Waking wind turbines from sleep

Abstract

A method of transitioning a wind turbine from a dormant state is provided, wherein a wind speed at the wind turbine is measured and the measured wind speed is compared to a wake-up threshold. If the wind speed exceeds the wake-up threshold, the wind turbine is transitioned to an active state. Prior to the comparison, the measured wind speed or the wake-up threshold is adjusted based on the result of at least one previous transition of the wind turbine from the dormant state.

Description

Technical Field

[0001] The present invention relates to the control of a wind turbine, and in particular to transitions between operating states of a wind turbine disconnected from an external grid. Background Art

[0002] Wind turbines operate in various operating states, where transitions between operating states are often dependent on the current wind speed. For example, when the wind speed is suitable for power production, the wind turbine may operate in a power production state, and when the wind speed is too low to maintain power production, the wind turbine may operate in an idle state.

[0003] During periods of disconnection from the external grid, such as during a national or regional utility grid failure, some wind turbines rely on self-generated backup power to sustain them. Such wind turbines may also have a dormant operating state in which multiple components or subsystems of the wind turbine are shut down to conserve power during very low wind speeds. Waking a wind turbine from such a dormant state may require a large amount of energy. If the wind speed is not yet sufficient to sustain a higher operating mode, the transition from the dormant state may fail, thereby wasting the energy consumed. Summary of the invention

[0004] A first aspect of the present invention provides a method for converting a wind turbine from a dormant state, in which the wind turbine is disconnected from an external power grid and powered by an internal power supply, in which the wind turbine does not provide power to non-essential systems but provides power to essential systems, the essential systems including a wind sensor at the wind turbine and a sub-control system to which the wind sensor is connected, the method comprising:

[0005] measuring wind speed using a wind sensor at the wind turbine to obtain a measured wind speed;

[0006] comparing the measured wind speed to a wake-up threshold; and

[0007] If the wind speed exceeds the wake-up threshold, transitioning the wind turbine from the dormant state to an active state, wherein the wind turbine remains disconnected from the external power grid and remains powered by the internal power source, wherein the wind turbine provides power to at least some non-essential systems;

[0008] Therein, prior to the comparison, the measured wind speed or the wake-up threshold is adjusted based on a result of at least one previous transition of the wind turbine from the dormant state.

[0009] In the dormant state as well as in the active state, the turbine is disconnected from the external grid (e.g. due to a grid failure or grid maintenance work). During this time, the wind turbine is powered by an internal power source, which is usually in the form of an onboard rechargeable battery. In the dormant state, the wind turbine has disconnected power to non-essential systems and only provides power to essential systems, in this way the limited power capacity of the internal power source can provide power to the wind turbine for an extended period of time. In the active state, the wind turbine "wakes up" other systems that utilize power from the internal power source.

[0010] The essential systems include at least a wind sensor and a sub-control system (sleep controller) for receiving the measured wind speed as input. The sub-controller can also switch the wind turbine from a sleep state to an active state, for example by operating a switch that enables the system to operate, thereby ensuring that other systems can use power. The sub-controller can also perform comparison steps and adjust wake-up thresholds and / or measure wind speed, as well as other controller tasks required during sleep and wake-up.

[0011] Essential systems may include other parts of a control system (hereinafter referred to as the entire control system). The control system may include multiple controller system components, including a main controller, multiple sub-controllers, and switches for an internal control communication system. In one embodiment, a portion of the control system components may be designated as essential systems, while a portion of the control system components may be designated as non-essential systems.

[0012] Essential systems may also include aviation and interior lights, elevator systems, and certain lubrication systems.

[0013] Non-essential systems may also include systems such as pitch systems and power production systems.

[0014] In some embodiments, if the at least one previous transition resulted in a failed transition from the sleep state, adjusting the measured wind speed or the wakeup threshold may include:

[0015] Reduce the measured wind speed or increase the wake-up threshold.

[0016] In some embodiments, if the at least one previous transition resulted in a successful transition from a dormant state, adjusting the measured wind speed or the wakeup threshold may include:

[0017] Increase the measured wind speed or lower the wake-up threshold.

[0018] In some embodiments, adjusting the measured wind speed or wake-up threshold may include:

[0019] determining a number of successful transitions and failed transitions among a plurality of previous transitions of the wind turbine; and

[0020] The measured wind speed or wake-up threshold is adjusted based on the number of successful transitions and / or failed transitions.

[0021] In some embodiments, the transitions in the plurality of previous transitions may include a predetermined number of most recent transitions of the wind turbine from a dormant state.

[0022] In some embodiments, adjusting the measured wind speed or the wake-up threshold may include decreasing the measured wind speed by a first adjustment amount or increasing the wake-up threshold by a first adjustment amount for each failed transition in the plurality of transitions; and / or increasing the measured wind speed by a second adjustment amount or decreasing the wake-up threshold by a second adjustment amount for each successful transition in the plurality of transitions. The first adjustment amount may be less than the second adjustment amount. The first adjustment amount and / or the second adjustment amount may be based on the magnitude of the success or failure of the corresponding transition.

[0023] In some embodiments, adjusting the measured wind speed or the wake-up threshold may include applying a previously determined adjustment amount to a corresponding one of the measured wind speed and the wake-up threshold.

[0024] In some embodiments, the result of a previous transition may be determined to be successful if the transition to the active state is achieved within a predetermined time.Alternatively or additionally, the result of a previous transition may be determined to be successful if the turbine's rotor speed or power generation exceeds a predetermined threshold.

[0025] The active state may be a state in which the wind turbine is generating power. In some embodiments, the active state may be a charging state of the wind turbine. The charging state may be considered a production state of the wind turbine in which power may be used to charge one or more power backup batteries of the turbine, but in which power is not supplied to the grid (e.g., due to grid unavailability). Thus, in the active state, the generated power is provided to an internal power source, typically in the form of one or more power backup batteries, to charge the internal power source.

[0026] In one embodiment, the active state is a power production state of the wind turbine, wherein the produced power is provided to a power consumer that is not an external grid or connected to an external grid. Such a power consumer may be, for example, an electrolysis plant, for example, for a power-to-X process using a wind turbine as a power source.

[0027] A second aspect of the present invention provides a wind turbine comprising:

[0028] Wind speed measurement systems; and

[0029] a controller configured to receive wind speed measurements from the wind speed measurement system;

[0030] Wherein, the controller is configured to execute the method of any embodiment of the first aspect.

[0031] A third aspect of the present invention comprises a computer program, the computer program comprising instructions, when the program is executed by a computer, the instructions cause the computer to perform the method of any embodiment of the first aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Embodiments of the present invention will now be described with reference to the accompanying drawings, in which:

[0033] Figure 1 An example of a wind turbine is illustrated in a schematic perspective view.

[0034] Figure 2 An embodiment of a control system in conjunction with elements of a wind turbine is schematically illustrated.

[0035] Figure 3 A method of transitioning a wind turbine from a dormant state is illustrated.

[0036] Figure 4 Alternative methods of transitioning a wind turbine from a dormant state are illustrated. DETAILED DESCRIPTION

[0037] Figure 1 An example of a wind turbine 100 is illustrated in a schematic perspective view. The wind turbine 100 includes a tower 102, a nacelle 103 at the apex of the tower, and a rotor 104 operably coupled to a generator housed in the nacelle 103. In addition to the generator, the nacelle also houses various components required to convert wind energy into electrical energy and various components required to operate, control and optimize the performance of the wind turbine 100. The rotor 104 of the wind turbine includes a central hub 105 and a plurality of rotor blades 106 protruding outward from the central hub 105. In the illustrated embodiment, the rotor 104 includes three rotor blades 106, but the number can vary. In addition, the wind turbine includes a control system. The control system can be placed in the nacelle or distributed in multiple locations within the turbine and communicated.

[0038] Wind turbine 100 may be included in a collection of other wind turbines belonging to a wind power plant (also referred to as a wind farm or wind farm) that functions as an electricity generation plant connected to an electrical grid via transmission lines. An electrical grid typically consists of a network of power generation stations, transmission circuits, and substations connected by a network of transmission lines that transmit electricity to loads in the form of end users and other customers of an electric utility company.

[0039] Figure 2An embodiment of a control system 200 is schematically illustrated with elements of a wind turbine. The wind turbine comprises rotor blades 106, which are mechanically connected to a generator 202 via a gearbox 203. In direct drive systems and other systems, the gearbox 203 may not be present. The electricity generated by the generator 202 is injected into a grid 204 via an electrical converter 205. The generator 202 and the converter 205 may be based on a full-size converter (FSC) architecture or a doubly fed induction generator (DFIG) architecture, but other types may also be used.

[0040] In the event of a disconnection of the external grid 204, in addition to the turbine being unable to provide power to the grid, the turbine is typically unable to obtain power from the grid, and therefore the wind turbine's power consuming systems need to be powered by an internal power source. The power required to power the onboard systems is distributed via an internal power system that connects the various power consumers to the internal power source. The internal power source is typically in the form of a battery.

[0041] The control system 200 includes a plurality of elements, including at least one main controller 220, the at least one main controller having a processor and a memory, so that the processor can perform computing tasks based on instructions stored in the memory. The control system may include a plurality of sub-controllers connected via an internal controller network, the controller network including switches for processing control signals. Typically, the wind turbine controller ensures that the wind turbine generates the requested power output level in operation. This is obtained by adjusting the pitch angle of the rotor blades 106 and / or the power extraction of the converter 205. To this end, the control system includes: a pitch system, which includes a pitch controller 207 using a pitch reference 208; and a power system, which includes a power controller 209 using a power reference 206. The wind turbine rotor includes rotor blades that can be pitched by a pitch mechanism. The rotor includes a separate pitch system that enables the rotor blades to be pitched individually, and may include a common pitch system that adjusts all pitch angles of all rotor blades simultaneously. The control system or elements of the control system may be placed in a power plant controller (not shown) so that the turbine can be operated based on externally provided instructions.

[0042] Control system 200 also includes a wind speed measurement system 210 that is configured to determine a current wind speed (e.g., free stream wind speed) experienced by wind turbine 100. Wind speed measurement system 210 may include or receive signals from a wind speed sensor, such as an anemometer on nacelle 103. Wind speed measurement system 210 may be incorporated into main controller 220 or any other controller or system of wind turbine 100 (hereinafter referred to as a dedicated sub-controller).

[0043] Various systems of the wind turbine 100, such as the electronics of the control system 200, require some power to operate. Power produced by the wind turbine 100 itself can be used to power the onboard systems. However, when wind speeds are low, the wind turbine 100 may not be able to produce enough power to maintain all of the onboard systems. In this case, most wind turbines can draw power from the grid 204. However, in some cases, the grid is not available, and instead, a local generator, such as a diesel generator, is used to generate the required power to directly power the systems or charge the batteries.

[0044] It is preferred to eliminate the need for a diesel engine and instead use onboard batteries to power the electronic devices, using the wind turbine 100 itself to charge the batteries when the wind speed is sufficient. When the grid 204 is not available, the wind turbine 100 can be placed in a charging state, in which electricity is generated and provided to the batteries. However, there are times when the wind speed is too low to even charge the batteries. In this case, the wind turbine can be placed in a dormant state, in which all systems except a selected set of essential systems are turned off or put into a low power / standby mode. The essential systems that remain can specifically include a wind speed measurement system to monitor the wind speed at the wind turbine 100. If the wind speed increases above a predetermined threshold, the wind turbine can be "woken up" - i.e., transitioned from a dormant state to an active state, such as a charging state (which depends on the wind speed, and whether the grid 204 is available).

[0045] Waking up the wind turbine 100 (including turning on dormant onboard systems) is energy intensive. If the transition to the active state fails, for example because sufficient rotor speed is not reached, a large amount of energy will be wasted. If too much energy is wasted, the wind turbine 100 may run out of backup power.

[0046] It has been recognized that a failed turbine wakeup may be caused by an incorrect wind speed reading. For example, the wind speed sensor of the wind turbine 100 may be inaccurate or poorly calibrated, or there may be a local disturbance in wind speed at the turbine that triggers an erroneous wakeup determination. Wind speed sensors can only be calibrated to a certain level, and may not be able to correct for local wind disturbances a priori, so these wind speed inaccuracies are difficult to avoid.

[0047] Figure 3 and Figure 4 Methods 300, 400 of transitioning a wind turbine 100 from a dormant state to an active state are illustrated that are intended to overcome these problems. The methods 300, 400 use the recent history of wake-up successes and failures for that particular wind turbine 100 to "correct" the measured wind speed and / or wake-up thresholds to reduce any positive and / or negative deviations in the turbine's wind speed measurements, thereby reducing the likelihood of a wake-up failure.

[0048] like Figure 3 As shown, method 300 begins at step 301 where a wind speed at wind turbine 100 is measured to obtain a measured wind speed.

[0049] The wind speed may be measured by a wind speed measurement system 210 of the wind turbine 100, which may be part of the control system 200 or may feed a signal indicative of the measured wind speed to the control system 200. The wind speed measurement system 210 may include, for example, a wind speed sensor (such as an anemometer) located on the nacelle 103 of the wind turbine 100. The wind speed measurement system 210 may include a controller configured to receive the signal from the wind speed sensor. The controller may be incorporated into another controller of the wind turbine 100 (such as a main controller 220).

[0050] In step 302, a wind speed adjustment (Δv) is determined based on the results of at least one previous transition of the wind turbine from a dormant state. In method 300, the adjustment is applied to the measured wind speed (v meas ). Alternatively, as shown in method 400, the adjustment amount may be applied to the wake-up threshold.

[0051] If the result of the previous transition was a failed transition from the dormant state, an adjustment (Δv) may be determined to reduce the measured wind speed (v meas ). This means that higher measured wind speeds are needed to trigger the transition to the active state, reducing the risk that wind speeds will not be sufficient to maintain the turbine in the active state.

[0052] Accordingly, if the result of the previous transition was a successful transition from the dormant state, an adjustment amount (Δv) may be determined to increase the measured wind speed (v meas ). This means that lower measured wind speeds would trigger a transition to the active state, potentially providing more time for the turbine to remain in the active state (e.g. providing more time to charge the batteries).

[0053] In some embodiments, the adjustment amount may be based on a number of previous transitions. In such embodiments, the determined total adjustment amount (Δv) may be based on the number of successful transitions (n success ) and the number of failed transitions (n fail For example, a first incremental adjustment (δv fail ), and a second incremental adjustment (δv success ), so that the total wind speed adjustment is equal to the sum of each of the first incremental adjustment and the second incremental adjustment (i.e., Δv = (δv success ×n success )-(δv fail ×nfail )).

[0054] The second incremental adjustment (δv success ) can be smaller than the first incremental adjustment amount (δv fail ). Such an arrangement may be preferred so that the adjustment amount tends to be more cautious. The first incremental adjustment amount (δv fail ) may be, for example, between 0.1 and 0.5 m / s, and may preferably be between 0.15 and 0.25 m / s. The second incremental adjustment amount (δv success ) may for example be between 0.05 and 0.3 m / s, and may preferably be between 0.05 and 0.15 m / s.

[0055] The number of transitions of a plurality of previous transitions may be limited to a predetermined number, for example between 3 and 10, or between 4 and 6. This limits the maximum size of the adjustment that may be applied, to prevent large scale changes to the measured wind speed.

[0056] The plurality of previous transitions may be a predetermined number of most recent transitions - i.e., the wake-up immediately preceding the current time. Alternatively, the adjustment amount may be based on an earlier set of transitions (such as the initial wake-up of the turbine after construction). The same adjustment amount may then be applied to each future wake-up attempt.

[0057] In an alternative embodiment, each incremental adjustment can be determined individually, rather than as a set value. For example, each incremental adjustment can be determined based on the magnitude of success or failure of the corresponding wake-up attempt. In particular, and as discussed in more detail below, determining whether the transition is successful can include comparing a performance characteristic (such as rotor speed or power) to a predetermined threshold. If the performance characteristic exceeds the predetermined threshold, the transition can be considered successful. In this case, each incremental adjustment can be based on the difference between the performance characteristic and the predetermined threshold for the corresponding wake-up attempt.

[0058] In some embodiments, the adjustment amount may be determined based only on failed wake-up attempts over multiple transitions, while ignoring successful wake-ups (thus effectively δv success =0).

[0059] In some embodiments, determining the adjustment may include retrieving a previously determined adjustment, such as looking up the value of the adjustment in a memory associated with wind turbine 100. The retrieved adjustment may then be used as the current adjustment, or the retrieved adjustment may be updated to take the most recent wakeup attempt into account.

[0060] Once the adjustment amount has been determined, the method proceeds to step 303. At step 303, the determined adjustment amount is applied to the measured wind speed to generate an adjusted wind speed.

[0061] The method then proceeds to step 304, where the adjusted wind speed is compared to the wake-up threshold. Specifically, it is determined whether the adjusted wind speed exceeds the wake-up threshold.

[0062] The wake-up threshold may be stored in a memory associated with wind turbine 100 (e.g., associated with control system 200). Adjusting the wind speed may include retrieving the wake-up threshold from the memory. The wake-up threshold may be a default setting (e.g., for all wind turbines of a particular type), or may be configured for a particular wind turbine 100 or location of a wind turbine.

[0063] If it is determined that the adjusted wind speed exceeds the wake-up threshold (by Figure 3 ), the method proceeds to step 306 where the wind turbine 100 transitions from the dormant state to the active state.

[0064] The active state is a state in which at least one dormant system is awakened. It can be a charging state in which wind turbine 100 generates power to power an onboard battery, but does not supply power to grid 204 (because grid 204 is unavailable). Transitioning wind turbine 100 to the active state can include, for example, determining which of a plurality of active states to transition to based on measured wind speed. The transitioning step can be performed by master controller 220, for example, by sending a signal to activate a subsystem of control system 200.

[0065] Transitioning to the active state may specifically include adjusting the pitch of the rotor blades 106 using the pitch controller 207. During the dormant phase, the pitch of the rotor blades 106 may be set to 90°. Transitioning the wind turbine 100 to the active state may include reducing the pitch angle of the rotor blades 106 to a wake-up pitch setting intended to facilitate turbine rotation.

[0066] The success or failure of the transition may then be recorded, such as stored in a memory associated with wind turbine 100, for future wind speed adjustments. As discussed above with respect to step 302, the stored adjustment value may be updated based on the transition to generate an adjustment amount that may be applied to future wind speed adjustments.

[0067] On the other hand, if the adjusted wind speed does not exceed the threshold, wind turbine 100 remains in the dormant state. Method 300 then returns to step 301 where a new wind speed is measured (eg, after a predetermined period of time).

[0068] It should be noted that step 302 of method 300 may be performed before step 301 - ie, the adjustment amount may be determined (or a previously determined value retrieved) before the current wind speed is measured.

[0069] The method 300 may also include determining whether one or more previous transitions from the dormant state were successful or failed. The wake-up transition may be considered successful if the transition to the active state is achieved within a predetermined time period. The predetermined time period may be between 2 minutes and 10 minutes. For example, where the active state is a charging state, the transition may be considered successful if continuous power is provided to the battery within a predetermined period of time. Alternatively or additionally, the transition may be considered successful if the rotor speed or the power generated by the wind turbine 100 reaches a corresponding threshold. The threshold may be based on a particular active state. For example, the threshold may be a portion of the maximum (e.g., rated) rotor speed / power for that operating state, such as 5%-10% of the maximum value.

[0070] In method 300, it is the measured wind speed that is adjusted and the adjusted wind speed is compared to the unadjusted wake-up threshold. However, equivalently, an adjustment amount may be applied to the threshold and the unadjusted measured wind speed may be compared to the adjusted threshold.

[0071] Figure 4 A method 400 of transitioning wind turbine 100 from a dormant state is illustrated in which a threshold value is adjusted instead of wind speed. Each step of method 400 is substantially similar to the corresponding step of method 300, but an adjustment is determined and applied to the threshold value.

[0072] In step 401 , wind speed is measured by a wind speed system of a wind turbine, as described with respect to step 301 .

[0073] At step 402 , an adjustment amount is determined based on a result of at least one previous transition of wind turbine 100 from a dormant state.

[0074] Since the adjustment amount in step 402 will be applied to the threshold, it is determined to increase the threshold in the event of a previous transition failure, and to decrease the threshold in the event of a previous transition success. In other words, the adjustment amount may have the same magnitude as determined in step 302, but with an opposite sign. Any of the methods of determining the threshold discussed in step 302 may be equally applied to step 402, although the sign of the determined adjustment amount or incremental adjustment amount is changed to account for the change from wind speed to the threshold.

[0075] At step 403, the adjustment amount is applied to the threshold to generate an adjusted threshold. The wake-up threshold to which the adjustment amount is applied may be a standard threshold of wind turbine 100 (eg, stored in a memory associated with wind turbine 100).

[0076] At step 404, the measured wind speed is compared to an adjusted threshold.

[0077] If the measured wind speed exceeds the adjusted wake-up threshold (given by Figure 4 If the decision step 405 in FIG. 4 is indicated), the method proceeds to step 406, in which the wind turbine 100 is transformed into an active state. Otherwise, the method returns to step 401, for example after a predetermined period of time.

[0078] As discussed with respect to method 300, the adjustment amount may be determined before measuring the wind speed. For example, the adjustment amount may be incrementally updated after each wake-up attempt and stored in memory. The stored adjustment amount may then be retrieved when a comparison with the wind speed is needed.

[0079] Any of the above methods may be incorporated into a computer program that, when executed by a processor (e.g., a processor of the main controller 220), causes the processor to perform the steps of the above method. The steps of the method may be stored on a computer-readable medium (e.g., a non-transitory computer-readable medium).

[0080] Although the invention has been described above with reference to one or more preferred embodiments, it will be appreciated that various changes or modifications may be made without departing from the scope of the invention as defined in the appended claims.

Claims

1. A method of converting a wind turbine from a dormant state, the wind turbine comprising a control system, the control system comprising a plurality of control system components, a portion of the control system components being designated as essential systems and a portion of the control system being designated as non-essential systems, the wind turbine being disconnected from an external power grid and powered by an internal power source in the dormant state, the wind turbine providing no power to the non-essential systems but providing power to the essential systems in the dormant state, the essential systems comprising a wind sensor at the wind turbine and a sub-control system to which the wind sensor is connected, and the non-essential systems comprising a pitch control system and an electric power production system, the method comprising: measuring wind speed using a wind sensor at the wind turbine to obtain a measured wind speed; comparing the measured wind speed to an arousal threshold; as well as If the wind speed exceeds the wake-up threshold, transitioning the wind turbine from the dormant state to an active state, wherein the wind turbine remains disconnected from the external power grid and remains powered by the internal power source, wherein the wind turbine provides power to at least some non-essential systems; Therein, prior to the comparison, the measured wind speed or the wake-up threshold is adjusted based on a result of at least one previous transition of the wind turbine from the dormant state.

2. The method according to claim 1, wherein: If the at least one previous transition resulted in a failed transition from the dormant state, adjusting the measured wind speed or wakeup threshold comprises: Reduce the measured wind speed or increase the wake-up threshold.

3. The method according to claim 1 or claim 2, wherein: If the at least one previous transition resulted in a successful transition from the dormant state, adjusting the measured wind speed or wake-up threshold comprises: Increase the measured wind speed or decrease the wake-up threshold.

4. The method according to claim 1, wherein: Adjusting the measured wind speed or the wake-up threshold comprises: determining a number of successful transitions and failed transitions in a plurality of previous transitions of the wind turbine; and The measured wind speed or wake-up threshold is adjusted based on the number of successful transitions and / or failed transitions.

5. The method according to claim 4, wherein: The transitions in the plurality of previous transitions include a predetermined number of most recent transitions of the wind turbine from the dormant state.

6. The method according to claim 4 or claim 5, wherein: Adjusting the measured wind speed or the wake-up threshold comprises: reducing the measured wind speed by a first adjustment amount or increasing the wake-up threshold by a first adjustment amount for each failed transition in the plurality of previous transitions; and / or The measured wind speed is increased or the wake-up threshold is decreased by a second adjustment amount for each successful transition in the plurality of previous transitions.

7. The method according to claim 6, wherein: The first adjustment amount is smaller than the second adjustment amount.

8. The method according to claim 6, wherein: The first adjustment amount and / or the second adjustment amount are based on a magnitude of success or failure of a corresponding previous transition.

9. The method according to claim 1 or claim 2, wherein: Adjusting the measured wind speed or the wake-up threshold includes applying a previously determined adjustment amount to a corresponding one of the measured wind speed and the wake-up threshold.

10. The method according to claim 1 or claim 2, wherein: If the transition to the active state is achieved within a predetermined time, the result of the previous transition is determined to be successful.

11. The method according to claim 1 or claim 2, wherein: If the turbine's rotor speed or power generation exceeds a predetermined threshold, the outcome of the previous transition is determined to be successful.

12. The method according to claim 1 or claim 2, wherein: The active state is a charging state of the wind turbine, wherein the produced electricity is provided to the internal power source to charge the internal power source.

13. The method according to claim 1 or claim 2, wherein: The active state is a power production state of the wind turbine, wherein the produced power is provided to power consumers which are not the external grid or are connected to the external grid.

14. A wind turbine comprising: Wind speed measurement system; as well as a controller configured to receive wind speed measurements from the wind speed measurement system; The controller is configured to execute the method according to any one of claims 1 to 13.

15. A computer program product comprising instructions which, when executed by a computer, cause the computer to perform the method according to any one of claims 1 to 13. 16 . A computer-readable storage medium having instructions stored thereon, which, when executed by a computer, cause the computer to execute the method according to claim 1 .

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