ARRANGEMENT FOR REGULATING A POWER FLOW IN AN AC VOLTAGE GRID AND METHOD FOR PROTECTING THE ARRANGEMENT
An arrangement for controlling a power flow in an AC voltage grid includes a converter arrangement having a first converter and a second converter. The converters are connectable to one another on the DC voltage side through a DC voltage link and are each connectable to the AC voltage grid on the AC voltage side. During the operation of the arrangement, the converters are correspondingly connected to the AC voltage grid. A switching branch is provided in the DC voltage link in parallel with the converters and at least one controllable switching element is provided in the switching branch. A method for protecting the arrangement in the case of an overload is also provided.
1 . An arrangement for controlling a power flow in an AC voltage grid, the arrangement comprising:
a DC voltage link; and
a converter arrangement including a first converter and a second converter, said converters configured to be connected to one another on a DC voltage side through said DC voltage link and said converters each configured to be connected on an AC voltage side to the AC voltage grid;
said DC voltage link containing a switching branch connected in parallel with said converters, said switching branch containing at least one controllable switching element.
2 . The arrangement according to claim 1 , wherein said at least one controllable switching element is configured for switching currents above 1 kA within less than 20 ms.
3 . The arrangement according to claim 1 , wherein said at least one controllable switching element is configured for switching currents above 1 kA within less than 10 ms.
4 . The arrangement according to claim 1 , wherein said at least one controllable switching element is a semiconductor switch.
5 . The arrangement according to claim 3 , wherein said semiconductor switch is a thyristor.
6 . The arrangement according to claim 1 , wherein said at least one controllable switching element includes a multiplicity of controllable switching elements connected to one another in a series circuit in said switching branch.
7 . The arrangement according to claim 1 , wherein at least one of said converters is a modular multilevel converter.
8 . The arrangement according to claim 7 , wherein said modular multilevel converter includes a number of series-connected switching modules, said number being dimensioned to cause said modular multilevel converter to generate a voltage being at least 5% greater than a predetermined rated voltage.
9 . The arrangement according to claim 8 , wherein said switching modules are half-bridge switching modules or full-bridge switching modules.
10 . The arrangement according to claim 8 , which further comprises protective circuit-breakers each being assigned to a respective one of said switching modules for limiting a current through said at least one controllable switching element.
11 . The arrangement according to claim 1 , which further comprises a matching transformer connecting said first converter to the AC voltage grid.
12 . The arrangement according to claim 1 , which further comprises a serial transformer connecting said second converter to the AC voltage grid.
13 . The arrangement according to claim 1 , which further comprises a bridging switch configured to bridge a connection of said first or second converter to the AC voltage grid.
14 . A method for protecting an arrangement for controlling a power flow in an AC voltage grid, the method comprising:
providing the arrangement according to claim 1 ;
identifying an overload fault in at least one of the AC voltage grid or the arrangement;
switching said at least one controllable switching element in said switching branch of the arrangement to enable a current flow through said switching branch; and
using a bridging switch to bridge a connection of said first or second converter to the AC voltage grid.