Ultra-low temperature direct cooling temperature control system and control method thereof

Abstract

The present invention relates to the field of battery detection technology, and specifically discloses an ultra-low temperature direct cooling temperature control system and a control method thereof. The ultra-low temperature direct cooling temperature control system includes a primary refrigeration system, a secondary refrigeration system, a first temperature sensor, a first pressure sensor, a second temperature sensor, a second pressure sensor, a third temperature sensor and a control system. The primary refrigeration system includes a first compressor, a condenser, a first electronic expansion valve and an intermediate heat exchanger, and the secondary refrigeration system includes a second compressor, an oil separator, a second electronic expansion valve and a third electronic expansion valve. By controlling the opening of the first electronic expansion valve, the second electronic expansion valve and the third electronic expansion valve, a variety of detection temperature environments can be provided for the battery pack, which has a wide range of applications, and, compared with the solution of controlling the detection temperature by controlling the opening of a single electronic expansion valve, the temperature control has higher accuracy and stability.

Description

Technical Field

[0001] The present invention relates to the technical field of battery detection, and in particular to an ultra-low temperature direct cooling temperature control system and a control method thereof. Background Art

[0002] Refrigeration type ultra-low temperature equipment is mainly used in fields such as new energy battery testing. The low-temperature refrigerant is passed into the battery testing heat exchange plate through the refrigeration system to maintain a stable evaporation temperature to ensure a stable testing temperature environment.

[0003] Traditional refrigeration-type ultra-low temperature equipment uses a single-stage refrigeration system, which cannot achieve ultra-low temperature cooling at -45°C and has a limited scope of application. In addition, traditional refrigeration-type ultra-low temperature equipment adjusts the evaporation pressure by controlling the opening of a single electronic expansion valve to achieve the purpose of temperature control. However, under different temperature requirements, the control method of the opening of a single electronic expansion valve is prone to large pressure fluctuations, affecting the stability of system operation.

[0004] Therefore, it is urgent to propose an ultra-low temperature direct cooling temperature control system and a control method thereof to solve the above technical problems. Summary of the invention

[0005] According to one aspect of the present invention, the present invention provides an ultra-low temperature direct cooling temperature control system, which can provide a variety of detection temperature environments, has a wide range of applications, and has high accuracy and stability in system temperature control.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] The ultra-low temperature direct cooling temperature control system is used to provide a detection temperature environment for the battery pack, the battery pack includes a battery heat exchanger, and the ultra-low temperature direct cooling temperature control system includes:

[0008] A primary refrigeration system, comprising a first compressor, a condenser, a first electronic expansion valve and an intermediate heat exchanger; the outlet of the first compressor is communicated with the inlet of the condenser, the outlet of the condenser is communicated with the inlet of the first electronic expansion valve, the outlet of the first electronic expansion valve is communicated with the first inlet of the intermediate heat exchanger, and the first outlet of the intermediate heat exchanger is communicated with the inlet of the first compressor;

[0009] A secondary refrigeration system, comprising a second compressor, an oil separator, a second electronic expansion valve and a third electronic expansion valve, wherein the outlet of the second compressor is communicated with the inlet of the oil separator, the outlet of the oil separator is communicated with the second inlet of the intermediate heat exchanger, the second outlet of the intermediate heat exchanger is communicated with the inlet of the second electronic expansion valve, the outlet of the second electronic expansion valve is communicated with the inlet of the battery heat exchanger, the outlet of the battery heat exchanger is communicated with the inlet of the second compressor, the inlet of the third electronic expansion valve is communicated with the outlet of the oil separator, and the outlet of the third electronic expansion valve is communicated with the inlet of the battery heat exchanger;

[0010] A first temperature sensor and a first pressure sensor are both arranged at the inlet of the first compressor, the first temperature sensor is used to obtain the actual inlet temperature T1 of the first compressor, and the first pressure sensor is used to obtain the actual inlet pressure P1 of the first compressor;

[0011] A second temperature sensor and a second pressure sensor, both of which are arranged at the inlet of the second compressor, the second temperature sensor is used to obtain the actual inlet temperature T2 of the second compressor, and the second pressure sensor is used to obtain the actual inlet pressure P2 of the second compressor;

[0012] A third temperature sensor is provided at the inlet of the battery heat exchanger and is used to obtain an actual inlet temperature T3 of the battery heat exchanger;

[0013] A control system is communicatively connected to the first electronic expansion valve, the second electronic expansion valve, the third electronic expansion valve, the first temperature sensor, the first pressure sensor, the second temperature sensor, the second pressure sensor and the third temperature sensor, and the control system is used to control the opening of the first electronic expansion valve, the second electronic expansion valve and the third electronic expansion valve according to the P1, the T1, the P2, the T2, the T3 and the detected temperature T0 of the battery pack.

[0014] Optionally, a third pressure sensor is provided at the inlet of the battery heat exchanger, and the third pressure sensor is used to obtain the actual inlet pressure of the battery heat exchanger; and / or, a fourth temperature sensor and a fourth pressure sensor are provided at the outlet of the second compressor, and the fourth temperature sensor is used to obtain the outlet temperature of the second compressor, and the fourth pressure sensor is used to obtain the outlet pressure of the second compressor.

[0015] Optionally, the primary refrigeration system further includes a first drying filter, the inlet of the first drying filter is connected to the outlet of the condenser, and the outlet of the first drying filter is connected to the inlet of the first electronic expansion valve; and / or, the secondary refrigeration system further includes a second drying filter, the inlet of the second drying filter is connected to the outlet of the oil separator, and the outlet of the second drying filter is connected to the second inlet of the intermediate heat exchanger.

[0016] According to another aspect of the present invention, the present invention further provides a control method for an ultra-low temperature direct cooling temperature control system, which is used to control the ultra-low temperature direct cooling temperature control system described in any of the above technical solutions to provide a detection temperature environment for a battery pack, and the control method of the ultra-low temperature direct cooling temperature control system includes using a first temperature control mode to control the operation of the ultra-low temperature direct cooling temperature control system, and the first temperature control mode includes:

[0017] S1, the control system obtains the detection temperature T0;

[0018] S2, starting the primary refrigeration system, and obtaining in real time the actual inlet pressure P1 and the actual inlet temperature T1 of the first compressor, and the actual inlet temperature T3 of the battery heat exchanger, the control system calculates the ideal inlet pressure P1.0 of the first compressor according to T1, and controls the opening of the first electronic expansion valve according to T0, T3, P1 and P1.0;

[0019] S3, starting the secondary refrigeration system after a first preset delay time, and the control system determines whether T0 is greater than the system pressure control boundary temperature T0.0;

[0020] If yes, the control system controls the opening of the third electronic expansion valve to be the first opening, and simultaneously controls the opening of the second electronic expansion valve to be the second opening;

[0021] If not, the control system controls the opening of the third electronic expansion valve to a third opening, and the third opening is smaller than the first opening; at the same time, the actual inlet pressure P2 and the actual inlet temperature T2 of the second compressor are obtained in real time, and the control system calculates the ideal inlet pressure P2.0 of the second compressor according to T2, and calculates the ideal inlet temperature T2.0 of the second compressor according to P2, and controls the opening of the second electronic expansion valve according to T0, T3, P2 and P2.0.

[0022] Optionally, controlling the opening degree of the second electronic expansion valve according to the T0, the T3, the P2 and the P2.0 specifically includes:

[0023] If T3<T0-the stop deviation of the second compressor, the control system controls the opening degree of the second electronic expansion valve to be a second initial opening degree;

[0024] If T3>T0+start-up deviation of the second compressor, the control system performs PID adjustment on the opening of the second electronic expansion valve according to the difference between P2 and P2.0;

[0025] If T0-the stop deviation of the second compressor ≤ T3 ≤ T0+the start deviation of the second compressor, the control system controls both the first compressor and the second compressor to stop, and controls the opening of the second electronic expansion valve to be the second initial opening.

[0026] Optionally, the first opening degree is 30%-40% of the full opening degree of the third electronic expansion valve, and the third opening degree is less than 10% of the full opening degree of the third electronic expansion valve.

[0027] Optionally, the control method of the ultra-low temperature direct cooling temperature control system further includes using a second temperature control mode to control the operation of the ultra-low temperature direct cooling temperature control system, the second temperature control mode and the first temperature control mode are used selectively, and the second temperature control mode includes:

[0028] S10, the control system obtains the detection temperature T0;

[0029] S20, starting the primary refrigeration system, and obtaining in real time the actual inlet pressure P1 and the actual inlet temperature T1 of the first compressor, and the actual inlet temperature T3 of the battery heat exchanger, the control system calculates the ideal inlet pressure P1.0 of the first compressor according to T1, and controls the opening of the first electronic expansion valve according to T0, T3, P1 and P1.0;

[0030] S30, starting the secondary refrigeration system after a delay of a second preset time, the control system performing PID adjustment on the opening of the third electronic expansion valve according to the difference between T3 and T0, and adjusting the opening of the second electronic expansion valve according to the opening of the third electronic expansion valve, the opening of the second electronic expansion valve being inversely proportional to the opening of the third electronic expansion valve.

[0031] Optionally, controlling the opening degree of the first electronic expansion valve according to the T0, the T3, the P1 and the P1.0 specifically includes:

[0032] If T3<T0-the stop deviation of the first compressor, the control system controls the opening degree of the first electronic expansion valve to be a first initial opening degree;

[0033] If T3>T0+start-up deviation of the first compressor, the control system performs PID adjustment on the opening of the first electronic expansion valve according to the difference between P1 and P1.0;

[0034] If T0-the stop deviation of the first compressor ≤ T3 ≤ T0+the start deviation of the first compressor, the control system controls both the first compressor and the second compressor to stop, and controls the opening of the first electronic expansion valve to be the first initial opening.

[0035] Optionally, the control method of the ultra-low temperature direct cooling temperature control system further includes using a defrost mode to control the operation of the ultra-low temperature direct cooling temperature control system, and the defrost mode includes:

[0036] S100, starting the primary refrigeration system, and the control system controls the opening of the first electronic expansion valve to be a first minimum opening;

[0037] S200, starting the secondary refrigeration system after a delay of a third preset time, the control system controls the opening of the second electronic expansion valve to be a second minimum opening, and the control system controls the opening of the third electronic expansion valve to be a fully open opening.

[0038] Optionally, the first minimum opening degree is 10% of the full opening degree of the first electronic expansion valve, and the second minimum opening degree is 10% of the full opening degree of the second electronic expansion valve.

[0039] The beneficial effects of the present invention are:

[0040] The present invention provides an ultra-low temperature direct cooling temperature control system for providing a detection temperature environment for a battery pack, comprising a primary refrigeration system, a secondary refrigeration system, a first temperature sensor, a first pressure sensor, a second temperature sensor, a second pressure sensor, a third temperature sensor and a control system. The primary refrigeration system comprises a first compressor, a condenser, a first electronic expansion valve and an intermediate heat exchanger, and the secondary refrigeration system comprises a second compressor, an oil separator, a second electronic expansion valve and a third electronic expansion valve. The ultra-low temperature direct cooling temperature control system can provide a variety of detection temperature environments for the battery pack by controlling the opening of the first electronic expansion valve, the second electronic expansion valve and the third electronic expansion valve, and has a wide range of applications. Moreover, compared with the solution in the prior art that controls the detection temperature of the battery pack by controlling the opening of a single electronic expansion valve, the temperature control has higher accuracy and stability, thereby improving the accuracy of the battery pack detection results.

[0041] The present invention also provides a control method for an ultra-low temperature direct cooling temperature control system. The control method for an ultra-low temperature direct cooling temperature control system can make the detection temperature provided by the ultra-low temperature direct cooling temperature control system for the battery pack more accurate and stable, thereby improving the accuracy of the battery pack detection results. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 A schematic structural diagram of an ultra-low temperature direct cooling temperature control system provided in an embodiment of the present invention.

[0043] Figure 2 This is a flow chart of the first temperature control mode provided by an embodiment of the present invention.

[0044] Figure 3 This is a flow chart of the second temperature control mode provided by an embodiment of the present invention.

[0045] Figure 4 This is a flow chart of the defrost mode provided by an embodiment of the present invention.

[0046] In the figure:

[0047] 10. Battery heat exchanger;

[0048] 11. First compressor; 12. Condenser; 13. First electronic expansion valve; 14. Intermediate heat exchanger; 15. First temperature sensor; 16. First pressure sensor; 17. First drying filter;

[0049] 21. Second compressor; 22. Oil separator; 23. Second electronic expansion valve; 24. Third electronic expansion valve; 25. Second temperature sensor; 26. Second pressure sensor; 27. Third temperature sensor; 28. Third pressure sensor; 29. ​​Fourth temperature sensor; 30. Fourth pressure sensor; 31. Second drying filter. DETAILED DESCRIPTION

[0050] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0051] In the description of the present invention, it should be noted that the orientations or positional relationships indicated by the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside", etc. are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance. Among them, the terms "first position" and "second position" are two different positions, and the first feature "above", "above" and "above" the second feature include the first feature being directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. The first feature "below", "below" and "below" the second feature include the first feature being directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0052] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0053] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0054] Embodiment 1

[0055] The present embodiment provides an ultra-low temperature direct cooling temperature control system, which can provide a variety of detection temperature environments, has a wide range of applications, and has high accuracy and stability in temperature control of the system.

[0056] like Figure 1 As shown, the ultra-low temperature direct cooling temperature control system includes a primary refrigeration system, a secondary refrigeration system, a first temperature sensor 15, a first pressure sensor 16, a second temperature sensor 25, a second pressure sensor 26, a third temperature sensor 27 and a control system.

[0057] Among them, the primary refrigeration system includes a first compressor 11, a condenser 12, a first electronic expansion valve 13 and an intermediate heat exchanger 14. Specifically, the outlet of the first compressor 11 is connected to the inlet of the condenser 12, the outlet of the condenser 12 is connected to the inlet of the first electronic expansion valve 13, the outlet of the first electronic expansion valve 13 is connected to the first inlet of the intermediate heat exchanger 14, the first outlet of the intermediate heat exchanger 14 is connected to the inlet of the first compressor 11, and a first temperature sensor 15 and a first pressure sensor 16 are provided at the inlet of the first compressor 11. The first temperature sensor 15 is used to obtain the actual inlet temperature T1 of the first compressor 11, and the first pressure sensor 16 is used to obtain the actual inlet pressure P1 of the first compressor 11.

[0058] The secondary refrigeration system includes a second compressor 21, an oil separator 22, a second electronic expansion valve 23 and a third electronic expansion valve 24. Specifically, the outlet of the second compressor 21 is connected to the inlet of the oil separator 22, the outlet of the oil separator 22 is connected to the second inlet of the intermediate heat exchanger 14, the second outlet of the intermediate heat exchanger 14 is connected to the inlet of the second electronic expansion valve 23, the outlet of the second electronic expansion valve 23 is connected to the inlet of the battery heat exchanger 10 of the battery pack, the outlet of the battery heat exchanger 10 is connected to the inlet of the second compressor 21, and the inlet of the second compressor 21 is provided with a There are a second temperature sensor 25 and a second pressure sensor 26. The second temperature sensor 25 is used to obtain the actual inlet temperature T2 of the second compressor 21. The second pressure sensor 26 is used to obtain the actual inlet pressure P2 of the second compressor 21. The inlet of the third electronic expansion valve 24 is connected to the outlet of the oil separator 22. The outlet of the third electronic expansion valve 24 is connected to the inlet of the battery heat exchanger 10 of the battery pack. A third temperature sensor 27 is provided at the inlet of the battery heat exchanger 10. The third temperature sensor 27 is used to obtain the actual inlet temperature T3 of the battery heat exchanger 10.

[0059] The control system is communicatively connected to the first electronic expansion valve 13, the second electronic expansion valve 23, the third electronic expansion valve 24, the first temperature sensor 15, the first pressure sensor 16, the second temperature sensor 25, the second pressure sensor 26 and the third temperature sensor 27. The control system is used to control the opening of the first electronic expansion valve 13, the second electronic expansion valve 23 and the third electronic expansion valve 24 according to P1, T1, P2, T2, T3 and the detected temperature T0 of the battery pack.

[0060] The ultra-low temperature direct cooling temperature control system provided in this embodiment can provide an ultra-low temperature (-40°C to -80°C) detection environment for the battery pack by cascading the primary refrigeration system and the secondary refrigeration system. By controlling the opening of the first electronic expansion valve 13, the second electronic expansion valve 23, and the third electronic expansion valve 24, a variety of detection temperature environments can be provided for the battery pack, which has a wide range of applications and does not require additional heat sources. In addition, compared with the solution in the prior art of controlling the detection temperature of the battery pack by controlling the opening of a single electronic expansion valve, the temperature control has higher accuracy and stability, which improves the accuracy of the battery pack detection results.

[0061] It is worth noting that the battery heat exchanger 10 is used to exchange heat with the battery pack to cool the battery pack.

[0062] Optionally, the control system may employ a PID controller.

[0063] Further, see Figure 1 In a possible embodiment, a third pressure sensor 28 is further provided at the inlet of the battery heat exchanger 10, and the third pressure sensor 28 is used to obtain the actual inlet pressure of the battery heat exchanger 10. By providing the third pressure sensor 28 at the inlet of the battery heat exchanger 10, the inlet pressure of the battery heat exchanger 10 can be monitored in real time.

[0064] Further, see Figure 1 In another possible embodiment, a fourth temperature sensor 29 and a fourth pressure sensor 30 may be provided at the outlet of the second compressor 21. The fourth temperature sensor 29 is used to obtain the outlet temperature of the second compressor 21, and the fourth pressure sensor 30 is used to obtain the outlet pressure of the second compressor 21. By monitoring the outlet temperature and outlet pressure of the second compressor 21 through the fourth temperature sensor 29 and the fourth pressure sensor 30, the working state of the second compressor 21 can be understood in real time.

[0065] In this embodiment, a third pressure sensor 28 is provided at the inlet of the battery heat exchanger 10 , and a fourth temperature sensor 29 and a fourth pressure sensor 30 are provided at the outlet of the second compressor 21 .

[0066] Optionally, continue to see Figure 1In a possible embodiment, the primary refrigeration system further includes a first drying filter 17, the inlet of the first drying filter 17 is connected to the outlet of the condenser 12, and the outlet of the first drying filter 17 is connected to the inlet of the first electronic expansion valve 13. The first drying filter 17 can block solid particles in the air and prevent them from entering the primary refrigeration system, thereby reducing the risk of clogging of pipelines and components in the primary refrigeration system and improving the working efficiency of the primary refrigeration system. In addition, the first drying filter 17 can also absorb moisture to prevent it from condensing into water in the primary refrigeration system, which helps to maintain the stability of the operation of the primary refrigeration system.

[0067] Optionally, continue to see Figure 1 In another possible embodiment, the secondary refrigeration system further includes a second filter dryer 31, the inlet of the second filter dryer 31 is connected to the outlet of the oil separator 22, and the outlet of the second filter dryer 31 is connected to the second inlet of the intermediate heat exchanger 14. The second filter dryer 31 can block solid particles in the air and prevent them from entering the secondary refrigeration system, thereby reducing the risk of blockage of pipelines and components in the secondary refrigeration system and improving the working efficiency of the secondary refrigeration system. In addition, the second filter dryer 31 can also absorb moisture to prevent it from condensing into water in the secondary refrigeration system, which helps to maintain the stability of the operation of the secondary refrigeration system.

[0068] Embodiment 2

[0069] The present embodiment provides a control method for an ultra-low temperature direct cooling temperature control system. The control method for an ultra-low temperature direct cooling temperature control system can make the detection temperature provided by the ultra-low temperature direct cooling temperature control system in Embodiment 1 for the battery pack more accurate and stable, thereby improving the accuracy of the battery pack detection results.

[0070] The control method of the ultra-low temperature direct cooling temperature control system includes using a first temperature control mode to control the operation of the ultra-low temperature direct cooling temperature control system.

[0071] Specifically, the control steps of the first temperature control mode include:

[0072] S1, the control system obtains the detection temperature T0;

[0073] It can be understood that the detected temperature T0 is the temperature that the battery pack is expected to reach, and is generally input into the control system by manual input.

[0074] S2, start the primary refrigeration system, and obtain the actual inlet pressure P1 and actual inlet temperature T1 of the first compressor 11, and the actual inlet temperature T3 of the battery heat exchanger 10 in real time. The control system calculates the ideal inlet pressure P1.0 of the first compressor 11 according to T1, and controls the opening of the first electronic expansion valve 13 according to T0, T3, P1 and P1.0;

[0075] It is worth noting that P1.0 can be obtained through T1 by using a table lookup method. For example, in this embodiment, the refrigerant of the primary refrigeration system uses R404A, and the temperature and pressure comparison table of R404A refrigerant can be consulted to obtain P1.0 corresponding to T1.

[0076] Optionally, controlling the opening degree of the first electronic expansion valve 13 according to T0, T3, P1 and P1.0 specifically includes:

[0077] If T3<T0-the stop deviation of the first compressor 11 , the control system controls the opening of the first electronic expansion valve 13 to be a first initial opening; optionally, the first initial opening may be 50% of the full opening of the first electronic expansion valve 13 .

[0078] If T3>T0+the starting deviation of the first compressor 11, the control system performs PID adjustment on the opening degree of the first electronic expansion valve 13 according to the difference between P1 and P1.0.

[0079] If T0-the stop deviation of the first compressor 11 ≤ T3 ≤ T0+the start deviation of the first compressor 11, the control system controls both the first compressor 11 and the second compressor 21 to stop, and controls the opening of the first electronic expansion valve 13 to be the first initial opening.

[0080] It is worth noting that when T0-the stop deviation of the first compressor 11 ≤ T3 ≤ T0 + the start deviation of the first compressor 11 is satisfied, it can be considered that the current temperature T3 has reached T0, and at this time, there is no need for the first compressor 11 and the second compressor 21 to continue working. This setting can avoid repeated start and stop of the first compressor 11 and the second compressor 21.

[0081] It is worth noting that the stop deviation and start deviation of the first compressor 11 can be calibrated through a large number of experiments. In this embodiment, the stop deviation of the first compressor 11 is 9°C, and the start deviation of the first compressor 11 is 3°C.

[0082] It is worth noting that the principle of PID regulation here is: if P1>P1.0, the opening of the first electronic expansion valve 13 is controlled to decrease, and if P1<P1.0, the opening of the first electronic expansion valve 13 is controlled to increase, so that the difference between P1 and P1.0 is reduced, and through repeated adjustments, P1 is finally made equal to P1.0. The specific algorithm of PID is the existing technology and will not be described in detail here.

[0083] S3, after a first preset delay time, the secondary refrigeration system is started, and the control system determines whether T0 is greater than the system pressure control boundary temperature T0.0;

[0084] If so, the control system controls the opening of the third electronic expansion valve 24 to be a first opening, and controls the opening of the second electronic expansion valve 23 to be a second opening; optionally, the second opening can be 20% of the full opening of the second electronic expansion valve 23.

[0085] If not, the control system controls the opening of the third electronic expansion valve 24 to a third opening, which is smaller than the first opening; at the same time, the actual inlet pressure P2 and the actual inlet temperature T2 of the second compressor 21 are obtained in real time, and the control system calculates the ideal inlet pressure P2.0 of the second compressor 21 according to T2, and the ideal inlet temperature T2.0 of the second compressor 21 according to P2, and controls the opening of the second electronic expansion valve 23 according to T0, T3, P2 and P2.0.

[0086] It is worth noting that P2.0 can be obtained through T2, and T2.0 can be obtained through P2 by looking up a table. For example, in this embodiment, the refrigerant of the two-stage refrigeration system uses R508B, and the temperature and pressure comparison table of R508B refrigerant can be consulted to obtain P2.0 corresponding to T2, and T2.0 corresponding to P2.

[0087] Of course, T2.0 can also be calculated by a formula. In this embodiment, the specific calculation formula is as follows:

[0088] When 2725.9Kpa≥P2>1127.9Kpa, T2.0=(33*LN(P2))-261;

[0089] When 1127.9Kpa≥P2>488.43Kpa, T2.0=(0.03*P2)-65;

[0090] When 488.43Kpa≥P2>149.51Kpa, T2.0=(0.06*P2)-78;

[0091] When 149.51≥P2, T2.0=(-0.0003*P2²)+(0.15*P2)-87.

[0092] It is worth noting that when the ultra-low temperature direct cooling temperature control system is running stably, under ideal conditions, T2.0 should be equal to T3, which indicates that the ultra-low temperature direct cooling temperature control system provides a stable ultra-low temperature environment for the battery pack. Therefore, the operating status of the ultra-low temperature direct cooling temperature control system can be monitored by the difference between T2.0 and T3. If it is always impossible to make T2.0 equal to T3, or to make the difference between T2.0 and T3 within the error range, there may be problems such as parts damage, refrigerant leakage, and refrigerant shortage, and the ultra-low temperature direct cooling temperature control system should be repaired.

[0093] Optionally, controlling the opening degree of the second electronic expansion valve 23 according to T0, T3, P2 and P2.0 specifically includes:

[0094] If T3<T0-the stop deviation of the second compressor 21 , the control system controls the opening of the second electronic expansion valve 23 to be a second initial opening; optionally, the second initial opening may be 50% of the full opening of the second electronic expansion valve 23 .

[0095] If T3>T0+the starting deviation of the second compressor 21, the control system performs PID adjustment on the opening degree of the second electronic expansion valve 23 according to the difference between P2 and P2.0.

[0096] If T0-the stop deviation of the second compressor 21 ≤ T3 ≤ T0+the start deviation of the second compressor 21, the control system controls both the first compressor 11 and the second compressor 21 to stop, and controls the opening of the second electronic expansion valve 23 to be the second initial opening.

[0097] It is worth noting that when T0-the stop deviation of the second compressor 21 ≤ T3 ≤ T0 + the start deviation of the second compressor 21 is satisfied, it can be considered that the current temperature T3 has reached T0, and at this time, there is no need for the first compressor 11 and the second compressor 21 to continue working. This setting can avoid repeated start and stop of the first compressor 11 and the second compressor 21.

[0098] It is worth noting that the stop deviation and start deviation of the second compressor 21 can be calibrated through a large number of experiments. In this embodiment, the stop deviation of the second compressor 21 is 9°C, and the start deviation of the second compressor 21 is 3°C.

[0099] It is worth noting that the principle of PID regulation here is: if P2>P2.0, the opening of the second electronic expansion valve 23 is controlled to decrease; if P2<P2.0, the opening of the second electronic expansion valve 23 is controlled to increase, so that the difference between P2 and P2.0 is reduced, and through repeated adjustment, P2 is finally made equal to P2.0.

[0100] Optionally, the first opening degree is 30%-40% of the full opening degree of the third electronic expansion valve 24 , and the third opening degree is less than 10% of the full opening degree of the third electronic expansion valve 24 .

[0101] Optionally, the control system adopts a PID controller.

[0102] Optionally, the first preset time may be 2 minutes to 3 minutes.

[0103] It is worth noting that the system pressure control boundary temperature T0.0 can be calibrated based on a large number of experiments. In this embodiment, T0.0=-42°C.

[0104] Furthermore, the control method of the ultra-low temperature direct cooling temperature control system also includes using a second temperature control mode to control the operation of the ultra-low temperature direct cooling temperature control system, and the second temperature control mode and the first temperature control mode are used selectively.

[0105] Specifically, the control steps of the second temperature control mode include:

[0106] S10, the control system obtains the detection temperature T0;

[0107] It can be understood that the detected temperature T0 is the temperature that the battery pack is expected to reach, and is generally input into the control system by manual input.

[0108] S20, start the primary refrigeration system, and obtain the actual inlet pressure P1 and actual inlet temperature T1 of the first compressor 11, and the actual inlet temperature T3 of the battery heat exchanger 10 in real time. The control system calculates the ideal inlet pressure P1.0 of the first compressor 11 according to T1, and controls the opening of the first electronic expansion valve 13 according to T0, T3, P1 and P1.0;

[0109] It is worth noting that P1.0 can be obtained through T1 by using a table lookup method. For example, in this embodiment, the refrigerant of the primary refrigeration system uses R404A, and the temperature and pressure comparison table of R404A refrigerant can be consulted to obtain P1.0 corresponding to T1.

[0110] Optionally, controlling the opening degree of the first electronic expansion valve 13 according to T0, T3, P1 and P1.0 specifically includes:

[0111] If T3<T0-the stop deviation of the first compressor 11 , the control system controls the opening of the first electronic expansion valve 13 to be a first initial opening; optionally, the first initial opening may be 50% of the full opening of the first electronic expansion valve 13 .

[0112] If T3>T0+the starting deviation of the first compressor 11, the control system performs PID adjustment on the opening degree of the first electronic expansion valve 13 according to the difference between P1 and P1.0.

[0113] If T0-the stop deviation of the first compressor 11 ≤ T3 ≤ T0+the start deviation of the first compressor 11, the control system controls both the first compressor 11 and the second compressor 21 to stop, and controls the opening of the first electronic expansion valve 13 to be the first initial opening.

[0114] It is worth noting that when T0-the stop deviation of the first compressor 11 ≤ T3 ≤ T0 + the start deviation of the first compressor 11 is satisfied, it can be considered that the current temperature T3 has reached T0, and at this time, there is no need for the first compressor 11 and the second compressor 21 to continue working. This setting can avoid repeated start and stop of the first compressor 11 and the second compressor 21.

[0115] It is worth noting that the stop deviation and start deviation of the first compressor 11 can be calibrated through a large number of experiments. In this embodiment, the stop deviation of the first compressor 11 is 9°C, and the start deviation of the first compressor 11 is 3°C.

[0116] It is worth noting that the principle of PID regulation here is: if P1>P1.0, the opening of the first electronic expansion valve 13 is controlled to decrease, and if P1<P1.0, the opening of the first electronic expansion valve 13 is controlled to increase, so that the difference between P1 and P1.0 is reduced, and through repeated adjustments, P1 is finally made equal to P1.0. The specific algorithm of PID is the existing technology and will not be described in detail here.

[0117] S30, starting the secondary refrigeration system after a delay of a second preset time, the control system performs PID adjustment on the opening of the third electronic expansion valve 24 according to the difference between T3 and T0, and adjusts the opening of the second electronic expansion valve 23 according to the opening of the third electronic expansion valve 24, and the opening of the second electronic expansion valve 23 is inversely proportional to the opening of the third electronic expansion valve 24.

[0118] It is worth noting that the principle of PID regulation here is: if T3>T0, the opening of the third electronic expansion valve 24 is controlled to decrease; if T3<T0, the opening of the third electronic expansion valve 24 is controlled to increase, so that the difference between T3 and T0 is reduced, and through repeated adjustment, T3 is finally made equal to T0.

[0119] Optionally, the second preset time may be 2 minutes to 3 minutes.

[0120] Furthermore, the control method of the ultra-low temperature direct cooling temperature control system also includes using a defrost mode to control the operation of the ultra-low temperature direct cooling temperature control system.

[0121] Specifically, the control steps of the defrost mode include:

[0122] S100 , starting the primary refrigeration system, and the control system controls the opening of the first electronic expansion valve 13 to be a first minimum opening; optionally, the first minimum opening may be 10% of the full opening of the first electronic expansion valve 13 .

[0123] S200, after a delay of a third preset time, the secondary refrigeration system is started, the control system controls the opening of the second electronic expansion valve 23 to be the second minimum opening, and the control system controls the opening of the third electronic expansion valve 24 to be the full opening. Optionally, the second minimum opening is 10% of the full opening of the second electronic expansion valve 23.

[0124] Optionally, the third preset time may be 2 minutes to 3 minutes.

[0125] It is worth mentioning that when the external ambient temperature is low and causes the first compressor 11 and the second compressor 21 to frost, the ultra-low temperature direct cooling temperature control system is generally started in the defrost mode first. After the first compressor 11 and the second compressor 21 are defrosted, the first temperature control mode and the second temperature control mode are selectively used to provide a detection temperature environment for the battery pack.

[0126] Obviously, the above embodiments of the present invention are only examples for clearly explaining the present invention, and are not intended to limit the implementation methods of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. An ultra-low temperature direct cooling temperature control system, used to provide a detection temperature environment for a battery pack, wherein the battery pack comprises a battery heat exchanger (10), characterized in that: The ultra-low temperature direct cooling temperature control system comprises: A primary refrigeration system, comprising a first compressor (11), a condenser (12), a first electronic expansion valve (13) and an intermediate heat exchanger (14); the outlet of the first compressor (11) is connected to the inlet of the condenser (12), the outlet of the condenser (12) is connected to the inlet of the first electronic expansion valve (13), the outlet of the first electronic expansion valve (13) is connected to the first inlet of the intermediate heat exchanger (14), and the first outlet of the intermediate heat exchanger (14) is connected to the inlet of the first compressor (11); A two-stage refrigeration system, comprising a second compressor (21), an oil separator (22), a second electronic expansion valve (23) and a third electronic expansion valve (24), wherein the outlet of the second compressor (21) is connected to the inlet of the oil separator (22), the outlet of the oil separator (22) is connected to the second inlet of the intermediate heat exchanger (14), the second outlet of the intermediate heat exchanger (14) is connected to the inlet of the second electronic expansion valve (23), the outlet of the second electronic expansion valve (23) is connected to the inlet of the battery heat exchanger (10), the outlet of the battery heat exchanger (10) is connected to the inlet of the second compressor (21), the inlet of the third electronic expansion valve (24) is connected to the outlet of the oil separator (22), and the outlet of the third electronic expansion valve (24) is connected to the inlet of the battery heat exchanger (10); a first temperature sensor (15) and a first pressure sensor (16), both of which are arranged at the inlet of the first compressor (11), the first temperature sensor (15) being used to obtain an actual inlet temperature T1 of the first compressor (11), and the first pressure sensor (16) being used to obtain an actual inlet pressure P1 of the first compressor (11); A second temperature sensor (25) and a second pressure sensor (26), both of which are arranged at the inlet of the second compressor (21), the second temperature sensor (25) being used to obtain an actual inlet temperature T2 of the second compressor (21), and the second pressure sensor (26) being used to obtain an actual inlet pressure P2 of the second compressor (21); a third temperature sensor (27), arranged at the inlet of the battery heat exchanger (10), and used to obtain an actual inlet temperature T3 of the battery heat exchanger (10); A control system is communicatively connected to the first electronic expansion valve (13), the second electronic expansion valve (23), the third electronic expansion valve (24), the first temperature sensor (15), the first pressure sensor (16), the second temperature sensor (25), the second pressure sensor (26) and the third temperature sensor (27), and the control system is used to control the opening of the first electronic expansion valve (13), the second electronic expansion valve (23) and the third electronic expansion valve (24) according to the P1, the T1, the P2, the T2, the T3 and the detected temperature T0 of the battery pack.

2. The ultra-low temperature direct cooling temperature control system according to claim 1, characterized in that: A third pressure sensor (28) is also provided at the inlet of the battery heat exchanger (10), and the third pressure sensor (28) is used to obtain the actual inlet pressure of the battery heat exchanger (10); And / or, a fourth temperature sensor (29) and a fourth pressure sensor (30) are provided at the outlet of the second compressor (21), the fourth temperature sensor (29) being used to obtain the outlet temperature of the second compressor (21), and the fourth pressure sensor (30) being used to obtain the outlet pressure of the second compressor (21).

3. The ultra-low temperature direct cooling temperature control system according to claim 1, characterized in that: The primary refrigeration system further comprises a first drying filter (17), wherein an inlet of the first drying filter (17) is communicated with an outlet of the condenser (12), and an outlet of the first drying filter (17) is communicated with an inlet of the first electronic expansion valve (13); And / or, the secondary refrigeration system further comprises a second drying filter (31), the inlet of the second drying filter (31) being connected to the outlet of the oil separator (22), and the outlet of the second drying filter (31) being connected to the second inlet of the intermediate heat exchanger (14).

4. A control method for an ultra-low temperature direct cooling temperature control system, used to control the ultra-low temperature direct cooling temperature control system according to any one of claims 1 to 3 to provide a detection temperature environment for a battery pack, characterized in that: The control method of the ultra-low temperature direct cooling temperature control system includes using a first temperature control mode to control the operation of the ultra-low temperature direct cooling temperature control system, and the first temperature control mode includes: S1, the control system obtains the detection temperature T0; S2, starting the primary refrigeration system, and obtaining in real time the actual inlet pressure P1 and the actual inlet temperature T1 of the first compressor (11), and the actual inlet temperature T3 of the battery heat exchanger (10), the control system calculating the ideal inlet pressure P1.0 of the first compressor (11) according to T1, and controlling the opening of the first electronic expansion valve (13) according to T0, T3, P1 and P1.0; S3, starting the secondary refrigeration system after a first preset delay time, and the control system determines whether T0 is greater than the system pressure control boundary temperature T0.0; If so, the control system controls the opening degree of the third electronic expansion valve (24) to be the first opening degree, and simultaneously controls the opening degree of the second electronic expansion valve (23) to be the second opening degree; If not, the control system controls the opening of the third electronic expansion valve (24) to be a third opening, wherein the third opening is smaller than the first opening; and simultaneously obtains in real time the actual inlet pressure P2 and the actual inlet temperature T2 of the second compressor (21), the control system calculates the ideal inlet pressure P2.0 of the second compressor (21) based on the T2, and calculates the ideal inlet temperature T2.0 of the second compressor (21) based on the P2, and controls the opening of the second electronic expansion valve (23) based on the T0, the T3, the P2 and the P2.

0.

5. The control method of the ultra-low temperature direct cooling temperature control system according to claim 4, characterized in that: Controlling the opening degree of the second electronic expansion valve (23) according to the T0, the T3, the P2 and the P2.0 specifically includes: If T3<T0-the stop deviation of the second compressor (21), the control system controls the opening degree of the second electronic expansion valve (23) to be a second initial opening degree; If T3>T0+start-up deviation of the second compressor (21), the control system performs PID adjustment on the opening degree of the second electronic expansion valve (23) according to the difference between P2 and P2.0; If T0-the stop deviation of the second compressor (21) ≤ T3 ≤ T0+the start deviation of the second compressor (21), the control system controls both the first compressor (11) and the second compressor (21) to stop, and simultaneously controls the opening degree of the second electronic expansion valve (23) to be the second initial opening degree.

6. The control method of the ultra-low temperature direct cooling temperature control system according to claim 4, characterized in that: The first opening degree is 30%-40% of the full opening degree of the third electronic expansion valve (24), and the third opening degree is less than 10% of the full opening degree of the third electronic expansion valve (24).

7. The control method of the ultra-low temperature direct cooling temperature control system according to claim 4, characterized in that: The control method of the ultra-low temperature direct cooling temperature control system further includes using a second temperature control mode to control the operation of the ultra-low temperature direct cooling temperature control system, wherein the second temperature control mode and the first temperature control mode are used selectively, and the second temperature control mode includes: S10, the control system obtains the detection temperature T0; S20, starting the primary refrigeration system, and obtaining in real time the actual inlet pressure P1 and the actual inlet temperature T1 of the first compressor (11), and the actual inlet temperature T3 of the battery heat exchanger (10), the control system calculating the ideal inlet pressure P1.0 of the first compressor (11) according to T1, and controlling the opening of the first electronic expansion valve (13) according to T0, T3, P1, and P1.0; S30, starting the secondary refrigeration system after a delay of a second preset time, the control system performing PID adjustment on the opening of the third electronic expansion valve (24) according to the difference between T3 and T0, and adjusting the opening of the second electronic expansion valve (23) according to the opening of the third electronic expansion valve (24), the opening of the second electronic expansion valve (23) being inversely proportional to the opening of the third electronic expansion valve (24).

8. The control method of the ultra-low temperature direct cooling temperature control system according to claim 4 or 7, characterized in that: Controlling the opening degree of the first electronic expansion valve (13) according to the T0, the T3, the P1 and the P1.0 specifically includes: If T3<T0-the stop deviation of the first compressor (11), the control system controls the opening degree of the first electronic expansion valve (13) to be a first initial opening degree; If T3>T0+start-up deviation of the first compressor (11), the control system performs PID adjustment on the opening degree of the first electronic expansion valve (13) according to the difference between P1 and P1.0; If T0-the stop deviation of the first compressor (11) ≤ T3 ≤ T0+the start deviation of the first compressor (11), the control system controls both the first compressor (11) and the second compressor (21) to stop, and simultaneously controls the opening of the first electronic expansion valve (13) to be the first initial opening.

9. The control method of the ultra-low temperature direct cooling temperature control system according to claim 4 or 7, characterized in that: The control method of the ultra-low temperature direct cooling temperature control system further includes using a defrost mode to control the operation of the ultra-low temperature direct cooling temperature control system, and the defrost mode includes: S100, starting the primary refrigeration system, and the control system controls the opening degree of the first electronic expansion valve (13) to be a first minimum opening degree; S200, starting the secondary refrigeration system after a delay of a third preset time, the control system controlling the opening of the second electronic expansion valve (23) to be a second minimum opening, and the control system controlling the opening of the third electronic expansion valve (24) to be a fully open opening.

10. The control method of the ultra-low temperature direct cooling temperature control system according to claim 9, characterized in that: The first minimum opening degree is 10% of the full opening degree of the first electronic expansion valve (13), and the second minimum opening degree is 10% of the full opening degree of the second electronic expansion valve (23).

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