Two-stage compression air conditioning system and method of controlling gas replenishment thereof

A two-stage compression air conditioning system comprising a two-stage compressor and a flash evaporator, wherein a first port of the flash evaporator is connected to one end of a stop valve by a first pipeline, and the other end of the stop valve is connected to a first gas intake of the two-stage compressor by a second pipeline, the system further comprising a first temperature sensing device, a second temperature sensing device, an intermediate pressure sensor, and a computing control device;

• wherein
• the first temperature sensing device and the intermediate pressure sensor are disposed on the first pipeline, the second temperature sensing device is disposed on the second pipeline, the first temperature sensing device obtains a first temperature value (Tm1) in the first pipeline, the second temperature sensing device obtains a second temperature value (Tm2) in the second pipeline, and the intermediate pressure sensor obtains an intermediate pressure value (Pm) in the first pipeline;
• the computing control device obtains a saturation vapor temperature (TmC) according to the intermediate pressure value (Pm);
• obtains a superheat degree (SH) of replenished gas according to the first temperature value (Tm1) and the saturation vapor temperature (TmC), wherein SH =Tm1−TmC;
• obtains a front-rear temperature difference (TH) of a stop valve according to the first temperature value (Tm1) and the second temperature value (Tm2), wherein TH=Tm1−Tm2;
• and controls the stop valve according to the superheat degree (SH) of replenished gas and the front-rear temperature difference (TH) of the stop valve.