Cooling medium control method for multi-connected air conditioning system

Abstract

To control operating parameters of the compressor and ensure stable operation of the air conditioning system, a cooling medium control method for a multi-connected air conditioning system includes: acquiring current operating values of target parameters of the compressor during the operation of the compressor; calculating deviation degrees of the target parameters of the compressor according to the current operating values of the target parameters of the compressor and standard operating ranges of the target parameters of the compressor; and selectively adjusting an opening degree of the outdoor expansion valve or the indoor expansion valve based on the deviation degrees; where the standard operating ranges of the target parameters are operating ranges of the target parameters specified by a normal operating state of the compressor. Here the opening degree of the indoor expansion valve or the outdoor expansion valve is adjusted in real time according to parameters of the compressor.

Claims

1. A cooling medium control method for a multi-connected air conditioning system, the multi-connected air conditioning system comprising a compressor, an outdoor unit, and a plurality of indoor units connected to the outdoor unit, the outdoor unit comprising an outdoor expansion valve, and each of the indoor units comprising an indoor expansion valve, the cooling medium control method comprising the following steps: S110 acquiring current operating values of target parameters of the compressor during the operation of the compressor; S120 calculating deviation degrees of the target parameters of the compressor according to the current operating values of the target parameters of the compressor and standard operating ranges of the target parameters of the compressor; and S130 selectively adjusting an opening degree of the outdoor expansion valve or the indoor expansion valve based on the deviation degrees; wherein the standard operating ranges of the target parameters are operating ranges of the target parameters specified by a normal operating state of the compressor, wherein in step S110, the target parameters comprise a high pressure, a low pressure, and a compression ratio of the compressor, the current operating value of the high pressure being Pd, the current operating value of the low pressure being Ps, and the compression ratio compRate=(Pd+1)/(Ps+1); and in step S120, when C.sub.lower limit≤compRate≤C.sub.upper limit, a deviation degree D.sub.c of the compression ratio is 0; when compRate>C.sub.upper limit, the deviation degree D.sub.c of the compression ratio is calculated according to the following formula: D.sub.c=C.sub.upper limit/compRate−1; and when compRate<C.sub.lower limit, the deviation degree D.sub.c of the compression ratio is calculated according to the following formula: D.sub.c=C.sub.lower limit/compRate−1; wherein C.sub.upper limit is a maximum value in the standard operating range of the compression ratio, and C.sub.lower limit is a minimum value in the standard operating range of the compression ratio.

2. The cooling medium control method for a multi-connected air conditioning system according to claim 1, wherein, in step S120, when Pd.sub.lower limit≤Pd.sub.upper limit, a deviation degree D.sub.pd of the high pressure Pd is 0; when Pd>Pd.sub.upper limit, the deviation degree D.sub.pd of the high pressure Pd is calculated according to the following formula: D.sub.pd=Pd.sub.upper limit/Pd−1; and when Pd<Pd.sub.lower limit, the deviation degree D.sub.pd of the high pressure Pd is calculated according to the following formula: D.sub.pd=Pd.sub.lower limit/Pd−1; wherein Pd.sub.upper limit is a maximum value in the standard operating range of the high pressure, and Pd.sub.lower limit is a minimum value in the standard operating range of the high pressure.

3. The cooling medium control method for a multi-connected air conditioning system according to claim 2, wherein, in step S120, when Ps.sub.lower limit≤Ps.sub.upper limit, a deviation degree D.sub.ps of the low pressure Ps is 0; when Ps>Ps.sub.upper limit, the deviation degree D.sub.ps of the low pressure Ps is calculated according to the following formula: D.sub.ps=Ps.sub.upper limit/Ps−1; and when Ps<Ps.sub.lower limit, the deviation degree D.sub.ps of the low pressure Ps is calculated according to the following formula: D.sub.ps=Ps.sub.lower limit/Ps−1; wherein Ps.sub.upper limit is a maximum value in the standard operating range of the low pressure, and Ps.sub.lower limit is a minimum value in the standard operating range of the low pressure.

4. The cooling medium control method for a multi-connected air conditioning system according to claim 1, wherein, in step S110, the target parameters further comprise an exhaust superheat degree of the compressor, and the current operating value of the exhaust superheat degree is Td; and, in step S120, when Td.sub.lower limit≤Td≤Td.sub.upper limit, a deviation degree D.sub.Td of the exhaust superheat degree Td is 0; when Td>Td.sub.upper limit, the deviation degree D.sub.Td of the exhaust superheat degree Td is calculated according to the following formula: D.sub.Td=Td/Td.sub.upper limit−1; and when Td<Td.sub.lower limit, the deviation degree D.sub.Td of the exhaust superheat degree Td is calculated according to the following formula: D.sub.Td=Td/Td.sub.lower limit−1; wherein Td.sub.upper limit is a maximum value in the standard operating range of the exhaust superheat degree, and Td.sub.lower limit is a minimum value in the standard operating range of the exhaust superheat degree.

5. The cooling medium control method for a multi-connected air conditioning system according to claim 4, wherein, in step S110, the target parameters further comprise an oil temperature superheat degree of the compressor, and the current operating value of the oil temperature superheat degree is Toil; and, in step S120, when Toil.sub.lower limit≤Toil≤Toil.sub.upper limit, a deviation degree D.sub.Toil of the oil temperature superheat degree Toil is 0; when Toil>Toil.sub.upper limit, the deviation degree D.sub.Toil of the oil temperature superheat degree Toil is calculated according to the following formula: D.sub.Toil=Toil/Toil.sub.upper limit−1; and when Toil<Toil.sub.lower limit, the deviation degree D.sub.Toil of the oil temperature superheat degree Toil is calculated according to the following formula: D.sub.Toil=Toil/Toil.sub.lower limit−1; wherein Toil.sub.upper limit is a maximum value in the standard operating range of the oil temperature superheat degree Toil, and Toil.sub.lower limit is a minimum value in the standard operating range of the oil temperature superheat degree Toil.

6. The cooling medium control method for a multi-connected air conditioning system according to claim 5, wherein step S130 comprises: calculating a total deviation degree D.sub.total of the compressor according to the deviation degree D.sub.pd, the deviation degree D.sub.ps, the deviation degree D.sub.c, the deviation degree D.sub.Td, and the deviation degree D.sub.Toil:
D.sub.total=W.sub.pd*D.sub.pd+W.sub.ps*D.sub.ps+W.sub.c*D.sub.c+W.sub.Td*D.sub.Td=W.sub.Toil*D.sub.Toil; wherein W.sub.pd, W.sub.ps, W.sub.c, W.sub.Td and W.sub.Toil are weight values set in advance for the high pressure, low pressure, compression ratio, exhaust superheat degree and oil temperature superheat degree of the compressor respectively; and selectively adjusting the opening degree of the outdoor expansion valve or the indoor expansion valve according to the total deviation degree D.sub.total.

7. The cooling medium control method for a multi-connected air conditioning system according to claim 6, wherein selectively adjusting the opening degree of the outdoor expansion valve or the indoor expansion valve according to the total deviation degree D.sub.total comprises: when D.sub.total>L.sub.up, increasing the opening degree of the indoor expansion valve or the opening degree of the outdoor expansion valve by P.sub.ls=P.sub.current*(D.sub.total−L.sub.up); when D.sub.total<L.sub.down, decreasing the opening degree of the indoor expansion valve or the opening degree of the outdoor expansion valve by P.sub.ls=P.sub.current*(L.sub.down−D.sub.total); and when L.sub.down≤D.sub.total≤L.sub.up, not adjusting the opening degree of the indoor expansion valve or the outdoor expansion valve; wherein P.sub.current is the current opening degree of the indoor expansion valve or the outdoor expansion valve, L.sub.Up is a preset upper limit threshold of the deviation degree, and L.sub.down is a preset lower limit threshold of the deviation degree.

8. The cooling medium control method for a multi-connected air conditioning system according to claim 7, wherein the preset upper limit threshold L.sub.up of the deviation degree is 0.1, and the preset lower limit threshold L.sub.down of the deviation degree is −0.08; and/or the total deviation degree D.sub.total of the compressor is calculated once every other preset time.

9. The cooling medium control method for a multi-connected air conditioning system according to claim 1, wherein when the multi-connected air conditioning system is operating in a cooling mode, only the opening degree of the indoor expansion valve is adjusted; and when the multi-connected air conditioning system is operating in a heating mode, only the opening degree of the outdoor engine expansion valve is adjusted; and/or an increase amount of the opening degree of the indoor expansion valve or the outdoor expansion valve does not exceed 5% of the current opening degree of the indoor expansion valve or the outdoor expansion valve; and a decrease amount of the opening degree of the indoor expansion valve or the outdoor expansion valve does not exceed 5% of the current opening degree of the indoor expansion valve or the outdoor expansion valve.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a main flowchart of a cooling medium control method for a multi-connected air conditioning system according to the present disclosure.

DETAILED DESCRIPTION

(2) In order to make the embodiments, technical solutions and advantages of the present disclosure be more obvious, the technical solutions of the present disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments as described are some embodiments of the present disclosure, not all of them. It should be understood by those skilled in the art that these embodiments are only used to explain the technical principles of the present disclosure, and are not intended to limit the scope of protection of the present disclosure.

(3) A multi-connected air conditioning system typically includes a compressor, an outdoor unit, and a plurality of indoor units connected to the outdoor unit. The outdoor unit includes an outdoor expansion valve, and each of the indoor units includes an indoor expansion valve. It may be understood by those skilled in the art that the circulation amount of the cooling medium may generally be adjusted by the indoor expansion valve or the outdoor expansion valve. During cooling operation, the opening degree of the indoor expansion valve is adjusted; and during heating operation, the opening degree of the outdoor expansion valve is adjusted. In the present disclosure, the opening degree of the indoor expansion valve or the outdoor expansion valve is adjusted in real time mainly according to the operating parameters of the compressor so that the circulation amount of the cooling medium of the air conditioning system is dynamically adjusted, thus controlling the compressor to operate in a normal range and ensuring a stable and reliable operation of the multi-connected air conditioning system.

(4) Specifically, referring to FIG. 1, a main flowchart of a cooling medium control method for a multi-connected air conditioning system according to the present disclosure is illustrated. As shown in FIG. 1, the cooling medium control method for the multi-connected air conditioning system according to the present disclosure includes the following steps: S110. acquiring current operating values of target parameters of a compressor during the operation of the compressor; S120. calculating deviation degrees of the target parameters of the compressor according to the current operating values of the target parameters of the compressor and standard operating ranges of the target parameters of the compressor; and S130. selectively adjusting an opening degree of an outdoor expansion valve or an indoor expansion valve based on the deviation degrees; wherein the standard operating ranges of the target parameters are operating ranges of the target parameters specified by a normal operating state of the compressor. The cooling medium control method according to the present disclosure will be described in detail below with reference to a specific embodiment.

(5) According to the specification of the compressor, the operating range of the compressor is controlled by a high pressure, a low pressure, a compression ratio, an exhaust superheat degree and an oil temperature superheat degree. In order to ensure the normal operation of the air conditioning system, these parameters must be controlled to be within specified ranges. In actual operation, these parameters affect each other, and the circulation amount of the cooling medium plays a decisive role.

(6) In this embodiment, the target parameters in step S110 may be the high pressure (the current operating value thereof being denoted as Pd), the low pressure (the current operating value thereof being denoted as Ps), the compression ratio (the current operating value thereof being denoted as compRate), the exhaust superheat degree (the current operating value thereof being denoted as Td) and the oil temperature superheat degree (the current operating value thereof being denoted as Toil). For the sake of clarity, the standard operating ranges and parameter descriptions of the above target parameters are shown in Table 1 below:

(7) TABLE-US-00001 TABLE 1 standard operating target parameter ranges description of target parameter high pressure Pd 17-38 kg low pressure Ps 3-10 kg compression ratio 2-8 compRate = (Pd + 1)/(Ps + 1) compRate exhaust superheat 25-60° C. Td = exhaust temperature − degree Td saturation temperature corresponding to high pressure Pd oil temperature 15-50° C. Toil = oil temperature − superheat degree saturation temperature Toil corresponding to high pressure Pd

(8) In step S120, the deviation degree of each of the above target parameters is calculated. It can be understood by those skilled in the art that in the above target parameters, control directions of the high pressure, the low pressure, and the compression ratio are consistent. If the values of the high pressure, the low pressure, and the compression ratio are too large, then the opening degree of the indoor expansion valve or the outdoor expansion valve is decreased, and if the values of the high pressure, the low pressure, and the compression ratio are too small, then the opening degree of the indoor expansion valve or the outdoor expansion valve is increased.

(9) Taking the calculation of the deviation degree of the low pressure as an example, the current operating value of the low pressure of the compressor is Ps; as shown in Table 1, the standard operating range of the low pressure is 3-10 Kg, a maximum value Ps.sub.upper limit in the standard operating range thereof is 10 kg, and a minimum value Ps.sub.lower limit in the standard operating range thereof is 3 kg. When Ps.sub.lower limit≤Ps≤Ps.sub.upper limit, the deviation degree D.sub.ps of the low pressure is 0; when Ps>Ps.sub.upper limit, the deviation degree D.sub.ps of the low pressure is calculated according to the following formula: D.sub.ps=Ps.sub.upper limit/Ps−1; and when Ps<Ps.sub.lower limit, the deviation degree D.sub.ps of the low pressure Ps is calculated according to the following formula: D.sub.ps=P.sub.lower limit/Ps−1. For example, when the current operating value of the low pressure of the compressor Ps=11 kg, the deviation degree D.sub.ps=10/11−1=−0.09; and when the current operating value of the low pressure of the compressor Ps=2.5 kg, the deviation degree D.sub.ps=3/2.5−1=0.2.

(10) Similarly, the current operating value of the high pressure is Pd; as shown in Table 1, a maximum value Pd.sub.upper limit in the standard operating range thereof is 38 kg, and a minimum value Pd.sub.lower limit in the standard operating range thereof is 17 kg. When Pd.sub.lower limit≤Pd≤Pd.sub.upper limit, the deviation degree D.sub.pd of the high pressure Pd is 0; when Pd>Pd.sub.upper limit, the deviation degree D.sub.pd of the high pressure Pd is calculated according to the following formula: D.sub.pd=Pd.sub.upper limit/Pd-1; and when Pd<Pd.sub.lower limit, the deviation degree D.sub.pd of the high pressure Pd is calculated according to the following formula: D.sub.pd=Pd.sub.lower limit/Pd-1.

(11) Similarly, the current compression ratio of the compressor is compRate; as shown in Table 1, a maximum value C.sub.upper limit in the standard operating range of the compression ratio is 8, and a minimum value C.sub.lower limit is 2. When C.sub.lower limit≤compRate≤C.sub.upper limit, the deviation degree D.sub.c of the compression ratio is 0; when compRate>C.sub.upper limit, the deviation degree D.sub.c of the compression ratio is calculated according to the following formula: D.sub.c=C.sub.upper limit/compRate-1; and when compRate<C.sub.lower limit, the deviation degree D.sub.c of the compression ratio is calculated according to the following formula: D.sub.c=C.sub.lower limit/compRate-1.

(12) It can be understood by those skilled in the art that in the above target parameters, control directions of the exhaust superheat degree Td and the oil temperature superheat degree Toil are consistent. If the exhaust superheat degree Td and the oil temperature superheat degree Toil are too large, then the opening degree of the indoor expansion valve or the outdoor expansion valve is increased, and if the exhaust superheat degree Td and the oil temperature superheat degree Toil are too small, then the opening degree of the indoor expansion valve or the outdoor expansion valve is decreased.

(13) Taking the calculation of the deviation degree of the exhaust superheat degree as an example, the current operating value of the exhaust superheat degree of the compressor is Td; as shown in Table 1, the standard operating range of the exhaust superheat degree is 25-60° C., a maximum value Td.sub.upper limit in the standard operating range thereof is 60° C., and a minimum value Td.sub.lower limit in the standard operating range thereof is 25° C. When Td.sub.lower limit≤Td≤Td.sub.upper limit, the deviation degree D.sub.Td of the exhaust superheat degree is 0; when Td>Td.sub.upper limit, the deviation degree D.sub.Td of the exhaust superheat degree is calculated according to the following formula: D.sub.Td=Td/Td.sub.upper limit−1; and when Td<Td.sub.lower limit, the deviation degree D.sub.Td of the exhaust superheat degree Td is calculated according to the following formula: D.sub.Td=Td/Td.sub.lower limit−1. For example, when Td=63° C., D.sub.Td=63/60−1=0.05; and when Td=17° C., D.sub.Td=17/25−1=−0.32.

(14) Similarly, the current operating value of the oil temperature superheat degree of the compressor is Toil; as shown in Table 1, the standard operating range of the oil temperature superheat degree is 15-50° C., a maximum value Toil.sub.upper limit in the standard operating range thereof is 50° C., and a minimum value Toil.sub.lower limit in the standard operating range thereof is 15° C. When Toil.sub.lower limit≤Toil≤Toil.sub.upper limit, the deviation degree D.sub.Toil of the oil temperature superheat degree is 0; when Toil>Toil.sub.upper limit, the deviation degree of the oil temperature superheat degree Toil is calculated according to the following formula: D.sub.Toil=Toil/Toil.sub.upper limit−1; and when Toil<Toil.sub.lower limit, the deviation degree D.sub.Toil of the oil temperature superheat degree is calculated according to the following formula: D.sub.Toil=Toil/Toil.sub.lower limit−1.

(15) In step S130, the step of selectively adjusting an opening degree of the outdoor expansion valve or the indoor expansion valve based on the deviation degrees specifically includes: calculating a total deviation degree D.sub.total of the compressor according to the deviation degrees of the above target parameters (i.e., the deviation degree D.sub.pd, the deviation degree D.sub.ps, the deviation degree D.sub.c, the deviation degree D.sub.Td, and the deviation degree D.sub.Toil). D.sub.total=W.sub.pd*D.sub.pd+W.sub.ps*D.sub.ps+W.sub.c*D.sub.c+W.sub.Td*D.sub.Td+W.sub.Toil*D.sub.Toil; wherein W.sub.pd, W.sub.ps, W.sub.c, W.sub.Td and W.sub.Toil are weight values set in advance for the high pressure, low pressure, compression ratio, exhaust superheat degree and oil temperature superheat degree of the compressor respectively. The weight of each target parameter may be set according to the specifications or recommendations of the compressor manufacturer (Table 2 below gives specific examples of a set of weights). Those skilled in the art may calculate the total deviation degree D.sub.total of the compressor once every other preset time, for example, every other 10 seconds or other suitable time interval, and the preset time may be set by those skilled in the art flexibly.

(16) Then, the opening degree of the outdoor expansion valve or the indoor expansion valve is selectively adjusted according to the total deviation degree of the compressor. Specifically, when D.sub.total>L.sub.up, the opening degree of the indoor expansion valve or the opening degree of the outdoor expansion valve is increased by P.sub.ls=P.sub.current*(D.sub.total−L.sub.up) so as to increase the circulation amount of the cooling medium; when D.sub.total<L.sub.down, the opening degree of the indoor expansion valve or the opening degree of the outdoor expansion valve is decreased by P.sub.ls=P.sub.current*(L.sub.down−D.sub.total) so as to decrease the circulation amount of the cooling medium; and when L.sub.down≤D.sub.total≤L.sub.up, the opening degree of the indoor expansion valve or the outdoor expansion valve is not adjusted; wherein P.sub.current is the current opening degree of the indoor expansion valve or the outdoor expansion valve, L.sub.up is a preset upper limit threshold of the deviation degree, and L.sub.down is a preset lower limit threshold of the deviation degree. It should be noted that the preset upper limit threshold L.sub.up and the preset lower limit threshold L.sub.down of the deviation degree may be set by those skilled in the art through experiments. As an example, the upper limit threshold L.sub.up may be set to 0.1, and the lower limit threshold L.sub.down may be set to −0.08.

(17) In order to ensure the stability of the air conditioning system without frequent fluctuations, limit values may be set for the adjustment of the opening degrees of the indoor expansion valve and the outdoor expansion valve. For example, the increase amount of the opening degree of the indoor expansion valve or the outdoor expansion valve does not exceed 5% of the current opening degree of the indoor expansion valve or the outdoor expansion valve; and the decrease amount of the opening degree of the indoor expansion valve or the outdoor expansion valve does not exceed 5% of the current opening degree of the indoor expansion valve or the outdoor expansion valve.

(18) As an example, referring to Table 2, the weight of each target parameter and the deviation degree of each target parameter in an embodiment is shown:

(19) TABLE-US-00002 TABLE 2 target parameter weight deviation degree high pressure 0.2 −0.08 low pressure 0.2 0.27 exhaust superheat 0.3 0.25 degree oil temperature 0.15 0.08 superheat degree compression ratio 0.15 −0.04

(20) When the multi-connected air conditioning system is operating in a cooling mode, only the opening degree of the indoor expansion valve is adjusted. According to the data in Table 2 above, the total deviation degree of the compressor D.sub.total=0.2*(−0.08)+0.2*0.27+0.3*0.25+0.15*0.08+0.15*(−0.04)=0.12. Since 0.12>0.1 (which is the set upper limit threshold L.sub.up), the opening degree of the indoor expansion valve needs to be increased. If five indoor units are connected in the multi-connected air conditioning system, the current opening degree of the indoor expansion valve of each indoor unit is P.sub.current1=115, P.sub.current2=120, P.sub.current3=132, P.sub.current4=108, and P.sub.current5=145; and the opening degree of the indoor expansion valve of each indoor unit is increased by P.sub.ls1=P.sub.current1*(D.sub.total−L.sub.up)=115*(0.12−0.1)≈2, P.sub.ls2=P.sub.current2*(D.sub.total−L.sub.up)=120*(0.12−0.1)≈2, P.sub.ls3=P.sub.current3*(D.sub.total−L.sub.up)=132*(0.12−0.1)≈3, P.sub.ls4=P.sub.current4*(D.sub.total−L.sub.up)=108*(0.12−0.1)≈2, and P.sub.ls5=P.sub.current5*(D.sub.total−L.sub.up)=145*(0.12−0.1)≈3. It should be noted that the increase amount of the opening degree of the indoor expansion valve is rounded to an integer, and the unit of the opening degree of the indoor expansion valve may be one circle, two circles, or other measurement units.

(21) When the multi-connected air conditioning system is operating in a heating mode, only the opening degree of the outdoor expansion valve is adjusted. For example, when the total deviation degree of the compressor D.sub.total=−0.16, the set lower limit threshold L.sub.down is −0.08. Since−0.16<−0.08, the opening degree of the outdoor expansion valve needs to be decreased. If the opening degree of the outdoor expansion valve is 150, the opening degree of the outdoor expansion valve is decreased by P.sub.ls=P.sub.current*(L.sub.down−D.sub.total)=150*(−0.08+0.16)=12. Since the decrease amount of the opening degree of the outdoor expansion valve is limited to no more than 5% of the current opening degree, namely, no more than 150*5%=7.5, the integer obtained after rounding is 8. In this case, it is only necessary to decrease the opening degree of the outdoor expansion valve by eight. The unit of the opening degree of the outdoor expansion valve may be one circle, two circles or other measurement units.

(22) As described above, in the present disclosure, the opening degree of the indoor expansion valve or the outdoor expansion valve is adjusted in real time according to the operating parameters of the compressor, so that the circulation amount of the cooling medium of the air conditioning system is dynamically adjusted, thus controlling the compressor to operate in a normal range and ensuring a stable and reliable operation of the multi-connected air conditioning system.

(23) Heretofore, the technical solutions of the present disclosure have been described in connection with the preferred embodiments shown in the drawings, but it can be easily understood by those skilled in the art that the scope of protection of the present disclosure is obviously not limited to these specific embodiments. Those skilled in the art can make equivalent changes or replacements to the related technical features without departing from the principle of the present disclosure. The technical solutions after the modification or replacement will fall within the scope of protection of the present disclosure.