Methods and apparatus for model predictive control in a real time controller

1. A method of controlling load on a machine using a controller comprising:

determining at least one of a process variable associated with the machine and a control output associated with the process variable using an iterative process, wherein a value of the process variable is received from a sensor and wherein the control output is output from the controller;

determining a maximum value of the process variable using a predictive model of the machine while holding the control output substantially constant over a prediction period; and

incrementing the control output of the controller if the determined maximum value of the process variable is within an allowable limit range; and

setting the control output of the controller to a last value of the control output determined that did not cause the process value to exceed the allowable range.

2. A method in accordance with claim 1 wherein the predictive model includes a plurality of states, each state relating to at least one associated set of process variables of the machine and wherein said method further comprises initializing a model state to a respective current machine state.

3. A method in accordance with claim 1 wherein determining a maximum value of a process variable comprises iteratively determining a current value of the process variable during the prediction period.

4. A method in accordance with claim 1 wherein determining a maximum value of a process variable comprises comparing a current value of the process variable to the maximum value of the process variable determined during the current prediction period.

5. A method in accordance with claim 1 wherein incrementing the control output comprises comparing the maximum value determined during the current prediction period to a predetermined process variable limit.

6. A method in accordance with claim 1 wherein setting the control output of the controller comprises generating a command to limit a power level of the machine to a level associated with the command.

7. A turbine engine control system comprising:

a plurality of sensors configured to determine a state of the turbine engine; and

a processor configured to:

determine at least one of a process variable associated with the turbine engine and a control output associated with the process variable using an iterative process, wherein a value of the process variable is received from a sensor and the wherein control output is output from said processor;

determine a maximum value of the process variable using a predictive model of the turbine engine while holding the control output substantially constant over a prediction period; and

increment the control output if the determined maximum value of the process variable is within an allowable limit range; and

set the control output to a last value of the control output determined that did not cause the process value to exceed the allowable range.

8. A system in accordance with claim 7 wherein said processor is further configured to initialize a model state to a respective current machine state.

9. A system in accordance with claim 7 wherein said processor is further configured to iteratively determine a current value of the process variable during the prediction period.

10. A system in accordance with claim 7 wherein said processor is further configured to compare a current value of the process variable to the maximum value of the process variable determined during the current prediction period.

11. A system in accordance with claim 7 wherein said processor is further configured to compare the maximum value determined during the current prediction period to a predetermined process variable limit.

12. A system in accordance with claim 7 wherein said processor is further configured to generate a command to limit a power level of the turbine engine to a level associated with the command.

13. A method for controlling load on a steam turbine generator based on a model of the steam turbine generator executing on a processor, said method comprising:

determining an initial state of the steam turbine generator model using an output of at least one of a plurality of sensors coupled to the steam turbine generator, wherein the state of the steam turbine generator is defined by a plurality of process variables associated with an output of a respective sensor;

predicting a future state of the steam turbine generator model based on a change of a control signal that is input to and output from the model;

wherein predicting a future state of the steam turbine generator model comprises maintaining the control signal input at a substantially constant value during the prediction period;

determining a maximum value of at least one of the process variables during a current prediction period;

comparing the future state of the steam turbine generator to at least one of the determined maximum value and a predetermined range for at least one of the plurality of process variables defining the future state;

iteratively incrementing the control signal input until at least one of the process variables associated with a next future state exceeds at least one of the determined maximum value and the predetermined range for that process parameter value; and

setting a control signal output for the steam turbine generator to a last value that did not cause the process variables of the future state to exceed at least one of the determined maximum value and the allowable range.

14. A method in accordance with claim 13 wherein predicting a future state of the steam turbine generator model comprises predicting a future state of the steam turbine generator model during a predetermined prediction time period.

15. A method in accordance with claim 13 further comprising comparing the maximum value of the process variable determined during the current prediction period to a predetermined process variable range.

16. A method in accordance with claim 13 further comprising:

generating a command to limit a power level of the steam turbine generator to a level associated with the command.