WO2019215466A1

WO2019215466A1 - A separate yaw-system for wind turbines

Info

Publication number: WO2019215466A1
Application number: PCT/IB2018/000573
Authority: WO
Inventors: Andres Sõnajalg; Oleg Sõnajalg
Original assignee: Sonajalg Andres; Sonajalg Oleg
Priority date: 2018-05-08
Filing date: 2018-05-08
Publication date: 2019-11-14

Abstract

The yaw-system used to rotate the wind turbine nacelle is assembled as a separate section, which is mounted separately to the upper flange of the wind turbine tower. The wind turbine nacelle with the generator, rotor head and blades is then attached to the yaw-system. The yaw-system includes a bearing section comprising a housing to which the upper and lower flanges are attached, a lower support plate for the motors, and a yaw-bearing. The bearing section has an upper support plate to support the motors, whereas the upper support plate is set at a fixed distance from the lower flange and lower support plate by means of spacers, with the air gap between the upper support plates and the bearing section housing.

Description

A separate yaw-system for wind turbines

FIELD OF THE INVENTION

Current invention relates to the equipment of production and storage of wind power, and more particularly, to the improved structure of the yaw-system used for turning the wind turbine nacelle, more particularly, to the separately assembled yaw-section, which is installed between the upper part of the wind turbine tower and the wind turbine nacelle, and the task of which is to turn the wind turbine rotor in the direction of the wind and to maintain/brake/lock it in an optimal position.

BACKGROUND ART OF INVENTION

Turbines generating electric energy from wind, or wind turbines, are widely known in the art by now. A typical wind turbine includes a tower and a nacelle attached to it, which in turn includes a power generator and aerodynamic rotor head to which a wind turbine rotor has been attached. Wind turbine nacelle is attached to the tower via a yaw-bearing in order to turn the nacelle in the horizontal plane in the direction of the wind, or to turn the nacelle together with the blades relative to the tower. Normally, the yaw-bearing is a bearing, which has a toothing (toothed rim) installed on its outer or inner collar and to which gear wheels engage, that are fixed to the shafts of the engines that are designed to turn the nacelle.

Power and torques from the main shaft of the wind turbine are transferred to the wind turbine tower through the yaw-bearing. Since the forces transferred to the bearing are enormous, the bearing must support the entire wind turbine nacelle together with the generator part and blades, weighing up to several hundred tons in total. Also, the yaw-bearing must withstand the nacelle tilting moment resulting from the change in the direction of winds. In addition, for example the effect of the salty and damp sea air on the wind turbine placed in the sea, causing the corrosion of structural elements, must be taken into account. Therefore, it has been attempted to design the nacelle rotation mechanism in several different ways. In addition, yaw systems are divided into active and passive ones. Active yaw systems are equipped with torque-generating devices that are capable of turning the nacelle of the wind turbine relative to the stationary wind turbine tower in the direction of the wind based on the automatic signals from corresponding direction sensors or commands given manually to the control system. Active yaw systems are currently the best-known and most frequently used for medium and large-scale wind turbines. The various components of the active yaw systems vary according to the respective design solutions and the conditions of use for which they are provided. Generally, all active yaw systems include a rotating connection between the wind turbine nacelle and the tower (yaw-bearing), an equipment for changing the rotor orientation (in the wind direction), or yaw-drive, an equipment for limiting the turning of the rotor head (yaw-brake), and a control system that processes signals from wind direction sensors and transmits corresponding control signals/commands to control mechanisms.

The system employed in active yaw systems is either the yaw-roller-electric yaw- drive-brake or the yaw-roller-bearing hydraulic yaw-drive. In the first case, the rotor head/wind turbine nacelle is mounted on the roller bearing and the nacelle is moved/rotated relative to the azimuth by a number of powerful electric drives. An electric or hydraulic braking system sets the position of the wind turbine nacelle when the position change is completed. This is necessary for reducing the fatigue load caused by the so-called rebound and the wear of the units and structural parts. These systems are used by most wind turbines as they are considered reliable and efficient. However, these systems are bulky and costly to manufacture. Due to their size and weight, their installation is often challenging.

In the second case, the rotor head/wind turbine nacelle is mounted on the roller bearing and the nacelle is moved/rotated relative to the azimuth by a number of powerful hydraulic motors or hydraulic cylinders. The high power-to-weight ratio and high reliability is regarded as the advantage of these hydraulic drive yaw- systems. At the same time, the main problem with hydraulic systems is always the leakage of hydraulic fluid and clogging of the high pressure hydraulic valves. Hydraulic yaw systems (depending on the design of the system) often enable to abandon the anti-slip braking mechanism, replacing it with, for example, shut-off valves.

Passive yaw systems are normally used in small-scale wind turbines, as the rotor head rotates freely relative to the wind turbine tower. Such a design assumes that the wind turbine has a tail. With regard to the objects of the present invention, passive yaw systems are not relevant. As stated above, one of the main components of the yaw system is a yaw-bearing, which can be a roller bearing or a friction bearing and which ensures the rotary motion of the wind turbine nacelle relative to the stationary tower of the wind turbine. This yaw-bearing has to take very high loads, which, in addition to the weight of the wind turbine blades and the nacelle, must withstand the bending moment caused to the rotor by the kinetic energy of the wind. The equipment for changing the orientation of the yaw system’s rotor (so-called yaw-drive) includes powerful electric motors that come with the torque-increasing reduction gear, to actively change the wind turbine nacelle position. The torque of larger wind turbines can reach up to 4000 kNm, with a gear ratio of 1/1500 to 1/1600, plus a 1 :12 tooth rim gear ratio, which means that the rotation speed of the yaw system is relatively slow. The third important component of the yaw system is the wind turbine nacelle braking system, which is needed to stabilize the yaw-roller while turning the wind turbine nacelle. One solution is to use electric motors for braking, giving them a steady small torque to brake the wind turbine nacelle.

The most important problem with modern wind turbines is the weight of the various structural units and their installation height above the ground or sea level. On the other hand, there are attempts to integrate the units, because each additional connection or unit is a danger spot due to the forces and moments (torque, torsion) imposed on the entire structure of the wind turbine.

For example, in EP 2,402,599, January 4, 2012, General Electric Company described a yaw-bearing system for a wind turbine, in which the wind turbine nacelle has a lower yaw-bearing and the upper yaw-bearing by which the nacelle is pivotally connected to the wind turbine tower. The peculiarity of the structure is a shaft reaching through the nacelle, with an upper bearing attached to the upper end, and a lower bearing attached to the lower end. The disadvantage of this structure is primarily its weight, which is very critical with modern wind turbines, since more powerful wind turbines mean larger dimensions of the wind turbine and higher weights. The weight plays a very important role primarily in putting together a wind turbine and raising its individual sections up to 190 m. Wind turbine or wind turbine park builders know that there are just a few cranes in the world that can lift individual units or sections weighing tens and hundreds of tons, that is to say, there are simply physical boundaries for cranes that can lift heavy structures high up.

On the other hand, attempts have been made to design mechanisms needed to rotate the nacelle by building separate sections that are not so heavy and that could be lifted to the required height when putting together a wind turbine.

In US 2015/0308414, dated 10/29/2015, Wobben Properties GmbH describes the design of a wind turbine that can reduce the load on the yaw-bearings. This wind turbine includes a nacelle with a generator, a tower and a yaw-bearing for turning the nacelle in the direction of the wind. The outer collar of the bearing is attached to the lower flange of the bearing section and the bearing section is fixed to the tower by the inner collar of the bearing. On the inner collar of the bearing, there is a internal gearing toothing to which engages a gear wheel that is mounted on the shaft of the motor(s) placed on the bearing section to rotate the wind turbine nacelle relative to the tower. Additionally, the motors are supported by circular plates, which in turn are attached/fixed to the housing of the bearing section. One support point for the motor is the lower plate and the second support point is on the top plate to which the motor is attached. A disadvantage of this structure is the fact that, by attaching horizontal circular plates to the bearing section housing, a line of stress concentration across the fixing circuit is created, which can cause cracks in the bearing section housing. The reason for this is the fact that when the wind turbine is in operation, the loads are transferred to the housing of the bearing section, resulting in the housing deforming into the oval shape, while the loads due to the structure affect the housing, and the diameter of the housing becomes even again. At the same time, the loads are affecting periodically, so the housing starts moving between the oval and the circle position deviation. As a result, tensions occur on the fixing points of the plates.

However, the braking performance of the motors is important for the rotation of the nacelle with respect to the tower. In particular, it relates to situations where the wind turbine must be turned away from the wind to stop the wind turbine, whereupon a real need emerges to brake the nacelle, so that it would not turn again in the direction of the wind. This means that the fastening of the motors used to rotate the nacelle in the bearing unit must be sufficient to keep the motors fixed on the horizontal plate.

DISCLOSURE OF THE INVENTION

It is an object of the present invention to provide such a wind turbine nacelle turning mechanism design that would enable:

- to better balance the nacelle placed on top of the wind turbine tower relative to the tower;

- to reduce the number of elements to be attached to the bearing section to zero to avoid excessive stress concentrations, thereby extending the lifespan of the wind turbine tower and the units attached thereto,

- to reduce the weight of the nacelle by preparing the structure or unit for rotating the nacelle as a separate section, so that, when putting a wind turbine together, this unit is lifted separately and connected to the upper part of the tower,

- to ensure the separation from the outside air of units used to rotate the nacelle, thereby again extending the life of the units.

To achieve the objectives, a mechanism for rotating the nacelle is prepared as a separate section, comprising a housing to which the upper and lower flanges are attached, a lower support plate for the motors, and a bearing. Constructing the yaw section separately allows it to be put together beforehand at the factory, and then to transport it to the wind turbine construction site and lift it separately on top of the wind turbine tower. A separately assembled yaw section allows to reduce the weight of the wind turbine nacelle, which is especially important when installing high-power wind turbines where the weight of the sections is not really dependent on how large a wind turbine can be constructed, but whether there is transportation and lifting equipment for lifting the sections to the required height during construction.

The bearing section has a top support plate for supporting motors, whereas the upper support plate is set at a fixed distance from the lower flange with spacers, and the motors are attached to the upper support plate. There is a gap between the upper support plate and the bearing section housing, so that the upper support plate does not touch the inner surface of the bearing section housing.

BRIEF DESCRIPTION OF DRAWINGS

The invention is described in the following exemplary embodiment with references to drawings in which

Fig. 1 is a wind turbine, which consists of a tower, a wind turbine nacelle attached to the upper part of the tower together with a generator part and rotor head and blades,

Fig. 2 is a close-up view of the upper part of the wind turbine tower to display the position of the bearing section used to turn the wind turbine nacelle,

Fig 3. shows a cross-sectional view of the bearing section to indicate the position of the motors used to rotate the nacelle in the bearing section; for clarity of the drawing, the fastening elements required for attaching the nacelle and bearing section and the bearing section and the upper part of the tower are not shown; also, for the sake of clarity, the fastening elements for the support plates and the fastening elements for the bearing are not shown;

Fig 4. shows a half-cross-sectional view of the bearing section in which is depicted a bearing with a toothing, a lower and upper support plate and a motor with a gear wheel, and a schematic view of the mounting of a bearing section to the upper part of the wind turbine tower;

Fig 5. is a sectional view of a bearing section to illustrate the arrangement and fastening of the upper and lower support plate, as well as the fastening of the inner collar of the bearing to the upper flange of the tower, and the fastening of the outer collar of the bearing to the lower support plate, lower flange of the bearing section and upper support plate;

Figs. 6A and 6B show a plan view and sectional view of the bearing section, respectively, without motors and a yaw-bearing;

Fig. 7 is a plan view of the bearing section in order to illustrate the layout of the openings provided for the attachment elements in the upper flange of the bearing section and the layout of the openings provided for attaching the motors;

Fig. 8 is a partial cross-sectional view of the bearing section to illustrate the layout of the openings for the fastening elements in the upper support plate;

Fig. 9 is displays the enlarged view shown in Fig. 8 to further illustrate the essential feature of the invention in which there is an air gap between the upper support plate and the bearing section housing 71 to compensate for changes in the shape of the bearing section in the operation of the wind turbine; in particular the shape of the bearing section housing changes between the oval and the circular as a result of the forces exerted by the wind to the blades;

Fig. 10 is a top view of the upper support plate;

Fig. 11 is the bearing section, in particular the lower support plate of the bearing section as seen from below.

DETAILED DESCRIPTION OF INVENTION

Fig. 1 shows a wind turbine (tower, nacelle, rotor, rotor head, blades), together with the upper section 2 of the wind turbine tower, which is typically attached to a wind turbine nacelle 3, comprising a main body 4 containing an electric generator, a rotor head 5 to which wind turbine blades 51 are attached, while the rotor head is connected to the wind turbine rotor. There is a yaw-system bearing section 7 installed between the wind turbine nacelle and the tower for turning the wind turbine nacelle in relation to the wind turbine tower. Fig. 2 displays also the yaw- bearing 6 of the yaw-system mounted on top of the uppermost section of the wind turbine tower and the yaw-system bearing section 7. Fig. 3 is a cross-sectional view of the yaw-system bearing section, which shows the inner collar 8 of the yaw- bearing, to which a toothing 80 with an inner engagement is secured, engaging a gear wheel 90 attached to the reduction gear shaft 92 of the electric drive 9. The electric drives (motors) for rotation of the nacelle rest upon the upper support plate and the electric drive reduction gears rest on the lower support plate, thus ensuring the fastening of the electric drive with two support surfaces, which allows the electric drives to be used in addition to the rotation of the nacelle to also stop the nacelle, or to keep the wind turbine in the direction of the wind.

There is an upper flange 10 fastened (welded) to the upper end/edge of the cylindrical housing of the bearing section 7, provided with threaded openings 14 (see Fig. 9, Fig. 10), which are required for the fasteners that connect the wind turbine nacelle 3 to the bearing section 7. Generally, the wind turbine nacelle is fastened to the upper flange 10 of the bearing system 7 of the yaw-system by means of stud bolts, whereas the stud bolts are screwed into the upper flange 10 of the bearing section 7 before the assembly and, upon the assembly of the wind turbine the wind turbine nacelle 3 is lifted beforehand to the yaw-section previously mounted on the tower so that the stud bolts attached previously to the bearing section pass through the openings drilled in the lower flange of the wind turbine nacelle. Appropriate washers and nuts are installed on the stud bolts to fasten the wind turbine nacelle against the bearing section. In the middle of the upper flange 10, a through hole 34 is formed to create a common space with the bearing section and nacelle, so that the service staff of the wind turbine could move freely within the bearing section and the nacelle.

A lower flange 11 is fastened (welded) to the lower part of the cylindrical housing of the bearing section 7, provided with the openings 15 for fasteners to fasten the flange 11 (as well as the bearing section) to the outer collar 61 of the yaw-bearing. Flere the stud bolts are secured to the threaded openings drilled in the outer collar of the yaw-bearing. The housing of the bearing section 7 is assembled with the upper part of the wind turbine tower, while allowing the wind turbine nacelle to be rotated relative to the stationary static wind turbine tower. A top support plate 12 is mounted and secured in the bearing section to the lower flange 11 of the bearing section. The lower support plate 13 is arranged between the lower flange 11 of the bearing section and the outer collar 61 of the yaw- bearing. Between the lower 13 and the upper support plate 12, there are spacers 19, 20 with through openings 18 (for mounting bolts) arranged during the assembly of the yaw-system bearing section, that are used to maintain a constant distance between the upper 12 and the lower support plate 13. This is necessary for attaching the electric drives with reduction gears required for rotating the yaw- system to the upper and lower support plates while maintaining the stiffness of the support plates.

The inner spacers 19 remain on the inner edge of the support plates, at the edge to the centre of the tower, and the outer spacers 20 remain on the outside edge of the support plates, on the edge to the side of the bearing section housing. There is an opening 16 in the upper support plate 12, through which passes a reduction gear 91 on the electric drive 9 together with the gear wheel 90 fixed to the reduction gear shaft. There are threaded openings 161 drilled at the edge of the opening along the perimeter of the opening to fasten the electric drive (fastening flange of the electric motor) to the upper support plate 12. There are openings 21 provided in the lower support plate that are gradual. There is a step formed in the openings in such a way that in the bottom plate an opening with a smaller diameter is drilled (the diameter of the opening is such that it can be fitted with the gear 90 attached to the end of the shaft of the electric drive gear when assembling the bearing section and installing the electric drives). The diameter of the openings on the base plate is then drilled wider on the surface of the support plate, with the height of the step being about half of the depth of the base plate. When assembling the bearing unit and installing the electric drives, the end face of the reducer rests against the step of the opening formed in the support plate (see Fig. 4). At the same time, the side face of the reduction gear end is seated in given hole, which reduces the displacement of the engine laterally. The engine with the reducer has two support points - one is the contact surface of the engine mounting flange and the upper support plate, and the other is the contact surface of the motor reducer and the lower support plate opening. This design makes the electric drive attachment more stable laterally, as the electric drive is supported by two support points: attachment of the electric drive mounting flange and upper support plate and attachment of the end of the electric drive reducer to the lower support plate step. In this way, the lateral torsional torque of the electric drive can be reduced in the upper supporting plate and the electric drive flange attachment that occurs when the electric drive power starts and begins to rotate the wind turbine or when the wind turbine rotor head is turned in the direction of the wind, and the yaw-system unit must keep the nacelle position stable (to brake).

The lower support plate rests on the outer collar of the bearing section yaw- bearing and its diameter corresponds to the outer diameter of the bearing section housing. In contrast, the diameter of the upper support plate 12 is smaller than the inner diameter of the bearing section 7 housing in such a way that the air gap S remains between the edge of the support plate and the inner wall of the housing. This allows the "play room" for the housing of the tower’s bearing section when, after the wind turbine has started to operate, the cross-section of the bearing section housing starts to alternate between the oval shape and the circular (cylindrical) shape. This alternation between the oval and cylindrical shape is caused by the loads (torques, vibrations, etc.), which influence the entire wind turbine tower when the wind turbine is operating, i.e. the blades of the wind turbine rotor head are turned in the direction of the wind and the generator generates energy.

In the sectional view shown in Fig. 5, there is a flange 30 attached (welded) to the upper part of the tower 2, having openings for fasteners distributed across the perimeter, by which the inner collar 8 of the bearing section yaw-bearing is attached to the flange. There is an inner collar 8 of the yaw-bearing 6 resting on the flange 30 of the upper part of the tower where there are threaded openings for the fastening means (stud bolt 28, nut 29), which secure/fasten the inner collar of the bearing to the flange 30 when attaching the bearing section 7 to the upper end of the tower 2. There are threaded openings in the outer collar 61 of the bearing for fasteners to attach the outer collar of the bearing to the lower support plate 13 of the bearing section and the lower flange 11 of the bearing section housing. When assembling the bearing section, the lower support plate 13 of the bearing section is placed onto the outer collar 61 of the yaw-bearing, then a bearing section with the lower flange is mounted on the lower support plate 13, and the bearing section together with the lower flange 11 and the lower support plate 13 are secured to the outer collar 61 of the yaw-bearing 6 by means of stud bolts. There is a lower and upper seal 32, 33 attached between the inner and outer collar of the bearing, preventing the salty sea air, dust, etc. from getting on the rolling elements of the bearing (balls, rollers). Besides, the seals are designed to prevent the lubricant from escaping from the bearing.

The outer collar of the yaw-bearing supports the lower plate of the bearing section 13 and this in turn supports the lower flange 11 attached to the bearing section 7 housing together with the bearing section housing. There are also openings extending along the perimeter of the flange for fastening means to attach the bearing section to the outer collar of the bearing. When assembling the bearing section, the outer spacers 20 are first placed on the lower flange 11 of the bearing section, which hold the upper support plate at a fixed distance from the lower support plate and provide the motor reduction gear with fit connection with the lower support plates. Spacers 20 in turn support the upper support plate 12. The upper support plate 12, flange 11 and lower support plate 13 are pulled by means of fasteners (stud bolt 26, nut 27) onto the outer collar of the yaw-bearing.

The upper flange 10 with threaded openings 14 for fasteners, which connect the nacelle to the bearing section, is fastened (welded) to the upper end of the bearing section housing 7.

The height of the bearing section is designed in such a way that it is possible to accommodate the controls and necessary cabling for motors used to rotate the nacelle and to allow people freely stand in the bearing section. List of components:

1 - wind turbine

2 - upper section

3 - nacelle

4 - main frame

5 - rotor head

51 - blades

6 - yaw-bearing

61 - outer collar of the yaw-bearing

7 - bearing section

71 - housing of the bearing section

8 - inner collar of the yaw-bearing

80 - toothing

9 - electric drive (motor)

90 - gear wheel

91 - reduction gear

92 - reduction gear shaft

93 - opening for the gear wheel

10 - upper flange

11 - lower flange

12 - upper support plate

13 - lower support plate

14 - threaded openings

15 - openings for fasteners

16 - opening for the reduction gear

161 - openings for fastening the electric drive 18 - through opening in spacers

19 - inner spacers

20 - outer spacers

21 - gradual opening

26 - stud bolt

27 - nut

28 - stud bolt

29 - nut

30 - flange attached to the upper end of the tower 32 - lower seal

33 - upper seal

34 - through opening

S - air gap

Claims

1. A separate wind turbine yaw-system, which includes a bearing section, which is placed and attached to the upper end of the wind turbine tower and to which is placed and attached a nacelle of the wind turbine, whereas the bearing section (7) includes a housing with the upper (10) and lower (11 ) flange, an upper (12) and lower (13) support plate, the motors for turning the nacelle, a yaw-bearing, the inner collar (8) of which is attached to the collar of the upper end of the wind turbine tower by fasteners, and the outer collar (6) of which is attached by means of fasteners to the lower support plate (13) of the bearing section, the lower flange (11 ) of the bearing section housing and the upper support plate (12), whereas there are inner spacers (19) placed between the lower support plate (13) and the upper support plate (12) of the bearing section and there are outer spacers (20) placed between the upper support plate (12) and the lower flange (11 ) of the bearing section in order to maintain a fixed distance between the support plates and the upper support plate and the lower flange of the bearing section, and that there is an air gap S between the support plates (12), which are required for attaching the motors used for turning the wind turbine nacelle (3), and the bearing section housing (7).

2. Separate wind turbine yaw-system according to claim 1 , characterized by that the upper support plate (12) diameter is smaller than the inner diameter of the bearing section housing (7), so that there is an air gap S between the outer edge of the support plate (12) and the bearing section housing (7).

3. Separate wind turbine yaw-system according to claim 1 , characterized by that there are openings in the upper support plate (12) of the bearing section for placing motors used to turn the nacelle, whereas the openings are provided with threaded openings along the perimeter for fasteners, which are used to secure the flanges of motors to the upper support plate and there are openings in the lower support plate (13) to support the reduction gears of the motors turning the nacelle, whereas the motors used to turn the nacelle are attached to the upper support plate (12) of the bearing section, and the ends of the motors on the gear wheel side are placed into the openings in the lower support plate (13) of the bearing section without clearance.

4. A separate wind turbine yaw-system according to claim 1 , characterized by that to the inner collar of the bearing section yaw-bearing a toothing with an inner engagement is secured, which engages the gear wheel secured to the shaft of the motors used to turn the nacelle.

5. Use according to claims 1 to 4 of a separate wind turbine yaw-system in a wind turbine (1 ), which includes a tower, a wind turbine nacelle (3) together with a generator part (4), rotor head (5) with three blades (51 ), turning mechanism of a nacelle, which includes bearing section (7), which is placed and attached to the upper end of the wind turbine tower and to which is placed and attached the nacelle of the wind turbine, whereas the bearing section (7) includes a housing with the upper (10) and lower (11 ) flange, an upper (12) and lower (13) support plate, the motors for turning the nacelle, a yaw-bearing, the inner collar (8) of which is attached to the collar of the upper end of the wind turbine tower by fasteners, and the outer collar (6) of which is attached by means of fasteners to the lower support plate (13), to the lower flange (11 ) of the bearing section housing and the upper support plate (12), whereas there are spacers (20) placed between the lower support plate (13) of the bearing section and the upper support plate (12) and the lower flange (11 ) and the upper support plate (12) in order to maintain the fixed distance between the upper support plate and the lower flange and the support plates, and that there is an air gap S between the support plates (12) and the bearing section housing (7).