Air conditioning systems and their control methods

Abstract

This invention relates to the field of air conditioning technology, specifically providing an air conditioning system and its control method, which at least solves the problem of uneven refrigerant distribution among outdoor units in existing multi-split outdoor unit air conditioning systems. The air conditioning system includes indoor units and outdoor units, with each outdoor unit comprising multiple outdoor units connected in parallel. The control method includes: acquiring the current low-pressure and current subcooling of each outdoor unit; comparing the current low-pressure of each outdoor unit with a corresponding first preset pressure threshold, and comparing the current subcooling of each outdoor unit with a corresponding first preset subcooling threshold, wherein the first preset pressure threshold is determined based on the current low-pressure of the remaining outdoor units, and the first preset subcooling threshold is determined based on the current subcooling of the remaining outdoor units; based on the comparison results, determining whether each outdoor unit is short of refrigerant, and executing a corresponding refrigerant distribution strategy according to the determination result. This invention is beneficial for promoting a balanced distribution of refrigerant flow among the outdoor units.

Description

Technical Field

[0001] This invention relates to the field of air conditioning technology, and specifically provides an air conditioning system and its control method. Background Technology

[0002] In large-scale cooling demand scenarios, such as shopping malls, office buildings, and villas, multiple indoor units are typically required to meet the heat exchange needs of multiple areas. When a multi-split indoor unit uses only a single outdoor unit, it is often difficult to meet the heat exchange requirements of the entire area. However, by using multiple outdoor units connected in parallel and then connected to the indoor units, the cooling capacity limit of a single outdoor unit can be effectively exceeded, thereby expanding the large-capacity application range of the multi-split system.

[0003] However, in the case of multiple outdoor units connected in parallel, in addition to ensuring uniform refrigerant distribution among indoor units in different operating states, it is also necessary to ensure balanced refrigerant flow distribution among multiple outdoor units connected in parallel. If the refrigerant distribution among multiple outdoor units is uneven, it can easily lead to system reliability risks, and at the same time affect the cooling effect of the unit, ultimately resulting in a double decline in overall cooling performance and operational stability. Summary of the Invention

[0004] The present invention aims to solve the above-mentioned technical problems, namely, to at least solve the problem of uneven refrigerant distribution among outdoor units in existing multi-split outdoor unit air conditioning systems.

[0005] In a first aspect, the present invention provides a control method for an air conditioning system, the air conditioning system including an indoor unit and an outdoor unit, the outdoor unit including a plurality of outdoor units connected in parallel, the control method including: acquiring the current low pressure and current subcooling degree of each outdoor unit; comparing the current low pressure of each outdoor unit with a corresponding first preset pressure threshold, and comparing the current subcooling degree of each outdoor unit with a corresponding first preset subcooling degree threshold, wherein the first preset pressure threshold is determined based on the current low pressure of the remaining outdoor units, and the first preset subcooling degree threshold is determined based on the current subcooling degree of the remaining outdoor units; based on the comparison results, determining whether each outdoor unit is short of refrigerant, and causing the air conditioning system to execute a corresponding refrigerant distribution strategy according to the determination results.

[0006] Compared to the traditional fixed threshold judgment mode, this invention adopts a dynamic threshold setting mechanism. By comparing the current low pressure and current subcooling of each outdoor unit with a preset threshold determined based on the real-time operating status of the other outdoor units, it achieves accurate identification of refrigerant shortage status. This effectively avoids the risk of misjudgment or omission caused by fluctuations in operating conditions in the traditional mode, ensuring the timeliness and accuracy of the refrigerant distribution strategy. In turn, it promotes the balanced distribution of refrigerant flow among the outdoor units, drives the overall cooling efficiency of the system, and effectively avoids the decrease in cooling effect and system reliability risk caused by uneven refrigerant distribution when multiple outdoor units are connected in parallel. This provides a core guarantee for the efficient and stable operation of multi-split air conditioning systems.

[0007] In some feasible implementations of the control method for the air conditioning system described above, the process of determining the first preset pressure threshold includes: multiplying the average value of the current low pressure of the remaining outdoor units by a first preset ratio to obtain the first preset pressure threshold; and / or, the process of determining the first preset subcooling threshold includes: multiplying the average value of the current subcooling of the remaining outdoor units by a second preset ratio to obtain the first preset subcooling threshold.

[0008] In some feasible implementations of the above-mentioned air conditioning system control method, the step of "determining whether each outdoor unit is short of refrigerant based on the comparison results" includes: if the current low pressure of the outdoor unit is less than the corresponding first preset pressure threshold, and the current subcooling degree of the outdoor unit is less than the corresponding first preset subcooling degree threshold, then the corresponding outdoor unit is determined to be short of refrigerant; if the current low pressure of the outdoor unit is greater than or equal to the corresponding first preset pressure threshold, then the corresponding outdoor unit is determined to be not short of refrigerant; if the current subcooling degree of the outdoor unit is greater than or equal to the corresponding first preset subcooling threshold, then the corresponding outdoor unit is determined to be not short of refrigerant.

[0009] In some feasible implementations of the above-mentioned air conditioning system control method, the "implementing the corresponding refrigerant distribution strategy of the air conditioning system according to the judgment result" includes: if at least one outdoor unit is short of refrigerant, then increase the outdoor fan speed of the outdoor unit short of refrigerant, decrease the outdoor fan speed of the other outdoor units, and / or increase the expansion valve opening of the outdoor unit short of refrigerant, and decrease the expansion valve opening of the other outdoor units; if all outdoor units are not short of refrigerant, then the air conditioning system maintains the current refrigerant distribution strategy.

[0010] In some feasible embodiments of the control method for the air conditioning system described above, the control method further includes: obtaining the exhaust temperature of the compressor of each outdoor unit before adjusting the refrigerant distribution strategy; and determining the adjustment amount of the outdoor fan speed and the adjustment amount of the expansion valve opening based on the exhaust temperature, the current low pressure, and the current subcooling.

[0011] In some feasible implementations of the above-described air conditioning system control method, after the air conditioning system executes the corresponding refrigerant distribution strategy based on the judgment result, the control method further includes: if the current low pressure of the outdoor unit is greater than or equal to the corresponding second preset pressure threshold and the duration reaches a first duration, and the current subcooling of the outdoor unit is greater than or equal to the corresponding second preset subcooling threshold and the duration reaches a second duration, then the first duration is compared with the first preset duration threshold, and the second duration is compared with the second preset duration threshold; based on the comparison result, it is determined whether to stop executing the current refrigerant distribution strategy; wherein, the second preset pressure threshold is greater than the first preset pressure threshold, and the second preset subcooling threshold is greater than the first preset subcooling threshold.

[0012] In some feasible implementations of the above-mentioned air conditioning system control method, the step of "determining whether to stop executing the current refrigerant allocation strategy based on the comparison result" includes: if the first duration is greater than or equal to the first preset duration threshold, then it is determined to stop executing the current refrigerant allocation strategy; if the second duration is greater than or equal to the second preset duration threshold, then it is determined to stop executing the current refrigerant allocation strategy; if the first duration is less than the first preset duration threshold and the second duration is less than the second preset duration threshold, then it is determined to maintain the current refrigerant allocation strategy.

[0013] In some feasible implementations of the above-mentioned air conditioning system control method, after the air conditioning system executes the corresponding refrigerant distribution strategy according to the judgment result, the control method further includes: if the current low pressure of the outdoor unit is less than the corresponding second preset pressure threshold, then the current refrigerant distribution strategy is maintained; if the current subcooling degree of the outdoor unit is less than the corresponding second preset subcooling degree threshold, then the current refrigerant distribution strategy is maintained.

[0014] In some feasible embodiments of the above-described air conditioning system control method, before the air conditioning system executes the corresponding refrigerant distribution strategy, the control method further includes: when the number of outdoor units is even and at least one outdoor unit is short of refrigerant, dividing the outdoor units into a first group and a second group of equal numbers, calculating the pressure difference between the sum of the current low-pressure values ​​of the outdoor units in the first group and the sum of the current low-pressure values ​​of the outdoor units in the second group, and calculating the ratio of the sum of the current subcooling values ​​of the outdoor units in the first group to the sum of the current subcooling values ​​of the outdoor units in the second group; comparing the pressure difference with a preset difference, and... The ratio value is compared with a third preset ratio; based on the comparison result of the pressure difference value and the preset difference value, and the comparison result of the ratio value and the third preset ratio, it is determined whether there is a refrigerant shortage in the first group of outdoor units; if the pressure difference value is less than the preset difference threshold value, and the ratio value is less than the third preset ratio, it is determined that there is a refrigerant shortage in the first group of outdoor units; if the pressure difference value is greater than or equal to the preset difference threshold value, or the ratio value is greater than or equal to the third preset ratio, it is determined that there is no refrigerant shortage in the first group of outdoor units.

[0015] In a second aspect, the present invention also provides an air conditioning system, the air conditioning system including a memory and a processor, the memory being adapted to store a plurality of program codes, the program codes being adapted to be loaded and run by the processor to execute the control method of the air conditioning system described in any of the foregoing technical solutions.

[0016] Those skilled in the art will understand that, since the air conditioning system is capable of executing the control method in any of the aforementioned technical solutions, it possesses all the technical effects that the aforementioned control method can achieve, and will not be elaborated further here. Attached Figure Description

[0017] The preferred embodiments of the present invention are described below with reference to the accompanying drawings, in which: Figure 1 A schematic diagram of an air conditioning system provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of the structure of an outdoor unit of an air conditioning system provided in an embodiment of the present invention; Figure 3 This is a schematic diagram of the structure of an indoor unit of an air conditioning system provided in an embodiment of the present invention; Figure 4 This is a flowchart illustrating a control method for an air conditioning system provided in an embodiment of the present invention.

[0018] Explanation of reference numerals in the attached figures: 1. Outdoor unit; 2. Indoor unit; 100. Outdoor unit; 101. Compressor; 102. High-pressure switch; 103. Oil separator; 104. High-pressure sensor; 105. Four-way valve; 106. Condenser; 107. Outdoor fan; 108. Filter; 109. First expansion valve; 110. Heat exchanger; 111. Flash evaporator; 112. Silencer; 113. Oil return capillary tube; 114. Bypass capillary tube; 115. Solenoid valve; 116. Low-pressure switch; 117. Gas-liquid separator; 118. Low-pressure sensor; 200. Indoor unit; 201. Evaporator; 202. Second expansion valve. Detailed Implementation

[0019] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of the invention and are not intended to limit the scope of protection of the invention. Those skilled in the art can make adjustments as needed to adapt to specific applications. Numerous specific details are set forth in the following detailed description to better illustrate the invention. Those skilled in the art should understand that the invention can be practiced without certain specific details.

[0020] In the description of this invention, terms such as "upper," "lower," "inner," "outer," "left," "right," "front," and "rear," which indicate direction or positional relationships, are based on actual application and are used merely for ease of description. They do not indicate or imply that the device to be protected must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as limiting the invention. Furthermore, ordinal numbers such as "first" and "second" are used only for convenience and are not intended to indicate or imply relative importance.

[0021] Furthermore, it should be noted that, in the description of this invention, unless otherwise explicitly specified and limited, the terms "installation" and "connection" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0022] like Figures 1 to 3As shown, the present invention provides an air conditioning system, which includes an indoor unit 1 and an outdoor unit 2. The outdoor unit 1 includes multiple outdoor units 100 connected in parallel. Each outdoor unit 100 includes a compressor 101, a high-pressure switch 102, an oil separator 103, a high-pressure sensor 104, a four-way valve 105, a condenser 106, an outdoor fan 107, a filter 108, a first expansion valve 109, a heat exchanger 110, a flash evaporator 111, a silencer 112, an oil return capillary tube 113, a bypass capillary tube 114, a solenoid valve 115, a low-pressure switch 116, a gas-liquid separator 117, and a low-pressure sensor 118. The indoor unit 2 includes multiple indoor units 200 connected in parallel. Each indoor unit 200 includes an evaporator 201, a second expansion valve 202, and an indoor fan.

[0023] Based on the aforementioned air conditioning system structure, such as Figure 4 As shown, the present invention also provides a control method for an air conditioning system, the control method comprising: S1. Obtain the current low-pressure and current subcooling of each outdoor unit.

[0024] Among them, such as Figure 2 As shown, the current low-pressure reading of each outdoor unit is the low-pressure parameter obtained by the low-pressure sensor of each outdoor unit; under the refrigeration cycle, the current subcooling of each outdoor unit is the sum of the high-pressure saturation temperature and the actual temperature at the condenser outlet (i.e., ...). Figure 2 The difference between the high-pressure saturation temperature and the high-pressure temperature of each outdoor unit is calculated from the high-pressure parameters obtained by the high-pressure sensors of each outdoor unit. Under heating cycle conditions, the original condenser becomes the new evaporator, and the current subcooling of each outdoor unit is the difference between the high-pressure saturation temperature and the actual outlet temperature of the original evaporator. The actual outlet temperature of the original evaporator is the average outlet temperature of the evaporators of each indoor unit (i.e., the difference between the high-pressure saturation temperature and the actual outlet temperature of the original evaporator). Figure 2 The average temperature Tei of each indoor unit. Furthermore, after the air conditioning system has been running for a period of time (e.g., 10 to 20 minutes), each parameter is acquired again to ensure the stability and accuracy of the acquired parameters.

[0025] S2. Compare the current low pressure of each outdoor unit with the corresponding first preset pressure threshold, and compare the current subcooling of each outdoor unit with the corresponding first preset subcooling threshold. The first preset pressure threshold is determined based on the current low pressure of the other outdoor units, and the first preset subcooling threshold is determined based on the current subcooling of the other outdoor units.

[0026] In this embodiment, the process of determining the first preset pressure threshold includes: multiplying the average value of the current low pressure of the remaining outdoor units by a first preset ratio to obtain the first preset pressure threshold. The first preset ratio ranges from 70% to 90%, for example, if the first preset ratio is 80%, then the first preset pressure threshold is equal to 80% of the average value of the current low pressure of the remaining outdoor units.

[0027] In this embodiment, the process of determining the first preset subcooling threshold includes: multiplying the average current subcooling of the remaining outdoor units by a second preset ratio to obtain the first preset subcooling threshold. The second preset ratio ranges from 70% to 90%, for example, if the second preset ratio is 80%, then the second preset subcooling threshold is equal to 80% of the average current subcooling of the remaining outdoor units.

[0028] It should be noted that the values ​​in the above examples are merely exemplary and should not be construed as limiting the scope of protection of this invention.

[0029] S3. Based on the comparison results, determine whether each outdoor unit is short of refrigerant, and execute the corresponding refrigerant distribution strategy of the air conditioning system according to the judgment results.

[0030] Specifically, based on the comparison results of the current low pressure of each outdoor unit with the corresponding first preset pressure threshold, and the comparison results of the current subcooling degree of each outdoor unit with the corresponding first preset subcooling degree threshold, it is determined whether each outdoor unit is short of refrigerant, which includes steps S31 to S33, as follows: S31. If the current low pressure of the outdoor unit is less than the corresponding first preset pressure threshold, and the current subcooling of the outdoor unit is less than the corresponding first preset subcooling threshold, then the corresponding outdoor unit is judged to be short of refrigerant.

[0031] When the current low pressure of the outdoor unit is less than the corresponding first preset pressure threshold, and the current subcooling of the outdoor unit is less than the corresponding first preset subcooling threshold, it indicates that the outdoor unit may have insufficient refrigerant supply: low low pressure reflects insufficient refrigerant circulation, and low subcooling indicates that the refrigerant in the evaporator has not evaporated sufficiently. Both indicate a refrigerant shortage, so it is determined that the outdoor unit is short of refrigerant and the refrigerant distribution adjustment strategy is triggered.

[0032] S32. If the current low pressure of the outdoor unit is greater than or equal to the corresponding first preset pressure threshold, it is determined that the corresponding outdoor unit does not lack refrigerant.

[0033] When the current low-pressure of the outdoor unit is greater than or equal to the corresponding first preset pressure threshold, it indicates that the high-pressure side pressure of the outdoor unit is sufficient, indicating that its refrigerant circulation volume meets the standard, and therefore it is determined that the outdoor unit is not short of refrigerant.

[0034] S33. If the current subcooling degree of the outdoor unit is greater than or equal to the corresponding first preset subcooling degree threshold, it is determined that the corresponding outdoor unit does not lack refrigerant.

[0035] When the current subcooling is greater than or equal to the corresponding first preset subcooling threshold, it indicates that the subcooling of the outdoor unit is sufficient, which means that its evaporator heat exchange efficiency is normal. Therefore, it is determined that the outdoor unit does not lack refrigerant.

[0036] Based on steps S32 and S33, when the current low-pressure of the outdoor unit is greater than or equal to the corresponding first preset pressure threshold, or the current subcooling is greater than or equal to the corresponding first preset subcooling threshold, it indicates that at least one key parameter of the outdoor unit is within the normal range: that is, sufficient high-pressure side pressure indicates that the refrigerant circulation volume meets the standard, and sufficient subcooling reflects that the evaporator heat exchange efficiency is normal. If either of these conditions is met, the risk of refrigerant shortage can be eliminated. Therefore, it is determined that the outdoor unit does not lack refrigerant and maintains the current refrigerant distribution state.

[0037] Furthermore, step S3, "based on the judgment result, executes the corresponding refrigerant distribution strategy of the air conditioning system," includes steps S34 and S35, as follows: S34. If at least one outdoor unit is short of refrigerant, increase the speed of the outdoor fan of the outdoor unit with short refrigerant, decrease the speed of the outdoor fan of the other outdoor units, and / or increase the opening of the expansion valve of the outdoor unit with short refrigerant, and decrease the opening of the expansion valve of the other outdoor units.

[0038] When at least one outdoor unit is short of refrigerant, a two-way adjustment strategy is adopted to directly achieve the directional distribution of refrigerant flow through "increasing the speed of the outdoor fan of the unit with short refrigerant and increasing the opening of the expansion valve" and "reducing the speed of the outdoor fan of other units and decreasing the opening of the expansion valve". The outdoor unit with short refrigerant has enhanced heat dissipation capacity due to the increased outdoor fan speed and increased refrigerant supply due to the increased expansion valve opening. The outdoor unit with sufficient refrigerant reduces refrigerant occupation by reducing the speed and opening, ultimately promoting the dynamic balance of refrigerant flow among multiple outdoor units.

[0039] Based on the above, for outdoor units lacking refrigerant, the compressor frequency can be appropriately increased to increase the refrigerant circulation volume and compensate for the decrease in cooling capacity caused by insufficient refrigerant. For outdoor units with sufficient refrigerant, the compressor frequency can be appropriately reduced to decrease refrigerant demand and avoid competing for refrigerant resources. While reducing the frequency, it is necessary to coordinate with reducing the speed of the outdoor fan and reducing the opening of the expansion valve to create a "flow release" effect, allowing more refrigerant to flow to the unit lacking refrigerant. However, the extent of frequency reduction should be based on the current low-pressure (if the pressure is too high, reduce it more) and subcooling (if the subcooling is sufficient, reduce it more) to ensure that the overall system flow is balanced and the operation is stable.

[0040] Furthermore, step S34 includes steps S341 and S342, as follows: S341. Before adjusting the refrigerant distribution strategy, obtain the discharge temperature of the compressor of each outdoor unit.

[0041] Specifically, Figure 2 The temperature Td in the figure represents the exhaust temperature of the outdoor unit's compressor. Figure 2 The temperature Ts in the figure represents the suction temperature of the compressor in the outdoor unit.

[0042] S342. Determine the adjustment amount of the external fan speed and the adjustment amount of the expansion valve opening based on the exhaust temperature, current low pressure and current subcooling.

[0043] Among them, such as Figure 2 As shown, the opening degree of the outdoor unit's expansion valve is the opening degree of the first expansion valve. Step S341 (obtaining the exhaust temperature) and step S342 (determining the adjustment amount by combining the low pressure and subcooling) together constitute the reference conditions for precise adjustment: the exhaust temperature reflects the compressor's operating load status, avoiding excessive adjustment that could lead to compressor overheating; the low pressure and subcooling are directly related to the refrigerant quantity status. The three factors are used together to calibrate the adjustment amount, ensuring that the adjustment is both timely and appropriate, that is, quickly responding to the refrigerant shortage while avoiding system oscillation caused by excessive adjustment.

[0044] In one implementation, when the system is running in cooling mode, the outdoor fan speed of the refrigerant-deficient outdoor unit increases. The formula for calculating the adjustment amount of the outdoor fan speed is: ΔN=K·M(PsMAX-Ps1), (where ΔN1 is the adjustment amount of the outdoor fan speed, K is the exhaust temperature correction coefficient, M is the outdoor unit subcooling correction coefficient, Ps1 is the current low pressure of the refrigerant-deficient outdoor unit, PsMAX is the maximum value of the current low pressure of the non-refrigerant-deficient outdoor unit, and Tsc is the current subcooling of the outdoor unit). Each time interval (e.g., 10s) is an adjustment cycle: when Td>100℃, K is a, 10<a≤20; when 80℃<Td≤100℃, K is b, 5<b≤10; when Td≤80℃, K is c, 0<c≤5. When Tsc > 10℃, M takes the value d, 0 < d ≤ 0.5; when 5℃ < Tsc ≤ 10℃, M takes the value e, 0.5 < e ≤ 1; when 0℃ < Tsc ≤ 5℃, M takes the value f, f > 1.

[0045] Based on the above, the outdoor fan speed of the outdoor unit without refrigerant shortage decreases. The formula for calculating the adjustment amount of the outdoor fan speed is: ΔN2=K·M(Ps1-PsMAX), (where ΔN2 is the adjustment amount of the outdoor fan speed, K is the exhaust temperature correction coefficient, M is the outdoor unit subcooling correction coefficient, Ps1 is the current low pressure of the outdoor unit with refrigerant shortage, PsMAX is the maximum value of the current low pressure of the outdoor unit without refrigerant shortage, and Tsc is the current subcooling of the outdoor unit). Each time interval (e.g., 10s) is an adjustment cycle: when Td>100℃, K takes the value a, 0<a≤5; when 80℃<Td≤100℃, K takes the value b, 5<b≤10; when Td≤80℃, K takes the value c, 10<c≤20. When Tsc > 10℃, M takes the value d, where d > 1; when 5℃ < Tsc ≤ 10℃, M takes the value e, where 0.5 < e ≤ 1; when 0℃ < Tsc ≤ 5℃, M takes the value f, where 0 < f ≤ 0.5.

[0046] In another implementation, when the system is running in heating mode, the opening of the expansion valve of the outdoor unit lacking refrigerant increases. The formula for calculating the adjustment amount of the expansion valve is ΔP1=K·M(PsMAX-Ps1) (where ΔP1 is the adjustment amount of the expansion valve, K is the exhaust temperature correction coefficient, M is the outdoor unit subcooling correction coefficient, Ps1 is the current low pressure of the outdoor unit lacking refrigerant, PsMAX is the maximum value of the current low pressure of the outdoor unit not lacking refrigerant, and Tsc is the current subcooling of the outdoor unit). Each time interval (e.g., 10s) is an adjustment cycle: when Td>100℃, K is a, 1<a≤2; when 80℃<Td≤100℃, K is b, 0.5<b≤1; when Td≤80℃, K is c, 0<c≤0.5. When Tsc > 10℃, M is d, where 0 < d ≤ 0.5; when 5℃ < Tsc ≤ 10℃, M is e, where 0.5 < e ≤ 1; when 0℃ < Tsc ≤ 5℃, M is f, where f > 1. Furthermore, before or simultaneously adjusting the opening of the outdoor unit's expansion valve (i.e., the opening of the first expansion valve), the opening of the indoor unit's expansion valve (i.e., the opening of the second expansion valve) can be adjusted to its maximum value. This helps to improve the refrigerant circulation rate, thereby increasing the refrigerant distribution rate to each outdoor unit.

[0047] S35. If all outdoor units have sufficient refrigerant, maintain the current refrigerant distribution strategy of the air conditioning system.

[0048] When all outdoor units of the air conditioning system have sufficient refrigerant, maintaining the current refrigerant distribution strategy helps to keep the air conditioning system running stably, avoids energy waste and system fluctuations caused by frequent adjustments, and forms a complete control closed loop of "dynamic adjustment + static maintenance".

[0049] Furthermore, before the air conditioning system executes the corresponding refrigerant distribution strategy, the control method also includes: S301. When the number of outdoor units is even and at least one outdoor unit is short of refrigerant, divide the outdoor units into a first group and a second group with an equal number of units. Calculate the pressure difference between the sum of the current low pressure of the outdoor units in the first group and the sum of the current low pressure of the outdoor units in the second group, and calculate the ratio between the sum of the current subcooling of the outdoor units in the first group and the sum of the current subcooling of the outdoor units in the second group.

[0050] By grouping even-numbered outdoor units and calculating the pressure difference and subcooling ratio, a verification dimension for inter-group comparison is constructed. Preferably, during grouping, outdoor units previously judged to be refrigerant deficient are placed in the first group. When there is a risk of local misjudgment in the judgment of a single outdoor unit (such as in steps S31-S33), the overall parameter differences after grouping can provide macroscopic verification evidence. For example, if the total low-pressure of the first group is significantly lower than that of the second group, it may reflect that the group has a collective tendency to be deficient in refrigerant. Combining this with cross-verification of the judgment of a single unit helps to avoid erroneous adjustments caused by single-point misjudgment.

[0051] S302. Compare the pressure difference with the preset difference and the ratio with the third preset ratio.

[0052] The pressure difference reflects the macroscopic difference in refrigerant supply between the two groups, while the subcooling ratio reflects the relative levels of heat exchange efficiency. Both provide quantitative basis for subsequent cross-validation, avoiding misjudgments caused by fluctuations in parameters of a single unit. The preset difference and the third preset ratio serve as thresholds to quantify the significance of the group parameter differences. Specifically, the third preset ratio ranges from 70% to 90%, and the preset difference is 0 Pa or 10% of the sum of the current low-pressure values ​​of the two outdoor units. For example, the preset difference is 0 Pa, and the third preset ratio is 80%. If the pressure difference is too small or the ratio is too low, it indicates that the refrigerant distribution imbalance between the two groups has exceeded the system's allowable range; conversely, it indicates that the parameter differences are within a reasonable range, and the reliability of the single-unit judgment is high, requiring no additional intervention.

[0053] S303. Based on the comparison results of the pressure difference and the preset difference, and the comparison results of the ratio value and the third preset ratio, determine whether there is a refrigerant shortage in the first group of outdoor units.

[0054] S3031. If the pressure difference is less than the preset difference threshold and the ratio is less than the third preset ratio, it is determined that there is a refrigerant shortage in the first group of outdoor units.

[0055] By judging the dual conditions of "pressure difference + ratio value", a definitive conclusion is formed on the refrigerant shortage status of the first group. When the pressure difference is less than the preset difference threshold and the ratio value is less than the third preset ratio, it can be confirmed that there are outdoor units in the first group that are short of refrigerant, and the corresponding refrigerant distribution strategy adjustment can be triggered.

[0056] S3032. If the pressure difference is greater than or equal to the preset difference threshold, or the ratio is greater than or equal to the third preset ratio, then it is determined that there is no refrigerant shortage in the first group of outdoor units.

[0057] When the pressure difference is greater than or equal to a preset difference threshold, or the ratio is greater than or equal to a third preset ratio, that is, when either of the above conditions is not met, the outdoor units in the first group are determined to have no refrigerant shortage. This indicates that there may have been a misjudgment in the previous steps, and the parameters need to be re-tested and re-judged. Through this dual mechanism of "macro-level group verification + micro-level single-unit judgment," the limitations of single-parameter judgment are compensated for, and the accuracy and reliability of refrigerant shortage identification are improved through system-level parameter linkage, ultimately ensuring the accuracy of refrigerant distribution strategy execution and system operational stability.

[0058] Furthermore, after instructing the air conditioning system to execute the corresponding refrigerant distribution strategy based on the judgment result, the control method also includes: S4. If the current low pressure of the outdoor unit is greater than or equal to the corresponding second preset pressure threshold and the duration reaches the first duration, and the current subcooling of the outdoor unit is greater than or equal to the corresponding second preset subcooling threshold and the duration reaches the second duration, then the first duration is compared with the first preset duration threshold, and the second duration is compared with the second preset duration threshold. Based on the comparison result, it is determined whether to stop executing the current refrigerant distribution strategy; wherein, the second preset pressure threshold is greater than the first preset pressure threshold, and the second preset subcooling threshold is greater than the first preset subcooling threshold.

[0059] By setting a second preset pressure threshold (which can be 90%–110% of the average current low-pressure of the remaining outdoor units) and a second preset subcooling threshold (which can be 90%–110% of the average current subcooling of the remaining outdoor units) that are greater than the first preset pressure threshold, and requiring these parameters to remain within the specified range for a corresponding duration, a system stability verification mechanism is established. Its function is to confirm that the system has transitioned from an "adjustment state" to a "stable and efficient operating state" through joint verification of higher-dimensional parameter thresholds and duration after the refrigerant distribution strategy is executed. This avoids erroneous strategy termination or frequent start-stop operations due to instantaneous parameter fluctuations, ensuring system operational stability.

[0060] S41. If the first duration is greater than or equal to the first preset duration threshold, it is determined that the current refrigerant allocation strategy should be stopped.

[0061] When the first duration (the duration during which the current low pressure of the refrigerant-deficient outdoor unit is greater than or equal to the second preset pressure threshold) reaches the first preset duration threshold, it is determined that the current low pressure of the refrigerant-deficient outdoor unit has stabilized at a higher level for a sufficient period of time. At this point, stopping the refrigerant distribution strategy can avoid over-adjustment and ensure that the entire system operates in an efficient state, achieving precise control of stopping as soon as the target is met.

[0062] S42. If the second duration is greater than or equal to the second preset duration threshold, it is determined that the current refrigerant allocation strategy should be stopped.

[0063] When the second duration (the duration during which the current subcooling of the refrigerant-deficient outdoor unit is greater than or equal to the second preset subcooling threshold) reaches the second preset duration threshold, the current subcooling of the refrigerant-deficient outdoor unit has stabilized at a higher level for a sufficient period of time. At this point, the stop strategy can ensure cooling efficiency and operational stability, and avoid the risk of decreased cooling performance due to subcooling not meeting the standard.

[0064] S43. If the first duration is less than the first preset duration threshold and the second duration is less than the second preset duration threshold, then it is determined that the current refrigerant allocation strategy should be maintained.

[0065] If neither the first duration nor the second duration reaches the preset duration threshold, it is determined that the parameters of the entire system are not yet fully stable. The current refrigerant distribution strategy should be maintained and optimized to avoid the risk of refrigerant distribution imbalance caused by premature termination of the strategy. Adjustments should only be stopped after the system status has been fully optimized.

[0066] S44. If the current low pressure of the outdoor unit is less than the corresponding second preset pressure threshold, the current refrigerant distribution strategy shall be maintained.

[0067] When the current low pressure of the outdoor unit lacking refrigerant is lower than the second preset pressure threshold, the current strategy is maintained directly to prevent the strategy from terminating prematurely due to pressure fluctuations. This ensures that the system continues to execute the accurate refrigerant distribution strategy and avoids the risk of decreased cooling performance or reliability due to insufficient pressure.

[0068] S45. If the current subcooling of the outdoor unit is less than the corresponding second preset subcooling threshold, the current refrigerant distribution strategy shall be maintained.

[0069] When the current subcooling of the outdoor unit is lower than the second preset subcooling threshold, the current strategy is maintained directly to prevent the strategy from being terminated erroneously due to subcooling fluctuations. This ensures that the system still executes the accurate refrigerant distribution strategy and avoids the risk of reduced evaporator heat exchange efficiency or system reliability caused by insufficient subcooling.

[0070] Compared to the traditional fixed threshold judgment mode, this invention adopts a dynamic threshold setting mechanism. By comparing the current low pressure and current subcooling of each outdoor unit with a preset threshold determined based on the real-time operating status of the other outdoor units, it achieves accurate identification of refrigerant shortage status. This effectively avoids the risk of misjudgment or omission caused by fluctuations in operating conditions in the traditional mode, ensuring the timeliness and accuracy of the refrigerant distribution strategy. In turn, it promotes the balanced distribution of refrigerant flow among the outdoor units, drives the overall cooling efficiency of the system, and effectively avoids the decrease in cooling effect and system reliability risk caused by uneven refrigerant distribution when multiple outdoor units are connected in parallel. This provides a core guarantee for the efficient and stable operation of multi-split air conditioning systems.

[0071] In addition, the air conditioning system also includes a memory and a processor. The memory is adapted to store multiple program codes, which are adapted to be loaded and run by the processor to execute the control method of the air conditioning system in any of the aforementioned technical solutions.

[0072] In the description of this invention, "processor" can include hardware, software, or a combination of both. A processor can be a central processing unit, microprocessor, image processor, digital signal processor, or any other suitable processor. A processor has data and / or signal processing capabilities. A processor can be implemented in software, in hardware, or a combination of both. Non-transitory computer-readable storage media includes any suitable medium capable of storing program code, such as magnetic disks, hard disks, optical disks, flash memory, read-only memory, random access memory, etc.

[0073] Those skilled in the art will understand that all or part of the processes in the methods of the above embodiments of the present invention can also be implemented by hardware related to computer program instructions. The computer program can be stored in a computer-readable storage medium, and when the computer program is executed by a processor, it can implement the steps of the various method embodiments described above. The computer program includes computer program code, which can be in the form of source code, object code, executable file, or some intermediate form. The computer-readable storage medium can include any entity or device capable of carrying computer program code, a medium, a USB flash drive, a portable hard drive, a magnetic disk, an optical disk, a computer memory, a read-only memory, a random access memory, an electrical carrier signal, a telecommunication signal, and a software distribution medium, etc.

[0074] The technical solution of the present invention has been described above with reference to the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after such changes or substitutions will all fall within the scope of protection of the present invention.

Claims

1. A control method for an air conditioning system, characterized in that, The air conditioning system includes an indoor unit and an outdoor unit, the outdoor unit includes multiple outdoor units connected in parallel, and the control method includes: Obtain the current low-pressure and current subcooling of each outdoor unit; The current low pressure of each outdoor unit is compared with the corresponding first preset pressure threshold, and the current subcooling of each outdoor unit is compared with the corresponding first preset subcooling threshold, wherein the first preset pressure threshold is determined based on the current low pressure of the other outdoor units, and the first preset subcooling threshold is determined based on the current subcooling of the other outdoor units. Based on the comparison results, it is determined whether each outdoor unit is short of refrigerant, and the air conditioning system executes the corresponding refrigerant distribution strategy according to the determination results.

2. The control method for the air conditioning system according to claim 1, characterized in that, The process of determining the first preset pressure threshold includes: multiplying the average current low pressure of the remaining outdoor units by a first preset ratio to obtain the first preset pressure threshold; and / or The process of determining the first preset subcooling threshold includes: multiplying the average value of the current subcooling of the remaining outdoor units by a second preset ratio to obtain the first preset subcooling threshold.

3. The control method for the air conditioning system according to claim 1 or 2, characterized in that, The aforementioned "determining whether each outdoor unit is short of refrigerant based on the comparison results" includes: If the current low pressure of the outdoor unit is less than the corresponding first preset pressure threshold, and the current subcooling of the outdoor unit is less than the corresponding first preset subcooling threshold, then it is determined that the corresponding outdoor unit is short of refrigerant. If the current low pressure of the outdoor unit is greater than or equal to the corresponding first preset pressure threshold, it is determined that the corresponding outdoor unit does not lack refrigerant. If the current subcooling degree of the outdoor unit is greater than or equal to the corresponding first preset subcooling degree threshold, it is determined that the corresponding outdoor unit does not lack refrigerant.

4. The control method for the air conditioning system according to claim 3, characterized in that, The phrase "based on the judgment result, the air conditioning system executes the corresponding refrigerant distribution strategy" includes: If at least one outdoor unit is short of refrigerant, increase the speed of the outdoor fan of the unit with short refrigerant and decrease the speed of the outdoor fan of the other outdoor units, and / or increase the opening of the expansion valve of the outdoor unit with short refrigerant and decrease the opening of the expansion valve of the other outdoor units. If all outdoor units have sufficient refrigerant, the air conditioning system will maintain its current refrigerant distribution strategy.

5. The control method for the air conditioning system according to claim 4, characterized in that, The control method further includes: Before adjusting the refrigerant distribution strategy, obtain the discharge temperature of the compressor of each outdoor unit; The adjustment amount of the external fan speed and the adjustment amount of the expansion valve opening are determined based on the exhaust temperature, the current low pressure, and the current subcooling.

6. The control method for the air conditioning system according to claim 3, characterized in that, After instructing the air conditioning system to execute the corresponding refrigerant distribution strategy based on the judgment result, the control method further includes: If the current low pressure of the outdoor unit is greater than or equal to the corresponding second preset pressure threshold and the duration reaches the first duration, and the current subcooling of the outdoor unit is greater than or equal to the corresponding second preset subcooling threshold and the duration reaches the second duration, then the first duration is compared with the first preset duration threshold, and the second duration is compared with the second preset duration threshold. Based on the comparison result, it is determined whether to stop executing the current refrigerant distribution strategy. Wherein, the second preset pressure threshold is greater than the first preset pressure threshold, and the second preset subcooling threshold is greater than the first preset subcooling threshold.

7. The control method for an air conditioning system according to claim 6, characterized in that, The phrase "determining whether to stop executing the current refrigerant allocation strategy based on the comparison results" includes: If the first duration is greater than or equal to the first preset duration threshold, it is determined that the current refrigerant allocation strategy will be stopped. If the second duration is greater than or equal to the second preset duration threshold, it is determined that the current refrigerant allocation strategy will be stopped. If the first duration is less than the first preset duration threshold and the second duration is less than the second preset duration threshold, then it is determined that the current refrigerant distribution strategy should be maintained.

8. The control method for an air conditioning system according to claim 6, characterized in that, After instructing the air conditioning system to execute the corresponding refrigerant distribution strategy based on the judgment result, the control method further includes: If the current low pressure of the outdoor unit is less than the corresponding second preset pressure threshold, the current refrigerant distribution strategy is maintained. If the current subcooling degree of the outdoor unit is less than the corresponding second preset subcooling degree threshold, the current refrigerant distribution strategy is maintained.

9. The control method for an air conditioning system according to claim 1, characterized in that, Before the air conditioning system executes the corresponding refrigerant distribution strategy, the control method further includes: When the number of outdoor units is even and at least one outdoor unit is short of refrigerant, the outdoor units are divided into a first group and a second group with an equal number of units. The pressure difference between the sum of the current low pressure of the outdoor units in the first group and the sum of the current low pressure of the outdoor units in the second group is calculated, and the ratio between the sum of the current subcooling of the outdoor units in the first group and the sum of the current subcooling of the outdoor units in the second group is calculated. The pressure difference is compared with a preset difference, and the ratio is compared with a third preset ratio; Based on the comparison results of the pressure difference and the preset difference, and the comparison results of the ratio and the third preset ratio, it is determined whether there is a refrigerant shortage in the first group of outdoor units; If the pressure difference is less than the preset difference threshold and the ratio is less than the third preset ratio, then it is determined that there is a refrigerant shortage in the first group of outdoor units. If the pressure difference is greater than or equal to the preset difference threshold, or the ratio is greater than or equal to the third preset ratio, then it is determined that there is no refrigerant shortage in the first group of outdoor units.

10. An air conditioning system, characterized in that, The air conditioning system includes a memory and a processor, the memory being adapted to store multiple program codes, the program codes being adapted to be loaded and run by the processor to perform the control method of the air conditioning system according to any one of claims 1 to 9.

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