METHOD FOR YAW CONTROL OF A WIND TURBINE AND A WIND TURBINE HAVING A YAW CONTROL

Abstract

A method is for yaw control of a wind turbine. The wind turbine includes a wind turbine controller, a regular power supply to supply the wind turbine with electric power in case of a normal mode of operation, and a power backup system to supply the wind turbine with electric power in case of a grid outage. The method includes: detecting a grid outage for the wind turbine, switching from the regular power supply to the power backup system in case of the detected grid outage, and switching the wind turbine from the normal mode of operation to a less-active mode of operation in which the electric power consumption of the wind turbine is reduced compared to the normal mode of operation.

Claims

1. A method for yaw control of a wind turbine, the wind turbine including a wind turbine controller, a regular power supply to supply the wind turbine with electric power in case of a normal mode of operation, and a power backup system to supply the wind turbine with electric power in case of a grid outage, the method comprising: detecting a grid outage for the wind turbine; switching from the regular power supply to the power backup system in case of the detected grid outage; and, switching the wind turbine from the normal mode of operation to a less-active mode of operation in which electric power consumption of the wind turbine is reduced compared to the normal mode of operation.

2. The method of claim 1, wherein the less-active mode of operation includes at least one of: increasing an averaging time of at least one relevant signal for the yaw control, wherein the increase takes place compared to the averaging time during the normal mode of operation; and, increasing an allowed misalignment of the nacelle with respect to the wind direction, wherein the increase takes place compared to the allowed misalignment of the nacelle with respect to the wind direction during the normal mode of operation.

3. The method of claim, wherein the less-active mode of operation includes at least one of: shutting down or reducing activities of a pitch system; and, shutting down or reducing temperatures of heaters and anti-icing systems.

4. The method of claim 1, wherein the less-active mode of operation includes applying at least one yaw brake after each yaw movement.

5. The method of claim 1, wherein a threshold value for wind speed is defined such that, in the less-active mode of operation an allowed misalignment of the nacelle with respect to wind direction is only increased if the value of the wind speed is below a threshold value.

6. The method of claim 1, wherein an averaging time of at least one signal is increased to 1 minute or more; and, wherein the at least one signal is chosen from an averaged yaw alignment, an averaged wind direction and an averaged torque value of yaw drives.

7. The method of claim 1, wherein an increased allowed misalignment of the nacelle with respect to wind direction is +/5 degrees or more.

8. The method of claim 7, wherein the allowed misalignment of the nacelle with respect to the wind direction depends on wind speed, wherein with increasing wind speed the allowed misalignment is smaller.

9. The method of claim 1, wherein the less-active mode of operation includes at least one of: measuring wind speed, measuring wind direction, heating the weather-mast, operating the wind turbine controller including communication systems and safety systems for basic turbine functions.

10. The method of claim 1 wherein the grid outage is detected by measuring grid voltage and comparing the measured value of the grid voltage to a predetermined value of the grid voltage for a predetermined time period of more than 30 s.

11. The method of claim 1, wherein a pitch system adjusts at least one rotor blade to a feathering position by using pitch batteries before the power backup system is switched on.

12. The method of claim 11, wherein the pitch system is shut off after the power backup system is switched on.

13. A wind turbine comprising: a wind turbine controller; a regular power supply configured to supply the wind turbine with electric power in case of a normal mode of operation; a power backup system configured to supply the wind turbine with electric power in case of a grid outage; said wind turbine controller being configured to: detect the grid outage for the wind turbine, switch from the regular power supply to the power backup system in case of the detected grid outage, and switch the wind turbine to a less-active mode of operation, in which electric power consumption of the wind turbine is reduced compared to the normal mode of operation.

14. The wind turbine of claim 13, wherein said wind turbine controller is configured to at least one of: increase an averaging time of at least one relevant signal for a yaw control, wherein the increase takes place compared to the averaging time during the normal mode of operation; and, allow an increased misalignment of the nacelle with respect to wind direction, wherein the increase takes place compared to the allowed misalignment of the nacelle with respect to the wind direction during the normal mode of operation.

15. The wind turbine of claim 13 further comprising a yaw system having at least one yaw brake and a yaw control, wherein said yaw control is configured to apply said at least one yaw brake after each yaw movement.

16. The wind turbine of claim 13, wherein said power backup system includes at least one of a battery, a diesel generator, and an ultra-capacitor for a power supply.

17. The wind turbine of claim 15, wherein an input signal for said yaw control includes at least one of a wind direction signal, a wind speed signal, and a turbulence intensity signal.

18. The wind turbine of claim 15, wherein the yaw control is configured to process signals with an increased average time of 1 minute or more.

19. The wind turbine of claim 15, wherein said yaw controller is configured to increase the allowed misalignment of the nacelle with respect to a wind direction of +/5 degree or more.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0026] The invention will now be described with reference to the drawings wherein:

[0027] FIG. 1 shows a wind turbine in a schematic view;

[0028] FIG. 2 shows a schematic view of a yaw system including yaw drives and yaw brakes;

[0029] FIG. 3 shows different areas of misalignment for the nacelle of the wind turbine; and,

[0030] FIG. 4 shows the control of the yaw brakes and the yaw drives in a less-active mode of operation.

DETAILED DESCRIPTION

[0031] FIG. 1 shows in a schematic view of a wind turbine having a tower A which bears a nacelle B. The nacelle B is rotatably mounted to a tower head and supports a drive train (not shown). The drive train bears a rotor hub C to which three rotor blades D are connected. The wind turbine uses a yaw system and a yaw control to align the nacelle B with the wind direction.

[0032] FIG. 2 shows in a schematic view a cross section of the yaw system. The yaw system includes a yaw drive 5 which has a gear pinion 51. The gear pinion 51 engages into a toothing 4 of an outer bearing ring of the yaw bearing. The inner bearing ring 2 of the yaw bearing is mounted to a base plate of the nacelle which also bears the yaw drive 5. As shown in FIG. 2 inner and outer yaw bearing rings include two bearing runs 6. Additionally, a yaw brake 7 is shown which interacts with a yaw brake disk 8. The yaw brake disk 8 is mounted to the tower of the wind turbine while the yaw brake is mounted to the base plate of the nacelle.

[0033] FIG. 3 shows the nacelle, the hub and the rotor blades in a schematic view from the top. An area of allowed misalignment 20 is shown in front of the rotor hub. The area of allowed misalignment is symmetric to the longitudinal axis of the nacelle. The yaw control does not correct the orientation of the nacelle with respect to the wind direction in the less-active mode of operation if the orientation of the nacelle falls within the area of allowed misalignment 20. It is possible that the area of allowed misalignment is reduced to the area 22 if the wind speed increases. This means, the higher the wind speed gets the less misalignment of the nacelle is accepted.

[0034] FIG. 4 shows the operation of the yaw control in the less-active mode of operation. As can be seen in the figure, a yaw program starts at a certain point in time for a certain period of time. The yaw brakes are applied, that is, the yaw brakes are closed to build up a braking torque, if no yaw adjustment is required. In situations in which yaw adjustment is required the yaw brakes are released, that is, the yaw brakes are opened and yawing takes place. After yawing has been finished and a yaw adjustment is no longer required the yaw brakes are applied again.

[0035] It is understood that the foregoing description is that of the preferred embodiments of the invention and that various changes and modifications may be made thereto without departing from the spirit and scope of the invention as defined in the appended claims.