Systems and methods for improved rate of change of frequency ride-through in electric power systems

1. An electric power system comprising:

a turbine;

a generator coupled to the turbine, wherein the generator is configured to provide power to an electrical grid; and

a controller configured to:

detect a grid event;

determine a rate of change of frequency value;

determine a predicted post-grid event governor set point based on the rate of change of frequency value;

determine a destination mode for combustion using the predicted post-grid event governor set point; and

initiate a change to at least one turbine operating parameter based on the predicted post-grid event governor set point;

wherein the change to the at least one turbine operating parameter causes the turbine to switch to a transition mode at a first time and the destination mode at a second time.

2. The electric power system of claim 1 , wherein the controller is further configured to:

determine a feed forward controller parameter based on the rate of change of frequency value.

3. The electric power system of claim 1 , wherein the controller is further configured to:

determine an estimated magnitude of the grid event based on the rate of change of frequency value.

4. The electric power system of claim 3 , wherein the predicted post-grid event governor set point is a function of droop and the estimated magnitude of the grid event.

5. The electric power system of claim 1 , wherein the controller is further configured to:

determine an estimated nadir, an estimated high value, and an estimated low value using the rate of change of frequency value.

6. The electric power system of claim 5 , wherein the controller is further configured to:

determine an updated nadir estimation after a threshold length of time has elapsed.

7. The electric power system of claim 1 , wherein the destination mode is selected from a set of available destination modes having different combustion configurations.

8. The electric power system of claim 7 , wherein the turbine transitions from a default mode to a transition mode, from the transition mode to a transition recovery mode, and from the transition recovery mode to the destination mode within 2 seconds of the grid event.

9. The electric power system of claim 1 , wherein the controller is further configured to:

determine an estimated system inertia prior to detecting the grid event.

10. The electric power system of claim 9 , wherein to determine the rate of change of frequency value, the controller is configured to:

determine a weighted average of the estimated system inertia, operating point of the turbine, and available megawatt margin of the electric power system.

11. The electric power system of claim 1 , wherein the turbine is configured to ride-through rate of change of frequency values of up to 2 Hz per second.

12. The electric power system of claim 1 , wherein the change to the at least one turbine operating parameter is a change to at least one of an air/fuel ratio, a dry low NOx mode, or a fuel split across combustion nozzles.

13. The electric power system of claim 1 , wherein the grid event is a frequency transient event, and wherein the rate of change of frequency value is determined within 300 milliseconds after the grid event is detected.

14. A method for riding-through grid events for gas turbines, the method comprising:

detecting, by a controller, a grid event;

determining a rate of change of frequency value;

determining a predicted post-grid event governor set point based on the rate of change of frequency value;

determining a destination mode for combustion using the predicted post-grid event governor set point; and

initiating a change to at least one turbine operating parameter for a gas turbine based on the predicted post-grid event governor set point, wherein the change to the at least one turbine operating parameter causes the turbine to switch to a transition mode at a first time and the destination mode at a second time.

15. A system for riding-through grid events for gas turbines, the system comprising:

a gas turbine;

a generator coupled to the gas turbine, wherein the generator is configured to provide power to an electrical grid; and

a controller configured to:

detect a grid event;

determine a rate of change of frequency value;

determine an estimated magnitude of the grid event based on the rate of change of frequency value;

determine a predicted post-grid event governor set point based on the estimated magnitude of the grid event;

determine a destination mode for combustion using the predicted post-grid event governor set point; and

initiate a change to an air/fuel ratio based on the destination mode, wherein the change to the at least one turbine operating parameter causes the turbine to switch to a transition mode at a first time and the destination mode at a second time.

16. The system of claim 15 , wherein the controller is further configured to:

determine an estimated nadir, an estimated high value, and an estimated low value using the rate of change of frequency value.

17. The system of claim 16 , wherein the controller is further configured to: determine an updated nadir estimation after a threshold length of time has elapsed.

18. The system of claim 15 , wherein the predicted post-grid event governor set point is a function of droop and the estimated magnitude of the grid event.

19. The system of claim 15 , wherein the destination mode is selected from a set of available destination modes having different combustion configurations.