Cascade refrigeration system and control method thereof

Abstract

The present invention discloses a cascade refrigeration system and a control method thereof, wherein the cascade refrigeration system comprises: a primary refrigeration system and a secondary refrigeration system; the primary refrigeration system comprises a primary compressor, a primary throttling mechanism, an evaporative condenser and a primary regenerator connected by pipelines to form a loop; the secondary refrigeration system comprises a secondary compressor, an evaporative condenser, a secondary throttling mechanism, a secondary regenerator and an evaporator connected by pipelines to form a loop; the primary refrigeration system and the secondary refrigeration system share an evaporative condenser; the inlet of the evaporator is connected to the secondary regenerator; the outlet of the evaporator is connected to the return air port of the secondary compressor through a refrigeration regulating module; the refrigeration regulating module is used to reduce the temperature of the secondary refrigerant between the outlet of the evaporator and the return air port of the secondary compressor. The technical solution of the present invention can improve the energy efficiency of the cascade refrigeration system.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor preparation, and in particular to a cascade refrigeration system and a control method thereof. Background Art

[0002] With the rapid development of the domestic semiconductor industry, temperature control is becoming more and more stringent during chip testing. Currently, the temperature range of chip testing is required to be -70℃~150℃, and there is a trend of expanding the temperature range. The current common practice for stable control is to use a double-stage cascade method in the low-temperature zone and a single-stage refrigeration or double-stage cascade method in the high-temperature zone.

[0003] However, in a high-temperature test environment, no matter which method is used, due to the high evaporator outlet temperature, it is necessary to bypass a portion of the refrigerant after throttling to cool the evaporator outlet refrigerant to avoid the compressor inhaling high-temperature gas and causing the exhaust temperature to be too high. As a result, during high-temperature testing, the cooling capacity decreases, and the requirements of chip heat dissipation and heating resistance cannot be met, and the system energy efficiency decreases. The higher the test temperature, the more obvious this phenomenon is, and it is difficult to meet the high-temperature test requirements of 200°C. Summary of the invention

[0004] The present invention provides a cascade refrigeration system and a control method thereof, so as to solve the problems existing in the prior art and improve the energy efficiency of the cascade refrigeration system.

[0005] In a first aspect, the present invention provides a cascade refrigeration system, comprising: a primary refrigeration system and a secondary refrigeration system;

[0006] The primary refrigeration system includes a primary compressor, a primary throttling mechanism, an evaporative condenser and a primary regenerator connected by pipelines to form a loop;

[0007] The secondary refrigeration system includes a secondary compressor, an evaporative condenser, a secondary throttling mechanism, a secondary regenerator and an evaporator connected by pipelines to form a loop;

[0008] The primary refrigeration system and the secondary refrigeration system share the evaporative condenser;

[0009] The inlet of the evaporator is connected to the secondary regenerator; the outlet of the evaporator is connected to the return air port of the secondary compressor through a refrigeration adjustment module;

[0010] The refrigeration regulating module is used to reduce the temperature of the secondary refrigerant between the evaporator outlet and the return air port of the secondary compressor.

[0011] In a second aspect, the present invention provides a control method for a cascade refrigeration system, wherein the cascade refrigeration system comprises a primary refrigeration system and a secondary refrigeration system; the primary refrigeration system comprises a primary compressor, a primary throttling mechanism, an evaporative condenser and a primary regenerator connected by pipelines to form a loop; the secondary refrigeration system comprises a secondary compressor, an evaporative condenser, a secondary throttling mechanism, a secondary regenerator and an evaporator connected by pipelines to form a loop; the primary refrigeration system and the secondary refrigeration system share the evaporative condenser; the inlet of the evaporator is connected to the secondary regenerator; the outlet of the evaporator is connected to the return air port of the secondary compressor through a refrigeration adjustment module; the control method comprises:

[0012] After the cascade refrigeration system is started, when the temperature of the outlet of the evaporator is greater than or equal to the saturation temperature of the secondary refrigerant at the return air port of the secondary compressor, the refrigeration regulating module is controlled to lower the temperature of the secondary refrigerant between the outlet of the evaporator and the return air port of the secondary compressor.

[0013] The technical solution of the present invention is to make the cascade refrigeration system include a primary refrigeration system and a secondary refrigeration system, wherein the primary refrigeration system includes a primary compressor, a primary throttling mechanism, an evaporative condenser and a primary regenerator connected by pipelines to form a loop, and the secondary refrigeration system includes a secondary compressor, an evaporative condenser, a secondary throttling mechanism, a secondary regenerator and an evaporator connected by pipelines to form a loop, and the primary refrigeration system and the secondary refrigeration system share the evaporative condenser. The inlet of the evaporator is connected to the secondary regenerator, and the outlet of the evaporator is connected to the return air port of the secondary compressor through a refrigeration adjustment module. The refrigeration adjustment module is used to reduce the temperature of the secondary refrigerant between the evaporator outlet and the return air port of the secondary compressor, so that in a high-temperature test environment, there is no need to sacrifice the refrigeration capacity to bypass a part of the refrigerant from the secondary throttling mechanism to reduce the temperature of the secondary refrigerant at the evaporator outlet, so that the secondary compressor can be prevented from inhaling high-temperature gas and causing the exhaust temperature to be too high, thereby improving the energy efficiency of the cascade refrigeration system, and then expanding the temperature range of the high-temperature zone, further meeting the needs of chip heat dissipation and heating resistance.

[0014] It should be understood that the contents described in this section are not intended to identify the key or important features of the embodiments of the present invention, nor are they intended to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0016] Figure 1 A schematic structural diagram of a cascade refrigeration system provided in an embodiment of the present invention.

[0017] Among them, 1: primary compressor, 2: dual-system plate heat exchanger, 2-1: first inlet of dual-system plate heat exchanger, 2-2: first outlet of dual-system plate heat exchanger, 2-3: second inlet of dual-system plate heat exchanger, 2-4: second outlet of dual-system plate heat exchanger, 3: primary drying filter, 4: primary throttling mechanism, 5: evaporative condenser, 5-1: first inlet of evaporative condenser, 5-2: first outlet of evaporative condenser, 5-3: second inlet of evaporative condenser, 5-4: second outlet of evaporative condenser, 6: primary regenerator, 6-1: first inlet of primary regenerator, 6-2: first outlet of primary regenerator, 6-3: second inlet of primary regenerator, 6-4: second outlet of primary regenerator, 7: secondary compressor, 8: secondary oil separator, 9: secondary drying filter, 10: secondary throttling mechanism, 11: secondary regenerator, 11-1: secondary regenerator Second inlet, 11-2: second outlet of secondary heat exchanger, 11-3: first inlet of secondary heat exchanger, 11-4: first outlet of secondary heat exchanger, 12: outlet stop valve, 13: return stop valve, 14: buffer tank, 15: unloading valve, 16: first high temperature valve, 17: second high temperature valve, 18: normal temperature valve, 19: first low temperature valve, 20: third low temperature valve, 21: fifth temperature acquisition unit, 22: ninth temperature acquisition unit, 23: first temperature acquisition unit, 24: second temperature acquisition unit, 25: third temperature acquisition unit, 26: fourth temperature acquisition unit, 27: sixth temperature acquisition unit, 28: seventh temperature acquisition unit, 29: precooler, 29-1: inlet of precooler, 29-2: outlet of precooler, 30: eighth temperature acquisition unit, 31: first pressure acquisition unit, 32: second low temperature valve, 33: evaporator, 34: second pressure acquisition unit. DETAILED DESCRIPTION

[0018] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0019] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the numbers used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein.

[0020] Figure 1 This is a schematic diagram of the structure of a cascade refrigeration system provided in an embodiment of the present invention. This embodiment provides a cascade refrigeration system, referring to Figure 1 As shown, the cascade refrigeration system includes a primary refrigeration system and a secondary refrigeration system, the primary refrigeration system includes a primary compressor 1, a primary throttling mechanism 4, an evaporative condenser 5 and a primary regenerator 6 which are connected by pipelines to form a loop; the secondary refrigeration system includes a secondary compressor 7, an evaporative condenser 5, a secondary throttling mechanism 10, a secondary regenerator 11 and an evaporator 33 which are connected by pipelines to form a loop; the primary refrigeration system and the secondary refrigeration system share the evaporative condenser 5, so that the primary refrigeration system and the secondary refrigeration system can perform heat exchange through the evaporative condenser 5; the inlet of the evaporator 33 is connected to the secondary regenerator 11; the outlet of the evaporator 33 is connected to the return air port of the secondary compressor 7 through a refrigeration regulating module; the refrigeration regulating module is used to reduce the temperature of the secondary refrigerant between the outlet of the evaporator 33 and the return air port of the secondary compressor 7.

[0021] Among them, in the primary refrigeration system, the exhaust port of the primary compressor 1 is connected to the first inlet 5-1 of the evaporative condenser through the primary throttling mechanism 4, the first outlet 5-2 of the evaporative condenser is connected to the first inlet 6-1 of the primary regenerator, and the first outlet 6-2 of the primary regenerator is connected to the return air port of the primary compressor 1; the pipeline of the first refrigeration system is filled with primary refrigerant.

[0022] In an optional embodiment, the primary refrigeration system further includes a primary drying filter 3, which is arranged between the exhaust port of the primary compressor 1 and the primary throttling mechanism 4 to absorb moisture in the primary refrigeration system and block impurities in the primary refrigeration system to prevent the pipelines of the primary refrigeration system from being blocked by ice and dirt.

[0023] In the secondary refrigeration system, the exhaust port of the secondary compressor 7 is connected to the second inlet 5-3 of the evaporative condenser, the second outlet 5-4 of the evaporative condenser is connected to the first inlet 11-3 of the secondary regenerator through the secondary throttling mechanism 10, the first outlet 11-4 of the secondary regenerator is connected to the inlet of the evaporator 33, and the outlet of the evaporator 33 is connected to the return air port of the secondary compressor 7 through the refrigeration adjustment module; the secondary refrigeration system is filled with secondary refrigerant. The outlet of the evaporator 33 is provided with an outlet stop valve 12 and a ninth temperature acquisition unit 22, and the inlet of the evaporator 33 is provided with a return stop valve 13 and a first temperature acquisition unit 23.

[0024] In an optional embodiment, the secondary refrigeration system also includes a secondary oil separator 8, the inlet of the secondary oil separator 8 is connected to the exhaust port of the secondary compressor 7, the first outlet of the secondary oil separator 8 is connected to the second inlet 5-3 of the evaporative condenser, and the second outlet of the secondary oil separator 8 is connected to the refrigerant return port of the secondary compressor 7, so that the refrigerant oil carried by the secondary refrigerant is deposited at the bottom of the secondary oil separator and returns to the secondary compressor 7 through the second outlet, thereby ensuring the lubrication effect of the secondary compressor 7 when working.

[0025] In an optional embodiment, the secondary refrigeration system also includes a secondary drying filter 9, which is arranged between the second outlet 5-4 of the evaporative condenser and the first inlet 11-3 of the secondary heat regenerator to absorb moisture in the secondary refrigeration system and block impurities in the secondary refrigeration system to prevent the pipelines of the secondary refrigeration system from being blocked by ice and dirt.

[0026] In an optional embodiment, the cascade refrigeration system also includes: a dual-system plate heat exchanger 2; the first inlet 2-1 of the dual-system plate heat exchanger is connected to the exhaust port of the first-stage compressor 1, and the first outlet 2-1 of the dual-system plate heat exchanger is connected to the first inlet 5-1 of the evaporative condenser; the second inlet 2-3 of the dual-system plate heat exchanger is connected to the exhaust port of the second-stage compressor 7, and the second outlet 2-4 of the dual-system plate heat exchanger is connected to the second inlet 5-3 of the evaporative condenser, so that the first-stage refrigeration system and the second-stage refrigeration system can perform heat exchange again through the dual-system plate heat exchanger 2. In addition, the dual-system plate heat exchanger 2 also has a cooling water inlet and a cooling water outlet, so that cooling water can be introduced into the dual-system plate heat exchanger, so that the refrigerant passing through the dual-system plate heat exchanger 2 dissipates heat to the outside under the action of the cooling water, thereby reducing the temperature of the first-stage refrigerant and the second-stage refrigerant, thereby further improving the energy efficiency of the cascade refrigeration system.

[0027] In an optional embodiment, the secondary refrigeration system also includes: a buffer module; the buffer module includes a unloading valve 15 and a buffer tank 14; the inlet of the unloading valve 15 is connected to the exhaust port of the secondary compressor 7, and the outlet of the unloading valve 15 is connected to the return air port of the secondary compressor 7 through the buffer tank 14. When the exhaust pressure of the secondary compressor 7 is greater than the unloading pressure of the unloading valve 15, the unloading valve 15 opens to bypass the secondary refrigerant to the buffer tank 14, thereby preventing the exhaust pressure of the secondary compressor 7 from being too high.

[0028] The outlet of the evaporator 33 is connected to the return air port of the secondary compressor 7 through a refrigeration regulating module, and the refrigeration regulating module is used to reduce the temperature of the secondary refrigerant between the outlet of the evaporator 33 and the return air port of the secondary compressor 7 to prevent the secondary compressor 7 from sucking in high-temperature gas and causing its exhaust temperature to be too high. In an optional embodiment, the refrigeration regulating module includes a precooler, and the purpose of reducing the temperature of the secondary refrigerant between the outlet of the evaporator 33 and the return air port of the secondary compressor 7 is achieved by passing the secondary refrigerant at the outlet of the evaporator 33 through the precooler through which cooling water is passed.

[0029] In this embodiment, the cascade refrigeration system includes a primary refrigeration system and a secondary refrigeration system, wherein the primary refrigeration system includes a primary compressor, a primary throttling mechanism, an evaporative condenser and a primary regenerator connected by pipes to form a loop, and the secondary refrigeration system includes a secondary compressor, an evaporative condenser, a secondary throttling mechanism, a secondary regenerator and an evaporator connected by pipes to form a loop, and the primary refrigeration system and the secondary refrigeration system share the evaporative condenser. The inlet of the evaporator is connected to the secondary regenerator, and the outlet of the evaporator is connected to the return air port of the secondary compressor through a refrigeration regulating module. The refrigeration regulating module is used to reduce the temperature of the secondary refrigerant between the evaporator outlet and the return air port of the secondary compressor, so that in a high-temperature test environment, there is no need to sacrifice the refrigeration capacity to bypass a part of the refrigerant from the secondary throttling mechanism to reduce the temperature of the secondary refrigerant at the evaporator outlet, so that the secondary compressor can be prevented from inhaling high-temperature gas and causing the exhaust temperature to be too high, thereby improving the energy efficiency of the cascade refrigeration system, and then expanding the temperature range of the high-temperature zone, further meeting the needs of chip heat dissipation and heating resistance.

[0030] Optionally, the cascade refrigeration system also includes: a sixth temperature collection unit 27, a fourth temperature collection unit 26, a second pressure collection unit 34 and a first pressure collection unit 31; the sixth temperature collection unit 27 and the second pressure collection unit 34 are both arranged at the return air port of the first-stage compressor 1; the fourth temperature collection unit 26 and the first pressure collection unit 31 are both arranged at the return air port of the second-stage compressor 7; the sixth temperature collection unit 27 is used to collect the temperature of the first-stage refrigerant at the return air port of the first-stage compressor 1; the fourth temperature collection unit 26 is used to collect the temperature of the second-stage refrigerant at the return air port of the second-stage compressor 7; the second pressure collection unit 34 is used to collect the pressure of the first-stage refrigerant at the return air port of the first-stage compressor 1; the first pressure collection unit 31 is used to collect the pressure of the second-stage refrigerant at the return air port of the second-stage compressor 7.

[0031] This embodiment also provides a control method for a cascade refrigeration system, the control method comprising:

[0032] S110. When a power-on command is received, the primary throttling mechanism and the secondary throttling mechanism are controlled to reset.

[0033] The power-on command may be understood as a command for starting the cascade refrigeration system, which may include, but is not limited to, a command sent by a user through a terminal or a command sent by a user through a key of the cascade refrigeration system. The resetting of the primary throttling mechanism 4 and the secondary throttling mechanism 10 may include first opening the primary throttling mechanism 4 and the secondary throttling mechanism 10 to the maximum opening, and then closing the primary throttling mechanism 4 and the secondary throttling mechanism 10 to zero opening, so as to detect whether the primary throttling mechanism 4 and the secondary throttling mechanism 10 can work normally.

[0034] S120, controlling the start-up of the first-stage compressor, and controlling the opening of the first-stage throttling mechanism according to the suction superheat of the first-stage compressor.

[0035] The suction superheat of the primary compressor 1 can be understood as the difference between the temperature of the primary refrigerant at the return port of the primary compressor 1 and the saturation temperature of the primary refrigerant corresponding to the pressure at the return port of the primary compressor 1. In an optional embodiment, the opening of the primary throttling mechanism 4 is controlled according to the suction superheat of the primary compressor 1. The opening of the primary throttling mechanism 4 is adjusted according to the suction superheat of the primary compressor 1 by using a PID algorithm.

[0036] S130: Acquire the second pressure collected by the second pressure collection unit.

[0037] The second pressure is the pressure at the return air port of the first-stage compressor 1 .

[0038] S140. When the saturation temperature of the primary refrigerant corresponding to the second pressure is less than or equal to the first temperature Ts, or the start time of the primary compressor is greater than or equal to the first time T1s, control the secondary compressor to start.

[0039] Among them, the first temperature Ts and the first time T1s can be determined according to the performance of the secondary compressor 7. When the saturation temperature of the primary refrigerant corresponding to the second pressure is less than or equal to the first temperature Ts, or the start time of the primary compressor 1 is greater than or equal to the first time T1s, the secondary compressor 7 will not report high pressure; in an exemplary embodiment, Ts≤-20℃, and the first time T1s≥3min.

[0040] S150, obtaining the first pressure collected by the first pressure collection unit, and controlling the opening of the secondary throttling mechanism according to the first pressure and the return air pressure setting value of the secondary compressor.

[0041] The first pressure is the pressure at the return air port of the secondary compressor 7. According to the first pressure and the return air pressure setting value of the secondary compressor 7, the opening of the primary throttling mechanism 4 is controlled by using a PID algorithm to adjust the opening of the secondary throttling mechanism 10 according to the first pressure and the return air pressure setting value of the secondary compressor 7.

[0042] S160: When the startup time of the secondary compressor 7 is greater than or equal to the second time T2s, it is determined that the startup of the cascade refrigeration system is completed.

[0043] The second time T2s is determined according to the stable operation time of the secondary compressor 7. When the startup time of the secondary compressor 7 is greater than or equal to the second time T2s, the secondary compressor 7 operates stably. In an exemplary embodiment, the second time T2s≥2min.

[0044] S170. After the cascade refrigeration system is started, when the temperature at the outlet of the evaporator is greater than or equal to the saturation temperature of the secondary refrigerant at the return air port of the secondary compressor, the temperature of the secondary refrigerant between the outlet of the evaporator and the return air port of the secondary compressor is reduced by the refrigeration regulating module.

[0045] Among them, the completion of the startup of the cascade refrigeration system can be understood as the cascade refrigeration system starting up and operating normally according to the startup procedure. In an optional embodiment, a first temperature acquisition unit 23 is provided at the outlet of the evaporator 33, and the first temperature acquisition unit is used to collect the temperature of the secondary refrigerant at the outlet of the evaporator 33. A first pressure acquisition unit 31 is provided at the return air port of the secondary compressor 7, and the first pressure acquisition unit is used to collect the pressure at the return air port of the secondary compressor 7, so as to determine the saturation temperature of the secondary refrigerant at the return air port of the secondary compressor 7 according to the pressure at the return air port of the secondary compressor 7 and the secondary refrigerant.

[0046] Specifically, if the temperature at the outlet of the evaporator 33 is greater than or equal to the saturation temperature of the secondary refrigerant at the return air port of the secondary compressor 7, it means that the temperature at the outlet of the evaporator 33 is too high, causing the secondary compressor 7 to inhale high-temperature gas and resulting in excessive exhaust temperature, thereby affecting the normal use of the secondary compressor 7. Therefore, a refrigeration adjustment module can be set between the outlet of the evaporator 33 and the return air port of the secondary compressor 7, and the refrigeration adjustment module can reduce the temperature of the secondary refrigerant between the outlet of the evaporator 33 and the return air port of the secondary compressor 7. There is no need to sacrifice the cooling capacity to bypass a part of the refrigerant from the secondary throttling mechanism 10 to reduce the temperature of the secondary refrigerant at the outlet of the evaporator 33. This can prevent the secondary compressor 7 from inhaling high-temperature gas and causing the exhaust temperature to be too high, which is beneficial to improving the energy efficiency of the cascade refrigeration system, and then expanding the temperature range of the high-temperature zone, further meeting the needs of chip heat dissipation and heating resistance.

[0047] Optionally, the cascade refrigeration system also includes a precooler 29, a first temperature collection unit 23 and an eighth temperature collection unit 30; the refrigeration adjustment module includes a first high-temperature valve 16 and a second high-temperature valve 17; the inlet of the first high-temperature valve 16 and the inlet of the second high-temperature valve 17 are respectively connected to the outlet of the evaporator; the outlet of the first high-temperature valve 16 is connected to the inlet 29-1 of the precooler; the outlet of the second high-temperature valve 17 and the outlet 29-2 of the precooler are both connected to the return air port of the secondary compressor 7, and an interlocking protection is set between the first high-temperature valve 16 and the second high-temperature valve 17; the first temperature collection unit 23 is arranged at the inlet of the first high-temperature valve 16 and the second high-temperature valve 17, and the first temperature collection unit 23 is used to collect the temperature of the secondary refrigerant at the inlet of the first high-temperature valve 16 and the second high-temperature valve 17; the eighth temperature collection unit 30 is arranged at the cooling water inlet of the precooler 29, and the eighth temperature collection unit 30 is used to collect the temperature of the cooling water at the cooling water inlet of the precooler 29.

[0048] The precooler 29 may be, but is not limited to, a plate heat exchanger, and the precooler 29 is also provided with a cooling water inlet and a cooling water outlet. Since the inlet of the first high temperature valve 16 is connected to the outlet of the evaporator 33, the outlet of the first high temperature valve 16 is connected to the inlet 29-1 of the precooler, and the outlet 29-2 of the precooler is connected to the return air port of the secondary compressor 7, when the first high temperature valve 16 is opened, the secondary refrigerant at the outlet of the evaporator 33 can pass through the precooler 29 and then enter the return air port of the secondary compressor 7. Cooling water is introduced into the precooler 29, so that the secondary refrigerant in the precooler 29 dissipates heat to the outside under the maximum use of cooling water, thereby reducing the temperature of the secondary refrigerant.

[0049] The first high temperature valve 16 and the second high temperature valve 17 may be, but are not limited to, high temperature solenoid valves, so that the states of the first high temperature valve 16 and the second high temperature valve 17 can be remotely controlled. The first temperature acquisition unit 23 and the eighth temperature acquisition unit 30 may include, but are not limited to, temperature sensors that can acquire the temperature of the corresponding position.

[0050] The inlet of the first high temperature valve 16 and the inlet of the second high temperature valve 17 are respectively connected to the outlet of the evaporator 33, the outlet of the first high temperature valve 16 is connected to the inlet 29-1 of the precooler, the outlet of the second high temperature valve 17 and the outlet 29-2 of the precooler are both connected to the return air port of the secondary compressor 7, and an interlocking protection is set between the first high temperature valve 16 and the second high temperature valve 17, so that when the first high temperature valve 16 is opened, the second high temperature valve 17 is closed, and the secondary refrigerant at the outlet of the evaporator 33 enters the return air port of the secondary compressor 7 after being cooled by the precooler 29, while when the first high temperature valve 16 is closed, the second high temperature valve 17 is opened, and the secondary refrigerant at the outlet of the evaporator 33 does not pass through the precooler 29, but directly enters the return air port of the secondary compressor 7 through a pipeline.

[0051] Optionally, in the control method of the cascade refrigeration system, S170 specifically includes:

[0052] S271 , acquiring a first temperature T1 acquired by a first temperature acquisition unit and a second temperature T2 acquired by an eighth temperature acquisition unit.

[0053] S272, determine whether the first temperature T1 and the second temperature T2 satisfy the first condition; if so, execute S213; if not, execute S214.

[0054] The first condition includes T1 ≥ T2 + T 偏1 Among them, T 偏1 Greater than or equal to the minimum heat exchange temperature of the precooler 29, illustratively, T 偏1 =5° C. The minimum heat exchange temperature of the precooler 29 can be understood as the difference between the inlet 29 - 1 temperature of the precooler and the outlet 29 - 2 temperature of the precooler when the precooler 29 can achieve effective heat exchange.

[0055] S273, open the first high-temperature valve and close the second high-temperature valve.

[0056] S274, close the first high-temperature valve and open the second high-temperature valve.

[0057] Specifically, when the first condition is satisfied between the first temperature T1 and the second temperature T2, that is, the temperature at the outlet of the evaporator 33 is greater than or equal to the sum of the temperature at the cooling water inlet of the precooler 29 and the minimum heat exchange temperature of the precooler 29, it indicates that the temperature of the secondary refrigerant at the outlet of the evaporator 33 is relatively high. At this time, the first high-temperature valve 16 can be opened and the second high-temperature valve 17 can be closed, so that the secondary refrigerant dissipates heat through the precooler 29; on the contrary, when the first condition is not satisfied between the first temperature T1 and the second temperature T2, that is, the temperature at the outlet of the evaporator 33 is less than the sum of the temperature at the cooling water inlet of the precooler 29 and the minimum heat exchange temperature of the precooler 29, at this time, the precooler 29 cannot effectively dissipate heat for the secondary refrigerant. Therefore, the first high-temperature valve 16 can be closed and the second high-temperature valve 17 can be opened so that the secondary refrigerant at the outlet of the evaporator 33 does not pass through the precooler 29. At this time, the input of cooling water to the precooler 29 can be stopped to reduce costs.

[0058] Optionally, the cascade refrigeration system also includes: a second temperature acquisition unit 24, a sixth temperature acquisition unit 27 and a seventh temperature acquisition unit 28; the refrigeration adjustment module includes: a normal temperature valve 18 and a first low temperature valve 19; the inlet of the normal temperature valve 18 and the inlet of the first low temperature valve 19 are respectively connected to the outlet of the evaporator 33; the outlet of the normal temperature valve 18 is connected to the second inlet 6-3 of the primary heat regenerator; the outlet of the first low temperature valve 19 and the second outlet 6-4 of the primary heat regenerator are respectively connected to the return air port of the secondary compressor 7; an interlock protection is set between the normal temperature valve 18 and the first low temperature valve 19; the second temperature acquisition unit 24 is arranged at the inlet of the normal temperature valve 18 and the first low temperature valve 19; the sixth temperature acquisition unit 27 is arranged at the return air port of the primary compressor 1, and the second temperature acquisition unit 24 is used to collect the temperature of the secondary refrigerant at the inlet of the normal temperature valve 18 and the first low temperature valve 19; the seventh temperature acquisition unit 28 is arranged at the exhaust port of the primary compressor 1, and the seventh temperature acquisition unit 28 is used to collect the temperature of the primary refrigerant at the exhaust port of the primary compressor 1.

[0059] The normal temperature valve 18 may be, but is not limited to, a normal temperature solenoid valve, and the first low temperature valve 19 may be, but is not limited to, a low temperature solenoid valve, so that the states of the normal temperature valve 18 and the first low temperature valve 19 can be remotely controlled. The second temperature acquisition unit 24, the sixth temperature acquisition unit 27, and the seventh temperature acquisition unit 28 may include, but are not limited to, temperature sensors that can acquire the temperature at the corresponding position.

[0060] The inlet of the normal temperature valve 18 and the inlet of the first low temperature valve 19 are respectively connected to the outlet of the evaporator 33; the outlet of the normal temperature valve 18 is connected to the second inlet 6-3 of the primary heat regenerator, and the outlet of the first low temperature valve 19 and the second outlet 6-4 of the primary heat regenerator are respectively connected to the return air port of the secondary compressor 7. Interlocking protection is set between the normal temperature valve 18 and the first low temperature valve 19, so that when the normal temperature valve 18 is opened, the first low temperature valve 19 is closed, and the secondary refrigerant enters the return air port of the secondary compressor 7 after being cooled by the primary heat regenerator 6. When the normal temperature valve 18 is closed, the first low temperature valve 19 is opened, and the secondary refrigerant does not dissipate heat through the primary heat regenerator 6, but directly enters the return air port of the secondary compressor 7 through the pipeline.

[0061] Optionally, in the control method of the cascade refrigeration system, S170 specifically includes:

[0062] S371, acquiring a third temperature T3 collected by the second temperature collection unit, a fourth temperature T4 collected by the sixth temperature collection unit, and a fifth temperature T5 collected by the seventh temperature collection unit;

[0063] S372, determine whether the third temperature T3, the fourth temperature T4 and the fifth temperature T5 satisfy the second condition; if so, execute S373; if not, execute S374.

[0064] The second condition includes T3 ≥ T4 + T 偏2 , and T5≤T5 预设 ; Among them, T 偏2 Greater than or equal to the minimum heat exchange temperature of the primary regenerator 6, exemplarily, T 偏2 =5℃. T5 预设 Less than or equal to the exhaust temperature warning value of the primary compressor 1. The minimum heat exchange temperature of the primary regenerator 6 can be understood as the difference between the second inlet temperature of the primary regenerator and the second outlet temperature of the primary regenerator when the primary regenerator 6 can achieve effective heat exchange.

[0065] S373, open the normal temperature valve and close the first low temperature valve.

[0066] S374, close the normal temperature valve and open the first low temperature valve.

[0067] Specifically, when the second condition is satisfied among the third temperature T3, the fourth temperature T4 and the fifth temperature T5, that is, the temperature of the secondary refrigerant at the inlet of the normal temperature valve 18 and the inlet of the first low temperature valve 19 is greater than or equal to the sum of the temperature at the second outlet 6-4 of the primary regenerator and the minimum heat exchange temperature of the primary regenerator 6, and the temperature of the exhaust port of the primary compressor 1 is less than or equal to the exhaust temperature warning value of the primary compressor 1, it indicates that the temperature of the secondary refrigerant at the inlet of the normal temperature valve 18 and the inlet of the first low temperature valve 19 is relatively high, and the primary regenerator 6 can dissipate heat for the secondary refrigerant. At this time, the normal temperature valve 18 can be opened, and the first low temperature valve 19 can be closed, so as to pass The secondary refrigerant dissipates heat through the first-stage reheater 6; on the contrary, when the second condition is not satisfied among the third temperature T3, the fourth temperature T4 and the fifth temperature T5, that is, the temperature of the secondary refrigerant at the inlet of the normal temperature valve 18 and the inlet of the first low-temperature valve 19 is less than the sum of the temperature at the second outlet 6-4 of the first-stage reheater and the minimum heat exchange temperature of the first-stage reheater 6, or the temperature of the exhaust port of the first-stage compressor 1 is less than or equal to the exhaust temperature warning value of the first-stage compressor 1, at this time, the normal temperature valve 18 can be closed and the first low-temperature valve 19 can be opened, so that the secondary refrigerant does not pass through the first-stage reheater 6, so that the primary refrigerant can fully dissipate heat through the first-stage reheater 6.

[0068] Optionally, a cascade refrigeration system is characterized in that it also includes: a third temperature acquisition unit 25 and a first pressure acquisition unit 31; the refrigeration adjustment module includes: a second low-temperature valve 32 and a third low-temperature valve 20; the inlets of the second low-temperature valve 32 and the third low-temperature valve 20 are respectively connected to the outlet of the evaporator 33; the outlet of the second low-temperature valve 32 is connected to the second inlet 11-1 of the secondary regenerator; the outlet of the third low-temperature valve 20 and the second outlet 11-2 of the secondary regenerator are connected to the return air port of the secondary compressor 7; an interlock protection is set between the second low-temperature valve 32 and the third low-temperature valve 20; the third temperature acquisition unit 25 is set at the inlet of the second low-temperature valve 32 and the third low-temperature valve 20, and the third temperature acquisition unit 25 is used to collect the temperature of the secondary refrigerant at the inlet of the second low-temperature valve 32 and the third low-temperature valve 20; the first pressure acquisition unit 31 is set at the return air port of the secondary compressor 7, and the first pressure acquisition unit 31 is used to collect the temperature of the secondary refrigerant at the return air port of the secondary compressor 7.

[0069] The second cryogenic valve 32 and the third cryogenic valve 20 may be, but are not limited to, cryogenic solenoid valves, so that the states of the second cryogenic valve 32 and the third cryogenic valve 20 can be remotely controlled. The third temperature acquisition unit 25 may include, but is not limited to, a temperature sensor capable of acquiring the temperature at the corresponding position. The first pressure acquisition unit 31 may include, but is not limited to, a pressure sensor capable of acquiring the pressure at the corresponding position.

[0070] The inlets of the second cryogenic valve 32 and the third cryogenic valve 20 are respectively connected to the outlets of the evaporator 33, the outlet of the second cryogenic valve 32 is connected to the second inlet 11-1 of the secondary heat regenerator, the outlet of the third cryogenic valve 20 and the second outlet 11-2 of the secondary heat regenerator are connected to the return air port of the secondary compressor 7, and an interlocking protection is arranged between the second cryogenic valve 32 and the third cryogenic valve 20, so that when the second cryogenic valve 32 is opened, the third cryogenic valve 20 is closed, and the secondary refrigerant enters the return air port of the secondary compressor 7 after being cooled by the secondary heat regenerator 11, while when the second cryogenic valve 32 is closed, the third cryogenic valve 20 is opened, and the secondary refrigerant does not dissipate heat through the secondary heat regenerator 11, but directly enters the return air port of the secondary compressor 7 through the pipeline.

[0071] Optionally, the control method of the cascade refrigeration system specifically includes:

[0072] S471. Acquire a sixth temperature T6 acquired by the third temperature acquisition unit and a first pressure acquired by the first pressure acquisition unit.

[0073] S472, determine whether the sixth temperature T6 satisfies the third condition; if so, execute S473; if not, execute S474.

[0074] The third condition includes T6 ≥ T 蒸发 +T 偏3 ; Among them, T 蒸发 Determined by the primary pressure and the secondary refrigerant; T 蒸发 is the saturation temperature of the secondary refrigerant corresponding to the pressure at the return air port of the secondary compressor 7. ; T 偏3 is greater than or equal to the minimum heat exchange temperature of the secondary heat exchanger 11. The minimum heat exchange temperature of the secondary heat exchanger 11 can be understood as the difference between the temperature of the second inlet 11-1 of the secondary heat exchanger and the temperature of the second outlet 11-2 of the secondary heat exchanger when the secondary heat exchanger 11 can achieve effective heat exchange. For example, T 偏3 =5℃.

[0075] S473, open the second cryogenic valve and close the third cryogenic valve.

[0076] S474, close the second cryogenic valve and open the third cryogenic valve.

[0077] Specifically, when the sixth temperature T6 satisfies the third condition, that is, the temperature of the secondary refrigerant at the inlet of the second cryogenic valve 32 and the third cryogenic valve 20 is greater than or equal to the sum of the saturation temperature of the secondary refrigerant corresponding to the pressure at the return air port of the secondary compressor 7 and the minimum heat exchange temperature of the secondary regenerator 11, it indicates that the temperature of the secondary refrigerant at the inlet of the second cryogenic valve 32 and the third cryogenic valve 20 is relatively high. At this time, the second cryogenic valve 32 can be opened and the third cryogenic valve 20 can be closed, so as to dissipate heat for the secondary refrigerant through the secondary regenerator 11; on the contrary, when the sixth temperature T6 does not satisfy the third condition, that is, the temperature of the secondary refrigerant at the inlet of the second cryogenic valve 32 and the third cryogenic valve 20 is less than the sum of the saturation temperature of the secondary refrigerant corresponding to the pressure at the return air port of the secondary compressor 7 and the minimum heat exchange temperature of the secondary regenerator 11, it indicates that the heat dissipation benefit of the secondary refrigerant at the inlet of the second cryogenic valve 32 and the third cryogenic valve 20 of the secondary regenerator 11 is relatively small. Therefore, the second cryogenic valve 32 can be closed and the third cryogenic valve 20 can be opened.

[0078] Optionally, the cascade refrigeration system is characterized in that it also includes: a fifth temperature collection unit 21; the fifth temperature collection unit 21 is arranged at the exhaust port of the secondary compressor 7, and the fifth temperature collection unit 21 is used to collect the temperature of the secondary refrigerant at the exhaust port of the secondary compressor 7.

[0079] The fifth temperature acquisition unit may include, but is not limited to, a temperature sensor capable of acquiring the temperature of the secondary refrigerant at the exhaust port of the secondary compressor 7 .

[0080] Optionally, the control method of the cascade refrigeration system specifically includes:

[0081] S571. Obtain a seventh temperature T7 collected by a fifth temperature collection unit.

[0082] S572: Determine whether the seventh temperature T7 satisfies the fourth condition; if so, execute S573.

[0083] The fourth condition includes T7 ≥ T7 预设 Among them, T7 预设 Less than or equal to the exhaust gas temperature warning value of the secondary compressor 7.

[0084] S573, close the third cryogenic valve and open the second cryogenic valve.

[0085] Specifically, when the seventh temperature T7 satisfies the fourth condition, that is, the temperature of the secondary refrigerant at the exhaust port of the secondary compressor 7 is greater than or equal to the exhaust temperature warning value of the secondary compressor 7, it is necessary to lower the exhaust temperature of the secondary compressor 7 to prevent the secondary compressor 7 from shutting down due to a high temperature alarm. Therefore, it is necessary to close the third cryogenic valve 20 and open the second cryogenic valve 32 so that the secondary heat regenerator can dissipate the heat for the secondary refrigerant at the inlet of the second cryogenic valve 32 and the third cryogenic valve 20, thereby lowering the exhaust temperature of the secondary compressor 7.

[0086] It should be noted that when the seventh temperature T7 satisfies the fourth condition, even if the sixth temperature T6 does not satisfy the third condition, the secondary heat regenerator 11 is required to dissipate the heat for the secondary refrigerant at the inlet of the second low-temperature valve 32 and the third low-temperature valve 20, so as to reduce the exhaust temperature of the secondary compressor and prevent the secondary compressor from shutting down due to high temperature alarm. Therefore, regardless of whether the sixth temperature T6 satisfies the third condition, as long as the seventh temperature T7 satisfies the fourth condition, the third low-temperature valve 20 is closed and the second low-temperature valve 32 is opened.

[0087] It should also be noted that the refrigeration control module may also include at least two groups of the first high temperature valve 16 and the second high temperature valve 17, the normal temperature valve 18 and the first low temperature valve 19, and the second low temperature valve 32 and the third low temperature valve 20, so as to further reduce the temperature of the secondary refrigerant at the return air port of the secondary compressor 7. When the refrigeration control module may also include at least two groups of the first high temperature valve 16 and the second high temperature valve 17, the normal temperature valve 18 and the first low temperature valve 19, and the second low temperature valve 32 and the third low temperature valve 20, the control scheme of the cascade refrigeration system is the same as the method in the above embodiment.

[0088] The above specific implementations do not constitute a limitation on the protection scope of the present invention. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modification, equivalent substitution and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A cascade refrigeration system, characterized in that: include: Primary refrigeration system, secondary refrigeration system and precooler (29); The primary refrigeration system comprises a primary compressor (1), a primary throttling mechanism (4), an evaporative condenser (5) and a primary regenerator (6) which are connected by pipelines to form a loop; The secondary refrigeration system comprises a secondary compressor (7), an evaporative condenser (5), a secondary throttling mechanism (10), a secondary regenerator (11) and an evaporator (33) which are connected by pipelines to form a loop; The primary refrigeration system and the secondary refrigeration system share the evaporative condenser (5); The inlet of the evaporator (33) is connected to the secondary regenerator (11); The outlet of the evaporator (33) is connected to the air return port of the secondary compressor (7) via a refrigeration adjustment module; The refrigeration regulating module comprises: a first high temperature valve (16), a second high temperature valve (17), a normal temperature valve (18), a first low temperature valve (19), a second low temperature valve (32), a third low temperature valve (20), a second low temperature valve (32) and a third low temperature valve; The inlet of the first high temperature valve (16) and the inlet of the second high temperature valve (17) are respectively connected to the outlet of the evaporator (33); the outlet of the first high temperature valve (16) is connected to the inlet (29-1) of the precooler; the outlet of the second high temperature valve (17) and the outlet (29-2) of the precooler are both connected to the return air port of the secondary compressor (7); an interlocking protection is provided between the first high temperature valve (16) and the second high temperature valve (17); The inlet of the normal temperature valve (18) and the inlet of the first low temperature valve (19) are respectively connected to the outlet of the evaporator (33); the outlet of the normal temperature valve (18) is connected to the second inlet (6-3) of the primary regenerator; the outlet of the first low temperature valve (19) and the second outlet (6-4) of the primary regenerator are respectively connected to the return air port of the secondary compressor (7); an interlocking protection is provided between the normal temperature valve (18) and the first low temperature valve (19); The inlets of the second cryogenic valve (32) and the third cryogenic valve (20) are respectively connected to the outlet of the evaporator (33); the outlet of the second cryogenic valve (32) is connected to the second inlet (11-1) of the secondary regenerator; the outlet of the third cryogenic valve (20) and the second outlet (11-2) of the secondary regenerator are connected to the return air port of the secondary compressor (7); an interlocking protection is provided between the second cryogenic valve (32) and the third cryogenic valve (20); The inlets of the second cryogenic valve (32) and the third cryogenic valve (20) are respectively connected to the outlet of the evaporator (33); the outlet of the second cryogenic valve (32) is connected to the second inlet (11-1) of the secondary regenerator; the outlet of the third cryogenic valve (20) and the second outlet (11-2) of the secondary regenerator are connected to the return air port of the secondary compressor (7); an interlocking protection is provided between the second cryogenic valve (32) and the third cryogenic valve (20); The refrigeration regulating module is used to reduce the temperature of the secondary refrigerant between the outlet of the evaporator (33) and the return air port of the secondary compressor (7).

2. The cascade refrigeration system according to claim 1, characterized in that: Also includes: A first temperature collection unit (23) and an eighth temperature collection unit (30); The first temperature collection unit (23) is arranged at the inlet of the first high-temperature valve (16) and the second high-temperature valve (17); and the eighth temperature collection unit (30) is arranged at the cooling water inlet of the precooler (29).

3. The cascade refrigeration system according to claim 1, characterized in that: Also includes: A second temperature collection unit (24), a sixth temperature collection unit (27) and a seventh temperature collection unit (28); The second temperature collection unit (24) is arranged at the inlet of the normal temperature valve (18) and the first low temperature valve (19); the sixth temperature collection unit (27) is arranged at the return air port of the first stage compressor (1); and the seventh temperature collection unit (28) is arranged at the exhaust port of the first stage compressor (1).

4. The cascade refrigeration system according to claim 1, characterized in that: Also includes: A third temperature collection unit (25) and a first pressure collection unit (31); The third temperature acquisition unit (25) is arranged at the inlet of the second cryogenic valve (32) and the third cryogenic valve (20); and the first pressure acquisition unit (31) is arranged at the return air port of the secondary compressor (7).

5. The cascade refrigeration system according to claim 1, characterized in that: Also includes: A fifth temperature collection unit (21); The fifth temperature collection unit (21) is arranged at the exhaust port of the secondary compressor (7).

6. The cascade refrigeration system according to claim 1, characterized in that: Also includes: A sixth temperature collection unit (27), a fourth temperature collection unit (26), a second pressure collection unit (34) and a first pressure collection unit (31); The sixth temperature collection unit (27) and the second pressure collection unit (34) are both arranged at the air return port of the first-stage compressor (1); The fourth temperature collection unit (26) and the first pressure collection unit (31) are both arranged at the air return port of the secondary compressor (7).

7. The cascade refrigeration system according to claim 1, characterized in that: Also includes: Dual system plate heat exchanger (2); The first inlet (2-1) of the dual-system plate heat exchanger is connected to the exhaust port of the primary compressor (1), and the first outlet (2-2) of the dual-system plate heat exchanger is connected to the first inlet (5-1) of the evaporative condenser; The second inlet (2-3) of the dual-system plate heat exchanger is connected to the exhaust port of the secondary compressor (7), and the second outlet (2-4) of the dual-system plate heat exchanger is connected to the second inlet (5-3) of the evaporative condenser.

8. The cascade refrigeration system according to claim 1, characterized in that: The secondary refrigeration system further includes: a buffer module; The buffer module comprises a relief valve (15) and a buffer tank (14); The inlet of the unloading valve (15) is connected to the exhaust port of the secondary compressor (7), and the outlet of the unloading valve (15) is connected to the return air port of the secondary compressor (7) through the buffer tank (14).

9. A control method for a cascade refrigeration system, characterized in that: Used to control a cascade refrigeration system according to any one of claims 1 to 8, the cascade refrigeration system comprising a primary refrigeration system and a secondary refrigeration system; the primary refrigeration system comprises a primary compressor (1), a primary throttling mechanism (4), an evaporative condenser (5) and a primary regenerator (6) which are connected by pipelines to form a loop; the secondary refrigeration system comprises a secondary compressor (7), an evaporative condenser (5), a secondary throttling mechanism (10), a secondary regenerator (11) and an evaporator (33) which are connected by pipelines to form a loop; the primary refrigeration system and the secondary refrigeration system share the evaporative condenser (5); and the inlet of the evaporator (33) is connected to the secondary regenerator (11); The outlet of the evaporator (33) is connected to the return air port of the secondary compressor (7) via a refrigeration adjustment module; the control method comprises: After the cascade refrigeration system is started, when the temperature of the outlet of the evaporator (33) is greater than or equal to the saturation temperature of the secondary refrigerant at the return air port of the secondary compressor (7), the refrigeration regulating module is controlled to reduce the temperature of the secondary refrigerant between the outlet of the evaporator (33) and the return air port of the secondary compressor (7).

10. The control method of the cascade refrigeration system according to claim 9, characterized in that: The cascade refrigeration system further comprises: a precooler (29), a first temperature acquisition unit (23) and an eighth temperature acquisition unit (30); the refrigeration regulation module comprises: a first high temperature valve (16) and a second high temperature valve (17); the inlet of the first high temperature valve (16) and the inlet of the second high temperature valve (17) are respectively connected to the outlet of the evaporator (33); the outlet of the first high temperature valve (16) is connected to the inlet (29-1) of the precooler; the outlet of the second high temperature valve (17) and the outlet (29-2) of the precooler are both connected to the return air port of the secondary compressor (7); an interlocking protection is provided between the first high temperature valve (16) and the second high temperature valve (17); the first temperature acquisition unit (23) is provided at the inlet of the first high temperature valve (16) and the second high temperature valve (17); the eighth temperature acquisition unit (30) is provided at the cooling water inlet of the precooler (29); the control method specifically comprises: Acquiring a first temperature T1 collected by the first temperature collection unit (23) and a second temperature T2 collected by the eighth temperature collection unit (30); Determine whether the first temperature T1 and the second temperature T2 satisfy a first condition; the first condition includes T1 ≥ T2 + T 偏1 ; wherein the T 偏1 Greater than or equal to the minimum heat exchange temperature of the precooler (29); If yes, then open the first high temperature valve (16) and close the second high temperature valve (17); If not, the first high-temperature valve (16) is closed and the second high-temperature valve (17) is opened.

11. The control method of the cascade refrigeration system according to claim 9, characterized in that: The cascade refrigeration system further comprises: a sixth temperature acquisition unit (27) and a seventh temperature acquisition unit (28); the refrigeration regulation module comprises: a normal temperature valve (18), a first low temperature valve (19) and a second temperature acquisition unit (24); the inlet of the normal temperature valve (18) and the inlet of the first low temperature valve (19) are respectively connected to the outlet of the evaporator (33); the outlet of the normal temperature valve (18) is connected to the second inlet (6-3) of the primary regenerator; the outlet of the first low temperature valve (19) is connected to the outlet of the primary regenerator The second outlet (6-4) of the heat exchanger is respectively connected to the return air port of the secondary compressor (7); the second temperature acquisition unit (24) is arranged at the inlet of the normal temperature valve (18) and the first low temperature valve (19); an interlock protection is arranged between the normal temperature valve (18) and the first low temperature valve (19); the sixth temperature acquisition unit (27) is arranged at the return air port of the primary compressor (1); the seventh temperature acquisition unit (28) is arranged at the exhaust port of the primary compressor (1); the control method specifically comprises: Acquire the third temperature T3 collected by the second temperature collection unit (24), the fourth temperature T4 collected by the sixth temperature collection unit (27), and the fifth temperature T5 collected by the seventh temperature collection unit (28); Determine whether the third temperature T3, the fourth temperature T4 and the fifth temperature T5 satisfy a second condition; the second condition includes T3 ≥ T4 + T 偏2 , and T5≤T5 预设 ; wherein the T 偏2 is greater than or equal to the minimum heat exchange temperature of the primary regenerator (6); the T5 预设 ≤ the exhaust temperature warning value of the first-stage compressor (1); If yes, open the normal temperature valve (18) and close the first low temperature valve (19); If not, close the normal temperature valve (18) and open the first low temperature valve (19).

12. The control method of the cascade refrigeration system according to claim 9, characterized in that: The cascade refrigeration system further comprises: a third temperature acquisition unit (25) and a first pressure acquisition unit (31); the refrigeration regulation module comprises: a second cryogenic valve (32) and a third cryogenic valve (20); the inlets of the second cryogenic valve (32) and the third cryogenic valve (20) are respectively connected to the outlet of the evaporator (33); the outlet of the second cryogenic valve (32) is connected to the second inlet (11-1) of the secondary regenerator; the outlet of the third cryogenic valve (20) and the second outlet (11-2) of the secondary regenerator are connected to the return air port of the secondary compressor (7); an interlocking protection is provided between the second cryogenic valve (32) and the third cryogenic valve (20); the third temperature acquisition unit (25) is provided at the inlets of the second cryogenic valve (32) and the third cryogenic valve (20); the first pressure acquisition unit is provided at the return air port of the secondary compressor (7); the control method specifically comprises: Acquiring a sixth temperature T6 acquired by the third temperature acquisition unit (25) and a first pressure acquired by the first pressure acquisition unit (31); Determine whether the sixth temperature T6 satisfies a third condition; the third condition includes T6 ≥ T 蒸发 +T 偏3 ; Among them, T 蒸发 is determined by the first pressure and the secondary refrigerant; T 偏3 Greater than or equal to the minimum heat exchange temperature of the secondary regenerator (11); If yes, opening the second cryogenic valve (32) and closing the third cryogenic valve (20); If not, the second cryogenic valve (32) is closed and the third cryogenic valve (20) is opened.

13. The control method of the cascade refrigeration system according to claim 9, characterized in that: The cascade refrigeration system further comprises: a fifth temperature acquisition unit (21); the refrigeration regulation module comprises: a second cryogenic valve (32) and a third cryogenic valve (20); the inlets of the second cryogenic valve (32) and the third cryogenic valve (20) are respectively connected to the outlet of the evaporator (33); the outlet of the second cryogenic valve (32) is connected to the second inlet (11-1) of the secondary regenerator; the outlet of the third cryogenic valve (20) and the second outlet (11-2) of the secondary regenerator are connected to the return air port of the secondary compressor (7); an interlocking protection is provided between the second cryogenic valve (32) and the third cryogenic valve (20); the fifth temperature acquisition unit (21) is provided at the exhaust port of the secondary compressor (7); the control method specifically comprises: Acquiring a seventh temperature T7 collected by the fifth temperature collection unit (21); Determine whether the seventh temperature T7 satisfies the fourth condition; the fourth condition includes T7 ≥ T7 预设 Among them, T7 预设 Less than or equal to the exhaust gas temperature warning value of the secondary compressor (7); If so, the third cryogenic valve (20) is closed and the second cryogenic valve (32) is opened.

14. The control method of a cascade refrigeration system according to any one of claims 10 to 12, characterized in that: The cascade refrigeration system further comprises: a sixth temperature acquisition unit (27), a fourth temperature acquisition unit (26), a second pressure acquisition unit (34) and a first pressure acquisition unit (31); the sixth temperature acquisition unit (27) and the second pressure acquisition unit (34) are both arranged at the return air port of the first-stage compressor (1); the fourth temperature acquisition unit (26) and the first pressure acquisition unit (31) are both arranged at the return air port of the second-stage compressor (7); the control method further comprises: When a power-on command is received, the first-level throttling mechanism (4) and the second-level throttling mechanism (10) are controlled to reset; Controlling the start-up of the first-stage compressor (1), and controlling the opening degree of the first-stage throttling mechanism (4) according to the suction superheat of the first-stage compressor (1); Acquiring a second pressure collected by the second pressure collection unit (34); When the saturation temperature of the primary refrigerant corresponding to the second pressure is less than or equal to Ts, or the start time of the primary compressor (1) is greater than or equal to the first time T1s, controlling the secondary compressor (7) to start; Acquiring a first pressure collected by the first pressure collection unit (31), and controlling the opening of the secondary throttling mechanism (10) according to the first pressure and a return air pressure setting value of the secondary compressor (7); When the startup time of the secondary compressor (7) is greater than or equal to the second time T2s, it is determined that the startup of the cascade refrigeration system is completed.

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