Fault protection in converter-based DC distribution systems

Patent metadata

Field	Value
Publication number	US-10693293-B2
Application number	US-201615344013-A
Country	US
Kind code	B2
Filing date	Nov 4, 2016
Priority date	May 4, 2014
Publication date	Jun 23, 2020
Grant date	Jun 23, 2020

Abstract

Methods and apparatus for protecting a direct-current (DC) electric power distribution system that includes one or more AC/DC converters and/or one more DC/DC converters, and one or more loads, connected by DC buses. An example method, which is carried out in response to the detection of a fault somewhere in the system, begins with limiting an output current of each of one or more of the converters so that each of the limited converters outputs a limited DC current at or about a corresponding predetermined current level. After the current limiting of the one or more converters has taken place, one or more protection devices in the system are activated, where the activating at least partly depends on the limited DC currents being at or about the predetermined fault current levels.

First claim

What is claimed is:

1. A method for protecting a direct-current (DC) electric power distribution system that includes one or more loads, one or more DC buses, and one or more converters, the converters comprising one or more AC/DC converters or one or more DC/DC converters, or both, the plurality of converters each having a fault current limiting function integrated into the converter, the method comprising, in response to a detection of a fault in the system:
coordinatively limiting, via activation of the fault current limiting function of each of the plurality of converters, an output current of each of a plurality of the converters so that each of the plurality of converters outputs a limited DC current, the limited DC current being coordinated such that at least one of a current level and a duration of the limited DC current for at least one of the plurality of converters during activation of the fault current limiting function is different than the current level and/or duration of the limited DC current of another one of the plurality of converters;
selectively activating one or more protection devices in the system to isolate the fault, wherein said selectively activating at least partly depends on the limited DC currents being discriminative with respect to at least one of current direction and current level; and
deactivating, after isolation of the fault, the fault current limiting function of each of the plurality of converters that are outside the portion of the system that has been isolated by isolation of the fault.

2. The method of claim 1 , wherein limiting the output current of one of the converters comprises directly controlling the converter to produce the limited DC current at or about a predetermined current level.

3. The method of claim 1 , wherein said activating comprises:
identifying a location for the detected fault, based on at least measurements of currents on the DC buses, wherein said identifying at least partly depends on the limited DC currents being at or about a predetermined current level; and
opening one or more DC switches in the system, based on the identified location of the detected fault.

4. The method of claim 3 , wherein identifying the location for the detected fault is based on measurements on the DC buses of one or more of:
current levels;
current derivatives;
voltages; and
current directionalities.

5. The method of claim 3 , wherein said opening of one or more DC switches in the system comprises opening all tie line and branch DC switches connected to a first DC bus in response to identifying the first DC bus as the location of the detected fault.

6. The method of claim 3 , wherein said opening of one or more DC switches in the system comprises opening a DC switch immediately upstream or DC switches on both sides of an identified fault location in response to identifying a DC branch as the location of the detected fault.

7. The method of claim 3 , further comprising, after said opening of one or more DC switches, reconfiguring at least a portion of the system by activating one or more alternative paths for connecting equipment affected by said opening of one or more DC switches.

8. The method of claim 3 , further comprising, after said opening of one or more DC switches:
determining that the fault has been isolated; and,
in response to said determining, discontinuing the limiting of output current in each of the converters that is limited to its corresponding predetermined current level.

9. The method of any of claim 1 , wherein limiting the output current for one or more of the plurality of converters comprises first limiting the output current to a first limited current level, for a first interval of time, and subsequently limiting the output current to a second limited current level.

10. The method of claim 9 , wherein said activating comprises an automatic opening of one or more protection devices, wherein the opening of each protection device is based on a respective device current exceeding at least one respective threshold for a respective period of time, and wherein the thresholds are based on the predetermined current levels.

11. A method for protecting a direct-current (DC) electric power distribution system that includes one or more loads, one or more DC buses, and a plurality of converters, the plurality of converters comprising one or more AC/DC converters or one or more DC/DC converters or both, the method comprising:
receiving measurements of DC bus currents;
receiving an indication of a fault in the system;
activating a fault limiting current function that is integrated into each of the plurality of converters;
coordinating an output of a limited DC current by the plurality of the converters such that, via activation of the fault limiting current function, at least one of a current level and a duration of the limited DC current outputted by at least one of the plurality of the converters is different than the current level and/or the duration of the limited DC current outputted by another converter of the plurality of converters;
identifying a location for the indicated fault, based on the measurements of DC bus currents, wherein said identifying at least partly depends on a predetermined, limited, DC current level for at least one of the converters;
opening one or more DC switches in the system, based on the identified location of the indicated fault; and
deactivating, after isolation of the fault, the fault current limiting function of each of the plurality of converters that are outside the identified location of the indicated fault.

12. The method of claim 11 , further comprising providing external control to at least one of the converters to produce its corresponding predetermined, limited, DC current.

13. The method of claim 11 , wherein identifying the location for the indicated fault is further based on measurements on the DC buses of one or more of:
current levels;
current derivatives;
voltages; and
current directionalities.

14. The method of claim 11 , wherein said opening of one or more DC switches in the system comprises opening all tie line and branch DC switches connected to a first DC bus in response to identifying the first DC bus as the location of the indicated fault.

15. The method of claim 11 , wherein said opening of one or more DC switches in the system comprises opening a DC switch immediately upstream or DC switches on both sides of an identified fault location in response to identifying a DC branch as the location of the indicated fault.

16. The method of claim 11 , further comprising, after said opening of one or more DC switches, reconfiguring at least a portion of the system by activating one or more alternative paths for connecting equipment affected by said opening of one or more DC switches.

17. The method of claim 11 , further comprising, after said opening of one or more DC switches:
determining that the fault has been isolated; and,
in response to said determining, discontinuing limiting of output current in each of the converters that is limited to its corresponding predetermined current level.

18. A direct-current (DC) electric power distribution system, comprising:
multiple DC buses, each either directly or through converters associated with one or more power sources and one or more loads, connected by branches and converters, wherein at least one of the converters is an AC/DC converter or DC/DC converter operable to produce a respective converter current at or about a predetermined, limited, DC current level in response to a detection

Assignees

• Abb Schweiz Ag

Inventors

• Qi Li
• Pan Jiuping
• Chen Yao
• Zhang Guoju

Classifications

• H02M7/04 Primary

  by static converters · CPC title

• H02H3/06

  with automatic reconnection · CPC title

• H02H3/025

  Disconnection after limiting, e.g. when limiting is not sufficient or for facilitating disconnection · CPC title

• H02H9/02

  responsive to excess current {(current limitation for voltage regulators G05F1/573; disconnection after limiting H02H3/025)} · CPC title

• H02H7/268 Primary

  for DC systems · CPC title