Prevention and control method for early intervention of lithium battery thermal runaway

Abstract

The invention discloses a prevention and control method for early intervention of thermal runaway of a lithium battery, and aims to solve the problems that in the prior art, an alarm can be given only when smoke and temperature are obviously increased, the reaction time is long, and early intervention cannot be realized. The prevention and control method is divided into a first-level keep-alive operation mechanism and a third-level early warning operation mechanism, and comprises the following steps: in a 0-level state, a PACK-level sensor and a master control maintain online heartbeat; the first-level state is that the PACK-level sensor detects data exception in the early stage; in the second-stage state, the PACK-stage sensor preliminarily considers that the battery is possibly in the early stage of thermal runaway, and the PACK detector sends a second-stage fire alarm state to the controller; and in the third-level state, the PACK level sensor determines that the battery PACK is in the thermal runaway state, and the PACK detector sends a third-level fire alarm state to the controller. According to the method, the temperature of the battery PACK is rapidly reduced through early intervention and low-quantity disposal strategies, the battery PACK is prevented from entering a thermal runaway state, and therefore fire disasters are avoided, economic losses are reduced, and the safety of the system is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of fire safety and energy storage system protection, and specifically relates to a method for early intervention, low-volume processing and high-volume fire extinguishing with liquid nitrogen. Background Art

[0002] With the rapid development of lithium-ion battery energy storage technology, the attention to its safety management is also increasing. The main causes of thermal runaway of lithium batteries can be divided into three categories: mechanical abuse, electrical abuse and thermal abuse. Mechanical abuse such as needle puncture, extrusion or external collision can easily lead to internal short circuit of the battery, which in turn causes thermal runaway.

[0003] There have been studies on the performance comparison of lithium battery fire extinguishing agents in China. The study used 10 fire extinguishing agents, including liquid nitrogen, heptafluoropropane, perfluorohexanone, dry powder, fine water mist, foam, and water-based fire extinguishing agents, to carry out a 60Ah lithium iron phosphate battery pack fire extinguishing test to compare and verify the fire extinguishing performance of liquid nitrogen. The test results show that liquid nitrogen has a good fire extinguishing effect on the 60Ah lithium iron phosphate battery pack fire, completely blocking the spread of the battery pack fire, and its fire extinguishing performance is better than the other 9 fire extinguishing agents. In terms of cooling, the cooling rate of liquid nitrogen is 4 times higher than that of fine water mist, and the cooling efficiency is excellent.

[0004] If the lithium battery in the energy storage power station experiences thermal runaway, it may not only cause fire and explosion, but also seriously threaten the life and property safety of users. Therefore, it is crucial to propose effective early warning and intervention measures for the thermal runaway risk of lithium batteries to ensure the stable operation of lithium battery energy storage systems. In the prior art, traditional fire protection systems mainly rely on smoke and temperature alarms. These detectors have a single function and can only sound an alarm when the smoke and temperature have increased significantly. The response time is long and early intervention cannot be achieved. In addition, traditional fire extinguishing methods are mostly high-volume fire extinguishing, which involves spraying a large amount of fire extinguishing agent when a fire has already occurred, which consumes a lot of resources, is costly, and may cause secondary damage to equipment and the environment.

[0005] To this end, the present invention proposes a liquid nitrogen early intervention, low-volume treatment, and high-volume fire extinguishing prevention and control method, which innovatively combines early intervention and low-volume disposal strategies for the prevention and control of thermal runaway of lithium batteries. The purpose of early intervention and low-volume disposal is to use an appropriate amount of liquid nitrogen for cooling treatment at the early stage of thermal runaway to quickly reduce the temperature of the battery PACK and prevent it from entering a thermal runaway state, thereby effectively avoiding the occurrence of fire, reducing economic losses, and improving the safety of the system. Summary of the invention

[0006] In view of the above-mentioned technical deficiencies, the purpose of the present invention is to provide a method for early intervention and prevention of thermal runaway of lithium batteries. The method rapidly reduces the temperature of the battery PACK through early intervention and low-volume treatment to prevent the occurrence of thermal runaway. In the event of thermal runaway of the battery, a high amount of liquid nitrogen is used to extinguish the fire, thereby improving the safety and reliability of the system. In order to solve the above technical problems, the present invention adopts the following technical solutions: A method for preventing and controlling early intervention of thermal runaway of lithium batteries, which is used to monitor whether thermal runaway failure occurs in lithium batteries in energy storage power stations, and implement a first-level life-keeping and third-level early warning operation mechanism according to the monitoring results; including: Level 0 status maintains online heartbeat for PACK-level sensors and the master control, and is used by the master control to monitor whether the PACK-level device is offline; Level 1 status means that the PACK-level sensor detects data anomalies in the early stage. At this time, the sensor will not send an alarm message to the main control system, but the PACK-level sensor will automatically increase the data collection frequency and be in a high-frequency inspection state. At the same time, the room fan will be turned on for exhaust and cooling; Level 2 status: the PACK-level sensor initially believes that the battery may be in the early stage of thermal runaway. The PACK detector will send a level 2 fire alarm status to the controller. The controller will activate the sound and light alarm, shut down the fan, start the pulse spraying of the fire extinguishing system, and turn on the "Do not vent" indicator light. The BMS can disconnect the PCS circuit breaker after obtaining the alarm information through the communication bus. Level 3 status: the PACK-level sensor has determined that the battery PACK is in a thermal runaway state. The PACK detector will send a level 3 fire alarm status to the controller. The controller will turn on the sound and light alarm, turn off the fan, start the fire extinguishing system to spray with a large flow rate, and turn on the air-do not enter indicator light. The BMS can disconnect the PCS circuit breaker after obtaining the alarm information through the communication bus. Furthermore, the level 1 status sensor detects abnormal data in the early stage based on: the temperature, CO, and H2 values ​​exceed the threshold and are judged as abnormal data. At this time, the sensor increases the sampling frequency and enters the inspection state. The system uploads abnormal alarm information, the controller will sound and light alarms, and start the fan for exhaust and cooling.

[0007] Furthermore, the basis for the level 2 status sensor to determine that the battery may be in the early stage of thermal runaway is: if any value of the sensor exceeds the threshold of this level, it can be preliminarily determined that the battery has entered the initial stage of thermal runaway. At this time, the sensor sends a primary warning to the system, the controller shuts down the fan, and outputs an alarm message to the external system (BMS), disconnects the PCS circuit breaker, and starts the pulse spraying of the liquid nitrogen fire extinguishing system.

[0008] Furthermore, in the three-level state, the sensor determines that the battery PACK is in a thermal runaway state based on: if the value exceeds the threshold of this level and the temperature reaches the threshold of this level, it is determined that the battery is in a thermal runaway state. At this time, the fire extinguishing system is started to continuously spray to extinguish the fire, the controller turns off the fan, and outputs an alarm message to the external system (BMS) at the same time, and disconnects the PCS circuit breaker.

[0009] Furthermore, the level 2 state starts the pulse spraying strategy of the fire extinguishing system: a liquid nitrogen low-flow spraying strategy is adopted.

[0010] Furthermore, the level 3 state starts the large-flow spraying strategy of the fire extinguishing system: a liquid nitrogen high-flow spraying strategy is adopted. The beneficial effects of the present invention are: 1. A multi-level early warning mechanism is designed to ensure that appropriate control measures are taken at different stages, and effective early warning and intervention measures can be implemented according to the different development stages of battery thermal runaway, especially early intervention and low-volume disposal strategies, so as to quickly reduce the temperature of the battery PACK and prevent it from entering a thermal runaway state, thereby minimizing the potential damage of fire to the battery and its surrounding environment, and improving the safety and reliability of the energy storage power station.

[0011] 2. It has the ability to flexibly adjust the amount of liquid nitrogen according to the early warning stage. In the early warning stage, the system uses a lower amount of liquid nitrogen to quickly reduce the battery temperature through an appropriate amount of liquid nitrogen, effectively control the potential risk of thermal runaway, prevent fires, and reduce economic losses. With the further upgrade of the early warning signal or the change of the battery system status, the system will gradually adjust to a higher liquid nitrogen injection amount to ensure that when the battery is in a higher risk state, it can quickly and effectively control the temperature within a safe range and effectively extinguish the fire. This strategy not only improves the flexibility and response speed of the system in fire response, but also significantly reduces resource consumption and costs during the fire extinguishing process, minimizing interference with the environment and equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0013] Figure 1 A workflow diagram of a hierarchical early warning prevention and control method for early intervention of thermal runaway of a lithium battery provided in Example 1 of the present invention.

[0014] Figure 2 A schematic diagram of the system architecture connection for hierarchical warning of a prevention and control method for early intervention of thermal runaway of a lithium battery provided in Example 1 of the present invention. DETAILED DESCRIPTION

[0015] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0016] Example 1 This embodiment uses a fire detector for monitoring. The detector is a composite thermal runaway detector equipped with a variety of sensors, including hydrogen (H2), carbon monoxide (CO) and temperature sensors. When the fire detector detects a fire, it reports it to the alarm host. The alarm host activates the liquid nitrogen explosion suppression and fire extinguishing device and the quick-opening valve installed on the battery pack. The liquid nitrogen is quickly sent into the battery pack to quickly cool down and extinguish the fire. The vaporized nitrogen quickly reduces the concentration of combustible gases to suppress the explosion. These sensor systems are divided into different warning levels according to the parameter values ​​they monitor, which becomes the basis for the system to implement graded warnings. In this design, once the parameter value monitored by any sensor exceeds the preset threshold, the corresponding level of warning alarm is triggered.

[0017] According to the severity of the fire detection information, the system implements the operation mechanism of level 1 keep-alive and level 3 warning. In this design, level 0 warning is mainly used to monitor the online status of PACK-level equipment. In the case of level 1 alarm, the system will not start the fire extinguishing system, but automatically enable the sound and light alarm system, and start the fan for exhaust and cooling to reduce the risk of fire. At this time, the system will not start the liquid nitrogen fire extinguishing system for fire extinguishing. Level 2 and level 3 alarms will start the pulse spraying and continuous spraying functions of the fire extinguishing system. Level 2 alarms use liquid nitrogen for small-scale treatment, while level 3 alarms use liquid nitrogen for large-scale fire extinguishing. In the case of level 2 alarms, the system uses low-volume liquid nitrogen treatment to quickly reduce the temperature of the PACK by implementing early intervention and low-volume disposal measures to prevent thermal runaway of the battery, thereby effectively preventing the occurrence of fire, reducing economic losses, and improving the overall safety of the system. In addition, the system will also perform other fire-fighting actions, such as pressure relief and ventilation exhaust linkage functions, to enhance the fire extinguishing effect and ensure the safety of equipment and environment.

[0018] like Figure 1 As shown, the present invention adopts a hierarchical warning mechanism, which is divided into a first-level keep-alive and a three-level warning operation mechanism: level 0 warning heartbeat maintenance, level 1 warning high-frequency inspection, level 2 warning low-volume processing, and level 3 warning high-volume disposal; the core warning parameters cover characteristic gas and temperature parameters, which are regarded as key values ​​of the entire thermal runaway warning system; 1. Level 0 warning Level 0 warning is also called level 0 status. Level 0 status means that the PACK-level sensor and the main control maintain an online heartbeat, which is used by the main control to monitor whether the PACK-level device is offline. The heartbeat frequency defaults to 2HZ, and the normal data transmission frequency is about 0.1HZ.

[0019] When the liquid nitrogen fire extinguishing system is in automatic working state, the control host will automatically traverse the PACK-level detectors, and the PACK-level detectors and the control host will maintain a keep-alive heartbeat (online state) 2. Level 1 warning Level 1 warning is also called Level 1 status. In Level 1 status, the PACK-level sensor detects data abnormalities in the early stage. At this time, the sensor will not send an alarm message to the main control system, but the PACK-level sensor will automatically increase the data collection frequency and be in a high-frequency inspection state. The controller automatically starts the sound and light alarm system and turns on the room fan for exhaust and cooling. At this time, the controller will not start the liquid nitrogen fire extinguishing system for fire extinguishing.

[0020] In the Level 1 state, when the sensor detects abnormal data in the early stage, that is, the value exceeds the threshold and is judged as abnormal data, the temperature threshold is 65-72℃, the CO threshold is 90-190ppm, and the H2 threshold is 100-200ppm. At this time, the sensor increases the sampling frequency and enters the inspection state. The system uploads abnormal alarm information, the controller will sound and light alarms, and start the fan for exhaust and cooling. Through early intervention, the occurrence of thermal runaway can be effectively prevented, economic losses can be reduced and the safety of the system can be improved.

[0021] 3. Level 2 warning Level 2 warning is also called level 2 status. Level 2 status means that the PACK sensor initially believes that the battery may be in the early stage of thermal runaway. The PACK detector will send a level 2 fire alarm status to the controller. The controller will turn on the sound and light alarm, turn off the fan, and start the pulse spraying of the fire extinguishing system, that is, adopt the liquid nitrogen low-flow spraying strategy, spray for 180 seconds for the first time, stop for 30 seconds, cycle once, spray for 60 seconds, stop for 30 seconds, and cycle three times. At the same time, turn on the do not enter the vent indicator light, and the BMS can disconnect the PCS circuit breaker after obtaining the alarm information through the communication bus.

[0022] In the Level 2 state, when the sensor determines that the battery may be in the early stage of thermal runaway, that is, any value of the sensor exceeds the threshold of this level, it can be preliminarily determined that the battery has entered the initial stage of thermal runaway. The temperature threshold is 72-78°C, the CO threshold is 190-350ppm, and the H2 threshold is 200-350ppm. At this time, the sensor sends a primary warning to the system, the controller shuts down the fan, and outputs an alarm message to the external system (BMS), disconnects the PCS circuit breaker, and starts the liquid nitrogen fire extinguishing system pulse spray. At this time, the system sprays a low amount of liquid nitrogen, aiming to intervene in thermal runaway early and inhibit further combustion of the battery, effectively reducing the temperature of the PACK battery pack, and preventing thermal runaway and potential fire events. This early intervention and low-volume disposal strategy aims to reduce economic losses and improve system safety.

[0023] 4. Level 3 warning Level 3 warning is also called level 3 status. Level 3 status means that the PACK-level sensor has determined that the battery PACK is in a thermal runaway state. The PACK detector will send a level 3 fire alarm status to the controller. The controller will activate the sound and light alarm, shut down the fan, start the fire extinguishing system to spray at a high flow rate, and turn on the "Do not vent" indicator light. The BMS can disconnect the PCS circuit breaker after obtaining the alarm information through the communication bus.

[0024] In the level 3 state, when the sensor determines that the battery PACK is in a thermal runaway state, that is, the value exceeds the threshold of this level and the temperature reaches the threshold of this level, it is determined that the battery is already in a thermal runaway state, the temperature threshold is greater than 78°C, the CO threshold is greater than 350ppm, and the H2 threshold is greater than 350ppm. At this time, the fire extinguishing system is started to spray continuously for fire extinguishing, that is, a liquid nitrogen high-flow spraying strategy is adopted, the first spray is 180s, stop for 30s, cycle once, spray again for 60s, stop for 30s, and cycle 3 times. The controller turns off the fan, outputs an alarm message to the external system (BMS), and disconnects the PCS circuit breaker.

[0025] This method uses early intervention and low-volume disposal strategies to quickly reduce the temperature of the battery PACK and prevent it from entering a thermal runaway state, thereby avoiding fires, reducing economic losses, and improving system safety. According to the different development stages of thermal runaway of lithium batteries, corresponding early warning measures and intervention actions are implemented. Specifically, when the PACK-level sensor detects abnormal data during high-frequency inspections, the system is in a warning state; when the PACK-level sensor determines that the battery may be in the early stages of thermal runaway, the system immediately adopts a low-volume liquid nitrogen treatment strategy, using an appropriate amount of liquid nitrogen to quickly cool it down and prevent the temperature from continuing to rise, thereby avoiding fires; once the PACK-level sensor confirms that the battery PACK has entered a thermal runaway state, the system switches to a high-volume liquid nitrogen fire extinguishing mode. Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A method for early intervention and prevention of thermal runaway of lithium batteries, which is used to monitor whether thermal runaway failure occurs in lithium batteries in energy storage power stations, and implement a first-level preservation and a third-level early warning operation mechanism according to the monitoring results; characterized in that: include: Level 0 status maintains online heartbeat for PACK-level sensors and the master control, and is used by the master control to monitor whether the PACK-level device is offline; Level 1 status means that the PACK-level sensor detects data anomalies in the early stage. At this time, the sensor will not send an alarm message to the main control system, but the PACK-level sensor will automatically increase the data collection frequency and be in a high-frequency inspection state. At the same time, the room fan will be turned on for exhaust and cooling; Level 2 status: the PACK-level sensor initially believes that the battery may be in the early stage of thermal runaway. The PACK detector will send a level 2 fire alarm status to the controller. The controller will activate the sound and light alarm, shut down the fan, start the pulse spraying of the fire extinguishing system, and turn on the "Do not vent" indicator light. The BMS can disconnect the PCS circuit breaker after obtaining the alarm information through the communication bus. Level 3 status means that the PACK-level sensor has determined that the battery PACK is in a thermal runaway state. The PACK detector will send a level 3 fire alarm status to the controller. The controller will activate the sound and light alarm, shut down the fan, start the fire extinguishing system to spray at a high flow rate, and turn on the "Do not vent" indicator light. The BMS can disconnect the PCS circuit breaker after obtaining the alarm information through the communication bus.

2. A method for preventing and controlling early intervention of thermal runaway of a lithium battery according to claim 1, characterized in that: The basis for the abnormal data detected in the early stage of the level 1 status sensor is: the temperature, CO, and H2 values ​​exceed the threshold and are judged as abnormal data. At this time, the sensor increases the sampling frequency and enters the inspection state. The system uploads abnormal alarm information, the controller will sound and light alarms, and start the fan for exhaust and cooling.

3. A method for preventing and controlling early intervention of thermal runaway of a lithium battery according to claim 1 or 2, characterized in that: The basis for the level 2 status sensor to determine that the battery may be in the early stage of thermal runaway is: if any value of the sensor exceeds the threshold of this level, it can be preliminarily determined that the battery has entered the initial stage of thermal runaway. At this time, the sensor sends a primary warning to the system, the controller turns off the fan, and outputs an alarm message to the external system BMS, disconnects the PCS circuit breaker, and starts the pulse spraying of the liquid nitrogen fire extinguishing system.

4. A method for preventing and controlling early intervention of thermal runaway of a lithium battery according to claim 3, characterized in that: In the three-level state, the sensor determines that the battery PACK is in a thermal runaway state based on: if the value exceeds the threshold of this level and the temperature reaches the threshold of this level, it is determined that the battery is in a thermal runaway state. At this time, the fire extinguishing system is started to continuously spray to extinguish the fire, the controller turns off the fan, and outputs an alarm message to the external system BMS, and disconnects the PCS circuit breaker.

5. A method for preventing and controlling early intervention of thermal runaway of a lithium battery according to claim 3, characterized in that: The pulse spraying strategy of the fire extinguishing system started in the level 2 state: a liquid nitrogen low-flow spraying strategy is adopted.

6. A method for preventing and controlling early intervention of thermal runaway of a lithium battery according to claim 4, characterized in that: The level 3 state starts the high-flow spraying strategy of the fire extinguishing system: a high-flow spraying strategy of liquid nitrogen is adopted.

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