Method and apparatus for limiting current in a direct voltage network of a power transmission system
First Claim
1. A current limiting apparatus for a direct voltage network of an HVDC system which is connected through a VSC-converter to an alternating voltage network, comprising:
- at least a first semiconductor switching element which can be electronically turned on or off connected in series with said direct voltage network; and
a surge diverter connected in parallel with said switching element, said surge diverter being connected in series with said direct voltage network and absorbing excess current in normal operation, and dissipating power flowing through said direct voltage network when said switching element is switched to a permanently off state in response to a high current condition thereby reducing current through said direct voltage network.
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Accused Products
Abstract
Apparatus and method for limiting current in a direct voltage network of a HVDC power distribution system. A direct voltage network is connected to an alternating voltage network through a VSC-converter. At least one parallel connection including a semiconductor switching element is connected in series with the direct voltage network. A surge diverter is connected in parallel with the semiconductor switching element. During a high current condition in the direct voltage network, the switching element is switched off interrupting the current flow which is then diverted through the surge diverter which reduces the current flowing in the direct voltage network. By inserting a plurality of parallel connections, and selectively turning off a number of the semiconductor switching elements, a number of different levels of over current conditions in the direct voltage network may be controlled.
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Citations
16 Claims
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1. A current limiting apparatus for a direct voltage network of an HVDC system which is connected through a VSC-converter to an alternating voltage network, comprising:
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at least a first semiconductor switching element which can be electronically turned on or off connected in series with said direct voltage network; and a surge diverter connected in parallel with said switching element, said surge diverter being connected in series with said direct voltage network and absorbing excess current in normal operation, and dissipating power flowing through said direct voltage network when said switching element is switched to a permanently off state in response to a high current condition thereby reducing current through said direct voltage network. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A current limiting apparatus for a direct voltage network of an HVDC system which is connected through a VSC-converter to an alternating voltage network, comprising:
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a first semiconductor switching element connected in series with said direct voltage network; a first diode connected in anti-parallel with said first semiconductor switching element to carry current in an opposite direction of said first semiconductor switching element; a second semiconductor switching element connected in series with said first semiconductor switching element and said first diode; a second diode connected in parallel with said second semiconductor switching element to carry current in an opposite direction of said second semiconductor switching element; and a surge diverter connected in parallel with said first and second semiconductor switching elements and said first and second diodes, said semiconductor switching elements providing permanent interruption of said current when excessive current is flowing in either of first or second directions in said direct voltage network, diverting current through said surge diverter dissipating an excessive current. - View Dependent Claims (8)
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9. A current limiting apparatus for a direct voltage network of an HVDC system which is connected through a VSC-converter to an alternating voltage network, comprising:
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a plurality of parallel circuits connected in series with said direct voltage network, each of said parallel circuits comprising a semiconductor switching element connected in parallel with a surge diverter; means for determining when the current in said direct voltage network exceeds a predetermined level; and means for switching a number of said semiconductor switching elements off, depending on the level of current which exceeds said predetermined level, thereby inserting a number of said surge diverters in said direct voltage network reducing said current level below said predetermined level. - View Dependent Claims (10)
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11. A method for reducing the current in a direct voltage network of an HVDC system connected to an alternating voltage network through a VSC-converter comprising:
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connecting a series of parallel circuits in said direct voltage network, each of said parallel circuits comprising a semiconductor switching element connected in parallel with a surge diverter; measuring the current flowing through said direct voltage network; and turning at least one of said semiconductor switching elements permanently off when said current exceeds a predetermined level while maintaining some of said semiconductor switching elements on whereby said surge diverter reduces said current to a level below said predetermined level. - View Dependent Claims (12)
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13. A method for reducing the current in a direct voltage network of an HVDC system connected to an alternating voltage network through a VSC-converter comprising:
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permanently interrupting current flowing at a plurality of locations in said direct voltage network; diverting said current at said plurality of locations through a plurality of surge diverters whereby said current through said direct voltage network is reduced. - View Dependent Claims (14)
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15. A method for reducing the current in a direct voltage network of an HVDC system connected to an alternating voltage network through a VSC-converter comprising:
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connecting a series of parallel circuits in said direct voltage network, each of said parallel circuits comprising a semiconductor switching element connected in parallel with a surge diverter; measuring the current flowing through said direct voltage network; and turning at least one of said semiconductor switching elements permanently off when said current exceeds a predetermined level while maintaining some of said semiconductor switching elements on, whereby said surge diverter reduces said current to a level below said predetermined level wherein a number of a said semiconductor elements of a plurality of said parallel circuits are switched off, said number being a function of the level of said current which exceeds said predetermined level.
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16. A method for reducing the current in a direct voltage network of an HVDC system connected to an alternating voltage network through a VSC-converter comprising:
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interrupting current flowing at a number of locations in said direct voltage network which are proportional to the amount of current reduction which is required to reduce said current to a predetermined level; and diverting said current at said number of locations through a plurality of surge diverters whereby said current through said direct voltage network is reduced.
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Specification