Multi-connected air conditioning unit and control method thereof

Abstract

The application relates to a multi-connected air conditioner unit and a control method thereof, and relates to the technical field of multi-connected air conditioner systems, and aims to solve the problem of excessively large oil discharge rate difference between multiple different types of compressors in parallel operation in the multi-connected air conditioner unit. The control method comprises the following steps: establishing a function model among the load, frequency and oil discharge rate parameters of a first compressor and a second compressor. According to the total load of the whole machine, the initial load of the first compressor and the second compressor is distributed. And the initial frequency is calculated according to the function model. According to the function model, the first oil discharge rate and the second oil discharge rate of the first compressor and the second compressor are calculated. The operating frequency of the first compressor and the second compressor is controlled and adjusted to reduce the oil discharge rate difference of the first compressor and the second compressor. The problem of compressor oil shortage or system oil accumulation caused by uneven distribution of lubricating oil is avoided, the long-term stable operation of the multi-connected air conditioner unit is ensured, and the whole machine operation efficiency and reliability of the unit are improved.

Description

Technical Field

[0001] This application relates to the field of multi-split air conditioning system technology, and in particular to a multi-split air conditioning unit and its control method. Background Technology

[0002] Multi-split air conditioning systems typically employ multiple compressors operating in parallel to meet larger rated load demands and allow for flexible adjustment to varying load ranges. However, due to structural differences or variations in characteristic parameters, especially between different types of compressors, the parallel operation of these compressors can lead to system instability.

[0003] Currently, multi-split air conditioning systems typically employ a fixed capacity allocation strategy. Combining different types of compressors in parallel can lead to significant differences in oil discharge rates and operating ranges. During operation, this can result in some compressors running out of oil or exceeding their operating range, affecting unit reliability and efficiency, and even damaging the compressors, ultimately causing the air conditioning unit to malfunction. Summary of the Invention

[0004] This application provides a multi-split air conditioning unit and its control method, aiming to solve the problem of excessive differences in oil discharge rates among multiple compressors of different types operating in parallel in a multi-split air conditioning unit.

[0005] In a first aspect, this application provides a control method for a multi-split air conditioning unit, the multi-split air conditioning unit including a first compressor and a second compressor arranged in parallel, the control method including: Establish a functional model relating the load, frequency, and oil discharge rate parameters of the first and second compressors.

[0006] The initial loads of the first and second compressors are allocated according to the total load of the machine, and the initial frequencies of the first and second compressors are calculated according to the function model.

[0007] Based on the function model, calculate the first oil discharge rate of the first compressor at the initial frequency, and calculate the second oil discharge rate of the second compressor at the initial frequency.

[0008] Control and adjust the operating frequency of the first compressor and the second compressor to reduce the difference in oil discharge rate between the first compressor and the second compressor.

[0009] In some implementations, controlling the operating frequency of the first compressor and the second compressor includes: Compare the magnitudes of the first and second oil discharge rates.

[0010] If the difference between the first oil discharge rate and the second oil discharge rate is greater than the first preset value, the operating frequency of the first compressor is controlled to decrease by the second preset value.

[0011] The third oil discharge rate and the adjusted operating load of the first compressor are calculated based on the function model and the adjusted operating frequency of the first compressor.

[0012] The adjusted operating load and operating frequency of the second compressor are calculated based on the total load of the entire machine and the adjusted operating load of the first compressor.

[0013] In some implementations, controlling the operating frequency of the first compressor and the second compressor includes: If the difference between the second oil discharge rate and the first oil discharge rate is greater than the first preset value, the operating frequency of the second compressor is controlled to decrease by the second preset value.

[0014] The fourth oil discharge rate and the adjusted operating load of the second compressor are calculated based on the function model and the adjusted operating frequency of the second compressor.

[0015] The adjusted operating load and operating frequency of the first compressor are calculated based on the overall operating load and the adjusted operating load of the second compressor.

[0016] In some embodiments, after controlling and adjusting the operating frequencies of the first compressor and the second compressor to reduce the difference in oil discharge rates between the first compressor and the second compressor, the control method includes: Obtain the cumulative operating time of the first compressor and the second compressor at the corresponding oil discharge rate.

[0017] Determine whether the percentage of time the first compressor and the second compressor are in the state where the oil discharge rate is less than the first threshold is greater than 70%.

[0018] If so, control the delayed oil return.

[0019] Otherwise, control the normal oil return.

[0020] In some implementations, the function model of the first compressor includes an operating load-operating frequency model and an operating frequency-oil discharge rate model. The function model of the second compressor includes an operating load-operating frequency model and an operating frequency-oil discharge rate model.

[0021] In some implementations, the operating frequency-discharge rate model has multiple frequency ranges set sequentially.

[0022] If the oil discharge rate of the first compressor is greater than that of the second compressor, the operating frequency of the first compressor is adjusted within its frequency range.

[0023] If the oil discharge rate of the second compressor is greater than that of the first compressor, the operating frequency of the second compressor is adjusted within the specified frequency range.

[0024] In some implementations, controlling the operating frequencies of the first compressor and the second compressor to reduce the difference in oil discharge rates between the two compressors includes: The operating frequencies of the first compressor and the second compressor are controlled and adjusted so that the absolute value of the difference in oil discharge rate between the first compressor and the second compressor is lower than a first preset value.

[0025] Secondly, this application provides a multi-split air conditioning unit, including a first compressor, a second compressor, and a control module. The second compressor is connected in parallel with the first compressor, and the control module is electrically connected to both the first and second compressors to obtain their operating loads and frequencies. The control module is configured to execute the control method for the multi-split air conditioning unit described in the first aspect.

[0026] In some implementations, the multi-split air conditioning unit includes a liquid level sensor. The liquid level sensor is installed in the first compressor and the second compressor. The liquid level sensor is electrically connected to the control module and is used to detect the oil level in the first compressor and the second compressor.

[0027] In some implementations, the multi-split air conditioning unit includes a pressure sensor. The pressure sensor is installed in the first compressor and the second compressor. The pressure sensor is electrically connected to the control module and is used to detect the oil pressure parameters in the first compressor and the second compressor.

[0028] Thirdly, this application provides a control module, including at least one communication interface, at least one bus connected to the at least one communication interface, at least one processor connected to the at least one bus, and at least one memory connected to the at least one bus. The processor is configured to execute the control method for a multi-split air conditioning unit as described in the first aspect.

[0029] Fourthly, this application also provides a computer storage medium storing computer-executable instructions for executing the control method of the multi-split air conditioning unit in the first aspect.

[0030] The technical solutions provided in this application have the following advantages compared with the prior art: By establishing a functional model relating the load, frequency, and oil discharge rate parameters of parallel compressors, and dynamically calculating and adjusting the operating frequency of each compressor based on this model, the difference in oil discharge rate between the first and second compressors is effectively reduced. Therefore, in parallel operation of multi-split air conditioning units, especially when different types of compressors are operating in parallel, a balanced distribution of lubricating oil can be achieved, avoiding compressor oil shortages or system oil accumulation problems caused by uneven lubricating oil distribution. This method improves the operational stability and reliability of the compressors, ensures the long-term stable operation of multi-split air conditioning units, and helps improve the overall operating efficiency of multi-split air conditioning units. Attached Figure Description

[0031] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0032] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0033] One or more embodiments are illustrated by way of example with reference numerals in the accompanying drawings. These illustrations do not constitute a limitation on the embodiments. Elements with the same reference numerals in the drawings are denoted as similar elements. Unless otherwise stated, the figures in the drawings are not to be limited by scale.

[0034] Figure 1 This application provides an electrical connection diagram of a multi-split air conditioning unit. Figure 2 A flowchart illustrating a control method for a multi-split air conditioning unit provided in this application embodiment; Figure 3 A flowchart illustrating another control method for a multi-split air conditioning unit provided in this application embodiment; Figure 4 A model curve of operating frequency and oil discharge rate provided for an embodiment of this application; Figure 5 This is a schematic diagram of the connection structure of a control module provided in an embodiment of this application.

[0035] Explanation of reference numerals in the attached figures: 10. First compressor; 20. Second compressor; 30. Control module; 31. Processor; 32. Communication interface; 33. Memory; 34. Communication bus; 40. Liquid level sensor; 50. Pressure sensor. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0037] The following disclosure provides numerous different embodiments or examples for implementing various structures of this application. To simplify the disclosure, specific examples of components and arrangements are described below. These are merely examples and are not intended to limit the scope of this application. Furthermore, reference numerals and / or letters may be repeated in different examples. Such repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed.

[0038] For ease of description, spatial relative terms may be used in the text to describe the relative position or movement of one element or feature relative to another element or feature, as shown in the figure. These relative terms include, for example, "inside," "outside," "middle," "outer," "below," "below," "above," "front," "back," etc. Such spatial relative terms are intended to include different orientations of the device in use or operation, other than those depicted in the figure. For example, if the device in the figure undergoes a positional flip, orientation change, or change of motion, these directional indications will change accordingly. For instance, an element described as "below other elements or features" or "below other elements or features" will subsequently be oriented "above other elements or features" or "above other elements or features." Therefore, the example term "below" can include both upper and lower orientations. The device may be otherwise oriented (rotated 90 degrees or in other directions), and the spatial relative descriptors used in the text will be interpreted accordingly.

[0039] Multi-split air conditioning systems typically employ multiple compressors operating in parallel to meet larger rated load demands and allow for flexible adjustment to varying load ranges. However, due to structural differences or variations in characteristic parameters, especially between different types of compressors, the parallel operation of these compressors can lead to system instability.

[0040] Currently, multi-split air conditioning systems typically employ a fixed capacity allocation strategy. Combining different types of compressors in parallel can lead to significant differences in oil discharge rates and operating ranges. During operation, this can result in some compressors running out of oil or exceeding their operating range, affecting unit reliability and potentially damaging the compressors, ultimately causing the air conditioning unit to malfunction.

[0041] Please see Figures 1 to 5 This application provides a multi-split air conditioning unit and its control method, aiming to solve the problem of excessive differences in oil discharge rates among multiple compressors of different types operating in parallel in a multi-split air conditioning unit.

[0042] This application provides a multi-split air conditioning unit, such as... Figure 1 As shown, the multi-split air conditioning unit includes a first compressor 10, a second compressor 20, and a control module 30. The first compressor 10 and the second compressor 20 are connected in parallel. The control module 30 is electrically connected to the first compressor 10 and the second compressor 20, and is used to acquire the operating load and operating frequency of the first compressor 10 and the second compressor 20. The control module is configured to execute the control method for the multi-split air conditioning unit.

[0043] It should be noted that, in the embodiments of this application, the first compressor 10 and the second compressor 20 can be the same type of compressor or different types of compressors. The difference lies in the fact that compressors of the same type have smaller structural and parametric differences, resulting in a smaller difference in oil discharge rate between them at the same operating frequency (or operating load). However, compressors of different types (such as two of scroll, rotary, or piston types) have larger structural differences, leading to a larger difference in oil discharge rate at the same operating frequency (or operating load).

[0044] A multi-split air conditioning unit may include multiple compressors connected in parallel with different types or parameters. The first compressor 10 and the second compressor 20 in the multi-split air conditioning unit are only used to describe the adjustment method when the oil discharge rate is different, and do not mean that the air conditioning unit only includes these two types of compressors.

[0045] like Figure 2 As shown, the control method includes: Step S100: Establish a functional model between the load, frequency and oil discharge rate parameters of the first compressor 10 and the second compressor 20.

[0046] Step S200: Allocate the initial load of the first compressor 10 and the second compressor 20 according to the total load of the whole machine, and calculate the initial frequency of the first compressor 10 and the second compressor 20 according to the function model.

[0047] Step S300: Calculate the first oil discharge rate of the first compressor 10 at the initial frequency according to the function model, and calculate the second oil discharge rate of the second compressor 20 at the initial frequency.

[0048] Step S400: Control and adjust the operating frequency of the first compressor 10 and the second compressor 20 to reduce the difference in oil discharge rate between the first compressor 10 and the second compressor 20.

[0049] The functional model relating load, frequency, and oil discharge rate is used to reflect the lubricating oil discharge characteristics of the compressor under different operating conditions. This model can be constructed based on historical operating data, experimental data, or simulation results, and is used to predict or calculate the oil discharge rate of the compressor under specific operating loads and frequencies.

[0050] Oil discharge rate refers to the ratio of the amount of lubricating oil discharged by the compressor per unit time to the total discharge volume of the compressor. The oil discharge rate directly affects the amount of lubricating oil remaining inside the compressor. An excessively high oil discharge rate may lead to insufficient oil inside the compressor, thus affecting the compressor's operational stability and service life. Conversely, an excessively low oil discharge rate indicates that the multi-split air conditioning unit is operating at low load for extended periods, potentially leading to liquid slugging due to oil accumulation within the system.

[0051] The oil discharge rate difference refers to the numerical difference in the oil discharge rate among multiple compressors operating in parallel. The magnitude of this difference reflects the evenness of lubricant distribution in each compressor. A smaller difference indicates a more even distribution of lubricant, resulting in higher compressor operational stability. A larger difference indicates a more uneven distribution of lubricant, potentially causing the compressor with the higher oil discharge rate to be in a state of oil shortage, thus affecting its operational stability and service life.

[0052] In the multi-split air conditioning unit of this embodiment, the first compressor 10 and the second compressor 20 are connected in parallel. When needed, both compressors can be configured to operate at full power to meet the high-load operation requirements of the system. Alternatively, when needed, both compressors can be configured to operate at low power, or only one compressor can be configured to operate to meet the low-load operation requirements of the system. This allows for a wide range of flexible adjustments to the system's operating load to meet different cooling or heating needs.

[0053] To effectively manage the oil discharge rate of the compressor, function models need to be established for the first compressor 10 and the second compressor 20 respectively. These function models can be mathematical functions, lookup tables, or models based on machine learning algorithms. Their input parameters can include the compressor's operating frequency, operating load, suction pressure, discharge pressure, operating temperature, and discharge volume, while the outputs are the corresponding operating frequency and oil discharge rate.

[0054] For example, extensive experiments can be conducted on different compressor models in a laboratory environment, recording their operating parameters and actual oil discharge under various working conditions, thereby fitting a curve or function reflecting the relationship between the oil discharge rate and the operating parameters. Another approach is to establish a physical model of the compressor using simulation software, simulating its internal fluid dynamics behavior under different operating conditions, and thus predicting the oil discharge rate. Alternatively, both methods can be used simultaneously: obtaining key parameters through experiments and constructing a simulation physical model based on these parameters to predict the oil discharge rate under different operating conditions.

[0055] When a multi-split air conditioning unit is in operation for the initial period or when the total load changes, it is necessary to perform initial load allocation for the first compressor 10 and the second compressor 20 based on the current total load of the entire unit. Initial load allocation can employ various strategies. For example, it can be based on the compressor's rated capacity, historical operating data, or a preset allocation ratio. One allocation method is to distribute the entire unit load evenly among the parallel compressors. Another method is to prioritize allocation to the compressor with the higher current efficiency based on the compressor's efficiency curve. Alternatively, the operating load of each compressor can be controlled to be evenly distributed according to its rated load ratio; that is, for a total load of 10 kW, for two compressors with rated powers of 12 kW and 8 kW, the initial load of the compressor with the larger rated power is 6 kW, and the initial load of the other compressor is 4 kW.

[0056] After the initial load allocation is completed, the initial frequencies corresponding to the first compressor 10 and the second compressor 20 under the initial load are calculated using the established function model. Subsequently, the first oil discharge rate Ra0 of the first compressor 10 at the current initial frequency and the second oil discharge rate Rb0 of the second compressor 20 at the current initial frequency can be calculated according to the function model.

[0057] For example, if the initial load corresponds to the operating frequency of the first compressor 10 as Xa, then Xa is input into the function model of the first compressor 10 to obtain the first oil discharge rate Ra0. Similarly, a similar calculation is performed on the second compressor 20 to obtain the second oil discharge rate Rb0. Alternatively, the function model can be configured to directly calculate the corresponding oil discharge rate based on the operating load; this is not limited.

[0058] After obtaining the oil discharge rates of the first compressor 10 and the second compressor 20, the operating frequencies of the first compressor 10 and the second compressor 20 need to be controlled and adjusted according to the relationship between the first oil discharge rate Ra0 and the second oil discharge rate Rb0, in order to reduce the difference in oil discharge rates between the two. This adjustment process aims to make the oil discharge rates of each compressor more balanced, avoiding a single compressor from running out of oil due to excessive oil discharge, or oil accumulation in the system pipeline due to insufficient oil discharge.

[0059] For example, by comparing the oil discharge rates of two compressors, the operating frequency of the compressor with the higher oil discharge rate can be appropriately reduced, while the operating frequency of the compressor with the lower oil discharge rate can be appropriately increased to maintain the overall load of the machine. This adjustment can be an iterative process, gradually reducing the difference in oil discharge rates through small-scale frequency adjustments and recalculation of the oil discharge rate until a preset equilibrium state is reached.

[0060] The above solutions can reduce or avoid the problem of excessive or insufficient lubricating oil inside some compressors, ensuring that the lubricating oil inside each compressor is kept in a suitable lubrication state. This reduces the operating resistance of the compressors and improves their operating efficiency, which is beneficial to improving the overall operating efficiency and reliability of multi-split air conditioning units.

[0061] This application establishes a functional model relating the load, frequency, and oil discharge rate parameters of parallel compressors, and dynamically calculates and adjusts the operating frequency of each compressor based on this model, thereby effectively reducing the difference in oil discharge rate between the first compressor 10 and the second compressor 20. Therefore, in the parallel operation of multi-split air conditioning units, especially when different types of compressors are operating in parallel, a balanced distribution of lubricating oil can be achieved, avoiding problems such as compressor oil shortage or system oil accumulation caused by uneven lubricating oil distribution. This method improves the operational stability and reliability of the compressors, ensures the long-term stable operation of the multi-split air conditioning unit, and helps improve the overall operating efficiency of the multi-split air conditioning unit.

[0062] Specifically, such as Figure 3 As shown, in step S400, the step of controlling and adjusting the operating frequency of the first compressor and the second compressor includes: Step S410: Compare the magnitudes of the first and second oil discharge rates.

[0063] Step S421: If the difference between the first oil discharge rate and the second oil discharge rate is greater than the first preset value, control the operating frequency of the first compressor to decrease by the second preset value.

[0064] Step S422: Calculate the third oil discharge rate and the adjusted operating load of the first compressor 10 based on the function model and the adjusted operating frequency of the first compressor 10.

[0065] Step S423: Calculate the adjusted operating load and operating frequency of the second compressor 20 based on the overall operating load and the adjusted operating load of the first compressor 10.

[0066] The first preset value is a positive number. If the difference between the first oil discharge rate and the second oil discharge rate is greater than the first preset value, it means that the first oil discharge rate is greater than the second oil discharge rate and the difference between the two is large. In other words, the degree of imbalance in the oil discharge rate has reached the level that requires intervention.

[0067] The second preset value defines the step size or amplitude of each load adjustment, ensuring the smoothness and controllability of the adjustment process and avoiding system oscillations caused by excessive adjustments. This step directly addresses the root cause of the oil discharge imbalance by conditionally reducing the load on the compressor with a high oil discharge rate.

[0068] Subsequently, based on the function model and the adjusted operating frequency of the first compressor 10, the third oil discharge rate Ra1 and the adjusted operating load of the first compressor 10 are calculated. This step utilizes a pre-established function model to predict or recalculate the oil discharge rate of the first compressor 10 after load adjustment, in order to evaluate the effect of this adjustment and provide a new data basis for subsequent further judgments and adjustments.

[0069] Finally, the adjusted operating load and operating frequency of the second compressor 20 are calculated based on the total load of the entire unit and the adjusted operating load of the first compressor 10. Since the total load of a multi-split air conditioning unit typically needs to remain stable, when the operating load of the first compressor 10 changes, the operating load of the second compressor 20 needs to be adjusted accordingly to ensure that the cooling or heating capacity of the entire unit is not affected and to maintain the balance of the total system load. For example, if the operating load of the first compressor 10 decreases by a preset value, the operating load of the second compressor 20 is increased by the same preset value.

[0070] By introducing a comparison mechanism based on the difference in oil discharge rates and a preset value judgment mechanism, the unit can intelligently identify the compressor that needs adjustment and reduce it in preset steps (such as a second preset value), avoiding blind or excessive adjustment. Simultaneously, by calculating the adjusted oil discharge rate in real time and compensatingly adjusting the load and frequency of the other compressor, the unit ensures that while optimizing the oil discharge rate balance, it maintains stable overall operating load, improves system efficiency and reliability, and extends compressor lifespan.

[0071] Or, such as Figure 3 As shown, step S400 further includes: Step S431: If the difference between the second oil discharge rate and the first oil discharge rate is greater than the first preset value, control the operating frequency of the second compressor to decrease by the second preset value.

[0072] Step S432: Calculate the fourth oil discharge rate and the adjusted operating load of the second compressor 20 based on the function model and the adjusted operating frequency of the second compressor 20.

[0073] Step S433: Calculate the adjusted operating load and operating frequency of the first compressor 10 based on the overall operating load and the adjusted operating load of the second compressor 20.

[0074] If the difference between the second and first oil discharge rates is greater than the first preset value, it indicates that the second oil discharge rate is greater than the first oil discharge rate, and the difference between the two is significant, meaning that the oil discharge rate imbalance has reached a level requiring intervention. The operating load of the second compressor 20 needs to be reduced accordingly to the second preset value.

[0075] Subsequently, the fourth oil discharge rate Rb1 of the second compressor 20 is calculated based on the function model and the adjusted operating frequency of the second compressor 20. This step uses a pre-established function model to predict or recalculate the oil discharge rate of the second compressor 20 after frequency adjustment, in order to evaluate the effect of this adjustment and provide a new data basis for further judgment and adjustment.

[0076] Finally, the adjusted operating load and operating frequency of the first compressor 10 are calculated based on the total load of the unit and the adjusted operating load of the second compressor 20. Since the total load of the multi-split air conditioning unit usually needs to be kept stable, when the operating load of the second compressor 20 changes, the operating load of the first compressor 10 needs to be adjusted accordingly to ensure that the cooling or heating capacity of the entire unit is not affected and to maintain the balance of the total system load.

[0077] Through the above technical solution, when the oil discharge rate of the second compressor 20 is significantly higher than that of the first compressor 10, the system can respond promptly and proactively reduce the operating frequency of the second compressor 20. This bidirectional frequency adjustment mechanism overcomes the limitations of adjusting only the first compressor 10, allowing the system to perform targeted optimization regardless of which compressor has a high oil discharge rate. By recalculating the adjusted oil discharge rate and adjusting the operating load and frequency of the other compressor in conjunction, the system ensures that the difference in oil discharge rates between the first compressor 10 and the second compressor 20 is continuously and effectively reduced while maintaining the overall unit load requirements. This not only helps avoid the risk of oil shortage caused by a single compressor having a long-term high oil discharge rate, but also promotes the even distribution and return of compressor oil, thereby extending the compressor's service life and improving the operational reliability of the multi-split air conditioning unit.

[0078] In some implementations, step S400 further includes: S440: Control and adjust the operating frequency of the first compressor 10 and the second compressor 20 so that the absolute value of the difference in oil discharge rate between the first compressor 10 and the second compressor 20 is lower than the first preset value.

[0079] In step S400, steps S421-S423 and S431-S433 are two parallel adjustment methods used to adjust the operating load of the corresponding compressors according to different differences in oil discharge rates. These two adjustment methods can be repeated until the difference in oil discharge rate between the first compressor 10 and the second compressor 20 meets a preset requirement range. Alternatively, in steps S423 and S433, the adjusted oil discharge rate of the two compressors can be calculated using a function model, and the result can be compared with the adjusted oil discharge rate in step S410 until the absolute value of the difference in oil discharge rate between the first compressor 10 and the second compressor 20 is lower than a first preset value.

[0080] For example, if the third oil discharge rate of the first compressor 10 is R01 and the fourth oil discharge rate of the second compressor 20 is Rb1, then the absolute value of the difference in oil discharge rates is |Ra1-Rb1|. By focusing on the absolute value, the degree of imbalance between the two can be uniformly measured. The "first preset value" is a pre-set threshold used to measure whether the difference in oil discharge rates has reached an acceptable balance state. This value is usually determined based on system design requirements, compressor characteristics, operating conditions, and desired oil balance accuracy; for example, it can be set to 0.5%, 1%, or a smaller percentage. When the absolute value of the oil discharge rate difference is less than or equal to this first preset value, the system considers the oil balance state of the compressor unit to have met the requirements and can stop or slow down load adjustment.

[0081] To achieve this goal, the control module 30 continuously monitors the oil discharge rates of the first compressor 10 and the second compressor 20 and calculates the absolute value of their difference. Then, it compares this absolute value with a first preset value. If the absolute value is greater than the first preset value, the control module 30 will, according to a preset control strategy, reduce the operating frequency of the higher-frequency compressor to decrease its oil discharge rate, and correspondingly increase the operating frequency of the lower-frequency compressor to increase its oil discharge rate while maintaining a constant total load, thereby reducing the difference in oil discharge rates. This process is iterative until the absolute value of the oil discharge rate difference falls below the first preset value.

[0082] The above technical solution specifies the goal of reducing the oil discharge rate difference as making its absolute value lower than a preset first value, thus providing a clear and quantifiable termination condition for adjusting the compressor's operating load. This avoids endless fine-tuning or premature cessation of adjustment, ensuring that the oil balance between the first compressor 10 and the second compressor 20 reaches a precise and stable state. This precise control helps prevent a compressor from having an excessively low oil level due to prolonged excessive oil discharge, or an excessively high oil level due to insufficient oil discharge, thereby effectively avoiding problems such as increased wear, decreased efficiency, or even compressor shutdown caused by oil imbalance. Ultimately, this significantly improves the operational reliability, stability, and overall energy efficiency of the multi-split air conditioning unit.

[0083] It should be noted that the function model of the first compressor 10 includes the operating load-operating frequency model and the operating frequency-oil discharge rate model (see...). Figure 4 The function model of the second compressor 20 includes the operating load-operating frequency model and the operating frequency-oil discharge rate model (see...). Figure 4 ).

[0084] The operating load-operating frequency model describes the mapping relationship between the compressor's operating load (such as cooling capacity demand) and its corresponding operating frequency (such as the inverter output frequency). Through this model, the control system can determine the optimal operating frequencies for the first compressor 10 and the second compressor 20 based on the current overall system operating load requirements. This model is typically established through experimental testing, theoretical calculations, or a combination of both, and can be represented in the form of lookup tables, polynomial functions, or neural network models to ensure that the compressors can operate efficiently at appropriate frequencies under different load conditions.

[0085] The operating frequency-oil discharge rate model establishes a direct correlation between the compressor's operating frequency and its oil discharge rate. The compressor's operating frequency directly affects the refrigerant flow rate, velocity, and system pressure, which in turn determine the efficiency of lubricating oil carrying and returning in the refrigerant circuit. Through this model, the system can accurately predict the compressor's current oil discharge rate based on its actual operating frequency. This model can also be constructed through extensive experimental data collection and regression analysis, existing in the form of curves, piecewise functions, or discrete data points. Its accuracy is crucial for achieving refined oil management.

[0086] Through the above technical solution, the single function model is refined into two cascaded sub-models: the operating load-operating frequency model and the operating frequency-oil discharge rate model. This makes the calculation of the oil discharge rate more precise and accurate. First, the operating load-operating frequency model can accurately determine the compressor's operating frequency based on actual load requirements. Second, the operating frequency-oil discharge rate model can accurately predict the compressor's oil discharge rate based on this operating frequency. This step-by-step modeling approach effectively improves the accuracy and reliability of the function model, thus providing a solid foundation for the subsequent accurate calculation of the difference in oil discharge rates between the first compressor 10 and the second compressor 20. Therefore, the system can more accurately determine the oil circulation state and make more precise adjustments to the operating load to effectively reduce the difference in oil discharge rates between the first compressor 10 and the second compressor 20, ensuring that the compressors are adequately lubricated while avoiding excessive oil accumulation in the system, thereby improving the operating efficiency, stability, and service life of the multi-split air conditioning unit.

[0087] It should be noted that this solution focuses on improving the overall stability and service life of multi-split air conditioning units by adjusting and reducing the difference in oil discharge rates between compressors as much as possible.

[0088] In some implementations, such as Figure 4 As shown, the operating frequency-oil discharge rate model has multiple frequency ranges set sequentially, such as 0-H1, H1-H2, and H2-H3. If the oil discharge rate of the first compressor 10 is greater than that of the second compressor 20, the first compressor 10 is controlled to adjust its operating frequency within the specified frequency range. If the oil discharge rate of the second compressor 20 is greater than that of the first compressor 10, the second compressor 20 is controlled to adjust its operating frequency within the specified frequency range.

[0089] By dividing the operating frequency-oil discharge rate model into multiple sequentially set frequency ranges and adjusting the operating load (i.e., operating frequency) of the compressor with the higher oil discharge rate within its current frequency range according to the difference in oil discharge rate, this application can more precisely capture the oil discharge characteristics of the compressor under different operating conditions. This frequency range-based local load adjustment strategy avoids abrupt changes in oil discharge characteristics or adjustment instability that may occur when crossing different frequency ranges, thus making the oil discharge rate balancing adjustment process smoother, more accurate, and more efficient. This not only helps to quickly reduce the difference in oil discharge rate between the first compressor 10 and the second compressor 20, ensuring a reasonable distribution of system oil, but also effectively avoids adverse effects on the compressor's service life caused by frequent and large-scale adjustments, improving the overall operational stability and reliability of the multi-split air conditioning unit.

[0090] Alternatively, the operating load-operating frequency model can be configured with multiple sequentially set load ranges, such as 0-W1, W1-W2, and W2-W3. If the oil discharge rate of the first compressor 10 is greater than that of the second compressor 20, the first compressor 10 is controlled to adjust its operating load within its specified load range. If the oil discharge rate of the second compressor 20 is greater than that of the first compressor 10, the second compressor 20 is controlled to adjust its operating load within the specified load range.

[0091] By dividing the operating load-operating frequency model into multiple sequentially set load ranges and adjusting the operating load of the compressor with the higher oil discharge rate within its current load range based on the difference in oil discharge rate, this application can more precisely capture the oil discharge characteristics of the compressor under different operating conditions. This local load adjustment strategy based on load range avoids abrupt changes in oil discharge characteristics or adjustment instability that may occur when crossing different load intervals, thus making the oil discharge rate balancing adjustment process smoother, more accurate, and more efficient. This not only helps to quickly reduce the difference in oil discharge rate between the first compressor 10 and the second compressor 20, ensuring a reasonable distribution of system oil, but also effectively avoids adverse effects on the compressor's service life caused by frequent and large-scale adjustments, improving the overall operational stability and reliability of the multi-split air conditioning unit.

[0092] In some embodiments, such as Figure 2 As shown, after step S400, the control method includes: Step S510: Obtain the cumulative operating time of the first compressor 10 and the second compressor 20 at the corresponding oil discharge rate.

[0093] Step S520: Determine whether the percentage of the running time of the first compressor 10 and the second compressor 20 when the oil discharge rate is less than the first threshold is greater than 70%.

[0094] Step S530: If so, control the delayed oil return.

[0095] Step S540: Otherwise, control the normal oil return.

[0096] The step of acquiring the cumulative operating time of the first compressor 10 and the second compressor 20 at corresponding oil discharge rates aims to continuously monitor and record the cumulative operating time of the first compressor 10 and the second compressor 20 at different oil discharge rate levels. The control module 30 can periodically acquire the current oil discharge rate data of the compressor. This oil discharge rate data can be calculated based on a pre-established function model (e.g., the operating load-operating frequency model and the operating frequency-oil discharge rate model as described in subsequent embodiments) combined with the current operating load and operating frequency. The control module 30 can internally set up multiple timers or data storage units, each corresponding to a different oil discharge rate range. When the oil discharge rate of the compressor falls into a specific range, the corresponding timer starts to accumulate the operating time. This cumulative duration data is stored in the memory of the control module for subsequent evaluation of the oil management status.

[0097] The determination step involves checking whether the operating time of the first compressor 10 and the second compressor 20 in the state where the oil discharge rate is less than a first threshold is greater than 70%. This determination step is used to assess whether the compressor's operating time in the low oil discharge rate state is too long, in order to identify whether the compressor needs immediate oil return replenishment. The first threshold (e.g., an oil discharge rate of 0.5%) is a preset oil discharge rate critical value, which should be set based on system design, refrigerant type, oil characteristics, and actual operating experience. Generally, a value lower than this means that a large amount of lubricating oil is still retained in the compressor to ensure lubrication and sealing effects. The 70% percentage is an exemplary empirical value, indicating that if the compressor is in the state where the oil discharge rate is lower than the first threshold for more than 70% of the total operating time, the overall system operation is considered to be good, and there is no need to execute the active loop strategy. The control module 30 calculates the percentage of operating time in this state by comparing the cumulative operating time in the low oil discharge rate state with the total operating time of the compressor.

[0098] If so, delay oil return will be controlled. When the judgment result is "yes," meaning the low oil discharge rate state operation time exceeds a preset value (e.g., 70%), the system will trigger a delayed oil return control strategy to reduce the extra time occupied in cooling or heating modes, thereby improving the user experience. The oil return mode is an active lubricant management mechanism designed to promote the return of lubricant in the system to the compressor as quickly as possible through specific operating mode adjustments.

[0099] For example, the control module instructs the compressor to operate at a load higher than the minimum required for normal oil return for a period of time before shutdown, thereby increasing the refrigerant flow rate and driving the refrigerant oil in the pipeline back. Alternatively, during system operation, the compressor load can be periodically and briefly increased to create pulsed high flow rates, promoting oil return. Or, the opening of the electronic expansion valve can be adjusted to optimize the refrigerant flow rate distribution within the evaporator, improving the oil return path.

[0100] Otherwise, normal oil return is controlled. When the judgment result is "no," meaning the proportion of low oil discharge rate operation time does not exceed the preset value, it indicates that the current oil management situation is within an acceptable range. The system will continue to operate according to the normal operating logic without needing to activate a special delayed oil return strategy. It is only necessary to ensure that the oil return strategy is executed within the preset time period (e.g., four hours). Normal loop control means that the system will maintain normal cooling or heating operation according to the set parameters such as temperature and pressure, and rely on the conventional oil separator and oil return pipeline for oil circulation. At this time, it is considered that the system can achieve good oil circulation through its own mechanism.

[0101] Through the above technical solution, this application, based on reducing the difference in oil discharge rate between the first compressor 10 and the second compressor 20, further introduces a monitoring and judgment mechanism for the cumulative operating time of the compressors at different oil discharge rates. This mechanism can effectively identify whether the system is in a state of low oil discharge rate for an extended period. When it is detected that the proportion of low oil discharge rate operating time is too high, the system can postpone the auxiliary oil return strategy by one to two hours to avoid additional occupation of the operating time in cooling or heating modes, thereby improving the user's continuous experience in cooling or heating modes and enhancing the user experience.

[0102] In some embodiments, such as Figure 1 As shown, the multi-split air conditioning unit includes a liquid level sensor 40. The liquid level sensor 40 is installed in the first compressor 10 and the second compressor 20. The liquid level sensor 40 is electrically connected to the control module 30 and is used to detect the oil level in the first compressor 10 and the second compressor 20.

[0103] The liquid level sensor 40 is a device capable of real-time monitoring of liquid level. It can be implemented in various ways, such as float-type, ultrasonic, capacitive, or photoelectric types. The liquid level sensor 40 is directly installed in the oil pan or oil tank inside the first compressor 10 and the second compressor 20, ensuring accurate and direct acquisition of the actual oil level information inside each compressor, rather than estimation through indirect means. The liquid level sensor 40 is electrically connected to the control module 30 via cable or wirelessly to transmit the detected oil level signal to the control module 30 in real time. After receiving these signals, the control module 30 performs necessary signal processing and conversion, such as analog-to-digital conversion and filtering, ultimately converting the sensor signal into identifiable oil level data. In this way, the control module 30 can continuously monitor the oil level status of each compressor, providing accurate basic data for subsequent oil management strategies.

[0104] Or, such as Figure 1 As shown, the multi-split air conditioning unit includes a pressure sensor 50. The pressure sensor 50 is installed in the first compressor 10 and the second compressor 20. The pressure sensor 50 is electrically connected to the control module 30 and is used to detect the oil pressure parameters in the first compressor 10 and the second compressor 20.

[0105] The pressure sensor 50 is a device that senses pressure signals and converts them into usable electrical signals. It can be of various types, such as piezoresistive, piezoelectric, capacitive, or strain gauge, to adapt to different accuracy, response speed, and environmental requirements. Directly placing the pressure sensor inside the first compressor 10 and the second compressor 20, for example, at a critical location in the compressor's oil circuit system, such as the oil pump outlet or inside the crankcase, ensures real-time and accurate acquisition of the actual oil pressure data of the lubricating oil inside the compressor, avoiding errors that may arise from indirect inference. The pressure sensor 50 is electrically connected to the control module 30 via a cable, transmitting the detected analog or digital pressure signals to the control module. The control module 30 integrates corresponding signal processing circuitry, capable of receiving, analyzing, and utilizing this oil pressure data. By detecting oil pressure parameters, the operating status of the compressor lubrication system can be monitored in real time, as oil pressure is a key indicator of adequate lubrication. A normal oil pressure range is fundamental to ensuring adequate lubrication of the moving parts inside the compressor, while excessively low or high oil pressures indicate potential malfunctions.

[0106] Through the above technical solution, the multi-split air conditioning unit can obtain the oil level information inside the first compressor 10 and the second compressor 20 in real time and directly. This makes up for the blind spots that may exist in oil management relying solely on function models, enabling the control module 30 to not only dynamically balance the oil discharge of each compressor, but also monitor and ensure that the oil level inside each compressor is within a safe range in real time. When combined with the control method of adjusting the operating frequency to reduce the difference in oil discharge rate, once the oil level of a compressor is detected to be too low, the control module can issue an early warning in time or take corresponding protective measures, such as adjusting the operating frequency of the compressor to promote oil return, or even shutting down for protection, thereby effectively avoiding compressor wear, overheating, or even damage caused by insufficient oil level, significantly improving the operational reliability, stability, and service life of the multi-split air conditioning unit.

[0107] In some implementations, such as Figure 5 As shown, the control module 30 includes a processor 31, a communication interface 32, a memory 33, and a communication bus 34. The processor 31, communication interface 32, and memory 33 communicate with each other via the communication bus 34. The memory 33 is used to store computer programs.

[0108] In one embodiment of this application, when the processor 31 executes the program stored in the memory 33, it implements the control method of the multi-split air conditioning unit provided in any of the foregoing method embodiments.

[0109] This application also provides a computer-readable storage medium storing a computer program thereon, which, when executed by a processor, implements the steps of the control method for a multi-split air conditioning unit as provided in any of the foregoing method embodiments.

[0110] It should be understood that the terminology used herein is for the purpose of describing particular exemplary embodiments only and is not intended to be limiting. Unless the context clearly indicates otherwise, the singular forms “a,” “an,” and “described” as used herein may also include the plural forms. The terms “comprising,” “including,” “containing,” and “having” are inclusive and therefore indicate the presence of the stated features, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, elements, components, and / or combinations thereof. The method steps, processes, and operations described herein are not construed as requiring them to be performed in a particular order described or illustrated unless the order of performance is explicitly indicated. It should also be understood that additional or alternative steps may be used.

[0111] Through the above description of the embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus a general-purpose hardware platform, and of course, it can also be implemented by hardware. Based on this understanding, the above technical solutions, in essence or the parts that contribute to the related technology, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., including several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods of various embodiments or some parts of embodiments.

[0112] Although terms such as first, second, third, etc., may be used in this document to describe multiple elements, components, regions, layers, and / or segments, these elements, components, regions, layers, and / or segments should not be limited by these terms. These terms may be used only to distinguish one element, component, region, layer, or segment from another. Unless the context clearly indicates otherwise, terms such as "first," "second," and other numerical terms used herein do not imply order or sequence. Therefore, the first element, component, region, layer, or segment discussed below may be referred to as the second element, component, region, layer, or segment without departing from the teachings of the exemplary embodiments.

[0113] The above are merely specific embodiments of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A control method for a multi-split air conditioning unit, characterized in that, The multi-split air conditioning unit includes a first compressor and a second compressor connected in parallel, and the control method includes: Establish a functional model between the load, frequency, and oil discharge rate parameters of the first compressor and the second compressor; The initial loads of the first compressor and the second compressor are allocated according to the total load of the whole machine, and the initial frequencies of the first compressor and the second compressor are calculated according to the function model. Based on the function model, calculate the first oil discharge rate of the first compressor at the initial frequency, and calculate the second oil discharge rate of the second compressor at the initial frequency; The operating frequencies of the first compressor and the second compressor are controlled and adjusted to reduce the difference in oil discharge rate between the first compressor and the second compressor.

2. The control method for a multi-split air conditioning unit according to claim 1, characterized in that, The control adjustment of the operating frequencies of the first compressor and the second compressor includes: Compare the magnitudes of the first oil discharge rate and the second oil discharge rate; If the difference between the first oil discharge rate and the second oil discharge rate is greater than a first preset value, the operating frequency of the first compressor is controlled to decrease by a second preset value. The third oil discharge rate and the adjusted operating load of the first compressor are calculated based on the function model and the adjusted operating frequency of the first compressor. The adjusted operating load and operating frequency of the second compressor are calculated based on the total load of the entire machine and the adjusted operating load of the first compressor.

3. The control method for a multi-split air conditioning unit according to claim 2, characterized in that, The control adjustment of the operating frequencies of the first compressor and the second compressor includes: If the difference between the second oil discharge rate and the first oil discharge rate is greater than the first preset value, the operating frequency of the second compressor is controlled to decrease by the second preset value. The fourth oil discharge rate and the adjusted operating load of the second compressor are calculated based on the function model and the adjusted operating frequency of the second compressor. The adjusted operating load and operating frequency of the first compressor are calculated based on the overall operating load and the adjusted operating load of the second compressor.

4. The control method for a multi-split air conditioning unit according to any one of claims 1-3, characterized in that, After adjusting the operating frequencies of the first compressor and the second compressor to reduce the difference in oil discharge rates between the first compressor and the second compressor, the control method includes: Obtain the cumulative operating time of the first compressor and the second compressor at the corresponding oil discharge rate; Determine whether the operating time of the first compressor and the second compressor in the state where the oil discharge rate is less than the first threshold is greater than 70%; If so, control the delayed oil return; Otherwise, control the normal oil return.

5. The control method for a multi-split air conditioning unit according to claim 2 or 3, characterized in that, The function model of the first compressor includes an operating load-operating frequency model and an operating frequency-oil discharge rate model; The function model of the second compressor includes an operating load-operating frequency model and an operating frequency-oil discharge rate model.

6. The control method for a multi-split air conditioning unit according to claim 5, characterized in that, The operating frequency-oil discharge rate model has multiple frequency ranges set sequentially. If the oil discharge rate of the first compressor is greater than that of the second compressor, the operating frequency of the first compressor is adjusted within its frequency range. If the oil discharge rate of the second compressor is greater than that of the first compressor, the operating frequency of the second compressor is adjusted within the specified frequency range.

7. The control method for a multi-split air conditioning unit according to any one of claims 1-3, characterized in that, The control adjustment of the operating frequencies of the first compressor and the second compressor to reduce the difference in oil discharge rates between the first compressor and the second compressor includes: The operating frequencies of the first compressor and the second compressor are controlled and adjusted so that the absolute value of the difference in oil discharge rate between the first compressor and the second compressor is lower than a first preset value.

8. A multi-split air conditioning unit, characterized in that, include: First compressor; The second compressor is connected in parallel with the first compressor; The system also includes a control module electrically connected to the first compressor and the second compressor, used to acquire the operating load and operating frequency of the first compressor and the second compressor; wherein the control module is configured to execute the control method of the multi-split air conditioning unit as described in any one of claims 1-7.

9. The multi-split air conditioning unit according to claim 8, characterized in that, The multi-split air conditioning unit includes a liquid level sensor. The liquid level sensor is installed in the first compressor and the second compressor. The liquid level sensor is electrically connected to the control module and is used to detect the oil level in the first compressor and the second compressor.

10. The multi-split air conditioning unit according to claim 8, characterized in that, The multi-split air conditioning unit includes a pressure sensor. The pressure sensor is installed in the first compressor and the second compressor. The pressure sensor is electrically connected to the control module and is used to detect the oil pressure parameters in the first compressor and the second compressor.

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