Coordination in multilayer process control and optimization schemes

• US 6,832,134 B2
• Filed: 11/12/2002
• Issued: 12/14/2004
• Est. Priority Date: 11/12/2002
• Status: Active Grant

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Havlena, Vladimir
• Primary Examiner(s): Paladini, Albert W.
• Assistant Examiner(s): Jarrett, Ryan A.
• Application Number:
  US10/292,708
• Publication Number:
  US 20040093124A1
• Time in Patent Office: 763 Days
• Field of Search: 700/28, 700/32, 700/33, 700/36, 700/44, 700/291
• US Class Current: 700/291
• CPC Class Codes: F22B 35/008 Control systems for two or more steam generators F22D5/36 takes precedence
• CPC Class Codes: G05B 13/026 using a predictor

Abstract

Loads 1, 2, . . . , N are controlled by predicting a total energy requirement for the loads 1, 2, . . . , N at prediction points k=0, 1, 2, . . . , K, by allocating the total energy requirement to the loads 1, 2, . . . , N at prediction points k=0, 1, 2, . . . , K, by determining a dynamic energy demand requirement for each of the loads 1, 2, . . . , N at prediction points k=0, 1, 2, . . . , K based on the allocated energy requirements, and by controlling the loads 1, 2, . . . , N based on the dynamic energy demand requirements.

Claims

1. A process control system for controlling a load comprising:

a predictive controller that predicts an energy requirement for the load at prediction points k =0, 1, 2, . . , K based on a steady state target energy requirement for the load; and

,

a real time cost optimizer that determines a cost optimized dynamic energy demand requirement for the load at the prediction points k =0, 1, 2, . . . , K based on the predicted energy requirement and that controls the load based on the dynamic energy demand requirement.

2. The process control system of claim 1 wherein the real time optimizer is arranged to constrain the dynamic energy demand requirement to a limit and controls the load based on the constrained dynamic energy demand requirement.

3. The process control system of claim 2 wherein the limit comprises a maximum limit.

4. The process control system of claim 2 wherein the limit comprises a minimum limit.

5. The process control system of claim 2 wherein the limit comprises a minimum limit and a maximum limit.

6. The process control system of claim 2 wherein the real time optimizer determines Δ

F^dyn according to the following equation;

7. The process control system of claim 6 wherein the limit for Δ

F^dyn comprises a maximum limit.

8. The process control system of claim 6 wherein the limit for Δ

F^dyn comprises a minimum limit.

9. The process control system of claim 6 wherein the limit for Δ

F^dyn comprises a minimum limit and a maximum limit.

10. The process control system of claim 1 wherein the predicted energy requirement is designated F^unconstr, wherein the dynamic energy demand requirement is designated F^dyn, and wherein F^dyn is determined by minimizing a quadratic function based on a difference between F^unconstr and F^dyn.

11. The process control system of claim 10 wherein F^unconstr and F^dyn each have dimensions K+1.

12. The process control system of claim 10 wherein the real time controller is arranged to constrain F^dyn to a limit and to control the load based on the constrained F^dyn.

13. The process control system of claim 12 wherein the limit comprises a maximum limit.

14. The process control system of claim 12 wherein the limit comprises a minimum limit.

15. The process control system of claim 12 wherein the limit comprises a minimum limit and a maximum limit.

16. A process control method for controlling parallel loads 1, 2, . . . , N comprising:

predicting, in a predictive controller, an energy requirement for each of the loads 1, 2, . . . , N at prediction points k=0, 1, 2, . . . , K based on a steady state target allocation for each of the parallel loads 1, 2, . . . , N;

determining, in a real time optimizer, a dynamic energy demand requirement for each of the parallel loads 1, 2, . . . , N at prediction points k=0, 1, 2, . . . , K based on the predicted energy requirements so as to cost effectively allocate load demand among the parallel load 1, 2, . . . , N; and

,

controlling the loads 1, 2, . . . , N based on the dynamic energy demand requirements.

17. The process control method of claim 16 wherein the controlling of the loads based on the dynamic energy demand requirements comprises:

constraining each of the dynamic energy demand requirements to a corresponding limit; and

,

controlling the loads 1, 2, . . . , N based on the corresponding constrained dynamic energy demand requirements.

18. The process control method of claim 17 wherein the corresponding limits comprise corresponding maximum limits.

19. The process control method of claim 17 wherein the corresponding limits comprise corresponding minimum limits.

20. The process control method of claim 17 wherein the corresponding limits comprise corresponding minimum limits and corresponding maximum limits.

21. The process control method of claim 17 further comprising;

determining Δ

F_i^dyn according to the following equation;

22. The process control method of claim 21 wherein the corresponding limits for Δ

F_i^dyn comprise corresponding maximum limits.

23. The process control method of claim 21 wherein the corresponding limits for Δ

F_i^dyn comprise corresponding minimum limits.

24. The process control method of claim 21 wherein the corresponding limits for Δ

F_i^dyn comprise corresponding minimum limits and corresponding maximum limits.

25. The process control method of claim 16 wherein the predicted energy requirement for each of the loads 1, 2, . . . , N is designated F_i^unconstr, wherein the dynamic energy demand requirement for each of the loads 1, 2, . . . , N is designated F_i^dyn, wherein F_i^dyn is determined by minimizing the following quadratic function:

26. The process control method of claim 25 wherein F^unconstr and F^dyn each have dimensions K+1.

27. The process control method of claim 25 wherein the controlling of the loads 1, 2, . . . , N based on the dynamic energy demand requirements comprises:

constraining F_i^dyn to corresponding limits; and

,

controlling the load based on the constrained F_I^dyn.

28. The process control method of claim 27 wherein the corresponding limits comprise corresponding maximum limits.

29. The process control method of claim 27 wherein the corresponding limits comprise corresponding minimum limits.

30. The process control method of claim 27 wherein the corresponding limits comprise corresponding minimum limits and maximum limits.

31. A process control method for controlling parallel loads 1, 2, . . . , N comprising:

predicting, by way of a predictive controller, a total energy requirement for the parallel loads 1, 2, . . . , N at prediction points k=0, 1, 2, . . . , K;

allocating, on a cost effective basis by way of a real time optimizer, the total energy requirement to the parallel loads 1, 2, . . . , N at the prediction points k=0, 1, 2, . . . , K based on a steady state target for each of the parallel loads 1, 2, . . . , N;

determining, by way of the real time optimizer, a dynamic energy demand requirement for each of the parallel loads 1, 2, . . . , N at the prediction points k=0, 1, 2, . . . , K based on the allocated energy requirements; and

,

controlling the parallel loads 1, 2, . . . , N based on the dynamic energy demand requirements.

32. The process control method of claim 31 wherein the allocating of the total energy requirement to the loads 1, 2, . . . , N comprises:

determining a change Δ

F^tot(k) in the total energy requirement according to the following equation;

$\mathrm{\Delta <br><br>}<br><br>\text{\hspace{1em}<br><br>}<br><br>F^{\mathrm{tot}}<br><br>\left(k\right)=F^{\mathrm{tot}}<br><br>\left(k\right)-\underset{i=1}{\overset{N}{\sum <br><br>}}<br><br>F_i^{\mathrm{targ}}<br><br>\left(k\right)$

for each of the parallel loads i=1, 2, . . . , N and for each of the prediction points k=0, 1, . . . , K; and

,

allocating the total energy requirement to the loads 1, 2, . . . , N at prediction points k=0, 1, 2, . . . , K according to the following equation;

33. The process control method of claim 32 wherein w_i^dyn(k) are set by an operator.

34. The process control method of claim 32 wherein w_i^dyn(k) are set by an economic load allocation module.

35. The process control method of claim 32 wherein F_i^targ(k) are set by an operator.

36. The process control method of claim 32 wherein F_i^targ(k) are set by an economic load allocation module.

37. The process control method of claim 31 wherein the controlling of the loads 1, 2, . . . , N based on the dynamic energy demand requirements comprises:

constraining each of the dynamic energy demand requirements to a corresponding limit; and

,

controlling the loads 1, 2, . . . , N based on the corresponding constrained dynamic energy demand requirements.

38. The process control method of claim 37 wherein the corresponding limits comprise corresponding maximum limits.

39. The process control method of claim 37 wherein the corresponding limits comprise corresponding minimum limits.

40. The process control method of claim 37 wherein the corresponding limits comprise corresponding minimum limits and corresponding maximum limits.

41. The process control method of claim 31 wherein the total energy requirements allocated to the loads 1, 2, . . . , N at prediction points k=0, 1, 2, . . . , K are designated F_i^dyn, and wherein the process control method further comprises;

determining a change Δ

F_i^dyn in the total energy requirements allocated to the loads 1, 2, . . . , N according to the following equation;

42. The process control method of claim 41 wherein the corresponding limits for Δ

F_i^dyn comprise corresponding maximum limits.

43. The process control method of claim 41 wherein the corresponding limits for Δ

F_i^dyn comprise corresponding minimum limits.

44. The process control method of claim 41 wherein the corresponding limits for Δ

F_i^dyn comprise corresponding minimum limits and corresponding maximum limits.

45. The process control method of claim 31 wherein the total energy requirement allocated to each of the loads 1, 2, . . . , N is designated F_i^unconstr, wherein the dynamic energy demand requirement for each of the loads 1, 2, . . . , N is designated F_i^dyn, and wherein F_i^dyn is determined by minimizing the following quadratic function:

46. The process control method of claim 45 wherein F^unconstr and F^dyn each have dimensions K+1.

47. The process control method of claim 45 wherein the controlling of the loads 1, 2, . . . , N based on the dynamic energy demand requirements comprises:

constraining F_i^dyn to corresponding limits; and

,

controlling the load based on the constrained F_i^dyn.

48. The process control method of claim 47 wherein the corresponding limits comprise corresponding maximum limits.

49. The process control method of claim 47 wherein the corresponding limits comprise corresponding minimum limits.

50. The process control method of claim 47 wherein the corresponding limits comprise corresponding minimum limits and maximum limits.

51. A process control system for controlling loads comprising:

a predictive controller that predicts energy requirements for the loads by projecting the energy requirements out to the end of a prediction horizon; and

,

a real time cost optimizer that dynamically responds to the predicted energy requirements by dynamically determining cost optimized dynamic energy demand requirements for the loads and by controlling the loads based on the dynamically determined energy demand requirements.