Control method of refrigerating system and refrigerating system

Abstract

The embodiment of the invention discloses a control method of a refrigerating system and the refrigerating system. The method comprises the steps that a refrigerating control instruction is received, and a first compressor is controlled to conduct refrigerating work on a target object based on the refrigerating control instruction; the method for controlling the first compressor to conduct refrigeration based on the refrigeration control instruction comprises the steps that whether the current temperature value of the target object is larger than a preset temperature threshold value or not is judged; if yes, the first compressor is controlled to work through a proportional-integral-differential control method by means of temperature deviation based on the refrigeration control instruction, and the temperature deviation is the difference value between the current temperature value of the target object and a preset temperature threshold value; and if not, the temperature deviation and the superheat degree of the refrigerating system are used for jointly controlling the first compressor to work. The technical problem that in the prior art, due to the fact that the large compressor and the small compressor are switched by only using the set temperature value, the temperature returning phenomenon or the overshoot phenomenon is likely to occur is solved, and the technical effects that the temperature returning phenomenon and the overshoot phenomenon can be avoided, and energy can be saved are achieved.

Description

[0001] This application is a divisional application of the Chinese patent application with application number "CN 202310504712.6", application date "May 6, 2023", and title "A control method for a refrigeration system and a refrigeration system". Technical Field

[0002] The embodiments of the present invention relate to the technical field of refrigeration systems, and in particular to a control method of a refrigeration system and a refrigeration system. Background Art

[0003] For the large and small compressors of the refrigeration system of environmental test equipment, the existing switching condition is to use the IS (inner signal). When the large compressor cools down, when the temperature reaches the set value, the small compressor starts. Usually, the delay to shut down the large compressor is set to 600s. After the temperature reaches the set temperature in the heating stage, the small compressor is directly started to maintain a constant temperature.

[0004] In the cooling stage, especially when the load is large, this switching method is prone to two problems. One is the problem of excessive temperature recovery. When the load stores a large amount of heat and the temperature reaches the set value, the small compressor starts and the large compressor is delayed to shut down for 600s. After 600s, the large compressor is shut down. The cooling capacity output by the small compressor is much lower than the heat released inside the load. At this time, there will be a temperature recovery phenomenon or the temperature cannot be reduced to the set value for a long time after the temperature is recovered. The other is the problem of overshoot. When the load is small, because it is not the demand for controlled cooling capacity; when the temperature is reached, the large compressor is always running with the minimum valve step delay for 600s, continuously providing cooling capacity, so that the box temperature continues to drop, resulting in the actual temperature being lower than the set temperature. This phenomenon is called temperature overshoot. When the overshoot problem occurs, the PID (proportional-integral-differential) regulation of the electric heating output increases accordingly, and the power consumption increases. After reaching 600S, the large compressor is shut down. After switching to the small compressor, the PID readjusts the cooling capacity output and the heating capacity output to reach a new balance. In this adjustment process, a small temperature recovery phenomenon will occur again. Summary of the invention

[0005] The embodiments of the present invention provide a control method and a refrigeration system for a refrigeration system, which solve the technical problem in the prior art that excessive temperature recovery or overshoot is easily caused by simply using a set temperature value to switch between large and small compressors.

[0006] An embodiment of the present invention provides a control method for a refrigeration system, wherein the refrigeration system includes a first compressor and a second compressor, the power of the first compressor is greater than that of the second compressor, the refrigeration system also includes two evaporators, two condensers and two electronic expansion valves, the first compressor and the second compressor are respectively connected to one of the condensers, one of the electronic expansion valves and one of the evaporators in sequence; the control method includes:

[0007] receiving a refrigeration control instruction, and controlling the first compressor to perform refrigeration work on a target object based on the refrigeration control instruction;

[0008] Controlling the first compressor to perform refrigeration based on the refrigeration control instruction includes:

[0009] Determine whether the current temperature value of the target object is greater than a preset temperature threshold;

[0010] If yes, based on the refrigeration control instruction, the operation of the first compressor is controlled by proportional-integral-differential control method using the temperature deviation, wherein the temperature deviation is the difference between the current temperature value of the target object and the preset temperature threshold;

[0011] If not, the temperature deviation and the superheat of the refrigeration system are used to jointly control the operation of the first compressor.

[0012] Further, based on the refrigeration control instruction, controlling the operation of the first compressor by using the temperature deviation through a proportional-integral-differential control method includes:

[0013] Obtaining a target cooling temperature in the cooling control instruction;

[0014] Based on the target refrigeration temperature and the temperature deviation, the proportional-integral-differential control method is used to calculate and obtain the corresponding expansion valve step and the refrigeration capacity of the first compressor.

[0015] Furthermore, using the temperature deviation and the superheat of the refrigeration system to jointly control the operation of the first compressor includes:

[0016] Obtaining a superheat degree of a refrigerant in the refrigeration system;

[0017] determining a valve step reduction speed of an electronic expansion valve based on the superheat, wherein the electronic expansion valve is an electronic expansion valve connected to the first compressor;

[0018] The valve step contraction of the electronic expansion valve is controlled based on the valve step reduction speed, and the operation of the first compressor is controlled by a proportional-integral-differential control method using the temperature deviation.

[0019] Further, determining whether the valve step of the electronic expansion valve of the refrigeration system is shrunk to a preset expansion valve valve step value;

[0020] If so, shut down the first compressor and start the second compressor to maintain the current refrigeration temperature of the target object;

[0021] If not, continue to use the first compressor to perform refrigeration work.

[0022] Furthermore, the control method further includes:

[0023] During the operation of the second compressor, if the refrigeration control instruction is received again, the second compressor is turned off, and the first compressor is restarted to perform refrigeration work based on the refrigeration control instruction.

[0024] Furthermore, before controlling the operation of the first compressor by using a proportional-integral-differential control method using a temperature deviation based on the refrigeration control instruction, the control method further includes:

[0025] A temperature deviation between the current temperature value and the preset temperature threshold is calculated.

[0026] Furthermore, the cooling capacity output range of the first compressor is 5-7HP, and the cooling capacity output range of the second compressor is 2-3HP.

[0027] Furthermore, the cooling capacity of the first compressor is 6HP, and the cooling capacity of the second compressor is 2HP.

[0028] An embodiment of the present invention also provides a refrigeration system, which executes the control method of the refrigeration system described in any of the above embodiments; the refrigeration system includes a first compressor and a second compressor, the power of the first compressor is greater than that of the second compressor, the refrigeration system also includes two evaporators, two condensers and two electronic expansion valves, the first compressor and the second compressor are respectively connected in sequence to one of the condensers, one of the electronic expansion valves and one of the evaporators.

[0029] The embodiment of the present invention discloses a control method and a refrigeration system for a refrigeration system, the method comprising receiving a refrigeration control instruction, and controlling a first compressor to perform refrigeration work on a target object based on the refrigeration control instruction; controlling the first compressor to perform refrigeration work based on the refrigeration control instruction comprises: judging whether the current temperature value of the target object is greater than a preset temperature threshold; if so, controlling the operation of the first compressor by a proportional-integral-differential control method using a temperature deviation based on the refrigeration control instruction, wherein the temperature deviation is the difference between the current temperature value of the target object and the preset temperature threshold; if not, controlling the operation of the first compressor by using the temperature deviation and the superheat of the refrigeration system. The present application uses the temperature deviation to control the refrigeration of a high-power compressor, and judges when to turn on a low-power compressor to maintain a constant temperature according to the valve step of an electronic expansion valve, thereby solving the technical problem of excessive temperature recovery or overshooting caused by simply using a set temperature value to switch between large and small compressors in the prior art, and achieves the technical effect of avoiding temperature recovery and overshooting and saving energy. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 is a structural diagram of a refrigeration system provided by an embodiment of the present invention;

[0031] Figure 2 is a flow chart of a control method for a refrigeration system provided by an embodiment of the invention;

[0032] Figure 3 It is a flow chart of another control method of a refrigeration system provided by an embodiment of the invention. DETAILED DESCRIPTION

[0033] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for ease of description, only parts related to the present invention, rather than all structures, are shown in the accompanying drawings.

[0034] It should be noted that the terms "first", "second", etc. in the specification, claims and drawings of the present invention are used to distinguish different objects, rather than to limit a specific order. The following embodiments of the present invention can be implemented separately, or in combination with each other, and the embodiments of the present invention do not impose specific limitations on this.

[0035] Figure 1 is a structural diagram of a refrigeration system provided by an embodiment of the present invention. Figure 1As shown, the refrigeration system includes a first compressor 10 and a second compressor 20, the power of the first compressor 10 is greater than that of the second compressor 20, and the refrigeration system also includes two evaporators 30, two condensers 40 and two electronic expansion valves 50, and the first compressor 10 and the second compressor 20 are connected to a condenser 40, an electronic expansion valve 50 and an evaporator 30 in sequence. Figure 1 As shown, the two evaporators 30 are arranged together, but do not interfere with each other during operation, and the two condensers 40 are also arranged together, but do not interfere with each other during operation.

[0036] Figure 2 It is a flow chart of a control method of a refrigeration system provided by an embodiment of the invention.

[0037] like Figure 2 As shown, the control method of the refrigeration system specifically includes the following steps:

[0038] S101, receiving a refrigeration control instruction, and controlling a first compressor to perform refrigeration work on a target object based on the refrigeration control instruction.

[0039] Specifically, during the operation of the refrigeration system, the user can send a refrigeration control instruction to the refrigeration system through the human-computer interaction module to set the target refrigeration temperature of the refrigeration system. After receiving the refrigeration control instruction, the refrigeration system controls the high-power first compressor to cool down the target object based on the target instruction temperature in the instruction. In an embodiment of the present invention, the target object can be the internal environment of the test box, and the temperature of the internal environment of the test box is adjusted by the refrigeration system, or it can be other environments that require the use of a compressor for refrigeration, which is not limited here.

[0040] S102, determining whether the valve step of the electronic expansion valve of the refrigeration system is shrunk to a preset expansion valve valve step value.

[0041] Specifically, in the process of the first compressor cooling the target object, when the temperature gradually decreases, the temperature of the target object gradually approaches the preset temperature threshold. At this time, the demand for cooling capacity decreases, and the valve step of the electronic expansion valve gradually shrinks accordingly. The valve step of the electronic expansion valve is detected in real time, and it is determined whether it has shrunk to the preset expansion valve step value to determine whether it is necessary to start the low-power second compressor.

[0042] S103: If yes, turn off the first compressor and start the second compressor to maintain the current cooling temperature of the target object.

[0043] Specifically, if the judgment result is that the valve step of the electronic expansion valve shrinks to the preset expansion valve valve step value, for example, the preset expansion valve valve step value is set to 75step, when the valve step of the electronic expansion valve is less than 75step, the second compressor is switched to operate, and the temperature constant mode is started at this time, achieving the purpose of energy saving, and the valve step of the electronic expansion valve is used as the switching basis, so that a relatively stable entry into the constant stage can be achieved. On the contrary, if the judgment result is that the valve step of the electronic expansion valve does not shrink to the preset expansion valve valve step value, the first compressor is continued to be used for refrigeration.

[0044] The present application uses temperature deviation to control the refrigeration of a high-power compressor, and determines when to start a low-power compressor to maintain a constant temperature according to the valve step of an electronic expansion valve. This solves the technical problem in the prior art of simply using a set temperature value to switch between large and small compressors, which easily leads to excessive temperature recovery or overshoot. This achieves the technical effect of avoiding temperature recovery and overshoot and saving energy.

[0045] On the basis of the above technical solutions, Figure 3 is a flow chart of another method for controlling a refrigeration system provided by an embodiment of the present invention. Figure 3 As shown, S101, controlling the first compressor to perform refrigeration work based on the refrigeration control instruction specifically includes the following steps:

[0046] S301, determining whether the current temperature value of the target object is greater than a preset temperature threshold.

[0047] Specifically, during the operation of the refrigeration system, it is first necessary to obtain the current temperature value of the target object, and then compare the current temperature value with the preset temperature threshold to determine whether the target object is currently in a high temperature segment or a low temperature segment, thereby determining whether superheat is required during the operation of the refrigeration system.

[0048] S302: If yes, then based on the refrigeration control instruction, the first compressor is controlled to operate by a proportional-integral-differential control method using a temperature deviation, wherein the temperature deviation is a difference between a current temperature value of the target object and a preset temperature threshold.

[0049] Specifically, if the current temperature value is higher than the preset temperature threshold, it indicates that it is in the high temperature section, and the temperature deviation is used to control the first compressor through the PID (proportional-integral-differential) control method. Specifically, the temperature deviation is used as the input of the PID control, and the PID control is used to output the cooling capacity of the first compressor based on the total cooling demand of the target object.

[0050] Optionally, in S302, before controlling the operation of the first compressor by a proportional-integral-differential control method using a temperature deviation based on a refrigeration control instruction, the control method further includes: calculating a temperature deviation between a current temperature value and a preset temperature threshold.

[0051] Specifically, in order to meet the subsequent control requirements of the refrigeration system, after comparing the current temperature value with the preset temperature threshold, it is necessary to make a difference between the two to obtain a temperature deviation between the current temperature value and the preset temperature threshold for standby use.

[0052] S303: If not, the temperature deviation and the superheat of the refrigeration system are used to control the operation of the first compressor.

[0053] Specifically, if the current temperature value is lower than the preset temperature threshold, it indicates that it is in the low temperature section. At this time, in addition to using temperature deviation and PID control to control the first compressor, it is also necessary to use the superheat of the refrigeration system to control the first compressor, where the superheat refers to the difference between the superheat temperature and the saturation temperature of the refrigerant under the same evaporation pressure.

[0054] Optionally, S302 specifically includes:

[0055] Obtaining the target cooling temperature in the cooling control instruction;

[0056] Based on the target refrigeration temperature and the temperature deviation, the corresponding expansion valve step and the refrigeration capacity of the first compressor are calculated through the proportional-integral-differential control method.

[0057] Specifically, after receiving the refrigeration control instruction, the target refrigeration temperature carried in the refrigeration control instruction is obtained, and then the refrigeration demand is determined based on the target refrigeration temperature. Finally, the valve step of the electronic expansion valve and the refrigeration capacity that the first compressor needs to output are calculated through the refrigeration demand and the temperature deviation.

[0058] Optionally, S303 specifically includes:

[0059] Obtain the superheat of the refrigerant in the refrigeration system;

[0060] Determining a valve step reduction speed of the electronic expansion valve based on the superheat, wherein the electronic expansion valve is an electronic expansion valve connected to the first compressor;

[0061] The valve step contraction of the electronic expansion valve is controlled based on the valve step reduction speed, and the operation of the first compressor is controlled by a proportional-integral-differential control method using the temperature deviation.

[0062] Specifically, if the current temperature value is lower than the preset temperature threshold, it indicates that it is in the low temperature section. At this time, it is necessary to obtain the superheat of the refrigerant in the refrigeration system. Specifically, there is a pressure transmitter between the evaporator and the compressor in the refrigeration system. The pressure signal generated by the pressure transmitter will be converted into the evaporation temperature of the refrigeration system in a saturated state. There is also a temperature sensor at the outlet of the evaporator. The difference between the temperature value detected by the temperature sensor and the evaporation temperature is the superheat of the refrigerant.

[0063] After obtaining the superheat of the refrigerant, the superheat is compared with a preset superheat threshold, and the valve step reduction speed of the electronic expansion valve is determined according to the comparison result, so as to control the valve step contraction of the electronic expansion valve by using the determined valve step reduction speed, and at the same time, the temperature deviation is used to control the operation of the first compressor through a proportional-integral-differential control method. It should be noted that the electronic expansion valve is an electronic expansion valve connected to the first compressor.

[0064] Optionally, the control method of the refrigeration system further includes:

[0065] During the operation of the second compressor, if a refrigeration control instruction is received again, the second compressor is turned off, and the first compressor is restarted to perform refrigeration work based on the refrigeration control instruction.

[0066] Specifically, during the constant temperature refrigeration process of the second compressor, if the user sends a refrigeration control command to the refrigeration system again through the human-computer interaction module, the low-power second compressor is controlled to be turned off, and the high-power first compressor is turned on to perform a refrigeration action on the target object based on the refrigeration control instruction.

[0067] Optionally, the refrigeration capacity output range of the first compressor is 5-7HP, and the refrigeration capacity output range of the second compressor is 2-3HP.

[0068] Specifically, in order to achieve high-power cooling and low-power constant temperature refrigeration mode to achieve energy-saving effects, the power of the first compressor and the second compressor need to be set to different models. Generally speaking, the cooling capacity range of the first compressor is 5-7HP, and the cooling capacity range of the second compressor is 2-3HP.

[0069] Preferably, the refrigeration capacity of the first compressor is 6HP, and the refrigeration capacity of the second compressor is 2HP.

[0070] Exemplarily, the cooling capacity of the first compressor can be set to 6HP, and the cooling capacity of the second compressor can be set to 2HP, wherein 1HP means that the cooling capacity of the compressor is 2500w, and 6HP means that the cooling capacity of the compressor is 15kw.

[0071] The embodiment of the present invention further provides a refrigeration system, which executes the control method of the refrigeration system in any of the above embodiments; Figure 1 As shown, the refrigeration system includes a first compressor 10 and a second compressor 20. The power of the first compressor 10 is greater than that of the second compressor 20. The refrigeration system also includes two evaporators 30, two condensers 40 and two electronic expansion valves 50. The first compressor 10 and the second compressor 20 are connected to a condenser 40, an electronic expansion valve 50 and an evaporator 30 in sequence respectively.

[0072] The refrigeration system provided in the embodiment of the present invention uses the control method of the refrigeration system in the above embodiment, so the refrigeration system provided in the embodiment of the present invention also has the beneficial effects described in the above embodiment, which will not be described again here.

[0073] In the description of the embodiments of the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0074] Finally, it should be noted that the above are only preferred embodiments of the present invention and the technical principles used. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and that various obvious changes, readjustments and substitutions can be made by those skilled in the art without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in more detail through the above embodiments, the present invention is not limited to the above embodiments, and may include more other equivalent embodiments without departing from the concept of the present invention, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. A control method for a refrigeration system, characterized in that: The refrigeration system includes a first compressor and a second compressor, the power of the first compressor is greater than that of the second compressor, the refrigeration system also includes two evaporators, two condensers and two electronic expansion valves, the first compressor and the second compressor are respectively connected to one of the condensers, one of the electronic expansion valves and one of the evaporators in sequence; the control method includes: receiving a refrigeration control instruction, and controlling the first compressor to perform refrigeration work on a target object based on the refrigeration control instruction; Controlling the first compressor to perform refrigeration based on the refrigeration control instruction includes: Determine whether the current temperature value of the target object is greater than a preset temperature threshold; If yes, based on the refrigeration control instruction, the operation of the first compressor is controlled by proportional-integral-differential control method using the temperature deviation, wherein the temperature deviation is the difference between the current temperature value of the target object and the preset temperature threshold; If not, the temperature deviation and the superheat of the refrigeration system are used to jointly control the operation of the first compressor.

2. The control method of the refrigeration system according to claim 1, characterized in that: Based on the refrigeration control instruction, controlling the operation of the first compressor by using the temperature deviation through a proportional-integral-differential control method includes: Obtaining a target cooling temperature in the cooling control instruction; Based on the target refrigeration temperature and the temperature deviation, the proportional-integral-differential control method is used to calculate and obtain the corresponding expansion valve step and the refrigeration capacity of the first compressor.

3. The control method of the refrigeration system according to claim 1, characterized in that: Using the temperature deviation and the superheat of the refrigeration system to jointly control the operation of the first compressor includes: Obtaining a superheat degree of a refrigerant in the refrigeration system; determining a valve step reduction speed of an electronic expansion valve based on the superheat, wherein the electronic expansion valve is an electronic expansion valve connected to the first compressor; The valve step contraction of the electronic expansion valve is controlled based on the valve step reduction speed, and the operation of the first compressor is controlled by a proportional-integral-differential control method using the temperature deviation.

4. The control method of the refrigeration system according to claim 1, characterized in that: Determining whether the valve step of the electronic expansion valve of the refrigeration system is shrunk to a preset expansion valve valve step value; If so, shut down the first compressor and start the second compressor to maintain the current refrigeration temperature of the target object; If not, continue to use the first compressor to perform refrigeration work.

5. The control method of the refrigeration system according to claim 4, characterized in that: The control method further comprises: During the operation of the second compressor, if the refrigeration control instruction is received again, the second compressor is turned off, and the first compressor is restarted to perform refrigeration work based on the refrigeration control instruction.

6. The control method of the refrigeration system according to claim 1, characterized in that: Before controlling the operation of the first compressor by using a proportional-integral-differential control method using a temperature deviation based on the refrigeration control instruction, the control method further includes: A temperature deviation between the current temperature value and the preset temperature threshold is calculated.

7. The control method of a refrigeration system according to claim 1, characterized in that: The cooling capacity output range of the first compressor is 5-7HP, and the cooling capacity output range of the second compressor is 2-3HP.

8. The control method of the refrigeration system according to claim 7, characterized in that: The cooling capacity of the first compressor is 6HP, and the cooling capacity of the second compressor is 2HP.

9. A refrigeration system, characterized in that: The refrigeration system executes the control method of the refrigeration system described in any one of claims 1 to 8; the refrigeration system includes a first compressor and a second compressor, the power of the first compressor is greater than that of the second compressor, the refrigeration system also includes two evaporators, two condensers and two electronic expansion valves, the first compressor and the second compressor are respectively connected in sequence to one of the condensers, one of the electronic expansion valves and one of the evaporators.

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