Assembly for fixing a rotor blade of a wind power plant

Abstract

The invention relates to an assembly and a method of fixing a rotor blade of a wind power plant. The wind power plant comprises a rotor blade, a pitch adjustment means, a bearing for the rotor blade and a brake disk. There is an electro-mechanical brake configured to apply a controlled brake force to the brake disk that is a function of the pitch angle of the rotor blade.

Claims

1. An assembly for fixing a rotor blade of a wind power plant comprising a rotor blade, a pitch adjustment means, a bearing for the rotor blade and a brake disk, wherein the assembly further comprises an electro-mechanical brake configured to apply a controlled brake force to the brake disk that is a function of the pitch angle of the rotor blade, and wherein the electro-mechanical brake is configured to apply a first controlled brake force to the brake disk in a first position of the rotor blade and a second controlled brake force in a second position of the rotor blade.

2. The assembly according to claim 1, wherein, in the first position, the brake force is such that the torque provided by the pitch adjustment means can overcome the brake force.

3. The assembly according to claim 2, wherein, in the second position, the brake force is such that the torque provided by the pitch adjustment means cannot overcome the brake force.

4. The assembly according to claim 1, wherein the first position is the 0°-position or an optimum working position.

5. The assembly according to claim 1, wherein the second position is 90°-position or feathering position.

6. The assembly according to claim 1, wherein the electro-mechanical brake is configured to apply a maximum brake force once a predefined rotation angle of the rotor blade is reached.

7. A wind energy plant comprising the assembly according to claim 1.

8. A method of fixing a rotor blade of a wind power plant, the wind power plant comprising a rotor blade, a pitch adjustment means, a bearing for the rotor blade and a brake disk, the method comprising the steps of: controlling an electro-mechanical brake so as to apply a controlled brake force to the brake disk which depends on the pitch angle, and controlling the electro-mechanical brake so as to apply a first controlled brake force to the brake disk in a first position of the rotor blade and a second controlled brake force in a second position of the rotor blade.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) Further aspects of the invention will ensue from the following description of an example embodiment of the invention with reference to the accompanying drawings, wherein

(2) FIG. 1 shows a simplified wind energy plant;

(3) FIG. 2 shows a simplified detailed view of the wind energy plant of FIG. 1;

(4) FIG. 3 shows a simplified cross sectional view through a rotor blade and the rotor blade root and parts of the hub of a wind power plant in accordance with an embodiment of the invention, and

(5) FIG. 4 shows a simplified flow chart illustrating the operation according to aspects of the invention.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

(6) FIG. 1 is a simplified view of a wind energy plant 2 having a supporting structure 4 carrying a generator 6 having a rotor with a rotor hub 8 carrying rotor blades 10 that are rotatable around a pitch axis PA by a pitch angle αP.

(7) FIG. 2 is a more detailed simplified view of the rotor hub 8 rotating around a rotor axis RA during operation of the wind energy plant 2. The rotor hub 8 carries a rotor blade 10 that is rotatable around a pitch axis PA by a pitch angle αP. An annular gear 12 (with annular bearing) is fixed to the rotor blade 10. A pitch drive PD is fixed to the rotor hub 8. The pitch drive PD comprises an electric motor 13 having a driven shaft that is mounted to a drive shaft (fast shaft) of an epicyclic gear 14. The driven shaft of the epicyclic gear 14 is mounted to a drive bevel 16 engaging the annular gear 12. The pitch drive PD applies a torque M to the annular gear 12 by rotating the drive bevel 16 by an angle α.

(8) In order to simplify the understanding, in the context of this specification, the torque M is indicated by a direction of rotation rather than by the corresponding torque vector. In this regard, the direction of rotation corresponds to a free movement of the pitch drive PD in response the corresponding torque M. The corresponding torque vector can be derived from the direction of rotation by help of the known right hand rule. Accordingly, the torque that is applied by the pitch drive PD is indicated by M that is directed in the same direction as the angle of rotation α of the drive bevel 16.

(9) In another embodiment, multiple pitch drives may be used.

(10) Furthermore, the present invention also applies to pitch adjustment means which are either hydraulic or mechanic.

(11) The blade torque (indicated by direction of rotation MB) is due to aerodynamic and gravitational forces on the rotor blade 10 and is generated during operation of the wind energy plant 2. During operation of the wind energy plant 2 in a wind regime where no pitch activity is necessary, the rotor blades 10 need to be set to an optimal pitch angle. This is typically referred to as αP=0° or 0°-position. The rotor blade 10 has to be fixed or held in this optimal position.

(12) In accordance with an embodiment of the invention, the rotor blade can be held in this position by an electro-mechanical brake. The torque applied by the electro-mechanical brake can then be just large enough for fixing the rotor blade, but not too large, so that the pitch drive or pitch drives can overcome the braking torque.

(13) However, in a 90°-position, the braking torque can be increased so that the pitch drive can not overcome the braking torque or brake force anymore.

(14) FIG. 3 shows a simplified cross sectional view through a rotor blade 10 and the rotor blade root 20 and parts of the hub 8 in accordance with an embodiment of the invention. There is a pitch drive PD that consists of the electric motor 13 and the gear 14 as well as the drive bevel 16 that is coupled to the inner side of an annular gear 12 (or bearing) for rotating the rotor blade 10 (only partially visible) around axis PA by an angle αP. The rotor blade 10 has a rotor blade root 20 to which the brake disk 31 is coupled. There is further the electro-mechanical brake 35 that comprises a mechanical part 33 and an electric motor 32 as well as brake shoes 34 which are coupled to the mechanical part 33. In response to a brake control signal BC from a control stage CNTL (anywhere in the wind power plant), the brake force applied by the brake shoes to the brake disk 31 is adjusted.

(15) The control stage can generate the required brake control signal BC in response to (as a function of) the rotational angle αP. The brake force can then be increased in order to assume a maximum in the 90°-position and a minimum or at least smaller value in the 0°-position.

(16) In order to avoid damage of the wind power blade, the control stage CNTL can be configured to control the electro-mechanical brake so as to provide a maximum brake force if a specific angle αP is reached or exceeded.

(17) The brake disk 31 can be a separate component that is coupled to the rotor blade root 20. It can also be integral part of the rotor blade.

(18) The brake disk 31 can be provided over the full inner circumference of the rotor blade, i.e. over 360°. However, the brake disk can also be limited to 120° of the inner circumference of the rotor blade root 20.

(19) In another embodiment, the brake disk can also be mounted on the hub, and the electro-mechanical brake may be mounted on the rotor blade root.

(20) FIG. 4 shows a simplified flow chart illustrating the operation according to aspects of the invention. After initializing the wind power plant that comprises the assembly in accordance with the invention, the pitch angle αP is adjusted in step S1 by controlling the pitch adjustment means (for example, a pitch drive). Once the pitch angle or rotational angle of the rotor blade αP has changed, the new angle is determined in step 82. In response to a change of the pitch angle αP, the brake force or braking torque of the electro-mechanical brake is adjusted. This is advantageously done as described above. After having adjusted the brake force in step S2, the system enters into a loop in which the conditions, as for example wind speed etc., are monitored. If a change of conditions occurs that requires adjustment of the pitch angle αP, the rotor blade is rotated in step S1, the new angle αP is determined and the braking force adjusted, if an adjustment is necessary. Generally, the brake force of the electro-mechanical brake is adjusted as a function of the pitch angle of the rotor blade.

(21) Although the invention has been described hereinabove with reference to specific embodiments, it is not limited to these embodiments and no doubt further alternatives will occur to the skilled person that lie within the scope of the invention as claimed.