A control method for a refrigeration system and a refrigeration system

Abstract

This invention discloses a control method and a refrigeration system for a refrigeration system. The method includes receiving a refrigeration control command and controlling a first compressor to refrigerate a target object based on the refrigeration control command. Controlling the first compressor to refrigerate based on the refrigeration control command includes: determining whether the current temperature value of the target object is greater than a preset temperature threshold; if so, controlling the first compressor to operate using a proportional-integral-derivative control method based on 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, controlling the first compressor to operate using the temperature deviation and the superheat of the refrigeration system together. This application solves the technical problem in the prior art where simply using a set temperature value to switch between large and small compressors easily leads to excessive temperature rebound or overshoot, achieving the technical effect of both avoiding temperature rebound and overshoot and saving energy.

Description

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

[0002] This invention relates to the field of refrigeration system technology, and in particular to a control method and a refrigeration system. Background Technology

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

[0004] During the cooling phase, especially under heavy loads, this switching method is prone to two problems. First, excessive temperature rebound can occur. When the load stores a large amount of heat and the temperature reaches the set value, the small compressor starts, while the large compressor shuts down after a 600-second delay. After 600 seconds, the large compressor shuts down, and the cooling output of the small compressor is far less than the heat released from the load. This can lead to temperature rebound, or the small compressor failing to bring the temperature down to the set value for an extended period after the temperature rebounds. Second, overshoot can occur. When the load is small, it's not focused on the cooling demand. Once the temperature is reached, the large compressor continues to operate with the minimum valve step delay for 600 seconds, continuously providing cooling, causing the chamber temperature to drop continuously, resulting in an actual temperature lower than the set temperature. This phenomenon is called temperature overshoot. When overshoot occurs, the PID (Proportional-Integral-Derivative) regulator increases the output of the electric heating element, increasing power consumption. After 600 seconds, the large compressor shuts down, and the small compressor switches to operation. The PID then readjusts the cooling and heating outputs to reach a new balance. During this adjustment process, a small temperature rebound can occur. Summary of the Invention

[0005] This invention provides a control method and a refrigeration system for a refrigeration system, which solves the technical problem in the prior art that the switching between large and small compressors is easily caused by simply using a set temperature value, resulting in excessive temperature return or overshoot.

[0006] This invention provides a control method for a refrigeration system. The refrigeration system includes a first compressor and a second compressor, wherein 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 sequentially connected to one of the condensers, one of the electronic expansion valves, and one of the evaporators, respectively. The control method includes:

[0007] Receive a refrigeration control command, and control the first compressor to refrigerate the target object based on the refrigeration control command;

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

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

[0010] If so, based on the refrigeration control command, the first compressor is controlled to work using a proportional-integral-derivative control method with respect to 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 operation of the first compressor is controlled by the temperature deviation and the superheat of the refrigeration system.

[0012] Furthermore, based on the refrigeration control command, controlling the operation of the first compressor using a proportional-integral-derivative control method based on the temperature deviation includes:

[0013] Obtain the target cooling temperature from the cooling control command;

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

[0015] Furthermore, controlling the operation of the first compressor using the temperature deviation and the superheat of the refrigeration system together includes:

[0016] Obtain the superheat of the refrigerant in the refrigeration system;

[0017] The valve step reduction speed of the electronic expansion valve is determined 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 the proportional-integral-derivative control method using the temperature deviation.

[0019] Further, it is determined whether the valve step of the electronic expansion valve of the refrigeration system has contracted to the preset expansion valve valve step value;

[0020] If so, then the first compressor is turned off and the second compressor is started to maintain the current cooling temperature of the target object;

[0021] If not, continue using the first compressor for refrigeration.

[0022] Furthermore, the control method further includes:

[0023] If the refrigeration control command is received again during the operation of the second compressor, the second compressor is shut down and the first compressor is restarted to perform refrigeration work based on the refrigeration control command.

[0024] Furthermore, before controlling the first compressor to operate using a proportional-integral-derivative control method based on the refrigeration control command and utilizing the temperature deviation, the control method further includes:

[0025] Calculate the temperature deviation between the current temperature value and the preset temperature threshold.

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

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

[0028] This invention also provides a refrigeration system that executes the control method for the refrigeration system described in any of the above embodiments. The refrigeration system includes a first compressor and a second compressor, wherein 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 sequentially connected to one of the condensers, one of the electronic expansion valves, and one of the evaporators, respectively.

[0029] This invention discloses a control method and a refrigeration system for a refrigeration system. The method includes receiving a refrigeration control command and controlling a first compressor to refrigerate a target object based on the refrigeration control command. Controlling the first compressor to refrigerate based on the refrigeration control command includes: determining whether the current temperature value of the target object is greater than a preset temperature threshold; if so, controlling the first compressor to operate using a proportional-integral-derivative control method based on 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, controlling the first compressor to operate using the temperature deviation and the superheat of the refrigeration system together. This application solves the technical problem of excessive temperature rebound or overshoot caused by simply using a set temperature value to switch between large and small compressors in the prior art by controlling the high-power compressor to refrigerate using temperature deviation and determining when to start the low-power compressor to maintain a constant temperature based on the valve step of the electronic expansion valve. This achieves the technical effect of avoiding both temperature rebound and overshoot, and saving energy. Attached Figure Description

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

[0031] Figure 2 This is a flowchart of a control method for a refrigeration system provided in an embodiment of the invention;

[0032] Figure 3 This is a flowchart of another control method for a refrigeration system provided in an embodiment of the invention. Detailed Implementation

[0033] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, and not all of the structures.

[0034] It should be noted that the terms "first," "second," etc., in the specification, claims, and drawings of this invention are used to distinguish different objects, not to limit a specific order. The various embodiments of this invention described below can be performed individually or in combination with each other; the embodiments of this invention do not impose specific limitations in this regard.

[0035] Figure 1 This is a structural diagram of a refrigeration system provided in an embodiment of the present invention. Figure 1As shown, the refrigeration system includes a first compressor 10 and a second compressor 20. The first compressor 10 has a higher power than 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 sequentially connected to one condenser 40, one electronic expansion valve 50, and one evaporator 30, respectively. Figure 1 As shown, the two evaporators 30 are set together, but do not interfere with each other during operation; the two condensers 40 are also set together, and do not interfere with each other during operation.

[0036] Figure 2 This is a flowchart of a control method for a refrigeration system provided in an embodiment of the invention.

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

[0038] S101 receives a refrigeration control command and controls the first compressor to perform refrigeration on the target object based on the refrigeration control command.

[0039] Specifically, during the operation of the refrigeration system, the user can send a refrigeration control command to the refrigeration system through the human-machine interface module to set the target refrigeration temperature. After receiving the refrigeration control command, the refrigeration system controls the high-power first compressor to cool the target object based on the target temperature command in the command. In this embodiment of the invention, the target object can be the internal environment of the test chamber, where the temperature of the internal environment of the test chamber is adjusted by the refrigeration system, or it can be any other environment that requires cooling using a compressor; no limitation is made here.

[0040] S102, determine whether the valve step of the electronic expansion valve of the refrigeration system has contracted to the preset expansion valve step value.

[0041] Specifically, during the cooling process of the first compressor, as 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 contracts accordingly. The valve step of the electronic expansion valve is detected in real time, and it is determined whether it has contracted to the preset expansion valve valve step value, so as to determine whether it is necessary to start the second compressor with low power.

[0042] S103, if so, then shut down the first compressor and start the second compressor to maintain the current cooling temperature of the target object.

[0043] Specifically, if the determination result is that the electronic expansion valve's valve step has contracted to the preset expansion valve step value, for example, the preset expansion valve step value is set to 75 steps, then when the electronic expansion valve's valve step is less than 75 steps, the system switches to the second compressor, initiating a constant temperature mode to achieve energy saving. Furthermore, using the electronic expansion valve's valve step as the switching criterion ensures a relatively stable entry into the constant temperature phase. Conversely, if the determination result is that the electronic expansion valve's valve step has not contracted to the preset expansion valve step value, then the first compressor continues to operate for refrigeration.

[0044] This application solves the technical problem in the prior art that the switching between large and small compressors is easily caused by simply using a set temperature value to switch between large and small compressors, which is achieved by using temperature deviation control to refrigerate the high-power compressor and determining when to start the low-power compressor to maintain a constant temperature based on the valve step of the electronic expansion valve. It achieves the technical effect of avoiding both temperature rebound and overshoot, and saving energy.

[0045] Based on the above technical solutions, Figure 3 This is a flowchart of another control method for a refrigeration system provided in an embodiment of the present invention, such as... Figure 3 As shown, S101, controlling the first compressor to perform refrigeration work based on the refrigeration control command specifically includes the following steps:

[0046] S301, determine whether the current temperature value of the target object is greater than the 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 the high temperature range or the low temperature range, thereby determining whether superheating is required during the operation of the refrigeration system.

[0048] S302, if so, then based on the refrigeration control command, the first compressor is controlled to work by using the proportional-integral-derivative control method with temperature deviation, where the temperature deviation is the difference between the current temperature value of the target object and the preset temperature threshold.

[0049] Specifically, if the current temperature value is higher than the preset temperature threshold, it indicates that the temperature is in the high-temperature range. The temperature deviation is then used to control the first compressor via PID (Proportional-Integral-Derivative) control. Specifically, the temperature deviation serves as the input to the PID control, and based on the total cooling demand of the target object, the PID control outputs the cooling capacity of the first compressor.

[0050] Optionally, in S302, before controlling the first compressor to work using a proportional-integral-derivative control method based on the refrigeration control command and utilizing the temperature deviation, the control method further includes: calculating the temperature deviation between the 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 calculate the difference between the two to obtain the temperature deviation between the current temperature value and the preset temperature threshold for later use.

[0052] S303, if not, then the operation of the first compressor is controlled by the temperature deviation and the superheat of the refrigeration system.

[0053] Specifically, if the current temperature value is lower than the preset temperature threshold, it indicates that the temperature is in the low temperature range. In this case, 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. 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] Obtain the target cooling temperature from the cooling control command;

[0056] Based on the target cooling temperature and temperature deviation, the proportional-integral-derivative control method is used to calculate the corresponding expansion valve step and the cooling capacity of the first compressor.

[0057] Specifically, after receiving the refrigeration control command, the target refrigeration temperature carried in the refrigeration control command 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 to be output by the first compressor are calculated based on the refrigeration demand and the temperature deviation.

[0058] Optionally, S303 specifically includes:

[0059] To obtain the superheat of the refrigerant in the refrigeration system;

[0060] The valve step reduction speed of the electronic expansion valve is determined 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 by the valve step reduction speed, and the operation of the first compressor is controlled by the proportional-integral-derivative control method using temperature deviation.

[0062] Specifically, if the current temperature value is lower than the preset temperature threshold, it indicates that the system is in the low-temperature range. 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 under saturation. 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 refrigerant superheat, the superheat is compared with a preset superheat threshold. Based on the comparison result, the valve step reduction speed of the electronic expansion valve is determined. This determined valve step reduction speed is then used to control the valve step contraction of the electronic expansion valve. Simultaneously, the temperature deviation is used to control the operation of the first compressor via a proportional-integral-derivative control method. It should be noted that this electronic expansion valve is connected to the first compressor.

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

[0065] If a refrigeration control command is received again during the operation of the second compressor, the second compressor will be shut down and the first compressor will be restarted to perform refrigeration work based on the refrigeration control command.

[0066] Specifically, during the constant-temperature cooling process of the second compressor, if the user sends a cooling control command to the cooling system again through the human-machine interaction module, the low-power second compressor will be shut down, and the high-power first compressor will be turned on to perform a cooling action on the target object based on the cooling control command.

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

[0068] Specifically, in order to achieve a cooling mode of high-power cooling and low-power constant temperature to achieve energy saving, the power of the first compressor and the second compressor needs to be set to different sizes. Generally speaking, the cooling capacity of the first compressor can be set to 5-7HP and the cooling capacity of the second compressor can be set to 2-3HP.

[0069] Preferably, the first compressor has a cooling capacity of 6 HP and the second compressor has a cooling capacity of 2 HP.

[0070] For example, the cooling capacity of the first compressor can be set to 6HP and the cooling capacity of the second compressor to 2HP. Here, 1HP means that the cooling capacity of the compressor is 2500W, and 6HP means that the cooling capacity of the compressor is 15kW.

[0071] This invention also provides a refrigeration system that executes the control method for the refrigeration system in any of the above embodiments; such as 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 sequentially to one condenser 40, one electronic expansion valve 50 and one evaporator 30, respectively.

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

[0073] In the description of the embodiments of the present invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in the present invention based on the specific circumstances.

[0074] Finally, it should be noted that the above are merely preferred embodiments of the present invention and the technical principles employed. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and various obvious changes, readjustments, and substitutions can be made without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments, and may include many other equivalent embodiments without departing from the concept of the present invention, the scope of which 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, wherein 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 sequentially connected to one of the condensers, one of the electronic expansion valves, and one of the evaporators, respectively. The control method includes: Receive a refrigeration control command, and control the first compressor to refrigerate the target object based on the refrigeration control command; Determine whether the valve step of the electronic expansion valve in the refrigeration system has contracted to the preset expansion valve step value; If so, then the first compressor is turned off and the second compressor is started to maintain the current cooling temperature of the target object; If not, continue using the first compressor for refrigeration. Controlling the first compressor to perform refrigeration based on the refrigeration control command includes: Determine whether the current temperature value of the target object is greater than a preset temperature threshold; If so, based on the refrigeration control command, the first compressor is controlled to work using a proportional-integral-derivative control method with respect to 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 operation of the first compressor is controlled by the temperature deviation and the superheat of the refrigeration system.

2. The control method for the refrigeration system according to claim 1, characterized in that, Based on the refrigeration control command, controlling the operation of the first compressor using a proportional-integral-derivative control method based on the temperature deviation includes: Obtain the target cooling temperature from the cooling control command; Based on the target cooling temperature and the temperature deviation, the proportional-integral-derivative control method is used to calculate the corresponding expansion valve step and the cooling capacity of the first compressor.

3. The control method for the refrigeration system according to claim 1, characterized in that, Controlling the operation of the first compressor using the temperature deviation and the superheat of the refrigeration system includes: Obtain the superheat of the refrigerant in the refrigeration system; The valve step reduction speed of the electronic expansion valve is determined 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 the proportional-integral-derivative control method using the temperature deviation.

4. The control method for the refrigeration system according to claim 1, characterized in that, The control method further includes: If the refrigeration control command is received again during the operation of the second compressor, the second compressor is shut down and the first compressor is restarted to perform refrigeration work based on the refrigeration control command.

5. The control method for the refrigeration system according to claim 1, characterized in that, Before controlling the first compressor to operate using a proportional-integral-derivative control method based on the refrigeration control command and utilizing the temperature deviation, the control method further includes: Calculate the temperature deviation between the current temperature value and the preset temperature threshold.

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

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

8. A refrigeration system, characterized in that, The refrigeration system executes the control method of the refrigeration system according to any one of claims 1 to 7; 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.

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