Multi-connected heat recovery air conditioning system and control method thereof

A control method of a multi-connected heat recovery air conditioning system comprising:

• comprising an indoor unit, an outdoor unit, and a hydraulic module, wherein the outdoor unit includes a compressor, an outdoor heat exchanger, a first four-way valve and a second four-way valve;
• the hydraulic module including a heat exchange water tank, ports d, e, c and s of the first four-way valve being connected to an output end of the compressor, one end of the indoor unit, port g of the second four-way valve, and a return end of the compressor, respectively, ports h, I, and f of the second four-way valve being connected to the outdoor heat exchanger, the return end of the compressor, and one end of a refrigerant flow path of the heat exchange water tank, respectively, the other end of the refrigerant flow path of the heat exchange water tank being connected in a bypass manner between a first solenoid valve and the outdoor heat exchanger via a first check valve, the other end of the outdoor unit being connected to the outdoor heat exchanger;
• the outdoor heat exchanger comprising three heat exchange coils arranged in parallel in a wind direction of fan blades thereof, wherein the three heat exchange coils are connected together at one end to connect to port h of the second four-way valve, and the other end of the three heat exchange coils are connected to preset first outdoor expansion valve, second outdoor expansion valve and third outdoor expansion valve, respectively, and then joint together to connect to the outdoor unit;
• further comprising an indoor unit temperature unit arranged in the indoor unit for detecting and obtaining an outlet temperature value of the indoor unit, a water temperature unit arranged at the heat exchange water tank for detecting and obtaining water temperature, and a high-pressure sensor and a low-pressure sensor arranged respectively at the output end and the return end of the compressor;
• wherein the air conditioning system includes a cooling mode, a heating mode, a hot water heat recovery mode, and a hot water production mode, wherein when the air conditioning system is powered on and runs in any mode, opening and closing conditions of each of the first, second and third outdoor expansion valves are adjusted accordingly based on predetermined conditions for each mode;
• in response to the air conditioning system is powered on and runs in the cooling mode, the opening and closing conditions of the first, second and third outdoor expansion valves are adjusted correspondingly based on a cooling demand ratio φ1 between a cooling capacity demand N1 of the indoor unit in operation and an overall cooling capacity Nt1 of the indoor unit, and the opening degree of each of the first, second and third outdoor expansion valves is adjusted based on the discharge pressure Tp of the compressor, wherein the larger the cooling demand ratio φ1, the greater a number of the first, second and third outdoor expansion valves is opened;
• in response to the air-conditioning system is powered on and runs in the heating mode, the opening and closing conditions of the first, second and third outdoor expansion valves are adjusted correspondingly based on a heating demand ratio φ2 between an actual heating capacity demand N2 of the indoor unit in operation and an overall heating capacity Nt2 of the indoor unit, and the opening degree of each of the first, second and third outdoor expansion valves is adjusted based on the discharge pressure Tp of the compressor, wherein the larger the heating demand ratio φ2, the greater a number of the first, second and third outdoor expansion valves is opened;
• in response to the air-conditioning system is powered on and runs in the heat recovery mode, the opening and closing conditions of the first, second and third outdoor expansion valves are adjusted accordingly based on an initial outlet temperature value T2B of the indoor unit in operation, wherein during the operation in the heat recovery mode, a real-time outlet temperature value T2B′ of the indoor unit is continuously monitored and the opening degree of each of the first, second and third outdoor expansion valves e is adjusted at intervals of a rated period based on the real-time outlet temperature value T2B′;
• and
• in response to the air conditioning system is powered on and runs in the hot water production mode, the opening and closing conditions of the first, second and third outdoor expansion valves are adjusted accordingly based on a water temperature difference ΔT between an actual water temperature T5 and a preset water temperature Ts of the hydraulic module, and the opening degree of each of the first, second and third outdoor expansion valves is adjusted correspondingly based on the discharge pressure Tp of the compressor.