Three-pipe multi-split air-conditioning system and control method thereof

A three-pipe multi-split hot water system, comprising:

• an outdoor unit comprising a compressor (1), an oil separator (2), a first four-way valve (3), a second four-way valve (4), a finned heat exchanger (5), a plate heat exchanger (6), a refrigerant reversing module (7), a first electronic expansion valve (8), a second electronic expansion valve (9), and a compressor heat dissipation module (10), wherein the compressor (1) is communicated with the oil separator (2);
• the compressor heat dissipation module (10) is communicated with the plate heat exchanger (6);
• and
• the plate heat exchanger (6) is communicated with the second electronic expansion valve (9);
• a multi-split indoor unit equipped with at least two indoor units, any two of the indoor units comprising a first indoor unit (11), a second indoor unit (12), an indoor unit heat exchanger (13), an indoor unit electronic expansion valve (14), and an indoor unit fan (15), wherein the indoor unit electronic expansion valve (14) is communicated with the indoor unit heat exchanger (13);
• and
• a hydraulic module comprising a refrigerant water heat exchanger (16), a water pump (17), a water flow switch (18), and an electromagnetic valve (19), wherein the water pump (17) is communicated with the water flow switch (18) and equipped with a water temperature detection sensor for detecting water temperature.