Medium-pressure oil return device of large transcritical CO2 refrigerating system

The invention provides a medium-pressure oil return device of a large transcritical CO2 refrigerating system, which comprises a transcritical CO2 compressor unit exhaust hot gas pipeline, a transcritical CO2 barrel pump oil return pipeline is arranged on the right side of the transcritical CO2 compressor unit exhaust hot gas pipeline, and the medium-pressure oil return device is characterized in that the inner side of the transcritical CO2 barrel pump oil return pipeline is in threaded connection with an oil return electromagnetic valve; a heater is mounted at an outlet of the transcritical CO2 barrel pump oil return pipeline; the outlet end of the transcritical CO2 compressor unit exhaust hot gas pipeline is connected with an ejector hot gas electromagnetic valve, a heater hot gas electromagnetic valve and a transcritical CO2 oil collector hot gas pressurization electromagnetic valve through pipelines. And an inlet end pipeline of the heater is connected with an ejector valve group. The high-pressure CO2 oil