Device and method for controlling a load flow in an alternating-voltage network
A device for controlling a load flow in an alternating-voltage network includes first and second modular series connections of double-pole switching modules interconnected in a parallel circuit to be inserted in series into a phase line of the alternating-voltage network. At least one switching module of each connection has an energy store and semiconductor switches to be switched on and off. The semiconductor switches can be controlled in such a way that a switching module voltage can be generated at terminals of the switching module. The switching module voltage corresponds to a positive or negative storage voltage or a zero voltage. A control apparatus for controlling the switching modules is configured to generate an equalizing current between the modular series connections. A method for controlling a load flow by using the device is also provided.
1. A device for controlling a load flow in an alternating-voltage network, the device comprising:
a first modular series connection of double-pole switching modules;
a second modular series connection of double-pole switching modules;
said first and second modular series connections being interconnected in a parallel circuit to be serially inserted into a phase line of the alternating-voltage network;
at least one of said switching modules of each of said modular series connections having terminals, an energy store and semiconductor switches being switchable on and off and controllable for generating a switching module voltage at said terminals of said switching module, the switching module voltage corresponding to a positive or negative energy storage voltage or to a zero voltage; and
a control device for controlling said switching modules, said control device configured to generate a circulating equalizing current between said modular series connections, the circulating equalizing current being an alternating current with a current frequency corresponding to a multiple of a line frequency of the alternating-voltage network.
2. The device according to claim 1 , which further comprises a controllable protection device for bypassing said modular series connections.
3. The device according to claim 2 , wherein said protection device includes a double thyristor switch.
4. The device according to claim 2 , wherein said protection device includes a power choke.
5. The device according to claim 1 , which further comprises a mechanical bypass switch configured to bypass said parallel circuit of said modular series connections.
6. The device according to claim 1 , which further comprises a series compensator switch connected in series with said parallel circuit of said modular series connections.
7. The device according to claim 1 , wherein said modular series connections include a respective parallel circuit of said series connections for each phase line of the alternating-voltage network.
8. The device according to claim 1 , wherein said switching modules are full bridge module circuits.
9. The device according to claim 1 , wherein said switching modules each include two respective oppositely directed half bridge module circuits.
10. A method for controlling a load flow in an alternating-voltage network, the method comprising:
providing a device according to claim 1 ; and
generating an equalizing current between said modular series connections for balancing the energy storage voltages.