Method and system for the maintenance of a wind energy installation from a group of wind energy installations

Abstract

A method for the maintenance of a first wind energy installation from a group of wind energy installations. In the method, a future maintenance time period is identified in which a boost power of the group of wind energy installations is greater than a prescribed threshold value, wherein the boost power results from a wind speed predicted for the future maintenance time period, said wind speed being greater than a rated wind speed. The power of the first wind energy installation is reduced after the start of the maintenance time period and a boost power is drawn from a plurality of wind energy installations from the group of wind energy installations. A maintenance process is carried out at the first wind energy installation. The invention furthermore relates to a control unit suitable for carrying out the method.

Claims

1. A method for the maintenance of a first wind energy installation (15) from a group of wind energy installations (14, 15) comprising the following steps: a. identifying a future maintenance time period (26) in which a boost power of the group of wind energy installations (14, 15) is greater than a prescribed threshold value, wherein the boost power results from a wind speed (23) predicted for the future maintenance time period (26), said wind speed being greater than a rated wind speed (24); b. reducing the power of the first wind energy installation (15) after the start of the maintenance time period and drawing a boost power from a plurality of wind energy installations (14) from the group of wind energy installations (14, 15); c. carrying out a maintenance process at the first wind energy installation (15).

2. The method of claim 1, wherein a future maintenance time period (26) is identified in which the predicted environmental conditions at at least one wind energy installation (15) are more favorable than the standard conditions assumed in the design of the wind energy installation (15) and in that the boost power is drawn from the wind energy installation (15) within a measurement range of the design.

3. The method of claim 1, wherein a future maintenance time period (26) is identified in which the predicted wind turbulence, a vertical and/or horizontal wind gradient, an upflow, a wake condition in the group of wind energy installations and/or an air density are low.

4. The method of claim 1, wherein the first wind energy installation (15) is brought to a standstill after the start of the maintenance time period (26).

5. The method of claim 1, wherein between a time (T0) at which the future maintenance time period (26) is identified and the start of the maintenance time period (26), a maintenance plan is created, which determines a maintenance process to be carried out in the future maintenance time period (26) for the first wind energy installation (15).

6. The method of claim 1, wherein the prescribed threshold value for the boost power is related to the power loss to be expected in the first wind energy installation (15) during the maintenance time period (26).

7. The method of claim 6, wherein the prescribed threshold value is selected so that it corresponds to at least 40%, preferably at least 80%, further preferably at least 100% of the power loss to be expected at the first wind energy installation (15).

8. The method of claim 1, wherein the future maintenance time period (26) is identified in which the power loss of the first wind energy installation (15) to be expected is lower than the rated power of the first wind energy installation (15).

9. The method of claim 1, wherein the future maintenance time period (26) is selected so that the boost power is greater than the prescribed threshold value over at least 40%, preferably over at least 60%, further preferably over at least 80% of the duration of the maintenance process.

10. The method of claim 1, wherein the first wind energy installation (15) is connected to a transmission network (18) via a first network infeed point (17) and in that the group comprises wind energy installations (14) that are connected to a transmission network (18) via a second network infeed point (28, 29).

11. The method of claim 10, wherein the permissible power that can be fed in via the second network infeed point (28, 29) is greater by an excess power than the sum of the rated powers of the wind energy installations (14) connected to the second network infeed point (28, 29).

12. A control unit for carrying out a maintenance process at a first wind energy installation (15) from a group of wind energy installations (14, 15), wherein the control unit (19) identifies, based on a wind prediction, a future maintenance time period (26) in which a boost power of the group of wind energy installations (14, 15) is greater than a prescribed threshold value, wherein the control unit (19) is designed to generate a control signal after the start of the maintenance time period (26) in order to reduce the power of the first wind energy installation (15) and to draw a boost power from a plurality of wind energy installations (14) from the group of wind energy installations (14, 15).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention is described by way of example in the following text with reference to the appended drawings based on advantageous embodiments. In the figures:

(2) FIG. 1 shows a group of wind energy installations in a first embodiment of the invention;

(3) FIG. 2 shows a schematic illustration of a future maintenance time period;

(4) FIG. 3 shows a group of wind energy installations in a second embodiment of the invention;

(5) FIGS. 4 and 5 show the view according to FIG. 2 at different times;

(6) FIG. 6 shows a schematic illustration of a system according to the invention.

DETAILED DESCRIPTION

(7) FIG. 1 illustrates a group of wind energy installations 14, 15. Each wind energy installation comprises a generator, which is connected to a rotor by means of a rotor shaft. The rotor, which is set in rotation by the wind, drives the generator so that electrical energy is provided.

(8) The group comprises a first wind energy installation 15, at which a cycle-based maintenance process is pending. The wind energy installations 14, 15 are connected to a network 16 inside a wind farm. The electrical energy provided by the wind energy installations 14, 15 is fed into a transmission network 18 at a network infeed point 17.

(9) A system according to the invention comprises, according to FIG. 6, a control unit 19, which receives a prediction about the wind conditions at a future time from a forecast module 20. A computation module 21 of the control unit 19 processes the prediction data obtained from the forecast module 20 and first of all checks whether there is a future time period in which the predicted wind speed is greater than the rated wind speed of the wind energy installations 14. For the sake of simplicity, it is assumed that the same wind forecast applies to all of the wind energy installations 14 and that all of the wind energy installations 14 have the same rated wind speed. If this is not the case, separate wind forecasts have to be used and compared individually with the rated wind speeds of the wind energy installations 14.

(10) If the computation module 21 has identified such a future time period, the amount of boost power that the wind energy installation 14 will probably be able to generate in the future time period is calculated in a next step for each wind energy installation 14. A total boost power of the group of wind energy installations results from the sum of the individual boost powers of the individual wind energy installations 14. Said total boost power of the group of wind energy installations is referred to as boost power within the scope of the invention.

(11) The total boost power is compared with a prescribed threshold value. If the total boost power is greater than the prescribed threshold value, the computation module 21 in a next step checks the length of the time period until the total boost power drops below the prescribed threshold value again. To this end, the prediction data for the immediately subsequent time period are evaluated.

(12) If the length of the time period is certain, the data about the start of the future time period, the end of the future time period and the amount of total boost power presumably available in the future time period are sent to a planning module 22. The planning module 22 compares the length of the future time period with the period of time necessary for carrying out the maintenance process at the first wind energy installation 15. If the future time period in which the boost power above the prescribed threshold value is available is longer than the period of time necessary for the maintenance process, the planning module 22 determines the future time period as a maintenance time period 26.

(13) In FIG. 2, the wind speed 23 is plotted against the time t. The current time is denoted as T0. The data before the time T0 are measured data of the actual wind speed. The data after the time T0 correspond to the prediction data of the forecast module 20. Before the time T0, the actual wind speed 23 was continuously lower than the rated wind speed 24. According to the prediction data, after the time T0, a rise in the wind speed 23 is to be expected, by which the rated wind speed 24 is briefly exceeded. After a brief drop below the rated wind speed 24, the wind speed according to the prediction data rises above the rated wind speed 24 for a longer time period.

(14) At the time T1, for the first time the wind speed 23 is greater than a threshold value 25 from which the boost power of the group of wind energy installations identified using the computation module 21 is greater than the rated power of the wind energy installation 15. The threshold value 25 corresponds to the prescribed threshold value for the boost power. According to the prediction data, the time period in which the boost power is greater than the prescribed threshold value ends at the time T2.

(15) The planning module 22 determines that the time period between the times T1 and T2 is longer than the time period necessary for the maintenance process at the wind energy installation 15 or that the period of time necessary for the maintenance process can be covered at least to a sufficient proportion. The time period is determined as the maintenance time period 26.

(16) At the start of the maintenance time period 26, the control unit 19 sends a control command to the first wind energy installation 15, according to which control command the wind energy installation 15 is powered down and brought to a standstill. At the same time, a control signal goes to the other wind energy installations 14 of the group, according to which control signal the wind energy installations 14 increase the output power beyond the rated power. The resulting boost power of the wind energy installations 14 corresponds precisely to the power loss resulting from the standstill of the first wind energy installation 15.

(17) In the maintenance time period 26, a service engineer located on site at the first wind energy installation 15 can carry out the cycle-based maintenance process. The maintenance process is concluded before the time T2. The service engineer sends a message about the conclusion of the maintenance process to the control unit 19. The control unit 19 sends a control signal to the first wind energy installation 15 to start operation again. In return for the electrical power fed in from the first wind energy installation 15, the boost power of the wind energy installations 14 is reduced until all of the wind energy installations 14, 15 have returned back to normal operation.

(18) FIG. 3 illustrates an embodiment in which the wind energy installations 14, 15 feed their electrical energy into the transmission network 18 via various network infeed points 17, 28, 29. The network infeed points 17, 28, 29 are physically remote from one another, with the result that the wind conditions differ from one another. The control unit 19 receives prediction data for all of the wind energy installations 14, 15 and attempts to identify a favorable maintenance time period 26 for the maintenance of the first wind energy installation 15. For example, a maintenance time period in which the wind energy installations 14, 15 connected to the first network infeed point 17 are exposed to a wind speed that is lower than the rated wind speed would be favorable. The power loss to be expected due to the shutdown of the first wind energy installation 15 is then lower than the rated power of the first wind energy installation 15. At the same time, the wind speed at the wind energy installations 14 connected to the second network infeed point 28 could be greater than the rated wind speed, with the result that a sufficient amount of boost power is available in order to compensate for the power loss at the first wind energy installation 15.

(19) It is then possible to determine a maintenance time period 26 in which the maintenance process is carried out at the first wind energy installation 15 and the power loss is compensated by boost power from the wind energy installations 14 connected to the second network infeed point 28. This is independent of what the wind conditions are like at the wind energy installations 14 connected to the third infeed point 29. If it were calm there such that all of the wind energy installations 14 connected to the third network infeed point 29 are at a standstill, this would not change anything about the fact that the power loss can be compensated by the first wind energy installation 15 by means of boost power provided at the second network infeed point 28. Other designs in which, for example, boost power is fed in via both network infeed points 28, 29 or only via the third network infeed point 29 are also possible.

(20) FIGS. 4 and 5 illustrate two examples in which the control unit 15 a maintenance time period 26 cannot be determined based on the prediction data available at the time T0. In FIG. 4, although the threshold value 25 is exceeded twice, the respective time period is shorter than the period of time necessary for the maintenance process at the first wind energy installation 15. In FIG. 5, although the time period in which the threshold value 25 is exceeded is long enough, such a high turbulence (or another measurement value having an influence on the loading of the wind energy installation) is predicted, for example, that the wind energy installations 14 would be loaded to too great an extent through the drawing of boost power. In both cases, the maintenance time period 26 is determined at a later time at which the prediction data are more favorable.