301, to continue to adjust the first operating parameters. The first preset temperature threshold may be customized by the user according to actual needs or use a value from the factory default settings, for example, any value between 1° C. and 3° C.

In some embodiments, step S601 includes the following steps:

- obtaining a refrigerant flow according to the frequency, the exhaust pressure, the return pressure and the return temperature of the compressor;
- obtaining a pressure drop of an exhaust pipeline of the compressor according to the exhaust temperature and the exhaust pressure of the compressor and the refrigerant flow;
- obtaining a heat leakage of the exhaust pipeline of the compressor according to the outdoor environment temperature, the exhaust temperature of the compressor, and the refrigerant flow;
- obtaining the heat exchanger inlet pressure according to the exhaust pressure of the compressor and the pressure drop of the exhaust pipeline;
- obtaining the heat exchanger inlet temperature according to the exhaust temperature of the compressor, the refrigerant flow, and the heat leakage of the exhaust pipeline;
- obtaining the saturation temperature corresponding to the heat exchanger inlet pressure according to the heat exchanger inlet pressure.

In practice, firstly a saturation temperature corresponding to the exhaust pressure of the compressor, that is, the condensation temperature, is calculated according to the exhaust pressure of the compressor, and a saturation temperature corresponding to the return pressure of the compressor, that is, the evaporation temperature, is calculated according to the return pressure of the compressor; and then the refrigerant flow is calculated according to the 10 coefficients of the compressor flow related to the frequency, the exhaust pressure, the return pressure and the return temperature of the compressor, the condensation temperature and the evaporation temperature.

In an embodiment, the calculation formulas of the refrigerant flow are as follows:

m=k1+k2*Te+k3*Tc+k4*Te{circumflex over ( )}2+k5*Te*Tc+K6*Tc{circumflex over ( )}2+k7*Te{circumflex over ( )}3+k8*Te{circumflex over ( )}2*Tc+k9*Te*Tc{circumflex over ( )}2+k1 0*Tc{circumflex over ( )}3

Te=b1/(ln(ps)−b2)−b3

Tc=b1/(ln(pd)−b2)−b3

The calculation formula of the pressure drop of the exhaust pipeline of the compressor is as follows:

dp1=f1(m,Td,pd)=A1*m*exp(B1*Tc)*(Td−Tc)

The calculation formula of the heat leakage of the exhaust pipeline of the compressor is as follows:

Q1=f2(m,Td,T0)=(Td−T0)*A2*m

The calculation formula of the heat exchanger inlet pressure is as follows:

p1=pd−dp1

The calculation formula of the heat exchanger inlet temperature is as follows:

T1=Td−Q1/(m*B2*Tds)

The calculation formula of the saturation temperature corresponding to the heat exchanger inlet pressure is as follows:

T1s=b1/(ln(p1)−b2)−b3

- where m is the refrigerant flow, k1˜k10 are the ten coefficients related to the frequency, the exhaust pressure pd, the return pressure ps and the return temperature Ts of the compressor, Te is the saturation temperature corresponding to the return pressure of the compressor, Tc is the saturation temperature corresponding to the exhaust pressure pd of the compressor, and B1˜B2 and b1˜b3 are refrigerant physical parameters related to the refrigerant type;
- dp1 is the pressure drop of the exhaust pipeline of the compressor, f1(m, Td, pd) is a function related to the exhaust temperature Td and the exhaust pressure pd of the compressor and the refrigerant flow m, and A1˜A2 are parameters related to the structure of the exhaust pipeline;
- Q1 is the heat leakage of the exhaust pipeline of the compressor, and f2(m, Td, TO) is a function related to the outdoor environment temperature TO, the exhaust temperature Td of the compressor, and the refrigerant flow m;
- p1 is the heat exchanger inlet pressure;
- T1 is the heat exchanger inlet temperature;
- T1s is the saturation temperature corresponding to the heat exchanger inlet pressure;
- * is a multiplication operator, {circumflex over ( )} is a exponentiation operator, / is an division operator, ln ( ) is a logarithmic function.

As shown in FIG. 5, in some embodiments, step S303 further includes:

Step S502, determining the refrigerant state at the outlet of the heat exchanger according to the outdoor environment temperature, the operating parameters of the heat exchanger, and the wind speed setting, if the refrigerant at the inlet of the heat exchanger is in an overheating state.

In practice, if the refrigerant at the inlet of the heat exchanger is in the overheating state, then it is possible to further determine the refrigerant state at the outlet of the heat exchanger according to the outdoor environment temperature, the operating parameters of the heat exchanger, and the wind speed setting. The operating parameters of the heat exchanger may include, but are not limited to, an inlet pressure, an outlet pressure, an inlet temperature and an outlet temperature of the heat exchanger, and the like. The inlet pressure, the outlet pressure, the inlet temperature and the outlet temperature of the heat exchanger may be detected by respective pressure sensors and temperature sensors, such as the heat exchanger inlet pressure sensor 31, the heat exchanger outlet pressure sensor 41, the heat exchanger inlet temperature sensor 32, and the heat exchanger outlet temperature sensor 42 shown in FIG. 1 or FIG. 2. In one embodiment, it is possible to calculate the heat exchanger outlet temperature and a saturation temperature corresponding to the heat exchanger outlet pressure according to the outdoor environment temperature, the refrigerant flow, the heat exchanger inlet pressure and inlet temperature, the saturation temperature corresponding to the heat exchanger inlet pressure and the wind speed setting, and then determine the refrigerant state at the outlet of the heat exchanger according to the heat exchanger outlet temperature and the saturation temperature corresponding to the heat exchanger outlet pressure.

As shown in FIG. 7, in some embodiments, step S502 includes the following steps S701 to S703:

At step S701, obtain the heat exchanger outlet temperature and the saturation temperature corresponding to the heat exchanger outlet pressure according to the outdoor environment temperature, the refrigerant flow, the operating parameters of the heat exchanger and the wind speed setting;

At step S702, if the heat exchanger outlet temperature is less than a difference between the saturation temperature corresponding to the heat exchanger outlet pressure and the first preset temperature threshold, then determine that the refrigerant at the outlet of the heat exchanger is in a supercooling state.

At step S703, if the heat exchanger outlet temperature is greater than or equal to the difference between the saturation temperature corresponding to the heat exchanger outlet pressure and the first preset temperature threshold, then determine that the refrigerant at the outlet of the heat exchanger is in a non-supercooling state, and adjust the first operating parameters of the air conditioning system.

In practice, after the heat exchanger outlet temperature and the saturation temperature corresponding to the heat exchanger outlet pressure have been calculated, it is possible to compare the heat exchanger outlet temperature with the difference between the saturation temperature corresponding to the heat exchanger outlet pressure and the first preset temperature threshold, then determine the refrigerant state at the outlet of the heat exchanger according to the comparison result. If the refrigerant at the outlet of the heat exchanger is in the supercooling state, then proceed to the next step, to continue to detect the refrigerant state at the outlet of the high-pressure liquid pipe. If the refrigerant at the inlet of the heat exchanger is in the non-supercooling state, then return to step S301, to continue to adjust the first operating parameters.

In some embodiments, step S701 includes the following steps:

- obtaining a refrigerant pressure drop of the heat exchanger according to the wind speed setting and the refrigerant flow;
- obtaining a heat exchange of the heat exchanger according to the outdoor environment temperature, the wind speed setting, the refrigerant flow, and the heat exchanger inlet pressure and the inlet temperature;
- obtaining the heat exchanger outlet pressure according to the heat exchanger inlet pressure and the refrigerant pressure drop of the heat exchanger;
- obtaining the heat exchanger outlet temperature according to the refrigerant flow, the heat exchange inlet temperature, the heat exchange of the heat exchange and the saturation temperature corresponding to the heat exchanger inlet pressure;
- obtaining the saturation temperature corresponding to the heat exchanger outlet pressure according to the heat exchanger outlet pressure.

In some embodiments, the calculation formula of the refrigerant pressure drop of the heat exchanger is as follows:

dp2=f3(m,F s)=A3*m(c0+c1*Fs)

The calculation formula of the heat exchange of the heat exchanger is as follows:

Q2=f4(m,T1s,F s,T0)=A4*M*[A5+A6*(T1s−T0)]*(c2+c3*Fs)

The calculation formula of the heat exchanger outlet pressure is as follows:

p2=p1−dp2

The calculation formula of the heat exchanger outlet temperature is as follows:

T2=T1−Q2/(m*B2*T1s)

The calculation formula of the saturation temperature corresponding to the heat exchanger outlet pressure is as follows:

T2s=b1/(ln(p2)−b2)−b3

- where dp2 is the refrigerant pressure drop of the compressor, f3(m, Fs) is a function related to the refrigerant flow m and the wind speed setting Fs, A3˜A6 are parameters related to the structure of the heat exchanger, and c0˜c3 are parameters related to the characteristics of the fan of the outdoor unit;
- Q2 is the heat exchange of the heat exchanger, f4(m, T1s, Fs, TO) is a function related to the refrigerant flow m, the saturation temperature T1s corresponding to the heat exchanger inlet pressure, the wind speed setting Fs, and the outdoor environment temperature TO;
- p2 is the heat exchanger outlet pressure;
- T2 is the heat exchanger outlet temperature;
- T2s is the saturation temperature corresponding to the heat exchanger outlet pressure.

As shown in FIG. 5, in some embodiments, step S303 further includes:

- step S503, if the refrigerant at the outlet of the heat exchanger is in the supercooling state, then determining the refrigerant state at the outlet of the high-pressure liquid pipe according to the outdoor environment temperature, the operating parameters of the heat exchanger and the opening degree of the first electronic expansion valve.

In practice, if the refrigerant at the outlet of the heat exchanger is in the supercooling state, then it is possible to further determine the refrigerant state at the outlet of the high-pressure liquid pipe according to the outdoor environment temperature, the operating parameters of the heat exchanger and the opening degree of the first electronic expansion valve. In one embodiment, it is possible to calculate the high-pressure liquid pipe outlet temperature and a saturation temperature corresponding to the high-pressure liquid pipe outlet pressure according to the outdoor environment temperature, the refrigerant flow, the heat exchanger outlet pressure and outlet temperature, the saturation temperature corresponding to the heat exchanger outlet pressure and the opening degree of the first electronic expansion valve, and then determine the refrigerant state at the outlet of the high-pressure liquid pipe according to the high-pressure liquid pipe outlet temperature and the saturation temperature corresponding to the high-pressure liquid pipe outlet pressure.

As shown in FIG. 8, in some embodiments, no matter whether the air conditioning system includes an economizer or not, step S503 includes the following steps S801 and S802:

At S801, obtain the high-pressure liquid pipe outlet temperature and the saturation temperature corresponding to the high-pressure liquid pipe outlet pressure according to the outdoor environment temperature, the refrigerant flow, the operating parameters of the heat exchanger and the opening degree of the first electronic expansion valve;

At S802, if the high-pressure liquid pipe outlet temperature is less than a difference between the saturation temperature corresponding to the high-pressure liquid pipe outlet pressure and the first preset temperature threshold, then determine that the refrigerant at the outlet of the high-pressure liquid pipe is in a supercooling state.

In practice, after the high-pressure liquid pipe outlet temperature and the saturation temperature corresponding to the high-pressure liquid pipe outlet pressure have been calculated, it is possible to compare the high-pressure liquid pipe outlet temperature with the difference between the saturation temperature corresponding to the high-pressure liquid pipe outlet pressure and the first preset temperature threshold, and then determine the refrigerant state at the outlet of the high-pressure liquid pipe according to the comparison result. For an air conditioning system without an economizer, it is possible to determine that the refrigerant at the outlet of the high-pressure liquid pipe is in a supercooling state or in a non-supercooling state according to the high-pressure liquid pipe outlet temperature and the saturation temperature corresponding to the high-pressure liquid pipe outlet pressure. For an air conditioning system with an economizer, it is only possible to determine the supercooling state of the refrigerant at the outlet of the high-pressure liquid pipe according to the high-pressure liquid pipe outlet temperature and the saturation temperature corresponding to the high-pressure liquid pipe outlet pressure, and the non-supercooling state should be determined according to an economizer inlet temperature and an economizer outlet temperature.

In some embodiments, step S801 includes the following steps:

- obtaining a refrigerant pressure drop of the high-pressure liquid pipe according to the refrigerant flow, the heat exchanger outlet temperature and the opening degree of the first electronic expansion valve;
- obtaining a heat leakage of the high-pressure liquid pipe according to the outdoor environment temperature, the refrigerant flow, and the heat exchanger outlet temperature;
- obtaining the high-pressure liquid pipe outlet pressure according to the heat exchanger outlet pressure and the refrigerant pressure drop of the high-pressure liquid pipe;
- obtaining the high-pressure liquid pipe outlet temperature according to the refrigerant flow, the heat exchanger outlet temperature, the saturation temperature corresponding to the heat exchanger outlet pressure and the heat leakage of the high-pressure liquid pipe;
- obtaining the saturation temperature corresponding to the high-pressure liquid pipe outlet pressure according to the high-pressure liquid pipe outlet pressure.

In some embodiments, the calculation formula of the refrigerant pressure drop of the high-pressure liquid pipe is as follows:

dp3=f5(m,T2,EXV)=[A7*m+m/(D0+D1*EXV)]*(B3*T2)

The calculation formula of the heat leakage of the high-pressure liquid pipe is as follows:

Q3=f6(m,T2,T0)=(T2−T0)*A8*m

The calculation formula of the high-pressure liquid pipe outlet pressure is as follows:

p3=p2−dp3

The calculation formula of the high-pressure liquid pipe outlet temperature is as follows:

T3=T2−Q3/(m*B2*T2s)

The calculation formula of the saturation temperature corresponding to the high-pressure liquid pipe outlet pressure is as follows:

T3s=b1/(ln(p3)−b2)−b3

- where dp3 is the refrigerant pressure drop of the high-pressure liquid pipe, f5(m, T2, EXV) is a function related to the refrigerant flow m, the heat exchanger outlet temperature T2 and the opening degree EXV of the first electronic expansion valve, A7˜A8 are parameters related to the structure of the high-pressure liquid pipe, D0˜D1 are parameters related to the characteristics of the first electronic expansion valve, and B3 is a refrigerant physical parameter related to the refrigerant type;
- Q3 is the heat leakage of the high-pressure liquid pipe, and f6(m, T2, T0) is a function related to the refrigerant flow m, the heat exchanger outlet temperature T2 and the outdoor environment temperature T0;
- p3 is the high-pressure liquid pipe outlet pressure;
- T3 is the high-pressure liquid pipe outlet temperature;
- T3s is the saturation temperature corresponding to the high-pressure liquid pipe outlet pressure.

The refrigerant state detection method provided in the embodiments corresponding to FIG. 8 may be applicable to refrigerant state detection for any air conditioning system.

As shown in FIG. 9, in some embodiments, the air conditioning system does not include an economizer, and step S503 further includes the following step S803:

At step S803, if the high-pressure liquid pipe outlet temperature is greater than or equal to the difference between the saturation temperature corresponding to the high-pressure liquid pipe outlet pressure and the first preset temperature threshold, then determine that the refrigerant at the outlet of the high-pressure liquid pipe is in a non-supercooling state.

The refrigerant state detection method provided in the embodiments corresponding to FIG. 9 may be applicable to refrigerant state detection for an air conditioning system that does not include an economizer.

As shown in FIG. 10, in some embodiments, the air conditioning system includes an economizer, and step S303 further includes the following step S504:

At step S504, if the refrigerant at the outlet of the heat exchanger is in the supercooling state, then determine the refrigerant state at the outlet of the high-pressure liquid pipe of the air conditioner outdoor unit according to the economizer inlet temperature and the economizer outlet temperature.

In practice, if the refrigerant at the outlet of the heat exchanger is in the supercooling state, then it is possible to further determine the refrigerant state at the outlet of the high-pressure liquid pipe according to the economizer inlet temperature and the economizer outlet temperature.

In some embodiments, step S504 includes the following steps:

- if a difference between the economizer outlet temperature and the economizer inlet temperature is less than a second preset temperature threshold, then determining that the refrigerant at the outlet of the high-pressure liquid pipe of the air conditioner outdoor unit is in a supercooling state;
- if the difference between the economizer outlet temperature and the economizer inlet temperature is greater than or equal to the second preset temperature threshold, then determining that the refrigerant at the outlet of the high-pressure liquid pipe of the air conditioner outdoor unit is in a non-supercooling state.