Converter Station

• US 20090168468A1
• Filed: 06/15/2006
• Published: 07/02/2009
• Est. Priority Date: 01/18/2006
• Status: Active Grant

• Current Assignee: ABB Power Grids Switzerland AG (ABB Limited)
• Original Assignee: ABB Technology Limited (ABB Ltd.)
• Inventors: Juhlin, Lars-Erik, Radbrant, Ulf
• Granted Patent: US 8,014,178 B2
• Time in Patent Office: Days
• US Class Current: 363/35
• CPC Class Codes: H02H 3/05 with means for increasing reliability, e.g. redundancy arrangements for logic circuits H03K19/003
• CPC Class Codes: H02J 3/36 Arrangements for transfer of electric power between ac networks via a high-tension dc link
• CPC Class Codes: Y02E 60/60 Arrangements for transfer of electric power between AC networks or generators via a high voltage DC link [HVCD]

Abstract

A converter station for connecting an AC system to a bipolar HVDC transmission line. A DC neutral arrangement is provided with first DC breakers enabling breaking of a first current path from a neutral bus of one pole of the transmission line to a neutral bus of another pole at bipolar operation of the station for isolation of a faulty section and changing to monopolar operation/metallic return thereof. The DC neutral arrangement has in the first current path at least two first DC breakers connected in series and adapted to act as a backup for each other would the other thereof fail to break the first current path upon a control to isolate a faulty section by changing from bipolar to monopolar operation.

Claims

1. A converter station for connecting an AC system to a bipolar HVDC transmission line, said station comprising:

two converters each having a DC-side thereof connected to a respective one of two poles of said transmission line on high potential and to a neutral bus for that pole of a DC neutral arrangement in common to the converters on zero potential by being earthed, and having an AC-side connected to said AC system,

said DC neutral arrangement having a member connecting to at least one electrode line and the arrangement being provided with first DC breakers enabling breaking of a first current path from the neutral bus of one pole to the neutral bus of the other pole at bipolar operation of the station for changing to monopolar operation thereof,

the station also comprising a control device adapted to control a said changing from bipolar to monopolar operation by controlling a said first DC breaker to open said current path between said two neutral buses and establish a current path to said electrode line connecting member for diverting the current from said one pole thereto,

wherein said DC neutral arrangement has in said first current path at least two first DC breakers connected in series and adapted to act as a backup for each other would the other thereof fail to break said first current path upon a control of said control device to change from bipolar to monopolar operation.

2. The converter station according to claim 1, wherein said DC neutral arrangement comprises at least two said first current paths each having at least two said first DC breakers connected in series for backup of each other, and wherein each first current path is designed to allow a current to flow therethrough for bipolar operation of the station irrespectively of the state of said first DC breakers in any other said first current path.

3. The converter station according to claim 1, wherein said DC neutral arrangement is provided with two said electrode line connecting members for connecting to a separate said electrode line each and a connector configured to connect each neutral bus to an optional of said two electrode line connecting members.

4. The converter station according to claim 3, wherein said connecting means comprises for each said neutral bus a series connection of three DC breakers shared by said neutral bus and a respective of said electrode line connecting members in a one and a half breaker system.

5. The converter station according to claim 4, wherein each said series connection of three DC breakers said neutral bus connects to the series connection between two of the DC breakers on one side of a mid DC breaker and said electrode line connecting member connects to the series connection between two of the DC breakers on the other side of said mid DC breaker.

6. The converter station according to claim 4, wherein said DC neutral arrangement comprises a first conducting bus to which each neutral bus is connected through one of said DC breakers of said series connection of three DC breakers associated therewith.

7. The converter station according to, claim 5, wherein the DC breakers connecting the neutral buses to said conducting bus are said first DC breakers connected in series in one said first current path.

8. The converter station according to claim 4, wherein said DC neutral arrangement comprises a second conducting bus to which each said electrode line connecting member is connected through one of said DC breakers of said series connection of three DC breakers associated therewith.

9. The converter station according to claim 5, wherein said two mid DC breakers and the two DC breakers connecting the electrode lines to said second bus are said first DC breakers connected in series in one said first current path.

10. The converter station according to claim 6, wherein said two conducting buses are interconnected through an additional line having a DC breaker and being in parallel with said two series connections of three DC breakers.

11. The converter station according to claim 10, further comprising:

a grounding switch is connected to a point of said additional line for being closed and grounding this additional line would none of said first DC breakers be able to break a current flowing from one neutral bus to the other when controlled to do so.

12. The converter station according to claim 6, wherein said first conducting bus is by a first disconnector connected to a midpoint of a line interconnecting said two poles of the HVDC transmission line, said first disconnector being adapted to be open at bipolar operation of the station, wherein the line interconnecting said two poles is provided with a disconnector on both sides of said midpoint, and wherein said control device is adapted to control said first disconnector to close and a disconnector connecting to one of the poles to close for metallic return of the current from the other pole at monopolar operation of the station after trip of said one pole.

13. The converter station according to claim 1, wherein the converter station is adapted for connecting an AC system to a bipolar HVDC transmission line adapted to have a voltage between each pole thereof and earth exceeding 200 kV.