Perfluorohexanone water immersion type grading fire extinguishing system

Abstract

The perfluorohexanone water immersion type grading fire extinguishing system is characterized in that the perfluorohexanone water immersion type grading fire extinguishing system comprises a probe arranged in a battery module; the probe is connected with a fire detector; the fire detection device is connected with the fire alarm controller; the fire alarm controller is connected with the BMS, the fire control valve and the perfluorohexanone fire extinguishing device; the perfluorohexanone fire extinguishing device is connected with the integrated puncture valve nozzle; the fire control valve is connected with the nozzle; and the BMS is used for acquiring temperature, voltage and current parameters of the distributed battery cells arranged in the battery module, and pre-judging and starting fire extinguishing measures in advance by combining a special algorithm. According to the invention, the fire-fighting controller obtains the temperature, voltage and current parameters of the distributed battery cells built in the BMS through information sharing with the BMS, and prejudges and starts fire extinguishing measures in advance in combination with a special algorithm, so that the fire risk of the battery module is effectively reduced, and the property loss is reduced. On the basis of perfluorohexanone fire extinguishment in the battery module, water fire extinguishment in the battery module is introduced.

Description

Technical Field

[0001] The invention relates to the field of batteries, in particular to a perfluorohexanone water immersion type graded fire fighting system. Background Art

[0002] With the continuous growth of the proportion of renewable energy such as wind and solar energy in the energy structure, the increasing demand for intermittent and fluctuating energy access, and the reduction of lithium battery costs, lithium battery energy storage power stations are being widely used in many fields such as new energy grid connection and power system auxiliary services. However, with the advancement of the construction of lithium battery energy storage power stations, the number of fire incidents in these power stations at home and abroad has gradually increased, which has aroused the public's high attention to the fire safety of lithium battery energy storage power stations.

[0003] Lithium batteries are usually composed of a positive electrode, a separator, a negative electrode, an organic electrolyte and a battery casing. The electrode materials, separators and electrolytes of lithium batteries are all flammable substances, among which the fire risk of the separator is particularly prominent.

[0004] Lithium batteries store a large amount of energy and pose safety risks. Thermal runaway is the main cause of fire. Thermal runaway is usually caused by the following factors: internal short circuit, due to lithium dendrites or copper dendrites penetrating thin diaphragms; overcharge and overdischarge, resulting in increased battery temperature and electrolyte decomposition; chemical reaction exothermic, battery voltage increase triggering side reactions; manufacturing process defects, such as excessively long battery tabs or micropores in the diaphragm; defects during use, such as inconsistent battery performance or physical damage. All of these factors may cause thermal runaway of lithium batteries, ultimately leading to fire or explosion.

[0005] Fire development is divided into four stages: initial, development, fierce and extinguished. In the initial stage, the fire has not spread, and the automatic alarm system can detect and deal with the fire in time to reduce damage. Currently, smoke and heat detectors are mainly used, but they can only warn after the smoke and temperature fill the space. The fire protection system and BMS are two relatively independent systems, becoming two independent islands, lacking data sharing and coordination of fire extinguishing measures, which affects the early detection and control of thermal runaway.

[0006] Lithium battery energy storage cabinets usually only use perfluorohexane (or heptafluoropropane) automatic fire extinguishing system, but this system cannot accurately act on the inside of the thermal runaway battery box and can only extinguish open flames. Although a water fire sprinkler system is installed in the energy storage cabinet, this system cannot accurately act on the inside of the thermal runaway battery box to quickly reduce the temperature of the thermal runaway battery to control the fire, which seriously affects the cooling and fire extinguishing effect. In addition, this method consumes a huge amount of water for cooling. In the case of insufficient water for firefighting, it may be impossible to control the fire.

[0007] Therefore, it is necessary to provide a perfluorohexanone water immersion graded fire protection system to achieve the above purpose. Summary of the invention

[0008] The purpose of the invention is to provide a perfluorohexanone water immersion type graded fire fighting system.

[0009] The present invention achieves the above object through the following technical solutions:

[0010] A perfluorohexanone water immersion hierarchical fire protection system, characterized in that: it includes a probe built into a battery module; the probe is connected to a fire detection device; the fire detection device is connected to a fire alarm controller; the fire alarm controller is connected to a BMS, a fire control valve and a perfluorohexanone fire extinguishing device; the perfluorohexanone fire extinguishing device is connected to an integrated puncture valve nozzle; the fire control valve is connected to the nozzle; the BMS is used to obtain the temperature, voltage and current parameters of the distributed battery cells built into the battery module, and predict and start fire extinguishing measures in advance in combination with a special algorithm; the special algorithm:

[0011] Thermal runaway detection temperature control threshold T S The selection criteria are lower than the melting temperature of the diaphragm and the inflection point of gas generation of the electrolyte, higher than the self-heating temperature, and considering the temperature difference ΔT between the temperature measurement point of the battery cell and the temperature inside the battery cell. Due to differences in measurement or materials, select a suitable tolerance temperature εT;

[0012] Self-heating temperature <Ts < diaphragm melting temperature and electrolyte gas generation inflection point;

[0013] Ts=Min(Tm,Ty)-ΔT-εT

[0014] When the detected cell temperature is greater than T S , it is judged that the battery cell has thermal runaway.

[0015] Compared with the prior art, the fire controller in the present invention shares information with the BMS, obtains the temperature, voltage, and current parameters of the distributed battery cells built into the BMS, and combines a dedicated algorithm to predict and initiate fire extinguishing measures in advance, thereby effectively reducing the risk of fire in the battery module and reducing property losses. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of the equivalent circuit of the battery cell.

[0017] Figure 2 This is a schematic diagram of the voltage and temperature curves of the lithium battery cells in the acupuncture test with different diaphragms.

[0018] Figure 3 It is a schematic diagram of the structure of the present invention.

[0019] Figure 4 It is the algorithm flow chart. DETAILED DESCRIPTION

[0020] See also Figures 1 to 4, a perfluorohexanone water immersion hierarchical fire protection system, including a probe built into a battery module; the probe is connected to a fire detection device; the fire detection device is connected to a fire alarm controller; the fire alarm controller is connected to a BMS, a fire control valve and a perfluorohexanone fire extinguishing device; the perfluorohexanone fire extinguishing device is connected to an integrated puncture valve nozzle; the fire control valve is connected to the nozzle; the BMS is used to obtain the temperature, voltage and current parameters of the distributed battery cells built into the battery module, and combine with a special algorithm to predict and start fire extinguishing measures in advance;

[0021] The present invention realizes a three-level fire fighting strategy of increasing levels by information sharing and linkage between fire fighting control and BMS. The first level fire fighting is that BMS detects the voltage, current, and battery temperature of the battery module, and turns off the charge and discharge switch of the battery module to prevent the battery module from overcharging, over-discharging, overloading, overheating, short circuiting, and other phenomena that are very likely to cause fires. This is also a function that BMS currently generally has. The second level fire fighting is that the fire alarm controller starts to spray perfluorohexanone for fire extinguishing. Based on the dielectric strength of perfluorohexanone ≥ 110kv, it is non-corrosive to electrical equipment, there is no special retention on site, and it will not cause secondary damage to the equipment and difficult cleaning. The characteristics can effectively reduce the equipment loss caused by the fire. The third level fire fighting is that the fire alarm controller starts to spray water for fire extinguishing. Water is an effective cooling fire extinguishing agent. Since water is directly sprayed inside the battery module where the fire occurs, compared with the traditional fire fighting rescue spraying water from the outside of the equipment to prevent temperature, the cooling effect is more direct and effective, which greatly reduces the water consumption for fire fighting and effectively prevents the risk of fire spreading.

[0022] Lithium battery thermal runaway refers to the process in which the temperature inside the battery rises rapidly, causing the electrolyte, electrode materials and other substances inside the battery to undergo violent chemical reactions, releasing a large amount of heat and gas. During the thermal runaway of lithium batteries, the toxic and harmful gases produced by lithium batteries mainly include hydrogen, carbon monoxide, carbon dioxide, methane and carbon fluoride. A fire detection device is installed inside the battery module. The functions of the fire alarm detection device include hydrogen, carbon monoxide detection and smoke and temperature sensing functions, so as to detect fire early and accurately locate the battery module with thermal runaway.

[0023] The inside of the battery module is detected by a hydrogen, carbon monoxide and smoke and temperature composite fire detection device (hereinafter referred to as the fire detection device). When the fire detection device detects that the hydrogen or carbon monoxide concentration exceeds the threshold concentration, the battery module has smoke or the temperature exceeds the threshold temperature, the fire detection device determines that the battery module has thermal runaway and a fire has occurred. The fire detection device sends a fire alarm signal to the fire alarm controller. The fire alarm controller starts the perfluorohexanone fire extinguishing device and sends a signal to start opening the integrated nozzle. The fire extinguishing agent in the perfluorohexanone fire extinguishing device is injected into the battery module cavity through the integrated nozzle. After being released from the nozzle, the perfluorohexanone fire extinguishing agent is rapidly converted from liquid to gas, absorbs the heat generated by the battery, rapidly reduces the temperature of the battery cell, and eliminates the ignition source (temperature) among the three elements of fire to play a role in extinguishing the fire. Since the density of perfluorohexanone fire extinguishing agent is 1600kg / m 3 After the vaporization, the volume of perfluorohexanone expands to cover the entire protection area and then plays the role of isolating oxygen, reducing the content of the combustion aid (oxygen) in the three elements of fire, so that it reaches below the combustion concentration to complete the fire extinguishing effect. Since the perfluorohexanone fire extinguishing agent is relatively stable, when the temperature in the protection area rises, it will cause chemical cracking, and some bonds in the fire extinguishing agent molecules will break, combining with the active free radicals produced during the flame combustion process, blocking the chain reaction of combustion, and playing a chemical inhibition and fire extinguishing function. Perfluorohexanone vaporizes quickly after release, and there will be no residue on the scene, which will not cause secondary damage to the equipment and make cleaning difficult. When the BMS and the fire alarm controller simultaneously detect a drop in the internal temperature of the battery module, the thermal runaway of the battery module is effectively controlled, that is, the higher-level water immersion fire fighting measures will not be activated, and the property loss will be minimized under the premise of controlling the fire.

[0024] Since lithium battery combustion does not rely on oxygen, continuous cooling is essential to suppress internal chemical reactions to prevent re-ignition. Water is an effective cooling fire extinguishing agent, and its cooling effect is significantly better than perfluorohexanone. The innovation is the introduction of three-level water firefighting on the basis of two-level perfluorohexanone fire extinguishing. When the perfluorohexanone fire extinguishing device is activated and the set three-level water firefighting activation judgment time is reached, the temperature drop value of the battery module detected by the fire alarm controller does not reach the set temperature drop value. The fire alarm controller activates the three-level water firefighting mode, turns on the fire water sprinkler, sprays water into the battery module, and cools the battery module.

[0025] The battery module is equipped with an explosion-proof valve. When the pressure inside the box exceeds the set value, the safety valve opens to release the pressure, preventing explosion and continuously cooling down. After the explosion-proof valve opens, the heat generated by the thermal runaway battery module is continuously discharged from the battery module by the fire cooling water, effectively maintaining the cooling effect and preventing re-ignition.

[0026] The dedicated algorithm is a thermal runaway prediction algorithm:

[0027] According to the simplified equivalent circuit of the actual battery cell Figure 1, where the battery cell in the equivalent circuit is an ideal battery, R1 is the self-discharge equivalent resistance of the battery cell, u1 is the terminal voltage of the ideal battery cell, R2 is the equivalent series internal resistance of the battery cell, u2 is the voltage drop on the equivalent series resistance of the battery cell, and u3 is the terminal voltage of the actual battery cell.

[0028] Needle puncture and internal short circuit detection methods:

[0029] When a lithium battery is punctured, the internal resistance R1 of the battery cell decreases significantly, and the battery cell discharges due to an internal short circuit. The voltage u1 will drop significantly and generate a lot of heat. At the same time, the battery cell voltage will also drop at the moment when the charging ends and the discharge begins, such as Figure 2 In order to eliminate the interference of voltage drop at the moment of battery charging end and start on the detection of puncture events, the judgment strategy adopted by the present invention is that when the voltage drop rate du3 / dt of the cell terminal voltage u3 is detected to be greater than the set thermal runaway cell voltage drop threshold Vs, and combined with the cell temperature rise caused by the internal short circuit of the cell, the interference caused by the instantaneous drop of the cell voltage caused by the cell charging end and the cell discharging start is eliminated, and the puncture and internal short circuit events can be effectively detected.

[0030] Detecting thermal runaway based on thermal runaway temperature threshold TS:

[0031] When the lithium battery is in a static state, if the temperature rise rate of the battery surface exceeds the ambient temperature rise rate, the lithium battery will enter the self-heating stage. When a large lithium iron phosphate battery experiences thermal runaway in an insulated and closed environment, the self-heating temperature is relatively low, with a typical value of 71°C. The melting of the SEI film on the surface of the battery's negative electrode material and the reaction between the electrolyte and the negative electrode material are the essential reasons for the battery's self-heating. At this stage, the battery's negative electrode material reacts with the electrolyte to release heat, the diaphragm continues to shrink and decompose, and the positive and negative electrodes inside the battery are in contact with a large range, resulting in a large-scale internal short circuit. The heat generated by the internal short circuit and various chemical reactions accelerates the internal chemical reactions.

[0032] When the battery surface temperature reaches a certain threshold (typical value 168°C), the voltage drops from the current voltage (such as 3.3V) to about 0.2V. At the same time, a chemical reaction occurs inside the battery to produce a large amount of gas and electrolyte volatilization, causing the internal pressure to increase. When the internal pressure reaches the upper pressure limit of the safety valve, the safety valve is broken, and the battery surface temperature drops, and then gradually rises to the thermal runaway temperature. The peak value of the temperature rise rate during the thermal runaway process exceeds 1.2°C / s, and the typical value of the thermal runaway trigger temperature is 200°C.

[0033] The overcharge, internal short circuit, puncture and external short circuit safety tests of the battery cell are all related to the melting point of the diaphragm. Based on the melting temperature T of the typical diaphragm m(For example, the melting temperature of diaphragm PE16 is 135°C), select the thermal runaway temperature threshold Ts. In addition, based on the characteristics of the electrolyte during thermal runaway, as the temperature rises, the gas production of the electrolyte gradually increases, reaching the "inflection point" temperature T between 180°C and 210°C. y Above this temperature threshold, the gas volume increases faster. The gas composition of the electrolyte is highly sensitive to temperature, with CO2 being the dominant gas, followed by H2 and CO.

[0034] Based on the above characteristics of lithium batteries when thermal runaway occurs, the thermal runaway detection temperature control threshold T S The selection criteria are to be less than the melting temperature of the diaphragm and the inflection point of electrolyte gas production, greater than the self-heating temperature, and to consider the temperature difference ΔT between the temperature measurement point of the battery cell and the temperature inside the battery cell. Due to differences in measurement or materials, an appropriate tolerance temperature εT is selected.

[0035] Self-heating temperature <Ts < diaphragm melting temperature and electrolyte gas generation inflection point;

[0036] Ts=Min(Tm,Ty)-ΔT-εT

[0037] When the detected cell temperature is greater than T S , it is judged that the battery cell has thermal runaway.

[0038] Detecting thermal runaway based on battery surface temperature rise:

[0039] When the battery surface temperature rise rate (℃ / s) is significantly greater than the ambient temperature rise rate Ta plus the self-heating temperature rise rate Tr under the rated maximum discharge current condition, it can be judged that the battery cell has thermal runaway. The thermal runaway temperature rise rate threshold formula is as follows:

[0040] Ts1=Ta+Tr+ΔT1

[0041] Ts2=Ta+Tr+ΔT2

[0042] Ts1 mainly detects and prevents the scenario where the temperature of the battery cell continues to rise slowly and eventually leads to thermal runaway after a short circuit occurs in the battery cell. Ts2 mainly detects and prevents the scenario where the temperature of the battery cell rises sharply in a short time and thermal runaway occurs after a short circuit occurs in the battery cell. The value of ΔT1 is less than ΔT2.

[0043] When the temperature rise rate is greater than the set temperature rise rate threshold, it is judged that the battery cell has thermal runaway. The temperature rise rate threshold is generally significantly higher than the ambient temperature rise rate, and significantly lower than the peak value of the thermal runaway temperature rise rate.

[0044] Based on the characteristics of equivalent distribution of self-consumption rate of normal cells in the battery pack, short circuit detection in the battery is carried out:

[0045] Under normal conditions, the self-discharge rate of the battery cells in the battery pack conforms to the normal distribution, that is, the self-consumption equivalent resistance R1 conforms to the normal distribution. When the battery cells in the battery pack pierce the diaphragm due to lithium dendrites formed by overcharging or copper dendrites formed by overdischarging, it will cause an internal short circuit in the battery cell, a sharp rise in temperature, and thermal runaway. After removing the abnormal battery cells with internal short circuits, the self-consumption equivalent resistance R1 of the remaining battery cells in the battery pack still conforms to the normal distribution. Based on the above principle, the dynamic threshold value of the voltage drop of the thermal runaway battery cell Vsd=μ+3σ is set. When the detected battery cell voltage drop is greater than Vsd, it can be determined that the self-consumption equivalent resistance R1 of this battery cell no longer conforms to the normal distribution, it is an abnormal battery cell, and an internal short circuit has occurred. The calculation formula of the dynamic threshold value Vsd of the voltage drop of the thermal runaway battery cell is as follows:

[0046] V sd =μ+3σ

[0047] The calculation formula of the voltage drop mean μ is:

[0048]

[0049] After removing the data of the cell with the largest voltage drop, the voltage drop standard deviation σ is calculated as:

[0050]

[0051] N represents the number of batteries after removing the cell with the largest voltage drop, and its value is equal to the total number of cells in series in the battery pack minus 1;

[0052] X i Represents the voltage drop ΔV of the i-th cell i , the calculation formula is:

[0053] x i =ΔV i =V1 i -V2 i

[0054] V1 i and V2 i They respectively represent the voltage of the i-th battery cell measured in the two previous and next sampling periods.

[0055] The thermal runaway cell voltage drop threshold Vs and the thermal runaway cell voltage drop dynamic threshold Vsd complement each other. Vsd can effectively reduce the interference of the cell voltage drop caused by battery charging and discharging on the thermal runaway voltage drop detection. Vs can effectively deal with various extreme abnormal conditions such as puncture, extrusion, overcharge, over discharge, etc. in the battery pack (including 1 cell), and internal short circuit occurs at the same time, to prevent thermal runaway.

[0056] The above are only some embodiments of the present invention. For those skilled in the art, several modifications and improvements can be made without departing from the creative concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A perfluorohexanone water immersion graded fire protection system, characterized in that: It includes a probe built into the battery module; the probe is connected to the fire detection device; the fire detection device is connected to the fire alarm controller; the fire alarm controller is connected to the BMS, the fire control valve and the perfluorohexanone fire extinguishing device; the perfluorohexanone fire extinguishing device is connected to the integrated puncture valve nozzle; the fire control valve is connected to the nozzle; the BMS is used to obtain the temperature, voltage and current parameters of the distributed battery cells built into the battery module, and combine the special algorithm to predict and start the fire extinguishing measures in advance; Dedicated algorithms: Thermal runaway detection temperature control threshold T S The selection criteria are lower than the melting temperature of the diaphragm and the inflection point of gas generation of the electrolyte, higher than the self-heating temperature, and considering the temperature difference ΔT between the temperature measurement point of the battery cell and the temperature inside the battery cell. Due to differences in measurement or materials, select a suitable tolerance temperature εT; Self-heating temperature <Ts < diaphragm melting temperature and electrolyte gas generation inflection point; Ts=Min(Tm,Ty)-ΔT-εT When the detected cell temperature is greater than T S , it is judged that the battery cell has thermal runaway.

2. A perfluorohexanone water immersion graded fire protection system according to claim 1, characterized in that: Dedicated algorithms also include thermal runaway detection based on battery surface temperature rise: When the battery surface temperature rise rate (℃ / s) is significantly greater than the ambient temperature rise rate Ta plus the self-heat temperature rise rate Tr under the rated maximum discharge current condition, it can be judged that the battery cell has thermal runaway; the thermal runaway temperature rise rate threshold formula is as follows: Ts1=Ta+Tr+ΔT1 Ts2=Ta+Tr+ΔT2 Ts1 is mainly used to detect and prevent the scene where the temperature of the battery cell continues to rise slowly and eventually leads to thermal runaway after a short circuit in the battery cell; Ts2 is mainly used to detect and prevent the scene where the temperature of the battery cell rises sharply in a short time and thermal runaway occurs after a short circuit in the battery cell; the value of ΔT1 is less than ΔT2; When the temperature rise rate is greater than the set temperature rise rate threshold, it is determined that thermal runaway has occurred in the battery cell.

3. A perfluorohexanone water immersion graded fire protection system according to claim 1, characterized in that: The system divides the battery into different areas according to the charge and discharge characteristic curves at different rates, SOC and charge and discharge current, and sets different balanced start voltage deviation values ​​Vs1 and balanced close voltage deviation values ​​Vs2 in each corresponding area.

4. A perfluorohexanone water immersion graded fire protection system according to claim 1, characterized in that: Algorithm for detecting short circuit in battery: Set the dynamic threshold of thermal runaway cell voltage drop Vsd = μ + 3σ. When the detected cell voltage drop is greater than Vsd, it can be determined that the self-consumption equivalent resistance R1 of this cell does not conform to the normal distribution, and it is an abnormal cell, and an internal short circuit has occurred. The calculation formula of the dynamic threshold of thermal runaway cell voltage drop Vsd is as follows: V sd =μ+3σ The calculation formula of the voltage drop mean μ is: After removing the data of the cell with the largest voltage drop, the voltage drop standard deviation σ is calculated as: N represents the number of batteries after removing the cell with the largest voltage drop, and its value is equal to the total number of cells in series in the battery pack minus 1; X i Indicates the voltage drop of the cell ΔV i , the calculation formula is: x i =ΔV i =V1 i -V2 i V1 i and V2 i They respectively represent the voltage of the i-th battery cell measured in the two previous and next sampling periods.

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