Method for controlling an electric generator

Patent metadata

Field	Value
Publication number	US-9920746-B2
Application number	US-201314414417-A
Country	US
Kind code	B2
Filing date	Jul 3, 2013
Priority date	Jul 13, 2012
Publication date	Mar 20, 2018
Grant date	Mar 20, 2018

Abstract

The invention relates to a method for controlling a generator of electric energy that is connected to an electrical supply grid on a grid connection point, comprising the following steps: feeding electrical power into the electrical supply grid, whereby the generator is operated in a first operating point, interrupting the feeding so that no power is fed into the supply grid if a fault in the electrical supply grid or a fault of the feeding into the electrical supply grid exists or is displayed, resuming the feeding so that electrical power is again fed into the supply grid, whereby the generator resumes the feeding in a second operating point or is gradually increased in said second operating point, and the second operating point is designed in such a way that it feeds into the supply grid with a higher stability reserve than the first operating point.

First claim

The invention claimed is:

1. A method for controlling an electric generator that is coupled to an electrical supply grid at a grid connection point, the method comprising:
feeding electrical power into the supply grid when the generator is operating at a first operating point;
monitoring the supply grid or the feeding of electrical power into the supply grid for a fault;
interrupting the feeding so that no power is fed into the supply grid when the fault is identified; and
resuming feeding so that electrical power is again fed into the supply grid, wherein resuming the feeding occurs at a second operating point or the feeding is gradually increased to the second operating point, and wherein the feeding into the supply grid at the second operating point takes place with a higher stability reserve than the first operating point, resuming the feeding includes:
feeding less of at least one of active power and reactive power into the supply grid at the second operating point than at the first operating point, wherein the feeding less of the at least one of the active power and the reactive power includes at least one of: reducing the active power by at least 10%, and reducing the reactive power by at least 10%.

2. The method according to claim 1 wherein the generator is at least one of a decentralized generator, a wind power installation, and a wind park comprising several wind power installations, and the generator uses a voltage-based feeding to feed in the electric power.

3. The method according to claim 1 wherein resuming the feeding comprises:
increasing the fed-in reactive power more quickly than the fed-in active power, so that a reactive power value at the second operating point is achieved earlier than an active power value at the second operating point.

4. The method according to claim 1 wherein the reactive power is adjusted to a value of the first or second operating point so as to support the grid, and then the active power is adjusted.

5. The method according to claim 1 wherein when resuming the feeding, the fed-in active power is increased with a predetermined course and the fed-in reactive power stabilizes the voltage, whereby the reactive power is based on a previously recorded grid characteristic of the electrical supply grid.

6. The method according to claim 1 wherein resuming the feeding occurs after a period of time.

7. The method according to claim 6 wherein the period of time is less than 10 seconds, and wherein resuming the feeding comprises a run-time in which a gradual increase to the second operating point occurs until the second operating point is reached.

8. The method according to claim 1 wherein the stability reserve is at least one of:
a smallest difference between the fed-in reactive power and the reactive power of stability boundary,
a smallest difference between the fed-in active power and the active power of stability boundary, or
a smallest difference between a voltage on the grid connection point and a voltage of stability boundary.

9. The method according to claim 8 wherein the stability reserve is based on at least one of:
a function of the grid voltage at the grid connection point depending on at least one of the fed-in reactive power and fed-in active power, and
a function of the fed-in active power depending on the fed-in reactive power, or vice versa,
wherein the stability boundary is provided as a curved surface in a space formed by the grid voltage on grid connection point, the fed-in reactive power and the fed-in active power.

10. The method according to claim 1 wherein the fault in the energy supply grid or in feeding electrical power into the energy supply grid is at least one of the following:
a loss of stability of the supply grid,
a loss of stability feeding into supply grid,
an overcurrent in the supply grid,
an overcurrent at the grid connection point,
a short circuit in the supply grid,
a voltage fall in the supply grid,
a voltage fall at the grid connection point, and
switching or stepping of transformers in the supply grid.

11. The method according to claim 10 wherein the fault is a loss of stability at the grid connection point, and wherein resuming the feeding includes at least one of the following:
switching from a first control to a stabilization control, wherein the stabilization control controls the generator with higher stability in comparison to the first control, and
the active power of generator that is to be fed in is limited to a value that is smaller than a nominal capacity of the generator.

12. The method according to claim 11 wherein when switching to the stabilization control, at least one of a limitation of the active power and a use of the central park control is maintained until it is identified that a loss of stability is no longer occurring.

13. The method according to claim 10 wherein the generator is a wind park that includes a plurality of wind power installations, wherein resuming the feeding includes switching from a first control to a central park control, wherein the central park coordinates and controls the wind power installations in the wind park so as to counteract a loss of stability.

14. The method according to claim 1 , further comprising:
resetting control of the generator to a first control by an external signal of a the stabilization control, and
annulling a limitation of the fed-in active power after a threatening loss of stability has been identified on the grid connection point or after resuming the feeding.

15. The method according to claim 1 wherein a wind park with several wind power installations is provided, wherein each wind power installation is a generator entity, wherein after interrupting the feeding of one or several wind power installation(s), said resuming feeding comprises resuming feeding said wind power installations individually and switching from a first control to a stabilization control that controls the respective wind power installation with higher stability in comparison to the first control.

16. The method according to claim 1 wherein resuming the feeding continues to occur while the fault still exists wholly or partly.

17. The method according to claim 1 wherein the generator remains coupled to supply grid and remains operating when the feeding is interrupted.

18. The method according to claim 1 wherein the reactive power and the active power are increased respectively with a ramp function in terms of time, and wherein the ramp function causes a reactive power value at the second operating point to be achieved earlier than an active power value at the second operating point.

Assignees

• Wobben Properties Gmbh

Inventors

• Diedrichs Volker
• Busker Kai
• Beekmann Alfred

Classifications

• H02J2101/28

  Wind energy · CPC title

• H02J3/0014

  for preventing or reducing power oscillations in networks · CPC title

• F03D7/04

  Automatic control; Regulation · CPC title

• H02J3/16

  by adjustment of reactive power · CPC title

• F03D9/255

  connected to electrical distribution networks; Arrangements therefor · CPC title