WO1984000053A1

WO1984000053A1 - Device for controlling the vane of a wind turbine

Info

Publication number: WO1984000053A1
Application number: PCT/SE1983/000247
Authority: WO
Inventors: Nils Eric Staffan Engstroem
Original assignee: Conort Eng Ab
Priority date: 1982-06-15
Filing date: 1983-06-15
Publication date: 1984-01-05
Also published as: SE8203721L

Abstract

A wind turbine comprises at least one vane which has a rigid inner vane portion (2) and an outer vane portion (3) which is rotatable in relation to the axis of the vane for controlling the power output of the wind turbine. An auxiliary turbine (20) is provided on each turbine vane at a distance from the shaft (30) of the wind turbine to be exposed to a wind velocity substantially corresponding to the rotational velocity of the auxiliary turbine (20) around shaft (30). The auxiliary turbine (20) is adapted to act upon means controlling the angular position of the vane top (3) in particularly the emergency angular position of the vanes of the wind power rotor.

Description

DEVICE FOR CONTROLLING THE VANE OF A WIND TURBINE

The invention refers to a wind turbine comprising at least one vane, at least one such vane, preferably all of them being provided with a control device for controlling the output power of the vane.

In conventional wind turbines normally the whole vane is vane angle controlled in order to limit the output power when the wind is so gale that the rated output power of the turbine is exceeded in order to facilitate the start of the turbine and in order to enable emergency breaking should, for example the load of the wind turbine drop out. Alternatively and preferably the vane angle control may be limited to the outer portion of the vane, for example the outer third of the vane, thereby reducing necessary control forces to about only 10 percent of the forces required when the whole vane is vane angle controlled, an additional advantage being that the heavily stress ed journal used for the vane angle control and provided adjacent the turbine hub is dispensed with.

Another alternative for limiting the power of a wind turbine is by stalling which occurs automatically when the wind speed exceeds a certain value, provided that the shape and rate of rotation o f the vane has been choos en in a suitable way. Also in this case a decive is required for emergency breaking should the load drop out.

Co nv e nt i o na l l y th e v a n e an g el i s c o n t r o l l e d hydraulically. The disadvatages with such an hydraulic device are high initial costs and high maintenance costs. The purity requirements of a hydraulic system used in a wind turbine also involve drawbacks . The trans fer of the hydraul ic fluid from a stationary unit with the aid of a swivel connection has caused problems in several plants . As an alternative the hydraulic unitς have been constructed such as to participate in the rotation of the primary shaft of the rotor ; however not all drawbacks have been eliminated thereby. It should be possible to vane angle control each individual vane with one control device each. Thereby it is achieved that the vanes can be adjusted independently of each other. Normally, the units are supplied from a common stationary hydraulic pressure source. Soiling of the distribution valve have however, caused harmful jam of the adjusting systems.

As an alternative of hydraulic means electric jacks have b e en u s ed. In the vane angl e control o f wind turbine s , however, a plurality of problems are encounted since the transfer of electric current to the adjusting means which rotate together with the turbine vanes must be made by means of slip rings which are not sufficiently reliable in emergency s ituations . A l ightning s troke in the turbine may, for example, burn away a great part of the electric cables . A battery participating in the rotation is a possible but unsuitable solution of the power supply problem.

Other possible but clumsy solutions of the problem to supply power to the control devices on the vane comprise compressed springs and pneumatic systems .

It is therefore a purpose of the invention to provide a wind turbine the vane control devices of which can be safely and simply supplied with power, in particular for emergency breaking of the wind turbine.

The invention starts from a wind turbine comprising at least one vane, at least one such an preferably all vanes being provided with a control device for controlling the power output of the vane, the invention being characterized in that an auxiliary wind turbine is provided on the vane provided with said control device radially spaced from the shaft of the wind turbine to be exposed to a wind speed substantially corresponding to the rotational velocity of the auxiliary turbine around the shaft and that the auxiliary turbine is adapted to drive the control device of the vane.

The control device compris e power varying means for varying the power output of the vane, a s ervo motor which normally is supplied with power and is controlled from a position remote from the wind turbine, and an adjusting device driven by the motor to act upon said power varying means, the auxiliary turbine being provided to drive and control the adjusting device to cause said power varying means to reduce the power output of the vane during malfunction in the operation of the wind turbine. Said power varying means may comprise a top portion of the vane, for example the outer third of the vane which is rotatable by means of a journal around the longitudinal axis of the vane in relation to the portion of the vane which is firmly connected to the turbine shaft. Alternatively said power varying means may comprise a flap connected to the vane and acting by increasing the breaking force and reducing the lifting force. The flap may also be able to turn the whole vane or a part thereof into the desired position.

The auxiliary turbine can be arranged to be connected by means of a clutch to the adjusting device in order to act upon the same and the clutch is suitably arranged to be activated when the power supply or the control of the servo motor drops out or when the number of revolutions of the wind turbine or auxiliary turbine exceeds a predetermined value.

In a wind turbine in which the angular position of the vane top is controlled the auxiliary turbine is preferably mounted near the area of the journal of the vane top and preferably on the stationary part of the vane, desireably in connection with the adjusting device.

The adjusting device may suitably comprise a mechanical jack of the type comprising a rotary, not shiftable screw which is rotated by the servo motor and which drives a shiftable nut, the one end of the jack being coupled to the pressure side of the stationary vane portion in the area at the dowstream edge of the vane, said one end of the jack containing the driving connection of the jack. The servo motor is suitably mounted in preferably direct connection to the jack, and the wind turbine is suitably mounted adjacent the servo motor, preferably coaxially therewith.

The clutch may be biased, for example by means of a spring, towards its coupling position, while an electro magnet is arranged to hold under the action of a control signal circuit the clutch in the released postion against the action of the spring. In this case the shaft of the auxiliary turbine may act upon a rotational-speed detector which is adapted to interrupt the control circuit at a rotational speed in excess of a predetermined value so that the clutch is activated and the auxiliary turbine actuates the adjusting device to cause the vanes of the wind turbine to be angularly adjusted. Possibly the control circuit can be arranged to interrupt the current supply of the servo motor when there is an interruption in the control circuit. Moreover the wind turbine may be arranged to be stopped if the number of revolutions of the auxiliary turbine is below a certain value when the wind turbine is rotating, for example with a number of revolutions of 20 percent or more of its rated number of revolutions. Preferably the servo motor is mounted externally of the vane to be cooled by air, to be easily accessable and not to interfere with the construction of the vane.

Hereafter the invention will be described in detail by reference to an example shown in the attached drawing. In which

Fig. 1 schematically shows a wind power plant according to the invention,

Fig. 2 is a section along line II-II in Fig. 1,

Fig. 3 is a schematical section taken along line III-III in fig. 2, and

Fig. 4 schematically illustrates a control circuit for the device according to Fig. 3.

In Fig. 1 there is shown a wind power plant comprising a wind power rotor 1 having two vanes. The horizontal shaft 30 of the rotor 1 is journalled in a movable engine house on a tower 40, said house containing a load connected to shaft 30, for example en electric generator 41. The rotor vanes comprise a rigid inner vane portion 2 and attached thereto a vane top portion 3 adapted to be angularly adjusted in relation to vane portion 2 about the longitudinal axis of the vane. The lenght of vane portion 2 amounts to about 70 percent of the entire length of the vane. A wind turbine 20 is mounted on each vane adjacent the journal of the vane top portion 3. The wind turbine 20 is adapted to be exposed to a wind velocity substantially corresponding to the rotational velocity of the wind turbine about shaft 30 of the rotor to supply power to a control device by means of which the angular position of the vane top 3 is adjusted.

In Fig. 2 there is shown the rigid portion 2 of the vane and the angularly adjustable top portion 3 which is connected to vane portion 2 by means of a shaft 4. The plane of rotation of rotor 1 is indicated by P. At the downstream edge and the pressure side of the rigid vane portion 2 a bracket 7 is provided and on the upstream portion of the pressure side of the vane top 3 a bracket 6 is provided. Between brackets 6 and 7 a jack 5 is inserted. The jack 5 comprises an axially shiftable nut which is driven by a rotatable screw within a housing 8. The wind turbine 20 is shown to be directly connected to housing 8.

Fig. 3 shows again the jack 5 with the screw housing 8 and a sleeve connecting the wind turbine 20 to the housing 8. A rotatable shaft 9 is adapted to rotate the screw in the housing 8 for driving the jack 5. Shaft 9 carries a conical cog-wheel 10 which cooperates with a conical cog-wheel 11 on the shaft of a servo motor 12. Turbine 20 comprises a rotor carrying vanes, the shaft of said rotor being coaxial with the shaft 12 of the servo motor. A clutch K is provided between the rotor shaft of the wind turbine and the shaft 12 of the servo motor.

From Fig. 4 showing an electric circuit for the wind turbine 20 it will be appreciated that servo motor 12 is remote controlled by means of electric current MS via a cable 60 containing a normally closed switch 61 controlled by an electro magnet 62. The electro magnet 62 is in series with a control circuit 70 containing a control central 71. In circuit 70 there is also enclosed an electro magnet 72 which when energized will hold clutch K open against the action of a presure spring 73 (Fig. 3) tending to move the clutch into engaged condition. Moreover circuit 70 comprises a normally closed switch 74 adapted to be controlled by a rotational speed counter V so that the switch 74 will open if the number of rotations of the auxiliary turbine is exceeding a predetermined value. If desired circuit 70 also may contain additional supervising normally closed switches so that circuit 70 is interrupted when the number of revolutions of the wind power rotor is exceeding a perdetermined value. This may be accomplished by means of a centrifugal force detector. As appears from Fig. 4, the current supply of the servo motor 12 will be interrupted and the clutch K will be activated when the number of revolutions of the auxiliary turbine is in exceeding a predetermined value or the control circuit 70 is interrupted unintentionally or deliberately. This will provide an emergency angular adjustment of the vanes of the wind power rotor under all conditions.

A large wind power turbine operates at a vane topspeed of about 100 meters/sek. At 70 percent of the radius the air flow speed thus amounts to 70 meters/sek. This is the air speed to which the wind turbine 20 will be exposed. A simple consideration will show that the wind turbine 20 only requires a diameter of 0.3 meter in order to offer at a low efficiency a sufficient power to drive the vane top adjustment of a wind turbine having a diameter of 70 meter (the generator output power is 2-4 MW).

There has been described a wind power rotor having a vane top control, but it should be appreciated that the invention also may be applied in wind power rotors in which the entire vane is vane angle controlled. Moreover it should be clear that the invention may be used in connection with wind power rotors of the type different from the turbine type shown here and that the wind turbine used may be arranged to provide power to devices for controlling the power output of the vane without any need of a servo motor, suitabl e control circuit being provided to control the connection of the wind turbine shaft to the adjustment device, a reverse gear suitable being incorporated to permit reversing the direction of angular adjustment of the vane.

Claims

1. Wind turbine comprising at least one vane (2, 3; 2, 3) at least one and prederably all such vanes being provided with a control device (3-12) for controlling the power output of the vane, characterized in that an auxiliary wind turbine (20) is provided on the vane (2, 3) provided with said control device radially spaced from the shaft (30) of the wind turbine (1) to be exposed to a wind speed substantially corresponding to the rotational velocity of the auxiliary turbine (20) around said shaft (30) and that the auxiliary turbine (20) is adapted to drive the control device of the vane (2, 3).

2. Wind turbine as claimed in claim 1, characterized in that the control device comprises a means (3, 4) for varying the power output of the vane (2, 3), a servo motor (12) which normally is supplied with power and controlled from a position remote from the vane of the wind turbine, and an adjusting device (5, 11) driven by the motor (12) for driving said power varying means, the auxiliary turbine (20) being adapted to drive and control the adjusting device (5-11) to cause said power varying means (3, 4) to reduce the power output of the vane upon malfunction in the operation of the wind turbine

(1).

3. Wind turbine as claimed in claim 2, characterized in that the auxiliary turbine (20) is adapted to be coupled by means of a clutch (K) to the adjusting device (5-11) to act upon the same and that the clutch (K) is adapted to be activated when there is a drop-out of the electric power supply (MS) or control (S) of the servo motor (12) or when the number of revolutions of the wind turbine (1) or auxiliary turbine (20) is in excess of a predetermined value.

4. Wind turbine as claimed in claim 2 or 3, characterized in that said power varying means (3, 4) comprises a top portion (3) of the vane, said top portion being rotatably means of a journal (4) around the longitudinal axis of the vane in relation to the portion (2) of the vane connected to shaft (30).

5. Wind turbine as claimed in any of claims 1-3, characterized in that said power varying means comprises a flap connected to said vane.

6. Wind turbine as claimed in claim 4, characterized in that the auxiliary turbine (20) is mounted adjacent the area of the joural (4) of the vane top (3) preferably on the rigid part of the vane (2) and in connection with the adjusting device (5- 11).

7. Wind turbine as claimed in any of claims 2-6, characterized in that the adjusting device comprises a mechanical jack which is in driving connection to the servo motor, the one end of the jack being connected to the pressure side of the rigid vane portion adjacent the downstream edge of the vane, the driving connection of the jack being positioned at said one end, the servo motor (12) being mounted adjacent to the jack and the auxiliary turbine (20) being mounted adjacent the servo motor.

8. Wind turbine as claimed in claim 3, characterized in that the clutch (K) is biased towards coupling position, that an electromagnet is arranged to hold under the action of a control signal circuit (70) the clutch in released position against the biasing force, that the shaft of the auxiliary turbine acts upon a rotational speed detector adapted to break the control circuit at a number of revolutions in excess of a predetermined value and that the control circuit may be arranged to break the current supply to the servo motor when is an interruption in the control circuit.

9. Wind turbine as claimed in any of preceding claims characterized in that the wind turbine is arranged to be stopped if the number of revolution of the auxiliary turbine (20) is below a certain value when the wind turbine is rotating, for example when the number of revolutions amounts to 20 percent or more of the rated rotational spedd of the wind turbine.

10. Wind turbine as claimed in any of claims 2-9, characterized in that the servo motor is disposed outside the vane.