WIND TURBINE

Abstract

Provided is a wind turbine including an active yaw system realized to maintain an upwind orientation of the wind turbine aerodynamic rotor during safe operating conditions, which active yaw system includes a number of yaw drive units, and wherein a yaw drive unit includes a negative brake; a principal power supply configured to supply power to the active yaw system during normal operation of the wind turbine; and a dedicated negative brake reserve power supply configured to supply power to the negative brakes in the event of a grid disconnect. A method of operating such a wind turbine is also provided.

Claims

1. A wind turbine comprising: an active yaw system configured to maintain an upwind orientation of a wind turbine aerodynamic rotor during safe operating conditions, the active yaw system comprising a plurality of yaw drive units, wherein a yaw drive unit comprises a negative brake; a principal power supply configured to supply power to the active yaw system during normal operation of the wind turbine; and a dedicated negative brake reserve power supply configured to supply power to the negative brakes in an event of a grid disconnect.

2. The wind turbine according to claim 1, comprising a reserve power supply controller configured to regulate the supply of power to the negative brakes.

3. The wind turbine according to claim 2, wherein the reserve power supply is configured to supply power to the reserve power supply controller.

4. The wind turbine according to claim 1, comprising a wind direction sensor configured to determine the wind direction, and wherein the reserve power supply is configured to regulate power to the negative brakes on a basis of the wind direction.

5. The wind turbine according to claim 4, wherein the reserve power supply is configured to remove power from the negative brakes during a constant wind direction interval.

6. The wind turbine according to claim 1, comprising a wind speed sensor configured to determine the wind speed, and wherein the reserve power supply is configured to regulate power to the negative brakes on a basis of the wind speed.

7. The wind turbine according to claim 6, wherein the reserve power supply is configured to remove power from the negative brakes during a low wind speed interval.

8. The wind turbine according to claim 4, wherein the dedicated negative brake reserve power supply is configured to also supply power to the wind direction sensor and/or to a wind speed sensor.

9. The wind turbine according to claim 1, wherein the dedicated negative brake reserve power supply is any of a battery, a fuel cell, a diesel generator.

10. The wind turbine according to claim 1, wherein the dedicated negative brake reserve power supply is configured to supply power to the negative brake for a duration of at least six hours.

11. The wind turbine according to claim 1, comprising a reserve power monitoring arrangement to monitor the available reserve power and to restrict reserve power to the negative brake when the available reserve power decreases to a predefined threshold level.

12. The wind turbine according to claim 1, comprising an independent monitoring arrangement for the dedicated negative brake reserve power supply and/or comprising a redundant dedicated negative brake reserve power supply.

13. A method of operating the wind turbine according to claim 1, the method comprising: driving the active yaw system from the principal power supply to maintain an upwind orientation of the wind turbine aerodynamic rotor during safe operating conditions; and actuating negative brakes from the dedicated negative brake reserve power supply in the event of the grid disconnect to permit passive turning of the aerodynamic rotor into a downwind orientation

14. The method according to claim 13, comprising a step of removing power from the negative brakes while the aerodynamic rotor is in the downwind orientation.

Description

BRIEF DESCRIPTION

[0025] Some of the embodiments will be described in detail, with reference to the following figures, wherein like designations denote like members, wherein:

[0026] FIG. 1 shows a yaw system in an embodiment of the wind turbine;

[0027] FIG. 2 shows a yaw system in a further embodiment of the inventive wind turbine;

[0028] FIG. 3 shows the inventive wind turbine in an upwind orientation;

[0029] FIG. 4 shows the inventive wind turbine in a downwind orientation; and

[0030] FIG. 5 shows a conventional yaw system in a wind turbine.

[0031] FIG. 1 shows a yaw system 1 in an embodiment of the inventive wind turbine. The diagram shows a yaw ring 20 at the top of a wind turbine tower 21. Other wind turbine components such as the nacelle, generator, aerodynamic rotor etc. may be assumed to be present but are not shown for the sake of clarity. In the diagram, only two yaw drive units 10 are indicated but it shall be understood that the yaw system 1 may comprise six or more yaw drive units 10 arranged to turn the nacelle relative to the wind turbine tower 21. Each yaw drive unit 10 comprises a motor unit 101 configured to turn a toothed pinion 102, which engages with the toothed yaw ring 20. The yaw drive units 10 are usually all operated in a synchronous manner to collectively turn the nacelle to align the aerodynamic rotor as desired. The motor units 101 are powered from the grid (indicated as a primary power supply 25) during normal operation of the wind turbine, i.e. as long as the wind turbine is connected to the grid. To hold a desired alignment, each yaw drive unit 10 comprises a negative brake 103 which, when closed, prevents rotation of the pinion 102. To release or open the negative brake 103, it is necessary to provide power to the negative brake 103. During normal operation of the wind turbine, the negative brakes 103 are also powered from the grid or primary power supply 25. In the event of a grid disconnect, the negative brakes 103 are provided with power by a dedicated negative brake reserve power supply 11. The capacity of the dedicated negative brake reserve power supply 11 need only be enough to provide power to the negative brakes 103 for a certain minimum length of time, for example up to six hours.

[0032] FIG. 2 shows a yaw system in a further embodiment of the inventive wind turbine. For clarity, the principal power supply 25 explained in FIG. 1 is left out. Here, the dedicated negative brake reserve power supply 11 is managed by a controller 110 which is realised to switch the power supply 11 on or off. Embodiments of the invention are based on the insight that, when the aerodynamic rotor is in the downwind position, it may be safe to remove power from the brakes under certain conditions. For example, if the wind is relatively steady and/or the wind speed is relatively low, it may be safe to close the brakes 103 and thereby save power. To this end, the controller 110 receives a wind speed signal 240 from a wind speed sensor 24, and a wind direction signal 230 from a wind direction sensor 23. The controller 110 evaluates the wind speed signal 240 to determine whether the wind speed is sufficiently low, i.e. whether the wind conditions qualify as a low wind speed interval. Similarly, the controller 110 evaluates the wind direction signal 230 to determine whether the wind direction is remaining essentially constant or at least steady within an acceptable range. If both conditions apply, the controller 110 may switch off the power supply 11 so that the negative brakes 103 are closed. The aerodynamic rotor will now hold its position. The controller 110 continues to monitor the wind speed signal 240 and the wind direction signal 230. As soon as the wind direction signal 230 changes by a minimum or predefined amount, the controller 110 switches the power supply 11 on again to open the brakes. The changed wind direction results in the aerodynamic rotor 22 being passively moved to return to the more optimal downwind position. With the controller 110 and the wind sensors 23, 24 it is possible to save power whenever conditions permit the brakes 103 to be closed. This allows the dedicated negative brake reserve power supply 11 to have a relatively low capacity (associated with lower cost) and/or to provide reserve power for a favourably long duration. The diagram also indicates an optional monitoring arrangement 111 that can monitor the available reserve power. When the available reserve power reaches a low level, the controller 110 may restrict reserve power to the negative brakes 103.

[0033] The dedicated negative brake reserve power supply 11 can comprise two batteries, so that one battery can take over if the other fails. As an additional fail-safe measure, the wind turbine may comprise an additional monitoring arrangement for the reserve power supply 11. For example, the monitoring arrangement 111 of the controller 110 may be duplicated. FIG. 3 shows an embodiment of the inventive wind turbine 2 in an upwind orientation UW. The diagram shows the aerodynamic rotor 22 facing into the wind. The yaw drive units 10 receive power from the grid during normal operation of the wind turbine 2.

[0034] FIG. 4 shows the wind turbine 2 of FIG. 3 in a downwind orientation DW. This position is assumed whenever the wind conditions are unsafe (e.g. during a storm, hurricane etc.) or whenever the wind turbine is disconnected from the grid. The diagram shows the aerodynamic rotor 22 facing out of the wind. The negative brakes 103 of the yaw drive units 10 receive power from the dedicated negative brake reserve power supply 11. The controller 110 of the dedicated negative brake reserve power supply 11 can conserve power by evaluating wind speed and wind direction signals 230, 240 provided by a wind direction sensor 23 and a wind speed sensor 24 as described in FIG. 2.

[0035] FIG. 5 shows a yaw system 5 in a prior art wind turbine. Here also, each yaw drive unit 10 comprises a motor unit 101 configured to turn a toothed pinion 102, which engages with a toothed yaw ring 20. To hold a desired alignment, each yaw drive unit 10 comprises a negative brake 103 which, when closed, prevents rotation of the pinion 102. Here also, the motor units 101 and negative brakes 103 are powered from the grid (indicated as a principal power supply 55) during normal operation of the wind turbine. To ensure safe operation of the prior art wind turbine, the yaw system 5 includes a reserve power supply 50 that has sufficient capacity to power the drive units 101 and also the negative brakes 103. Because the capacity of the reserve power supply 50 must be large enough to power these units during a grid outage, the cost of the reserve power supply 50 is correspondingly high. Furthermore, the level of complexity is such that the likelihood of failure is also quite high.

[0036] Although the present invention has been disclosed in the form of preferred embodiments and variations thereon, it will be understood that numerous additional modifications and variations could be made thereto without departing from the scope of the invention.

[0037] For the sake of clarity, it is to be understood that the use of “a” or “an” throughout this application does not exclude a plurality, and “comprising” does not exclude other steps or elements.