Multi-split heating operation electronic expansion valve minimum opening degree cooperative adjustment method and multi-split heating operation electronic expansion valve minimum opening degree cooperative adjustment system

Abstract

The invention relates to the field of automatic control of refrigerant circulating systems, and provides a method and a system for cooperatively adjusting the minimum opening degree of a heating operation electronic expansion valve of a multi-split air conditioner in order to accurately evaluate the refrigerant flow balance condition of an indoor unit and effectively reduce system resistance caused by a fixed minimum opening degree value. Whether the refrigerant flow of the indoor unit is balanced or not is evaluated according to the supercooling degree difference index, if the supercooling degree difference is large, it is proved that the refrigerant flow of the indoor unit is unbalanced, and at the moment, the refrigerant flow of the indoor unit is balanced as much as possible by reducing the minimum opening degree of an expansion valve; if the difference degree is small, the refrigerant flow of the indoor unit is relatively balanced; on the premise that the refrigerant flow of the indoor unit is balanced, the pipeline resistance is reduced by increasing the minimum opening degree of the expansion valve, and therefore the energy efficiency is improved.

Description

Technical Field

[0001] The present invention relates to the field of automatic control of refrigerant circulation systems, and in particular to a method and system for coordinated regulation of the minimum opening of electronic expansion valves in heating operation of a multi-split machine. Background Art

[0002] During the multi-split heating operation, the refrigerant flow of each indoor unit is balanced by controlling the electronic expansion valve of the indoor unit. The minimum opening is usually set to a fixed value to ensure the refrigerant flow of the indoor unit. In order to meet the needs of refrigerant flow balance of each indoor unit under different installation conditions, the fixed value is designed to be relatively low. When operating under certain working conditions, the unbalanced refrigerant flow is not serious. When some indoor units are operating, there is a large refrigerant flow, but the opening of the indoor units is closed to the minimum opening. The system refrigerant operation resistance increases, the exhaust temperature increases, and the energy consumption to overcome the resistance of the electronic expansion valve increases, and the system reliability decreases.

[0003] The existing technology dynamically adjusts the indoor subcooling target value in response to the increase in exhaust temperature, but this method cannot comprehensively evaluate the refrigerant balance of the indoor unit, and cannot solve the problem of small opening of the electronic expansion valve caused by a fixed minimum opening value and increased energy consumption caused by increased pipe resistance in the refrigeration system. Summary of the invention

[0004] In order to accurately evaluate the refrigerant flow balance of the indoor unit and effectively reduce the system resistance caused by the fixed minimum opening value, the present application provides a method and system for coordinated adjustment of the minimum opening of the electronic expansion valve of a multi-split heating operation.

[0005] The technical solution adopted by the present invention to solve the above problems is:

[0006] A method for coordinating the minimum opening of an electronic expansion valve in a multi-split heating system, comprising:

[0007] Step 1: Calculate the subcooling degree difference index SCD at preset intervals, SCD = σ / μ, σ is the standard deviation of the subcooling degrees of all indoor units, and μ is the mean of the subcooling degrees of all indoor units;

[0008] Step 2: If SCD is greater than K1, then β = β0-α·(SCD-K1);

[0009] If SCD is less than K2, then β = β0 + γ·(K2-SCD);

[0010] Wherein, K1 and K2 are preset thresholds, and K1 is greater than K2, β is the minimum opening of the indoor unit expansion valve after adjustment, β0 is the current minimum opening of the indoor unit expansion valve, and α and γ are preset parameters;

[0011] Step 3: Detect the minimum opening of all indoor unit expansion valves. If it is detected that the minimum opening of a certain indoor unit expansion valve is less than β, adjust the minimum opening of the indoor unit expansion valve to β.

[0012] Furthermore, the value ranges of K1 and K2 are [0.2, 0.5] and [0.1, 0.4] respectively.

[0013] Furthermore, the value ranges of α and γ are both [0.1, 0.2].

[0014] Furthermore, the preset time is 60s.

[0015] Furthermore, step 2 also includes: if β<β_min, then β is set to β_min, where β_min is a preset minimum opening threshold.

[0016] Furthermore, the indoor unit subcooling degree SC=T_sat-T_out, T_sat is the condensation saturation temperature, and T_out is the evaporator outlet temperature.

[0017] The multi-split heating operation electronic expansion valve minimum opening coordinated adjustment system includes:

[0018] Temperature collection unit: used to collect the evaporator outlet temperature;

[0019] Condensation saturation temperature acquisition unit: used to obtain condensation saturation temperature;

[0020] Subcooling degree difference index calculation unit: calculate the indoor unit subcooling degree according to the evaporator outlet temperature and the condensing saturation temperature, and calculate the subcooling degree difference index SCD according to the subcooling degree of each indoor unit, SCD = σ / μ, σ is the standard deviation of the subcooling degree of all indoor units, and μ is the mean value of the subcooling degree of all indoor units;

[0021] Minimum opening calculation unit: calculates the minimum opening according to SCD and preset thresholds K1 and K2, K1 is greater than K2;

[0022] If SCD is greater than K1, then β = β0-α·(SCD-K1);

[0023] If SCD is less than K2, then β = β0 + γ·(K2-SCD);

[0024] β is the minimum opening degree of the indoor unit expansion valve after adjustment, β0 is the current minimum opening degree of the indoor unit expansion valve, and α and γ are preset parameters;

[0025] Opening adjustment unit: detect the minimum opening of all indoor unit expansion valves. If it is detected that the minimum opening of a certain expansion valve is less than β, the minimum opening of the expansion valve is adjusted to β.

[0026] Compared with the prior art, the present invention has the following beneficial effects: the subcooling difference index is used to evaluate whether the refrigerant flow of the indoor unit is balanced. If the subcooling difference is large, it proves that the refrigerant flow of the indoor unit is unbalanced. At this time, the refrigerant flow of the indoor unit can be balanced as much as possible by reducing the minimum opening of the expansion valve; if the difference is small, the refrigerant flow of the indoor unit is relatively balanced; under the premise that the refrigerant flow of the indoor unit is balanced, the pipeline resistance is reduced by increasing the minimum opening of the expansion valve, thereby improving energy efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a flow chart of the method for coordinated regulation of the minimum opening of the electronic expansion valve in the heating operation of a multi-split unit;

[0028] Figure 2 This is the architecture diagram of the coordinated regulation system for the minimum opening degree of the electronic expansion valve in the multi-split heating operation. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0030] like Figure 1 As shown, the method for coordinated regulation of the minimum opening degree of the electronic expansion valve of the multi-split heating machine includes:

[0031] Step 1: Calculate the subcooling difference index SCD every preset time, SCD = σ / μ, σ is the standard deviation of the subcooling of all indoor units, μ is the mean of the subcooling of all indoor units; Indoor unit subcooling SC = T_sat-T_out, T_sat is the condensing saturation temperature, T_out is the evaporator outlet temperature. The condensing saturation temperature T_sat can be converted by the condensing pressure P_cond. In this embodiment, the subcooling difference index is calculated every 60s, and the specific value of the preset time can also be selected according to actual needs.

[0032] Taking ten indoor units as an example, the indoor unit subcooling degree is shown in the following table:

[0033] Indoor unit number Subcooling degree SC_i(℃) EV1 6.8 EV2 7.2 EV3 5.5 EV4 7.5 EV5 6.9 EV6 7 EV7 8 EV8 6.7 EV9 7.1 EV10 6.5

[0034] Mean μ = (6.8 + 7.2 + 5.5 + 7.5 + 6.9 + 7.0 + 8.0 + 6.7 + 7.1 + 6.5) / 10 = 6.92 ° C;

[0035] Standard deviation σ=√[Σ(SC_i-μ)2 / (n-1)]=0.87℃;

[0036] SCD=σ / μ=0.87 / 6.92≈0.126.

[0037] The subcooling difference index is used to evaluate whether the refrigerant flow of the indoor unit is balanced. Under the premise that the refrigerant flow of the indoor unit is balanced, increasing the minimum opening of the expansion valve can reduce the pipeline resistance and thus improve energy efficiency.

[0038] Step 2: If SCD is greater than K1, then β = β0-α·(SCD-K1);

[0039] If SCD is less than K2, then β = β0 + γ·(K2-SCD);

[0040] Among them, K1 and K2 are preset thresholds, and K1 is greater than K2, β is the minimum opening of the indoor unit expansion valve after adjustment, β0 is the current minimum opening of the indoor unit expansion valve, and α and γ are preset parameters; when SCD is greater than K1, it indicates that the indoor unit refrigerant flow is unbalanced. At this time, the indoor unit refrigerant flow is balanced as much as possible by reducing the minimum opening of the expansion valve. When SCD is less than K2, it indicates that the indoor unit refrigerant flow is relatively balanced. The pipeline resistance can be reduced by increasing the minimum opening of the expansion valve to improve energy efficiency. When SCD is in the range of [K2, K1], the current opening does not need to be adjusted. Among them, the optimal value ranges of K1 and K2 are [0.2, 0.5] and [0.1, 0.4], respectively, and the optimal values ​​of K1 and K2 are 0.5 and 0.1, respectively; the optimal value ranges of α and γ are [0.1, 0.2], and the optimal values ​​of α and γ are 0.1 and 0.2, respectively, allowing for differential design of the two. The above parameters are executed in percentage based on the expansion valve opening. If absolute steps are used, α and γ are the percentage execution coefficient × the number of expansion valve full opening steps.

[0041] Step 3: Detect the minimum opening of all indoor unit expansion valves. If it is detected that the minimum opening of a certain indoor unit expansion valve is less than β, adjust the minimum opening of the indoor unit expansion valve to β.

[0042] Furthermore, step 2 also includes: if β<β_min, then β is set to β_min, where β_min is a preset minimum opening threshold.

[0043] Correspondingly, this embodiment also provides a multi-split heating operation electronic expansion valve minimum opening coordinated adjustment system, such as Figure 2 As shown, including:

[0044] Temperature collection unit: used to collect the evaporator outlet temperature;

[0045] Condensation saturation temperature acquisition unit: used to obtain condensation saturation temperature;

[0046] Subcooling degree difference index calculation unit: calculate the indoor unit subcooling degree according to the evaporator outlet temperature and the condensing saturation temperature, and calculate the subcooling degree difference index SCD according to the subcooling degree of each indoor unit, SCD = σ / μ, σ is the standard deviation of the subcooling degree of all indoor units, and μ is the mean value of the subcooling degree of all indoor units;

[0047] Minimum opening calculation unit: calculates the minimum opening according to SCD and preset thresholds K1 and K2, K1 is greater than K2;

[0048] If SCD is greater than K1, then β = β0-α·(SCD-K1);

[0049] If SCD is less than K2, then β = β0 + γ·(K2-SCD);

[0050] β is the minimum opening degree of the indoor unit expansion valve after adjustment, β0 is the current minimum opening degree of the indoor unit expansion valve, and α and γ are preset parameters;

[0051] Opening adjustment unit: detect the minimum opening of all indoor unit expansion valves. If it is detected that the minimum opening of a certain expansion valve is less than β, the minimum opening of the expansion valve is adjusted to β.

Claims

1. A method for coordinating the minimum opening of an electronic expansion valve in a multi-unit heating operation, characterized in that: include: Step 1: Calculate the subcooling degree difference index SCD at preset intervals, SCD = σ / μ, σ is the standard deviation of the subcooling degrees of all indoor units, and μ is the mean of the subcooling degrees of all indoor units; Step 2: If SCD is greater than K1, then β = β0-α·(SCD-K1); If SCD is less than K2, then β = β0 + γ·(K2-SCD); Wherein, K1 and K2 are preset thresholds, and K1 is greater than K2, β is the minimum opening of the indoor unit expansion valve after adjustment, β0 is the current minimum opening of the indoor unit expansion valve, and α and γ are preset parameters; Step 3: Detect the minimum opening of all indoor unit expansion valves. If it is detected that the minimum opening of a certain indoor unit expansion valve is less than β, adjust the minimum opening of the indoor unit expansion valve to β.

2. The method for coordinated regulation of the minimum opening degree of the electronic expansion valve in the heating operation of a multi-unit heat exchanger according to claim 1 is characterized in that: The value ranges of K1 and K2 are [0.2, 0.5] and [0.1, 0.4] respectively.

3. The method for coordinated regulation of the minimum opening degree of the electronic expansion valve in the heating operation of a multi-unit heat exchanger according to claim 2 is characterized in that: The value range of α and γ is [0.1, 0.2].

4. The method for coordinated regulation of the minimum opening degree of electronic expansion valves in heating operation of a multi-unit heat exchanger according to claim 1 is characterized in that: The default time is 60s.

5. The method for coordinated regulation of the minimum opening degree of electronic expansion valves in heating operation of a multi-unit heat exchanger according to claim 1 is characterized in that: Step 2 also includes: if β<β_min, then β takes β_min, where β_min is a preset minimum opening threshold.

6. The method for coordinated regulation of the minimum opening degree of electronic expansion valves in heating operation of a multi-unit heat exchanger according to claim 1, characterized in that: Indoor unit subcooling SC = T_sat-T_out, T_sat is the condensation saturation temperature, T_out is the evaporator outlet temperature.

7. A coordinated regulation system for the minimum opening of electronic expansion valves in multi-unit heating operation, characterized in that: include: Temperature collection unit: used to collect the evaporator outlet temperature; Condensation saturation temperature acquisition unit: used to obtain condensation saturation temperature; Subcooling degree difference index calculation unit: calculate the indoor unit subcooling degree according to the evaporator outlet temperature and the condensing saturation temperature, and calculate the subcooling degree difference index SCD according to the subcooling degree of each indoor unit, SCD = σ / μ, σ is the standard deviation of the subcooling degree of all indoor units, and μ is the mean value of the subcooling degree of all indoor units; Minimum opening calculation unit: calculates the minimum opening according to SCD and preset thresholds K1 and K2, K1 is greater than K2; If SCD is greater than K1, then β = β0-α·(SCD-K1); If SCD is less than K2, then β = β0 + γ·(K2-SCD); β is the minimum opening degree of the indoor unit expansion valve after adjustment, β0 is the current minimum opening degree of the indoor unit expansion valve, and α and γ are preset parameters; Opening adjustment unit: detect the minimum opening of all indoor unit expansion valves. If it is detected that the minimum opening of a certain expansion valve is less than β, the minimum opening of the expansion valve is adjusted to β.

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