CO2 refrigeration system with supercritical subcooling control

A refrigeration system comprising:

• a heat exchanger configured to remove heat from a refrigerant and discharge the refrigerant into a conduit;
• a temperature sensor located along the conduit and configured to measure a temperature of the refrigerant discharging from the heat exchanger;
• a pressure sensor located along the conduit and configured to measure a pressure of the refrigerant discharging from the heat exchanger;
• a pressure control valve located along the conduit and operable to regulate the pressure of the refrigerant leaving the heat exchanger;
• and
• a controller communicably coupled to the temperature sensor, the pressure sensor, and the pressure control valve and configured to perform operations comprising:
• determining that the refrigerant leaving the heat exchanger is outside of a subcritical region based on at least one of the measured temperature of the refrigerant and the measured pressure of the refrigerant;
• determining a target temperature that is based at least in part on a pseudo-subcooling temperature value and the measured temperature of the refrigerant;
• determining a supercritical pseudo-saturated pressure based on the target temperature;
• determining an offset factor for a pressure offset, the offset factor comprising a dynamic value based at least in part on the measured temperature of the refrigerant, a dynamic offset factor enable setpoint, and a maximum operating pressure of the refrigeration system;
• determining the pressure offset based on the target temperature, the maximum operating pressure of the refrigeration system, and the offset factor comprising the dynamic value;
• and
• operating the pressure control valve to drive the pressure of the refrigerant leaving the heat exchanger to a target pressure that is based on the supercritical pseudo-saturated pressure and the pressure offset.