Air-conditioning system and control method

The invention provides an air conditioning system and a control method thereof. The air conditioning system comprises a compressor, a four-way valve, an outdoor heat exchanger, a main electronic expansion valve, an indoor heat exchanger, an auxiliary electronic expansion valve, an unloading valve and a temperature sensing device, wherein the compressor is communicated with the four-way valve through a first pipeline, one port of the main electronic expansion valve is communicated with the outdoor heat exchanger through a second pipeline, and the other port of the main electronic expansion valve is communicated with the indoor heat exchanger through a third pipeline; one port of the auxiliary electronic expansion valve is communicated with the first pipeline through a fourth pipeline, and the other port of the auxiliary electronic expansion valve is communicated with the second pipeline; one port of the unloading valve is communicated with the fourth pipeline, and the other port of the unloading valve is communicated with the third pipeline. According to the air conditioning system provided by the invention, through additionally arranging the auxiliary electronic expansion valve and the unloading valve in the whole system, so that the connection/disconnection of pipelines, where the auxiliary electronic expansion valve and the unloading valve are located, of the air conditioning system can be changed according to different circumstances, the switchover of different modes of the air conditioning system is realized, and thus, the comfort of a product during use is improved.