System for transmitting electrical power

1. A system for transmitting electrical power between a first alternating voltage network and a second alternating voltage network, the system comprising:

an unregulated rectifier connectable to the first alternating voltage network on an alternating voltage side;

a direct voltage link;

a self-commutated converter connectable to the second alternating voltage network and connected to said unregulated rectifier via said direct voltage link, said self-commutated converter having a direct voltage terminal;

a network generation device connectable to the first alternating voltage network, said network generation device generating an alternating voltage in the first alternating voltage network, said network generation device is set up for an exchange of reactive power and active power with the first alternating voltage network;

a measuring device configured to record a network frequency in the first alternating voltage network; and

a control device configured to convert the network frequency recorded by said measuring device into control signals for a regulation of the voltage on the direct voltage terminal of said self-commutated converter.

2. The system according to claim 1 , wherein said unregulated rectifier is a diode rectifier.

3. The system according to claim 1 , wherein said unregulated rectifier is connected via the first alternating voltage network to a wind farm disposed in a lake or sea.

4. The system according to claim 1 , wherein said unregulated rectifier is disposed on an offshore platform, and said self-commutated converter is disposed onshore.

5. The system according to claim 1 , wherein said network generation device has a rotating phase shifter.

6. The system according to claim 1 , wherein said network generation device contains a static-synchronous-compensator device.

7. The system according to claim 1 , further comprising an auxiliary energy supply unit for an alternative supply of energy to said network generation device.

8. The system according to claim 1 , wherein said self-commutated converter is a modular multi-stage converter.

9. The system according to claim 1 , wherein said unregulated rectifier has passive air cooling.

10. The system according to claim 1 , further comprising at least one transformer, said unregulated rectifier is connected to the first alternating voltage network via said at least one transformer.

11. The system according to claim 1 , further comprising at least one direct voltage smoothing reactor disposed in said direct voltage link.

12. A method for stabilizing a network frequency in a first alternating voltage network connected to a system for transmitting electrical power between the first alternating voltage network and a second alternating voltage network, which comprises the steps of:

providing the system with a self-commutated converter which is connectable to the second alternating voltage network and connected to an unregulated rectifier via a direct voltage link, the unregulated rectifier is connectable to the first alternating voltage network on an alternating voltage side;

providing the system with a network generation device which is connectable to the first alternating voltage network, the network generation device provided for generating an alternating voltage in the first alternating voltage network, the network generation device is set up for an exchange of active power and reactive power with the first alternating voltage network;

regulating the network frequency in the first alternating voltage network by an adjustment of a voltage at a direct voltage terminal of the self-commutated converter;

providing a measuring device which records the network frequency in the first alternating voltage network; and

providing a control device which converts the network frequency recorded into control signals for a regulation of the voltage on the direct voltage terminal of the self-commutated converter.