A method and system for thermal management of energy storage batteries in low temperature environments

Abstract

The present application relates to the technical field of energy storage battery thermal management, in particular to an energy storage battery thermal management method and system for low-temperature environment, the method comprising: setting a jet augmenting branch comprising a branch throttling element and an intermediate heat exchanger; judging whether the compressor pressure difference is abnormal in the cold start stage based on the real-time collected compressor discharge pressure and suction pressure; if so, adjusting the branch throttling element to a preset fixed throttling opening, injecting refrigerant into the compressor intermediate cavity until the preset maintenance time length is met or the superheat degree is greater than 0K; based on the real-time detection value of the compressor discharge temperature, dynamically adjusting the throttling opening of the branch throttling element to realize switching between the energy efficiency priority control mode and the safety priority control mode. Through the method and system, the problem of slow condensing pressure build-up of the working medium under low-temperature or even extremely low-temperature working conditions can be effectively solved.

Description

Technical Field

[0001] This invention relates to the field of thermal management technology for energy storage batteries, and in particular to a thermal management method and system for energy storage batteries in low-temperature environments. Background Technology

[0002] Thermal management of energy storage systems is a key technology for ensuring the safe, efficient, and long-life operation of electrochemical energy storage systems. Its main function is to maintain the battery within a suitable temperature range (optimal operating temperature is approximately 10 to 35 degrees Celsius) through heat dissipation, heating, and temperature equalization control, preventing the risk of thermal runaway and optimizing performance. The thermal management performance of energy storage batteries has become a critical factor in ensuring their safety, lifespan, and efficiency.

[0003] Several management systems have been proposed in the prior art, such as the Chinese invention patent document with publication number CN120767468A, publication date October 10, 2025, entitled "Energy Storage Direct Cooling Temperature Control System"; and another example, the Chinese invention patent document with publication number CN119742503A, publication date April 1, 2025, entitled "A Direct Cooling Thermal Management System, Energy Storage Container and Control Method".

[0004] The existing technologies, represented by the aforementioned patent documents, lack cold-start strategies for low-temperature and extremely low-temperature operating conditions. For energy storage systems with high thermal inertia, the core challenge during cold starts at temperatures below 0°C and below -20°C is the inability to establish a system pressure differential. This results in ineffective refrigerant circulation, leading to zero or extremely weak heating capacity. Furthermore, the more complex the system, the slower the temperature equalization during cold starts, potentially making startup even more difficult. The control logic of existing technical solutions is based on the assumption that the system has already established a circulating pressure differential, without considering the difficulties of cold starts in low-temperature and extremely low-temperature environments.

[0005] In the prior art, a Chinese invention patent document with publication number CN116294271A and publication date of June 23, 2023, discloses the following technical solution: a method for handling excessively high exhaust temperature during low-temperature startup of a heat pump fixed-frequency enthalpy-injected compressor, mainly used to solve the problem of excessively high exhaust temperature during low-temperature startup of a fixed-frequency compressor. Structurally, it includes a compressor, a four-way valve, a heat exchanger, an economizer, and two parallel cooling pipelines: one is an enthalpy-injected pipeline that exchanges heat through the economizer, and the other is a liquid-injected pipeline that directly enters the gas inlet. Its core principle is to predict the startup load based on the ambient temperature and outlet water temperature, select to open the liquid-injected valve or the enthalpy-injected valve during the startup phase, and switch between the two based on the exhaust temperature during the formal operation phase, utilizing the more direct cooling effect of liquid injection to compensate for the lag in enthalpy-injected cooling.

[0006] This invention patent document describes a dual-branch phased control system that divides the operating state into two stages: startup and formal operation. During startup, the system determines whether to open the liquid injection electronic expansion valve or the enthalpy injection electronic expansion valve based on the ambient and outlet water temperatures. Specifically, the initial opening degree of the enthalpy injection electronic expansion valve is determined based on the ambient and outlet water temperatures, while the initial opening degree of the liquid injection electronic expansion valve is set to a fixed number of steps. The startup stage is fixed at M minutes. After M minutes, the unit enters the formal operation stage. During formal operation, the system determines whether to switch the opening states of the two electronic expansion valves based on the current exhaust temperature or the opening degree of the currently open electronic expansion valve, and then periodically adjusts the opening degree of the open electronic expansion valve.

[0007] The above-mentioned technical solution cannot meet the actual operating requirements of the energy storage battery thermal management system in actual use: the technical solution only focuses on solving the problem of unit shutdown caused by excessive exhaust temperature, without taking into account the problem that in actual engineering applications, due to the series and parallel connection of multiple battery module cold plates as evaporators in the refrigeration cycle, the system thermal inertia is too large, the high load causes the high pressure side pressure of the system to fail to build up for a long time, the system cannot reach the normal operating pressure difference range, and the start-up is difficult. Summary of the Invention

[0008] To address the aforementioned technical problems, this invention proposes a thermal management method and system for energy storage batteries in low-temperature environments. It adopts a hardware architecture similar to existing technologies and effectively solves the problem that when a large-capacity energy storage battery is used as a load with high thermal inertia, the high-voltage side pressure of the system cannot be established for a long time, causing the system to be unable to enter the normal operating pressure difference range.

[0009] This invention is achieved by adopting the following technical solution: A thermal management method for energy storage batteries in low-temperature environments includes the following steps: Step S1. Integrate a jet enthalpy-increasing branch in the thermal management subsystem. The branch includes a branch throttling element and an intermediate heat exchanger. One end of the branch throttling element is connected to the outlet of the plate heat exchange component in the thermal management subsystem, and the other end is connected to the low-temperature side channel of the intermediate heat exchanger. The outlet of the low-temperature side channel of the intermediate heat exchanger is connected to the compressor's gas injection port in the thermal management subsystem, and the high-temperature side channel of the intermediate heat exchanger is connected to the main refrigerant circulation loop of the thermal management subsystem. Step S2. Based on the real-time collected compressor discharge pressure and suction pressure, determine whether the compressor pressure difference is abnormal during the cold start phase; if so, start the open-loop feedforward injection control: adjust the branch throttling element to the preset fixed throttling opening, inject refrigerant into the compressor intermediate cavity until the preset maintenance time is met or the injection superheat is greater than 0K. Step S3. Based on the real-time detection value of the compressor exhaust temperature, dynamically adjust the throttling opening of the branch throttling element to achieve adaptive switching between energy efficiency priority control mode and safety priority control mode.

[0010] The method for determining whether the compressor pressure difference is abnormal during the cold start phase includes: real-time acquisition of the compressor's discharge pressure and suction pressure, and calculation of the real-time pressure difference between the two; if the real-time pressure difference remains at or above a preset pressure difference threshold for a preset stabilization time during the cold start phase, then it is determined that the compressor has an abnormal pressure difference establishment.

[0011] The open-loop feedforward injection control specifically includes: Adjust the branch throttling element to the preset fixed throttling opening and lock it in operation, while starting the timing unit; Real-time acquisition of the gas supply temperature before the compressor's gas supply port T inj and replenishment pressure P inj Based on the replenishment pressure P inj corresponding saturation temperature T inj_sat ( P inj Calculate the superheat of the supplementary gas. SH inj : SH inj = T inj - T inj_sat ( P inj ); When the timing unit runs t inj Exceeding the preset duration, or overheating during Qi replenishment. SH inj If the value is greater than 0K, exit open-loop feedforward injection control.

[0012] The preset fixed throttling opening is 30% to 40% of the total valve body opening.

[0013] A hysteresis zone is set between the energy efficiency priority control mode and the safety priority control mode to avoid frequent switching.

[0014] Step S3 specifically includes: Real-time monitoring of compressor discharge temperature T out Three key thresholds are preset from low to high: the upper limit temperature of energy efficiency mode, the trigger temperature of safety mode, and the protection cut-off temperature; When exhaust temperature Tout When the temperature is below the upper limit of the energy efficiency mode, the energy efficiency priority control mode is executed: the superheat of the replenished gas is used as the controlled variable, and the control is performed incrementally. PID The algorithm adjusts the throttling opening of the branch throttling element; When exhaust temperature T out When the temperature exceeds the safety mode trigger temperature, the safety priority control mode is executed: based on the exhaust temperature. T out For the controlled variable, use incremental method PID The algorithm adjusts the throttling opening of the branch throttling element; When exhaust temperature T out When the temperature is between the upper limit of the energy efficiency mode and the trigger temperature of the safety mode, the control mode of the previous moment remains unchanged, and it is determined whether the control mode needs to be switched. When exhaust temperature T out When the temperature exceeds the protection cutoff temperature, the over-temperature protection action is triggered.

[0015] Using the superheat of the replenished gas as the controlled variable, through incremental... PID The algorithm adjusts the throttling opening of the branch throttling element, specifically including the following steps: Determine whether the real-time calculated superheat of the supplementary gas is lower than the preset low value of superheat. If so, reduce the throttling opening of the branch throttling element according to the preset opening change amount until the superheat of the supplementary gas is not lower than the preset low value of superheat. Calculate the deviation between the supplementary superheat and the target superheat, and determine the adjustment direction of the throttling opening of the branch throttling element based on the relationship between the deviation and the preset dead zone. According to incremental PID Algorithm to calculate the theoretical change in opening degree ; Change in theoretical opening The single step limit and the upper and lower opening limits are executed sequentially to obtain the final opening adjustment amount.

[0016] exhaust temperature T out For the controlled variable, use incremental method PID The algorithm adjusts the throttling opening of the branch throttling element, specifically including the following steps: Calculate the deviation between the current exhaust temperature and the target control temperature, and determine the adjustment direction of the throttling opening of the branch throttling element based on the relationship between the deviation and the preset dead zone; According to incremental PID Algorithm to calculate the theoretical change in opening degree The control policies are executed in the following priority order: Configure backflow prevention fuse protection; calculate exhaust superheat in real time. DSH When the exhaust is superheated DSH If the value is less than the preset limit, the command to increase the opening will be blocked until the exhaust superheat is reached. DSH Not less than the preset limit value; Set safety constraints: Determine if the gas replenishment superheat is less than 0; if so, ignore the incremental type. PID The algorithm's control command reduces the throttling opening of the branch throttling element according to the preset opening change amount, until the superheat of the supplementary gas is greater than or equal to 0. Change in theoretical opening By applying the upper and lower limits of the opening, the final opening adjustment amount is obtained; When the anti-return melt fuse protection has blocked the opening increase command, and at the same time the gas replenishment superheat is detected to be less than 0, the anti-return melt fuse protection is given the highest priority, and the throttling opening decrease command in the safety constraint is no longer executed.

[0017] Based on the relationship between the deviation and the preset dead zone, the adjustment direction of the throttling opening of the branch throttling element is determined. Specifically, if the deviation is greater than the positive value of the preset dead zone, the throttling opening of the branch throttling element is increased; if the deviation is less than the negative value of the preset dead zone, the throttling opening of the branch throttling element is decreased; if the deviation is between the positive and negative values ​​of the preset dead zone, the throttling opening of the current branch throttling element remains unchanged.

[0018] Theoretical opening change The calculation method is as follows: , In the formula, K p It is a proportionality constant. K i Let be the integration constant. K d Let be the differential constant. e ( t ) represents the current deviation. e ( t -1) represents the deviation from the previous sampling period. e ( t -2) represents the deviation from the previous sampling period.

[0019] The method for calculating the exhaust superheat is as follows: , In the formula, DSH For exhaust superheat, T out The exhaust temperature, To be based on exhaust pressure P out The corresponding saturation temperature.

[0020] Determining whether a control mode switch is needed specifically refers to: if the exhaust temperature is within the hysteresis holding region... T out When the temperature exceeds the safety mode trigger temperature, switch to safety priority control mode and reset the incremental control. PID Algorithm deviation history; if within the hysteresis holding region, exhaust temperature T out If the temperature is below the upper limit of the energy efficiency mode, switch to the energy efficiency priority control mode and reset the incremental temperature. PID Algorithm deviation history; if within the hysteresis holding region, exhaust temperature T out Located between the upper limit temperature of energy efficiency mode and the trigger temperature of safety mode, the control mode of the previous moment remains unchanged.

[0021] When the safety priority control mode is executed, the lower limit control of the makeup gas superheat is released, allowing the makeup gas superheat to drop to 0K to enable wet steam cooling.

[0022] A thermal management system for energy storage batteries in low-temperature environments includes a thermal management subsystem, a vapor injection enthalpy-increasing branch, a sensor array, and a controller. The thermal management subsystem includes a compressor, a four-way reversing valve, an outdoor heat exchanger, a main circuit throttling element, and a plate heat exchanger, which together form a main refrigerant circulation loop. The branch includes a branch throttling element and an intermediate heat exchanger. One end of the branch throttling element is connected to the outlet of the plate heat exchanger, and the other end is connected to the low-temperature side flow channel of the intermediate heat exchanger. The outlet of the low-temperature side flow channel of the intermediate heat exchanger is connected to the compressor's gas injection port, and the high-temperature side flow channel of the intermediate heat exchanger is connected to the main refrigerant circulation loop. The vapor injection enthalpy-enhancing branch is configured as follows: when the compressor differential pressure is abnormally established during the cold start phase, open-loop feedforward injection control is activated: the branch throttling element is adjusted to a preset fixed throttling opening, and refrigerant is injected into the compressor intermediate cavity until the preset maintenance duration or the injection superheat is greater than 0K is met; and after the open-loop feedforward injection control is completed, the throttling opening of the branch throttling element is dynamically adjusted to achieve adaptive switching between energy efficiency priority control mode and safety priority control mode.

[0023] The sensor group includes an exhaust temperature sensor, an exhaust pressure sensor, an intake pressure sensor, a supplementary air temperature sensor, and a supplementary air pressure sensor.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. A 5MWh-level energy storage battery system is a huge "thermal inertia body." During cold starts at temperatures below 0°C or even below -20°C, the battery itself is extremely cold, making it difficult to establish both evaporation pressure (low pressure) and condensation pressure (high pressure). The system pressure difference is too small, the refrigerant circulation is insufficient, the heating capacity is weak, and the battery temperature rises extremely slowly. This invention addresses the pain point of "slow pressure establishment" unique to high-load direct-cooling systems by using the difference between exhaust pressure and intake pressure as a feedforward parameter to establish a cold start enthalpy-increasing control process. That is, it initiates open-loop feedforward injection control to actively and forcibly establish high pressure in the early stage of startup, enabling the thermal management system to quickly break out of the "low pressure difference dead loop" and enter an effective working state, significantly improving the system's response speed and availability in cold environments.

[0025] Furthermore, this invention proposes a "dual-modal decoupling control based on exhaust temperature hysteresis," which achieves intelligent switching of control objectives and resolves the contradiction between "safety" and "performance" under high-pressure conditions. It pursues maximum energy efficiency (controlling the superheat of the injection gas) at safe temperatures; when the exhaust temperature is dangerous, it seamlessly switches to a safety-priority control mode (controlling the exhaust temperature), even allowing controllable "wet steam injection" for powerful cooling. This ensures both the long-term safe operation of the compressor and maximizes the system's heating potential.

[0026] This invention achieves precise adjustment of cold start enthalpy enhancement control and dual-mode decoupling control by precisely intervening in the opening of the branch throttling element of the jet enthalpy enhancement branch. It can not only solve the problem of slow condensation pressure build-up caused by the large load thermal inertia of the working fluid (such as R410A) under low temperature or even extremely low temperature conditions, but also solve the contradiction between exhaust temperature protection and heating performance during high pressure ratio operation.

[0027] 2. Under non-extreme operating conditions, the system operates in an energy efficiency-priority control mode. By precisely controlling the superheat of the supplementary gas, the jet enthalpy enhancement technology is always operating at its optimal point, improving the compressor's COP. Simultaneously, the hysteresis holding region set in the control logic avoids frequent oscillations in the control mode near the critical point, protecting actuators such as the electronic expansion valve, making the system operate more smoothly and reliably, and extending equipment lifespan.

[0028] 3. When determining whether the differential pressure establishment is abnormal, this invention not only considers whether the real-time differential pressure is lower than the preset differential pressure threshold, but also takes into account the duration for which the real-time differential pressure remains above the preset differential pressure threshold. This can prevent false triggering caused by sensor signal fluctuations and significantly improve the accuracy of abnormality judgment.

[0029] 4. The open-loop feedforward injection control method of this invention ignores the current exhaust temperature or injection superheat parameters when the cold start outlet pressure difference has not yet been effectively established, i.e., it ignores the hysteresis or unreliability of these parameters, and immediately adjusts the opening of the branch throttling element to a preset fixed throttling opening and locks it in operation. Through feedforward active intervention, pressure can still be quickly established even when the sensor feedback signal is not yet stable or the system is in an unsteady state, significantly improving the cold start success rate in low and extremely low temperature environments. At the same time, through dual exit criteria, it takes into account both start-up efficiency and compressor liquid slugging safety, avoiding the risk of wet compression caused by blindly continuing injection.

[0030] 5. When the energy efficiency priority control mode is executed in this invention, it is based on incremental... PID The algorithm calculates the theoretical change in aperture. It is not executed directly, but rather through a triple filtration process, executed sequentially according to priority. This includes: setting safety constraints, namely ensuring that the superheat of the replenished gas is not lower than the preset low superheat value, ensuring that the refrigerant entering the compressor intermediate cavity is superheated vapor, and preventing liquid refrigerant from entering; then limiting the number of steps at a time to prevent pressure oscillations caused by sudden changes in refrigerant flow; and finally, limiting the opening degree to ensure that the final number of steps is within the physical range of the valve.

[0031] By employing the aforementioned layered and orderly control methods, not only is the safety and convenience of the system ensured during high-efficiency operation, but the stability, robustness, and reliability of the control process are also significantly improved.

[0032] 6. When the safety priority control mode is executed in this invention, it is based on incremental... PID The algorithm calculates the theoretical change in aperture. It also undergoes triple filtration, executed sequentially according to priority, including anti-backflow fuse protection, safety constraints, and upper and lower limit locking of the opening. This control method prioritizes compressor safety and can effectively avoid serious failures such as wet compression and liquid slugging even under high-risk operating conditions, significantly improving system reliability and fault tolerance.

[0033] 7. Through this control method, the present invention allows the superheat of the make-up gas to drop to 0K, indicating that the present invention allows a trace amount of gas-liquid two-phase mixture (wet vapor) to enter the intermediate cavity of the compressor. By utilizing the sensible and latent heat absorbed during the flash evaporation of liquid refrigerant, the exhaust temperature is significantly reduced, preventing the system from triggering shutdown protection due to excessively high exhaust temperature.

[0034] 8. This control system can not only solve the problem of slow condensation pressure build-up caused by the large load thermal inertia of the working fluid (such as R410A) under low temperature or even extremely low temperature conditions, but also solve the contradiction between exhaust temperature protection and heating performance during high pressure operation. Attached Figure Description

[0035] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments, wherein: Figure 1 This is a schematic diagram of the control system in this invention; Figure 2 This is a schematic diagram of the cold start enthalpy increase control process in this invention; Figure 3 This is a schematic diagram of the dual-modal decoupling control process in this invention; Marked in the image: 1. Compressor, 2. Four-way reversing valve, 3. Outdoor heat exchanger, 4. Main circuit throttling element, 5. Plate heat exchanger component, 6. Branch circuit throttling element, 7. Intermediate heat exchanger. Detailed Implementation

[0036] Example 1 As a basic embodiment of the present invention, the present invention includes a thermal management method for energy storage batteries in low-temperature environments, comprising the following steps: Step S1. Integrate the vapor injection enthalpy-enhancing branch into the existing thermal management subsystem. The vapor injection enthalpy-enhancing branch includes a branch throttling element 6 and an intermediate heat exchanger 7. One end of the branch throttling element 6 is connected to the outlet of the plate heat exchanger 5 in the thermal management subsystem, and the other end is connected to the low-temperature side channel of the intermediate heat exchanger 7. The outlet of the low-temperature side channel of the intermediate heat exchanger 7 is connected to the gas injection port of the compressor 1 in the thermal management subsystem, and the high-temperature side channel of the intermediate heat exchanger 7 is connected to the main refrigerant circulation loop of the thermal management subsystem.

[0037] Step S2. Based on the real-time collected discharge pressure and suction pressure of compressor 1, determine whether the pressure difference of compressor 1 is abnormal during the cold start phase. If so, start the open-loop feedforward injection control: adjust the branch throttling element 6 to the preset fixed throttling opening, inject refrigerant into the intermediate cavity of compressor 1 until the preset maintenance time is met or the injection superheat is greater than 0K, and then proceed to step S3.

[0038] Step S3. Based on the real-time detection value of the exhaust temperature of compressor 1, dynamically adjust the throttling opening of the branch throttling element 6 to achieve adaptive switching of the control target, that is, to achieve switching between energy efficiency priority control mode and safety priority control mode.

[0039] Example 2 In a preferred embodiment of the present invention, the present invention includes a thermal management method for energy storage batteries in low-temperature environments, comprising the following steps: Step S1. Integrate the vapor injection enthalpy-increasing branch in the thermal management subsystem. The branch includes a branch throttling element 6 and an intermediate heat exchanger 7. One end of the branch throttling element 6 is connected to the outlet of the plate heat exchanger 5 in the thermal management subsystem, and the other end is connected to the low-temperature side flow channel of the intermediate heat exchanger 7. The outlet of the low-temperature side flow channel of the intermediate heat exchanger 7 is connected to the gas injection port of the compressor 1 in the thermal management subsystem, and the high-temperature side flow channel of the intermediate heat exchanger 7 is connected to the main refrigerant circulation loop of the thermal management subsystem.

[0040] Step S2. Based on the real-time collected discharge and suction pressures of compressor 1, determine whether the pressure difference of compressor 1 is abnormally established during the cold start phase. Specifically, the discharge and suction pressures of compressor 1 are collected in real time, and the real-time pressure difference between them is calculated. If, during the cold start phase, the real-time pressure difference remains at or above a preset pressure difference threshold for a preset stabilization time, it is determined that compressor 1 has an abnormal pressure difference establishment.

[0041] If the differential pressure establishment of compressor 1 is found to be abnormal during the cold start phase, the open-loop feedforward injection control is activated: the branch throttling element 6 is adjusted to a preset fixed throttling opening, and refrigerant is injected into the intermediate cavity of compressor 1 until the preset maintenance time is met or the injection superheat is greater than 0K, then proceed to step S3. Specifically, this includes: Adjust the branch throttling element 6 to the preset fixed throttling opening and lock it in operation, while simultaneously starting the timing unit.

[0042] Real-time acquisition of the gas supply temperature before the gas supply port of compressor 1 T inj and replenishment pressure P inj Based on the replenishment pressure P inj corresponding saturation temperature T inj_sat ( P inj Calculate the superheat of the supplementary gas. SH inj : SH inj = T inj - T inj_sat ( P inj ).

[0043] When the timing unit runs t inj Exceeding the preset duration, or overheating during Qi replenishment. SH inj If the value is greater than 0K, exit open-loop feedforward injection control.

[0044] Step S3. Based on the real-time detected value of the compressor 1's exhaust temperature, dynamically adjust the throttling opening of the branch throttling element 6 to achieve adaptive switching of the control target, that is, to switch between the energy efficiency priority control mode and the safety priority control mode. A hysteresis holding zone is also set between the energy efficiency priority control mode and the safety priority control mode to avoid frequent switching.

[0045] Example 3 In another preferred embodiment of the present invention, the present invention includes a thermal management method for energy storage batteries in low-temperature environments, comprising the following steps: Step S1. Integrate the vapor injection enthalpy-increasing branch in the thermal management subsystem. The branch includes a branch throttling element 6 and an intermediate heat exchanger 7. One end of the branch throttling element 6 is connected to the outlet of the plate heat exchanger 5 in the thermal management subsystem, and the other end is connected to the low-temperature side flow channel of the intermediate heat exchanger 7. The outlet of the low-temperature side flow channel of the intermediate heat exchanger 7 is connected to the gas injection port of the compressor 1 in the thermal management subsystem, and the high-temperature side flow channel of the intermediate heat exchanger 7 is connected to the main refrigerant circulation loop of the thermal management subsystem.

[0046] Step S2. Based on the real-time collected discharge pressure and suction pressure of compressor 1, determine whether the pressure difference of compressor 1 is abnormal during the cold start phase. If so, start the open-loop feedforward injection control: adjust the branch throttling element 6 to the preset fixed throttling opening, inject refrigerant into the intermediate cavity of compressor 1 until the preset maintenance time is met or the injection superheat is greater than 0K, and then proceed to step S3.

[0047] Step S3. Based on the real-time detected value of the compressor 1's exhaust temperature, dynamically adjust the throttling opening of the branch throttling element 6 to achieve adaptive switching of the control target, that is, to switch between the energy efficiency priority control mode and the safety priority control mode. A hysteresis holding zone is also set between the energy efficiency priority control mode and the safety priority control mode to avoid frequent switching.

[0048] Specifically, the exhaust temperature of compressor 1 is monitored in real time. T out It presets three key thresholds from low to high: the upper limit temperature of energy efficiency mode, the trigger temperature of safety mode, and the protection cut-off temperature.

[0049] When exhaust temperature T out When the temperature is below the upper limit of the energy efficiency mode, the energy efficiency priority control mode is executed: the superheat of the replenished gas is used as the controlled variable, and the control is performed incrementally. PID The algorithm adjusts the throttling opening of the branch throttling element 6. When the exhaust temperature... T out When the temperature exceeds the safety mode trigger temperature, the safety priority control mode is executed: based on the exhaust temperature. T outFor the controlled variable, use incremental method PID The algorithm adjusts the throttling opening of the branch throttling element 6. When the exhaust temperature... T out When the temperature is between the upper limit of energy efficiency mode and the trigger temperature of safety mode, the control mode remains unchanged from the previous moment, while simultaneously determining whether a control mode switch is necessary. (When the exhaust temperature...) T out When the temperature exceeds the protection cutoff temperature, the over-temperature protection action is triggered.

[0050] Among them, the superheat of the replenished gas is used as the controlled variable, and the incremental method is used. PID The algorithm adjusts the throttling opening of the branch throttling element 6, specifically including the following steps: Step 1. Determine whether the real-time calculated superheat of the supplementary gas is lower than the preset low value of superheat. If so, reduce the throttling opening of the branch throttling element 6 according to the preset opening change amount until the superheat of the supplementary gas is not lower than the preset low value of superheat.

[0051] Step 2. Calculate the deviation between the supplementary superheat and the target superheat, and based on the relationship between the deviation and the preset dead zone, determine the adjustment direction of the throttling opening of the branch throttling element 6.

[0052] Step 3. Based on the incremental formula PID Algorithm to calculate the theoretical change in opening degree .

[0053] Step 4. Calculate the theoretical opening change. The single step limit and the upper and lower opening limits are executed sequentially to obtain the final opening adjustment amount.

[0054] Among them, exhaust temperature T out For the controlled variable, use incremental method PID The algorithm adjusts the throttling opening of the branch throttling element 6, specifically including the following steps: Calculate the deviation between the current exhaust temperature and the target control temperature, and based on the relationship between the deviation and the preset dead zone, determine the adjustment direction of the throttling opening of the branch throttling element 6. According to incremental... PID Algorithm to calculate the theoretical change in opening degree The control policies are executed in the following priority order: Configure backflow prevention fuse protection; calculate exhaust superheat in real time. DSH When the exhaust is superheated DSH If the value is less than the preset limit, the command to increase the opening will be blocked until the exhaust superheat is reached. DSH Not less than the preset limit value; Set safety constraints: Determine if the gas replenishment superheat is less than 0; if so, ignore the incremental type. PIDThe algorithm's control command reduces the throttling opening of the branch throttling element 6 according to the preset opening change amount, until the superheat of the supplementary gas is greater than or equal to 0. Change in theoretical opening By applying the upper and lower limits of the opening, the final opening adjustment amount is obtained.

[0055] When the anti-return melt fuse protection has blocked the opening increase command, and at the same time the gas replenishment superheat is detected to be less than 0, the anti-return melt fuse protection is given the highest priority, and the throttling opening decrease command in the safety constraint is no longer executed.

[0056] Example 4 In another preferred embodiment of the present invention, the present invention includes a thermal management method for energy storage batteries in low-temperature environments, comprising the following steps: Step S1. Refer to the instruction manual appendix. Figure 1 The thermal management subsystem integrates a vapor injection enthalpy-increasing branch. Along the refrigerant flow direction, the thermal management subsystem includes, in sequence, a compressor 1, a four-way reversing valve 2, an outdoor heat exchanger 3, a main throttling element 4, and a plate heat exchanger 5, forming the main refrigerant circulation loop. This main refrigerant circulation loop is used to achieve basic cooling and heating functions. The thermal management subsystem also includes a sensor array and a controller.

[0057] The compressor 1 is a compressor with a jet enthalpy-increasing port, used to compress low-temperature, low-pressure gaseous refrigerant into high-temperature, high-pressure gaseous refrigerant. The four-way reversing valve 2 is used to switch the cooling / heating operation mode of the thermal management subsystem. The four-way reversing valve 2 has four ports; during cooling, DC and ES are connected respectively; during heating, DE and CS are connected respectively. The outdoor heat exchanger 3, as a component for heat exchange with ambient air, acts as an evaporator to absorb heat in heating mode and as a condenser to release heat in cooling mode. The main circuit throttling element 4 can be a main circuit electronic expansion valve, used to regulate the refrigerant flow rate and superheat of the main cycle. In the R410A working fluid phase change direct cooling heat pump thermal management subsystem of a large-scale energy storage container, the indoor heat exchanger is preferably a direct cooling plate, attached to the surface of the energy storage battery pack, used for direct cooling or heating of the battery.

[0058] The branch circuit includes a branch throttling element 6 and an intermediate heat exchanger 7. The branch throttling element 6 can be a branch electronic expansion valve, serving as a flow regulation and throttling element for the branch circuit. In this application, the opening degree of the branch electronic expansion valve is precisely adjusted by a controller, used both to control the superheat of the make-up gas and to perform open-loop injection under extreme operating conditions. The intermediate heat exchanger 7 can be an economizer. One end of the branch electronic expansion valve is connected to the outlet of the plate heat exchange component 5, and the other end is connected to the low-temperature side channel of the intermediate heat exchanger 7. The outlet of the low-temperature side channel of the intermediate heat exchanger 7 is connected to the make-up gas port of the compressor 1, and the high-temperature side channel of the intermediate heat exchanger 7 is connected between the outdoor heat exchanger 3 and the main throttling element 4, connecting the main refrigerant circulation loop. After the branch refrigerant flows through the branch electronic expansion valve for throttling and pressure reduction, it enters the low-temperature side channel of the economizer, where it undergoes counter-current heat exchange with the main refrigerant in the high-temperature side channel of the economizer.

[0059] The sensor group includes an exhaust temperature sensor, an exhaust pressure sensor, an intake pressure sensor, a makeup air temperature sensor, and a makeup air pressure sensor. The exhaust temperature sensor is located at the exhaust port of compressor 1 and is used to monitor the exhaust temperature in real time. T out The exhaust pressure sensor is located at the exhaust port of compressor 1 and is used to monitor the exhaust pressure in real time. P out The suction pressure sensor is located at the suction port of compressor 1 and is used to monitor the suction pressure in real time. P in The gas supply temperature sensor is installed at the gas supply port of compressor 1 to monitor the gas supply temperature in real time. T inj The gas supply pressure sensor is installed at the gas supply port of compressor 1 to monitor the gas supply pressure in real time. P inj .

[0060] The controller includes a microprocessor whose signal input is electrically connected to the aforementioned sensors, and whose output is connected to the main electronic expansion valve, the branch electronic expansion valve, and the compressor 1 driver. The controller internally stores computer programs for executing the following "cold start enthalpy increase control" and "dual-mode decoupling control" to resolve the problem of slow condensation pressure build-up caused by the large load thermal inertia of R410A refrigerant under low or even extremely low temperature conditions, as well as the contradiction between exhaust temperature protection and heating performance during high-pressure operation.

[0061] During system operation, the main circuit electronic expansion valve is independently adjusted according to the preset conventional target superheat logic. The control logic of this invention mainly targets the branch circuit electronic expansion valves. By precisely intervening in the opening of the branch circuit electronic expansion valves in the jet enthalpy-increasing branch, precise adjustment of cold start enthalpy-increasing control and dual-mode decoupling control is achieved.

[0062] Step S2. Cold start enthalpy control.

[0063] The cold start enthalpy increase control is mainly used in the initial stage of heating mode startup at low ambient temperatures. By forcibly opening the gas replenishment circuit, the condensing pressure is quickly established before the condensing temperature rises. This solves the problem that when a large-capacity energy storage battery is used as a load with high thermal inertia, the high-pressure side pressure of the system cannot be established for a long time, causing the system to be unable to enter the normal operating pressure difference range.

[0064] During the initial startup phase at low or even extremely low temperatures, the electronic expansion valve in the fixed-opening control branch forces refrigerant into the compressor 1's injection port. The increased refrigerant mass flow rate rapidly increases the refrigerant density on the discharge side of compressor 1, thereby physically and quickly raising the condensing pressure before the battery-side heat exchanger temperature has risen significantly, enabling the system to quickly reach the pressure differential conditions required for stable operation.

[0065] For details, please refer to the instruction manual appendix. Figure 2 This includes the following steps: Step S 21 Compressor 1 starts running. At this time, the initialization begins, and the controller initializes the branch electronic expansion valve to the fully closed state (opening degree = 0), while the main electronic expansion valve is adjusted according to the conventional superheat logic.

[0066] Step S 22 Determine if there is any abnormality in the differential pressure buildup of compressor 1 during the cold start phase. Specifically, collect the discharge pressure of compressor 1 in real time. P out and inhalation pressure P in And calculate the real-time pressure difference between the two. If it is during the cold start phase, the real-time differential pressure... The pressure difference remains no lower than the preset threshold. The duration reaches the preset stable time If the following triggering conditions are met, it is determined that compressor 1 has a pressure differential establishment anomaly: , In this embodiment, a preset differential pressure threshold is used. It can be set to 4.0 bar; preset stabilization time It can be set to 5 seconds to prevent false triggering caused by fluctuations in sensor signals. This is the value of the timer inside the controller, used for delay determination. Logic. The timing rules are as follows: The timer starts counting down; The timer is reset.

[0067] Step S 23 When an abnormality in differential pressure establishment is detected in compressor 1, open-loop feedforward injection is initiated. That is, once the triggering condition is met, the controller ignores the current exhaust temperature or superheat parameter of the injection gas and immediately adjusts the opening of the branch electronic expansion valve to a preset fixed throttling opening, injecting refrigerant into the intermediate cavity of compressor 1. In this embodiment, the preset fixed throttling opening is set to 30%~40% of the total valve body opening.

[0068] Step S 24 Maintain and exit the operation. The preset fixed throttling opening is maintained and locked during operation, while the timing unit is activated. The timing unit can be a countdown timer. The real-time temperature of the supplementary air before the compressor 1's supplementary air inlet is collected. T inj and replenishment pressure P inj Based on the replenishment pressure P inj corresponding saturation temperature T inj_sat ( P inj Calculate the superheat of the supplementary gas. SH inj : SH inj = T inj - T inj_sat ( P inj ).

[0069] When the timing unit runs t inj Exceeding the preset duration (e.g., 120 seconds), or overheating during Qi replenishment. SH inj A reading greater than 0K (indicating that the economizer has begun to effectively absorb heat and the liquid refrigerant has completely evaporated within the economizer) indicates that the open-loop feedforward injection control has been discontinued.

[0070] After exiting, maintain the opening of the branch electronic expansion valve and automatically switch to the following dual-mode decoupling control.

[0071] Step S3. Dual-modal decoupling control. The dual-modal decoupling control uses state machine logic, based on the exhaust temperature. T outThe system dynamically adjusts the throttling opening of the branch throttling element 6 based on real-time values, achieving adaptive switching of the control objective. This means switching between energy efficiency-priority control mode and safety-priority control mode, thus dynamically decoupling system energy efficiency from operational safety. A hysteresis holding region is also provided between the energy efficiency-priority control mode and the safety-priority control mode to avoid frequent switching. (Refer to the attached manual.) Figure 3 Specifically, it includes: Parameter definition and status monitoring. Real-time monitoring of the discharge temperature of compressor 1. T out The system presets three key thresholds from low to high: the upper limit temperature for energy efficiency mode, the trigger temperature for safety mode, and the protection cut-off temperature. In this embodiment, the upper limit temperature for energy efficiency mode can be set to 100℃, the trigger temperature for safety mode can be set to 108℃, and the protection cut-off temperature, which is the shutdown protection line, can be set to 115℃.

[0072] When the system is in steady state and the exhaust temperature T out When the temperature is below the upper limit of the energy efficiency mode, i.e. T out At temperatures below 100℃, the controller executes an energy efficiency priority control mode: using the superheat of the supplementary gas as the controlled variable, and controlling the temperature using an incremental method. PID The algorithm adjusts the throttling opening of the branch throttling element 6. When the exhaust temperature... T out When the temperature exceeds the safe mode trigger temperature, i.e. T out If the temperature exceeds 108℃, execute the safety priority control mode: based on the exhaust temperature. T out For the controlled variable, use incremental method PID The algorithm adjusts the throttling opening of the branch throttling element 6. When the exhaust temperature... T out When the temperature is between the upper limit of the energy efficiency mode and the trigger temperature of the safety mode, i.e., 100℃≤ T out If the temperature is ≤108℃, the controller maintains the control mode from the previous moment and simultaneously determines whether a control mode switch is necessary. When the exhaust temperature... T out When the temperature exceeds the protection cutoff temperature, i.e. T out If the temperature exceeds 115℃, the over-temperature protection will be triggered.

[0073] Specifically, implementing the energy efficiency priority control mode refers to: To replenish Qi and reduce excessive heat SH inj As the only controlled variable, set the target overheat level. SH inj_set The controller uses incremental PIDThe algorithm adjusts the opening of the branch electronic expansion valve. The target superheat... SH inj_set Preferably, the value is set to 5K~8K. PID Controlled sampling period T Set to 10s~20s.

[0074] Calculate the superheat of the gas replenishment SH inj With target overheating SH inj_set Current deviation between : Based on deviation With preset dead zone e dead Based on the relationship between the two factors, determine the direction of adjustment of the throttling opening of the branch throttling element 6: If the deviation is greater than the positive value of the preset dead zone, that is e ( t > e dead Increase the throttling opening of the branch throttling element 6; if the deviation is less than the negative value of the preset dead zone, i.e. e ( t )<- e dead Reduce the throttling opening of the branch throttling element 6; if the deviation is between the positive and negative values ​​of the preset dead zone, - e dead ≤ e ( t )≤ e dead The throttling opening of the current branch throttling element 6 remains unchanged. In this embodiment, a preset dead zone is used. e dead =0.5K.

[0075] According to incremental PID The algorithm calculates the theoretical change in aperture size for each iteration. : , In the formula, e ( t This represents the current deviation between the replenished superheat and the target superheat. e ( t -1) represents the deviation from the previous sampling period. e ( t -2) represents the deviation from the sampling period two weeks prior. In the initial calculation period of mode switching, let... e ( t -1)= e ( t -2)= e ( t). K p It is a proportionality constant. K i Let be the integration constant. K d It is a differential constant. K p 、K i 、K d The parameters are obtained through pre-tuning via experiments based on the hysteresis characteristics and thermal inertia of the controlled object. The specific values ​​are closely related to the actual physical parameters of the controlled object (such as valve flow capacity, system volume, thermal resistance, etc.). Those skilled in the art can adjust them according to the specific application scenario using conventional critical proportionality method, attenuation curve method or intelligent optimization algorithm. The final values ​​depend on the specific implementation method, and no specific numerical range is limited here.

[0076] After the calculation is completed, it is not executed directly. It needs to go through the following three layers of filtering and be executed in order of priority: Level 1: Set safety constraints. Determine the real-time calculated gas replenishment superheat. SH inj If the temperature is below the preset low value for superheat, reduce the throttling opening of the branch throttling element 6 according to the preset opening change amount until the superheat of the replenished gas is reached. SH inj The temperature should not be lower than the preset low superheat value. The preset low superheat value can be set to 2K. The preset opening change can be per cycle. =-10 steps, until the Qi replenishment exceeds the heat level. SH inj ≥2 is required to restore normal function. PID Adjustment. This security constraint has the highest priority. PID Before outputting, a check must be performed; both checks must not be performed simultaneously. Ensure that the refrigerant entering the intermediate chamber of compressor 1 is superheated vapor to prevent liquid refrigerant from entering.

[0077] Level 2: Single step limit, | |≤ m step, m The preferred steps are 10 to 20 steps to prevent pressure fluctuations caused by sudden changes in refrigerant flow.

[0078] Level 3: Locking the upper and lower limits of the valve opening to ensure that the final number of steps is within the valve's physical range.

[0079] When the exhaust temperature is between the upper limit temperature of energy efficiency mode and the trigger temperature of safety mode, determine whether a control mode switch is needed. Specifically, if it is within the hysteresis holding zone, the exhaust temperature... T outWhen the temperature exceeds the safety mode trigger temperature, switch to safety priority control mode and reset the incremental control. PID Algorithm deviation history; if within the hysteresis holding region, exhaust temperature T out If the temperature is below the upper limit of the energy efficiency mode, switch to the energy efficiency priority control mode and reset the incremental temperature. PID Algorithm deviation history; if within the hysteresis holding region, exhaust temperature T out Located between the upper limit temperature of energy efficiency mode and the trigger temperature of safety mode, the control mode of the previous moment remains unchanged.

[0080] By introducing a hysteresis holding region, the control logic can be prevented from frequently switching near the critical temperature point, avoiding repeated oscillations in the adjustment action of the branch electronic expansion valve, thereby extending the service life of the actuator and maintaining the stability of system operation.

[0081] Specifically, implementing the safety priority control mode means: when the exhaust temperature is detected... T out When the temperature is higher than the safe mode trigger temperature, i.e. T out When the temperature exceeds 108℃, the controller switches to safety-priority control mode. Superheating of the supplementary gas is stopped. SH inj The control was shifted to exhaust temperature. T out This is the controlled variable. Set the target control temperature; in this embodiment, it can be set to 108℃. Controller switching. PID Parameter group, PID Controlled sampling period T Set to 5s~10s, and execute the following control: Calculate the current deviation between exhaust temperature and target control temperature. e ( t ) safe : e ( t ) safe = T out -108.

[0082] Based on the relationship between deviation and preset dead zone, the adjustment direction of the throttling opening of branch throttling element 6 is determined. Preset dead zone e dead The value is 0.5K. If the deviation is greater than the positive value of the preset dead zone, that is... e ( t ) safe > e dead Increase the throttling opening of the branch throttling element 6; if the deviation is less than the negative value of the preset dead zone, i.e.e ( t ) safe <- e dead Reduce the throttling opening of the branch throttling element 6; if the deviation is between the positive and negative values ​​of the preset dead zone, - e dead ≤ e ( t ) safe ≤ e dead The throttling opening of the current branch throttling element 6 remains unchanged. This applies for N consecutive sampling cycles (N is preferably 3-5 cycles). e ( t ) safe <- e dead Exit the safety priority control mode and switch to the hysteresis holding region. At any moment of switching control objectives, PID Deviation history e ( t -1) and e ( t -2) All need to be reset to prevent deviations in the old mode from interfering with the initial calculation of the new mode.

[0083] In this mode, the controller also uses a standard incremental approach. PID Algorithm controls the opening degree of branch electronic expansion valve, switching K p 、K i 、K d Parameter group, obtain parameters , as well as .

[0084] According to incremental PID The algorithm calculates the theoretical change in aperture size for each iteration. .

[0085] .

[0086] In the formula, It is a proportionality constant. Let be the integration constant. Let be the differential constant. e ( t ) safe This represents the current deviation between the exhaust temperature and the target control temperature. e ( t -1) represents the deviation from the previous sampling period. e ( t -2) represents the deviation from the previous sampling period.

[0087] After the calculation is completed, it is not executed directly. It needs to go through the following three layers of filtering and be executed according to the following priority order of the control strategy: Configure backflow prevention fuse protection; calculate exhaust superheat in real time. DSH : , In the formula, To be based on exhaust pressure P out The corresponding saturation temperature.

[0088] When the exhaust is superheated DSH If the value is less than the preset limit (preferably 10K), the controller forcibly takes over the control of the branch electronic expansion valve, blocks the opening increase command, and ensures the safe operation of compressor 1 until the exhaust superheat value is reached. DSH The block can only be lifted if the value is not less than the preset limit. This level takes precedence over [other levels]. PID Output and all levels below.

[0089] Set safety constraints: Determine if the gas replenishment superheat is less than 0; if so, ignore the incremental type. PID The algorithm's control commands reduce the throttling opening of branch throttling element 6 according to a preset opening change amount, until the superheat of the supplementary gas is greater than or equal to 0. The preset opening change amount can be per cycle. =-10 steps. Among them, the backflow prevention fuse protection and the safety constraint cannot be superimposed. When the backflow prevention fuse protection has blocked the opening increase command, and at the same time the gas replenishment superheat is detected to be less than 0, the backflow prevention fuse protection has the highest priority, and the throttling opening decrease command in the safety constraint will not be superimposed.

[0090] Change in theoretical opening Implement upper and lower opening limits to determine the final number of steps within the valve's physical range.

[0091] In the above process, the superheat of the make-up gas is allowed to drop to 0K to enable wet steam cooling. This means that a small amount of gas-liquid two-phase mixture (wet steam) is allowed to enter the intermediate cavity of compressor 1. By utilizing the sensible and latent heat absorbed during the flash evaporation of the liquid refrigerant, the exhaust temperature is significantly reduced, preventing the system from triggering shutdown protection due to excessively high exhaust temperature.

[0092] Example 5 In another preferred embodiment of the present invention, the present invention includes a thermal management system for energy storage batteries in low-temperature environments, comprising a thermal management subsystem, a vapor injection enthalpy-increasing branch, a sensor group, and a controller. The thermal management subsystem includes a compressor 1, a four-way reversing valve 2, an outdoor heat exchanger 3, a main circuit throttling element 4, and a plate heat exchanger component 5, collectively forming a main refrigerant circulation loop. The branch includes a branch throttling element 6 and an intermediate heat exchanger 7. One end of the branch throttling element 6 is connected to the outlet of the plate heat exchanger component 5, and the other end is connected to the low-temperature side flow channel of the intermediate heat exchanger 7. The outlet of the low-temperature side flow channel of the intermediate heat exchanger 7 is connected to the gas injection port of the compressor 1, and the high-temperature side flow channel of the intermediate heat exchanger 7 is connected to the main refrigerant circulation loop. Specifically, the high-temperature side flow channel of the intermediate heat exchanger 7 can be located between the main circuit throttling element 4 and the outdoor heat exchanger 3.

[0093] The enthalpy-increasing injection branch is configured as follows: During the cold start phase, when the differential pressure of compressor 1 is abnormal, open-loop feedforward injection control is initiated: the branch throttling element 6 is adjusted to a preset fixed throttling opening, and refrigerant is injected into the intermediate cavity of compressor 1 until a preset maintenance duration is met or the injection superheat is greater than 0K. After completing the open-loop feedforward injection control, the throttling opening of the branch throttling element 6 is dynamically adjusted to achieve adaptive switching of the control objective, i.e., switching between energy efficiency-priority control mode and safety-priority control mode. A hysteresis holding region is provided between the energy efficiency-priority control mode and the safety-priority control mode to avoid frequent switching.

[0094] This system can be used alone or in any of the methods in Examples 1 to 4.

[0095] In summary, any other corresponding modifications made by those skilled in the art after reading this invention document, without requiring creative mental effort, based on the technical solutions and concepts of this invention, are all within the scope of protection of this invention.

Claims

1. A thermal management method for energy storage batteries in low-temperature environments, characterized in that: Includes the following steps: Step S1. Integrate a jet enthalpy-increasing branch in the thermal management subsystem. The branch includes a branch throttling element (6) and an intermediate heat exchanger (7). One end of the branch throttling element (6) is connected to the outlet of the plate heat exchange component (5) in the thermal management subsystem, and the other end is connected to the low-temperature side channel of the intermediate heat exchanger (7). The outlet of the low-temperature side channel of the intermediate heat exchanger (7) is connected to the gas injection port of the compressor (1) in the thermal management subsystem, and the high-temperature side channel of the intermediate heat exchanger (7) is connected to the main refrigerant circulation loop of the thermal management subsystem. Step S2. Based on the real-time collected discharge pressure and suction pressure of the compressor (1), determine whether the pressure difference of the compressor (1) is abnormal during the cold start stage; if so, start the open-loop feedforward injection control: adjust the branch throttling element (6) to the preset fixed throttling opening, inject refrigerant into the intermediate cavity of the compressor (1) until the preset maintenance time or the superheat of the injection gas is greater than 0K. Step S3. Based on the real-time detection value of the compressor (1) exhaust temperature, dynamically adjust the throttling opening of the branch throttling element (6) to achieve adaptive switching between energy efficiency priority control mode and safety priority control mode.

2. The thermal management method for energy storage batteries in low-temperature environments according to claim 1, characterized in that: The method for determining whether the pressure difference of the compressor (1) is abnormal during the cold start phase includes: collecting the discharge pressure and suction pressure of the compressor (1) in real time and calculating the real-time pressure difference between them; if the real-time pressure difference is not lower than the preset pressure difference threshold for a period of time during the cold start phase, it is determined that the compressor (1) has an abnormal pressure difference.

3. The thermal management method for energy storage batteries in low-temperature environments according to claim 1, characterized in that: The open-loop feedforward injection control specifically includes: Adjust the branch throttling element (6) to the preset fixed throttling opening and lock it in operation, while starting the timing unit; Real-time acquisition of the gas supply temperature before the compressor (1) gas supply port T inj and replenishment pressure P inj Based on the replenishment pressure P inj corresponding saturation temperature T inj_sat ( P inj Calculate the superheat of the supplementary gas. SH inj : SH inj = T inj - T inj_sat ( P inj )； When the timing unit runs t inj Exceeding the preset duration, or overheating during Qi replenishment. SH inj If the value is greater than 0K, exit open-loop feedforward injection control.

4. The thermal management method for energy storage batteries in low-temperature environments according to claim 3, characterized in that: The preset fixed throttling opening is 30% to 40% of the total valve body opening.

5. The thermal management method for energy storage batteries in low-temperature environments according to claim 1, characterized in that: A hysteresis zone is set between the energy efficiency priority control mode and the safety priority control mode to avoid frequent switching.

6. The thermal management method for energy storage batteries in low-temperature environments according to claim 5, characterized in that: Step S3 specifically includes: Real-time monitoring of the exhaust temperature of compressor (1) T out Three key thresholds are preset from low to high: the upper limit temperature of energy efficiency mode, the trigger temperature of safety mode, and the protection cut-off temperature; When exhaust temperature T out When the temperature is below the upper limit of the energy efficiency mode, the energy efficiency priority control mode is executed: the superheat of the replenished gas is used as the controlled variable, and the control is performed incrementally. PID The algorithm adjusts the throttling opening of the branch throttling element (6); When exhaust temperature T out When the temperature exceeds the safety mode trigger temperature, the safety priority control mode is executed: based on the exhaust temperature. T out For the controlled variable, use incremental method PID The algorithm adjusts the throttling opening of the branch throttling element (6); When exhaust temperature T out When the temperature is between the upper limit of the energy efficiency mode and the trigger temperature of the safety mode, the control mode of the previous moment remains unchanged, and it is determined whether the control mode needs to be switched. When exhaust temperature T out When the temperature exceeds the protection cutoff temperature, the over-temperature protection action is triggered.

7. A thermal management method for energy storage batteries in low-temperature environments according to claim 6, characterized in that: Using the superheat of the replenished gas as the controlled variable, through incremental... PID The algorithm adjusts the throttling opening of the branch throttling element (6) by the following steps: Determine whether the real-time calculated superheat of the supplementary gas is lower than the preset low value of superheat. If so, reduce the throttling opening of the branch throttling element (6) according to the preset opening change amount until the superheat of the supplementary gas is not lower than the preset low value of superheat. Calculate the deviation between the superheat of the supplementary gas and the target superheat, and based on the relationship between the deviation and the preset dead zone, determine the adjustment direction of the throttling opening of the branch throttling element (6); According to incremental PID Algorithm to calculate the theoretical change in opening degree ; Change in theoretical opening The single step limit and the upper and lower opening limits are executed sequentially to obtain the final opening adjustment amount.

8. A thermal management method for energy storage batteries in low-temperature environments according to claim 6, characterized in that: exhaust temperature T out For the controlled variable, use incremental method PID The algorithm adjusts the throttling opening of the branch throttling element (6) by the following steps: Calculate the deviation between the current exhaust temperature and the target control temperature, and based on the relationship between the deviation and the preset dead zone, determine the adjustment direction of the throttling opening of the branch throttling element (6); According to incremental PID Algorithm to calculate the theoretical change in opening degree The control policies are executed in the following priority order: Configure backflow prevention fuse protection; calculate exhaust superheat in real time. DSH When the exhaust is superheated DSH If the value is less than the preset limit, the command to increase the opening will be blocked until the exhaust superheat is reached. DSH Not less than the preset limit value; Set safety constraints: Determine if the gas replenishment superheat is less than 0; if so, ignore the incremental type. PID The algorithm's control command reduces the throttling opening of the branch throttling element (6) according to the preset opening change amount, until the superheat of the supplementary gas is greater than or equal to 0; Change in theoretical opening By applying the upper and lower limits of the opening, the final opening adjustment amount is obtained; When the anti-return melt fuse protection has blocked the opening increase command, and at the same time the gas replenishment superheat is detected to be less than 0, the anti-return melt fuse protection is given the highest priority, and the throttling opening decrease command in the safety constraint is no longer executed.

9. A thermal management method for energy storage batteries in low-temperature environments according to claim 7 or 8, characterized in that: Based on the relationship between the deviation and the preset dead zone, the adjustment direction of the throttling opening of the branch throttling element (6) is determined. Specifically, if the deviation is greater than the positive value of the preset dead zone, the throttling opening of the branch throttling element (6) is increased; if the deviation is less than the negative value of the preset dead zone, the throttling opening of the branch throttling element (6) is decreased; if the deviation is between the positive and negative values ​​of the preset dead zone, the throttling opening of the current branch throttling element (6) remains unchanged.

10. A thermal management method for energy storage batteries in low-temperature environments according to claim 7 or 8, characterized in that: Theoretical opening change The calculation method is as follows: ， In the formula, K p It is a proportionality constant. K i Let be the integration constant. K d Let be the differential constant. e ( t ) represents the current deviation. e ( t -1) represents the deviation from the previous sampling period. e ( t -2) represents the deviation from the previous sampling period.

11. A thermal management method for energy storage batteries in low-temperature environments according to claim 8, characterized in that: The method for calculating the exhaust superheat is as follows: ， In the formula, DSH For exhaust superheat, T out The exhaust temperature, To be based on exhaust pressure P out The corresponding saturation temperature.

12. A thermal management method for energy storage batteries in low-temperature environments according to claim 6, characterized in that: Determining whether a control mode switch is needed specifically refers to: if the exhaust temperature is within the hysteresis holding region... T out When the temperature exceeds the safety mode trigger temperature, switch to safety priority control mode and reset the incremental control. PID Algorithm deviation history; if within the hysteresis holding region, exhaust temperature T out If the temperature is below the upper limit of the energy efficiency mode, switch to the energy efficiency priority control mode and reset the incremental temperature. PID Algorithm deviation history; if within the hysteresis holding region, exhaust temperature T out Located between the upper limit temperature of energy efficiency mode and the trigger temperature of safety mode, the control mode of the previous moment remains unchanged.

13. A thermal management method for energy storage batteries in low-temperature environments according to claim 8, characterized in that: When the safety priority control mode is executed, the lower limit control of the makeup gas superheat is released, allowing the makeup gas superheat to drop to 0K to enable wet steam cooling.

14. A thermal management system for energy storage batteries designed for low-temperature environments, characterized in that: It includes a thermal management subsystem, a jet enthalpy-increasing branch, a sensor group, and a controller; the thermal management subsystem includes a compressor (1), a four-way reversing valve (2), an outdoor heat exchanger (3), a main throttling element (4), and a plate heat exchange component (5), which together constitute the main refrigerant circulation loop; the branch includes a branch throttling element (6) and an intermediate heat exchanger (7); one end of the branch throttling element (6) is connected to the outlet of the plate heat exchange component (5), and the other end is connected to the low-temperature side flow channel of the intermediate heat exchanger (7); the outlet of the low-temperature side flow channel of the intermediate heat exchanger (7) is connected to the gas injection port of the compressor (1), and the high-temperature side flow channel of the intermediate heat exchanger (7) is connected to the main refrigerant circulation loop; The jet enthalpy-increasing branch is configured as follows: when the differential pressure of the compressor (1) is abnormal during the cold start stage, the open-loop feedforward injection control is started: the branch throttling element (6) is adjusted to the preset fixed throttling opening, and refrigerant is injected into the intermediate cavity of the compressor (1) until the preset maintenance time or the injection superheat is greater than 0K is met; and after the open-loop feedforward injection control is completed, the throttling opening of the branch throttling element (6) is dynamically adjusted to realize the adaptive switching between the energy efficiency priority control mode and the safety priority control mode.

15. A thermal management system for energy storage batteries in low-temperature environments according to claim 14, characterized in that: The sensor group includes an exhaust temperature sensor, an exhaust pressure sensor, an intake pressure sensor, a supplementary air temperature sensor, and a supplementary air pressure sensor.

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