Mitigation of stall vibrations of a wind turbine

Abstract

A method of mitigating vibrations of a wind turbine (1) not receiving power from a utility grid (21) is described, the method comprising: receiving power from an energy storage system (13) of the wind turbine (1); detecting a wind direction (16) with the power received from the energy storage system; and adjusting an orientation of a rotor axis (18) of a rotor shaft (7) if a criterion is met, taking into account at least a relative orientation of the rotor axis (18) and the detected wind direction (16) and / or taking into account a vibration level.

Description

Technical Field

[0001] The present invention relates to a method and arrangement for mitigating vibrations, particularly stationary vibrations, in wind turbines that do not receive energy from a public power grid, and further to a wind turbine including said arrangement. Background Technology

[0002] A wind turbine comprises a wind turbine tower, a nacelle mounted on top of the tower, and a rotor shaft driving an electric generator within the nacelle. Multiple rotor blades are mounted on the rotor shaft. In the event of a grid failure or other circumstances, the wind turbine may not receive power from the grid to operate specific components, such as the yaw system and blade pitch system. When the wind turbine is not connected to the grid, it may idle and can be stopped, in particular, by using braking devices. In either case, the wind turbine is considered to be stationary.

[0003] When a wind turbine is not operating, stagnant vibrations of the wind turbine tower (such as vortex-induced vibrations) may occur at specific wind speeds during stagnant periods. These vibrations may occur at all rotor alignments, but the danger of these vibrations accumulating most often occurs when the rotor alignment is not aligned with the incoming wind direction, where rotor alignment is considered to be if the rotor plane is perpendicular to the incoming wind direction or equivalently, if the rotor axis is parallel to the wind direction.

[0004] Stagnation vibrations can occur at the rotor blades due to the unsteady aerodynamics of the airfoils at high angles of attack. During operation, the rotor blades of a wind turbine typically operate such that the airfoils, including the blades, interact with the wind at small angles of attack. During stagnation and at specific wind speeds, the wind may interact with these airfoils at large angles of attack. The unsteady aerodynamics associated with these large angles of attack typically lead to a reduction in aerodynamic damping, and in some cases, negative damping.

[0005] Traditionally, wind turbines in full operation align their rotors with the wind to reduce overall load and thus minimize the risk of vibration accumulation due to high blade damping. However, in the aforementioned off-grid scenario where the turbine is unable to track the wind direction and activate the yaw system to align the rotor and nacelle, the turbine may be in a situation where vibrations are likely to occur in the low-damping direction, posing a high risk of catastrophic vibration accumulation.

[0006] Traditionally, passive solutions have been used to avoid stationary vibrations in wind turbines off-grid conditions. These include energy damping solutions such as adjustable mass dampers and sloshing dampers. Solutions to prevent vibration accumulation have also been used, such as installing helical arrays or other flow disturbance arrangements around the tower and blades. These have been applied both as temporary measures and as permanent fixation solutions.

[0007] Another way to avoid stationary vibrations in off-grid conditions is through the inherent design of the wind turbine. The stationary positions of components (such as the pitch orientation of the blades when stationary) can be designed to minimize these vibrations. The structure itself can provide a certain amount of damping, just as the interaction between the base and the soil can provide damping. Similarly, the wind turbine can be designed such that the natural frequencies of the structure are not aligned with or matched with the dominant frequencies of the eddies or other forms of unstable aerodynamics generated by the wind turbine.

[0008] However, there are negative consequences associated with these passive solutions, as they almost always involve additional weight, complexity, or cost to the wind turbine.

[0009] Therefore, a method and corresponding arrangement structure may be needed that, in particular, mitigates the stall vibration of wind turbines that do not receive power from the public power grid, thereby preventing damage to wind turbine components and avoiding the aforementioned negative consequences. Summary of the Invention

[0010] This requirement can be met by the subject matter according to the independent claims. The dependent claims describe advantageous embodiments of the invention.

[0011] According to embodiments of the present invention, a method is provided for mitigating vibrations (particularly stationary vibrations) in wind turbines that do not receive power from a public power grid (particularly not connected to a public power grid), the method comprising: receiving power from an energy storage system of the wind turbine; using the power received from the energy storage system: detecting wind direction; and, taking into account at least the relative orientation of the rotor shaft and the detected wind direction and / or the vibration level, adjusting the orientation of the rotor shaft (particularly using a yaw system) to a favorable orientation relative to the detected wind direction if criteria are met.

[0012] Stagnant vibration can refer to all types of vibration that may occur when the device is stationary, such as the vibrations mentioned above.

[0013] Vortex-induced vibration (ViV) of towers is one type of vibration, but there are other types of vibration, such as the unstable aerodynamics of blade airfoils during severe stall.

[0014] A stationary wind turbine can refer to a wind turbine that is stationary with or without braking devices; that is, a stationary turbine can also be slowly (rotating) while idling.

[0015] The method can be performed or implemented by an arrangement structure according to an embodiment of the invention for mitigating vibrations of a wind turbine. The method can be implemented, for example, by a controller implementing the arrangement structure, which is either part of or an integral part of the wind turbine controller. The vibrations may specifically involve vortex-induced vibrations or vibrations involving oscillating movements of the tower, blades, and / or nacelle.

[0016] To avoid this, energy received from the energy storage system can be used to adjust the orientation of the rotor shaft axis relative to the detected wind direction, such as to a favorable orientation. For example, a favorable orientation can be obtained when the wind direction is at least approximately parallel to the rotor axis. A favorable orientation can be the desired orientation during periods of disconnection from the public power grid and during periods of wind turbine inactivity. Consequently, the rotor blades can also be pitched in a feathering position, such that the leading edge of the blades faces the wind.

[0017] Energy storage systems can be implemented in different configurations, as explained below. The energy storage system can supply electrical energy to a wind direction sensor and a yaw system configured to adjust the orientation of the rotor axis. The detected wind direction may be related to the actual (three-dimensional) wind direction or the wind direction projected onto a horizontal plane (and therefore two-dimensional).

[0018] The criteria are based on the relative (three-dimensional or two-dimensional projection) orientation of the rotor axis and the detected wind direction and / or vibration level. The criteria may also be based on other factors, as explained below. When a wind turbine is aligned so that the rotor axis is substantially aligned with or closer to the wind direction (at least projected onto a horizontal plane), not only vortex-induced vibrations in directions parallel to the rotor axis are reduced or mitigated, but other types of vibrations are also reduced or mitigated. This protects wind turbine components from potential damage. Furthermore, energy savings in the energy storage system are possible only when the aforementioned criteria are met when adjusting the rotor axis orientation. This provides effective damping and can mitigate or even prevent potentially dangerous vibrations in certain parts of the wind turbine, particularly including the tower, blades, and / or nacelle.

[0019] Yaw can be implemented not only when there is a certain yaw misalignment exceeding a certain threshold, but also when vibration is detected, for example, when it exceeds a vibration threshold. For example, if the vibration level accumulates, the wind turbine can yaw towards alignment between the rotor axis and the wind direction (e.g., towards a more favorable orientation).

[0020] This provides two layers of protection: by using orientation as part of the standard, vibration can be prevented from occurring, and by measuring the vibration and taking the vibration level into account, a response can be made when vibration occurs.

[0021] According to an embodiment of the invention, if the criteria are not met, the orientation of the rotor axis is not adjusted; and / or the criteria include the presence of an unfavorable orientation of wind direction relative to the rotor axis direction or the presence of accumulated vibration.

[0022] Therefore, the rotor shaft orientation can only be adjusted when the orientation of the rotor shaft relative to the detected wind direction would lead to adverse conditions, potentially allowing the induction of potentially dangerous vibrations, or when vibrations are detected. This allows for energy savings in the energy storage system for other, more dangerous situations or conditions.

[0023] An unfavorable wind orientation relative to the rotor axis can be such that it carries the risk of inducing nacelle and tower vibrations in directions aligned with or collinear with the rotor axis. The rotor axis orientation can be adjusted to eliminate this unfavorable orientation. Additionally, passive measures described above for mitigating existing vibrations can be applied.

[0024] According to an embodiment of the invention, the unfavorable orientation is defined by the angle α between the wind direction and the rotor axis direction, which satisfies the following: 120° > α > 60°, particularly 110° > α > 70°, and further particularly 100° > α > 80°.

[0025] Angle α can be defined as an angle that includes both the wind direction and the rotor axis direction, both projected onto a horizontal plane. Thus, a simple method for defining an unfavorable orientation is provided, which can be used in a simplified implementation of the method. An angle α of approximately 90° can be considered the most unfavorable orientation because, in this case, the wind direction is perpendicular to the rotor axis, which may be equivalent to the statement that the wind direction lies within the plane of the rotor blades. The plane of the rotor blades can be approximately perpendicular to the rotor axis. The angular range Δα_unfavorable that defines the unfavorable orientation can also depend on the wind speed that can be measured and accounted for in other embodiments.

[0026] In particular, the higher the wind speed, the wider the range of angle values ​​that limit unfavorable orientation. Therefore, embodiments of the present invention can set a specific range that limits unfavorable orientation based on wind speed.

[0027] According to an embodiment of the invention, a favorable orientation is defined by the absolute value α_absolute of the angle α between the wind direction and the rotor axis direction, satisfying the following condition: α_absolute < 70°, wherein if a favorable orientation exists, the orientation of the rotor axis is not adjusted. Thus, the range of favorable angles Δα_favorable can be defined.

[0028] When the angle between the wind direction and the rotor axis is approximately 0°, there may be an optimal orientation that minimizes vibrations, particularly vortex-induced vibrations caused by the oscillating movement of nacelle and tower components in a direction parallel to the rotor axis. If the rotor axis orientation is not adjusted when an optimal orientation exists, energy savings in the energy storage system can be achieved, especially in the event of a potentially unfavorable orientation in the future.

[0029] According to an embodiment of the invention, the method further includes detecting wind speed, wherein the criterion further includes the wind speed being within an unfavorable wind speed range, particularly depending on the wind direction relative to the rotor axis.

[0030] When an unfavorable orientation exists, higher wind speeds can potentially trigger or excite stronger and more dangerous vibrations. Specifically, when wind speeds are not within the unfavorable range, it is not necessary to adjust the rotor axis to a favorable orientation, thus conserving energy in the energy storage system. For example, if the wind speed is below a certain threshold, no adjustment to the rotor axis orientation is required even if the actual orientation is unfavorable. Whether the wind speed is within the unfavorable range can depend on the wind direction relative to the rotor axis. Therefore, it is also considered that wind speed can protect wind turbine components, even in modified ways, while conserving energy in the energy storage system.

[0031] According to embodiments of the invention, a plurality of unfavorable wind speed ranges are defined in association with different orientations of the wind direction relative to the rotor axis direction, wherein the criteria further include the presence of one of the unfavorable wind speed ranges associated with the respective orientation, wherein at least one of the unfavorable wind speed ranges is specifically defined as a wind speed greater than a threshold depending on the orientation.

[0032] For example, for a given orientation of the wind direction relative to the rotor axis, an associated wind speed range can be defined, representing unfavorable conditions, specifically those that might induce undesirable or unwanted vibrations. Thus, multi-dimensional logic can be implemented, involving both the rotor axis orientation relative to the wind direction and wind speed, to define under what conditions a readjustment of the rotor axis orientation will be performed. This allows for effective protection of wind turbine components and energy conservation in the energy storage system.

[0033] According to an embodiment of the invention, the standard further includes the rotor blades mounted on the rotor shaft being pitched in a feathered position or at least deviating from the feathered position by a maximum of 20°, particularly 10°, and further particularly 5°. The feathered position can be the position where the upstream edge of the rotor blades faces the wind when wind impacts the hub of the wind turbine on which the rotor blades are mounted in a direction parallel to the rotor axis. The feathered position can be the standard idling pitch position of the rotor blades. In the feathered position, the impacting wind (from the front) will cause restricted rotation of the rotor, also known as idling rotation. When in the feathered position, the wind turbine may be easily excited into vortex-induced vibrations because the damping of vibrations parallel to the rotor axis may be minimal. However, the feathered position must be used because it may be desirable or even necessary to keep the wind turbine stationary during disconnection from the public power grid.

[0034] According to embodiments of the invention, the energy storage system can supply electrical energy to one or more sensors capable of detecting motion, particularly vibrations involving oscillating movement of the tower, blades, and / or nacelle. The method further includes measuring the intensity of vibrations of a portion of the wind turbine, particularly at locations where the expected maximum vibration is expected, such as the top portion of the tower or the nacelle or blades, using one or more accelerometers and / or strain sensors and / or inclinometers. The criteria include vibration intensity greater than a vibration intensity threshold, particularly depending on the unfavorable wind speed range and / or unfavorable orientation. This embodiment can further conserve energy in the energy storage system, as vibration reduction may be necessary only when the measured vibration is considerably large or particularly above the vibration intensity threshold. In other cases, the vibration may be so small that even in unfavorable orientations and / or unfavorable wind speed ranges, readjustment of the rotor axis orientation may not be necessary. Thus, energy savings in the storage system can be achieved for more hazardous situations. The lower the vibration intensity threshold can be set, the higher the detected wind speed and / or the more unfavorable the rotor axis orientation relative to the wind direction.

[0035] If the rotor axis is not in an unfavorable orientation relative to the wind direction, but is not perfectly aligned with the wind direction (the most favorable orientation), then detecting vibrations exceeding a predetermined threshold can cause the rotor axis orientation to be adjusted to be more aligned with the wind direction.

[0036] Even if the yaw orientation is outside the "adverse zone," if vibration accumulation is detected, it may still be necessary to yaw closer to the wind direction. Thus, if the "adverse zone" is not large enough, it may lead to "fail-safe" behavior.

[0037] According to embodiments of the invention, measuring the intensity of vibration includes detecting the oscillating motion of the tower, blades, and / or nacelle, the method further comprising, in particular, filtering the measured intensity of the vibration to obtain the intensity of a stationary vibration. The oscillating motion of the tower, blades, and / or nacelle can be identified or detected by a pre-known or at least calculable frequency expected for such oscillation. The expected frequency of the oscillation can be calculated using the physical characteristics of the wind turbine tower, as well as the nacelle and rotor blades, particularly considering mass, material, geometry, and structural properties. The filtering may, in particular, include frequency filtering. The fundamental mode or one or more higher harmonic modes of the oscillation can be detected.

[0038] According to embodiments of the invention, the energy storage system includes a generator powered by an internal combustion engine, particularly a diesel motor, and / or a battery system and / or a fuel cell. Thus, conventionally available energy storage systems can be supported. The electrical energy provided by the energy storage system can be appropriately converted to a desired voltage and / or to a desired frequency, which is necessary for yaw systems and / or wind direction / speed detectors and / or vibration detection systems.

[0039] According to an embodiment of the invention, the method further includes determining the remaining energy capacity of the energy storage system; particularly, when the remaining energy capacity is less than an energy threshold, sending information about the remaining energy capacity to the operator. Specifically, based on the remaining energy capacity of the energy storage system, the aforementioned unfavorable or favorable orientations, as well as unfavorable angle ranges or wind speed ranges, can be selected. Therefore, for an increasingly smaller remaining energy capacity determined for the energy storage system, if it is in an increasingly unfavorable orientation or unfavorable situation, only the orientation of the rotor shaft can be adjusted. When information about the remaining energy capacity is sent to the operator, the operator can take steps to recharge the energy storage system before it no longer contains any energy.

[0040] According to embodiments of the invention, the method further includes recharging the energy storage system using energy provided by the rotating wind turbine rotor, particularly via the wind turbine generator, especially only when the remaining energy capacity is less than an energy threshold. When the energy storage system is recharged using energy provided by the rotating wind turbine rotor, the wind turbine may be prepared for potential future disconnection from the public power grid. Recharging can be implemented, for example, when the available power that the wind turbine can generate exceeds the power required by the wind turbine operator or the grid operator.

[0041] It should be understood that the features described, disclosed, explained, or provided for methods of mitigating wind turbine vibration (alone or in any combination) can also be applied, alone or in any combination, to the arrangement structure for mitigating wind turbine vibration according to embodiments of the present invention, and vice versa.

[0042] According to an embodiment of the present invention, an arrangement is provided for mitigating vibrations of a wind turbine that does not receive power from a public power grid. The arrangement includes: an energy storage system for the wind turbine; a wind direction sensor; particularly one or more vibration sensors; a yaw system; and a processor. The arrangement is adapted to supply power received from the energy storage system to: the wind direction sensor and / or the vibration sensor to detect wind direction and vibration level, respectively; and the yaw system to adjust the orientation of the rotor shaft when the processor determines that a criterion is met, taking into account at least the relative orientation of the rotor shaft and the detected wind direction or the vibration level.

[0043] The arrangement may be, for example, the software and / or hardware portion of a wind turbine controller and / or other components of the wind turbine. The processor may be, for example, the software or hardware portion of the wind turbine controller. The yaw system, as well as wind direction and vibration sensors, may be available or included in conventionally available wind turbines. The arrangement may include a switching system or switching capability to selectively supply electrical energy from the utility grid to the yaw system during normal operation or to supply energy from an electrical storage system to the yaw system during grid disconnection, particularly during wind turbine downtime.

[0044] Embodiments of the present invention can detect vibration and yaw, and / or pitch the blades (and / or rotate the rotor) until the vibration decreases.

[0045] Furthermore, according to embodiments of the present invention, a wind turbine including the arrangement structure explained above is provided.

[0046] The aspects defined above and other aspects of the present invention will become apparent from examples of embodiments described below and will be explained with reference to those examples. The invention will be described in more detail below with reference to examples of embodiments, but the invention is not limited thereto. Attached Figure Description

[0047] The accompanying drawings schematically illustrate a wind turbine according to an embodiment of the present invention. Detailed Implementation

[0048] The accompanying drawings schematically illustrate a wind turbine according to an embodiment of the present invention, which includes an arrangement structure for mitigating vibrations of the wind turbine according to an embodiment of the present invention, the arrangement structure being adapted to perform a method for mitigating vibrations of the wind turbine according to an embodiment of the present invention.

[0049] The wind turbine 1 illustrated in the accompanying drawings, according to an embodiment of the present invention, includes a nacelle 3 mounted on top of a wind turbine tower 5, wherein the wind turbine nacelle 3 houses a rotor shaft 7, and a plurality of rotor blades 9 are mounted on the rotor shaft 7. The wind turbine further includes an arrangement structure 11 according to an embodiment of the present invention for mitigating vibration 10 of the wind turbine. The arrangement structure 11 includes an energy storage system 13, a wind direction sensor 15 and one or more vibration sensors 22, a yaw system 17, and a processor 19.

[0050] The arrangement 11 is adapted to supply power received from the energy storage system 13 to the wind direction sensor 15 to detect wind direction, to one or more vibration sensors 22 to detect oscillating motions of the tower, blades, and / or nacelle (e.g., the level of oscillating motion), and to the yaw system 17 to adjust the orientation of the rotor axis 18 (about which the rotation shaft 7 rotates) when the processor 19 determines that a criterion is met, taking into account at least the relative orientation of the rotor axis 18 and the detected wind direction 16 and / or the vibration level. Thus, the energy storage system 13 provides energy to the wind direction sensor 15 and the yaw system 17 when the wind turbine 1 is disconnected from the utility grid 21 and, in particular, does not receive any energy from the utility system 21.

[0051] As shown in the accompanying drawings, during normal operation, the circuit breaker 23 connecting wind turbine 1 to common coupling point 25 (potentially several other wind turbines 26 connected to common coupling point 25) is opened, disconnecting wind turbine 1 from the public power grid 21 connected to common coupling point 25 via wind farm transformer 27. Wind turbine 1 includes a generator (not shown) driven by rotor shaft 7 and outputting AC power 29 during normal operation.

[0052] However, the method implemented by the arrangement structure 11 for mitigating the vibration 10 of the wind turbine is carried out during disconnection from the public power grid 21, particularly during periods of stagnation of the wind turbine 1 (i.e., when the rotating shaft 7 is not rotating or is rotating slowly / idling). This method avoids vibrations caused by the oscillating movement 10 of components involving the nacelle 3 and the tower 5 in a direction aligned with the rotor axis 18. Vibrations, particularly vortex-induced vibrations, are particularly excited in this direction 18 when the wind direction 16 is approximately perpendicular to the rotor axis 18. Furthermore, depending on the wind speed, vibrations along the rotor axis 18 are also excited when there is an unfavorable orientation of the wind direction relative to the rotor axis direction 18, particularly within the angular range Δα_unfavorable. When the wind direction 16 is within the angular range Δα_unfavorable, there is an unfavorable orientation of the wind direction 16 relative to the rotor axis direction 18, potentially exciting undesirable vibrations in the direction of the rotor axis 18. This angular range can be defined by an angle between the wind direction 16 and the rotor axis 18, for example, satisfying 110° > α > 70°. Depending on the wind speed, this unfavorable orientation range can be defined by other angular ranges. The favorable orientation range of wind direction 16 and rotor axis direction 18 can be expressed as Δα_favorable, which can be defined as a deviation of, for example, less than 70° between the wind direction and the direction of rotor axis 18.

[0053] Specifically, the wind direction sensor 15 may also be able to measure wind speed, and the decision to adjust the orientation of the rotor shaft 18 may also depend on the measured wind speed value (in addition to the relative orientation of the rotor shaft 18 and the wind direction 16). During the idling state of the rotor 7, and especially during periods of stagnation, the rotor blades 9 can be pitched so that the leading edge 31 is oriented in the leading plane and the trailing edge 33 is arranged in the trailing plane. This pitch position is also called the feathering position, thus generating a limited driving force on the rotor even when the wind impacts the leading plane.

[0054] During normal operation, the energy storage system 13 can be recharged using energy obtained from the rotating rotor, particularly provided by the generator of the wind turbine as the rotor 7 rotates.

[0055] Further details of embodiments of the present invention are described below. It should be understood that these details generally represent optional features that may not be included in all embodiments of the present invention.

[0056] The wind turbine 1 is designed with an energy storage system 13, which enables it to provide power to the auxiliary systems of the wind turbine in the event of a power outage in the power grid or network. This energy storage system provides power to at least the wind direction sensing system 15 and / or one or more vibration sensors, controllers or processors 19, and the system 17 for aligning the rotor plane (i.e., the yaw system).

[0057] In its simplest application, this energy storage system becomes active when the wind turbine loses grid power. However, in this off-grid situation, the wind direction sensing system determines the prevailing wind direction. The unfavorable rotor alignment range relative to the wind direction is included as information within the controller (e.g., in the electronic storage device of processor 19).

[0058] If the relative wind direction is close to an unfavorable alignment range, the controller commands the yaw system to adjust the rotor alignment. An unfavorable range can deviate from the dominant wind direction by + / - 70°. The unfavorable range can also be offset from the left or right side of the rotor plane to the wind, and can consist of multiple ranges. For example, alignments with 70° to 110° and -60° to -120° relative to the wind direction may be unfavorable.

[0059] Another embodiment of the invention also includes measuring wind speed. In this way, the controller, in conjunction with the relative wind direction, determines when the wind speed is within an unfavorable range. In this way, if the wind speed exceeds the range where stagnant vibrations may occur, energy is conserved. Similarly, the controller may include a set of dynamically unfavorable relative wind direction ranges, determined as a function of wind speed, in order to avoid stagnant vibrations and conserve energy in an optimal manner.

[0060] Another embodiment of the invention also includes measuring the vibration or motion of the wind turbine structure at any location using a single sensor or multiple sensors. In this way, the controller monitors the motion of the wind turbine to detect the early occurrence of stall vibrations. This monitoring can be combined with one or both of the previous embodiments, such that the rotor alignment is changed only upon detection of the early occurrence of stall vibrations. This further conserves energy while maintaining the wind turbine structure. The early occurrence of stall vibrations can be detected using accelerometers, strain gauges, inclinometers, or any other sensor technology capable of detecting motion of wind turbine components. In the simplest application, the sensor is capable of detecting vibrations at the top of the wind turbine tower, representing a first fundamental vibration mode. This motion detection involves using digital signal filtering to monitor only the frequencies associated with this vibration mode, and thus avoiding reactions to motions not associated with ViV.

[0061] According to the embodiment, only the vibration level is assessed and yaw alignment is adjusted accordingly, regardless of the criteria associated with "adverse areas". Wind direction may still need to be measured to align with the wind, but "favorable" and "adverse areas" may not be relevant for the decision to yaw or not yaw.

[0062] Another embodiment of the invention relates to one or more sensors placed at different locations for detecting a first fundamental vibration mode, as well as additional higher-order modes and vibrations of other wind turbine components, including the blades. In this manner, motion detection involves filtering for multiple frequencies.

[0063] The energy storage system 13 may consist of a diesel (or other fuel) powered generator configured to automatically turn on and off in the event of grid loss, or a battery storage system, fuel cell, or any other form of energy storage device. In its simplest application, the energy storage system has sufficient energy capacity to provide energy for a known duration while the wind turbine is off-grid. In this configuration, the energy storage system can be replenished by the wind turbine operator at regular intervals to avoid loss of available energy. This may involve refueling the diesel generator or replacing or recharging the battery.

[0064] Another embodiment of the invention includes providing information about remaining energy capacity to controller 19, and then providing this information to operator 20 via a communication system. When energy capacity (e.g., fuel level, battery charge status) is nearing depletion, a communication message is sent to operator 20 to provide information that energy must be replenished.

[0065] Another embodiment of the invention includes using the rotor of a wind turbine to provide electrical power for recharging an energy storage system. The energy storage system can be of the type capable of being replenished using electrical power, such as a battery system or fuel cell using hydrogen formed through electrolysis. In this way, the energy storage system provides power for the operation of the wind turbine in the absence of grid power. Once the wind turbine is operating, it can provide power back to the energy storage system to maintain the energy supply.

[0066] Another embodiment of the invention extends the previous embodiment by using a controller to monitor the remaining energy in the energy storage system and only operating the wind turbine when the energy supply is nearly exhausted.

[0067] Energy storage systems can be physically located inside, outside, or near wind turbines, or in locations separate from wind turbines and potentially serving multiple wind turbines simultaneously.

[0068] The following describes specific advantages and technical effects according to embodiments of the present invention:

[0069] By using an energy storage system to actively control rotor orientation to avoid stalling vibrations when off-grid, the number of passive damping or eddy current interference devices required is significantly reduced. This saves both cost and weight. Weight savings can then have a cascading effect, reducing the cost and weight of other structural components.

[0070] Energy storage systems can be used to provide power for off-grid scenarios, as well as to provide control strategies for operating such systems in an energy-efficient manner.

[0071] By taking into account the time period during which the turbine is disconnected from the grid, this allows the turbine to avoid severe situations within its existing design and system. This invention can significantly reduce the risk of structural damage due to stall vibrations during the lifespan of a wind turbine.

[0072] It should be noted that the term "comprising" does not exclude other elements or steps, and "a" or "an" does not exclude multiple. Furthermore, elements described in different embodiments may be combined. It should also be noted that reference numerals in the claims should not be construed as limiting the scope of the claims.

Claims

1. A method for mitigating vibration (10) of a wind turbine (1) that does not receive power from a public power grid (21), the method comprising: Power is received from the energy storage system (13) of the wind turbine (1); Utilizing the power received from the energy storage system: Detect wind direction (16). At least the relative orientation of the rotor shaft (18) and the detected wind direction (16) and the vibration level are taken into account. If the criteria are met, the orientation of the rotor shaft (7) of the rotor shaft (18) is adjusted, and Detect wind speed, The standard further includes the wind speed being within the unfavorable wind speed range. Among them, several unfavorable wind speed ranges are defined in relation to different orientations of the wind direction (16) relative to the rotor axis (18), and The criteria further include the presence of one of the unfavorable wind speed ranges associated with the corresponding orientation.

2. The method according to claim 1, in, If the criteria are not met, the orientation of the rotor shaft (18) will not be adjusted, and / or The criteria include an unfavorable orientation in which the wind direction (16) is relative to the rotor axis (18).

3. The method according to claim 2, wherein, The unfavorable orientation is defined by the angle α between the wind direction (16) and the direction of the rotor axis (18) satisfying the following: 120° > α > 60°。 4. The method according to any one of claims 1 to 3, wherein, The favorable orientation is determined by the angle α between the wind direction (16) and the rotor axis (18), which satisfies the following absolute value α_absolute constraint: α_absolutely < 70° If a favorable orientation exists, the orientation of the rotor shaft is not adjusted.

5. The method according to any one of claims 1 to 3, wherein, The standard further includes that the rotor blades (9) mounted on the rotor shaft (7) are pitched in a feathering position or at least deviated from the feathering position by up to 20°.

6. The method according to any one of claims 1 to 3, further comprising: Power is received from the energy storage system (13) for measuring the vibration intensity of one or more parts of the wind turbine (1), wherein the criterion includes a vibration intensity greater than a vibration intensity threshold.

7. The method according to claim 6, wherein, Measuring vibration intensity includes detecting the vibration level of the top of the wind turbine tower (5) and / or the nacelle (3) and / or one or more blades.

8. The method according to any one of claims 1 to 3, wherein, The energy storage system (13) includes a generator powered by an internal combustion engine, and / or a battery system and / or a fuel cell.

9. The method according to any one of claims 1 to 3, further comprising: Determine the remaining energy capacity of the energy storage system (13); Send information about remaining energy capacity to the operator.

10. The method according to any one of claims 1 to 3, further comprising: The energy storage system (13) is recharged using energy provided by the rotating wind turbine rotor shaft (7).

11. The method according to claim 1, wherein, Consideration of specific vibration levels includes: Consider vibration levels that are above the vibration threshold.

12. The method according to claim 3, wherein, The unfavorable orientation is defined by the angle α between the wind direction (16) and the direction of the rotor axis (18) satisfying the following: 110° > α > 70°。 13. The method according to claim 12, wherein, The unfavorable orientation is defined by the angle α between the wind direction (16) and the direction of the rotor axis (18) satisfying the following: 100° > α > 80°。 14. The method according to claim 1, wherein, The unfavorable wind speed range depends on the wind direction relative to the rotor axis.

15. The method according to claim 1, wherein, At least one of the unfavorable wind speed ranges is defined as wind speeds greater than a threshold.

16. The method according to claim 5, wherein, The standard includes that the rotor blades (9) mounted on the rotor shaft (7) are pitched in a feathering position or at least deviated from the feathering position by a maximum of 10°.

17. The method according to claim 16, wherein, The standard includes that the rotor blades (9) mounted on the rotor shaft (7) are pitched in a feathering position or at least deviated from the feathering position by a maximum of 5°.

18. The method according to claim 6, wherein, The measurements are performed using one or more accelerometers and / or strain sensors and / or inclinometers.

19. The method according to claim 6, wherein, One or more parts of the wind turbine (1) are blades, nacelles or the top of the tower (5).

20. The method according to claim 6, wherein, The vibration intensity threshold depends on the unfavorable wind speed range and / or unfavorable orientation.

21. The method of claim 7, further comprising: The measured intensity of the vibration is filtered to obtain the intensity of the stationary vibration.

22. The method according to claim 8, wherein, The internal combustion engine is a diesel motor.

23. The method according to claim 9, wherein, Sending information about remaining energy capacity includes: When the remaining energy capacity is less than the energy threshold, send information about the remaining energy capacity.

24. The method according to claim 10, wherein, Recharging the energy storage system (13) includes: The energy storage system (13) is recharged only when the remaining energy capacity is less than the energy threshold.

25. The method according to claim 10, wherein, Recharging the energy storage system (13) includes: The energy storage system (13) is recharged via a wind turbine generator.

26. An arrangement structure (11) for mitigating vibration (10) of a wind turbine (1) that does not receive power from a public power grid, the arrangement structure comprising: The energy storage system (13) of the wind turbine; Wind direction sensor (15); One or more vibration sensors; Yaw system (17); Processor (19). The arrangement is adapted to supply the power received from the energy storage system (13) to: The wind direction sensor (15) is used to detect wind direction (16) and wind speed; and The yaw system (17) adjusts the orientation of the rotor shaft (7) of the rotor shaft (18) to meet the criteria when the processor (19) considers at least the direction of the rotor shaft (18) and the relative orientation of the detected wind direction (16) and the vibration level. The standard further includes the wind speed being within the unfavorable wind speed range. Among them, several unfavorable wind speed ranges are defined in relation to different orientations of the wind direction (16) relative to the rotor axis (18), and The criteria further include the presence of one of the unfavorable wind speed ranges associated with the corresponding orientation.

27. A wind turbine (1) comprising the arrangement (11) according to claim 26.

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