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

• US 8,005,575 B2
• Filed: 06/01/2006
• Issued: 08/23/2011
• Est. Priority Date: 06/01/2006
• Status: Active Grant

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Kirchhof, Darrin Glen
• Primary Examiner(s): Chaki; Kakali
• Assistant Examiner(s): LAUGHLIN, NATHAN L
• Application Number:
  US11/444,637
• Publication Number:
  US 20070282487A1
• Time in Patent Office: 1,909 Days
• Field of Search: 700/287, 700/289, 700/290, 700/29, 700/44, 700/33
• US Class Current: 700/287
• CPC Class Codes: F01D 17/04 responsive to load
• CPC Class Codes: F02C 9/28 Regulating systems responsive to plant or ambient parameters, e.g. temperature, pressure, rotor speed F02C9/30 - F02C9/38, F02C9/44 take precedence
• CPC Class Codes: F05D 2220/31 in steam turbines
• CPC Class Codes: F05D 2220/72 a steam turbine
• CPC Class Codes: F05D 2270/16 to control water or steam injection
• CPC Class Codes: G05B 13/048 using a predictor

Abstract

Methods and apparatus for controlling load on a machine are provided. The method includes determining a maximum value of a process variable using a predictive model of the machine while holding a control output associated with the process variable substantially constant over a prediction period, incrementing the control output if the determined maximum value of the process variable is within an allowable limit range, and setting the control output to the last value of the process variable that did not cause the process value to exceed the allowable range.

Claims

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.