Control method and device for double-compressor parallel structure

Abstract

The embodiment of the invention relates to a control method and device for a double-compressor parallel connection structure, the double-compressor parallel connection structure comprises a first compressor, a second compressor, a first check valve, a second check valve, a first pressure release valve, a second pressure release valve, a first refrigerant branch and a second refrigerant branch, and the control method comprises the steps that target state parameters are detected; on the basis of the target state parameters, the opening and closing states of a first pressure release valve and a second pressure release valve are controlled, so that the pressure difference between the refrigerant inflow side and the refrigerant outflow side of the target check valve is reduced; wherein the target check valve comprises the first check valve and the second check valve; the target state parameters comprise the host current of the first compressor and the host current of the second compressor; and / or the pressure difference between the air inlet side and the air outlet side of the first check valve and the pressure difference between the air inlet side and the air outlet side of the second check valve. Therefore, the refrigerating effect of the refrigerating system where the double-compressor parallel structure is located can be improved.

Description

Technical Field

[0001] This application relates to the field of refrigeration technology, and particularly to a control method and device for a dual-compressor parallel structure. Background Art

[0002] In a dual-compressor parallel system, the two compressors operate in parallel and share a set of refrigeration systems. In such a system, a check valve is added at the compressor exhaust to prevent bypass of the other compressor when a single compressor is operating, resulting in abnormal system operation.

[0003] During the actual experiment of the unit, when one compressor is running and another compressor is started, since the compressor that is already running has compressed the refrigerant in the condenser to a relatively high pressure, while the other compressor is in a just-started state with a low running speed and small pressure output, it will not be able to open its corresponding exhaust check valve, resulting in a continuous increase in the temperature of the refrigerant in the pipeline in front of the check valve at its exhaust (during the experiment, the temperature exceeds 100 degrees Celsius). As long as the running speed of the later-running compressor cannot be significantly greater than that of the already-running compressor, this state cannot be relieved. At this time, it is necessary to manually increase the frequency of the later-running compressor and increase the speed to break this state.

[0004] After the above state is broken, since it is difficult for the running frequencies (speeds) of the two compressors to be exactly the same, there is always a slight difference in time. The compressor with a higher frequency has a larger exhaust pressure output, and the compressor with a lower frequency has a smaller exhaust pressure output. When the pressure difference reaches the closing pressure difference of the check valve, the exhaust check valve of the compressor with a lower frequency will close, resulting in a continuous increase in the temperature from the compressor exhaust port to the front of the check valve. When the running frequency is increased again, this state will be broken.

[0005] The above solution solves the problem of unit operation by increasing the running frequency of the compressor and increasing the speed. In fact, the maximum running frequency of the compressor is limited by various factors and cannot be increased indefinitely. Therefore, the problem of unit operation cannot be effectively solved.

[0006] It can be seen that how to improve the refrigeration effect of the refrigeration system with a dual-compressor parallel structure is a technical problem worthy of attention. Summary of the Invention

[0007] In view of this, to solve the above partial or all technical problems, the embodiments of this application provide a control method and device for a dual-compressor parallel structure.

[0008] In a first aspect, an embodiment of the present application provides a control method for a dual-compressor parallel structure. The dual-compressor parallel structure includes a first compressor, a second compressor, a first check valve, a second check valve, a first pressure relief valve, a second pressure relief valve, a first refrigerant branch, and a second refrigerant branch. The first compressor and the first check valve are arranged on the first refrigerant branch, and the second compressor and the second check valve are arranged on the second refrigerant branch. The first check valve is arranged on the exhaust side of the first compressor, and the second check valve is arranged on the exhaust side of the second compressor. The first pressure relief valve is connected to the intake side of the first compressor and the exhaust side of the first check valve through a pipeline, and the second pressure relief valve is connected to the intake side of the second compressor and the exhaust side of the second check valve through a pipeline. The method includes:

[0009] Detect the target state parameters; based on the target state parameters, control the opening and closing states of the first pressure relief valve and the second pressure relief valve to reduce the pressure difference between the refrigerant inflow side and the refrigerant outflow side of the target check valve;

[0010] Wherein, the target check valve includes: the first check valve and the second check valve;

[0011] The target state parameters include:

[0012] The main motor current of the first compressor and the main motor current of the second compressor; and / or,

[0013] The pressure difference between the intake side and the exhaust side of the first check valve and the pressure difference between the intake side and the exhaust side of the second check valve.

[0014] In some possible implementation manners, the controlling the opening and closing states of the first pressure relief valve and the second pressure relief valve based on the target state parameters includes:

[0015] Based on the target state parameters, determine whether there is a target compressor that has been started among the first compressor and the second compressor;

[0016] In the case where there is the target compressor, control the opening and closing states of the first pressure relief valve and the second pressure relief valve based on the target compressor;

[0017] In the case where there is no target compressor, control the first pressure relief valve and the second pressure relief valve to close.

[0018] In some possible implementation manners, the controlling the opening and closing states of the first pressure relief valve and the second pressure relief valve based on the target compressor includes:

[0019] When the target compressor is the first compressor, determine the target pressure difference between the intake side and the exhaust side of the first check valve;

[0020] When the target pressure difference is greater than a preset pressure difference threshold, control the first pressure relief valve to open and the second pressure relief valve to close;

[0021] When the target pressure difference is less than or equal to the preset pressure difference threshold, control the first pressure relief valve and the second pressure relief valve to close.

[0022] In some possible implementation manners, controlling the opening and closing states of the first pressure relief valve and the second pressure relief valve based on the target compressor includes:

[0023] When the target compressor is the first compressor, determine the target main engine current of the first compressor;

[0024] When the target main engine current is greater than or equal to a first current threshold, control the first pressure relief valve to open and the second pressure relief valve to close;

[0025] When the target main engine current is greater than or equal to a second current threshold, control the first pressure relief valve and the second pressure relief valve to close;

[0026] Wherein, the second current threshold is greater than the first current threshold.

[0027] In some possible implementation manners, controlling the opening and closing states of the first pressure relief valve and the second pressure relief valve based on the target compressor includes:

[0028] When the number of target compressors is 2, control the first pressure relief valve and the second pressure relief valve to close.

[0029] In some possible implementation manners, the intake side of the first check valve and the intake side of the second check valve are connected through a target pipeline, and a balance valve is arranged on the target pipeline;

[0030] The method further includes:

[0031] Control the opening and closing state of the balance valve based on the target state parameter.

[0032] In some possible implementation manners, controlling the opening and closing state of the balance valve based on the target state parameter includes:

[0033] Based on the target state parameter, determine whether there is a target compressor that has been started in the first compressor and the second compressor;

[0034] In the presence of the target compressor, based on the target compressor, control the opening and closing state of the balance valve;

[0035] In the absence of the target compressor, control the balance valve to close.

[0036] In some possible implementation manners, the controlling the opening and closing state of the balance valve based on the target compressor includes:

[0037] When the number of the target compressors is 1, control the balance valve to close;

[0038] When the number of the target compressors is 2, control the balance valve to open.

[0039] In some possible implementation manners, the exhaust side of the first compressor is: the intake port of the first compressor, and the exhaust side of the second compressor is: the intake port of the second compressor; or,

[0040] The exhaust side of the first compressor is: the gas replenishing port of the first compressor, and the exhaust side of the second compressor is: the gas replenishing port of the second compressor.

[0041] In a second aspect, an embodiment of the present application provides a control device for a dual-compressor parallel structure, and the device is configured to implement the control method for the dual-compressor parallel structure according to any one of the above first aspects.

[0042] In a third aspect, an embodiment of the present application provides a dual-compressor parallel structure, including a first compressor, a second compressor, a first check valve, a second check valve, a first pressure relief valve, a second pressure relief valve, a first refrigerant branch and a second refrigerant branch. The first compressor and the first check valve are arranged on the first refrigerant branch, the second compressor and the second check valve are arranged on the second refrigerant branch. The first check valve is arranged on the exhaust side of the first compressor, the second check valve is arranged on the exhaust side of the second compressor. The first pressure relief valve is connected to the intake side of the first compressor and the exhaust side of the first check valve through a pipeline, and the second pressure relief valve is connected to the intake side of the second compressor and the exhaust side of the second check valve through a pipeline;

[0043] The dual-compressor parallel structure further includes a control device. The first pressure relief valve and the second pressure relief valve are respectively electrically connected to the control device, and the control device is configured to implement the control method for the dual-compressor parallel structure according to any one of the above first aspects.

[0044] In a fourth aspect, an embodiment of the present application provides a refrigeration device, characterized in that the refrigeration device includes the dual-compressor parallel structure according to the above third aspect.

[0045] The dual-compressor parallel structure in the control method provided by the embodiments of the present application includes a first compressor, a second compressor, a first check valve, a second check valve, a first pressure relief valve, a second pressure relief valve, a first refrigerant branch and a second refrigerant branch. The first refrigerant branch is provided with the first compressor and the first check valve, and the second refrigerant branch is provided with the second compressor and the second check valve. The first check valve is arranged on the exhaust side of the first compressor, and the second check valve is arranged on the exhaust side of the second compressor. The first pressure relief valve is connected to the intake side of the first compressor and the exhaust side of the first check valve through a pipeline, and the second pressure relief valve is connected to the intake side of the second compressor and the exhaust side of the second check valve through a pipeline. The above method detects target state parameters, and then, based on the target state parameters, controls the opening and closing states of the first pressure relief valve and the second pressure relief valve to reduce the pressure difference between the refrigerant inflow side and the refrigerant outflow side of the target check valve. Wherein, the target check valve includes: the first check valve and the second check valve; the target state parameters include: the main engine current of the first compressor, the main engine current of the second compressor; and / or, the pressure difference between the intake side and the exhaust side of the first check valve, the pressure difference between the intake side and the exhaust side of the second check valve. Thus, the opening and closing states of the pressure relief valve can be controlled by the main engine current of the compressor and the pressure difference between the intake side and the exhaust side of the check valve, so as to achieve the goal of reducing the pressure difference between the refrigerant inflow side and the refrigerant outflow side of the check valve. In this way, the normal operation of the check valve can be ensured, and further the refrigeration effect of the refrigeration system where the dual-compressor parallel structure is located can be improved. Description of the Drawings

[0046] The drawings here are incorporated into the specification and form a part of this specification, showing the embodiments in line with the present application, and are used together with the specification to explain the principles of the present application.

[0047] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, for those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0048] One or more embodiments are illustrated by way of example in the pictures in the corresponding drawings. These exemplary illustrations do not constitute limitations on the embodiments. Elements with the same reference numerals in the drawings are represented as similar elements. Unless otherwise stated, the drawings in the drawings do not constitute a proportional limitation.

[0049] Figure 1 It is a schematic structural diagram of a dual-compressor parallel structure provided by the embodiments of the present application.

[0050] Figure 2Schematic flowchart of a control method for a dual-compressor parallel structure provided by an embodiment of the present application.

[0051] Figure 3 Schematic diagram of a dual-compressor parallel structure provided in the prior art.

[0052] Figure 4 Schematic diagram of another dual-compressor parallel structure provided by an embodiment of the present application.

[0053] Figure 5 Schematic diagram of yet another dual-compressor parallel structure provided by an embodiment of the present application.

[0054] Figure 6 Control timing diagram of a dual-compressor parallel structure provided by an embodiment of the present application.

[0055] Reference numerals:

[0056] 1. Evaporator; 2. Condenser; 3. Flash tank;

[0057] 4. First compressor; 5. Second compressor;

[0058] 6. First check valve; 7. Second check valve;

[0059] 8. First throttle valve; 9. Second throttle valve

[0060] 10. First suction pipe; 11. Second suction pipe;

[0061] 12. First exhaust pipe; 13. Second exhaust pipe;

[0062] 21. First pressure relief valve; 22. Second pressure relief valve;

[0063] 23. Balance valve. Detailed implementation manners

[0064] Now, various exemplary embodiments of the present application will be described in detail with reference to the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present application, rather than all of them. It should be noted that: unless otherwise specifically stated, the relative arrangements of components and steps, numerical expressions, and values set forth in these embodiments do not limit the scope of the present application.

[0065] Those skilled in the art can understand that terms such as "first" and "second" in the embodiments of the present application are only used to distinguish different steps, devices, or modules, etc., without representing any specific technical meaning and without indicating the logical order between them.

[0066] It should also be understood that in this embodiment, "a plurality of" may refer to two or more, and "at least one" may refer to one, two, or more.

[0067] It should also be understood that for any component, data, or structure mentioned in the embodiments of the present application, in the absence of a clear definition or contrary indication in the context, it is generally understood as one or more.

[0068] In addition, the term "and / or" in the present application is merely a description of the association relationship of associated objects, indicating that three relationships can exist. For example, A and / or B can represent three situations: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in the present application generally represents an "or" relationship between the associated objects before and after.

[0069] It should also be understood that the description of each embodiment in the present application emphasizes the differences between the embodiments, and their similarities or similarities can be referred to each other. For the sake of brevity, they will not be elaborated one by one.

[0070] The following description of at least one exemplary embodiment is actually only illustrative and does not constitute any limitation to the present application and its application or use.

[0071] Techniques, methods, and devices known to those of ordinary skill in the relevant art may not be discussed in detail, but in appropriate cases, the above techniques, methods, and devices should be regarded as part of the specification.

[0072] It should be noted that similar reference numerals and letters denote similar items in the following figures. Therefore, once an item is defined in one figure, it does not need to be further discussed in subsequent figures.

[0073] It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments can be combined with each other. For the convenience of understanding the embodiments of the present application, the present application will be described in detail below with reference to the drawings and in combination with the embodiments. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative efforts shall fall within the scope of protection of the present application.

[0074] In order to solve the technical problem of how to improve the refrigeration effect of the refrigeration system where the dual-compressor parallel structure is located in the prior art, the present application provides a control method and device for the dual-compressor parallel structure, which can improve the refrigeration effect of the refrigeration system where the dual-compressor parallel structure is located.

[0075] Figure 1 It is a schematic structural diagram of a dual-compressor parallel structure provided for the embodiments of the present application.

[0076] Such as Figure 1As shown in the figure, the dual-compressor parallel structure includes a first compressor 4, a second compressor 5, a first check valve 6, a second check valve 7, a first pressure relief valve 21, a second pressure relief valve 22, a first refrigerant branch and a second refrigerant branch. The first refrigerant branch is provided with the first compressor 4 and the first check valve 6, and the second refrigerant branch is provided with the second compressor 5 and the second check valve 7. The first check valve 6 is arranged on the exhaust side of the first compressor 4, and the second check valve 7 is arranged on the exhaust side of the second compressor 5. The first pressure relief valve 21 is connected to the intake side of the first compressor 4 and the exhaust side of the first check valve 6 through a pipeline, and the second pressure relief valve 22 is connected to the intake side of the second compressor 5 and the exhaust side of the second check valve 7 through a pipeline.

[0077] Please refer to Figure 2 , Figure 2 which is a schematic flow chart of a control method for a dual-compressor parallel structure provided by an embodiment of the present application.

[0078] As Figure 2 shown in the figure, the method specifically includes:

[0079] Step 101, detecting target state parameters.

[0080] In this embodiment, the target state parameters include at least one of the following:

[0081] The first item: the main machine current of the first compressor 4 and the main machine current of the second compressor 5.

[0082] The second item: the pressure difference between the intake side and the exhaust side of the first check valve 6 and the pressure difference between the intake side and the exhaust side of the second check valve 7.

[0083] In addition, the target state parameters further include the exhaust volume of the first compressor 4, the exhaust volume of the second compressor 5, etc.

[0084] Step 102, based on the target state parameters, controlling the opening and closing states of the first pressure relief valve and the second pressure relief valve to reduce the pressure difference between the refrigerant inflow side and the refrigerant outflow side of the target check valve.

[0085] In this embodiment, after detecting the above target state parameters, the opening and closing states of the first pressure relief valve 21 and the second pressure relief valve 22 can be further controlled based on the above target state parameters to reduce the pressure difference between the refrigerant inflow side and the refrigerant outflow side of the target check valve.

[0086] The target check valve includes: the first check valve 6 or the second check valve 7.

[0087] In some optional implementation manners of this embodiment, the following method can be adopted to control the opening and closing states of the first pressure relief valve 21 and the second pressure relief valve 22 based on the target state parameters:

[0088] In the first step, based on the target state parameters, determine whether there is a target compressor that has been turned on among the first compressor 4 and the second compressor 5.

[0089] As an example, when the target state parameters include the main motor current of the first compressor 4, it can be determined whether the first compressor 4 is the target compressor that has been turned on by the magnitude of the main motor current of the first compressor 4 (for example, whether the main motor current is greater than the second current threshold). When the target state parameters include the main motor current of the second compressor 5, it can be determined whether the second compressor 5 is the target compressor that has been turned on by the magnitude of the main motor current of the second compressor 5 (for example, whether the main motor current is greater than the second current threshold).

[0090] As another example, when the target state parameters include the pressure difference between the intake side and the exhaust side of the first check valve 6, it can be determined whether the first compressor 4 is the target compressor that has been turned on by the magnitude of the pressure difference between the intake side and the exhaust side of the first check valve 6 (for example, whether the pressure difference is greater than the preset pressure difference threshold). When the target state parameters include the pressure difference between the intake side and the exhaust side of the second check valve 7, it can be determined whether the second compressor 5 is the target compressor that has been turned on by the magnitude of the pressure difference between the intake side and the exhaust side of the second check valve 7 (for example, whether the pressure difference is greater than the preset pressure difference threshold).

[0091] As yet another example, when the target state parameters include the discharge volume of the first compressor 4, it can be determined whether the first compressor 4 is the target compressor that has been turned on by the magnitude of the discharge volume of the first compressor 4 (for example, whether the discharge volume is greater than the preset discharge volume threshold). When the target state parameters include the discharge volume of the second compressor 5, it can be determined whether the second compressor 5 is the target compressor that has been turned on by the magnitude of the discharge volume of the second compressor 5 (for example, whether the discharge volume is greater than the preset discharge volume threshold).

[0092] Therefore, the situation where there is a target compressor can include the following three cases: the first compressor is on and the second compressor is off, the second compressor is on and the first compressor is off, and both the first compressor and the second compressor are on.

[0093] In the second step, when there is a target compressor, based on the target compressor, control the opening and closing states of the first pressure relief valve 21 and the second pressure relief valve 22. Alternatively, when there is no target compressor, control the first pressure relief valve 21 and the second pressure relief valve 22 to close.

[0094] It can be understood that in the above optional implementation manners, the opening and closing states of the first pressure relief valve 21 and the second pressure relief valve 22 can be adaptively controlled according to the operating states of the first compressor 4 and the second compressor 5, so as to achieve the goal of reducing the pressure difference between the refrigerant inflow side and the refrigerant outflow side of the check valve. Thus, the normal operation of the check valve can be ensured, and further, the refrigeration effect of the refrigeration system where the dual-compressor parallel structure is located can be improved.

[0095] In some application scenarios of the above optional implementation manners, the following method can be adopted to control the opening and closing states of the first pressure relief valve 21 and the second pressure relief valve 22 based on the target compressor:

[0096] First step, when the target compressor is the first compressor 4, determine the target pressure difference between the intake side and the exhaust side of the first check valve 6.

[0097] Wherein, the target pressure difference is the pressure difference between the intake side and the exhaust side of the first check valve 6.

[0098] Second step, when the target pressure difference is greater than the preset pressure difference threshold, control the first pressure relief valve 21 to open and the second pressure relief valve 22 to close; when the target pressure difference is less than or equal to the preset pressure difference threshold, control the first pressure relief valve 21 and the second pressure relief valve 22 to close.

[0099] It can be understood that in the above optional implementation manners, the opening and closing states of the first pressure relief valve 21 and the second pressure relief valve 22 can be adaptively controlled according to the pressure difference corresponding to the check valve provided on the refrigerant branch where the single operating compressor is located, so as to achieve the goal of reducing the pressure difference between the refrigerant inflow side and the refrigerant outflow side of the check valve. Thus, the normal operation of the check valve can be ensured, and further, the refrigeration effect of the refrigeration system where the dual-compressor parallel structure is located can be improved.

[0100] In some application scenarios of the above optional implementation manners, the following method can be adopted to control the opening and closing states of the first pressure relief valve 21 and the second pressure relief valve 22 based on the target compressor:

[0101] First step, when the target compressor is the first compressor 4, determine the target main motor current of the first compressor 4.

[0102] Wherein, the target main motor current is the main motor current of the single operating compressor.

[0103] Second step, when the target main motor current is greater than or equal to the first current threshold, control the first pressure relief valve 21 to open and the second pressure relief valve 22 to close; when the target main motor current is greater than or equal to the second current threshold, control the first pressure relief valve 21 and the second pressure relief valve 22 to close.

[0104] Wherein, the second current threshold is greater than the first current threshold.

[0105] As an example, the second current threshold may be the rated current of the target compressor. The first current threshold may be 0.

[0106] It can be understood that in the above optional implementation manners, the opening and closing states of the first pressure relief valve 21 and the second pressure relief valve 22 can be adaptively controlled by the main machine current of the single compressor that has been started, so as to achieve the goal of reducing the pressure difference between the refrigerant inflow side and the refrigerant outflow side of the check valve. Since the opening and closing states of the first pressure relief valve 21 and the second pressure relief valve 22 are controlled by current, the pressure relief valves can be controlled more accurately and quickly, and thus the refrigeration effect of the refrigeration system where the dual-compressor parallel structure is located can be further improved.

[0107] In some application scenarios of the above optional implementation manners, the following method can be adopted to control the opening and closing states of the first pressure relief valve 21 and the second pressure relief valve 22 based on the target compressor:

[0108] When the number of target compressors is 2, control the first pressure relief valve 21 and the second pressure relief valve 22 to close.

[0109] It can be understood that in the above application scenario, when both the first compressor and the second compressor have been started, the first pressure relief valve and the second pressure relief valve can be closed to avoid the reduction of refrigeration efficiency caused by the opening of the pressure relief valves, and thus the refrigeration effect of the refrigeration system where the dual-compressor parallel structure is located can be further improved.

[0110] In some optional implementation manners of this embodiment, the intake side of the first check valve 6 and the intake side of the second check valve 7 are connected through a target pipeline, and a balance valve 23 is arranged on the target pipeline. On this basis, the opening and closing state of the balance valve 23 can also be controlled based on the target state parameter.

[0111] It can be understood that in the above optional implementation manners, after the above target state parameter is detected, the opening and closing state of the balance valve 23 can be further controlled based on the above target state parameter to reduce the pressure difference between the two refrigerant branches, and thus the refrigeration effect of the refrigeration system where the dual-compressor parallel structure is located can be further improved.

[0112] In some application scenarios of the above optional implementation manners, the following method can be adopted to control the opening and closing state of the balance valve 23 based on the target state parameter:

[0113] The first step is to determine whether there is a target compressor that has been started in the first compressor 4 and the second compressor 5 based on the target state parameter.

[0114] As an example, when the target state parameter includes the main motor current of the first compressor 4, it is possible to determine whether the first compressor 4 is the target compressor that has been turned on by the magnitude of the main motor current of the first compressor 4 (for example, whether the main motor current is greater than the second current threshold). When the target state parameter includes the main motor current of the second compressor 5, it is possible to determine whether the second compressor 5 is the target compressor that has been turned on by the magnitude of the main motor current of the second compressor 5 (for example, whether the main motor current is greater than the second current threshold).

[0115] As another example, when the target state parameter includes the pressure difference between the intake side and the exhaust side of the first check valve 6, it is possible to determine whether the first compressor 4 is the target compressor that has been turned on by the magnitude of the pressure difference between the intake side and the exhaust side of the first check valve 6 (for example, whether the pressure difference is greater than the preset pressure difference threshold). When the target state parameter includes the pressure difference between the intake side and the exhaust side of the second check valve 7, it is possible to determine whether the second compressor 5 is the target compressor that has been turned on by the magnitude of the pressure difference between the intake side and the exhaust side of the second check valve 7 (for example, whether the pressure difference is greater than the preset pressure difference threshold).

[0116] As yet another example, when the target state parameter includes the displacement of the first compressor 4, it is possible to determine whether the first compressor 4 is the target compressor that has been turned on by the magnitude of the displacement of the first compressor 4 (for example, whether the displacement is greater than the preset displacement threshold). When the target state parameter includes the displacement of the second compressor 5, it is possible to determine whether the second compressor 5 is the target compressor that has been turned on by the magnitude of the displacement of the second compressor 5 (for example, whether the displacement is greater than the preset displacement threshold).

[0117] Therefore, the situation where there is a target compressor can include the following three cases: the first compressor is on and the second compressor is off, the second compressor is on and the first compressor is off, and both the first compressor and the second compressor are on.

[0118] In the second step, when there is a target compressor, based on the target compressor, control the opening and closing state of the balance valve 23; when there is no target compressor, control the balance valve 23 to close.

[0119] It can be understood that in the above optional implementation manners, the opening and closing state of the balance valve 23 can be adaptively controlled through the operating states of the first compressor 4 and the second compressor 5, thereby reducing the pressure difference between the two refrigerant branches, which can further improve the refrigeration effect of the refrigeration system where the dual-compressor parallel structure is located.

[0120] In some examples of the above application scenarios, the following method can be adopted to control the opening and closing state of the balance valve 23 based on the target compressor: when the number of target compressors is 1, control the balance valve 23 to close; when the number of target compressors is 2, control the balance valve 23 to open.

[0121] It can be understood that in the above examples, when only one of the first compressor and the second compressor is an opened compressor, the balance valve 23 can be closed to prevent the refrigerant from flowing into the pipeline where the balance valve 23 is located; when both the first compressor and the second compressor are opened, the balance valve 23 can be opened to reduce the pressure difference between the two refrigerant branches, thereby further improving the refrigeration effect of the refrigeration system where the dual-compressor parallel structure is located.

[0122] In some optional implementation manners of this embodiment, the exhaust side of the first compressor 4 is: the intake port of the first compressor 4, and the exhaust side of the second compressor 5 is: the intake port of the second compressor 5.

[0123] It can be understood that in the above optional implementation manners, by connecting the pressure relief valve to the intake port of the compressor and the exhaust side of the check valve, the pressure difference between the intake port of the compressor and the exhaust side of the check valve can be reduced by opening the pressure relief valve. In this way, this solution can be applied to a refrigeration system with a relatively high ratio of the pressure of the condenser 2 to the pressure of the evaporator 1 (for example, the ratio is greater than 2), can effectively unload the pressure, ensure the normal operation of the check valve, and ensure the reliable operation of the dual-compressor parallel structure.

[0124] In some optional implementation manners of this embodiment, the exhaust side of the first compressor 4 is: the gas replenishing port of the first compressor 4, and the exhaust side of the second compressor 5 is: the gas replenishing port of the second compressor 5.

[0125] It can be understood that in the above optional implementation manners, by connecting the pressure relief valve to the gas replenishing port of the compressor and the exhaust side of the check valve, the pressure difference between the gas replenishing port of the compressor and the exhaust side of the check valve can be reduced by opening the pressure relief valve. In this way, the control cost of the dual-compressor parallel structure can be reduced, and it is more applicable to a refrigeration system with a relatively low ratio of the pressure of the condenser 2 to the pressure of the evaporator 1 (for example, the ratio is less than 2).

[0126] It should be noted that, without conflict, the technical features recorded in different optional implementation manners can be included in the same embodiment. For the sake of concise description, they are not elaborated here.

[0127] The dual compressor parallel structure in the control method of the dual compressor parallel structure provided in the embodiment of the present application includes a first compressor, a second compressor, a first check valve, a second check valve, a first pressure relief valve, a second pressure relief valve, a first refrigerant branch and a second refrigerant branch. The first refrigerant branch is provided with a first compressor and a first check valve, and the second refrigerant branch is provided with a second compressor and a second check valve. The first check valve is provided on the exhaust side of the first compressor, and the second check valve is provided on the exhaust side of the second compressor. The first pressure relief valve is connected to the intake side of the first compressor and the exhaust side of the first check valve through a pipeline. The second The pressure relief valve is connected to the air intake side of the second compressor and the exhaust side of the second check valve through a pipeline. The above method detects the target state parameter, and then controls the opening and closing state of the first pressure relief valve and the second pressure relief valve based on the target state parameter to reduce the pressure difference between the refrigerant inlet side and the refrigerant outlet side of the target check valve, wherein the target check valve includes: the first check valve and the second check valve; the target state parameter includes: the host current of the first compressor, the host current of the second compressor; and / or, the pressure difference between the air intake side and the exhaust side of the first check valve, and the pressure difference between the air intake side and the exhaust side of the second check valve. Thus, the opening and closing state of the pressure relief valve can be controlled by the host current of the compressor and the pressure difference between the air intake side and the exhaust side of the check valve, so as to achieve the goal of reducing the pressure difference between the refrigerant inlet side and the refrigerant outlet side of the check valve, so that the normal operation of the check valve can be guaranteed, and then the refrigeration effect of the refrigeration system where the dual compressor parallel structure is located can be improved.

[0128] The following is an illustrative description of the embodiments of the present application, but it should be noted that the following content is only used to understand the technical solutions of the embodiments of the present application and does not constitute a limitation on the protection scope of the embodiments of the present application.

[0129] In the related art, in a single-system dual-compressor parallel centrifuge system, the dual compressors operate in parallel and share a refrigeration system. In this type of system, a check valve is added at the compressor exhaust to prevent the other compressor from bypassing when a single compressor is running, causing the system to fail to operate normally.

[0130] During the actual experiment of the unit, when one compressor is running and another compressor is started, the running compressor has compressed the refrigerant in the condenser to a higher pressure, while the other compressor has just been started, with a low running speed and a small pressure output, and its corresponding exhaust check valve cannot be opened, causing the refrigerant temperature in the pipe from the exhaust to the front end of the check valve to continue to rise (during the experiment, its temperature exceeded 100 degrees Celsius). As long as the speed of the compressor running later is not significantly higher than that of the compressor that has been running, this state cannot be released. At this time, the frequency of the compressor running later needs to be artificially increased to increase the speed in order to break this state.

[0131] When the above state is broken, since it is very difficult for the operating frequencies (speeds) of the two compressors to remain exactly the same, there are always slight differences in time. The compressor with a higher frequency has a larger exhaust pressure output, while the compressor with a lower frequency has a smaller exhaust pressure output. When the pressure difference reaches the closing pressure difference of the check valve, the exhaust check valve of the compressor with a lower frequency will close, resulting in a continuous increase in the temperature from the exhaust port of the compressor to the front end of the check valve. This state will only be broken when the operating frequency is increased again.

[0132] In the above solutions, this problem is solved by increasing the operating frequency of the compressor and increasing the rotational speed. In fact, the maximum operating frequency of the compressor is restricted by various factors and cannot be increased indefinitely. Therefore, for such units with two compressors in parallel sharing a set of refrigeration systems, the operating method of the two compressors remains an urgent problem to be solved.

[0133] To solve the above problem, in this solution, pressure measurement points are set before and after the check valve of the compressor to monitor the pressure value, and a pressure relief valve and a balance valve are set. According to the monitored pressure value, the pressure relief valve and the balance valve are controlled to open or close to unload and balance the pressure before and after the check valve, ensure its normal operation, and ensure the reliable operation of the system.

[0134] This solution aims to solve the problem that in a single-system two-compressor parallel centrifuge system, due to the asynchronous operation of the two compressors, the check valve closes abnormally and the exhaust temperature exceeds the limit.

[0135] In the related technology, due to the asynchronous operation of the two compressors, the check valve closes abnormally and the exhaust temperature exceeds the limit. By adopting this solution, the normal operation of the check valve can be ensured and the reliability of the system can be improved.

[0136] In this solution, pressure measurement points are set before and after the check valve of the compressor to monitor the pressure value, and a pressure relief valve and a balance valve are set. According to the monitored pressure value, the pressure relief valve and the balance valve are controlled to open or close to unload and balance the pressure before and after the check valve, ensure its normal operation, and ensure the reliability of the system operation.

[0137] Specifically, as Figure 3As shown in the figure, the single-system dual-compressor parallel centrifuge system is briefly described as follows: The first compressor 4 and the second compressor 5 operate in parallel and share a set of refrigeration system components such as an evaporator 1, a condenser 2, and a flash tank 3. The first compressor 4 and the second compressor 5 respectively compress the gaseous refrigerant in the evaporator 1 into the condenser 2 through the first suction pipe 10 and the second suction pipe 11. First check valves 6 and second check valves 7 are respectively arranged on their exhaust pipes, the first exhaust pipe 12 and the second exhaust pipe 13. After compression, the high-temperature and high-pressure gaseous refrigerant exchanges heat with cooling water in the condenser 2 and condenses into a high-temperature and high-pressure liquid refrigerant. Then, after throttling through a primary throttle valve 6, a flash tank 3, and a secondary throttle valve 9, it flashes and enters the evaporator 1 to evaporate into a gas state, while exchanging heat with chilled water to reduce the temperature of the chilled water. The gaseous refrigerant is then compressed by the first compressor 4 and the second compressor 5 again and enters the next refrigeration cycle. A gas supply pipe is arranged at the top of the flash tank 3 to supply gas to the outlets of the first-stage impellers of the first compressor 4 and the second compressor 5 respectively.

[0138] As Figure 3 shown, in the single-system dual-compressor parallel centrifuge system, when the first compressor 4 is running and the second compressor 5 is started again, since the first compressor 4 that is already running has compressed the refrigerant in the condenser 2 to a relatively high pressure, while the second compressor 5 is in a just-started state with a low operating speed and a small pressure output, the pressure difference before and after the second check valve 7 is large, and the second check valve 7 cannot be opened, resulting in the continuous increase of the temperature of the refrigerant in the pipeline at the front end of the second check valve 7 (the temperature exceeds 100 degrees Celsius during the experiment). As long as the rotational speed of the second compressor 5 cannot be significantly greater than that of the first compressor 4 that is already running, this state cannot be relieved. At this time, it is necessary to artificially increase the operating frequency of the second compressor 5 and increase the rotational speed to break this state. After the above state is broken, since it is difficult for the operating frequencies (rotational speeds) of the first compressor 4 and the second compressor 5 to be exactly the same, there are always slight differences in time. The compressor with a higher frequency has a larger exhaust pressure output, and the compressor with a lower frequency has a smaller exhaust pressure output. When the pressure difference reaches the closing pressure difference of the first check valve 6 or the second check valve 7, the exhaust check valve of the compressor with a lower operating frequency will close, resulting in the phenomenon of continuous increase in the temperature from the compressor exhaust port to the front end of the check valve. When its operating frequency is increased again, this state will be broken. When the second compressor 5 is running and the first compressor 4 is started again, such a phenomenon will also occur.

[0139] As Figure 3 shown, as described above, the single-system dual-compressor parallel centrifuge system has the problem that due to the asynchronous operation of the two compressors, the check valve closes abnormally and the exhaust temperature exceeds the limit.

[0140] The structure of the dual-compressor parallel structure in this solution is as Figure 4As shown, in a single-system dual-compressor parallel centrifuge system, pressure measurement points P1 and P3 are set before and after the first check valve 6, and pressure measurement points P2 and P4 are set before and after the second check valve 7; a first pressure relief valve 21 and its pipeline are provided between the first suction pipe 10 at the front end of the first compressor 4 and the first discharge pipe 12 at the rear end of the first check valve 6; a second pressure relief valve 22 and its pipeline are provided between the second suction pipe 11 at the front end of the second compressor 5 and the second discharge pipe 13 at the rear end of the second check valve 7; a balance valve 23 and its pipeline are provided between the outlet of the first compressor 4, the front end of the first check valve 6 and the outlet of the second compressor 5, the front end of the second check valve 7.

[0141] Among them, P3 - P1 represents the difference between the pipeline pressure at point P3 and the pipeline pressure at point P1, that is, the pressure difference between the inlet side and the outlet side of the first check valve 6. P4 - P2 represents the difference between the pipeline pressure at point P4 and the pipeline pressure at point P2, that is, the pressure difference between the inlet side and the outlet side of the second check valve 7.

[0142] As Figure 4 shown, in a single-system dual-compressor parallel centrifuge system, the pressure values at points P1, P2, P3, and P4 are detected. When the first compressor 4 is in the operating state and the second compressor 5 is closed, when P3 - P1 is greater than the closing pressure of the first check valve 6 (that is, the above-mentioned preset pressure threshold), the second pressure relief valve 22 is closed, the balance valve 23 is closed, and the first pressure relief valve 21 is opened to unload the P3 pressure to keep the first check valve 6 normally open; when P3 - P1 is less than or equal to the closing pressure of the first check valve 6, the second pressure relief valve 22 is closed, the balance valve 23 is closed, and the first pressure relief valve 21 is closed; when the second compressor 5 is in the operating state and the first compressor 4 is closed, when P4 - P2 is greater than the closing pressure of the second check valve 7, the first pressure relief valve 21 is closed, the balance valve 23 is closed, and the second pressure relief valve 22 is opened to unload the P4 pressure to keep the second check valve 7 normally open; when P4 - P2 is less than or equal to the closing pressure of the second check valve 7, the second pressure relief valve 22 is closed, the balance valve 23 is closed, and the first pressure relief valve 21 is closed; when both the first compressor 4 and the second compressor 5 are in the operating state, the first pressure relief valve 21 and the second pressure relief valve 22 are closed, and the balance valve 23 is opened to balance the pressure between the first compressor 4 and the second compressor 5; when both the first compressor 4 and the second compressor 5 are in the closed state, the first pressure relief valve 21 and the second pressure relief valve 22 are closed, and the balance valve 23 is closed.

[0143] As Figure 4As shown, since the pressure relief points of the first pressure relief valve 21 and the second pressure relief valve 22 are the first suction pipe 10 and the second suction pipe 11 respectively, when the first compressor 4 and the second compressor 5 are operating, the first suction pipe 10 and the second suction pipe 11 are the lowest pressure points in the system. Therefore, this method is applicable to refrigeration systems with a relatively high ratio of the condenser 2 pressure to the evaporator 1 pressure (generally the ratio is greater than 2), which can effectively unload the pressure, ensure the normal operation of the check valve, and ensure the reliable operation of the system.

[0144] As Figure 5 shown, for refrigeration systems with a relatively low ratio of the condenser 2 pressure to the evaporator 1 pressure (generally the ratio is less than 2), a more economical method can be selected. The pressure relief point of the first pressure relief valve 21 can be set between the exhaust port of the first-stage impeller and the intake port of the second-stage impeller of the first compressor 4 (compressor air intake port), and the pressure relief point of the second pressure relief valve 22 can be set between the exhaust of the first-stage impeller and the intake port of the second-stage impeller of the second compressor 5 (compressor air intake port). The control methods of the first pressure relief valve 21, the second pressure relief valve 22, and the balance valve 23 are the same as those described above. In this method, the pressure at the pressure relief point is the intermediate pressure, which can not only unload the pressure, ensure the normal operation of the check valve, and ensure the reliable operation of the system, but also prevent excessive bypass flow and excessive system loss due to the too large pressure difference before and after the first pressure relief valve 21 and the second pressure relief valve 22.

[0145] This solution can set pressure measurement points before and after the compressor check valve to monitor the pressure value, set pressure relief valves and balance valves, and control the opening or closing of the pressure relief valves and balance valves according to the monitored pressure value, so as to unload and balance the pressure before and after the check valve, ensure its normal operation, and improve the reliability of the system operation.

[0146] In some solutions, the balance valve solution is to lead the high pressure to the low pressure to balance the pressure between the high-pressure chamber and the low-pressure chamber and relieve the pressure of the high-pressure chamber. The function of the balance valve 23 in this solution is to lead the exhaust of the first-running compressor to the exhaust of the second-running compressor. The application method is to balance the high-pressure exhaust of the first-running compressor and the high-pressure exhaust of the second-running compressor. Compared with the solution of unloading the high pressure to the low pressure at the front end of the compressor by the first pressure relief valve 21 and the second pressure relief valve 22, the significant advantage of this solution is that it does not consume the refrigerant vapor that has been compressed in the system. That is, the compressed refrigerant vapor after passing through the balance valve 23 finally always passes through the compressor exhaust pipe and enters the condenser 2 for heat exchange, participating in the entire refrigeration cycle. In the solution of the first pressure relief valve 21 and the second pressure relief valve 22, unloading the exhaust to the front end of the compressor causes the compressor to do useless work and reduces the energy efficiency of the system.

[0147] This solution can control the opening and closing of the first pressure relief valve 21, the second pressure relief valve 22, and the balance valve 23 by detecting the pressures at points P1 - P4. Further, the opening and closing of the valves can be controlled according to the change in the current of the main motor of the compressor (the operating current of the main motor of the compressor can more accurately and quickly reflect the change in the exhaust pressure of the compressor compared to the pressure measurement points). The control timing diagram is as Figure 6 shown:

[0148] The operation of the unit is divided into several stages: starting up, rated operation, load regulation, partial load operation, and shutting down. Taking the first compressor 1 running first as an example.

[0149] Starting up stage: The main motor of the first compressor 4 starts and gradually loads (the main motor current is greater than or equal to the first current threshold). The second compressor 5 is closed, the first pressure relief valve 21 is opened, the outlet pressure of the first check valve 6 is the same as the suction pressure of the compressor, and the first check valve 6 opens normally. The second pressure relief valve 22 and the balance valve 23 are closed. After the main motor current of the first compressor 4 is loaded to 100% (the main motor current is greater than or equal to the second current threshold), the first pressure relief valve 21 is closed. After the unit stabilizes for 60 seconds, the second compressor 5 starts to load, the second pressure relief valve 22 is opened, the outlet pressure of the second check valve 7 is the same as the suction pressure of the compressor, and the second check valve 7 opens normally. After the main motor current of the second compressor 5 is loaded to 100%, the second pressure relief valve 22 is closed, and the unit completes the starting up stage.

[0150] Rated operation stage: Both the first compressor 4 and the second compressor 5 are operating at full load. The balance valve 23 is opened to balance the high exhaust pressures of the first compressor 4 and the second compressor 5, preventing the abnormal closing of the first check valve 6 and the second check valve 7, and the unit operates normally in the rated operation stage.

[0151] Load regulation stage: When the required load changes, the unit enters the load regulation stage. The balance valve 23 is closed, the first compressor 4 starts to unload current, the first pressure relief valve 21 is opened, the outlet pressure of the first check valve 6 is the same as the suction pressure of the compressor, and the first check valve 6 opens normally. When the main motor current of the first compressor 4 is unloaded to the target value and the unit stabilizes for 60 seconds, the second compressor 5 starts to unload, the second pressure relief valve 22 is opened, the outlet pressure of the second check valve 7 is the same as the suction pressure of the compressor, and the second check valve 7 opens normally. After the main motor current of the second compressor 5 is unloaded to the target value, the first pressure relief valve 21 and the second pressure relief valve 22 are closed, and the unit completes the load regulation stage.

[0152] Partial load operation stage: Both the first compressor 4 and the second compressor 5 are operating at partial load. The balance valve 23 is opened to balance the high exhaust pressures of the first compressor 4 and the second compressor 5, preventing the abnormal closing of the first check valve 6 and the second check valve 7, and the unit operates normally in the partial load operation stage.

[0153] Shutdown phase: Close the balance valve 23, the first compressor 4, and the second compressor 5, and the unit shuts down.

[0154] Using the main motor current control compared with the pressure detection control described above, one advantage is that the number of detections decreases, reducing control abnormalities caused by malfunctions of the detection sensors themselves. The main motor current is the core control parameter of the unit, and this parameter is required for the normal operation control of the unit without the need to additionally increase the detection quantity. The pressure measurement points described above are new measurement points in this solution and are non-essential parameters for the normal operation of the unit. On the other hand, the main motor current can quickly feedback changes in the unit pressure and exhaust volume. If controlled by relying on the pressure measurement points, the kinetic energy of the gaseous refrigerant discharged by the unit compressor needs to be first converted into pressure energy and then read by the sensor, and a pressure sensor with high sensitivity and fast enough response speed is required to measure the pressure pulsation.

[0155] It should be noted that in addition to the content recorded above, this embodiment may also include the technical features described in the above embodiments, thereby achieving the technical effects of the control method of the dual-compressor parallel structure shown above. For details, please refer to the above description. For the sake of concise description, it will not be elaborated here.

[0156] In this solution, pressure measurement points are set before and after the compressor check valve to monitor the pressure value. And a pressure relief valve and a balance valve are set, and the pressure relief valve and the balance valve can be controlled to open or close according to the monitored pressure value and the main engine current, so as to unload and balance the pressure before and after the check valve, ensure its normal operation, and thus improve the system reliability.

[0157] The embodiment of the present application also provides a control device for a dual-compressor parallel structure.

[0158] The control device for the dual-compressor parallel structure provided in this embodiment is configured to implement all the steps of the control methods for the above-mentioned dual-compressor parallel structures, thereby achieving the technical effects of the control methods for the above-mentioned dual-compressor parallel structures. For details, please refer to the above relevant descriptions. For the sake of concise description, it will not be elaborated here.

[0159] The embodiment of the present application further provides a dual-compressor parallel structure, which includes a first compressor 4, a second compressor 5, a first check valve 6, a second check valve 7, a first pressure relief valve 21, a second pressure relief valve 22, a first refrigerant branch and a second refrigerant branch. The first compressor 4 and the first check valve 6 are arranged on the first refrigerant branch, and the second compressor 5 and the second check valve 7 are arranged on the second refrigerant branch. The first check valve 6 is arranged on the exhaust side of the first compressor 4, and the second check valve 7 is arranged on the exhaust side of the second compressor 5. The first pressure relief valve 21 is connected to the intake side of the first compressor 4 and the exhaust side of the first check valve 6 through a pipeline, and the second pressure relief valve 22 is connected to the intake side of the second compressor 5 and the exhaust side of the second check valve 7 through a pipeline;

[0160] The dual-compressor parallel structure further includes a control device. The first pressure relief valve 21 and the second pressure relief valve 22 are respectively electrically connected to the control device. The control device is configured to implement all steps of the control method of the above-mentioned dual-compressor parallel structure, and thus achieve the technical effects of the control method of the above-mentioned dual-compressor parallel structure. For specific reference, please refer to the above relevant descriptions. For the sake of brevity, it will not be elaborated here.

[0161] The embodiment of the present application further provides a refrigeration device, which includes the above-mentioned dual-compressor parallel structure. For specific reference, please refer to the above relevant descriptions. For the sake of brevity, it will not be elaborated here.

[0162] It should be understood that the terms used herein are only for the purpose of describing specific example embodiments and are not intended to be limiting. Unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" as used herein may also include the plural forms. The terms "include", "comprise", "contain" and "have" are inclusive and thus specify the presence of the stated features, steps, operations, elements and / or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and / or combinations thereof. The method steps, processes, and operations described herein are not to be construed as necessarily requiring them to be performed in the particular order described or illustrated, unless the order of performance is explicitly stated. It should also be understood that alternative or additional steps may be used.

[0163] The above description is only the specific implementation manners of the present application, enabling those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown herein, but will be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A control method for a parallel structure of two compressors, characterized in that, The dual-compressor parallel structure includes a first compressor, a second compressor, a first check valve, a second check valve, a first pressure relief valve, a second pressure relief valve, a first refrigerant branch, and a second refrigerant branch. The first compressor and the first check valve are arranged on the first refrigerant branch, and the second compressor and the second check valve are arranged on the second refrigerant branch. The first check valve is arranged on the exhaust side of the first compressor, and the second check valve is arranged on the exhaust side of the second compressor. The first pressure relief valve is connected to the intake side of the first compressor and the exhaust side of the first check valve through a pipeline, and the second pressure relief valve is connected to the intake side of the second compressor and the exhaust side of the second check valve through a pipeline. The method includes: Detect the target state parameters; based on the target state parameters, control the opening and closing states of the first pressure relief valve and the second pressure relief valve to reduce the pressure difference between the refrigerant inflow side and the refrigerant outflow side of the target check valve; Wherein, the target check valve includes: the first check valve and the second check valve; The target state parameters include: The main engine current of the first compressor and the main engine current of the second compressor; and / or, The pressure difference between the intake side and the exhaust side of the first check valve and the pressure difference between the intake side and the exhaust side of the second check valve.

2. The method according to claim 1, wherein The controlling the opening and closing states of the first pressure relief valve and the second pressure relief valve based on the target state parameters includes: Based on the target state parameters, determine whether there is a target compressor that has been started among the first compressor and the second compressor; In the case where there is a target compressor, control the opening and closing states of the first pressure relief valve and the second pressure relief valve based on the target compressor; In the case where there is no target compressor, control the first pressure relief valve and the second pressure relief valve to close.

3. The method according to claim 2, wherein The controlling the opening and closing states of the first pressure relief valve and the second pressure relief valve based on the target compressor includes: In the case where the target compressor is the first compressor, determine the target pressure difference between the intake side and the exhaust side of the first check valve; In the case where the target pressure difference is greater than the preset pressure difference threshold, control the first pressure relief valve to open and the second pressure relief valve to close; In the case where the target pressure difference is less than or equal to the preset pressure difference threshold, control the first pressure relief valve and the second pressure relief valve to close.

4. The method according to claim 2, wherein The controlling the opening and closing states of the first pressure relief valve and the second pressure relief valve based on the target compressor includes: In the case where the target compressor is the first compressor, determine the target main engine current of the first compressor; In the case where the target main engine current is greater than or equal to the first current threshold, control the first pressure relief valve to open and the second pressure relief valve to close; In the case where the target main engine current is greater than or equal to the second current threshold, control the first pressure relief valve and the second pressure relief valve to close; Wherein, the second current threshold is greater than the first current threshold.

5. The method according to claim 2, characterized in that, The controlling the opening and closing states of the first pressure relief valve and the second pressure relief valve based on the target compressor includes: When the number of the target compressors is 2, control the first pressure relief valve and the second pressure relief valve to close.

6. The method according to claim 1, wherein The intake side of the first check valve and the intake side of the second check valve are communicated through a target pipeline, and a balance valve is arranged on the target pipeline; The method further includes: Based on the target state parameter, control the opening and closing state of the balance valve.

7. The method according to claim 6, wherein The controlling the opening and closing state of the balance valve based on the target state parameter includes: Based on the target state parameter, determine whether there is a target compressor that has been started among the first compressor and the second compressor; When there is the target compressor, based on the target compressor, control the opening and closing state of the balance valve; When there is no target compressor, control the balance valve to close.

8. The method according to claim 7, wherein The controlling the opening and closing state of the balance valve based on the target compressor includes: When the number of the target compressors is 1, control the balance valve to close; When the number of the target compressors is 2, control the balance valve to open.

9. The method according to any one of claims 1-8, characterized in that: The exhaust side of the first compressor is: the intake port of the first compressor, and the exhaust side of the second compressor is: the intake port of the second compressor; or, The exhaust side of the first compressor is: the gas replenishing port of the first compressor, and the exhaust side of the second compressor is: the gas replenishing port of the second compressor.

10. A control device for a parallel structure of two compressors, characterized in that, The device is configured to implement the control method of the dual-compressor parallel structure according to any one of claims 1-9.

11. A parallel structure of two compressors, characterized in that, It includes a first compressor, a second compressor, a first check valve, a second check valve, a first pressure relief valve, a second pressure relief valve, a first refrigerant branch and a second refrigerant branch. The first compressor and the first check valve are arranged on the first refrigerant branch, the second compressor and the second check valve are arranged on the second refrigerant branch. The first check valve is arranged on the exhaust side of the first compressor, the second check valve is arranged on the exhaust side of the second compressor. The first pressure relief valve is connected to the intake side of the first compressor and the exhaust side of the first check valve through a pipeline, and the second pressure relief valve is connected to the intake side of the second compressor and the exhaust side of the second check valve through a pipeline; The dual-compressor parallel structure further includes a control device. The first pressure relief valve and the second pressure relief valve are respectively electrically connected to the control device. The control device is configured to implement the control method of the dual-compressor parallel structure according to any one of claims 1-9.

12. A refrigeration device, characterized in that, The refrigeration equipment includes the dual-compressor parallel structure according to claim 11.

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