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 flash tank connected to receive refrigerant output from the gas cooler/condenser, a high pressure valve (HPV) connected to an output of the gas cooler/condenser to control the flow of refrigerant from the gas cooler/condenser to the flash tank, a bypass valve (BGV) between the flash tank and a suction side of the compressor to control a flow of refrigerant from the flash tank to the suction side of the compressor, and a fan including a motor and positioned to supply a flow of air into the gas cooler/condenser, the controller comprising:

• a processor;
• and
• a memory, the processor configured by instructions stored in the memory to perform the steps of:
• receiving a measurement of an exit pressure of the refrigerant from the gas cooler/condenser;
• operating the fan with a fan speed percentage at or above a first speed threshold when the controller determines based on the measurement of the exit pressure that the exit pressure is greater or equal to a pressure threshold of the refrigerant from the gas cooler/condenser;
• and
• variably controlling an open percentage of the HPV to cause the exit pressure of the refrigerant in the flow of refrigerant from the gas cooler/condenser to move toward a target exit pressure when the fan speed percentage is greater than or equal to the first speed threshold.

A method of controlling 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 flash tank connected to receive refrigerant output from the gas cooler/condenser, a high pressure valve (HPV) connected to an output of the gas cooler/condenser to control the flow of refrigerant from the gas cooler/condenser to the flash tank, a bypass valve (BGV) between the flash tank and a suction side of the compressor to control a flow of refrigerant from the flash tank to the suction side of the compressor, a fan including a motor and positioned to supply a flow of air into the gas cooler/condenser, and a controller, the method comprising:

• receiving, by the controller, a measurement of an exit pressure of the refrigerant from the gas cooler/condenser;
• operating, by the controller, the fan with a fan speed percentage at or above a first speed threshold when the controller determines based on the measurement of the exit pressure that the exit pressure is greater or equal to a pressure threshold of the refrigerant from the gas cooler/condenser;
• and
• variably controlling, by the controller, an open percentage of the HPV to cause the exit pressure of the refrigerant in the flow of refrigerant from the gas cooler/condenser to move toward a target exit pressure when the fan speed percentage is greater than or equal to the first speed threshold.