Control method of cascade refrigeration system in refrigeration equipment, and refrigeration equipment

Abstract

The present application relates to a control method for a cascade refrigeration system in a refrigeration device, and a refrigeration device, the method comprising: after the refrigeration device is powered on, controlling the high-temperature compressor to start running for a preset running time, controlling the low-temperature compressor to start running; when it is detected that the exhaust pressure of the low-temperature compressor has not risen to a preset pressure value, and the exhaust pressure of the low-temperature compressor is decreasing, adjusting the speed of the low-temperature compressor to a preset maximum speed; when the exhaust pressure of the low-temperature compressor rises to a preset pressure value, adjusting the speed of the low-temperature compressor to a preset minimum speed, and controlling the low-temperature compressor to increase from the preset minimum speed to the preset maximum speed at a first preset frequency increase rate. Through the present application, when the exhaust pressure of the low-temperature compressor is decreasing and a low flow rate occurs, the speed of the low-temperature compressor can be adjusted to the preset maximum speed to increase the inlet and outlet pressure difference of the compressor, that is, to increase the exhaust pressure of the low-temperature compressor, thereby increasing the low-temperature flow rate.

Description

Technical Field

[0001] The present application relates to the field of cascade refrigeration systems, and in particular to a control method for a cascade refrigeration system in a refrigeration device and a refrigeration device. Background Art

[0002] With the advancement of science and technology and the improvement of people's quality of life, low-temperature refrigeration technology is increasingly being used in healthcare, food storage, and other fields. To achieve a low-temperature environment, single-stage or two-stage vapor compression refrigeration systems are difficult to implement and have low operating efficiency. While cascade refrigeration systems are effective in achieving low-temperature environments, they can easily lead to excessively high exhaust pressure during compressor startup.

[0003] In order to avoid the compressor exhaust pressure being too high and exceeding the compressor operating conditions, thereby causing the compressor to trip. The existing technology is to reasonably adjust the frequency conversion compressor frequency increase rate after the compressor is started, so as to control the system pressure within a reasonable range. Since the compressor operating speed is within a certain range, such as 2000-4500r / min. However, when the heat load is large, the variable frequency compressor maintains operation at the lowest speed, and the exhaust pressure will be too high, or even exceed the pressure limit. For this reason, the intermediate heat exchanger can be increased to enhance the heat exchange of the refrigerant between the high and low temperature stages, thereby reducing the exhaust pressure when the compressor starts. However, it is easy to cause the low-temperature refrigerant to accumulate in liquid form in the intermediate heat exchanger, and the refrigerant flow is low when the low-temperature compressor starts, and the cooling rate is slow. Summary of the Invention

[0004] The present application provides a control method for a cascade refrigeration system in a refrigeration device and a refrigeration device to solve the problem in the prior art that in a cascade refrigeration system, increasing the intermediate heat exchanger to enhance the heat exchange of the refrigerant between high and low temperature stages will result in a low refrigerant flow rate when the low-temperature compressor is started, resulting in a slow cooling rate.

[0005] In the first aspect, the present application provides a control method for a cascade refrigeration system in a refrigeration equipment, wherein the cascade refrigeration system includes: a high-temperature compressor and a low-temperature compressor, and the method includes: after the refrigeration equipment is powered on, controlling the high-temperature compressor to start running for a preset running time, and controlling the low-temperature compressor to start running; wherein the preset running time is determined according to the ambient temperature and the refrigeration temperature of the refrigeration equipment; when it is detected that the exhaust pressure of the low-temperature compressor has not risen to the preset pressure value, and the exhaust pressure of the low-temperature compressor is decreasing, adjusting the speed of the low-temperature compressor to a preset maximum speed; when the exhaust pressure of the low-temperature compressor rises to the preset pressure value, adjusting the speed of the low-temperature compressor to a preset minimum speed, and controlling the low-temperature compressor to increase from the preset minimum speed to the preset maximum speed at a first preset frequency increase rate.

[0006] In the second aspect, the present application provides a refrigeration device, which includes a cascade refrigeration system, and the cascade refrigeration system includes: a high-temperature compressor and a low-temperature compressor, and the refrigeration device also includes: a first control module, which is used to control the high-temperature compressor to start running for a preset running time after the refrigeration device is powered on, and control the low-temperature compressor to start running; wherein the preset running time is determined according to the ambient temperature and the refrigeration temperature of the refrigeration device; an adjustment module, which is used to adjust the speed of the low-temperature compressor to a preset maximum speed when it is detected that the exhaust pressure of the low-temperature compressor has not risen to the preset pressure value and the exhaust pressure of the low-temperature compressor is decreasing; a first processing module, which is used to adjust the speed of the low-temperature compressor to a preset minimum speed when the exhaust pressure of the low-temperature compressor rises to the preset pressure value, and control the low-temperature compressor to increase from the preset minimum speed to the preset maximum speed at a first preset frequency increase rate.

[0007] In a third aspect, the present application provides a refrigeration device, comprising: at least one communication interface; at least one bus connected to the at least one communication interface; at least one processor connected to the at least one bus; and at least one memory connected to the at least one bus, wherein the processor is configured to execute the control method of the cascade refrigeration system in the refrigeration device described in any one of the above items of the present application.

[0008] In a fourth aspect, the present application further provides a computer storage medium storing computer executable instructions, wherein the computer executable instructions are used to execute the control method of the cascade refrigeration system in the refrigeration equipment described in any one of the above items of the present application.

[0009] The above technical solution provided by the embodiment of the present application has the following advantages over the prior art: through the method provided by the embodiment of the present application, when the high-temperature compressor starts to run for a preset running time, the low-temperature compressor is controlled to start running. If it is detected that the exhaust pressure of the low-temperature compressor has not risen to the preset pressure value and the exhaust pressure of the low-temperature compressor is decreasing, it indicates that the low-temperature compressor has a low flow rate and is insufficient to meet the normal refrigeration needs. Therefore, the low-temperature compressor speed is adjusted to a preset maximum speed to increase the compressor inlet and outlet pressure difference, that is, to increase the exhaust pressure of the low-temperature compressor, thereby increasing the low-temperature flow rate to improve the low-temperature flow rate. After the exhaust pressure of the low-temperature compressor rises to the preset pressure value, the low-temperature compressor speed is adjusted to a preset minimum speed and the low-temperature compressor is controlled to increase from the preset minimum speed to the preset maximum speed at a conventional first preset ramp rate. At this time, both the high and low temperature compressors are running at the highest speed to ensure that the refrigeration equipment quickly meets the refrigeration requirements. Through the method of the embodiment of the present application, the problem of the prior art that in a cascade refrigeration system, by increasing the intermediate heat exchanger to enhance the refrigerant heat exchange between the high and low temperature stages, the refrigerant flow rate at the start of the low-temperature compressor is low, resulting in a slow cooling rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0011] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0012] One or more embodiments are exemplarily illustrated by pictures in the corresponding drawings. These exemplifications 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 figures in the drawings do not constitute proportional limitations.

[0013] Figure 1 This is one of the flow charts of a method for controlling a cascade refrigeration system in a refrigeration device provided in an embodiment of the present application;

[0014] Figure 2 This is a second flow chart of a method for controlling a cascade refrigeration system in a refrigeration device provided in an embodiment of the present application;

[0015] Figure 3 A flow chart of a reliable startup control method for a cascade refrigeration system provided in an embodiment of the present application;

[0016] Figure 4 One of the structural diagrams of the refrigeration equipment provided in the embodiment of the present application;

[0017] Figure 5 This is the second structural diagram of the refrigeration equipment provided in the embodiment of the present application. DETAILED DESCRIPTION

[0018] To make the purpose, technical solutions, and advantages of the embodiments of this application more clear, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0019] The disclosure below provides many different embodiments or examples for implementing different configurations of the present invention. To simplify the disclosure of the present invention, the components and configurations of specific examples are described below. Of course, these are merely examples and are not intended to limit the present invention. In addition, the present invention may repeat reference numerals and / or letters in different examples. Such repetition is for the purpose of simplicity and clarity and does not in itself indicate the relationship between the various embodiments and / or configurations discussed.

[0020] Figure 1 The present invention provides a method for controlling a cascade refrigeration system in a refrigeration device. The cascade refrigeration system includes a high-temperature compressor and a low-temperature compressor. Based on this, the method steps of the embodiment of the present invention include:

[0021] Step 101: After the refrigeration equipment is powered on, the high-temperature compressor is controlled to start running for a preset operating time, and the low-temperature compressor is controlled to start running; wherein the preset operating time is determined according to the ambient temperature and the refrigeration temperature of the refrigeration equipment;

[0022] The cascade refrigeration system in this application and the embodiments consists of two parts: a high-temperature stage and a low-temperature stage. The high-temperature stage system (including a high-temperature stage compressor) and the low-temperature stage system (including a low-temperature stage compressor) are connected in parallel through a sleeve-type intermediate heat exchanger. Increasing the heat exchange area of ​​the intermediate heat exchanger can enhance the heat exchange of the refrigerant between the high and low temperature stages and reduce the exhaust pressure of the low-temperature stage compressor. In the embodiments of the present application, a pressure sensor can be connected to the exhaust pipe of the low-temperature stage compressor to monitor the exhaust pressure of the low-temperature stage compressor. The test pressure is fed back to the mainboard controller in real time, and the compressor speed and start and stop are controlled by the frequency converter.

[0023] In a specific example, the preset operating time refers to the time it takes for the high-temperature compressor to increase its speed from the lowest speed to the highest speed, for example, the lowest speed is 33Hz and the highest speed is 75Hz. It should be noted that the speed in the embodiment of the present application refers to the rotational frequency of the compressor. Moreover, the corresponding operating time is different under different ambient temperatures and different refrigeration temperatures. In the embodiment of the present application, it is possible to obtain the corresponding relationship between the three according to the startup rules of the high-temperature compressor in the cascade refrigeration system, as shown in Table 1.

[0024]

[0025] Table 1

[0026] It should be noted that the ambient temperature T a and cooling temperature T d The higher the value, the shorter the startup time t of the high temperature compressor. For example, t 11 Less than t 12 .

[0027] Step 102: When it is detected that the exhaust pressure of the low-temperature compressor has not risen to a preset pressure value and the exhaust pressure of the low-temperature compressor is decreasing, the speed of the low-temperature compressor is adjusted to a preset maximum speed;

[0028] It should be noted that if the heat exchange capacity of the intermediate heat exchanger is large, the high-temperature compressor provides more cooling capacity to the low-temperature compressor. After the low-temperature compressor is started, most of the refrigerant is cooled and exists in the casing, resulting in less refrigerant in the low-temperature system. This is reflected in the pressure that the exhaust pressure of the low-temperature compressor will rise when it is just started. As the refrigerant accumulates in the casing, the refrigerant flow rate decreases and the exhaust pressure decreases. Therefore, after the low-temperature compressor is started (such as starting at the lowest speed of 33Hz), if the exhaust pressure of the low-temperature compressor does not rise to the preset pressure value, and the pressure is gradually decreasing, it indicates that the low-temperature compressor has a low flow rate and is insufficient to meet the needs of normal refrigeration. Therefore, by adjusting the speed of the low-temperature compressor to the preset maximum speed to increase the inlet and outlet pressure difference of the compressor, that is, to increase the exhaust pressure of the low-temperature compressor, thereby increasing the low-temperature flow rate, in order to improve the low flow rate of the low-temperature stage.

[0029] Step 103, when the exhaust pressure of the low-temperature stage compressor rises to a preset pressure value, adjust the speed of the low-temperature stage compressor to a preset minimum speed, and control the low-temperature stage compressor to increase from the preset minimum speed to the preset maximum speed at a first preset frequency increase rate.

[0030] Through the above steps 101 to 103, when the high-temperature compressor starts to run for a preset running time, the low-temperature compressor is controlled to start running. If it is detected that the exhaust pressure of the low-temperature compressor has not risen to the preset pressure value and the exhaust pressure of the low-temperature compressor is decreasing, it indicates that the low-temperature compressor has a low flow rate and is insufficient to meet the normal refrigeration needs. Therefore, the low-temperature compressor speed is adjusted to a preset maximum speed to increase the compressor inlet and outlet pressure difference, that is, to increase the exhaust pressure of the low-temperature compressor, thereby increasing the low-temperature flow rate to improve the low-temperature flow rate. After the exhaust pressure of the low-temperature compressor rises to the preset pressure value, the low-temperature compressor speed is adjusted to a preset minimum speed, and the low-temperature compressor is controlled to increase from the preset minimum speed to the preset maximum speed at a conventional first preset frequency increase rate. At this time, both the high and low temperature compressors are running at the highest speed to ensure that the refrigeration equipment quickly meets the refrigeration requirements. Through the embodiment of the present application, the problem of low refrigerant flow rate when the low-temperature compressor is started, which makes the cooling rate slow, is solved in the prior art by increasing the intermediate heat exchanger to enhance the refrigerant heat exchange between the high and low temperature stages in the cascade refrigeration system.

[0031] In an optional implementation of an embodiment of the present application, for the above step 102, if it is currently detected that the exhaust pressure of the low-temperature compressor has risen to a preset pressure value, it indicates that the low-temperature compressor is not in a low-flow situation and can meet the normal refrigeration needs, and the low-temperature compressor is controlled to increase from the preset minimum speed to the preset maximum speed at a normal first preset frequency increase rate. In other words, under the normal condition where low flow does not occur, the startup process of the high and low temperature compressors is: after the refrigeration equipment is powered on, the high-temperature compressor starts running at the lowest speed, and after increasing from the preset minimum speed to the preset maximum speed at a second preset frequency increase rate, the low-temperature compressor is controlled to start running, and the low-temperature compressor is controlled to increase from the preset minimum speed to the preset maximum speed at a normal first preset frequency increase rate.

[0032] In an optional implementation manner of the embodiment of the present application, Figure 2 As shown, the method of the embodiment of the present application may further include:

[0033] Step 201: After the low-temperature compressor is running at a preset maximum speed and the exhaust pressure of the low-temperature compressor has not risen to a preset pressure value, the high-temperature compressor is controlled to stop, and the low-temperature compressor is controlled to switch from running at the preset maximum speed to running at a preset minimum speed;

[0034] In a specific example, the preset pressure value in the embodiment of the present application may be 20 bar. Of course, the preset pressure value may also be set according to actual needs. The above is merely an example.

[0035] Step 202: After the low-temperature compressor is running at a preset minimum speed, when the exhaust pressure of the low-temperature compressor rises to a preset pressure value, the high-temperature compressor is controlled to restart and the speed of the high-temperature compressor is increased to a preset maximum speed;

[0036] Step 203: Control the low-temperature compressor to increase its speed from a preset minimum speed to a preset maximum speed at a first preset speed-up rate.

[0037] If after passing through the above steps 101 to 103, the exhaust pressure of the low-temperature compressor may still not rise to the preset pressure value, in the embodiment of the present application, the exhaust pressure of the low temperature and compressor can also be increased through the above steps 201 to 203, that is, first control the high-temperature compressor to stop, and control the low-temperature compressor to switch from running at the preset maximum speed to running at the preset minimum speed. Since the high-temperature compressor is stopped, the low-temperature system is not cooled, and the refrigerant accumulated in the casing evaporates into gas and flows again, is sucked in by the low-temperature compressor, compressed and then discharged, and the exhaust pressure naturally increases. After the exhaust pressure of the low-temperature compressor rises to the preset pressure value, the high-temperature compressor is controlled to restart, and the speed of the high-temperature compressor is increased to the preset maximum speed. The low-temperature compressor is increased from the preset minimum speed to the preset maximum speed at the conventional first preset frequency increase rate. At this time, both the high and low temperature compressors are running at the highest speed, ensuring that the refrigeration equipment quickly meets the refrigeration requirements.

[0038] In an optional implementation manner of an embodiment of the present application, the method of controlling the high-temperature compressor to start running for a preset operating time involved in the above-mentioned step 101 can further include: controlling the high-temperature compressor to start running at a preset minimum speed, and increasing the speed from the preset minimum speed to the preset maximum speed at a second preset frequency increase rate; wherein, the operating time of the high-temperature compressor from the lowest speed to the preset maximum speed is the preset operating time.

[0039] It can be seen that in the embodiment of the present application, the preset operating time is the time it takes for the high-temperature compressor to increase from the preset minimum speed (such as 33 Hz) to the preset maximum speed (75 Hz) at different ambient temperatures and different cooling temperatures through the second preset frequency increase rate. As shown in Table 1, if the current ambient temperature is 25°C and the cooling temperature is -10°C, the preset operating time is t 23 If the current ambient temperature is 35°C and the cooling temperature is -50°C, the preset running time is t 15 .

[0040] In an optional implementation manner of the embodiment of the present application, after controlling the low-temperature stage compressor to increase the speed from a preset minimum speed to a preset maximum speed at a first preset frequency increase rate, the method steps of the embodiment of the present application may further include:

[0041] Step 21, obtaining the shortened operating time of the high-temperature compressor at the ambient temperature and the refrigeration temperature;

[0042] Step 22: Based on the shortened operating time, the preset operating time corresponding to the ambient temperature and the refrigeration temperature is updated in the preset mapping table, wherein the preset mapping table is used to characterize the mapping relationship between the preset operating time corresponding to different refrigeration temperatures and different ambient temperatures.

[0043] In the embodiment of the present application, the low-temperature stage flow rate can be increased by the above steps 101 to 103, or after the above steps 101 to 203, the startup time of the high-temperature stage compressor at the corresponding ambient temperature and refrigeration temperature (the time it takes to increase from the lowest speed to the highest speed after power-on) can be shortened. For example, the ambient temperature T a The cooling temperature is 32℃, T d If the temperature is -30℃, the operating time of the high temperature compressor is t 14 If each time the above steps 101 to 103, or the above steps 101 to 203 can be shortened by 30s, then after the next power-on, the high-temperature compressor startup time is t 14 -30s, you can synchronize the preset mapping table t 14 The above is just an example, and the shortening time can be measured or set accordingly according to the actual situation. For example, the shortening time can be 25s, 40s, etc. in different application scenarios.

[0044] In addition, in an optional implementation of the embodiment of the present application, after controlling the low-temperature stage compressor to increase the speed from a preset minimum speed to a preset maximum speed at a first preset frequency increase rate, the method steps of the embodiment of the present application may further include:

[0045] Step 23: Lower the preset maximum speed of the high-temperature compressor after the refrigeration equipment is powered on next time.

[0046] It can be seen that in an embodiment of the present application, the low-temperature stage flow rate can be increased through the above-mentioned steps 101 to step 103, or after the above-mentioned steps 101 to step 203, so as to shorten the start-up and operation time of the high-temperature stage compressor at the corresponding ambient temperature and refrigeration temperature. The preset maximum speed of the high-temperature stage compressor can also be reduced after the refrigeration equipment is powered on next time. For example, the current maximum speed of the high-temperature stage compressor is 75Hz. Through the above-mentioned steps 101 to step 103, or after the above-mentioned steps 101 to step 203, the maximum speed can be reduced to 50Hz.

[0047] The present application is explained below in conjunction with the specific implementation of the embodiment of the present application. This specific implementation provides a reliable startup control method for a cascade refrigeration system, such as Figure 3 As shown, the steps of the method include:

[0048] Step 301: The refrigeration equipment is powered on and the high-temperature compressor is turned on.

[0049] Step 302: After the high-temperature compressor has run for a period of time, the low-temperature compressor is turned on;

[0050] Step 303, determining whether the exhaust pressure of the low-temperature compressor reaches a preset pressure value, if yes, proceed to step 304, if not, proceed to step 305;

[0051] Step 304: The low-temperature compressor performs frequency increase according to the previously set frequency increase rate (first frequency increase rate);

[0052] Step 305: The low-temperature compressor is quickly increased to full frequency (preset maximum speed);

[0053] Step 306, determining whether the exhaust pressure of the low temperature compressor reaches a preset pressure value, if yes, proceed to step 307, if not, proceed to step 308;

[0054] Step 307: The low-temperature compressor is reduced to the lowest frequency and then frequency-increased according to the previously set frequency-increase rate.

[0055] Step 308: The high-temperature compressor is shut down, and the low-temperature compressor is reduced to the lowest frequency;

[0056] Step 309: When the exhaust pressure of the low-temperature compressor reaches a preset pressure value, the high-temperature compressor is controlled to increase to full frequency (preset maximum speed), and the low-temperature compressor is upgraded according to the originally set frequency increase rate;

[0057] Step 310: The next time the refrigeration equipment is powered on, the maximum frequency of the high-temperature compressor startup operation is reduced or the startup operation time of the high-temperature compressor is reduced.

[0058] As can be seen from steps 301 to 310 above, since the compressors have a rated speed range, the high-temperature compressor in the cascade refrigeration system starts at the lowest speed and increases to the highest speed at a specific ramp-up rate. After the high-temperature compressor has been running for a period of time, the low-temperature compressor starts at the lowest speed and increases to the highest speed at the specific ramp-up rate. At this point, both the high- and low-temperature compressors are running at their highest speeds, ensuring that the refrigeration equipment quickly meets cooling requirements.

[0059] If the low-temperature compressor is started at the lowest speed, if the exhaust pressure of the low-temperature compressor does not rise to the preset pressure value, the pressure will gradually decrease. When the decrease reaches a certain value, the speed of the low-temperature compressor will quickly increase to the maximum speed. When the pressure rises to the preset pressure value, the speed of the low-temperature compressor will be switched to the lowest speed, and then the low-temperature compressor will be increased to the maximum speed according to the original specific increase rate, and the temperature of the refrigeration equipment before the low-temperature compressor is started will be recorded.

[0060] If the above startup method cannot overcome the problem of low refrigerant flow, that is, when the low-temperature compressor speed is quickly increased to the maximum speed, the exhaust pressure rises slightly and then begins to drop, and still does not reach the preset pressure value, then the high-temperature compressor is shut down and the low-temperature compressor is started at the lowest speed. When the exhaust pressure rises to the preset pressure value, the high-temperature compressor is restarted and the speed is quickly increased to the maximum speed. The low-temperature compressor is then increased to the maximum speed according to the original specific speed increase rate to overcome the problem of low refrigerant flow.

[0061] After the above specific implementation, the next time the refrigeration equipment is powered on and heated, the startup time of the high-temperature compressor before the low-temperature compressor starts is shortened, or the maximum speed of the high-temperature compressor before the low-temperature compressor starts is reduced. The normal startup of the high and low-temperature compressors is performed, that is, after the high-temperature compressor starts and runs for a period of time, the low-temperature compressor starts and runs at the lowest speed. When the low-temperature exhaust pressure reaches the preset pressure value, the high-temperature speed is switched to the highest speed, and the low-temperature compressor is increased to the highest speed at the original specific frequency increase rate.

[0062] In specific application scenarios, variable-frequency compressors have a rated speed range, such as 2000 to 4500 rpm, corresponding to the inverter's 33 Hz to 75 Hz speed. When the refrigeration equipment is powered on, the high-temperature compressor in the cascade refrigeration system starts at the lowest speed, 33 Hz, and increases to its maximum speed, corresponding to 75 Hz, at a specific frequency ramp rate. After the high-temperature compressor has been running for a period of time, t, the low-temperature compressor starts at the lowest speed, 33 Hz, and then increases to its maximum speed at a specific frequency ramp rate. At this point, both the high- and low-temperature compressors are running at their maximum speed, ensuring that the refrigeration equipment quickly meets cooling requirements. Table 1 shows the high-temperature compressor startup time, t, before the low-temperature compressor starts.

[0063] When the high temperature compressor starts running for the set time, for example, the ambient temperature Ta is 32°C and the cooling temperature T d If the temperature is -30℃, the high temperature compressor startup time will reach t 14, the low-temperature compressor starts at the lowest speed, corresponding to 33Hz. If the low-temperature compressor exhaust pressure P does not rise to the preset pressure value Ps, optionally, Ps is 20bar, the exhaust pressure will gradually decrease. When the decrease reaches a certain value, such as when the low-temperature compressor is turned on, the exhaust pressure rises rapidly. When it rises to 15bar, the pressure begins to drop to 13bar, with a decrease of 2bar, indicating that the low-temperature stage has a low flow condition and is insufficient to meet the normal refrigeration needs. At this time, the speed of the low-temperature compressor quickly rises to the maximum speed, corresponding to 75Hz. The purpose of this approach is to increase the inlet and outlet pressure difference of the compressor, thereby increasing the low-temperature flow rate and improving the problem of low flow rate of the low-temperature stage. When the low-temperature exhaust pressure P rises to the preset pressure value Ps, in order to avoid the high speed causing the compressor exhaust pressure to be too high and trip, the low-temperature compressor speed is quickly switched to the lowest speed, and then the low-temperature compressor is increased to the highest speed according to the original specific frequency increase rate. At the same time, the ambient temperature T before the low-temperature compressor is started is recorded a and cooling temperature T d .

[0064] If the above-mentioned method of rapidly increasing the frequency of the low-temperature compressor still fails to overcome the problem of low-temperature refrigerant flow, that is, when the low-temperature compressor speed is rapidly increased to the maximum speed, the exhaust pressure P increases slightly and then begins to decrease, and has not yet reached the preset pressure value Ps. In this case, the high-temperature compressor is shut down and the low-temperature compressor is started at the lowest speed, corresponding to 33Hz. When the exhaust pressure P rises to the preset pressure value Ps, the high-temperature compressor is restarted and rapidly increased to the maximum speed, corresponding to 75Hz. At this time, the low-temperature compressor is increased to the maximum speed according to the original specific frequency increase rate.

[0065] As long as any of the above two actions occurs, that is, low flow occurs at the low temperature stage, the corresponding ambient temperature T a and cooling temperature T d The start-up time t of the high-temperature compressor is shortened by 30s each time. If the ambient temperature Ta is 32°C and the cooling temperature T d If the temperature is -30℃, the start-up time of the high-temperature compressor is updated to t 14-30s. The next time the refrigeration equipment is powered on and heated, the startup and running time of the high-temperature compressor is updated to the latest value. Alternatively, the maximum speed of the high-temperature compressor before the low-temperature compressor is started can be reduced accordingly. For example, the operating frequency of the high-temperature compressor can be reduced from the maximum frequency of 75Hz to 50Hz. After the high-temperature compressor has started and run for a period of time t, the low-temperature compressor starts running at the lowest speed. When the low-temperature exhaust pressure P reaches the preset pressure value Ps, indicating that the low-temperature flow rate is normal, to avoid the compressor tripping caused by excessive low-temperature exhaust pressure, the high-temperature speed is switched to the highest speed to enhance the low-temperature condensation heat exchange, and the low-temperature compressor is increased to the maximum speed at the original specific frequency increase rate.

[0066] Corresponding to the above Figure 1 The embodiment of the present application further provides a refrigeration device, the refrigeration device includes a cascade refrigeration system, the cascade refrigeration system includes: a high-temperature compressor and a low-temperature compressor, such as Figure 4 As shown, the refrigeration equipment also includes:

[0067] The first control module 402 is configured to control the high-temperature compressor to start running for a preset operating time after the refrigeration equipment is powered on, and to control the low-temperature compressor to start running; wherein the preset operating time is determined based on the ambient temperature and the refrigeration temperature of the refrigeration equipment;

[0068] The adjustment module 404 is configured to adjust the speed of the low-temperature compressor to a preset maximum speed when it is detected that the exhaust pressure of the low-temperature compressor has not risen to a preset pressure value and the exhaust pressure of the low-temperature compressor is decreasing;

[0069] The first processing module 406 is used to adjust the speed of the low-temperature stage compressor to a preset minimum speed when the exhaust pressure of the low-temperature stage compressor rises to a preset pressure value, and control the low-temperature stage compressor to increase from the preset minimum speed to the preset maximum speed at a first preset frequency increase rate.

[0070] In the refrigeration equipment of the embodiment of the present application, when the high-temperature compressor starts to run for a preset running time, the low-temperature compressor is controlled to start running. If it is detected that the exhaust pressure of the low-temperature compressor has not risen to the preset pressure value and the exhaust pressure of the low-temperature compressor is decreasing, it indicates that the low-temperature compressor has a low flow rate and is insufficient to meet the normal refrigeration needs. Therefore, the low-temperature compressor speed is adjusted to a preset maximum speed to increase the compressor inlet and outlet pressure difference, that is, to increase the exhaust pressure of the low-temperature compressor, thereby increasing the low-temperature flow rate to improve the low-temperature flow rate. After the exhaust pressure of the low-temperature compressor rises to the preset pressure value, the low-temperature compressor speed is adjusted to a preset minimum speed, and the low-temperature compressor is controlled to increase from the preset minimum speed to the preset maximum speed at a conventional first preset frequency increase rate. At this time, both the high and low temperature compressors are running at the highest speed to ensure that the refrigeration equipment quickly meets the refrigeration requirements. Through the method of the embodiment of the present application, the problem of low refrigerant flow at the start of the low-temperature compressor and slow cooling rate caused by increasing the intermediate heat exchanger in the cascade refrigeration system in the prior art is solved.

[0071] Optionally, the refrigeration equipment of the embodiment of the present application may further include: a second control module, used to control the high-temperature stage compressor to stop and control the low-temperature stage compressor to switch from running at the preset maximum speed to running at a preset minimum speed after the low-temperature stage compressor runs at a preset maximum speed and the exhaust pressure of the low-temperature stage compressor has not risen to a preset pressure value; a second processing module, used to control the high-temperature stage compressor to restart and increase the speed of the high-temperature stage compressor to a preset maximum speed after the low-temperature stage compressor runs at a preset minimum speed and the exhaust pressure of the low-temperature stage compressor rises to a preset pressure value; a third control module, used to control the low-temperature stage compressor to increase from a preset minimum speed to a preset maximum speed at a first preset frequency increase rate.

[0072] Optionally, the refrigeration equipment of the embodiment of the present application may further include: an acquisition module for acquiring the shortened operating time of the high-temperature compressor at the ambient temperature and the refrigeration temperature after controlling the low-temperature compressor to increase from a preset minimum speed to a preset maximum speed at a first preset frequency increase rate; an update module for updating the preset operating time corresponding to the ambient temperature and the refrigeration temperature in the preset mapping table based on the shortened operating time, wherein the preset mapping table is used to characterize the mapping relationship between the preset operating time corresponding to different refrigeration temperatures and different ambient temperatures.

[0073] Optionally, the refrigeration equipment of the embodiment of the present application may further include: a third processing module, which is used to reduce the preset maximum speed of the high-temperature compressor after the refrigeration equipment is powered on next time after controlling the low-temperature compressor to increase from a preset minimum speed to a preset maximum speed at a first preset frequency increase rate.

[0074] Optionally, the first control module of the embodiment of the present application may include: a control unit for controlling the high-temperature stage compressor to start running at a preset minimum speed, and to increase the speed from the preset minimum speed to the preset maximum speed at a second preset frequency increase rate; wherein, the running time of the high-temperature stage compressor from the lowest speed to the preset maximum speed is the preset running time.

[0075] Optionally, the refrigeration equipment of the embodiment of the present application may further include: a fourth control module, which is used to control the low-temperature stage compressor to increase the speed from a preset minimum speed to a preset maximum speed at a first preset frequency increase rate when it is detected that the exhaust pressure of the low-temperature stage compressor rises to a preset pressure value.

[0076] like Figure 5 As shown, the embodiment of the present application provides a refrigeration device, including a processor 511, a communication interface 512, a memory 513 and a communication bus 514, wherein the processor 511, the communication interface 512, and the memory 513 communicate with each other through the communication bus 514.

[0077] Memory 513, for storing computer programs;

[0078] In one embodiment of the present application, the processor 511 is used to execute the program stored in the memory 513 to implement the control method of the cascade refrigeration system in the refrigeration equipment provided by any of the aforementioned method embodiments. The role it plays is similar and will not be repeated here.

[0079] An embodiment of the present application further provides a computer-readable storage medium having a computer program stored thereon. When the computer program is executed by a processor, the steps of the method for controlling a cascade refrigeration system in a refrigeration device as provided in any of the aforementioned method embodiments are implemented.

[0080] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed across multiple network units. Some or all of the modules may be selected based on actual needs to achieve the objectives of this embodiment.

[0081] Through the description of the above embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus a general hardware platform, or of course, by hardware. Based on this understanding, the above technical solution, in essence, or the part that contributes to the relevant technology, can be embodied in the form of a software product. The computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, a magnetic disk, an optical disk, etc., and includes a number of instructions for enabling a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in each embodiment or certain parts of the embodiment.

[0082] It should be understood that the terms used herein are for the purpose of describing specific example embodiments only and are not intended to be limiting. Unless the context clearly indicates otherwise, the singular forms "one", "an" and "said" as used herein may also be meant to include plural forms. The terms "comprise", "include", "contain" and "have" are inclusive and therefore specify the presence of stated features, steps, operations, elements and / or parts, but do not exclude the presence or addition of one or more other features, steps, operations, elements, parts, 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 specific order described or illustrated, unless the order of execution is clearly indicated. It should also be understood that additional or alternative steps may be used.

[0083] The foregoing description is intended only to provide specific embodiments of the present invention, which will enable those skilled in the art to understand and implement the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not intended to be limited to the embodiments shown herein, but is intended to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for controlling a cascade refrigeration system in a refrigeration device, the cascade refrigeration system comprising: The high-temperature stage compressor and the low-temperature stage compressor are characterized in that the method comprises: After the refrigeration equipment is powered on, the high-temperature stage compressor is controlled to start running for a preset running time, and the low-temperature stage compressor is controlled to start running; wherein the preset running time is determined according to the ambient temperature and the refrigeration temperature of the refrigeration equipment; When it is detected that the exhaust pressure of the low-temperature compressor has not risen to the preset pressure value and the exhaust pressure of the low-temperature compressor is decreasing, adjusting the speed of the low-temperature compressor to a preset maximum speed; When the exhaust pressure of the low-temperature compressor rises to the preset pressure value, adjusting the speed of the low-temperature compressor to a preset minimum speed, and controlling the low-temperature compressor to increase from the preset minimum speed to the preset maximum speed at a first preset frequency increase rate; After the low-temperature stage compressor is running at a preset maximum speed and the exhaust pressure of the low-temperature stage compressor has not risen to the preset pressure value, the high-temperature stage compressor is controlled to stop, and the low-temperature stage compressor is controlled to switch from running at the preset maximum speed to running at the preset minimum speed; After the low-temperature compressor is running at the preset minimum speed, when the exhaust pressure of the low-temperature compressor rises to the preset pressure value, controlling the high-temperature compressor to restart and increasing the speed of the high-temperature compressor to the preset maximum speed; The low-temperature stage compressor is controlled to increase the speed from the preset minimum speed to the preset maximum speed at the first preset speed increase rate.

2. The method according to claim 1, characterized in that After controlling the low-temperature stage compressor to increase the speed from the preset minimum speed to the preset maximum speed at the first preset speed-up rate, the method further includes: Obtaining a shortened operating time of the high-temperature stage compressor at the ambient temperature and the refrigeration temperature; Based on the shortened operating time, the preset operating time corresponding to the ambient temperature and the refrigeration temperature is updated in a preset mapping table, wherein the preset mapping table is used to characterize the mapping relationship between the preset operating time corresponding to different refrigeration temperatures and different ambient temperatures.

3. The method according to claim 1, characterized in that After controlling the low-temperature stage compressor to increase the speed from the preset minimum speed to the preset maximum speed at the first preset speed-up rate, the method further includes: The preset maximum speed of the high-temperature stage compressor is reduced the next time the refrigeration equipment is powered on.

4. The method according to claim 1, wherein The controlling the high temperature stage compressor to start and run for a preset running time includes: The high-temperature stage compressor is controlled to start running at a preset minimum speed, and to increase from the preset minimum speed to the preset maximum speed at a second preset frequency increase rate; wherein the running time of the high-temperature stage compressor from the minimum speed to the preset maximum speed is the preset running time.

5. The method according to claim 1, wherein The method further comprises: When it is detected that the exhaust pressure of the low-temperature stage compressor rises to the preset pressure value, the low-temperature stage compressor is controlled to increase from the preset minimum speed to the preset maximum speed at the first preset speed increase rate.

6. A refrigeration device, comprising a cascade refrigeration system, the cascade refrigeration system comprising: A high-temperature compressor and a low-temperature compressor, characterized in that the refrigeration equipment further comprises: a first control module, configured to control the high-temperature stage compressor to start running for a preset operating time after the refrigeration equipment is powered on, and to control the low-temperature stage compressor to start running; wherein the preset operating time is determined according to the ambient temperature and the refrigeration temperature of the refrigeration equipment; an adjusting module, configured to adjust the rotational speed of the cryogenic compressor to a preset maximum rotational speed when detecting that the exhaust pressure of the cryogenic compressor has not risen to a preset pressure value and the exhaust pressure of the cryogenic compressor is decreasing; a first processing module, configured to adjust the rotational speed of the low-temperature compressor to a preset minimum rotational speed when the exhaust pressure of the low-temperature compressor rises to the preset pressure value, and control the low-temperature compressor to increase the rotational speed from the preset minimum rotational speed to the preset maximum rotational speed at a first preset frequency increase rate; a second control module, configured to, after the low-temperature stage compressor is running at a preset maximum speed and if the exhaust pressure of the low-temperature stage compressor does not rise to the preset pressure value, control the high-temperature stage compressor to stop, and control the low-temperature stage compressor to switch from running at the preset maximum speed to running at the preset minimum speed; a second processing module, configured to control the high-temperature stage compressor to restart and increase the speed of the high-temperature stage compressor to the preset maximum speed when the exhaust pressure of the low-temperature stage compressor rises to the preset pressure value after the low-temperature stage compressor runs at the preset minimum speed; The third control module is configured to control the low-temperature stage compressor to increase the speed from the preset minimum speed to the preset maximum speed at the first preset frequency increase rate.

7. A refrigeration device, characterized in that: It includes a processor, a communication interface, a memory and a communication bus, wherein the processor, the communication interface and the memory communicate with each other via the communication bus; Memory for storing computer programs; A processor, configured to implement the method according to any one of claims 1 to 5 when executing a program stored in a memory.

8. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the program is executed by a processor, the method according to any one of claims 1 to 5 is implemented.

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