Systems, controllers, and methods for controlling a CO2 refrigeration system

A controller for a CO2 refrigeration system including a compressor, a gas cooler/condenser that receives refrigerant discharged from the compressor and outputs a flow of refrigerant, a valve connected to an output of the gas cooler/condenser to control the flow of refrigerant from the gas cooler/condenser, and a fan positioned to supply a flow of air into the gas cooler/condenser, a first temperature sensor positioned to detect an inlet air temperature of the flow of air into the gas cooler/condenser, a second temperature sensor positioned to detect an exit temperature of the flow of refrigerant from the gas cooler/condenser, and a pressure sensor positioned to detect an exit pressure of the refrigerant in the flow of refrigerant from the gas cooler/condenser, the controller comprising:

• at least one input configured to receive the inlet air temperature from the first temperature sensor, the exit temperature from the second temperature sensor, and the exit pressure from the pressure sensor;
• at least one output for controlling the valve and the fan;
• a memory;
• and
• a processor configured by instructions stored in the memory to:
• receive, through the at least one input, the inlet air temperature from the first temperature sensor;
• determine a target exit pressure based on the inlet air temperature;
• determine a target exit temperature based on the inlet air temperature;
• and
• control, through the at least one output, the valve based on the target exit pressure and the fan based on the target exit temperature both when the CO2 refrigeration system is operating in a transcritical mode and when the CO2 refrigeration system is operating in a subcritical mode, without determining whether the system is operating in the transcritical mode or the subcritical mode.