NO810842L - SYSTEM FOR ADJUSTING THE RISE OF WINDOWS - Google Patents

Description

The present invention relates to a wind turbine, more specifically a system for adjusting the pitch of wind turbine blades with variable pitch.

With a view to optimal operation, it is appropriate to equip wind turbines with blades that have an adjustable pitch. The blade pitch is adjusted by selectively turning the blades about their longitudinal axes, and this will, in addition to facilitating the start-up of the turbine and preventing operation at too high a speed

(by blade repositioning) in high speed winds, enable the wind turbine to operate at maximum efficiency over a large wind speed range.

Various mechanisms for regulation have been proposed

of wind turbine blade pitch. Such a mechanism, which is known from US patent 4,083,651, is based on the use of turbine blades which are torsionally twisted by means of connected pendulum elements which, through the influence of centrifugal force, react to the wind turbine's rotor speed by turning the blades and thereby varying the pitch of the blades over the wind turbine's total operating range. The blade adjustment range for such a system is of course automatic and unable to be regulated continuously during turbine operation, and it may prove impossible to achieve pitch regulation over extremely large areas.

Another pitch adjustment system for wind turbine blades works by using a sliding block which rotates with the wind turbine and is slidably supported on its main shaft. Through a number of strong links, the wind turbine blades are connected, which are mounted on a rotation hub and can thereby be rotated about their own axes. By means of a storage device, the block is also connected to a number of fixed operating mechanisms. During adjustment of the blade pitch, the operating mechanisms acting through the storage device will displace the slide block in a straight line along the shaft, thereby moving the joints which in turn turn the blades. It is obvious that this system for adjusting the blade pitch requires an energy consumption that is sufficient to overcome the wings' own resistance to such movement, and also to overcome the mass of the joint couplings, the slide block and the support device and the frictional losses associated with the slide block's support and movement along the shaft. As the commercial applicability of wind turbines is not only dependent on the amount of collected energy, but also on the losses that occur in connection with the operation of the wind turbine, it is obvious that large losses, such as those mentioned here, which are associated with this known system for blade pitch adjustment, may render the turbine commercially unsuitable under marginal wind conditions.

Although various pitch control mechanisms have been proposed for aircraft propellers, such systems have generally proven unsuitable for use in wind turbines. Examples of such pitch change mechanisms are known from US patents 1,908,894 and 3,163,232. According to the first-mentioned patent document 1,908,894, the pitch of the propeller blades is changed by means of a hub-mounted electric motor which, through a gearbox, drives the propeller blades pivotably. Such a gear transmission that connects the electric motor to the blades will contribute significantly to increasing the weight of the turbine hub, thereby causing significant losses in the system. According to the last-mentioned patent document 3,163,232, the blades are given a pitch change movement by means of a hydraulic motor and through a relatively massive, rotating cam-cone drive system which contributes significant weight and significant energy losses in the system.

It is therefore an object of the present invention

to produce a pitch adjustment system for wind turbine blades, where the disadvantages of the known technique are eliminated.

Another object of the invention is to produce such a pitch adjustment system, where all blades can be set simultaneously in different pitch angles under the control of a controller.

Another object of the invention is to produce such a pitch adjustment system of light weight.

Another object of the invention is to produce such a pitch adjustment system, where the losses that occur in connection with each connection between the system's drive devices and the blades are reduced.

A further object of the invention is to produce such a system which is characterized by economy of construction.

The above-mentioned and other purposes will appear more clearly from the subsequent, detailed description together with the patent claims and the accompanying drawings which comprise a blade pitch adjustment system for a wind turbine, where each blade is operated by a separate hydraulic operating device mounted on the hub, for to be turned with this, and directly connected to the blade, thereby eliminating the need for intermediate connecting devices such as joints, cams, drives etc., and the associated losses. The operating devices are controlled independently through a regulating device which is placed outside the hub and which supplies hydraulic fluid to the operating devices through a suitable fluid transfer device, e.g. a transmission bearing which is preferably arranged on the main turbine shaft. An emergency supply source for blade rotation Iling can also be mounted on the hub in direct connection with the operating devices. A feedback means, e.g. a linear variable displacement transducer supplies a continuous input value to the control system, indicating the turbine blade pitch. The feedback device receives driving force through a suitable device, for example a slip ring brush assembly which can also form a connection

between the feedback output and the control device.

The invention will be described in more detail in the following,

with reference to the accompanying drawings, in which:

Fig. 1 shows a side view of a large wind turbine in which the blade pitch adjustment system according to the present invention is used, and where a part is omitted for illustration of construction details in the turbine. Fig. 2 shows a schematic partial side view, partly in section, of a part of the blade pitch adjustment system according to the invention. Fig. 3 shows a schematic partial side view, partly in section,

of another part of the blade pitch system according to the invention.

As can be seen from the drawings, the pitch control system according to the present invention for wind turbine blades is designed for use in a wind turbine, where two or more blades 10 and 12 with variable pitch are mounted on suitable (not shown) bearings on a rotatable hub 14 (fig 2) which is covered by a propeller hub capsule 15, whereby the blades are selectively turned only about their longitudinal axes, for regulation of the wind turbine's operating speed over a wide range of wind conditions, and for readjustment of the blades when the wind turbine is to be shut down. The hub is attached to a rotating shaft 16 which can drive any desired load, such as an electric dynamo 18 or the like. With the aid of a suitable gearbox 20, the shaft's rotational speed can be increased or decreased as desired. The load and gearbox 20 can, together with various control devices 50, be placed in a nacelle 22, mounted on a swivel a freely rotatable axle pin 24 on a tower 26, usually behind the blades 10 and 12.

The blade pitch adjustment mechanism according to the present invention comprises first and second hydraulic operating devices or motors 28 which individually regulate the pitch of a single turbine blade, by direct connection with the blade. Although in the preferred embodiment two blades and two operating devices are shown, it is obvious that the invention includes any number of blades and associated operating devices. Each operating device comprises a cylinder 30 with a piston 34 and associated connecting rod 36 which is arranged in the cylinder, for forward movement

and backward direction in relation to this. The cylinder receives and delivers hydraulic fluid on opposite sides of the piston, through hydraulic lines 38 and 40.

As is most clearly evident from fig. 2, is the free end

of each operating device's connecting rod connected to the root part of the corresponding turbine blade through a first fork link 42, the coupling being arranged at a distance d from the blade's longitudinal axis a, whereby a reciprocating movement of the piston causes the blade to rotate about its longitudinal axis. The opposite end of the operating device, at the closed end of the cylinder, is pivotally connected at 4 4 to a central portion 46 of the hub 14, to reduce wind obstruction due to the blade operating mechanism. As each operating device must only operate a single turbine blade, these devices generally have little weight and are of compact design compared to the various known blade pitch adjustment systems, in which a single operating device controls all blades during the pitch adjustment. Consequently, the use of several operating devices, instead of a single and more powerful operating device, will not represent a serious weight problem for

the turbine hub. It also appears that the use of a single, hub-mounted operating device of light weight for each turbine blade enables a direct connection between the operating device and the blade, thereby eliminating the need for heavy and space-consuming mechanical connections between the turbine blade and the operating device, in the form of sliding blocks, joint couplings and bearings used in known wind turbines, and rotating cam and gear assemblies used in known propeller pitch control mechanisms. As previously discussed, these known pitch control mechanisms will reduce the system's efficiency, by introducing losses in the system due to the weight of the components and the induced frictional forces due to the interaction between the components. Furthermore, the arrangement according to the invention will enable individual adjustment of the pitch of each blade so that the blades, with the help of the regulation system, can be set at the same time with different pitch.

As can be seen from fig. 2 and 3, the wires run 38 and

40 from each operating device 28 axially through the center of the hub 14 to the regulating device 50 through a first transmission means 52. It should be noted that the regulating device 50 controls the operation of the operating devices 28. If these are of the hydraulic type, as shown, the regulating device, naturally include means for controlling the hydraulic fluid flow, so that the cylinders 30 can be selectively pressurized and drained on opposite sides of the pistons 34. Such control means are described in Norwegian patent application 810845.

As shown in fig. 1, the regulation device 50 is preferably mounted in the gondola 22.

If hydraulic blade operating devices are used, the first transfer means will include a transfer bearing with a first (outer) member 54 and a second (inner) member 56 concentric therewith which in the preferred embodiment is arranged rotatably with the shaft 16 on a bearing 57 and equipped with a thus integrated party. The inner element 56 comprises a number of channels 58 for hydraulic fluid, each with an outer, radial part 60 and an inner, longitudinal part 64. Through each channel 58, hydraulic fluid is transferred under pressure to the lines connected to the operating devices 28 and blade adjustment - the device, as described in what follows. A radial part of each channel 58 is in connection with an adjacent, ring-shaped channel 66 in the outer element 54, which is connected to the regulation device 50 through lines 68 in the outer element 54 and extension lines 69.

The pitch adjustment system according to the invention also includes feedback devices 70 which are individually mounted on the hub and connected to a corresponding turbine blade, and which emit a signal to the control device 50, which indicates the pitch of the turbine blade, so that the control device, on the basis of the feedback signals, can adjust the operating devices 28 for precise setting of the turbine blades. In the preferred embodiment, the feedback means comprises an electrical transducer with a movable core which, through a second fork joint 72, is pivotally connected to the blade root, whereby the transducer is primarily and secondarily (the stator) pivotally connected to the hub at 74. It is therefore obviously, that when the blades are turned by the operating devices 28, the relative position between the core and the windings will vary, whereby the output signal from the secondary side varies in accordance with the pitch of the blades. the feedback device runs radially inwards and backwards through the hub shaft and the inner transmission bearing element 56 to a second transmission means 80.

It appears from fig. 3, that when using electrical feedback devices 70, the second transmission device 80 will comprise a number of slip rings 82 which can rotate with the hub, at the same or with a greater rotational speed, at the output of the gearbox 20. In the preferred embodiment, the slip rings are mounted on an integral extension of the inner transfer bearing member 56, although other, equivalent constructions will also be apparent to those skilled in the art. As is most clearly evident from fig. 3, the electrical leads are routed longitudinally through the inner member or shaft 56 and radially outward, and are soldered or otherwise connected to the sides of the drag rings. The drag rings 82 engage stationary brushes 84 which are slidable on the drag rings and mounted on a stationary brush holder 86. Power leads 88 connect the brushes to the controller.

As previously discussed, the regulating device 50 controls the supply of hydraulic fluid to the operating devices 28 under the influence of a pitch position signal delivered by the feedback device 70, although the details of the regulating device are not covered by the invention. It is therefore obvious that the regulation device comprises interacting, electrical and fluid, logical circuits in one or another appropriate pattern. Reference is made in this connection to the above-mentioned patent application which describes a hydraulic control circuit which is suitable for use in a pitch adjustment system according to the present invention. If there is a need for independent control of the operating devices, the control device will of course be equipped with redundant logic circuits for simultaneous setting of the individual turbine blades with different pitch, if the operating conditions require this.

The pitch adjustment system according to the invention can also be equipped with devices which in critical situations can adjust the turbine blades independently of the fluid supply to the operating devices, and which will consequently be able to function even if this fluid supply fails. In the preferred embodiment, these devices comprise a tank or accumulator 90 for hydraulic fluid under pressure, which through a line 91 and a servo valve 92 is in connection with the side of the device in question, which must be brought under pressure for conversion of the corresponding turbine blade. The servo valve 9 2 can be controlled by fluid pressure or electrically through the control device 50. In case of fluid control, the servo part or the control part in the valve can communicate with the control device 50 through the channels in the transfer bearing. In the case of electrical control, the valve will be operated by means of the electrical part of the regulation device and will be connected to this through the slip ring brush assembly in the second transmission means 80.

It will thus appear that the system according to the present invention makes it possible to adjust the pitch of the wind turbine blades efficiently and effectively without the use of the heavy and often complicated mechanical aggregates of a known type, which connect the turbine blades to the associated operating devices. The operating devices which work separately, independently of the others, and only operate a single turbine blade, can consequently be relatively light. The connections between the operating devices and the regulating device are also created with construction economy, which further reduces the power required in such a system, thereby reducing the overall efficiency of a wind turbine using a pitch adjustment system. Installation of changeover accumulators on the hub, close to the turbine blades, ensures the possibility of blade changeover in the system, even if the primary fluid supply to the operating device is interrupted.

Claims (10)

1. System for adjusting the pitch of wind turbine blades, characterized in that it comprises a rotatable hub (14), at least two blades (10,12) which run in the main direction' radially outward from the hub to rotate with it, where each of the blades can rotates about its longitudinal axis (a) for regulation of the blade pitch, and where operating devices (28) are mounted on the hub which rotate with the hub and are directly connected to the turbine blades, for setting the preselected blade pitch, and where the system further includes feedback devices (701 which are mounted on the hub and cooperatively connected to the turbine blades, for producing a signal indicating the blade pitch, a control device (50) which is spaced from the hub and arranged to control the operating devices (28) in dependence, at least in part, of the signal produced by the feedback devices, and first and second transmission means (52,80) which are arranged to connect along a rotating, stationary interface te between the regulation device (50). and respectively the operating devices and the feedback devices (70). 2.. System in accordance with claim 1, characterized in that the operating devices (28) comprise hydraulic control organs which react to supplied hydraulic pressure fluid. 3. System in accordance with claim 2, characterized in that the pitch of each turbine blade is adjusted individually by at least one hydraulic operating device (28), so that the blades can be set simultaneously with mutually different pitch angles. 4. System in accordance with claim 3, characterized in that the first transmission means (52) comprises a hydraulic transmission bearing with first and second, concentric elements (54, 56) of which one element is driven rotatably with the hub (14). , and is equipped with liquid channels in connection with the hydraulic operating devices, and where the other element is stationary and equipped with liquid channels in connection with the channels in the aforementioned bearing element and also in connection with the regulation device (50). 5. System in accordance with one of claims 2-4, characterized in that each of the hydraulic operating devices (28) comprises a hydraulic cylinder (30) with a ■ piston (34) which can be moved back and forth in the cylinder, and that the operating devices is pivotably connected to a root part of the turbine blades (10,12). and with a central part of the hub. 6. System in accordance with one of the preceding claims, characterized in that it further comprises adjustment devices which are mounted on the hub, to rotate with it, and which, depending on a signal from the primary control device, hydraulically transmit pressure fluid to the operating devices which thereby carry out adjustment of the turbine blades. 7. System in accordance with claim 6, characterized in that the conversion devices comprise a container (90). for hydraulic pressure fluid and a servo valve (92) which is connected to the pressure fluid container and the hydraulic operating devices (28), to regulate the flow of hydraulic fluid between them in dependence on control signals from the primary control device. 8. System in accordance with one of the preceding requirements, characterized by .' . that the feedback inputs (70) comprise a linear, variable differential transducer which is cooperatively connected to the turbine blades, whereby the output signal from the transducer varies in accordance with the pitch position of the turbine blades. 9. System in accordance with claim 8, characterized in that each turbine blade is connected to one and the same linear, variable differential transducer. 10. System in accordance with claim 8 or 9, characterized in that the second transmission means comprises a number of slip rings (82) which are rotatable with the hub and electrically connected to the linear, variable differential transducer, and further comprises a number of stationary brushes (84) each of which is in sliding electrical contact with a corresponding slip ring and is arranged for electrical connection with the primary regulation device (50).