Dc electrical network

Patent metadata

Field	Value
Publication number	US-2017331281-A1
Application number	US-201515535296-A
Country	US
Kind code	A1
Filing date	Dec 10, 2015
Priority date	Dec 12, 2014
Publication date	Nov 16, 2017
Grant date	—

Abstract

A DC electrical network comprising DC terminals operatively connectable to a converter; and DC transmission paths arranged to interconnect the DC terminals, and including a DC power transmission medium and a switching apparatus. The DC network further including: an active power electronic device connected in at the DC transmission paths, the active power electronic device; a detector configured to detect faults in the DC transmission paths; and a control unit programmed to operate the active power electronic device to vary an apparent impedance of a faulty DC transmission path to force a current flowing in the faulty DC transmission path to reduce to a target current level, and operate the switching apparatus to block current from flowing in the faulty DC transmission path when the current flowing in the faulty corresponding DC transmission path is reduced to the target current level.

First claim

1 . A DC electrical network comprising:
a plurality of DC terminals, each being operatively connectable to a converter; a plurality of DC transmission paths, each DC transmission path being arranged to interconnect two or more of the plurality of DC terminals, each DC transmission path including a DC power transmission medium, each DC transmission path further including a switching apparatus operable to selectively block current from flowing in the corresponding DC transmission path; at least one active power electronic device connected in at least one of the plurality of DC transmission paths, the or each active power electronic device being configured to be operable to selectively vary an apparent impedance of the or each corresponding DC transmission path; a detector configured to detect one or more faults occurring in the plurality of DC transmission paths; and a control unit programmed to operate the or each active power electronic device to vary an apparent impedance of a faulty corresponding DC transmission path so as to force a current flowing in the faulty corresponding DC transmission path to reduce to a target current level, the control unit being further programmed to operate the or each switching apparatus to block current from flowing in the faulty corresponding DC transmission path when the current flowing in the faulty corresponding DC transmission path is reduced to the target current level, wherein the target current level corresponds to a current threshold at or below which the switching apparatus can be operated to block current from flowing in the corresponding DC transmission path.

2 . A DC electrical network according to claim 1 , wherein the target current level is zero or substantially zero.

3 . A DC electrical network according to claim 1 , wherein the switching apparatus is a disconnector or isolator.

4 . A DC electrical network according to claim 1 , wherein the or each active power electronic device is configured to be operable to selectively vary an apparent impedance of the or each corresponding DC transmission path and thereby direct current from at least one of the plurality of DC transmission paths to at least one other of the plurality of DC transmission paths, and the control unit is programmed to operate the or each active power electronic device to vary an apparent impedance of the faulty corresponding DC transmission path and thereby divert current from at least one of the plurality of DC transmission paths to at least one other of the plurality of DC transmission paths so as to force a current flowing in the faulty corresponding DC transmission path to reduce to the target current level.

5 . A DC electrical network according to claim 1 , wherein the or each active power electronic device is configured to be operable to selectively inject a voltage drop in the or each corresponding DC transmission path and thereby vary an apparent impedance of the or each corresponding DC transmission path.

6 . A DC electrical network according to claim 1 , comprising a plurality of active power electronic devices, wherein the control unit is programmed to coordinate the operation of the plurality of active power electronic devices to vary an apparent impedance of a faulty corresponding DC transmission path so as to force a current flowing in the faulty corresponding DC transmission path to reduce to the target current level.

7 . A DC electrical network according to claim 1 , wherein the or each active power electronic device is a current flow controller that comprises:
a plurality of connecting points, each connecting point being connected in at least one of the DC transmission paths; and a current flow controller interconnecting the plurality of connecting points, the current flow controller including a plurality of interconnected current flow control sub-units each of which is, in use, connected in a respective DC transmission path, each current flow control sub-unit including at least one switching element, the or each switching element of each current flow control sub-unit being operable to selectively establish a current path through the current flow controller between at least one DC transmission path and at least one other DC transmission path, and the or each switching element further being connected to at least one energy storage device to selectively provide a voltage source, wherein the control unit comprises a switching control unit to control switching of each switching element of the current flow controller to selectively establish the said current path through the current flow controller and to selectively connect the or each energy storage device between the said at least one DC transmission path and the said at least one other DC transmission path in order to inject a voltage drop, in use, into at least one of the DC transmission paths and thereby direct current through the current path from the said at least one DC transmission path to the said at least one other DC transmission path so as to force the current in the faulty corresponding DC transmission path to reduce to the target current level.

8 . A method of fault clearance for a DC electrical network, wherein the DC electrical network includes: a plurality of DC terminals, each DC terminal being operatively connectable to a converter; and a plurality of DC transmission paths, each DC transmission path being arranged to interconnect two or more of the plurality of DC terminals, each DC transmission path including a DC power transmission medium, each DC transmission path further including a switching apparatus operable to selectively block current from flowing in the corresponding DC transmission path, the DC electrical network further including at least one active power electronic device connected in at least one of the plurality of DC transmission paths, the or each active power electronic device being configured to be operable to selectively vary an apparent impedance of the or each corresponding DC transmission path, the method comprising:
detecting a fault occurring in one or more of the plurality of DC transmission paths; after detecting the fault occurring in one or more of the plurality of DC transmission paths, operating the or each active power electronic device to vary an apparent impedance of a faulty corresponding DC transmission path so as to force a current flowing in the faulty corresponding DC transmission path to reduce to a target current level; and operating the or each switching apparatus to block current from flowing in the faulty corresponding DC transmission path when the current flowing in the faulty corresponding DC transmission path is reduced to the target current level, wherein the target current level corresponds to a current threshold at or below which the switching apparatus can be operated to block current from flowing in the corresponding DC transmission path.

Assignees

• General Electric Technology Gmbh

Inventors

• Whitehouse Robert Stephen
• Barker Carl David

Classifications

• H02H3/021

  concerning the disconnection itself, e.g. at a particular instant, particularly at zero value of current, disconnection in a predetermined order (disconnection at zero value in general H03K17/18) · CPC title

• H02H7/268 Primary

  for DC systems · CPC title

• H02H3/025

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

• H02H7/28

  for meshed systems · CPC title