Central plant optimization with optimization modification

Patent metadata

Field	Value
Publication number	US-11281198-B2
Application number	US-201916428548-A
Country	US
Kind code	B2
Filing date	May 31, 2019
Priority date	May 31, 2019
Publication date	Mar 22, 2022
Grant date	Mar 22, 2022

Abstract

A control system for a central plant having subplants including devices operating to serve energy loads of a building. The system includes a high level optimization module that performs high level optimization of thermal loads subject to constraints to generate subplant load allocations. The control system includes a low level optimization module that performs low level optimization of the subplant load allocations to determine operating states for the devices. The control system includes a constraint modifier that modifies the constraints for the high level optimization module based on equipment schedules. The control system also includes a binary optimization modifier including a pruner module that receives the minimum off schedule to determine adjusted branches and a seeder module that receives the minimum on schedule to determine a starting node for use in binary optimization performed by the low optimization module.

First claim

What is claimed is:

1. A control system for a central plant comprising a plurality of subplants, wherein each of the plurality of subplants comprises one or more devices that operate to serve one or more energy loads of a building, the control system comprising:
a high level optimization module configured to perform a high level optimization of a plurality of thermal loads subject to a plurality of constraints to generate a plurality of subplant load allocations in an optimization period;
a low level optimization module configured to perform a low level optimization of the plurality of subplant load allocations to determine in the optimization period a plurality of operating states for each of the one or more devices included in each of the plurality of subplants included in the central plant;
a constraint modifier configured to lower an upper bound or raise a lower bound of the plurality of constraints for use by the high level optimization module based on a plurality of minimum off schedules and a plurality of minimum on schedules associated with the one or more devices; and
a binary optimization modifier configured to generate a plurality of simplified solutions for use by the low level optimization module, wherein the binary optimization modifier comprises:
a pruning module configured to receive the plurality of minimum off schedules and determine, using the plurality of minimum off schedules, a plurality of adjusted branches for use in a binary optimization process by the low level optimization module; and
a seeding module configured to receive the plurality of minimum on schedules to determine, using the plurality of minimum on schedules, a starting node for use in the binary optimization process by the low level optimization module.

2. The control system of claim 1 , wherein the constraint modifier is configured to modify the plurality of constraints based on a plurality of must run schedules, wherein each of the plurality of must run schedules is associated with one of the one or more devices.

3. The control system of claim 1 , wherein the low level optimization module is further configured to perform the binary optimization process, wherein the binary optimization process is configured to select one or more of the one or more devices to operate for each time step in the optimization period.

4. The control system of claim 1 , wherein the constraint modifier is configured to generate a decayed penalty value for at least one of the plurality of constraints, wherein the generated decayed penalty value defines at least one of a prioritization scheme for satisfying a plurality of operational constraints and a decaying penalty for violating the plurality of operational constraints throughout an optimization period.

5. The control system of claim 1 , wherein the constraint modifier is configured to generate the upper bound based on the plurality of minimum off schedules, wherein the upper bound is used by the high level optimization module in a high level optimization process.

6. The control system of claim 1 , wherein the constraint modifier is configured to raise a value of the lower bound to a minimum turndown value for a particular device based on one of the plurality of minimum on schedules associated with the particular device.

7. The control system of claim 1 , wherein the binary optimization modifier further comprises a hysteresis modifier configured to receive an identification of a combination of dispatched devices for a previous time step from the low level optimization module, wherein the hysteresis modifier is configured to calculate an adjusted heat transfer rate value for the combination of dispatched devices for the previous time step.

8. The control system of claim 7 , wherein the low level optimization module is configured to receive the adjusted heat transfer rate value from the hysteresis modifier and calculate an energy consumption value associated with the adjusted heat transfer rate value.

9. A method of controlling a central plant having a plurality of subplants, wherein each of the plurality of subplants comprises one or more devices operating to serve one or more energy loads of a building, the method comprising:
receiving a plurality of minimum off schedules and a plurality of minimum on schedules associated with each of the one or more devices;
using the plurality of minimum off schedules to determine one or more modified upper bound constraints and the plurality of minimum on schedules to determine one or more modified lower bound constraints, wherein a plurality of adjusted constraints comprise the one or more modified upper bound constraints and the one or more modified lower bound constraints;
performing a high level optimization of the plurality of subplants subject to one or more of the plurality of adjusted constraints to generate a plurality of subplant load allocations;
using the plurality of minimum off schedules to determine a plurality of adjusted branches for use in a binary optimization process;
using the plurality of minimum on schedules to determine a starting node for use in the binary optimization process;
performing the binary optimization process using the plurality of adjusted branches and the starting node to determine a plurality of operating states, wherein each of the plurality of operating states are associated with the one or more devices included in the plurality of subplants; and
using the plurality of operating states and the plurality of subplant load allocations to determine a plurality of control actions for the one or more devices included in the plurality of subplants.

10. The method of claim 9 , wherein performing the binary optimization process comprises performing a branch and bound process.

11. The method of claim 9 , further comprising:
receiving an identification of a combination of dispatched devices for a previous time step; and
calculating an adjusted heat transfer rate value for the combination of dispatched devices for the previous time step.

12. The method of claim 11 , wherein the method further involves using the adjusted heat transfer rate value to calculate an energy consumption value associated with the adjusted heat transfer rate value.

13. The method of claim 9 , wherein using the plurality of minimum on schedules to determine the one or more modified lower bound constraints further comprises increasing the value of one or more modified lower bound constraints to at least one or more minimum turndown values for the one or more devices associated with the plurality of minimum on schedules.

14. The method of claim 9 , wherein the method further involves generating a decayed penalty value for each of the plurality of adjusted constraints, wherein the generated decayed penalty value defines at least one of a prioritization scheme for satisfying a plurality of operational constraints and a decaying penalty for violating the plurality of operational constraints throughout an optimization period.

15. A control system for a central plant comprising a plurality of subplants, wherein each of the plurality of subplants comprises one or more devices that operate to serve one or more energy loads of a building, the control system comprising:
a high level optimization module configured to perform a high level optimization of a plurality of thermal loads subject to a plurality of constraints to generate a plurality of subplant load allocations in an optimization period;
a low level optimization module configured to perform a low level optimization of the plurality of subplant load allocations to determine in the optimization period a plurality o

Assignees

• Johnson Controls Tyco IP Holdings LLP

Inventors

• Fread Jared W
• Willmott Graeme
• Beaty Ryan C
• Schlagenhaft Shawn A
• Ellis Matthew J
• Wenzel Michael J

Classifications

• G05B2219/32291

  Task sequence optimization · CPC title

• G05B2219/2614

  HVAC, heating, ventillation, climate control · CPC title

• G05B19/042 Primary

  using digital processors (G05B19/05 takes precedence) · CPC title

• G05B19/4188 Primary

  characterised by CIM planning or realisation · CPC title

• G05B2219/31001

  CIM, total factory control · CPC title