CO2 refrigeration system with convertible compressors

A refrigeration system, comprising:

• a receiver configured to collect refrigerant produced by the refrigeration system and comprising an outlet through which the gas refrigerant exits the receiver;
• a gas bypass valve fluidly coupled to the outlet and operable to control a pressure of the refrigerant in the receiver by controlling a flow of the gas refrigerant from the receiver through the gas bypass valve;
• a medium temperature subsystem, comprising:
• one or more expansion valves;
• one or more medium temperature evaporators;
• and
• a suction group comprising two or more transcritical compressors operable to compress gas refrigerant and discharge the compressed gas refrigerant into a discharge line;
• a first valve system fluidly coupled to a first one of the transcritical compressors;
• a second valve system fluidly coupled to a second one of the transcritical compressors;
• an oil management subsystem, comprising oil reservoir;
• and
• a controller configured to:
• determine that one or more first operating parameters are within a first operating range;
• in response to the determination that the one or more first operating parameters are within the first operating range, activate the first one of the transcritical compressors to operate as a parallel compressor by modulating the first valve system to switch a suction input of the first one of the transcritical compressors from an evaporator outlet of the one or more medium temperature evaporators to the outlet of the receiver;
• determine that one or more second operating parameters are within a second operating range;
• in response to the determination that the one or more second operating parameters are within the second operating range, activate the second one of the transcritical compressors to operate as a parallel compressor by modulating the second valve system to switch a suction input of the second one of the transcritical compressors from an evaporator outlet of the one or more medium temperature evaporators to the outlet of the receiver;
• and
• in response to receiving a signal calling for oil from a compressor that is operating as a parallel compressor:
• deactivating the compressor from operating as a parallel compressor by modulating the input flow of refrigerant to the compressor from the outlet of the receiver to one or more evaporators,
• activate another one of the transcritical compressors to operate as a parallel compressor by modulating an input flow of refrigerant from the one or more evaporators to the outlet of the receiver, and
• provide oil from the reservoir to compressor that has been deactivated as a parallel compressor.

A refrigeration system, comprising:

• a receiver configured to collect refrigerant produced by the refrigeration system and comprising an outlet through which the gas refrigerant exits the receiver;
• a gas bypass valve fluidly coupled to the outlet and operable to control a pressure of the refrigerant in the receiver by controlling a flow of the gas refrigerant from the receiver through the gas bypass valve;
• a medium temperature subsystem comprising:
• one or more expansion valves;
• one or more medium temperature evaporators;
• and
• a suction group comprising two or more transcritical compressors operable to compress gas refrigerant and discharge the compressed gas refrigerant into a discharge line;
• a first valve system fluidly coupled to a first one of the transcritical compressors;
• a second valve system fluidly coupled to a second one of the transcritical compressors;
• a controller configured to:
• determine that one or more first operating parameters are within a first operating range;
• in response to the determination that the one or more first operating parameters are within the first operating range, activate the first one of the transcritical compressors to operate as a parallel compressor by modulating the first valve system to switch a suction input of the first one of the transcritical compressors from an evaporator outlet of the one or more medium temperature evaporators to the outlet of the receiver;
• determine that one or more second operating parameters are within a second operating range;
• and
• in response to the determination that the one or more second operating parameters are within the second operating range, activate the second one of the transcritical compressors to operate as a parallel compressor by modulating the second valve system to switch a suction input of the second one of the transcritical compressors from an evaporator outlet of the one or more medium temperature evaporators to the outlet of the receiver;
• wherein the one or more first operating parameters comprise a flash gas generated in the receiver, and the flash gas generated is determined from a percentage of flash gas bypass valve opening.

A refrigeration system, comprising:

• a receiver configured to collect refrigerant produced by the refrigeration system and comprising an outlet through which the gas refrigerant exits the receiver;
• a gas bypass valve fluidly coupled to the outlet and operable to control a pressure of the refrigerant in the receiver by controlling a flow of the gas refrigerant from the receiver through the gas bypass valve;
• a low temperature subsystem comprising one or more low temperature evaporators and one or more subcritical compressors, the one or more low temperature evaporators configured to receive liquid refrigerant from the receiver;
• a medium temperature subsystem comprising:
• one or more expansion valves;
• one or more medium temperature evaporators;
• and
• a suction group comprising two or more transcritical compressors operable to receive gas refrigerant from the one or more subcritical compressors, compress the gas refrigerant, and discharge the compressed gas refrigerant into a discharge line;
• a first valve system fluidly coupled to a first one of the transcritical compressors;
• a second valve system fluidly coupled to a second one of the transcritical compressors;
• a controller configured to:
• determine that one or more first operating parameters are within a first operating range;
• in response to the determination that the one or more first operating parameters are within the first operating range, activate the first one of the transcritical compressors to operate as a parallel compressor by modulating the first valve system to switch a suction input of the first one of the transcritical compressors from an evaporator outlet of the one or more medium temperature evaporators to the outlet of the receiver;
• determine that one or more second operating parameters are within a second operating range;
• in response to the determination that the one or more second operating parameters are within the second operating range, activate the second one of the transcritical compressors to operate as a parallel compressor by modulating the second valve system to switch a suction input of the second one of the transcritical compressors from an evaporator outlet of the one or more medium temperature evaporators to the outlet of the receiver;
• and
• in response to a determination that one or more third operating parameters are within a third operating range, deactivate the second of the transcritical compressors from operating as a parallel compressor.

A refrigeration system, comprising:

• a receiver configured to collect refrigerant produced by the refrigeration system and comprising an outlet through which the gas refrigerant exits the receiver;
• a gas bypass valve fluidly coupled to the outlet and operable to control a pressure of the refrigerant in the receiver by controlling a flow of the gas refrigerant from the receiver through the gas bypass valve;
• a low temperature subsystem comprising one or more low temperature evaporators and one or more subcritical compressors, the one or more low temperature evaporators configured to receive liquid refrigerant from the receiver;
• a medium temperature subsystem comprising:
• one or more expansion valves;
• one or more medium temperature evaporators;
• and
• a suction group comprising two or more transcritical compressors operable to receive gas refrigerant from the one or more subcritical compressors, compress the gas refrigerant, and discharge the compressed gas refrigerant into a discharge line;
• a first valve system fluidly coupled to a first one of the transcritical compressors;
• a second valve system fluidly coupled to a second one of the transcritical compressors;
• a controller configured to:
• determine that one or more first operating parameters are within a first operating range;
• in response to the determination that the one or more first operating parameters are within the first operating range, activate the first one of the transcritical compressors to operate as a parallel compressor by modulating the first valve system to switch a suction input of the first one of the transcritical compressors from an evaporator outlet of the one or more medium temperature evaporators to the outlet of the receiver;
• determine that one or more second operating parameters are within a second operating range;
• in response to the determination that the one or more second operating parameters are within the second operating range, activate the second one of the transcritical compressors to operate as a parallel compressor by modulating the second valve system to switch a suction input of the second one of the transcritical compressors from an evaporator outlet of the one or more medium temperature evaporators to the outlet of the receiver;
• determine that one or more third operating parameters are within a third operating range;
• and
• in response to the determination that the one or more third operating parameters are within the third operating range, activate a third one of the transcritical compressors to operate as a parallel compressor by modulating a third valve system to switch a suction input of the third one of the transcritical compressors from an evaporator outlet of the one or more medium temperature evaporators to the outlet of the receiver.