CONVERSION OF AC LINES TO HVDC LINES
First Claim
1. An electric power transmission system, comprising:
- a high voltage direct current line transmission line comprising three conductors; and
a converter station arranged at each end of the high voltage direct current line transmission line, the converter station is configured to convert an alternating voltage into a direct voltage for transmitting direct current between said stations in all three conductors, each converter station comprises voltage source converter comprising at least one phase legs having current valves of turn-off semiconductor devices and rectifying members arranged anti-parallel the semiconductor devices, the rectifying members being connected in series between a first and a second pole conductor of said conductors and a midpoint being connected to an alternating voltage side of the converter, and a control unit for switching the current valves by controlling the semiconductor devices thereof for converting said alternating voltage into a direct voltage applied to said two pole conductors, wherein the converter station further comprises an extra phase leg of current valves of semiconductor devices of turn-off type and rectifying members connected in anti-parallel therewith connected in series between said two pole conductors on the direct voltage side of said converter, wherein a third of said conductors is connected to a midpoint between current valves of said extra phase leg, and wherein the converter station further comprises an arrangement adapted to control said current valves of said extra phase leg to switch for connecting said third conductor either to the first pole conductor or the second pole conductor for utilizing the third conductor for conducting current between said stations.
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Accused Products
Abstract
An electric power transmission system includes at each end of a high voltage direct current transmission line including three conductors, a converter station for conversion of an alternating voltage into a direct voltage for transmitting direct current between the stations in all three conductors. Each station has a voltage source converter and an extra phase leg connected between the two pole conductors of the direct voltage side of the converter. A third of the conductors is connected to a midpoint between current valves of the extra phase leg. An arrangement is adapted to control the current valves of the extra phase leg to switch for connecting the third conductor either to the first pole conductor or the second pole conductor for utilizing the third conductor for conducting current between the stations.
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Citations
21 Claims
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1. An electric power transmission system, comprising:
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a high voltage direct current line transmission line comprising three conductors; and a converter station arranged at each end of the high voltage direct current line transmission line, the converter station is configured to convert an alternating voltage into a direct voltage for transmitting direct current between said stations in all three conductors, each converter station comprises voltage source converter comprising at least one phase legs having current valves of turn-off semiconductor devices and rectifying members arranged anti-parallel the semiconductor devices, the rectifying members being connected in series between a first and a second pole conductor of said conductors and a midpoint being connected to an alternating voltage side of the converter, and a control unit for switching the current valves by controlling the semiconductor devices thereof for converting said alternating voltage into a direct voltage applied to said two pole conductors, wherein the converter station further comprises an extra phase leg of current valves of semiconductor devices of turn-off type and rectifying members connected in anti-parallel therewith connected in series between said two pole conductors on the direct voltage side of said converter, wherein a third of said conductors is connected to a midpoint between current valves of said extra phase leg, and wherein the converter station further comprises an arrangement adapted to control said current valves of said extra phase leg to switch for connecting said third conductor either to the first pole conductor or the second pole conductor for utilizing the third conductor for conducting current between said stations. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A converter station for converting an alternating voltage into a direct voltage, comprising:
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a voltage source converter comprising at least one phase legs comprising current valves of turn-off semiconductor devices and rectifying members arranged anti-parallel with the semiconductor devices, the rectifying members being connected in series between a first and a second pole conductor of said conductors and a midpoint being connected to an alternating voltage side of the converter, and a control unit for switching the current valves by controlling the semiconductor devices thereof for converting said alternating voltage into a direct voltage applied to said two pole conductors; an extra phase leg of current valves of turn-off semiconductor devices and rectifying members connected in anti-parallel with the turn-off semiconductor device connected in series between said two pole conductors on the direct voltage side of said converter, wherein a third of said conductors is connected to a midpoint between current valves of said extra phase leg; and an arrangement adapted to control said current valves of said extra phase leg to switch for connecting said third conductor either to the first pole conductor or the second pole conductor for utilizing the third conductor for conducting current between said stations.
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12. A method for controlling a flow of electric power in an electric power transmission system comprising at each end of a high voltage direct current transmission line comprising three conductors, a converter station for conversion of an alternating voltage into a direct voltage for transmitting direct current between said stations in all three conductors, the method comprising:
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carrying out the control for a system in which each converter station comprises a voltage source converter with one or more phase legs having current valves of turn-off semiconductor devices and rectifying members in anti-parallel therewith connected in series between a first and a second pole conductor of said conductors and a midpoint being connected to an alternating voltage side of the converter, and a control unit for switching the current valves by controlling the semiconductor devices thereof for converting said alternating voltage into a direct voltage applied to said two pole conductors, the station further comprising an extra phase leg of current valves of semiconductor devices of turn-off type and rectifying members connected in anti-parallel therewith connected in series between said two pole conductors on the direct voltage side of said converter, in which a third of said conductors is connected to a midpoint between current valves of said extra phase leg, and controlling the current valves of said extra phase leg to switch for connecting said third conductor either to the first pole conductor or the second pole conductor for utilizing the third conductor for conducting current between said stations. - View Dependent Claims (13, 14, 15, 16, 17, 18)
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19. A computer program product, comprising:
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a computer readable medium; and computer program instructions recorded on the computer readable medium and executable by a processor for carrying out a method for controlling a flow of electric power in an electric power transmission system comprising at each end of a high voltage direct current transmission line comprising three conductors, a converter station for conversion of an alternating voltage into a direct voltage for transmitting direct current between said stations in all three conductors, the method comprising; carrying out the control for a system in which each converter station comprises a voltage source converter with one or more phase legs having current valves of turn-off semiconductor devices and rectifying members in anti-parallel therewith connected in series between a first and a second pole conductor of said conductors and a midpoint being connected to an alternating voltage side of the converter, and a control unit for switching the current valves by controlling the semiconductor devices thereof for converting said alternating voltage into a direct voltage applied to said two pole conductors, the station further comprising an extra phase leg of current valves of semiconductor devices of turn-off type and rectifying members connected in anti-parallel therewith connected in series between said two pole conductors on the direct voltage side of said converter, in which a third of said conductors is connected to a midpoint between current valves of said extra phase leg, and controlling the current valves of said extra phase leg to switch for connecting said third conductor either to the first pole conductor or the second pole conductor for utilizing the third conductor for conducting current between said stations. - View Dependent Claims (20)
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21. (canceled)
Specification