METHOD OF MOUNTING A WIND TURBINE ROTOR BLADE

Abstract

A method of mounting a wind turbine rotor blade to a partial assembly is provided, the partial assembly including a number of rotor blades mounted to a hub which in turn is connected to a rotor shaft of a wind turbine, the method including the steps of A) effecting a rotation of the rotor shaft to turn the partial assembly from its starting position through an initial arc (.sub.0); B1) allowing the partial assembly to swing through a free swing arc in the opposite direction; B2) effecting a rotation of the rotor shaft to extend the free swing arc () by a further arc (); and C) repeating steps B1 and B2 until the partial assembly has reached a final position at an angular displacement of 120 to the initial position.

Claims

1. A method of mounting a wind turbine rotor blade to a partial assembly, the partial assembly comprising a number of rotor blades mounted to a hub which in turn is connected to a rotor shaft of a wind turbine, the method comprising: A) effecting a rotation of the rotor shaft to turn the partial assembly from its starting position through an initial arc; B1) allowing the partial assembly to swing through a free swing arc in the opposite direction; B2) effecting a rotation of the rotor shaft to extend the free swing arc by a further arc; and C) repeating steps B1 and B2 until the partial assembly has reached a final position at an angular displacement of 120 to the initial position.

2. The method according to claim 1, wherein the wind turbine comprises a full-scale converter, and a rotation of the rotor shaft is effected by control of the full-scale converter.

3. The method according to claim 2, wherein the wind turbine comprises a backup power supply arranged to provide power to the full-scale converter during the rotor blade mounting procedure.

4. The method according to claim 1, wherein the final position is at an angular displacement of 120 relative to the initial position.

5. The method according to claim 1, wherein the initial arc comprises at most 40.

6. The method according to claim 1, wherein a further arc comprises one of at most 20, and at most 10.

7. The method according to claim 1, wherein the sum of the initial arc and the further arcs is one of at most 80 and at most 60.

8. The method according to claim 1, comprising a step of determining the power consumption required to turn the partial assembly through a further arc.

9. The method according to claim 1, wherein a rotation of the rotor shaft to extend the free swing arc by a further arc is effected when the rotational speed of the partial assembly decreases to a predetermined threshold.

10. The method according to claim 1, wherein a rotor blade is held in a vertical orientation during mounting to the hub.

11. A wind turbine comprising: a generator; a full-scale converter arranged between the generator and a grid; a hub connected via a rotor shaft to the generator; and a controller configured to control the full-scale converter to carry out the method according to claim 1 during the rotor blade mounting procedure.

12. The wind turbine according to claim 11, wherein the wind turbine comprises a backup power supply arranged to provide power to the full-scale converter during the rotor blade mounting procedure.

13. The wind turbine according to claim 11, wherein the backup power supply comprises a solid-state battery.

14. The wind turbine according to claim 11, comprising a means of monitoring the rotational velocity of the rotor shaft throughout a free swing arc.

15. The wind turbine according to claim 10, wherein the wind turbine is an offshore wind turbine.

Description

BRIEF DESCRIPTION

[0031] Some of the embodiments will be described in detail, with reference to the following figures, wherein like designations denote like members, wherein:

[0032] FIG. 1 shows a wind turbine with one rotor blade mounted to the hub;

[0033] FIG. 2 illustrates steps of the inventive method carried out on the wind turbine of FIG. 1;

[0034] FIG. 3 illustrates steps of the inventive method carried out on the wind turbine of FIG. 1;

[0035] FIG. 4 illustrates steps of the inventive method carried out on the wind turbine of FIG. 1;

[0036] FIG. 5 illustrates steps of the inventive method carried out on the wind turbine of FIG. 1;

[0037] FIG. 6 shows the wind turbine with two rotor blades mounted to the hub;

[0038] FIG. 7 illustrates steps of the inventive method carried out on the wind turbine of FIG. 6;

[0039] FIG. 8 illustrates steps of the inventive method carried out on the wind turbine of FIG. 6;

[0040] FIG. 9 illustrates steps of the inventive method carried out on the wind turbine of FIG. 6;

[0041] FIG. 10 illustrates steps of the inventive method carried out on the wind turbine of FIG. 6;

[0042] FIG. 11 shows the wind turbine with all three rotor blades mounted to the hub;

[0043] FIG. 12 shows a block diagram of a wind turbine during implementation of the inventive method to mount the rotor blades;

[0044] FIG. 13 shows a block diagram of a wind turbine during implementation of a conventional art method to mount the rotor blades;

[0045] FIG. 14 indicates the power consumption of the inventive method; and

[0046] FIG. 15 indicates the power consumption of a conventional art method.

DETAILED DESCRIPTION

[0047] FIGS. 1-5 illustrate a first stage in the inventive method. An offshore wind turbine installation procedure is shown, but the description applies equally well to an onshore wind turbine. It shall be understood that the wind turbine 1 shown in the diagrams is equipped with a full-scale converter and a backup power supply that provides power to the full-scale converter. Such components can be housed in the nacelle 17 mounted at the top of a tower 18. Here, the tower 18 is supported by an offshore monopile 19, and assembly of the wind turbine can be done with the aid of an installation vessel and one or more cranes as will be known to the skilled person.

[0048] As shown in FIG. 1, a first rotor blade R1 has been mounted to the hub 10 at the 6 o'clock position, so that the partial assembly AR1 comprises the hub 10 and one rotor blade R1. The diagram indicates a vertical mounting axis Mx that indicates the position of the longitudinal axis of a rotor blade during the mounting procedure. In order to mount the second rotor blade, the hub 10 must be turned through 120, and in that position the first rotor blade R1 will have been brought to the 10 o'clock position (indicated by the line pointing towards the left-hand corner of the page).

[0049] Instead of simply turning the hub 10 clockwise through 120 in a single step (resulting in large peak power consumption), the FSC of the wind turbine 1 is controlled to initially turn the hub 10 through an arc .sub.0 as shown in FIG. 2 (for clarity, the first rotor blade R1 is indicated by its longitudinal axis R1x in these diagrams). The FSC then ceases to turn the rotor. Subsequently, under the force of gravity as illustrated in FIG. 3, the partial assembly AR1 swings freely in the opposite direction. The momentum of the partial assembly allows it to swing through a free swing arc , which (under favorable conditions) can even exceed the initial arc .sub.0. At some point during the free swing arc , the angular velocity of the partial assembly AR1 reaches a maximum, and the FSC resumes control to turn the rotor further through an additional boost arc . Then, as illustrated in FIG. 4, the partial assembly AR1 is again allowed to freely swing back in the opposite direction. This time, the momentum of the partial assembly AR1 carries it through an even larger free swing arc . Again, at a suitable instant, the FSC resumes control and turns the rotor shaft to extend the rotational travel by a boost arc . These steps can be repeated as necessary to bring the partial assembly to its final position (for this stage of the assembly procedure) in which the first rotor blade R1 is at the 10 o'clock position as shown in FIG. 5. In this example, the first rotor blade R1 reaches the 10 o'clock position after a total of four steps, with a final free swing arc followed by a boost arc . The FSC must only provide boost power through a total angular distance given by the sum of the initial arc .sub.0 and the boost arcs , which sum is less than 120. Furthermore, because the partial assembly AR1 is already in motion by the time the FSC works to turn the rotor through a boost arc , the amplitude of the peak power does not exceed the upper limit of the backup power supply.

[0050] With the first rotor blade R1 at the 10 o'clock position (the final position for this stage of assembly), the second rotor blade R2 can be attached as shown in FIG. 6, so that the partial assembly AR12 now comprises the hub 10 and two rotor blades R1, R2.

[0051] The mass of the partial assembly AR12 is now larger, as is the momentum when the partial assembly is allowed to swing back and forth as illustrated in FIGS. 8-10 through increasingly larger free swing arcs . Again, the FSC needs only to turn the partial assembly AR12 through the first arc .sub.0 as shown in FIG. 7 and to augment each gravity-driven swing of the partial assembly by an additional boost arc as shown in FIGS. 8-10. After a sufficient number of iterations, the partial assembly AR12 reaches its desired orientation with the first rotor blade R1 at the 2 o'clock position and the second rotor blade R2 at the 10 o'clock position, so that the third rotor blade R3 can be mounted as shown in FIG. 11 to complete the aerodynamic rotor AR.

[0052] FIG. 12 is a simplified diagram of a wind turbine 1, showing a partially assembled aerodynamic rotor AR12 and the rotor shaft 10R leading to the generator 11. A full-scale converter 12 is provided, which, during operation of the wind turbine 1, is controlled by the wind turbine controller 14 to convert the generator output power for export to the grid G via a step-up transformer 13 as will be known to the skilled person. During installation of the wind turbine 1, specifically during a rotor blade mounting procedure according to embodiments of the invention, the FSC 12 is controlled to turn the rotor shaft 10R as described above in order to turn the partial assembly AR12 through the relatively small arcs .sub.0, as described in FIGS. 2-5 and FIGS. 7-10 above. Power is supplied by the wind turbine backup power supply 15 as shown here. Because of the favorably low current required by the converter to turn the rotor shaft 10R (and the partial assembly AR12), there is no need for a larger external power supply such as a large diesel generator. In this way, material costs are reduced (no need to transport a large diesel generator to the installation site) and time is also saved (no need to connect and disconnect a diesel generator to the FSC).

[0053] FIG. 13 shows a block diagram of a wind turbine during implementation of a conventional art method to assemble the aerodynamic rotor. The wind turbine 2 has the same configuration shown in FIG. 12, with a rotor shaft 20R leading to a generator 21; a full-scale converter 22; a wind turbine controller 24; a step-up transformer 23, etc.

[0054] Here, a first rotor blade R1 has already been mounted. The FSC 22 is then controlled to turn the rotor shaft 10R through 120 so that the second rotor blade R2 can be mounted. Subsequently, the FSC 22 is controlled to turn the rotor shaft 10R through another 120 so that the third rotor blade can be mounted. In order to provide the necessary torque to turn the first partial assembly AR1 and the heavier second partial assembly AR12, power is provided by an external power supply such as a 750 kW diesel generator 3, which can be conveyed to the installation site by an offshore installation vessel, for example. A large capacity generator 3 is necessary in order to move the total mass of the heavier partial assembly AR12 with two rotor blades R1, R2 (each of which can have a mass in the order of 30 tonnes), and this must be turned through 120 while working against the downward pull of gravity. A backup power supply 25 of the wind turbine 2 is unable to deliver the necessary peak current/voltage to effect a rotation of the partial assembly AR1, AR12 through 120. The material costs of providing the external power supply 3 are significant and are increased further by the time required to connect and disconnect the generator 3.

[0055] FIG. 14 illustrates an advantage of the inventive method. The diagram shows the relationship between power consumption (Y-axis in kW) against time. The peak power P.sub.141 required by the FSC to turning the first partial assembly AR1 through a relatively small arc .sub.0, as described in FIGS. 2-5 does not exceed the upper limit P.sub.lim of the backup power supply 15. Similarly, the peak power P.sub.142 required by the FSC to turn the second partial assembly AR12 as described in FIGS. 7-10 also does not exceed the upper limit P.sub.lim of the backup power supply 15. The diagram indicates that power is only required to turn the partial assembly AR1, AR12 through an arc .sub.0, . Between these active turning stages, the partial assembly AR1, AR12 swings freely through a free swing arc and power is not required.

[0056] In contrast, the conventional art approach is to turn each partial assembly AR1, AR12 through 120. The peak power P.sub.151 required by the FSC to effect a rotation of the first partial assembly AR1 through 120 can already exceed the upper limit P.sub.lim of the wind turbine's backup power supply, as shown in FIG. 15, so that the larger external power supply 16 of FIG. 13 is required. The peak power P.sub.152 required by the FSC to effect a rotation of the second, heavier partial assembly AR12 through 120 is even greater.

[0057] Although the present invention has been disclosed in the form of 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. For example, instead of raising each rotor blade along a vertical mounting axis Mx as shown in the drawings, the mounting axis Mx may be horizontal.

[0058] 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.