DYNAMIC FAULT RIDE THROUGH BANDS FOR WIND POWER INSTALLATIONS

Abstract

Provided is a method for controlling at least two frequency-converter-based infeeders. The method includes specifying a first droop for a first frequency-converter-based infeeder and specifying a second droop for a second frequency-converter-based infeeder, where the second droop is different from the first droop. The method includes, controlling the first frequency-converter-based infeeder in dependence on the first droop, and controlling the second frequency-converter-based infeeder in dependence on the second droop.

Claims

1. A method for controlling at least two frequency-converter-based feed-in devices, comprising: setting a first droop for a first frequency-converter-based feed-in device of the at least two frequency-converter-based feed-in devices; setting a second droop for a second frequency-converter-based feed-in device of the at least two frequency-converter-based feed-in devices, wherein the second droop is different from the first droop; and controlling the first frequency-converter-based feed-in device based on the first droop, and controlling the second frequency-converter-based feed-in device based on the second droop.

2. The method as claimed in claim 1, wherein: the first droop has a first dead-band, the second droop has a second dead-band, and the first dead-band is different from the second dead-band.

3. The method as claimed in claim 2, wherein the first dead-band is shorter than the second dead-band.

4. The method as claimed in claim 1, wherein at least a portion of the first droop is steeper than the second droop.

5. The method as claimed in claim 1, wherein at least a portion of the first droop is constant.

6. The method as claimed in claim 1, wherein the first droop is a reactive-current voltage droop.

7. The method as claimed in claim 1, wherein the second droop is a reactive-current voltage droop.

8. The method as claimed in claim 1, comprising: coordinating the setting of the first droop and the second droop such that the first droop and the second droop jointly substantially correspond to a third droop.

9. The method as claimed in claim 8, wherein: the third droop is set by a grid operator, and/or the first droop raises a voltage within a second dead-band of the second droop.

10. The method as claimed in claim 1, wherein the first droop, the second droop or both the first and second droops are substantially symmetrical in an overvoltage range and an undervoltage range.

11. The method as claimed in claim 1, wherein the at least two frequency-converter-based feed-in devices are each a wind power installation or a wind farm.

12. The method as claimed in claim 1, wherein the at least two frequency-converter-based feed-in devices are part of a wind farm.

13. The method as claimed in claim 1, wherein the at least two frequency-converter-based feed-in devices form a wind farm.

14. A wind power installation, comprising: at least one controller; and a feed-in device coupled to the controller and including a frequency converter for feeding-in electrical power, wherein the controller is configured to: store at least one droop selected from a first droop and a second droop; and control the frequency converter based on the at least one droop.

15. The wind power installation as claimed in claim 14, wherein the feed-in device is an inverter or a converter.

16. A wind farm, comprising: at least two wind power installations including the wind power installation as claimed in claim 14; and a wind-farm controller.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0055] The present invention is now explained exemplarily in greater detail below, on the basis of exemplary embodiments with reference to the accompanying figures, with the same references being used for assemblies that are the same or similar.

[0056] FIG. 1 shows a schematic view of a wind power installation according to an embodiment.

[0057] FIG. 2 shows a schematic view of two FRT two band of two wind power installations.

[0058] FIG. 3 shows a schematic view of the effect of the proposed method.

[0059] FIG. 4 shows a block diagram of a wind power installation.

DETAILED DESCRIPTION

[0060] FIG. 1 shows a schematic view of a wind power installation 100 according to an embodiment.

[0061] The wind power installation 100 has a tower 102 and a nacelle 104.

[0062] Arranged on the nacelle 104 there is an aerodynamic rotor 106 that has three rotor blades 108 and a spinner 110.

[0063] During operation, the rotor 106 is put into rotary motion by the wind and thereby drives a generator in the nacelle 104.

[0064] The generator is also connected to a frequency converter described herein.

[0065] The wind power installation is thus realized as a frequency-converter-based infeeder (frequency-converter-based feed-in device).

[0066] For the purpose of operating the wind power installation, and in particular the frequency converter, a control unit (e.g., controller), described herein, is also provided, in particular for executing and/or participating in a method described herein.

[0067] FIG. 2 shows a schematic view 200 of two droops, in particular FRT bands, of two wind power installations that in particular are connected to an electrical supply grid.

[0068] The schematic view 200 in this case shows, in particular, a grid-voltage reactive-current diagram, with the actual voltage of the electrical supply grid plotted on the abscissa, and the reactive current fed-in by the wind power installation plotted on the ordinate.

[0069] The first wind power installation has a first droop 210, 210′, 210″ with a first dead-band T1.

[0070] The first droop 210, 210′, 210″ in this case comprises, in particular, three portions.

[0071] The, in particular first, portion 210 of the first droop 210, 210′, 210″ has a constant characteristic between 0.95 p.u. and 1.05 p.u. of the actual voltage of the electrical supply grid, and may also be referred to as a dead-band T1.

[0072] The, in particular second, portion 210′ of the first droop 210, 210′, 210″ extends linearly between 0.95 p.u. and 0.85 p.u., and between 1.05 p.u. and 1.15 p.u., and has a first slope that is other than 0.

[0073] The, in particular third, portion 210″ of the first droop 210, 210′, 210″ has a constant characteristic between 0.85 p.u. and 0, and between 1.15 p.u. and infinity, and has a second slope equal to 0. The, in particular, third portion 210″ therefore has a substantially constant characteristic.

[0074] The second wind power installation has a second droop 220, 220′ with a second dead-band T2.

[0075] The second droop 220, 220′ in this case comprises, in particular, two portions.

[0076] The, in particular first, portion 220 of the second droop 220, 220′ has a constant characteristic between 0.85 p.u. and 1.15 p.u. of the actual voltage of the electrical supply grid, and may also be referred to as a dead-band T2 of the second droop 220, 220′.

[0077] The, in particular second, portion 220′ of the second droop 220, 220′ extends between 0.85 p.u. and 0, and between 1.15 p.u. and infinity.

[0078] The first dead-band T1 is thus different from the second dead-band T2; in particular, the first dead-band T1 is smaller than the second dead-band T2.

[0079] In addition, the first droop 210, 210′, 210″ and the second droop 220, 220′ are coordinated so as to substantially correspond to a third droop 230, 230′, 230″ that represents, for example, the wish of a grid operator.

[0080] FIG. 3 shows a schematic view of the effect of the proposed method.

[0081] The ordinate shows the actual voltage of the electrical supply grid Vgrid and the reactive currents of the wind power installations Iq_wpi1, Iq_wpi2.

[0082] The time progression t is shown on the abscissa.

[0083] The actual voltage of the electrical supply grid Vgrid remains at the specified level until the instant t1, e.g., Oms, i.e., as desired by the grid operator.

[0084] At the instant t1, e.g., Oms, the actual voltage of the electrical supply grid Vgrid dips, e.g., due to load switching operations within the electrical supply grid.

[0085] Here, voltage goes below a first limit voltage Vfrt_wpi1 of the first wind power installation, triggering the FRT property of the first wind power installation by means of the first droop, as shown in FIG. 2.

[0086] As a result, at instant the t2, e.g., 30 ms, the first wind power installation feeds in an increased reactive current, which supports the electrical supply grid, and in particular results in a recovery of the actual voltage of the electrical supply grid.

[0087] This means that the first wind power installation is successfully supporting the electrical supply grid. Nevertheless, the first wind power installation is still in the FRT mode because the electrical supply grid still has an undervoltage. Without further additional support, e.g., from the second wind power installation, the first wind power installation would disconnect from the electrical supply grid after a fault time has elapsed.

[0088] At the instant t4, e.g., 1000 ms, the second wind power installation likewise feeds in an increased reactive current, which likewise supports the electrical supply grid and results in a further recovery of the actual voltage of the electrical supply grid.

[0089] This is due, for example, to a higher-order voltage closed-loop control of the wind farm, for example a Q(V) control, as the second part of the wind power installations does not operate in fault mode and can thus continuously support the voltage via the wind-farm closed-loop control.

[0090] At the instant t6, e.g., 4000 ms, the actual voltage of the electrical supply grid then returns to the specified range.

[0091] The fact that the two wind power installations react differently to the same voltage dip is due to the previously described droops and the reaction of the higher-order closed-loop control.

[0092] FIG. 4 shows a block diagram of a wind power installation 400. The wind power installation 400 includes at least one control unit (e.g., controller) 402 and a feed-in unit (e.g., converter or inverter) 404 that is connected to the control unit 402 and that comprises a frequency converter 406 for feeding-in electrical power. The control unit 402 is configured to store a first and/or second droop and to control the frequency converter in dependence on this droop.

LIST OF REFERENCES

[0093] 100 wind power installation [0094] 102 tower, in particular of a wind power installation [0095] 104 nacelle, in particular of a wind power installation [0096] 106 aerodynamic rotor, in particular of a wind power installation [0097] 108 rotor blade, in particular of a wind power installation [0098] 110 spinner, in particular of a wind power installation [0099] 210 first portion of the first droop [0100] 210′ second portion of the first droop [0101] 210″ third portion of the first droop [0102] 220 first portion of the second droop [0103] 220′ second portion of the second droop [0104] 230 first portion of the third droop, in particular of the overall droop [0105] 230′ second portion of the third droop, in particular of the overall droop [0106] 230″ third portion of the third droop, in particular of the overall droop [0107] T1 dead-band of the first droop [0108] T2 dead-band of the second droop [0109] Vgrid actual voltage, in particular of the electrical supply grid [0110] Vfrt_wpi1 limit voltage, in particular of the first wind power installation [0111] Vfrt_wpi2 limit voltage, in particular of the second wind power installation [0112] Iq_wpi1 reactive current of the first wind power installation [0113] Iq_wpi2 reactive current of the second wind power installation [0114] t time

[0115] The various embodiments described above can be combined to provide further embodiments. These and other changes can be made to the embodiments in light of the above-detailed description. In general, in the following claims, the terms used should not be construed to limit the claims to the specific embodiments disclosed in the specification and the claims, but should be construed to include all possible embodiments along with the full scope of equivalents to which such claims are entitled. Accordingly, the claims are not limited by the disclosure.