Compressor discharge temperature control via electronic expansion valve

Abstract

Examples of the present disclosure relate to systems and methods for controlling the positioning of a modulating valve of a heat pump based on a discharge temperature setpoint of a compressor during periods of low ambient outdoor temperatures. A supervisory switching controller may determine that the climate control system should use a discharge temperature controller or a superheat controller to control the modulating valve. Upon detection of ambient outdoor temperatures below a minimum threshold and the detection of discharge temperatures of a compressor above a maximum threshold a discharge temperature controller may control the modulating valve. The discharge temperature controller may control the positioning of the modulating valve based on a discharge temperature setpoint and a map-based controller. The map-based controller may map a calculated discharge temperature error to a position of the modulating valve as a function of a calculated superheat value and a measured suction pressure.

1 . A climate control system comprising:
 a compressor including an inlet port and a discharge port;   an evaporator fluidly coupled to the inlet port of the compressor;   a modulating valve fluidly coupled to the evaporator and configured to control a flow of a refrigerant fluid delivered to the evaporator; and   control circuitry communicatively coupled to the modulating valve, the control circuitry configured to at least:
 control the modulating valve according to a superheat setpoint; 
 transfer control of the modulating valve from the superheat setpoint to a discharge temperature setpoint based, at least in part, on one or more conditions; and 
 control the modulating valve according to the discharge temperature setpoint, including the control circuitry further configured to at least:
 receive a discharge temperature signal representing a temperature of a refrigerant fluid flowing through the discharge port of the compressor; 
 compare the discharge temperature signal to the discharge temperature setpoint; 
 determine a discharge temperature error based, at least in part, on the comparison; and 
 adjust a position of the modulating valve based, at least in part, on reducing the discharge temperature error. 
 
   
     
     
         2 . The climate control system of  claim 1 , wherein the one or more conditions includes one or more of an ambient outdoor temperature threshold or a discharge temperature threshold, and
 wherein the discharge temperature setpoint is less than the discharge temperature threshold.   
     
     
         3 . The climate control system of  claim 2 , wherein the control circuitry is further configured to at least:
 receive an ambient outdoor temperature signal representing a temperature of an ambient outdoor environment of the compressor;   determine that the ambient outdoor temperature signal is less than the ambient outdoor temperature threshold; and   determine that the discharge temperature signal is greater than the discharge temperature threshold.   
     
     
         4 . The climate control system of  claim 1 , wherein the discharge temperature setpoint is predetermined based, at least in part, on a requirement to reduce an enthalpy of a portion of the refrigerant fluid flowing through the discharge port of the compressor, and wherein the control circuitry is further configured to at least:
 increase the flow of the refrigerant fluid delivered to the evaporator.   
     
     
         5 . The climate control system of  claim 1 , wherein the position of the modulating valve is adjusted based on a pre-populated map between a change in the position of the modulating valve correlating to a change in a suction pressure of the refrigerant fluid flowing through the inlet port of the compressor. 
     
     
         6 . The climate control system of  claim 1 , wherein the control circuitry is further configured to at least:
 determine a change in a suction pressure setpoint based, at least in part, on the discharge temperature error;   receive a suction pressure signal representing a suction pressure of the refrigerant fluid flowing through the inlet port of the compressor;   compare a predicted change in the suction pressure signal, to the change in the suction pressure setpoint, wherein the predicted change in the suction pressure signal is based, at least in part, on a change in the position of the modulating valve;   determine a final change in the suction pressure signal based, at least in part, on the comparison;   adjust the position of the modulating valve based, at least in part, on reducing an error between the change in the suction pressure and the predicted change in the suction pressure signal, wherein the position of the modulating valve is adjusted based on a pre-populated map between a plurality of changes in position of the modulating valve that each correlate to a change in the suction pressure of the refrigerant fluid flowing through the inlet port of the compressor; and   update the final change in the suction pressure signal based, at least in part, on a superheat value and the suction pressure signal.   
     
     
         7 . The climate control system of  claim 1 , wherein the control circuitry is further configured to at least:
 determine a change in a saturated suction temperature signal based, at least in part, on the discharge temperature error;   calculate a predicted change in the saturated suction temperature signal, wherein the predicted change in the saturated suction temperature signal is based, at least in part, on a change in the position of the modulating valve;   compare the predicted change in the saturated suction temperature signal to the determined change in the saturated suction temperature signal;   determine an adjustment for the position of the modulating valve based, at least in part, on the comparison; and   adjust the position of the modulating valve based, at least in part, on the adjustment for the position of the modulating valve.   
     
     
         8 . The climate control system of  claim 1 , wherein the control circuitry is further configured to at least:
 receive a saturated suction temperature signal representing a saturated suction temperature of the refrigerant fluid flowing through the evaporator;   receive a suction temperature signal representing a suction temperature of the refrigerant fluid flowing through the inlet port of the compressor;   determine a superheat value based, at least in part, on a difference between the saturated suction temperature signal and the suction temperature signal; and   adjust the position of the modulating valve based, at least in part, on reducing the superheat value toward the superheat setpoint.   
     
     
         9 . The climate control system of  claim 1 , further comprising:
 a plurality of sensors includes one or more of a temperature sensor or a pressure sensor coupled to one or more of the inlet port of the compressor, the discharge port of the compressor, or the evaporator, and   wherein each sensor of the plurality of sensors is configured to provide a signal representative of one or more of a temperature or a pressure.   
     
     
         10 . A method for controlling a modulating valve of a climate control system according to a discharge temperature setpoint, the method comprising:
 controlling the modulating valve according to a superheat setpoint;   transferring control of the modulating valve from the superheat setpoint to a discharge temperature setpoint based, at least in part, on one or more conditions; and   controlling the modulating valve according to the discharge temperature setpoint;   receiving a discharge temperature signal representing a temperature of a refrigerant fluid flowing through a discharge port of a compressor;   comparing the discharge temperature signal to the discharge temperature setpoint;   determining a discharge temperature error based, at least in part, on the comparison; and   adjusting a position of the modulating valve based, at least in part, on reducing the discharge temperature error.   
     
     
         11 . The method of  claim 10 , wherein the one or more conditions includes one or more of an ambient outdoor temperature threshold or a discharge temperature threshold, and
 wherein the discharge temperature setpoint is less than the discharge temperature threshold.   
     
     
         12 . The method of  claim 11 , further comprising:
 receiving an ambient outdoor temperature signal representing a temperature of an ambient outdoor environment;   determining that the ambient outdoor temperature signal is less than the ambient outdoor temperature threshold; and   determining that the discharge temperature signal is greater than the discharge temperature threshold.   
     
     
         13 . The method of  claim 10 , wherein the discharge temperature setpoint is predetermined based, at least in part, on a requirement to reduce an enthalpy of a portion of the refrigerant fluid flowing through the discharge port of the compressor, and the method further comprises:
 increasing the flow of the refrigerant fluid delivered to an evaporator.   
     
     
         14 . The method of  claim 10 , wherein the position of the modulating valve is adjusted based on a pre-populated map between a change in the position of the modulating valve correlating to a change in a suction pressure of the refrigerant fluid flowing through an inlet port of the compressor. 
     
     
         15 . The method of  claim 10 , further comprising:
 determining a change in a suction pressure setpoint based, at least in part, on the discharge temperature error;   receiving a suction pressure signal representing a suction pressure of the refrigerant fluid flowing through an inlet port of the compressor;   comparing a predicted change in the suction pressure signal, to the change in the suction pressure setpoint, wherein the predicted change in the suction pressure signal is based, at least in part, on a change in the position of the modulating valve;   determining a final change in the suction pressure signal based, at least in part, on the comparison;   adjusting the position of the modulating valve based, at least in part, on reducing an error between the change in the suction pressure and the predicted change in the suction pressure signal, wherein the position of the modulating valve is adjusted based on a pre-populated map between a plurality of changes in position of the modulating valve that each correlate to a change in the suction pressure of the refrigerant fluid flowing through the inlet port of the compressor; and   updating the final change in the suction pressure signal based, at least in part, on a superheat value and the suction pressure signal.   
     
     
         16 . The method of  claim 10 , further comprising:
 determining a change in a saturated suction temperature signal based, at least in part, on the discharge temperature error;   calculating a predicted change in the saturated suction temperature signal, wherein the predicted change in the saturated suction temperature signal is based, at least in part, on a change in the position of the modulating valve;   comparing the predicted change in the saturated suction temperature signal to the determined change in the saturated suction temperature signal;   determining an adjustment for the position of the modulating valve based, at least in part, on the comparison; and   adjusting the position of the modulating valve based, at least in part, on the adjustment for the position of the modulating valve.   
     
     
         17 . The method of  claim 10 , further comprises:
 receiving a saturated suction temperature signal representing a saturated suction temperature of the refrigerant fluid flowing through an evaporator;   receiving a suction temperature signal representing a suction temperature of the refrigerant fluid flowing through an inlet port of the compressor;   determining a superheat value based, at least in part, on a difference between the saturated suction temperature signal and the suction temperature signal; and   adjusting the position of the modulating valve based, at least in part, on reducing the superheat value toward the superheat setpoint.   
     
     
         18 . A control circuit for a climate control system, the control circuit comprising:
 a memory configured to store executable program code;   a processor configured to access the memory, and execute the executable program code to cause the control circuit to at least:
 access a superheat controller for controlling a modulating valve according to a superheat setpoint; 
 access a switching controller for transferring control of the modulating valve from the superheat setpoint to a discharge temperature setpoint based, at least in part, on one or more conditions; and 
 access a discharge temperature controller for controlling the modulating valve according to the discharge temperature setpoint, further causing the control circuit to at least:
 receive a discharge temperature signal representing a temperature of a refrigerant fluid flowing through a discharge port of a compressor; 
 compare the discharge temperature signal to the discharge temperature setpoint; 
 determine a discharge temperature error based, at least in part, on the comparison; and 
 transmit a position signal representative of an adjustment to a position of the modulating valve based, at least in part, on reducing the discharge temperature error. 
 
   
     
     
         19 . The control circuit of  claim 18 , wherein the one or more conditions includes one or more of an ambient outdoor temperature threshold or a discharge temperature threshold, and
 wherein the discharge temperature setpoint is less than the discharge temperature threshold.   
     
     
         20 . The control circuit of  claim 19 , further caused to at least:
 receive an ambient outdoor temperature signal representing a temperature of an ambient outdoor environment of the compressor;   determine that the ambient outdoor temperature signal is less than the ambient outdoor temperature threshold; and   determine that the discharge temperature signal is greater than the discharge temperature threshold.