A safe management system of energy storage power station based on flame-retardant foaming to realize thermal runaway grading early warning

Abstract

The application discloses a kind of energy storage power station safety management systems based on flame-retardant foaming realizes thermal runaway grading early warning, by controlling refrigerant spraying and initiating foaming device opening, high-temperature-resistant flame-retardant foaming agent is released quickly in large quantities, battery module is rapidly wrapped and isolated oxygen, by refrigerant spraying and foaming material combination, avoid the further spread risk of battery module thermal runaway, realize the safety management of energy storage power station.Through the control of valve, the application can realize the switching of different operation modes, realize the safety management of energy storage power station thermal runaway grading early warning.The system sets two-stage grading early warning stage to energy storage power station battery, realizes the battery cooling operation mode of two-stage early warning stage, and the blocking mode of battery thermal runaway under one-stage early warning mode, can reasonably regulate and control battery operating temperature, improve the operating efficiency of battery, and effectively block the risk propagation of battery thermal runaway.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrochemical energy storage power stations, and relates to the thermal management and safe operation of electrochemical energy storage power stations and thermal runaway early warning protection of energy storage batteries. It is an energy storage power station safety management system based on flame-retardant foaming to achieve graded early warning of thermal runaway. Background Art

[0002] Electrochemical energy storage power station systems enable rapid charging and discharging, responding quickly to demand, and are suitable for load regulation and frequency regulation in power grids. Furthermore, energy storage stations can flexibly increase or decrease storage capacity based on demand to accommodate applications of varying scales. However, safety issues with their energy storage batteries, such as overcharging, overdischarging, and short circuits, can create thermal runaway safety hazards, including overheating, fire, and even explosions. Thermal safety is the single biggest factor limiting the further development of battery energy storage systems. Uncontrolled thermal runaway events in localized areas of a battery pack can spread to surrounding batteries, leading to uncontrollable hazards. Therefore, battery thermal management methods that can effectively suppress thermal runaway are crucial.

[0003] Currently available battery thermal management technologies include air cooling, liquid cooling, phase change material cooling, and composite cooling. These technologies differ in their operating principles, equipment installation, temperature control, temperature balancing, and operation and maintenance. While they can provide basic heat dissipation support in some application scenarios, these technologies cannot effectively address potential thermal runaway issues when faced with high power density, complex operating conditions, or extreme environments. Therefore, achieving safe and efficient thermal management of batteries in energy storage power plants is a pressing technical challenge. Summary of the Invention

[0004] To overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to propose a safety management system for energy storage power stations that implements graded early warning of thermal runaway based on flame-retardant foaming, mainly to solve the problem that the battery cannot effectively block the spread of thermal runaway phenomena such as overheating and combustion.

[0005] To achieve the above object, the technical solution adopted by the present invention is:

[0006] A safety management system for an energy storage power station that implements graded thermal runaway warnings based on flame-retardant foaming. The battery pack of the energy storage power station is divided into multiple battery modules. The temperature of each battery module is measured by a temperature sensor, and the measured temperature signal is transmitted to a control center. The safety management system includes a compressor circuit, a direct cooling plate branch, a spray branch, and several valves. The compressor circuit is used to generate refrigerant liquid. The direct cooling plate branch and the spray branch are connected in parallel to the refrigerant liquid pipeline of the compressor circuit. The direct cooling plate branch includes a direct cooling plate arranged at the top of the battery module and a foaming device at the bottom. The spray branch includes a spray head arranged between the direct cooling plate and the battery module.

[0007] The safety management system sets a first-level temperature warning value T1 and a second-level temperature warning value T2; according to the temperature Tt measured by the temperature sensor, the safety management system executes the following modes:

[0008] When Tt <T2,控制阀门使制冷剂工质仅在所述压缩机回路流动;

[0009] When T2 <Tt<T1,控制阀门使制冷剂工质在所述压缩机回路和直冷板支路流动,通过所述直冷板为相应电池模组降温;

[0010] When Tt>T1, the control valve allows the refrigerant to flow in the compressor circuit and the spray branch, sprays the refrigerant liquid to the corresponding battery module through the spray head, and at the same time controls the foaming device of the corresponding battery module to release the flame retardant foaming material.

[0011] In one embodiment, the compressor circuit includes a compressor, a condenser, a liquid storage tank, an expansion valve, an evaporator, an evaporation pressure regulating valve, a gas-liquid separator and a drying filter; a three-way valve 1 is arranged between the expansion valve and the evaporator, a three-way valve 2 is arranged between the evaporation pressure regulating valve and the gas-liquid separator, the direct cooling plate branch and the spray branch are connected in parallel through three-way valve 3 and three-way valve 4, and are connected in parallel with the compressor circuit through three-way valve 1 and three-way valve 2.

[0012] In one embodiment, the three-way valve one, three-way valve two, three-way valve three and three-way valve four are all proportional-integral control valves.

[0013] In one embodiment, port A of the three-way valve one is connected to the outlet of the expansion valve, port B is connected to the inlet of the evaporator, and port C is connected to port A of the three-way valve three; port A of the three-way valve two is connected to the inlet of the gas-liquid separator, port B is connected to the outlet of the evaporation pressure regulating valve, and port C is connected to port A of the three-way valve four; port B of the three-way valve three is connected to the inlet of the direct cooling plate branch, and port C is connected to the inlet of the spray branch; port B of the three-way valve four is connected to the outlet of the direct cooling plate branch, and port C is connected to the outlet of the spray branch.

[0014] In one embodiment, the direct cooling plate is a flat plate with multiple fluid channels therein, and uses a two-phase refrigerant as a medium for heat exchange. The refrigerant is evenly distributed in the fluid channels to achieve uniform heat exchange with the battery module.

[0015] In one embodiment, the foaming device includes a cylinder, a nozzle and a powder nozzle. The cylinder stores flame retardant foaming material. The device is controlled by a solenoid valve. The nozzle is a pressure type nozzle and works through the solenoid valve, a control unit and a power module.

[0016] In one embodiment, the power module provides stable power to the solenoid valve and the control unit. The power module and the control unit are located in a control center. The control unit uses a microcontroller to receive electrical signals and control the opening and closing of the solenoid valve.

[0017] In one embodiment, the foaming device is disposed at the bottom of the battery module, and the nozzle outlet thereof is located inside the mold shell of the battery module.

[0018] In one embodiment, each of the battery modules has a plurality of single cells, and each single cell is configured with a temperature sensor. In each battery module, the highest detection value of each temperature sensor is used as the temperature Tt.

[0019] In one embodiment, the temperature sensor is arranged at a cell tab of each single battery.

[0020] Compared with existing technologies, this invention achieves cooling of the battery module and blocking of potential thermal runaway through the rational arrangement of the evaporator pressure regulating valve, three-way valve, and foaming device. Through monitoring and control by various sensors, it implements thermal safety management of the electrochemical energy storage system with different strategies under different operating conditions. More importantly, it blocks potential thermal runaway. This improves the operating efficiency of the energy storage battery and effectively mitigates the risk of thermal runaway in energy storage power plants. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a structural diagram of the energy storage power station safety management system of the present invention that realizes thermal runaway graded early warning based on flame retardant foaming.

[0022] Figure 2 Schematic diagram of the structure of three-way valve 1 and three-way valve 3 of the present invention.

[0023] Figure 3 Schematic diagram of the structure of three-way valve 2 and three-way valve 4 of the present invention.

[0024] Figure 4 Schematic diagram of the foaming device of the present invention.

[0025] In the figure: 1- compressor; 2- condenser; 3- liquid storage tank; 4- expansion valve; 5- three-way valve 1; 6- evaporator; 7- evaporation pressure regulating valve; 8- three-way valve 2; 9- gas-liquid separator; 10- drying filter; 11- three-way valve 3; 12- direct cooling plate; 13- three-way valve 4; 14- spray pipe; 15- spray head; 16- battery module; 17- battery cell; 18- temperature sensor; 19- foaming device; 20- control center; 21- solenoid valve 22- cylinder; 23- nozzle; 24- powder nozzle. DETAILED DESCRIPTION

[0026] The specific implementation manner is clearly and completely described below with reference to the accompanying drawings.

[0027] like Figure 1 As shown, the present invention is a safety management system for energy storage power stations that realizes thermal runaway graded warning based on flame retardant foaming. In the energy storage power station, the battery pack is divided into multiple battery modules 16. Figure 1 The battery pack is divided into four battery modules 16. Each battery module 16 is equipped with a temperature sensor 18 to measure its temperature. The measured temperature signal is transmitted to the control center 20, which then executes protective actions based on the different real-time temperature measurements. Traditional protective actions are generally based on a single threshold, which is difficult to meet the real-world needs of high power density, complex operating conditions, or extreme environments.

[0028] To this end, the safety management system of the present invention is designed with a compressor circuit, a direct cooling plate branch, and a spray branch, which performs different actions by switching valves and combining different threshold conditions.

[0029] Specifically, the compressor circuit utilizes a refrigerant circulation, and the refrigerant switches between refrigerant gas and refrigerant liquid. In the present invention, it is mainly used to provide refrigerant liquid to the direct cooling plate branch and the spray branch. The direct cooling plate branch and the spray branch are connected in parallel to the refrigerant liquid pipeline of the compressor circuit, and the refrigerant liquid can be controlled by a valve to flow to the direct cooling plate branch and / or the spray branch.

[0030] In the present invention, the direct cooling plate branch circuit primarily comprises a direct cooling plate 12 and a foaming device 19. The direct cooling plate 12 is located on top of the battery module 16 and cools the battery module 16 through heat exchange when a refrigerant liquid is introduced. The foaming device 19 is located at the bottom of the battery module 16 and, when activated, rapidly sprays and releases a flame-retardant foaming material toward the battery module 16.

[0031] In the present invention, the spray branch includes a spray pipe 14 and a spray head 15. The spray head 15 is installed on the spray pipe 14 and faces the battery module 16. Preferably, the spray head 15 is located between the direct cooling plate 12 and the battery module 16.

[0032] The safety management system of the present invention sets two thresholds, namely the first-level temperature warning value T1 and the second-level temperature warning value T2. According to the real-time temperature Tt measured by the temperature sensor 18, the safety management system of the present invention executes the following modes:

[0033] Normal temperature operation mode: Tt <T2,此时系统运行正常,控制阀门使制冷剂工质仅在压缩机回路流动,无需对电池模组16降温。

[0034] Secondary warning cooling mode: T2 <Tt<T1,此时系统具有一定的高温风险,需给予干涉,具体是指进行散热的散热阶段。控制阀门使制冷剂工质在压缩机回路和直冷板支路流动,制冷剂工质被送入直冷板12,并仅通过直冷板12为相应电池模组16降温。

[0035] Level 1 Warning Blocking Mode: When Tt>T1, the system faces an imminent high-temperature risk and requires strong intervention, specifically a firefighting phase involving a combination of spraying and foaming the thermally runaway battery. Control valves allow refrigerant to flow through the compressor circuit and the spray branch. The refrigerant is fed into the spray pipe 14, where it is sprayed through the spray head 15 onto the corresponding battery module 16 to provide strong cooling. Simultaneously, the foaming device 19 of the corresponding battery module 16 is controlled to release flame-retardant foam material to encapsulate the battery module 16 and isolate it from oxygen. This combined refrigerant spraying and foaming prevents the spread of thermal runaway, such as combustion.

[0036] The system of the present invention switches between different operating modes through valve control, enabling safe management of graded thermal runaway warnings in energy storage power plants. By setting up two levels of early warning for the batteries in energy storage power plants, a battery cooling mode in the second-level early warning stage and a thermal runaway blocking mode in the first-level early warning mode are implemented. This allows for reasonable regulation of battery operating temperature, improving battery operating efficiency and effectively preventing the spread of thermal runaway risks.

[0037] According to the above system management method, the present invention realizes thermal safety management with different strategies under different working conditions, and can combine refrigerant spraying and foaming materials to block potential thermal runaway, greatly reducing the risk of thermal runaway in the energy storage power station.

[0038] In a further embodiment of the present invention, reference Figure 1 、 Figure 2 and Figure 3The compressor circuit comprises a compressor 1, a condenser 2, a liquid accumulator 3, an expansion valve 4, an evaporator 6, an evaporating pressure regulating valve 7, a gas-liquid separator 9 and a dry filter 10. A three-way valve one 5 is arranged between the expansion valve 4 and the evaporator 6, and a three-way valve two 8 is arranged between the evaporating pressure regulating valve 7 and the gas-liquid separator 9. The direct cooling plate branch and the spray branch are connected in parallel through a three-way valve three 11 and a three-way valve four 13, and are connected in parallel with the compressor circuit through the three-way valve one 5 and the three-way valve two 8. Specifically, the outlet of the compressor 1 is connected to the inlet of the condenser 2, the inlet of the condenser 2 is connected to the inlet of the liquid accumulator 3, the outlet of the liquid accumulator 3 is connected to the inlet of the expansion valve 4, the outlet of the expansion valve 4 is connected to the A port of the three-way valve one 5, the B port of the three-way valve one 5 is connected to the inlet of the evaporator 6, the outlet of the evaporator 6 is connected to the inlet of the evaporating pressure regulating valve 7, the outlet of the evaporating pressure regulating valve 7 is connected to the B port of the three-way valve two 8, the A port of the three-way valve two 8 is connected to the inlet of the gas-liquid separator 9, the outlet of the gas-liquid separator 9 is connected to the inlet of the dry filter 10, and the inlet of the dry filter 10 is connected to the inlet of the compressor 1. The A port of the three-way valve three 11 is connected to the C port of the three-way valve one 5, the B port of the three-way valve three 11 is connected to the inlet of the direct cooling plate 12, the outlet of the direct cooling plate 12 is connected to the B port of the three-way valve four 13, the A port of the three-way valve four 13 is connected to the C port of the three-way valve two 8, the C port of the three-way valve three 11 is connected to the inlet of the spray pipeline 14, and the outlet of the spray pipeline 14 is connected to the C port of the three-way valve four 13.

[0039] Each three-way valve of the present application is an electronic regulating valve, for example, a proportional integral regulating valve, typically a VB7000 series electric three-way valve, which can adjust the passage by electric control to meet the automation demand.

[0040] In combination with the above compressor circuit, the three modes of the present application are further described as follows:

[0041] 1. System normal temperature operation mode: when the energy storage power station is running, the temperature Tt measured by the temperature sensor 18 is less than the system secondary warning temperature T2, and the system starts the normal temperature operation mode. At this time, the control center controls the A port and the B port of the three-way valve one 5 to be opened and the C port to be closed, and the A port and the B port of the three-way valve two 8 to be opened and the C port to be closed.

[0042] The specific circulation process is as follows: the refrigerant working medium flows out from the outlet of the compressor 1, passes through the condenser 2, the liquid accumulator 3, the expansion valve 4, the three-way valve one 5, the evaporator 6, the evaporating pressure regulating valve 7, the three-way valve two 8, the gas-liquid separator 9 and the dry filter 10 in sequence, and finally returns to the compressor 1 to complete the circulation.

[0043] The circulation principle is as follows: low-temperature, low-pressure refrigerant gas is compressed by compressor 1 to become high-temperature, high-pressure refrigerant gas. The high-temperature, high-pressure refrigerant gas passes through condenser 2 and becomes a low-pressure refrigerant liquid with a certain temperature. The refrigerant flows through liquid storage tank 3, which is used to store the refrigerant liquid, balance the system pressure, and regulate the refrigerant flow in the system cycle. The refrigerant liquid flowing out of liquid storage tank 3 passes through expansion valve 4 to become a low-temperature, low-pressure refrigerant liquid. It then flows through evaporator 6 to become a low-temperature, low-pressure refrigerant gas. The refrigerant is separated into gas and liquid by gas-liquid separator 9, and then passes through drying filter 10 to ensure that the refrigerant flowing into compressor 1 is gas. Finally, it flows into the compressor to complete the circulation.

[0044] 2. System Level 2 Warning Cooling Mode: When the energy storage power station is operating and the system Level 2 warning temperature T2 < the temperature Tt measured by temperature sensor 18 < the system Level 1 warning temperature T1, the system activates Level 2 warning cooling mode. At this point, ports A, B, and C of three-way valve 1 (5) are open; ports A, B, and C of three-way valve 2 (8) are open. Refrigerant flows in parallel in the compressor circuit and the direct cooling plate circuit.

[0045] The specific circulation process is as follows: the refrigerant flows from the outlet of compressor 1, passes through condenser 2, liquid storage tank 3, expansion valve 4, ports A and B of three-way valve 1 5, evaporator 6, evaporation pressure regulating valve 7, and ports A and B of three-way valve 2 8. After flowing through three-way valve 1 5, the refrigerant is divided into two paths. One path flows through gas-liquid separator 9 and filter drier 10, and finally returns to compressor 1 to complete the compressor circuit cycle. The other refrigerant path flows through port B of three-way valve 3 11, direct cooling plate 12, and port B of three-way valve 4 13, completing the direct cooling plate branch cycle.

[0046] The cycle works as follows: Low-temperature, low-pressure refrigerant gas is compressed by compressor 1 into high-temperature, high-pressure refrigerant gas. This high-temperature, high-pressure refrigerant gas then passes through condenser 2 and becomes a low-pressure refrigerant liquid at a predetermined temperature. This refrigerant then flows through a liquid storage tank 3, which stores the refrigerant liquid, balances the system pressure, and regulates the refrigerant flow rate within the system. The refrigerant liquid exits the liquid storage tank and passes through expansion valve 4, becoming a low-temperature, low-pressure refrigerant liquid. After passing through three-way valve 1 (5), the refrigerant is split into two paths. One path flows through evaporator 6, becoming a low-temperature, low-pressure refrigerant gas. A gas-liquid separator 9 separates the refrigerant from the liquid phase. The refrigerant then passes through filter drier 10, ensuring that the refrigerant entering the compressor is gaseous. Finally, the refrigerant flows into compressor 1, completing the compressor-compressor circuit. The other path flows through direct cooling plate 12, where the low-temperature, low-pressure refrigerant liquid absorbs heat generated by the battery during operation, reducing the battery temperature to a suitable operating range. Finally, the refrigerant is reunited at three-way valve 2 (8), completing the direct cooling plate branch circuit.

[0047] 3. System Level 1 Warning Blocking Mode: When the energy storage power station is operating, the temperature Tt measured by temperature sensor 18 exceeds the system Level 1 warning temperature T1, and the system activates Level 1 Warning Blocking Mode. At this point, ports B of three-way valves 15, 28, 311, and 413 are disconnected, while ports C of three-way valves 311 and 413 are opened. Refrigerant is released directly through the spray pipe 14 and spray head 15. Simultaneously, the temperature signal measured by temperature sensor 18 is transmitted to control center 20, which sends a start-up command to foaming device 19. Foaming device 19 rapidly releases high-temperature resistant foam material to wrap the battery module, isolating it from oxygen and preventing the spread of thermal runaway, such as combustion.

[0048] The specific working process is as follows: the battery temperature Tt measured by the temperature sensor 18 exceeds the system's first-level warning temperature value T1, the control center 20 receives the temperature signal sent by the temperature sensor 18, and sends a start-up device command to the foaming device 19. The foaming device 19 immediately and quickly releases the high-temperature resistant flame-retardant foaming agent, which quickly foams to wrap the battery module 16 and isolate it from oxygen, and blocks the spread of thermal runaway such as combustion through the combination of refrigerant spraying and foaming materials.

[0049] In a further embodiment of the present invention, the direct cooling plate 12 is a flat plate with multiple fluid channels therein, which uses a two-phase refrigerant as a medium for heat exchange. The two-phase refrigerant can be evenly distributed in the fluid channel, thereby achieving uniform heat exchange with the top surface of the battery module 16. The distance between the direct cooling plate 12 and the battery module 16 is designed based on the actual space and the expected heat generation of the battery, the cold flow rate that the direct cooling plate 12 can provide, etc. The main material of the direct cooling plate 12 is a metal material with high thermal conductivity (such as copper or aluminum), and its main function is to quickly conduct the heat generated by the battery module 16. Multiple flow channels are designed in the flat plate, and the shape of the flow channels can be parallel, staggered or microchannel structures. The diameter and direction of the flow channel are optimized to reduce the flow resistance and improve the heat exchange efficiency of the fluid.

[0050] In a further embodiment of the present invention, reference Figure 1 and Figure 4 The foaming device 19 can be set at the bottom of the battery module 16. By reading the conditional trigger signal of the control center 20, when the measured temperature exceeds the system's first-level warning temperature, the foaming device 19 is triggered to start releasing foaming materials such as B1-level flame-retardant and fire-resistant polyurethane foaming agent. The foaming material can achieve rapid release and structural shaping as well as high temperature resistance. Structurally, the foaming device 19 mainly includes a cylinder 22, a nozzle 23 and a powder nozzle 24. The outlet of the nozzle 23 is located in the mold shell of the battery module 16. The cylinder 22 is used to store flame-retardant foaming materials. The operation of the entire device is controlled by a solenoid valve 21. Multiple foaming devices 19 can share one solenoid valve 21, or each foaming device 19 can be provided with one solenoid valve 21. The solenoid valve 21 can be, for example, a 2 / 2 valve or a 3 / 2 valve.

[0051] The nozzle 23 of the foaming device 19 of the present invention is a pressure-type nozzle, which operates through a solenoid valve 21, a control unit, and a power module. Specifically, the power module provides a stable power supply for the solenoid valve 21 and the control unit. The power module and the control unit are located in the control center 20. The control unit uses a microcontroller (such as a single-chip microcomputer or Arduino) to receive electrical signals and control the opening and closing of the solenoid valve 21. The specific operating principle is that the control unit receives an electrical signal from the temperature sensor 18 and then analyzes the input signal based on preset logic (designed temperature threshold, system level 1 warning temperature value) to determine whether to open the nozzle 23. If the control unit decides to open the nozzle 23, it sends a control signal (such as a high-level signal) to the solenoid valve 21. The electromagnetic coil inside the solenoid valve 21 is activated, generating a magnetic field, which pushes the valve core to move and open the valve. If the nozzle needs to be closed, the control unit sends a low-level signal, causing the solenoid valve 21 to release current, and the valve core returns to the closed state under the action of the spring. When the solenoid valve 21 is controlled to open, the stored foaming material is released through the nozzle 23.

[0052] In a further embodiment of the present invention, each battery module 16 has a plurality of single cells 17. Figure 1 In the illustrated structure, each battery module 16 has four battery cells 17. In the present invention, each battery cell 17 is preferably equipped with a temperature sensor 18. Specifically, the temperature sensor 18 can be located at the cell tab of each battery cell 17 to detect the temperature of the battery cells 17 within the battery module 16. In each battery module 16, the highest detected value of each temperature sensor 18 is used as the temperature Tt. That is, the highest temperature of a single battery cell 17 is used as the measured temperature of the battery module 16 to which it belongs.

[0053] In summary, the present invention provides a safety management system for energy storage power stations that implements graded early warning of thermal runaway based on flame-retardant foaming. Sensors are used to monitor battery modules, and the system is switched between different modes by a control center to achieve normal operation of the battery modules. The system is also provided with a first-level early warning mode. When the battery temperature is too high and thermal runaway is about to occur, the control center controls the refrigerant spray and triggers the foaming device to start, quickly releasing a large amount of high-temperature resistant flame-retardant foaming agent, quickly wrapping the battery module and isolating it from oxygen. The combination of refrigerant spraying and foaming materials is used to avoid the risk of further spread of thermal runaway of the battery module. The entire safety management system is simple in structure and easy to maintain. It can realize the operating status of battery modules at different temperatures, effectively warn and handle potential thermal runaway during operation, and extend the operational stability and efficiency of the energy storage power station.

Claims

1. A safety management system for an energy storage power station based on flame retardant foaming to achieve thermal runaway graded warning, wherein the battery pack of the energy storage power station is divided into a plurality of battery modules (16), the temperature of each battery module (16) is measured by a temperature sensor (18), and the measured temperature signal is transmitted to a control center (20); characterized in that: The described safety management system includes a compressor circuit, a direct cooling plate branch, a spray branch, and several valves. The compressor circuit is used to generate refrigerant liquid. The direct cooling plate branch and the spray branch are connected in parallel to the refrigerant liquid pipeline of the compressor circuit. The compressor circuit includes a compressor (1), a condenser (2), a liquid storage tank (3), an expansion valve (4), an evaporator (6), an evaporation pressure regulating valve (7), a gas-liquid separator (9), and a dryer filter (10). A first three-way valve (5) is arranged between the expansion valve (4) and the evaporator (6), and a second three-way valve (8) is arranged between the evaporation pressure regulating valve (7) and the gas-liquid separator (9). The direct cooling plate branch and the spray branch are connected in parallel through a third three-way valve (11) and a fourth three-way valve (13), and are connected in parallel with the compressor circuit through the first three-way valve (5) and the second three-way valve (8). The direct cooling plate branch includes a direct cooling plate (12) arranged at the top of the battery module (16) and a foaming device (19) arranged at the bottom. The spray branch includes a spray head (15) arranged between the direct cooling plate (12) and the battery module (16). The safety management system sets a first-level temperature warning value T1 and a second-level temperature warning value T2. According to the temperature Tt measured by the temperature sensor (18), the safety management system executes the following modes: When Tt < T2, control the valves to make the refrigerant working medium flow only in the compressor circuit. When T2 < Tt < T1, control the valves to make the refrigerant working medium flow in the compressor circuit and the direct cooling plate branch, and cool the corresponding battery module (16) through the direct cooling plate (12). When Tt > T1, control the valves to make the refrigerant working medium flow in the compressor circuit and the spray branch, spray refrigerant liquid on the corresponding battery module (16) through the spray head (15), and at the same time control the foaming device (19) of the corresponding battery module (16) to release a flame-retardant foaming material.

2. The energy storage power station safety management system based on flame retardant foaming to achieve thermal runaway graded warning according to claim 1 is characterized in that: The first three-way valve (5), the second three-way valve (8), the third three-way valve (11), and the fourth three-way valve (13) are all proportional integral regulating valves.

3. The energy storage power station safety management system based on flame retardant foaming to achieve thermal runaway graded warning according to claim 1 or 2, characterized in that: The A port of the first three-way valve (5) is connected to the outlet of the expansion valve (4), the B port is connected to the inlet of the evaporator (6), and the C port is connected to the A port of the third three-way valve (11). The A port of the second three-way valve (8) is connected to the inlet of the gas-liquid separator (9), the B port is connected to the outlet of the evaporation pressure regulating valve (7), and the C port is connected to the A port of the fourth three-way valve (13). The B port of the third three-way valve (11) is connected to the inlet of the direct cooling plate branch, and the C port is connected to the inlet of the spray branch. The B port of the fourth three-way valve (13) is connected to the outlet of the direct cooling plate branch, and the C port is connected to the outlet of the spray branch.

4. The energy storage power station safety management system based on flame retardant foaming to achieve thermal runaway graded warning according to claim 1 is characterized in that: The direct cooling plate (12) is a flat plate with multiple fluid channels inside, exchanges heat with two-phase refrigerant as the medium, and the refrigerant is evenly distributed in the fluid channels to achieve uniform heat exchange with the battery module (16).

5. The energy storage power station safety management system based on flame retardant foaming to achieve thermal runaway graded warning according to claim 1 is characterized in that: The foaming device (19) comprises a barrel (22), a nozzle (23) and a powder nozzle (24); the barrel (22) stores a flame retardant foaming material; the nozzle (23) is a pressure-type nozzle and operates through a solenoid valve (21), a control unit and a power module.

6. The energy storage power station safety management system based on flame retardant foaming to achieve thermal runaway graded warning according to claim 5 is characterized in that: The power module provides a stable power supply for the solenoid valve (21) and the control unit. The power module and the control unit are located in the control center (20). The control unit uses a microcontroller to receive electrical signals and control the opening and closing of the solenoid valve (21).

7. The energy storage power station safety management system based on flame retardant foaming to achieve thermal runaway graded warning according to claim 1, 5 or 6, characterized in that: The foaming device (19) is arranged at the bottom of the battery module (16), and the outlet of the nozzle (23) thereof is located inside the mold shell of the battery module (16).

8. The energy storage power station safety management system based on flame retardant foaming to achieve thermal runaway graded warning according to claim 1 is characterized in that: Each of the battery modules (16) has a plurality of single cells (17), and each single cell (17) is provided with a temperature sensor (18). In each of the battery modules (16), the highest detection value of each temperature sensor (18) is used as the temperature Tt.

9. The energy storage power station safety management system based on flame retardant foaming to achieve thermal runaway graded warning according to claim 8, characterized in that: The temperature sensor (18) is arranged at the battery cell tab of each single battery (17).

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