Oil return control method, operation control device, multi-connection system and storage medium

Abstract

The present invention discloses an oil return control method, an operation control device, a multi-split system, and a storage medium. The oil return control method, wherein the multi-split system also includes multiple indoor units, comprises: when a preset oil return condition is met, obtaining the outdoor ambient temperature and the total energy demand of the indoor units, wherein the total energy demand of the indoor units is the sum of the capacities of the indoor units in operation; when the outdoor ambient temperature is greater than a first preset temperature and the total energy demand of the indoor units is less than the product of the outdoor unit capacities and a first proportional value, obtaining the mid-evaporator temperatures of all indoor units in operation and calculating the average mid-evaporator temperature; and controlling the operating frequency of the compressor based on the average mid-evaporator temperature. This can avoid sudden frequency increase and oil return, which leads to untimely heat dissipation in the indoor units and causes heat accumulation in the indoor units, and avoid triggering a high-pressure protection shutdown.

Description

Technical Field

[0001] The present invention relates to the technical field of air conditioning, and in particular to an oil return control method, an operation control device, a multi-connected system and a storage medium. Background Art

[0002] Multi-unit, multi-split systems offer a wide range of indoor unit combinations, allowing the combined capacity of the indoor units to be anywhere from 50% to 135% of the outdoor unit capacity, or even higher. When only a small number of indoor units are required, the compressor and outdoor fan run at minimum frequency and speed. Due to the long piping in multi-unit systems, prolonged low-frequency operation necessitates switching to high-frequency oil return. Due to the heat accumulated in the indoor units, a sudden increase in frequency for oil return can cause a sharp increase in exhaust pressure, triggering a high-pressure shutdown and negatively impacting the user experience. Summary of the Invention

[0003] The purpose of the present invention is to solve at least one of the technical problems existing in the prior art, and to provide an oil return control method, an operation control device, a multi-split system and a storage medium, which can avoid the untimely heat dissipation of the internal machine, thereby causing heat accumulation in the internal machine and triggering a high-voltage protection shutdown.

[0004] In a first aspect, an embodiment of the present invention provides an oil return control method, which is applied to an external unit in a multi-split system, wherein the multi-split system further includes a plurality of internal units. The method includes:

[0005] When the preset oil return condition is met, the outdoor ambient temperature and the total energy demand of the indoor units are obtained, where the total energy demand of the indoor units is the sum of the capacities of the indoor units in operation;

[0006] When the outdoor ambient temperature is greater than a first preset temperature and the total energy required by the indoor unit is less than the product of the capacity of the outdoor unit and the first proportional value, obtaining the middle temperature of the evaporator of all indoor units in operation and calculating an average of the middle temperature of the evaporator;

[0007] The operating frequency of the compressor is controlled according to the average temperature of the middle portion of the evaporator.

[0008] The oil return control method provided in the embodiment of the present invention has at least the following beneficial effects: when the preset oil return conditions are met, the outdoor ambient temperature and the total energy demand of the indoor unit are first obtained. If the outdoor ambient temperature is greater than the first preset temperature, it indicates that the current state is high-temperature heating, which may easily cause the compressor exhaust temperature and exhaust pressure to be too high, thereby triggering a high-pressure protection shutdown; and if the total energy demand of the indoor unit is less than the product of the outdoor unit capacity and the first proportional value, it indicates that there are fewer indoor units in operation, and the indoor units have accumulated heat. If the frequency is suddenly increased and the oil return is performed, the exhaust pressure will rise sharply and a high-pressure protection shutdown will occur; at this time, the operating frequency of the compressor is controlled according to the middle temperature of the evaporator of all indoor units in operation, which can avoid the sudden increase in frequency and oil return, which will cause the indoor unit to dissipate heat in time and cause heat accumulation in the indoor unit, and avoid triggering a high-pressure protection shutdown.

[0009] In the above-mentioned oil return control method, controlling the operating frequency of the compressor according to the average temperature of the middle portion of the evaporator includes:

[0010] When T2p≤T2s1, the compressor is controlled to directly increase the frequency to the preset oil return frequency;

[0011] When T2s1<T2p≤T2s2, the operating frequency of the compressor is controlled to increase step by step, and each step runs for the first preset time;

[0012] When T2s2<T2p≤T2s3, the operating frequency of the compressor is controlled to remain unchanged and run for the second preset time;

[0013] When T2p>T2s3, the compressor is controlled to stop running;

[0014] Among them: T2p is the average temperature of the middle part of the evaporator, T2s1 and T2s2 are preset temperature values, T2s3 is the preset temperature value for shutdown protection, and T2s1<T2s2<T2s3.

[0015] In the above oil return control method, when T2p≤T2s2, it is determined again whether T2p is greater than T2s2 every third preset time period.

[0016] The above oil return control method further includes:

[0017] When the preset oil return condition is met, the electronic expansion valves corresponding to all the indoor units are controlled to open to a preset opening;

[0018] When the first control signal is received, the opening of the electronic expansion valve corresponding to the indoor unit is adjusted according to the middle temperature of the evaporator of the indoor unit. The first control signal is issued when the middle temperature of the evaporator of the indoor unit in operation is greater than T2s2, which is used to indicate that there is a risk of high-temperature tripping and assistance is required.

[0019] In the above-mentioned oil return control method, adjusting the opening of the electronic expansion valve corresponding to the indoor unit according to the middle temperature of the evaporator of the indoor unit includes:

[0020] When T2>T2s2, the opening of the electronic expansion valve corresponding to the indoor unit is increased every fourth preset time;

[0021] When T2≤T2s2, reducing the opening of the electronic expansion valve corresponding to the indoor unit every fourth preset time;

[0022] Among them, T2 is the middle temperature of the evaporator of the indoor unit.

[0023] The above oil return control method further includes:

[0024] The first control signal is forwarded to the indoor unit in the standby state, so that the indoor unit operates the indoor fan of the indoor unit at the highest speed gear when detecting that there is no one in the corresponding area.

[0025] The above oil return control method further includes:

[0026] When the outdoor ambient temperature is greater than a first preset temperature and the total energy required by the indoor unit is less than the product of the capacity of the outdoor unit and the first proportional value, a second control signal is sent to the indoor unit in operation so that the indoor unit controls the speed of the indoor fan according to the middle temperature of its own evaporator.

[0027] In a second aspect, an embodiment of the present invention provides an oil return control method, which is applied to an indoor unit in a multi-split system, wherein the indoor unit is provided with multiple units and the multi-split system further includes an outdoor unit. The method comprises:

[0028] For the indoor unit in the running state, when receiving the second control signal from the outdoor unit, the speed of the indoor fan is controlled according to the middle temperature of its own evaporator;

[0029] For the indoor unit in the standby state, when receiving the first control signal from the outdoor unit, it detects whether there is anyone in the corresponding area of ​​the indoor unit, and when it detects that there is no one in the corresponding area, the indoor fan of the indoor unit is operated at the highest speed gear.

[0030] In the above-mentioned oil return control method, the control of the internal fan speed according to the middle temperature of the evaporator itself includes:

[0031] When T2<T2s1, the speed of the internal fan is controlled to remain unchanged;

[0032] When T2≥T2s1, the internal fan is controlled to run at the highest speed gear;

[0033] When T2 ≥ T2s2, a first control signal is sent to the outdoor unit so that the outdoor unit forwards the first control signal to the indoor unit in the standby state; and whether T2 is less than T2s2 is determined again every fifth preset time;

[0034] When T2≥T2s3, a high temperature protection shutdown signal is sent to the outdoor unit, and the indoor fan is controlled to shut down after running for the sixth preset time;

[0035] Wherein: T2 is the middle temperature of the evaporator, T2s1 and T2s2 are preset temperature values, T2s3 is the preset temperature value for shutdown protection, and T2s1<T2s2<T2s3.

[0036] In the above oil return control method, for the indoor unit in the standby state, it is detected whether the first control signal is received every seventh preset time.

[0037] In a third aspect, an embodiment of the present invention provides an oil return control method, which is applied to a multi-split system, wherein the multi-split system includes an external unit and multiple internal units, and the method includes:

[0038] When the preset oil return condition is met, the outdoor unit obtains the outdoor ambient temperature and the total energy demand of the indoor unit, where the total energy demand of the indoor unit is the sum of the capacities of the indoor units in operation;

[0039] When the outdoor ambient temperature is greater than a first preset temperature and the total energy required by the indoor unit is less than the product of the capacity of the outdoor unit and a first proportional value, the outdoor unit obtains the middle temperature of the evaporators of all indoor units in operation and calculates an average of the middle temperature of the evaporators, and then controls the operating frequency of the compressor according to the average temperature of the middle temperature of the evaporators; the outdoor unit also sends a second control signal to the indoor unit in operation;

[0040] The indoor unit receives the second control signal and controls the speed of the indoor fan according to the middle temperature of its own evaporator.

[0041] The oil return control method provided by the embodiment of the present invention has at least the following beneficial effects: when the preset oil return condition is met, the outdoor unit first obtains the outdoor ambient temperature and the total energy demand of the indoor unit. If the outdoor ambient temperature is greater than the first preset temperature, it indicates that the current state is high-temperature heating, which may easily cause the compressor exhaust temperature and exhaust pressure to be too high, thereby triggering a high-pressure protection shutdown; and if the total energy demand of the indoor unit is less than the product of the outdoor unit capacity and the first proportional value, it indicates that there are fewer indoor units in operation and the indoor units have accumulated heat. If the frequency is suddenly increased and the oil return is performed, the exhaust pressure will rise sharply, resulting in a high-pressure protection shutdown; at this time, the outdoor unit controls the operating frequency of the compressor according to the middle temperature of the evaporator of all indoor units in operation, which can avoid the sudden increase in frequency and oil return causing the indoor unit to dissipate heat in time and cause heat accumulation in the indoor unit, thereby avoiding triggering a high-pressure protection shutdown; in addition, the outdoor unit also sends a second control signal to the indoor unit in operation, so that the indoor unit that receives the second control signal can control the speed of the indoor fan according to its own middle temperature of the evaporator, thereby achieving effective heat dissipation of the indoor unit and avoiding heat accumulation in the indoor unit.

[0042] In the above-mentioned oil return control method, controlling the operating frequency of the compressor according to the average temperature of the middle portion of the evaporator includes:

[0043] When T2p≤T2s1, the compressor is controlled to directly increase the frequency to the preset oil return frequency;

[0044] When T2s1<T2p≤T2s2, the operating frequency of the compressor is controlled to increase step by step, and each step runs for the first preset time;

[0045] When T2s2<T2p≤T2s3, the operating frequency of the compressor is controlled to remain unchanged and run for the second preset time;

[0046] When T2p>T2s3, the compressor is controlled to stop running;

[0047] Among them: T2p is the average temperature of the middle part of the evaporator, T2s1 and T2s2 are preset temperature values, T2s3 is the preset temperature value for shutdown protection, and T2s1<T2s2<T2s3.

[0048] In the above-mentioned oil return control method, the control of the internal fan speed according to the middle temperature of the evaporator itself includes:

[0049] When T2<T2s1, the speed of the internal fan is controlled to remain unchanged;

[0050] When T2≥T2s1, the internal fan is controlled to run at the highest speed gear;

[0051] When T2 ≥ T2s2, a first control signal is sent to the outdoor unit, so that the outdoor unit forwards the first control signal to the indoor unit in the standby state, wherein the first control signal is used to indicate that there is a risk of high-temperature tripping and assistance is required; and whether T2 is less than T2s2 is determined again every fifth preset time;

[0052] When T2≥T2s3, a high temperature protection shutdown signal is sent to the outdoor unit, and the indoor fan is controlled to shut down after running for the sixth preset time;

[0053] Wherein: T2 is the middle temperature of the evaporator, T2s1 and T2s2 are preset temperature values, T2s3 is the preset temperature value for shutdown protection, and T2s1<T2s2<T2s3.

[0054] The above oil return control method further includes:

[0055] When the preset oil return condition is met, the outdoor unit controls the electronic expansion valves corresponding to all the indoor units to open to a preset opening;

[0056] When the outdoor unit receives the first control signal, it adjusts the opening of the electronic expansion valve corresponding to the indoor unit according to the middle temperature of the evaporator of the indoor unit; and forwards the first control signal to the indoor unit in the standby state, so that the indoor unit can operate the indoor fan of the indoor unit at the highest speed gear when it detects that there is no one in the corresponding area.

[0057] In the above-mentioned oil return control method, adjusting the opening of the electronic expansion valve corresponding to the indoor unit according to the middle temperature of the evaporator of the indoor unit includes:

[0058] When T2>T2s2, the opening of the electronic expansion valve corresponding to the indoor unit is increased every fourth preset time;

[0059] When T2≤T2s2, reducing the opening of the electronic expansion valve corresponding to the indoor unit every fourth preset time;

[0060] Among them, T2 is the middle temperature of the evaporator of the indoor unit.

[0061] In a fourth aspect, an embodiment of the present invention provides an operation control device, comprising at least one control processor and a memory for communicating with the at least one control processor; the memory stores instructions that can be executed by the at least one control processor, and the instructions are executed by the at least one control processor so that the at least one control processor can execute the return oil control method as described in the embodiment of the first aspect above or execute the return oil control method as described in the embodiment of the second aspect above.

[0062] In a fifth aspect, an embodiment of the present invention provides a multi-connected system, comprising the operation control device as described in the embodiment of the fourth aspect above.

[0063] In a sixth aspect, an embodiment of the present invention provides a computer-readable storage medium, wherein the computer-readable storage medium stores computer-executable instructions, and the computer-executable instructions are used to enable a computer to execute the oil return control method described in the embodiment of the first aspect or the oil return control method described in the embodiment of the second aspect.

[0064] Other features and advantages of the present invention will be described in the following description, and in part will become apparent from the description, or will be understood by practicing the present invention. The purposes and other advantages of the present invention can be realized and obtained by the structures particularly pointed out in the description, claims and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] The accompanying drawings are used to provide a further understanding of the technical solution of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the technical solution of the present invention and do not constitute a limitation to the technical solution of the present invention.

[0066] The present invention will be further described below with reference to the accompanying drawings and embodiments;

[0067] Figure 1 This is a structural diagram of a multi-connected system provided by an embodiment of the present invention;

[0068] Figure 2 This is a flow chart of an oil return control method provided in Example 1 of the present invention;

[0069] Figure 3 This is a flow chart of an oil return control method provided by the second embodiment of the present invention;

[0070] Figure 4 This is a flow chart of an oil return control method provided by Example 3 of the present invention;

[0071] Figure 5 This is a flow chart of an oil return control method provided by the fourth embodiment of the present invention;

[0072] Figure 6 This is a flow chart of an oil return control method provided by Example 5 of the present invention;

[0073] Figure 7 This is a flow chart of an oil return control method provided by Example 6 of the present invention;

[0074] Figure 8 It is a structural diagram of an operation control device provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0075] This section will describe in detail the specific embodiments of the present invention. The preferred embodiments of the present invention are shown in the accompanying drawings. The purpose of the accompanying drawings is to supplement the description of the text part of the specification with graphics, so that people can intuitively and vividly understand each technical feature and the overall technical solution of the present invention, but it should not be understood as a limitation on the scope of protection of the present invention.

[0076] In the description of the present invention, if there is a description of first and second, it is only for the purpose of distinguishing the technical features, and cannot be understood as indicating or implying the relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0077] In the description of the present invention, unless otherwise clearly defined, terms such as setting, installing, and connecting should be understood in a broad sense, and technicians in the relevant technical field can reasonably determine the specific meanings of the above terms in the present invention based on the specific content of the technical solution.

[0078] Currently, when multi-tube, multi-split air conditioners are using the heating function in high-temperature outdoor environments, in order to reduce the problem of high-pressure protection shutdown caused by high ambient temperature operation, the control technologies used include controlling the compressor frequency to maintain a low frequency as much as possible to avoid excessive exhaust pressure and triggering high-pressure protection and shutdown; adjusting the speed of the external fan to reduce outdoor heat exchange, thereby reducing the suction pressure and temperature, thereby reducing exhaust pressure and temperature, or increasing the speed of the internal fan to increase indoor heat exchange, thereby reducing high-pressure pressure and avoiding triggering high-pressure protection and shutdown. In addition, to prevent long-term low-frequency operation from causing compressor lubricating oil to enter the system and be unable to flow back to the compressor, causing oil shortage and wear of the compressor, the compressor frequency is regularly controlled to increase to achieve oil return. The above technologies have greatly expanded the application range of air conditioners, improved user experience, and better met market demand.

[0079] Multi-unit, multi-split systems offer a wide variety of indoor unit combinations, allowing the combined capacity of the indoor units to reach 50% to 135% of the outdoor unit capacity, or even higher. Therefore, when using only the smallest indoor unit for heating, the difference in heat exchange area between the indoor and outdoor units is significant, leading to high system pressure. Even when the compressor is running at minimum frequency and the outdoor fan at minimum speed, insufficient heat dissipation from the indoor units can still easily lead to internal pressure buildup and a high-pressure trip.

[0080] Furthermore, due to the long piping of multi-split systems, prolonged low-frequency operation requires switching to high-frequency oil return. Due to the accumulated heat in the indoor units, a sudden increase in frequency for oil return can cause a sharp increase in exhaust pressure, leading to a high-pressure protection shutdown. Once shut down, the indoor units automatically restart three minutes later with a cold air protection program. The indoor unit fan will not restart until it reaches a certain coil temperature. Therefore, the indoor units cannot dissipate heat in time, making it more likely to reach the high-pressure protection pressure and shut down, affecting the user experience.

[0081] The embodiments of the present invention provide an oil return control method, an operation control device, a multi-split system and a storage medium, which can avoid untimely heat dissipation of an internal unit, thereby causing heat accumulation in the internal unit and triggering a high-voltage protection shutdown.

[0082] The embodiments of the present invention are further described below with reference to the accompanying drawings.

[0083] Reference Figure 1 , Figure 1 This is a structural diagram of a multi-connected system provided by an embodiment of the present invention. The multi-connected system includes one external unit and multiple internal units. Figure 1 In the figure, four indoor units are set as an example, namely indoor unit A, indoor unit B, indoor unit C and indoor unit D. Each indoor unit is provided with an evaporator and an indoor fan. The outdoor unit includes a compressor, a four-way valve, a condenser, a gas-liquid separator and four electronic expansion valves corresponding to the four indoor units. The four electronic expansion valves are electronic expansion valve 1, electronic expansion valve 2, electronic expansion valve 3 and electronic expansion valve 4. The exhaust port of the compressor is connected to the four-way valve, the four-way valve is connected to one end of the condenser, and the other end of the condenser is connected to one end of the four electronic expansion valves respectively. The other ends of the four electronic expansion valves are respectively connected to one end of the evaporator of the corresponding indoor unit, and the other ends of the evaporators of the four indoor units are connected together and connected to the four-way valve. The four-way valve is also connected to the gas-liquid separator, and the gas-liquid separator is then connected to the compressor.

[0084] Reference Figure 2 , Figure 2 Flowchart of an oil return control method provided by Example 1 of the present invention. A first aspect of the present invention provides an oil return control method applied to an external unit in a multi-split system, the multi-split system also including multiple internal units, the method including but not limited to steps S210 to S230.

[0085] Step S210: When the preset oil return condition is met, the outdoor ambient temperature and the total energy requirement of the indoor units are obtained. The total energy requirement of the indoor units is the sum of the capacities of the indoor units in operation.

[0086] It should be noted that the preset oil return condition of a multi-split system generally refers to the compressor operating at a low frequency for a long period of time, for example, the compressor's operating frequency is lower than a certain set frequency value and the continuous operation time reaches a certain set length of time. It is understandable that the preset oil return condition can also be other. For example, if the multi-split system is equipped with a liquid level detection device in the oil sump of the compressor, the preset oil return condition can be set to the detected liquid level of the compressor's oil sump is lower than a certain set liquid level height. This embodiment does not make clear limitations on the preset oil return condition of the multi-split system. Any multi-split system with oil return control can be considered to have a preset oil return condition.

[0087] Step S220: When the outdoor ambient temperature is greater than the first preset temperature and the total energy required by the indoor unit is less than the product of the outdoor unit capacity and the first ratio value, the middle temperature of the evaporator of all indoor units in operation is obtained and the average temperature of the middle evaporator is calculated.

[0088] It is understandable that the outdoor ambient temperature will affect the inlet air temperature of the multi-split system, thereby affecting the heat exchange of the condenser of the outdoor unit; the smaller the total energy required for the indoor unit, the greater the difference in heat exchange area between the indoor and outdoor units, which can easily cause excessive system pressure.

[0089] Step S230: controlling the operating frequency of the compressor according to the average temperature of the middle portion of the evaporator.

[0090] According to the oil return control method provided by an embodiment of the present invention, when the preset oil return conditions are met, the outdoor ambient temperature and the total energy demand of the indoor unit are first obtained. If the outdoor ambient temperature is greater than the first preset temperature, it indicates that the current state is high-temperature heating, which may easily cause the compressor exhaust temperature and exhaust pressure to be too high, thereby triggering a high-pressure protection shutdown; and if the total energy demand of the indoor unit is less than the product of the outdoor unit capacity and the first proportional value, it indicates that there are fewer indoor units in operation, and the indoor units have accumulated heat. If the frequency is suddenly increased and the oil return is performed, the exhaust pressure will rise sharply and a high-pressure protection shutdown will occur; at this time, the operating frequency of the compressor is controlled according to the middle temperature of the evaporator of all indoor units in operation, which can avoid the sudden increase in frequency and oil return, which will cause the indoor unit to dissipate heat in time and cause heat accumulation in the indoor unit, and avoid triggering a high-pressure protection shutdown.

[0091] Reference Figure 3 , Figure 3 This is a flow chart of an oil return control method provided by the second embodiment of the present invention. Figure 2 In the oil return control method of the illustrated embodiment, controlling the operating frequency of the compressor according to the average temperature of the middle portion of the evaporator in step S230 includes:

[0092] When T2p≤T2s1, the compressor is controlled to directly increase the frequency to the preset oil return frequency;

[0093] When T2s1<T2p≤T2s2, the operating frequency of the compressor is controlled to increase step by step, and each step runs for the first preset time;

[0094] When T2s2<T2p≤T2s3, the operating frequency of the compressor is controlled to remain unchanged and run for the second preset time;

[0095] When T2p>T2s3, the compressor is controlled to stop running;

[0096] Among them: T2p is the average temperature of the middle part of the evaporator, T2s1 and T2s2 are preset temperature values, T2s3 is the preset temperature value for shutdown protection, and T2s1<T2s2<T2s3.

[0097] It can be understood that when the average temperature T2p in the middle of the evaporator is less than or equal to the preset temperature value T2s1, it means that the heat accumulation of the indoor unit currently in operation is small, and the risk of high-temperature tripping is low. Therefore, the compressor can directly increase the frequency to the preset oil return frequency to realize the oil return operation of the multi-split system; when the average temperature T2p in the middle of the evaporator is greater than the preset temperature value T2s1 and less than or equal to the preset temperature value T2s2, it means that the heat accumulation of the indoor unit currently in operation is not large, and the risk of high-temperature tripping is not high. Therefore, the compressor can be controlled to increase the frequency, but the operating frequency needs to be increased step by step, and after each step of the operating frequency is increased, it needs to run for the first preset time. Only then can the gear be shifted up again, which can avoid the compressor's exhaust pressure rising sharply and quickly triggering the high-pressure protection shutdown; when the average temperature T2p in the middle of the evaporator is greater than the preset temperature value T2s2 and less than or equal to the preset temperature value T2s3, it means that the heat of the indoor unit currently in operation has accumulated a lot. At this time, it is not advisable to continue to increase the operating frequency of the compressor, otherwise it will easily trigger the high-pressure protection shutdown. The operating frequency of the compressor is controlled to remain unchanged. After running for the second preset time, the oil return timing can be started; when the average temperature T2p in the middle of the evaporator is greater than the shutdown protection preset temperature value T2s3, the high-pressure protection shutdown is triggered, the compressor stops running, and the preset oil return condition is reset.

[0098] Reference Figure 3 In the above oil return control method, when T2p≤T2s2, it is determined again whether T2p is greater than T2s2 every third preset time period.

[0099] Since the operating frequency of the compressor will increase when the average temperature T2p in the middle of the evaporator is less than or equal to the preset temperature value T2s2, the average temperature T2p in the middle of the evaporator will also increase. Therefore, it is necessary to compare the average temperature T2p in the middle of the evaporator and the preset temperature value T2s2 again at regular intervals. If the average temperature T2p in the middle of the evaporator changes to be greater than the preset temperature value T2s2, the operating frequency of the compressor can no longer be increased.

[0100] Reference Figure 4 , Figure 4 This is a flow chart of an oil return control method provided by the third embodiment of the present invention. Figure 2 The oil return control method for an external unit in a multi-split system further includes step S410 and step S420.

[0101] Step S410: When the preset oil return condition is met, the electronic expansion valves corresponding to all indoor units are controlled to open to a preset opening;

[0102] Step S420: When the first control signal is received, the opening of the electronic expansion valve of the corresponding indoor unit is adjusted according to the middle temperature of the evaporator of the indoor unit. The first control signal is issued when the middle temperature of the evaporator of the indoor unit in operation is greater than T2s2, which is used to indicate that there is a risk of high-temperature tripping and assistance is needed.

[0103] After the preset oil return conditions are met, the multi-split system needs to perform oil return control operations, such as compressor frequency increase. At this time, the electronic expansion valves of all indoor units are controlled to open to a certain degree, which can make the refrigerant circulation loop of the multi-split system more unobstructed and better achieve oil return; when the temperature of the middle evaporator of the indoor unit in operation is greater than the preset temperature value T2s2, it means that the indoor unit has accumulated a lot of heat and is likely to trigger a high-pressure protection shutdown. Therefore, a first control signal is sent, indicating that there is a risk of high-temperature tripping and assistance is required. After the outdoor unit receives the first control signal, it adjusts the opening of the electronic expansion valve of the corresponding indoor unit according to the temperature of the middle of the evaporator of the indoor unit, which can effectively reduce the possibility of the indoor unit triggering a high-pressure protection shutdown.

[0104] Reference Figure 5 , Figure 5 This is a flow chart of an oil return control method provided by the fourth embodiment of the present invention. Figure 4 In the oil return control method, step S420 of adjusting the opening of the electronic expansion valve of the corresponding indoor unit according to the middle temperature of the evaporator of the indoor unit includes:

[0105] When T2>T2s2, the opening of the electronic expansion valve of the corresponding indoor unit is increased every fourth preset time;

[0106] When T2≤T2s2, the opening of the electronic expansion valve of the corresponding indoor unit is reduced every fourth preset time;

[0107] Among them, T2 is the middle temperature of the evaporator of the indoor unit.

[0108] It can be understood that if the middle temperature T2 of the evaporator of the indoor unit is greater than the preset temperature value T2s2, the indoor unit has accumulated a lot of heat and is likely to trigger a high-pressure protection shutdown. The outdoor unit controls the opening of the electronic expansion valve of the indoor unit to increase, which is beneficial to reducing the evaporator pressure of the indoor unit and avoiding triggering the high-pressure shutdown protection; if the middle temperature T2 of the evaporator of the indoor unit is less than or equal to the preset temperature value T2s2, it means that the indoor unit has not accumulated much heat and the risk of high-temperature shutdown is not high. The outdoor unit controls the opening of the electronic expansion valve of the indoor unit to decrease, which is beneficial to reducing the evaporator pressure of other indoor units in the system and avoiding other indoor units triggering high-pressure shutdown protection.

[0109] The above oil return control method further includes:

[0110] The first control signal is forwarded to the indoor unit in the standby state, so that the indoor unit operates the indoor fan at the highest speed gear when detecting that there is no one in the corresponding area.

[0111] It can be understood that the outdoor unit receives the first control signal sent by the indoor unit that is at risk of tripping due to high temperature and needs assistance, and forwards it to the indoor unit in standby state, thereby seeking assistance from the indoor unit in standby state. When the indoor unit in standby state detects that there is no one in the corresponding area, it turns on the indoor fan to the maximum speed, which is beneficial to reduce the high pressure of the multi-split system, thereby reducing the shutdown risk of the indoor unit that is at risk of tripping due to high temperature.

[0112] The above oil return control method further includes:

[0113] When the outdoor ambient temperature is greater than the first preset temperature and the total energy required by the indoor unit is less than the product of the outdoor unit capacity and the first proportional value, a second control signal is sent to the indoor unit in operation so that the indoor unit controls the speed of the indoor fan according to the middle temperature of its own evaporator.

[0114] It can be understood that if the outdoor ambient temperature is greater than the first preset temperature, it means that the current state is high-temperature heating, which may easily cause the compressor exhaust temperature and exhaust pressure to be too high, thereby triggering a high-pressure protection shutdown; and if the total energy required by the indoor unit is less than the product of the outdoor unit capacity and the first proportional value, it means that there are fewer indoor units in operation, and the indoor units have accumulated heat. If the frequency is suddenly increased and the oil is returned, the exhaust pressure will rise sharply and a high-pressure protection shutdown will occur; at this time, the outdoor unit sends a second control signal to the indoor unit in operation, so that the indoor unit can control the speed of the internal fan according to the middle temperature of its own evaporator, better adjust the heat exchange effect of its own evaporator, and avoid the middle temperature of the evaporator being too high and reaching the shutdown protection preset temperature value, resulting in a shutdown trigger.

[0115] In addition, a second embodiment of the present invention provides an oil return control method, which is applied to an indoor unit in a multi-split system, wherein the indoor unit is provided with multiple units and the multi-split system also includes an outdoor unit. The method includes:

[0116] For the indoor unit in operation, when receiving the second control signal from the outdoor unit, the speed of the indoor fan is controlled according to the middle temperature of its own evaporator;

[0117] For the indoor unit in the standby state, when receiving the first control signal from the outdoor unit, it detects whether there is anyone in the corresponding area of ​​the indoor unit, and if it is detected that there is no one in the corresponding area, the indoor fan of the indoor unit is operated at the highest speed gear.

[0118] The indoor unit in the running state, after receiving the second control signal from the outdoor unit, controls the speed of the indoor fan according to the middle temperature of its own evaporator, which can better adjust the heat exchange effect of its own evaporator, and avoid the middle temperature of the evaporator being too high and reaching the preset temperature value of the shutdown protection, resulting in triggering a shutdown; the indoor unit in the standby state, after receiving the first control signal from the outdoor unit, detects that there is no one in the corresponding area, and turns the indoor fan to the maximum speed, which is beneficial to reduce the high pressure of the multi-split system, thereby reducing the shutdown risk of the indoor unit that is at risk of high temperature tripping.

[0119] In the above-mentioned oil return control method for an indoor unit in a multi-split system, the speed of the indoor fan is controlled according to the middle temperature of its own evaporator, including:

[0120] When T2<T2s1, the speed of the internal fan is controlled to remain unchanged;

[0121] When T2≥T2s1, the internal fan is controlled to run at the highest speed gear;

[0122] When T2 ≥ T2s2, a first control signal is sent to the outdoor unit so that the outdoor unit forwards the first control signal to the indoor unit in the standby state; and every fifth preset time, it is determined again whether T2 is less than T2s2;

[0123] When T2≥T2s3, a high temperature protection shutdown signal is sent to the outdoor unit, and the indoor fan is controlled to shut down after running for the sixth preset time;

[0124] Wherein: T2 is the middle temperature of the evaporator, T2s1 and T2s2 are preset temperature values, T2s3 is the preset temperature value for shutdown protection, and T2s1<T2s2<T2s3.

[0125] It can be understood that when the middle temperature T2 of the evaporator of the indoor unit is less than or equal to the preset temperature value T2s1, it means that the current middle temperature T2 of the evaporator is low, the risk of high temperature tripping is low, and there is no need to adjust the heat exchange effect of the evaporator; when the average temperature T2p of the middle of the evaporator is greater than the preset temperature value T2s1, it means that the current middle temperature T2 of the evaporator is high, and there is a risk of high temperature tripping, so the indoor fan is controlled to run at the highest speed gear to improve the heat exchange effect of the evaporator, which can reduce the middle temperature T2 of the evaporator and avoid triggering the high temperature protection shutdown of the indoor unit; when the middle temperature T2 of the evaporator is greater than the preset temperature value T2s2, it means that the current middle temperature T2 of the evaporator is very high, and simply increasing the fan speed will cause the indoor unit to trip. The speed cannot reduce the temperature T2 in the middle of the evaporator, which is likely to trigger the high-temperature protection of the indoor unit to trip. At this time, a first control signal is sent to the outdoor unit, so that the outdoor unit forwards the first control signal to the indoor unit in standby state, and requires the assistance of the indoor unit in standby state to reduce the high pressure of the multi-connected system, thereby reducing the temperature T2 in the middle of the evaporator of the indoor unit and reducing the risk of triggering the high-temperature protection of the indoor unit to trip. When the temperature T2 in the middle of the evaporator is greater than the preset temperature value T2s3 of the shutdown protection, the high-temperature protection shutdown is triggered, and a high-temperature protection shutdown signal is sent to the outdoor unit, requesting the outdoor unit to shut down, and controlling the indoor fan to continue running for a period of time before shutting down, which can reduce the evaporator temperature of the indoor unit and is conducive to the normal startup of the indoor unit when it is restarted next time.

[0126] In the above oil return control method, for the indoor unit in the standby state, it is detected whether the first control signal is received every seventh preset time.

[0127] Reference Figure 6 , Figure 6 Flowchart of an oil return control method provided by Embodiment 5 of the present invention. A third embodiment of the present invention provides an oil return control method applied to a multi-split system, the multi-split system including an external unit and multiple internal units, the method including but not limited to steps S610 to S630.

[0128] Step S610: When the preset oil return condition is met, the outdoor unit obtains the outdoor ambient temperature and the total energy demand of the indoor unit, where the total energy demand of the indoor unit is the sum of the capacities of the indoor units in operation;

[0129] Step S620: When the outdoor ambient temperature is greater than a first preset temperature and the total energy required by the indoor unit is less than the product of the outdoor unit capacity and the first proportional value, the outdoor unit obtains the middle temperature of the evaporators of all running indoor units and calculates an average of the middle temperature of the evaporators, and then controls the operating frequency of the compressor based on the average temperature of the middle temperature of the evaporators. The outdoor unit also sends a second control signal to the running indoor unit.

[0130] Step S630: The indoor unit receives the second control signal and controls the speed of the indoor fan according to the middle temperature of its own evaporator.

[0131] According to the oil return control method provided by an embodiment of the present invention, when the preset oil return conditions are met, the outdoor unit first obtains the outdoor ambient temperature and the total energy demand of the indoor unit. If the outdoor ambient temperature is greater than the first preset temperature, it indicates that the current state is high-temperature heating, which may easily cause the compressor exhaust temperature and exhaust pressure to be too high, thereby triggering a high-pressure protection shutdown; and if the total energy demand of the indoor unit is less than the product of the outdoor unit capacity and the first proportional value, it indicates that there are fewer indoor units in operation and the indoor units have accumulated heat. If the frequency is suddenly increased and the oil return is performed, the exhaust pressure will rise sharply and a high-pressure protection shutdown will occur; at this time, the outdoor unit controls the operating frequency of the compressor according to the middle temperature of the evaporator of all indoor units in operation, which can avoid the sudden increase in frequency and oil return causing the indoor unit to dissipate heat in time and cause heat accumulation in the indoor unit, thereby avoiding triggering a high-pressure protection shutdown; in addition, the outdoor unit also sends a second control signal to the indoor unit in operation, so that the indoor unit that receives the second control signal can control the speed of the indoor fan according to its own middle temperature of the evaporator, thereby achieving effective heat dissipation of the indoor unit and avoiding heat accumulation in the indoor unit.

[0132] In addition, it can be understood that after the indoor unit in operation receives the second control signal from the outdoor unit, it controls the speed of the indoor fan according to the middle temperature of its own evaporator, which can better adjust the heat exchange effect of its own evaporator and avoid the middle temperature of the evaporator being too high and reaching the preset temperature value of the shutdown protection, causing the shutdown to be triggered.

[0133] In the above Figure 6 In the oil return control method of the third embodiment provided, controlling the operating frequency of the compressor according to the average temperature of the middle portion of the evaporator in step S620 includes:

[0134] When T2p≤T2s1, the compressor is controlled to directly increase the frequency to the preset oil return frequency;

[0135] When T2s1<T2p≤T2s2, the operating frequency of the compressor is controlled to increase step by step, and each step runs for the first preset time;

[0136] When T2s2<T2p≤T2s3, the operating frequency of the compressor is controlled to remain unchanged and run for the second preset time;

[0137] When T2p>T2s3, the compressor is controlled to stop running;

[0138] Among them: T2p is the average temperature of the middle part of the evaporator, T2s1 and T2s2 are preset temperature values, T2s3 is the preset temperature value for shutdown protection, and T2s1<T2s2<T2s3.

[0139] It can be understood that when the average temperature T2p in the middle of the evaporator is less than or equal to the preset temperature value T2s1, it means that the heat accumulation of the indoor unit currently in operation is small, and the risk of high-temperature tripping is low. Therefore, the compressor can directly increase the frequency to the preset oil return frequency to realize the oil return operation of the multi-split system; when the average temperature T2p in the middle of the evaporator is greater than the preset temperature value T2s1 and less than or equal to the preset temperature value T2s2, it means that the heat accumulation of the indoor unit currently in operation is not large, and the risk of high-temperature tripping is not high. Therefore, the compressor can be controlled to increase the frequency, but the operating frequency needs to be increased step by step, and after each step of the operating frequency is increased, it needs to run for the first preset time. Only then can the gear be shifted up again, which can avoid the compressor's exhaust pressure rising sharply and quickly triggering the high-pressure protection shutdown; when the average temperature T2p in the middle of the evaporator is greater than the preset temperature value T2s2 and less than or equal to the preset temperature value T2s3, it means that the heat of the indoor unit currently in operation has accumulated a lot. At this time, it is not advisable to continue to increase the operating frequency of the compressor, otherwise it will easily trigger the high-pressure protection shutdown. The operating frequency of the compressor is controlled to remain unchanged. After running for the second preset time, the oil return timing can be started; when the average temperature T2p in the middle of the evaporator is greater than the shutdown protection preset temperature value T2s3, the high-pressure protection shutdown is triggered, the compressor stops running, and the preset oil return condition is reset.

[0140] In the above Figure 6 In the oil return control method of the third embodiment provided, controlling the internal fan speed according to the middle temperature of the evaporator itself in step S630 includes:

[0141] When T2<T2s1, the speed of the internal fan is controlled to remain unchanged;

[0142] When T2≥T2s1, the internal fan is controlled to run at the highest speed gear;

[0143] When T2 ≥ T2s2, a first control signal is sent to the outdoor unit, so that the outdoor unit forwards the first control signal to the indoor unit in the standby state. The first control signal is used to indicate that there is a risk of high temperature tripping and assistance is required. Every fifth preset time, it is determined again whether T2 is less than T2s2.

[0144] When T2≥T2s3, a high temperature protection shutdown signal is sent to the outdoor unit, and the indoor fan is controlled to shut down after running for the sixth preset time;

[0145] Wherein: T2 is the middle temperature of the evaporator, T2s1 and T2s2 are preset temperature values, T2s3 is the preset temperature value for shutdown protection, and T2s1<T2s2<T2s3.

[0146] It can be understood that when the middle temperature T2 of the evaporator of the indoor unit is less than or equal to the preset temperature value T2s1, it means that the current middle temperature T2 of the evaporator is low, the risk of high temperature tripping is low, and there is no need to adjust the heat exchange effect of the evaporator; when the average temperature T2p of the middle of the evaporator is greater than the preset temperature value T2s1, it means that the current middle temperature T2 of the evaporator is high, and there is a risk of high temperature tripping, so the indoor fan is controlled to run at the highest speed gear to improve the heat exchange effect of the evaporator, which can reduce the middle temperature T2 of the evaporator and avoid triggering the high temperature protection shutdown of the indoor unit; when the middle temperature T2 of the evaporator is greater than the preset temperature value T2s2, it means that the current middle temperature T2 of the evaporator is very high, and simply increasing the fan speed will cause the indoor unit to trip. The speed cannot reduce the temperature T2 in the middle of the evaporator, which is likely to trigger the high-temperature protection of the indoor unit to trip. At this time, a first control signal is sent to the outdoor unit, so that the outdoor unit forwards the first control signal to the indoor unit in standby state, and requires the assistance of the indoor unit in standby state to reduce the high pressure of the multi-connected system, thereby reducing the temperature T2 in the middle of the evaporator of the indoor unit and reducing the risk of triggering the high-temperature protection of the indoor unit to trip. When the temperature T2 in the middle of the evaporator is greater than the preset temperature value T2s3 of the shutdown protection, the high-temperature protection shutdown is triggered, and a high-temperature protection shutdown signal is sent to the outdoor unit, requesting the outdoor unit to shut down, and controlling the indoor fan to continue running for a period of time before shutting down, which can reduce the evaporator temperature of the indoor unit and is conducive to the normal startup of the indoor unit when it is restarted next time.

[0147] In addition, in the above Figure 6 In the oil return control method of the third embodiment provided, when T2p≤T2s2, it is determined again whether T2p is greater than T2s2 every third preset time period.

[0148] Since the operating frequency of the compressor will increase when the average temperature T2p in the middle of the evaporator is less than or equal to the preset temperature value T2s2, the average temperature T2p in the middle of the evaporator will also increase. Therefore, it is necessary to compare the average temperature T2p in the middle of the evaporator and the preset temperature value T2s2 again at regular intervals. If the average temperature T2p in the middle of the evaporator changes to be greater than the preset temperature value T2s2, the operating frequency of the compressor can no longer be increased.

[0149] In the above Figure 6 The oil return control method of the third embodiment provided further includes:

[0150] When the preset oil return conditions are met, the outdoor unit controls the electronic expansion valves corresponding to all indoor units to open to the preset opening;

[0151] When the outdoor unit receives the first control signal, it adjusts the opening of the electronic expansion valve of the corresponding indoor unit according to the middle temperature of the evaporator of the indoor unit; and forwards the first control signal to the indoor unit in the standby state, so that the indoor unit can operate the indoor fan at the highest speed when it detects that there is no one in the corresponding area.

[0152] After the preset oil return conditions are met, the multi-split system needs to perform oil return control operations, such as compressor frequency increase. At this time, the electronic expansion valves of all indoor units are controlled to open to a certain degree, which can make the refrigerant circulation loop of the multi-split system more unobstructed and better achieve oil return; when the temperature of the middle evaporator of the indoor unit in operation is greater than the preset temperature value T2s2, it means that the indoor unit has accumulated a lot of heat and is likely to trigger a high-pressure protection shutdown. Therefore, a first control signal is sent, indicating that there is a risk of high-temperature tripping and assistance is required. After the outdoor unit receives the first control signal, it adjusts the opening of the electronic expansion valve of the corresponding indoor unit according to the temperature of the middle of the evaporator of the indoor unit, which can effectively reduce the possibility of the indoor unit triggering a high-pressure protection shutdown.

[0153] In addition, it can be understood that the outdoor unit receives the first control signal sent by the indoor unit that is at risk of tripping due to high temperature and needs assistance, and forwards it to the indoor unit in standby state, thereby seeking assistance from the indoor unit in standby state. When the indoor unit in standby state detects that there is no one in the corresponding area, it turns on the indoor fan to the maximum speed, which is beneficial to reduce the high pressure of the multi-split system, thereby reducing the shutdown risk of the indoor unit that is at risk of tripping due to high temperature.

[0154] In the above-mentioned oil return control method, adjusting the opening of the electronic expansion valve of the corresponding indoor unit according to the middle temperature of the evaporator of the indoor unit includes:

[0155] When T2>T2s2, the opening of the electronic expansion valve of the corresponding indoor unit is increased every fourth preset time;

[0156] When T2≤T2s2, the opening of the electronic expansion valve of the corresponding indoor unit is reduced every fourth preset time;

[0157] Among them, T2 is the middle temperature of the evaporator of the indoor unit.

[0158] It can be understood that if the middle temperature T2 of the evaporator of the indoor unit is greater than the preset temperature value T2s2, the indoor unit has accumulated a lot of heat and is likely to trigger a high-pressure protection shutdown. The outdoor unit controls the opening of the electronic expansion valve of the indoor unit to increase, which is beneficial to reducing the evaporator pressure of the indoor unit and avoiding triggering the high-pressure shutdown protection; if the middle temperature T2 of the evaporator of the indoor unit is less than or equal to the preset temperature value T2s2, it means that the indoor unit has not accumulated much heat and the risk of high-temperature shutdown is not high. The outdoor unit controls the opening of the electronic expansion valve of the indoor unit to decrease, which is beneficial to reducing the evaporator pressure of other indoor units in the system and avoiding other indoor units triggering high-pressure shutdown protection.

[0159] Next, combine Figure 1 The structural diagram of the multi-connection system and Figure 7 The control flow chart of the multi-contact system is used to introduce the embodiment of the present invention in detail.

[0160] First, the VRF system starts heating and, after the preset oil return conditions are met, the outdoor unit detects the outdoor ambient temperature T4 and compares it with a first preset temperature Ta. If the outdoor ambient temperature T4 is greater than the first preset temperature Ta, high-temperature heating control is initiated. The first preset temperature Ta can range from 16°C to 26°C. In this example, the first preset temperature Ta is 20°C.

[0161] Next, obtain the capacity of all running indoor units, calculate the sum of the capacities of all running indoor units, and obtain the total energy demand of the indoor units An_in; obtain the capacity of the outdoor units An_out; compare the total energy demand of the indoor units An_in with the capacity of the outdoor units An_out to determine whether there is a trip risk. That is, the relationship between the total energy demand of the indoor units An_in and the capacity of the outdoor units An_out is:

[0162] (1) If An_in ≥ K*An_out, then enter normal heating oil return control;

[0163] (2) If An_in<K*An_out, the system will enter the high-heat anti-trip stop heating and oil return control mode;

[0164] Here, K is a first proportional value, and the value range of K is 0.18 to 0.4. In this example, the value of K is 0.25.

[0165] 1. For normal heating oil return control, the multi-split system performs the following operations:

[0166] 1.1. The compressor directly runs at the preset oil return frequency and exits after the running time meets the time tH. The value range of tH is 3min to 5min;

[0167] 1.2. The electronic expansion valves corresponding to all indoor units are opened to the preset oil return opening PH. After the oil return is completed, the opening of the electronic expansion valves is adjusted to the previous state. The preset oil return opening PH is set to 300P. In this example, the opening range of the electronic expansion valves is 0P to 480P.

[0168] 1.3. The internal fan and air guide plate of the indoor unit remain in their original state.

[0169] 2. For the high-temperature anti-tripping and heating oil return control, the indoor and outdoor units in the multi-split system perform different control operations respectively. The indoor units include those in the running state and those in the standby state. The indoor units in the running state are the energy-demanding indoor units, and the indoor units in the standby state are the standby indoor units. The control of the outdoor units includes the control of the compressor and the control of each electronic expansion valve. The following are detailed introductions:

[0170] 2.1. Control of indoor units, including the control of indoor units by control boxes that have energy demand indoor units.

[0171] 2.1.1. Control of energy-demand indoor units:

[0172] 1. T2_trg-b≤T2<T2_trg+b, maintain the internal fan speed of the indoor unit;

[0173] 2. T2 ≥ T2_trg + b, the indoor fan of the indoor unit immediately runs at the highest wind speed;

[0174] Where T2 is the middle temperature of the indoor unit's evaporator, T2_trg is the heating target temperature, generally ranging from 42°C to 52°C, and in this example, 47°C. b is a correction temperature value, which generally ensures that the heating target temperature T2_trg is within the range of 42°C to 52°C, i.e., b is 5°C. It should be noted that T2_trg + b is the preset temperature value T2s1 in each of the above embodiments.

[0175] 3. If T2>T2_OFF-c, the indoor unit sends a high-temperature trip assist flag to the outdoor unit; the detection is performed once every tb interval, where the value range of time tb can be set to 20s to 120s, and in this example, the value is 40s; T2_OFF is the preset temperature value for shutdown protection, which is also the preset temperature value T2s3 in the above-mentioned embodiments. The preset shutdown protection temperature value T2_OFF is generally set to 62°C; c is a temperature constant, which can be set to a value range of 4°C to 8°C, and in this example, the value is 6°C. In addition, it should be noted that the high-temperature trip assist flag is the first control signal in each of the above-mentioned embodiments; T2_OFF-c is the preset temperature value T2s2 in each of the above-mentioned embodiments;

[0176] 4. When T2>T2_OFF:

[0177] i. The indoor unit sends a high temperature protection shutdown signal, please shut down the outdoor unit;

[0178] ii. The indoor fan of the indoor unit will be turned off after running for ty time according to the set windshield. Restarting the unit or adjusting the settings will clear this command;

[0179] The time ty can be set in the range of 0.5 minutes to 2 minutes. In this example, the time ty is set to 1 minute.

[0180] 2.1.2、Control of the machine within the machine:

[0181] First, determine whether there is someone in the area corresponding to the standby indoor unit; if the infrared device of the standby indoor unit does not detect anyone or the infrared device of the standby indoor unit fails, it is determined that there is someone in the area corresponding to the standby indoor unit;

[0182] The standby indoor units in the corresponding area where people are present will operate according to the mode set by the user, i.e. no adjustments will be made;

[0183] There is no one on standby indoor unit in the corresponding area. It further detects whether it has received the high-temperature trip assistance flag forwarded by the outdoor unit, and detects it once every tz time; if it is detected that the high-temperature trip assistance flag is received, the indoor fan corresponding to the indoor unit is controlled to run at the highest wind speed. If the high-temperature trip assistance flag is not received, the indoor fan corresponding to the indoor unit is controlled to be turned off.

[0184] 2.2 Control of external units, including control of compressors and control of various electronic expansion valves.

[0185] 2.2.1. Control of compressor:

[0186] Summarize the evaporator middle temperatures T2 of all indoor units, and calculate the average evaporator middle temperature T2_Avg based on the evaporator middle temperatures T2 of all indoor units. Make a judgment based on the average evaporator middle temperature T2_Avg:

[0187] 1. T2_Avg≤T2_trg+d, the compressor directly increases the frequency to the preset oil return frequency;

[0188] 2. T2_trg+d<T2_Avg≤T2_OFF-c, the compressor frequency is adjusted one level at a time, and each level stays for ta time. The value range of ta can be set from 10s to 60s. In this example, the value is 20s;

[0189] In steps 1 and 2 above, a check is performed every tb interval to determine whether T2_Avg>T2_OFF-c is satisfied to determine whether there is a trip risk. Time tb is set to be shorter than time ta. For example, the value range of time tb can be set to 10s to 30s. In this embodiment, the value is 10s. If there is no risk, the oil return frequency is increased until the preset oil return frequency is reached, and then the oil return timer starts for 5 minutes. If there is a risk, the process proceeds to step 3 or step 4.

[0190] 3. T2_Avg>T2_OFF-c, the compressor frequency maintains the current frequency. After the current frequency is maintained for ta+a time, the oil return timer starts for 5 minutes. a is the time constant, which can be set from 5s to 20s. In this example, it can be set to 10s.

[0191] 4. T2>T2_OFF, high temperature trip shutdown, oil return conditions are cleared.

[0192] After the above oil return is completed, the frequency returns to the frequency before oil return.

[0193] 2.2.2. Control of each electronic expansion valve:

[0194] After receiving the oil return command, all indoor units adjust the opening of the corresponding electronic expansion valve to the preset oil return opening PH. The preset oil return opening PH can be set in the range of 200P to 350P. In this example, the value is 300P.

[0195] If the outdoor unit receives the high temperature trip assist flag, the opening of the electronic expansion valve of the corresponding indoor unit is adjusted according to the middle temperature T2 of the indoor unit's evaporator:

[0196] The temperature of the middle part of the evaporator of the indoor unit is T2>T2_OFF-c, and the opening of the electronic expansion valve corresponding to the indoor unit increases by P1 every time interval tz;

[0197] The middle temperature of the evaporator of the indoor unit T2 is less than T2_OFF-c, and the opening of the electronic expansion valve corresponding to the indoor unit is reduced by P2 at every interval tz, and is reduced to the heating standby opening P0 at the lowest; the value range of the heating standby opening P0 can be set to 40P to 80P, and the value is 60P in this example; among them, the value range of the time tz can be set to 20s to 120s, and the value is 20s in this example; T2_OFF is the preset temperature value of the shutdown protection, generally 62°C; c is the temperature constant, and the value range can be set to 4°C to 8°C, and the value in this example is 6°C; the value range of the opening P1 can be set to 10P to 20P, and the value in this example is 15P; the value range of the opening P2 can be set to 5P to 15P, and the value in this example is 10P.

[0198] After the oil return is completed, the opening of the electronic expansion valve returns to the opening before the oil return control.

[0199] In addition, refer to Figure 8 In a fourth aspect, an embodiment of the present invention provides an operation control device 800, comprising at least one control processor 810 and a memory 820 for communicating with the at least one control processor 810; the memory 820 stores instructions that can be executed by the at least one control processor 810, and the instructions are executed by the at least one control processor 810 to enable the at least one control processor 810 to execute the oil return control method of the first embodiment or the oil return control method of the second embodiment, for example, to execute Figure 2 Steps S210 to S230 of the method, execution Figure 3 Method flow chart, execution Figure 4 Steps S410 to S420 of the method, execution Figure 5 Method flow chart, execution Figure 6 Steps S610 to S630 of the method or execution Figure 7 Flowchart of the method in .

[0200] In a fifth aspect, an embodiment of the present invention provides a multi-connected system, comprising the operation control device 800 of the embodiment of the fourth aspect above.

[0201] In a sixth aspect, an embodiment of the present invention provides a computer-readable storage medium, wherein the computer-readable storage medium stores computer-executable instructions, and the computer-executable instructions are used to cause a computer to execute the oil return control method of the first embodiment or the oil return control method of the second embodiment, for example, to execute Figure 2 Steps S210 to S230 of the method, execution Figure 3 Method flow chart, execution Figure 4 Steps S410 to S420 of the method, execution Figure 5 Method flow chart, execution Figure 6 Steps S610 to S630 of the method or execution Figure 7 Flowchart of the method in .

[0202] It will be understood by those skilled in the art that all or some of the steps and systems in the methods disclosed above can be implemented as software, firmware, hardware, and appropriate combinations thereof. Some or all of the physical components can be implemented as software executed by a processor, such as a central processing unit, a digital signal processor, or a microprocessor, or as hardware, or as an integrated circuit, such as an application-specific integrated circuit. Such software can be distributed on computer-readable media, which can include computer storage media or non-transitory media and communication media or transient media. As is well known to those skilled in the art, the term computer storage media includes volatile and non-volatile, removable and non-removable media implemented in any method or technology for storing information such as computer-readable instructions, data structures, program modules, or other data. Computer storage media includes, but is not limited to, RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital versatile disks (DVDs) or other optical disk storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to store desired information and can be accessed by a computer. Furthermore, as is well known to those skilled in the art, communication media typically embodies computer-readable instructions, data structures, program modules, or other data in a modulated data signal such as a carrier wave or other transport mechanism, and may include any information delivery media.

[0203] The embodiments of the present invention are described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Various changes can be made within the scope of knowledge possessed by ordinary technicians in the technical field without departing from the spirit of the present invention.

Claims

1. An oil return control method, applied to an external unit in a multi-split system, wherein the multi-split system further comprises a plurality of internal units, each of which is provided with an evaporator and an internal fan, characterized in that: The method comprises: The multi-split system is started and operates for heating; When the preset oil return condition is met, the outdoor ambient temperature and the total energy demand of the indoor units are obtained, where the total energy demand of the indoor units is the sum of the capacities of the indoor units in operation; When the outdoor ambient temperature is greater than a first preset temperature and the total energy required by the indoor unit is less than the product of the capacity of the outdoor unit and the first proportional value, obtaining the middle temperature of the evaporator of all indoor units in operation and calculating an average of the middle temperature of the evaporator; controlling the operating frequency of the compressor according to the average temperature of the middle portion of the evaporator; The oil return control method further includes: When the preset oil return condition is met, the electronic expansion valves corresponding to all indoor units are controlled to open to a preset opening; Upon receiving a first control signal, adjusting the opening of the electronic expansion valve corresponding to the running indoor unit according to the middle temperature of the evaporator of the running indoor unit, wherein the first control signal is issued when the middle temperature of the evaporator of the running indoor unit is greater than a preset temperature value, indicating that there is a risk of high-temperature tripping and assistance is required; The first control signal is forwarded to the indoor unit in the standby state, so that the indoor unit operates the indoor fan of the indoor unit at the highest speed gear when detecting that there is no one in the corresponding area.

2. The oil return control method according to claim 1, characterized in that: The controlling the operating frequency of the compressor according to the average temperature of the middle portion of the evaporator comprises: When T2p≤T2s1, the compressor is controlled to directly increase the frequency to the preset oil return frequency; When T2s1<T2p≤T2s2, the operating frequency of the compressor is controlled to increase step by step, and each step runs for the first preset time; When T2s2<T2p≤T2s3, the operating frequency of the compressor is controlled to remain unchanged and run for the second preset time; When T2p>T2s3, the compressor is controlled to stop running; Among them: T2p is the average temperature of the middle part of the evaporator, T2s1 and T2s2 are preset temperature values, T2s3 is the preset temperature value for shutdown protection, and T2s1<T2s2<T2s3.

3. The oil return control method according to claim 2, characterized in that: When T2p≤T2s2, it is determined again whether T2p is greater than T2s2 every third preset time period.

4. The oil return control method according to claim 1, characterized in that: The adjusting the opening of the electronic expansion valve corresponding to the indoor unit according to the middle temperature of the evaporator of the indoor unit includes: When T2>T2s2, the opening of the electronic expansion valve corresponding to the indoor unit is increased every fourth preset time; When T2≤T2s2, reducing the opening of the electronic expansion valve corresponding to the indoor unit every fourth preset time; Among them, T2 is the middle temperature of the evaporator of the indoor unit.

5. The oil return control method according to claim 1, characterized in that: Also includes: When the outdoor ambient temperature is greater than a first preset temperature and the total energy required by the indoor unit is less than the product of the capacity of the outdoor unit and the first proportional value, a second control signal is sent to the indoor unit in operation so that the indoor unit controls the speed of the indoor fan according to the middle temperature of its own evaporator.

6. An oil return control method, applied to an indoor unit in a multi-split system, wherein the indoor unit is provided with a plurality of units, each of which is provided with an evaporator and an indoor fan, and the multi-split system further includes an outdoor unit, characterized in that: The method comprises: The multi-split system is started and operates for heating; For the indoor unit in the running state, when receiving the second control signal from the outdoor unit, the speed of the indoor fan is controlled according to the middle temperature of its own evaporator; For the indoor unit in the standby state, when it receives the first control signal from the outdoor unit, it detects whether there is anyone in the corresponding area of ​​the indoor unit, and when it detects that there is no one in the corresponding area, it operates the indoor fan of the indoor unit at the highest speed gear; wherein, the first control signal is sent by the indoor unit in the running state to the outdoor unit and forwarded by the outdoor unit when the temperature in the middle of the evaporator is greater than the preset temperature value, and is used to indicate that there is a risk of high-temperature tripping and assistance is needed.

7. The oil return control method according to claim 6, characterized in that: The method of controlling the internal fan speed according to the middle temperature of the evaporator itself includes: When T2<T2s1, the speed of the internal fan is controlled to remain unchanged; When T2≥T2s1, the internal fan is controlled to run at the highest speed gear; When T2 ≥ T2s2, a first control signal is sent to the outdoor unit so that the outdoor unit forwards the first control signal to the indoor unit in the standby state; and whether T2 is less than T2s2 is determined again every fifth preset time; When T2≥T2s3, a high temperature protection shutdown signal is sent to the outdoor unit, and the indoor fan is controlled to shut down after running for the sixth preset time; Wherein: T2 is the middle temperature of the evaporator, T2s1 and T2s2 are preset temperature values, T2s3 is the preset temperature value for shutdown protection, and T2s1<T2s2<T2s3.

8. The oil return control method according to claim 6, characterized in that: For the indoor unit in the standby state, it is detected whether the first control signal is received every seventh preset time.

9. An oil return control method, applied to a multi-split system, wherein the multi-split system includes an external unit and multiple internal units, each of which is provided with an evaporator and an internal fan, characterized in that: The method comprises: The multi-split system is started and operates for heating; When the preset oil return condition is met, the outdoor unit obtains the outdoor ambient temperature and the total energy demand of the indoor unit, where the total energy demand of the indoor unit is the sum of the capacities of the indoor units in operation; When the outdoor ambient temperature is greater than a first preset temperature and the total energy required by the indoor unit is less than the product of the capacity of the outdoor unit and a first proportional value, the outdoor unit obtains the middle temperature of the evaporators of all indoor units in operation and calculates an average of the middle temperature of the evaporators, and then controls the operating frequency of the compressor according to the average temperature of the middle temperature of the evaporators; the outdoor unit also sends a second control signal to the indoor unit in operation; The indoor unit receives the second control signal and controls the speed of the indoor fan according to the middle temperature of its own evaporator; The oil return control method further includes: When the preset oil return condition is met, the outdoor unit controls the electronic expansion valves corresponding to all indoor units to open to a preset opening; When the outdoor unit receives the first control signal, the opening of the electronic expansion valve corresponding to the indoor unit is adjusted according to the middle temperature of the evaporator of the indoor unit in operation. The first control signal is issued when the middle temperature of the evaporator of the indoor unit in operation is greater than a preset temperature value, indicating that there is a risk of high-temperature tripping and assistance is required; The outdoor unit forwards the first control signal to the indoor unit in a standby state, so that the indoor unit operates the indoor fan at the highest speed gear when detecting that no one is in the corresponding area.

10. The oil return control method according to claim 9, characterized in that: The controlling the operating frequency of the compressor according to the average temperature of the middle portion of the evaporator comprises: When T2p≤T2s1, the compressor is controlled to directly increase the frequency to the preset oil return frequency; When T2s1<T2p≤T2s2, the operating frequency of the compressor is controlled to increase step by step, and each step runs for the first preset time; When T2s2<T2p≤T2s3, the operating frequency of the compressor is controlled to remain unchanged and run for the second preset time; When T2p>T2s3, the compressor is controlled to stop running; Among them: T2p is the average temperature of the middle part of the evaporator, T2s1 and T2s2 are preset temperature values, T2s3 is the preset temperature value for shutdown protection, and T2s1<T2s2<T2s3.

11. The oil return control method according to claim 9, characterized in that: The method of controlling the internal fan speed according to the middle temperature of the evaporator itself includes: When T2<T2s1, the speed of the internal fan is controlled to remain unchanged; When T2≥T2s1, the internal fan is controlled to run at the highest speed gear; When T2 ≥ T2s2, a first control signal is sent to the outdoor unit, so that the outdoor unit forwards the first control signal to the indoor unit in the standby state, wherein the first control signal is used to indicate the risk of high-temperature tripping. Whether T2 is less than T2s2 is determined again every fifth preset time interval. When T2≥T2s3, a high temperature protection shutdown signal is sent to the outdoor unit, and the indoor fan is controlled to shut down after running for the sixth preset time; Wherein: T2 is the middle temperature of the evaporator, T2s1 and T2s2 are preset temperature values, T2s3 is the preset temperature value for shutdown protection, and T2s1<T2s2<T2s3.

12. The oil return control method according to claim 11, characterized in that: The adjusting the opening of the electronic expansion valve corresponding to the indoor unit according to the middle temperature of the evaporator of the indoor unit includes: When T2>T2s2, the opening of the electronic expansion valve corresponding to the indoor unit is increased every fourth preset time; When T2≤T2s2, reducing the opening of the electronic expansion valve corresponding to the indoor unit every fourth preset time; Among them, T2 is the middle temperature of the evaporator of the indoor unit.

13. An operation control device, characterized in that: The invention comprises at least one control processor and a memory for communicating with the at least one control processor; the memory stores instructions executable by the at least one control processor, and the instructions are executed by the at least one control processor to enable the at least one control processor to execute the oil return control method according to any one of claims 1 to 5 or the oil return control method according to any one of claims 6 to 8.

14. A multi-connection system, characterized in that: Including the operation control device according to claim 13.

15. A computer-readable storage medium, characterized in that The computer-readable storage medium stores computer-executable instructions, and the computer-executable instructions are used to enable a computer to execute the oil return control method according to any one of claims 1 to 5 or the oil return control method according to any one of claims 6 to 8.

Images