Chopper-boosted converter for wind turbines

1. A converter system for providing power to a network from a wind turbine having a generator connected to a converter, the converter system comprising:

a converter control that includes a dynamic current limit value that is associated with a limit of current provided by the converter that is allowable for a first tolerance time and a static current limit value that is associated with a limit of current provided by the converter that is allowable for unlimited time;

a chopper; and

an overcurrent module that includes

a limit value expander configured to increase the static current limit value by a portion of the difference from the dynamic current limit value, and

a dynamic module configured to interact with the limit value expander such that overcurrents between an increased static current limit value and the dynamic current limit value are routed in a first stage to the converter and in a second stage at least partially to the chopper while the converter continues to provide current, wherein the overcurrent module is configured to switch from the first stage to the second stage after a second tolerance time.

2. The converter system of claim 1 , wherein the second tolerance time is less than the first tolerance time.

3. The converter system of claim 1 , wherein the dynamic module determines the second tolerance time as a function of current.

4. The converter system of claim 1 , wherein the overcurrent module has a third stage in which the first and second stages are activated simultaneously.

5. The converter system of claim 1 , wherein the limit value expander has a blocking element connected to a blocking input and configured to block the increase of the static current limit value.

6. The converter system of claim 1 , comprising a wind gust module having inputs for power of one or both of the wind turbine and wind speed and configured to output a blocking signal if a limit value is exceeded.

7. The converter system of claim 6 , wherein the output of the wind gust module is connected to the input of a blocking element of the limit expander, the blocking element connected to a blocking input and configured to block the increase of the static limit value.

8. The converter system of claim 6 , wherein the wind gust module has multiple outputs for controlling multiple wind turbines.

9. A wind farm comprising a wind farm master and a plurality of wind turbines, each wind turbine having a generator, a converter including a converter control, a chopper, and an overcurrent module, wherein the converter control includes a dynamic current limit value that is associated with a limit of current provided by the converter that is allowable for a first tolerance time and a static current limit value that is associated with a limit of current provided by the converter that is allowable for unlimited time, wherein the overcurrent module includes a limit value expander configured to increase the static current limit value by a portion of the difference from the dynamic limit value, and a dynamic module configured to interact with the limit value expander such that overcurrents between an increased static current limit value and the dynamic current limit value are routed in a first stage to the converter and in a second stage at least partially to the chopper while the converter continues to provide current, wherein the overcurrent module is configured to switch from the first stage to the second stage after a second tolerance time.

10. The wind farm of claim 9 , wherein the overcurrent module is situated at each of the wind turbines.

11. The wind farm of claim 9 , wherein the overcurrent module is situated at the wind farm master.

12. The wind farm of claim 9 , comprising a wind gust module having inputs for power of one or both of the wind turbine and wind speed and configured to output a blocking signal if a limit value is exceeded.

13. The wind farm of claim 12 , wherein the wind gust module has a plurality of outputs for the individual wind turbines of the wind farm.

14. The wind farm of claim 9 , wherein the second tolerance time is less than the first tolerance time.

15. A method for operating a converter for a wind turbine including a generator connected to the converter, a chopper and a converter control for the converter, wherein the converter control includes a dynamic current limit value that is associated with a limit of current provided by the converter that is allowable for a first tolerance time and a static current limit value that is associated with a limit of current provided by the converter that is allowable for unlimited time, the method comprising providing an additional current with the aid of an overcurrent module by increasing the static current limit value of the converter by a portion of the difference from the dynamic current limit value, wherein overcurrents between an increased static current limit value and the dynamic current limit value are routed in a first stage to the converter and in a second stage at least partially to the chopper while the converter continues to provide current, wherein the first stage is switched to the second stage after a second tolerance time.

16. The method of claim 15 , wherein the second tolerance time is less than the first tolerance time.

17. The method of claim 15 , wherein the converter is used in wind turbines of a wind farm.

18. The converter system of claim 3 , wherein the dynamic module determines the second tolerance time as a function of current via a current-time integral.

19. The converter system of claim 8 , wherein the wind gust module is situated at a wind farm master of a wind farm.

20. The wind farm of claim 12 , wherein the wind gust module is situated at the wind farm master.

21. The method of claim 17 , wherein load monitoring is provided at a wind farm master with the aid of a wind gust module.