Method for detecting formation of a separate system

Patent metadata

Field	Value
Publication number	US-11081886-B2
Application number	US-201816607675-A
Country	US
Kind code	B2
Filing date	Apr 24, 2018
Priority date	Apr 24, 2017
Publication date	Aug 3, 2021
Grant date	Aug 3, 2021

Abstract

A method for controlling a generating unit that feeds into an electrical supply system. The generating unit feeds into the electrical supply system using one or more converters or inverters. The method is provided for the purpose of detecting a system separation or formation of a separate system, and the method includes controlling the feed by a feed controller operating with at least one current controller, detecting at least one current control error and testing the detected current control error for a disparity from a predetermined reference range. The method includes identifying a system separation involving a separate system that is disconnected from the electrical supply system and to which the generating unit is connected if a disparity from the predetermined reference range has been detected.

First claim

The invention claimed is:

1. A method for controlling a generation unit that feeds an electrical supply network using one or more converters or inverters and for detecting network isolation or formation of a separate network, comprising:
controlling, by a feed controller that operates at least using current control, feeding the electrical supply network;
detecting current control deviation;
determining whether the detected current control deviation deviates from a predetermined reference range, wherein determining whether the detected current control deviation deviates from the predetermined reference range includes:
identifying a checking variable or checking function from the current control deviation; and
comparing the checking variable or checking function with at least one reference variable or reference function; and

if the detected current control deviation deviates from the predetermined reference range, identifying the network isolation in the case of which the separate network is formed, the separate network being separated from the electrical supply network and connected to the generation unit.

2. The method as claimed in claim 1 , wherein the separate network is a network to which only the generation unit and one or more further generation units are connected and wherein no generation units with a directly coupled synchronous generator are connected to the separate network.

3. A method for controlling a generation unit that feeds an electrical supply network using one or more converters or inverters, comprising:
determining whether a first-degree separate network fault is present by:
detecting current control deviation; and
determining whether the detected current control deviation deviates from a predetermined reference range, wherein determining whether the detected current control deviation deviates from the predetermined reference range includes:
identifying a checking variable or checking function from the current control deviation; and
comparing the checking variable or checking function with at least one reference variable or reference function;

if the first-degree separate network fault is present, determining whether a second-degree separate network fault is present; and
identifying network isolation in the case of which a separate network is produced, the separate network being separated from the electrical supply network and the generation unit being connected to the separate network.

4. The method as claimed in claim 3 , comprising:
if the first-degree separate network fault is present, setting a desired current value, for which the current control deviation is detected, to zero, and
if the second-degree separate network fault is present:
opening a circuit breaker; and
interrupting a current on which the current control deviation is based.

5. The method as claimed in claim 1 , comprising:
defining or changing the predetermined reference range based on an operating mode or operating state of the generation unit or the feed controller.

6. The method as claimed in claim 1 , comprising:
setting the current control deviation to a difference between a desired current and an actual current or a desired current component and an actual current component of a current to be fed in.

7. The method as claimed in claim 1 , comprising determining that the detected current control deviation deviates from the predetermined reference range when:
an absolute value of the checking variable or the checking function exceeds a predefined limit value,
the checking variable or the checking function leaves a predefined normal band, or
the checking variable or the checking function changes with a temporal gradient having an absolute value that exceeds a predefined limit gradient.

8. The method as claimed in claim 1 , comprising:
feeding the electrical supply network using a three-phase feed current composed of three phase currents, wherein a desired current value is predefined for each phase current of the three-phase feed current; and
determining whether the detected current control deviation deviates from the predetermined reference range by determining whether each phase current deviates from the desired current value of the respective phase.

9. The method as claimed in claim 1 , wherein an absolute value of the current control deviation, the checking variable or the checking function is related to a tolerance bandwidth or an average tolerance bandwidth.

10. The method as claimed in claim 1 , comprising:
feeding a three-phase feed current into the electrical supply network by predefining current components using vector control,
dividing the three-phase feed current into a d component and a q component using a d-q transformation, and
setting the current control deviation to a difference between a desired value and an actual value of the d component or the q component.

11. The method as claimed in claim 1 , comprising:
interpreting the identification of the network isolation or the formation of the separate network by detecting the deviation from the predetermined reference range as an identification of a first-degree separate network fault; and
further operating the generation unit after identifying the first-degree separate network fault.

12. The method as claimed in claim 11 , wherein
after identifying the first-degree separate network fault,
further operating the generation unit with a desired current value set to zero;
checking for a presence of a second-degree separate network fault; and
determining that the second-degree separate network fault is present if the current control deviation is identified though the desired current value in the feed controller is zero.

13. The method as claimed in claim 1 , comprising:
keeping the generation unit connected to the electrical supply network or to the separate network after a first-degree separate network fault is identified; and
isolating the generation unit in a DC fashion from the electrical supply network or the separate network after a second-degree separate network fault is identified.

14. A generation unit, comprising:
one or more converters or inverters configured to feed electrical power into an electrical supply network;
an installation controller configured to detect network isolation or a formation of a separate network;
a feed controller configured to control feeding the electrical power at least by current control;
a detection device configured to detect current control deviation; and
a checking device configured to check whether the detected current control deviation deviates from a predetermined reference range by at least:
identifying a checking variable or checking function from the current control deviation; and
comparing the checking variable or checking function with at least one reference variable or reference function,

wherein the installation controller is configured to, if the checking device detects the deviation from the predetermined reference range, identify the network isolation in the case of which the separate network is formed, the separate network being separated from the electrical supply network and the generation unit being connected to the separate network.

15. A wind farm having a plurality of wind power installations, wherein at least one of the plurality of wind power installations is the generation unit as claimed in claim 14 .

16. The method as claimed in claim 8 , comprising:
determining whether the detected current control deviation deviates from the predetermined reference range by determining, based on a vector metric, absolute valu

Assignees

• Wobben Properties Gmbh

Inventors

• Diedrichs Volker

Classifications

• H02J2101/28

  Wind energy · CPC title

• H02J3/38 Primary

  Arrangements for feeding a single network from two or more generators or sources in parallel; Arrangements for feeding already energised networks from additional generators or sources in parallel · CPC title

• G01R19/2513

  Arrangements for monitoring electric power systems, e.g. power lines or loads; Logging · CPC title

• H02M7/53875

  with analogue control of three-phase output · CPC title

• F03D7/0284

  in relation to the state of the electric grid · CPC title