Operating wind turbine with damaged yaw ring

Abstract

A method of operating a wind turbine, the wind turbine comprising a rotor and a yaw system, the yaw system comprising: a yaw ring and a pinion engaged with the yaw ring. The method includes: a) operating the yaw system to yaw the rotor in response to a wind direction change, thereby changing a rotor yaw direction; b) identifying the position of damaged or missing teeth of the yaw ring; c) determining a safe sector and a restricted sector based on the identified position of the damaged or missing tooth and the position of the pinion, where the pinion coincides with the position of the damaged or missing tooth when the rotor yaw direction is within the restricted sector; d) when the yaw direction of the rotor is in the safe sector, generating electricity by using the rotor; and e) disabling or otherwise modifying the operation of the wind turbine to substantially avoid power generation by the rotor if the rotor yaw direction is within the restricted sector.

Description

Technical Field

[0001] This invention relates to a method for operating a wind turbine, a control system configured for operating a wind turbine, and a wind turbine including such a control system. Specifically, this invention relates to a method and related equipment for operating a wind turbine including a yaw ring with damaged or missing teeth. Background Technology

[0002] A wind turbine typically comprises a wind turbine tower mounted on a base or similar structure, anchored to the ground or seabed or possibly floating, extending in a generally vertical longitudinal direction. A nacelle carrying a rotor with one or more wind turbine blades is typically mounted on the wind turbine tower via a yaw system. The yaw system allows the nacelle to perform yaw motion, i.e., rotational motion relative to the wind turbine tower about an axis of rotation substantially coinciding with the longitudinal direction of the wind turbine tower. This allows the rotor to be appropriately oriented relative to the wind direction, and also as the wind direction changes.

[0003] Yaw systems can be active, where the cabin actively yaws via a yaw actuator (e.g., in response to wind direction measurements). Alternatively, yaw systems can be passive, allowing the cabin to passively follow the wind direction. This is sometimes referred to as "free yaw." As another alternative, yaw systems can be of the type that operate sometimes actively and sometimes passively.

[0004] US10634119B2 discloses a method for operating a yaw assembly of a wind turbine, the yaw assembly including a yaw ring and a plurality of yaw drive units. Each yaw drive unit includes a pinion gear configured to mesh with the yaw ring. The method includes the steps of: identifying damaged teeth on the yaw ring; providing damage descriptor parameters to a yaw drive controller; and controlling the yaw drive units based on the damage descriptor parameters to reduce the force exerted by their pinions on the damaged teeth.

[0005] WO2021 / 209110A1 discloses a method for controlling a wind turbine yaw system. The yaw system includes a toothed yaw ring connected to one of the tower or nacelle, and an active yaw mechanism including at least one yaw actuator connected to the other of the tower or nacelle. Each yaw actuator includes a pinion configured to mesh with the toothed yaw ring and a drive mechanism configured to drive the pinion. When wind speed and / or turbulence and / or wind-induced loads acting on the wind turbine exceed a predetermined threshold, the active yaw mechanism is decoupled by decoupling at least one drive mechanism of at least one yaw actuator from the yaw system. Subsequently, the nacelle is allowed to perform yaw motion relative to the tower via free yaw. Summary of the Invention

[0006] A first aspect of the invention provides a method of operating a wind turbine, the wind turbine including a rotor and a yaw system, the yaw system including a yaw ring and a pinion meshing with the yaw ring, the method comprising: a) operating the yaw system to yaw the rotor in response to a change in wind direction, thereby changing the rotor yaw direction; b) identifying the location of damaged or missing teeth on the yaw ring; c) determining a safe sector and a restricted sector based on the identified locations of the damaged or missing teeth and the location of the pinion, wherein the location of the pinion coincides with the location of the damaged or missing teeth when the rotor yaw direction is within the restricted sector; d) generating electricity using the rotor when the rotor yaw direction is within the safe sector; and e) disabling or otherwise modifying the operation of the wind turbine to substantially avoid generating electricity from the rotor when the rotor yaw direction is within the restricted sector.

[0007] Optionally, the wind turbine also includes a yaw function in step a) to automatically control the yaw system to yaw the rotor in response to a change in wind direction; and step e) includes disabling or otherwise modifying the yaw function in response to a change in wind direction from a safe sector to a restricted sector to prevent the yaw system from changing the rotor yaw direction from a safe sector to a restricted sector.

[0008] Optionally, step e) includes: in response to a change in wind direction from a safe sector to a restricted sector, shutting down or otherwise modifying the operation of the wind turbine so that the rotor generates virtually no electricity.

[0009] Optionally, the pinion is one of a set of adjacent pinions that mesh with the yaw ring. The restricted sector and the safe sector are determined based on the position of the set of adjacent pinions, and when the rotor yaw direction is within the restricted sector, the position of the set of adjacent pinions coincides with that of the damaged or missing teeth.

[0010] Optionally, the yaw system has two or more pinions, each pinion meshing with a yaw ring at a corresponding position; step b) includes: determining two or more safety sectors and two or more restricted sectors based on the identified positions of damaged or missing teeth and the positions of these pinions, wherein the safety sectors and restricted sectors alternate, and when the rotor yaw direction is within each restricted sector, the position of the corresponding pinion coincides with the position of the damaged or missing tooth; and step e) includes: disabling or otherwise modifying the operation of the wind turbine to substantially prevent rotor power generation when the rotor yaw direction is within a restricted sector.

[0011] Optionally, step e) includes: in response to a change in wind direction from one of the safe sectors to one of the restricted sectors, disabling or otherwise modifying the yaw function to prevent the yaw system from changing the rotor yaw direction from one of the safe sectors to one of the restricted sectors.

[0012] Optionally, the method further includes: in response to a change in wind direction from a first safe sector to a second safe sector, operating a yaw system to change the rotor yaw direction from the first safe sector to the second safe sector, wherein the rotor yaw direction passes through an intermediate restricted sector; wherein, when the rotor yaw direction passes through the intermediate restricted sector, the position of one of the pinions coincides with the position of a damaged or missing tooth.

[0013] Optionally, step e) includes: in response to a change in wind direction, shutting down or otherwise modifying the operation of the wind turbine such that the rotor generates virtually no electricity when the rotor yaws through one of the intermediate restricted sectors.

[0014] Optionally, step d) includes: generating electricity using the rotor when the rotor yaw direction is within the first safety sector; and the method further includes: generating electricity using the rotor when the rotor yaw direction is within the second safety sector.

[0015] Alternatively, shutting down or otherwise modifying the operation of a wind turbine so that the rotor generates virtually no electricity includes changing the pitch angle of one or more blades of the rotor.

[0016] Optionally, the restricted sector is determined in step c) by identifying the angular range in which the position of the pinion coincides with the position of the damaged or missing tooth; and by adding a buffer at each edge of the angular range.

[0017] Optionally, the wind turbine further includes a yaw function in step a) to automatically control the yaw system to yaw the rotor in response to a wind direction change exceeding a threshold; and the method further includes increasing the threshold in response to the rotor yaw direction approaching the edge of a safety sector.

[0018] Another aspect of the present invention provides a control system configured to operate a wind turbine by means of the methods described in the foregoing aspects.

[0019] Another aspect of the present invention provides a wind turbine comprising: a rotor; a yaw system including a yaw ring and a pinion meshing with the yaw ring; and a control system according to the foregoing aspect.

[0020] A computer program product is provided, comprising software code adapted to operate a wind turbine when executed on a data processing system, the computer program product being adapted to perform the method of the first aspect. Attached Figure Description

[0021] Embodiments of the present invention will now be described with reference to the accompanying drawings, in which: Figure 1 A wind turbine was shown; Figure 2The implementation of the control system and the components of the wind turbine are illustrated schematically. Figure 3 The yaw system was displayed; Figure 4 This demonstrates how to operate a wind turbine; Figure 5 This shows the rotor yaw direction at the boundary between the restricted sector and the safe sector; Figure 6 This shows the rotor yaw direction at another boundary between the restricted sector and the safe sector; Figure 7 Showing Figure 4 More details on the method; Figure 8 It shows an example of how the yaw function can operate; Figure 9 It shows a modified example of how the yaw function can be operated; Figure 10 Examples of damaged sectors are shown; and Figure 11 The yaw ring with three expanded restricted sectors is shown. Detailed Implementation

[0022] Figure 1 A wind turbine 1 is shown in a schematic perspective view. The wind turbine 1 includes a tower 2 and a rotor-nacelle assembly (RNA) at the top of the tower 2. The RNA includes a nacelle 3 and a rotor 4, the rotor 4 being operatively coupled to a generator housed within the nacelle 3. In addition to the generator, the nacelle 3 also houses various components required for converting wind energy into electrical energy, as well as various components required for operating and controlling the wind turbine 1.

[0023] Rotor 4 includes a central hub and multiple blades 5 projecting outward from the central hub. In the wind turbine 1 shown, rotor 4 includes three blades 5, but the number can be varied. The rotor rotates about its rotor axis and generates thrust aligned with the rotor axis. The yaw angle of the rotor axis defines the rotor yaw direction, which in turn... Figure 1 and Figure 3 The arrow 35 in the middle indicates the direction of the thrust.

[0024] Figure 2 The schematic illustration shows an implementation of the control system 20 together with the components of the wind turbine 1. The rotor is mechanically connected to the generator 7 via a gearbox 9 (there is no gearbox in a direct-drive system). The electricity generated by the generator 7 is injected into the power grid 24 via an electrical converter 25. The generator 7 and converter 25 can be based on a full-power converter (FSC) architecture or a doubly-fed induction generator (DFIG) architecture, but other types may also be used.

[0025] The control system 20 includes multiple components, including at least one main controller 10 with a processor and memory, enabling the processor to perform computational tasks based on instructions stored in the memory. Typically, the main controller 10 ensures that the wind turbine produces the requested power output level during operation. This is achieved by adjusting the blade pitch, or pitch angle, and / or the power extraction of the converter 25. For this purpose, the control system 20 includes: a pitch system comprising a pitch controller 27 using a pitch reference signal 28; and a power system comprising a power controller 29 using a power reference signal 26. The rotor blades 5 can change their pitch via a pitch mechanism. The rotor includes individual pitch systems capable of individually adjusting the pitch angle of the rotor blades 5, and may include a common pitch system that simultaneously adjusts all pitch angles on all rotor blades. The control system 20 or its components may be connected to a power plant controller (not shown) or other control systems to receive externally provided instructions.

[0026] The wind turbine 1 also includes a yaw system 30, which is configured to rotate RNA 3, 4 about a vertical yaw axis to control the rotor yaw direction 35.

[0027] An input device 11, such as a keyboard, may be provided to enable the user to input information into the main controller 10 or any other element of the control system 20.

[0028] Figure 3 Some components of the yaw system 30 are shown from a top-down angle aligned with the vertical yaw axis. The yaw system 30 includes a toothed yaw ring 31 mounted to the tower 2. The yaw ring 31 can act as a sliding bearing between the nacelle 3 and the tower 2, and transmit forces from the nacelle 3 to the tower 2.

[0029] The yaw system 30 also includes an active yaw mechanism comprising eight yaw actuators, each connected to the main frame of the nacelle 3. Each yaw actuator includes a pinion gear meshing with a yaw ring 31. Each pinion gear is connected to a corresponding yaw motor via a yaw gear.

[0030] Figure 3 An exemplary yaw drive is shown, comprising a vertically mounted pinion 36 driven by a horizontally mounted yaw motor 37 and a yaw gear 38. For Figure 3 The remaining yaw drives are shown only as pinions, while the yaw motor and yaw gear are shown separately for clarity. Figure 3 Omitted in .

[0031] In this example, the yaw ring 31 is bolted to the top flange of the tower 2 and therefore does not rotate with the cabin. In other embodiments, the yaw ring 31 may rotate with RNA3, 4 instead of the yaw actuator.

[0032] In this example, the teeth of the yaw ring 31 are on the outside of the yaw ring 31, but in other embodiments, the teeth may be on the inside.

[0033] The eight pinions are arranged into three adjacent groups: a large group 32 consisting of four pinions (including exemplary pinion 36); a first small group 33 consisting of two pinions; and a second small group 34 consisting of two pinions. The large group 32 is aligned with the rotor axis, as shown below. Figure 3 The direction indicated by the middle arrow 35. Note that the number and grouping of the pinions may differ. Figure 3 Example. The yaw system 30 may also have only one pinion, but preferably multiple pinions. The known position of the pinions relative to the rotor yaw direction 35 is stored in memory.

[0034] Figure 3 The yaw system 30 can operate in either active or passive mode. In active mode, the yaw system 30 performs yaw motion by operating the yaw motor, thereby rotating the pinions 32-34. This, in turn, results in relative rotational motion between the toothed yaw ring 31 and the yaw actuator, and thus between the tower 2 and RNAs 3, 4.

[0035] During active mode, the yaw function 15 automatically controls the yaw system 30 to yaw RNA 3 and 4 in response to changes in wind direction.

[0036] During wind turbine operation, one or more teeth of the yaw ring 31 may be damaged or completely broken (leaving missing teeth). The most vulnerable area is the region that is in the same direction as the thrust generated by the rotor, which acts in the direction of arrow 35. Figure 3 Damaged tooth 39 is shown in this area.

[0037] This example shows only a single damaged tooth 39, but sometimes multiple teeth may break or be damaged simultaneously. In such cases, multiple broken / missing teeth are usually adjacent to each other. The following discussion will refer to a single damaged tooth 39, but the invention is equally applicable to cases with multiple damaged teeth, or one or more missing teeth.

[0038] If the rotor 4 generates electricity when the damaged tooth 39 is engaged by the pinion, the tooth 39 may be further damaged. Undesirable oscillations may also occur in this case. Figure 4 An example of a method for operating a wind turbine 1 to avoid such problems is given.

[0039] Figure 4 The method uses various secure sectors and restricted sectors. Figure 3An example of such sectors is given based on the location of the damaged tooth 39 and the known locations of the pinion sets 32-34. In this example, there are three safe sectors 43-45 and three restricted sectors 40-42. Restricted sectors 40-42 have boundaries 40a, 40b; 41a, 41b; 42a, 42b that are adjacent to safe sectors 43-45.

[0040] Figure 4 Most of the steps are performed by the main controller 10 and / or the yaw function 15, each including a computer program product containing software code adapted to operate the wind turbine when executed on the data processing system. Figure 4 Certain steps of the method.

[0041] In step 100, the yaw function 15 automatically controls the yaw system 30 to yaw the rotor 4 in response to a change in wind direction, and the generator 7 generates electricity to inject into the power grid 24.

[0042] The process of step 100 continues until a broken or missing tooth is identified in step 101, for example, by a decline in the performance of the wind turbine. In step 102, the location of the broken or missing tooth is typically identified by visual inspection of the yaw ring 31. This location can be input to the main controller 10 via input device 11 or in any other way.

[0043] Next, in step 103, based on the identified locations of damaged or missing teeth and the known locations of pinions, the main controller 10 determines various safe sectors and restricted sectors and stores them in memory. Figure 3 An example is given based on the input location of the damaged tooth 39 and the known locations of the pinion sets 32-34. Safe sectors 43-45 alternate with restricted sectors 40-42.

[0044] Each restricted sector 40-42 corresponds to a set of 32-34 in the adjacent pinion. For example... Figure 3 As shown, when the rotor yaw direction 35 is within the restricted sector 40, the pinion gear set 32 ​​coincides with the position of the damaged tooth 39. When the rotor yaw direction 35 is within the restricted sector 41, the pinion gear set 34 coincides with the position of the damaged tooth 39. When the rotor yaw direction 35 is within the restricted sector 42, the pinion gear set 33 coincides with the position of the damaged tooth 39.

[0045] When the rotor yaw direction 35 is within one of the safety sectors 43-45, no pinion coincides with the position of the damaged tooth 39. Figure 5 An example is given where the rotor yaw direction 35 is at the boundary 40b between the restricted sector 40 and the safe sector 43. At this point, the pinion gear set 32 ​​has just left the broken tooth 39. Figure 6An example is given where the rotor yaw direction 35 is at the boundary 41a between the restricted sector 41 and the safe sector 43.

[0046] In step 104, it is determined whether the rotor yaw direction 35 is currently within the restricted sector, for example, if Figure 3 As shown, the rotor yaw direction 35 is within the restricted sector 40. If not, the process jumps to step 109, which will be described below. If yes, in step 105, the main controller 10 commands the yaw system 30 to yaw to the nearest safe sector, such as safe sector 43.

[0047] In step 106, the yaw function 15 is disabled or otherwise modified to prevent the yaw system 30 from changing the rotor yaw direction 35 from the safe sector 43 back to the restricted sector 40.

[0048] In step 106, the wind turbine is also shut down or otherwise modified so that the rotor 4 and generator 7 are essentially not generating electricity. This modification can be performed by changing the pitch of one or more blades 5 of the rotor 5, for example, by "feathering" the blades so that they do not generate forces that would cause the rotor to rotate.

[0049] The wind turbine remains off until the wind direction changes to a safe sector and remains so for a preset time period. When this is determined in step 107, the previous step 106 is reversed in step 108 (i.e., the wind turbine starts and the yaw function 15 is activated). In step 109, the yaw function 15 commands the yaw system 30 to yaw the rotor into the wind, and since the rotor direction is now within the safe sector, the rotor 4 and generator 7 generate electricity to inject into the power grid 24.

[0050] This power generation continues until a change in wind direction from the safe sector to the restricted sector is detected at step 110. In response to this change in wind direction, the process proceeds to step 106, where the yaw function 15 is disabled or otherwise modified to prevent the yaw system 30 from changing the rotor yaw direction 35 from the safe sector to the restricted sector. In step 106, the wind turbine is also shut down or otherwise modified so that the rotor generates virtually no power. As previously described, this modification in step 106 can be performed by changing the pitch of one or more blades 5 of the rotor 5.

[0051] In short, by following Figure 4 In the process, when the rotor yaw direction 35 is within the safe sector, the wind turbine generates electricity using the rotor in step 109; and in step 106, the operation of the wind turbine is disabled or otherwise modified to substantially prevent the rotor from generating electricity when the rotor yaw direction 35 is within the restricted sector.

[0052] In the example above, the wind turbine is shut down and the yaw function is disabled in step 106. In alternative implementations, only one of these functions may be performed in step 106. That is, the wind turbine may be shut down in step 106 without disabling the yaw function, or the yaw function may be disabled in step 106 without shutting down the wind turbine. These alternative implementations are less preferred, but still achieve the goal of substantially avoiding rotor power generation when the rotor yaw direction 35 is within a confined sector.

[0053] Figure 7 Showing Figure 4 Further details of the process in the event that the wind direction changes from the first safety sector (e.g., safety sector 43) to the second safety sector (e.g., safety sector 44). When such a change is detected in step 200, the wind turbine is shut down or otherwise modified in step 201 so that the rotor essentially does not generate electricity. This modification can be performed by changing the pitch of one or more blades 5 of the rotor 5, for example, by "feathering" the blades so that they do not generate forces that would cause the rotor to rotate.

[0054] Then, in step 202, yaw function 15 operates yaw system 30 to change rotor yaw direction 35 from the first safety sector to the second safety sector. During this process, rotor yaw direction 35 passes through an intermediate restricted sector (e.g., restricted sector 41). When rotor yaw direction 35 passes through restricted sector 41, the position of pinion gear 34 coincides with the position of the damaged tooth 39, but the rotor generates virtually no electricity during this process. This avoids further damage to the damaged tooth 39 and also avoids undesirable oscillations that might occur when the damaged tooth 39 is engaged by the pinion gear.

[0055] After the rotor reaches the second safety sector in the yaw direction 35, the wind turbine is started in step 203 by reversing step 201 (e.g., by changing the blade pitch angle).

[0056] If the wind direction does not change from the first safety sector to the second safety sector in step 200, then in step 204, the yaw function 15 commands the yaw system 30 to yaw the rotor in the wind within the current safety sector, and since the rotor yaw direction 35 is still within the safety sector, the generator 7 continues to generate power and inject it into the grid 24.

[0057] Figure 8An example of how yaw function 15 can operate to automatically control yaw system 30 in the above process is shown. Yaw function 15 measures yaw error, which is the angle between rotor yaw direction 35 and wind direction. When rotor yaw direction 35 is parallel to wind direction, yaw error is zero, and if wind direction changes, a non-zero yaw error is introduced. When this yaw error increases to exceed a threshold (e.g., 6 degrees) in step 300, then in step 301, yaw function 15 causes yaw system 30 to actively yaw rotor until yaw error returns to zero.

[0058] Figure 9 A modified example of how the yaw function 15 can operate to automatically control the yaw system 30 when the rotor yaw direction 35 is within the safety sector is given.

[0059] In step 400, it is determined whether the rotor yaw direction 35 is close to the edge of the safety sector, for example, within a certain degree from the edge. If not, the yaw function 15 automatically controls the yaw system in steps 401 and 402 to yaw the rotor into the wind in response to a wind direction change exceeding a 6-degree threshold. In other words, the yaw error threshold is set to 6 degrees. If yes, the threshold is increased in step 403 (e.g., increased to 10 degrees). Then, the yaw function 15 automatically controls the yaw system in steps 403 and 402 to yaw the rotor in response to the yaw error rising above the increased threshold. Figure 9 This method enables wind turbines to maintain power generation for longer periods when the wind direction is at or near the boundary between restricted and safe sectors.

[0060] If the wind direction changes and enters a restricted sector, the wind turbine is shut down and the yaw function is disabled in step 106, as described in the process above.

[0061] Based on the position of the pinion around the yaw ring. Figure 3 The image shows three restricted sectors 40-42, in which the damaged yaw tooth 39 can engage with the pinion.

[0062] For example, a large restricted sector 40 may have an angle range of 50 degrees between its edges 40a and 40b, while smaller restricted sectors 41 and 42 may each have an angle range of 15 degrees between their respective edges 41a and 41b and 42a and 42b.

[0063] Optionally, a buffer can be added at each edge of the restricted sector. If a total of 10 degrees of buffer is added (5 degrees at each edge), the size of the restricted sector 40-42 can be increased to have the following increased angular range. : Based on the increased angle range described above, the total maximum range of the safety sector is: These maximum secure sectors are as follows: Based on the number of damaged teeth and the total number of teeth in yaw ring 31, the angle of the damaged sector can be calculated. Above this angle, a standard + / - 6 degree yaw error threshold can be considered to obtain the angle of the damaged sector. As shown below: Figure 10 The damaged sector (angle) is given when there are two adjacent damaged teeth at 60°. Examples of ).

[0064] Within the secure sector, Figure 10 Damaged sectors should not overlap with any restricted sectors. Therefore, the angular range of safe sectors may be reduced compared to the maximum safe sector as follows: Figure 11 The diagram shows the yaw ring 31 and its three expanded restricted sectors 140, 141, and 142, which are expanded according to the principles described above. The expanded restricted sectors 140, 141, and 142 alternate with the three reduced safe sectors 143, 144, and 145. The boundaries between sectors 140 and 145 are indicated by solid lines.

[0065] Each expanded restricted sector 140-142 includes Figure 3 One of the restricted sectors 40-42, plus a pair of 5-degree buffer sectors, and an angle range of... A pair of sectors of 2.

[0066] As described above, when the rotor yaw direction is 35°... Figure 3 When within any restricted sector of 40-42, the pinion coincides with the location of a damaged or missing tooth. For Figure 11 The same applies to the expanded restricted sectors 140-142, but with increased error margin.

[0067] Although the invention has been described above with reference to one or more preferred embodiments, it should be understood 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 operating a wind turbine, the wind turbine including a rotor and a yaw system, the yaw system including: The method includes: a) operating the yaw system to yaw the rotor in response to a change in wind direction, thereby changing the rotor yaw direction; b) identifying the location of damaged or missing teeth on the yaw ring; c) determining a safe sector and a restricted sector based on the identified locations of the damaged or missing teeth and the location of the pinion, wherein the location of the pinion coincides with the location of the damaged or missing teeth when the rotor yaw direction is within the restricted sector; d) generating electricity using the rotor when the rotor yaw direction is within the safe sector; and e) disabling or otherwise modifying the operation of the wind turbine to substantially avoid generating electricity from the rotor when the rotor yaw direction is within the restricted sector.

2. The method according to claim 1, wherein, The wind turbine also includes a yaw function in step a) to automatically control the yaw system to yaw the rotor in response to a change in wind direction; and step e) includes disabling or otherwise modifying the yaw function in response to a change in wind direction from a safe sector to a restricted sector to prevent the yaw system from changing the rotor yaw direction from a safe sector to a restricted sector.

3. The method according to claim 1 or 2, wherein, Step e) includes: in response to a change in wind direction from a safe sector to a restricted sector, shutting down or otherwise modifying the operation of the wind turbine so that the rotor generates virtually no electricity.

4. The method according to any one of the preceding claims, wherein, The pinion is one of a set of adjacent pinions that mesh with the yaw ring. The restricted sector and the safe sector are determined based on the position of the set of adjacent pinions, and when the rotor yaw direction is within the restricted sector, the position of the set of adjacent pinions coincides with the position of the damaged or missing tooth.

5. The method according to any one of the preceding claims, wherein, The yaw system has two or more pinions, each pinion meshing with a yaw ring at a corresponding position; step b) includes: determining two or more safety sectors and two or more restricted sectors based on the identified positions of damaged or missing teeth and the positions of each pinion, wherein the safety sectors and restricted sectors alternate, and when the rotor yaw direction is within each restricted sector, the position of the corresponding pinion coincides with the position of the damaged or missing tooth; and step e) includes: disabling or otherwise modifying the operation of the wind turbine to substantially prevent rotor power generation when the rotor yaw direction is within a restricted sector.

6. The method according to claims 2 and 5, wherein, Step e) includes: in response to a change in wind direction from one of the safe sectors to one of the restricted sectors, disabling or otherwise modifying the yaw function to prevent the yaw system from changing the rotor yaw direction from one of the safe sectors to one of the restricted sectors.

7. The method according to claim 5, further comprising: In response to a change in wind direction from a first safety sector to a second safety sector, the yaw system is operated to change the rotor yaw direction from the first safety sector to the second safety sector, during which the rotor yaw direction passes through an intermediate restricted sector; wherein, when the rotor yaw direction passes through the intermediate restricted sector, the position of one of the pinions coincides with the position of a damaged or missing tooth.

8. The method according to claim 7, wherein, Step e) includes: in response to a change in wind direction, shutting down or otherwise modifying the operation of the wind turbine such that the rotor generates virtually no electricity when the rotor yaws through one of the intermediate restricted sectors.

9. The method according to claim 8, wherein, Step d) includes generating electricity using the rotor when the rotor yaw direction is within the first safety sector; and the method further includes generating electricity using the rotor when the rotor yaw direction is within the second safety sector.

10. The method according to claim 3 or 8, wherein, Shutting down or otherwise modifying a wind turbine so that the rotor generates virtually no electricity includes changing the pitch of one or more blades of the rotor.

11. The method according to any one of the preceding claims, wherein, The restricted sector is determined in step c) by identifying the angular range in which the position of the pinion coincides with the position of the damaged or missing tooth; and by adding a buffer at each edge of the angular range.

12. The method according to any one of the preceding claims, wherein, The wind turbine also includes a yaw function in step a) to automatically control the yaw system to yaw the rotor in response to a wind direction change exceeding a threshold; and the method further includes increasing the threshold in response to the rotor yaw direction approaching the edge of a safety sector.

13. A control system configured to operate a wind turbine by means of any one of the preceding claims.

14. A wind turbine comprising: Rotor; A yaw system, which includes a yaw ring and a pinion gear that meshes with the yaw ring; And the control system according to claim 13.

15. A computer program product comprising software code adapted to operate a wind turbine when executed on a data processing system, the computer program product being adapted to perform the method according to any one of claims 1 to 12.

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