WO2021209110A1 - A method for controlling a yaw system of a wind turbine - Google Patents

A method for controlling a yaw system of a wind turbine Download PDF

Info

Publication number
WO2021209110A1
WO2021209110A1 PCT/DK2021/050110 DK2021050110W WO2021209110A1 WO 2021209110 A1 WO2021209110 A1 WO 2021209110A1 DK 2021050110 W DK2021050110 W DK 2021050110W WO 2021209110 A1 WO2021209110 A1 WO 2021209110A1
Authority
WO
WIPO (PCT)
Prior art keywords
yaw
wind turbine
wind
active
tower
Prior art date
Application number
PCT/DK2021/050110
Other languages
French (fr)
Inventor
Simon Stevns KAZAR
Torben Ladegaard Baun
Thomas S. Bjertrup Nielsen
Torben Juul Larsen
Kim Hylling SØRENSEN
Jesper Lykkegaard NEUBAUER
Niels Hansborg PETTERSEN
Original Assignee
Vestas Wind Systems A/S
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Vestas Wind Systems A/S filed Critical Vestas Wind Systems A/S
Publication of WO2021209110A1 publication Critical patent/WO2021209110A1/en

Links

Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
    • F03D—WIND MOTORS
    • F03D7/00—Controlling wind motors 
    • F03D7/02—Controlling wind motors  the wind motors having rotation axis substantially parallel to the air flow entering the rotor
    • F03D7/0204—Controlling wind motors  the wind motors having rotation axis substantially parallel to the air flow entering the rotor for orientation in relation to wind direction
    • F03D7/0208—Orientating out of wind
    • F03D7/0212—Orientating out of wind the rotating axis remaining horizontal
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05B—INDEXING SCHEME RELATING TO WIND, SPRING, WEIGHT, INERTIA OR LIKE MOTORS, TO MACHINES OR ENGINES FOR LIQUIDS COVERED BY SUBCLASSES F03B, F03D AND F03G
    • F05B2240/00—Components
    • F05B2240/20—Rotors
    • F05B2240/21—Rotors for wind turbines
    • F05B2240/221—Rotors for wind turbines with horizontal axis
    • F05B2240/2213—Rotors for wind turbines with horizontal axis and with the rotor downwind from the yaw pivot axis
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05B—INDEXING SCHEME RELATING TO WIND, SPRING, WEIGHT, INERTIA OR LIKE MOTORS, TO MACHINES OR ENGINES FOR LIQUIDS COVERED BY SUBCLASSES F03B, F03D AND F03G
    • F05B2260/00—Function
    • F05B2260/50—Kinematic linkage, i.e. transmission of position
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05B—INDEXING SCHEME RELATING TO WIND, SPRING, WEIGHT, INERTIA OR LIKE MOTORS, TO MACHINES OR ENGINES FOR LIQUIDS COVERED BY SUBCLASSES F03B, F03D AND F03G
    • F05B2260/00—Function
    • F05B2260/82—Forecasts
    • F05B2260/821—Parameter estimation or prediction
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05B—INDEXING SCHEME RELATING TO WIND, SPRING, WEIGHT, INERTIA OR LIKE MOTORS, TO MACHINES OR ENGINES FOR LIQUIDS COVERED BY SUBCLASSES F03B, F03D AND F03G
    • F05B2270/00—Control
    • F05B2270/30—Control parameters, e.g. input parameters
    • F05B2270/32—Wind speeds
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/70—Wind energy
    • Y02E10/72—Wind turbines with rotation axis in wind direction

Definitions

  • the present invention relates to a method for controlling a yaw system of a wind turbine. More particularly, the method according to the invention switches the yaw system between an active mode, in which a yaw angle is adjusted by means of an active yaw mechanism, and a passive mode, in which the yaw angle is adjusted by means of free yawing.
  • the invention further provides a wind turbine comprising a yaw system being controlled in accordance with such a method.
  • Wind turbines normally comprise a wind turbine tower mounted on a foundation or similar structure, which is anchored to the ground or the sea bed, the wind turbine tower extending along a longitudinal direction which is normally substantially vertical.
  • a nacelle carrying a rotor with one or more wind turbine blades is normally mounted on the wind turbine tower via a yaw system.
  • the yaw system allows the nacelle to perform yaw movements, i.e. rotating movements about a rotation axis which substantially coincides with the longitudinal direction of the wind turbine tower, relative to the wind turbine tower.
  • the rotor can be appropriately directed relative to the direction of the wind, also when the direction of the wind changes.
  • the yaw system may be of an active kind, where the nacelle is actively yawed by means of yaw drives, e.g. in response to measurements of the wind direction.
  • the yaw system may be of a passive kind, where the nacelle is allowed to passively follow the direction of the wind. This is sometimes referred to as 'free yawing'.
  • the yaw system may be of a kind which is sometimes operated in an active manner and sometimes in a passive manner.
  • US 8,277,167 B2 discloses an apparatus and a method for operating a wind turbine capable of preventing the occurrence of damage of the blades by evading excessive irregular loads from acting on the blades in the slanting direction in the event of power failure when strong wind blows.
  • a yaw motor is provided for performing yaw control of the wind turbine and a yaw motor brake for braking the rotation of the yaw motor.
  • a controller allows the yaw control to be stopped, the yaw brake to be released, and the yaw motor brake to be applied to allow the wind turbine to naturally follow the direction of the wind after the wind turbine is shifted to a downwind position.
  • the yaw motor brake restricts the rotation speed of the yaw motor in order to prevent damage to the yaw motor.
  • EP 3 124 788 A1 discloses a wind power generator including a nacelle that supports a rotor rotating in response to wind and a tower that supports the nacelle in a rotating manner.
  • a plurality of yaw driving units changes a position of the nacelle with respect to the tower.
  • An abnormality detector detects abnormality of at least one of the yaw driving units, and a releasing unit releases drive force from being transmitted to the yaw driving unit, in which the abnormality has been detected, in response to a command in a case where the abnormality detector detects an abnormality.
  • the invention provides a method for controlling a yaw system of a wind turbine, the yaw system interconnecting a wind turbine tower and a nacelle of the wind turbine, and allowing the nacelle to perform yaw movements relative to the tower, the yaw system comprising a toothed yaw ring connected to one of the tower or the nacelle and an active yaw mechanism comprising at least one yaw drive connected to the other of the tower or the nacelle, each yaw drive comprising a pinion configured to be arranged in engagement with the toothed yaw ring and a drive mechanism configured to drive the pinion, the method comprising the steps of:
  • decoupling the active yaw mechanism by decoupling at least the drive mechanism of at least one of the yaw drives from the yaw system, and
  • the method according to the first aspect of the invention is a method for controlling a yaw system of a wind turbine.
  • the yaw system interconnects a wind turbine tower and a nacelle of the wind turbine, and the yaw system thereby allows the nacelle to perform yaw movements relative to the tower, in the manner described above.
  • the yaw system comprises a toothed yaw ring connected to one of the tower or the nacelle and an active yaw mechanism connected to the other of the tower or the nacelle.
  • the active yaw mechanism is connected to the nacelle.
  • the active yaw mechanism is connected to the tower.
  • the toothed yaw ring and the active yaw mechanism are connected to respective parts which perform relative movements with respect to each other during yaw movements, and thereby the toothed yaw ring and the active yaw mechanism also perform relative movements with respect to each other during yaw movements.
  • the toothed yaw ring may have teeth formed on an inner rim or on an outer rim of the yaw ring.
  • the active yaw mechanism comprises at least one yaw drive.
  • the active yaw mechanism may comprise at least two yaw drives, such as two, three, four or even more yaw drives, e.g. eight yaw drivees.
  • Each yaw drive comprises a pinion configured to be arranged in engagement with the toothed yaw ring and a drive mechanism configured to drive the pinion.
  • the active yaw mechanism can be operated to cause active yawing of the wind turbine.
  • a yaw angle of the wind turbine is initially adjusted in accordance with an occurring wind direction by means of the active yaw mechanism. Accordingly, the yaw system is initially operated in an active manner.
  • the predefined threshold value may, thus, be a value of the wind speed, the turbulence and/or the wind driven loads which represents that the available energy in the wind is at a minimum threshold value which allows reliable free yawing of the wind turbine.
  • a pinion arranged in engagement with the toothed yaw ring will be rotated if the nacelle performs yaw movements relative to the tower by means of free yawing. If the pinion is connected to a corresponding drive mechanism, this rotating movement will be transferred to the drive mechanism, thereby risking damage to the drive mechanism.
  • the active yaw mechanism is decoupled by decoupling at least the drive mechanism of at least one of the yaw drives from the yaw system.
  • the drive mechanism of the yaw drive(s) is mechanically separated from the yaw system. Accordingly, even though the nacelle rotates relative to the tower, due to the wind acting thereon, there is no risk of causing damage to the drive mechanisms of the yaw drives.
  • each yaw drive may be decoupled from the yaw system the manner described above.
  • the active yaw mechanism is completely and efficiently decoupled from the yaw system.
  • some of the yaw drives may not be decoupled.
  • some of the yaw drives may be able to withstand higher loads than other yaw drives, and these may remain coupled to the yaw system while the less durable yaw drives are decoupled and thereby protected.
  • the nacelle is allowed to perform yaw movements relative to the tower by means of free yawing.
  • the yaw system has been switched from an active mode to a passive mode, and the wind turbine is accordingly yawed passively. Since the active yaw mechanism is only decoupled when the wind speed and/or the turbulence and/or the wind driven loads exceeds the predefined threshold value, it is ensured that the yaw system is only switched to the passive mode when the wind conditions are suitable for causing passive yawing of the wind turbine.
  • a switch from operating the yaw system in an active mode to operating the yaw system in a passive mode is performed when the prevailing conditions are appropriate, i.e. when it is ensured that the wind conditions allow reliable free yawing or passive yawing. Furthermore, by decoupling at least the drive mechanism of each yaw drive from the yaw system, it is ensured that the wind turbine can perform free yawing without risking damage to the drive mechanisms.
  • Each yaw drive may further comprise a yaw gear interconnecting the drive mechanism and the pinion, and the step of decoupling the active yaw mechanism may further comprise decoupling at least part of the yaw gear from the yaw system.
  • the yaw gears interconnecting the pinions and the drive mechanisms of the respective yaw drives are decoupled from the yaw system.
  • the yaw gears are also protected from possible damage caused by the passive yawing of the nacelle.
  • the step of decoupling the active yaw mechanism may comprise releasing a holding mechanism configured to fixate a gear part of the yaw gear.
  • the gear part could, e.g., be a ring gear of the planetary gear.
  • the ring gear is simply allowed to rotate freely once the holding mechanism has been released. Thereby, even if the pinion is still arranged in engagement with the toothed gear ring, rotations of the pinion due to the passive yawing of the wind turbine will only be transferred to the yaw gear, which will simply rotate along as a single unit, with the ring gear sliding essentially without friction, and thereby there will be no force transfer. Accordingly, the yaw gear as well as the drive mechanism is protected from damage.
  • the gear part could be another part of the yaw gear, e.g. a planetary stage.
  • the yaw gear could be another kind of gear than a planet gear, e.g. a worm gear.
  • the entire worm gear is preferably decoupled from the yaw mechanism.
  • the holding mechanism could, e.g., be or comprise movable brake pads, pistons, such as hydromechanic pistons, movable locking pins, or any other suitable kind of holding mechanism which could be moved between a holding position and a released position.
  • the step of decoupling the active yaw mechanism may comprise moving the pinion of each yaw drive out of engagement with the toothed yaw ring.
  • the entire active yaw mechanism is entirely decoupled from the yaw system, in the sense that the force transferring connections between the pinions and the toothed yaw ring is interrupted.
  • the toothed yaw ring and the yaw drives are free to perform movements relative to each other, thereby enabling passive yawing without any forces being transferred to the yaw drives.
  • the pinions may remain in engagement with the toothed yaw ring, as long as these pinions are decoupled from the respective drive mechanisms, e.g. in the manner described above.
  • the drive mechanism of each yaw drive may comprise a variable displacement pump comprising a plurality of pistons and a swash plate, and the step of decoupling the active yaw mechanism may comprise moving the swash plate of each drive mechanism to a neutral position.
  • the drive mechanisms are operated by sequentially pumping a suitable fluid medium, such as hydraulic oil, into a plurality of pistons of a variable displacement pump, thereby sequentially operating the pistons.
  • the pistons are arranged in contact with a swash plate, and the sequential operation of the pistons thereby causes rotation of the swash plate, resulting in rotation of a drive shaft connected thereto.
  • the rotation of the swash plate depends on an angular position of the swash plate.
  • the drive mechanism may comprise a motor, such as an electrical motor.
  • the step of decoupling the active yaw mechanism may comprise decoupling the toothed yaw ring from the tower or the nacelle.
  • the toothed yaw ring is allowed to slide relative to the part of the wind turbine, to which it is normally connected, i.e. relative to the tower or to the nacelle.
  • no relative movements take place between the toothed yaw ring and the yaw drives when the wind turbine performs yaw movements by means of free yawing, i.e. when the yaw system is in the passive mode.
  • the toothed yaw ring may, e.g., be decoupled from the tower or the nacelle by releasing a holding mechanism acting on the toothed yaw ring, e.g. in the form of a clutch mechanism, movable brake pads, pistons, movable locking pins, etc.
  • the decoupling of the active yaw mechanism may be performed by operating a hydraulic mechanism.
  • the wind turbine may be a downwind wind turbine, i.e. a wind turbine in which the rotor is positioned downstream relative to the tower, along the direction of the incoming wind.
  • Downwind wind turbines are particularly suitable for performing passive yawing or free yawing.
  • the wind turbine may be an upwind wind turbine, and the method may further comprise the steps of, in the case that the wind speed and/or the turbulence and/or the wind driven loads exceeds the predefined threshold value:
  • the step of decoupling the active yaw mechanism may be performed while the wind turbine is in the downwind position.
  • the term 'upwind wind turbine' should be interpreted to mean a wind turbine in which the rotor is positioned upstream relative to the tower, along the direction of the incoming wind, i.e. the rotor is directed towards the incoming wind.
  • downwind wind turbines are more suitable for performing passive yawing than upwind wind turbines. Therefore, according to this embodiment, when it is determined that the wind speed and/or the turbulence and/or the wind driven loads on the wind turbine is above the predefined threshold value, the wind turbine is actively yawed to a downwind position, i.e. by means of the active yaw mechanism, in order to orient the rotor in a manner which is suitable for passive yawing. However, before doing so, the operation of the wind turbine is switched to idle mode, in order to avoid excessive loads on the wind turbine as the rotor is moved away from a position where it is aligned with the direction of the wind.
  • the active yaw mechanism is decoupled in the manner described above, i.e. the yaw system is switched to the passive mode.
  • the method may further comprise the step of determining cable twist of the wind turbine, and the step of yawing the wind turbine to a downwind position may be performed in such a manner that cable untwist is obtained.
  • Yawing the wind turbine from an upwind position to a downwind position normally involves rotating the nacelle through approximately 180°. Accordingly, it makes little difference in which direction the yaw movement is performed. Therefore, according to this embodiment, it is investigated whether or not and to which extend cable twist is occurring in the wind turbine. If this is the case, then the yawing of the wind turbine to the downwind position is performed in such a manner that the cable is untwisted, i.e. the nacelle is rotated in the direction which causes the cable to untwist. Thereby it is avoided that the cable is twisted further, and a separate cable untwist operation may be avoided at a later point in time.
  • the method may further comprise the steps of:
  • a yaw error of the wind turbine is monitored.
  • the term 'yaw error' should be interpreted to mean a difference between an actual yaw position of the nacelle and a position in which the rotor is correctly aligned with respect to the direction of the wind.
  • the active yaw mechanism is re-coupled, and the yaw error is corrected by means of the active yaw mechanism.
  • the method may further comprise the steps of:
  • the active yaw mechanism is re-coupled, and the yaw velocity is corrected by means of the active yaw mechanism, preferably by slowing down the yaw movements, or at least ensuring that the yaw velocity is not increased further.
  • the method may further comprise the steps of:
  • the active yaw mechanism when the active yaw mechanism has been decoupled from the yaw system and the nacelle therefore performs yaw movements by means of free yawing, the wind speed and/or turbulence and/or wind driven loads on the wind turbine are monitored, in the manner described above, in order to establish whether or not the conditions for operating the yaw system passively are still applying.
  • the active yaw mechanism is re-coupled, and the yaw angle is subsequently adjusted in accordance with an occurring wind direction by means of the active yaw mechanism, i.e. the yaw system is switched from the passive mode to the active mode.
  • the cut-in threshold value is preferably a value which is lower than the predefined threshold value which is applied for deciding that the yaw system is to be switched from the active mode to the passive mode.
  • the step of monitoring a wind speed and/or turbulence at a location of the wind turbine may comprise estimating an expected wind speed and/or turbulence during a future time interval based on a weather forecast.
  • the decision regarding whether or not to switch the yaw system from the active mode to the passive mode is made at least partly based on an estimate or a prediction of the conditions at the position of the wind turbine. Thereby it is possible to take measures before these conditions are actually applying.
  • the weather forecast could, e.g., be based on measurements performed by weather stations and/or metmast positioned near the wind turbine, on satellite data, and/or on any other suitable kind of source.
  • a forecast may be based on measurements performed by other wind turbines, e.g. arranged in the vicinity of the wind turbine, and/or by wind turbines arranged in wind farms within the same geographical area or region.
  • the method may further comprise the step of allowing the nacelle to slide relative to the wind turbine tower, via an interface defined in the yaw system, in the case that a torque in the yaw system exceeds a predefined threshold level.
  • the yaw system is provided with an additional safety mechanism which allows the nacelle to slide relative to the wind turbine tower, without causing damage to any parts of the yaw system, if the wind turbine is subjected to forces which introduce a high torque in the yaw system.
  • the invention provides a wind turbine comprising a wind turbine tower and a nacelle connected to the wind turbine tower via a yaw system, wherein the yaw system comprises:
  • the active yaw mechanism comprises at least one yaw drive comprising a pinion configured to be arranged in engagement with the toothed yaw ring and a yaw drive mechanism configured to drive the pinion, and wherein at least one of the yaw drives comprises a decoupling device configured to selectively decouple at least the drive mechanism of the yaw drive from the yaw system.
  • the yaw system of the wind turbine according to the second aspect of the invention may advantageously be controlled in accordance with a method according to the first aspect of the invention.
  • a person skilled in the art would therefore readily understand that any feature described in combination with the first aspect of the invention could also be combined with the second aspect of the invention, and vice versa.
  • the decoupling device of the wind turbine according to the second aspect of the invention allows at least the drive mechanism of each yaw drive to be mechanically decoupled from the yaw system, in the manner described above with reference to the first aspect of the invention.
  • the decoupling device may be operated in accordance with the method according to the first aspect of the invention, i.e. the decoupling may take place in the manner described above.
  • the decoupling device may be arranged to decouple the toothed yaw ring from the tower or the nacelle.
  • the wind turbine may comprise a bearing arranged between the toothed yaw ring and the tower or the nacelle.
  • FIG. 1 and 2 show a yaw system for a wind turbine according to a first embodiment of the invention from two different angles
  • Figs. 3-5 show the yaw system of Figs. 1 and 2 at rest, during active yawing and during passive yawing, respectively,
  • FIG. 6 shows details of the yaw system of Figs. 1-5
  • Figs. 7 and 8 show a yaw system for a wind turbine according to a second embodiment of the invention from two different angles
  • Fig. 9 is a yaw gear for the yaw system of Figs. 7 and 8, and
  • Figs. 10 and 11 show a yaw system for a wind turbine according to a third embodiment of the invention from two different angles.
  • Figs. 1 and 2 show a yaw system 1 for a wind turbine according to a first embodiment of the invention from two different angles.
  • the yaw system 1 comprises a toothed yaw ring 2 which is connected to a wind turbine tower (not shown).
  • the yaw system 1 further comprises an active yaw mechanism comprising eight yaw drives 3, each being connected to a main frame 4 of a nacelle.
  • Each yaw drive 3 comprises a toothed pinion 5 which can be arranged in engagement with the toothed yaw ring 2.
  • the pinion 5 is connected to a yaw motor 6, via a yaw gear (not shown).
  • the yaw system 1 of Figs. 1 and 2 can be operated in an active mode or in a passive mode.
  • the wind turbine performs yaw movements by operating the yaw motors 6, thereby causing the pinions 5 to rotate. This, in turn, causes a relative rotational movement between the toothed yaw ring 2 and the yaw drives 3, and thereby between the wind turbine tower and the nacelle.
  • the wind turbine performs yaw movements by means of free yawing, i.e. the nacelle passively follows the direction of the wind in order to orient the rotor of the wind turbine in accordance with the direction of the wind.
  • the yaw system 1 of Figs. 1 and 2 is operated in the passive mode, the toothed yaw ring 2 is decoupled from the wind turbine tower. Thereby the toothed yaw ring 2 rotates along with the yaw drives 3 and the nacelle during free yawing movements.
  • the yaw system 1 of Figs. 1 and 2 may be controlled in the following manner. While the yaw system 1 is operated in the active mode, as described above, the wind speed and/or turbulence at the location of the wind turbine, and/or wind driven loads on the wind turbine are monitored. In the case that the wind speed and/or turbulence and/or wind driven loads exceeds a predefined threshold value, it is determined that the wind conditions are appropriate for free yawing of the wind turbine. For instance, the available energy in the wind may be sufficient to ensure that the nacelle is able to follow the wind direction correctly, thereby ensuring appropriate orientation of the rotor of the wind turbine.
  • Figs. 3-5 are schematic views of the yaw system 1 of Figs. 1 and 2 from below. Furthermore, the nacelle 7, the tower 8 and a hub 9 of the wind turbine are shown. In Fig. 3 the yaw system 1 is shown at rest, i.e. it is not performing yaw movements.
  • the yaw system 1 is performing active yaw movements by operating the yaw drives 3, thereby rotating the pinions and causing a relative movement between the toothed yaw ring 2 and the yaw drives 3. This results in rotation of the nacelle 7 relative to the tower 8, as illustrated by arrow 10.
  • the yaw system 1 is performing passive yaw movements or free yawing, as illustrated by arrow 11.
  • the toothed yaw ring 2 has been decoupled from the tower 8, and it therefore rotates along with the nacelle 7, and there is therefore no force transfer from the toothed yaw ring 2 to the yaw drives 3.
  • the decoupling of the toothed yaw ring 2 may, e.g., be accomplished by releasing brakes 12.
  • Fig. 6 is a cross sectional view of a part of the yaw system 1 of Figs. 1-5, showing one of the yaw drives 3 with its pinion 5 arranged in engagement with the toothed yaw ring 2.
  • Bearing 14 ensures that the bedframe 4 of the nacelle is able to rotate relative to the tower 8.
  • the bearing 14 is illustrated as a ball bearing.
  • the bearing 14 could be any other suitable kind of bearing, e.g. a sliding bearing.
  • the toothed yaw ring 2 is connected to the tower 8 via a yaw claw 13 with braking pads 12 arranged between the yaw claw 13 and the toothed yaw ring 2.
  • the braking pads 12 are in a locking position in which they fixate the toothed yaw ring 2 relative to the yaw claw 13, and thereby relative to the tower 8.
  • the braking pads 12 are released, in the sense that they are moved out of the locking position, so that they no longer fixate the toothed yaw ring 2 relative to the yaw claw 13.
  • Figs. 7 and 8 show a yaw system 1 for a wind turbine according to a second embodiment of the invention from two different angles.
  • the yaw system 1 of Figs. 7 and 8 is very similar to the yaw system 1 of Figs. 1 and 2, and it will therefore not be described in detail here.
  • the toothed yaw ring 2 is fixedly connected to the tower of the wind turbine. Instead, a part of the yaw gear of each yaw drive 3 can be decoupled, thereby decoupling at least the yaw motors 6 from the yaw system 1. Accordingly, when the yaw system 1 is operated in the passive mode, the relative movements of the nacelle and the tower cause the pinions 5 of the yaw drives 3 to rotate, since they are arranged in engagement with the toothed yaw ring 2. However, this rotational movement is not transferred to the yaw motors 6 because part of the yaw gears has been decoupled.
  • Fig. 9 shows a yaw gear 15 for the yaw system of Figs. 7 and 8.
  • the yaw gear 15 is in the form of a planetary gear with a ring gear 16, three planet gears 17 and a sun gear 18.
  • a shaft 19 connected to the sun gear 18 is connectable to a pinion.
  • a plurality of hydromechanic pistons 20 having brake pads mounted thereon are arranged circumferentially with respect to the ring gear 16.
  • the pistons 20 are thereby able to move the brake pads into and out of engagement with the ring gear 16.
  • the ring gear 16 is fixated relative to a yaw motor, and thereby the yaw system is operated in the active mode.
  • the brake pads are not arranged in engagement with the ring gear 16, the ring gear 16 is allowed to rotate relative to the yaw motor, and thereby the yaw motor is decoupled from the pinion.
  • the power supply to the yaw motor may advantageously be of a kind which ensures that no cable twisting occurs as a result of the yaw gear 15 rotating relative to the yaw motor during free yawing.
  • electrical power may be transferred to the yaw motor via a slip ring.
  • power may be supplied to the yaw motor via a hydraulic rotating union.
  • Figs. 10 and 11 show a yaw system 1 for a wind turbine according to a third embodiment of the invention from two different angles.
  • the yaw system 1 of Figs. 10 and 11 is very similar to the yaw system 1 of Figs. 1 and 2, and it will therefore not be described in detail here.
  • the yaw system 1 of Figs. 10 and 11 is not provided with yaw drives of the kind shown in Figs. 1 and 2. Instead, the yaw system 1 comprises four hydraulic cylinders 21 and four locking devices 22. Each locking device 22 is provided with a toothed portion which may be arranged in engagement with the toothed yaw ring 2. The locking devices 22 can be moved into and out of engagement with the toothed yaw ring 2 by appropriately operating the hydraulic cylinders 21.
  • the nacelle When none of the four locking devices 22 is arranged in engagement with the toothed yaw ring 2, the nacelle can rotate freely relative to the tower. Thereby the yaw system 1 can perform free yawing without any force transfer between the toothed yaw ring 2 and the hydraulic cylinders 21. Accordingly, the hydraulic cylinders 21 are, in this case, decoupled from the yaw system 1, and the yaw system 1 is operated in the passive mode. The yaw system 1 may further be operated in an active mode. In this case the hydraulic cylinders 21 are operated in such a manner that the locking devices 22 move in a manner similar to a pair of scissors, thereby causing relative movements between the nacelle and the tower.

Landscapes

  • Engineering & Computer Science (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Sustainable Development (AREA)
  • Sustainable Energy (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Wind Motors (AREA)

Abstract

A method for controlling a yaw system (1) of a wind turbine is disclosed. The yaw system (1) comprises a toothed yaw ring (2) connected to one of a tower (8) or a nacelle (7) and an active yaw mechanism comprising at least one yaw drive (3) connected to the other of the tower (8) or the nacelle (7). Each yaw drive (3) comprises a pinion (5) configured to be arranged in engagement with the toothed yaw ring (2) and a drive mechanism (6) configured to drive the pinion (5). In the case that a wind speed and/or a turbulence and/or wind driven loads on the wind turbine exceeds a predefined threshold value, the active yaw mechanism is decoupled by decoupling at least the drive mechanism (6) of at least one of the yaw drives (3) from the yaw system (1). Subsequently the nacelle (7) is allowed to perform yaw movements relative to the tower (8) by means of free yawing.

Description

A METHOD FOR CONTROLLING A YAW SYSTEM OF A WIND TURBINE
FIELD OF THE INVENTION
The present invention relates to a method for controlling a yaw system of a wind turbine. More particularly, the method according to the invention switches the yaw system between an active mode, in which a yaw angle is adjusted by means of an active yaw mechanism, and a passive mode, in which the yaw angle is adjusted by means of free yawing. The invention further provides a wind turbine comprising a yaw system being controlled in accordance with such a method.
BACKGROUND OF THE INVENTION
Wind turbines normally comprise a wind turbine tower mounted on a foundation or similar structure, which is anchored to the ground or the sea bed, the wind turbine tower extending along a longitudinal direction which is normally substantially vertical. A nacelle carrying a rotor with one or more wind turbine blades is normally mounted on the wind turbine tower via a yaw system. The yaw system allows the nacelle to perform yaw movements, i.e. rotating movements about a rotation axis which substantially coincides with the longitudinal direction of the wind turbine tower, relative to the wind turbine tower. Thereby the rotor can be appropriately directed relative to the direction of the wind, also when the direction of the wind changes.
The yaw system may be of an active kind, where the nacelle is actively yawed by means of yaw drives, e.g. in response to measurements of the wind direction. As an alternative, the yaw system may be of a passive kind, where the nacelle is allowed to passively follow the direction of the wind. This is sometimes referred to as 'free yawing'. As another alternative, the yaw system may be of a kind which is sometimes operated in an active manner and sometimes in a passive manner. US 8,277,167 B2 discloses an apparatus and a method for operating a wind turbine capable of preventing the occurrence of damage of the blades by evading excessive irregular loads from acting on the blades in the slanting direction in the event of power failure when strong wind blows. A yaw motor is provided for performing yaw control of the wind turbine and a yaw motor brake for braking the rotation of the yaw motor. A controller allows the yaw control to be stopped, the yaw brake to be released, and the yaw motor brake to be applied to allow the wind turbine to naturally follow the direction of the wind after the wind turbine is shifted to a downwind position. The yaw motor brake restricts the rotation speed of the yaw motor in order to prevent damage to the yaw motor.
EP 3 124 788 A1 discloses a wind power generator including a nacelle that supports a rotor rotating in response to wind and a tower that supports the nacelle in a rotating manner. A plurality of yaw driving units changes a position of the nacelle with respect to the tower. An abnormality detector detects abnormality of at least one of the yaw driving units, and a releasing unit releases drive force from being transmitted to the yaw driving unit, in which the abnormality has been detected, in response to a command in a case where the abnormality detector detects an abnormality.
DESCRIPTION OF THE INVENTION
It is an object of embodiments of the invention to provide a method for controlling a yaw system in which damage to the yaw system is efficiently prevented during free yawing.
It is a further object of embodiments of the invention to provide a wind turbine in which the yaw system is efficiently protected from damage during free yawing.
According to a first aspect the invention provides a method for controlling a yaw system of a wind turbine, the yaw system interconnecting a wind turbine tower and a nacelle of the wind turbine, and allowing the nacelle to perform yaw movements relative to the tower, the yaw system comprising a toothed yaw ring connected to one of the tower or the nacelle and an active yaw mechanism comprising at least one yaw drive connected to the other of the tower or the nacelle, each yaw drive comprising a pinion configured to be arranged in engagement with the toothed yaw ring and a drive mechanism configured to drive the pinion, the method comprising the steps of:
- adjusting a yaw angle of the wind turbine in accordance with an occurring wind direction by means of the active yaw mechanism,
- monitoring a wind speed and/or turbulence at a location of the wind turbine, and/or wind driven loads on the wind turbine,
- in the case that the wind speed and/or the turbulence and/or the wind driven loads on the wind turbine exceeds a predefined threshold value, decoupling the active yaw mechanism by decoupling at least the drive mechanism of at least one of the yaw drives from the yaw system, and
- subsequently allowing the nacelle to perform yaw movements relative to the tower by means of free yawing.
Thus, the method according to the first aspect of the invention is a method for controlling a yaw system of a wind turbine. The yaw system interconnects a wind turbine tower and a nacelle of the wind turbine, and the yaw system thereby allows the nacelle to perform yaw movements relative to the tower, in the manner described above.
The yaw system comprises a toothed yaw ring connected to one of the tower or the nacelle and an active yaw mechanism connected to the other of the tower or the nacelle. Thus, in the case that the toothed yaw ring is connected to the tower, then the active yaw mechanism is connected to the nacelle. Similarly, in the case that the toothed yaw ring is connected to the nacelle, then the active yaw mechanism is connected to the tower. Accordingly, the toothed yaw ring and the active yaw mechanism are connected to respective parts which perform relative movements with respect to each other during yaw movements, and thereby the toothed yaw ring and the active yaw mechanism also perform relative movements with respect to each other during yaw movements. The toothed yaw ring may have teeth formed on an inner rim or on an outer rim of the yaw ring.
The active yaw mechanism comprises at least one yaw drive. Preferably, the active yaw mechanism may comprise at least two yaw drives, such as two, three, four or even more yaw drives, e.g. eight yaw drivees. Each yaw drive comprises a pinion configured to be arranged in engagement with the toothed yaw ring and a drive mechanism configured to drive the pinion. Thus, when the pinion is arranged in engagement with the toothed yaw ring and the drive mechanism is appropriately operated, force transfer takes place between the pinion and the toothed yaw ring, which causes a relative movement between the toothed yaw ring and the active yaw mechanism, which in turn causes the nacelle to perform yaw movements relative to the wind turbine tower. Accordingly, the active yaw mechanism can be operated to cause active yawing of the wind turbine.
In the method according to the first aspect of the invention, a yaw angle of the wind turbine is initially adjusted in accordance with an occurring wind direction by means of the active yaw mechanism. Accordingly, the yaw system is initially operated in an active manner.
While the yaw system is operated in this manner, a wind speed and/or turbulence at a location of the wind turbine, and/or wind driven loads on the wind turbine are monitored. In the case that the wind speed and/or the turbulence experienced by the wind turbine is high, or if the wind turbine experiences high wind driven loads for other reasons, this is an indication that the available energy in the wind is sufficient to ensure that the wind turbine can perform reliable free yawing or passive yawing, and that the yaw system is thereby capable of ensuring that the rotor is directed correctly relative to the wind direction in a passive manner, i.e. without the use of the active yaw mechanism. The predefined threshold value may, thus, be a value of the wind speed, the turbulence and/or the wind driven loads which represents that the available energy in the wind is at a minimum threshold value which allows reliable free yawing of the wind turbine.
Furthermore, in the case of high wind speeds, high turbulence and/or high wind driven loads, there is a risk that the wind acting on the wind turbine may cause damage to the yaw system, in particular to the yaw drives or other parts of the active yaw mechanism. For instance, a pinion arranged in engagement with the toothed yaw ring will be rotated if the nacelle performs yaw movements relative to the tower by means of free yawing. If the pinion is connected to a corresponding drive mechanism, this rotating movement will be transferred to the drive mechanism, thereby risking damage to the drive mechanism.
Therefore, in the case that the wind speed and/or the turbulence and/or the wind driven loads on the wind turbine exceeds a predefined threshold value, the active yaw mechanism is decoupled by decoupling at least the drive mechanism of at least one of the yaw drives from the yaw system. Thereby the drive mechanism of the yaw drive(s) is mechanically separated from the yaw system. Accordingly, even though the nacelle rotates relative to the tower, due to the wind acting thereon, there is no risk of causing damage to the drive mechanisms of the yaw drives.
At least the drive mechanism of each yaw drive may be decoupled from the yaw system the manner described above. In this case, the active yaw mechanism is completely and efficiently decoupled from the yaw system. As an alternative, some of the yaw drives may not be decoupled. For instance, some of the yaw drives may be able to withstand higher loads than other yaw drives, and these may remain coupled to the yaw system while the less durable yaw drives are decoupled and thereby protected.
Once the active yaw mechanism has been decoupled, the nacelle is allowed to perform yaw movements relative to the tower by means of free yawing. Thus, the yaw system has been switched from an active mode to a passive mode, and the wind turbine is accordingly yawed passively. Since the active yaw mechanism is only decoupled when the wind speed and/or the turbulence and/or the wind driven loads exceeds the predefined threshold value, it is ensured that the yaw system is only switched to the passive mode when the wind conditions are suitable for causing passive yawing of the wind turbine.
Thus, in the method according to the first aspect of the invention, a switch from operating the yaw system in an active mode to operating the yaw system in a passive mode is performed when the prevailing conditions are appropriate, i.e. when it is ensured that the wind conditions allow reliable free yawing or passive yawing. Furthermore, by decoupling at least the drive mechanism of each yaw drive from the yaw system, it is ensured that the wind turbine can perform free yawing without risking damage to the drive mechanisms.
Each yaw drive may further comprise a yaw gear interconnecting the drive mechanism and the pinion, and the step of decoupling the active yaw mechanism may further comprise decoupling at least part of the yaw gear from the yaw system.
According to this embodiment, not only the drive mechanisms of the yaw drives, but also the yaw gears interconnecting the pinions and the drive mechanisms of the respective yaw drives, are decoupled from the yaw system. Thereby the yaw gears are also protected from possible damage caused by the passive yawing of the nacelle.
The step of decoupling the active yaw mechanism may comprise releasing a holding mechanism configured to fixate a gear part of the yaw gear. In the case that the yaw gear is a planetary gear, the gear part could, e.g., be a ring gear of the planetary gear. In this case, the ring gear is simply allowed to rotate freely once the holding mechanism has been released. Thereby, even if the pinion is still arranged in engagement with the toothed gear ring, rotations of the pinion due to the passive yawing of the wind turbine will only be transferred to the yaw gear, which will simply rotate along as a single unit, with the ring gear sliding essentially without friction, and thereby there will be no force transfer. Accordingly, the yaw gear as well as the drive mechanism is protected from damage.
As an alternative, the gear part could be another part of the yaw gear, e.g. a planetary stage.
As another alternative, the yaw gear could be another kind of gear than a planet gear, e.g. a worm gear. In this case the entire worm gear is preferably decoupled from the yaw mechanism.
The holding mechanism could, e.g., be or comprise movable brake pads, pistons, such as hydromechanic pistons, movable locking pins, or any other suitable kind of holding mechanism which could be moved between a holding position and a released position.
The step of decoupling the active yaw mechanism may comprise moving the pinion of each yaw drive out of engagement with the toothed yaw ring.
According to this embodiment, the entire active yaw mechanism is entirely decoupled from the yaw system, in the sense that the force transferring connections between the pinions and the toothed yaw ring is interrupted. Thereby the toothed yaw ring and the yaw drives are free to perform movements relative to each other, thereby enabling passive yawing without any forces being transferred to the yaw drives.
As an alternative, at least some of the pinions may remain in engagement with the toothed yaw ring, as long as these pinions are decoupled from the respective drive mechanisms, e.g. in the manner described above.
The drive mechanism of each yaw drive may comprise a variable displacement pump comprising a plurality of pistons and a swash plate, and the step of decoupling the active yaw mechanism may comprise moving the swash plate of each drive mechanism to a neutral position.
According to this embodiment, the drive mechanisms are operated by sequentially pumping a suitable fluid medium, such as hydraulic oil, into a plurality of pistons of a variable displacement pump, thereby sequentially operating the pistons. The pistons are arranged in contact with a swash plate, and the sequential operation of the pistons thereby causes rotation of the swash plate, resulting in rotation of a drive shaft connected thereto. The rotation of the swash plate depends on an angular position of the swash plate. When the swash plate is moved into a neutral position, i.e. to a zero angle position, there is no force transfer between the pistons and the swash plate, and thereby no force transfer between the drive shaft and the drive mechanism. Accordingly, this results in the drive mechanism being decoupled from the yaw system.
As an alternative, the drive mechanism may comprise a motor, such as an electrical motor.
The step of decoupling the active yaw mechanism may comprise decoupling the toothed yaw ring from the tower or the nacelle. According to this embodiment, the toothed yaw ring is allowed to slide relative to the part of the wind turbine, to which it is normally connected, i.e. relative to the tower or to the nacelle. Thus, no relative movements take place between the toothed yaw ring and the yaw drives when the wind turbine performs yaw movements by means of free yawing, i.e. when the yaw system is in the passive mode. Thereby it is also ensured that there is no force transfer to the yaw drives as a consequence of the passive yaw movements, even if the pinions remain in engagement with the toothed yaw ring. Thus, according to this embodiment, when the yaw system is in the active mode, the toothed yaw ring and the yaw drives are each connected to one of the tower and the nacelle, and force transfer between the two therefore results in active yawing. On the other, when the yaw system is in the passive mode, the toothed yaw ring and the yaw drives move together or remain stationary together during passive yawing, and thereby no force transfer takes place between the two, as described above.
It is an advantage to decouple the active yaw mechanism by decoupling the toothed yaw ring from the tower or the nacelle, because thereby force transfer between the toothed yaw ring and the yaw drives is completely avoided. This prevents fast rotations in the yaw drives which may be potentially damaging to the yaw drives, due to inertia in the yaw drives. Furthermore, wear on the toothed connection between the toothed yaw ring and the pinions is avoided. Accordingly, all parts of the yaw system are protected, including the teeth of the toothed yaw ring, the pinions, all parts of the yaw drives, etc.
The toothed yaw ring may, e.g., be decoupled from the tower or the nacelle by releasing a holding mechanism acting on the toothed yaw ring, e.g. in the form of a clutch mechanism, movable brake pads, pistons, movable locking pins, etc.
The decoupling of the active yaw mechanism may be performed by operating a hydraulic mechanism. This could, e.g., include the embodiment including the variable displacement pump or an embodiment including a holding mechanism with hydraulic pistons, as described above.
The wind turbine may be a downwind wind turbine, i.e. a wind turbine in which the rotor is positioned downstream relative to the tower, along the direction of the incoming wind. Downwind wind turbines are particularly suitable for performing passive yawing or free yawing.
As an alternative, the wind turbine may be an upwind wind turbine, and the method may further comprise the steps of, in the case that the wind speed and/or the turbulence and/or the wind driven loads exceeds the predefined threshold value:
- switching operation of the wind turbine to idle mode, and
- yawing the wind turbine to a downwind position by means of the active yaw mechanism, and the step of decoupling the active yaw mechanism may be performed while the wind turbine is in the downwind position.
In the present context the term 'upwind wind turbine' should be interpreted to mean a wind turbine in which the rotor is positioned upstream relative to the tower, along the direction of the incoming wind, i.e. the rotor is directed towards the incoming wind. As described above, downwind wind turbines are more suitable for performing passive yawing than upwind wind turbines. Therefore, according to this embodiment, when it is determined that the wind speed and/or the turbulence and/or the wind driven loads on the wind turbine is above the predefined threshold value, the wind turbine is actively yawed to a downwind position, i.e. by means of the active yaw mechanism, in order to orient the rotor in a manner which is suitable for passive yawing. However, before doing so, the operation of the wind turbine is switched to idle mode, in order to avoid excessive loads on the wind turbine as the rotor is moved away from a position where it is aligned with the direction of the wind.
When the yawing of the wind turbine into the downwind position has been completed, the active yaw mechanism is decoupled in the manner described above, i.e. the yaw system is switched to the passive mode.
The method may further comprise the step of determining cable twist of the wind turbine, and the step of yawing the wind turbine to a downwind position may be performed in such a manner that cable untwist is obtained.
Yawing the wind turbine from an upwind position to a downwind position normally involves rotating the nacelle through approximately 180°. Accordingly, it makes little difference in which direction the yaw movement is performed. Therefore, according to this embodiment, it is investigated whether or not and to which extend cable twist is occurring in the wind turbine. If this is the case, then the yawing of the wind turbine to the downwind position is performed in such a manner that the cable is untwisted, i.e. the nacelle is rotated in the direction which causes the cable to untwist. Thereby it is avoided that the cable is twisted further, and a separate cable untwist operation may be avoided at a later point in time.
The method may further comprise the steps of:
- monitoring yaw error of the wind turbine while allowing the nacelle to perform yaw movements relative to the tower by means of free yawing, - re-coupling the active yaw mechanism in the case that the yaw error exceeds a predefined threshold level, and
- correcting the yaw error by means of the active yaw mechanism.
According to this embodiment, following the switch of the yaw system to a passive mode, a yaw error of the wind turbine is monitored. In the present context the term 'yaw error' should be interpreted to mean a difference between an actual yaw position of the nacelle and a position in which the rotor is correctly aligned with respect to the direction of the wind.
In the case that a yaw error occurs while the nacelle is allowed to perform yaw movements relative to the tower by means of free yawing, this is an indication that the free yawing is not performed properly, i.e. that the nacelle is not passively following the direction of the wind in an accurate manner. This introduces the risk that uneven loads are applied to the wind turbine, and a situation may even occur in which the yaw error is self-perpetuating in the sense that a small yaw error may in itself cause the yaw error to increase, thereby making the problem worse.
Therefore, in the case that the yaw error exceeds a predefined threshold level, the active yaw mechanism is re-coupled, and the yaw error is corrected by means of the active yaw mechanism.
Alternatively or additionally, the method may further comprise the steps of:
- monitoring a yaw velocity of the wind turbine while allowing the nacelle to perform yaw movements relative to the tower by means of free yawing,
- re-coupling the active yaw mechanism in the case that the yaw velocity exceeds a predefined threshold level, and correcting the yaw velocity by means of the active yaw mechanism. This is similar to the embodiment described above. However, in this case a yaw velocity of the wind turbine, rather than the yaw error, is monitored. Performing the yaw movements at a too high velocity may introduce undesired loads in the wind turbine, e.g. in the form of oscillations and/or uneven impact from the wind across the rotor plane.
Therefore, according to this embodiment, in the case that the yaw velocity exceeds a predefined threshold level, the active yaw mechanism is re-coupled, and the yaw velocity is corrected by means of the active yaw mechanism, preferably by slowing down the yaw movements, or at least ensuring that the yaw velocity is not increased further.
The method may further comprise the steps of:
- monitoring a wind speed and/or turbulence at the location of the wind turbine, and/or wind driven loads on the wind turbine, while allowing the nacelle to perform yaw movements relative to the tower by means of free yawing,
- in the case that the wind speed and/or the turbulence and/or the wind driven loads on the wind turbine decreases below a predefined cut-in threshold value, re-coupling the active yaw mechanism, and
- subsequently adjusting the yaw angle of the wind turbine in accordance with an occurring wind direction by means of the active yaw mechanism.
According to this embodiment, when the active yaw mechanism has been decoupled from the yaw system and the nacelle therefore performs yaw movements by means of free yawing, the wind speed and/or turbulence and/or wind driven loads on the wind turbine are monitored, in the manner described above, in order to establish whether or not the conditions for operating the yaw system passively are still applying.
In the case that the wind speed and/or the turbulence and/or the wind driven loads on the wind turbine decreases below a predefined cut-in threshold value, it can be concluded that the conditions for operating the yaw system in a passive manner no longer apply. Therefore, when this is the case, the active yaw mechanism is re-coupled, and the yaw angle is subsequently adjusted in accordance with an occurring wind direction by means of the active yaw mechanism, i.e. the yaw system is switched from the passive mode to the active mode.
The cut-in threshold value is preferably a value which is lower than the predefined threshold value which is applied for deciding that the yaw system is to be switched from the active mode to the passive mode. Thereby it is ensured that the yaw system is only switched between the two modes when the conditions have truly changed, and it is avoided that the yaw system is repeatedly switched between the two modes if the wind speed and/or turbulence and/or wind driven loads is approximately at the threshold level.
The step of monitoring a wind speed and/or turbulence at a location of the wind turbine may comprise estimating an expected wind speed and/or turbulence during a future time interval based on a weather forecast. According to this embodiment, the decision regarding whether or not to switch the yaw system from the active mode to the passive mode is made at least partly based on an estimate or a prediction of the conditions at the position of the wind turbine. Thereby it is possible to take measures before these conditions are actually applying.
The weather forecast could, e.g., be based on measurements performed by weather stations and/or metmast positioned near the wind turbine, on satellite data, and/or on any other suitable kind of source.
Alternatively or additionally, a forecast may be based on measurements performed by other wind turbines, e.g. arranged in the vicinity of the wind turbine, and/or by wind turbines arranged in wind farms within the same geographical area or region. The method may further comprise the step of allowing the nacelle to slide relative to the wind turbine tower, via an interface defined in the yaw system, in the case that a torque in the yaw system exceeds a predefined threshold level.
According to this embodiment, the yaw system is provided with an additional safety mechanism which allows the nacelle to slide relative to the wind turbine tower, without causing damage to any parts of the yaw system, if the wind turbine is subjected to forces which introduce a high torque in the yaw system.
According to a second aspect the invention provides a wind turbine comprising a wind turbine tower and a nacelle connected to the wind turbine tower via a yaw system, wherein the yaw system comprises:
- a toothed yaw ring connected to one of the tower or the nacelle,
- an active yaw mechanism connected to the other of the tower or the nacelle, wherein the active yaw mechanism comprises at least one yaw drive comprising a pinion configured to be arranged in engagement with the toothed yaw ring and a yaw drive mechanism configured to drive the pinion, and wherein at least one of the yaw drives comprises a decoupling device configured to selectively decouple at least the drive mechanism of the yaw drive from the yaw system.
The yaw system of the wind turbine according to the second aspect of the invention may advantageously be controlled in accordance with a method according to the first aspect of the invention. A person skilled in the art would therefore readily understand that any feature described in combination with the first aspect of the invention could also be combined with the second aspect of the invention, and vice versa. In particular, the decoupling device of the wind turbine according to the second aspect of the invention allows at least the drive mechanism of each yaw drive to be mechanically decoupled from the yaw system, in the manner described above with reference to the first aspect of the invention. Thus, the decoupling device may be operated in accordance with the method according to the first aspect of the invention, i.e. the decoupling may take place in the manner described above. For instance, the decoupling device may be arranged to decouple the toothed yaw ring from the tower or the nacelle. In this case the wind turbine may comprise a bearing arranged between the toothed yaw ring and the tower or the nacelle.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will now be described in further detail with reference to the accompanying drawings in which Figs. 1 and 2 show a yaw system for a wind turbine according to a first embodiment of the invention from two different angles,
Figs. 3-5 show the yaw system of Figs. 1 and 2 at rest, during active yawing and during passive yawing, respectively,
Fig. 6 shows details of the yaw system of Figs. 1-5, Figs. 7 and 8 show a yaw system for a wind turbine according to a second embodiment of the invention from two different angles,
Fig. 9 is a yaw gear for the yaw system of Figs. 7 and 8, and
Figs. 10 and 11 show a yaw system for a wind turbine according to a third embodiment of the invention from two different angles. DETAILED DESCRIPTION OF THE DRAWINGS
Figs. 1 and 2 show a yaw system 1 for a wind turbine according to a first embodiment of the invention from two different angles. The yaw system 1 comprises a toothed yaw ring 2 which is connected to a wind turbine tower (not shown). The yaw system 1 further comprises an active yaw mechanism comprising eight yaw drives 3, each being connected to a main frame 4 of a nacelle. Each yaw drive 3 comprises a toothed pinion 5 which can be arranged in engagement with the toothed yaw ring 2. The pinion 5 is connected to a yaw motor 6, via a yaw gear (not shown).
The yaw system 1 of Figs. 1 and 2 can be operated in an active mode or in a passive mode. In the active mode, the wind turbine performs yaw movements by operating the yaw motors 6, thereby causing the pinions 5 to rotate. This, in turn, causes a relative rotational movement between the toothed yaw ring 2 and the yaw drives 3, and thereby between the wind turbine tower and the nacelle.
In the passive mode, the wind turbine performs yaw movements by means of free yawing, i.e. the nacelle passively follows the direction of the wind in order to orient the rotor of the wind turbine in accordance with the direction of the wind. When the yaw system 1 of Figs. 1 and 2 is operated in the passive mode, the toothed yaw ring 2 is decoupled from the wind turbine tower. Thereby the toothed yaw ring 2 rotates along with the yaw drives 3 and the nacelle during free yawing movements. Accordingly, even though the pinions 5 are arranged in engagement with the toothed yaw ring 2, the free yawing movements will not cause a rotation of the pinions 5, and thereby there is no force transfer to the yaw drives 3, notably to the yaw gears and/or the yaw motors 6. This will be described in further detail below with reference to Figs. 6-9.
The yaw system 1 of Figs. 1 and 2 may be controlled in the following manner. While the yaw system 1 is operated in the active mode, as described above, the wind speed and/or turbulence at the location of the wind turbine, and/or wind driven loads on the wind turbine are monitored. In the case that the wind speed and/or turbulence and/or wind driven loads exceeds a predefined threshold value, it is determined that the wind conditions are appropriate for free yawing of the wind turbine. For instance, the available energy in the wind may be sufficient to ensure that the nacelle is able to follow the wind direction correctly, thereby ensuring appropriate orientation of the rotor of the wind turbine.
Thus, when this occurs, the yaw system 1 is switched to the passive mode by decoupling the toothed yaw ring 2 from the wind turbine tower. Figs. 3-5 are schematic views of the yaw system 1 of Figs. 1 and 2 from below. Furthermore, the nacelle 7, the tower 8 and a hub 9 of the wind turbine are shown. In Fig. 3 the yaw system 1 is shown at rest, i.e. it is not performing yaw movements.
In Fig. 4, the yaw system 1 is performing active yaw movements by operating the yaw drives 3, thereby rotating the pinions and causing a relative movement between the toothed yaw ring 2 and the yaw drives 3. This results in rotation of the nacelle 7 relative to the tower 8, as illustrated by arrow 10.
In Fig. 5, the yaw system 1 is performing passive yaw movements or free yawing, as illustrated by arrow 11. The toothed yaw ring 2 has been decoupled from the tower 8, and it therefore rotates along with the nacelle 7, and there is therefore no force transfer from the toothed yaw ring 2 to the yaw drives 3. The decoupling of the toothed yaw ring 2 may, e.g., be accomplished by releasing brakes 12.
Fig. 6 is a cross sectional view of a part of the yaw system 1 of Figs. 1-5, showing one of the yaw drives 3 with its pinion 5 arranged in engagement with the toothed yaw ring 2. Bearing 14 ensures that the bedframe 4 of the nacelle is able to rotate relative to the tower 8. In Fig. 6, the bearing 14 is illustrated as a ball bearing. However, it should be noted that the bearing 14 could be any other suitable kind of bearing, e.g. a sliding bearing.
It can be seen that the toothed yaw ring 2 is connected to the tower 8 via a yaw claw 13 with braking pads 12 arranged between the yaw claw 13 and the toothed yaw ring 2. When the yaw system is operated in the active mode, the braking pads 12 are in a locking position in which they fixate the toothed yaw ring 2 relative to the yaw claw 13, and thereby relative to the tower 8. When the yaw system 1 is switched to the passive mode, the braking pads 12 are released, in the sense that they are moved out of the locking position, so that they no longer fixate the toothed yaw ring 2 relative to the yaw claw 13.
Thereby the toothed yaw ring 2 is allowed to move relative to the tower 8, and it therefore moves along with the yaw drives 3 and the bedframe 4 of the nacelle during the free yawing movements, as described above. Figs. 7 and 8 show a yaw system 1 for a wind turbine according to a second embodiment of the invention from two different angles. The yaw system 1 of Figs. 7 and 8 is very similar to the yaw system 1 of Figs. 1 and 2, and it will therefore not be described in detail here.
However, in the yaw system 1 of Figs. 7 and 8, the toothed yaw ring 2 is fixedly connected to the tower of the wind turbine. Instead, a part of the yaw gear of each yaw drive 3 can be decoupled, thereby decoupling at least the yaw motors 6 from the yaw system 1. Accordingly, when the yaw system 1 is operated in the passive mode, the relative movements of the nacelle and the tower cause the pinions 5 of the yaw drives 3 to rotate, since they are arranged in engagement with the toothed yaw ring 2. However, this rotational movement is not transferred to the yaw motors 6 because part of the yaw gears has been decoupled.
Fig. 9 shows a yaw gear 15 for the yaw system of Figs. 7 and 8. The yaw gear 15 is in the form of a planetary gear with a ring gear 16, three planet gears 17 and a sun gear 18. A shaft 19 connected to the sun gear 18 is connectable to a pinion.
A plurality of hydromechanic pistons 20 having brake pads mounted thereon are arranged circumferentially with respect to the ring gear 16. The pistons 20 are thereby able to move the brake pads into and out of engagement with the ring gear 16. When the brake pads are arranged in engagement with the ring gear 16, the ring gear 16 is fixated relative to a yaw motor, and thereby the yaw system is operated in the active mode. However, when the brake pads are not arranged in engagement with the ring gear 16, the ring gear 16 is allowed to rotate relative to the yaw motor, and thereby the yaw motor is decoupled from the pinion. Thus, when the pinion rotates as a result of free yawing movements and due to the pinion being arranged in engagement with a toothed yaw ring, the entire yaw gear 15 rotates along, but without transferring force to the yaw motor.
According to this embodiment, the power supply to the yaw motor may advantageously be of a kind which ensures that no cable twisting occurs as a result of the yaw gear 15 rotating relative to the yaw motor during free yawing. For instance, electrical power may be transferred to the yaw motor via a slip ring. In the case of a hydraulic system, power may be supplied to the yaw motor via a hydraulic rotating union. Figs. 10 and 11 show a yaw system 1 for a wind turbine according to a third embodiment of the invention from two different angles. The yaw system 1 of Figs. 10 and 11 is very similar to the yaw system 1 of Figs. 1 and 2, and it will therefore not be described in detail here.
However, the yaw system 1 of Figs. 10 and 11 is not provided with yaw drives of the kind shown in Figs. 1 and 2. Instead, the yaw system 1 comprises four hydraulic cylinders 21 and four locking devices 22. Each locking device 22 is provided with a toothed portion which may be arranged in engagement with the toothed yaw ring 2. The locking devices 22 can be moved into and out of engagement with the toothed yaw ring 2 by appropriately operating the hydraulic cylinders 21.
When all four locking devices 22 are arranged in engagement with the toothed yaw ring 2, the yaw system 1 is locked in the sense that the nacelle is not allowed to rotate relative to the tower.
When none of the four locking devices 22 is arranged in engagement with the toothed yaw ring 2, the nacelle can rotate freely relative to the tower. Thereby the yaw system 1 can perform free yawing without any force transfer between the toothed yaw ring 2 and the hydraulic cylinders 21. Accordingly, the hydraulic cylinders 21 are, in this case, decoupled from the yaw system 1, and the yaw system 1 is operated in the passive mode. The yaw system 1 may further be operated in an active mode. In this case the hydraulic cylinders 21 are operated in such a manner that the locking devices 22 move in a manner similar to a pair of scissors, thereby causing relative movements between the nacelle and the tower.

Claims

1. A method for controlling a yaw system (1) of a wind turbine, the yaw system (1) interconnecting a wind turbine tower (8) and a nacelle (7) of the wind turbine, and allowing the nacelle (7) to perform yaw movements relative to the tower (8), the yaw system (1) comprising a toothed yaw ring (2) connected to one of the tower (8) or the nacelle (7) and an active yaw mechanism comprising at least one yaw drive (3) connected to the other of the tower (8) or the nacelle (7), each yaw drive (3) comprising a pinion (5) configured to be arranged in engagement with the toothed yaw ring (2) and a drive mechanism (6) configured to drive the pinion (5), the method comprising the steps of:
- adjusting a yaw angle of the wind turbine in accordance with an occurring wind direction by means of the active yaw mechanism,
- monitoring a wind speed and/or turbulence at a location of the wind turbine, and/or wind driven loads on the wind turbine,
- in the case that the wind speed and/or the turbulence and/or the wind driven loads on the wind turbine exceeds a predefined threshold value, decoupling the active yaw mechanism by decoupling at least the drive mechanism (6) of at least one of the yaw drives (3) from the yaw system (1), and
- subsequently allowing the nacelle (7) to perform yaw movements relative to the tower (8) by means of free yawing.
2. A method according to claim 1, wherein each yaw drive (3) further comprises a yaw gear (15) interconnecting the drive mechanism (6) and the pinion (5), and wherein the step of decoupling the active yaw mechanism further comprises decoupling at least part of the yaw gear (15) from the yaw system (1).
3. A method according to claim 2, wherein the step of decoupling the active yaw mechanism comprises releasing a holding mechanism (20) configured to fixate a gear part (16) of the yaw gear (15).
4. A method according to any of the preceding claims, wherein the step of decoupling the active yaw mechanism comprises moving the pinion (5) of each yaw drive (3) out of engagement with the toothed yaw ring (2).
5. A method according to any of the preceding claims, wherein the drive mechanism of each yaw drive (3) comprises a variable displacement pump comprising a plurality of pistons and a swash plate, and wherein the step of decoupling the active yaw mechanism comprises moving the swash plate of each drive mechanism to a neutral position.
6. A method according to any of the preceding claims, wherein the step of decoupling the active yaw mechanism comprises decoupling the toothed yaw ring (2) from the tower (8) or the nacelle (7).
7. A method according to any of the preceding claims, wherein the decoupling of the active yaw mechanism is performed by operating a hydraulic mechanism (20, 21).
8. A method according to any of the preceding claims, wherein the wind turbine is a downwind wind turbine.
9. A method according to any of claims 1-7, wherein the wind turbine is an upwind wind turbine, and wherein the method further comprises the steps of, in the case that the wind speed and/or the turbulence and/or the wind driven loads exceeds the predefined threshold value:
- switching operation of the wind turbine to idle mode, and
- yawing the wind turbine to a downwind position by means of the active yaw mechanism, and wherein the step of decoupling the active yaw mechanism is performed while the wind turbine is in the downwind position.
10. A method according to claim 9, further comprising the step of determining cable twist of the wind turbine, and wherein the step of yawing the wind turbine to a downwind position is performed in such a manner that cable untwist is obtained.
11. A method according to any of the preceding claims, further comprising the steps of:
- monitoring yaw error of the wind turbine while allowing the nacelle (7) to perform yaw movements relative to the tower (8) by means of free yawing, - re-coupling the active yaw mechanism in the case that the yaw error exceeds a predefined threshold level, and
- correcting the yaw error by means of the active yaw mechanism.
12. A method according to any of the preceding claims, further comprising the steps of: - monitoring a yaw velocity of the wind turbine while allowing the nacelle
(7) to perform yaw movements relative to the tower (8) by means of free yawing,
- re-coupling the active yaw mechanism in the case that the yaw velocity exceeds a predefined threshold level, and - correcting the yaw velocity by means of the active yaw mechanism.
13. A method according to any of the preceding claims, further comprising the steps of:
- monitoring a wind speed and/or turbulence at the location of the wind turbine, and/or wind driven loads on the wind turbine, while allowing the nacelle (7) to perform yaw movements relative to the tower (8) by means of free yawing,
- in the case that the wind speed and/or the turbulence and/or the wind driven loads on the wind turbine decreases below a predefined cut-in threshold value, re-coupling the active yaw mechanism, and
- subsequently adjusting the yaw angle of the wind turbine in accordance with an occurring wind direction by means of the active yaw mechanism.
14. A method according to any of the preceding claims, wherein the step of monitoring a wind speed and/or turbulence at a location of the wind turbine comprises estimating an expected wind speed and/or turbulence during a future time interval based on a weather forecast.
15. A method according to any of the preceding claims, further comprising the step of allowing the nacelle (7) to slide relative to the wind turbine tower (8), via an interface defined in the yaw system (1), in the case that a torque in the yaw system (1) exceeds a predefined threshold level.
16. A wind turbine comprising a wind turbine tower (8) and a nacelle (7) connected to the wind turbine tower (8) via a yaw system (1), wherein the yaw system (1) comprises:
- a toothed yaw ring (2) connected to one of the tower (8) or the nacelle
(7),
- an active yaw mechanism connected to the other of the tower (8) or the nacelle (7), wherein the active yaw mechanism comprises at least one yaw drive (3) comprising a pinion (5) configured to be arranged in engagement with the toothed yaw ring (2) and a yaw drive mechanism (6) configured to drive the pinion (5), and wherein at least one of the yaw drives (3) comprises a decoupling device configured to selectively decouple at least the drive mechanism (6) of the yaw drive (3) from the yaw system (1).
PCT/DK2021/050110 2020-04-15 2021-04-15 A method for controlling a yaw system of a wind turbine WO2021209110A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DKPA202070233 2020-04-15
DKPA202070233 2020-04-15

Publications (1)

Publication Number Publication Date
WO2021209110A1 true WO2021209110A1 (en) 2021-10-21

Family

ID=75659753

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/DK2021/050110 WO2021209110A1 (en) 2020-04-15 2021-04-15 A method for controlling a yaw system of a wind turbine

Country Status (1)

Country Link
WO (1) WO2021209110A1 (en)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114060214A (en) * 2021-11-16 2022-02-18 向雨 Yaw device
CN114109931A (en) * 2021-12-03 2022-03-01 哈电风能有限公司 Yaw brake control method and system for wind generating set
CN117052603A (en) * 2023-07-10 2023-11-14 太原重工股份有限公司 Yaw starting control method for wind turbine generator

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2004232500A (en) * 2003-01-28 2004-08-19 Komatsu Ltd Nacelle turn drive device for wind power generation equipment, and its operating method
US8277167B2 (en) 2001-12-28 2012-10-02 Mitsubishi Heavy Industries, Ltd. Wind turbine operating apparatus and operating method
EP3124788A1 (en) 2015-07-28 2017-02-01 Hitachi, Ltd. Wind power generator

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8277167B2 (en) 2001-12-28 2012-10-02 Mitsubishi Heavy Industries, Ltd. Wind turbine operating apparatus and operating method
JP2004232500A (en) * 2003-01-28 2004-08-19 Komatsu Ltd Nacelle turn drive device for wind power generation equipment, and its operating method
EP3124788A1 (en) 2015-07-28 2017-02-01 Hitachi, Ltd. Wind power generator

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114060214A (en) * 2021-11-16 2022-02-18 向雨 Yaw device
CN114109931A (en) * 2021-12-03 2022-03-01 哈电风能有限公司 Yaw brake control method and system for wind generating set
CN114109931B (en) * 2021-12-03 2024-04-05 哈电风能有限公司 Yaw brake control method and system for wind generating set
CN117052603A (en) * 2023-07-10 2023-11-14 太原重工股份有限公司 Yaw starting control method for wind turbine generator
CN117052603B (en) * 2023-07-10 2024-04-19 太原重工股份有限公司 Yaw starting control method for wind turbine generator

Similar Documents

Publication Publication Date Title
WO2021209110A1 (en) A method for controlling a yaw system of a wind turbine
US8172532B2 (en) Device for adjustment of a rotor blade, wind energy converter, and method for adjusting a rotor blade
US20110280725A1 (en) Long Term Rotor Parking on a Wind Turbine
CA2822976C (en) System and method for braking a wind turbine rotor at an overspeed condition
CA2871278C (en) System and method for stopping the operation of a wind turbine
US20090001724A1 (en) Method and apparatus for controlling vertical axis wind power generation system
US20130088009A1 (en) Method to Prevent Over Torque of Yaw Drive Components in a Wind Turbine
US9470208B2 (en) Wind turbine and locking method
US20100068057A1 (en) Method for stopping a wind turbine in two stages
EP2466124A2 (en) Hydraulic yaw drive system for a wind turbine and method of operating the same
US10982649B2 (en) System and method for detecting a pitch fault in a wind turbine via voltage, current, torque, or force monitoring
US9528494B2 (en) Method and system for operating a wind turbine during a fault
EP3643915B1 (en) System and method for application of a brake for a wind turbine
KR102042259B1 (en) Wind-Electric Power Generation System and Driving Stop Method Thereof
US20140248118A1 (en) Start-up method for a wind turbine and a control assembly
US20240229764A9 (en) Protection of wind turbine components during yawing
EP4361434A1 (en) Protection of wind turbine components during yawing
CN117795196A (en) Method of operating a wind turbine with a faulty blade in an active idle mode
CN101514673A (en) Wind generating set vane

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 21720994

Country of ref document: EP

Kind code of ref document: A1

NENP Non-entry into the national phase

Ref country code: DE

122 Ep: pct application non-entry in european phase

Ref document number: 21720994

Country of ref document: EP

Kind code of ref document: A1