Refrigerant system and controlling method thereof for equalizing pressure difference between oil separator and evaporator

A refrigerant system, comprising:

• a compressor, having an input end and an output end opposite to the input end;
• an oil separator, connected to the output end of the compressor, configured to supply lubricating oil before the compressor starts;
• an oil solenoid valve, disposed between the oil separator and the compressor;
• a condenser, connected to the oil separator;
• an evaporator, connected to the condenser;
• a bypass pipe, having a first end and a second end opposite to the first end, wherein the first end is connected between the oil separator and the condenser, and the second end is connected between the evaporator and the input end of the compressor;
• and
• a bypass solenoid valve, disposed on the bypass pipe and configured to be opened in response to a pressure difference between the oil separator and the evaporator being greater than a pressure difference setting value to equalize the pressure difference;
• the oil solenoid valve is configured to be opened in response to the pressure difference having become less than or equal to the pressure difference setting value to supply lubricating oil from the oil separator to the compressor before the compressor starts;
• after the oil solenoid valve has been open for a first set time, the compressor is started;
• after the compressor has been started for a second set time, the bypass solenoid valve is closed.