Monitoring and control method of adjustable single screw compressor regenerative cascade low temperature refrigeration system

Abstract

The monitoring and control method of an adjustable single-screw compressor regenerative cascade low-temperature refrigeration system belongs to the field of monitoring or testing devices for regulating systems. The system includes a refrigerant circuit and a monitoring-control circuit. The refrigerant circuit connects the high-temperature and low-temperature circuits by a condenser evaporator, and the controller is simultaneously connected to the compressor motor, compressor slide valve power device, throttling element, bypass element, liquid injection control element, pressure sensor and temperature sensor. After setting the target refrigeration temperature and refrigeration capacity, the controller is guided by the monitoring data of each sensor to adjust the compressor motor, compressor slide valve power device, throttling element, bypass element, and liquid injection control element of each level of the system to achieve functions such as variable refrigeration temperature, variable refrigeration capacity, variable motor frequency, variable compressor content ratio, variable overheat / undercooling temperature, liquid injection, and air replenishment, so that the system operation is more stable and the performance is improved.

Description

Technical Field

[0001] The present invention relates to the field of monitoring or testing devices for general regulating systems, and in particular to a monitoring and control method for an adjustable single-screw compressor regenerative cascade low-temperature refrigeration system. Background Art

[0002] Energy conservation and emission reduction to improve energy efficiency has become a research focus; low-temperature refrigeration systems consume significant electrical energy in the process of producing lower temperatures. When operating under variable ambient temperature, refrigeration temperature, and cooling capacity conditions, system stability is significantly affected, resulting in poor system performance and low energy utilization. The stable operation of the system is inseparable from real-time monitoring and precise control. As a commonly used system for producing low temperatures of -50℃ to -100℃, the cascade refrigeration system has both reliability and safety. However, since the cascade refrigeration system consists of a high-temperature and low-temperature two-stage system, the two-stage system complements and influences each other. Any change in operating parameters will cause fluctuations in the two-stage system. Therefore, variable operating conditions will bring more problems such as imbalance in inter-stage matching, which will have an adverse effect on the long-term stable operation of the cascade refrigeration system. Reasonable monitoring and control of the system is an effective means to improve system performance, system operating life, and energy utilization. Summary of the invention

[0003] The purpose of the present invention is to provide a monitoring and control method for an adjustable single-screw compressor heat-recovery cascade low-temperature refrigeration system, which is used to improve the performance and operation adjustment stability of the heat-recovery cascade low-temperature refrigeration system and provide an energy-saving and efficient monitoring and control method for the system to cope with different operating conditions.

[0004] To achieve the above purpose, the present invention adopts the following technical solutions.

[0005] The utility model relates to an adjustable single screw compressor heat recovery cascade low temperature refrigeration system, which is composed of a refrigerant circuit and a monitoring-control circuit.

[0006] The adjustable single screw compressor heat recovery cascade low temperature refrigeration system is used to produce a low temperature of 0°C to -80°C; the refrigerant circuit comprises: a high and low temperature stage refrigeration main circuit connected by a condenser evaporator (13), a high temperature stage primary throttling branch, a high temperature stage heat recovery branch, a high temperature stage liquid injection branch, a low temperature stage primary throttling branch, a low temperature stage heat recovery branch, and a low temperature stage liquid injection branch.

[0007] The high and low temperature refrigeration main circuit comprises a high temperature secondary flow meter (12), a high temperature compressor (1), a condenser (2), a high temperature refrigerant storage tank (3), a high temperature subcooler (5), a high temperature regenerator (8), a high temperature secondary throttling element (10), a condenser evaporator (13), a low temperature refrigerant storage tank (14), a low temperature subcooler (16), a low temperature regenerator (20), a low temperature secondary throttling element (22), an evaporator (23), a high temperature secondary flow meter (25), and a low temperature compressor (18).

[0008] Furthermore, the operation logic of the high and low temperature refrigeration main circuit is as follows: the high temperature compressor (1) is adjusted to a corresponding content volume ratio gear position by calculation according to the working conditions corresponding to the ambient temperature and the refrigeration temperature and is turned on; the high temperature refrigerant (29) flows from the outlet a of the high temperature compressor (1) into the condenser (2) to exchange heat with the environment, and then flows through the high temperature refrigerant storage tank (3), the inlet a of the high temperature subcooler (5), the outlet c of the high temperature subcooler (5), the inlet a of the high temperature regenerator (8), and the outlet b of the high temperature regenerator (8) to flow into the condenser (2). The high-temperature secondary throttling element (10) is opened by the high-temperature secondary throttling element (10) to control the pressure of the high-temperature refrigerant flowing into the inlet a of the condenser evaporator (13). After heat exchange with the low-temperature refrigerant in the condenser evaporator (13), the high-temperature refrigerant flows out of the outlet b of the condenser evaporator (13), flows through the inlet c of the high-temperature regenerator (8), the outlet d of the high-temperature regenerator (8), and the high-temperature secondary flow meter (12) and flows into the inlet d of the high-temperature compressor (1); the low-temperature compressor (18) is adjusted according to the ambient temperature and the refrigeration temperature. The corresponding working condition is adjusted to the corresponding volume ratio gear by calculation and the low-temperature refrigerant (30) flows from the outlet a of the low-temperature compressor (18) into the inlet c of the condenser evaporator (13) to exchange heat with the high-temperature refrigerant, then flows out from the outlet d of the condenser evaporator (13), flows through the low-temperature refrigerant storage tank (14), the inlet a of the low-temperature subcooler (16), the outlet c of the low-temperature subcooler (16), the inlet a of the low-temperature regenerator (20), the outlet b of the low-temperature regenerator (20), and flows into the low-temperature secondary throttling element The low-temperature secondary throttling element (22) is used to adjust the opening degree to control the temperature of the low-temperature refrigerant flowing out of the evaporator (23) outlet, and flows out of the evaporator (23) outlet, flows through the low-temperature regenerator (20) inlet c, the low-temperature regenerator (20) outlet d, and the low-temperature secondary flow meter (25) to flow into the low-temperature compressor (18) inlet d; at the same time, the high and low temperature refrigeration main circuit can adjust the refrigeration capacity by adjusting the motor speed of the high-temperature compressor (1) and the motor speed of the low-temperature compressor (18).

[0009] The high-temperature stage primary throttling branch is divided into another branch after the outlet of the high-temperature stage refrigerant storage tank (3) and connected to the inlet of the high-temperature stage primary throttling element (4). The outlet of the high-temperature stage primary throttling element (4) is connected to the inlet b of the high-temperature stage subcooler (5). After flowing out of the outlet d of the high-temperature stage subcooler (5), the high-temperature stage primary flow meter (6) flows into the inlet b of the high-temperature stage compressor (1).

[0010] Furthermore, the operation logic of the high-temperature stage primary throttling branch is as follows: when the temperature at the outlet a of the high-temperature stage compressor (1) is relatively high, the high-temperature stage primary throttling element (4) adjusts its opening degree so that a portion of the high-temperature stage refrigerant at the outlet of the high-temperature stage refrigerant storage tank (3) flows through the high-temperature stage primary throttling element (4) and then flows into the inlet b of the high-temperature stage subcooler (5), exchanges heat with the high-temperature stage refrigerant in the high- and low-temperature stage refrigeration main circuit in the high-temperature stage subcooler (5), flows out from the outlet d of the high-temperature stage subcooler (5), flows through the high-temperature stage primary flowmeter (6) and flows into the inlet b of the high-temperature stage compressor (1).

[0011] High-temperature regenerator branch: The two ends of the high-temperature regenerator liquid bypass element (7) are respectively connected to the inlet a of the high-temperature regenerator (8) and the outlet b of the high-temperature regenerator (8), so that the high-temperature regenerator liquid bypass element (7) is connected in parallel with the inlet a of the high-temperature regenerator (8) and the outlet b of the high-temperature regenerator (8); The two ends of the high-temperature regenerator gas bypass element (11) are respectively connected to the inlet c of the high-temperature regenerator (8) and the outlet d of the high-temperature regenerator (8), so that the high-temperature regenerator gas bypass element (11) is connected in parallel with the inlet c of the high-temperature regenerator (8) and the outlet d of the high-temperature regenerator (8).

[0012] Furthermore, the high-temperature regenerator branch operation logic is as follows: when the high-temperature regenerator subcooling temperature is not satisfied, the opening of the high-temperature regenerator liquid bypass element (7) is adjusted so that a portion of the high-temperature refrigerant at the high-temperature subcooler (5) outlet c flows through the high-temperature regenerator liquid bypass element (7), and then mixes with the high-temperature refrigerant flowing through the high-temperature regenerator (8) inlet a and the high-temperature regenerator (8) outlet b, and then flows into the high-temperature secondary throttling element (10), thereby adjusting the high-temperature regenerator subcooling temperature. degree; when the superheat temperature of the high-temperature stage regenerator is not satisfied, the opening degree of the high-temperature stage regenerator gas bypass element (11) is adjusted so that a portion of the high-temperature stage refrigerant at the outlet b of the condenser evaporator (13) flows through the high-temperature stage regenerator gas bypass element (11), and then mixes with the high-temperature stage refrigerant flowing through the inlet c of the high-temperature stage regenerator (8) and the outlet d of the high-temperature stage regenerator (8), and then flows through the high-temperature secondary flowmeter (12) and flows into the inlet d of the high-temperature stage compressor (1), thereby adjusting the superheat temperature of the high-temperature stage regenerator.

[0013] High temperature liquid injection branch: a branch is separated from the inlet of the high temperature secondary throttling element (10) and connected to the inlet of the high temperature liquid injection control element (9); the outlet of the high temperature liquid injection control element (9) is connected to the inlet c of the high temperature compressor (1).

[0014] Furthermore, the operation logic of the high-temperature stage liquid injection branch is as follows: when the temperature at the outlet a of the high-temperature stage compressor (1) is relatively high, the high-temperature stage liquid injection control element (9) adjusts its opening degree so that a portion of the high-temperature stage refrigerant before the high-temperature stage secondary throttling element (10) flows through the high-temperature stage liquid injection control element (9) and then flows into the inlet c of the high-temperature stage compressor (1).

[0015] Low-temperature stage primary throttling branch: after the outlet of the low-temperature stage refrigerant storage tank (14), another branch is separated and connected to the inlet of the low-temperature stage primary throttling element (15). The outlet of the low-temperature stage primary throttling element (15) is connected to the inlet b of the low-temperature stage subcooler (16). After flowing out of the outlet d of the low-temperature stage subcooler (16), the liquid flows into the inlet b of the low-temperature stage compressor (18) through the low-temperature stage primary flowmeter (17).

[0016] Furthermore, the operation logic of the low-temperature primary throttling branch is as follows: when the temperature at the outlet a of the low-temperature compressor (18) is relatively high, the low-temperature primary throttling element (15) adjusts its opening so that a portion of the low-temperature refrigerant at the outlet of the low-temperature refrigerant storage tank (14) flows through the low-temperature primary throttling element (15) and then flows into the inlet b of the low-temperature subcooler (16), exchanges heat with the low-temperature refrigerant in the high- and low-temperature refrigeration main circuit in the low-temperature subcooler (16), flows out from the outlet d of the low-temperature subcooler (16), flows through the low-temperature primary flowmeter (17) and flows into the inlet b of the low-temperature compressor (18).

[0017] Low-temperature regenerator branch: The two ends of the low-temperature regenerator liquid bypass element (19) are respectively connected to the inlet a of the low-temperature regenerator (20) and the outlet b of the low-temperature regenerator (20), so that the low-temperature regenerator liquid bypass element (19) and the inlet a of the low-temperature regenerator (20) and the outlet b of the low-temperature regenerator (20) are connected in parallel; the two ends of the low-temperature regenerator gas bypass element (24) are respectively connected to the inlet c of the low-temperature regenerator (20) and the outlet d of the low-temperature regenerator (20), so that the low-temperature regenerator gas bypass element (24) and the inlet c of the low-temperature regenerator (20) and the outlet d of the low-temperature regenerator (20) are connected in parallel.

[0018] Furthermore, the low-temperature regenerator branch operation logic is as follows: when the low-temperature regenerator subcooling temperature is not satisfied, the opening of the low-temperature regenerator liquid bypass element (19) is adjusted so that a portion of the low-temperature refrigerant at the outlet c of the low-temperature subcooler (16) flows through the low-temperature regenerator liquid bypass element (19), and then mixes with the low-temperature refrigerant flowing through the inlet a of the low-temperature regenerator (20) and the outlet b of the low-temperature regenerator (20), and then flows into the low-temperature secondary throttling element (22), thereby adjusting the low-temperature regenerator overcooling temperature. Cold temperature; when the superheat temperature of the low-temperature regenerator is not met, the opening of the low-temperature regenerator gas bypass element (24) is adjusted so that a portion of the low-temperature refrigerant at the outlet of the evaporator (23) flows through the low-temperature refrigerant gas bypass element (24), and then mixes with the low-temperature refrigerant flowing through the inlet c of the low-temperature regenerator (20) and the outlet d of the low-temperature regenerator (20), and then flows through the low-temperature secondary flow meter (25) and flows into the inlet d of the low-temperature compressor (18), thereby adjusting the superheat temperature of the low-temperature regenerator.

[0019] A low-temperature liquid injection branch is branched off from the inlet of the low-temperature secondary throttling element (22) to be connected to the inlet of the low-temperature liquid injection control element (21), and the outlet of the low-temperature liquid injection control element (21) is connected to the inlet c of the low-temperature compressor (18).

[0020] Furthermore, the operation logic of the low-temperature stage liquid injection branch is as follows: when the temperature at the outlet a of the low-temperature stage compressor (18) is relatively high, the low-temperature stage liquid injection control element (21) adjusts its opening degree so that a portion of the low-temperature stage refrigerant before the low-temperature stage secondary throttling element (22) flows through the low-temperature stage liquid injection control element (21) and then flows into the inlet c of the low-temperature stage compressor (18).

[0021] The monitoring-control circuit is composed of a controller (26) connected to an inlet e of a high-temperature compressor (1) and an inlet e of a low-temperature compressor (18) in the system, and is used to control the gear adjustment of the internal volume ratio of the high-temperature compressor (1) and the low-temperature compressor (18). The controller (26) is connected to an inlet f of the high-temperature compressor (1) and an inlet f of the low-temperature compressor (18) in the system, and is used to control the speed adjustment of the motor of the high-temperature compressor (1) and the low-temperature compressor (18); the controller (26) is connected to a high-temperature primary throttling element (4), a high-temperature secondary throttling element (10), a high-temperature regenerator liquid bypass element (7), a high-temperature regenerator gas bypass element (11), and a high-temperature liquid injection control element in the system. (9), a low-temperature primary throttling element (15), a low-temperature secondary throttling element (22), a low-temperature regenerator liquid bypass element (19), a low-temperature regenerator gas bypass element (24), and a low-temperature liquid injection control element (21) are connected to control the opening of each element; a controller (26) is connected to a high-temperature primary flow meter (6), a high-temperature secondary flow meter (12), a low-temperature primary flow meter (17), and a low-temperature secondary flow meter (25) in the system to monitor the flow of the high-temperature primary throttling branch, the high and low temperature refrigerant circuit, and the low-temperature primary flow branch; the controller (26) is connected to each pressure sensor and each temperature sensor in the system to monitor the system.

[0022] Furthermore, the controller (26) has a built-in monitoring module, a calculation module and a control module to implement the monitoring and control method; the monitoring module monitors the pressure, temperature, ambient temperature, refrigeration temperature and refrigerant flow before and after the main components in the system by connecting with various pressure sensors, various temperature sensors, primary flow meters at various levels and secondary flow meters at various levels; the calculation module processes the data by setting specific temperature difference, protection pressure, protection temperature value, refrigerant saturation temperature-pressure database, calculation formula, empirical formula, characteristic curve and other calculation tools, and guides the control module to adjust; the control module realizes the control function of the system by connecting various compressor slide valve devices, various compressor motors, various primary throttling elements, various secondary throttling elements, various regenerator liquid bypass elements, various regenerator gas bypass elements and the like.

[0023] Furthermore, the controller (26) sets the temperature difference in the calculation module to ΔT1, which is used to calculate the target condensing temperature according to the measured ambient temperature, and sets the temperature difference to ΔT2, which is used to calculate the target evaporating temperature according to the target refrigeration temperature; sets the protection condensing pressure P con,b , protect the condensation and evaporation high temperature side pressure P c-e,l,b , protect the condensation and evaporation low temperature side pressure P c-e,h,b , Protect evaporation pressure P eva,b ; Set the target compressor outlet temperature T pq,m, protect the compressor outlet temperature T pq,b .

[0024] Adjustable single screw compressor regenerative cascade low temperature refrigeration system sets the target refrigeration temperature T before starting c,m , Target cooling capacity W c,m .

[0025] Further, according to the target cooling temperature T c,m , Target cooling capacity W c,m , the measured ambient temperature T1, the built-in calculation module of the controller (26) calls the calculation formula to obtain the target condensation temperature T con,m (T con,m =T1-ΔT1), target evaporation temperature T eva,m (T eva,m =T c,m -ΔT2), the calculation module calls the refrigerant saturation temperature-pressure database to obtain T con,m Corresponding target condensing pressure P con,m , get T eva,m Corresponding target evaporation pressure P eva,m ; The calculation module uses the empirical formula to obtain the target condensation and evaporation temperature T c-e,m The calculation module calls the refrigerant saturation temperature-pressure database to obtain T c-e,m The corresponding target condensation and evaporation high temperature side pressure P c-e,h,m , get T c-e,m The corresponding target condensation and evaporation low temperature side pressure P c-e,l,m ; The calculation module calls the calculation formula according to P con,m / P c-e,h,m Get the target high temperature compressor volume ratio V h,m According to P c-e,l,m / P eva,m Get the target low temperature compressor volume ratio V l,m ; The calculation module uses the empirical formula to obtain the target high temperature stage superheat temperature T h,gr,m 、Target high temperature level subcooling temperature T h,gl,m , target low temperature stage superheat temperature T l,gr,m 、Target high and low temperature level subcooling temperature T l,gl,m ; Target high temperature stage primary throttling opening temperature T bq,h,m , Target high temperature stage primary throttling pressure P bq,h,m , Target low temperature stage primary throttling opening temperature T bq,l,m , Target low temperature stage primary throttling pressure P bq,l,m .

[0026] Furthermore, the above target values ​​are used as the basis for the adjustment of the control module of the controller (26); the monitoring module of the controller (26) monitors the temperature and pressure sensors in the system, and the monitoring values ​​are used as the measured values; when the error between the target value and the measured value of the corresponding measuring point is within a certain range, it is considered that the system is running stably, and the control module of the controller (26) suspends the adjustment of the system; when the measured value of the corresponding measuring point exceeds the protection value, the control module of the controller (26) immediately shuts down the system and cuts off the power of the control system.

[0027] The monitoring module monitoring data includes:

[0028] Real-time pressure value P of the high-temperature compressor (1) inlet pressure sensor (101) 101 , the real-time temperature value T of the temperature sensor (102) at the inlet of the high-temperature compressor (1) 102 , the real-time temperature value T of the temperature sensor (103) at the outlet of the high-temperature compressor (1) 103 , the real-time pressure value P of the high-temperature compressor (1) outlet pressure sensor (104) 104 , the real-time temperature value T of the temperature sensor (107) at the inlet of the high-temperature compressor (1) 107 , the real-time pressure value P of the pressure sensor (108) at the inlet b of the high-temperature compressor (1) 108 ; Real-time pressure value P of the pressure sensor (1801) at the inlet of the low-temperature compressor (18) 1801 , the real-time temperature value T of the temperature sensor (1802) at the inlet of the low-temperature compressor (18) 1802 , the real-time temperature value T of the temperature sensor (1803) at the outlet of the low-temperature compressor (18) 1803 , the real-time pressure value P of the outlet a pressure sensor (1804) of the low-temperature compressor (18) 1804 , the real-time temperature value T of the temperature sensor (1807) at the inlet of the low-temperature compressor (18) 1807 , the real-time pressure value P of the pressure sensor (1808) at the inlet b of the low-temperature compressor (18) 1808 ;

[0029] Real-time pressure value P of the inlet pressure sensor (401) of the high-temperature stage primary throttling element (4) 401 , the real-time temperature value T of the inlet temperature sensor (402) of the high-temperature stage primary throttling element (4) 402 , the real-time temperature value T of the outlet temperature sensor (403) of the high-temperature stage primary throttling element (4) 403 , the real-time pressure value P of the outlet pressure sensor (404) of the high-temperature stage primary throttling element (4) 404 ; Real-time temperature value T of high temperature stage subcooler (5) outlet temperature sensor (501) 501, the real-time pressure value P of the high-temperature subcooler (5) outlet pressure sensor (502) 502 ; Real-time pressure value P of the inlet pressure sensor (1501) of the low-temperature primary throttling element (15) 1501 , the real-time temperature value T of the inlet temperature sensor (1502) of the low-temperature stage primary throttling element (15) 1502 , the real-time temperature value T of the outlet temperature sensor (1503) of the low-temperature stage primary throttling element (15) 1503 , the real-time pressure value P of the outlet pressure sensor (1504) of the low-temperature stage primary throttling element (15) 1504 ; Real-time temperature value T of the temperature sensor (1601) at the outlet of the low-temperature subcooler (16) 1601 , the real-time pressure value P of the pressure sensor (1602) at the outlet of the low-temperature subcooler (16) 1602 ;

[0030] Real-time pressure value P of the inlet pressure sensor (701) of the high-temperature stage regenerator liquid bypass element (7) 701 , the real-time temperature value T of the inlet temperature sensor (702) of the high-temperature stage regenerator liquid bypass element (7) 702 , the real-time temperature value T of the outlet temperature sensor (703) of the high-temperature stage regenerator liquid bypass element (7) 703 , the real-time pressure value P of the outlet pressure sensor (704) of the high-temperature stage regenerator liquid bypass element (7) 704 ; Real-time pressure value P of the pressure sensor (801) at the inlet of the high-temperature regenerator (8) 801 , the real-time temperature value T of the temperature sensor (802) at the inlet of the high-temperature regenerator (8) 802 , the real-time temperature value T of the temperature sensor (803) at the outlet b of the high-temperature regenerator (8) 803 , the real-time pressure value P of the outlet pressure sensor (804) of the high-temperature regenerator (8) 804 , the real-time pressure value P of the high-temperature regenerator (8) inlet c pressure sensor (805) 805 , the real-time temperature value T of the temperature sensor (806) at the inlet of the high-temperature regenerator (8) 806 , the real-time temperature value T of the temperature sensor (807) at the outlet of the high-temperature regenerator (8) 807 , the real-time pressure value P of the outlet pressure sensor (808) of the high-temperature regenerator (8) 808 ; Real-time pressure value P of the inlet pressure sensor (1101) of the high-temperature regenerator gas bypass element (11) 1101 , the real-time temperature value T of the inlet temperature sensor (1102) of the high-temperature stage regenerator gas bypass element (11) 1102 , the real-time temperature value T of the outlet temperature sensor (1103) of the high-temperature stage regenerator gas bypass element (11)1103 , the real-time pressure value P of the outlet pressure sensor (1104) of the high-temperature stage regenerator gas bypass element (11) 1104 ; Real-time pressure value P of the inlet pressure sensor (1901) of the low-temperature stage regenerator liquid bypass element (19) 1901 , the real-time temperature value T of the inlet temperature sensor (1902) of the low temperature stage regenerator liquid bypass element (19) 1902 , the real-time temperature value T of the outlet temperature sensor (1903) of the liquid bypass element (19) of the low-temperature stage regenerator 1903 , the real-time pressure value P of the outlet pressure sensor (1904) of the low-temperature stage regenerator liquid bypass element (19) 1904 ; Low temperature stage regenerator (20) inlet a pressure sensor (2001) real-time pressure value P 2001 , the real-time temperature value T of the temperature sensor (2002) at the inlet of the low-temperature stage regenerator (20) 2002 , the real-time temperature value T of the temperature sensor (2003) at the outlet b of the low-temperature stage regenerator (20) 2003 , the real-time pressure value P of the outlet pressure sensor (2004) of the low-temperature stage regenerator (20) 2004 , the real-time pressure value P of the pressure sensor (2005) at the inlet of the low-temperature stage regenerator (20) 2005 , the real-time temperature value T of the temperature sensor (2006) at the inlet of the low-temperature stage regenerator (20) 2006 , the real-time temperature value T of the outlet temperature sensor (2007) of the low-temperature stage regenerator (20) 2007 , the real-time pressure value P of the outlet pressure sensor (2008) of the low-temperature stage regenerator (20) 2008 ;

[0031] Condenser (2) inlet pressure sensor (201) real-time pressure value P 201 , the real-time temperature value T of the condenser (2) inlet temperature sensor (202) 202 , the real-time temperature value T of the condenser (2) outlet temperature sensor (203) 203 , the real-time pressure value P of the condenser (2) outlet pressure sensor (204) 204 ; Real-time pressure value P of the pressure sensor (1301) at the inlet of the condenser evaporator (13) 1301 , the real-time temperature value T of the temperature sensor (1302) at the inlet of the condenser evaporator (13) 1302 , the real-time temperature value T of the temperature sensor (1303) at the outlet b of the condenser evaporator (13) 1303 , the real-time pressure value P of the pressure sensor (1304) at the outlet b of the condenser evaporator (13) 1304 , the real-time pressure value P of the pressure sensor (1305) at the inlet c of the condenser evaporator (13) 1305, the real-time temperature value T of the temperature sensor (1306) at the inlet of the condenser evaporator (13) 1306 , the real-time temperature value T of the condenser evaporator (13) outlet temperature sensor (1307) 1307 , the real-time pressure value P of the pressure sensor (1308) at the outlet of the condenser evaporator (13) 1308 ; Real-time pressure value P of the evaporator (23) inlet pressure sensor (2301) 2301 , the real-time temperature value T of the evaporator (23) inlet temperature sensor (2302) 2302 , the real-time temperature value T of the evaporator (23) outlet temperature sensor (2303) 2303 , the real-time pressure value P of the evaporator (23) outlet pressure sensor (2304) 2304 ;

[0032] High temperature grade primary flow meter real-time flow value V6, high temperature grade secondary flow meter real-time flow value V 12 , low temperature level primary flow meter real-time flow value V 17 , low temperature secondary flow meter real-time flow value V 25 ;

[0033] The ambient temperature sensor (27) has a real-time temperature value T1, and the refrigeration temperature sensor (28) has a real-time temperature value T2.

[0034] When the adjustable single screw compressor regenerative cascade low temperature refrigeration system is started, the high and low temperature stage refrigeration main circuits are operated first, and the controller (26) control module controls the rotation of the motor (106) of the high temperature stage compressor (1), and the controller (26) control module adjusts the slide valve power device (105) of the high temperature stage compressor (1) to move to the position closest to V h,m The compressor internal volume ratio gear is set, and at the same time, the controller (26) control module controls the opening of the high-temperature stage secondary throttling element (10).

[0035] Furthermore, the high temperature stage secondary throttling element (10) opening control logic: the monitoring module monitors P 204 Value, in P con,m As a target, at the same time, the monitoring module monitors P 1304 Value, in P c-e,h,m As a target, the opening degree of the high temperature stage secondary throttling element (10) is adjusted.

[0036] After the high temperature compressor has been running for a period of time, the controller (26) control module controls the low temperature compressor (18) motor (1806) to rotate, and the controller (26) control module adjusts the low temperature compressor (18) slide valve power device (1805) to move to the position closest to V l,mThe compressor internal volume ratio gear is set, and at the same time, the controller (26) control module controls the opening of the low-temperature stage secondary throttling element (22).

[0037] Further, the low temperature stage secondary throttling element (22) opening control logic: the monitoring module monitors P 2304 Value, in P eva,m As a target, at the same time, the monitoring module monitors P 1308 Value, in P c-e,l,m As a target, the opening degree of the low temperature stage secondary throttling element (21) is adjusted.

[0038] After the adjustable single screw compressor regenerative cascade low temperature refrigeration system is started, the monitoring system monitors T2 and T c,m As a goal, it runs continuously; when the monitoring module detects that T2 = T c,m Calculate the real-time cooling capacity W L , with W c,m To achieve this goal, the controller adjusts the motor speeds of the high-temperature compressor (1) and the low-temperature compressor (18).

[0039] Furthermore, the controller adjusts the control logic of the motor speed of the high-temperature compressor (1) and the low-temperature compressor (18): the monitoring module monitors P 101 , T 102 The calculation module calls the refrigerant saturation temperature-pressure database to obtain P 101 , T 102 The corresponding density ρ 1,d ; Monitoring module monitors P 1301 , T 1302 The calculation module calls the refrigerant saturation temperature-pressure database to obtain P 1301 , T 1302 The corresponding enthalpy value h 13,b ; Monitoring module monitors P 1304 , T 1303 The calculation module calls the refrigerant saturation temperature-pressure database to obtain P 1304 , T 1303 The corresponding enthalpy value h 13,a The calculation module uses the calculation formula to calculate the real-time high temperature cooling capacity W H ; Monitoring module monitors P 1801 , T 1802 The calculation module calls the refrigerant saturation temperature-pressure database to obtain P 1801 , T 1802 The corresponding density ρ 18,d ; Monitoring module monitors P 2301 , T 2302 The calculation module calls the refrigerant saturation temperature-pressure database to obtain P 2301 , T 2302The corresponding enthalpy value h 23,in ; Monitoring module monitors P 2304 , T 2303 The calculation module calls the refrigerant saturation temperature-pressure database to obtain P 2304 , T 2303 The corresponding enthalpy value h 23,out , the calculation module calls the calculation formula to calculate the real-time cooling capacity W L When W L Less than W c,m When W L Greater than W c,m When the control module controls the motor speed of the high temperature compressor (1) and the low temperature compressor (18) to decrease appropriately; during the adjustment process, W is always maintained. L Less than W H .

[0040] After the adjustable single-screw compressor heat recovery cascade low-temperature refrigeration system is started up and operated, the high-temperature stage primary throttling branch, the high-temperature stage heat regenerator branch, the high-temperature stage liquid injection branch, the low-temperature stage primary throttling branch, the low-temperature stage heat recovery branch, and the low-temperature stage liquid injection branch can be operated as needed.

[0041] Furthermore, the high-temperature stage primary throttling branch is used to reduce the outlet temperature a of the high-temperature stage compressor (1), and the monitoring system monitors T 103 , with T bq,h,m As the goal, when T 103 Greater than or equal to T bq,h,m When the control module controls the high temperature stage primary throttling element (4) to open, the monitoring module monitors P 404 , with P bq,h,m As the target, the opening of the high-temperature stage primary throttling element (4) is adjusted; the monitoring system monitors P 101 , T 102 , T 203 , P 204 , T 107 , P 108 , P 801 , T 802 , V6, V 12 , the opening of the high temperature stage primary throttling element (4) is checked by calculation.

[0042] Furthermore, the high temperature regenerator branch is used to adjust the high temperature cycle superheat temperature and high temperature cycle subcooling temperature. The monitoring system monitors T 702 , T 703 , T 802 , T 803 , T 806 , T 807 , T 1102 , T1103 , with T h,gl,m As the target, the opening of the high temperature stage regenerator liquid bypass element (7) and the high temperature stage regenerator gas bypass element (11) is adjusted; when (T 802 -T 803 ) is greater than T h,gl,m When (T 802 -T 803 ) is less than T h,gl,m When (T 702 -T 703 ) is equal to T h,gl,m When T h,gr,m As the target, when (T 807 -T 806 ) is greater than T h,gr,m When (T 807 -T 806 ) is less than T h,gr,m When (T 1103 -T 1102 ) is equal to T h,gr,m When the temperature is high, the opening of the high temperature stage regenerator gas bypass element (11) is maintained.

[0043] Furthermore, the high temperature stage liquid injection branch is used to reduce the outlet temperature of the high temperature stage compressor. The monitoring system monitors T 103 , with T pq,m As the goal, when T 103 Greater than or equal to T pq,m When the high temperature stage liquid injection control element (9) is turned on, the control module controls the high temperature stage liquid injection control element (9) to be turned on.

[0044] Furthermore, the low-temperature stage primary throttling branch is used to reduce the outlet temperature of the low-temperature stage compressor. The monitoring system monitors T 1803 , with T bq,l,m As the goal, when T 1803 Greater than or equal to T bq,l,m When the control module controls the low temperature stage primary throttling element (15) to open, the monitoring module monitors P 1504 , with P bq,l,m As the target, the opening of the low temperature stage primary throttling element (15) is adjusted; the monitoring system monitors P 1801 , T 1802 , T 1307 , P 1308 , T 1807 , P 1808 , P 2001 , T2002 、V 17 、V 25 , the opening of the low temperature stage primary throttling element (15) is checked by calculation.

[0045] Furthermore, the low temperature regenerator branch is used to adjust the low temperature cycle superheat temperature and low temperature cycle subcooling temperature. The monitoring system monitors T 1902 , T 1903 , T 2002 , T 2003 , T 2006 , T 2007 , T 2402 , T 2403 , with T l,gl,m As the target, the opening of the low temperature stage regenerator liquid bypass element (19) and the low temperature stage regenerator gas bypass element (24) is adjusted; when (T 2002 -T 2003 ) is greater than T l,gl,m When (T 2002 -T 2003 ) is less than T l,gl,m When (T 1902 -T 1903 ) is equal to T l,gl,m When T l,gr,m As the target, when (T 2007 -T 2006 ) is greater than T l,gr,m When (T 2007 -T 2006 ) is less than T l,gr,m When (T 2403 -T 2402 ) is equal to T l,gl,m When the temperature is low, the opening of the low temperature stage regenerator gas bypass element (24) is maintained.

[0046] Furthermore, the low temperature stage liquid injection branch is used to reduce the outlet temperature of the low temperature stage compressor. The monitoring system monitors T 1803 , with T pq,m As the goal, when T 1803 Greater than T pq,m When the low temperature stage liquid injection control element (21) is turned on, the control module controls the low temperature stage liquid injection control element (21) to be turned on.

[0047] Furthermore, during the operation of the system, the monitoring system monitors T 103 , T 1803 , when T 103Greater than or equal to T pq,b or T 1803 Greater than or equal to T pq,b Or both, the control module immediately controls the system to shut down and cut off power; the monitoring system monitors P 204 , when P 204 Greater than or equal to P con,b When the control module immediately controls the system to shut down and cut off power; the monitoring system monitors P 1304 , when P 1304 Greater than or equal to P c-e,b When the control module immediately controls the system to shut down and cut off the power; the monitoring system monitors P 2304 , when P 2304 Greater than or equal to P eva,b When the control module immediately shuts down the system and cuts off the power to ensure safety.

[0048] The system of the present invention comprises a refrigerant circuit and a monitoring-control circuit. The refrigerant circuit connects the high-temperature and low-temperature circuits by a condenser evaporator, and the controller is simultaneously connected to a compressor motor, a compressor slide valve power device, a throttling element, a bypass element, a liquid injection control element, a pressure sensor and a temperature sensor. After setting the target refrigeration temperature and refrigeration capacity, the controller is guided to adjust the compressor motor, the compressor slide valve power device, the throttling element, the bypass element and the liquid injection control element of each level of the system through the monitoring data of each sensor, so as to realize the functions of variable refrigeration temperature, variable refrigeration capacity, variable motor frequency, variable compressor content ratio, variable overheating / undercooling temperature, liquid injection, air replenishment, etc., to make accurate judgment and adjustment, improve the matching degree of the high and low temperature two-level system circuits, more efficiently adapt to a variety of ambient temperatures and refrigeration temperature and refrigeration capacity requirements; make the system run more stably and improve the performance; this method solves the problem that the system cannot run more stably and efficiently under the conditions of variable ambient temperature operation and variable refrigeration temperature and refrigeration capacity, and is of great help to improve the system operation life and performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 , flow chart of control method of adjustable single screw compressor regenerative cascade low temperature refrigeration system;

[0050] Figure 2 , schematic diagram of an adjustable single screw compressor regenerative cascade low temperature refrigeration system;

[0051] Figure 3 , Schematic diagram of the measuring points of the inlet and outlet temperature and pressure sensors of the high-temperature compressor;

[0052] Figure 4 , Schematic diagram of the measuring points of the inlet and outlet temperature and pressure sensors of the low-temperature compressor;

[0053] Figure 5, Schematic diagram of the temperature and pressure sensor measuring points of the high-temperature stage primary throttling inlet and outlet;

[0054] Figure 6 , schematic diagram of the temperature and pressure sensor measuring points of the low-temperature stage primary throttling inlet and outlet;

[0055] Figure 7 , Schematic diagram of the temperature and pressure sensor measuring points of the high temperature stage heat recovery and bypass inlet and outlet;

[0056] Figure 8 , schematic diagram of the control of low temperature stage heat recovery and bypass inlet and outlet temperature and pressure sensor measurement points;

[0057] Fig. 9 , schematic diagram of the measuring points of the condenser, condenser evaporator, and evaporator inlet and outlet temperatures and pressure sensors;

[0058] Description of reference numerals:

[0059] A high temperature compressor (1), a high temperature compressor inlet d pressure sensor (101), a high temperature compressor inlet d temperature sensor (102), a high temperature compressor outlet a temperature sensor (103), a high temperature compressor outlet a pressure sensor (104), a high temperature compressor slide valve power device (105), a high temperature compressor motor (106), a high temperature compressor inlet b temperature sensor (107), a high temperature compressor inlet b pressure sensor (108), a condenser (2), a condenser inlet pressure sensor (201), a condenser inlet temperature sensor (202), a condenser outlet temperature sensor (203), a high temperature compressor outlet pressure sensor (104), a high temperature compressor slide valve power device (105), a high temperature compressor motor (106), a high temperature compressor inlet b temperature sensor (107), a high temperature compressor inlet b pressure sensor (108), a condenser (2), a condenser inlet pressure sensor (201), a condenser inlet temperature sensor (202), a condenser outlet temperature sensor (204), a high temperature compressor outlet pressure sensor (105), a high temperature compressor outlet pressure sensor (106), a high temperature compressor outlet pressure sensor (108), a condenser (2), a condenser inlet pressure sensor (201), a condenser inlet temperature sensor (202), a condenser outlet temperature sensor (204), a high temperature compressor outlet pressure sensor (104), a high temperature compressor outlet pressure sensor (105), a high temperature compressor outlet pressure sensor (105), a high temperature compressor motor (106), a high temperature compressor inlet b temperature sensor (107), a high temperature compressor outlet pressure sensor (108), a condenser 3), condenser outlet pressure sensor (204), high temperature refrigerant storage tank (3), high temperature primary throttling element (4), high temperature primary throttling element inlet pressure sensor (401), high temperature primary throttling element inlet temperature sensor (402), high temperature primary throttling element outlet temperature sensor (403), high temperature primary throttling element outlet pressure sensor (404), high temperature subcooler (5), high temperature subcooler outlet d temperature sensor (501), high temperature subcooler outlet d pressure sensor (502), high temperature primary flowmeter (6), high temperature regenerator liquid bypass element (7), high temperature a regenerator liquid bypass element inlet pressure sensor (701), a high temperature stage regenerator liquid bypass element inlet temperature sensor (702), a high temperature stage regenerator liquid bypass element outlet temperature sensor (703), a high temperature stage regenerator liquid bypass element outlet pressure sensor (704), a high temperature stage regenerator (8), a high temperature stage regenerator inlet a pressure sensor (801), a high temperature stage regenerator inlet a temperature sensor (802), a high temperature stage regenerator outlet b temperature sensor (803), a high temperature stage regenerator outlet b pressure sensor (804), a high temperature stage regenerator inlet c pressure sensor (805), a high temperature stage regenerator inlet c temperature sensor (806), high temperature regenerator outlet d temperature sensor (807), high temperature regenerator outlet d pressure sensor (808), high temperature liquid injection control element (9), high temperature secondary throttling element (10), high temperature regenerator gas bypass element (11), high temperature regenerator gas bypass element inlet pressure sensor (1101), high temperature regenerator gas bypass element inlet temperature sensor (1102), high temperature regenerator gas bypass element outlet temperature sensor (1103), high temperature regenerator gas bypass element outlet pressure sensor (1104), high temperature secondary flow meter (12),Condenser evaporator (13), condenser evaporator inlet a pressure sensor (1301), condenser evaporator inlet a temperature sensor (1302), condenser evaporator outlet b temperature sensor (1303), condenser evaporator outlet b pressure sensor (1304), condenser evaporator inlet c pressure sensor (1305), condenser evaporator inlet c temperature sensor (1306), condenser evaporator outlet d temperature sensor (1307), condenser evaporator outlet d pressure sensor (1308).

[0060] A cryogenic refrigerant storage tank (14), a cryogenic primary throttling element (15), a cryogenic primary throttling element inlet pressure sensor (1501), a cryogenic primary throttling element inlet temperature sensor (1502), a cryogenic primary throttling element outlet temperature sensor (1503), a cryogenic primary throttling element outlet pressure sensor (1504), a cryogenic subcooler (16), a cryogenic subcooler outlet d temperature sensor (1601), a cryogenic subcooler outlet d pressure sensor (1602), a cryogenic primary flow meter (17), a cryogenic compressor (18), a cryogenic compressor inlet d pressure sensor (1801), a cryogenic compressor inlet d temperature sensor (1802) )、low temperature compressor outlet a temperature sensor (1803), low temperature compressor outlet a pressure sensor (1804), low temperature compressor slide valve power device (1805), low temperature compressor motor (1806), low temperature compressor inlet b temperature sensor (1807), low temperature compressor inlet d pressure sensor (1808), low temperature regenerator liquid bypass element (19), low temperature regenerator liquid bypass element inlet pressure sensor (1901), low temperature regenerator liquid bypass element inlet temperature sensor (1902), low temperature regenerator liquid bypass element outlet temperature sensor (1903), low temperature regenerator liquid bypass element outlet pressure sensor (19 04), low temperature stage regenerator (20), low temperature stage regenerator inlet a pressure sensor (2001), low temperature stage regenerator inlet a temperature sensor (2002), low temperature stage regenerator outlet b temperature sensor (2003), low temperature stage regenerator outlet b pressure sensor (2004), low temperature stage regenerator inlet c pressure sensor (2005), low temperature stage regenerator inlet c temperature sensor (2006), low temperature stage regenerator outlet d temperature sensor (2007), low temperature stage regenerator outlet d pressure sensor (2008), low temperature stage liquid injection control element (21), low temperature stage secondary throttling element (22), evaporator (23), evaporator inlet pressure sensor (2301), evaporator an evaporator inlet temperature sensor (2302), an evaporator outlet temperature sensor (2303), an evaporator outlet pressure sensor (2304), a low-temperature regenerator gas bypass element (24), a low-temperature regenerator gas bypass element inlet pressure sensor (2401), a low-temperature regenerator gas bypass element inlet temperature sensor (2402), a low-temperature regenerator gas bypass element outlet temperature sensor (2403), a low-temperature regenerator gas bypass element outlet pressure sensor (2404), a low-temperature secondary flow meter (25), a controller (26), an ambient temperature sensor (27), a refrigeration temperature sensor (28), a high-temperature refrigerant (29), and a low-temperature refrigerant (30). DETAILED DESCRIPTION

[0061] The present invention is further described below in conjunction with the embodiments, but the present invention is not limited to the following embodiments; the structures of the high temperature compressor (1) and the low temperature compressor (18) can be found in the relevant patent number: ZL 2016 10729709.4

[0062] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, a detailed description is given below; it is obvious that the described embodiments are part of the embodiments of the present invention, rather than all the embodiments; based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without making any creative work all fall within the scope of protection of the present invention.

[0063] In the description of the present invention, it is to be understood that when a component is considered to be "connected" to another component, it may be directly connected to the other component or there may be a centrally disposed component at the same time, and when a component is considered to be "set on" another component, it may be directly set on the other component or there may be a centrally disposed component at the same time.

[0064] In addition, terms such as "long", "short", "inside" and "outside" indicating directions or positional relationships are based on the directions or positional relationships shown in the accompanying drawings and are only used to facilitate the description of the present invention. They do not indicate or imply that the device or component referred to must have this specific direction or operate with a specific direction structure, and should not be understood as a limitation of the present invention.

[0065] The pressure sensors and temperature sensor monitoring points not mentioned in the following embodiments also play an important role in the system, providing measurement support for the monitoring and control methods of other embodiments.

[0066] The technical solution of the present invention is described in detail below with reference to the accompanying drawings and through specific implementation methods.

[0067] See also Figure 2-9 The present invention is based on a monitoring and control method for an adjustable single screw compressor regenerative cascade low temperature refrigeration system. The sensor measuring points for monitoring are arranged in Figure 3-Figure 9 , the refrigerant circuit and circuit connection for implementing the control method refer to Figure 2 .

[0068] In order to efficiently achieve the target cooling temperature T c,m , Target cooling capacity W c,m , a monitoring and control method for a regenerative cascade cryogenic refrigeration system using an adjustable single screw compressor.

[0069] The adjustable single screw compressor regenerative cascade low temperature refrigeration system has a built-in monitoring module in the controller to monitor the ambient temperature as T1 before starting up, and a built-in calculation module in the controller 26 calls a calculation formula to obtain a target condensing temperature T con,m(T con,m =T1-ΔT1), target evaporation temperature T eva,m (T eva,m =T c,m -ΔT2); the calculation module calls the high-temperature refrigerant 29 saturation temperature-pressure database to obtain T con,m Corresponding target condensing pressure P con,m , call the low-temperature refrigerant 30 saturation temperature-pressure database to obtain T eva,m Corresponding target evaporation pressure P eva,m ; The calculation module uses the intermediate pressure empirical formula to obtain the target condensation and evaporation temperature T c-e,m The calculation module calls the high-temperature refrigerant 29 saturation temperature-pressure database to obtain T c-e,m The corresponding target condensation and evaporation high temperature side pressure P c-e,h,m , call the low-temperature refrigerant 30 saturation temperature-pressure database to obtain T c-e,m The corresponding target condensation and evaporation low temperature side pressure P c-e,l,m ; The calculation module calls the volume ratio-pressure ratio calculation formula according to P con,m / P c-e,h,m Get the target high temperature compressor volume ratio V h,m According to P c-e,l,m / P eva,m Get the target low temperature compressor volume ratio V l,m ; The calculation module uses the superheat-subcooling temperature empirical formula to obtain the target high temperature level superheat temperature T h,gr,m 、Target high temperature level subcooling temperature T h,gl,m , target low temperature stage superheat temperature T l,gr,m 、Target high and low temperature level subcooling temperature T l,gl,m ; The calculation module uses the empirical formula of the air supply pressure to obtain the target high-temperature stage primary throttling pressure P bq,h,m , Target low temperature stage primary throttling pressure P bq,l,m .

[0070] When the adjustable single screw compressor regenerative cascade low temperature refrigeration system is started, the high and low temperature stage refrigeration main circuits are operated first, and the controller 26 control module controls the high temperature stage compressor 1 motor 106 to rotate, and the controller 26 control module adjusts the high temperature stage compressor 1 slide valve power device 105 to move to the position closest to V h,m The compressor volume ratio gear position, at the same time, the controller 26 control module controls the opening of the high temperature stage secondary throttling element 10; the monitoring module monitors P 204 Value, in P con,m As a target, at the same time, the monitoring module monitors P 1304 Value, in P c-e,h,mAs a goal, the opening of the high-temperature secondary throttling element 10 is adjusted; after the high-temperature compressor 1 has been running for a period of time, the controller 26 control module controls the low-temperature compressor 18 motor 1806 to rotate, and the controller 26 control module adjusts the low-temperature compressor 18 slide valve power device 1805 to move to the closest V l,m The compressor volume ratio gear position, at the same time, the controller 26 control module controls the low temperature stage secondary throttling element 22 opening; the monitoring module monitors P 2304 Value, in P eva,m As a target, at the same time, the monitoring module monitors P 1308 Value, in P c-e,l,m As a target, the opening of the low-temperature secondary throttling element 22 is adjusted; during the adjustment process, the difference between the real-time pressure of the above pressure measuring points and the target pressure is monitored. When the difference is less than 5%, the opening of the secondary throttling elements at all levels is kept basically unchanged to maintain the stable operation of the system; after the system has been running stably for a period of time, if the difference between the measured pressure at the measuring point and the target pressure increases by more than 5%, the controller 26 control module controls the opening adjustment of the secondary throttling element to make the system stable again; the pressure adjustment strategy of the high-temperature secondary throttling element 10 and the low-temperature secondary throttling element 22 is a common technology in the industry, so it will not be described in detail; when P 204 Greater than the protection condensing pressure P con,b (i.e. P 204 Greater than P con,b ) or when P 1304 Less than the high temperature side pressure P to protect the condensation and evaporation c-e,l,b (i.e. P 1304 Less than P c-e,l,b ) or when P 1308 Greater than the low temperature side pressure P to protect the condensation and evaporation c-e,h,b (i.e. P 1308 Greater than P c-e,h,b ), or when P 2304 Less than the protective evaporation pressure P eva,b (i.e. P 2304 Less than P eva,b ), the control module shuts down the system to ensure safe operation of the system.

[0071] After the adjustable single screw compressor regenerative cascade low temperature refrigeration system is started, the monitoring system monitors T2 and T c,m As a goal, it runs continuously; when the monitoring module detects that T2 is equal to T c,m Calculate the real-time cooling capacity W L , the monitoring module monitors P 101 , T 102 The calculation module calls the high-temperature refrigerant 29 saturation temperature-pressure database to obtain P 101 , T 102The corresponding density ρ 1,d ; Monitoring module monitors P 1301 , T 1302 The calculation module calls the high-temperature refrigerant 29 saturation temperature-pressure database to obtain P 1301 , T 1302 The corresponding enthalpy value h 13,b ; Monitoring module monitors P 1304 , T 1303 The calculation module calls the high-temperature refrigerant 29 saturation temperature-pressure database to obtain P 1304 , T 1303 The corresponding enthalpy value h 13,a ; The monitoring module monitors V 12 ; The calculation module calculates the real-time high temperature cooling capacity W H =V 12 * 1,d *(h 13,b -h 13,a );Monitoring module monitors P 1801 , T 1802 The calculation module calls the low-temperature refrigerant 30 saturation temperature-pressure database to obtain P 1801 , T 1802 The corresponding density ρ 18,d ; Monitoring module monitors P 2301 , T 2302 The calculation module calls the low-temperature refrigerant 30 saturation temperature-pressure database to obtain P 2301 , T 2302 The corresponding enthalpy value h 23,in ; Monitoring module monitors P 2304 , T 2303 The calculation module calls the low-temperature refrigerant 30 saturation temperature-pressure database to obtain P 2304 , T 2303 The corresponding enthalpy value h 23,out ; The monitoring module monitors V 25 ; The calculation module calculates the real-time cooling capacity W L =V 25 * 18,d *(h 23,out -h 23,in ); when W L Less than W c,m Less than W H When the control module controls to increase the low temperature compressor 18 motor speed, the monitoring module monitors P 101 , T 102 , P 1301 , T 1302 , P 1801 , T 1802 , P 2304 , T 2303, the calculation module calculates the real-time high temperature cooling capacity W H , calculate the real-time cooling capacity W L ,|W L -W c,m |When it is less than 5%, keep the motor speed of each level of compressor basically unchanged, maintain the stable operation of the system, and always keep W during the adjustment process L Less than W H When W L Less than W H Less than W c,m When the control module controls to increase the motor speed of the high temperature compressor 1 and the low temperature compressor 18, the monitoring module monitors P 101 , T 102 , P 1301 , T 1302 , P 1801 , T 1802 , P 2304 , T 2303 , the calculation module calculates the real-time high temperature cooling capacity W H , calculate the real-time cooling capacity W L ,|W L -W c,m |When it is less than 5%, keep the motor speed of each level of compressor basically unchanged, maintain the stable operation of the system, and always keep W during the adjustment process L Less than W H When W c,m Campus W L When the control module controls to reduce the motor speed of the high-temperature compressor and the low-temperature compressor, the monitoring module monitors P 101 , T 102 , P 1301 , T 1302 , P 1801 , T 1802 , P 2304 , T 2303 , the calculation module calculates the real-time high temperature cooling capacity W H , calculate the real-time cooling capacity W L ,|W L -W c,m |When it is less than 5%, keep the motor speed of each level of compressor basically unchanged, maintain the stable operation of the system, and always keep W during the adjustment process L Less than W H ; Monitoring module monitors P 201 , T 202 The calculation module calls the high-temperature refrigerant 29 saturation temperature-pressure database to obtain P 201 , T 202 The corresponding enthalpy value h 2,out , used to calculate the system COP; the monitoring module monitors P 801 , T802 The calculation module calls the high-temperature refrigerant 29 saturation temperature-pressure database to obtain P 801 , T 802 The corresponding enthalpy value h 8,a ; Monitoring module monitors P 804 , T 803 The calculation module calls the high-temperature refrigerant 29 saturation temperature-pressure database to obtain P 804 , T 803 The corresponding enthalpy value h 8,b ; Monitoring module monitors P 805 , T 806 The calculation module calls the high-temperature refrigerant 29 saturation temperature-pressure database to obtain P 805 , T 806 The corresponding enthalpy value h 8,c ; Monitoring module monitors P 808 , T 807 The calculation module calls the high-temperature refrigerant 29 saturation temperature-pressure database to obtain P 808 , T 807 The corresponding enthalpy value h 8,d , the calculation module calls the calculation formula to calculate (h 8,a -h 8,b ) and (h 8,d -h 8,c ), used to check the heat balance in the high temperature stage regenerator (8); the monitoring module monitors P 1305 , T 1306 The calculation module calls the low-temperature refrigerant 30 saturation temperature-pressure database to obtain P 1305 , T 1306 The corresponding enthalpy value h 13,c ; Monitoring module monitors P 1308 , T 1307 The calculation module calls the low-temperature refrigerant 30 saturation temperature-pressure database to obtain P 1308 , T 1307 The corresponding enthalpy value h 13,d , the calculation module calls the calculation formula to calculate (h 13,a -h 13,b ) and (h 13,d -h 13,c ), used to check the heat balance in the condenser evaporator 13; the monitoring module monitors P 2001 , T 2002 The calculation module calls the low-temperature refrigerant 30 saturation temperature-pressure database to obtain P 2001 , T 2002 The corresponding enthalpy value h 20,a ; Monitoring module monitors P 2004 , T 2003The calculation module calls the low-temperature refrigerant 30 saturation temperature-pressure database to obtain P 2004 , T 2003 The corresponding enthalpy value h 20,b ; Monitoring module monitors P 2005 , T 2006 The calculation module calls the low-temperature refrigerant 30 saturation temperature-pressure database to obtain P 2005 , T 2006 The corresponding enthalpy value h 20,c ; Monitoring module monitors P 2008 , T 2007 The calculation module calls the low-temperature refrigerant 30 saturation temperature-pressure database to obtain P 2008 , T 2007 The corresponding enthalpy value h 20,d , the calculation module calls the calculation formula to calculate (h 20,a -h 20,b ) and (h 20,d -h 20,c ) is used to check the heat balance in the low temperature stage regenerator 20.

[0072] After the adjustable single screw compressor heat recovery cascade low temperature refrigeration system is started and operated for a period of time, the monitoring module monitors T 103 , with T bq,h,m As the goal, when T 103 Greater than or equal to T bq,h,m When the control module controls the high temperature stage primary throttling element 4 to open, the high temperature stage primary throttling branch is opened; the monitoring module monitors P 404 , with P bq,h,s As the target, adjust the opening of the high-temperature stage primary throttling element 4; when |P 404 -P bq,h,m | is less than 5%, keep the opening of the high temperature stage primary throttling element 4 basically unchanged, check the opening of the high temperature stage primary throttling element; the monitoring module monitors P 108 , T 107 The calculation module calls the high-temperature refrigerant 29 saturation temperature-pressure database to obtain P 108 , T 107 The corresponding density ρ 1,b , enthalpy value h 1b ; Monitoring module monitors P 101 , T 102 The calculation module calls the high-temperature refrigerant 29 saturation temperature-pressure database to obtain P 101 , T 102 The corresponding density ρ 1,d , enthalpy value h 1,d ; Monitoring module monitors P 204 , T 203The calculation module calls the high-temperature refrigerant 29 saturation temperature-pressure database to obtain P 204 , T 203 The corresponding enthalpy value h 2,out ; Monitoring module monitors P 801 , T 802 The calculation module calls the high-temperature refrigerant 29 saturation temperature-pressure database to obtain P 801 , T 802 The corresponding enthalpy value h 8,a ; The monitoring module monitors V6, V 12 ; The calculation module uses the relative air supply volume calculation formula to calculate the relative air supply volume a of the high temperature compressor 1,h =(ρ 1,b* V6) / (ρ 1,d* V 12 ), the calculation module uses the circulating air supply volume calculation formula to calculate the circulating air supply volume a of the high temperature compressor 2,h =(h 2,out -h 8,a ) / (h 1,d -h 2,out ); when a 1,h Greater than a 2,h When a 1,h Less than a 2,h When a 1,h =a 2,h When the high temperature stage primary throttling element 4 is opened, the opening degree is kept unchanged to maintain the stable operation of the system; the monitoring module monitors P 401 , T 402 The calculation module calls the high-temperature refrigerant 29 saturation temperature-pressure database to obtain P 401 , T 402 The corresponding enthalpy value h 4,in ; Monitoring module monitors P 801 , T 802 The calculation module calls the high-temperature refrigerant 29 saturation temperature-pressure database to obtain P 801 , T 802 The corresponding enthalpy value h 8,a ; Monitoring module monitors P 404 , T 403 The calculation module calls the high-temperature refrigerant 29 saturation temperature-pressure database to obtain P 404 , T 403 The corresponding enthalpy value h 4,out ; Monitoring module monitors P 502 , T 501 The calculation module calls the high-temperature refrigerant 29 saturation temperature-pressure database to obtain P 502 , T501 The corresponding enthalpy value h 5,out ; The calculation module calls the calculation formula to calculate (h 4,in -h 8,a ) and (h 5,out -h 4,out ), used to check the heat balance of high temperature stage subcooler 5.

[0073] After the adjustable single screw compressor heat recovery cascade low temperature refrigeration system is started and operated for a period of time, the monitoring system monitors T 702 , T 703 , T 802 , T 803 , T 806 , T 807 , T 1102 , T 1103 , with T h,gl,m As the target, when (T 802 -T 803 ) is greater than T h,gl,m When (T 802 -T 803 ) is less than T h,gl,m When (T 702 -T 703 ) is equal to T h,gl,m When T h,gr,m As the target, when (T 807 -T 806 ) is greater than T h,gr,m When (T 807 -T 806 ) is less than T h,gr,m When (T 1103 -T 1102 ) is equal to T h,gr,m When the temperature is high, maintain the opening of the high temperature stage regenerator gas bypass element.

[0074] After the adjustable single screw compressor heat recovery cascade low temperature refrigeration system is started and operated for a period of time, the monitoring module monitors T 103 , with T pq,m As the goal, when T 103 Greater than or equal to T pq,m When T 103 Less than T pq,m When T 103 Greater than or equal to Tpq,b When the control module controls the system to shut down to ensure the safe operation of the system.

[0075] After the adjustable single screw compressor heat recovery cascade low temperature refrigeration system is started and operated for a period of time, the monitoring module monitors T 1803 , with T bq,l,m As the goal, when T 1803 Greater than or equal to T bq,l,m When the control module controls the low temperature stage primary throttling element 15 to open, the low temperature stage primary throttling branch is opened; the monitoring module monitors P 1504 , with P bq,l,m As the target, adjust the opening of the low temperature stage primary throttling element 15; when P 1504 Less than P bq,l,m When P 1504 Greater than P bq,l,m When |P 1504 -P bq,l,m | is less than 5%, keep the opening of the low-temperature stage primary throttling element 15 basically unchanged, check the opening of the low-temperature stage primary throttling element; the monitoring module monitors P 1808 , T 1807 The calculation module calls the low-temperature refrigerant 30 saturation temperature-pressure database to obtain P 1808 , T 1807 The corresponding density ρ 18,b , enthalpy value h 18,b ; Monitoring module monitors P 1801 , T 1802 The calculation module calls the low-temperature refrigerant 30 saturation temperature-pressure database to obtain P 1801 , T 1802 The corresponding density ρ 18,d , enthalpy value h 18,d ; Monitoring module monitors P 1308 , T 1307 The calculation module calls the low-temperature refrigerant 30 saturation temperature-pressure database to obtain P 1308 , T 1307 The corresponding enthalpy value h 13,d ; Monitoring module monitors P 2001 , T 2002 The calculation module calls the low-temperature refrigerant 30 saturation temperature-pressure database to obtain P 2001 , T 2002 The corresponding enthalpy value h 20,a ; The monitoring module monitors V 17 、V 25 ; The calculation module uses the relative air supply volume calculation formula to calculate the relative air supply volume a of the low temperature compressor 1,l =(ρ18,b* V 17 ) / (ρ 18,d* V 25 ), the calculation module uses the circulating air supply volume calculation formula to calculate the circulating air supply volume a of the low-temperature compressor 2,l =(h 13,d -h 20,a ) / (h 18,d -h 13,d ); when a 1,l Greater than a 2,l When a 1,l Less than a 2,l When a 1,l Equal to a 2,l When the low temperature stage primary throttling element 15 is opened, the system is kept running stably; the monitoring module monitors P 1501 , T 1502 The calculation module calls the low-temperature refrigerant 30 saturation temperature-pressure database to obtain P 1501 , T 1502 The corresponding enthalpy value h 15,in ; Monitoring module monitors P 2001 , T 2002 The calculation module calls the low-temperature refrigerant 30 saturation temperature-pressure database to obtain P 2001 , T 2002 The corresponding enthalpy value h 20,a ; Monitoring module monitors P 1504 , T 1503 The calculation module calls the low-temperature refrigerant 30 saturation temperature-pressure database to obtain P 1504 , T 1503 The corresponding enthalpy value h 15,out ; Monitoring module monitors P 1602 , T 1601 The calculation module calls the low-temperature refrigerant 30 saturation temperature-pressure database to obtain P 1602 , T 1601 The corresponding enthalpy value h 16,out ; The calculation module calls the calculation formula to calculate (h 15,in -h 20,a ) and (h 16,out -h 15,out ) is used to check the thermal balance of the low temperature stage subcooler 16.

[0076] After the adjustable single screw compressor heat recovery cascade low temperature refrigeration system is started and operated for a period of time, the monitoring system monitors T 1902 , T 1903 , T 2002 , T 2003, T 2006 , T 2007 , T 2402 , T 2403 , with T l,gl,m As the target, when (T 2002 -T 2003 ) is greater than T l,gl,m When (T 2002 -T 2003 ) is less than T l,gl,m When (T 1902 -T 1903 ) is equal to T l,gl,m When T l,gr,m As the target, when (T 2007 -T 2006 ) is greater than T l,gr,m When (T 2007 -T 2006 ) is less than T l,gr,m When (T 2403 -T 2402 ) is equal to T l,gr,m When the temperature is low, maintain the opening of the low temperature stage regenerator gas bypass element.

[0077] After the adjustable single screw compressor heat recovery cascade low temperature refrigeration system is started and operated for a period of time, the monitoring module monitors T 1803 , with T pq,m As the goal, when T 1803 Greater than or equal to T pq,m When T 1803 Less than T pq,m When T 1803 Greater than or equal to T pq,b When the control module controls the system to shut down to ensure the safe operation of the system.

[0078] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention 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 embodiments of the present invention.

Claims

1. A monitoring and control method for an adjustable single screw compressor regenerative cascade low temperature refrigeration system, used to monitor and control the system to achieve a set refrigeration temperature and refrigeration capacity under different ambient temperatures, characterized in that: An adjustable single screw compressor regenerative cascade low temperature refrigeration system, consisting of a refrigerant circuit and a monitoring-control circuit; The refrigerant circuit comprises: a high and low temperature stage refrigeration main circuit connected by a condenser evaporator (13), a high temperature stage primary throttling branch, a high temperature stage heat regenerator branch, a high temperature stage liquid injection branch, a low temperature stage primary throttling branch, a low temperature stage heat regenerator branch, and a low temperature stage liquid injection branch; High and low temperature refrigeration main circuit: including a high temperature secondary flow meter (12), a high temperature compressor (1), a condenser (2), a high temperature refrigerant storage tank (3), a high temperature subcooler (5), a high temperature regenerator (8), a high temperature secondary throttling element (10), a condenser evaporator (13), a low temperature refrigerant storage tank (14), a low temperature subcooler (16), a low temperature regenerator (20), a low temperature secondary throttling element (22), an evaporator (23), a low temperature secondary flow meter (25), and a low temperature compressor (18); The operation logic of the high and low temperature refrigeration main circuit is as follows: the high temperature compressor (1) is adjusted to the corresponding content volume ratio gear by calculation according to the working conditions corresponding to the ambient temperature and the refrigeration temperature and is turned on; the high temperature refrigerant (29) flows from the outlet a of the high temperature compressor (1) into the condenser (2) to exchange heat with the environment, and then flows through the high temperature refrigerant storage tank (3), the inlet a of the high temperature subcooler (5), the outlet c of the high temperature subcooler (5), the inlet a of the high temperature regenerator (8), the outlet b of the high temperature regenerator (8) and flows into the high temperature regenerator (8). The high-temperature secondary throttling element (10) is used to adjust the opening degree of the high-temperature secondary throttling element (10) to control the pressure of the high-temperature refrigerant flowing into the inlet a of the condenser evaporator (13). After heat exchange with the low-temperature refrigerant in the condenser evaporator (13), the high-temperature refrigerant flows out of the outlet b of the condenser evaporator (13), flows through the inlet c of the high-temperature regenerator (8), the outlet d of the high-temperature regenerator (8), and the high-temperature secondary flow meter (12), and flows into the inlet d of the high-temperature compressor (1); the low-temperature compressor (18) adjusts the pressure of the high-temperature refrigerant according to the ambient temperature and the refrigeration temperature. The corresponding working condition is adjusted to the corresponding volume ratio gear by calculation and the machine is turned on. The low-temperature refrigerant (30) flows from the outlet a of the low-temperature compressor (18) into the inlet c of the condenser evaporator (13) to exchange heat with the high-temperature refrigerant, and then flows out from the outlet d of the condenser evaporator (13), flows through the low-temperature refrigerant storage tank (14), the inlet a of the low-temperature subcooler (16), the outlet c of the low-temperature subcooler (16), the inlet a of the low-temperature reheater (20), and the outlet b of the low-temperature reheater (20) to flow into the low-temperature secondary throttling element (22), the opening degree of the low-temperature secondary throttling element (22) is adjusted to control the temperature of the low-temperature refrigerant flowing out of the evaporator (23) outlet, and the refrigerant flows out of the evaporator (23) outlet, flows through the low-temperature regenerator (20) inlet c, the low-temperature regenerator (20) outlet d, and the low-temperature secondary flow meter (25) and flows into the low-temperature compressor (18) inlet d; at the same time, the high and low temperature refrigeration main circuit can adjust the refrigeration capacity by adjusting the motor speed of the high-temperature compressor (1) and the motor speed of the low-temperature compressor (18); The high-temperature primary throttling branch is divided into another branch after the outlet of the high-temperature refrigerant storage tank (3) and connected to the inlet of the high-temperature primary throttling element (4). The outlet of the high-temperature primary throttling element (4) is connected to the inlet b of the high-temperature subcooler (5). After flowing out of the outlet d of the high-temperature subcooler (5), the high-temperature primary flow meter (6) flows into the inlet b of the high-temperature compressor (1); The operation logic of the high-temperature primary throttling branch is as follows: when the temperature at the outlet a of the high-temperature compressor (1) is relatively high, the high-temperature primary throttling element (4) adjusts its opening degree so that a portion of the high-temperature refrigerant at the outlet of the high-temperature refrigerant storage tank (3) flows through the high-temperature primary throttling element (4) and then flows into the inlet b of the high-temperature subcooler (5), exchanges heat with the high-temperature refrigerant in the high- and low-temperature refrigeration main circuit in the high-temperature subcooler (5), flows out from the outlet d of the high-temperature subcooler (5), flows through the high-temperature primary flowmeter (6) and flows into the inlet b of the high-temperature compressor (1); High-temperature regenerator branch: the two ends of the high-temperature regenerator liquid bypass element (7) are respectively connected to the inlet a of the high-temperature regenerator (8) and the outlet b of the high-temperature regenerator (8), so that the high-temperature regenerator liquid bypass element (7) is connected in parallel with the inlet a of the high-temperature regenerator (8) and the outlet b of the high-temperature regenerator (8); the two ends of the high-temperature regenerator gas bypass element (11) are respectively connected to the inlet c of the high-temperature regenerator (8) and the outlet d of the high-temperature regenerator (8), so that the high-temperature regenerator gas bypass element (11) is connected in parallel with the inlet c of the high-temperature regenerator (8) and the outlet d of the high-temperature regenerator (8); The operation logic of the high-temperature regenerator branch is as follows: when the subcooling temperature of the high-temperature regenerator is not satisfied, the opening of the high-temperature regenerator liquid bypass element (7) is adjusted so that a portion of the high-temperature refrigerant at the outlet c of the high-temperature subcooler (5) flows through the high-temperature refrigerant liquid bypass element (7), and then mixes with the high-temperature refrigerant flowing through the inlet a of the high-temperature regenerator (8) and the outlet b of the high-temperature regenerator (8), and then flows into the high-temperature secondary throttling element (10) to adjust the subcooling temperature of the high-temperature regenerator; When the superheat temperature of the high-temperature regenerator is not satisfied, the opening of the high-temperature regenerator gas bypass element (11) is adjusted so that a portion of the high-temperature refrigerant at the outlet b of the condenser evaporator (13) flows through the high-temperature refrigerant gas bypass element (11), and then mixes with the high-temperature refrigerant flowing through the inlet c of the high-temperature regenerator (8) and the outlet d of the high-temperature regenerator (8), and then flows through the high-temperature secondary flow meter (12) and flows into the inlet d of the high-temperature compressor (1), thereby adjusting the superheat temperature of the high-temperature regenerator; High-temperature liquid injection branch: a branch is separated from the inlet of the high-temperature secondary throttling element (10) and connected to the inlet of the high-temperature liquid injection control element (9); the outlet of the high-temperature liquid injection control element (9) is connected to the inlet c of the high-temperature compressor (1); The operation logic of the high-temperature liquid injection branch is as follows: when the temperature of the outlet a of the high-temperature compressor (1) is relatively high, the high-temperature liquid injection control element (9) adjusts the opening degree so that a portion of the high-temperature refrigerant before the high-temperature secondary throttling element (10) flows through the high-temperature liquid injection control element (9) and then flows into the inlet c of the high-temperature compressor (1); Low-temperature stage primary throttling branch: after the outlet of the low-temperature stage refrigerant storage tank (14), another branch is separated and connected to the inlet of the low-temperature stage primary throttling element (15); the outlet of the low-temperature stage primary throttling element (15) is connected to the inlet b of the low-temperature stage subcooler (16); after flowing out of the outlet d of the low-temperature stage subcooler (16), the liquid flows into the inlet b of the low-temperature stage compressor (18) through the low-temperature stage primary flowmeter (17); The operation logic of the low-temperature primary throttling branch is as follows: when the temperature at the outlet a of the low-temperature compressor (18) is relatively high, the low-temperature primary throttling element (15) adjusts its opening degree so that a portion of the low-temperature refrigerant at the outlet of the low-temperature refrigerant storage tank (14) flows through the low-temperature primary throttling element (15) and then flows into the inlet b of the low-temperature subcooler (16), exchanges heat with the low-temperature refrigerant in the high- and low-temperature refrigeration main circuit in the low-temperature subcooler (16), flows out from the outlet d of the low-temperature subcooler (16), flows through the low-temperature primary flowmeter (17) and flows into the inlet b of the low-temperature compressor (18); Low-temperature regenerator branch: two ends of the low-temperature regenerator liquid bypass element (19) are respectively connected to the inlet a of the low-temperature regenerator (20) and the outlet b of the low-temperature regenerator (20), so that the low-temperature regenerator liquid bypass element (19) and the inlet a of the low-temperature regenerator (20) and the outlet b of the low-temperature regenerator (20) are connected in parallel; two ends of the low-temperature regenerator gas bypass element (24) are respectively connected to the inlet c of the low-temperature regenerator (20) and the outlet d of the low-temperature regenerator (20), so that the low-temperature regenerator gas bypass element (24) and the inlet c of the low-temperature regenerator (20) and the outlet d of the low-temperature regenerator (20) are connected in parallel; The operation logic of the low-temperature regenerator branch is as follows: when the low-temperature regenerator subcooling temperature is not satisfied, the opening of the low-temperature regenerator liquid bypass element (19) is adjusted so that a portion of the low-temperature refrigerant at the outlet c of the low-temperature subcooler (16) flows through the low-temperature refrigerant liquid bypass element (19), and then mixes with the low-temperature refrigerant flowing through the inlet a of the low-temperature regenerator (20) and the outlet b of the low-temperature regenerator (20), and then flows into the low-temperature secondary throttling element (22), so as to adjust the low-temperature regenerator subcooling temperature. degree; when the superheat temperature of the low-temperature regenerator is not satisfied, the opening degree of the low-temperature regenerator gas bypass element (24) is adjusted so that a portion of the low-temperature refrigerant at the outlet of the evaporator (23) flows through the low-temperature regenerator gas bypass element (24), and then mixes with the low-temperature refrigerant flowing through the inlet c of the low-temperature regenerator (20) and the outlet d of the low-temperature regenerator (20), and then flows through the low-temperature secondary flow meter (25) and flows into the inlet d of the low-temperature compressor (18), thereby adjusting the superheat temperature of the low-temperature regenerator; A branch of the low-temperature liquid injection branch is separated from the inlet of the low-temperature secondary throttling element (22) and connected to the inlet of the low-temperature liquid injection control element (21), and the outlet of the low-temperature liquid injection control element (21) is connected to the inlet c of the low-temperature compressor (18); The operation logic of the low-temperature liquid injection branch is as follows: when the temperature of the outlet a of the low-temperature compressor (18) is relatively high, the low-temperature liquid injection control element (21) adjusts the opening degree so that a portion of the low-temperature refrigerant before the low-temperature secondary throttling element (22) flows through the low-temperature liquid injection control element (21) and then flows into the inlet c of the low-temperature compressor (18); The monitoring-control circuit is composed of a controller (26) connected to an inlet e of a high-temperature compressor (1) and an inlet e of a low-temperature compressor (18) in the system, and is used to control the gear adjustment of the internal volume ratio of the high-temperature compressor (1) and the low-temperature compressor (18). The controller (26) is connected to an inlet f of the high-temperature compressor (1) and an inlet f of the low-temperature compressor (18) in the system, and is used to control the speed adjustment of the motor of the high-temperature compressor (1) and the low-temperature compressor (18); the controller (26) is connected to a high-temperature primary throttling element (4), a high-temperature secondary throttling element (10), a high-temperature regenerator liquid bypass element (7), a high-temperature regenerator gas bypass element (11), and a high-temperature liquid injection control element in the system. (9), a low-temperature primary throttling element (15), a low-temperature secondary throttling element (22), a low-temperature regenerator liquid bypass element (19), a low-temperature regenerator gas bypass element (24), and a low-temperature liquid injection control element (21), and are used to control the opening of each element; a controller (26) is connected to a high-temperature primary flow meter (6), a high-temperature secondary flow meter (12), a low-temperature primary flow meter (17), and a low-temperature secondary flow meter (25) in the system, and is used to monitor the flow of the high-temperature primary throttling branch, the high and low temperature refrigerant circuit, and the low-temperature primary flow branch; the controller (26) is connected to each pressure sensor and each temperature sensor in the system, and is used to monitor the system; The controller (26) has a built-in monitoring module, a calculation module and a control module to implement the monitoring and control method; the monitoring module monitors the pressure, temperature, ambient temperature, refrigeration temperature and refrigerant flow rate before and after the main components in the system by connecting with various pressure sensors, various temperature sensors, primary flow meters at various levels and secondary flow meters at various levels; the calculation module processes the data by setting specific temperature difference, protection pressure, protection temperature value, refrigerant saturation temperature-pressure database, calculation formula, empirical formula, characteristic curve and other calculation tools, and guides the control module to adjust; the control module realizes the control function of the system by connecting various compressor slide valve devices, various compressor motors, various primary throttling elements, various secondary throttling elements, various regenerator liquid bypass elements, various regenerator gas bypass elements and the like; The controller (26) calculates a temperature difference in a calculation module as ΔT1, which is used to calculate a target condensing temperature according to the measured ambient temperature, and a temperature difference as ΔT2, which is used to calculate a target evaporating temperature according to a target refrigeration temperature; and sets a protection condensing pressure P con,b , protect the condensation and evaporation high temperature side pressure P c-e,l,b , protect the condensation and evaporation low temperature side pressure P c-e,h,b , Protect evaporation pressure P eva,b ; Set the target compressor outlet temperature T pq,m , protect the compressor outlet temperature T pq,b ; Adjustable single screw compressor regenerative cascade low temperature refrigeration system sets the target refrigeration temperature T before starting c,m , Target cooling capacity W c,m ; According to the target cooling temperature T c,m , Target cooling capacity W c,m , the measured ambient temperature T1, the built-in calculation module of the controller (26) calls the calculation formula to obtain the target condensation temperature T con,m (T con,m =T1-ΔT1), target evaporation temperature T eva,m (T eva,m =T c,m -ΔT2), the calculation module calls the refrigerant saturation temperature-pressure database to obtain T con,m Corresponding target condensing pressure P con,m , get T eva,m Corresponding target evaporation pressure P eva,m ; The calculation module uses the empirical formula to obtain the target condensation and evaporation temperature T c-e,m The calculation module calls the refrigerant saturation temperature-pressure database to obtain T c-e,m The corresponding target condensation and evaporation high temperature side pressure P c-e,h,m , get T c-e,m The corresponding target condensation and evaporation low temperature side pressure P c-e,l,m ; The calculation module calls the calculation formula according to P con,m / P c-e,h,m Get the target high temperature compressor volume ratio V h,m According to P c-e,l,m / P eva,m Get the target low temperature compressor volume ratio V l,m ; The calculation module uses the empirical formula to obtain the target high temperature stage superheat temperature T h,gr,m 、Target high temperature level subcooling temperature T h,gl,m , target low temperature stage superheat temperature T l,gr,m 、Target high and low temperature level subcooling temperature T l,gl,m ; Target high temperature stage primary throttling opening temperature T bq,h,m , Target high temperature stage primary throttling pressure P bq,h,m , Target low temperature stage primary throttling opening temperature T bq,l,m , Target low temperature stage primary throttling pressure P bq,l,m ; The above target values ​​are used as the basis for the adjustment of the control module of the controller (26); the monitoring module of the controller (26) monitors the temperature and pressure sensors in the system, and the monitoring values ​​are used as the measured values; when the error between the target value and the measured value of the corresponding measuring point meets a certain range, it is considered that the system is running stably, and the control module of the controller (26) suspends the adjustment of the system; when the measured value of the corresponding measuring point exceeds the protection value, the control module of the controller (26) immediately shuts down the system and the control system is powered off; The monitoring module monitoring data includes: Real-time pressure value P of the high-temperature compressor (1) inlet pressure sensor (101) 101 , the real-time temperature value T of the temperature sensor (102) at the inlet of the high-temperature compressor (1) 102 , the real-time temperature value T of the temperature sensor (103) at the outlet of the high-temperature compressor (1) 103 , the real-time pressure value P of the high-temperature compressor (1) outlet pressure sensor (104) 104 , the real-time temperature value T of the temperature sensor (107) at the inlet of the high-temperature compressor (1) 107 , the real-time pressure value P of the pressure sensor (108) at the inlet b of the high-temperature compressor (1) 108 ; Real-time pressure value P of the pressure sensor (1801) at the inlet of the low-temperature compressor (18) 1801 , the real-time temperature value T of the temperature sensor (1802) at the inlet of the low-temperature compressor (18) 1802 , the real-time temperature value T of the temperature sensor (1803) at the outlet of the low-temperature compressor (18) 1803 , the real-time pressure value P of the outlet a pressure sensor (1804) of the low-temperature compressor (18) 1804 , the real-time temperature value T of the temperature sensor (1807) at the inlet of the low-temperature compressor (18) 1807 , the real-time pressure value P of the pressure sensor (1808) at the inlet b of the low-temperature compressor (18) 1808 ; Real-time pressure value P of the inlet pressure sensor (401) of the high-temperature stage primary throttling element (4) 401 , the real-time temperature value T of the inlet temperature sensor (402) of the high-temperature stage primary throttling element (4) 402 , the real-time temperature value T of the outlet temperature sensor (403) of the high-temperature stage primary throttling element (4) 403 , the real-time pressure value P of the outlet pressure sensor (404) of the high-temperature stage primary throttling element (4) 404 ; Real-time temperature value T of high temperature stage subcooler (5) outlet temperature sensor (501) 501 , the real-time pressure value P of the high-temperature subcooler (5) outlet pressure sensor (502) 502 ; Real-time pressure value P of the inlet pressure sensor (1501) of the low-temperature primary throttling element (15) 1501 , the real-time temperature value T of the inlet temperature sensor (1502) of the low-temperature stage primary throttling element (15) 1502 , the real-time temperature value T of the outlet temperature sensor (1503) of the low-temperature stage primary throttling element (15) 1503 , the real-time pressure value P of the outlet pressure sensor (1504) of the low-temperature stage primary throttling element (15) 1504 ; Real-time temperature value T of the temperature sensor (1601) at the outlet of the low-temperature subcooler (16) 1601 , the real-time pressure value P of the pressure sensor (1602) at the outlet of the low-temperature subcooler (16) 1602 ; Real-time pressure value P of the inlet pressure sensor (701) of the high-temperature stage regenerator liquid bypass element (7) 701 , the real-time temperature value T of the inlet temperature sensor (702) of the high-temperature stage regenerator liquid bypass element (7) 702 , the real-time temperature value T of the outlet temperature sensor (703) of the high-temperature stage regenerator liquid bypass element (7) 703 , the real-time pressure value P of the outlet pressure sensor (704) of the high-temperature stage regenerator liquid bypass element (7) 704 ; Real-time pressure value P of the pressure sensor (801) at the inlet of the high-temperature regenerator (8) 801 , the real-time temperature value T of the temperature sensor (802) at the inlet of the high-temperature regenerator (8) 802 , the real-time temperature value T of the temperature sensor (803) at the outlet b of the high-temperature regenerator (8) 803 , the real-time pressure value P of the outlet pressure sensor (804) of the high-temperature regenerator (8) 804 , the real-time pressure value P of the pressure sensor (805) at the inlet of the high-temperature heat exchanger (8) 805 , the real-time temperature value T of the temperature sensor (806) at the inlet of the high-temperature regenerator (8) 806 , the real-time temperature value T of the temperature sensor (807) at the outlet of the high-temperature regenerator (8) 807 , the real-time pressure value P of the outlet pressure sensor (808) of the high-temperature regenerator (8) 808 ; Real-time pressure value P of the inlet pressure sensor (1101) of the high-temperature regenerator gas bypass element (11) 1101 , the real-time temperature value T of the inlet temperature sensor (1102) of the high-temperature stage regenerator gas bypass element (11) 1102 , the real-time temperature value T of the outlet temperature sensor (1103) of the high-temperature stage regenerator gas bypass element (11) 1103 , the real-time pressure value P of the outlet pressure sensor (1104) of the high-temperature stage regenerator gas bypass element (11) 1104 ; Real-time pressure value P of the inlet pressure sensor (1901) of the low-temperature stage regenerator liquid bypass element (19) 1901 , the real-time temperature value T of the inlet temperature sensor (1902) of the low temperature stage regenerator liquid bypass element (19) 1902 , the real-time temperature value T of the outlet temperature sensor (1903) of the liquid bypass element (19) of the low-temperature stage regenerator 1903 , the real-time pressure value P of the outlet pressure sensor (1904) of the low-temperature stage regenerator liquid bypass element (19) 1904 ; Low temperature stage regenerator (20) inlet a pressure sensor (2001) real-time pressure value P 2001 , the real-time temperature value T of the temperature sensor (2002) at the inlet of the low-temperature stage regenerator (20) 2002 , the real-time temperature value T of the temperature sensor (2003) at the outlet b of the low-temperature stage regenerator (20) 2003 , the real-time pressure value P of the outlet pressure sensor (20) of the low-temperature stage regenerator (20) 2004 , the real-time pressure value P of the pressure sensor (2005) at the inlet of the low-temperature stage regenerator (20) 2005 , the real-time temperature value T of the temperature sensor (2006) at the inlet of the low-temperature stage regenerator (20) 2006 , the real-time temperature value T of the outlet temperature sensor (2007) of the low-temperature stage regenerator (20) 2007 , the real-time pressure value P of the outlet pressure sensor (2008) of the low-temperature stage regenerator (20) 2008 ; Condenser (2) inlet pressure sensor (201) real-time pressure value P 201 , the real-time temperature value T of the condenser (2) inlet temperature sensor (202) 202 , the real-time temperature value T of the condenser (2) outlet temperature sensor (203) 203 , the real-time pressure value P of the condenser (2) outlet pressure sensor (204) 204 ; Real-time pressure value P of the pressure sensor (1301) at the inlet of the condenser evaporator (13) 1301 , the real-time temperature value T of the temperature sensor (1302) at the inlet of the condenser evaporator (13) 1302 , the real-time temperature value T of the temperature sensor (1303) at the outlet b of the condenser evaporator (13) 1303 , the real-time pressure value P of the pressure sensor (1304) at the outlet b of the condenser evaporator (13) 1304 , the real-time pressure value P of the pressure sensor (1305) at the inlet c of the condenser evaporator (13) 1305 , the real-time temperature value T of the temperature sensor (1306) at the inlet of the condenser evaporator (13) 1306 , the real-time temperature value T of the condenser evaporator (13) outlet temperature sensor (1307) 1307 , the real-time pressure value P of the pressure sensor (1308) at the outlet of the condenser evaporator (13) 1308 ; Real-time pressure value P of the evaporator (23) inlet pressure sensor (2301) 2301 , the real-time temperature value T of the evaporator (23) inlet temperature sensor (2302) 2302 , the real-time temperature value T of the evaporator (23) outlet temperature sensor (2303) 2303 , the real-time pressure value P of the evaporator (23) outlet pressure sensor (2304) 2304 ; High temperature grade primary flow meter real-time flow value V6, high temperature grade secondary flow meter real-time flow value V 12 , low temperature level primary flow meter real-time flow value V 17 , low temperature secondary flow meter real-time flow value V 25 ; The real-time temperature value T1 of the ambient temperature sensor (27) and the real-time temperature value T2 of the refrigeration temperature sensor (28); When the adjustable single screw compressor regenerative cascade low temperature refrigeration system is turned on, the high and low temperature stage refrigeration main circuits are operated first, and the controller (26) control module controls the rotation of the motor (106) of the high temperature stage compressor (1), and the controller (26) control module adjusts the slide valve power device (105) of the high temperature stage compressor (1) to move to the position closest to V h,m The compressor internal volume ratio gear is set, and at the same time, the controller (26) controls the opening of the high-temperature stage secondary throttling element (10); High temperature secondary throttling element (10) opening control logic: monitoring module monitors P 204 Value, in P con,m As a target, at the same time, the monitoring module monitors P 1304 Value, in P c-e,h,m As a target, the opening of the high temperature stage secondary throttling element (10) is adjusted; After the high temperature compressor has been running for a period of time, the controller (26) control module controls the low temperature compressor (18) motor (1806) to rotate, and the controller (26) control module adjusts the low temperature compressor (18) slide valve power device (1805) to move to the position closest to V l,m The compressor internal volume ratio gear position, and at the same time, the controller (26) control module controls the opening of the low-temperature stage secondary throttling element (22); Low temperature secondary throttling element (22) opening control logic: monitoring module monitors P 2304 Value, in P eva,m As a target, at the same time, the monitoring module monitors P 1308 Value, in P c-e,l,m As a target, the opening of the low temperature stage secondary throttling element (22) is adjusted; After the adjustable single screw compressor regenerative cascade low temperature refrigeration system is started, the monitoring system monitors T2 and T c,m As a goal, it runs continuously; when the monitoring module detects that T2 = T c,m Calculate the real-time cooling capacity W L , with W c,m For the purpose, the controller adjusts the motor speeds of the high temperature stage compressor (1) and the low temperature stage compressor (18); The controller adjusts the control logic of the motor speed of the high-temperature compressor (1) and the low-temperature compressor (18): the monitoring module monitors P 101 、T 102 The calculation module calls the refrigerant saturation temperature-pressure database to obtain P 101 、T 102 The corresponding density ρ 1,d ; Monitoring module monitors P 1301 、T 1302 The calculation module calls the refrigerant saturation temperature-pressure database to obtain P 1301 、T 1302 The corresponding enthalpy value h 13,b ; Monitoring module monitors P 1304 、T 1303 The calculation module calls the refrigerant saturation temperature-pressure database to obtain P 1304 、T 1303 The corresponding enthalpy value h 13,a The calculation module uses the calculation formula to calculate the real-time high temperature cooling capacity W H ; Monitoring module monitors P 1801 、T 1802 The calculation module calls the refrigerant saturation temperature-pressure database to obtain P 1801 、T 1802 The corresponding density ρ 18,d ; Monitoring module monitors P 2301 、T 2302 The calculation module calls the refrigerant saturation temperature-pressure database to obtain P 2301 、T 2302 The corresponding enthalpy value h 23,in ; Monitoring module monitors P 2304 、T 2303 The calculation module calls the refrigerant saturation temperature-pressure database to obtain P 2304 、T 2303 The corresponding enthalpy value h 23,out , the calculation module calls the calculation formula to calculate the real-time cooling capacity W L When W L Less than W c,m When W L Greater than W c,m When the control module controls the motor speed of the high temperature compressor (1) and the low temperature compressor (18) to decrease appropriately; during the adjustment process, W is always maintained. L Less than W H ; After the adjustable single screw compressor heat recovery cascade low temperature refrigeration system is started up, the high temperature stage primary throttling branch, high temperature stage heat recovery branch, high temperature stage liquid injection branch, low temperature stage primary throttling branch, low temperature stage heat recovery branch, and low temperature stage liquid injection branch can be operated as needed; The high temperature stage primary throttling branch is used to reduce the outlet temperature of the high temperature stage compressor (1). The monitoring system monitors T 103 , with T bq,h,m As the goal, when T 103 Greater than or equal to T bq,h,m When the control module controls the high temperature stage primary throttling element (4) to open, the monitoring module monitors P 404 , with P bq,h,m As the target, the opening of the high-temperature stage primary throttling element (4) is adjusted; the monitoring system monitors P 101 、T 102 、T 203 , P 204 、T 107 , P 108 , P 801 、T 802 , V6, V 12 , by calculating and checking the opening of the high temperature stage primary throttling element (4); The high temperature regenerator branch is used to adjust the high temperature cycle superheat temperature and high temperature cycle subcooling temperature. The monitoring system monitors T 702 、T 703 、T 802 、T 803 、T 806 、T 807 、T 1102 、T 1103 , with T h,gl,m As the target, the opening of the high temperature stage regenerator liquid bypass element (7) and the high temperature stage regenerator gas bypass element (11) is adjusted; when (T 802 -T 803 ) is greater than T h,gl,m When (T 802 -T 803 ) is less than T h,gl,m When (T 702 -T 703 ) is equal to T h,gl,m When T h,gr,m As the target, when (T 807 -T 806 ) is greater than T h,gr,m When (T 807 -T 806 ) is less than T h,gr,m When (T 1103 -T 1102 ) is equal to T h,gr,m When the gas bypass element (11) of the high temperature stage regenerator is opened, the opening degree is maintained; The high temperature stage liquid injection branch is used to reduce the outlet temperature of the high temperature stage compressor. The monitoring system monitors T 103 , with T pq,m As the goal, when T 103 Greater than or equal to T pq,m When the control module controls the high temperature level liquid spray control element (9) to open; The low temperature stage primary throttling branch is used to reduce the outlet temperature of the low temperature stage compressor. The monitoring system monitors T 1803 , with T bq,l,m As the goal, when T 1803 Greater than or equal to T bq,l,m When the control module controls the low temperature stage primary throttling element (15) to open, the monitoring module monitors P 1504 , with P bq,l,m As the target, the opening of the low temperature stage primary throttling element (15) is adjusted; the monitoring system monitors P 1801 、T 1802 、T 1307 , P 1308 、T 1807 , P 1808 , P 2001 、T 2002 、V 17 、V 25 , by calculating and checking the opening of the low temperature stage primary throttling element (15); The low temperature regenerator branch is used to adjust the low temperature cycle superheat temperature and low temperature cycle subcooling temperature. The monitoring system monitors T 1902 、T 1903 、T 2002 、T 2003 、T 2006 、T 2007 、T 2402 、T 2403 , with T l,gl,m As the target, the opening of the low temperature stage regenerator liquid bypass element (19) and the low temperature stage regenerator gas bypass element (24) is adjusted; when (T 2002 -T 2003 ) is greater than T l,gl,m When (T 2002 -T 2003 ) is less than T l,gl,m When (T 1902 -T 1903 ) is equal to T l,gl,m When T l,gr,m As the target, when (T 2007 -T 2006 ) is greater than T l,gr,m When (T 2007 -T 2006 ) is less than T l,gr,m When (T 2403 -T 2402 ) is equal to T l,gl,m When the low temperature stage regenerator gas bypass element (24) is opened, the opening degree is maintained; The low temperature stage liquid injection branch is used to reduce the outlet temperature of the low temperature stage compressor. The monitoring system monitors T 1803 , with T pq,m As the goal, when T 1803 Greater than T pq,m When the control module controls the low temperature stage liquid spray control element (21) to open; During system operation, the monitoring system monitors T 103 、T 1803 , when T 103 Greater than or equal to T pq,b or T 1803 Greater than or equal to T pq,b Or both, the control module immediately controls the system to shut down and cut off power; the monitoring system monitors P 204 , when P 204 Greater than or equal to P con,b When the control module immediately controls the system to shut down and cut off power; the monitoring system monitors P 1304 , when P 1304 Greater than or equal to P c-e,b When the control module immediately controls the system to shut down and cut off the power; the monitoring system monitors P 2304 , when P 2304 Greater than or equal to P eva,b When the control module immediately shuts down the system and cuts off the power to ensure safety.

2. The monitoring and control method according to claim 1, characterized in that: Used to produce low temperatures of 0℃ to -80℃.

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