A control method and device of a multi-connected air conditioner and the multi-connected air conditioner

Abstract

The application discloses a kind of control method, device and multiple connection air conditioners of multiple connection air conditioner, it is related to air conditioning technical field, the control method of the multiple connection air conditioner includes: detecting the load reduction of the indoor unit of multiple connection air conditioner, when the load reduction of indoor unit exceeds preset threshold, the number of the outdoor unit of start-up is detected;When the number of the outdoor unit of start-up is reduced to preset number, the high pressure of the outdoor unit of start-up is monitored, and recorded as first high pressure, the high pressure of the outdoor unit of shutdown is monitored, and recorded as second high pressure;When first high pressure is greater than second high pressure, based on the operating mode of multiple connection air conditioner, first high pressure and second high pressure control the expansion valve of the outdoor unit of shutdown or the expansion valve of the indoor unit of shutdown is opened, to reduce the high pressure of the outdoor unit of start-up.The application can make the refrigerant flow direction of the outdoor unit of start-up side low pressure side when the high pressure of the outdoor unit of start-up is higher, reduce the high pressure of the outdoor unit of start-up side, reduce high pressure protection risk.

Description

Technical Field

[0001] This invention relates to the field of air conditioning technology, and more specifically, to a control method, device, and multi-split air conditioner. Background Technology

[0002] Multi-split air conditioners typically consist of one outdoor unit and multiple indoor units, and are used in large venues such as shopping malls and office buildings. In some places with high cooling requirements, when one outdoor unit cannot meet the needs of multiple indoor units, and the capacity of the outdoor unit cannot be increased, multiple outdoor units can be used in parallel. For example, when a multi-split air conditioner includes two outdoor units, if the indoor unit's operating load is high, both outdoor units can be used simultaneously. If the indoor unit's operating load decreases, the outdoor unit switches from dual outdoor unit operation to single outdoor unit operation. However, when the number of operating outdoor units in a multi-split air conditioner decreases, a large amount of refrigerant can easily accumulate on the side of the operating outdoor unit, causing the high pressure on the operating outdoor unit side to rise rapidly, posing a significant risk to high pressure protection. Summary of the Invention

[0003] To address the aforementioned issues, this invention provides a control method, device, and multi-split air conditioner. When the high pressure of the outdoor unit is high during startup, the refrigerant on the outdoor unit side can be directed to the low-pressure side, thereby reducing the high pressure on the outdoor unit side and mitigating the risk of high-pressure protection failure.

[0004] According to an embodiment of the present invention, a control method for a multi-split air conditioner is provided. The multi-split air conditioner includes multiple outdoor units. The method includes: detecting the reduction in load of the indoor units of the multi-split air conditioner; when the reduction in load of the indoor units exceeds a preset threshold, detecting the number of outdoor units that are in operation; when the number of outdoor units in operation decreases to a preset number, monitoring the high-pressure of the outdoor units in operation and recording it as a first high-pressure, and monitoring the high-pressure of the outdoor units that are out of operation and recording it as a second high-pressure; when the first high-pressure is greater than the second high-pressure, controlling the expansion valve of the outdoor unit that is out of operation or the expansion valve of the indoor unit that is out of operation to open based on the operating mode of the multi-split air conditioner, the first high-pressure, and the second high-pressure, so as to reduce the high-pressure of the outdoor units in operation.

[0005] By adopting the above technical solution, when the indoor unit load is reduced significantly, the number of outdoor units in operation is reduced, and the high pressure of the outdoor units in operation is high, the expansion valve of the outdoor unit in operation or the indoor unit in operation can be opened according to the high pressure of the outdoor units in operation and the high pressure of the outdoor units in operation. This allows the refrigerant on the outdoor unit in operation to flow to the low-pressure side, reducing the high pressure on the outdoor unit in operation and reducing the risk of high pressure protection.

[0006] Preferably, the step of controlling the opening of the expansion valve of the shut-down outdoor unit or the shut-down indoor unit based on the operating mode of the multi-split air conditioner, the first high-pressure pressure, and the second high-pressure pressure includes: when the operating mode is cooling mode, monitoring the outdoor ambient temperature, and periodically controlling the opening degree of the expansion valve of the shut-down outdoor unit based on the outdoor ambient temperature, the first high-pressure pressure, and the second high-pressure pressure; when the operating mode is heating mode, periodically controlling the opening degree of the expansion valve of the shut-down indoor unit based on the first high-pressure pressure and the second high-pressure pressure.

[0007] By adopting the above technical solution, in cooling mode, controlling the opening of the expansion valve of the outdoor unit that is shut down allows the refrigerant on the outdoor unit side to flow into the condenser of the outdoor unit that is shut down, thus reducing the high pressure of the outdoor unit that is shut down; in heating mode, controlling the opening of the expansion valve of the indoor unit that is shut down allows the refrigerant on the outdoor unit side to flow to the low-pressure side, thus reducing the risk of high pressure protection.

[0008] Preferably, the step of periodically controlling the opening of the expansion valve of the outdoor unit that is shut down based on the outdoor ambient temperature, the first high pressure, and the second high pressure includes: periodically calculating the target opening of the expansion valve of the outdoor unit that is shut down, and controlling the expansion valve of the outdoor unit that is shut down to operate at the target opening; wherein, the calculation formula for the target opening is: P = N(Pd1 - Pd2), Pd1 is the first high pressure, Pd2 is the second high pressure, N is the outer loop correction coefficient, and the outer loop correction coefficient is positively correlated with the outdoor ambient temperature.

[0009] By adopting the above technical solution, the greater the pressure difference between the first high-pressure unit and the second high-pressure unit, the more refrigerant needs to be leaked to the side of the off outdoor unit. The calculated expansion valve opening of the off outdoor unit is also larger, and more refrigerant flows from the on outdoor unit to the off outdoor unit. This allows the high-pressure of the on outdoor unit to be reduced rapidly. By setting different control target values ​​for the expansion valve opening of the off outdoor unit, the refrigerant flow control is made more precise, the expansion valve opening adjustment is made more reasonable, and the reliability of the control to reduce high-pressure protection risks is improved.

[0010] Preferably, the control method of the multi-split air conditioner further includes: when the outdoor ambient temperature Tao ≤ T1℃, the outer loop correction coefficient N is a; when T1℃ < the outdoor ambient temperature Tao ≤ T2℃, the outer loop correction coefficient N is b; when T2℃ < the outdoor ambient temperature Tao ≤ T3℃, the outer loop correction coefficient N is c; when the outdoor ambient temperature Tao > T3℃, the outer loop correction coefficient N is d; wherein, a < b < c < d.

[0011] By adopting the above technical solution and using an outer loop correction coefficient, a higher outer loop correction coefficient is set when the outdoor ambient temperature is high. This results in a larger opening of the expansion valve of the outdoor unit when it is turned off, which increases the speed at which the high pressure of the outdoor unit decreases when it is turned on, avoids high pressure protection of the air conditioner, and improves the stability of the multi-split air conditioner operation.

[0012] Preferably, the control method of the multi-split air conditioner further includes: if Pd1-Pd2>0 is detected for a consecutive preset number of cycles, the compressor frequency of the outdoor unit is controlled to decrease by a first preset frequency, and the opening degree of the expansion valve of the indoor unit is controlled to increase by a first preset degree; if Pd1-Pd2≤0 is detected for a consecutive preset number of cycles, the expansion valve of the outdoor unit is controlled to close.

[0013] By adopting the above technical solution, when the high pressure of the outdoor unit is still high after the expansion valve of the outdoor unit is opened when it is turned off, the compressor frequency is reduced and the opening of the expansion valve of the indoor unit is increased when it is turned on, so that the refrigerant flows from the high pressure side to the low pressure side, thereby reducing the high pressure of the outdoor unit when it is turned on. When the high pressure of the outdoor unit when it is turned on has dropped to the normal range, the expansion valve of the outdoor unit when it is turned off is closed, so that the multi-split air conditioner can resume normal operation and improve the reliability of the air conditioner operation.

[0014] Preferably, the step of periodically controlling the opening of the expansion valve of the shut-down indoor unit based on the first high pressure and the second high pressure includes: periodically determining whether the first high pressure Pd1 and the second high pressure Pd2 satisfy Pd1-Pd2>0; if so, controlling the expansion valve of the shut-down indoor unit to increase the second preset opening degree in each cycle.

[0015] By adopting the above technical solution, when the first high-pressure is detected to be greater than the second high-pressure in each cycle, the opening of the expansion valve of the shut-down indoor unit is increased to increase the speed at which refrigerant flows to the shut-down indoor unit, increase the speed at which the high-pressure of the start-up outdoor unit decreases, and reduce the risk of high-pressure protection.

[0016] Preferably, the control method of the multi-split air conditioner further includes: if Pd1-Pd2>0 is detected for a consecutive preset number of cycles, the opening degree of the expansion valve of the shut-down outdoor unit is increased by a third preset degree in each cycle.

[0017] By adopting the above technical solution, the opening of the expansion valve of the outdoor unit that is shut down is periodically increased, so that the refrigerant in the outdoor unit that is in operation flows to both the indoor unit and the outdoor unit that is shut down. This minimizes the high pressure of the outdoor unit that is in operation and increases the speed at which the high pressure of the indoor unit that is in operation decreases, thus preventing the multi-split air conditioner from triggering high pressure protection.

[0018] Preferably, the control method of the multi-split air conditioner further includes: when the expansion valve of the shut-down outdoor unit is opened, monitoring the defrost temperature, suction temperature, and low pressure of the shut-down outdoor unit; if Pd1-Pd2≤0 is detected for a consecutive preset number of cycles, or if the rate of increase of the defrost temperature, the suction temperature, and the low pressure is detected for a consecutive preset number of cycles, the expansion valve of the shut-down outdoor unit is controlled to close, and the compressor frequency of the operating outdoor unit is controlled to decrease to a second preset frequency.

[0019] By adopting the above technical solution, the expansion valve of the outdoor unit is closed when the unit is stopped, and the compressor frequency is reduced to reduce the risk of refrigerant backflow and avoid the risk of liquid slugging when the compressor is restarted. At the same time, the compressor displacement is reduced, the system high pressure is lowered, and the reliability of the multi-split air conditioning control is improved.

[0020] According to an embodiment of the present invention, another aspect provides a control device for a multi-split air conditioner, comprising: a detection module, configured to detect the reduction in load of the indoor unit of the multi-split air conditioner, and when the reduction in load of the indoor unit exceeds a preset threshold, detect the number of outdoor units in operation; a monitoring module, configured to monitor the high pressure of the outdoor units in operation, denoted as a first high pressure, when the number of outdoor units in operation decreases to a preset number, and monitor the high pressure of the outdoor units in shutdown, denoted as a second high pressure; and a control module, configured to control the expansion valve of the outdoor unit in shutdown or the indoor unit in shutdown to open based on the operating mode of the multi-split air conditioner, the first high pressure, and the second high pressure, so as to reduce the high pressure of the outdoor units in operation.

[0021] According to an embodiment of the present invention, another aspect provides a multi-split air conditioner, comprising: a plurality of outdoor units, a computer-readable storage medium storing a computer program, and a processor, wherein the computer program is read and executed by the processor to implement the method as described in any of the first aspects.

[0022] The present invention has the following beneficial effects: by controlling the opening of the expansion valve of the shut-down outdoor unit or the expansion valve of the shut-down indoor unit according to the high pressure of the shut-down outdoor unit and the high pressure of the shut-down outdoor unit when the indoor unit load is reduced significantly and the number of outdoor units in operation is reduced, the refrigerant on the outdoor unit side can flow to the low-pressure side, thereby reducing the high pressure on the outdoor unit side and reducing the risk of high pressure protection. Attached Figure Description

[0023] To more clearly illustrate the embodiments of the present invention or the technical solutions in 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 merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0024] The structures, proportions, sizes, etc. illustrated in this specification are only for the purpose of assisting those skilled in the art in understanding and reading the content disclosed herein, and are not intended to limit the conditions under which the present invention can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportions, or adjustments to the size, without affecting the effects and objectives that the present invention can produce, should still fall within the scope of the technical content disclosed in the present invention.

[0025] Figure 1 A flowchart of a control method for a multi-split air conditioner provided by the present invention;

[0026] Figure 2 This invention provides a schematic diagram of a multi-split air conditioner with dual outdoor units;

[0027] Figure 3 This is a schematic diagram of the control device structure for a multi-split air conditioner provided by the present invention. Detailed Implementation

[0028] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0030] This embodiment provides a control method for a multi-split air conditioner. This method can be applied to multi-split air conditioners, which include multiple outdoor units connected in parallel, as shown in the example below. Figure 1 The flowchart of the control method for a multi-split air conditioner shown here mainly includes the following steps S102 to S106:

[0031] Step S102: Detect the reduction in indoor unit load of the multi-split air conditioner. When the reduction in indoor unit load exceeds a preset threshold, detect the number of outdoor units that are turned on.

[0032] The aforementioned preset threshold can be X*40% to X*60%, with X*50% being the preferred value, where X is the load value of the indoor unit before the load decreases. The total load of the indoor units of the multi-split air conditioner is monitored in real time. When the reduction in indoor unit load exceeds the preset threshold, it indicates a significant change in indoor unit load. The number of outdoor units currently in operation is then detected to determine whether the number of outdoor units in operation has decreased.

[0033] Step S104: When the number of outdoor units in operation decreases to the preset number, monitor the high pressure of the outdoor units in operation and record it as the first high pressure, and monitor the high pressure of the outdoor units in shutdown and record it as the second high pressure.

[0034] The aforementioned multi-split air conditioner may include two or more outdoor units. The aforementioned preset number of units can be determined based on the number of outdoor units included in the multi-split air conditioner. For example, when the aforementioned multi-split air conditioner includes two outdoor units, the aforementioned preset number of units may be 1.

[0035] When the indoor unit load decreases significantly and the number of outdoor units in operation decreases, a large amount of refrigerant accumulates on the condenser side of the outdoor unit in operation, causing the high pressure of the outdoor unit in operation to rise rapidly. Therefore, the multi-split air conditioner is controlled to enter the over-fluorine regulation mode. The high pressure of the outdoor unit in operation is detected by the pressure sensor in the outdoor unit in operation and recorded as the first high pressure. The high pressure of the outdoor unit in shutdown is detected by the pressure sensor in the outdoor unit in shutdown and recorded as the second high pressure.

[0036] Step S106: When the first high pressure is greater than the second high pressure, the expansion valve of the outdoor unit that is shut down or the expansion valve of the indoor unit that is shut down is opened based on the operating mode of the multi-split air conditioner, the first high pressure and the second high pressure, so as to reduce the high pressure of the outdoor unit that is turned on.

[0037] To determine the current operating mode of a multi-split air conditioner, since the refrigerant circulation direction differs under different operating modes, compare the first high-pressure pressure of the outdoor unit when it is running with the second high-pressure pressure of the outdoor unit when it is stopped. If the first high-pressure pressure of the outdoor unit when it is running is consistently greater than the second high-pressure pressure of the outdoor unit when it is stopped, it indicates that the high-pressure pressure of the outdoor unit when it is running is higher. By controlling the opening of the expansion valve of the outdoor unit when it is stopped or the expansion valve of the indoor unit when it is stopped, the refrigerant can flow to the outdoor unit when it is stopped or the indoor unit when it is stopped, thereby reducing the high-pressure pressure on the outdoor unit when it is running.

[0038] The multi-split air conditioner control method provided in this embodiment controls the opening of the expansion valve of the shut-off outdoor unit or the expansion valve of the shut-off indoor unit based on the high pressure of the shut-off outdoor unit and the high pressure of the shut-off outdoor unit when the indoor unit load is reduced significantly and the number of outdoor units in operation is reduced. This allows the refrigerant on the outdoor unit side to flow to the low-pressure side, reducing the high pressure on the outdoor unit side and lowering the risk of high pressure protection.

[0039] In one embodiment, in order to reduce the high-pressure protection risk of multi-split air conditioners, this embodiment provides an implementation method that controls the opening of the expansion valve of the outdoor unit or the indoor unit based on the operating mode of the multi-split air conditioner, the first high-pressure pressure, and the second high-pressure pressure. Specifically, the following steps (1) to (2) can be performed:

[0040] Step (1): When the operating mode is cooling mode, monitor the outdoor ambient temperature, and periodically control the opening of the expansion valve of the outdoor unit to be shut down based on the outdoor ambient temperature, the first high pressure and the second high pressure.

[0041] In cooling mode, the outdoor ambient temperature is detected by a temperature sensor. The outer loop correction coefficient is determined based on the outdoor ambient temperature. Then, the opening of the expansion valve of the outdoor unit to be shut down is calculated based on the outer loop correction coefficient, the first high pressure, and the second high pressure. The higher the first high pressure, the greater the high pressure of the outdoor unit to be turned on. Therefore, the opening of the expansion valve of the outdoor unit to be turned off is larger, so as to quickly reduce the high pressure of the outdoor unit to be turned on.

[0042] In one specific implementation, the target opening degree of the outdoor unit's expansion valve is periodically calculated, and the outdoor unit's expansion valve is controlled to operate at the target opening degree. The calculation formula for the target opening degree is: P = N(Pd1 - Pd2), where Pd1 is the first high-pressure level, Pd2 is the second high-pressure level, and N is the outer loop correction coefficient, which is positively correlated with the outdoor ambient temperature. The higher the outdoor ambient temperature, the larger the outer loop correction coefficient, and the larger the calculated opening degree of the outdoor unit's expansion valve. The calculation period T can range from 4 to 6 seconds, with a preferred value of 5 seconds.

[0043] The greater the pressure difference between the first high-pressure unit and the second high-pressure unit, the more refrigerant needs to be released to the off outdoor unit. The larger the calculated opening of the expansion valve of the off outdoor unit, the more refrigerant flows from the on outdoor unit to the off outdoor unit. This allows the high-pressure of the on outdoor unit to be reduced rapidly, improving the reliability of high-pressure protection risk control.

[0044] In one specific implementation, the method provided in this embodiment further includes: determining the outer ring correction coefficient based on the outdoor ambient temperature.

[0045] When the outdoor ambient temperature Tao ≤ T1℃, the outer ring correction factor N is a, where 0 < a ≤ 0.5; the value of T1 can be 34℃~36℃, with 35℃ being the preferred value.

[0046] When T1℃ < outdoor ambient temperature Tao ≤ T2℃, the outer ring correction factor N is b, and 0.5 < b ≤ 1; the value of T2 can be 42℃~45℃, with 43℃ being the preferred value.

[0047] When T2℃ < outdoor ambient temperature Tao ≤ T3℃, the outer ring correction factor N is taken as c, where 1 < c ≤ 2; the value of T3 can be in the range of 46℃~49℃, with 48℃ being the preferred value.

[0048] When the outdoor ambient temperature Tao > T3℃, the outer ring correction factor N is d; where a < b < c < d, 2 < d ≤ 3.

[0049] Because the higher the outdoor ambient temperature, the higher the high pressure of the air conditioning system will be, by using an outer loop correction coefficient to correct this, a higher outer loop correction coefficient is set when the outdoor ambient temperature is high, the expansion valve opening of the outdoor unit when it is turned off will be larger, which will increase the speed at which the high pressure of the outdoor unit decreases when it is turned on, avoid the air conditioner from triggering high pressure protection, and improve the stability of multi-split air conditioning operation.

[0050] In one embodiment, the method provided in this embodiment further includes: if Pd1-Pd2>0 is detected for a consecutive preset number of cycles, controlling the compressor frequency of the outdoor unit to decrease by a first preset frequency, and controlling the expansion valve opening of the indoor unit to increase by a first preset opening.

[0051] The value range of the first preset opening degree can be 5% to 15%, with a preferred value of 10% (i.e., total opening degree * 10%). The value range of the first preset frequency can be 5% to 15% of the current frequency, with a preferred value of 10% of the current frequency. The value range of the preset quantity can be 2 to 4, with a preferred value of 3. If Pd1-Pd2>0 is detected for several consecutive cycles, it indicates that the amount of refrigerant circulating in the condenser of the indoor unit is too large. Even after the expansion valve of the outdoor unit is opened to control the shutdown, the high pressure of the outdoor unit remains high. By controlling the compressor frequency to decrease and simultaneously increasing the opening of the expansion valve of the indoor unit, the refrigerant flows from the high-pressure side to the low-pressure side, reducing the high pressure of the outdoor unit.

[0052] If Pd1-Pd2≤0 is detected for a consecutive preset number of cycles, the expansion valve of the outdoor unit is closed, exiting the over-refrigerant regulation mode, thus stopping the control method of the multi-split air conditioner described above. If Pd1-Pd2≤0 is detected for several consecutive cycles, it indicates that the high pressure of the outdoor unit has dropped to the normal range, and there is no need to open the expansion valve of the outdoor unit that is shut down. By closing the expansion valve of the outdoor unit that is shut down when the high pressure of the outdoor unit has dropped to the normal range, the multi-split air conditioner can resume normal operation, improving the reliability of the air conditioner.

[0053] Step (2): When the operating mode is heating mode, the opening degree of the expansion valve of the indoor unit that is shut down is periodically controlled based on the first high pressure and the second high pressure.

[0054] When a multi-split air conditioner is running in heating mode, if the first high-pressure pressure is greater than the second high-pressure pressure, it indicates that the high-pressure pressure on the outdoor unit side is high, and a large amount of refrigerant accumulates on the high-pressure side, which can easily trigger high-pressure protection. This will control the indoor unit to increase the opening of the valve, allowing as much refrigerant as possible to flow to the low-pressure side and reduce the pressure on the high-pressure side.

[0055] By controlling the opening of the expansion valve of the outdoor unit that is shut down during cooling mode, the refrigerant on the outdoor unit side of the operating unit can flow into the condenser of the outdoor unit that is shut down, thus reducing the high pressure of the outdoor unit that is operating. By controlling the opening of the expansion valve of the indoor unit that is shut down during heating mode, the refrigerant on the outdoor unit side of the operating unit can flow to the low-pressure side, thus reducing the risk of high pressure protection.

[0056] In one specific implementation, it is periodically determined whether the first high pressure Pd1 and the second high pressure Pd2 satisfy Pd1-Pd2>0. If so, the expansion valve of the indoor unit is controlled to increase the second preset opening degree in each cycle.

[0057] The duration of each cycle can range from 4 to 6 seconds, with a preferred value of 5 seconds. The second preset opening degree can range from 5% to 15%, with a preferred value of 10% (i.e., total opening degree * 10%). By increasing the opening degree of the expansion valve of the shut-down indoor unit when the first high-pressure pressure is detected to be greater than the second high-pressure pressure in each cycle, the speed at which refrigerant flows to the shut-down indoor unit is increased, thereby increasing the speed at which the high-pressure pressure of the start-up outdoor unit decreases and reducing the risk of high-pressure protection.

[0058] In one embodiment, when the operating mode is heating mode, the method provided in this embodiment further includes: if Pd1-Pd2>0 is detected for a consecutive preset number of cycles, the opening degree of the expansion valve of the outdoor unit to be stopped is increased by a third preset degree in each cycle.

[0059] The preset number can range from 2 to 5, with a preferred value of 3 times. When the multi-split air conditioner is running in heating mode, if Pd1-Pd2>0 is detected for several consecutive cycles, and the expansion valve of the shut-off indoor unit is in an increased state for several consecutive cycles, it indicates that the high pressure of the operating outdoor unit is always greater than that of the shut-off outdoor unit. Simply opening the expansion valve of the shut-off indoor unit is no longer sufficient to maximize the discharge from the high-pressure side. By controlling the periodic increase of the opening of the expansion valve of the shut-off outdoor unit, the refrigerant in the operating outdoor unit flows to both the shut-off indoor unit and the shut-off outdoor unit simultaneously, thereby minimizing the high pressure of the operating outdoor unit and increasing the speed of high pressure reduction in the operating indoor unit, thus preventing the multi-split air conditioner from triggering high-pressure protection.

[0060] In one embodiment, the method provided in this embodiment further includes: when the expansion valve of the outdoor unit that is shut down opens, monitoring the defrost temperature, suction temperature, and low-pressure of the outdoor unit that is shut down; if Pd1-Pd2≤0 is detected for a consecutive preset number of cycles, or if the rate of increase of the defrost temperature Tdef, suction temperature Ts, and low-pressure Ps is detected for a consecutive preset number of cycles, the expansion valve of the outdoor unit that is shut down is controlled to close, and the compressor frequency of the outdoor unit that is started is controlled to decrease to a second preset frequency. The value range of the second preset frequency can be from the current frequency * 15% to the current frequency * 25%, and the preferred value is the current frequency * 20%, that is, controlling the compressor to decrease by 20% based on the current frequency.

[0061] In heating mode, when the expansion valve of the outdoor unit is shut down opens wide, the refrigerant will flow through the condenser to the gas separator. If the gas separator is full of liquid, there is a risk that the refrigerant will flow back into the compressor, which may cause liquid slugging when the unit is restarted. The condition for closing the expansion valve of the outdoor unit is determined by judging whether Pd1-Pd2≤0, or the defrosting temperature, suction temperature and low pressure.

[0062] If Pd1-Pd2≤0 is detected for several consecutive cycles, it indicates that the high pressure of the outdoor unit has dropped to the normal range, and there is no need to open the expansion valve of the outdoor unit that is shut down. If the rate of increase of defrost temperature, suction temperature and low pressure is detected for several consecutive cycles, all of which are greater than the preset rate, the preset rate can be 5% to 15%, and the preferred value is 10% (i.e., an increase of 10% based on the current temperature or pressure), it indicates that after the expansion valve of the outdoor unit that is shut down is opened, the defrost temperature, suction temperature and low pressure rise rapidly in a short period of time, which poses a risk of refrigerant backflow. By controlling the expansion valve of the outdoor unit that is shut down to close and controlling the compressor frequency to reduce the risk of refrigerant backflow, the risk of liquid slugging caused by restarting the compressor is avoided. At the same time, the compressor displacement is reduced, the system high pressure is reduced, and the reliability of the multi-split air conditioning control is improved.

[0063] For example, this embodiment provides an example of controlling a multi-split air conditioner with two outdoor units based on the above-described multi-split air conditioner control method: The unit starts running in cooling mode, automatically identifies system parameters, the indoor unit load change decreases by more than 50%, and it is detected that only one outdoor unit is running, entering over-refrigerant regulation control. The system detects that the ambient temperature Tao = 40℃, so the N value is 1, Pd1 is 30 bar, Pd2 is 20 bar, and the target opening degree of the electronic expansion valve of the outdoor unit for the next cycle is P = 1 × (30 - 20) = 10 pls. The outdoor unit valve remains open for three consecutive cycles. The compressor operating frequency is 50 Hz at the current moment, so the compressor frequency will decrease by 10% to 45 Hz at the next adjustment moment, and at the same time, the indoor unit valve will increase by 10% from the current 100 pls to 110 pls.

[0064] The control method for multi-split air conditioners provided in this embodiment reduces the risk of high-pressure protection in the system by opening the electronic expansion valve of the shut-down outdoor unit when the number of indoor units and outdoor units in operation is greatly reduced. The rationality of the expansion valve opening adjustment is improved by setting the target opening degree of the shut-down outdoor unit expansion valve according to the outer loop correction coefficient, the first high-pressure pressure, and the second high-pressure pressure when controlling the electronic expansion valve of the shut-down outdoor unit.

[0065] Corresponding to the control method for multi-split air conditioners provided in the above embodiments, this embodiment of the invention provides an example of using the control method for multi-split air conditioners to perform parallel refrigerant regulation control of dual outdoor units in a multi-split system, see example... Figure 2 The diagram shows a multi-split air conditioner with two outdoor units. This multi-split air conditioner includes two outdoor units and multiple indoor units. Any one outdoor unit can be defined as the main unit, and the other as the sub-unit. Each outdoor unit includes a compressor 21, a high-pressure sensor Pd (for detecting high-pressure), a low-pressure sensor Ps (for detecting low-pressure), a four-way valve 22, a vapor separator 23, an electronic expansion valve 24, an outer-loop temperature sensor Tao (for detecting outdoor ambient temperature), a finned condenser 25, a defrost temperature sensor Tdef (for detecting defrost temperature), and a suction temperature sensor Ts (for detecting suction temperature).

[0066] Please refer to the following steps for specific instructions:

[0067] Step 1: When the multi-split air conditioner is running in cooling mode, identify the load changes of the indoor unit in real time.

[0068] When the indoor unit load decreases by more than 50% and only one outdoor unit is detected to be running, the control enters the over-refrigerant regulation mode; otherwise, it operates in normal control mode. The over-refrigerant regulation mode includes:

[0069] (1) The target opening degree of the electronic expansion valve of the outdoor unit controlled for shutdown is P = N(Pd1 - Pd2) (N is the outer loop correction coefficient), and each adjustment cycle is 5 seconds:

[0070] Pd1 represents the high voltage of the outdoor unit when it is powered on, which is detected by the high voltage sensor of the outdoor unit when it is powered on. Pd2 represents the high voltage of the outdoor unit when it is powered off, which is detected by the high voltage sensor of the outdoor unit when it is powered off.

[0071] When Tao ≤ 35℃, N takes the value a, where 0 < a ≤ 0.5;

[0072] When 35℃<Tao≤43℃, N takes the value b, and 0.5<b≤1;

[0073] When 43℃<Tao≤48℃, N takes the value c, 1<c≤2;

[0074] When Tao > 48℃, N takes the value d, where 2 < d ≤ 3;

[0075] (2) If the calculated value of the expansion valve opening P of the outdoor unit is positive for three consecutive cycles of shutdown, that is, the valve is kept open, then the frequency of the compressor of the outdoor unit is reduced by 10% and the opening of the expansion valve of the indoor unit is increased by 10%.

[0076] (3) If the calculated value of the outdoor unit valve opening P is ≤0 for three consecutive cycles of shutdown, the outdoor unit valve will be closed to 0pls and the over-fluorine regulation mode will be exited.

[0077] In a refrigeration cycle, when the load on the indoor units of a dual-outdoor-unit parallel system fluctuates significantly, fewer indoor units are turned on, leading to a large accumulation of refrigerant on the condenser side of the outdoor unit. This causes a rapid increase in high pressure, potentially triggering high-pressure protection. In this situation, the excess refrigerant can be released into the condenser of the outdoor unit that is turned off by opening its electronic expansion valve (with a one-way vent valve, there is no risk of refrigerant backflow). The high pressure of the outdoor unit will then decrease, reducing the risk of high-pressure protection.

[0078] The expansion valve opening is adjusted using the formula P = N(Pd1 - Pd2). The high pressure difference between the main unit and the outdoor unit determines the opening to be adjusted in the next cycle. A larger pressure difference indicates that more refrigerant needs to be released to the outdoor unit, requiring a larger valve opening, and vice versa. Simultaneously, an outer loop coefficient is used for correction. A higher outer loop coefficient results in higher high pressure, necessitating a larger valve opening, thus requiring a larger correction coefficient.

[0079] If the outdoor unit's electronic expansion valve remains wide open for three consecutive shutdown cycles, it indicates that there is too much refrigerant circulating in the outdoor unit's condenser when it is turned on. The effect of turning on and off the valve cannot be achieved immediately. It is necessary to reduce the compressor frequency and flow rate, and at the same time, open the indoor unit valve to allow the refrigerant to flow from the high-pressure side to the low-pressure side.

[0080] If the calculated value of the opening degree P of the outdoor unit's electronic expansion valve is ≤0 for three consecutive shutdown cycles, it indicates that the high pressure of the outdoor unit in operation has dropped to the normal range, and there is no need to open the expansion valve of the outdoor unit in shutdown.

[0081] When the indoor unit load decreases by no more than 50%, or the number of outdoor units in operation does not decrease to 1, the unit will be controlled in the normal control mode.

[0082] Step 2: When the multi-split air conditioner is running in heating mode, the load change of the indoor unit is identified in real time.

[0083] If the indoor unit load decreases by more than 50% and only one outdoor unit is detected to be running, the system enters over-refrigerant regulation mode; otherwise, it operates in normal control mode. Over-refrigerant regulation modes include:

[0084] (1) If Pd1-Pd2>0 is detected, the electronic expansion valve of the indoor unit will be opened by 10% and 5s is an adjustment cycle. If Pd1-Pd2>0 is detected for 3 consecutive cycles, the electronic expansion valve of the indoor unit will be in the open state and the electronic expansion valve of the outdoor unit will be opened from 0pls to 10pls and 5s is an adjustment cycle. Each cycle will be opened by 10pls.

[0085] (2) If any of the following conditions are identified in three consecutive cycles:

[0086] ① Pd1 - Pd2 ≤ 0;

[0087] ② Tdef increases by 10% per cycle; Ts increases by 10% per cycle; Ps increases by 10% per cycle;

[0088] The electronic expansion valve of the outdoor unit will immediately close to 0pls when the unit is shut down, and the compressor frequency of the outdoor unit will decrease by 20% when the unit is turned on, thus exiting the refrigerant regulation mode.

[0089] In a heating cycle, when the load on the indoor units of a dual-unit parallel system fluctuates significantly, fewer indoor units are turned on, leading to a large accumulation of refrigerant on the high-pressure side. This causes a rapid rise in high pressure, potentially triggering high-pressure protection. At this point, the expansion valve of the shut-off indoor unit increases its opening by 10% to allow as much refrigerant as possible to flow to the low-pressure side. If the expansion valve of the shut-off indoor unit remains fully open for three consecutive cycles, it indicates that simply opening the shut-off indoor unit's expansion valve is insufficient to maximize the discharge from the high-pressure side, necessitating a fuller opening of the shut-off outdoor unit's expansion valve. However, opening the shut-off outdoor unit's expansion valve too fully would cause refrigerant to flow through the condenser to the gas separator. If the gas separator is full, there is a risk of refrigerant backflow into the compressor, potentially causing liquid slugging upon restart. Therefore, the parameters Tdef, Ts, and Ps are used to determine if there is excessive refrigerant. If all three parameters rise rapidly within a short period, there is a risk of refrigerant backflow. In this case, the outdoor unit's expansion valve should be immediately shut off, and the compressor frequency of the outdoor unit should be reduced by 20% to decrease compressor displacement and lower high-pressure.

[0090] Corresponding to the control method for multi-split air conditioners provided in the above embodiments, this invention provides a control device for multi-split air conditioners. This device can be applied to multi-split air conditioners, see below. Figure 3 The diagram shows the structure of the control device for a multi-split air conditioner, which includes the following modules:

[0091] The detection module 31 is used to detect the reduction in load of the indoor unit of the multi-split air conditioner. When the reduction in load of the indoor unit exceeds a preset threshold, it detects the number of outdoor units that are turned on.

[0092] Monitoring module 32 is used to monitor the high pressure of the outdoor unit when the number of outdoor units in operation decreases to a preset number, and record it as the first high pressure; and to monitor the high pressure of the outdoor unit when it is shut down, and record it as the second high pressure.

[0093] The control module 33 is used to control the opening of the expansion valve of the outdoor unit that is shut down or the expansion valve of the indoor unit that is shut down, based on the operating mode of the multi-split air conditioner, the first high pressure, and the second high pressure, so as to reduce the high pressure of the outdoor unit that is turned on.

[0094] The control device for the multi-split air conditioner provided in this embodiment controls the opening of the expansion valve of the shut-off outdoor unit or the expansion valve of the shut-off indoor unit based on the high pressure of the shut-off outdoor unit and the high pressure of the shut-off outdoor unit when the indoor unit load is reduced significantly and the number of outdoor units in operation is reduced. This allows the refrigerant on the outdoor unit side to flow to the low-pressure side, reducing the high pressure on the outdoor unit side and lowering the risk of high pressure protection.

[0095] In one embodiment, the control module 33 is used to monitor the outdoor ambient temperature when the operating mode is cooling mode, and periodically control the opening of the expansion valve of the outdoor unit that is shut down based on the outdoor ambient temperature, the first high pressure and the second high pressure; when the operating mode is heating mode, it periodically controls the opening of the expansion valve of the indoor unit that is shut down based on the first high pressure and the second high pressure.

[0096] In one embodiment, the control module 33 is used to periodically calculate the target opening degree of the outdoor unit expansion valve and control the outdoor unit expansion valve to operate at the target opening degree; wherein, the calculation formula for the target opening degree is: P = N(Pd1-Pd2), Pd1 is the first high pressure, Pd2 is the second high pressure, N is the outer loop correction coefficient, and the outer loop correction coefficient is positively correlated with the outdoor ambient temperature.

[0097] In one embodiment, the above-mentioned device further includes:

[0098] The module determines the outer loop correction factor N as follows: when the outdoor ambient temperature Tao ≤ T1℃, the outer loop correction factor N is a, where 0 < a ≤ 0.5; when T1℃ < outdoor ambient temperature Tao ≤ T2℃, the outer loop correction factor N is b, where 0.5 < b ≤ 1; when T2℃ < outdoor ambient temperature Tao ≤ T3℃, the outer loop correction factor N is c, where 1 < c ≤ 2; and when the outdoor ambient temperature Tao > T3℃, the outer loop correction factor N is d, where 2 < d ≤ 3.

[0099] The second control module is used to control the compressor frequency of the outdoor unit to decrease by a first preset frequency and the expansion valve opening of the indoor unit to increase by a first preset degree if Pd1-Pd2>0 is detected for a consecutive preset number of cycles.

[0100] The third control module is used to control the expansion valve of the outdoor unit to close if Pd1-Pd2≤0 is detected for a consecutive preset number of cycles.

[0101] In one embodiment, the control module 33 is used to periodically determine whether the first high pressure Pd1 and the second high pressure Pd2 satisfy Pd1-Pd2>0. If so, it controls the expansion valve of the shut-down indoor unit to increase the second preset opening degree in each cycle.

[0102] In one embodiment, the above-mentioned device further includes:

[0103] The fourth control module is used to control the expansion valve opening of the outdoor unit to increase by a third preset opening degree in each cycle if Pd1-Pd2>0 is detected for a consecutive preset number of cycles.

[0104] The fifth control module is used to monitor the defrost temperature, suction temperature, and low pressure of the outdoor unit when the expansion valve of the outdoor unit is opened. If Pd1-Pd2≤0 is detected for a consecutive preset number of cycles, or if the rate of increase of defrost temperature, suction temperature, and low pressure is greater than the preset rate for a consecutive preset number of cycles, the module controls the expansion valve of the outdoor unit to close and controls the compressor frequency of the outdoor unit to decrease to a second preset frequency.

[0105] The control device for the multi-split air conditioner provided in this embodiment can reduce the risk of high-pressure protection of the system by opening the electronic expansion valve of the shut-down outdoor unit when the number of indoor units and outdoor units in operation of the multi-split air conditioner is greatly reduced. By setting the target opening degree of the shut-down outdoor unit expansion valve according to the outer loop correction coefficient, the first high pressure, and the second high pressure when controlling the electronic expansion valve of the shut-down outdoor unit, the rationality of the expansion valve opening adjustment is improved.

[0106] Corresponding to the control method of multi-split air conditioner provided in the above embodiments, this embodiment provides a multi-split air conditioner, which includes multiple outdoor units, a computer-readable storage medium storing a computer program, and a processor. The computer program is read and executed by the processor to implement the control method of multi-split air conditioner provided in the above embodiments.

[0107] This embodiment also provides a computer-readable storage medium storing a computer program. When executed by a processor, this computer program implements the various processes of the control method embodiment for the multi-split air conditioner described above, and achieves the same technical effect. To avoid repetition, it will not be described again here. The computer-readable storage medium may be a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disk, etc.

[0108] Of course, those skilled in the art will understand that all or part of the processes in the above embodiments can be implemented by computer-controlled devices. The program can be stored in a computer-readable storage medium. When the program is executed, it can include the processes of the above method embodiments. The storage medium can be a memory, a disk, an optical disk, etc.

[0109] While the present invention has been disclosed above, it is not limited thereto. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of the invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

[0110] Finally, it should be noted that in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0111] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. Regarding the control device and air conditioner for multi-split air conditioners disclosed in the embodiments, since they correspond to the control method for multi-split air conditioners disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0112] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

[0113] While the present invention has been disclosed above, it is not limited thereto. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of the invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. A control method for a multi-split air conditioner, characterized in that, The multi-split air conditioner includes multiple outdoor units, and the method includes: The reduction in load of the indoor unit of the multi-split air conditioner is detected. When the reduction in load of the indoor unit exceeds a preset threshold, the number of outdoor units that are turned on is detected. When the number of outdoor units in operation decreases to a preset number, the high pressure of the outdoor units in operation is monitored and recorded as the first high pressure; the high pressure of the outdoor units in shutdown is monitored and recorded as the second high pressure. When the first high pressure is greater than the second high pressure, the expansion valve of the shut-down outdoor unit or the expansion valve of the shut-down indoor unit is opened based on the operating mode of the multi-split air conditioner, the first high pressure, and the second high pressure, so as to reduce the high pressure of the operating outdoor unit. The step of controlling the opening of the expansion valve of the outdoor unit or the indoor unit that is shut down based on the operating mode of the multi-split air conditioner, the first high pressure, and the second high pressure includes: When the operating mode is cooling mode, the outdoor ambient temperature is monitored, an outer loop correction coefficient is determined based on the outdoor ambient temperature, and the target opening degree of the outdoor unit expansion valve is calculated based on the first high pressure and the second high pressure using the outer loop correction coefficient; wherein, the target opening degree is positively correlated with the first high pressure and the outer loop correction coefficient is positively correlated with the outdoor ambient temperature; When the operating mode is heating mode, it is periodically determined whether the first high pressure Pd1 and the second high pressure Pd2 satisfy Pd1-Pd2>0. If so, the expansion valve of the shut-down indoor unit is controlled to increase the second preset opening degree in each cycle.

2. The control method for a multi-split air conditioner as described in claim 1, characterized in that, The step of periodically controlling the opening of the expansion valve of the shut-down outdoor unit based on the outdoor ambient temperature, the first high-pressure pressure, and the second high-pressure pressure includes: The target opening degree of the outdoor unit expansion valve is periodically calculated, and the outdoor unit expansion valve is controlled to operate at the target opening degree; wherein, the calculation formula for the target opening degree is: P=N(Pd1-Pd2), Pd1 is the first high pressure, Pd2 is the second high pressure, and N is the outer loop correction coefficient.

3. The control method for a multi-split air conditioner as described in claim 2, characterized in that, Also includes: When the outdoor ambient temperature Tao ≤ T1℃, the outer ring correction coefficient N is a; When T1℃ < the outdoor ambient temperature Tao ≤ T2℃, the outer ring correction coefficient N is taken as b; When T2℃ < the outdoor ambient temperature Tao ≤ T3℃, the outer ring correction coefficient N is taken as c; When the outdoor ambient temperature Tao > T3℃, the outer ring correction coefficient N is d; where a < b < c < d.

4. The control method for a multi-split air conditioner as described in claim 2, characterized in that, Also includes: If Pd1-Pd2>0 is detected for a consecutive preset number of cycles, the compressor frequency of the outdoor unit is controlled to decrease by a first preset frequency, and the expansion valve opening of the indoor unit is controlled to increase by a first preset opening. If Pd1-Pd2≤0 is detected for a consecutive preset number of cycles, the expansion valve of the outdoor unit to be shut down will be closed.

5. The control method for a multi-split air conditioner as described in claim 1, characterized in that, Also includes: If Pd1-Pd2>0 is detected for a consecutive preset number of cycles, the opening degree of the expansion valve of the outdoor unit that is shut down is increased by a third preset degree in each cycle.

6. The control method for a multi-split air conditioner as described in claim 5, characterized in that, Also includes: When the expansion valve of the outdoor unit that is shut down is opened, monitor the defrosting temperature, intake temperature and low pressure of the outdoor unit that is shut down. If Pd1-Pd2≤0 is detected for a consecutive preset number of cycles, or if the rate of increase of the defrosting temperature, the suction temperature, and the low pressure is detected for a consecutive preset number of cycles, the expansion valve of the outdoor unit that is shut down is closed, and the compressor frequency of the outdoor unit that is started is reduced to a second preset frequency.

7. A control device for a multi-split air conditioner, characterized in that, include: The detection module is used to detect the reduction in load of the indoor unit of the multi-split air conditioner. When the reduction in load of the indoor unit exceeds a preset threshold, the number of outdoor units that are turned on is detected. The monitoring module is used to monitor the high pressure of the outdoor unit when the number of the outdoor units in operation decreases to a preset number, and record it as the first high pressure; and to monitor the high pressure of the outdoor unit when it is shut down, and record it as the second high pressure. The control module is used to control the expansion valve of the shut-down outdoor unit or the expansion valve of the shut-down indoor unit to open based on the operating mode of the multi-split air conditioner, the first high pressure and the second high pressure, so as to reduce the high pressure of the operating outdoor unit. The control module is further configured to monitor the outdoor ambient temperature when the operating mode is cooling mode, determine the outer loop correction coefficient based on the outdoor ambient temperature, and calculate the target opening degree of the expansion valve of the shut-down outdoor unit based on the first high pressure and the second high pressure based on the outer loop correction coefficient; wherein the target opening degree is positively correlated with the first high pressure and the outer loop correction coefficient is positively correlated with the outdoor ambient temperature; when the operating mode is heating mode, periodically determine whether the first high pressure Pd1 and the second high pressure Pd2 satisfy Pd1 - Pd2 > 0, and if so, control the expansion valve of the shut-down indoor unit to increase the second preset opening degree in each cycle.

8. A multi-split air conditioner, characterized in that, include: The invention comprises multiple outdoor units, a computer-readable storage medium storing a computer program, and a processor, wherein the computer program is read and executed by the processor to implement the method as described in any one of claims 1-6.

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