A battery cooling system and cooling control method thereof

Abstract

The present invention discloses a battery cooling system and a cooling control method thereof, which comprises a battery module and a direct cooling unit, wherein the battery module is connected to the direct cooling unit via a refrigerant pipeline, the battery module comprises a plurality of battery assemblies arranged in parallel, the battery assembly comprises an expansion valve and a battery pack arranged in series via a refrigerant pipeline, wherein the inlet of the expansion valve is connected to the outlet of the direct cooling unit, and the outlet of the battery pack is connected to the inlet of the direct cooling unit. The present invention eliminates the heat exchange module, and takes away the heat of the battery module by vaporizing the refrigerant of the refrigerant, which can effectively provide an energy efficiency ratio.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to a battery cooling system and a cooling control method thereof. Background Art

[0002] With the rapid development of new energy vehicles, energy storage power stations and other industries, energy storage batteries, as core components, are receiving more and more attention for their performance stability and safety. In actual use, energy storage batteries will generate a lot of heat. In order to avoid the energy storage battery temperature being too high, in the prior art, a corresponding air cooling or liquid cooling system is usually set up to cool the energy storage battery. However, in the process of cooling the energy storage battery, indirect cooling systems such as air cooling or liquid cooling need to first cool the coolant or air with a refrigerant, and then cool the energy storage battery with the coolant or air. The loss of cooling capacity in this process is large, which makes the system energy efficiency of the cooling system relatively low. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a battery cooling system and a cooling control method thereof, so as to solve the problem of relatively low energy efficiency of the existing battery cooling system.

[0004] In order to solve the above technical problems, the technical solution adopted by the present invention is: a battery cooling system, which includes a direct cooling unit and a battery module, the direct cooling unit includes a compressor, a condenser and a heater, the compressor, condenser and heater are connected in series through a refrigerant pipe in sequence, and the inlet of the compressor is connected to the outlet of the battery module, and the outlet of the heater is connected to the inlet of the battery module.

[0005] Furthermore, in the battery cooling system described in the present invention, the battery module includes a plurality of battery assemblies arranged in parallel, and the battery assembly includes an expansion valve and a battery pack arranged in series, wherein the inlet of the expansion valve is connected to the outlet of the heater, and the outlet of the battery pack is connected to the inlet of the compressor.

[0006] Furthermore, in the battery cooling system of the present invention, the battery assembly further includes a temperature sensor, and the temperature sensor is disposed between the expansion valve and the battery pack.

[0007] Accordingly, another object of the present invention is to disclose a cooling control method, which is applied to the battery cooling system as described above, and the method comprises the following steps:

[0008] S1: Obtaining the heat load of the battery module, the cooling capacity of the direct cooling unit, and the condensing temperature of the unit;

[0009] S2: determining the opening of the expansion valve in each battery assembly in the battery module according to the heat load, the cooling capacity of the unit and the condensing temperature of the unit;

[0010] S3: According to the opening of the expansion valve in each battery assembly, the opening of the corresponding expansion valve is adjusted.

[0011] Furthermore, in the cooling control method of the present invention, in step S2, the following steps are included:

[0012] S21: Calculating the ratio of the heat load to the cooling capacity of the unit;

[0013] S22: comparing the ratio with a plurality of preset ratio intervals to determine a target interval in which the ratio is located, wherein the plurality of preset ratio intervals include a first ratio interval, a second ratio interval, and a third ratio interval;

[0014] S23: Determine the opening of the expansion valve in each battery assembly according to the target interval and the unit condensing temperature.

[0015] Further, in the cooling control method of the present invention, in step S23, the target interval is a first ratio interval, and the unit condensing temperature is compared with a plurality of temperature intervals corresponding to the first ratio interval:

[0016] When the condensing temperature of the unit is within the first temperature range, the openings of the plurality of expansion valves are correspondingly set to a first opening combination;

[0017] When the condensing temperature of the unit is within the second temperature range, the openings of the plurality of expansion valves are correspondingly set to a second opening combination;

[0018] When the condensing temperature of the unit is within the third temperature range, the openings of the plurality of expansion valves are correspondingly set to a third opening combination.

[0019] Furthermore, in the cooling control method of the present invention, in step S23, the following steps are included:

[0020] When the target interval is a second ratio interval, obtaining a plurality of temperature intervals corresponding to the second ratio interval;

[0021] The opening degree of the expansion valve in each battery assembly is determined according to the unit condensing temperature and a plurality of temperature intervals corresponding to the second ratio interval.

[0022] Further, in the cooling control method of the present invention, when the unit condensing temperature and the multiple temperature intervals corresponding to the second ratio interval include a fourth temperature interval and a fifth temperature interval, in step S23, the following steps are also included:

[0023] When the condensing temperature of the unit is within the fourth temperature range, the openings of the plurality of expansion valves are correspondingly set to a fourth opening combination;

[0024] When the condensing temperature of the unit is within the fifth temperature range, the openings of the plurality of expansion valves are correspondingly set to the fifth opening combination.

[0025] Furthermore, in the cooling control method of the present invention, in step S23, the following steps are included:

[0026] When the target interval is a third ratio interval, obtaining a plurality of temperature intervals corresponding to the third ratio interval;

[0027] The opening degree of the expansion valve in each battery assembly is determined according to the unit condensing temperature and a plurality of temperature intervals corresponding to the third ratio interval.

[0028] Further, in the cooling control method of the present invention, when the unit condensing temperature and the multiple temperature intervals corresponding to the third ratio interval include a sixth temperature interval and a seventh temperature interval, in step S23, the following steps are also included:

[0029] When the condensing temperature of the unit is within the sixth temperature range, the openings of the plurality of expansion valves are correspondingly set to the sixth opening combination;

[0030] When the condensing temperature of the unit is within the seventh temperature range, the openings of the plurality of expansion valves are correspondingly set to the seventh opening combination.

[0031] The beneficial effect of the present invention is that compared with indirect cooling (such as air cooling or liquid cooling), the present invention reduces the link of cooling the coolant or air by the refrigerant, and directly cools the battery module by the refrigerant, thereby reducing the loss of the refrigerant and improving the energy efficiency of the battery cooling system. In other words, the battery cooling system of the present invention eliminates the heat exchange module, and directly takes away the heat of the battery module by the vaporization of the refrigerant, thereby effectively improving the energy efficiency of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 A schematic diagram of the system structure of a battery cooling system according to an embodiment of the present invention;

[0033] Figure 2 A flowchart of the steps of the cooling control method according to the present invention in one embodiment;

[0034] Figure 3 The present invention is another flowchart of the cooling control method in one embodiment.

[0035] Description of labels:

[0036] 1. Compressor;

[0037] 2. Condenser;

[0038] 3. Condensing fan;

[0039] 4. Heater;

[0040] 5. Battery module;

[0041] 6. Expansion valve;

[0042] 7. Battery pack;

[0043] 8. Temperature sensor;

[0044] 9. Refrigerant pipeline. DETAILED DESCRIPTION

[0045] In order to explain the technical content, achieved objectives and effects of the present invention in detail, the following is an explanation in combination with the implementation modes and the accompanying drawings.

[0046] In the field of new energy storage, as the capacity of energy storage containers gradually expands, the requirements for operating conditions gradually increase. In order to maintain the appropriate charging and discharging operating temperature range of the battery, corresponding units can be set up to provide continuous cooling and heat to the battery pack thermal management system through the units. For the unit, if an indirect cooling unit is used, since the indirect cooling (air cooling or liquid cooling) unit needs to cool the coolant or air through the refrigerant, and then cool the battery through the coolant or air, there is a loss of cooling capacity, and the system energy efficiency ratio is more difficult to improve by relying solely on system solution design, electrical equipment selection and other means. To this end, this solution provides a battery cooling system for a direct cooling unit, that is, directly cooling the battery pack through the refrigerant, reducing the link of refrigerant cooling the coolant or air, so as to improve the energy efficiency ratio of the battery cooling system.

[0047] like Figure 1 As shown, the present invention relates to a battery cooling system, which is provided with a direct cooling unit (i.e., a direct cooling unit), which can meet the larger cooling power and heating power requirements, and belongs to the larger unit type in the energy storage industry. The direct cooling unit also has the advantages of high comprehensive energy efficiency ratio, multi-functional matching, high installation freedom, etc. It can provide direct cooling and heat output for the battery module within a large range of ambient temperatures, while greatly improving the system energy efficiency ratio. It should be noted that the energy efficiency ratio is the ratio between cooling capacity (or cooling power) and input energy (usually electricity). The energy efficiency ratio can be used to reflect the efficiency of the system in converting electrical energy into cooling capacity under specific working conditions. In addition, it should also be noted that this solution is for a single battery cluster system with a battery pack capacity of less than 1500V and a capacity of less than 400kwh. The following is combined with Figure 1 The battery cooling system of the present invention is specifically described.

[0048] like Figure 1 As shown, the battery cooling system of the present invention includes a direct cooling unit and a battery module 5, wherein the direct cooling unit includes a compressor 1, a condenser 2 and a heater 4, wherein the compressor, the condenser and the heater are connected in series through a refrigerant pipe 9 in sequence, and the inlet of the compressor 1 is connected to the outlet of the battery module 5, and the outlet of the heater 4 is connected to the inlet of the battery module 5.

[0049] Compressor: Responsible for sucking in low-temperature and low-pressure refrigerant vapor and compressing it into high-temperature and high-pressure superheated steam through mechanical work, providing power for the refrigeration cycle.

[0050] Condenser: It is a heat-releasing component in the refrigeration system, responsible for cooling the high-temperature and high-pressure refrigerant vapor discharged from the compressor into a high-pressure liquid refrigerant, while releasing a large amount of heat. In actual use, after the high-temperature and high-pressure refrigerant vapor enters the condenser, it exchanges heat with the surrounding air or cooling water through the heat sink. The refrigerant vapor gradually loses heat, the temperature decreases, and finally condenses into a high-pressure liquid refrigerant. In addition, it should be noted that in an optional embodiment, a condensing fan can also be provided on the refrigerant pipeline. The condensing fan 3 is an auxiliary equipment of the condenser. The condensing fan 3 can generate wind force by rotation to blow away the hot air around the condenser, thereby quickly taking away the heat released by the condenser, reducing the temperature of the condenser, and thereby ensuring that the condenser can continuously and efficiently condense the refrigerant vapor into a liquid.

[0051] Heater: In the battery cooling system, the heater mainly heats the battery pack by heating the refrigerant at low temperatures.

[0052] From the above description, it can be seen that compared with indirect cooling (air cooling or liquid cooling), the present invention eliminates the heat exchange module between the refrigerant and the coolant, and directly cools the battery module with the refrigerant, reducing the link of cooling the coolant or air, thereby reducing the loss of the refrigerant and improving the energy efficiency of the battery cooling system. In other words, the battery cooling system of the present invention eliminates the plate heat exchanger, and removes the heat of the battery module by vaporizing the refrigerant, and the thermal efficiency is higher than that of a conventional water cooling unit.

[0053] Furthermore, in the battery cooling system described in the present invention, the battery module includes a plurality of battery assemblies arranged in parallel, and the battery assembly includes an expansion valve 6 and a battery pack 7 arranged in series, wherein the inlet of the expansion valve 6 is connected to the outlet of the heater, and the outlet of the battery pack 7 is connected to the inlet of the compressor.

[0054] In actual applications, the battery module may include multiple battery assemblies (such as eight), and each battery assembly is correspondingly provided with an expansion valve and a battery pack. It should be noted that the above-mentioned expansion valve is used to adjust the flow rate of refrigerant flowing into the battery pack. The above-mentioned refrigerant pipeline is used for the circulation of refrigerant (such as R410A), that is, refrigerant circulates in the refrigerant pipeline, and the material of the refrigerant pipeline can be copper or aluminum, etc., which has no chemical reaction with the refrigerant. In addition, it should be noted that the expansion valve and the heater, as well as the battery pack and the compressor are connected through the refrigerant pipeline. Similarly, adjacent battery assemblies in the battery module and adjacent components in the battery assembly can also be connected through the refrigerant pipeline.

[0055] From the above description, it can be seen that by setting a corresponding expansion valve in each battery assembly and adjusting the opening of the expansion valve in different battery assemblies to control the refrigerant flow rate flowing into the cooling channel (i.e., the refrigerant pipe 9) corresponding to each battery pack, the refrigerant flow rate of each battery assembly can be adjusted separately, so as to subsequently adjust the flow rate flowing into the battery pack, and then effectively adjust the temperature of each battery pack.

[0056] Furthermore, in the battery cooling system of the present invention, the battery assembly further includes a temperature sensor 8, and the temperature sensor 8 is disposed between the expansion valve and the battery pack.

[0057] The temperature sensor is used to measure the temperature of the corresponding battery pack, which is the liquid outlet temperature of the unit (ie, the evaporation temperature TL). In actual use, by setting the temperature sensor, the temperature of the corresponding battery pack can be obtained.

[0058] Accordingly, another object of the present invention is to provide a cooling control method. Figure 2 It can be seen that in this embodiment, the battery cooling system designed by the present invention can be used to implement the following cooling control method, which specifically includes the following steps:

[0059] S1: Obtaining the heat load of the battery module, the cooling capacity of the direct cooling unit, and the condensing temperature of the unit;

[0060] S2: determining the opening of the expansion valve in each battery assembly in the battery module according to the heat load, the cooling capacity of the unit and the condensing temperature of the unit;

[0061] S3: According to the opening of the expansion valve in each battery assembly, the opening of the corresponding expansion valve is adjusted.

[0062] The heat load is the amount of heat generated by the battery module under different operating conditions, that is, the heat generated by the battery module during operation due to internal chemical reactions, resistance heating, etc. This heat needs to be dissipated through effective thermal management methods to ensure that the battery operates at a safe temperature. In other words, the above heat load refers to the total amount of heat that needs to be removed from the battery module per unit time to ensure that the temperature is maintained at a set level.

[0063] The cooling capacity of the unit refers to the maximum amount of heat generated by the battery that the unit can remove. The unit condensing temperature (Tcon) refers to the temperature at which the refrigerant condenses (the refrigerant changes from gas to liquid), that is, the temperature at which the refrigerant in the condenser condenses from gas to liquid under a certain pressure.

[0064] The beneficial effect of the present invention is that: the battery module includes multiple battery assemblies, and each battery module is correspondingly provided with an expansion valve and a battery pack, wherein the expansion valve is used to adjust the refrigerant flow rate flowing into the cooling channel, that is, to adjust the refrigerant flow rate flowing into the battery pack. The present application obtains real-time operating data of the battery cooling system, such as the thermal load of the battery module, the cooling capacity of the unit, and the condensing temperature of the unit, and adjusts the opening of the expansion valve corresponding to each battery pack according to the above operating data to adjust the refrigerant flow rate flowing into each battery pack, thereby correspondingly adjusting the temperature of each battery pack to ensure that the temperature difference of each battery pack is within a certain range.

[0065] As described above, the opening of the expansion valve in each battery assembly in the battery module can be determined according to the heat load, the cooling capacity of the unit and the condensing temperature of the unit. The specific operation is as follows:

[0066] First of all, it should be noted that the battery module of the present invention may include eight battery assemblies, that is, the battery module includes eight battery packs. For this reason, when obtaining the opening of the expansion valve, it is necessary to obtain the opening of the expansion valve corresponding to the eight battery packs. In actual application, the cooling capacity of the unit, the condensing temperature of the unit and the thermal load of the battery module can be obtained first, and the ratio of the thermal load to the cooling capacity of the unit can be calculated. After that, the ratio of the thermal load to the cooling capacity of the unit is compared with a plurality of preset ratio intervals to determine in which ratio interval the thermal load is located. After determining which ratio interval it is, the opening of each expansion valve is determined according to the multiple temperature intervals corresponding to the ratio interval. The specific steps can be as follows:

[0067] Further, in an embodiment of the present invention, in step S2, the following steps are included:

[0068] S21: Calculating the ratio of the heat load to the cooling capacity of the unit;

[0069] S22: comparing the ratio with a plurality of preset ratio intervals to determine a target interval in which the ratio is located, wherein the plurality of preset ratio intervals include a first ratio interval, a second ratio interval, and a third ratio interval;

[0070] S23: Determine the opening of the expansion valve in each battery assembly according to the target interval and the unit condensing temperature.

[0071] It should be noted that after obtaining the heat load and the unit cooling capacity, the heat load value is divided by the unit cooling capacity value (i.e., heat load / unit cooling capacity) to obtain the corresponding ratio, and then the opening of each expansion valve is obtained based on the ratio and the unit condensing temperature (i.e., condensing temperature). It should be noted that the unit cooling capacity design value must be greater than or equal to the heat load, so the ratio is less than or equal to 100%. In actual applications, the ambient temperature will affect the cooling capacity of the compressor, so the condensing temperature is used to characterize the impact of the ambient temperature on the cooling capacity.

[0072] In practical applications, multiple continuous ratio intervals may be set accordingly, and adjacent ratio intervals may be in a connected relationship, that is, the endpoints of two adjacent ratio intervals are connected, but the interiors do not intersect. In addition, the number of ratio intervals may be set and selected according to actual conditions, and is not limited here. In an optional embodiment, if Figure 3 As shown, it can be divided into three ratio intervals, namely, the first ratio interval is 0-35% (including 35%), the second ratio interval is 35%-70% (including 70%), and the third ratio interval is 70%-100% (including 100%). Afterwards, the calculated ratio of the heat load to the cooling capacity of the unit is compared with the above three ratio intervals to determine the target interval. Correspondingly, according to the actual numerical value of the ratio of the heat load to the cooling capacity of the unit, there are three situations for determining the target interval, specifically: the ratio of the heat load to the cooling capacity of the unit is in the first ratio interval (that is, the target interval is the first ratio interval); the ratio of the heat load to the cooling capacity of the unit is in the second ratio interval; the ratio of the heat load to the cooling capacity of the unit is in the third ratio interval. The following specifically describes how to determine the opening of the expansion valve according to the condensing temperature of the unit in the above three situations.

[0073] In the first case, the heat load is in the first ratio range. Figure 3 As shown, further, in step S23, the target interval is a first ratio interval, and the unit condensing temperature is compared with a plurality of temperature intervals corresponding to the first ratio interval:

[0074] When the condensing temperature of the unit is within the first temperature range, the openings of the plurality of expansion valves are correspondingly set to a first opening combination;

[0075] When the condensing temperature of the unit is within the second temperature range, the openings of the plurality of expansion valves are correspondingly set to a second opening combination;

[0076] When the condensing temperature of the unit is within the third temperature range, the openings of the plurality of expansion valves are correspondingly set to a third opening combination.

[0077] In practical applications, multiple temperature intervals corresponding to the above multiple ratio intervals can be set in advance, for example, three continuous temperature intervals can be set for the first ratio interval, namely the first temperature interval, the second temperature interval and the third temperature interval; two continuous temperature intervals can be set for the second ratio interval, namely the third temperature interval and the fourth temperature interval; two continuous temperature intervals can be set for the third ratio interval, namely the fifth temperature interval and the sixth temperature interval. It should be noted that the settings of the above temperature intervals (such as the number and the actual size) can be selected according to the actual situation and are not limited here.

[0078] In this embodiment, if the target interval is a first ratio interval, multiple temperature intervals corresponding to the first ratio interval are obtained, and the multiple temperature intervals corresponding to the first ratio interval include a first temperature interval, a second temperature interval, and a third temperature interval. In actual applications, if the ratio of the heat load to the cooling capacity of the unit is within the first ratio interval, multiple temperature intervals corresponding to the first ratio interval are obtained. It should be noted that multiple continuous temperature intervals can be set accordingly, and adjacent temperature intervals can be in a connected relationship, that is, the endpoints of two adjacent temperature intervals are connected, but the interiors do not intersect, and the number of temperature intervals can be selected according to actual conditions, and is not limited here. Figure 3 As shown, the number of temperature intervals associated with the first ratio interval can be three, wherein the first temperature interval can be: unit condensing temperature Tcon ≤ 10°C, the second temperature interval can be: 10-20°C (including 20°C), and the third temperature interval can be: 20-34°C (including 34°C). Based on the above temperature interval settings, if the unit condensing temperature is in different temperature intervals, the openings of the expansion valves corresponding to each battery pack are also different: (1) If the unit condensing temperature is in the first temperature interval, the unit condensing temperature is low at this time, then the openings of the eight expansion valves can be set to 10%, at this time the compressor flow is small, the resistance is small, and the flow distribution is uniform. (2) If the unit condensing temperature is in the second temperature interval, then the openings of expansion valves 1&2 corresponding to battery packs 1&2 can be set to 8%, and the openings of expansion valves 3-8 corresponding to battery packs 3-8 can be set to 12%. (3) If the condensing temperature of the unit is within the third temperature range, the openings of the expansion valves 1, 2, and 3 corresponding to the battery packs 1, 2, and 3 can all be set to 15%, and the openings of the expansion valves 4-8 corresponding to the battery packs 4-8 can be set to 20%.

[0079] In the second case, the ratio of the heat load to the cooling capacity of the unit is in the second ratio range.

[0080] like Figure 3 As shown, further, in an embodiment of the present invention, step S23 may include the following steps:

[0081] If the target interval is a second ratio interval, obtaining a plurality of temperature intervals corresponding to the second ratio interval;

[0082] The opening degree of the expansion valve in each battery assembly is determined according to the unit condensing temperature and a plurality of temperature intervals corresponding to the second ratio interval.

[0083] Further, in an embodiment of the present invention, if the multiple temperature intervals corresponding to the second ratio interval include a fourth temperature interval and a fifth temperature interval, then in step S23, the following steps are also included:

[0084] If the condensing temperature of the unit is within the fourth temperature range, the openings of the plurality of expansion valves are correspondingly set to a fourth opening combination;

[0085] If the condensing temperature of the unit is within the fifth temperature range, the openings of the plurality of expansion valves are correspondingly set to the fifth opening combination.

[0086] In practical applications, if the ratio of the heat load to the cooling capacity of the unit is within the second ratio interval, multiple temperature intervals corresponding to the second ratio interval are obtained. It should be noted that multiple continuous temperature intervals can be set accordingly, and the adjacent temperature intervals can be in a connected relationship, that is, the endpoints of two adjacent temperature intervals are connected, but the interiors do not intersect, and the number of temperature intervals can be selected according to actual conditions, and is not limited here. Figure 3 As shown, the number of temperature intervals associated with the second ratio interval can be two, wherein the fourth temperature interval can be: 34-42°C (including 42°C), and the fifth temperature interval can be: 42-50°C (including 50°C). Based on the above temperature interval settings, if the unit condensing temperature is in different temperature intervals, the openings of the expansion valves corresponding to each battery pack are also different: (1) If the unit condensing temperature is in the fourth temperature interval, the openings of the eight expansion valves can be set to: the openings of expansion valves 1&2 corresponding to battery packs 1&2 are both 25%, the openings of expansion valves 3-5 corresponding to battery packs 3-5 are set to 30%, and the openings of expansion valves 6-8 corresponding to battery packs 6-8 are all 35%. (2) If the unit condensing temperature is in the fifth temperature interval, the openings of the eight expansion valves can be set to: the openings of expansion valves 1&2&3 corresponding to battery packs 1&2&3 are all 30%, the openings of expansion valves 4-5 corresponding to battery packs 4-5 are all 35%, and the openings of expansion valves 6-8 corresponding to battery packs 6-8 are all 40%.

[0087] In the third case, the heat load is located in the third ratio interval.

[0088] like Figure 3 As shown, further, in an embodiment of the present invention, step S23 may include the following steps:

[0089] If the target interval is a third ratio interval, obtaining a plurality of temperature intervals corresponding to the third ratio interval;

[0090] The opening degree of the expansion valve in each battery assembly is determined according to the unit condensing temperature and a plurality of temperature intervals corresponding to the third ratio interval.

[0091] Further, in an embodiment of the present invention, if the multiple temperature intervals corresponding to the third ratio interval include a sixth temperature interval and a seventh temperature interval, then in step S23, the following steps are also included:

[0092] If the condensing temperature of the unit is within the sixth temperature range, the openings of the plurality of expansion valves are correspondingly set to the sixth opening combination;

[0093] If the condensing temperature of the unit is within the seventh temperature range, the openings of the plurality of expansion valves are correspondingly set to the seventh opening combination.

[0094] In practical applications, if the ratio of heat load to unit cooling capacity is within the third ratio interval, multiple temperature intervals corresponding to the third ratio interval are obtained. It should be noted that multiple continuous temperature intervals can be set accordingly, and adjacent temperature intervals can be in a connected relationship, that is, the endpoints of two adjacent temperature intervals are connected, but the interiors do not intersect, and the number of temperature intervals can be selected according to actual conditions, which is not limited here. Figure 3 As shown, the number of temperature intervals associated with the third ratio interval can be two, wherein the sixth temperature interval can be: 50-58°C (including 58°C), and the seventh temperature interval can be: greater than 58°C. Based on the above temperature interval settings, if the unit condensing temperature is in different temperature intervals, the openings of the expansion valves corresponding to each battery pack are also different: (1) If the unit condensing temperature is in the sixth temperature interval, the openings of the eight expansion valves can be set to: the openings of expansion valves 1&2 corresponding to battery packs 1&2 are both 35%, the openings of expansion valves 3-5 corresponding to battery packs 3-5 are both 40%, and the openings of expansion valves 6-8 corresponding to battery packs 6-8 are all 50%. (2) If the unit condensing temperature is in the seventh temperature interval, the openings of the eight expansion valves can be set to: the openings of expansion valves 1&2 corresponding to battery packs 1&2 are both 35%, the openings of expansion valves 3-5 corresponding to battery packs 3-5 are both 50%, and the openings of expansion valves 6-8 corresponding to battery packs 6-8 are all 60%.

[0095] From the above description, it can be seen that according to the ratio of heat load / unit cooling capacity and the unit condensing temperature, the opening of the expansion valve corresponding to each battery pack is determined to adjust the refrigerant flow into each battery pack so that the flow into each battery pack can be consistent, thereby ensuring the cooling effect of each battery pack is consistent. In practical applications, by adjusting the opening of each expansion valve to make the flow of each battery pack consistent, the temperature difference of each battery pack can be ensured to be within a certain range.

[0096] In summary, the battery cooling system and cooling control method provided by the present invention: (1) The heat exchange module between the refrigerant and the coolant is eliminated, and the battery pack is directly cooled by the refrigerant. At the same time, the expansion valve opening is reasonably controlled to improve the system energy efficiency ratio (such as an increase of more than 30%), while keeping the battery pack temperature difference within a certain temperature range (such as within 5°C). (2) The new direct cooling unit of the present invention can meet the larger cooling power and heating power requirements, and belongs to the larger unit type in the energy storage industry. The new unit also has the advantages of high comprehensive energy efficiency ratio, multi-functional matching, high installation freedom, etc., and can provide direct cooling and heat output for battery pack thermal management within a large span of ambient temperature range, while greatly improving the system energy efficiency ratio. (3) Under the same ratio and unit condensing temperature, the expansion valve opening of different battery packs is adjusted so that the opening of multiple battery packs in the battery module can be different, so that the refrigerant flow rate flowing into each battery pack is consistent, thereby ensuring that the temperature difference of each battery pack is within a certain range. It should be noted that if the opening of each battery pack is the same, the flow rate of each pack will be different. In order to ensure consistent cooling effect, the flow rate must be consistent. Specifically, due to the different distances between the battery pack and the compressor, the closer the battery pack is to the compressor, the smaller the pipeline resistance and the greater the flow rate. Therefore, the flow rate of each battery pack is different. In the present invention, by adjusting the opening of the expansion valve corresponding to each battery pack, the pipeline resistance is changed by the opening, and the flow rate is kept consistent as much as possible, the closer the flow rate. In addition, it should be noted that the speed of the compressor is different for different heat loads, the speed of the compressor is different, and the flow resistance of the copper tube is different. Therefore, in order to ensure uniform refrigerant flow in the battery pack, the opening of the expansion valve needs to be adjusted according to the working conditions.

[0097] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent transformations made using the contents of the present invention's specification and drawings, or directly or indirectly applied in related technical fields, are also included in the patent protection of the present invention.

Claims

1. A cooling control method for a battery cooling system, characterized in that: The battery cooling system comprises a direct cooling unit and a battery module, wherein the direct cooling unit comprises a compressor, a condenser and a heater, wherein the compressor, the condenser and the heater are connected in series in sequence through a refrigerant pipeline, and the inlet of the compressor is connected to the outlet of the battery module, and the outlet of the heater is connected to the inlet of the battery module; wherein the battery module comprises eight battery assemblies arranged in parallel, and the battery assembly comprises an expansion valve and a battery pack arranged in series, wherein the inlet of the expansion valve is connected to the outlet of the heater, and the outlet of the battery pack is connected to the inlet of the compressor; the battery assembly further comprises a temperature sensor, and the temperature sensor is arranged between the expansion valve and the battery pack; the cooling control method comprises the following steps: S1: Obtaining the heat load of the battery module, the cooling capacity of the direct cooling unit, and the condensing temperature of the unit; S2: determining the opening of the expansion valve in each battery assembly in the battery module according to the heat load, the cooling capacity of the unit and the condensing temperature of the unit; S3: adjusting the opening of the corresponding expansion valve according to the opening of the expansion valve in each battery assembly; In step S2, the following steps are included: S21: calculating the ratio of the heat load to the cooling capacity of the unit; S22: comparing the ratio with a plurality of preset ratio intervals to determine a target interval in which the ratio is located, wherein the plurality of preset ratio intervals include a first ratio interval, a second ratio interval, and a third ratio interval; S23: determining the opening of the expansion valve in each battery assembly according to the target interval and the condensing temperature of the unit; In step S23, when the target interval is the first ratio interval, the unit condensing temperature is compared with multiple temperature intervals corresponding to the first ratio interval: when the unit condensing temperature is within the first temperature interval, the openings of the eight expansion valves corresponding to the eight battery packs are all set to 10%; when the unit condensing temperature is within the second temperature interval, the openings of the expansion valves 1-2 corresponding to the battery packs 1-2 among the eight battery packs are set to 8%, and the openings of the expansion valves 3-8 corresponding to the battery packs 3-8 are set to 12%; when the unit condensing temperature is within the third temperature interval, the openings of the expansion valves 1-3 corresponding to the battery packs 1-3 among the eight battery packs are set to 15%, and the openings of the expansion valves 4-8 corresponding to the battery packs 4-8 are set to 20%; Among them, the heat load of the battery module is the heat generated by the battery module under different working conditions; the cooling capacity of the unit refers to the maximum battery heat generated by the unit; and the condensing temperature of the unit refers to the temperature when the refrigerant condenses.

2. The cooling control method according to claim 1, characterized in that: In step S23, the following steps are included: When the target interval is a second ratio interval, obtaining a plurality of temperature intervals corresponding to the second ratio interval; Determining the opening of the expansion valve in each battery assembly according to the unit condensing temperature and a plurality of temperature intervals corresponding to the second ratio interval; When the unit condensing temperature and the multiple temperature intervals corresponding to the second ratio interval include a fourth temperature interval and a fifth temperature interval, step S23 further includes the following steps: When the condensing temperature of the unit is within the fourth temperature range, the opening degree of the expansion valve 1-2 corresponding to the battery pack 1-2 among the eight battery packs is set to 25%, the opening degree of the expansion valve 3-5 corresponding to the battery pack 3-5 is set to 30%, and the opening degree of the expansion valve 6-8 corresponding to the battery pack 6-8 is set to 35%; When the condensing temperature of the unit is within the fifth temperature range, the opening of expansion valve 1-3 corresponding to battery pack 1-3 among the eight battery packs is set to 30%, the opening of expansion valve 4-5 corresponding to battery pack 4-5 is set to 35%, and the opening of expansion valve 6-8 corresponding to battery pack 6-8 is set to 40%.

3. The cooling control method according to claim 1, characterized in that: In step S23, the following steps are included: When the target interval is a third ratio interval, obtaining a plurality of temperature intervals corresponding to the third ratio interval; Determining the opening of the expansion valve in each battery assembly according to the unit condensing temperature and a plurality of temperature intervals corresponding to the third ratio interval; When the unit condensing temperature and the multiple temperature intervals corresponding to the third ratio interval include the sixth temperature interval and the seventh temperature interval, step S23 further includes the following steps: When the condensing temperature of the unit is within the sixth temperature range, the opening degree of the expansion valve 1-2 corresponding to the battery pack 1-2 among the eight battery packs is set to 35%, the opening degree of the expansion valve 3-5 corresponding to the battery pack 3-5 is set to 40%, and the opening degree of the expansion valve 6-8 corresponding to the battery pack 6-8 is set to 50%; When the condensing temperature of the unit is within the seventh temperature range, the opening of the expansion valve 1-2 corresponding to the battery pack 1-2 among the eight battery packs is set to 35%, the opening of the expansion valve 3-5 corresponding to the battery pack 3-5 is set to 50%, and the opening of the expansion valve 6-8 corresponding to the battery pack 6-8 is set to 60%.

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