Systems and methods for cascaded model predictive control

• US 10,580,097 B2
• Filed: 11/09/2017
• Issued: 03/03/2020
• Est. Priority Date: 03/13/2013
• Status: Active Grant

• Current Assignee: Johnson Controls Technology Company (Johnson Controls International plc)
• Original Assignee: Johnson Controls Technology Company (Johnson Controls International plc)
• Inventors: Turney, Robert D., Wenzel, Michael J.
• Primary Examiner(s): Flynn, Kevin H
• Assistant Examiner(s): Zeroual, Omar
• Application Number:
  US15/808,388
• Publication Number:
  US 20180075549A1
• Time in Patent Office: 845 Days
• CPC Class Codes: G06Q 20/085 involving remote charge determination or related payment systems
• CPC Class Codes: G06Q 20/145 Payments according to the detected use or quantity
• CPC Class Codes: G06Q 50/06 Energy or water supply

Abstract

A cascaded model predictive control system includes an inner controller and an outer controller. The outer controller determines an amount of power to defer from a predicted power usage to optimize a total cost of power usage. A power setpoint is calculated based on a difference between the predicted power usage and the amount of power to defer. The inner controller determines an operating setpoint for building equipment in order to achieve the power setpoint.

Claims

1. A heating, ventilation, or air conditioning (HVAC) system for a building, the HVAC system comprising:

a building system comprising one or more measurement devices configured to measure at least one of a measured temperature of the building or a measured power usage of the building and generate a feedback signal comprising at least one of the measured temperature of the building or the measured power usage of the building;

a load predictor configured to predict a future power usage of the building;

an outer controller configured to receive the feedback signal from the building system, receive time-varying pricing information, perform an optimization process to determine an amount of power to defer from the predicted future power usage based on the feedback signal and the pricing information, and output a power control signal indicating the amount of power to defer, wherein the amount of power to defer optimizes a total cost of power usage of the building;

an inner controller configured to receive a power setpoint representing a difference between the predicted future power usage and the amount of power to defer, determine an operating setpoint for the building system predicted to achieve the power setpoint, and output a second control signal indicating the operating setpoint; and

HVAC equipment comprising one or more physical devices, wherein the building system is configured to operate the HVAC equipment to achieve the operating setpoint;

wherein at least one of the outer controller or the inner controller is an electronic device comprising a communications interface and a processing circuit.

2. The HVAC system of claim 1, wherein the feedback signal includes both information representative of the measured temperature and information representative of the measured power usage of the building.

3. The HVAC system of claim 2, wherein the outer controller is configured to:

receive a dynamic model describing heat transfer characteristics of the building and temperature constraints defining an acceptable range for the measured temperature;

use the dynamic model and the feedback signal to estimate a temperature state for the building as a function of power usage; and

use an optimization procedure to determine a power usage for the building which minimizes the total cost of the power usage while maintaining the estimated temperature state within the acceptable range.

4. The HVAC system of claim 1, wherein the outer controller and the inner controller have different sampling and control intervals, wherein the sampling and control interval of the outer controller is longer than the sampling and control interval of the inner controller.

5. The HVAC system of claim 1, wherein the outer controller and the inner controller are physically decoupled in location.

6. The HVAC system of claim 1, wherein the time-varying pricing information includes demand charge information defining a cost per unit of power corresponding to a maximum power usage within a pricing period.

7. The HVAC system of claim 6, wherein the time-varying pricing information includes the demand charge information for two or more of a plurality of pricing periods.

8. The HVAC system of claim 1, wherein the second control signal includes at least one of:

the operating setpoint;

or

a derivative of the operating setpoint.

9. The HVAC system of claim 1, wherein the power control signal includes at least one of:

the power setpoint received by the inner controller;

or

the amount of power to defer from the predicted future power usage, wherein the amount of power to defer is subtracted from the predicted future power usage to calculate the power setpoint received by the inner controller.

10. The HVAC system of claim 9, wherein the load predictor configured to:

receive the operating setpoint and at least one of;

current weather information, past weather information, or past building power usage; and

output the predicted power future usage, wherein the power control signal is the amount of power to defer from the predicted future power usage.

11. A method for heating, ventilating, or air conditioning a building, the method comprising:

measuring, by a measuring device, at least one of a measured temperature of the building or a measured power usage of the building;

generating, by the measuring device, a feedback signal comprising at least one of the measured temperature of the building or the measured power usage of the building;

predicting, by a load predictor, a future power usage of the building based on historical weather and power usage data;

performing, by an outer controller, an optimization process to determine an amount of power to defer from the predicted future power usage based on the feedback signal and time-varying pricing information;

generating, by the outer controller, a power control signal indicating the amount of power to defer, wherein the amount of power to defer optimizes a total cost of the power usage of the building;

calculating, by the outer controller, a power setpoint representing a difference between the predicted future power usage and the amount of power to defer;

determining, by an inner controller, an operating setpoint predicted to achieve the power setpoint;

generating, by the inner controller, a second control signal indicating the operating setpoint; and

operating, by at least one of the measuring device, the load predictor, the outer controller and the inner controller, HVAC equipment to achieve the operating setpoint, the HVAC equipment comprising one or more physical devices.

12. The method of claim 11, wherein the feedback signal includes both information representative of the measured temperature and information representative of the measured power usage of the building.

13. The method of claim 12, further comprising:

receiving a dynamic model describing heat transfer characteristics of the building and temperature constraints defining an acceptable range for the measured temperature;

using the dynamic model and the feedback signal to estimate a temperature state for the building as a function of the power usage; and

using an optimization procedure to determine a power usage for the building which minimizes the total cost of the power usage while maintaining the estimated temperature state within the acceptable range.

14. The method of claim 11, wherein the power control signal is generated by the outer controller having a first sampling and control interval and the second control signal is generated by the inner controller having a second sampling and control interval shorter than the first sampling and control interval.

15. The method of claim 11, wherein the power control signal is generated by the outer controller and the second control signal is generated by the inner controller physically decoupled in location from the outer controller.

16. The method of claim 11, wherein the time-varying pricing information includes demand charge information defining a cost per unit of power corresponding to a maximum power usage within a pricing period.

17. The method of claim 16, wherein the time-varying pricing information includes the demand charge information for two or more of a plurality of pricing periods.

18. The method of claim 11, wherein the second control signal includes at least one of:

the operating setpoint;

or

a derivative of the operating setpoint.

19. The method of claim 11, further comprising subtracting the amount of power to defer from the predicted future power usage to calculate the power setpoint;

wherein the power control signal includes at least one of the power setpoint or the amount of power to defer from the predicted future power usage.

20. The method of claim 19, further comprising:

receiving the operating setpoint and at least one of;

current weather information, past weather information, and past building power usage; and

outputting the predicted future power usage, wherein the power control signal is the amount of power to defer from the predicted future power usage.