A coolant direct cooling and direct heating battery system and control method

Abstract

The application discloses a kind of refrigerant direct cooling direct heating battery systems and control method, system includes control unit, detection unit, execution unit and refrigerant circulation loop;Refrigerant circulation loop includes sequentially through pipeline connection and form circulation loop compressor, second heat exchanger, the cold plate of battery system and first heat exchanger;Detection unit includes pressure detection piece and temperature detection piece;Execution unit includes first electromagnetic valve, first expansion valve, second expansion valve and third electromagnetic valve;First electromagnetic valve is connected in parallel on second heat exchanger;First expansion valve is located between first heat exchanger and the cold plate of battery system;Second expansion valve and third electromagnetic valve are connected in parallel to each other and located between cold plate and the low pressure side of first heat exchanger;Control unit is used to control execution unit, compressor, second heat exchanger and first heat exchanger according to temperature signal and pressure signal, to realize direct cooling mode or direct heating mode.The application has the advantages of accurate control, efficient heat distribution etc..

Description

Technical Field

[0001] This invention relates to the field of thermal management technology, specifically to a refrigerant direct cooling and direct heating battery system and its control method. Background Technology

[0002] Thermal management technology is one of the key technologies in lithium-ion battery systems, as battery temperature directly affects performance, safety, and lifespan. If the battery temperature is too high, internal chemical reactions intensify, leading to rapid capacity decay and potentially thermal runaway, causing safety incidents. Conversely, if the battery temperature is too low, internal activity decreases, resulting in a significant drop in effective capacity and output power, leading to insufficient battery output. More dangerously, charging at low temperatures can trigger internal lithium plating, causing short circuits and also inducing thermal runaway. Furthermore, large temperature differences between different locations within the battery pack can lead to uneven aging rates, affecting the overall performance and lifespan of the battery pack. Therefore, battery thermal management systems typically use cooling, heating, and insulation methods to ensure the battery operates within a comfortable temperature range (usually between 10°C and 35°C) and maintain uniform internal temperature as much as possible.

[0003] The current main thermal management technology route for battery systems is liquid cooling and liquid heating. Compared with traditional liquid cooling and liquid heating technologies, direct cooling and direct heating technologies reduce the water circulation system, thus having a simpler system architecture and becoming one of the important directions for the next generation of battery thermal management technologies.

[0004] Direct cooling and heating technologies reduce the need for a water circulation system, allowing the refrigerant to directly enter the battery pack and exchange heat with the battery. However, this also introduces new technical challenges, the main ones of which are as follows:

[0005] 1. Refrigerant state control issues in direct cooling mode. To ensure temperature consistency in the battery system, it is necessary to ensure that the refrigerant entering and leaving the battery pack is in a saturated state, and that the refrigerant exiting the pack is within a certain dryness level (e.g., 0.9) to maintain stable heat exchange performance;

[0006] 2. Refrigerant state control issues in direct heating mode. To ensure temperature consistency in the battery system, the refrigerant entering and exiting the battery pack must be in a saturated state, and the inlet refrigerant should be within a certain dryness level (e.g., 0.9) to maintain stable heat exchange performance. Furthermore, the refrigerant saturation temperature needs to be adjusted according to the refrigerant's heat carrying capacity and the cell's temperature state to achieve a balance between heat exchange capacity and heat carrying capacity.

[0007] 3. Refrigerant distribution in parallel branches. The resistance characteristics of two-phase flow are quite complex, and the battery pack of a battery system is generally composed of multiple branches connected in parallel. The flow distribution among the parallel branches must ensure that the flow rate of each branch is greater than the minimum requirement. Summary of the Invention

[0008] To address the technical problems existing in the prior art, this invention provides a refrigerant direct cooling and direct heating battery system and control method with precise temperature control.

[0009] To solve the above-mentioned technical problems, the technical solution proposed by this invention is as follows:

[0010] A refrigerant direct cooling and direct heating battery system includes a control unit, a detection unit, an execution unit, and a refrigerant circulation loop;

[0011] The refrigerant circulation loop includes a compressor, a second heat exchanger, a cold plate of the battery system, and a first heat exchanger; the compressor, the second heat exchanger, the cold plate of the battery system, and the first heat exchanger are connected in sequence through pipelines to form a circulation loop.

[0012] The detection unit includes a pressure detection element for detecting pressure at various points in the system and a temperature detection element for detecting temperature at various points in the system.

[0013] The execution unit includes a first solenoid valve, a first expansion valve, a second expansion valve, and a third solenoid valve; the first solenoid valve is connected in parallel to the second heat exchanger; the first expansion valve is located between the first heat exchanger and the cold plate of the battery system; the second expansion valve and the third solenoid valve are connected in parallel to each other and are located between the cold plate of the battery system and the low-pressure side of the first heat exchanger.

[0014] The control unit is connected to the detection unit, the execution unit, the compressor, the second heat exchanger, and the first heat exchanger respectively, and is used to control the execution unit, the compressor, the second heat exchanger, and the first heat exchanger according to the temperature signal and pressure signal of the detection unit, so as to realize the direct cooling mode or the direct heating mode.

[0015] As a further improvement to the above technical solution:

[0016] The pressure detection device includes a first pressure sensor, a second pressure sensor, and a third pressure sensor; the first pressure sensor is used to collect the compressor suction pressure; the second pressure sensor is used to collect the compressor discharge pressure; and the third pressure sensor is used to collect the refrigerant pressure at the battery system inlet.

[0017] The temperature detection device includes a first temperature sensor, a second temperature sensor, a third temperature sensor, a fourth temperature sensor, a fifth temperature sensor, a sixth temperature sensor, and a seventh temperature sensor;

[0018] The first temperature sensor is used to collect the compressor suction temperature; the second temperature sensor is used to collect the compressor discharge temperature; the third temperature sensor is used to collect the refrigerant temperature at the high-pressure side inlet of the first heat exchanger; the fourth temperature sensor is used to collect the high-pressure side outlet temperature of the first heat exchanger; the fifth temperature sensor is used to collect the refrigerant temperature at the low-pressure side inlet of the first heat exchanger; the sixth temperature sensor is used to collect the battery system outlet temperature; and the seventh temperature sensor is used to collect the refrigerant temperature at the battery system inlet.

[0019] A second solenoid valve is connected in parallel to the first expansion valve for bypassing the first expansion valve.

[0020] A heater is provided between the cold plate of the battery system and the first heat exchanger, and the heater is connected to the control unit.

[0021] It also includes a third expansion valve, which is connected in series with the first solenoid valve and then in parallel with the inlet and outlet of the second heat exchanger, and is used to adjust the refrigerant flow of the second heat exchanger in direct cooling mode or direct heating mode.

[0022] It also includes a fourth expansion valve and a fifth expansion valve; the fourth expansion valve is connected in parallel between the inlet and outlet of the low-pressure side of the first heat exchanger; the fifth expansion valve is connected in parallel between the inlet and outlet of the high-pressure side of the first heat exchanger; the fourth expansion valve and the fifth expansion valve are used to control the heat exchange capacity of the first heat exchanger.

[0023] This invention also discloses a control method for a refrigerant direct-cooling and direct-heating battery system as described above, including direct-cooling mode control and direct-heating mode control; the direct-cooling mode control includes the following steps:

[0024] S11. Obtain the real-time cell temperature fed back by the battery system. T cell and real-time heat generation P cell Determine the target value of the refrigerant saturation temperature at the battery system inlet. T inlet And the corresponding target value of inlet saturation pressure;

[0025] S12. Based on the target value of the inlet refrigerant saturation temperature obtained in step S11 T inlet Real-time temperature of the battery cell T cell Estimate the heat exchange between the battery pack and the refrigerant. P ex ;

[0026] S13. Set the initial cooling capacity, the initial operating frequency of the compressor, and the initial frequency of the heat exchanger fan; wherein the initial cooling capacity and the initial operating frequency of the compressor are based on the heat exchange... Pex get;

[0027] S14. Simultaneously start the compressor and heat exchanger fan; dynamically adjust the frequency of the heat exchanger fan with the suction superheat at the compressor inlet as the control target; when the suction superheat is lower than the target range, reduce the frequency of the heat exchanger fan to reduce heat dissipation; when the suction superheat is higher than the target range, increase the frequency of the heat exchanger fan to enhance heat dissipation.

[0028] S15. The refrigerant pressure at the inlet of the battery system is throttled and adjusted by the first expansion valve to meet the target value of the inlet saturation pressure of the battery system.

[0029] Simultaneously, the refrigerant status at the battery system outlet is acquired; if the refrigerant dryness at the outlet is greater than the target upper limit, the compressor frequency is increased; if the refrigerant dryness at the outlet is within the target range, the compressor frequency is maintained or appropriately increased to ensure the refrigerant dryness at the battery system outlet.

[0030] Preferably, in step S15, if the target value of the refrigerant saturation temperature at the battery system inlet is high, causing the corresponding inlet saturation pressure to exceed the compressor's suction pressure, the third solenoid valve is closed, and secondary throttling is performed through the second expansion valve to control the compressor's suction pressure and ensure safe operation.

[0031] Preferably, in step S11, the target value of the refrigerant saturation temperature at the battery system inlet is... T inlet The calculation formula is:

[0032]

[0033] In the formula, T base This serves as the reference value for the refrigerant temperature at the battery system inlet. This is a correction factor for real-time heat generation and cell temperature. t s The filtering time for battery heating power; P cell To generate heat for the battery in real time; Heat generated under rated operating conditions for the battery pack; Real-time battery temperature; The thermal resistance of the battery pack is given in °C / kW. T c-H To set the battery startup cooling temperature, T c-L The battery stops cooling at this temperature; This is the preset temperature threshold.

[0034] Preferably, the direct heating mode control includes the following steps:

[0035] S21. Request heating power based on battery system Real-time temperature of the battery cell Determine the target saturation temperature of the refrigerant at the battery system inlet. ;

[0036] S22. Based on the target value of saturation temperature With requested heating power Calculate the target operating frequency of the compressor. f ;

[0037] S23. During compressor startup, control the compressor to gradually increase its frequency to the target frequency. f ;

[0038] Synchronously adjust the first expansion valve to bring the battery system inlet saturation temperature close to the target value. ;

[0039] The second expansion valve is adjusted synchronously to ensure that the superheat at the compressor inlet is within the target range.

[0040] Preferably, the specific process of step S22 is as follows:

[0041] S221. Request heating power Multiply by magnification factor S The initial requested input electrical power of the compressor is obtained. ;

[0042] S222. Based on the target saturation temperature of the inlet refrigerant. With preset throttling temperature difference Calculate the initial intake saturation temperature ;

[0043] S223. Requested input electrical power based on the compressor With initial inspiratory saturation temperature T evap By using the compressor characteristic table, the compressor operating frequency can be preliminarily determined. f ;

[0044] S224. Verify the compressor operating frequency obtained in step S223. f and the corresponding refrigerant mass flow rate; if the refrigerant mass flow rate is lower than the requested heating power. If the refrigerant flow rate is n times the corresponding refrigerant flow rate, then the compressor operating frequency is increased; if the calculated compressor operating frequency is... f If the compressor's operating frequency exceeds 90% of its maximum operating frequency, the heater is activated for heat compensation; the compressor's requested electrical power is updated based on the heater's heating power. Then return to step S223 to recalculate the compressor operating frequency.

[0045] Compared with the prior art, the advantages of the present invention are as follows:

[0046] This invention solves the problems of temperature unevenness caused by uneven refrigerant state control at the inlet and outlet of the battery system and uneven distribution across multiple branches in direct cooling and direct heating battery systems. Through measures such as heat exchanger regeneration, active control of the condenser fan, adjustment of the opening degree of each expansion valve, and selection of heaters, combined with optimized control methods, the system can achieve stable control of the refrigerant saturation state at the inlet and outlet of the battery cold plate and maintain a specified dryness. Furthermore, the system achieves stable operation control through excess refrigerant flow, mitigating the problem of uneven refrigerant flow distribution in parallel branches by allowing excess refrigerant flow through the battery system.

[0047] This invention achieves heat exchange (regeneration) between the high-pressure refrigerant at the outlet of the second heat exchanger and the low-pressure refrigerant at the outlet of the battery cold plate by setting up a first heat exchanger. Based on this, combined with active control of the condenser fan speed, the heat exchange within the first heat exchanger can be precisely adjusted. This collaborative control mechanism enables the system to finely adjust the state of the refrigerant entering the battery system, ultimately achieving precise control of the refrigerant dryness at the inlet and outlet of the battery cold plate over a wide range. Specifically, through the synergistic modulation of the regeneration effect, active fan speed regulation, and the opening of the first expansion valve, the system can ensure that the refrigerant at both the inlet and outlet of the battery cold plate is saturated and stably maintained at the specified target dryness.

[0048] In direct heating mode, the system achieves stable operation without the need for an external evaporator by using a first heat exchanger for internal heat exchange and combining this with the opening of the condenser bypass solenoid valve. In this architecture, the first expansion valve regulates the saturation temperature of the refrigerant entering the battery pack, thereby directly controlling the heat exchange temperature difference between the refrigerant and the battery cells, effectively preventing overcooling of the refrigerant at the battery outlet. Furthermore, an optional heater in the loop can provide necessary supplementary heating to increase the total heating power of the system. Through the coordinated operation of the first heat exchanger, bypass solenoid valve, first expansion valve, and optional heater, accurate control of the refrigerant state at the battery cold plate inlet and outlet is achieved in direct heating mode, ensuring the system's heating effect and temperature uniformity.

[0049] This invention utilizes a first heat exchanger for reheating, ensuring that the saturated refrigerant at the cold plate outlet can further absorb heat, transforming into a stable superheated state before safely returning to the compressor. The enthalpy of the refrigerant at the condenser outlet is controlled by fan speed regulation, achieving precise adjustment of the refrigerant dryness at the cold plate outlet. The system operates with an excess refrigerant flow rate. This excess flow design ensures that even with significant flow unevenness between parallel branches (supporting a maximum unevenness of over 50%), the branch with the lowest actual flow rate still receives enough refrigerant to meet its minimum heat exchange requirements, effectively mitigating temperature unevenness caused by uneven flow distribution. Attached Figure Description

[0050] Figure 1 This is one of the topological diagrams of the refrigerant direct cooling and direct heating battery system of the present invention in an embodiment.

[0051] Figure 2 This is a schematic diagram illustrating the working principle of the refrigerant direct cooling and direct heating battery system of the present invention in direct cooling mode.

[0052] Figure 3 This is a thermodynamic cycle diagram of the refrigerant direct cooling and direct heating battery system of the present invention in direct cooling mode.

[0053] Figure 4 This is a schematic diagram illustrating the working principle of the refrigerant direct cooling and direct heating battery system of the present invention in direct heating mode.

[0054] Figure 5 This is a thermodynamic cycle diagram of the refrigerant direct cooling and direct heating battery system of the present invention in direct heating mode.

[0055] Figure 6 This is the second topological diagram of the refrigerant direct cooling and direct heating battery system of the present invention in an embodiment.

[0056] Figure 7 This is a flowchart of the control method for the refrigerant direct cooling and direct heating battery system of the present invention in direct cooling mode.

[0057] Figure 8 This is a flowchart of the control method for the refrigerant direct cooling and direct heating battery system of the present invention in direct heating mode.

[0058] Legend: 101, Second heat exchanger; 102, First heat exchanger; 201, Heat exchanger fan; 202, First solenoid valve; 203, Compressor; 204, Heater; 205, First expansion valve; 206, Second solenoid valve; 207, Second expansion valve; 208, Third solenoid valve; 209, Controller; 210, Battery system; 301, First temperature sensor; 302, Second temperature sensor; 303, Third temperature sensor; 304, Fourth temperature sensor; 305, Fifth temperature sensor; 306, Sixth temperature sensor; 307, Seventh temperature sensor; 401, First pressure sensor; 402, Second pressure sensor; 403, Third pressure sensor. Detailed Implementation

[0059] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0060] like Figure 1 As shown, the refrigerant direct cooling and direct heating battery system provided in this embodiment of the invention includes a control unit (such as controller 209), a detection unit, an execution unit, and a refrigerant circulation loop;

[0061] The refrigerant circulation loop includes compressor 203, second heat exchanger 101, cold plate of battery system 210, and first heat exchanger 102; compressor 203, second heat exchanger 101, cold plate of battery system 210, and first heat exchanger 102 are connected in sequence through pipelines to form a circulation loop;

[0062] The detection unit includes pressure detection devices for detecting pressure at various points in the system and temperature detection devices for detecting temperature at various points in the system; wherein the pressure detection devices include a first pressure sensor 401, a second pressure sensor 402 and a third pressure sensor 403; the first pressure sensor 401 is used to collect the compressor suction pressure; the second pressure sensor 402 is used to collect the compressor discharge pressure; and the third pressure sensor 403 is used to collect the refrigerant pressure at the battery system inlet.

[0063] The temperature detection device includes a first temperature sensor 301, a second temperature sensor 302, a third temperature sensor 303, a fourth temperature sensor 304, a fifth temperature sensor 305, a sixth temperature sensor 306, and a seventh temperature sensor 307.

[0064] The first temperature sensor 301 is used to collect the compressor suction temperature; the second temperature sensor 302 is used to collect the compressor discharge temperature; the third temperature sensor 303 is used to collect the refrigerant temperature at the high-pressure side inlet of the first heat exchanger 102; the fourth temperature sensor 304 is used to collect the high-pressure side outlet temperature of the first heat exchanger 102; the fifth temperature sensor 305 is used to collect the refrigerant temperature at the low-pressure side inlet of the first heat exchanger 102; the sixth temperature sensor 306 is used to collect the outlet temperature of the battery system 210; and the seventh temperature sensor 307 is used to collect the refrigerant temperature at the inlet of the battery system 210.

[0065] The execution unit includes a first solenoid valve 202, a first expansion valve 205, a second expansion valve 207, and a third solenoid valve 208. The first solenoid valve 202 is connected in parallel to the second heat exchanger 101. The first expansion valve 205 is located between the first heat exchanger 102 and the cold plate of the battery system 210. The second expansion valve 207 and the third solenoid valve 208 are connected in parallel and located between the cold plate of the battery system 210 and the low-pressure side of the first heat exchanger 102. A second solenoid valve 206 is connected in parallel to the first expansion valve 205 for bypassing the first expansion valve 205 (when the heating demand temperature is high and the first expansion valve 205 is not needed for temperature regulation, the second solenoid valve 206 can be used for direct bypass).

[0066] The control unit is connected to the detection unit, the execution unit, the compressor 203, the second heat exchanger 101 and the first heat exchanger 102 respectively, and is used to control the execution unit, the compressor 203, the second heat exchanger 101 and the first heat exchanger 102 according to the temperature signal and pressure signal of the detection unit, so as to realize the direct cooling mode or the direct heating mode.

[0067] A heater 204 is provided between the cold plate of the battery system 210 and the first heat exchanger 102, and the heater 204 is connected to the control unit.

[0068] like Figure 2 As shown, in direct cooling mode, the first solenoid valve 202, the second solenoid valve 206, and the second expansion valve 207 are closed, while the third solenoid valve 208 is open. High-pressure refrigerant is discharged from the compressor outlet 203. Figure 2 Point A in the diagram enters the second heat exchanger 101 connected to it for initial cooling. After cooling ( Figure 2 Points B and C in the diagram enter the first heat exchanger 102, where they exchange heat with the low-pressure refrigerant flowing out of the battery system 210 for secondary cooling. Figure 2 Point D in the middle), after secondary cooling, passes through the first expansion valve 205 for throttling ( Figure 2 At point E in the diagram, the saturated refrigerant, at a specified temperature and pressure, enters the battery system 210. After absorbing the heat released by the battery during operation in the cold plate of the battery system 210, it flows out of the battery system 210. Figure 2Point F in the middle), passing through the third solenoid valve 208 ( Figure 2 Point G in the middle), heater 204 ( Figure 2 After passing through point H in the code, the refrigerant enters the first heat exchanger 102 and exchanges heat with the high-pressure refrigerant flowing out of the second heat exchanger 101. Corresponding control ensures that the refrigerant flowing from the first heat exchanger 102 into the compressor 102 is in a superheated state. Figure 2 Point I in the text), the superheated refrigerant is compressed by compressor 203 and then discharged again ( Figure 2 (Point A in the diagram). This completes the direct cooling cycle. The thermal cycle in direct cooling mode is as follows: Figure 3 As shown.

[0069] like Figure 4 As shown, in direct heating mode, the typical workflow of the system is as follows: Figure 4 As shown: the first solenoid valve 202 is open, and the second solenoid valve 206 and the third solenoid valve 208 are closed. High-pressure refrigerant is discharged from the compressor outlet 203. Figure 4 Point A in the diagram), bypassing the second heat exchanger 101 via the first solenoid valve 202. Figure 4 Points B and C in the diagram enter the first heat exchanger 102, where they exchange heat with the low-pressure refrigerant flowing out of the battery system 210 for cooling. Figure 4 Point D in the diagram), after cooling, passes through the first expansion valve 205 for throttling ( Figure 4 At point E in the diagram, the saturated refrigerant, at a specified temperature and pressure, enters the battery system 210. After further cooling by releasing heat to the battery cells in the cold plate of the battery system 210, it flows out of the battery system 210. Figure 4 Point F in the middle), passing through the second expansion valve 207 ( Figure 4 Point G in the middle), heater 204 ( Figure 4 After passing through point H in the code, the refrigerant enters the first heat exchanger 102 and exchanges heat with the high-pressure refrigerant discharged from the compressor 203. Corresponding control ensures that the refrigerant flowing from the first heat exchanger 102 into the compressor 203 is in a superheated state. Figure 4 Point I in the text), the superheated refrigerant is compressed by compressor 203 and then discharged again ( Figure 4 Point A in the diagram represents the point where the direct heating cycle is complete. The heat cycle in direct heating mode is as follows: Figure 5 As shown.

[0070] like Figure 6As shown, it also includes a third expansion valve 211, a fourth expansion valve 212, and a fifth expansion valve 213; wherein the third expansion valve 211 is connected in series with the first solenoid valve 202 and then in parallel with the inlet and outlet of the second heat exchanger 101, which can adjust the refrigerant flow of the second heat exchanger 101 in direct cooling and direct heating modes, and can replace the condenser heat exchange control of fan speed regulation, or can be used with fan speed regulation to achieve a wider heat exchange adjustment range; the fourth expansion valve 212 is connected in parallel between the inlet and outlet of the low-pressure side of the first heat exchanger 102, and the fifth expansion valve 213 is connected in parallel between the inlet and outlet of the high-pressure side of the first heat exchanger 102. The fourth expansion valve 212 and the fifth expansion valve 213 are used to control the heat exchange of the first heat exchanger 102.

[0071] like Figure 7 As shown, this embodiment of the invention also provides a control method for a refrigerant direct cooling and direct heating battery system as described above, including direct cooling mode control and direct heating mode control;

[0072] When the battery temperature exceeds a threshold, triggering a cooling demand, the system enters direct cooling mode. The control targets are the inlet refrigerant pressure of the battery system 210, the outlet refrigerant dryness, and the compressor suction superheat. The inlet refrigerant pressure is calculated based on the cell temperature and power, and the temperature difference between the inlet refrigerant pressure and the saturation temperature and the cell temperature is determined based on the battery pack structure. The outlet refrigerant dryness of the battery system 210 is mainly achieved by adjusting the frequency of the compressor 203 and the heat exchanger fan 201, controlling the outlet refrigerant dryness between 0.6 and 0.9. This wide range of outlet dryness maintains excess flow, thereby solving the problem of uneven distribution in parallel branches. When the calculated saturation temperature is high, the second expansion valve 207 can be adjusted for further pressure control. In the above control process, it is not a single controlled object modulation; the coupling relationship between various variables needs to be fully considered for comprehensive control.

[0073] The specific control process of the direct cooling mode is as follows:

[0074] S11. Obtain the real-time cell temperature fed back by the battery system 210. T cell and real-time heat generation P cell Determine the target value of the refrigerant saturation temperature at the 210 inlet of the battery system. T inlet , and by T inlet The corresponding target value of inlet saturation pressure is obtained;

[0075] When the refrigerant at the inlet of the battery system 210 is in a saturated state, its temperature corresponds one-to-one with the saturation pressure, and the inlet refrigerant temperature can be directly adjusted by adjusting the inlet refrigerant pressure.

[0076] Among them, the target value of the refrigerant saturation temperature at the 210 inlet of the battery system T inlet The calculation formula is:

[0077] (1)

[0078] In the formula, T base This serves as the reference value for the refrigerant temperature at the battery system inlet. This is a correction factor for real-time heat generation and cell temperature. Depending on the specific project, it can be selected between 5 and 15°C, but the target value for the inlet refrigerant temperature remains constant. T inlet It cannot exceed the cell temperature. T cell ; t s The filtering time is used to determine the battery's heat generation power, and the heat generated by the battery cell is averaged based on this time. P cell To generate heat for the battery in real time; Heat generated by the battery pack under rated operating conditions, in kW; Real-time battery temperature; The thermal resistance of the battery pack (cell-cooling medium, mainly determined by the battery pack structure) is expressed in °C / kW. T c-H To set the battery startup cooling temperature, T c-L The battery stops cooling at this temperature; The preset temperature rise threshold is the allowable temperature rise of the battery when it is at its rated heat generation temperature, relative to the cooling start-up temperature threshold. It can be selected between 5 and 15°C depending on the actual situation.

[0079] Reference value of battery system inlet refrigerant temperature T base It is determined by the following formula:

[0080] (2).

[0081] S12. Based on the target value of the inlet refrigerant saturation temperature obtained in step S11 T inlet Real-time temperature of the battery cell T cell The heat exchange between the battery pack and the refrigerant is estimated using equation (3). P ex ;

[0082] (3)

[0083] S13. Initialize the operating parameters of each component:

[0084] The cooling capacity is calculated by multiplying the heat exchange rate estimated in step S12 by 1.8.

[0085] The initial value of the compressor's operating frequency is initially set by consulting the compressor's performance characteristic curve based on the cooling capacity requirement and the suction and discharge pressures collected in real time when the system starts up.

[0086] The initial frequency of the heat exchanger fan 201 is set according to the ambient temperature;

[0087] S14. Simultaneously start compressor 203 and heat exchanger fan 201;

[0088] The frequency of the heat exchanger fan 201 is dynamically adjusted with the suction superheat at the inlet of compressor 203 as the control target. When the superheat is lower than the target range (the target range of superheat is 6 to 10°C), the fan frequency needs to be reduced to weaken heat dissipation. When the superheat is higher than the target range, the fan frequency needs to be increased to enhance heat dissipation.

[0089] S15. After the system starts, the inlet refrigerant pressure, outlet refrigerant dryness, and compressor suction pressure are adjusted.

[0090] First, the refrigerant pressure at the inlet of the battery system 210 is throttled and adjusted by the first expansion valve 205 to meet the target value requirement of the inlet saturation pressure of the battery system 210.

[0091] Simultaneously observe the refrigerant status at the outlet of battery system 210; if the refrigerant dryness at the outlet is greater than the target upper limit (e.g., 0.9), increase the compressor frequency; if the refrigerant dryness at the outlet is within the target range (e.g., 0.6-0.9), maintain or appropriately increase the compressor frequency (2% to 5%) to ensure the refrigerant dryness at the outlet of battery system 210.

[0092] When the battery temperature is high or the continuous power is high, the target temperature of the refrigerant at the inlet of the battery system 210 is high, which may exceed the suction pressure of the compressor. At this time, the third solenoid valve 208 is closed, and secondary throttling is performed through the second expansion valve 207 to control the suction pressure of the compressor and ensure safe operation.

[0093] Because of the coupling relationship between the various components, the above adjustment process is carried out cyclically based on the real-time status data collected by the system after the system is started.

[0094] like Figure 8 As shown, when the battery temperature falls below a threshold, triggering a heating demand, the system enters direct heating mode. The main control targets of the system are the inlet refrigerant pressure, outlet refrigerant dryness, and compressor suction superheat. The inlet refrigerant pressure is calculated based on the cell temperature. The temperature difference between the inlet refrigerant pressure and the saturation temperature and the cell temperature is determined based on the battery pack structure and adjusted in real time, with a recommended range of 3–15°C.

[0095] The refrigerant at the inlet of battery system 210 is in a saturated state, and its temperature corresponds one-to-one with its saturation pressure. The inlet saturation temperature can be directly adjusted by regulating the inlet saturation pressure. The inlet saturation temperature is calculated comprehensively based on the cell temperature, system heating capacity, and battery pack thermal resistance.

[0096] The outlet refrigerant dryness is mainly achieved by adjusting the frequency of compressor 203 and the power of heater 204 (if applicable), and the outlet refrigerant dryness is controlled between 0.1 and 0.4. In the above control process, it is not a single controlled object that is modulated, but the coupling relationship between various variables needs to be fully considered and comprehensive control is carried out.

[0097] The control process for direct heating mode is as follows:

[0098] S21. Request heating power based on battery system 210 Real-time temperature of the battery cell Determine the target value of the saturation temperature of the refrigerant at the 210 inlet of the battery system. And the corresponding target value of inlet saturation pressure;

[0099] Specifically, the target value of the refrigerant saturation temperature at the inlet of the battery system 210. T inlet The calculation formula is:

[0100] (4)

[0101] The thermal resistance of the battery pack (cell-cooling medium, mainly determined by the battery pack structure) is expressed in °C / kW.

[0102] S22. Based on the target value of saturation temperature obtained in step S21 With requested heating power The target operating frequency of the compressor is calculated, and the specific process is as follows:

[0103] S221. Request heating power Multiply by magnification factor S The initial requested input electrical power of the compressor is obtained. As shown in equation (5):

[0104] (5)

[0105] In the formula The value is between 1 and 1.5, and it is mainly used for heat leakage compensation in the refrigerant flow path.

[0106] S222. Based on the target saturation temperature of the inlet refrigerant. With preset throttling temperature difference Calculate the initial intake saturation temperature The calculation formula is as follows:

[0107] (6)

[0108] S223. Requested input electrical power based on the compressor With initial inspiratory saturation temperature T evap By using the compressor characteristic table, the compressor operating frequency can be preliminarily determined. f ;

[0109] S224. Verify the compressor operating frequency obtained in step S223. f and the corresponding refrigerant mass flow rate; if the refrigerant mass flow rate is lower than the requested heating power. If the refrigerant flow rate is 1.5 times the required amount, the compressor operating frequency will be increased to ensure that the mass flow rate meets the requested heating power. The corresponding refrigerant flow rate is more than 1.5 times the required value; if the calculated compressor frequency is... f If the operating frequency exceeds 90% of the compressor's maximum operating frequency, heater 204 will be activated for heat compensation; if the heater's heating power is... Then the compressor's requested input power is updated using equation (7). Then return to step S223 to recalculate the compressor frequency;

[0110] (7)

[0111] S23. During the compressor startup process, control the compressor to gradually increase its frequency to the target frequency finally determined in S22;

[0112] The first expansion valve 205 and the second expansion valve 207 are adjusted synchronously; the adjustment target of the first expansion valve 205 is the inlet saturation temperature of the battery system 210; the adjustment target of the second expansion valve 207 is the compressor inlet superheat, with a target range of 6 to 10°C.

[0113] During the entire direct heating mode operation, as the battery temperature gradually rises, the system needs to adjust the heating power and the target value of the inlet refrigerant temperature in real time according to the updated battery status, and cyclically execute the above steps S21-S23 to achieve precise and efficient thermal management.

[0114] In the above operating mode, the dryness difference between the inlet and outlet of the battery system 210 is recommended to be controlled between 0.4 and 0.7 to ensure sufficient refrigerant flow through the battery system 210 and alleviate the problem caused by uneven refrigerant flow distribution in the parallel branches. Based on this, the design flow rate of the compressor needs to exceed the rated cooling capacity by 1 to 2 times when designing this system.

[0115] The dryness difference is mainly ensured by the system's mass flow rate. The main measure is to ensure that the refrigerant mass flow rate corresponding to the compressor's operating base frequency is more than 1.5 times the system's required cooling capacity. Based on this, the frequency is fine-tuned in combination with the system's operating parameters, and the dryness difference of the inlet and outlet refrigerants is ensured by the excess refrigerant flow rate.

[0116] This invention solves the problems of uneven temperature distribution caused by inconsistent refrigerant state control at the inlet and outlet of the refrigerant system 210 in both direct cooling and direct heating modes. Through measures such as heat exchanger regeneration, active control of the condenser fan, adjustment of the opening of each expansion valve, and selection of heaters, combined with optimized control methods, the system can achieve stable control of the refrigerant saturation state at the inlet and outlet of the battery cold plate and maintain a specified dryness. Furthermore, the system achieves stable operation control through excess refrigerant flow, mitigating the problem of uneven refrigerant flow distribution in parallel branches by allowing excess refrigerant flow through the battery system 210.

[0117] This invention achieves heat exchange (regeneration) between the high-pressure refrigerant at the outlet of the second heat exchanger 101 and the low-pressure refrigerant at the outlet of the battery cold plate by setting up a first heat exchanger 102. Based on this, combined with active control of the condenser fan 201 speed, the heat exchange within the first heat exchanger 102 can be precisely adjusted. This collaborative control mechanism enables the system to finely adjust the state of the refrigerant entering the battery system 210, ultimately achieving precise control of the refrigerant dryness at the inlet and outlet of the battery cold plate over a wide range. Specifically, through the synergistic modulation of the regeneration effect, active fan speed regulation, and the opening of the first expansion valve 205, the system can ensure that the refrigerant at both the inlet and outlet of the battery cold plate is saturated and stably maintained at the specified target dryness.

[0118] In direct heating mode, the system achieves stable operation without the need for an external evaporator by using the first heat exchanger 102 for internal heat exchange and combining this with the opening of the condenser bypass solenoid valve 202. In this architecture, the first expansion valve 205 regulates the saturation temperature of the refrigerant entering the battery pack, thereby directly controlling the heat exchange temperature difference between the refrigerant and the battery cells, effectively preventing overcooling of the refrigerant at the battery outlet. Furthermore, the optional heater 204 in the circuit provides necessary supplementary heating to increase the total heating power of the system. Through the coordinated operation of the first heat exchanger 102, the bypass solenoid valve 202, the first expansion valve 205, and the optional heater 204, accurate control of the refrigerant state at the battery cold plate inlet and outlet is achieved in direct heating mode, ensuring the system's heating effect and temperature uniformity.

[0119] This invention utilizes a first heat exchanger 102 for heat recovery, ensuring that the saturated refrigerant at the cold plate outlet can further absorb heat, transforming into a stable superheated state before safely returning to the compressor. The enthalpy of the refrigerant at the condenser outlet is controlled by fan speed regulation, achieving precise adjustment of the refrigerant dryness at the cold plate outlet. The system operates with an excess refrigerant flow. This excess refrigerant flow design ensures, at the system level, that even with significant flow distribution unevenness between parallel branches (supporting a maximum unevenness of over 50%), the branch with the lowest actual flow still receives enough refrigerant to meet its minimum heat exchange requirements, effectively mitigating temperature unevenness caused by uneven flow distribution.

[0120] The above are merely preferred embodiments of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should be considered within the scope of protection of the present invention.

Claims

1. A control method of a direct cooling direct heating battery system based on a refrigerant, characterized by, The refrigerant direct cooling direct heating battery system comprises a control unit, a detection unit, an execution unit and a refrigerant circulation loop; The refrigerant circulation loop comprises a compressor (203), a second heat exchanger (101), a cold plate of a battery system (210) and a first heat exchanger (102); the compressor (203), the second heat exchanger (101), the cold plate of the battery system (210) and the first heat exchanger (102) are sequentially connected by pipelines to form a circulation loop; The detection unit comprises pressure detection components for detecting the pressure at various positions of the system and temperature detection components for detecting the temperature at various positions of the system; The execution unit comprises a first electromagnetic valve (202), a first expansion valve (205), a second expansion valve (207) and a third electromagnetic valve (208); the first electromagnetic valve (202) is connected in parallel to the second heat exchanger (101); the first expansion valve (205) is located between the first heat exchanger (102) and the cold plate of the battery system (210); the second expansion valve (207) and the third electromagnetic valve (208) are connected in parallel to each other and are located between the cold plate of the battery system (210) and the low-pressure side of the first heat exchanger (102); The control unit is connected to the detection unit, the execution unit, the compressor (203), the second heat exchanger (101) and the first heat exchanger (102) respectively, and is used for controlling the execution unit, the compressor (203), the second heat exchanger (101) and the first heat exchanger (102) according to the temperature signals and the pressure signals of the detection unit to realize the direct cooling mode or the direct heating mode; The control method comprises direct cooling mode control and direct heating mode control; the direct cooling mode control comprises the following steps: S11. Obtain the real-time temperature of the battery cell fed back by the battery system (210) T cell and the real-time heat generation P cell Determine the battery system (210) inlet refrigerant saturation temperature target value T inlet and the corresponding inlet refrigerant saturation pressure target value; S12. Based on the inlet refrigerant saturation temperature target value obtained in step S11 T inlet with the real-time temperature of the battery cell T cell , estimate the heat exchange amount between the battery pack and the refrigerant P ex ; S13. Set an initial refrigeration capacity, an initial operating frequency of the compressor (203), and an initial frequency of the heat exchanger fan (201); wherein the initial refrigeration capacity and the initial operating frequency of the compressor (203) are obtained according to the heat exchange amount P ex ​ S14. The compressor (203) and the heat exchanger fan (201) are started synchronously; the frequency of the heat exchanger fan (201) is dynamically adjusted with the suction gas superheat degree at the inlet of the compressor (203) as a control target; when the suction gas superheat degree is lower than a target range, the frequency of the heat exchanger fan (201) is reduced to weaken heat dissipation; when the suction gas superheat degree is higher than the target range, the frequency of the heat exchanger fan (201) is increased to enhance heat dissipation; S15. The inlet refrigerant pressure of the battery system (210) is adjusted to approach the target value of the inlet refrigerant saturation pressure by the first expansion valve (205); Meanwhile, the outlet refrigerant state of the battery system (210) is obtained; if the outlet refrigerant dryness is greater than an upper limit target, the frequency of the compressor (203) is increased; if the outlet refrigerant dryness is within a target range, the frequency of the compressor (203) is maintained or appropriately increased to ensure the outlet refrigerant dryness of the battery system (210); In step S11, the battery system (210) inlet refrigerant saturation temperature target value T inlet The calculation formula is: In the formula, T base is a reference value of the battery system inlet refrigerant temperature; is a correction coefficient of real-time heat and battery temperature; t s is a filtering time length of battery heat generation power; P cell is a real-time heat generation of the battery; is a rated operating heat generation of the battery pack; is a real-time temperature of the battery; is a thermal resistance of the battery pack, ℃ / kW; T c-H is a battery start refrigeration temperature, T c-L is a battery stop refrigeration temperature; is a preset temperature rise threshold; Reference value of battery system inlet refrigerant temperature T base The calculation formula is: The heat exchange amount in step S12 P ex The calculation formula is: 。 2. The control method according to claim 1, characterized by, In step S15, if the target value of the inlet refrigerant saturation temperature of the battery system (210) is high, the corresponding inlet refrigerant saturation pressure exceeds the suction pressure of the compressor, at this time, the third electromagnetic valve (208) is closed, the second expansion valve (207) is used for secondary throttling, the suction pressure of the compressor (203) is controlled, and the safety of operation is ensured.

3. The control method according to claim 1, characterized by, The direct heating mode control comprises the following steps: S21. Request heating power based on battery system Real-time temperature of the battery cell Determine the target value of the saturation temperature of the battery system (210) inlet refrigerant ; S22. based on the saturation temperature target value with the requested heating power , the compressor (203) operating target frequency is calculated f ; S23. During the start-up process of the compressor (203), gradually increase the frequency of the compressor (203) to the target frequency f ; synchronously regulating the first expansion valve (205) so that the battery system (210) inlet saturation temperature approaches a target value ; The second expansion valve (207) is synchronously adjusted to make the inlet refrigerant superheat degree of the compressor (203) within a target range; Battery system (210) inlet refrigerant saturation temperature target value in step S21 T inlet The calculation formula is: a heating thermal resistance for the battery pack; The specific process of step S22 is as follows: S221. Request heating power times the amplification factor S , resulting in the initial requested input electric power of the compressor ; S222. according to the saturation temperature target value of the inlet refrigerant with a preset throttle temperature difference , calculate the initial suction saturation temperature ; S223. Input electric power based on request of compressor (203) With initial suction saturation temperature T evap Preliminary determination of compressor (203) operating frequency by compressor (203) characteristic table f ; S224. Review the compressor (203) operating frequency obtained in step S223 f and the corresponding refrigerant mass flow; if the refrigerant mass flow is lower than the requested heating power times the corresponding refrigerant flow, then increase the compressor operating frequency; if the calculated compressor (203) operating frequency f exceeds 90% of the maximum compressor (203) operating frequency, then start the heater (204) to compensate for heat; update the requested input electric power of the compressor (203) according to the heating power of the heater (204) , and return to step S223 to recalculate the compressor (203) operating frequency.

4. The control method according to claim 1 or 2, characterized by, The pressure detection member comprises a first pressure sensor (401), a second pressure sensor (402), and a third pressure sensor (403); the first pressure sensor (401) is used to collect the suction pressure of the compressor (203); the second pressure sensor (402) is used to collect the discharge pressure of the compressor (203); and the third pressure sensor (403) is used to collect the inlet refrigerant pressure of the battery system (210).

5. The control method according to claim 1 or 2, characterized by, The temperature detection member comprises a first temperature sensor (301), a second temperature sensor (302), a third temperature sensor (303), a fourth temperature sensor (304), a fifth temperature sensor (305), a sixth temperature sensor (306), and a seventh temperature sensor (307). The first temperature sensor (301) is used to collect the suction temperature of the compressor (203); the second temperature sensor (302) is used to collect the discharge temperature of the compressor (203); the third temperature sensor (303) is used to collect the inlet refrigerant temperature of the high-pressure side of the first heat exchanger (102); the fourth temperature sensor (304) is used to collect the outlet refrigerant temperature of the high-pressure side of the first heat exchanger (102); the fifth temperature sensor (305) is used to collect the inlet refrigerant temperature of the low-pressure side of the first heat exchanger (102); the sixth temperature sensor (306) is used to collect the outlet refrigerant temperature of the battery system (210); and the seventh temperature sensor (307) is used to collect the inlet refrigerant temperature of the battery system (210).

6. The control method according to claim 1 or 2, characterized by, The first expansion valve (205) is connected in parallel with a second electromagnetic valve (206) for bypassing the first expansion valve (205).

7. The control method according to claim 1 or 2, characterized by, A heater (204) is arranged between the cold plate of the battery system (210) and the first heat exchanger (102), and the heater (204) is connected to the control unit.

8. The control method according to claim 1 or 2, characterized by, A third expansion valve (211) is further included, which is connected in parallel to the inlet and outlet of the second heat exchanger (101) after being connected in series with the first electromagnetic valve (202), and is used to adjust the refrigerant flow of the second heat exchanger (101) in the direct cooling mode or the direct heating mode.

9. The control method according to claim 1 or 2, characterized by, A fourth expansion valve (212) and a fifth expansion valve (213) are further included; the fourth expansion valve (212) is connected in parallel between the inlet and outlet of the low-pressure side of the first heat exchanger (102); the fifth expansion valve (213) is connected in parallel between the inlet and outlet of the high-pressure side of the first heat exchanger (102); and the fourth expansion valve (212) and the fifth expansion valve (213) are used to control the heat exchange amount of the first heat exchanger (102).

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