Air-conditioning system and control method

The invention discloses an air conditioning system and a control method thereof. The air conditioning system comprises a compressor, a back pressure valve, a condenser, a throttle device and an evaporator; an air outlet of the compressor is communicated with an inlet of the back pressure valve; an outlet of the back pressure valve is connected with one end of the condenser through an air exhaust pipeline; the other end of the condenser is connected with one end of the throttle device; the other end of the throttle device is connected with one end of the evaporator; the other end of the evaporator is connected with an air return opening of the compressor through an air suction pipeline; the back pressure valve is provided with an external balance opening; the external balance opening is connected with the air suction pipeline and the air exhaust pipeline through a first pipeline and a second pipeline respectively; a first control valve and a second control valve are arranged on the first pipeline and the second pipeline respectively. According to the air conditioning system and the control method thereof, the sufficient high and low pressure difference can be rapidly established through the system to ensure the smooth oil supply and cooling of the compressor and the reversing of the compressor can be avoided to ensure that a refrigeration system is safely and stably operated for a long time.