Air conditioning system

Abstract

The application discloses an air conditioning system, comprising an outdoor unit with a compressor, at least one indoor unit connected with the outdoor unit through a refrigerant pipeline, a detection device for collecting indoor temperature and indoor unit liquid pipe temperature, and a controller. The controller is configured to determine whether the air conditioning system is in a preset low-frequency operation state, and if so, to obtain an indoor target temperature, a real-time indoor temperature and an indoor unit liquid pipe temperature; to determine a basic evaporation temperature according to the indoor temperature and the target temperature, to calculate a dynamic correction value according to a set temperature difference between the indoor temperature and the target temperature, to compensate the basic evaporation temperature, and to obtain a corrected target evaporation temperature. The corrected target evaporation temperature is compared with the indoor unit liquid pipe temperature, and the compressor operation frequency is regulated. The evaporation temperature is dynamically adjusted according to the indoor cold and hot load, the temperature control lag defect under the super-low-frequency operation condition is improved, faults such as indoor unit frosting and icing, insufficient compressor pressure difference and poor oil return are avoided, and the low-frequency operation stability of the air conditioner is improved.

Description

Technical Field

[0001] This invention relates to the technical field of air conditioning systems, and particularly to an air conditioning system. Background Technology

[0002] Various refrigeration and air conditioning systems are widely used in residential, office, and commercial buildings due to their advantages such as independent adjustment of indoor cooling capacity, flexible installation, and energy-saving operation. During actual operation, the indoor load fluctuates continuously with changes in ambient temperature, occupant movement, and the opening and closing of doors and windows. Under conditions such as low load at night and in small, enclosed spaces, air conditioning units often need to enter an ultra-low frequency, low-load cooling operation mode to match extremely low indoor cooling demand, avoid frequent start-stop of the unit, and improve overall energy efficiency and indoor temperature control comfort.

[0003] Currently, most conventional air conditioning control schemes use a fixed target evaporation temperature, or simply generate a single, unchanging base evaporation temperature based on the static temperature difference between the real-time indoor temperature and the set temperature. Then, the compressor operating frequency is directly adjusted by comparing the target evaporation temperature with the indoor unit liquid pipe temperature.

[0004] The existing solution relies solely on instantaneous indoor temperature difference for regulation and control, resulting in significant lag in the regulation process. When the indoor temperature fluctuates continuously, the compressor's frequency adjustment response is slow, leading to large fluctuations in room temperature, poor uniformity of indoor cooling, and low user comfort. Especially under ultra-low frequency operation conditions, the system refrigerant flow is low, and the heat exchanger's heat exchange state is highly sensitive to temperature changes. Using a static target evaporation temperature can easily cause heat exchange imbalance: if the target evaporation temperature is set too high, frost will easily form on the surface of the indoor heat exchanger, and the unit will frequently trigger anti-freeze protection; if the target evaporation temperature is set too low, it will cause insufficient compressor operating pressure differential, poor system oil return effect, and increased overall energy consumption, resulting in operational reliability defects.

[0005] In view of the above, this application is hereby submitted. Summary of the Invention

[0006] The present invention aims to at least partially solve the technical problems in related technologies, such as difficulty in adapting to ultra-low frequency refrigeration conditions, temperature control lag, large room temperature fluctuations, and weak unit stability.

[0007] Therefore, according to embodiments of this disclosure, an air conditioning system is proposed, comprising: The outdoor unit is equipped with a compressor; At least one indoor unit, which is connected to the outdoor unit via a refrigerant pipeline; The detection device is used to collect indoor temperature and indoor unit liquid pipe temperature; The controller is configured to: Determine whether the air conditioning system has entered a preset low-frequency operating state. When it enters the preset low-frequency operating state, obtain the user-set indoor target temperature, the indoor temperature collected by the detection device, and the indoor unit liquid pipe temperature. The base evaporation temperature is determined based on the indoor temperature and the target indoor temperature. Calculate a dynamic correction value based on the target indoor temperature and the indoor temperature; Based on the base evaporation temperature and the dynamic correction value, the corrected target evaporation temperature is obtained; Based on the comparison between the corrected target evaporation temperature and the indoor unit liquid pipe temperature, the operating frequency of the compressor in the air conditioning system is controlled.

[0008] In the above technical solution, temperature data is collected by a detection device. Under low-frequency operating conditions, the controller first obtains the baseline evaporation temperature, then introduces a dynamic correction value to complete temperature compensation, generating a corrected target evaporation temperature that matches the real-time room temperature change trend. The compressor frequency is then adjusted in conjunction with the corrected evaporation temperature. In this way, the reference evaporation temperature can be dynamically adjusted in real time according to the indoor heating and cooling load, significantly alleviating the temperature control lag problem under ultra-low frequency operating conditions. This avoids excessively high evaporation temperatures that could lead to large heat exchange temperature differences and surface frost or ice buildup in the indoor unit. At the same time, it prevents problems such as insufficient compressor operating pressure difference and poor oil return caused by persistently low evaporation temperatures, improving the stability of the unit's low-frequency operation, taking into account the cooling needs of each room in a multi-split system, and optimizing the overall indoor temperature control comfort and the reliability of the entire unit.

[0009] In some embodiments, the controller is further configured to calculate and update the dynamic correction value at preset time intervals; Based on the updated dynamic correction value, the corrected target evaporation temperature is calculated synchronously.

[0010] In the above technical solution, the controller continuously iterates and updates the dynamic correction values ​​at a fixed cycle, and simultaneously updates the target evaporation temperature for overall unit control. This enables continuous tracking of indoor temperature change trends, allowing for real-time capture of minute temperature differences and rapid feedback to the evaporation temperature reference, avoiding adjustment delays caused by single long-term sampling; it also allows the target evaporation temperature to continuously and slightly adapt to fluctuations in the indoor load, with smooth frequency adjustment without abrupt changes, avoiding frequent compressor frequency increases and decreases, reducing unit operating noise, and extending compressor lifespan.

[0011] In some embodiments, the controller is further configured to calculate a dynamic correction value based on the indoor target temperature and the indoor temperature, including: The dynamic correction value stored at the previous sampling time is obtained as the reference value, wherein when it is the first sampling time, the reference value is a preset initial value; Based on the indoor target temperature and the indoor temperature, the correction difference corresponding to the current sampling time is obtained; The difference between the baseline value and the correction difference corresponding to the current sampling time is calculated to obtain the dynamic correction value at the current sampling time.

[0012] In the above technical solution, the built-in initial correction value is directly called at the first sampling moment, and the numerical update is completed by subtracting the correction difference at the current sampling moment from the correction value at the previous sampling moment at subsequent sampling moments. This solves the problem of computational blanks when the controller first enters low-frequency operation mode without historical correction parameters, ensuring that the dynamic correction logic can be stably started from power-on. At the same time, the use of the difference iterative update method makes the numerical changes smooth and controllable, and will not cause drastic deviations in evaporation temperature due to abrupt changes in correction values, thus ensuring a stable adjustment process in ultra-low frequency operation.

[0013] In some embodiments, the controller is further configured to obtain a correction difference corresponding to the current sampling time based on the indoor target temperature and the indoor temperature, including: Calculate the temperature difference between the indoor temperature and the indoor target temperature at the current sampling time, and record it as the first difference; Calculate the temperature difference between the indoor temperature and the indoor target temperature at the previous sampling time, and record it as the second difference; Based on the first difference, the second difference, the preset ratio parameter, and the time interval, the corrected difference corresponding to the current sampling time is calculated.

[0014] In the above technical solution, the correction value is calculated in a closed loop based on the temperature difference between the sampling times, the set parameters, and the interval duration. It can simultaneously take into account both the instantaneous magnitude of the temperature difference and the continuous cumulative change of the temperature difference. The preset proportional parameter can quickly respond to sudden changes in room temperature and eliminate steady-state temperature deviation. It can accurately predict the long-term trend of continuous temperature rise and fall, adjust the correction value in advance, significantly shorten the temperature regulation response time, reduce the steady-state temperature difference in the room, and improve the constant temperature effect.

[0015] In some embodiments, the controller is further configured to obtain a correction difference corresponding to the current sampling time based on the indoor target temperature and the indoor temperature, and further includes: Calculate the temperature difference between the indoor temperature and the indoor target temperature at the current sampling time, and record it as the first difference; The temperature difference between the indoor temperature and the indoor target temperature at the previous sampling time is calculated and recorded as the second difference value; Calculate the difference between the first difference and the second difference to obtain the temperature difference change; Based on the comparison between the first difference and the preset room temperature difference, and the comparison between the temperature difference change and the preset temperature difference change range, the correction difference corresponding to the current sampling time is determined.

[0016] In the above technical solution, the correction difference at the current sampling time is determined by comparing the first difference with the preset room temperature difference and the temperature difference change with the preset temperature difference change range. This eliminates the need for complex floating-point closed-loop calculations, significantly reducing the controller's computing power consumption and making it compatible with low-cost, low-performance main control chips. The interval levels are clearly defined, the control logic is simple, and debugging and calibration are convenient. The values ​​in the table can be quickly modified according to the load characteristics of different models, reducing product development and adaptation costs.

[0017] In some embodiments, the controller is further configured to determine the correction difference within the current time interval based on a comparison between the first difference and a preset room temperature difference, and a comparison between the temperature difference change and a preset temperature difference change amplitude, including: Based on the comparison between the first difference and the preset room temperature difference, multiple room temperature difference ranges are obtained; based on the comparison between the temperature difference change and the preset temperature difference change range, multiple temperature difference change ranges are obtained. Any one of the room temperature difference ranges and any one of the temperature difference variation ranges are paired together, and each pair of ranges is pre-stored with a unique corresponding correction difference value. Determine the room temperature difference range to which the current first difference belongs; at the same time, determine the temperature difference change range to which the current temperature difference change belongs; Based on the determined room temperature difference range and the temperature difference variation range, the corresponding correction difference value pre-stored in the combination of the ranges is retrieved, and the correction difference value is used as the correction difference value in the current interval time period.

[0018] In the above technical solution, by setting multiple indoor temperature difference ranges and multiple temperature difference change ranges, each range combination is independently configured with a dedicated correction difference value, so as to achieve fine-grained and layered control over the room temperature temperature and the speed of temperature rise and fall, and to match different correction strengths for different load change scenarios; to avoid the defect that a single correction value cannot adapt to a wide range of room temperature fluctuations, and to take into account the adjustment accuracy under slight load fluctuations and severe load fluctuations, so that the temperature control adaptation range is wider.

[0019] In some embodiments, the controller is further configured to determine a base evaporation temperature based on the indoor temperature and the indoor target temperature, including: Multiple sets of temperature correspondences are pre-stored. Each set of temperature correspondences matches the temperature difference between the indoor temperature and the indoor target temperature. Each temperature difference corresponds to a target evaporation temperature. Calculate the difference between the real-time collected indoor temperature and the indoor target temperature; Based on the temperature correspondence corresponding to the difference matching, the basic evaporation temperature corresponding to the current indoor temperature is obtained.

[0020] In the above technical solution, by pre-storing multiple sets of temperature differences and the corresponding relationship between the basic evaporation temperature, and relying on the real-time indoor temperature difference to retrieve the reference temperature, the basic evaporation temperature can be made to match the indoor basic load requirements, and the conventional cooling load can be matched without the addition of dynamic correction values; different room temperature differences correspond to different reference temperatures, providing a reasonable reference range for subsequent dynamic correction, and avoiding excessive compensation of correction amount caused by the basic temperature deviating from the reasonable range.

[0021] In some embodiments, the controller is further configured to obtain a corrected target evaporation temperature based on the base evaporation temperature and the dynamic correction value, including: The base evaporation temperature and corresponding dynamic correction value of the indoor unit are obtained for each operating state. Calculate the sum of the base evaporation temperature and the corresponding dynamic correction value for each indoor unit to obtain the corrected target evaporation temperature for a single indoor unit. Compare the corrected target evaporation temperatures of all indoor units and select the minimum value as the corrected target evaporation temperature of the air conditioning system.

[0022] In the above technical solution, by calculating the exclusive corrected evaporation temperature of a single indoor unit and selecting the minimum value of all indoor units as the control benchmark for the whole unit, it can prioritize the heat exchange needs of rooms with the greatest cooling demand and higher temperatures for multi-split systems with different room loads. It avoids insufficient cooling in some rooms due to temperature control of only a single room, balances the heat exchange conditions of all indoor units, and eliminates the problems of temperature difference in some rooms and imbalance of zone temperature control.

[0023] In some embodiments, the controller is further configured to control the compressor operating frequency of the air conditioning system based on a comparison between the corrected target evaporation temperature and the indoor unit liquid pipe temperature, including: When the temperature of the liquid pipe in the indoor unit is lower than the corrected target evaporation temperature, the compressor is controlled to reduce its operating frequency. When the temperature of the liquid pipe in the indoor unit is higher than the corrected target evaporation temperature, the compressor is controlled to increase its operating frequency. When the temperature of the liquid pipe in the indoor unit is close to the corrected target evaporation temperature, the current operating frequency of the compressor is maintained unchanged.

[0024] In the above technical solution, the frequency is reduced when the liquid pipe temperature is lower than the reference evaporation temperature, increased when it is higher than the reference temperature, and maintained when the temperature is close to the reference temperature. Thus, using the actual indoor heat exchange temperature as the basis for frequency adjustment, a closed-loop negative feedback regulation logic is formed. The controller continuously collects the actual liquid pipe temperature and compares it with the target evaporation temperature. Based on the deviation between the two, the compressor output power is adjusted in reverse to continuously offset the difference between indoor cooling supply and demand, driving the actual heat exchange temperature to approach the set reference temperature. When indoor cooling is insufficient, the compressor output is automatically increased; when cooling is excessive, the output is automatically reduced. After the room temperature stabilizes, the frequency is locked, avoiding frequent start-stop cycles, reducing energy consumption during low-frequency operation, and improving temperature control comfort.

[0025] In some embodiments, determining whether the air conditioning system has entered a preset low-frequency operating state includes: Obtain the real-time operating frequency of the compressor; The real-time operating frequency is compared with a preset ultra-low frequency threshold. When the real-time operating frequency is not greater than the preset ultra-low frequency threshold, the unit is determined to have entered the ultra-low frequency operating state.

[0026] In the above technical solution, the compressor's real-time operating frequency is directly collected and compared with a preset frequency threshold to identify the unit's ultra-low load operating scenarios. This determination method relies solely on the compressor's inherent operating parameters to complete the operating condition identification, eliminating the need for additional temperature and load sensors, effectively reducing the overall hardware assembly cost. Simultaneously, the frequency signal sampling response is fast, instantly triggering dynamic correction logic when the unit is in the low-frequency operating range, eliminating operating condition identification delays and ensuring the activation of ultra-low frequency adaptive temperature control.

[0027] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit this application. Attached Figure Description

[0028] Figure 1 This is a logic diagram of controlling the compressor frequency in existing technology; Figure 2 This is a schematic diagram of the connection of an air conditioning system according to an embodiment of this application; Figure 3 This is a schematic diagram illustrating the acquisition of the basic air valve temperature according to an embodiment of this application; Figure 4 This is a schematic diagram of the control flow according to an embodiment of this application; Figure 5 This is a schematic diagram of the control flow for obtaining dynamic correction values ​​according to an embodiment of this application; Figure 6 This is a schematic diagram of the specific control flow for obtaining dynamic correction values ​​according to an embodiment of this application; Figure 7This is a schematic diagram of the specific control flow for obtaining dynamic correction values ​​according to another embodiment of this application; Figure 8 This is a schematic diagram of the control flow for adjusting the compressor frequency according to an embodiment of this application; Figure 9 This is a flowchart illustrating the process of determining whether a low-frequency operating condition has been entered according to an embodiment of this application. Figure 10 This is a schematic diagram of the control flow of a controller according to an embodiment of this application.

[0029] Figure label: 100. Outdoor unit; 101. Compressor; 102. Four-way reversing valve; 103. Outdoor heat exchanger; 104. Outdoor fan; 105. Outdoor unit expansion valve; 106. Gas-liquid separator; 200. Indoor unit; 201. Indoor unit expansion valve; 202. Indoor heat exchanger; 203. Indoor fan; 204. Gas-side shut-off valve; 205. Liquid-side shut-off valve. Detailed Implementation

[0030] Typical embodiments embodying the features and advantages of the present invention will be described in detail in the following description. It should be understood that the present invention can have various variations in different embodiments without departing from the scope of the present invention, and the descriptions and illustrations herein are for illustrative purposes only and not intended to limit the present invention.

[0031] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, features defined as "first" or "second" may explicitly or implicitly include one or more features. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0032] Various types of inverter air conditioners, with their advantages of adjustable cooling capacity, convenient installation, and excellent energy efficiency, are widely used in various scenarios such as residential, office, and commercial buildings. These include both ordinary split-type air conditioners that operate independently in a single room and multi-split air conditioning systems that can independently control the temperature of multiple rooms simultaneously. During actual operation, the indoor load fluctuates continuously due to changes in ambient temperature, occupant movement, and the opening and closing of doors and windows. Especially under conditions of low load at night, in small, enclosed spaces, and with a small temperature difference between the outdoor and indoor set temperatures, the air conditioning unit often needs to enter an ultra-low frequency, low-load cooling operation mode to match the extremely low indoor cooling demand, avoid frequent start-stop cycles, and improve overall energy efficiency and indoor temperature comfort.

[0033] Currently, most conventional air conditioning control schemes use a fixed target evaporation temperature or rely solely on the static temperature difference between the real-time indoor temperature and the set temperature to generate a single, unchanging base evaporation temperature. The compressor operating frequency is then directly adjusted by comparing the target evaporation temperature with the indoor unit's liquid pipe temperature. However, as shown in Figure 1, this static adjustment method relying on instantaneous indoor temperature differences has inherent flaws: the adjustment response is delayed; the compressor's frequency adjustment is sluggish when the indoor temperature is continuously rising or falling; room temperature fluctuations are large; cooling uniformity is poor; and user comfort is low. Under ultra-low frequency conditions, the system refrigerant flow is small; the heat exchanger's heat exchange state is highly sensitive to temperature parameters; and the static target evaporation temperature easily causes heat exchange imbalance. If the target evaporation temperature is set too high, the indoor heat exchanger is prone to frosting, and the unit frequently triggers anti-freeze protection. If the setting is too low, reliability issues such as insufficient compressor operating pressure differential, poor system oil return effect, and increased overall energy consumption may occur.

[0034] Furthermore, when a multi-split air conditioner connects a single outdoor unit to multiple indoor units distributed across different areas, the loads of each room vary independently and differ significantly. The entire system relies solely on a uniform, fixed static target evaporation temperature to control the compressor, failing to consider the real-time heat exchange status of different indoor units. When some rooms are under low load while others are under normal load, the uniform static evaporation temperature cannot adapt to the differentiated heat exchange needs of each terminal unit, easily leading to contradictory operating conditions such as some indoor unit coils frosting while others have insufficient cooling capacity. Coupled with the uneven refrigerant distribution characteristic of the ultra-low frequency operating range, this exacerbates multiple problems such as difficulty in oil return, temperature control imbalance in each room, and frequent triggering of unit protection mechanisms, severely limiting the operational stability and user experience of the multi-split air conditioner in the low-load range.

[0035] To address the aforementioned technical issues, this application discloses an air conditioning system. By setting up a detection device to collect indoor temperature and indoor unit liquid pipe temperature in real time, after the controller determines that the unit has entered an ultra-low frequency operating state, it first determines the base evaporation temperature based on the indoor temperature and the indoor target temperature, and then introduces a dynamic correction value related to the indoor target temperature and the indoor temperature to complete temperature compensation, generating a corrected target evaporation temperature that fits the real-time room temperature change trend. The compressor frequency is adjusted in conjunction with the corrected evaporation temperature, thereby achieving dynamic adaptive adjustment of the evaporation temperature reference under ultra-low frequency operating conditions, improving the low-frequency operation stability of the unit and indoor temperature control comfort.

[0036] In this application, reference is made to Figure 2The air conditioning system provided in this embodiment includes an outdoor unit 100, at least one indoor unit 200, a detection device, and a controller. The outdoor unit 100 is equipped with one or more compressors 101, preferably DC inverter scroll compressors 101, which can achieve stepless adjustment over a wide frequency range, thereby dynamically adjusting the cooling capacity output according to actual load requirements. The operating frequency of the compressor 101 can be continuously adjusted within a range of 10% to 100% of the rated frequency, with a minimum operating frequency as low as 6Hz or even 4Hz to meet the requirements of ultra-low frequency, low-load operation.

[0037] The outdoor unit 100 also integrates core components such as an outdoor heat exchanger 103, an outdoor fan 104, a four-way reversing valve 102, an outdoor unit expansion valve 105, and a gas-liquid separator 106. The outdoor heat exchanger 103 can employ a hydrophilic aluminum foil and internally threaded copper tube structure, working in conjunction with the DC inverter outdoor fan 104 to adjust the fan speed in real time according to ambient temperature and frost conditions, improving heat exchange efficiency under high and low temperature conditions. The outdoor unit expansion valve 105, as a main circuit throttling device, is driven by a stepper motor and can precisely adjust its opening degree according to the system subcooling or exhaust superheat, controlling the refrigerant flow distribution.

[0038] At least one indoor unit 200 is connected to the outdoor unit 100 via refrigerant piping, forming a closed refrigerant circulation loop. The refrigerant piping includes gas-side piping, with a liquid-side shut-off valve 205 installed on the liquid-side piping and a gas-side shut-off valve 204 installed on the gas-side piping. The number of indoor units 200 can be one (one-to-one) or multiple (one-to-many), such as two, three, or more, installed in different rooms or areas to meet multi-zone independent temperature control requirements. Each indoor unit 200 is independently equipped with an indoor heat exchanger 202, an indoor fan 203, an indoor unit expansion valve 201, and corresponding temperature sensing elements.

[0039] In the refrigeration cycle, the indoor heat exchanger 202 acts as an evaporator. Liquid refrigerant, after being throttled and depressurized by the indoor unit's expansion valve 201, becomes a low-temperature two-phase refrigerant. It then enters the indoor heat exchanger 202 to exchange heat with the indoor return air, absorbing heat from the indoor air and becoming superheated refrigerant gas, which returns to the outdoor unit 100 via the gas-side piping. The indoor fan 203 can be driven by a DC brushless motor with cross-flow or centrifugal fan blades, enabling multi-level or stepless speed adjustment according to indoor load requirements, optimizing heat exchange efficiency and airflow comfort.

[0040] The detection device is used to collect indoor temperature and indoor unit liquid pipe temperature. In this application, reference is made to... Figure 10The detection device specifically includes: an indoor temperature sensor installed at the return air vent of each indoor unit 200 to detect the actual indoor return air temperature, denoted as Ti; and a liquid pipe temperature sensor installed at the liquid-side piping inlet of each indoor unit 200, i.e., at the liquid pipe position before the expansion valve 201 of the indoor unit, to detect the indoor unit liquid pipe temperature, denoted as Tl. The liquid pipe temperature sensor typically uses a platinum resistance temperature sensor or a thermistor sensor, closely attached to the outer wall of the copper pipe and covered with an insulation layer to accurately reflect the temperature of the liquid refrigerant before entering the electronic expansion valve of the indoor unit 200. For multi-split systems, each indoor unit 200 in operation is equipped with an independent liquid pipe temperature sensor and an indoor temperature sensor. The detection data from each sensor are uploaded to the controller via a communication bus, such as RS485 or CAN bus.

[0041] The controller is the core decision-making unit of the air conditioning system. It typically uses an embedded microprocessor, such as a 32-bit ARM Cortex-M4 core microcontroller, integrating data acquisition, logic operation, storage, communication, and drive modules. The controller can be independently located in the electrical box of the outdoor unit 100 or integrated into the main control board of the outdoor unit 100. Internally, the controller integrates a real-time clock and non-volatile memory for storing control parameters, temperature correspondence tables, and correction difference mapping tables. It is electrically connected to the compressor 101 inverter driver, the outdoor fan 104 driver, the electronic expansion valve drivers, and the controllers of each indoor unit 200 via drive circuits, enabling centralized control.

[0042] In this application, reference is made to Figure 4 The controller is configured to perform the following control steps: Step S100: Determine whether the air conditioning system has entered the preset low-frequency operation state.

[0043] During the operation of the air conditioning system, the controller continuously monitors the real-time operating frequency of the compressor, denoted as Fr (in Hz). The real-time operating frequency of the compressor is fed back to the controller in real time by the inverter driver, with a sampling period of, for example, once every 1 second. The controller has a preset ultra-low frequency threshold, denoted as Fth (in Hz). The value of this preset ultra-low frequency threshold Fth is determined comprehensively based on factors such as compressor type, system refrigerant charge, and indoor unit configuration, and generally ranges from 6Hz to 12Hz. In this embodiment, the preset ultra-low frequency threshold Fth can be 10Hz.

[0044] The controller compares the real-time operating frequency Fr with the preset ultra-low frequency threshold Fth. When Fr ≤ Fth, the controller determines that the unit has entered the preset low-frequency operating state, i.e., the ultra-low frequency operating state. When Fr > Fth, the controller determines that the unit is in the normal frequency operating range, does not trigger the dynamic correction logic, and operates according to the normal target evaporation temperature control strategy.

[0045] It should be noted that additional auxiliary conditions can be added to the conditions for entering the ultra-low frequency operation state. For example, the percentage of total cooling demand of all operating indoor units may be lower than a certain set value, such as below 30%, or the outdoor ambient temperature may be within a specific range, such as 20℃ to 35℃, to avoid erroneously triggering the ultra-low frequency correction logic during the initial startup or transitional conditions such as defrosting. This embodiment uses a single compressor frequency determination condition to simplify the control logic and improve response speed.

[0046] Step S200: When entering the preset low-frequency operation state, acquire the indoor target temperature set by the user, the indoor temperature collected by the detection device, and the indoor unit liquid pipe temperature.

[0047] When the controller determines that the unit has entered the ultra-low frequency operation state, the controller immediately obtains the following data through the communication bus: the user-set indoor target temperature of each indoor unit in operation, denoted as Ts (unit °C); the indoor temperature collected by the indoor temperature sensor of each indoor unit in operation, i.e., the actual indoor return air temperature, denoted as Ti (unit °C); and the indoor unit liquid pipe temperature collected by the liquid pipe temperature sensor of each indoor unit in operation, denoted as Tl (unit °C).

[0048] Users set the target indoor temperature Ts via a wired controller, remote control, or mobile app, and upload the set value to the controller via the communication network, where it is stored in non-volatile memory. The controller reads real-time data from each sensor according to a preset sampling period, such as every 10 seconds, and verifies the validity of the read data, such as determining whether it is within a reasonable range. After removing obvious outliers, the valid data is temporarily stored in memory for subsequent calculations.

[0049] Step S300: Determine the base evaporation temperature based on the indoor temperature and the indoor target temperature.

[0050] The controller has multiple pre-stored temperature correspondences, namely the basic evaporation temperature mapping table. This mapping table was obtained through a large number of bench tests and reflects the basic evaporation temperature value required to maintain basic cooling capacity under different temperature differences between indoor temperature Ti and indoor target temperature Ts.

[0051] Specifically, the controller calculates the difference between the real-time indoor temperature Ti and the target indoor temperature Ts. Difference A positive value indicates that the actual room temperature is higher than the set temperature, indicating insufficient cooling capacity and a need to increase cooling power; the difference value indicates that the actual room temperature is higher than the set temperature. A negative value indicates that the room temperature is lower than the set temperature, resulting in excessive cooling capacity, and the cooling capacity needs to be reduced. The controller then calculates the difference. By matching the pre-stored temperature correspondence, the base evaporation temperature under the current operating conditions is obtained, denoted as . (Unit: °C)

[0052] Among them, the basic evaporation temperature With difference As the room heat load increases (i.e., Ti is significantly higher than Ts), a lower evaporation temperature is required, i.e., a smaller base evaporation temperature. In a refrigeration cycle, the lower the target evaporation temperature, the more frequently the compressor needs to operate to generate lower evaporation pressure, thereby providing greater cooling capacity to increase the cooling output.

[0053] Step S400: Calculate the dynamic correction value based on the indoor target temperature and the indoor temperature.

[0054] Under ultra-low frequency operation, relying solely on the basic evaporation temperature It is difficult to adapt to real-time changes in indoor load, especially when the room temperature rises or falls slowly and continuously, and the static base evaporation temperature is low. The inability to respond in a timely manner leads to a lag in compressor frequency adjustment. Therefore, this application introduces a dynamic correction value. It compensates for the base evaporation temperature in real time.

[0055] Step S500: Based on the base evaporation temperature and the dynamic correction value, the corrected target evaporation temperature is obtained.

[0056] The base evaporation temperature was calculated for each indoor unit that was in operation. and dynamic correction value Then, the controller calculates the corrected target evaporation temperature Teo(j) for each indoor unit. The calculation formula is:

[0057] Where j represents the indoor unit number (j=1, 2, …, m, where m is the total number of indoor units in operation). The base evaporation temperature of the j-th indoor unit. Let be the dynamic correction value for the j-th indoor unit. The target evaporation temperature is the corrected value for the j-th indoor unit.

[0058] It should be noted that, in some implementations, to simplify the control logic, the same dynamic correction value may be used for all indoor units. For example, taking the dynamic correction value from each indoor unit. The average or minimum value is taken, but in this embodiment, the dynamic correction value of each indoor unit is calculated independently. To accurately adapt to the different load characteristics of different rooms.

[0059] Step S600: Based on the comparison between the corrected target evaporation temperature and the indoor unit liquid pipe temperature, control the operating frequency of the compressor.

[0060] The controller compares the real-time liquid pipe temperature Tl(j) of each operating indoor unit with the unified target evaporation temperature of the entire unit. A comparison is made, and the compressor's operating frequency is adjusted based on the comparison results. Since all indoor units in a multi-split system share the same compressor, the compressor's frequency adjustment is based on a comprehensive consideration of the liquid line temperatures of all indoor units and the unified target evaporation temperature of the entire system. A comprehensive decision made after considering the deviations.

[0061] In this way, by setting up a detection device to collect temperature data, the controller first obtains the baseline evaporation temperature under low-frequency operating conditions, and then introduces a dynamic correction value to complete temperature compensation, generating a corrected target evaporation temperature that fits the real-time room temperature change trend. The compressor frequency is then adjusted in conjunction with the corrected evaporation temperature. In this way, the reference evaporation temperature can be dynamically adjusted in real time according to the indoor cooling and heating load, which greatly alleviates the temperature control lag problem under ultra-low frequency operating conditions, avoids excessively high evaporation temperatures that cause excessive heat exchange temperature difference and surface frost and ice formation in the indoor unit, and prevents insufficient compressor operating pressure difference and poor oil return caused by continuously low evaporation temperatures. This improves the stability of the unit's low-frequency operation, takes into account the cooling needs of each room in a multi-split system, and optimizes the overall indoor temperature control comfort and the reliability of the entire unit.

[0062] In some embodiments of this application, the controller is further configured to calculate and update dynamic correction values ​​at preset time intervals; based on the updated dynamic correction values, the corrected target evaporation temperature is calculated synchronously, and the compressor frequency is adjusted in real time. This periodic iterative update mechanism ensures that the control strategy can continuously track the changing trend of indoor temperature, rather than relying solely on static values ​​from a single sample.

[0063] Specifically, the controller has a timer interrupt service routine. The controller triggers a dynamic correction value update calculation at a preset time interval DT, such as every 60 seconds or every 80 seconds, and periodically iterates and updates the dynamic correction value. Dynamic correction value The initial value is a preset initial value, which is the value taken when the unit first enters the ultra-low frequency operation state. This initial value can be pre-calibrated according to the characteristics of the unit, and the general range is 5 to 10. In this embodiment, the preset initial value can be 8.

[0064] During each service interruption, the controller reads the current cycle's indoor temperature Ti(n) and target indoor temperature Ts(n), calculates the dynamic correction value for the current cycle based on the current cycle's indoor temperature Ti(n) and target indoor temperature Ts(n), and then recalculates the target evaporation temperature Teo(j) for each indoor unit and the target evaporation temperature of the entire unit. Finally, based on the new target evaporation temperature Based on the comparison results with the current liquid pipe temperature Tl(j) of each indoor unit, adjust the compressor frequency or keep it unchanged.

[0065] In this way, the controller continuously iterates and updates the dynamic correction values ​​at a fixed cycle, and simultaneously updates the target evaporation temperature for overall unit control. This enables continuous tracking of indoor temperature change trends, allowing for real-time capture of minute temperature differences and rapid feedback to the evaporation temperature reference, avoiding adjustment delays caused by single long-term sampling; it also allows the target evaporation temperature to continuously and slightly adapt to fluctuations in the indoor load, with smooth frequency adjustment without abrupt changes, avoiding frequent compressor frequency increases and decreases, reducing unit operating noise, and extending compressor lifespan.

[0066] In some embodiments of this application, reference is made to Figure 5 The controller is also configured to calculate a dynamic correction value based on the indoor target temperature and the indoor temperature, including: obtaining the dynamic correction value stored at the previous sampling time as a reference value, wherein the reference value is a preset initial value when it is the first sampling time; obtaining the correction difference corresponding to the current sampling time based on the indoor target temperature and the indoor temperature; and calculating the difference between the reference value and the correction difference corresponding to the current sampling time to obtain the dynamic correction value at the current sampling time.

[0067] Specifically, in ultra-low frequency operation, the controller periodically triggers iterative update calculations of the dynamic correction value at preset fixed time intervals DT (e.g., every 30 seconds or every 60 seconds). At the start of each update cycle, the controller first reads the dynamic correction value stored in the previous sampling time from its internal non-volatile memory or random access memory, and uses it as the base value for this iteration calculation. It is important to note that when the unit first enters ultra-low frequency operation and no historical correction data has been established (i.e., at the first sampling time (n=1), since there is no valid value from the previous sampling time in the memory, the controller automatically calls a preset initial value as the base value for this calculation, thereby filling the data gap during the first run and ensuring that the iteration logic can start normally. This initial value can be pre-calibrated according to the unit characteristics, generally ranging from 5 to 10. The preset initial value is the optimal starting point obtained statistically from a large amount of bench test data. Under different machine models, refrigerant types, and ambient temperature conditions, the initial value that enables the system to quickly stabilize to near the target evaporation temperature after entering the ultra-low frequency state is usually concentrated in the range of 6 to 10. Considering both convergence speed and overshoot suppression, the preset initial value in this embodiment can be 8. Of course, in other embodiments, this initial value can be calibrated and adjusted according to the heat transfer characteristics of the actual machine model. For example, it can be appropriately increased to 10 for large-capacity units and decreased to 6 for small-capacity units to adapt to different system inertia. In addition, the controller can also dynamically correct the initial value based on the operating parameters at the moment before entering the ultra-low frequency state, such as the compressor frequency change trend and the rate of change of indoor temperature, to achieve a smoother operating condition transition. However, as a basic solution, a fixed initial value can meet the needs of most application scenarios.

[0068] After successfully acquiring the baseline value, the controller immediately proceeds to calculate the correction difference. This calculation aims to quantify the deviation between the current indoor temperature and the set temperature, and its trend, thus providing a basis for the direction and magnitude of dynamic correction adjustments. Specifically, the controller first acquires the actual indoor temperature Ti(n) collected by the indoor temperature sensor at the current sampling time and the user-set indoor target temperature Ts(n), and calculates the difference between the two to obtain the room temperature difference at the current sampling time. At the same time, the controller retrieves the room temperature difference recorded at the previous sampling moment from memory. On the first run, Take and The same value is used to avoid unnecessary differential perturbations at the initial moment.

[0069] After obtaining the temperature difference at the current sampling time and the temperature difference at the previous sampling time, the controller calculates the correction difference at the current sampling time according to the preset calculation rules. After calculating the correction difference at the current sampling time, the controller performs an iterative update operation on the dynamic correction value, that is, using the reference value from the previous sampling time. Subtract the correction difference at the current sampling time The dynamic correction value at the current sampling time is obtained. Its mathematical expression is:

[0070] When the room temperature is high (ΔT1(n)>0) and continues to rise (ΔT1(n)-ΔT1(n-1)>0), the calculated It is a positive value. Compared to Decrease, meaning the dynamic correction value is adjusted downwards. The corrected target evaporation temperature will be calculated subsequently. At that time, due to the dynamic correction value of the current cycle Reducing will lead to Lowering the target evaporation temperature. As mentioned earlier, when the target evaporation temperature is lower than the indoor unit's liquid pipe temperature, it means the system needs to operate at a higher compressor frequency to provide stronger cooling capacity, thereby suppressing the continuous rise in room temperature and achieving a negative feedback closed loop. Conversely, when the room temperature is low or continues to drop, It is a negative value. Increase As the temperature rises, the compressor frequency decreases accordingly, reducing cooling output and preventing excessive temperature drop. This negative feedback mechanism ensures that the system automatically adjusts itself to eliminate temperature deviations, eventually converging to a steady state.

[0071] The dynamic correction value at the current sampling time. After calculation, the controller stores the value in memory as the reference value for the next sampling time. Simultaneously, the controller also stores the room temperature difference ΔT1(n) at the current sampling time into memory, overwriting the record from the previous sampling time, preparing data for the difference calculation at the next sampling time. This completes one iteration cycle of the dynamic correction value. When the next preset interval DT arrives, the controller repeats the above process to... As a new baseline value, a new correction difference is calculated and updated again. This process is repeated to achieve continuous, smooth, and adaptive tracking of the dynamic correction value.

[0072] In this way, by directly calling the built-in initial correction value at the first sampling moment, subsequent sampling moments update the value by subtracting the correction difference at the current sampling moment from the correction value at the previous sampling moment. This solves the problem of computational blanks when the controller first enters low-frequency operation without historical correction parameters, ensuring that the dynamic correction logic can be stably started from power-on. At the same time, the use of an iterative update method based on differences makes the numerical changes smooth and controllable, preventing drastic deviations in evaporation temperature caused by abrupt changes in correction values, and ensuring a stable adjustment process during ultra-low frequency operation.

[0073] In some embodiments of this application, reference is made to Figure 6 The controller is also configured to obtain a correction difference corresponding to the current sampling time based on the indoor target temperature and the indoor temperature, including: Calculate the temperature difference between the indoor temperature and the target indoor temperature at the current sampling time, and record it as the first difference; calculate the temperature difference between the indoor temperature and the target indoor temperature at the previous sampling time, and record it as the second difference; based on the first difference, the second difference, the preset proportional parameter and the interval time, calculate the correction difference at the current sampling time.

[0074] Specifically, the controller calculates the temperature difference between the indoor temperature Ti and the indoor target temperature Ts at the current sampling time, and records it as the first difference. The calculation formula is as follows:

[0075] At the same time, the temperature difference at the previous sampling time is calculated and recorded as the second difference. The calculation formula is as follows:

[0076] Then, based on the first difference Second difference Preset ratio parameters Preset integration parameters The correction difference at the current sampling time is calculated using the time interval DT. The calculation formula uses PID control:

[0077] It should be noted that the proportional parameters The function lies in amplifying or attenuating the rate of change of room temperature difference (i.e., how fast the temperature rises or falls). When the room temperature deviates rapidly from the set value, the proportional term can quickly generate a large correction difference, driving the dynamic correction value to adjust rapidly in the direction of system stability, thereby suppressing further temperature deviation; integral parameter The key is to accumulate and weight the continuous deviation of room temperature. When the room temperature is higher or lower than the set value for a long time and the proportional term is not enough to completely eliminate the deviation, the integral term can continuously accumulate the deviation signal, gradually increase the correction difference, until the steady-state deviation is completely eliminated, thereby ensuring that the system has zero steady-state error regulation capability.

[0078] Among them, the proportionality coefficient Integral coefficient These are all parameters pre-tuned for the PID controller. Their values ​​need to be determined based on system characteristics and experimental calibration. In this embodiment, when DT is in seconds, the proportional coefficient is... It can be 0.5, the integral coefficient. It can be 0.02. Of course, in other embodiments, the proportional coefficient can be adjusted according to the heat transfer inertia, sensor response characteristics, and control accuracy requirements of different models. The value can be adjusted between 0.2 and 1.0, and the integral coefficient... The value can be adjusted between 0.005 and 0.05.

[0079] In this method, the proportional term This reflects the rate of change of room temperature difference, i.e., the slope of the temperature change. When the room temperature rises or falls rapidly, this term can respond quickly and adjust the correction value in advance; integral term This reflects the cumulative effect of persistent room temperature deviation, eliminating steady-state temperature deviation and ensuring that the room temperature eventually approaches the set value. The combination of these two methods enables rapid and precise control of the dynamic correction value without steady-state error.

[0080] In this way, the correction value is calculated in a closed loop based on the temperature difference between the preceding and following time intervals, the set parameters, and the interval duration. It can simultaneously take into account both the instantaneous magnitude of the temperature difference and the continuous cumulative change of the temperature difference. The preset proportional parameters can quickly respond to sudden changes in room temperature and eliminate steady-state temperature deviations. It can accurately predict the long-term trend of continuous temperature rise and fall, adjust the correction value in advance, significantly shorten the temperature regulation response time, reduce the steady-state temperature difference in the room, and improve the constant temperature effect.

[0081] In some embodiments of this application, reference is made to Figure 7 The controller is also configured to obtain a correction difference corresponding to the current sampling time based on the indoor target temperature and the indoor temperature, and also includes: Calculate the temperature difference between the indoor temperature and the target indoor temperature at the current sampling time, and record it as the first difference; calculate the temperature difference between the indoor temperature and the target indoor temperature at the previous sampling time, and record it as the second difference; calculate the difference between the first difference and the second difference to obtain the temperature difference change; based on the comparison relationship between the first difference and the preset room temperature difference, and the comparison relationship between the temperature difference change and the preset temperature difference change amplitude, determine the correction difference at the current sampling time.

[0082] Specifically, in this method, the controller also calculates the first difference at the current sampling time. The second difference with the previous sampling time Then, calculate the difference between the first and second differences to obtain the temperature change. The calculation formula is as follows:

[0083] Then, the controller is based on the first difference. By comparing the temperature difference with the preset room temperature, the current room temperature range is determined; simultaneously, based on the change in temperature difference... By comparing the current temperature difference range with a preset range of temperature variation, the current temperature difference range is determined. Based on the determined room temperature range and temperature difference range, the unique correction difference value corresponding to this range combination is retrieved from a pre-stored mapping table. .

[0084] In this way, by comparing the first difference with the preset room temperature difference and the temperature difference change with the preset temperature difference change range, the correction difference at the current sampling time is determined. There is no need to perform complex floating-point closed-loop calculations, which greatly reduces the computing power consumption of the controller and is compatible with low-cost, low-performance main control chips. The interval level division is clear, the control logic is simple, and the debugging and calibration are convenient. The values ​​in the table can be quickly modified according to the load characteristics of different models, reducing the product development and adaptation costs.

[0085] In some embodiments of this application, the controller is further configured to determine a correction difference at the current sampling time based on a comparison between a first difference and a preset room temperature difference, and a comparison between the amount of temperature difference change and a preset temperature difference change amplitude, including: Based on the comparison between the first difference and the preset room temperature difference, multiple room temperature difference ranges are obtained; based on the comparison between the temperature difference change and the preset temperature difference change range, multiple temperature difference change ranges are obtained; any room temperature difference range is paired with any temperature difference change range, and each pair of ranges is pre-stored with a unique corresponding correction difference value. Determine the room temperature difference range to which the current first difference belongs; simultaneously determine the temperature difference change range to which the current temperature difference change belongs; based on the determined room temperature difference range and temperature difference change range, retrieve the corresponding correction difference value pre-stored for this set of ranges, and use this correction difference value as the correction difference value within the current interval time period.

[0086] For example, based on the comparison between the first difference and the preset room temperature difference, the preset room temperature difference range can be divided into the following five levels: Interval A1: <-1℃ Interval A2: -1℃ ≤ <0℃ Interval A3: 0℃ ≤ ≤ 1℃ Interval A4: 1℃ ≤ 2℃ Range A5: 2℃

[0087] Based on the comparison between the temperature difference change and the preset temperature difference change range, the preset temperature difference change range can be divided into the following four levels: Interval B1: ≤ -1 Interval B2: -1 < ≤ 0 Interval B3: 0 < ≤ 1 Interval B4: 1<

[0088] The five room temperature difference ranges and four temperature difference ranges are paired to obtain a total of 20 range combinations. Each combination has a unique corresponding correction difference value pre-stored. For example, the mapping table can be represented as follows:

[0089] Based on the calculated initial difference and the temperature change, the controller locates the corresponding row and column position in the aforementioned mapping table and directly reads the corrected difference. The value is obtained. This lookup table method does not require floating-point multiplication and division operations, but only simple comparison and lookup operations, resulting in extremely high computational efficiency, making it suitable for implementation in low-cost microcontrollers.

[0090] In the above technical solution, by setting multiple indoor temperature difference ranges and multiple temperature difference change ranges, each range combination is independently configured with a dedicated correction difference value, so as to achieve fine-grained and layered control over the room temperature temperature and the speed of temperature rise and fall, and to match different correction strengths for different load change scenarios; to avoid the defect that a single correction value cannot adapt to a wide range of room temperature fluctuations, and to take into account the adjustment accuracy under slight load fluctuations and severe load fluctuations, so that the temperature control adaptation range is wider.

[0091] It should be noted that when obtaining the corrected difference... In this case, those skilled in the art can flexibly choose between the two acquisition methods described above based on the actual hardware platform and control requirements. Regardless of the method used, the controller periodically updates and corrects the difference according to a preset interval DT. and dynamic correction value This enables continuous iteration of the dynamic correction value.

[0092] In some embodiments of this application, reference is made to Figure 3 The controller is also configured to determine the base evaporation temperature based on the indoor temperature and the indoor target temperature, including: Multiple sets of temperature correspondences are pre-stored. Each set of temperature correspondences matches the temperature difference between a set of indoor temperatures and the indoor target temperature. Each temperature difference corresponds to a target evaporation temperature. The difference between the real-time collected indoor temperature and the indoor target temperature is calculated. Based on the difference, the corresponding temperature correspondence is matched to obtain the basic evaporation temperature corresponding to the current indoor temperature.

[0093] Specifically, the controller's internal non-volatile memory (such as EEPROM or built-in Flash) pre-stores multiple sets of temperature correspondences. These temperature correspondences are essentially the relationship between the temperature difference ΔT1 between the indoor temperature Ti and the indoor target temperature Ts and the base evaporation temperature. A numerical mapping table is used. This mapping relationship is not arbitrarily set, but obtained through extensive bench tests. For different models (such as 1 HP, 1.5 HP, and 2 HP indoor units), under rated and variable operating conditions, parameters such as compressor frequency and electronic expansion valve opening are adjusted to achieve steady-state operation. The optimal evaporation temperature value required to maintain a stable room temperature under different indoor and outdoor conditions is recorded. After data processing and curve fitting, a basic evaporation temperature mapping table specific to this model is formed and is fixed in the controller as a factory parameter.

[0094] For example, refer to Figure 3 In this embodiment, for a side-discharge multi-split air conditioning system using R32 refrigerant, five indoor temperature differences are pre-defined, namely... =0、 =1、 =2、 =3 and =4, each temperature difference corresponds to an independent linear mapping curve Teo0, Teo1, Teo2, Teo3, Teo4. The overall trend of the five curves is consistent, all showing a linear positive growth law: within any curve, as the indoor temperature Ti represented by the horizontal axis gradually increases from 15℃ to 30℃, the basic evaporation temperature represented by the vertical axis increases synchronously and continuously linearly, ensuring that the basic evaporation temperature follows the actual indoor return air temperature smoothly and continuously, without any numerical abrupt changes.

[0095] In other words, all curves synchronously satisfy the following: as the indoor temperature Ti increases, the base evaporation temperature increases synchronously and linearly; at the same indoor temperature, the indoor temperature difference... The larger the value, the smaller the corresponding base evaporation temperature. When the controller is running, it first calculates the difference between the real-time indoor temperature and the target indoor temperature, matches the curve corresponding to the range of the difference, and then reads the corresponding temperature value from the matched curve based on the currently collected indoor temperature. This temperature value is the base evaporation temperature of the current indoor unit. Obtaining the base evaporation temperature provides a reference temperature for subsequent dynamic correction values.

[0096] In this way, by pre-storing multiple sets of temperature differences and the corresponding relationship between the base evaporation temperature, and relying on the real-time indoor temperature difference to retrieve the reference temperature, the base evaporation temperature can be made to match the indoor base load requirements, and the conventional cooling load can be matched without the addition of dynamic correction values; different room temperature differences correspond to different reference temperatures, providing a reasonable reference range for subsequent dynamic correction, and avoiding excessive compensation of correction amount caused by the base temperature deviating from the reasonable range.

[0097] In some embodiments of this application, the controller is further configured to obtain a corrected target evaporation temperature based on a base evaporation temperature and a dynamic correction value, including: Obtain the base evaporation temperature and corresponding dynamic correction value of the indoor unit for each operating state; calculate the sum of the base evaporation temperature and corresponding dynamic correction value of each indoor unit to obtain the corrected target evaporation temperature of a single indoor unit; compare the corrected target evaporation temperatures of all indoor units and select the minimum value as the corrected target evaporation temperature of the air conditioning system.

[0098] Specifically, in a multi-split air conditioning system, the outdoor unit is connected to multiple indoor units (e.g., 3, 4, or more) via refrigerant piping. Each indoor unit is installed in a different room or area, independently monitoring the indoor temperature Ti(j) and liquid line temperature Tl(j) of its respective room, and independently receiving the target indoor temperature Ts(j) set by the user via a wired controller or remote control. Because the size, orientation, insulation conditions, activity levels, and user temperature preferences of each room may vary significantly, the heat load faced by each indoor unit at any given time will differ. Therefore, each indoor unit needs to independently calculate its base evaporation temperature and dynamic correction value to accurately reflect the real-time load status of its respective room.

[0099] Specifically, the controller first calculates the base evaporation temperature of each indoor unit j (j=1, 2, …, m, where m is the total number of indoor units currently in operation) according to the method described in the previous embodiments. This calculation is based on the difference between the indoor temperature Ti(j) of the room where the indoor unit is located and the user-set temperature Ts(j), obtained through a pre-stored temperature correspondence. Simultaneously, the controller calculates the dynamic correction value for each operating indoor unit according to the iterative update method described in the previous embodiments. This dynamic correction value is based on the difference between the current period's room temperature difference and the previous period's room temperature difference, obtained through incremental PID calculation or interval lookup, and is periodically iteratively updated according to a preset time interval DT.

[0100] After obtaining the independent base evaporation temperature and dynamic correction value for each indoor unit, the controller performs a summation operation on each indoor unit to calculate its corrected target evaporation temperature. The calculation formula is as follows:

[0101] in, The symbol is a function representing the base evaporation temperature calculated based on room temperature and the temperature difference between room temperature and room temperature.

[0102] This summation operation algebraically adds the base evaporation temperature to the dynamic correction value. As mentioned earlier, when the room heat load increases (room temperature rises), the dynamic correction value tends to decrease after iterative calculation, resulting in a lower target evaporation temperature relative to the base evaporation temperature. This drives the compressor to increase its frequency in subsequent frequency control, thereby enhancing cooling output. Conversely, when the room heat load decreases (room temperature falls), the dynamic correction value tends to increase, the target evaporation temperature rises, and the compressor to decrease its frequency, thereby reducing cooling output. The corrected target evaporation temperature for each indoor unit is independent and updated in real time, fully reflecting the personalized cooling needs of the room at that moment.

[0103] After calculating the corrected target evaporation temperature for all m operating indoor units, the controller enters the multi-indoor unit integrated decision-making stage. In this stage, the controller compares the corrected target evaporation temperature values ​​for all indoor units and selects the minimum value as the unified target evaporation temperature for the entire air conditioning system.

[0104] In a multi-split air conditioning system, all indoor units share a single outdoor compressor and the same refrigerant circulation loop. The compressor's discharge capacity and operating frequency can only output a uniform cooling capacity level at any given time. When the system operates at a target evaporation temperature, the indoor unit with the lowest evaporation temperature (i.e., the lowest Teo value) represents the unit with the most urgent cooling demand. In other words, this room has the highest heat load or the fastest temperature rise, making it the weakest link in the entire system's heat exchange process. If the overall target evaporation temperature is higher than the required value for this indoor unit, it will not receive sufficient cooling capacity due to the excessively high evaporation temperature setting, resulting in a persistently high room temperature that fails to meet the user's set requirements. Therefore, by calculating the dedicated corrected evaporation temperature for each indoor unit and selecting the minimum value from all indoor units as the overall system control benchmark, it is possible to prioritize the heat exchange needs of rooms with the highest cooling demand and higher temperatures, addressing the differentiated room loads in multi-split systems. This avoids insufficient cooling in some rooms due to single-room temperature control, balances the heat exchange conditions of all indoor units, and eliminates problems such as uneven temperature distribution and zone temperature control imbalances.

[0105] In some embodiments of this application, reference is made to Figure 8 and Figure 10 The controller is also configured to control the compressor operating frequency of the air conditioning system based on a comparison between the corrected target evaporation temperature and the indoor unit liquid line temperature, including: When the indoor unit liquid pipe temperature is lower than the corrected target evaporation temperature, the compressor is controlled to reduce its operating frequency; when the indoor unit liquid pipe temperature is higher than the corrected target evaporation temperature, the compressor is controlled to increase its operating frequency; when the indoor unit liquid pipe temperature is close to the corrected target evaporation temperature, the compressor's current operating frequency is maintained unchanged.

[0106] Specifically, in the refrigeration cycle, the indoor unit liquid line temperature, i.e., the temperature of the liquid refrigerant before entering the electronic expansion valve of the indoor unit, has a definite physical correlation with the evaporation temperature. During steady-state system operation, the liquid line temperature is typically higher than the evaporation temperature by a certain value, i.e., subcooling. The difference between the two is determined by factors such as the subcooling capacity of the condenser, the piping length, and the insulation effect. Therefore, the indoor unit liquid line temperature can be considered an indirect but reliable characterization parameter of the evaporation temperature. Furthermore, compared to pressure sensors that directly measure evaporation pressure, liquid line temperature sensors offer advantages such as lower cost, easier installation, and higher reliability, making them a widely adopted alternative measurement solution in engineering practice.

[0107] After determining the unified target evaporation temperature for the entire unit, the controller compares the real-time liquid line temperature of each operating indoor unit with this target evaporation temperature one by one. When the liquid line temperature of any operating indoor unit is lower than the target evaporation temperature, the controller determines that the actual evaporation temperature of that indoor unit is lower than the target value, meaning that the evaporation pressure is too low and the refrigerant in the heat exchanger is excessively evaporating. This situation usually occurs when the system's cooling capacity is excessive relative to the room load, the overall refrigerant circulation flow is too large, and the evaporation temperature remains low. Although the instantaneous cooling capacity is sufficient, the excessively low evaporation temperature will significantly increase the compressor's compression ratio, causing the compressor's input power consumption to rise rapidly and the unit's energy efficiency ratio (COP) to decrease significantly. At the same time, the excessively low evaporation temperature will cause the indoor heat exchanger wall temperature to be lower than the air dew point, producing a large amount of condensate. Under extreme conditions, the heat exchanger coils will frost and ice over, blocking the ventilation ducts, significantly reducing the heat exchange capacity, and may also trigger the unit's anti-freeze protection to force a shutdown. Therefore, when the controller detects that the liquid pipe temperature of any indoor unit is lower than the target evaporation temperature, it immediately issues a frequency reduction command, controls the compressor to gradually reduce the operating frequency at a preset frequency reduction rate, such as reducing it by 1Hz every 10 seconds, reduces the amount of refrigerant circulating in the whole unit, increases the system evaporation pressure, and makes the liquid pipe temperature rise back to near the target value.

[0108] Conversely, when the liquid line temperature of any operating indoor unit exceeds the target evaporation temperature, the controller determines that the current system's cooling capacity is insufficient, resulting in an overall high evaporation temperature and pressure. A high evaporation temperature weakens the refrigerant's heat absorption capacity in the indoor heat exchanger, reducing the unit refrigerant cooling capacity, leading to poor indoor air cooling and a room cooling rate that fails to meet the set requirements. In this situation, the controller issues a frequency increase command, controlling the compressor to gradually increase its operating frequency at a preset rate, for example, increasing it by 1Hz every 10 seconds. This increases the refrigerant circulation volume, reduces the system evaporation pressure, and causes the liquid line temperature to drop back to near the target value.

[0109] When the liquid pipe temperature of each operating indoor unit is within the tolerance range of the target evaporation temperature, the controller determines that the current system cooling capacity is well matched with the total room load and the actual evaporation temperature is close to the target value. No frequency adjustment is required, and the current operating frequency of the compressor remains unchanged, entering a steady-state locked operation state.

[0110] Thus, when the liquid pipe temperature is lower than the reference evaporation temperature, the frequency decreases; when it is higher than the reference temperature, the frequency increases; and when the temperature is close, the current frequency is maintained. This uses the actual indoor heat exchange temperature as the basis for frequency adjustment, forming a closed-loop negative feedback control logic. The controller continuously collects the actual liquid pipe temperature and compares it with the target evaporation temperature. Based on the deviation between the two, it adjusts the compressor output power in the opposite direction, continuously offsetting the difference between indoor cooling supply and demand, driving the actual heat exchange temperature closer to the set reference temperature. When indoor cooling is insufficient, the compressor output is automatically increased; when cooling is excessive, the output is automatically reduced. After the room temperature stabilizes, the frequency is locked, avoiding frequent start-stop cycles, reducing low-frequency operation energy consumption, and improving constant temperature comfort.

[0111] It should be noted that in the multi-indoor unit system of this application, the liquid pipe temperatures of each indoor unit may differ, and some indoor units may even have temperatures below the target evaporation temperature while others have temperatures above it. In this case, the controller needs to employ a comprehensive decision-making strategy to determine whether to increase or decrease the frequency. In this embodiment, a frequency reduction priority strategy is preferred, meaning that as long as the Tl(j) of any operating indoor unit is below the target evaporation temperature, the controller executes a frequency reduction command, regardless of whether other indoor units are at excessively high temperatures. This is because a Tl below the target value indicates a risk of low evaporation pressure and excessive refrigerant evaporation in the heat exchanger, potentially leading to frosting or energy efficiency deterioration, which is a safety boundary issue requiring priority handling; while a Tl above the target value only indicates insufficient cooling capacity, which can be addressed with appropriate delay. This priority distinction ensures that safe system operation takes precedence over comfort optimization. Of course, in other embodiments, other strategies can also be used to determine the direction and magnitude of frequency adjustment.

[0112] In some embodiments of this application, reference is made to Figure 9 To determine whether the air conditioning system has entered a preset low-frequency operating state, the following steps are taken: obtaining the real-time operating frequency of the compressor; comparing the real-time operating frequency with a preset ultra-low frequency threshold; and determining that the unit has entered an ultra-low frequency operating state when the real-time operating frequency is not greater than the preset ultra-low frequency threshold.

[0113] Specifically, the real-time operating frequency of the compressor is obtained through communication between the compressor's variable frequency drive (VFD) and the controller. The VFD monitors signals such as the compressor's armature current and rotor position in real time, accurately calculates the compressor's real-time operating frequency using a closed-loop vector control algorithm, and sends this frequency value as a digital signal to the controller via the communication bus. Upon receiving this frequency value, the controller temporarily stores it in a frequency variable in its memory for subsequent comparison and judgment.

[0114] The controller has a pre-stored ultra-low frequency threshold, which is determined based on the compressor's rated frequency range, the system's minimum stable operating frequency, and the optimal energy efficiency operating range. Taking the DC inverter scroll compressor used in this embodiment as an example, its rated frequency range is 10Hz to 120Hz. When the compressor's operating frequency is below 10Hz, the system enters a special ultra-low frequency operating range. Within this range, the traditional target evaporation temperature control strategy is no longer applicable because the evaporation temperature deviates significantly from the design conditions, necessitating the introduction of the dynamic correction control method proposed in this application. Therefore, when the compressor's real-time operating frequency is not greater than the pre-stored ultra-low frequency threshold, the controller determines that the unit has entered a pre-stored low-frequency operating state and immediately triggers the dynamic correction control logic. It then performs a series of operations according to the methods described in the aforementioned embodiments, including determining the basic target evaporation temperature, iteratively calculating the dynamic correction value, synthesizing the corrected target evaporation temperature, and frequency regulation based on liquid pipe temperature comparison.

[0115] It should be noted that the specific value of the preset ultra-low frequency threshold is not fixed, but can be adaptively adjusted according to different compressor types, displacements, refrigerant types, and system configurations. For example, for multi-split systems using larger displacement compressors, the minimum stable operating frequency may be lower (e.g., 6Hz), so the preset ultra-low frequency threshold can be set accordingly to 6Hz or 7Hz; for systems using smaller displacement compressors, the ultra-low frequency boundary may be higher (e.g., 12Hz), so the preset ultra-low frequency threshold can be set to 12Hz. Furthermore, the controller can also set different preset ultra-low frequency threshold values ​​according to the system operating mode (cooling or heating), because the lubrication and oil return requirements of the compressor differ under heating conditions compared to cooling conditions, and the boundary of ultra-low frequency operation may shift.

[0116] In this way, the compressor's real-time operating frequency is directly collected and compared with a preset frequency threshold to identify ultra-low load operating scenarios. This determination method can complete the operating condition identification based solely on the compressor's inherent operating parameters, without the need for additional temperature or load sensors, effectively reducing the overall hardware assembly cost. At the same time, the frequency signal sampling response speed is fast, and the dynamic correction logic can be triggered immediately when the unit is in the low-frequency operating range, eliminating operating condition identification delays and ensuring that ultra-low frequency adaptive temperature control can be activated.

[0117] Although the invention has been described with reference to several typical embodiments, it should be understood that the terminology used is descriptive and exemplary, and not restrictive. Since the invention can be embodied in many forms without departing from the spirit or essence of the invention, it should be understood that the above embodiments are not limited to any of the foregoing details, but should be interpreted broadly within the spirit and scope defined by the appended claims. Therefore, all variations and modifications falling within the scope of the claims or their equivalents should be covered by the appended claims.

Claims

1. An air conditioning system, characterized in that, include: The outdoor unit is equipped with a compressor; At least one indoor unit, which is connected to the outdoor unit via a refrigerant pipeline; The detection device is used to collect indoor temperature and indoor unit liquid pipe temperature; The controller is configured to: Determine whether the air conditioning system has entered a preset low-frequency operating state. When it enters the preset low-frequency operating state, obtain the user-set indoor target temperature, the indoor temperature collected by the detection device, and the indoor unit liquid pipe temperature. The base evaporation temperature is determined based on the indoor temperature and the target indoor temperature. Calculate a dynamic correction value based on the target indoor temperature and the indoor temperature; Based on the base evaporation temperature and the dynamic correction value, the corrected target evaporation temperature is obtained; Based on the comparison between the corrected target evaporation temperature and the indoor unit liquid pipe temperature, the operating frequency of the compressor is controlled.

2. The air conditioning system according to claim 1, characterized in that, The controller is also configured to, The dynamic correction value is calculated and updated according to a preset time interval; Based on the updated dynamic correction value, the corrected target evaporation temperature is calculated synchronously.

3. The air conditioning system according to claim 2, characterized in that, The controller is further configured to calculate a dynamic correction value based on the indoor target temperature and the indoor temperature, including: The dynamic correction value stored at the previous sampling time is obtained as the reference value, wherein when it is the first sampling time, the reference value is a preset initial value; Based on the indoor target temperature and the indoor temperature, the correction difference corresponding to the current sampling time is obtained; The difference between the baseline value and the correction difference corresponding to the current sampling time is calculated to obtain the dynamic correction value at the current sampling time.

4. The air conditioning system according to claim 3, characterized in that, The controller is further configured to obtain a correction difference corresponding to the current sampling time based on the indoor target temperature and the indoor temperature, including: Calculate the temperature difference between the indoor temperature and the indoor target temperature at the current sampling time, and record it as the first difference; Calculate the temperature difference between the indoor temperature and the indoor target temperature at the previous sampling time, and record it as the second difference; Based on the first difference, the second difference, the preset ratio parameter, and the time interval, the corrected difference corresponding to the current sampling time is calculated.

5. The air conditioning system according to claim 3, characterized in that, The controller is further configured to obtain a correction difference value corresponding to the current sampling time based on the indoor target temperature and the indoor temperature, and further includes: Calculate the temperature difference between the indoor temperature and the indoor target temperature at the current sampling time, and record it as the first difference; The temperature difference between the indoor temperature and the indoor target temperature at the previous sampling time is calculated and recorded as the second difference value; Calculate the difference between the first difference and the second difference to obtain the temperature difference change; Based on the comparison between the first difference and the preset room temperature difference, and the comparison between the temperature difference change and the preset temperature difference change range, the correction difference corresponding to the current sampling time is determined.

6. The air conditioning system according to claim 5, characterized in that, The controller is further configured to determine the correction difference within the current time interval based on a comparison between the first difference and a preset room temperature difference, and a comparison between the temperature difference change and a preset temperature difference change amplitude, including: Based on the comparison between the first difference and the preset room temperature difference, multiple room temperature difference ranges are obtained; based on the comparison between the temperature difference change and the preset temperature difference change range, multiple temperature difference change ranges are obtained. Any one of the room temperature difference ranges and any one of the temperature difference variation ranges are paired together, and each pair of ranges is pre-stored with a unique corresponding correction difference value. Determine the room temperature difference range to which the current first difference belongs; at the same time, determine the temperature difference change range to which the current temperature difference change belongs; Based on the determined room temperature difference range and the temperature difference variation range, the corresponding correction difference value pre-stored in the combination of the ranges is retrieved, and the correction difference value is used as the correction difference value in the current interval time period.

7. The air conditioning system according to any one of claims 1-6, characterized in that, The controller is further configured to determine a base evaporation temperature based on the indoor temperature and the target indoor temperature, including: Multiple sets of temperature correspondences are pre-stored. Each set of temperature correspondences matches the temperature difference between the indoor temperature and the indoor target temperature. Each temperature difference corresponds to a target evaporation temperature. Calculate the difference between the real-time collected indoor temperature and the indoor target temperature; Based on the temperature correspondence corresponding to the difference matching, the basic evaporation temperature corresponding to the current indoor temperature is obtained.

8. The air conditioning system according to any one of claims 1-6, characterized in that, The controller is further configured to obtain a corrected target evaporation temperature based on the base evaporation temperature and the dynamic correction value, including: The base evaporation temperature and corresponding dynamic correction value of the indoor unit are obtained for each operating state. Calculate the sum of the base evaporation temperature and the corresponding dynamic correction value for each indoor unit to obtain the corrected target evaporation temperature for a single indoor unit. Compare the corrected target evaporation temperatures of all indoor units and select the minimum value as the corrected target evaporation temperature of the air conditioning system.

9. The air conditioning system according to any one of claims 1-6, characterized in that, The controller is further configured to control the compressor operating frequency of the air conditioning system based on a comparison between the corrected target evaporation temperature and the indoor unit liquid pipe temperature, including: When the temperature of the liquid pipe in the indoor unit is lower than the corrected target evaporation temperature, the compressor is controlled to reduce its operating frequency. When the temperature of the liquid pipe in the indoor unit is higher than the corrected target evaporation temperature, the compressor is controlled to increase its operating frequency. When the temperature of the liquid pipe in the indoor unit is close to the corrected target evaporation temperature, the current operating frequency of the compressor is maintained unchanged.

10. The air conditioning system according to claim 1, characterized in that, The controller is further configured to determine whether the air conditioning system has entered a preset low-frequency operating state, including: Obtain the real-time operating frequency of the compressor; The real-time operating frequency is compared with a preset ultra-low frequency threshold. When the real-time operating frequency is not greater than the preset ultra-low frequency threshold, the unit is determined to have entered the ultra-low frequency operating state.

Images