Compound refrigeration system control method, storage medium, system, refrigerator and cold storage

Abstract

The present invention provides a control method, storage medium, system, refrigerator and cold storage of a cascade refrigeration system. The control method of the cascade refrigeration system includes obtaining a heat exchange pressure range, detecting and adjusting the operating frequency of the compressor according to the evaporation pressure of the high-temperature stage system and / or the condensation pressure of the low-temperature stage system, so that the evaporation pressure of the high-temperature stage system and / or the condensation pressure of the low-temperature stage system are always within the heat exchange pressure range. The computer-readable storage medium can implement the control method of the above-mentioned cascade refrigeration system. The cascade refrigeration system includes a high-temperature stage system and a low-temperature stage system and can implement the control method of the above-mentioned cascade refrigeration system. The refrigerator and cold storage include the above-mentioned cascade refrigeration system and can implement the control method of the above-mentioned cascade refrigeration system. Such an arrangement can improve the operating efficiency of the cascade refrigeration system.

Description

Technical Field

[0001] The present invention relates to the field of refrigeration technology, and in particular to a control method, storage medium, system, refrigerator, and cold storage of a cascade refrigeration system. Background Art

[0002] With the advancement of science and technology, refrigeration technology is increasingly required to provide low-temperature environments. For example, in healthcare, low-temperature freezers are needed to store vaccines and other medications. For warehousing seafood and other food ingredients, cold storage facilities are needed to quickly freeze and store them for long periods. In daily life, refrigerators may also be needed to store special ingredients or items at low temperatures. The refrigeration system is a key component of refrigeration equipment that provides low-temperature environments. The efficiency of the refrigeration system directly affects the operating cost and stability of the refrigeration equipment. Achieving low temperatures, such as below -30°C, is difficult with a single refrigeration system. Instead, a cascade refrigeration system can be used. A cascade refrigeration system is composed of several relatively independent refrigeration systems operating with different refrigerants. A cascade refrigeration system consists of a high-temperature stage and a low-temperature stage. The evaporation of the refrigerant in the high-temperature stage absorbs heat to condense the refrigerant in the low-temperature stage. The evaporation of the refrigerant in the low-temperature stage then provides cooling.

[0003] The control scheme of most cascade refrigeration systems in the prior art is to make the heat absorption of the high-temperature stage system equal to the heat dissipation of the low-temperature stage system, and based on this, match the high-temperature stage system and the low-temperature stage system.

[0004] However, this method has the following drawbacks: the operating efficiency of the cascade refrigeration system needs to be improved. Summary of the Invention

[0005] The object of the present invention is to provide a control method for a cascade refrigeration system, a storage medium, a cascade refrigeration system, a refrigerator and a cold storage that can improve the operating efficiency of the cascade refrigeration system. By adjusting the operating frequency of the compressor, the evaporator of the high-temperature stage system and the condenser of the low-temperature stage system always operate within the heat exchange pressure range, thereby improving the operating efficiency of the cascade refrigeration system.

[0006] To achieve the above-mentioned object of the invention, an embodiment of the present invention provides a control method for a cascade refrigeration system, wherein the control method includes:

[0007] Get the heat exchange pressure range;

[0008] detecting the evaporation pressure of the high-temperature stage system and / or the condensation pressure of the low-temperature stage system;

[0009] determining whether the evaporation pressure of the high-temperature stage system and / or the condensation pressure of the low-temperature stage system are within the heat exchange pressure range;

[0010] If not, adjust the operating frequency of the compressor of the high-temperature stage system and / or the compressor of the low-temperature stage system until the evaporating pressure of the high-temperature stage system and / or the condensing pressure of the low-temperature stage system are in the first pressure range, and the operating frequency of the compressor of the high-temperature stage system is negatively correlated with the evaporating pressure of the high-temperature stage system, and the operating frequency of the compressor of the low-temperature stage system is positively correlated with the condensing pressure of the low-temperature stage system.

[0011] As a further improvement of an embodiment of the present invention, “obtaining the heat exchange pressure range” includes:

[0012] After receiving the power-on signal, the temperature of the refrigeration compartment is detected;

[0013] When the temperature change value of the refrigeration compartment is within a preset range within a preset time period, the first condensing temperature of the high-temperature stage system and the first evaporating temperature of the low-temperature stage system are detected;

[0014] Calculating the heat exchange condensing pressure of the high-temperature stage system according to the first condensing temperature, and calculating the heat exchange evaporating pressure of the low-temperature stage system according to the first evaporating temperature;

[0015] Calculate the intermediate pressure between the heat exchange condensing pressure of the high-temperature stage system and the heat exchange evaporating pressure of the low-temperature stage system, as well as the heat exchange pressure range,

[0016] Among them, the

[0017] The upper limit of the heat exchange range = intermediate pressure + first preset value,

[0018] The lower limit of the heat exchange range = intermediate pressure - second preset value.

[0019] As a further improvement of an embodiment of the present invention, “obtaining the heat exchange pressure range” includes:

[0020] After receiving the power-on signal, the temperature of the refrigeration compartment is detected;

[0021] When the temperature change value of the refrigeration compartment is within a preset range within a preset time, the first condensing temperature of the high-temperature system and the first evaporating temperature of the low-temperature system are detected, and

[0022] detecting a first ambient temperature of a condenser of the high-temperature stage system and a second ambient temperature of an evaporator of the low-temperature stage system;

[0023] Obtaining a preset condensing temperature range for the operation of the condenser of the high-temperature stage system corresponding to the first ambient temperature;

[0024] determining whether the first condensing temperature is within the preset condensing temperature range;

[0025] If yes, then calculating the heat exchange condensing pressure of the high temperature stage system according to the first condensing temperature;

[0026] If not, then obtain the preset condensation temperature, the preset condensation temperature is within the preset condensation temperature range, and

[0027] Calculating the heat exchange condensation pressure of the high temperature stage system according to the preset condensation temperature;

[0028] determining whether the second ambient temperature is within a preset evaporation ambient temperature;

[0029] If so, calculating the heat exchange evaporation pressure of the low temperature stage system according to the first evaporation temperature;

[0030] If not, the preset evaporation temperature is obtained according to the preset evaporation ambient temperature, and

[0031] Calculating the heat exchange evaporation pressure of the low temperature stage system according to the preset evaporation temperature;

[0032] Calculate the intermediate pressure between the heat exchange condensing pressure of the high-temperature stage system and the heat exchange evaporating pressure of the low-temperature stage system, as well as the heat exchange pressure range,

[0033] Among them, the

[0034] The upper limit of the heat exchange range = intermediate pressure + first preset value,

[0035] The lower limit of the heat exchange range = intermediate pressure - second preset value.

[0036] As a further improvement of an embodiment of the present invention, the control method includes:

[0037] Determining whether the evaporation pressure of the high-temperature stage system is higher than the upper limit of the preset heat exchange pressure range;

[0038] If so, increasing the operating frequency of the compressor of the high temperature stage system;

[0039] Determining whether the evaporation pressure of the high-temperature stage system is lower than the lower limit of the preset heat exchange pressure range;

[0040] If so, the operating frequency of the compressor of the high temperature stage system is reduced.

[0041] As a further improvement of an embodiment of the present invention, the control method includes:

[0042] Determining whether the condensing pressure of the low-temperature stage system is lower than the lower limit of the preset heat exchange pressure range;

[0043] If so, increasing the operating frequency of the compressor of the low temperature stage system;

[0044] Determining whether the condensing pressure of the low-temperature stage system is higher than the upper limit of the preset heat exchange pressure range;

[0045] If not, the operating frequency of the compressor of the low temperature stage system is reduced.

[0046] To achieve the above-mentioned purpose of the invention, one embodiment of the present invention provides a computer-readable storage medium, wherein the computer-readable storage medium stores a computer program thereon, and when the computer program is executed by a processor, the steps in the control method of the cascade refrigeration system described in any of the above-mentioned embodiments are implemented.

[0047] To achieve the above-mentioned purpose of the invention, one embodiment of the present invention provides a cascade refrigeration system, wherein the cascade refrigeration system includes a high-temperature stage system and a low-temperature stage system, the high-temperature stage system includes a connected high-temperature stage compressor, a high-temperature stage evaporator, and a high-temperature stage condenser, the low-temperature stage system includes a connected low-temperature stage compressor, a low-temperature stage condenser, and a low-temperature stage evaporator, the temperature of the high-temperature stage evaporator is lower than the temperature of the low-temperature stage condenser, the high-temperature stage evaporator and the low-temperature stage condenser constitute a heat exchange module, the high-temperature stage compressor and / or the low-temperature stage compressor are variable frequency compressors, the cascade refrigeration system also includes a pressure detection device, the cascade refrigeration system also includes a memory and a processor, the memory stores a computer program that can be run on the processor, and when the processor executes the computer program, the steps in the control method of the cascade refrigeration system described in any of the above-mentioned embodiments are implemented.

[0048] As a further improvement of one embodiment of the present invention, the cascade refrigeration system is a two-stage cascade refrigeration system including a high-temperature stage system and a low-temperature stage system, and both the high-temperature stage system and the low-temperature stage system are single-stage circulation systems including a compressor.

[0049] To achieve the above-mentioned object of the invention, one embodiment of the present invention provides a refrigerator, wherein the refrigerator includes a cabinet and a cascade refrigeration system, the cascade refrigeration system including a high-temperature stage system and a low-temperature stage system, the high-temperature stage system including a connected high-temperature stage compressor, a high-temperature stage evaporator, and a high-temperature stage condenser, the low-temperature stage system including a connected low-temperature stage compressor, a low-temperature stage condenser, and a low-temperature stage evaporator, the temperature of the high-temperature stage evaporator is lower than the temperature of the low-temperature stage condenser, the high-temperature stage evaporator and the low-temperature stage condenser constitute a heat exchange module, a refrigeration compartment is provided in the cabinet, the cascade refrigeration system is used to supply cold air to the refrigeration compartment, the high-temperature stage compressor and / or the low-temperature stage compressor are variable frequency compressors, the cascade refrigeration system further includes a pressure detection device, the cascade refrigeration system further includes a memory and a processor, the memory stores a computer program that can be run on the processor, and when the processor executes the computer program, the steps of the control method of the cascade refrigeration system described in any of the above-mentioned embodiments are implemented.

[0050] To achieve the above-mentioned object of the invention, one embodiment of the present invention provides a cold storage, wherein the cold storage includes a storage room and a cascade refrigeration system, the cascade refrigeration system includes a high-temperature system and a low-temperature system, the high-temperature system includes a connected high-temperature compressor, a high-temperature evaporator, and a high-temperature condenser, the low-temperature system includes a connected low-temperature compressor, a low-temperature condenser, and a low-temperature evaporator, the temperature of the high-temperature evaporator is lower than the temperature of the low-temperature condenser, the high-temperature evaporator and the low-temperature condenser constitute a heat exchange module, the cascade refrigeration system is used to supply cooling to the storage room, the high-temperature compressor and / or the low-temperature compressor is a variable frequency compressor, the cascade refrigeration system also includes a pressure detection device, the cascade refrigeration system also includes a memory and a processor, the memory stores a computer program that can be run on the processor, and when the processor executes the computer program, the steps in the control method of the cascade refrigeration system described in any of the above-mentioned embodiments are implemented.

[0051] The present invention provides a technical solution for calculating the intermediate pressure by obtaining the condensing pressure of the high-temperature stage system and the evaporating pressure of the low-temperature stage system when the system is running stably, obtaining the heat exchange pressure range by the intermediate pressure and the preset value, and using the heat exchange pressure range as the optimal operating parameter range of the cascade refrigeration system. By adjusting the operating frequency of the compressor, the evaporator of the high-temperature stage system and the condenser of the low-temperature stage system are always operated within the heat exchange pressure range.

[0052] Compared with the prior art, the beneficial effects of the present invention are: enabling the cascade refrigeration system to operate within a better operating parameter range, thereby improving the operating efficiency of the cascade refrigeration system. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 is a schematic diagram of a cascade refrigeration system according to one embodiment of the present invention;

[0054] Figure 2 is a flow chart of a control method for a cascade refrigeration system according to one embodiment of the present invention;

[0055] Figure 3 is a flow chart of a control method for obtaining a heat exchange pressure range according to one embodiment of the present invention;

[0056] Figure 4 is a flow chart of a control method for obtaining a heat exchange pressure range according to another embodiment of the present invention;

[0057] Figure 5 is a flow chart of a control method for a high temperature stage system according to one embodiment of the present invention;

[0058] Figure 6 This is a flowchart of a control method for a low-temperature stage system according to one embodiment of the present invention. DETAILED DESCRIPTION

[0059] The present invention will be described in detail below with reference to the specific embodiments shown in the accompanying drawings. However, these embodiments do not limit the present invention, and any structural, methodological, or functional changes made by those skilled in the art based on these embodiments are all within the scope of protection of the present invention.

[0060] Figure 1 A cascade refrigeration system 100 according to an embodiment of the present invention is shown.

[0061] like Figure 1 As shown, in one embodiment of the present invention, the cascade refrigeration system 100 may include a high-temperature stage system 10 and a low-temperature stage system 20, the high-temperature stage system 10 may include a high-temperature stage compressor 11, a high-temperature stage evaporator 31, and a high-temperature stage condenser 12 that are connected to each other, and the low-temperature stage system 20 may include a low-temperature stage compressor 21, a low-temperature stage condenser 32, and a low-temperature stage evaporator 22 that are connected to each other, the temperature of the high-temperature stage evaporator 31 is lower than the temperature of the low-temperature stage condenser 32, and the high-temperature stage evaporator 31 and the low-temperature stage condenser 32 may form a heat exchange module 30.

[0062] The high-temperature stage system 10 may include a first refrigerant 14. The first refrigerant 14 may flow between the high-temperature stage compressor 11, the high-temperature stage condenser 12, and the high-temperature stage evaporator 31. The first refrigerant 14 may release heat to the outside in the high-temperature stage condenser 12 and absorb heat from the outside in the high-temperature stage evaporator 31.

[0063] The low-temperature stage system 20 may include a second refrigerant 24. The second refrigerant 24 may flow between the low-temperature stage compressor 21, the low-temperature stage condenser 32, and the low-temperature stage evaporator 22. The second refrigerant 24 may release heat to the outside in the low-temperature stage condenser 32 and absorb heat from the outside in the low-temperature stage evaporator 22.

[0064] The first refrigerant 14 and the second refrigerant 24 may be the same refrigerant or different refrigerants.

[0065] The heat exchange module 30 may be a module consisting of a high-temperature evaporator 31 and a low-temperature condenser 32, capable of performing heat exchange between the first refrigerant 14 and the second refrigerant 24. When heat exchange is performed in the heat exchange module 30, the evaporation temperature of the high-temperature evaporator 31 should be lower than the condensation temperature of the low-temperature condenser 32.

[0066] The heat exchange module 30 may be an integrated evaporative condenser. The evaporative condenser may be configured such that the piping of the condenser of the low-temperature stage system 20 is inserted into the piping of the evaporator of the high-temperature stage system 10 to facilitate heat exchange between the first refrigerant 14 and the second refrigerant 24.

[0067] The space in which the high-temperature stage condenser 12 and the high-temperature stage compressor 11 of the cascade refrigeration system 100 are located can be collectively referred to as the external environment 13 of the cascade refrigeration system 100. The high-temperature stage condenser 12 can be connected to the external environment 13 and can exchange heat with the external environment 13. The condensing temperature of the high-temperature stage condenser 12 should be higher than the temperature of the external environment 13 to enable the high-temperature stage condenser 12 to release heat to the external environment 13.

[0068] The cascade refrigeration system 100 can be used to cool a refrigeration compartment 23. Items such as food that require low-temperature storage can be stored in the refrigeration compartment 23. The low-temperature evaporator 22 can communicate with the refrigeration compartment 23 and exchange heat with the refrigeration compartment 23. The evaporation temperature of the low-temperature evaporator 22 should be lower than the temperature within the refrigeration compartment 23 to allow the low-temperature evaporator 22 to absorb heat from the refrigeration compartment 23.

[0069] In this embodiment, the high-temperature stage compressor 11 and / or the low-temperature stage compressor 21 can be a variable frequency compressor, and the flow rate of the refrigerant in the refrigeration system can be adjusted by adjusting the operating frequency of the compressor, thereby adjusting the heat exchange between the first refrigerant 14 and the second refrigerant 24 in the heat exchange module 30.

[0070] In order to ensure that when the heat exchange module 30 is performing heat exchange, the temperature of the high-temperature evaporator 31 is lower than the temperature of the low-temperature condenser 32 and has a higher heat exchange efficiency, the cascade refrigeration system 100 can be dynamically controlled to achieve matching between the high-temperature system 10 and the low-temperature system 20.

[0071] In one embodiment of the present invention, one of the high-temperature system 10 and the low-temperature system 20 may be configured to be dynamically adjustable, so that one can be adjusted to match the other.

[0072] For example, the high-temperature compressor 11 can be set as a variable-frequency compressor, and the high-temperature system 10 can be matched with the low-temperature system 20 by dynamically adjusting the operating frequency of the high-temperature compressor 11. For another example, the low-temperature compressor 21 can be set as a variable-frequency compressor, and the low-temperature system 20 can be matched with the high-temperature system 10 by dynamically adjusting the operating frequency of the low-temperature compressor 21.

[0073] Such an arrangement can simplify the structure of the cascade refrigeration system 100 , reduce costs, and facilitate control while ensuring that the high-temperature stage system 10 and the low-temperature stage system 20 to which the heat exchange module 30 belong match.

[0074] Preferably, in one embodiment of the present invention, both the high-temperature system 10 and the low-temperature system 20 can be configured to be dynamically adjustable to achieve mutual matching of the two systems.

[0075] Furthermore, the high-temperature stage compressor 11 and the low-temperature stage compressor 21 can both be set as variable-frequency compressors, and the high-temperature stage system 10 and the low-temperature stage system 20 can be matched with each other by dynamically adjusting the operating frequency of the high-temperature stage compressor 11 and the operating frequency of the low-temperature stage compressor 21 at the same time.

[0076] Such a setting can better match the high-temperature system 10 and the low-temperature system 20, so that both the high-temperature system 10 and the low-temperature system 20 are in a better working state, thereby improving the overall operating efficiency of the cascade refrigeration system 100, reducing energy loss, reducing energy waste, and improving the stability and reliability of the system refrigeration operation.

[0077] Furthermore, in this embodiment, the cascade refrigeration system 100 may further include a pressure detection device.

[0078] The pressure detection device may include a pressure sensor disposed at the heat exchange module 30. The pressure sensor may include a first pressure sensor and a second pressure sensor. The first pressure sensor may be connected to a pipeline of the high-temperature stage evaporator 31 to detect the evaporation pressure of the first refrigerant 14 in the high-temperature stage evaporator 31. The second pressure sensor may be connected to a pipeline of the low-temperature stage condenser 32 to detect the condensation pressure of the second refrigerant 24 in the low-temperature stage condenser 32.

[0079] Evaporation pressure may refer to the internal pressure in the evaporator when the refrigerant absorbs heat from the outside.

[0080] Condensing pressure may refer to the internal pressure in the condenser when the refrigerant releases heat to the outside.

[0081] With such a configuration, the operation status of the cascade refrigeration system 100 can be monitored according to the heat exchange pressure at the heat exchange module 30, and the operating frequency of the compressor in the cascade refrigeration system 100 can be regulated according to the heat exchange pressure at the heat exchange module 30, so as to better achieve the matching of the high-temperature stage system 10 and the low-temperature stage system 20, reduce energy loss, reduce energy waste, improve the overall operation efficiency of the cascade refrigeration system 100, and improve the stability and reliability of the operation of the refrigeration system.

[0082] Furthermore, in one embodiment of the present invention, the cascade refrigeration system 100 can be a two-stage cascade refrigeration system 100 including a high-temperature stage system 10 and a low-temperature stage system 20, and the high-temperature stage system 10 and the low-temperature stage system 20 can both be single-stage circulation systems including a compressor.

[0083] Such an arrangement can make the overall structure of the cascade refrigeration system 100 simpler, easier to control, and reduce costs and space occupation.

[0084] Figure 2 A control method of a cascade refrigeration system 100 according to an embodiment of the present invention is shown.

[0085] The cascade refrigeration system 100 can refer to the above description. Figure 2 As shown, the control method includes:

[0086] Get the heat exchange pressure range;

[0087] detecting the evaporation pressure of the high-temperature stage system 10 and / or the condensation pressure of the low-temperature stage system 20;

[0088] Determining whether the evaporation pressure of the high-temperature stage system 10 and / or the condensation pressure of the low-temperature stage system 20 are within the heat exchange pressure range;

[0089] If not, the operating frequency of the compressor of the high-temperature stage system 10 and / or the compressor of the low-temperature stage system 20 is adjusted until the evaporation pressure of the high-temperature stage system 10 and / or the condensation pressure of the low-temperature stage system 20 are within the heat exchange pressure range, and the operating frequency of the compressor of the high-temperature stage system 10 is negatively correlated with the evaporation pressure of the high-temperature stage system 10, and the operating frequency of the compressor of the low-temperature stage system 20 is positively correlated with the condensation pressure of the low-temperature stage system 20.

[0090] If the evaporation pressure of the high-temperature stage system 10 and / or the condensation pressure of the low-temperature stage system 20 are within the preset heat exchange pressure range, the compressor of the high-temperature stage system and / or the compressor 21 of the low-temperature stage system may continue to operate at the current frequency.

[0091] The heat exchange pressure may refer to the evaporation pressure in the high-temperature stage evaporator 31 or the condensation pressure in the low-temperature stage condenser 32 during heat exchange in the heat exchange module 30 .

[0092] The heat exchange pressure range can be a pre-set or calculated numerical range, including an upper limit of the heat exchange pressure range and a lower limit of the heat exchange pressure range. When the heat exchange pressure is within the heat exchange pressure range, the cascade refrigeration system 100 can have a higher operating efficiency.

[0093] With such a setting, the heat exchange pressure range can be used as the preferred operating parameter point of the cascade refrigeration system 100, and the correlation between the compressor operating frequency and the heat exchange pressure can be utilized to adjust the heat exchange pressure at the heat exchange module 30 by controlling the operating frequency of the compressor, so that the heat exchange pressure at the heat exchange module 30 always fluctuates within the heat exchange pressure range, thereby better achieving the matching of the high-temperature stage system 10 and the low-temperature stage system 20, reducing energy loss, reducing energy waste, improving the overall operating efficiency of the cascade refrigeration system 100, and improving the stability and reliability of the refrigeration system operation.

[0094] In one embodiment of the present invention, the cascade refrigeration system 100 can use a high-temperature stage system 10 to match the low-temperature stage system 20, that is, the high-temperature stage compressor 11 can be set as a variable frequency compressor, and a first pressure sensor is set on the high-temperature stage evaporator 31 to detect the evaporation pressure of the high-temperature stage evaporator 31, and by controlling the operating frequency of the high-temperature stage compressor 11, the evaporation pressure of the high-temperature stage evaporator 31 always fluctuates within the heat exchange pressure range.

[0095] The cascade refrigeration system 100 can also use a low-temperature stage system 20 to match the high-temperature stage system 10, that is, the low-temperature stage compressor 21 can be set as a variable frequency compressor, and a second pressure sensor can be set on the low-temperature stage condenser 32 to detect the condensing pressure of the low-temperature stage condenser 32, and by adjusting the operating frequency of the low-temperature stage compressor 21, the condensing pressure of the low-temperature stage condenser 32 can always fluctuate within the heat exchange pressure range.

[0096] Such an arrangement can improve the operating efficiency of the cascade refrigeration system 100 while simplifying the structure of the cascade refrigeration system 100, reducing costs and facilitating control.

[0097] Preferably, in one embodiment of the present invention, the cascade refrigeration system 100 can adopt a high-temperature stage system 10 and a low-temperature stage system 20 to match each other, that is, the high-temperature stage compressor 11 and the low-temperature stage compressor are both set as variable-frequency compressors, a first pressure sensor is set on the high-temperature stage evaporator 31, and a second pressure sensor is set on the low-temperature stage condenser 32. The evaporation pressure of the high-temperature stage evaporator 31 and the condensation pressure of the low-temperature stage condenser 32 are monitored at the same time, and the operating frequency of the high-temperature stage compressor 11 and the low-temperature stage compressor 21 are controlled to make the evaporation pressure of the high-temperature stage evaporator 31 and the condensation pressure of the low-temperature stage condenser 32 always fluctuate within the heat exchange pressure range.

[0098] Such a setting can better match the high-temperature system 10 and the low-temperature system 20, so that both the high-temperature system 10 and the low-temperature system 20 are in a better working state, thereby improving the overall operating efficiency of the cascade refrigeration system 100, reducing energy loss, reducing energy waste, and improving the stability and reliability of the system refrigeration operation.

[0099] Figure 3 A flow chart of a control method for obtaining a heat exchange pressure range in a first embodiment of the present invention is shown.

[0100] like Figure 3 As shown, in one embodiment of the present invention, the “obtaining the heat exchange pressure range” may include:

[0101] After receiving the power-on signal, the temperature of the refrigeration compartment 23 is detected;

[0102] When the temperature change value of the refrigeration compartment 23 is within a preset range within a preset time period, the first condensing temperature of the high-temperature system 10 and the first evaporating temperature of the low-temperature system 20 are detected;

[0103] Calculating the heat exchange condensing pressure of the high-temperature stage system 10 according to the first condensing temperature, and calculating the heat exchange evaporating pressure of the low-temperature stage system 20 according to the first evaporating temperature;

[0104] Calculate the intermediate pressure between the heat exchange condensing pressure of the high-temperature stage system 10 and the heat exchange evaporating pressure of the low-temperature stage system 20, as well as the heat exchange pressure range,

[0105] Among them, the

[0106] The upper limit of the heat exchange pressure range = intermediate pressure + first preset value,

[0107] The lower limit of the heat exchange pressure range = intermediate pressure - second preset value.

[0108] The condensing temperature may refer to the temperature at the condenser when the refrigerant releases heat to the outside.

[0109] The evaporation temperature may refer to the temperature at the evaporator when the refrigerant absorbs heat from the outside.

[0110] Accordingly, in one embodiment of the present invention, the cascade refrigeration system 100 may further include a temperature detection device. The temperature detection device may include a first temperature sensor disposed in the refrigeration compartment 23. The first temperature sensor may be used to detect the temperature in the refrigeration compartment 23.

[0111] After the cascade refrigeration system 100 is turned on, the high-temperature stage system 10 and the low-temperature stage system 20 are generally not operated simultaneously. Typically, the high-temperature stage system 10 is operated for a period of time before the low-temperature stage system 20 is operated. The temperature within the refrigeration compartment 23 also generally decreases gradually after the system is turned on, eventually stabilizing within a certain temperature range.

[0112] After the cascade refrigeration system 100 is started up, if the temperature of the refrigeration compartment 23 fluctuates stably within a preset range for a preset period of time, the cascade refrigeration system 100 can be considered to have reached a stable startup state. After the cascade refrigeration system 100 reaches a stable startup state, the high-temperature stage system 10 and the low-temperature stage system 20 are further matched to dynamically adjust the operating frequency of the compressor in the cascade refrigeration system 100.

[0113] The preset range may be a set temperature range. For example, it may be set that after the cascade refrigeration system 100 is started up, if the temperature of the refrigeration compartment 23 fluctuates stably between -35°C and -40°C for five minutes, the cascade refrigeration system 100 is determined to have reached a stable startup state.

[0114] The preset range may also be a set temperature variation difference range. For example, it may be set that if the temperature variation difference of the refrigeration compartment 23 remains stable within 5° C. for five minutes after the cascade refrigeration system 100 is turned on, it is determined that the cascade refrigeration system 100 has reached a stable startup state.

[0115] With such an arrangement, after the cascade refrigeration system 100 reaches a stable startup state, the cascade refrigeration system 100 can be dynamically adjusted to better match the high-temperature stage system 10 and the low-temperature stage system 20, so that both the high-temperature stage system 10 and the low-temperature stage system 20 are in a better working state, thereby improving the overall operating efficiency of the cascade refrigeration system 100, reducing energy loss, reducing energy waste, and improving the stability and reliability of the system operation.

[0116] The heat exchange condensing pressure may refer to a certain condensing pressure value of the first refrigerant 14 in the high temperature stage system 10 used to calculate the intermediate pressure.

[0117] The heat exchange evaporation pressure may refer to a certain evaporation pressure value of the second refrigerant 24 in the low-temperature stage system 20 used to calculate the intermediate pressure.

[0118] In one embodiment of the present invention, the heat exchange condensing pressure and the heat exchange evaporating pressure can be obtained by direct detection. For example, a third pressure sensor and a fourth pressure sensor can be provided at the high-temperature stage condenser 12 and the low-temperature stage evaporator 22, respectively, to detect the heat exchange condensing pressure and the heat exchange evaporating pressure, respectively.

[0119] Preferably, in one embodiment of the present invention, the heat exchange condensation pressure and the heat exchange evaporation pressure can be obtained by calculation and query according to the condensation temperature and the evaporation temperature respectively.

[0120] For example, the first refrigerant 14 may be R22 refrigerant, and the second refrigerant may be R134a refrigerant. R22 refrigerant is also known as difluorochloromethane, which is a type of Freon refrigerant. R134a refrigerant is also known as tetrafluoroethane.

[0121] A data comparison table for the condensing temperature and condensing pressure of R22 refrigerant, as well as a data comparison table for the evaporating temperature and evaporating pressure of R134a refrigerant, can be pre-stored. When the condensing temperature of R22 refrigerant and the evaporating temperature of R23 refrigerant are obtained and the corresponding condensing pressure and evaporating pressure are needed, they can be directly queried through the table.

[0122] Condensation temperature and condensation pressure comparison table of R22 refrigerant

[0123]

[0124] Comparison table of evaporation temperature and evaporation pressure of R134a refrigerant

[0125]

[0126] Since the temperature detection device in the refrigeration system has a simpler structure than the pressure detection device, is more convenient to install and has a lower cost, such an arrangement can simplify the structure of the cascade refrigeration system 100 and reduce production costs.

[0127] In this embodiment, the temperature detection device may include a second temperature sensor provided at the high-temperature stage condenser 12 and a third temperature sensor provided at the low-temperature stage evaporator 22 .

[0128] The second temperature sensor can detect the temperature of the high-temperature condenser 12 after the cascade refrigeration system 100 reaches a stable startup state, thereby obtaining the first condensing temperature. The third temperature sensor can be used to detect the temperature of the low-temperature evaporator 22 after the cascade refrigeration system 100 reaches a stable startup state, thereby obtaining the first evaporating temperature.

[0129] The heat exchange condensing pressure of the first refrigerant 14 in the high temperature stage system 10 corresponding to the first condensing temperature can be obtained by querying a pre-stored data table.

[0130] The heat exchange evaporation pressure of the second refrigerant 24 in the low-temperature stage system 20 corresponding to the first evaporation temperature can be obtained by querying a pre-stored data table.

[0131] The intermediate pressure between the heat exchange condensation pressure and the heat exchange evaporation pressure can be calculated using a theoretical or empirical formula. In this embodiment, the intermediate pressure can be calculated using the empirical formula described above.

[0132] The first set value and the second set value may be allowable deviation values based on the intermediate pressure. The first set value and the second set value may be the same or different.

[0133] With such an arrangement, after the cascade refrigeration system 100 reaches a stable startup state, the intermediate pressure between the condensing pressure of the high-temperature stage system 10 and the evaporating pressure of the low-temperature stage system 20 can be used as a parameter point to dynamically regulate the circulation parameters of the high-temperature stage system 10 and the low-temperature stage system 20, so as to better match the high-temperature stage system 10 and the low-temperature stage system 20, so that both the high-temperature stage system 10 and the low-temperature stage system 20 are in a better working state, thereby improving the overall operating efficiency of the cascade refrigeration system 100, reducing energy loss, reducing energy waste, and improving the stability and reliability of the system refrigeration operation.

[0134] Figure 4 A flow chart of a control method for obtaining a heat exchange pressure range in another embodiment of the present invention is shown.

[0135] like Figure 4As shown, in another embodiment of the present invention, “obtaining the heat exchange pressure range” may include:

[0136] After receiving the power-on signal, the temperature of the refrigeration compartment 23 is detected;

[0137] When the temperature change value of the refrigeration compartment 23 is within a preset range within a preset time, the first condensing temperature of the high-temperature system 10 and the first evaporating temperature of the low-temperature system 20 are detected, and

[0138] Detecting a first ambient temperature of the condenser of the high-temperature stage system 10 and a second ambient temperature of the evaporator of the low-temperature stage system 20;

[0139] Obtaining a preset condensing temperature range for the condenser of the high-temperature system 10 corresponding to the first ambient temperature;

[0140] determining whether the first condensing temperature is within the preset condensing temperature range;

[0141] If so, the heat exchange condensing pressure of the high-temperature stage system 10 is calculated according to the first condensing temperature;

[0142] If not, then obtain the preset condensation temperature, the preset condensation temperature is within the preset condensation temperature range, and

[0143] Calculating the heat exchange condensation pressure of the high temperature stage system 10 according to the preset condensation temperature;

[0144] determining whether the second ambient temperature is within a preset evaporation ambient temperature;

[0145] If so, the heat exchange evaporation pressure of the low temperature stage system 20 is calculated according to the first evaporation temperature;

[0146] If not, the preset evaporation temperature is obtained according to the preset evaporation ambient temperature, and

[0147] Calculating the heat exchange evaporation pressure of the low temperature stage system 20 according to the preset evaporation temperature;

[0148] Calculate the intermediate pressure between the heat exchange condensing pressure of the high-temperature stage system 10 and the heat exchange evaporating pressure of the low-temperature stage system 20 and the heat exchange pressure range,

[0149] Among them, the

[0150] The upper limit of the heat exchange range = intermediate pressure + first preset value,

[0151] The lower limit of the heat exchange range = intermediate pressure - second preset value.

[0152] Accordingly, in this embodiment, the temperature detection device of the cascade refrigeration system may include a fourth temperature sensor disposed in the external environment 13 .

[0153] The first ambient temperature may refer to the temperature of the external environment 13 detected by the fourth temperature sensor after the cascade refrigeration system 100 reaches a startup stable state.

[0154] The second ambient temperature may refer to the temperature of the refrigeration compartment 23 detected by the first temperature sensor after the cascade refrigeration system 100 reaches a startup stable state.

[0155] In order to ensure the heat exchange efficiency between the high temperature stage condenser 12 and the external environment 13 , the condensation temperature of the high temperature stage condenser 12 should be higher than the temperature of the external environment 13 and should have a certain temperature difference with the temperature of the external environment 13 .

[0156] The preset condensing temperature range may refer to a preferred condensing temperature range of the high-temperature condenser 12 corresponding to a preset specific temperature of the external environment 13. For example, when the first ambient temperature is 20°C, the preset condensing temperature range may be 25°C to 30°C.

[0157] The preset condensing temperature may be any value within the preset condensing temperature range. The preset condensing temperature may be manually input and set, such as directly stored in a memory at the factory, or may be automatically selected by the cascade refrigeration system 100 according to an operating program.

[0158] In order to ensure the heat exchange efficiency between the low temperature evaporator 22 and the refrigeration compartment 23 , the evaporation temperature of the low temperature evaporator 22 should be lower than the temperature of the refrigeration compartment 23 and there should be a certain temperature difference between the evaporation temperature of the low temperature evaporator 22 and the temperature of the refrigeration compartment 23 .

[0159] The preset evaporation environment temperature may refer to a preset preferred storage temperature range of the refrigeration compartment 23. For example, the preset evaporation environment temperature may be -60°C to -65°C.

[0160] The preset evaporation environment temperature may be manually input and set, such as being directly stored in a memory at the factory, or may be automatically selected by the cascade refrigeration system 100 according to an operating program.

[0161] The preset evaporation temperature may refer to a preferred evaporation temperature value of the low-temperature evaporator 22 corresponding to the preset evaporation ambient temperature. For example, when the preset evaporation ambient temperature is -60°C to -65°C, the preset evaporation temperature may be set to -70°C.

[0162] Such a setting can realize the variable adjustment of the condensing temperature of the high-temperature condenser 12 and the temperature of the refrigeration chamber 23, so that the operating temperature of the cascade refrigeration system 100 is more reasonable and more in line with the needs. At the same time, it can make the calculation of the intermediate pressure more accurate. After the cascade refrigeration system 100 reaches the stable state after startup, the intermediate pressure between the condensing pressure of the high-temperature system 10 and the evaporating pressure of the low-temperature system 20 is used as a parameter point to dynamically regulate the cycle parameters of the high-temperature system 10 and the low-temperature system 20, so as to better match the high-temperature system 10 and the low-temperature system 20, so that both the high-temperature system 10 and the low-temperature system 20 are in a better working state, thereby improving the overall operating efficiency of the cascade refrigeration system 100, reducing energy loss, reducing energy waste, and improving the stability and reliability of the system operation.

[0163] Figure 5 A control method for a high temperature stage system in one embodiment of the present invention is shown.

[0164] In one embodiment of the present invention, Figure 5 As shown, the control method includes:

[0165] Determining whether the evaporation pressure of the high-temperature stage system 10 is higher than the upper limit of the preset heat exchange pressure range;

[0166] If so, increasing the operating frequency of the compressor of the high temperature stage system 10;

[0167] Determining whether the evaporation pressure of the high-temperature stage system 10 is lower than the lower limit of the preset heat exchange pressure range;

[0168] If so, the operating frequency of the compressor of the high temperature stage system 10 is reduced.

[0169] If the evaporation pressure of the high temperature stage system 10 is within the preset heat exchange pressure range, the high temperature stage compressor 11 may continue to operate at the current frequency.

[0170] With such a setting, the heat exchange pressure range can be used as the preferred operating parameter point of the cascade refrigeration system 100, and the correlation between the compressor operating frequency and the heat exchange pressure can be used to adjust the heat exchange pressure at the heat exchange module 30 by controlling the operating frequency of the compressor, so that the heat exchange pressure at the heat exchange module 30 always fluctuates within the heat exchange pressure range, thereby better achieving the matching of the high-temperature stage system 10 and the low-temperature stage system 20, reducing energy loss, reducing energy waste, improving the overall operating efficiency of the cascade refrigeration system 100, and improving the stability and reliability of the system refrigeration operation.

[0171] Figure 6 A control method for a low temperature stage system according to an embodiment of the present invention is shown.

[0172] In one embodiment of the present invention, Figure 6 As shown, the control method includes:

[0173] Determining whether the condensing pressure of the low-temperature stage system 20 is lower than the lower limit of the preset heat exchange pressure range;

[0174] If so, increasing the operating frequency of the compressor of the low temperature stage system 20;

[0175] Determining whether the condensing pressure of the low-temperature stage system 20 is higher than the upper limit of the preset heat exchange pressure range;

[0176] If not, the operating frequency of the compressor of the low temperature stage system 20 is reduced.

[0177] If the condensing pressure of the low-temperature stage system 20 is within the preset heat exchange pressure range, the low-temperature stage compressor 21 may continue to operate at the current frequency.

[0178] With such a setting, the heat exchange pressure range can be used as the preferred operating parameter point of the cascade refrigeration system 100, and the correlation between the compressor operating frequency and the heat exchange pressure can be used to adjust the heat exchange pressure at the heat exchange module 30 by controlling the operating frequency of the compressor, so that the heat exchange pressure at the heat exchange module 30 always fluctuates within the heat exchange pressure range, thereby better achieving the matching of the high-temperature stage system 10 and the low-temperature stage system 20, reducing energy loss, reducing energy waste, improving the overall operating efficiency of the cascade refrigeration system 100, and improving the stability and reliability of the system refrigeration operation.

[0179] Furthermore, in one embodiment of the present invention, the cascade refrigeration system 100 may further include a memory and a processor. The memory stores a computer program executable on the processor. When the processor executes the computer program, the steps of the control method for the cascade refrigeration system 100 described in any of the above embodiments can be implemented. This configuration enables automatic operation and control of the cascade refrigeration system 100, achieves dynamic matching between the high-temperature stage system 10 and the low-temperature stage system 20, improves the overall operating efficiency of the cascade refrigeration system 100, reduces energy loss, and improves the stability and reliability of the system's operation.

[0180] A computer-readable storage medium according to one embodiment of the present invention stores a computer program thereon, wherein, when executed by a processor, the computer program implements the steps of the control method for the cascade refrigeration system 100 described in any of the above-described embodiments. This configuration enables automatic operation and control of the cascade refrigeration system 100, achieves dynamic matching between the high-temperature stage system 10 and the low-temperature stage system 20, improves the overall operating efficiency of the cascade refrigeration system 100, reduces energy loss, and enhances the stability and reliability of the refrigeration system's operation.

[0181] A refrigerator according to an embodiment of the present invention may include a refrigerator body and the cascade refrigeration system 100 according to any one of the above embodiments. The cascade refrigeration system 100 may include a high-temperature stage system 10 and a low-temperature stage system 20. The high-temperature stage system 10 includes a high-temperature stage compressor 11, a high-temperature stage evaporator 31, and a high-temperature stage condenser 12, which are connected to each other. The low-temperature stage system 20 includes a low-temperature stage compressor 21, a low-temperature stage condenser 32, and a low-temperature stage evaporator 22, wherein the temperature of the high-temperature stage evaporator 31 is lower than that of the low-temperature stage condenser 32. The high-temperature stage evaporator 31 and the low-temperature stage condenser 32 constitute a heat exchange module 30. A refrigeration compartment 23 is provided in the housing. The cascade refrigeration system 100 is configured to supply cold air to the refrigeration compartment 23. The high-temperature stage compressor 11 and / or the low-temperature stage compressor 21 are variable frequency compressors. The cascade refrigeration system 100 further includes a pressure detection device. The cascade refrigeration system 100 further includes a memory and a processor. The memory stores a computer program executable on the processor. When the processor executes the computer program, the steps of the control method of the cascade refrigeration system 100 in any of the above-mentioned embodiments can be implemented.

[0182] Such a setting can realize a refrigerator that can provide a low-temperature storage environment, improve the operating efficiency of the refrigerator, reduce energy loss, reduce energy waste, and improve the stability and reliability of the refrigerator operation.

[0183] A cold storage according to an embodiment of the present invention may include a storage room and a cascade refrigeration system 100 according to any of the above embodiments, wherein the cascade refrigeration system 100 includes a high-temperature stage system 10 and a low-temperature stage system 20, wherein the high-temperature stage system 10 includes a high-temperature stage compressor 11, a high-temperature stage evaporator 31, and a high-temperature stage condenser 12 connected to each other, and the low-temperature stage system 20 includes a low-temperature stage compressor 21, a low-temperature stage condenser 32, and a low-temperature stage evaporator 22 connected to each other, wherein the temperature of the high-temperature stage evaporator 31 is lower than the temperature of the low-temperature stage condenser 32, and the high-temperature stage evaporator 22 is lower than the temperature of the low-temperature stage condenser 32. 31 and the low-temperature stage condenser 32 constitute a heat exchange module 30, the cascade refrigeration system 100 is used to supply cooling to the storage compartment, the high-temperature stage compressor 11 and / or the low-temperature stage compressor 21 are variable frequency compressors, the cascade refrigeration system 100 also includes a pressure detection device, the cascade refrigeration system 100 also includes a memory and a processor, the memory stores a computer program that can be run on the processor, and when the processor executes the computer program, the steps in the control method of the cascade refrigeration system 100 in any of the above embodiments are implemented.

[0184] Such a setting can realize a cold storage that can provide a low-temperature storage environment, improve the operating efficiency of the cold storage, reduce energy loss, reduce energy waste, and improve the stability and reliability of the cold storage operation.

[0185] In summary, the control method of the cascade refrigeration system 100, the storage medium, the cascade refrigeration system 100, the refrigerator, and the cold storage of the present invention can solve the problem in the prior art that the operating efficiency of the cascade refrigeration system 100 needs to be improved.

[0186] By adopting the technical solution in the present application, the heat exchange pressure range can be used as the preferred operating parameter point of the cascade refrigeration system 100. By utilizing the correlation between the compressor operating frequency and the heat exchange pressure, the heat exchange pressure at the heat exchange module 30 can be adjusted by controlling the operating frequency of the compressor, so that the heat exchange pressure at the heat exchange module 30 always fluctuates within the heat exchange pressure range, thereby better achieving the matching of the high-temperature stage system 10 and the low-temperature stage system 20, reducing energy loss, reducing energy waste, improving the overall operating efficiency of the cascade refrigeration system 100, and improving the stability and reliability of the system refrigeration operation.

[0187] Those skilled in the art will clearly understand that, for the convenience and brevity of description, the specific working processes of the above-described systems, systems and modules can refer to the corresponding processes in the aforementioned method implementation methods and will not be repeated here.

[0188] In the several embodiments provided in this application, it should be understood that the disclosed systems, systems and methods can be implemented in other ways. For example, the system implementation described above is only illustrative. For example, the division of the modules is only a logical function division. In actual implementation, there may be other division methods, such as multiple modules or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of systems or modules, which can be electrical, mechanical or other forms.

[0189] The modules described as separate components may or may not be physically separate, and the components shown as modules may or may not be physical modules, that is, they may be located in one place or distributed across multiple network modules. Some or all of the modules may be selected according to actual needs to achieve the purpose of this embodiment.

[0190] In addition, the functional modules in each embodiment of the present application may be integrated into a processing module, or each module may exist physically separately, or two or more modules may be integrated into a single module. The above-mentioned integrated modules may be implemented in the form of hardware or in the form of hardware plus software functional modules.

[0191] The above-mentioned integrated module implemented in the form of a software function module can be stored in a computer-readable storage medium. The above-mentioned software function module is stored in a storage medium and includes a number of instructions for causing a computer system (which can be a personal computer, server, or network system, etc.) or a processor to execute some steps of the method described in each embodiment of the present application. The aforementioned storage medium includes: a USB flash drive, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk or an optical disk, and other media that can store program code.

[0192] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present application.

Claims

1. A control method for a cascade refrigeration system, characterized in that: The control method includes: Get the heat exchange pressure range; Detecting the evaporation pressure of the high-temperature stage system and / or the condensation pressure of the low-temperature stage system; determining whether the evaporation pressure of the high-temperature stage system and / or the condensation pressure of the low-temperature stage system are within the heat exchange pressure range; If not, adjusting the operating frequency of the compressor of the high-temperature stage system and / or the compressor of the low-temperature stage system until the evaporation pressure of the high-temperature stage system and / or the condensation pressure of the low-temperature stage system are within the heat exchange pressure range, the operating frequency of the compressor of the high-temperature stage system is negatively correlated with the evaporation pressure of the high-temperature stage system, and the operating frequency of the compressor of the low-temperature stage system is positively correlated with the condensation pressure of the low-temperature stage system; “Obtaining the heat exchange pressure range” includes: After receiving the power-on signal, the temperature of the refrigeration compartment is detected; When the temperature change value of the refrigeration compartment is within a preset range within a preset time period, the first condensing temperature of the high-temperature stage system and the first evaporating temperature of the low-temperature stage system are detected; Calculating the heat exchange condensing pressure of the high-temperature stage system according to the first condensing temperature, and calculating the heat exchange evaporating pressure of the low-temperature stage system according to the first evaporating temperature; Calculate the intermediate pressure between the heat exchange condensing pressure of the high-temperature stage system and the heat exchange evaporating pressure of the low-temperature stage system, as well as the heat exchange pressure range, Wherein, the intermediate pressure = , The upper limit of the heat exchange pressure range = intermediate pressure + first preset value, The lower limit of the heat exchange pressure range = intermediate pressure - second preset value; Alternatively, “obtaining the heat exchange pressure range” includes: After receiving the power-on signal, the temperature of the refrigeration compartment is detected; When the temperature change value of the refrigeration compartment is within a preset range within a preset time, the first condensing temperature of the high-temperature system and the first evaporating temperature of the low-temperature system are detected, and Detecting a first ambient temperature of the condenser of the high-temperature stage system and a second ambient temperature of the evaporator of the low-temperature stage system; Obtaining a preset condensing temperature range for the operation of the condenser of the high-temperature stage system corresponding to the first ambient temperature; determining whether the first condensing temperature is within the preset condensing temperature range; If yes, then calculating the heat exchange condensing pressure of the high temperature stage system according to the first condensing temperature; If not, then obtain the preset condensation temperature, the preset condensation temperature is within the preset condensation temperature range, and Calculating the heat exchange condensation pressure of the high temperature stage system according to the preset condensation temperature; determining whether the second ambient temperature is within a preset evaporation ambient temperature; If so, the heat exchange evaporation pressure of the low temperature stage system is calculated according to the first evaporation temperature; If not, the preset evaporation temperature is obtained according to the preset evaporation ambient temperature, and Calculating the heat exchange evaporation pressure of the low temperature stage system according to the preset evaporation temperature; Calculate the intermediate pressure between the heat exchange condensing pressure of the high-temperature stage system and the heat exchange evaporating pressure of the low-temperature stage system, as well as the heat exchange pressure range, Wherein, the intermediate pressure = , The upper limit of the heat exchange pressure range = intermediate pressure + first preset value, The lower limit of the heat exchange pressure range=intermediate pressure-second preset value.

2. The control method of the cascade refrigeration system according to claim 1, wherein: The control method includes: Determining whether the evaporation pressure of the high-temperature stage system is higher than the upper limit of a preset heat exchange pressure range; If so, increasing the operating frequency of the compressor of the high temperature stage system; Determining whether the evaporation pressure of the high-temperature stage system is lower than the lower limit of a preset heat exchange pressure range; If so, the operating frequency of the compressor of the high temperature stage system is reduced.

3. The control method of the cascade refrigeration system according to claim 1, wherein: The control method includes: Determining whether the condensing pressure of the low-temperature stage system is lower than the lower limit of a preset heat exchange pressure range; If so, increasing the operating frequency of the compressor of the low temperature stage system; Determining whether the condensing pressure of the low-temperature stage system is higher than the upper limit of a preset heat exchange pressure range; If not, the operating frequency of the compressor of the low temperature stage system is reduced.

4. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the control method of the cascade refrigeration system according to any one of claims 1 to 3 are implemented.

5. A cascade refrigeration system comprising a high-temperature stage system and a low-temperature stage system, wherein the high-temperature stage system comprises a high-temperature stage compressor, a high-temperature stage evaporator, and a high-temperature stage condenser connected to each other; the low-temperature stage system comprises a low-temperature stage compressor, a low-temperature stage condenser, and a low-temperature stage evaporator connected to each other; the temperature of the high-temperature stage evaporator is lower than that of the low-temperature stage condenser; the high-temperature stage evaporator and the low-temperature stage condenser constitute a heat exchange module, characterized in that: The high-temperature stage compressor and / or the low-temperature stage compressor are variable frequency compressors, the cascade refrigeration system also includes a pressure detection device, the cascade refrigeration system also includes a memory and a processor, the memory stores a computer program that can be run on the processor, and when the processor executes the computer program, the steps in the control method of the cascade refrigeration system described in any one of claims 1 to 3 are implemented.

6. The cascade refrigeration system according to claim 5, wherein: The cascade refrigeration system is a two-stage cascade refrigeration system including a high-temperature stage system and a low-temperature stage system. Both the high-temperature stage system and the low-temperature stage system are single-stage circulation systems including a compressor.

7. A refrigerator comprising a cabinet and a cascade refrigeration system, wherein the cascade refrigeration system comprises a high-temperature stage system and a low-temperature stage system, wherein the high-temperature stage system comprises a high-temperature stage compressor, a high-temperature stage evaporator, and a high-temperature stage condenser that are connected to each other, and the low-temperature stage system comprises a low-temperature stage compressor, a low-temperature stage condenser, and a low-temperature stage evaporator that are connected to each other, wherein the temperature of the high-temperature stage evaporator is lower than that of the low-temperature stage condenser, and the high-temperature stage evaporator and the low-temperature stage condenser constitute a heat exchange module, and a refrigeration compartment is provided in the cabinet, characterized in that: The cascade refrigeration system is used to supply cooling to the refrigeration compartment, the high-temperature stage compressor and / or the low-temperature stage compressor are variable frequency compressors, the cascade refrigeration system further includes a pressure detection device, the cascade refrigeration system further includes a memory and a processor, the memory stores a computer program that can be run on the processor, and when the processor executes the computer program, the steps in the control method of the cascade refrigeration system described in any one of claims 1 to 3 are implemented.

8. A cold storage comprising a storage compartment and a cascade refrigeration system, wherein the cascade refrigeration system comprises a high-temperature stage system and a low-temperature stage system, wherein the high-temperature stage system comprises a high-temperature stage compressor, a high-temperature stage evaporator, and a high-temperature stage condenser that are connected to each other, and the low-temperature stage system comprises a low-temperature stage compressor, a low-temperature stage condenser, and a low-temperature stage evaporator that are connected to each other, wherein the temperature of the high-temperature stage evaporator is lower than that of the low-temperature stage condenser, and the high-temperature stage evaporator and the low-temperature stage condenser constitute a heat exchange module, characterized in that: The cascade refrigeration system is used to supply cooling to the storage compartment, the high-temperature stage compressor and / or the low-temperature stage compressor is a variable frequency compressor, the cascade refrigeration system also includes a pressure detection device, the cascade refrigeration system also includes a memory and a processor, the memory stores a computer program that can be run on the processor, and when the processor executes the computer program, the steps in the control method of the cascade refrigeration system described in any one of claims 1 to 3 are implemented.

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