Multiple expansion valves smart control for refrigerant circuit system

Abstract

A control input represents directed flow rate of refrigerant through a virtual refrigerant metering device. For a plurality of parallel-connected, real, non-virtual, refrigerant metering devices, control input is determined for each, based on refrigerant flow characteristic of each refrigerant metering device, to produce individual flow rates through the refrigerant metering devices that provide an aggregate flow rate equivalent to the directed flow rate. Control signals are sent to the refrigerant metering devices.

What is claimed is: 
     
         1 . A method of operating a refrigerant circuit system, comprising:
 receiving a control input that represents a directed flow rate of a refrigerant through a virtual refrigerant metering device;   for each refrigerant metering device of a plurality of parallel-connected, real, non-virtual, refrigerant metering devices of the refrigerant circuit system,
 determining individual control input for the refrigerant metering device, based, at least in part, on the control input that represents the directed flow rate, and a refrigerant flow characteristic of the refrigerant metering device, to produce a plurality of individual flow rates through the plurality of refrigerant metering devices that provide an aggregate flow rate that is substantially equivalent to the directed flow rate; and 
   sending a plurality of control inputs to the plurality of refrigerant metering devices based on the determining of the individual control inputs for the plurality of refrigerant metering devices.   
     
     
         2 . The method of  claim 1 , wherein the sending comprises:
 sending a first control input of the plurality of control inputs to a first refrigerant metering device of the plurality of refrigerant metering devices; and   sending a second control input of the plurality of control inputs to a second refrigerant metering device of the plurality of refrigerant metering devices, wherein
 the refrigerant flow characteristic of the refrigerant metering device comprises a characteristic curve that governs a refrigerant flow rate of the refrigerant through the refrigerant metering device, 
 the refrigerant flow characteristic of the first refrigerant metering device comprises a first characteristic curve that governs a first refrigerant flow rate of the refrigerant through the first refrigerant metering device, 
 the refrigerant flow characteristic of the second metering device comprises a second characteristic curve that governs a second refrigerant flow rate of the refrigerant through the second refrigerant metering device, and 
 the determining the individual control input for the first refrigerant metering device and the individual control input for the second refrigerant metering device is performed such that the aggregate flow rate comprises a combination of the first refrigerant flow rate and the second refrigerant flow rate. 
   
     
     
         3 . The method of  claim 2 , wherein
 the individual control input for the first refrigerant metering device according to the first characteristic curve and the individual control input for the second refrigerant metering device according to the second characteristic curve are determined to follow a target characteristic curve of the virtual refrigerant metering device.   
     
     
         4 . The method of  claim 3 , wherein:
 the first characteristic curve is a first flow coefficient versus refrigerant metering device setting curve,   the second characteristic curve is a second flow coefficient versus refrigerant metering device setting curve,   the individual control input for the first refrigerant metering device is determined, at least in part, by
 determining a first refrigerant metering device setting, based, at least in part, on a first weighting function, the first characteristic curve, and the target characteristic curve of the virtual refrigerant metering device, and 
   the individual control input for the second refrigerant metering device is determined, at least in part, by
 determining a second refrigerant metering device setting, based, at least in part, on a second weighting function, the second characteristic curve, and the target characteristic curve of the virtual refrigerant metering device. 
   
     
     
         5 . The method of  claim 4 , wherein
 the first refrigerant metering device is a first electronic expansion valve,   the second refrigerant metering device is a second electronic expansion valve,   the first refrigerant metering device setting is a first valve opening percentage, and   the second refrigerant metering device setting is a second valve opening percentage.   
     
     
         6 . The method of  claim 4 , wherein
 for a point on the target characteristic curve of the virtual refrigerant metering device, the first weighting function and the second weighting function transition between a first phase and a second phase relative to the first characteristic curve and the second characteristic curve.   
     
     
         7 . The method of  claim 6 , wherein
 the first weighting function and the second weighting function provide hysteresis in refrigerant metering device operation relative to the first characteristic curve and the second characteristic curve.   
     
     
         8 . The method of  claim 1 , wherein
 the individual control input for the refrigerant metering device differs between ones of the plurality of refrigerant metering devices as a result of the characteristic curve of the refrigerant metering device differing between the ones of the plurality of refrigerant metering devices.   
     
     
         9 . The method of  claim 1 , wherein
 each refrigerant metering device is of a respective refrigerant metering device type such that the characteristic curve of each one of the plurality of refrigerant metering devices is different from at least one other refrigerant metering device of the plurality of refrigerant metering devices.   
     
     
         10 . The method of  claim 9 , wherein
 the respective refrigerant metering device type is selected from a set consisting of a low-volume expansion valve, and
 a high-volume expansion valve; and wherein 
   a maximum flow rate of the low-volume expansion valve is lower than a maximum flow rate of the high-volume expansion valve.   
     
     
         11 . The method of  claim 1 , further comprising:
 determining the directed flow rate, based on the control input; and   encoding the directed flow rate in the individual control input for the refrigerant metering device, for each of the plurality of refrigerant metering devices.   
     
     
         12 . The method of  claim 1 , wherein
 the refrigerant is a metered refrigerant,   the plurality of control inputs are of a single signal type, and   the single signal type is one of an electrical signal or a mechanical signal.   
     
     
         13 . The method of  claim 11 , wherein
 the plurality of refrigerant metering devices is of a single metering device type, and   the single metering device type comprises one of an electronic expansion valve, a thermal expansion valve, an externally-equalized expansion valve, or an internally-equalized expansion valve.   
     
     
         14 . A controller comprising:
 one or more processors, wherein
 the controller is configured to receive a control input that represents a directed flow rate of a refrigerant through a virtual refrigerant metering device; 
   one or more outputs, coupled to the one or more processors and configured to be communicatively coupled to a plurality of parallel-connected, real, non-virtual refrigerant metering devices; and   a computer-readable storage medium coupled to the one or more processors, comprising program instructions, which, when executed by the one or more processors, cause the controller to:
 receive the control input that represents the directed flow rate of the refrigerant through the virtual refrigerant metering device; 
 for each refrigerant metering device of the plurality of refrigerant metering devices,
 determine individual control input for the refrigerant metering device, based, at least in part, on the control input that represents the directed flow rate, and a refrigerant flow characteristic of the refrigerant metering device, to produce a plurality of individual flow rates through the plurality of refrigerant metering devices that provides an aggregate flow rate that is substantially equivalent to the directed flow rate, and 
 
 send, via the one or more outputs, one or more control inputs to the plurality of refrigerant metering devices based on the determined individual control inputs for the plurality of refrigerant metering devices. 
   
     
     
         15 . The controller of  claim 14 , wherein the program instructions that send the one or more control signals comprise further program instructions that cause the controller to:
 send a first control input of the one or more control inputs to a first refrigerant metering device of the plurality of refrigerant metering devices; and   send a second control input of the one or more control inputs to a second refrigerant metering device of the plurality of refrigerant metering devices, wherein
 that refrigerant flow characteristic of the refrigerant metering device comprises a characteristic curve that governs a refrigerant flow rate of the refrigerant through the refrigerant metering device, 
 the characteristic of the first refrigerant metering device comprises a first characteristic curve that governs a first refrigerant flow rate of the refrigerant through the first refrigerant metering device, 
 the characteristic of the second refrigerant metering device is described by a second characteristic curve that governs a second refrigerant flow rate of the refrigerant through the second refrigerant metering device, and 
 the individual control input for the first refrigerant metering device and the individual control input for the second refrigerant metering device are determined such that the aggregate refrigerant flow rate comprises a combination of the first refrigerant flow rate and the second refrigerant flow rate. 
   
     
     
         16 . The controller of  claim 15 , wherein
 the individual control input for the first refrigerant metering device according to the first characteristic curve and the individual control input for the second refrigerant metering device according to the second characteristic curve are determined to follow a target characteristic curve of the virtual refrigerant metering device,   the first characteristic curve is a first flow coefficient versus refrigerant metering device setting curve,   the second characteristic curve is a second flow coefficient versus refrigerant metering device setting curve,   the individual control input for the first refrigerant metering device is determined, at least in part, by
 determining a first refrigerant metering device setting, based, at least in part, on a first weighting function, the first characteristic curve, and the target characteristic curve of the virtual refrigerant metering device, and 
   the individual control input for the second refrigerant metering device is determined, at least in part, by
 determining a second refrigerant metering device setting, based, at least in part, on a second weighting function, the second characteristic curve, and the target characteristic curve of the virtual refrigerant metering device. 
   
     
     
         17 . The controller of  claim 16 , wherein
 the first refrigerant metering device is a first electronic expansion valve,   the second refrigerant metering device is a second electronic expansion valve,   the first refrigerant metering device setting is a first valve opening percentage, and   the second refrigerant metering device setting is a second valve opening percentage.   
     
     
         18 . The controller of  claim 16 , wherein
 for a point on the target characteristic curve of the virtual refrigerant metering device, the first weighting function and the second weighting function transition between a first phase and a second phase relative to the first characteristic curve and the second characteristic curve, and   the first weighting function and the second weighting function provide hysteresis in refrigerant metering device operation relative to the first characteristic curve and the second characteristic curve.   
     
     
         19 . The controller of  claim 14 , wherein
 the individual control input for the refrigerant metering device differs between ones of the plurality of refrigerant metering devices as a result of the characteristic curve of the refrigerant metering device differing between the ones of the plurality of refrigerant metering devices, and   the characteristic of the refrigerant metering device comprises a maximum flow rate of the refrigerant metering device.   
     
     
         20 . The controller of  claim 14 , wherein
 each refrigerant metering device is of a respective refrigerant metering device type such that the characteristic curve of each one of the plurality of refrigerant metering devices is different from at least one other refrigerant metering device of the plurality of refrigerant metering devices,   the respective refrigerant metering device type is selected from a set consisting of a low-volume expansion valve, and
 a high-volume expansion valve; and wherein 
   a maximum flow rate of the low-volume expansion valve is lower than a maximum flow rate of the high-volume expansion valve.   
     
     
         21 . The controller of  claim 14 , wherein
 the controller is in a system that comprises another controller,   the controller is communicatively coupled to receive the control input from the another controller, and   the another controller is configured to
 determine the directed flow rate, 
 encode the directed flow rate in the control input, and 
 send the control input to the controller.