Method and device for judging refrigerant charge of multi-split air conditioning system

Abstract

The application provides a refrigerant charge amount judgment method of a multi-connected air conditioning system, which comprises the following steps: obtaining the current operation mode of the air conditioning system and the outdoor environment temperature; if the environment temperature meets the temperature condition corresponding to the current operation mode, then turn on the indoor unit with the smallest nominal capacity in the system and turn off the remaining indoor units; adjust the system operation parameters until the fluctuation value of the system high pressure within a continuous preset time length is less than a preset pressure threshold value, and determine that the system enters a stable operation state; in the stable operation state, collect the judgment parameters corresponding to the current operation mode; determine the dynamic threshold values corresponding to each judgment parameter according to the environment temperature; compare the judgment parameters with the dynamic threshold values to judge the refrigerant charge amount state. The application solves the problem of the existing refrigerant amount judgment method based on system operation parameters, that is, the parameters are greatly affected by the environment temperature, which leads to the instability of the parameter judgment logic at different temperatures and the misjudgment problem.

Description

Technical Field

[0001] This invention relates to the field of air conditioner technology, and in particular to a method and device for determining the refrigerant charge of a multi-split air conditioning system. Background Technology

[0002] Multi-split air conditioning systems are widely used in commercial and large residential sectors because they can connect multiple indoor units and meet the cooling / heating needs of large or complex spaces. However, accurately determining and charging the appropriate amount of refrigerant during installation and commissioning has become a key technical challenge.

[0003] Unlike ordinary household air conditioners, multi-split air conditioning systems have a larger number of indoor units, and the pipes connecting the indoor and outdoor units are longer and more complex. The actual pipe length and number of indoor units vary significantly for each installation project. Usually, the amount of refrigerant pre-stored in the outdoor unit at the factory is only enough to meet the operating needs of the outdoor unit itself and the standard short pipes. Therefore, during on-site installation and commissioning, the amount of refrigerant must be calculated and supplemented according to the actual total capacity of the indoor units, the specifications and length of the liquid pipes.

[0004] The current industry practice is for installers to measure the length and diameter of each section of pipe on-site, record the indoor unit model, and then manually calculate the amount of refrigerant needed based on the manufacturer's calculation formula or reference table. Finally, they use an electronic scale to weigh and charge the refrigerant. This method has significant drawbacks: First, the operation is cumbersome and requires a high level of professionalism and responsibility from the installers. Second, the accuracy of the calculation depends entirely on the precision of the pipe measurements. In complex multi-split air conditioning projects, with long pipes and many branch pipes, measurement errors or recording mistakes are easily made, leading to inaccurate calculation results. Furthermore, for some renovation projects, the original pipe information may have been lost, making accurate calculation impossible. Human error in calculation directly results in too much or too little refrigerant in the system, leading to a series of operational problems: too much refrigerant may cause system liquid return, compressor liquid slugging, and high-pressure overheating triggering protection shutdown; too little refrigerant will result in insufficient indoor unit capacity, poor cooling / heating performance, and high exhaust temperature or low pressure protection due to excessive superheating.

[0005] To overcome the shortcomings of manual calculation, existing technologies have developed several methods for judging refrigerant quantity based on system operating parameters. For example, the refrigerant quantity status can be inferred by monitoring parameters such as compressor discharge temperature, discharge superheat, and system high and low pressure. However, these methods still have limitations and risks of misjudgment in practical applications. Specifically, because system operating parameters, especially pressure and temperature, are significantly affected by outdoor ambient temperature, the same refrigerant quantity may exhibit different parameter values ​​under different ambient temperature conditions, and the same parameter value may also correspond to different refrigerant quantity states. This leads to insufficient stability of the judgment logic based on a single or a few parameters at different temperatures, making misjudgments easy to occur. For example, in low-temperature environments, system pressure is generally low, which may be misjudged as insufficient refrigerant; in high-temperature environments, pressure is high, which may be misjudged as excessive refrigerant. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a method and apparatus for determining the refrigerant charge amount of a multi-split air conditioning system. This method solves the problem that existing methods for determining refrigerant charge based on system operating parameters are greatly affected by ambient temperature, leading to insufficient stability of the judgment logic for a single or a few parameters at different temperatures and a tendency to make misjudgments.

[0007] According to an embodiment of the present invention, a method for determining the refrigerant charge of a multi-split air conditioning system is provided. The air conditioning system includes an outdoor unit and a plurality of indoor units connected to the outdoor unit. The determination method includes the following steps:

[0008] Obtain the current operating mode of the air conditioning system and the outdoor ambient temperature;

[0009] If the outdoor ambient temperature meets the preset ambient temperature condition corresponding to the current operating mode, then the indoor unit with the smallest nominal capacity in the air conditioning system is turned on, and the remaining indoor units are turned off.

[0010] Adjust the operating parameters of the air conditioning system until the fluctuation value of the high pressure of the air conditioning system within a continuous preset time period is less than the preset pressure fluctuation threshold, and determine that the air conditioning system has entered a stable operating state.

[0011] Under the stable operating state, judgment parameters corresponding to the current operating mode are collected;

[0012] Based on the outdoor ambient temperature, the dynamic threshold corresponding to each of the judgment parameters is determined by calculation or query through a preset correspondence.

[0013] The judgment parameter is compared with the dynamic threshold, and the refrigerant charge status is determined according to the preset logical relationship;

[0014] When the air conditioning system is in cooling mode, the judgment parameters include the opening degree of the electronic expansion valve of the indoor unit and the exhaust temperature of the compressor.

[0015] When the air conditioning system is in heating mode, the judgment parameters include the high-pressure saturation temperature of the outdoor unit, the opening degree of the electronic expansion valve of the outdoor unit, the opening degree of the electronic expansion valve of the indoor unit, and the exhaust temperature of the compressor.

[0016] On the other hand, according to embodiments of the present invention, a refrigerant charge determination device for a multi-split air conditioning system is also provided, the determination device comprising:

[0017] The acquisition module is used to acquire the current operating mode of the air conditioning system and the outdoor ambient temperature;

[0018] The operating condition control module is used to turn on the indoor unit with the smallest nominal capacity in the air conditioning system and turn off the other indoor units when the outdoor ambient temperature meets the preset ambient temperature conditions corresponding to the current operating mode.

[0019] The operation control module is used to adjust the operating parameters of the air conditioning system so that the air conditioning system enters a stable operating state.

[0020] The data acquisition module is used to collect judgment parameters corresponding to the current operating mode under stable operating conditions.

[0021] The threshold determination module is used to determine the dynamic threshold corresponding to each judgment parameter based on the outdoor ambient temperature.

[0022] The status judgment module is used to compare the judgment parameters with the dynamic threshold and determine the refrigerant charge status according to the preset logical relationship.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] By acquiring the current operating mode of the air conditioning system and the outdoor ambient temperature, and setting preset ambient temperature conditions, different refrigerant charge judgment logics can be selected according to the current operating mode of the air conditioning system and the ambient temperature. This ensures that the refrigerant charge judgment is only performed within the effective and standard operating conditions, avoiding judgment failure caused by drastic changes in system operating characteristics under extreme temperatures, and guaranteeing the accuracy of refrigerant charge judgment from the source.

[0025] By turning on the indoor unit with the smallest nominal capacity in the air conditioning system and turning off the remaining indoor units, the air conditioning system is forced to operate under the simplest and least load-bearing single-unit condition. This greatly simplifies and unifies the internal operating state of the air conditioning system, eliminates interference caused by different on / off combinations of multiple indoor units, and provides a stable internal environment for subsequent parameter acquisition and threshold comparison, thereby further improving the reliability of refrigerant charge determination.

[0026] By determining dynamic thresholds corresponding to each judgment parameter based on the outdoor ambient temperature, the thresholds for subsequent threshold comparisons can be dynamically adjusted in real time according to the external environment. This ensures that the judgment benchmark always matches the actual state of the air conditioning system under different seasons and climate conditions, thereby significantly improving the accuracy of refrigerant charge determination.

[0027] The system is determined to be in a stable operating state only when the fluctuation value of the high pressure of the air conditioning system is less than a preset pressure fluctuation threshold within a continuous preset time period. This ensures that the judgment parameters collected subsequently can accurately and stably reflect the refrigerant charge status of the air conditioning system, avoiding false collection and misjudgment caused by transient fluctuations in the air conditioning system. Attached Figure Description

[0028] Figure 1 This is a flowchart illustrating the refrigerant charge determination method for a multi-split air conditioning system according to Embodiment 1 of the present invention.

[0029] Figure 2 This is a flowchart illustrating the refrigerant charge determination logic in the refrigeration mode of Embodiment 2 of the present invention.

[0030] Figure 3 This is a flowchart illustrating the refrigerant charge determination logic in the heating mode of Embodiment 3 of the present invention.

[0031] Figure 4 This is a control principle diagram of a refrigerant charge determination device for a multi-split air conditioning system according to Embodiment 4 of the present invention.

[0032] In the above attached diagram: 1. Acquisition module; 2. Operating condition control module; 3. Operation control module; 4. Data acquisition module; 5. Threshold determination module; 6. Status judgment module; 7. Storage module. Detailed Implementation

[0033] The technical solutions of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0034] Example 1

[0035] As attached Figure 1As shown in the figure, this invention proposes a method for determining the refrigerant charge of a multi-split air conditioning system. The air conditioning system includes an outdoor unit and several indoor units connected to the outdoor unit. The determination method includes the following steps:

[0036] S1. Obtain the current operating mode of the air conditioning system and the outdoor ambient temperature;

[0037] S2. If the outdoor ambient temperature meets the preset ambient temperature condition corresponding to the current operating mode, then turn on the indoor unit with the smallest nominal capacity in the air conditioning system and turn off the other indoor units.

[0038] Specifically, when the air conditioning system is in cooling mode, the outdoor ambient temperature is within a first temperature range; when the air conditioning system is in heating mode, the outdoor ambient temperature is within a second temperature range; the temperature within the first temperature range is higher than the temperature within the second temperature range.

[0039] S3. Adjust the operating parameters of the air conditioning system until the fluctuation value of the high pressure of the air conditioning system within a continuous preset time period is less than the preset pressure fluctuation threshold, and determine that the air conditioning system has entered a stable operating state.

[0040] S4. Under the stable operating state, collect the judgment parameters corresponding to the current operating mode;

[0041] S5. Based on the outdoor ambient temperature, calculate or query through a preset correspondence to determine the dynamic threshold corresponding to each of the judgment parameters.

[0042] S6. Compare the judgment parameter with the dynamic threshold, and determine the refrigerant charge status according to the preset logical relationship;

[0043] When the air conditioning system is in cooling mode, the judgment parameters include the opening degree of the electronic expansion valve of the indoor unit and the exhaust temperature of the compressor.

[0044] When the air conditioning system is in heating mode, the judgment parameters include the high-pressure saturation temperature of the outdoor unit, the opening degree of the electronic expansion valve of the outdoor unit, the opening degree of the electronic expansion valve of the indoor unit, and the exhaust temperature of the compressor.

[0045] In this embodiment, since the air conditioning system has completely different meanings in cooling and heating modes, such as the high and low pressure sides, refrigerant flow direction, and key parameters (e.g., subcooling and superheating), this invention obtains the current operating mode of the air conditioning system and the outdoor ambient temperature, and sets preset ambient temperature conditions. This allows for the selection of different refrigerant charge judgment logic based on the current operating mode and ambient temperature, ensuring that the refrigerant charge judgment is only performed within a valid and standard operating range. This avoids judgment failure caused by drastic changes in system operating characteristics at extreme temperatures, thus guaranteeing the accuracy of refrigerant charge judgment from the source.

[0046] Traditional methods for refrigerant charge detection often involve air conditioning systems operating in various states (e.g., multiple indoor units are turned on or off in different combinations, operating at different capacity levels). This complex internal condition leads to significant fluctuations in key parameters such as system pressure and temperature. This invention, however, forces the air conditioning system to operate under the simplest, lowest-load single-unit condition by turning on the indoor unit with the lowest nominal capacity and turning off the others. This greatly simplifies and unifies the internal operating state of the air conditioning system, eliminating interference from different on / off combinations of multiple indoor units. This provides a stable internal environment for subsequent parameter acquisition and threshold comparison, further improving the reliability of refrigerant charge determination.

[0047] Traditional methods typically use static thresholds as the judgment standard, which can easily lead to misjudgments in high-temperature summer and low-temperature winter environments. However, this invention determines dynamic thresholds corresponding to each judgment parameter based on the outdoor ambient temperature, thereby enabling the thresholds for subsequent comparisons to be dynamically adjusted in real time according to the external environment. This ensures that the judgment benchmark always matches the actual state of the air conditioning system under different seasons and climate conditions, thus significantly improving the accuracy of refrigerant charge determination.

[0048] Traditional methods for detecting refrigerant levels often fail to effectively distinguish between "normal operating condition fluctuations" and "pressure anomalies caused by refrigerant abnormalities" (the high-pressure side of the air conditioning system is prone to fluctuations during operation), or lack a clear "stable state" criterion. This results in judgment parameters collected directly under unstable pressure failing to accurately and stably reflect the refrigerant charge status, leading to decreased reliability. In contrast, this invention determines that the air conditioning system has entered a stable operating state only when the fluctuation value of the high-pressure in the air conditioning system is less than a preset pressure fluctuation threshold within a continuous preset time period. This ensures that subsequent judgment parameters accurately and stably reflect the refrigerant charge status of the air conditioning system, avoiding false acquisition and misjudgment caused by transient fluctuations in the air conditioning system.

[0050] Example 2

[0051] As attached Figure 2 As shown, based on Embodiment 1, when the air conditioning system is in cooling mode, the operating parameters of the air conditioning system are adjusted until the fluctuation value of the high pressure of the air conditioning system within a continuous preset time period is less than a preset pressure fluctuation threshold. Specifically, this includes:

[0052] Adjust the outdoor fan speed so that the difference between the outdoor unit's high-pressure saturation temperature and the outdoor unit's coolant pipe temperature is less than or equal to the first temperature threshold.

[0053] The step of adjusting the outdoor fan speed so that the difference between the outdoor unit's high-pressure saturation temperature and the outdoor unit's coolant pipe temperature is less than or equal to a first temperature threshold specifically includes:

[0054] Obtain the high-pressure saturation temperature of the outdoor unit and the coolant pipe temperature of the outdoor unit, and calculate the difference between the high-pressure saturation temperature of the outdoor unit and the coolant pipe temperature of the outdoor unit.

[0055] If the difference is less than or equal to the first temperature threshold, the speed of the outdoor fan is maintained; otherwise, the speed of the outdoor fan is increased to reduce the difference until the difference is less than or equal to the first temperature threshold.

[0056] Specifically, when the air conditioning system is in cooling mode, the outdoor fan speed is first adjusted (in heating mode, the high-pressure gaseous refrigerant flowing from the outdoor unit to the indoor unit has good fluidity and is not easy to stagnate in the pipes; therefore, it is not necessary to adjust the outdoor fan speed to control the heat exchange temperature difference of the outdoor unit condenser), so that the heat exchange temperature difference of the outdoor unit condenser (the heat exchange temperature difference of the outdoor unit condenser = the high-pressure saturation temperature of the outdoor unit - the coolant pipe temperature of the outdoor unit) is ≤ the first temperature threshold A, thus forcibly stabilizing the heat exchange process of the condenser in a preset, efficient small temperature difference state, thereby actively resisting external interference such as changes in ambient temperature and creating a stable condensation environment for the cooling side of the air conditioning system.

[0057] Preferably, the first temperature threshold A is in the range of 2-4℃.

[0058] After the difference is less than or equal to the first temperature threshold, the operating parameters of the air conditioning system are adjusted until the fluctuation value of the high pressure of the air conditioning system within a continuous preset time period is less than the preset pressure fluctuation threshold.

[0059] Specifically, when the air conditioning system is in cooling mode, after the heat exchange temperature difference of the outdoor unit condenser is ≤ the first temperature threshold A, the operating parameters of the air conditioning system are adjusted to make the fluctuation value of the high pressure of the air conditioning system less than the preset pressure fluctuation threshold. When the fluctuation value of the high pressure of the air conditioning system is less than the preset pressure fluctuation threshold for a continuous preset time, the air conditioning system is determined to have entered a stable operating state. Only when both the "stable heat exchange temperature difference" and "continuously stable high pressure fluctuation" conditions are met can the air conditioning system be determined to have entered a stable operating state that can be used for high-precision diagnosis. Compared with the traditional judgment method that simply relies on the running time, the judgment result is more accurate and fundamentally avoids false data collection and misjudgment caused by transient fluctuations in the system.

[0060] Furthermore, when the air conditioning system is in cooling mode, the judgment parameter is compared with the dynamic threshold, and the refrigerant charge status is determined according to a preset logical relationship, specifically including:

[0061] Determine whether the opening degree of the electronic expansion valve of the indoor unit that is turned on is greater than the first opening degree threshold;

[0062] If the opening degree of the electronic expansion valve of the indoor unit is greater than the first opening threshold, it is further determined whether the exhaust temperature of the compressor is greater than the second temperature threshold; otherwise, it is further determined whether the opening degree of the electronic expansion valve of the indoor unit is less than the second opening threshold, wherein the second opening threshold is less than the first opening threshold.

[0063] If the exhaust temperature of the compressor is greater than the second temperature threshold, it is determined that the refrigerant charge is seriously insufficient; otherwise, it is determined that the refrigerant charge is insufficient.

[0064] If the opening degree of the electronic expansion valve of the indoor unit is less than the second opening threshold, it is determined that the refrigerant charge is excessive; otherwise, it is further determined whether the exhaust temperature of the compressor is less than or equal to the second temperature threshold.

[0065] If the compressor's exhaust temperature is less than or equal to the second temperature threshold, the refrigerant charge is deemed appropriate; otherwise, the refrigerant charge is deemed insufficient.

[0066] Specifically, when determining the refrigerant charge amount, firstly, it is determined whether the opening degree of the electronic expansion valve of the opened indoor unit is greater than a first opening threshold X (the value range of the first preset opening threshold X is preferably 90% of the maximum opening degree of the electronic expansion valve); if the opening degree of the electronic expansion valve of the opened indoor unit is greater than the first opening threshold X, then it is further determined whether the discharge temperature of the compressor is greater than a second temperature threshold P; otherwise, it is further determined whether the opening degree of the electronic expansion valve of the opened indoor unit is less than a second opening threshold Y (the value range of the second preset opening threshold Y is preferably 40% of the maximum opening degree of the electronic expansion valve); if the discharge temperature of the compressor is greater than the second temperature threshold P, then it is determined that the refrigerant charge amount is seriously insufficient; otherwise, it is determined that the refrigerant charge amount is insufficient; if the opening degree of the electronic expansion valve of the opened indoor unit is less than the second opening threshold X, then it is determined that the refrigerant charge amount is excessive; otherwise, it is further determined whether the discharge temperature of the compressor is less than or equal to the second temperature threshold P; if the discharge temperature of the compressor is less than or equal to the second temperature threshold P, then it is determined that the refrigerant charge amount is appropriate; otherwise, it is determined that the refrigerant charge amount is insufficient.

[0068] Example 3

[0069] As attached Figure 3 As shown, based on Embodiment 1, when the air conditioning system is in heating mode, the judgment parameter is compared with the dynamic threshold, and the refrigerant charge status is determined according to a preset logical relationship, specifically including:

[0070] Determine whether the high-pressure saturation temperature of the outdoor unit is greater than the third temperature threshold;

[0071] If the high-pressure saturation temperature of the outdoor unit is greater than the third temperature threshold, then it is further determined whether the opening degree of the electronic expansion valve of the outdoor unit is less than the third opening degree threshold; otherwise, it is determined that the refrigerant charge is insufficient.

[0072] If the opening degree of the electronic expansion valve of the outdoor unit is less than the third opening degree threshold, it is determined that the refrigerant charge is excessive; otherwise, it is further determined whether the opening degree of the electronic expansion valve of the indoor unit is greater than or equal to the fourth opening degree threshold.

[0073] If the opening degree of the electronic expansion valve of the indoor unit is greater than or equal to the fourth opening threshold, then it is further determined whether the difference between the compressor's exhaust temperature and the high-pressure saturation temperature of the outdoor unit is greater than the fourth temperature threshold; otherwise, it is determined that the refrigerant charge is insufficient.

[0074] If the difference between the compressor's exhaust temperature and the outdoor unit's high-pressure saturation temperature is greater than the fourth temperature threshold, the refrigerant charge is determined to be appropriate; otherwise, the refrigerant charge is determined to be insufficient.

[0075] Specifically, when determining the refrigerant charge amount, firstly, it is determined whether the high-pressure saturation temperature of the outdoor unit is greater than the third preset temperature threshold T (the value of the third preset temperature threshold T is preferably the high-pressure value during stable operation of the air conditioning system, such as 48-50℃); if the high-pressure saturation temperature of the outdoor unit is greater than the third preset temperature threshold T, then it is further determined whether the opening degree of the electronic expansion valve of the outdoor unit is less than the third preset opening degree threshold M (the value of the third preset opening degree threshold M is preferably 50% of the opening degree of the electronic expansion valve); otherwise, it is determined that the refrigerant charge amount is insufficient; if the opening degree of the electronic expansion valve of the outdoor unit is less than the third preset opening degree threshold M, it is determined that the refrigerant charge amount is excessive; otherwise, it is further determined that the refrigerant charge amount is excessive. Determine whether the opening degree of the electronic expansion valve of the indoor unit is ≥ the fourth preset opening threshold Z (the value range of the fourth preset opening threshold Z is preferably 70% of the opening degree of the electronic expansion valve); if the opening degree of the electronic expansion valve of the indoor unit is ≥ the fourth preset opening threshold Z, then further determine whether the difference between the compressor's exhaust temperature and the high-pressure saturation temperature of the outdoor unit is > the fourth preset temperature threshold N (the value range of the fourth preset temperature threshold N is preferably 20-30℃); otherwise, determine that the refrigerant charge is insufficient; if the difference between the compressor's exhaust temperature and the high-pressure saturation temperature of the outdoor unit is > the fourth preset temperature threshold N, then determine that the refrigerant charge is appropriate; otherwise, determine that the refrigerant charge is insufficient.

[0077] Example 4

[0078] As attached Figure 4 As shown, in another aspect, embodiments of the present invention also provide a refrigerant charge determination device for a multi-split air conditioning system, the determination device comprising:

[0079] Module 1 is used to acquire the current operating mode of the air conditioning system and the outdoor ambient temperature;

[0080] Operating condition control module 2 is used to turn on the indoor unit with the smallest nominal capacity in the air conditioning system and turn off the other indoor units when the outdoor ambient temperature meets the preset ambient temperature conditions corresponding to the current operating mode.

[0081] The operation control module 3 is used to adjust the operating parameters of the air conditioning system so that the air conditioning system enters a stable operating state.

[0082] Acquisition module 4 is used to acquire judgment parameters corresponding to the current operating mode under stable operating conditions;

[0083] The threshold determination module 5 is used to determine the dynamic threshold corresponding to each judgment parameter based on the outdoor ambient temperature.

[0084] The status judgment module 6 is used to compare the judgment parameters with the dynamic threshold and determine the refrigerant charge status according to the preset logical relationship.

[0085] Furthermore, the judgment device also includes a storage module 7, which is used to store the correspondence between judgment parameters and dynamic thresholds, and after receiving a call instruction sent by the threshold determination module 5, sends the correspondence between judgment parameters and dynamic thresholds to the threshold determination module 5.

[0086] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for determining the refrigerant charge amount of a multi-split air conditioning system, the air conditioning system comprising an outdoor unit and a plurality of indoor units connected to the outdoor unit, characterized in that, The determination method includes the following steps: Obtain the current operating mode of the air conditioning system and the outdoor ambient temperature; If the outdoor ambient temperature meets the preset ambient temperature condition corresponding to the current operating mode, then the indoor unit with the smallest nominal capacity in the air conditioning system is turned on, and the remaining indoor units are turned off. Adjust the operating parameters of the air conditioning system until the fluctuation value of the high pressure of the air conditioning system within a continuous preset time period is less than the preset pressure fluctuation threshold, and determine that the air conditioning system has entered a stable operating state. In the stable operating state, judgment parameters corresponding to the current operating mode are collected; Based on the outdoor ambient temperature, the dynamic threshold corresponding to each of the judgment parameters is determined by calculation or query through a preset correspondence. The judgment parameter is compared with the dynamic threshold, and the refrigerant charge status is determined according to the preset logical relationship; When the air conditioning system is in cooling mode, the judgment parameters include the opening degree of the electronic expansion valve of the indoor unit and the exhaust temperature of the compressor. When the air conditioning system is in heating mode, the judgment parameters include the high-pressure saturation temperature of the outdoor unit, the opening degree of the electronic expansion valve of the outdoor unit, the opening degree of the electronic expansion valve of the indoor unit, and the exhaust temperature of the compressor.

2. The method for determining the refrigerant charge amount of a multi-split air conditioning system as described in claim 1, characterized in that, When the air conditioning system is in cooling mode, the operating parameters of the air conditioning system are adjusted until the fluctuation value of the high pressure of the air conditioning system within a continuous preset time period is less than a preset pressure fluctuation threshold, specifically including: Adjust the outdoor fan speed so that the difference between the outdoor unit's high-pressure saturation temperature and the outdoor unit's coolant pipe temperature is less than or equal to the first temperature threshold. After the difference is less than or equal to the first temperature threshold, the operating parameters of the air conditioning system are adjusted until the fluctuation value of the high pressure of the air conditioning system within a continuous preset time period is less than the preset pressure fluctuation threshold.

3. The method for determining the refrigerant charge amount of a multi-split air conditioning system as described in claim 2, characterized in that, The adjustment of the outdoor fan speed to ensure that the difference between the outdoor unit's high-pressure saturation temperature and the outdoor unit's coolant pipe temperature is less than or equal to a first temperature threshold specifically includes: Obtain the high-pressure saturation temperature of the outdoor unit and the coolant pipe temperature of the outdoor unit, and calculate the difference between the high-pressure saturation temperature of the outdoor unit and the coolant pipe temperature of the outdoor unit. If the difference is less than or equal to the first temperature threshold, the speed of the outdoor fan is maintained; otherwise, the speed of the outdoor fan is increased to reduce the difference until the difference is less than or equal to the first temperature threshold.

4. The method for determining the refrigerant charge amount of a multi-split air conditioning system as described in claim 3, characterized in that, The first temperature threshold ranges from 2 to 4°C.

5. The method for determining the refrigerant charge amount of a multi-split air conditioning system as described in claim 1, characterized in that, When the air conditioning system is in cooling mode, the outdoor ambient temperature is within a first temperature range; when the air conditioning system is in heating mode, the outdoor ambient temperature is within a second temperature range; the temperature in the first temperature range is higher than the temperature in the second temperature range.

6. The method for determining the refrigerant charge amount of a multi-split air conditioning system as described in claim 1, characterized in that, When the air conditioning system is in cooling mode, the judgment parameter is compared with the dynamic threshold, and the refrigerant charge status is determined according to a preset logical relationship, specifically including: Determine whether the opening degree of the electronic expansion valve of the indoor unit that is turned on is greater than the first opening degree threshold; If the opening degree of the electronic expansion valve of the indoor unit is greater than the first opening threshold, it is further determined whether the exhaust temperature of the compressor is greater than the second temperature threshold; otherwise, it is further determined whether the opening degree of the electronic expansion valve of the indoor unit is less than the second opening threshold, wherein the second opening threshold is less than the first opening threshold. If the exhaust temperature of the compressor is greater than the second temperature threshold, it is determined that the refrigerant charge is seriously insufficient; otherwise, it is determined that the refrigerant charge is insufficient. If the opening degree of the electronic expansion valve of the indoor unit is less than the second opening threshold, it is determined that the refrigerant charge is excessive; otherwise, it is further determined whether the exhaust temperature of the compressor is less than or equal to the second temperature threshold. If the compressor's exhaust temperature is less than or equal to the second temperature threshold, the refrigerant charge is deemed appropriate; otherwise, the refrigerant charge is deemed insufficient.

7. The method for determining the refrigerant charge amount of a multi-split air conditioning system as described in claim 1, characterized in that, When the air conditioning system is in heating mode, the judgment parameter is compared with the dynamic threshold, and the refrigerant charge status is determined according to a preset logical relationship, specifically including: Determine whether the high-pressure saturation temperature of the outdoor unit is greater than the third temperature threshold; If the high-pressure saturation temperature of the outdoor unit is greater than the third temperature threshold, then it is further determined whether the opening degree of the electronic expansion valve of the outdoor unit is less than the third opening degree threshold; otherwise, it is determined that the refrigerant charge is insufficient. If the opening degree of the electronic expansion valve of the outdoor unit is less than the third opening degree threshold, it is determined that the refrigerant charge is excessive; otherwise, it is further determined whether the opening degree of the electronic expansion valve of the indoor unit is greater than or equal to the fourth opening degree threshold. If the opening degree of the electronic expansion valve of the indoor unit is greater than or equal to the fourth opening threshold, then it is further determined whether the difference between the compressor's exhaust temperature and the high-pressure saturation temperature of the outdoor unit is greater than the fourth temperature threshold; otherwise, it is determined that the refrigerant charge is insufficient. If the difference between the compressor's exhaust temperature and the outdoor unit's high-pressure saturation temperature is greater than the fourth temperature threshold, the refrigerant charge is determined to be appropriate; otherwise, the refrigerant charge is determined to be insufficient.

8. A refrigerant charge quantity determination device for a multi-split air conditioning system, employing the refrigerant charge quantity determination method for a multi-split air conditioning system as described in any one of claims 1-7, characterized in that, The determining device includes: The acquisition module is used to acquire the current operating mode of the air conditioning system and the outdoor ambient temperature; The operating condition control module is used to turn on the indoor unit with the smallest nominal capacity in the air conditioning system and turn off the other indoor units when the outdoor ambient temperature meets the preset ambient temperature conditions corresponding to the current operating mode. The operation control module is used to adjust the operating parameters of the air conditioning system so that the air conditioning system enters a stable operating state. The data acquisition module is used to collect judgment parameters corresponding to the current operating mode under stable operating conditions. The threshold determination module is used to determine the dynamic threshold corresponding to each judgment parameter based on the outdoor ambient temperature. The status judgment module is used to compare the judgment parameters with the dynamic threshold and determine the refrigerant charge status according to the preset logical relationship.

9. The refrigerant charge determination device for a multi-split air conditioning system as described in claim 8, characterized in that, The judgment device further includes a storage module, which stores the correspondence between judgment parameters and dynamic thresholds, and sends the correspondence between judgment parameters and dynamic thresholds to the threshold determination module after receiving a call instruction from the threshold determination module.

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