System and method for controlling multi-zone vapor compression systems

• US 10,174,957 B2
• Filed: 07/27/2015
• Issued: 01/08/2019
• Est. Priority Date: 07/27/2015
• Status: Active Grant

• Current Assignee: Mitsubishi Electric Research Laboratories, Inc. (Mitsubishi Electric Corporation)
• Original Assignee: Mitsubishi Electric Research Laboratories, Inc. (Mitsubishi Electric Corporation)
• Inventors: Burns, Daniel J., Di Cairano, Stefano, Bortoff, Scott A., Laughman, Christopher R.
• Primary Examiner(s): Ciric, Ljiljana
• Application Number:
  US14/809,545
• Publication Number:
  US 20170030598A1
• Time in Patent Office: 1,261 Days
• CPC Class Codes: F24F 1/0007 Indoor units, e.g. fan coil units self-contained units F24F1/02
• CPC Class Codes: F24F 1/0043 characterised by mounting arrangements
• CPC Class Codes: F24F 11/30 for purposes related to the operation of the system, e.g. for safety or monitoring
• CPC Class Codes: F24F 11/46 Improving electric energy efficiency or saving
• CPC Class Codes: F24F 11/54 using one central controller connected to several sub-controllers
• CPC Class Codes: F24F 11/62 characterised by the type of control or by internal processing, e.g. using fuzzy logic, adaptive control or estimation of values
• CPC Class Codes: F24F 11/63 Electronic processing
• CPC Class Codes: F24F 11/83 by controlling the supply of heat-exchange fluids to heat-exchangers
• CPC Class Codes: F24F 11/84 using valves
• CPC Class Codes: F24F 2110/00 Control inputs relating to air properties
• CPC Class Codes: F24F 2140/50 Load
• CPC Class Codes: F24F 2140/60 Energy consumption
• CPC Class Codes: F24F 3/065 with a plurality of evaporators or condensers
• CPC Class Codes: F25B 13/00 Compression machines, plants or systems, with reversible cycle defrosting cycles F25B47/02
• CPC Class Codes: F25B 2313/0233 in parallel arrangements
• CPC Class Codes: F25B 49/02 for compression type machines, plants or systems
• CPC Class Codes: F25B 49/027 Condenser control arrangements
• CPC Class Codes: F25B 5/02 arranged in parallel
• CPC Class Codes: F25B 6/02 arranged in parallel

Abstract

A multi-zone vapor compression system (MZ-VCS) includes a compressor connected to a set of heat exchangers controlling environments in a set of zones. A supervisory controller includes a processor configured for optimizing a cost function subject to constraints on an operation of the MZ-VCS to produce a set of values of the thermal capacity requested for the set of heat exchangers to achieve setpoint temperatures in the corresponding zones. The supervisory controller is a model predictive controller for determining the set of control inputs using a model of the MZ-VCS including a linear relationship between the thermal capacity of each heat exchanger and the temperature in a corresponding zone controlled by the heat exchanger. A set of capacity controllers, wherein there is one capacity controller for each heat exchanger, such that each capacity controller is configured for controlling the corresponding heat exchanger to achieve the requested thermal capacity.

Claims

1. A multi-zone vapor compression system (MZ-VCS), comprising:

a compressor connected to a set of heat exchangers controlling the environments in a set of zones, wherein there is at least one heat exchanger for each zone;

a supervisory controller including a processor determining a set of control inputs for controlling a vapor compression cycle of the MZ-VCS, wherein the supervisory controller is a model predictive controller determining the set of control inputs using a model of the MZ-VCS including a linear relationship between the thermal capacity of each heat exchanger and the temperature in a corresponding zone controlled by the heat exchanger; and

a set of capacity controllers, wherein there is one capacity controller for each heat exchanger, each capacity controller enforces the linear relationship between the thermal capacity and the temperature in the corresponding zone.

2. The MZ-VCS of claim 1, wherein the supervisory controller optimizes a cost function subject to constraints on the vapor compression cycle to produce the set of control inputs including a value of the thermal capacity requested for each heat exchanger to achieve a setpoint temperature in the corresponding zone, wherein the capacity controller determines a setpoint temperature of a refrigerant passing through the heat exchanger using a value of the requested thermal capacity and a setpoint function mapping values of the requested thermal capacity to values of the temperature of refrigerant and iteratively enforces the linear relationship by adjusting a position of a valve controlling the refrigerant passing through the heat exchanger to reduce an error between the setpoint temperature of the refrigerant and a measured temperature of the refrigerant.

3. The MZ-VCS of claim 2, wherein the heat exchanger includes an inlet header pipe connected to a set of paths for passing the refrigerant, wherein the inlet header pipe splits the refrigerant into the set of paths, wherein the capacity controller selects the path from the set of paths for controlling the position of the valve based on the requested thermal capacity and uses the measured temperature of the refrigerant in the selected path to adjust the position of the valve.

4. The MZ-VCS of claim 3, wherein the capacity controller selects a sensor from a set of sensors for measuring the temperature of the refrigerant in the set of paths of the corresponding heat exchanger and adjusts the position of the valve based on the measured temperature measured by the selected sensor.

5. The MZ-VCS of claim 4, wherein the setpoint function is a continuous function that switches at a point of saturation of each sensor in the set of sensors.

6. The MZ-VCS of claim 4, wherein the capacity controller includes a feedback controller, wherein a gain of the feedback controller is selected based on the selected sensor, such that different sensors in the set are associated with different gains.

7. The MZ-VCS of claim 4, wherein the capacity controller selects a sensor from the set of sensors for measuring the temperature of the refrigerant in the set of paths of the corresponding heat exchanger based on the requested thermal capacity and the setpoint function and adjusts the position of the valve based on the measured temperature measured by the selected sensor, wherein the setpoint function is a continuous function that switches at a point of saturation of each sensor in the set of sensors.

8. The MZ-VCS of claim 7, wherein the capacity controller includes a feedback controller, wherein a gain of the feedback controller is selected based on the selected sensor, such that different sensors in the set are associated with different gains.

9. The MZ-VCS of claim 1, wherein the supervisory controller optimizes a cost function subject to constraints on the vapor compression cycle to determine the set of control inputs achieving a plurality of setpoints including zone temperature setpoints and a performance setpoint specifying a trade-off between an amount of heat per unit of consumed energy and the thermal capacities of the heat exchangers, wherein the cost function penalizes for deviation from each setpoint.

10. The MZ-VCS of claim 1, wherein the supervisory controller is configured to execute an estimator module and a solver module, wherein the estimator module determines iteratively states of the MZ-VCS, such that a difference between outputs of the operation of the MZ-VCS estimated using the states and measured outputs of the operation of the MZ-VCS asymptotically approaches zero, and wherein the solver module determines the set of control inputs using the states of the MZ-VCS.

11. The MZ-VCS of claim 10, wherein the supervisory controller is configured to determine, in response to receiving at least one value of a setpoint, values of the measured outputs of the operation of the MZ-VCS, the measured outputs including at least one performance output controlled according to the value of the setpoint and at least one constrained output controlled to satisfy constraints independent from the value of the setpoint.

12. The MZ-VCS of claim 11,

wherein the estimator module determines the states of the MZ-VCS using an estimator model of the MZ-VCS defining a relationship between the states of the MZ-VCS, control inputs and controlled outputs, such that a difference between outputs predicted using the estimator model and the measured outputs asymptotically approaches zero, wherein the states of the MZ-VCS include a main state representing the operation of the MZ-VCS and an auxiliary state representing the effect of unknown disturbances on each measured output of the MZ-VCS, and

wherein the solver module determines the control inputs for controlling the operation of the MZ-VCS using a prediction model defining a relationship between the states of the MZ-VCS, the control inputs, the performance and constrained outputs, and the value of the setpoint, such that the constrained output satisfies the constraints, and a difference between the performance output and the value of the setpoint asymptotically approaches zero.

13. The MZ-VCS of claim 1, wherein the supervisory controller optimizes a cost function achieving a plurality of setpoints including zone temperature setpoints and a performance setpoint specifying a trade-off between an amount of heat per unit of consumed energy and the thermal capacities of the heat exchangers, wherein the cost function penalizes for deviation from each setpoint.

14. A multi-zone vapor compression system (MZ-VCS), comprising:

a set of heat exchangers configured for controlling environments in a set of zones, wherein there is at least one heat exchanger for each zone, wherein the heat exchanger includes an inlet header pipe connected to a set of paths for passing the refrigerant, and wherein the inlet header pipe splits the refrigerant into the set of paths;

a supervisory controller including a processor configured for optimizing a cost function subject to constraints on an operation of the MZ-VCS to produce a set of values of the thermal capacity requested for the set of heat exchangers to achieve setpoint temperatures in the corresponding zones, wherein the supervisory controller is a model predictive controller for determining the set of control inputs using a model of the MZ-VSC including a linear relationship between the thermal capacity of each heat exchanger and the temperature in a corresponding zone controlled by the heat exchanger; and

a set of capacity controllers, there is one capacity controller for each heat exchanger, wherein each capacity controller is configured for controlling the corresponding heat exchanger to achieve the requested thermal capacity.

15. The MZ-VCS of claim 14, wherein the capacity controller determines a setpoint temperature of a refrigerant passing through the heat exchanger using a value of the requested thermal capacity and a setpoint function mapping values of the requested thermal capacity to values of the temperature of refrigerant and iteratively enforces the linear relationship by adjusting a position of a valve controlling the refrigerant passing through the heat exchanger to reduce an error between the setpoint temperature of the refrigerant and a measured temperature of the refrigerant.

16. The MZ-VCS of claim 14, wherein the supervisory controller is configured to execute an estimator module and a solver module, wherein the estimator module determines iteratively states of the MZ-VCS, such that a difference between outputs of the operation of the MZ-VCS estimated using the states and measured outputs of the operation of the MZ-VCS asymptotically approaches zero, and wherein the solver module determines the set of control inputs using the states of the MZ-VCS.

17. The MZ-VCS of claim 16, wherein the supervisory controller is configured to determine, in response to receiving at least one value of a setpoint, values of the measured outputs of the operation of the MZ-VCS, the measured outputs including at least one performance output controlled according to the value of the setpoint and at least one constrained output controlled to satisfy constraints independent from the value of the setpoint.

18. The MZ-VCS of claim 17,

wherein the estimator module determines the states of the MZ-VCS using an estimator model of the MZ-VCS defining a relationship between the states of the MZ-VCS, control inputs and controlled outputs, such that a difference between outputs predicted using the estimator model and the measured outputs asymptotically approaches zero, wherein the states of the MZ-VCS include a main state representing the operation of the VCS and an auxiliary state representing the effect of unknown disturbances on each measured output of the MZ-VCS, and

wherein the solver module determines the control inputs for controlling the operation of the MZ-VCS using a prediction model defining a relationship between the states of the MZ-VCS, the control inputs, the performance and constrained outputs, and the value of the setpoint, such that the constrained output satisfies the constraints, and a difference between the performance output and the value of the setpoint asymptotically approaches zero.