Multi-connected air conditioning system

Abstract

The application discloses a multi-connected air conditioner system, indoor units, multiple are arranged, outdoor units, at least 1 is arranged, connected with the indoor unit, the outdoor unit is provided with a high pressure sensor and a liquid pipe temperature sensor; a first pressure relief pipeline; a first pressure relief valve connected on the first pressure relief pipeline; the control part is configured to: obtain the capacity ratio of the running indoor unit and the running outdoor unit; the exhaust pressure value of the exhaust pressure sensor and the outdoor heat exchanger liquid pipe side temperature value; when it is determined that the capacity ratio of the running indoor unit and the running outdoor unit reaches the set ratio range, there is a target outdoor unit in the outdoor unit, the exhaust pressure value of which reaches the preset pressure interval range and the supercooling degree value reaches the preset supercooling degree interval range, the first pressure relief valve of the target outdoor unit is controlled to be turned on. The multi-connected air conditioner system can detect liquid sealing and can release the high pressure of the system when detecting that liquid sealing is about to occur, so that the stable operation of the system in low-temperature small-load refrigeration is ensured.

Description

Technical Field

[0001] This invention relates to the field of multi-split air conditioning technology, and more specifically to an improvement in the structure of a multi-split air conditioning system. Background Technology

[0002] For multi-split air conditioning systems, one outdoor unit may connect to multiple indoor units to form a system, or multiple outdoor units may connect to multiple indoor units to form a system. However, in actual use, the number of indoor units operating is random. In most cases, they will operate under low load, with the indoor unit capacity / outdoor unit capacity ratio being less than 30%. This is especially true during transitional periods or when the outdoor ambient temperature is low (taking cooling as an example). Often, only one indoor unit will be operating, and the indoor unit capacity / outdoor unit capacity ratio will be very small, below 20% or 10%.

[0003] Because the outdoor ambient temperature is low, for example below 15℃, and the indoor ambient temperature is also low, for example below 20℃, only one indoor unit is turned on for cooling while the rest are turned off. Due to the low indoor and outdoor ambient temperatures, the cooling capacity demand is relatively small, requiring the compressor frequency to be low. The compressor is basically operating at its lowest frequency. At this time, the valve opening of the indoor unit is also small, and the refrigerant circulation is relatively small. Since the other indoor units are turned off, most of the refrigerant may be stored in the outdoor unit. Over time, the refrigerant in the outdoor unit increases and cannot be discharged, which is a liquid seal phenomenon. The system high pressure gradually increases, and the system load gradually increases. After a certain period of time, the system load is large enough that the instantaneous value of the system current exceeds the maximum value that the drive module can bear, resulting in an alarm and shutdown. Summary of the Invention

[0004] In response to the problems mentioned in the background art, the present invention proposes a multi-split air conditioning system that can detect liquid seals and, when a liquid seal is detected to be about to occur, controls the first pressure relief valve to be opened for a period of time to relieve the high pressure of the system, thereby ensuring the stable operation of the entire multi-split system under low temperature and low load cooling.

[0005] In some embodiments of this application, a multi-split air conditioning system is proposed, comprising: Multiple indoor units are installed. At least one outdoor unit shall be installed and connected to the indoor unit via refrigerant piping. This includes a compressor, an outdoor heat exchanger, and a gas-liquid separator connected via refrigerant pipes; The exhaust pressure sensor detects the exhaust pressure value on the compressor's exhaust side; Liquid pipe temperature sensor detects the temperature on the liquid pipe side of the outdoor heat exchanger; The first pressure relief line is connected between the compressor discharge side and the gas-liquid separator; The first pressure relief valve is connected to the first pressure relief pipeline and is used to control the opening and closing of the first pressure relief pipeline; The control unit is configured to: acquire the capacity ratio of the operating indoor unit to the operating outdoor unit when the system is cooling; Obtain the exhaust pressure value from the exhaust pressure sensor of the outdoor unit; The subcooling value is obtained by combining the corresponding outdoor heat exchanger liquid pipe side temperature value with the exhaust saturation temperature corresponding to the exhaust pressure value. When the capacity ratio of the operating indoor unit to the operating outdoor unit reaches a set ratio range, and there is a target outdoor unit whose exhaust pressure value reaches a preset pressure range and whose subcooling value reaches a preset subcooling range, the first pressure relief valve of the target outdoor unit is controlled to open. The opening time of the first pressure relief valve is determined based on the preset pressure range and the preset subcooling range.

[0006] The above embodiments have the following advantages and effects: By acquiring the capacity ratio of the indoor and outdoor units of the refrigeration system, the exhaust pressure value of the exhaust pressure sensor, and the subcooling value of the outdoor heat exchanger, it is possible to determine whether the system is operating under low refrigeration load. Furthermore, when it is determined that the system is about to experience a liquid seal, the duration of the first pressure relief valve can be controlled to quickly relieve pressure and prevent the system from experiencing high pressure.

[0007] In some embodiments of this application, the preset pressure range includes multiple pressure sub-ranges; The preset subcooling range includes multiple subcooling sub-ranges, and each pressure sub-range corresponds to a subcooling sub-range. Each pressure sub-interval and its corresponding subcooling sub-interval correspond to a first pressure relief valve opening time; When the detected exhaust pressure value and subcooling value simultaneously reach the corresponding pressure sub-range and subcooling sub-range, the control unit controls the first pressure relief valve to be turned on for a period of time. The higher the exhaust pressure and subcooling values, the longer the conduction time of the first pressure relief valve corresponding to the pressure sub-range and subcooling sub-range.

[0008] The above embodiments have the following advantages and effects: By setting the preset pressure range corresponding to the detected exhaust pressure value into multiple pressure sub-ranges, and setting the preset subcooling range corresponding to the subcooling value into multiple subcooling sub-ranges, the detected exhaust pressure value and subcooling value can be precisely defined to a certain pressure sub-range or subcooling sub-range.

[0009] During adjustment, the first pressure relief valve can be controlled according to the pressure sub-range and subcooling sub-range it falls into, so that the opening time of the first pressure relief valve matches the exhaust pressure value and the subcooling value, ensuring pressure relief on the high-pressure side of the system and preventing liquid seal.

[0010] In some embodiments of this application, the multi-split air conditioning system includes a suction temperature sensor for detecting the suction temperature on the suction side of the compressor; The suction pressure sensor detects the suction pressure on the suction side of the compressor to obtain the suction pressure saturation temperature; The control unit is configured to: control the first pressure relief valve to open when it is determined that the difference between the intake temperature and the intake pressure saturation temperature reaches the set temperature range; The opening time of the first pressure relief valve is determined based on the preset pressure range and the preset subcooling range.

[0011] The above embodiments have the following advantages and effects: The compressor suction superheat is obtained by the difference between the suction temperature and the suction saturation temperature. The compressor suction superheat needs to be kept within the set temperature range to prevent liquid return from the compressor. Therefore, before the first pressure relief valve is opened, the compressor suction superheat needs to be kept within the set temperature range to ensure that the compressor does not return liquid.

[0012] In some embodiments of this application, The compressor is equipped with a drive module for driving the compressor to operate; The control unit is configured to: The compressor's operating current and the preset current value in the drive module are obtained. When the difference between the preset current and the operating current reaches the preset current range, the first pressure relief valve is controlled to open. The opening time of the first pressure relief valve is determined based on the preset pressure range and the preset subcooling range.

[0013] The above embodiments have the following advantages and effects: When the system is running in cooling mode, the detection of system parameters is combined with the detection of compressor operating current. By combining the detected compressor operating current parameters with the detection of discharge pressure sensor values, outdoor heat exchanger subcooling values, and the ratio of indoor unit capacity to outdoor unit capacity, a more accurate determination of liquid seal occurrence can be achieved.

[0014] In some embodiments of this application, a multi-split air conditioning system is proposed, comprising: Multiple indoor units are installed. At least one outdoor unit is installed, which is connected to multiple indoor units via piping. This includes: a compressor, an outdoor heat exchanger, and a gas-liquid separator connected via refrigerant pipes; The exhaust pressure sensor detects the exhaust pressure value on the compressor's exhaust side. Liquid pipe temperature sensor detects the temperature on the liquid pipe side of the outdoor heat exchanger; The second pressure relief pipeline is connected between the outdoor heat exchanger and the gas-liquid separator. When it is turned on, it transfers the excess refrigerant from the outdoor heat exchanger to the gas-liquid separator to relieve pressure. The second pressure relief valve is connected to the second pressure relief pipeline; The control unit is configured to: acquire the capacity ratio of the operating indoor unit to the operating outdoor unit when the system is cooling; Obtain the exhaust pressure value from the exhaust pressure sensor of the outdoor unit; The subcooling value is obtained by combining the corresponding outdoor heat exchanger liquid pipe side temperature value with the exhaust saturation temperature corresponding to the exhaust pressure value. When the capacity ratio of the indoor unit and the outdoor unit reaches the set ratio range, and there is a target outdoor unit whose exhaust pressure value reaches the preset pressure range and whose subcooling value reaches the preset subcooling range, the target outdoor unit is controlled to increase the opening of the second pressure relief valve and decrease the opening adjustment cycle. The adjustment amount and adjustment cycle of the second pressure relief valve opening are determined according to the preset pressure range and the preset subcooling range.

[0015] The above embodiments have the following advantages and effects: By acquiring the capacity ratio of the indoor and outdoor units of the refrigeration system, the exhaust pressure value of the exhaust pressure sensor, and the subcooling value of the outdoor heat exchanger, it is possible to determine whether the system is operating under low refrigeration load. Furthermore, when it is determined that the system is about to experience a liquid seal, the opening degree and adjustment cycle of the second pressure relief valve can be controlled to increase its opening degree and shorten the adjustment cycle for rapid pressure relief, thus preventing the system from experiencing high pressure.

[0016] If a target outdoor unit that meets the above conditions is detected among the operating outdoor units, it indicates that the system is operating under low-load cooling. The target outdoor unit has a high exhaust pressure and a high degree of subcooling, making it highly likely that a liquid seal will occur.

[0017] When a liquid seal is detected, the opening of the second pressure relief valve is increased and the adjustment cycle is shortened, which allows the refrigerant in the outdoor heat exchanger to be quickly transferred to the gas-liquid separator. This achieves a rapid decrease in the pressure on the outdoor heat exchanger side, a rapid reduction in the amount of refrigerant, and a rapid depressurization and pressure relief effect on the system, thus avoiding alarm shutdowns caused by liquid seals.

[0018] In some embodiments of this application, the preset pressure range includes multiple pressure sub-ranges; The preset subcooling range includes multiple subcooling sub-ranges, and each pressure sub-range corresponds to a subcooling sub-range. Each pressure sub-range and its corresponding subcooling sub-range correspond to the opening adjustment amount and opening adjustment cycle of a second pressure relief valve; When the detected exhaust pressure value and subcooling value simultaneously reach the corresponding pressure sub-range and subcooling sub-range, the control unit controls the second pressure relief valve to increase the opening degree and decrease the opening degree adjustment cycle. The higher the exhaust pressure and subcooling values, the greater the opening adjustment of the second pressure relief valve corresponding to the pressure sub-range and subcooling sub-range, and the shorter the adjustment cycle.

[0019] The above embodiments have the following advantages and effects: By setting the preset pressure range corresponding to the detected exhaust pressure value into multiple pressure sub-ranges, and setting the preset subcooling range corresponding to the subcooling value into multiple subcooling sub-ranges, the detected exhaust pressure value and subcooling value can be precisely defined to a certain pressure sub-range or subcooling sub-range.

[0020] During adjustment, the opening adjustment amount and adjustment cycle of the second pressure relief valve corresponding to the pressure sub-range and subcooling sub-range into which it falls can be controlled accordingly. This ensures that the opening adjustment amount and adjustment cycle of the second pressure relief valve match the exhaust pressure value and subcooling value, thereby guaranteeing pressure relief on the high-pressure side of the system and preventing liquid seal from occurring.

[0021] In some embodiments of this application, the multi-split air conditioning system includes: Intake temperature sensor, used to detect the intake temperature on the intake side of the compressor; The intake and exhaust pressure sensor detects the intake pressure on the compressor's intake side to obtain the intake pressure saturation temperature. The control unit is configured to increase the opening degree of the second pressure relief valve and shorten the opening degree adjustment cycle when the difference between the intake temperature and the intake pressure saturation temperature reaches the set temperature range.

[0022] The above embodiments have the following advantages and effects: The compressor suction superheat is obtained by the difference between the suction temperature and the suction saturation temperature. The compressor suction superheat needs to be kept within the set temperature range to prevent liquid return from the compressor. Therefore, before controlling the second pressure relief valve, it is necessary to ensure that the compressor suction superheat is within the set temperature range to prevent liquid return from the compressor.

[0023] In some embodiments of this application, the compressor is configured with a drive module for driving the compressor to operate; The control unit is configured to: The compressor's operating current and the preset current value in the drive module are obtained. When the difference between the preset current and the operating current reaches the preset current range, the opening degree of the second pressure relief valve is increased and the opening degree adjustment cycle is shortened.

[0024] The above embodiments have the following advantages and effects: When the system is running in cooling mode, the detection of the system liquid seal condition is combined with the detection of the compressor operating current. By combining the detected compressor operating current parameters with the detection of the discharge pressure sensor value, the subcooling value of the outdoor heat exchanger, and the ratio of the capacity of the indoor unit to the outdoor unit, a more accurate determination of the occurrence of liquid seal can be achieved.

[0025] In some embodiments of this application, a multi-split air conditioning system is proposed, comprising: Multiple indoor units are installed. At least one outdoor unit shall be installed and connected to the indoor unit via refrigerant piping. This includes a compressor, an outdoor heat exchanger, and a gas-liquid separator connected via refrigerant pipes; The exhaust pressure sensor detects the exhaust pressure value on the compressor's exhaust side; Liquid pipe temperature sensor detects the temperature on the liquid pipe side of the outdoor heat exchanger; The first pressure relief line is connected between the gas-liquid separator and the compressor exhaust side, and a first pressure relief valve is installed above it to control the opening and closing of the first pressure relief line; The second pressure relief pipeline is connected between the outdoor heat exchanger and the gas-liquid separator, and a second pressure relief valve is installed above it. The control unit is configured to: acquire the capacity ratio of the operating indoor unit to the operating outdoor unit during system cooling operation; Obtain the exhaust pressure value from the exhaust pressure sensor of the operating outdoor unit, and The subcooling value is obtained by combining the corresponding outdoor heat exchanger liquid pipe side temperature value with the exhaust saturation temperature corresponding to the exhaust pressure value. When it is determined that the ratio of the capacity of the indoor unit and the outdoor unit reaches the set ratio range, and there is a target outdoor unit whose exhaust pressure value reaches the preset pressure range and whose subcooling value reaches the preset subcooling range, the first pressure relief valve of the target outdoor unit is controlled to open or / and the opening degree of the second pressure relief valve is increased and the opening degree adjustment cycle is reduced. The conduction time of the first pressure relief valve, the opening adjustment amount of the second pressure relief valve, and the opening adjustment cycle are determined according to the preset pressure range and the preset subcooling range.

[0026] The above embodiments have the following advantages and effects: By detecting the system's operating mode, the ratio of the capacity of the indoor unit to the outdoor unit, the exhaust pressure value of the exhaust pressure sensor, and the liquid pipe temperature on the outdoor heat exchanger side, it is possible to detect whether the system is in a low-load cooling operation state and whether a liquid seal is about to occur. Furthermore, when a liquid seal is detected, the first pressure relief valve and / or the second pressure relief valve can be controlled accordingly to quickly depressurize the system and prevent the system from alarming and shutting down due to high pressure.

[0027] In some embodiments of this application, multiple outdoor units are provided and connected in parallel. Each outdoor unit is equipped with a control valve, and some of the outdoor units are in operation while others are in a stopped state. The control unit is configured to: when the system is cooling, acquire the capacity ratio of the indoor unit and the outdoor unit, acquire the exhaust pressure value of the exhaust pressure sensor of the outdoor unit, and acquire the liquid pipe side temperature value of the outdoor heat exchanger of the outdoor unit, and obtain the subcooling value by combining the exhaust saturation temperature corresponding to the exhaust pressure value. When the ratio of the capacity of the operating indoor unit to the operating outdoor unit reaches the set ratio range, and there is a target outdoor unit whose exhaust pressure value reaches the preset pressure range and whose subcooling value reaches the preset subcooling range, the control valve of one or more outdoor units in the shutdown state is opened to allow the refrigerant of the target outdoor unit to enter one or more outdoor units in the shutdown state.

[0028] The above embodiments have the following advantages and effects: By opening the control valve of the outdoor unit when it is stopped, the refrigerant in the outdoor heat exchanger of the outdoor unit with excessive pressure during operation can be transferred to the outdoor heat exchanger of the outdoor unit when it is stopped, thereby achieving the effect of refrigerant transfer in the high-pressure outdoor heat exchanger and reducing the system pressure.

[0029] Other features and advantages of the present invention will become clearer after reading the detailed embodiments of the invention in conjunction with the accompanying drawings. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 This is a schematic diagram of the structure of a single-module system according to an embodiment; Figure 2 This is a schematic diagram of the structure of a multi-module system according to an embodiment; Figure 3 This is a schematic diagram of the outdoor unit structure of a multi-split air conditioning system according to an embodiment; Figure 4 This is a schematic diagram of the control flow when the first pressure relief valve of the multi-split air conditioning system according to the embodiment is in the first control mode; Figure 5 This is a schematic diagram of the control flow when the first pressure relief valve of the multi-split air conditioning system according to the embodiment is in the second control mode; Figure 6 This is a schematic diagram of the control flow of the first pressure relief valve of the multi-split air conditioning system according to an embodiment, when it corresponds to two pressure sub-zones and a subcooling sub-zone. Figure 7 This is a schematic diagram of the control flow of the second pressure relief valve of the multi-split air conditioning system according to an embodiment when the system is operating under low cooling load. Figure 8 This is a schematic diagram of the control flow of the second pressure relief valve of the multi-split air conditioning system according to the embodiment, when it corresponds to two pressure sub-zones and a subcooling sub-zone. Figure 9 This is a schematic diagram of the control flow of the first and second pressure relief valves of the multi-split air conditioning system according to an embodiment when the system is operating at a low cooling load. Figure 10 This is a schematic diagram of the control process of the outdoor unit of a multi-split air conditioning system in the off state when it is running under low cooling load, according to an embodiment.

[0032] Figure label: 100, Outdoor unit; 110, Compressor; 120, Outdoor heat exchanger; 130, First pressure relief pipeline; 131, First pressure relief valve; 140, Second pressure relief pipeline; 141, Second pressure relief valve; 150, Control valve; 160, Gas-liquid separator; 170, Subcooler; 200, Indoor unit. Detailed Implementation

[0033] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0034] In the description of this application, it should be understood that the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0035] 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, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0036] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0037] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0038] The following disclosure provides many different embodiments or examples for implementing various structures of the invention. To simplify the disclosure, specific examples of components and arrangements are described below. These are merely examples and are not intended to limit the invention. Furthermore, reference numerals and / or letters may be repeated in different examples; such repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed. In addition, examples of various specific processes and materials are provided in this invention, but those skilled in the art will recognize the application of other processes and / or the use of other materials.

[0039] In some embodiments of this application, a multi-split air conditioning system is proposed, which consists of at least one outdoor unit 100 and multiple indoor units 200 connected together.

[0040] In some embodiments of this application, the multi-split air conditioning system comprises one outdoor unit 100 and multiple indoor units 200 connected together to form a single-module system, as described above. Figure 1 As shown, the number of indoor units 200 can be 8, less than 8, or more than 8.

[0041] In some embodiments of this application, reference is made to Figure 2 As shown, the multi-split air conditioning system consists of multiple outdoor units 100 and multiple indoor units 200 connected together, forming a multi-module system. There are four outdoor units 100, taking four as an example. The number of outdoor units 100 can be less than four or more than four. There are eight indoor units 200, taking eight as an example. The number of indoor units 200 can be less than eight or more than eight.

[0042] Reference Figure 3 As shown, each outdoor unit 100 includes at least a compressor 110, an outdoor heat exchanger 120, a gas-liquid separator 160, and a four-way valve connected via an outdoor refrigerant pipeline.

[0043] The indoor unit 200 includes an indoor heat exchanger.

[0044] An air conditioner executes a refrigeration cycle using a compressor 110, a condenser, an expansion valve, and an evaporator. The refrigeration cycle includes a series of processes involving compression, condensation, expansion, and evaporation to cool or heat an indoor space.

[0045] Low-temperature, low-pressure refrigerant enters compressor 110, which compresses it into a high-temperature, high-pressure refrigerant gas and discharges the compressed refrigerant gas. The discharged refrigerant gas flows into the condenser. The condenser condenses the compressed refrigerant into a liquid phase, and the heat is released to the surrounding environment through the condensation process.

[0046] The expansion valve expands the high-temperature, high-pressure liquid refrigerant that condenses in the condenser into a low-pressure liquid refrigerant. The evaporator evaporates the expanded refrigerant in the expansion valve and returns the low-temperature, low-pressure refrigerant gas to the compressor 110. The evaporator achieves a cooling effect by utilizing the latent heat of refrigerant evaporation to exchange heat with the material being cooled. Throughout the cycle, the air conditioner regulates the temperature of the indoor space.

[0047] The indoor heat exchanger and outdoor heat exchanger 120 are used as condensers or evaporators. When the indoor heat exchanger is used as a condenser, the air conditioner is used as a heater in heating mode; when the indoor heat exchanger is used as an evaporator, the air conditioner is used as a cooler in cooling mode.

[0048] In some embodiments of this application, the outdoor refrigerant pipeline includes a gas-side refrigerant pipeline and a liquid-side refrigerant pipeline. A gas-side shut-off valve and a liquid-side shut-off valve are respectively installed on the gas-side refrigerant pipeline and the liquid-side refrigerant pipeline to control the on / off of the gas-side refrigerant pipeline and the liquid-side refrigerant pipeline.

[0049] In some embodiments of this application, an exhaust pressure sensor is provided at the exhaust side of the compressor 110 of each outdoor unit 100. The exhaust pressure sensor can detect the exhaust pressure of the compressor 110 and thus determine the high-pressure side exhaust pressure value of the entire multi-split air conditioning system.

[0050] When the exhaust pressure sensor detects that the exhaust pressure of compressor 110 is too high, the high pressure needs to be released to ensure the stable operation of the multi-split air conditioning system.

[0051] A pressure switch is installed on the exhaust side of the compressor 110 of each outdoor unit 100 to automatically disconnect and protect the multi-split air conditioning system.

[0052] For example, for R410A refrigerant, the design pressure is 4.15 MPa. To prevent the high-pressure side pressure from exceeding the design pressure, a serial pressure switch is installed at the discharge port of each compressor 110. The disconnection value of the pressure switch will be less than 4.15 MPa, for example, set to 3.9 MPa. When this discharge pressure value is reached, the pressure switch will automatically disconnect.

[0053] A low-pressure sensor is installed on the return gas side of compressor 110 to detect the pressure on the return gas side of compressor 110 in order to determine the magnitude of the low-pressure side pressure of compressor 110.

[0054] In some embodiments of this application, a liquid pipe temperature sensor is provided at the liquid pipe of the outdoor heat exchanger 120 of each outdoor unit 100 to detect the temperature value on the liquid pipe side of the outdoor heat exchanger 120.

[0055] The subcooling value of the outdoor heat exchanger 120 can be obtained by detecting the liquid pipe side temperature value of the outdoor heat exchanger 120, which can then be used to determine whether the outdoor heat exchanger 120 is under high pressure, providing a basis for liquid seal detection of multi-split air conditioning systems.

[0056] In some embodiments of this application, the outdoor unit 100 includes a first pressure relief pipe 130 connected between the exhaust side of the compressor 110 and the gas-liquid separator 160.

[0057] The first pressure relief valve 131 is installed on the first pressure relief pipeline 130 and is used to control the opening and closing of the first pressure relief pipeline 130. The first pressure relief valve 131 is a bypass valve, which is mainly used to achieve the effect of high and low pressure bypass.

[0058] When the first pressure relief valve 131 is opened, the first pressure relief line 130 is connected, and the refrigerant can flow between the compressor 110 and the gas-liquid separator 160. When the first pressure relief valve 131 is closed, the first pressure relief line 130 is disconnected.

[0059] The control of the first pressure relief valve 131 includes a first control mode corresponding to the multi-split air conditioning system operating at low temperature and low load during cooling and a second control mode corresponding to the multi-split system operating normally.

[0060] When a multi-split air conditioning system is running, first check whether the system is in low-temperature, low-load operation mode or normal operation mode.

[0061] When the multi-split air conditioning system is detected to be operating at low temperature and low load, the first pressure relief valve 131 is controlled to enter the first control mode.

[0062] Reference Figure 4 As shown, the specific control method for low-temperature, low-load refrigeration operation includes the following steps: S101: During system cooling operation, obtain the capacity ratio of the operating indoor unit 200 and the operating outdoor unit 200; Obtain the exhaust pressure value from the exhaust pressure sensor of the outdoor unit 100. The temperature value of the liquid pipe side of the outdoor heat exchanger 120 of the outdoor unit 100 is used to obtain the subcooling value.

[0063] When the system is in low-load cooling operation mode, the ratio of the capacity of the indoor unit 200 to the outdoor unit 100 is relatively small. Therefore, during testing, the ratio of their capacities can be used to determine whether the multi-split air conditioning system is in low-load operation.

[0064] When the system is operating at a low load and refrigerant is continuously accumulating in the outdoor heat exchanger 120, the pressure on the outdoor heat exchanger 120 side will continuously increase, leading to high pressure on the discharge side of the compressor 110 connected to it. Therefore, by detecting the discharge side pressure of the compressor 110, it is possible to detect whether the pressure on the outdoor heat exchanger 120 side is too high and whether a large amount of refrigerant has been stored.

[0065] The liquid pipe side temperature of the outdoor heat exchanger 120 can be used to calculate the subcooling of the outdoor heat exchanger 120. When the subcooling of the outdoor heat exchanger 120 is high, it can also be inferred that the pressure of the outdoor heat exchanger 120 is too high.

[0066] By obtaining the above three conditions, it is possible to determine relatively accurately whether a multi-split air conditioning system is operating under low load.

[0067] S102: Determine whether the capacity ratio of the operating indoor unit 200 and the operating outdoor unit 100 reaches the set ratio range, and whether there is a target outdoor unit 100 among the operating outdoor units 100 whose exhaust pressure value reaches the preset pressure range and whose subcooling value reaches the preset subcooling range. The set ratio range is used to determine whether the ratio of the capacity of the indoor unit 200 to the outdoor unit 100 meets the conditions for low-load cooling operation.

[0068] The preset pressure range is used to determine whether the exhaust pressure of compressor 110 is too high. If the exhaust pressure value reaches the preset pressure range, it means that the exhaust pressure value is too high.

[0069] The preset subcooling range is used to determine whether the subcooling of the outdoor heat exchanger 120 is too large. If the preset subcooling range is reached, it means that the subcooling is too large.

[0070] A high degree of subcooling indicates that the outdoor unit's heat exchanger contains a large amount of refrigerant and has high internal pressure.

[0071] S103: When it is determined that the capacity ratio of the operating indoor unit 200 and the operating outdoor unit 100 reaches the set ratio range, and there is a target outdoor unit 100 in the operating outdoor unit 100 whose exhaust pressure value reaches the preset pressure range and whose subcooling value reaches the preset subcooling range, the first pressure relief valve 131 of the target outdoor unit 100 is controlled to open.

[0072] The opening time of the first pressure relief valve 131 is determined according to the preset pressure range and the preset subcooling range.

[0073] When a target outdoor unit 100 that meets the above conditions is detected among the operating outdoor units 100, it indicates that the system is operating under low-load cooling. The target outdoor unit 100 has a high exhaust pressure and a large subcooling value, and the probability of liquid sealing is very high. At this time, it is necessary to depressurize this part of the target outdoor units 100 to reduce the pressure on the outdoor heat exchanger 120 side and achieve the purpose of stabilizing the system.

[0074] If any of the above conditions are not met, it is impossible to determine whether a liquid seal should occur.

[0075] If only the exhaust pressure value is detected to be high, it may be that the system is not in a low-load operation mode, which may also lead to a situation where the pressure is high and needs to be released.

[0076] Alternatively, it may only detect that the capacity ratio of the outdoor unit 100 and the indoor unit 200 meets the conditions, but the subcooling and exhaust pressure values ​​do not reach the preset subcooling range, and the preset pressure range cannot determine whether liquid seal should occur.

[0077] By acquiring the system's operating mode, the capacity ratio of the indoor unit 200 and the outdoor unit 100, the discharge pressure value on the discharge side of the compressor 110, and the subcooling value of the outdoor heat exchanger 120, accurate detection of liquid seal occurrence is achieved. It can quickly detect the occurrence of liquid seal when the system is running under low load cooling, and can promptly control the first pressure relief valve 131 to operate when liquid seal is detected to be about to occur, thus avoiding the problem of system shutdown alarm caused by liquid seal.

[0078] When a liquid seal is detected, the first pressure relief valve 131 is kept on for a set time, so that the refrigerant in the compressor 110 can be continuously transferred to the gas-liquid separator 160 for a period of time, so as to achieve the effect of rapid pressure reduction on the outdoor heat exchanger 120 side and rapid pressure reduction of the system.

[0079] Meanwhile, by setting the opening time of the first pressure relief valve 131 according to the preset pressure range and the preset subcooling range, the control unit can adjust and control the opening time of the first pressure relief valve 131 in an appropriate manner according to the preset pressure range and the preset subcooling range when controlling the opening time of the first pressure relief valve 131.

[0080] If the multi-split air conditioning system is detected to not meet the conditions described in step S103 above, namely, "the ratio of the capacity of the operating indoor unit 200 and the operating outdoor unit 100 reaches the set ratio range, and there is a target outdoor unit 100 in the operating outdoor unit 100 whose exhaust pressure value reaches the preset pressure range and whose subcooling value reaches the preset subcooling range", then the first pressure relief valve 131 can be controlled to enter the second control mode corresponding to the normal operation of the multi-split air conditioning system.

[0081] Reference Figure 5 As shown, the control method for a multi-split air conditioning system in normal operating mode includes the following steps: S201: Obtain the value from the exhaust pressure sensor; S202: Has the exhaust pressure sensor reached the first pressure value? The first pressure value is greater than the upper limit of the preset pressure range. The first pressure value is the set pressure relief value. If the first pressure value is greater than the upper limit of the preset pressure range, it means that the system pressure is very high and is not within the preset pressure range corresponding to low temperature and low load. At this time, the first pressure relief valve 131 can be controlled according to the second control mode.

[0082] S203: When the exhaust pressure sensor reaches the first pressure value, control the first pressure relief valve 131 to open, and relieve the high pressure by controlling the first pressure relief valve 131 to open; When the system pressure is high, the first pressure relief valve 131 can be opened to bypass and relieve high and low pressure.

[0083] S204: Has the exhaust pressure sensor reached the second pressure value? S205: When the exhaust pressure sensor detects that the pressure value is less than the second pressure value but greater than the upper limit of the preset pressure range, control the first pressure relief valve 131 to close.

[0084] When the exhaust pressure is less than the second pressure, it means that the system pressure has been unloaded and the system can operate stably. At this time, the first pressure relief valve 131 can be closed.

[0085] The first pressure value is set to a+0.5, and the second pressure value is a+0.3.

[0086] That is, when pa > a + 0.5, the pressure is released; when pa < a + 0.3, the first pressure relief valve 131 is closed.

[0087] When the multi-split air conditioning system controls the first pressure relief valve 131, if the value of the exhaust pressure sensor is simultaneously satisfied with the pressure conditions for low-temperature cooling low-load operation and normal operation, the second control mode corresponding to low-temperature cooling low-load will be executed first.

[0088] In some embodiments of this application, the preset pressure range includes multiple non-overlapping pressure sub-ranges, and the lower and upper limits of the multiple pressure sub-ranges increase sequentially.

[0089] The preset subcooling range includes multiple subcooling sub-ranges, the lower limits of the multiple subcooling sub-ranges increase incrementally, and the multiple pressure sub-ranges and the multiple subcooling sub-ranges have a one-to-one correspondence.

[0090] The first pressure relief valve 131 has multiple conduction time periods of different durations.

[0091] A set of pressure sub-intervals and supercooling sub-intervals correspond to a conduction time period.

[0092] The detected exhaust pressure and subcooling values ​​may fall into different pressure sub-ranges and subcooling sub-ranges. When the pressure sub-range and subcooling sub-range do not correspond to each other, the first pressure relief valve 131 is not controlled to open.

[0093] The first pressure relief valve 131 is controlled to open for a set time only when the detected exhaust pressure value and subcooling value fall into the corresponding pressure sub-range and subcooling sub-range at the same time.

[0094] The duration of the first pressure relief valve 131's conduction time is related to the pressure sub-range and subcooling sub-range into which the exhaust pressure value and subcooling value fall.

[0095] The larger the upper and lower limits of the pressure sub-range, the larger the lower limit of the subcooling sub-range, and the longer the conduction time of the first pressure relief valve 131.

[0096] By setting the preset pressure range corresponding to the detected exhaust pressure value into multiple pressure sub-ranges, and setting the preset subcooling range corresponding to the subcooling value into multiple subcooling sub-ranges, the detected exhaust pressure value and subcooling value can be precisely defined to a certain pressure sub-range or subcooling sub-range.

[0097] During adjustment, the first pressure relief valve 131 can be controlled according to the conduction time of the pressure sub-range and subcooling sub-range into which it falls, so that the conduction time of the first pressure relief valve 131 matches the magnitude of the exhaust pressure value and the subcooling value, ensuring that the high-pressure side of the system is quickly depressurized without causing the system pressure to be too low, thus preventing the occurrence of liquid seal.

[0098] In some embodiments of this application, two pressure sub-intervals are provided, namely a first pressure sub-interval and a second pressure sub-interval, and two subcooling sub-intervals are provided, namely a first subcooling sub-interval and a second subcooling sub-interval.

[0099] The exhaust pressure is set to Pa, and the first pressure sub-interval is: a ≤ Pa ≤ a + 0.2; The second pressure sub-interval is: a+0.2≤Pa≤a+0.5; The subcooling value is Tc-Te, where Tc represents the saturation temperature corresponding to the exhaust side pressure, and Te represents the liquid pipe side temperature of the outdoor heat exchanger 120. The exhaust side pressure is obtained through the exhaust pressure sensor, and its corresponding saturation temperature can be directly obtained by querying.

[0100] The first sub-interval of supercooling is: Tc-Te≥b; The second supercooling subinterval is: Tc-Te≥b+2.

[0101] Assume that the ratio of the indoor unit capacity of 200 to the outdoor unit capacity of 100 satisfies ≤ e, where e is 30%. This condition is only satisfied when the system is operating under low load.

[0102] Reference Figure 6 As shown, the specific steps of the control method for the corresponding two pressure sub-intervals and subcooling sub-intervals of the system are as follows: S301: When the system is in cooling operation, acquire the exhaust pressure value of the exhaust pressure sensor of the outdoor unit 100, the subcooling value of the outdoor heat exchanger 120, and the capacity ratio of the indoor unit 200 and the outdoor unit 100. S302: Determine whether the detected exhaust pressure and subcooling values ​​are within the first pressure sub-range and the first subcooling sub-range, and whether the capacity ratio of the operating indoor unit 200 and the operating outdoor unit 100 is less than e: S303: When the pressure and subcooling are detected to meet the conditions that the pressure is in the first pressure sub-range and the subcooling is in the first subcooling sub-range, and the capacity ratio of the operating indoor unit 200 and the operating outdoor unit 100 is less than e, the first pressure relief valve 131 is controlled to open for t1 seconds.

[0103] S304: When the pressure and subcooling are not detected to be in the first pressure sub-range and the first subcooling sub-range, whether the pressure and subcooling satisfy the conditions that the pressure is in the second pressure sub-range and the subcooling is in the second subcooling sub-range, and whether the capacity ratio of the indoor unit 200 and the outdoor unit 100 is less than e. S305: When the pressure and subcooling are detected to be in the second pressure sub-range and the second subcooling sub-range, and the capacity ratio of the operating indoor unit 200 and the operating outdoor unit 100 is less than e, control the first pressure relief valve 131 to open for t1+10 seconds.

[0104] In some embodiments of this application, the multi-split air conditioning system further includes an intake temperature sensor for detecting the intake temperature of the compressor.

[0105] The suction pressure sensor detects the suction side pressure of the compressor to obtain the saturation temperature of the suction pressure.

[0106] The control unit is configured to control the first pressure relief valve 131 to open for a set time when the difference between the intake temperature and the intake pressure corresponding to the intake saturation temperature reaches the set temperature range. The length of the set time is determined according to the preset pressure range and the preset subcooling range.

[0107] The compressor suction superheat is obtained by the difference between the suction temperature and the suction saturation temperature. The compressor suction superheat needs to be kept within the set temperature range to prevent liquid return from the compressor. Therefore, before the first pressure relief valve is opened, the compressor suction superheat needs to be kept within the set temperature range to ensure that the compressor does not return liquid.

[0108] When the superheat of the intake gas is detected to reach the set temperature range, it indicates that the compressor will not return liquid. At this time, the first pressure relief valve 131 can be controlled to open for a set time to relieve pressure.

[0109] In some embodiments of this application, the compressor is configured with a drive module for driving the compressor to operate; The control unit is configured to: The compressor operating current is obtained, and when the difference between the preset current and the operating current reaches the preset current range, the first pressure relief valve 131 is controlled to be turned on for a period of time.

[0110] When too much refrigerant is stored in the outdoor heat exchanger 120, the system pressure will increase, the system high pressure will gradually rise, and the system load will gradually increase. After a certain period of time, the system load will be large enough that the instantaneous value of the compressor's operating current will exceed the preset current, i.e., the maximum current value, in the compressor's drive module, and an alarm will occur and the compressor will shut down.

[0111] When the compressor operating current value is detected to be continuously increasing and the difference between the preset current and the preset current reaches the set preset current range, the pressure can be released by the first pressure relief valve 131 for a set time to avoid liquid seal.

[0112] Let the compressor's operating current be Iinv, and the preset current be Imax. Then the operating current and the preset current satisfy: Imax-Iinv≤d.

[0113] During system cooling operation, the system simultaneously detects the exhaust pressure value of the exhaust pressure sensor, the subcooling value of the outdoor heat exchanger 120, the capacity ratio of the indoor unit 200 and the outdoor unit 100, and the operating current value of the compressor. By using these four parameters, the liquid seal is detected and determined, making the determination of the liquid seal more accurate and precise.

[0114] In some embodiments of this application, a multi-split air conditioning system is proposed, comprising: At least one outdoor unit 100 is provided, which includes at least a compressor 110 and an outdoor heat exchanger 120. Each outdoor unit 100 is equipped with an exhaust pressure sensor for detecting the exhaust pressure of the compressor 110 and a liquid pipe temperature sensor for detecting the liquid pipe temperature of the outdoor heat exchanger 120.

[0115] Multiple indoor units 200 are provided and connected to the outdoor unit 100. The outdoor unit includes: a second pressure relief pipe 140, which is connected between the outdoor heat exchanger 120 and the gas-liquid separator 160; The second pressure relief valve 141 is connected to the second pressure relief pipeline 140.

[0116] The second pressure relief valve 141 is an electronic expansion valve, which is connected to the second pressure relief line 140. It is used to increase the subcooling of the refrigerant. When a liquid seal is detected in the system, it can also be used to quickly relieve pressure by adjusting its opening.

[0117] In some embodiments of this application, a subcooler 170 is provided on the liquid-side refrigerant pipeline of the outdoor heat exchanger 120. The subcooler 170 is connected to the second pressure relief pipeline 140. The refrigerant flowing from the outdoor heat exchanger 120 into the second pressure relief pipeline 140 first flows through the subcooler 170 for subcooling before entering the second pressure relief valve 141 and the gas-liquid separator 160, thereby achieving subcooling of the refrigerant flowing out of the outdoor heat exchanger 120.

[0118] When the multi-split air conditioning system is in normal operation, the second pressure relief valve 141 is mainly used to control the exhaust superheat of the outdoor heat exchanger 120. The exhaust superheat is kept within a suitable superheat range by adjusting the opening size of the valve.

[0119] The second pressure relief valve 141 can also be used to relieve pressure in multi-split air conditioning systems operating at low temperature and low load.

[0120] Reference Figure 7 As shown, the specific control method for low-temperature, low-load cooling operation of a multi-split air conditioning system with a second pressure relief valve 141 includes the following steps: S401: When the system is cooling, obtain the capacity ratio of the operating indoor unit 200 and the operating outdoor unit 100; Obtain the exhaust pressure value from the exhaust pressure sensor of the outdoor unit 100. The temperature value of the liquid pipe side of the outdoor heat exchanger 120 of the outdoor unit 100 is used to obtain the subcooling value.

[0121] By obtaining the above three conditions, it is possible to determine whether a multi-split air conditioning system is operating under low load.

[0122] S402: Determine whether the capacity ratio of the operating outdoor unit 100 to the indoor unit reaches the set ratio range, and whether there is a target outdoor unit 100 whose exhaust pressure value reaches the preset pressure range and whose subcooling value reaches the preset subcooling range. S403: When it is determined that the capacity ratio of the operating indoor unit 200 and the operating outdoor unit 100 reaches the set ratio range, and there is a target outdoor unit 100 in the operating outdoor unit 100 whose exhaust pressure value reaches the preset pressure range and whose subcooling value reaches the preset subcooling range, the target outdoor unit 100 is controlled to increase the opening of the second pressure relief valve 141 and decrease the opening adjustment cycle.

[0123] The adjustment amount and adjustment cycle of the second pressure relief valve 141 are determined according to the preset pressure range and the preset subcooling range.

[0124] When a target outdoor unit 100 that meets the above conditions is detected among the operating outdoor units 100, it indicates that the system is in low-load cooling operation. The target outdoor unit 100 has a large exhaust pressure value and a large subcooling value, and the probability of liquid sealing is very high.

[0125] When a liquid seal is detected, the opening of the second pressure relief valve 141 is increased and the adjustment cycle is shortened, which allows the refrigerant in the outdoor heat exchanger 120 to be quickly transferred to the gas-liquid separator 160. This achieves a rapid decrease in the pressure on the outdoor heat exchanger 120 side, a rapid reduction in the amount of refrigerant, and a rapid depressurization and pressure relief effect on the system, thus avoiding alarm shutdown caused by the liquid seal.

[0126] Meanwhile, by setting the opening adjustment amount and adjustment cycle of the second pressure relief valve 141 to be determined according to the preset pressure range and the preset subcooling range, the control unit can adaptively adjust the increase in opening amount and the adjustment cycle of opening according to different preset pressure ranges and preset subcooling ranges when adjusting the second pressure relief valve 141.

[0127] In some embodiments of this application, the preset pressure range includes multiple non-overlapping pressure sub-ranges, and the lower and upper limits of the multiple pressure sub-ranges increase sequentially.

[0128] The preset subcooling range includes multiple subcooling sub-ranges, and the lower limits of the multiple subcooling sub-ranges increase progressively. Each pressure sub-range corresponds to a subcooling sub-range.

[0129] The second pressure relief valve 141 has multiple opening adjustment ranges and opening adjustment cycles.

[0130] A set of pressure sub-intervals and subcooling sub-intervals correspond to an opening adjustment amount and an opening adjustment cycle.

[0131] The detected exhaust pressure and subcooling values ​​may fall into different pressure sub-ranges and subcooling sub-ranges. When the pressure sub-ranges and subcooling sub-ranges do not correspond to each other, the second pressure relief valve 141 is not controlled.

[0132] The second pressure relief valve 141 is only controlled to increase its opening degree when the detected exhaust pressure value and subcooling value fall into the corresponding pressure sub-range and subcooling sub-range at the same time.

[0133] The opening adjustment amount of the second pressure relief valve 141 and the length of the regulating cycle are related to the pressure sub-range and sub-range into which the exhaust pressure value and subcooling value fall.

[0134] The larger the upper and lower limits of the pressure sub-range, the larger the lower limit of the subcooling sub-range, the larger the opening adjustment of the second pressure relief valve 141 and the shorter the regulating cycle.

[0135] By setting the preset pressure range corresponding to the detected exhaust pressure value into multiple pressure sub-ranges, and setting the preset subcooling range corresponding to the subcooling value into multiple subcooling sub-ranges, the detected exhaust pressure value and subcooling value can be precisely defined to a certain pressure sub-range or subcooling sub-range.

[0136] During adjustment, the opening adjustment amount and opening adjustment cycle of the second pressure relief valve 141 corresponding to the pressure sub-range and subcooling sub-range into which it falls can be controlled accordingly, so that the opening adjustment amount and adjustment cycle of the second pressure relief valve 141 match the exhaust pressure value and subcooling value, ensuring pressure relief on the high-pressure side of the system and preventing liquid seal from occurring.

[0137] In some embodiments of this application, two pressure sub-intervals are provided, namely a first pressure sub-interval and a second pressure sub-interval, and two subcooling sub-intervals are provided, namely a first subcooling sub-interval and a second subcooling sub-interval.

[0138] The exhaust pressure is set to Pa, and the first pressure sub-interval is: a ≤ Pa ≤ a + 0.2; The second pressure sub-interval is: a+0.2≤Pa≤a+0.3; The subcooling value is Tc-Te, where Tc represents the saturation temperature corresponding to the exhaust side pressure, and Te represents the liquid pipe side temperature of the outdoor heat exchanger 120. The exhaust side pressure is obtained through the exhaust pressure sensor, and its corresponding saturation temperature can be directly obtained by querying.

[0139] The first sub-interval of supercooling is: Tc-Te≥b; The second supercooling subinterval is: Tc-Te≥b+2.

[0140] Assume that the indoor unit's operating capacity of 200 and the outdoor unit's capacity of 100 satisfy ≤e, where e is 30%. This condition is only satisfied when the system is operating under low load.

[0141] Reference Figure 8 As shown, the specific steps of the control method for the corresponding two pressure sub-intervals and two subcooling sub-intervals of the system are as follows: S501: When the system is in cooling operation, acquire the exhaust pressure value of the exhaust pressure sensor of the outdoor unit 100, the subcooling value of the outdoor heat exchanger 120, and the capacity ratio of the indoor unit 200 and the outdoor unit 100. S502: Are the detected exhaust pressure and subcooling values ​​within the first pressure sub-range and the first subcooling sub-range, and is the capacity ratio of the operating indoor unit 200 to the operating outdoor unit 100 less than e? S503: When the pressure and subcooling are detected to meet the conditions that the pressure is in the first pressure sub-range and the subcooling is in the first subcooling sub-range, and the capacity ratio of the operating indoor unit 200 and the operating outdoor unit 100 is less than e, the second pressure relief valve 141 is controlled to increase the first opening adjustment amount, with an adjustment cycle of 15s.

[0142] S504: If the detected exhaust pressure value and subcooling value are not in the first pressure sub-range and the first subcooling sub-range, whether the detected pressure and subcooling are in the second pressure sub-range and the second subcooling sub-range, and whether the capacity ratio of the indoor unit 200 and the outdoor unit 100 is less than e. S505: The detected exhaust pressure value and subcooling value are in the second pressure sub-range and the second subcooling sub-range, so the second pressure relief valve 141 is controlled to increase the second opening adjustment amount, with an adjustment cycle of 10s, wherein the second opening adjustment amount is greater than the first opening adjustment amount.

[0143] In some embodiments of this application, the multi-split air conditioning system includes a suction temperature sensor for detecting the suction temperature of the compressor.

[0144] The suction pressure sensor detects the suction side pressure of the compressor to obtain the saturation temperature of the suction pressure.

[0145] The control unit is configured to increase the opening degree of the second pressure relief valve 141 and shorten the opening degree adjustment cycle when the difference between the intake temperature and the intake pressure saturation temperature reaches the set temperature range.

[0146] The compressor suction superheat is obtained by the difference between the suction temperature and the suction saturation temperature. The compressor suction superheat needs to be kept within the set temperature range to prevent liquid return from the compressor. Therefore, before controlling the second pressure relief valve, it is necessary to ensure that the compressor suction superheat is within the set temperature range to prevent liquid return from the compressor.

[0147] When the superheat of the intake gas is detected to reach the set temperature range, the opening of the second pressure relief valve 141 can be increased and the adjustment cycle shortened to relieve pressure, ensuring that the compressor does not return liquid.

[0148] In some embodiments of this application, the compressor is configured with a drive module for driving the compressor to operate; The control unit is configured to: The compressor's operating current and the preset current value in the drive module are obtained. When the difference between the preset current and the operating current reaches the preset current range, the opening degree of the second pressure relief valve is increased and the opening degree adjustment cycle is shortened.

[0149] When too much refrigerant is stored in the outdoor heat exchanger 120, the system pressure will increase, the system high pressure will gradually rise, and the system load will gradually increase. After a certain period of time, the system load will be large enough that the instantaneous value of the compressor operating current will exceed the preset current that can be carried in the compressor drive module, i.e., the maximum current value, and an alarm shutdown will occur.

[0150] When the compressor operating current value is detected to be continuously increasing and the difference between the preset current and the preset current reaches the set preset current range, it indicates that liquid seal is about to occur. By controlling the opening of the second pressure relief valve 141 to increase and shorten the opening adjustment cycle, pressure can be quickly released to avoid liquid seal.

[0151] Let the compressor operating current be Iinv, and the preset current be Imax. Then the operating current and the preset current satisfy: Imax-Iinv≤d.

[0152] During system cooling operation, the system simultaneously detects the exhaust pressure value of the exhaust pressure sensor, the subcooling value of the outdoor heat exchanger 120, the capacity ratio of the operating indoor unit 200 and the operating outdoor unit 100, and the system operating current value. By using these four parameters, the system can detect and determine the occurrence of liquid seal, making the determination of liquid seal more accurate and precise.

[0153] In some embodiments of this application, a multi-split air conditioning system is proposed, comprising: At least one outdoor unit 100 is provided, which includes a compressor 110 and an outdoor heat exchanger 120. The outdoor unit 100 is equipped with an exhaust pressure sensor for detecting the exhaust pressure of the compressor 110 and a liquid pipe temperature sensor for detecting the liquid pipe temperature of the outdoor heat exchanger 120.

[0154] Multiple indoor units 200 are provided and connected to the outdoor unit 100. The first pressure relief line 130 is connected between the exhaust side of the compressor 110 and the gas-liquid separator 160, and a first pressure relief valve 131 for controlling the opening and closing of the first pressure relief line 130 is provided above it. The second pressure relief pipeline 140 is connected between the outdoor heat exchanger 120 and the gas-liquid separator 160, and a second pressure relief valve 141 is installed above it.

[0155] Among them, the first pressure relief valve 131 is a bypass valve, and the second pressure relief valve 141 is an electronic expansion valve.

[0156] The first pressure relief line 130 and the second pressure relief line 140 can be used together to achieve rapid pressure relief of the system.

[0157] Reference Figure 9As shown, the specific control method for low-temperature, low-load cooling operation of a multi-split air conditioning system with a first pressure relief valve 131 and a second pressure relief valve 141 includes the following steps: S601: Obtain the capacity ratio of the operating outdoor unit 100 and the operating indoor unit 200; Obtain the exhaust pressure value from the exhaust pressure sensor of the operating outdoor unit 100, and And the corresponding outdoor heat exchanger 120 liquid pipe side temperature value, combined with the exhaust saturation temperature corresponding to the above exhaust pressure value, to obtain the subcooling value. By obtaining the above three conditions, it is possible to determine whether a multi-split air conditioning system is operating under low load.

[0158] S602: During system cooling operation, determine whether the capacity ratio of the operating indoor unit 200 and the operating outdoor unit 100 reaches the set ratio range, and whether there is a target outdoor unit 100 among the operating outdoor units 100 whose exhaust pressure value reaches the preset pressure range and whose subcooling value reaches the preset subcooling range. S603: When it is determined that the capacity ratio of the operating indoor unit 200 and the operating outdoor unit 100 reaches the set ratio range, and there is a target outdoor unit 100 in the operating outdoor unit 100 whose exhaust pressure value reaches the preset pressure range and whose subcooling value reaches the preset subcooling range, the first pressure relief valve 131 of the target outdoor unit 100 is controlled to open or / and the opening degree of the second pressure relief valve 141 is controlled to increase and the opening degree adjustment cycle is reduced.

[0159] The conduction time of the first pressure relief valve 131, the opening adjustment amount of the second pressure relief valve 141, and the opening adjustment cycle are determined according to the preset pressure range and the preset subcooling range.

[0160] When a target outdoor unit 100 that meets the above conditions is detected among the operating outdoor units 100, it indicates that the system is in low-load cooling operation. The target outdoor unit 100 has a large exhaust pressure value and a large subcooling value, and the probability of liquid sealing is very high.

[0161] When a liquid seal is detected to be about to occur, the control unit can selectively control the first pressure relief valve 131 to perform the set opening time according to the exhaust pressure value and the subcooling value, so as to quickly relieve pressure through the first pressure relief valve 131.

[0162] Alternatively, the second pressure relief valve 141 can be controlled to increase its opening degree and decrease its opening degree adjustment cycle, thereby rapidly relieving pressure through the second pressure relief valve 141.

[0163] Alternatively, the first pressure relief valve 131 can be turned on for a set time, the opening of the second pressure relief valve 141 can be increased, and the opening adjustment cycle can be reduced. The effect of rapid pressure relief can be achieved by cooperating the first pressure relief valve 131 and the second pressure relief valve 141.

[0164] In some embodiments of this application, multiple outdoor units 100 are provided and connected in parallel. Each outdoor unit 100 is equipped with a control valve 150, which is an electronic expansion valve connected to the outdoor heat exchanger 120 side.

[0165] For multi-module systems, there are multiple outdoor units 100. During operation, some outdoor units 100 may be running while others are in a shutdown state.

[0166] When the outdoor unit 100 is in the off state, the control valve 150 is closed, and the refrigerant will not enter the outdoor heat exchanger 120 of the outdoor unit 100 in the off state.

[0167] Reference Figure 10 As shown, the pressure relief for multi-module systems also includes the following control methods: S701: When the system is running in cooling mode, obtain the capacity ratio of the indoor unit 200 and the outdoor unit 100, obtain the exhaust pressure value of the exhaust pressure sensor of the outdoor unit 100, and obtain the liquid pipe side temperature value of the outdoor heat exchanger 120 of the outdoor unit 100. S702: Determine whether the capacity ratio of the operating indoor unit 200 and the operating outdoor unit 100 reaches the set ratio range, and whether there is a target outdoor unit 100 among the operating outdoor units 100 whose exhaust pressure value reaches the preset pressure range and whose subcooling value reaches the preset subcooling range. S703: When it is determined that the capacity ratio of the operating indoor unit 200 and the operating outdoor unit 100 reaches the set ratio range, and there is a target outdoor unit 100 among the operating outdoor units 100 whose exhaust pressure value reaches the preset pressure range and whose subcooling value reaches the preset subcooling range, the control valve 150 of one or more outdoor units 100 in the shutdown state is opened so that the refrigerant of the target outdoor unit 100 enters into one or more outdoor units 100 in the shutdown state.

[0168] By opening the control valve 150 of the outdoor unit 100 in the shutdown state, the refrigerant in the outdoor heat exchanger 120 of the outdoor unit 100 with excessive pressure during operation can be transferred to the outdoor heat exchanger 120 of the shutdown outdoor unit 100, thereby achieving the effect of refrigerant transfer in the high-pressure outdoor heat exchanger 120 and system pressure reduction.

[0169] In the description of the above embodiments, specific features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments or examples.

[0170] The above are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A multi-split air conditioning system, characterized in that, Including: Multiple indoor units are installed. At least one outdoor unit shall be installed and connected to the indoor unit via refrigerant piping. This includes a compressor, an outdoor heat exchanger, and a gas-liquid separator connected via refrigerant pipes; The exhaust pressure sensor detects the exhaust pressure value on the compressor's exhaust side; Liquid pipe temperature sensor detects the temperature on the liquid pipe side of the outdoor heat exchanger; The first pressure relief line is connected between the compressor discharge side and the gas-liquid separator; The first pressure relief valve is connected to the first pressure relief pipeline and is used to control the opening and closing of the first pressure relief pipeline; The control unit is configured to: acquire the capacity ratio of the operating indoor unit to the operating outdoor unit when the system is cooling; Obtain the exhaust pressure value from the exhaust pressure sensor of the outdoor unit; The subcooling value is obtained by combining the corresponding outdoor heat exchanger liquid pipe side temperature value with the exhaust saturation temperature corresponding to the exhaust pressure value. When the capacity ratio of the operating indoor unit to the operating outdoor unit reaches a set ratio range, and there is a target outdoor unit whose exhaust pressure value reaches a preset pressure range and whose subcooling value reaches a preset subcooling range, the first pressure relief valve of the target outdoor unit is controlled to open. The opening time of the first pressure relief valve is determined based on the preset pressure range and the preset subcooling range.

2. The multi-split air conditioning system according to claim 1, characterized in that, The preset pressure range includes multiple pressure sub-ranges; The preset subcooling range includes multiple subcooling sub-ranges, and each subcooling sub-range corresponds to a pressure sub-range; Each pressure sub-interval and its corresponding subcooling sub-interval correspond to a first pressure relief valve opening time; When the detected exhaust pressure value and subcooling value simultaneously reach the corresponding pressure sub-range and subcooling sub-range, the control unit controls the first pressure relief valve to be turned on for a period of time. The higher the exhaust pressure and subcooling values, the longer the conduction time of the first pressure relief valve corresponding to the pressure sub-range and subcooling sub-range.

3. The multi-split air conditioning system according to claim 1, characterized in that, Includes: a suction temperature sensor, used to detect the suction temperature on the suction side of the compressor; The suction pressure sensor detects the suction pressure on the suction side of the compressor to obtain the suction pressure saturation temperature; The control unit is configured to: control the first pressure relief valve to open when it is determined that the difference between the intake temperature and the intake pressure saturation temperature reaches the set temperature range; The opening time of the first pressure relief valve is determined based on the preset pressure range and the preset subcooling range.

4. The multi-split air conditioning system according to claim 1, characterized in that, The compressor is equipped with a drive module for driving the compressor to operate; The control unit is configured to: The compressor's operating current and the preset current value in the drive module are obtained. When the difference between the preset current and the operating current reaches the preset current range, the first pressure relief valve is controlled to open. The opening time of the first pressure relief valve is determined based on the preset pressure range and the preset subcooling range.

5. A multi-split air conditioning system, characterized in that, Including: Multiple indoor units are installed. At least one outdoor unit is installed, which is connected to multiple indoor units via piping. This includes: a compressor, an outdoor heat exchanger, and a gas-liquid separator connected via refrigerant pipes; The exhaust pressure sensor detects the exhaust pressure value on the compressor's exhaust side. Liquid pipe temperature sensor detects the temperature on the liquid pipe side of the outdoor heat exchanger; The second pressure relief pipeline is connected between the outdoor heat exchanger and the gas-liquid separator. When it is turned on, it transfers the excess refrigerant from the outdoor heat exchanger to the gas-liquid separator to relieve pressure. The second pressure relief valve is connected to the second pressure relief pipeline; The control unit is configured to: acquire the capacity ratio of the operating indoor unit to the operating outdoor unit when the system is cooling; Obtain the exhaust pressure value from the exhaust pressure sensor of the outdoor unit; The subcooling value is obtained by combining the corresponding outdoor heat exchanger liquid pipe side temperature value with the exhaust saturation temperature corresponding to the exhaust pressure value. When the capacity ratio of the indoor unit and the outdoor unit reaches the set ratio range, and there is a target outdoor unit whose exhaust pressure value reaches the preset pressure range and whose subcooling value reaches the preset subcooling range, the target outdoor unit is controlled to increase the opening of the second pressure relief valve and decrease the opening adjustment cycle. The adjustment amount and adjustment cycle of the second pressure relief valve opening are determined according to the preset pressure range and the preset subcooling range.

6. The multi-split air conditioning system according to claim 1, characterized in that, The preset pressure range includes multiple pressure sub-ranges; The preset subcooling range includes multiple subcooling sub-ranges, and each subcooling sub-range corresponds to a pressure sub-range; Each pressure sub-range and its corresponding subcooling sub-range correspond to the opening adjustment amount and opening adjustment cycle of a second pressure relief valve; When the detected exhaust pressure value and subcooling value simultaneously reach the corresponding pressure sub-range and subcooling sub-range, the control unit controls the second pressure relief valve to increase the opening degree and decrease the opening degree adjustment cycle. The higher the exhaust pressure and subcooling values, the greater the opening adjustment of the second pressure relief valve corresponding to the pressure sub-range and subcooling sub-range, and the shorter the adjustment cycle.

7. The multi-split air conditioning system according to claim 1, characterized in that, It also includes: a suction temperature sensor, used to detect the suction temperature on the suction side of the compressor; The intake and exhaust pressure sensor detects the intake pressure on the compressor's intake side to obtain the intake pressure saturation temperature. The control unit is configured to increase the opening degree of the second pressure relief valve and shorten the opening degree adjustment cycle when the difference between the intake temperature and the intake pressure saturation temperature reaches the set temperature range.

8. The multi-split air conditioning system according to claim 1, characterized in that, The compressor is equipped with a drive module for driving the compressor to operate; The control unit is configured to: The compressor's operating current and the preset current value in the drive module are obtained. When the difference between the preset current and the operating current reaches the preset current range, the opening degree of the second pressure relief valve is increased and the opening degree adjustment cycle is shortened.

9. A multi-split air conditioning system, characterized in that, Including: Multiple indoor units are installed. At least one outdoor unit shall be installed and connected to the indoor unit via refrigerant piping. This includes a compressor, an outdoor heat exchanger, and a gas-liquid separator connected via refrigerant pipes; The exhaust pressure sensor detects the exhaust pressure value on the compressor's exhaust side; Liquid pipe temperature sensor detects the temperature on the liquid pipe side of the outdoor heat exchanger; The first pressure relief line is connected between the gas-liquid separator and the compressor exhaust side, and a first pressure relief valve is installed above it to control the opening and closing of the first pressure relief line; The second pressure relief pipeline is connected between the outdoor heat exchanger and the gas-liquid separator, and a second pressure relief valve is installed above it. The control unit is configured to: acquire the capacity ratio of the operating indoor unit to the operating outdoor unit during system cooling operation; Obtain the exhaust pressure value from the exhaust pressure sensor of the operating outdoor unit, and The subcooling value is obtained by combining the corresponding outdoor heat exchanger liquid pipe side temperature value with the exhaust saturation temperature corresponding to the exhaust pressure value. When it is determined that the ratio of the capacity of the indoor unit and the outdoor unit reaches the set ratio range, and there is a target outdoor unit whose exhaust pressure value reaches the preset pressure range and whose subcooling value reaches the preset subcooling range, the first pressure relief valve of the target outdoor unit is controlled to open or / and the opening degree of the second pressure relief valve is increased and the opening degree adjustment cycle is reduced. The conduction time of the first pressure relief valve, the opening adjustment amount of the second pressure relief valve, and the opening adjustment cycle are determined according to the preset pressure range and the preset subcooling range.

10. The multi-split air conditioning system according to claim 9, characterized in that, The outdoor unit is installed in multiple units and connected in parallel. Each outdoor unit is equipped with a control valve. Some of the outdoor units are in operation and some are in a stopped state. The control unit is configured to: obtain the capacity ratio of the operating indoor unit to the operating outdoor unit when the system is cooling; Obtain the exhaust pressure value from the exhaust pressure sensor of the outdoor unit in operation; The subcooling value is obtained by combining the temperature value of the liquid pipe side of the outdoor heat exchanger of the operating outdoor unit with the exhaust saturation temperature corresponding to the exhaust pressure value. When the ratio of the capacity of the operating indoor unit to the operating outdoor unit reaches the set ratio range, and there is a target outdoor unit whose exhaust pressure value reaches the preset pressure range and whose subcooling value reaches the preset subcooling range, the control valve of one or more outdoor units in the shutdown state is opened to allow the refrigerant of the target outdoor unit to enter one or more outdoor units in the shutdown state.

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