0.1 seconds and 3 seconds, and particularly within a time span between 0.5 seconds and 2 seconds.

[0031] For example, when one segment of a segmented spoiler located on the suction side of the rotor blades is activated, the airflow may be at least partially disturbed, resulting in airflow deceleration at that segment of the rotor blades. Depending on the number of segments activated or turned on, the reduction in lift can be adjusted in steps, for example, within the range of 10% to 70%, 20% to 60%, or 20% to 50%. Other values ​​of lift reduction are also possible depending on the specific airflow control system used, and, for example, the number of segments in the case of segmented spoilers. When this reduction is achieved within a relatively small time span between 0.1 seconds and 3 seconds, a rapid response to voltage dips in the utility grid can be made possible. Therefore, the risk of rotor overspeed can be reduced or even avoided.

[0032] According to an embodiment of the present invention, the airflow adjustment system includes an adjustment setting that depends on: at least one operating parameter of the wind turbine; at least one external condition; at least one nature of the power grid disturbance, the external condition particularly including at least one of wind speed and wind turbulence, and the operating parameter particularly including one of the following: the pitch angle of the rotor blades; the rotational speed of the rotor; and the power output.

[0033] Depending on the operating parameters, external conditions, and / or the nature of grid disturbances, varying degrees of aerodynamic lift reduction may be required or implemented. Furthermore, variations in rotor blade lift can be influenced by the movement or change in the position and / or orientation of the moving surface elements of the airflow conditioning system, which may differ for different operating parameters of the wind turbine. For example, for any operating point of the wind turbine (including the definition of multiple operating parameters), there may be a pre-defined relationship or characteristic between the aerodynamic lift of the rotor blades and the mechanical settings (e.g., angles or distances) of the moving surfaces of the airflow conditioning system. For instance, when the wind turbine is at an operating point where a small change in the mechanical adjustment parameters of the airflow conditioning system results in a relatively large change in aerodynamic lift, the mechanical adjustment value of the airflow conditioning system may vary to a smaller extent compared to another operating point, where the change in aerodynamic lift is smaller for the same amount of change in the mechanical adjustment parameters of the airflow conditioning system.

[0034] The method can be further improved by taking into account the nature of operating parameters and / or external conditions and / or grid disturbances to adapt the airflow conditioning system, ensuring reliable and safe operation of the wind turbine.

[0035] According to an embodiment of the invention, the airflow adjustment system is further based on the operating point of the wind turbine, wherein at a first operating point where changes in the settings of the airflow adjustment system have a greater impact on the lift of the rotor blades, the settings of the airflow adjustment system change to a lesser extent (with less impact on airflow / stall / lift) (e.g., changes in the position and / or orientation of the moving surfaces) compared to a second operating point where changes in the settings have a smaller impact on the lift of the rotor blades.

[0036] The state or setting of an airflow control system can be defined by the position and / or orientation of one or more moving surface portions of the system. For example, in the case of a segmented spoiler, the state or setting can be defined by the number of segments in the open state (i.e., fully tilted outwards, including the outward-tilted moving surface portions) and the number of segments in the closed state (i.e., in which the moving surface portions are fully retracted to avoid interfering with the airflow throughout the suction side of the wind turbine). In the closed state, lift is not reduced, while in the open state, lift is removed to the maximum extent.

[0037] For example, in the case of trailing edge flaps, the settings or state can be defined by continuous values ​​of mechanical adjustment, such as the amount of flap removal or the angle of flap tilting. Therefore, changes in the settings of the airflow control system involve changes in the mechanical adjustment parameters of one or more moving surface portions. This embodiment also relates to adapting the gain scheduling of the airflow control system. Therefore, the response to grid disturbances can be improved for different operating conditions.

[0038] According to an embodiment of the invention, the method further includes maintaining the pitch angle of the rotor blades at least substantially constant for at least a portion of the disturbance duration; or the method further includes changing the pitch angle of the rotor blades based on information during the disturbance duration, particularly to reduce the lift of the rotor blades.

[0039] Maintaining a substantially constant pitch angle avoids high loads on the pitch bearings. Keeping the rotor blade pitch angle at least substantially constant can only be achieved under conditions where aerodynamic lift can be sufficiently reduced by adjusting the airflow control system. If this is no longer possible, the pitch angle can be additionally changed in one direction to further reduce rotor blade lift. Therefore, the response to grid disturbances can be further improved, particularly depending on the severity of the disturbances, especially the severity of grid voltage dips.

[0040] According to an embodiment of the present invention, if the power grid fails to return to normal operation within a predetermined threshold time range, the method includes: stopping the wind turbine, particularly including: adjusting the airflow regulation system to achieve maximum airflow deceleration; and / or pitching the rotor blades; and / or braking the rotor.

[0041] In this scenario, stopping the wind turbine might be required by grid regulations, or at least a safety measure to protect the turbine's components. Pitching the rotor blades could involve changing the pitch angle, thereby further reducing lift. Braking the rotor could include mechanical or electric braking.

[0042] According to an embodiment of the present invention, after a power grid disturbance, the power grid is restored to the nominal power grid state, particularly the nominal power grid voltage. The method includes: adjusting the airflow conditioning system to increase the lift of the rotor blades, particularly to increase the pre-disturbance lift that existed before the disturbance (and / or the pre-disturbance setting of the airflow conditioning device), particularly based on at least one of the following: the duration of the power grid disturbance, the rate of re-establishment (pre-disturbance) power output, the rotor speed, and the blade pitch angle.

[0043] The pre-disturbance lift (and / or the pre-disturbance setting of the airflow conditioning device) may have been stored in electronic memory. Increasing the aerodynamic lift of the rotor blades can restore the power output of the wind turbine, as it existed before the grid disturbance. By appropriately controlling, for example, a converter connected to the generator, the power output can be restored or at least increased after the duration of the grid disturbance. Through this control for restoring the wind turbine's output power, the generator torque can be increased in a stepwise or continuous manner. Corresponding to this stepwise or continuous increase in generator torque, the aerodynamic torque (e.g., achieved through an increase in rotor blade lift) can also be increased, particularly substantially in parallel or in a corresponding manner. Therefore, the rotor speed can be appropriately controlled to reach or maintain the nominal rotor speed.

[0044] According to an embodiment of the invention, the airflow adjustment system is adjusted to achieve pre-disturbance lift within a time span of 0.1 seconds to 3 seconds, particularly between 0.5 seconds and 2 seconds. When pre-disturbance lift is achieved within this relatively short time span, the wind turbine output power can also be restored to the pre-disturbance output power. Therefore, efficiency can be improved.

[0045] According to embodiments of the present invention, receiving information about a power grid disturbance includes: detecting the power grid disturbance; and deriving information based on the detected power grid disturbance. The power grid disturbance can be detected, for example, by comparing a measured grid voltage with a nominal grid voltage. Detection of the power grid disturbance can also be performed, for example, by a wind turbine controller or by a measurement or monitoring system, for example, external to or internal to the wind turbine. The information may include, for example, characteristics of the power grid disturbance, such as whether the disturbance is a voltage drop, a frequency drop, or a similar condition. Furthermore, the information may include information about the value or amount of the voltage drop or the severity of the power grid disturbance.

[0046] According to an embodiment of the present invention, the airflow regulation system includes at least one of the following: flaps, particularly flaps arranged at the trailing edge of the rotor blades; particularly segmented spoilers arranged at the suction surface of the blades, wherein the airflow regulation system is different from the pitch angle changing system.

[0047] Therefore, conventionally available control systems can be supported. The spoiler may, for example, comprise five to ten segments arranged side by side along the longitudinal direction of the rotor blades and positioned or mounted on the suction side of the rotor blades.

[0048] It should be understood that the features disclosed, described, explained, or provided for the method of operating at least one adjustable airflow control system may, individually or in any combination, be applied to the apparatus for operating at least one adjustable airflow control system according to embodiments of the present invention, and vice versa.

[0049] According to an embodiment of the present invention, an apparatus is provided for operating at least one adjustable airflow conditioning system for at least one rotor blade of a wind turbine connected to a public power grid in the event of a power grid disturbance, the apparatus comprising: a processor adapted to derive control signals based on information about the power grid disturbance in order to adjust the airflow conditioning system during the disturbance, wherein adjusting the airflow conditioning system (13) includes moving the position and / or orientation of at least one aerodynamic active surface of the airflow conditioning system relative to the airfoil portion of the rotor blade.

[0050] The device may, for example, be part of a wind turbine controller. According to embodiments of the invention, the device may further include an actuator configured to receive a control signal and adjust the position and / or orientation of at least one moving surface portion of the airflow conditioning system. For example, the actuator may include a compressor connected to a hose that can cause changes in the position and / or orientation of the moving surface portion (e.g., a spoiler or trailing edge flap) of the airflow conditioning system during inflation or deflation.

[0051] According to an embodiment of the present invention, a wind turbine is also provided, comprising: a wind turbine nacelle; a rotor shaft housed in the nacelle, a plurality of rotor blades mounted on the rotor shaft, at least one rotor blade having at least one adjustable airflow regulation system; and means according to the foregoing embodiment connected to control the airflow regulation system.

[0052] The above and other aspects of the invention will be apparent from the examples of embodiments described below, and will be explained with reference to the examples of embodiments. The invention will be described in more detail below with reference to examples of embodiments, but the invention is not limited thereto.

[0053] Embodiments of the present invention will now be described with reference to the accompanying drawings. The present invention is not limited to the embodiments illustrated or described. Attached Figure Description

[0054] Figure 1 A wind turbine according to an embodiment of the present invention is schematically illustrated, the wind turbine including means according to an embodiment of the present invention; and

[0055] Figure 2 The illustration depicts a method for operating at least one adjustable airflow control system for at least one rotor blade of a wind turbine connected to a public power grid in the event of grid disturbances. This method may, for example, be derived from... Figure 1 The device shown is used for execution. Detailed Implementation

[0056] The illustrations in the attached diagram are schematic.

[0057] Figure 1The schematically illustrated wind turbine 1 includes a wind turbine tower 3 erected on a base (not shown). The wind turbine also includes a nacelle 5 rotatably mounted on top of the wind turbine tower 3. The wind turbine nacelle 5 includes a rotor shaft 7 (with an axis 8) mounted within the nacelle 5. The rotor shaft drives a generator 9, which generates electrical energy. This electrical energy is supplied to a converter 11, which converts the frequency-converted AC power stream into a power stream of a substantially fixed frequency. This substantially fixed-frequency power stream is then supplied to a wind turbine transformer, which converts the output voltage to a higher value.

[0058] The wind turbine 1 also includes a device 20 for controlling at least one adjustable airflow conditioning system 13, which is disposed at at least one wind turbine blade 15. The rotor shaft 7 has a hub 17, and a plurality of rotor blades 15 (having blade tips 25) are mounted at the hub 17 via blade roots 12. At least one rotor blade has the flow conditioning system 13.

[0059] In the illustrated embodiment, the flow control system includes segmented spoilers having spoiler sections 19a, 19b, 19c, 19d, 19e, and 19f arranged along the longitudinal axis 21 of the rotor blades 15 on the suction side 14. The airflow control system 13 may also include at least one flap at the trailing edge 16, wherein the flap is indicated by reference numeral 23.

[0060] Device 20 is adapted to control the adjustable airflow conditioning system 13. Therefore, device 20 performs actions such as... Figure 2 Method 30 is shown. In method step 31, information about power grid disturbances is received. This information may, for example, be received from the operator of the public power grid 6, wherein the information is... Figure 1 The part is indicated by reference numeral 10 in the attached drawing and is received by device 20 via signal line 41.

[0061] Figure 1 The illustrated apparatus 20 includes a processor (not shown) configured to perform a method for adjusting or adapting the airflow regulation system 13 according to an embodiment of the present invention. In method step 33, while the wind turbine remains connected to the public power grid, the airflow regulation system (e.g., [the system]) is adjusted (or modified or set to a specific state) based on information 10. Figure 1 (System 13 in the system). Therefore, the wind turbine 1 provides AC power output 18 to the public power grid 6 via the power line 22.

[0062] Depending on the application, the device 20 may be arranged, for example, inside the hub 17 of the wind turbine, or inside the nacelle 5.

[0063] The device 20 then controls the flow regulation systems 19a, 19b, 19c, 19d, 19e, 19f and / or 23 by supplying appropriate control signals, for example via control lines 47 to the respective segments 19a, ..., 19f and control lines 48 to the flaps 23. These segments 19a-19f can then be individually opened or closed, for example if they comprise two different or separate states. In other embodiments, additionally or alternatively, continuous adjustment of the flow regulation device 13 can be performed, for example by continuously moving the orientation and / or position of the trailing edge flaps 23. By controlling the airflow regulation system 13 by the device 20, an appropriate response or reaction to disturbances in the utility power grid 6 can be achieved.

[0064] Each spoiler section 19a, ..., 19s has a corresponding aerodynamic movable surface that is exposed to the airflow around or throughout the rotor blade 15 (the suction side 14). This movable surface moves in position and / or orientation due to control signals supplied from the device 20. For example, in the open state, the movable surface can be flipped outwards to a certain degree, for example using an inflation hose arranged below the movable surface. For example, in the closed state, the movable surface can be flipped inwards so that it is completely retracted so as not to disturb or affect the airflow throughout the suction side surface 14 of the rotor blade 15.

[0065] Whenever a grid event that may require or will reduce generator torque is detected, embodiments of the present invention utilize a movable blade attachment to unload the rotor of the wind turbine.

[0066] Compared to airflow regulation systems mounted on or on the rotor blade surface, conventional pitch control systems for adjusting rotor blade lift can be relatively slow. Generally, the time constant of a pitch control system can be large, making larger turbines more susceptible to events such as grid outages.

[0067] Active blade attachments (such as airflow control system 13, including spoilers and / or trailing edge flaps) can significantly alter rotor lift in a very short time. Therefore, the effects of grid slippage can be compensated for much faster than by applying pitch control, especially when the pitch system has limited capacity (or can be manufactured cheaper without such high demand). Similarly, lift variations (i.e., aerodynamic variations in lift achieved by rotor blades) can fail rapidly after a fault to re-establish full power production.

[0068] The public power grid 6 has a nominal grid voltage. During grid disturbances, the voltage may drop significantly, for example, between 0% and 100% of the nominal grid voltage. The method according to embodiments of the invention can handle situations where the voltage drops, for example, between 0% and 50% of the nominal grid voltage. By operating the airflow conditioning system 13, lift can be reduced before grid disturbances, for example, by 10% to 70%.

[0069] The wind turbine 1 also includes a pitch system 40 (not shown in detail), which is capable of changing the pitch angle of each rotor blade 15, i.e., setting a specific rotation angle α about the longitudinal axis 21 of the corresponding rotor blade 15. According to an embodiment of the invention, only the airflow regulation system 13 is adjusted, while the pitch system 40 is not activated in response to grid disturbances.

[0070] In other embodiments, the airflow regulation system 13 is adapted, and the pitch system 40 is also activated, so that the rotor blades including the airflow regulation system 13 are configured to a state in which lift is significantly reduced, depending on the severity of grid disturbances and other operating parameters of the wind turbine.

[0071] Specific implementations of the method according to embodiments are described below; however, the invention is not limited thereto:

[0072] 1) Detect power grid faults.

[0073] 2) Applying a movable blade attachment (to remove lift from the rotor blades) to unload the turbine rotor - the action from the movable blade attachment can be added to or replace pitch generation.

[0074] - Actions from the active blade attachment can be scheduled through gain control, adjusting the effect to the operating point, for example, applying smaller variations at operating points where the attachment has a higher effect (gain) on the rotor's lift / torque / thrust or rotor aerodynamics.

[0075] 3) If the power grid returns to normal operation, remove the action from the blade attachment.

[0076] - The removal of blade attachments can be scheduled based on the duration of the grid fault, the rate of power re-establishment, rotor speed, and pitch angle.

[0077] - If the power grid does not return to normal operation, the turbine will stop and the blade attachment can be removed.

[0078] The embodiments of the present invention can provide the following advantages:

[0079] • Grid dip load conditions can be design-driven and can increase the cost of wind turbines because they need to be able to pitch more quickly after grid voltage dips or withstand additional extreme loads caused by grid disturbances. Introducing handles to mitigate the impact of grid dips can lead to cheaper designs with less load.

[0080] • The likelihood of driving the turbine into an overspeed event (i.e., rotor overspeed event) or exposing it to final load after a drop in grid voltage can be reduced through this additional control approach used to adjust the airflow conditioning system.

[0081] • Because the capacity of hydraulic or electric pitch systems can be reduced, costs can be lowered.

[0082] • The ability to produce cost-competitive wind turbines has improved.

[0083] • Improved ability to meet stringent grid specifications for re-establishing power generation.

[0084] It should be noted that the term "comprising" does not exclude other elements or steps, and "a" or "one" does not exclude multiple. Elements described in conjunction with different embodiments may also be combined.

Claims

1. A method of operating at least one adjustable airflow conditioning system (13) of at least one rotor blade (15) of a wind turbine (1) connected to a public power grid (6), the method comprising: Receive information about power grid disturbances (10); While the wind turbine (1) remains connected to the public power grid (6), the airflow regulation system (13) is adjusted based on the information (10). The airflow regulation system (13) includes: The position and / or orientation of at least one aerodynamically active surface of the airflow control system is moved relative to the airfoil portion of the rotor blades; The adjustment of the airflow regulation system (13) is also based on the operating point of the wind turbine. At the first operating point, where the change in the setting of the airflow regulation system has a greater impact on the lift of the rotor blade (15), the degree of change in the setting of the airflow regulation system (13) is less than that at the second operating point, where the change in the setting has a smaller impact on the lift of the rotor blade (15).

2. The method according to claim 1, further comprising adjusting the airflow control system (13) based on the information (10) during the duration of the disturbance.

3. The method according to claim 1 or 2, wherein, The grid disturbance includes a grid voltage drop, wherein the airflow adjustment system (13) is only executed when the grid voltage drop is greater than a threshold.

4. The method according to claim 3, wherein, The grid voltage drops to between 0% and 50% of the nominal grid voltage over a period of time between 0.1 seconds and 10 seconds.

5. The method according to claim 3, wherein, Due to the adjustment of the airflow regulation system (13), the greater the drop in the grid voltage, the more the aerodynamic lift and / or aerodynamic torque of the rotor blades (15) are reduced.

6. The method according to claim 1 or 2, wherein, Adjusting the airflow regulation system (13) includes reducing the aerodynamic lift of the rotor blades (15) and / or the aerodynamic torque acting on the rotor on which the rotor blades (15) are mounted.

7. The method according to claim 6, wherein, Before the disturbance, lift or torque is reduced by 10% to 70% respectively over a time span between 0.1 seconds and 3 seconds.

8. The method according to claim 6, wherein, Before the disturbance, within a time span between 0.5 seconds and 2 seconds, the lift or torque is reduced by 10% to 70% respectively.

9. The method according to claim 1 or 2, wherein, Adjusting the airflow regulation system (13) includes adjusting settings that depend on at least one of the following: At least one operating parameter (l) of the wind turbine; At least one external condition; At least one property of the power grid disturbance, The external conditions include at least one of the following: Wind speed, Wind turbulence, The operating parameters include at least one of the following: The pitch angle of the rotor blades; Rotational speed of the rotor; Power output.

10. The method according to claim 1 or 2, wherein, At least during part of the disturbance duration, it also includes: The pitch angle (α) of the rotor blades (15) is kept at least substantially constant; or The method further includes, during the duration of the disturbance: Based on the information, the pitch angle (α) of the rotor blade (15) is changed in order to reduce the lift of the rotor blade (15).

11. The method according to claim 1 or 2, wherein, If the power grid does not return to normal operation within a predetermined threshold time range, the method includes: Stopping the wind turbine (1) includes: Adjust the airflow control system (13) to achieve maximum airflow velocity; and / or To pitch the rotor blades (15); and / or Brake the rotor.

12. The method according to claim 1 or 2, wherein, Following the power grid disturbance, the power grid (6) returns to its nominal state, the method comprising: The airflow regulation system (13) is adjusted to increase the lift of the rotor blades (15) based on at least one of the following: Duration of power grid disturbance Re-establish the rate of power output (before the disturbance). Rotor speed, Pitch angle (α).

13. The method according to claim 12, wherein, After the power grid disturbance, the power grid (6) returns to the nominal grid voltage.

14. The method of claim 12, further comprising adapting the airflow conditioning system (13) to increase the pre-disturbance lift present prior to the disturbance.

15. The method according to claim 14, wherein, The adjustment of the airflow regulation system (13) to the pre-disturbance lift is performed within a time span of 0.1 seconds to 3 seconds.

16. The method of claim 14, wherein, The adjustment of the airflow regulation system (13) to the pre-disturbance lift is performed within a time span of 0.5 seconds to 2 seconds.

17. The method according to claim 1 or 2, wherein, Receiving information (10) regarding the power grid disturbance includes: Detecting the power grid disturbance; and The information (10) is derived based on the detected power grid disturbances.

18. The method according to claim 1 or 2, wherein, The airflow regulation system includes at least one of the following: Flaps (23); A spoiler (19a...19f) is arranged at the suction surface (14) of the rotor blade (15). The airflow regulation system (13) is different from the pitch angle changing system.

19. The method according to claim 18, wherein, The flap (23) is arranged at the trailing edge (16) of the rotor blade (15).

20. The method according to claim 18, wherein, The spoilers (19a……19f) are segmented spoilers.

21. A device (20) for operating at least one adjustable airflow conditioning system (13) of at least one rotor blade (15) of a wind turbine (1) connected to a public power grid (6) in the event of grid disturbance, the device comprising: The processor is adapted to derive control signals based on information about the power grid disturbance in order to adjust the airflow regulation system (13) during the duration of the disturbance. The adjustment of the airflow regulation system (13) includes: The position and / or orientation of at least one aerodynamically active surface of the airflow control system is moved relative to the airfoil portion of the rotor blades; The adjustment of the airflow regulation system (13) is also based on the operating point of the wind turbine. At the first operating point, where the change in the setting of the airflow regulation system has a greater impact on the lift of the rotor blade (15), the degree of change in the setting of the airflow regulation system (13) is less than that at the second operating point, where the change in the setting has a smaller impact on the lift of the rotor blade (15).

22. A wind turbine (1), comprising: Wind turbine nacelle (5); A rotor shaft (7) is housed in the nacelle, and a plurality of rotor blades (15) are mounted on the rotor shaft, at least one rotor blade having at least one adjustable airflow regulation system (13); as well as The device (20) according to claim 21 is connected to control the airflow regulation system.

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