Methods for operating electrical power systems

1. A method for operating an electrical power system, the method comprising:

disabling bridge switching of one of the rotor-side converter or line-side converter;

gating on the dynamic brake after the disabling occurs;

comparing a power converter input variable to a primary predetermined variable threshold; and

forcing the gated-on dynamic brake to a 100 percent duty cycle when the power converter input variable exceeds the primary predetermined variable threshold.

2. The method of claim 1 , further comprising:

comparing, after forcing occurs, the power converter input variable to a secondary predetermined variable threshold; and

terminating the forced 100 percent duty cycle of the gated-on dynamic brake when the power converter input variable is less than the secondary predetermined variable threshold.

3. The method of claim 1 , wherein the secondary predetermined variable threshold is different from the primary predetermined variable threshold.

4. The method of claim 1 , wherein the power converter input variable comprises one or more of a DC link voltage, a DC link energy, a DC link current, a rotor-side converter bridge current magnitude, a rotor-side converter bridge voltage magnitude, a rotor-side converter bridge instantaneous current, a rotor-side converter bridge instantaneous voltage, a line-side converter bridge current magnitude, a line-side converter bridge voltage magnitude, a line-side converter bridge instantaneous current, a line-side converter bridge instantaneous voltage, or a power converter component temperature.

5. The method of claim 1 , further comprising:

comparing one of a DC link voltage or a DC link energy to a primary predetermined crowbar threshold; and

activating a crowbar when the one of the DC link voltage or a DC link energy exceeds the primary predetermined crowbar threshold.

6. The method of claim 5 , wherein the crowbar comprises switching elements of the rotor-side converter.

7. The method of claim 5 , wherein the crowbar comprises switching elements disposed upstream of the rotor-side converter within the power converter.

8. The method of claim 1 , wherein the one of the rotor-side converter or line-side converter is a plurality of rotor-side converters connected in parallel or a plurality of line-side converters connected in parallel.

9. The method of claim 1 , further comprising:

detecting a bridge current magnitude in a rotor-side converter or line-side converter of a power converter, the power converter electrically coupled between a generator rotor and a transformer and comprising a DC link and a dynamic brake; and

comparing the bridge current magnitude in the one of the rotor-side converter or line-side converter to a primary predetermined magnitude threshold,

wherein disabling occurs when the bridge current magnitude exceeds the primary predetermined magnitude threshold.

10. The method of claim 9 , further comprising:

comparing, after disabling occurs, the bridge current magnitude in the one of the rotor-side converter or line-side converter to a secondary predetermined threshold; and

enabling bridge switching of the one of the rotor-side converter or line-side converter when the bridge current magnitude is less than the secondary predetermined threshold.

11. An electrical power system, comprising:

a doubly fed induction generator having a rotor and a stator, the stator providing AC power to a stator bus;

a power converter coupled to the rotor of the doubly fed induction generator, the power converter providing an output to a line bus, the power converter comprising a rotor-side converter, a line-side converter, a DC link and a dynamic brake;

a transformer coupled to the stator bus and the line bus; and

a controller communicatively coupled to the power converter, the controller configured to perform one or more operations, the one or more operations comprising:

disabling bridge switching of one of the rotor-side converter or line-side converter;

gating on the dynamic brake after the disabling occurs;

comparing a power converter input variable to a primary predetermined variable threshold; and

forcing the gated-on dynamic brake to a 100 percent duty cycle when the power converter input variable exceeds the primary predetermined variable threshold.

12. The electrical power system of claim 11 , wherein the one or more operations further comprises:

comparing, after forcing occurs, the power converter input variable to a secondary predetermined variable threshold; and

terminating the forced 100 percent duty cycle of the gated-on dynamic brake when the power converter input variable is less than the secondary predetermined variable threshold.

13. The electrical power system of claim 11 , wherein the secondary predetermined variable threshold is different from the primary predetermined variable threshold.

14. The electrical power system of claim 11 , wherein the power converter input variable comprises one or more of a DC link voltage, a DC link energy, a DC link current, a rotor-side converter bridge current magnitude, a rotor-side converter bridge voltage magnitude, a rotor-side converter bridge instantaneous current, a rotor-side converter bridge instantaneous voltage, a line-side converter bridge current magnitude, a line-side converter bridge voltage magnitude, a line-side converter bridge instantaneous current, a line-side converter bridge instantaneous voltage, or a power converter component temperature.

15. The electrical power system of claim 11 , wherein the one or more operations further comprises:

comparing one of a DC link voltage or a DC link energy to a primary predetermined crowbar threshold; and

activating a crowbar when the one of the DC link voltage or a DC link energy exceeds the primary predetermined crowbar threshold.

16. The electrical power system of claim 15 , wherein the crowbar comprises switching elements of the rotor-side converter.

17. The electrical power system of claim 15 , wherein the crowbar comprises switching elements disposed upstream of the rotor-side converter within the power converter.

18. The electrical power system of claim 11 , wherein the one of the rotor-side converter or line-side converter is a plurality of rotor-side converters connected in parallel or a plurality of line-side converters connected in parallel.

19. The electrical power system of claim 11 , wherein the one or more operations further comprises:

detecting a bridge current magnitude in the rotor-side converter or line-side converter; and

comparing the bridge current magnitude in the one of the rotor-side converter or line-side converter to a primary predetermined magnitude threshold,

wherein disabling occurs when the bridge current magnitude exceeds the primary predetermined magnitude threshold.

20. The electrical power system of claim 19 , wherein the one or more operations further comprises:

comparing, after disabling occurs, the bridge current magnitude in the one of the rotor-side converter or line-side converter to a secondary predetermined threshold; and

enabling bridge switching of the one of the rotor-side converter or line-side converter when the bridge current magnitude is less than the secondary predetermined threshold.