CN117091722A - Optical monitoring method and optical monitoring device for thermal runaway of energy storage battery - Google Patents
Optical monitoring method and optical monitoring device for thermal runaway of energy storage battery Download PDFInfo
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- 238000004146 energy storage Methods 0.000 title claims abstract description 52
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- 238000000034 method Methods 0.000 title claims abstract description 30
- 238000012544 monitoring process Methods 0.000 title claims abstract description 20
- 238000012806 monitoring device Methods 0.000 title claims abstract description 14
- 239000007789 gas Substances 0.000 claims abstract description 93
- 239000013307 optical fiber Substances 0.000 claims abstract description 65
- 230000014509 gene expression Effects 0.000 claims abstract description 48
- 239000000835 fiber Substances 0.000 claims abstract description 43
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- 238000004364 calculation method Methods 0.000 claims abstract description 7
- 238000005259 measurement Methods 0.000 claims description 10
- 230000008901 benefit Effects 0.000 claims description 9
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 5
- 238000009529 body temperature measurement Methods 0.000 claims description 5
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims description 3
- 229910052799 carbon Inorganic materials 0.000 claims description 3
- 229910052739 hydrogen Inorganic materials 0.000 claims description 3
- 239000001257 hydrogen Substances 0.000 claims description 3
- 238000010606 normalization Methods 0.000 claims description 3
- 238000005381 potential energy Methods 0.000 claims description 3
- 238000001514 detection method Methods 0.000 abstract description 12
- 238000005457 optimization Methods 0.000 abstract description 7
- 238000000354 decomposition reaction Methods 0.000 abstract description 3
- 239000002121 nanofiber Substances 0.000 abstract description 2
- 238000005516 engineering process Methods 0.000 description 12
- 230000000694 effects Effects 0.000 description 10
- 238000002474 experimental method Methods 0.000 description 5
- 238000011161 development Methods 0.000 description 4
- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 description 4
- 239000000463 material Substances 0.000 description 3
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 2
- 239000004642 Polyimide Substances 0.000 description 2
- 238000010521 absorption reaction Methods 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
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- 238000012983 electrochemical energy storage Methods 0.000 description 2
- 230000007613 environmental effect Effects 0.000 description 2
- 238000004880 explosion Methods 0.000 description 2
- 229910001416 lithium ion Inorganic materials 0.000 description 2
- 229920001721 polyimide Polymers 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- 230000035945 sensitivity Effects 0.000 description 2
- 238000001228 spectrum Methods 0.000 description 2
- NCZYUKGXRHBAHE-UHFFFAOYSA-K [Li+].P(=O)([O-])([O-])[O-].[Fe+2].[Li+] Chemical compound [Li+].P(=O)([O-])([O-])[O-].[Fe+2].[Li+] NCZYUKGXRHBAHE-UHFFFAOYSA-K 0.000 description 1
- 230000002159 abnormal effect Effects 0.000 description 1
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- 239000002041 carbon nanotube Substances 0.000 description 1
- 229910021393 carbon nanotube Inorganic materials 0.000 description 1
- 238000000180 cavity ring-down spectroscopy Methods 0.000 description 1
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- 238000004870 electrical engineering Methods 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
- G01K11/00—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00
- G01K11/32—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00 using changes in transmittance, scattering or luminescence in optical fibres
- G01K11/3206—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00 using changes in transmittance, scattering or luminescence in optical fibres at discrete locations in the fibre, e.g. using Bragg scattering
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
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- G01D5/26—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light
- G01D5/32—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light
- G01D5/34—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells
- G01D5/353—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre
- G01D5/35306—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre using an interferometer arrangement
- G01D5/35309—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre using an interferometer arrangement using multiple waves interferometer
- G01D5/35316—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre using an interferometer arrangement using multiple waves interferometer using a Bragg gratings
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
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- G01R31/36—Arrangements for testing, measuring or monitoring the electrical condition of accumulators or electric batteries, e.g. capacity or state of charge [SoC]
- G01R31/392—Determining battery ageing or deterioration, e.g. state of health
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Abstract
The invention provides an optical monitoring method and an optical monitoring device for thermal runaway of an energy storage battery, which are used for establishing an optical fiber annular cavity calculation model so as to obtain a relational expression between ring-down time variation and extra loss; optimizing for a temperature in the temperature expression; optimizing a gas concentration in the gas concentration expression; based on the traditional fiber ring cavity ring-down system, two fiber rings are used for realizing the same system, two physical quantities, temperature and gas concentration are measured, fiber Bragg gratings are used for measuring the temperature change of the energy storage battery, processed micro-nano fibers are used for carrying out the thermal runaway characteristic gas concentration change of the energy storage battery, the two groups of data are subjected to targeted optimization, the temperature detection part is subjected to noise reduction by using decomposition noise, and the gas detection part is subjected to cross interference among different thermal runaway gases by using gibbs energy.
Description
Technical Field
The invention relates to the fields of optical engineering and electrical engineering, in particular to an optical monitoring method and an optical monitoring device for thermal runaway of an energy storage battery.
Background
With the development of technology and the demand of people for large-capacity mobile energy storage devices, lithium ion batteries for converting chemical energy into electric energy are applied toMore and more fields. Along with the development of the economy in China, the scale of an energy storage system and the capacity of a lithium ion battery are rapidly increased, and the development of an energy storage industry is well-developed, wherein the electrochemical energy storage industry is also a rapidly-increased market. The direction of the novel electric power energy storage system taking the new energy as a main body is also determined. The energy storage power station uses renewable energy sources to generate electricity for storing the electricity, and is an indispensable part of a power grid system. Lithium iron phosphate batteries are the primary choice of energy storage units in electrochemical energy storage due to their high safety, excellent electrochemical performance, long cycle life and environmental friendliness. In the energy storage system of the power grid, the energy storage units and the electrical equipment are generally uniformly arranged in the prefabricated cabin, so that higher capacity, stronger environment adaptability and convenience in installation are realized. However, due to the combustibility of the body materials (organic electrolyte, diaphragm, graphite, etc.) of the energy storage battery, there is a risk of thermal runaway of the battery under abnormal operation conditions, and the internal or external temperature of the battery is too high, which causes thermal runaway of a part of the battery, and after the battery starts violent reaction, the internal electrolyte and other components generate CO along with the reaction 2 、H 2 The energy storage prefabricated cabin is relatively airtight, so that the battery stacking density in the operation environment is high, the flammable gas is accumulated, the temperature of the whole battery pack is increased along with the diffusion of thermal runaway, and accordingly the flammable gas generated by the battery in the thermal runaway process is ignited, and explosion accidents are caused in the prefabricated cabin with limited space. The explosion accident not only can form a serious threat to the whole energy storage power station, but also can negatively and negatively influence the popularization of the energy storage technology and the social evaluation.
In order to ensure safe and stable operation of the energy storage power station, the temperature of the lithium iron phosphate battery and the type and content of the released thermal runaway gas of the lithium iron phosphate battery in the use process are monitored in real time, so that the working state of the lithium iron phosphate battery pack can be known in real time, and the method has important significance for safe operation of the energy storage power station. The traditional energy storage battery gas detection mostly uses an electrochemical gas detector, and the series of gas detectors have the defects of low transmission rate, easiness in electromagnetic interference, high price and insufficient resistance to severe environmental conditions.
Disclosure of Invention
The invention aims to overcome the defects of the prior art, and provides an optical monitoring method and an optical monitoring device for thermal runaway of an energy storage battery, which can measure the temperature change of a lithium iron phosphate lithium battery and the concentration of a thermal runaway characteristic gas.
In order to achieve the above purpose, the invention adopts the following technical scheme:
the invention provides an optical monitoring method for thermal runaway of an energy storage battery, which comprises the following steps:
s1, establishing an optical fiber annular cavity calculation model, so as to obtain a relational expression between the ring-down time variation and the extra loss;
s2, based on a relation between the ring-down time variation and the extra loss, deforming to establish a temperature expression and a gas concentration expression;
s3, analyzing the temperature expression and the gas concentration expression to determine variables in the temperature expression and the gas concentration expression;
s4, optimizing the temperature in the temperature expression to obtain a temperature value to be measured;
and S5, optimizing the gas concentration in the gas concentration expression to obtain a gas concentration value to be measured.
Further, the specific steps of S1 are as follows:
s101, the optical fiber annular cavity calculation model is as follows:
（1）；
wherein,is ring down time; />Is the refractive index of the optical fiber ring; />Is the total length of the optical fiber ring; />Is the inherent loss of the system; />Is the propagation speed of light in vacuum;
s102, during actual measurement, the optical fiber annular cavity is influenced by the measured temperature and the gas concentration, so that the optical fiber loss is aggravated, and extra loss is introducedThen the ring down time in actual measurement +.>The method comprises the following steps:
（2）；
s103, obtaining a relation between the ring-down time variation and the extra loss according to the formula (1) and the formula (2), wherein the relation is as follows:
（3）。
further, the S2 includes:
s201, the influence of temperature on the fiber Bragg grating is reflected in the two aspects of thermal-optical benefit and thermal expansion benefit, and the expression of refractive light change caused by the change of grating period is as follows:
（4）；
wherein,is the center wavelength; />Is a constant; />Is the temperature;
the ring down time varies due to the variation of the center wavelength, and is obtained by combining formula (3):
（5）；
wherein,extra loss under the fiber loop for temperature measurement;
s202, the temperature expression is:
（6）。
further, the S2 further includes:
s203, gas measurement relies on the treated micro-nano optical fiber to adsorb the gas, so that the refractive index of the optical fiber is changed, and the ring-down time is changed:
（7）；
（8）；
wherein,measuring the extra loss under the optical fiber loop for the gas; />The refractive index of the micro-nano optical fiber is treated; />Is a constant; />The concentration of the gas to be measured;
s204, the gas concentration expression is:
（9）。
further, the step S3 specifically includes:
since the structure of the fiber optic ring cavity system is established, the propagation velocity of light in vacuumConstant->Constant ofRefractive index of optical fiber ring>Total length of optical fiber ring->Also determined is the extra loss +.>And extra loss under the gas measuring fiber loop +.>Is a variable;
order of principleIs->Let->Is->Extra loss under the temperature measuring fiber loop>Is->Extra loss under gas measuring fiber loop>Is->The variable expressions of the temperature expression and the gas concentration expression are:
（10）；
due toAnd->For the fixed value, only the +.>、/>And optimizing to obtain the temperature value and the gas concentration value to be measured.
Further, the S4 specifically is:
s401, pairNoise reduction treatment is carried out, record->Is the original signal containing noise, then decompose +.>Post-secondary signalThe method comprises the following steps:
（11）；
（12）；
wherein,is a first order residual component;
s402, willAdd compensation noise->Decomposition->And (3) obtaining:
（13）；
wherein,to compensate for white noise;
s403, decompose thePersonal->Secondary (S)/(S)>Is a coefficient of->Is->，/>The order residual component is:
（14）；
（15）；
s404, repeating S401-S403 untilFailing to decompose, then:
（16）；
s405, the obtained noise reduction signal is:
（17）。
further, the step S5 specifically includes:
s501, pairOptimizing, wherein the total Gibbs energy is as follows:
（18）；
wherein,is->Group gibbs energy; />Is a universal gas constant; />Is at normal temperature; />Is->Group data->；/>Is the total number of characteristic gas species; />Is->Grouping the mole number of the gas to be tested;
s502, to make the total Gibbs energyAt a minimum, atomic conservation must obey:
（19）；
wherein,is the mole number of element A; />Is the total number of elements; />Is hydrogen; />Is a carbon element;
s503, obtaining total Gibbs energy by using the formula (19) as a constraint conditionIs obtained by the minimum value of (1):
（20）；
wherein,is element->Element potential energy of (2), then simultaneous normalization condition, < ->Thereby obtaining the optimized。
Further, an optical monitoring device for thermal runaway of an energy storage battery is realized by the monitoring method for thermal runaway of the energy storage battery, and the optical monitoring device further comprises: the first annular cavity consists of a first coupler, a fourth coupler and a circulator, and the second annular cavity consists of a second coupler, a third coupler and a treated micro-nano optical fiber; an optical fiber extension line is connected between the first coupler and the second coupler; and one end of the first coupler, which is separated from the optical fiber extension line, is sequentially connected with the isolator, the laser and the function generator.
Further, the output end of the fourth coupler and the output end of the third coupler are sequentially connected with the beam combiner, the erbium-doped fiber amplifier, the photoelectric detector and the oscilloscope; the output end of the circulator is connected with the fiber Bragg grating.
The beneficial effects of the invention are as follows: based on the traditional fiber ring cavity ring-down system, two fiber rings are used for realizing the same system, two physical quantities, temperature and gas concentration are measured, fiber Bragg gratings are used for measuring the temperature change of the energy storage battery, processed micro-nano fibers are used for carrying out the thermal runaway characteristic gas concentration change of the energy storage battery, the two groups of data are subjected to targeted optimization, the temperature detection part is subjected to noise reduction by using decomposition noise, and the gas detection part is subjected to cross interference among different thermal runaway gases by using gibbs energy.
Drawings
FIG. 1 is a schematic diagram of an optical monitoring method and an optical monitoring device for thermal runaway of an energy storage battery according to the present invention;
FIG. 2 is a graph of temperature versus additional loss for non-optimization in example one;
FIG. 3 is a graph of temperature versus additional loss after optimization in accordance with the first embodiment;
FIG. 4 is a graph of unoptimized gas concentration versus additional loss for example one;
FIG. 5 is a graph of optimized gas concentration versus additional loss in the first embodiment.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings, in order to make the objects, technical solutions and advantages of the present invention more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.
An optical monitoring method for thermal runaway of an energy storage battery, comprising the steps of:
s1, establishing an optical fiber annular cavity calculation model, so as to obtain a relational expression between the ring-down time variation and the extra loss;
s2, based on a relation between the ring-down time variation and the extra loss, deforming to establish a temperature expression and a gas concentration expression;
s3, analyzing the temperature expression and the gas concentration expression to determine variables in the temperature expression and the gas concentration expression;
s4, optimizing the temperature in the temperature expression to obtain a temperature value to be measured;
and S5, optimizing the gas concentration in the gas concentration expression to obtain a gas concentration value to be measured.
The specific steps of the S1 are as follows:
s101, the optical fiber annular cavity calculation model is as follows:
（1）；
wherein,is ring down time; />Is the refractive index of the optical fiber ring; />Is the total length of the optical fiber ring; />Is the inherent loss of the system; />Is the propagation speed of light in vacuum;
s102, during actual measurement, the optical fiber ring cavity system is influenced by the measured temperature and the gas concentration, so that the optical fiber loss is aggravated, and extra loss is introducedThen the ring down time in actual measurement +.>The method comprises the following steps:
（2）；
s103, obtaining a relation between the ring-down time variation and the extra loss according to the formula (1) and the formula (2), wherein the relation is as follows:
（3）。
the step S2 comprises the following steps:
s201, the influence of temperature on the fiber Bragg grating is reflected in the two aspects of thermal-optical benefit and thermal expansion benefit, and the expression of refractive light change caused by the change of grating period is as follows:
（4）；
wherein,is the center wavelength; />Is a constant; />Is the temperature;
the ring down time varies due to the variation of the center wavelength, and is obtained by combining formula (3):
（5）；
wherein,extra loss under the fiber loop for temperature measurement;
s202, the temperature expression is:
（6）。
the S2 further includes:
s203, gas measurement relies on the treated micro-nano optical fiber to adsorb the gas, so that the refractive index of the optical fiber is changed, and the ring-down time is changed:
（7）；
（8）；
wherein,measuring the extra loss under the optical fiber loop for the gas; />The refractive index of the micro-nano optical fiber is treated; />Is a constant; />The concentration of the gas to be measured;
in a specific embodiment, the micro-nano optical fiber is processed in the following manner: the optical fiber coating is performed by using a special material, and the special material can be a carbon nano tube.
S204, the gas concentration expression is:
（9）。
the step S3 is specifically as follows:
since the structure of the fiber optic ring cavity system is established, the propagation velocity of light in vacuumConstant->Constant ofRefractive index of optical fiber ring>Total length of optical fiber ring->Also determined is the extra loss +.>And extra loss under the gas measuring fiber loop +.>Is a variable;
order of principleIs->Let->Is->Extra loss under the temperature measuring fiber loop>Is->Extra loss under gas measuring fiber loop>Is->The variable expressions of the temperature expression and the gas concentration expression are:
（10）；
due toAnd->For the fixed value, only the +.>、/>And optimizing to obtain the temperature value and the gas concentration value to be measured.
The step S4 specifically comprises the following steps:
s401, pairNoise reduction treatment is carried out, record->Is the original signal containing noise, then decompose +.>Post-secondary signalThe method comprises the following steps:
（11）；
（12）；
wherein,is a first order residual component;
s402, willAdd compensation noise->Decomposition->And (3) obtaining:
（13）；
wherein,to compensate for white noise;
s403, decompose thePersonal->Secondary (S)/(S)>Is a coefficient of->Is->，/>The order residual component is:
（14）；
（15）；
s404, repeating S401-S403 untilFailing to decompose, then:
（16）；
s405, the obtained noise reduction signal is:
（17）。
in a specific embodiment, the pair ofPerforming decomposition to gradually separate noise signals until the noise signals cannot be decomposed, and finally obtaining the optimized +.>。
The step S5 specifically comprises the following steps:
S501、for a pair ofOptimizing, wherein the total Gibbs energy is as follows:
（18）；
wherein,is->Group gibbs energy; />Is a universal gas constant; />Is at normal temperature; />Is->Group data->；Is the total number of characteristic gas species; />Is->Grouping the mole number of the gas to be tested;
s502, to make the total Gibbs energyAt a minimum, atomic conservation must obey:
（19）；
wherein,is the mole number of element A; />Is the total number of elements; />Is hydrogen; />Is a carbon element;
s503, obtaining total Gibbs energy by using the formula (19) as a constraint conditionIs obtained by the minimum value of (1):
（20）；
wherein,is element->Element potential energy of (2), then simultaneous normalization condition, < ->Thereby obtaining the optimized。
In a specific embodiment, the characteristic gas concentration detection is used to detect a flammable and explosive CH mainly when the gas concentration detection is performed by using a fiber optic annular cavity 4 Mainly, the facing disturbances are mainly due to mutual disturbances between characteristic gas components, e.g. C 2 H 2 、C 2 H 4 、C 2 H 6 And H 2 Thus using total Gibbs energyCalculation to excludeAnd->Interference of atoms.
Referring to fig. 1, in one embodiment, the fiber optic annular cavity is an optical monitoring device for thermal runaway of an energy storage cell.
An optical monitoring device for thermal runaway of an energy storage battery, implemented by a monitoring method for thermal runaway of an energy storage battery, further comprising: a first annular cavity and a second annular cavity, wherein the first annular cavity is composed of a first coupler 4, a fourth coupler 11 and an circulator 5, and the second annular cavity is composed of a second coupler 8, a third coupler 10 and a treated micro-nano optical fiber 9; an optical fiber extension line 7 is connected between the first coupler 4 and the second coupler 8; the end of the first coupler 4, which is separated from the optical fiber extension line 7, is sequentially connected with the isolator 3, the laser 2 and the function generator 1.
The output end of the fourth coupler 11 and the output end of the third coupler 10 are sequentially connected with a beam combiner 12, an erbium-doped fiber amplifier 13, a photoelectric detector 14 and an oscilloscope 15; the output end of the circulator 5 is connected with a fiber bragg grating 6.
A function generator 1 for emitting a specific light pulse for driving the laser to emit laser light of a specific wavelength band;
a laser 2 that emits a specific laser beam and detects the laser beam in the wavelength band;
the isolator 3 prevents light emitted by the annular cavity from polluting the light source, so that the purity of the light source output spectrum is reduced;
a first coupler 4 for transmitting and distributing optical signals with a split ratio of 85:15;
the circulator 5 transmits the optical signal to the fiber Bragg grating and ensures that the signal strength is unchanged;
the optical fiber Bragg grating 6 is stuck on the surface of the energy storage battery by using a polyimide tape and is used for monitoring the temperature change of the energy storage battery;
the optical fiber extension line 7 enables optical signals to be transmitted in the optical fiber extension line to achieve the effect of attenuation, and the length of the optical fiber extension line is 500 meters;
a second coupler 8 for transmitting and distributing optical signals with a split ratio of 85:15;
the treated micro-nano optical fiber 9 is placed in the energy storage cabin and is used for measuring the gas concentration;
a third coupler 10 for transmitting and distributing optical signals with a split ratio of 85:15;
a fourth coupler 11 for transmitting and distributing optical signals with a split ratio of 85:15;
a combiner 12 that combines the two sets of optical signals;
an erbium-doped fiber amplifier 13 that converts an optical signal into an electrical signal;
oscilloscope 15 observes ring down curves and stores data for analysis at the PC side.
The function generator 1 controls the light emitted by the laser 2 to pass through the first annular cavity, after passing through the fiber bragg grating 6, one part of the light signals are detected by the photoelectric detector 14, the other part of the light signals enter the second annular cavity, the processed micro-nano optical fiber 9 is used for obtaining a second group of light signals, and then the two groups of light signals are processed, so that a result is obtained, and the specific operation mode is as follows:
(1) Turning on the function generator 1, setting parameters of the function generator 1, setting pulse signal frequency to 6.2KHz and amplitude to 7V pp The duty cycle is set to 5%;
(2) Self-calibrating operation is carried out on the laser 2 so as to enable the laser to work in an optimal state;
(3) Sticking the fiber Bragg grating on the energy storage battery by using a polyimide adhesive tape;
(4) Placing the treated micro-nano optical fiber 9 in an energy storage prefabricated cabin;
(5) Opening the laser 2 to enable laser emitted by the laser to enter the annular cavity;
(6) The laser is split through the first coupler 4, and part of the laser enters the first annular cavity and passes through the fiber Bragg grating 6 for temperature measurement; the other part enters the second annular cavity and passes through the micro-nano optical fiber 9 for measuring the concentration of the characteristic gas of thermal runaway;
(7) The two groups of signals are synthesized by a beam combiner 12, and then the signal power is improved by an erbium-doped fiber amplifier 13;
(8) The optical signal detected by the photodetector 14 is converted into an electrical signal and transmitted to the oscilloscope 15;
(9) The signals stored in the oscilloscope 15 are transmitted to the PC terminal, and the obtained waveform data are analyzed and optimized to meet the requirements.
(10) And closing the function generator 1, the laser 2 and the oscilloscope 15, taking out the micro-nano optical fiber and the optical fiber Bragg grating of the energy storage prefabricated cabin, and ending the experiment.
To verify the optimizing effect of the device, the monitoring device for the thermal runaway of the energy storage battery is used for monitoring the temperature of the energy storage battery and the characteristic gas CH of the thermal runaway 4 And detecting, comparing the optimized data graph with the non-optimized data graph, and reflecting the actual effect of the system by fitting curve fitting degree.
Twenty groups of experiments are carried out on each temperature gradient by measuring the system loss at 25 ℃, 30 ℃, 35 ℃, 40 ℃ and 45 ℃, the average value of the system loss under each temperature gradient is calculated, and the temperature and the corresponding average value of the system loss are plotted by using Origin plotting software, as shown in figure 2; the above experiment was repeated and the data was optimized using the method described in S4 and plotted using Origin as shown in fig. 3. By comparison, the fitting degree before optimization is 0.878, the error is larger, the requirement of accurate early warning cannot be met, the fitting degree reaches 0.996 after the noise reduction by the method of S4, the detection accuracy of the system is improved, and the early warning timeliness of the thermal runaway of the energy storage battery can be met.
Twenty sets of experiments were performed for each concentration gradient by measuring the system loss at 0ppm, 50ppm, 100ppm, 150ppm, 200ppm, and the average value of the system loss for each concentration gradient was calculated, and the corresponding average value of the system loss for the gas concentration was plotted using Origin plotting software, as shown in fig. 4; the above experiment was repeated and the data was optimized using the method described in S5 and plotted using Origin as shown in fig. 5. It can be seen through comparison that the fitting degree before optimization is 0.804, the system accuracy is poor due to the interference of other thermal runaway characteristic gases, the Gibbs energy used in S5 reaches 0.993 after optimization, the system detection accuracy is improved, the gas concentration detection effect is better, and trace characteristic gases released in early stage of thermal runaway can be timely detected.
The fiber ring cavity ring down spectroscopy technology, which is an emerging ultra-sensitive absorption spectroscopy technology, is a technology combining the fiber ring down spectroscopy technology with the fiber sensing technology, has very high sensitivity in detecting optical loss, and has shown great advantages in many fields, such as optical loss of an optical measuring device, concentration of liquid, refraction, external pressure, strain and the like. Optical fiber sensing technology is developed along with development of optical communication technology, and optical fiber sensors have a series of unique advantages compared with conventional sensors of various types. Besides the characteristic of strong sensing function of the optical fiber device, the optical fiber cavity ring-down system also has the characteristic of high sensitivity, so that the optical fiber cavity ring-down system can be applied to a plurality of severe environments, and the detection limit can be reached by the optical fiber cavity ring-down system, which cannot be reached by the prior single-path evanescent field spectrum technology and technology. The devices of such systems, whether they are expanded to larger physical structures or scaled down to the dimensions used for microanalysis, have little effect on the optical stability of the system. The fiber Bragg grating FBG is mainly influenced by temperature only and is mainly characterized in that the thermal-optical effect and the thermal expansion effect are realized, the refractive index of the FBG is changed by the thermal-optical effect, the grating period is influenced by the expansion deformation of the FBG by the thermal expansion effect, the central wavelength of transmitted light is changed by changing the grating period after the FBG detects the temperature change, and the linear relation between the temperature and the central wavelength offset can be obtained after the central wavelength offset and the temperature change are fitted, so that the temperature measurement purpose is achieved. The optical fiber gas sensing technology is that light and gas interact in the fiber core or near the surface, the intensity and the phase of the light are changed, heat, sound waves or new light wavelength are generated, and the type and the content of the gas can be obtained by detecting the changes. For the gas with stronger absorption in the working wave band, the spectral loss or dispersion of the gas can be directly detected, or the phase change of the detection light caused by the absorption of the pumping light by the gas can be measured based on photo-thermal and photo-acoustic effects, and the working wavelength can be selected from ultraviolet, visible light or infrared wave bands according to the measurement requirement.
Using the monitoring device for thermal runaway of energy storage battery for characteristic gas CH of temperature and thermal runaway 4 And (3) detecting, namely comparing the optimized and non-optimized data graphs, and reflecting the actual effect of the system by fitting curve fitting degree as shown in fig. 2 and 3.
The foregoing examples merely illustrate embodiments of the invention and are described in more detail and are not to be construed as limiting the scope of the invention. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the invention, which are all within the scope of the invention. Accordingly, the scope of protection of the present invention is to be determined by the appended claims.
Claims (9)
1. An optical monitoring method for thermal runaway of an energy storage battery, comprising the steps of:
s1, establishing an optical fiber annular cavity calculation model, so as to obtain a relational expression between the ring-down time variation and the extra loss;
s2, based on a relation between the ring-down time variation and the extra loss, deforming to establish a temperature expression and a gas concentration expression;
s3, analyzing the temperature expression and the gas concentration expression to determine variables in the temperature expression and the gas concentration expression;
s4, optimizing the temperature in the temperature expression to obtain a temperature value to be measured;
and S5, optimizing the gas concentration in the gas concentration expression to obtain a gas concentration value to be measured.
2. The optical monitoring method for thermal runaway of an energy storage battery according to claim 1, wherein the specific steps of S1 are as follows:
s101, the optical fiber annular cavity calculation model is as follows:
（1）；
wherein,is ring down time; />Is the refractive index of the optical fiber ring; />Is the total length of the optical fiber ring; />Is the inherent loss of the system; />Is the propagation speed of light in vacuum;
s102, during actual measurement, the optical fiber annular cavity is influenced by the measured temperature and the gas concentration, so that the optical fiber loss is aggravated, and extra loss is introducedThen the ring down time in actual measurement +.>The method comprises the following steps:
（2）；
s103, obtaining a relation between the ring-down time variation and the extra loss according to the formula (1) and the formula (2), wherein the relation is as follows:
（3）。
3. an optical monitoring method for thermal runaway of an energy storage battery according to claim 2, wherein S2 comprises:
s201, the influence of temperature on the fiber Bragg grating is reflected in the two aspects of thermal-optical benefit and thermal expansion benefit, and the expression of refractive light change caused by the change of grating period is as follows:
（4）；
wherein,is the center wavelength; />Is a constant; />Is the temperature;
the ring down time varies due to the variation of the center wavelength, and is obtained by combining formula (3):
（5）；
wherein,extra loss under the fiber loop for temperature measurement;
s202, the temperature expression is:
（6）。
4. an optical monitoring method for thermal runaway of an energy storage battery according to claim 3, wherein S2 further comprises:
s203, gas measurement relies on the treated micro-nano optical fiber to adsorb the gas, so that the refractive index of the optical fiber is changed, and the ring-down time is changed:
（7）；
（8）；
wherein,measuring the extra loss under the optical fiber loop for the gas; />The refractive index of the micro-nano optical fiber is treated; />Is a constant; />The concentration of the gas to be measured;
s204, the gas concentration expression is:
（9）。
5. an optical monitoring method for thermal runaway of an energy storage battery according to claim 4, characterized in that: the step S3 is specifically as follows:
since the structure of the fiber optic ring cavity system is established, the propagation velocity of light in vacuumConstant->Constant->Refractive index of optical fiber ring>Total length of optical fiber ring->Also determined is the extra loss +.>And extra loss under the gas measuring fiber loop +.>Is a variable;
order of principleIs->Let->Is->Extra loss under the temperature measuring fiber loop>Is->Extra loss under gas measuring fiber loop>Is->The variable expressions of the temperature expression and the gas concentration expression are:
（10）；
due toAnd->For the fixed value, only the +.>、/>And optimizing to obtain the temperature value and the gas concentration value to be measured.
6. The optical monitoring method for thermal runaway of an energy storage battery according to claim 5, wherein S4 is specifically:
s401, pairNoise reduction treatment is carried out, record->Is the original signal containing noise, then decompose +.>Post-secondary signal->The method comprises the following steps:
（11）；
（12）；
wherein,is a first order residual component;
s402, willAdd compensation noise->Decomposition->And (3) obtaining:
（13）；
wherein,to compensate for white noise;
s403, decompose thePersonal->Secondary (S)/(S)>Is a coefficient of->Is->，/>The order residual component is:
（14）；
（15）；
s404, repeating S401-S403 untilFailing to decompose, then:
（16）；
s405, the obtained noise reduction signal is:
（17）。
7. the optical monitoring method for thermal runaway of an energy storage battery according to claim 6, wherein S5 is specifically:
s501, pairOptimizing, wherein the total Gibbs energy is as follows:
（18）；
wherein,is->Group gibbs energy; />Is a universal gas constant; />Is at normal temperature; />Is->Group data->；/>Is the total number of characteristic gas species; />Is->Grouping the mole number of the gas to be tested;
s502, to make the total Gibbs energyAt a minimum, atomic conservation must obey:
（19）；
wherein,is the mole number of element A; />Is the elementTotal number of elements; />Is hydrogen; />Is a carbon element;
s503, obtaining total Gibbs energy by using the formula (19) as a constraint conditionIs obtained by the minimum value of (1):
（20）；
wherein,is element->Element potential energy of (2), then simultaneous normalization condition, < ->Thereby obtaining optimized +.>。
8. An optical monitoring device for thermal runaway of an energy storage battery, characterized in that: achieved by the optical monitoring method for thermal runaway of an energy storage battery according to any one of claims 1 to 7, further comprising: the device comprises a first annular cavity and a second annular cavity, wherein the first annular cavity consists of a first coupler (4), a fourth coupler (11) and a circulator (5), and the second annular cavity consists of a second coupler (8), a third coupler (10) and a treated micro-nano optical fiber (9); an optical fiber extension line (7) is connected between the first coupler (4) and the second coupler (8); one end of the first coupler (4) which is separated from the optical fiber extension line (7) is sequentially connected with the isolator (3), the laser (2) and the function generator (1).
9. An optical monitoring device for thermal runaway of an energy storage battery according to claim 8, wherein: the output end of the fourth coupler (11) and the output end of the third coupler (10) are sequentially connected with the beam combiner (12), the erbium-doped fiber amplifier (13), the photoelectric detector (14) and the oscilloscope (15); the output end of the circulator (5) is connected with the fiber Bragg grating (6).
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