Control method for multi-split air conditioning system and multi-split air conditioning system

Abstract

The present application relates to a control method for a multi-split air conditioning system and a multi-split air conditioning system. When the multi-split air conditioning system is in a cold-blast prevention mode, the control method comprises: when multiple indoor units of the multi-split air conditioning system are started at the same time, controlling an electronic expansion valve of each indoor unit to be opened at an initial opening degree; setting a target opening sequence of the electronic expansion valves of the multiple indoor units; obtaining a running frequency of a compressor of the multi-split air conditioning system; comparing the running frequency with a preset frequency threshold; when the running frequency exceeds the preset frequency threshold, controlling the electronic expansion valves of the multiple indoor units to be opened one by one at a maximum opening degree according to the target opening sequence, wherein the initial opening degree is smaller than the maximum opening degree. The control method can effectively shorten the time of cold-blast prevention and improve the user experience.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of refrigeration systems, in particular to a control method for a multi-split air conditioning system and a multi-split air conditioning system. BACKGROUND

[0002] A multi-split air conditioning system (or "multi-connected system") generally refers to an air conditioner with N indoor units (N is an integer greater than 1). During use, the user will randomly turn on one, two, three, or N indoor units according to actual needs. For example, Chinese patent CN106352611B discloses such a multi-split air conditioning system. The multi-split air conditioning system includes an outdoor unit and at least two indoor heat exchangers (equivalent to two indoor units) that can form a refrigeration circuit with the outdoor unit. The outdoor unit includes a compressor, a four-way valve, an outdoor heat exchanger, and an electronic expansion valve arranged in the same refrigeration circuit. The outdoor unit can also include more than one compressor to meet larger load requirements.

[0003] To ensure user experience, a multi-split air conditioning system, like other types of air conditioners, usually has a "anti-cold wind mode". When the indoor environment temperature is low, the indoor unit fan will not start immediately after the indoor unit is turned on. Only when the indoor heat exchanger coil temperature exceeds a certain threshold, the indoor unit fan will start to avoid blowing cold air when the indoor unit is heating. However, when multiple indoor units of a multi-split air conditioning system are turned on at the same time, due to the long refrigerant pipe between the indoor and outdoor units, and other factors such as outdoor low temperature, the suction pressure of the compressor will be too small and the operating frequency will be too low, resulting in a long anti-cold wind time and greatly reducing user experience.

[0004] Therefore, there is a need in the art for a new technical solution to solve the above problems. SUMMARY

[0005] To solve the technical problem of the anti-cold wind time being too long when multiple indoor units of a multi-split air conditioning system are turned on at the same time in the prior art, the present application provides a control method for a multi-split air conditioning system. When the multi-split air conditioning system is in an anti-cold wind mode, the control method comprises: when multiple indoor units of the multi-split air conditioning system are turned on at the same time, controlling the electronic expansion valve of each indoor unit to open at an initial opening degree; setting a target opening sequence of the electronic expansion valves of the multiple indoor units; obtaining the operating frequency of the compressor of the multi-split air conditioning system; comparing the operating frequency with a preset frequency threshold; when the operating frequency exceeds the preset frequency threshold, controlling the electronic expansion valves of the multiple indoor units to open one by one at a maximum opening degree according to the target opening sequence, wherein the initial opening degree is less than the maximum opening degree.

[0006] In the control method for a multi-split air conditioning system, when the multi-split air conditioning system is in a cold-blast prevention mode and when multiple indoor units of the multi-split air conditioning system are started at the same time, first, an electronic expansion valve of each started indoor unit is controlled to be initially opened. Then, a target opening sequence of the electronic expansion valves of the multiple started indoor units is set. Then, a running frequency of a compressor of the multi-split air conditioning system is obtained. The obtained running frequency of the compressor is compared with a preset frequency threshold. When the running frequency exceeds the preset frequency threshold, it indicates that the running frequency of the compressor is high at this time, and the suction pressure is also maintained at a high level, and then the electronic expansion valves of the multiple indoor units are controlled to be opened at a maximum opening degree according to the set target opening sequence one by one. In this way, it can be avoided that the electronic expansion valves of all the started indoor units are opened at the maximum opening degree at the same time, and the suction pressure of the compressor is prevented from being too small to trigger low pressure protection, so that the compressor can run smoothly at a high running frequency, thereby shortening the total time of cold-blast prevention and improving the user experience.

[0007] In the preferred technical solution of the control method for a multi-split air conditioning system, the step of setting the target opening sequence of the electronic expansion valves of the multiple indoor units comprises: obtaining a tonnage of each of the multiple indoor units; and determining the target opening sequence according to the tonnages, wherein the smaller the tonnage, the earlier the corresponding electronic expansion valve is in the target opening sequence. According to the tonnages of the indoor units, the target opening sequence of the electronic expansion valves is set, and the smaller the tonnage, the earlier the corresponding electronic expansion valve is in the target opening sequence. This not only makes the operation of the entire multi-split air conditioning system more stable, but also simplifies the setting logic of the target opening sequence.

[0008] In the preferred technical solution of the control method for a multi-split air conditioning system, the step of setting the target opening sequence of the electronic expansion valves of the multiple indoor units further comprises: when the tonnages of at least some of the multiple indoor units are the same, obtaining a distance of a refrigerant pipeline between each of the indoor units with the same tonnage and the compressor; and determining the target opening sequence according to the distances of the refrigerant pipelines, wherein the smaller the distance of the refrigerant pipeline, the earlier the corresponding electronic expansion valve is in the target opening sequence. When the tonnages of multiple indoor units are the same, the target opening sequence is set according to the distances of the refrigerant pipelines between the indoor units and the compressor, and the smaller the distance of the refrigerant pipeline, the earlier the corresponding electronic expansion valve is in the target opening sequence. This can further simplify the setting logic of the target opening sequence and determine the stable operation of the system.

[0009] In the preferred technical scheme of the control method for the multi-split air conditioning system, when the operating frequency does not exceed the preset frequency threshold, the compressor is controlled to increase the frequency at a preset frequency increasing rate. When the operating frequency of the compressor does not exceed the preset frequency threshold, it indicates that the operating frequency of the compressor is relatively low at this time, and the compressor is controlled to increase the frequency at a preset frequency increasing rate to meet the load requirement of the system.

[0010] In the preferred technical scheme of the control method for the multi-split air conditioning system, after a preset time period, the suction pressure of the compressor is obtained, the suction pressure is compared with a preset suction pressure threshold, when the suction pressure exceeds the preset suction pressure threshold, the compressor continues to be controlled to increase the frequency at the preset frequency increasing rate, and when the suction pressure does not exceed the preset suction pressure threshold, the compressor is kept operating at the current operating frequency. Through the above setting, the compressor is controlled to increase the frequency based on the suction pressure, so as to gradually increase the operating frequency of the compressor on the basis of ensuring that the suction pressure has a relatively high level, so as to meet the cold wind prevention requirement when multiple indoor units are started at the same time.

[0011] In the preferred technical scheme of the control method for the multi-split air conditioning system, the preset suction pressure threshold is 0.3-0.5 MPa. Through the above setting, the preset suction pressure threshold has a moderate range.

[0012] In the preferred technical scheme of the control method for the multi-split air conditioning system, when the electronic expansion valve of the indoor unit is opened at the maximum opening degree, the control method further comprises: obtaining the temperature of the corresponding indoor unit; comparing the temperature of the corresponding indoor unit with a preset coil temperature threshold; and when the temperature of the corresponding indoor unit exceeds the preset coil temperature threshold, controlling the indoor fan of the corresponding indoor unit to be started. When the electronic expansion valve of the indoor unit is opened at the maximum opening degree, the indoor fan of the corresponding indoor unit is controlled to be started by comparing the temperature of the corresponding indoor unit with the preset coil temperature, so as to control the indoor unit to exit the cold wind prevention mode.

[0013] In the preferred technical scheme of the control method for the multi-split air conditioning system, the ratio between the initial opening degree and the maximum opening degree ranges from 1 / 6 to 1 / 3. Through the above setting, the initial opening degree has a moderate range.

[0014] In the preferred technical scheme of the control method for the multi-split air conditioning system, the preset frequency threshold ranges from 60 Hz to 80 Hz. Through the above setting, the preset frequency threshold has a moderate range.

[0015] To solve the technical problem of long anti-cold air time when multiple indoor units of a multi-split air conditioning system are started simultaneously in the prior art, the present application provides a multi-split air conditioning system. The control method for a multi-split air conditioning system according to any one of the above is performed in the multi-split air conditioning system. By adopting the control method for a multi-split air conditioning system according to any one of the above, the multi-split air conditioning system of the present application can avoid that the electronic expansion valves of all the started indoor units are opened together at the maximum opening degree at the same time, prevent the triggering of low-pressure protection due to too small suction pressure of the compressor, enable the compressor to run smoothly at a higher operating frequency, thereby shortening the total anti-cold air time and improving the user experience. BRIEF DESCRIPTION OF DRAWINGS

[0016] The preferred embodiments of the present application are described below with reference to the accompanying drawings, in which:

[0017] Figure 1 is a system schematic diagram of an embodiment of the multi-split air conditioning system of the present application;

[0018] Figure 2 is a flowchart of the control method for a multi-split air conditioning system of the present application;

[0019] Figure 3 is a flowchart of an embodiment of the control method for a multi-split air conditioning system of the present application.

[0020] Reference Signs:

[0021] 1, multi-split air conditioning system; 11, outdoor unit; 111, compressor; 112, gas-liquid separator; 113, outdoor heat exchanger; 114, outdoor fan; 115, distributor; 116, four-way valve; 117, liquid stop valve; 118, gas stop valve; 119, gaseous refrigerant header; 120, liquid refrigerant header; 121a, first filter; 121b, second filter; 121c, third filter; 121d, fourth filter; 122a, first electronic expansion valve; 122b, second electronic expansion valve; 122c, third electronic expansion valve; 122d, fourth electronic expansion valve; 123a, first gas pipe connection branch; 123b, second gas pipe connection branch; 123c, third gas pipe connection branch; 123d, fourth gas pipe connection branch; 124a, first liquid pipe connection branch; 124b, second liquid pipe connection branch; 124c, third liquid pipe connection branch; 124d, fourth liquid pipe connection branch; 125, discharge pressure sensor; 126, outdoor heat exchanger temperature sensor; 127, defrosting sensor; 128, outdoor electronic expansion valve; 21, indoor unit; 211, indoor heat exchanger; 212, indoor fan; 213, indoor heat exchanger temperature sensor. DETAILED DESCRIPTION

[0022] The preferred embodiments of the present application will be described below with reference to the accompanying drawings. Those skilled in the art will appreciate that the embodiments are only used to explain the technical principles of the present application and are not intended to limit the scope of protection of the present application.

[0023] To solve the technical problem of long anti-cold wind time when multiple indoor units of a multi-split air conditioning system are started simultaneously in the prior art, the present application provides a control method for a multi-split air conditioning system 1. When the multi-split air conditioning system 1 is in an anti-cold wind mode, the control method comprises: when multiple indoor units 21 of the multi-split air conditioning system 1 are started simultaneously, controlling an electronic expansion valve of each indoor unit 21 to be opened at an initial opening degree (step S1); setting a target opening sequence of the electronic expansion valves of the multiple indoor units 21 (step S2); obtaining a running frequency of a compressor 111 of the multi-split air conditioning system 1; comparing the running frequency with a preset frequency threshold (step S3); and when the running frequency exceeds the preset frequency threshold, controlling the electronic expansion valves of the multiple indoor units 21 to be opened one by one at a maximum opening degree according to the target opening sequence, wherein the initial opening degree is less than the maximum opening degree (step S4).

[0024] Figure 1 is a system schematic diagram of an embodiment of the multi-split air conditioning system of the present application. As shown in Figure 1 In one or more embodiments, the multi-split air conditioning system 1 of the present application includes an outdoor unit 11 (which is generally arranged in an outdoor environment) and multiple parallel indoor units 21 (which are generally arranged in an indoor or room) that can be interconnected into a refrigeration circuit allowing refrigerant to flow therein. In one or more embodiments, the multi-split air conditioning system 1 has four parallel indoor units 21. Figure 1 Only one indoor unit A is shown, and the remaining three indoor units B-D are omitted. The configuration of the four indoor units 21 can be the same or different according to actual needs. Alternatively, the multi-split air conditioning system 1 can have two indoor units 21, three indoor units 21, or more than four indoor units 21.

[0025] As shown in Figure 1 In one or more embodiments, the outdoor unit 11 mainly includes a compressor 111, a gas-liquid separator 112, an outdoor heat exchanger 113, an outdoor fan 114, a four-way valve 116, and an electronic expansion valve, etc. Due to the presence of the four-way valve 116, the multi-split air conditioning system 1 of the present application at least has refrigeration and heating functions. Alternatively, the outdoor unit 11 can not include the four-way valve 116, which means that the multi-split air conditioning system 1 only has heating function.

[0026] As shown in Figure 1As shown, in one or more embodiments, the compressor 111 is a variable speed compressor. Alternatively, the compressor 111 can include two or more compressors connected in parallel. These compressors can all be variable speed compressors or can include some variable speed compressors. The compressor 111 has a suction port and a discharge port (not shown). The discharge port of the compressor 111 is connected to a compressor connection port on the four-way valve 116 through refrigerant lines (i.e., pipes that allow refrigerant to flow therethrough). An discharge pressure sensor 125 is disposed on the refrigerant line near the discharge port of the compressor 111 to measure the discharge pressure of the compressor 111. The suction port of the compressor 111 is connected to an outlet port on the gas-liquid separator 112 through a refrigerant line, and an inlet port on the gas-liquid separator 112 is connected to a gas-liquid separator connection port on the four-way valve 116 through a refrigerant line. A suction pressure sensor (not shown) is also disposed on the refrigerant line near the suction port of the compressor 111 to measure the suction pressure of the compressor 111. The four-way valve 116 also has an outdoor heat exchanger connection port and an indoor heat exchanger connection port. One end of the outdoor heat exchanger 113 is connected to the outdoor heat exchanger connection port of the four-way valve 116 through a refrigerant line. The outdoor heat exchanger 113 can be, but is not limited to, a finned coil heat exchanger and a plate heat exchanger, and is provided with an outdoor fan 114. The other end of the outdoor heat exchanger 113 is connected to the distributor 115. The outdoor heat exchanger 113 also has an outdoor heat exchanger temperature sensor 126 and a defrost sensor 127 disposed thereon, respectively.

[0027] As shown, Figure 1 The indoor heat exchanger connection port of the four-way valve 116 is connected to a gaseous refrigerant header 119 through a refrigerant line, and a gas shut-off valve 118 is disposed on the refrigerant line. The gaseous refrigerant header 119 has four gas tube connection branches, a first gas tube connection branch 123a, a second gas tube connection branch 123b, a third gas tube connection branch 123c, and a fourth gas tube connection branch 123d. Each gas tube connection branch can be connected to a corresponding indoor unit 21.

[0028] As shown, Figure 1As shown, the distributor 115 is connected to the liquid refrigerant header 120 through a refrigerant line, and a liquid shut-off valve 117 and an outdoor electronic expansion valve 128 are arranged on the refrigerant line. The liquid refrigerant header 120 is provided with four liquid pipe connection branches, i.e., a first liquid pipe connection branch 124a, a second liquid pipe connection branch 124b, a third liquid pipe connection branch 124c and a fourth liquid pipe connection branch 124d. Each liquid pipe connection branch can be connected to a corresponding indoor unit 21. In addition, a first filter 121a and a first electronic expansion valve 122a are arranged on the first liquid pipe connection branch 124a, wherein the first filter 121a is located between the corresponding indoor unit 21 and the first electronic expansion valve 122a. A second filter 121b and a second electronic expansion valve 122b are arranged on the second liquid pipe connection branch 124b, wherein the second filter 121b is located between the corresponding indoor unit 21 and the second electronic expansion valve 122b. A third filter 121c and a third electronic expansion valve 122c are arranged on the third liquid pipe connection branch 124c, wherein the third filter 121c is located between the corresponding indoor unit 21 and the third electronic expansion valve 122c. A fourth filter 121d and a fourth electronic expansion valve 122d are arranged on the fourth liquid pipe connection branch 124d, wherein the fourth filter 121d is located between the corresponding indoor unit 21 and the fourth electronic expansion valve 122d.

[0029] It should be noted that, in this article, unless explicitly stated otherwise, the technical term "electronic expansion valve of an indoor unit" refers to the electronic expansion valve corresponding to each indoor unit 21, rather than the outdoor electronic expansion valve 128. For example, the first electronic expansion valve 122a corresponding to the indoor unit A, the second electronic expansion valve 122b corresponding to the indoor unit B, the third electronic expansion valve 122c corresponding to the indoor unit C, and the fourth electronic expansion valve 122d corresponding to the indoor unit D. In the normal cooling mode, the outdoor electronic expansion valve 128 is fully open, and the electronic expansion valves of the indoor units play the role of expansion pressure reduction in the refrigeration system by adjusting the respective opening degrees; in the normal heating case, the electronic expansion valves of the indoor units are fully open, and the outdoor electronic expansion valve 128 plays the role of expansion pressure reduction in the refrigeration system by adjusting its own opening degree.

[0030] Next, the control method of the present application for the multi-split air conditioning system 1 will be described in detail. Figures 2-3 The control method of the present application for the multi-split air conditioning system 1 will be described in detail.

[0031] Figure 2 is a flowchart of the control method of the present application for the multi-split air conditioning system. As shown in the flowchart, the control method comprises the following steps. Figure 2As shown, in one or more embodiments, when the present application is used in a VRF air conditioning system 1 in the anti-cold wind mode, after the control method starts, first, step S1 is performed, that is, when multiple indoor units 21 of the VRF air conditioning system 1 are started at the same time, the electronic expansion valve of each indoor unit 21 is opened at an initial opening degree. The condition for entering the anti-cold wind mode can be set according to actual needs. For example, when the indoor environment temperature is 10°C, and the coil temperature (i.e., the coil temperature of the indoor heat exchanger 211) of the indoor unit 21 that is started is lower than 20°C, the VRF air conditioning system 1 enters the anti-cold wind mode. After multiple indoor units 21 obtain the start signal at the same time, the control method of the present application does not open the electronic expansion valve of each indoor unit 21 at the maximum opening degree, but at the initial opening degree. Then, the control method performs step S2, that is, sets the target opening sequence of the electronic expansion valve of multiple indoor units 21. Then, the control method proceeds to step S3, and obtains the operating frequency of the compressor 111 of the VRF air conditioning system 1. After step S3 is completed, the operating frequency is compared with the preset frequency threshold value (i.e., step S4). In one or more embodiments, the preset frequency threshold value ranges from 60Hz to 80Hz. For example, the preset frequency threshold value can be 60Hz, 70Hz, 80Hz, etc. When the operating frequency exceeds the preset frequency threshold value, the electronic expansion valve of each indoor unit 21 is controlled to be opened at the maximum opening degree according to the target opening sequence, wherein the initial opening degree is less than the maximum opening degree (i.e., step S5). In one or more embodiments, the ratio of the initial opening degree to the maximum opening degree ranges from 1 / 6 to 1 / 3. For example, the maximum opening degree of the electronic expansion valve is 300 steps, and the initial opening degree is 50 steps. By opening the electronic expansion valve of each indoor unit 21 according to the set target opening sequence one by one instead of simultaneously, the control method of the present application can make the compressor 111 have a higher operating frequency, shorten the total time of anti-cold wind, and improve the user experience.

[0032] Figure 3 is a flowchart of an embodiment of the control method of the present application for a VRF air conditioning system. As Figure 3As shown, in one or more embodiments, when the multi-split air conditioning system 1 is in the anti-cold-blast mode, the control method for the multi-split air conditioning system 1 of the present application, after starting, first performs step S1, i.e. when multiple indoor units 21 of the multi-split air conditioning system 1 are started at the same time, controls the electronic expansion valve of each indoor unit 21 to open at an initial opening degree. Then, the number of matches of each of the multiple indoor units 21 is obtained (i.e. step S20). Then, according to the size of the number of matches, the target opening sequence is determined (i.e. step S21). Among them, the smaller the number of matches, the earlier the corresponding electronic expansion valve is in the target opening sequence. For example, four indoor units A-D are started at the same time, the number of matches of indoor unit A is 1.5P, the number of matches of indoor unit B is 2P, the number of matches of indoor unit C is 2.5P, and the number of matches of indoor unit D is 3P. Then, the target opening sequence of the four indoor units 21 is indoor unit A, indoor unit B, indoor unit C, and indoor unit D. In one or more embodiments, when the number of matches of at least part of the multiple indoor units 21 is the same, the step of setting the target opening sequence further includes: obtaining the distance of the refrigerant pipeline between each of the indoor units 21 with the same number of matches and the compressor 111; according to the size of the distance of the refrigerant pipeline, the target opening sequence is determined, wherein the smaller the distance of the refrigerant pipeline, the earlier the corresponding electronic expansion valve is in the target opening sequence. For example, five indoor units a-e are started at the same time, the number of matches of indoor units a and b is 1.5P, the number of matches of indoor units c and d is 2P, and the number of matches of indoor unit e is 2.5P. The refrigerant pipeline between indoor unit a and the compressor 111 is shorter than the refrigerant pipeline between indoor unit b and the compressor 111, and the refrigerant pipeline between indoor unit c and the compressor 111 is longer than the refrigerant pipeline between indoor unit d and the compressor 111. Then, the set target opening sequence is indoor unit a, indoor unit b, indoor unit d, indoor unit c, and indoor unit e. Through the above setting, the stable operation of the multi-split air conditioning system 1 can be ensured on the basis of simplifying the setting logic of the target opening sequence.

[0033] Continuing to refer to Figure 3 When step S21 is completed, the control method proceeds to step S30, i.e. the running frequency of the compressor 111 of the multi-split air conditioning system 1 is obtained. Then, it is judged whether the running frequency is greater than a preset frequency threshold (i.e. step S40). When the judgment result is yes, it means that the running frequency of the compressor 111 is high at this time, and then the electronic expansion valves of the multiple indoor units 21 are controlled to open at the maximum opening degree according to the target opening sequence (step S50).

[0034] Continuing to refer to Figure 3When the electronic expansion valve of the indoor unit 21 is opened at the maximum opening degree, the control method further performs step S60, i.e. acquires the corresponding indoor unit 21 coil temperature. In one or more embodiments, the coil temperature of the indoor unit 21 can be measured by the indoor heat exchanger temperature sensor 213 arranged at the indoor heat exchanger 211. Then, it is judged whether the coil temperature is greater than a preset coil temperature threshold (i.e. step S61). In one or more embodiments, the preset coil temperature threshold is a certain fixed value, for example 21℃, 23℃, 25℃, etc. Alternatively, the preset coil temperature threshold can also be set as a variable value adjusted according to the indoor environment temperature. For example, when the indoor environment temperature is 10℃, the preset coil temperature threshold is 20℃; when the indoor environment temperature is 15℃, the preset coil temperature threshold is 25℃. When the judgment result is no, it means that the coil temperature of the indoor unit 21 is still low at this time, and then step S60 is repeatedly performed, i.e. the corresponding indoor unit 21 coil temperature is continuously acquired. When the judgment result is yes, it means that the coil temperature of the indoor unit 21 is already high at this time, and then the indoor fan 212 of the corresponding indoor unit 21 is controlled to be turned on (step S62), so as to control the indoor unit 21 to exit the cold blast prevention mode.

[0035] With reference back to Figure 3After step S40 is performed, if the result of the determination is no, indicating that the operating frequency of the compressor 111 is still low at this time, the compressor 111 is controlled to increase the operating frequency at a preset frequency increasing rate (i.e., step S70). The specific value of the preset frequency increasing rate can be adjusted according to actual needs and the type of the compressor 111. Then, after a preset time period, the suction pressure of the compressor 111 is obtained (i.e., step S71). In one or more embodiments, the preset time period is 5 s. Alternatively, the preset time period can also be set to other suitable times longer or shorter than 5 s. The suction pressure of the compressor 111 can be measured by a suction pressure sensor arranged near the suction port of the compressor 111. Then, it is determined whether the suction pressure is greater than a preset suction pressure threshold. In one or more embodiments, the preset suction pressure threshold ranges from 0.3 MPa to 0.5 MPa. Alternatively, the preset suction pressure threshold can also be set to other suitable values. When the result of the determination is yes, the compressor 111 is controlled to continue to increase the operating frequency at the preset frequency increasing rate (i.e., step S74). After step S74 is completed, the control method repeats step S30, i.e., the operating frequency of the compressor 111 of the multi-split air conditioning system 1 is re-obtained. When the result of the determination is no, indicating that the suction pressure of the compressor 111 is too small at this time and is likely to trigger low-pressure protection, the compressor 111 is kept operating at the current operating frequency (step S73). After step S73 is completed, the control method repeats step S30, i.e., the operating frequency of the compressor 111 of the multi-split air conditioning system 1 is re-obtained, until the operating frequency of the compressor 111 exceeds the preset frequency threshold, and then the electronic expansion valves of the multiple indoor units 21 are controlled to open at the maximum opening degree one by one according to the target opening sequence. When all the indoor units 21 that receive the start signal exit the anti-cold-blast mode, the control method ends.

[0036] It should be noted that after the electronic expansion valve of a certain indoor unit 21 (e.g., indoor unit A) is opened at the maximum opening degree according to the target opening sequence, whether the electronic expansion valve of the next indoor unit B can be opened at the maximum opening degree also needs to repeat step S30, i.e., the operating frequency of the compressor 111 of the multi-split air conditioning system 1 is obtained. Only when the operating frequency exceeds the preset frequency threshold, the electronic expansion valve of the indoor unit B is opened at the maximum opening degree. If the operating frequency of the compressor 111 does not exceed the preset frequency threshold at this time, the control method performs step S70, i.e., the compressor 111 is controlled to increase the operating frequency at the preset frequency increasing rate, until the operating frequency of the compressor 111 exceeds the preset frequency threshold, and then the electronic expansion valve of the indoor unit B is opened at the maximum opening degree. Therefore, the control method of the present application can avoid the electronic expansion valves of multiple indoor units 21 that start at the same time being opened at the maximum opening degree at the same time, prevent the suction pressure of the compressor 111 from being too small to limit the frequency increasing speed, and effectively shorten the anti-cold-blast time and improve the user experience.

[0037] The technical scheme of the present application has been described in combination with the preferred embodiments shown in the drawings, but it is easy for those skilled in the art to understand that the protection scope of the present application is obviously not limited to these specific embodiments. Those skilled in the art can make equivalent changes or replacements to the related technical features without departing from the principles of the present application, and the technical schemes after the changes or replacements will all fall within the protection scope of the present application.

Claims

1. A control method for a multi-split air conditioning system, characterized in that, The control method comprises the following steps when the multi-split air conditioning system is in the anti-cold air mode: When multiple indoor units of the multi-split air conditioning system are started at the same time, controlling electronic expansion valves of each of the indoor units to be opened at an initial opening degree; Setting a target opening sequence of the electronic expansion valves of the multiple indoor units; Obtaining a running frequency of a compressor of the multi-split air conditioning system; Comparing the running frequency with a preset frequency threshold value; When the running frequency exceeds the preset frequency threshold value, controlling the electronic expansion valves of the multiple indoor units to be opened at a maximum opening degree according to the target opening sequence, wherein the initial opening degree is less than the maximum opening degree; When the running frequency does not exceed the preset frequency threshold value, controlling the compressor to increase the frequency at a preset frequency increasing rate; After a preset time period, obtaining a suction pressure of the compressor; Comparing the suction pressure with a preset suction pressure threshold value; When the suction pressure exceeds the preset suction pressure threshold value, continuing to control the compressor to increase the frequency at the preset frequency increasing rate; and when the suction pressure does not exceed the preset suction pressure threshold value, keeping the compressor running at the current running frequency.

2. The control method for a multi-split air conditioning system according to claim 1, wherein, The step of setting the target opening sequence of the electronic expansion valves of the multiple indoor units comprises: Obtaining a number of matched units of each of the multiple indoor units; According to the size of the number of matched units, determining the target opening sequence, wherein the smaller the number of matched units is, the earlier the corresponding electronic expansion valve is in the target opening sequence. 3.The control method of a multi-split air conditioning system according to claim 2, wherein, The step of setting the target opening sequence of the electronic expansion valves of the multiple indoor units further comprises: When the number of matched units of at least some of the multiple indoor units is the same, obtaining a distance of a refrigerant pipeline between each of the indoor units with the same number of matched units and the compressor; According to the size of the distance of the refrigerant pipeline, determining the target opening sequence, wherein the smaller the distance of the refrigerant pipeline is, the earlier the corresponding electronic expansion valve is in the target opening sequence. 4.The control method of a multi-split air conditioning system according to claim 1, wherein, The preset suction pressure threshold value is 0.3-0.5 MPa. 5.The control method of a multi-split air conditioning system according to claim 1, wherein, When the electronic expansion valve of the indoor unit is opened at the maximum opening degree, the control method further comprises: Obtaining a temperature of a coil of the corresponding indoor unit; Comparing the temperature of the coil with a preset coil temperature threshold value; When the temperature of the coil exceeds the preset coil temperature threshold value, controlling an indoor fan of the corresponding indoor unit to be started. 6.The control method of a multi-split air conditioning system according to claim 3, wherein, The ratio between the initial opening degree and the maximum opening degree ranges from 1 / 6 to 1 / 3.

7. The control method for a multi-split air conditioning system according to claim 1, wherein, The preset frequency threshold value ranges from 60 Hz to 80 Hz.

8. A multi-split air conditioning system, characterized in that, The control method for a multi-split air conditioning system according to any one of claims 1-7 is executed in the multi-split air conditioning system.

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