CN110265745A - A kind of temperature control strategy of lithium-ion battery systems Convective Heat Transfer - Google Patents

A kind of temperature control strategy of lithium-ion battery systems Convective Heat Transfer Download PDF

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CN110265745A
CN110265745A CN201910441964.2A CN201910441964A CN110265745A CN 110265745 A CN110265745 A CN 110265745A CN 201910441964 A CN201910441964 A CN 201910441964A CN 110265745 A CN110265745 A CN 110265745A
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lithium
ion battery
moment
battery monomer
formula
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杨世春
华旸
范智伟
周新岸
周思达
闫啸宇
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Beihang University
Beijing University of Aeronautics and Astronautics
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
    • G01K13/00—Thermometers specially adapted for specific purposes
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
    • G01K17/00—Measuring quantity of heat
    • G01K17/06—Measuring quantity of heat conveyed by flowing media, e.g. in heating systems e.g. the quantity of heat in a transporting medium, delivered to or consumed in an expenditure device
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/36—Arrangements for testing, measuring or monitoring the electrical condition of accumulators or electric batteries, e.g. capacity or state of charge [SoC]
    • G01R31/382—Arrangements for monitoring battery or accumulator variables, e.g. SoC
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/36—Arrangements for testing, measuring or monitoring the electrical condition of accumulators or electric batteries, e.g. capacity or state of charge [SoC]
    • G01R31/389—Measuring internal impedance, internal conductance or related variables
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/60—Heating or cooling; Temperature control
    • H01M10/61—Types of temperature control
    • H01M10/613—Cooling or keeping cold
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/60—Heating or cooling; Temperature control
    • H01M10/62—Heating or cooling; Temperature control specially adapted for specific applications
    • H01M10/625—Vehicles
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/60—Heating or cooling; Temperature control
    • H01M10/63—Control systems
    • H01M10/633—Control systems characterised by algorithms, flow charts, software details or the like
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

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Abstract

The invention discloses a kind of temperature control strategy of lithium-ion battery systems Convective Heat Transfer, include the following steps: to derive t moment temperature T according to the conservation of energy and battery heat dissipation equationtRecurrence formula；State space equation is established according to lithium-ion battery monomer second order equivalent-circuit model；On the basis of state space equation, estimate several lithium-ion battery monomers in the internal resistance at t-1 moment with DEKF algorithm；It brings obtained internal resistance into recurrence formula, obtains several lithium-ion battery monomers in t moment temperature TtAnd it is ranked up, compared with preset value, change the corresponding intensity of cooling to lithium-ion battery systems according to different comparison results, it is more than normal range (NR) and sub-cooled which, which can improve temperature control hysteresis to avoid operating temperature in lithium-ion battery systems Convective Heat Transfer,.

Description

A kind of temperature control strategy of lithium-ion battery systems Convective Heat Transfer
Technical field
The present invention relates to lithium-ion battery systems temperature management fields, are related to a kind of control strategy, especially suitable for cooling Mode is the temperature control of the battery of air-cooled or liquid cooling electric car, in particular, being related to a kind of lithium-ion battery systems pair Flow the temperature control strategy of heat transfer process.
Background technique
In recent years, various countries increasingly pay attention to energy conservation and environmental protection, and electric car is increasingly becoming because of the characteristics of its clean and effective The first choice of traditional combustion engine automobile is substituted, as the power resources of electric car, power lithium-ion battery directly affects electronic The performance and mileage travelled of automobile.Temperature has a major impact the performance of power battery, safety and service life.If lithium-ion electric Pond works under high temperature environment for a long time, and not only the efficiency for charge-discharge of battery will be greatly reduced, but also battery life also can be obvious Shorten, personal safety may be jeopardized when serious.Lithium ion battery operation at the same time needs suitable temperature, and sub-cooled is not The normal operation for only influencing battery, also will increase energy consumption.Cooling system is mainly anti-according to the temperature sensor of battery surface at present Feedback has certain hysteresis.
Therefore, temperature control hysteresis can be improved and then avoid lithium-ion battery systems operating temperature by how providing one kind The temperature control strategy of the lithium-ion battery systems Convective Heat Transfer of performance and safety may be influenced when more than normal range (NR) just Become those skilled in the art's technical problem urgently to be solved.
Summary of the invention
It is more than normal range (NR) in order to improve temperature control hysteresis and then avoid lithium-ion battery systems operating temperature Shi Keneng influences battery performance and safety, and the invention proposes a kind of controls of the temperature of lithium-ion battery systems Convective Heat Transfer Strategy.
Include the following steps:
Step 1: radiated equation according to the conservation of energy and battery, derive in t moment lithium-ion battery systems several lithiums from The temperature T of sub- battery celltRecurrence formula, it is as follows:
Step 1.1: the heat of lithium-ion battery monomer, radiation processes are the unstable state for typically having time-varying inner heat source Conduction process, energy conservation equation are as follows:
In formula, mPFor the quality of lithium-ion battery monomer, cpFor the specific heat capacity of lithium-ion battery monomer, TtFor t moment lithium from The temperature of sub- battery cell,For t moment lithium-ion battery monomer heat power,For the heat dissipation of t moment lithium-ion battery monomer Power；
Step 1.2: not considering heat radiation and phase transformation heat production, the equation of lithium-ion battery monomer heat power are as follows:
In formula, ItFor t moment lithium-ion battery monomer operating current, RtFor the total internal resistance of t moment lithium-ion battery monomer,For Temperature affection factor；
Step 1.3: lithium-ion battery monomer radiating mode is heat convection, the equation of lithium-ion battery monomer heat radiation power Are as follows:
In formula, h is lithium-ion battery monomer and fluid heat transfer coefficient, and A is lithium-ion battery monomer heat dissipation area, Ta,tFor t The environment temperature at moment；
Step 1.4: simultaneous formula (1), formula (2) and formula (3) estimate t moment with the t-1 moment, obtain t moment temperature TtRecurrence formula, it is as follows:
In formula, It-1For t-1 moment lithium-ion battery monomer operating current, Rt-1It is total for t-1 moment lithium-ion battery monomer Internal resistance, Ta,t-1For t-1 moment environment temperature；
Step 2: state space equation is established according to lithium-ion battery monomer second order equivalent-circuit model, as follows:
Step 2.1: lithium-ion battery monomer second order equivalent-circuit model has following equation:
The total internal resistance equation of t moment lithium-ion battery monomer are as follows:
In formula,WithFor lithium-ion battery monomer polarizing voltage, R0For lithium-ion battery monomer ohmic internal resistance, R1 And R2For lithium-ion battery monomer polarization resistance, C1And C2For lithium-ion battery monomer polarization capacity, I is lithium-ion battery monomer Operating current, VocvFor the open-circuit voltage of lithium-ion battery monomer, U is lithium-ion battery monomer end voltage；
Step 2.2: sampling period τ, τ are the time interval at t-1 moment and t moment, are carried out at discretization to formula (5) Reason, can obtain state space equation, as follows:
In formula, state vectorut-1For the input vector at t-1 moment, ut-1=It-1, yt-1 For the output vector at t-1 moment, yt-1=Ut-1, t and t-1 respectively indicate t moment and t-1 moment, wt-1And vt-1It respectively represented The noise and measurement noise at journey t-1 moment, wt-1And vt-1Covariance be respectively QwAnd Qv, Qw=E (w × wT), Qv=E (v × vT),
Step 2.3: setting parameter vector θ=[R0 C1 R1 C2 R2 Vocv]T, the equation of the dynamic characteristic of the parameter is described such as Under:
In formula,Using a random small vector rt-1The time-varying for carrying out characterising parameter θ is special Property, et-1For evaluated error, rt-1And et-1Covariance be respectively QrAnd Qe,Qr=E (r × rT)Qe=E (e × eT), t and t-1 divide It Biao Shi not t moment and t-1 moment；
Step 3: on the basis of state space equation, estimating that several lithium-ion battery monomers exist respectively with DEKF algorithm Total internal resistance R at t-1 momentt-1；
Step 4: by the total internal resistance R of several lithium-ion battery monomers obtained in step 3t-1Bring recurrence formula (4) into respectively In, obtain the temperature T of several lithium-ion battery monomers of t momentt, compared with given preset value and according to different comparison results To adjust the intensity of cooling of battery cooling system.
Preferably, the step 3 is as follows:
Step 3.1: initialization sets initial state vector x0|0, initial parameter vector θ0|0And the association side of process noise Poor Qw, measurement noise covariance Qv, parameter vector covariance QrWith estimation error covariance QeInitial value；
Step 3.2: according to state vector xt-1, process noise covariance Qw, measurement noise covariance QvAcquisition state Prior estimate x of the vector x in t momentt|t-1:
xt|t-1=At-1xt-1|t-1+Bt-1ut-1 (9)
In formula, xt-1|t-1For the Posterior estimator of t-1 moment x；
Step 3.3: according to the covariance Q of the prior estimate determination process noise of acquisitionwIn the prior uncertainty association side of t moment Poor Pt|t-1:
Pt|t-1=At-1Pt-1|t-1At-1 T+Qw (10)
In formula, Pt-1|t-1For the posteriori error covariance at t-1 moment；
Step 3.4: according to the prior uncertainty covariance P of acquisitiont|t-1Obtain kalman gain Kt:
In formula,ForTransposed matrix,
Step 3.5: according to prior estimate xt|t-1With the kalman gain K of acquisitiont, determine state vector xtIn t moment Posterior estimator xt|t:
Step 3.6: according to the Posterior estimator x of acquisitiont|tThe covariance Q of renewal process noisewIn the posteriori error of t moment Covariance Pt|tAre as follows:
In formula, E is unit matrix；
Step 3.7: get parms vector θ t moment prior estimate θt|t-1:
θt|t-1=θt-1|t-1 (14)
In formula, under be designated as t-1 | t-1 is expressed as the Posterior estimator of t-1 moment θ；
Step 3.8: the covariance Q of parameter vector is determined according to the prior estimate of acquisitionrIn the prior uncertainty association side of t moment Difference
In formula, under be designated as t-1 | t-1 is expressed as t-1 moment posteriori error covariance；
Step 3.9: according toObtain parameter kalman gain
Step 3.10: according to prior estimate θt|t-1With the kalman gain of acquisitionDetermine state vector θtIn t moment Posterior estimator θt|t:
Step 3.11: according to the Posterior estimator θ of acquisitiont|tThe covariance Q of undated parameter vectorrIn the posteriori error of t moment CovarianceAre as follows:
Step 3.12: judging whether t moment is equal to n-hour, the n-hour is the temperature for needing to learn lithium-ion battery monomer At the time of spending, if so, obtaining the Posterior estimator x at t-1 moment according to step 3.2 to step 3.11t-1With Posterior estimator θt-1, And formula (6) are combined, lithium-ion battery monomer is obtained in the total internal resistance R of lithium-ion battery monomer at t-1 momentt-1。
Preferably, in the step 4, by the temperature T of several lithium-ion battery monomers of obtained t momenttIt is arranged Sequence chooses the temperature maximum T of the lithium-ion battery monomer in several lithium-ion battery monomer temperaturet,max, lithium ion battery list The temperature minimum value T of bodyt,minWith the temperature intermediate value T of lithium-ion battery monomert,mid, given preset value is Tpreset1With Tpreset2, wherein Tpreset1<Tpreset2If Tt,max<Tpreset1, then the battery cooling system does not work, if Tpreset1≤Tt,mid <Tt,max≤Tpreset2, then the battery cooling system is in tick-over, if Tpreset1≤Tt,mid≤Tpreset2<Tt,max, then institute It states battery cooling system and is in middling speed working condition, if Tt,min>Tpreset2, then the battery cooling system is in high speed operation.
Preferably, the τ is 0.03s.
Preferably, the Temperature affection factor in the step 1.2Acquisition methods it is as follows:
Lithium-ion battery monomer contains capacitance from 0 to 100%, is step-length with 10%, measures lithium ion under different temperatures T Battery cell corresponding open-circuit voltage V containing capacitanceocv, the current residual of fitting calculating lithium-ion battery monomer is containing capacitance value Lower VocvThe slope of T curve, and so on, obtain the current residual range containing capacity curve of full lithium-ion battery monomer Curve, and then the heat power for lithium-ion battery monomer being used for after curve progress piecewise fittingCalculation formula.
Preferably, lithium-ion battery monomer in the step 1.3 and the acquisition methods of fluid heat transfer coefficient h are as follows:
Lithium-ion battery monomer is put into experiment runner, a thin layer sheet metal is coated on its surface, using electric current to it Heating, the electric current and voltage drop for measuring sheet metal later can determine lithium-ion battery monomer surface heat flux, and measure lithium Ion battery monomer surface temperature calculates the size of the coefficient of heat transfer with Newtonian Cooling formula, by changing in experiment runner Fluid flow rate, can get it is different in flow rate under the coefficient of heat transfer, and tabulate, required h chooses from table, if actual flow velocity is not real Institute's velocity measurement is tested, then is calculated with interpolation method, to obtain the lithium-ion battery monomer under the flow velocity and air fluid heat transfer Coefficient h.
Preferably, the battery cooling system is the air cooling system for including fan, adjusted by adjusting the revolving speed of fan Wind speed is saved so that battery cooling system is the working condition of low speed or midium speed or high speed.
Preferably, the battery cooling system is the liquid cooling system for including water pump, adjusted by adjusting pump power Flow velocity is so that battery cooling system is the working condition of low speed or midium speed or high speed.
Preferably, the sequence of step 1 and step 2 can be interchanged.
The temperature control strategy of lithium-ion battery systems Convective Heat Transfer provided by the invention has following technology effect Fruit:
1. the control strategy that the present invention uses is by estimation subsequent time lithium ion battery temperature, so as to improve temperature control Hysteresis processed avoids lithium-ion battery systems operating temperature that from may influencing performance and security situation generation when being more than normal range (NR). Wherein, the internal resistance of several lithium-ion battery monomers can be accurately estimated with DEKF algorithm, and then can accurately estimate lithium-ion electric Pond monomer temperature.
2. the present invention a variety of intensities of cooling settable according to demand, can under the premise of lithium-ion battery monomer works normally Energy saving.
Detailed description of the invention
Fig. 1 is lithium-ion battery monomer second order equivalent-circuit model schematic diagram.
Specific embodiment
As shown in Figure 1, Fig. 1 is lithium-ion battery monomer second order equivalent-circuit model schematic diagram.
The present invention provides a kind of temperature control strategy of lithium-ion battery systems Convective Heat Transfer comprising following step It is rapid:
Step 1: radiated equation according to the conservation of energy and battery, derive in t moment lithium-ion battery systems several lithiums from The temperature T of sub- battery celltRecurrence formula, it is as follows:
Step 1.1: the heat of lithium-ion battery monomer, radiation processes are the unstable state for typically having time-varying inner heat source Conduction process, energy conservation equation are as follows:
In formula, mPFor the quality of lithium-ion battery monomer, cpFor the specific heat capacity of lithium-ion battery monomer, TtFor t moment lithium from The temperature of sub- battery cell,For t moment lithium-ion battery monomer heat power,For the heat dissipation of t moment lithium-ion battery monomer Power；
Step 1.2: not considering heat radiation and phase transformation heat production, the equation of lithium-ion battery monomer heat power are as follows:
In formula, ItFor t moment lithium-ion battery monomer operating current, RtFor the total internal resistance of t moment lithium-ion battery monomer,For Temperature affection factor；
Step 1.3: lithium-ion battery monomer radiating mode is heat convection, the equation of lithium-ion battery monomer heat radiation power Are as follows:
In formula, h is lithium-ion battery monomer and fluid heat transfer coefficient, and A is lithium-ion battery monomer heat dissipation area, Ta,tFor t The environment temperature at moment；
Step 1.4: simultaneous formula (1), formula (2) and formula (3) estimate t moment with the t-1 moment, obtain t moment temperature TtRecurrence formula, it is as follows:
In formula, It-1For t-1 moment lithium-ion battery monomer operating current, Rt-1It is total for t-1 moment lithium-ion battery monomer Internal resistance, Ta,t-1For t-1 moment environment temperature；
Step 2: state space equation is established according to lithium-ion battery monomer second order equivalent-circuit model, as follows:
Step 2.1: lithium-ion battery monomer second order equivalent-circuit model has following equation:
The total internal resistance equation of t moment lithium-ion battery monomer are as follows:
In formula,WithFor lithium-ion battery monomer polarizing voltage, R0For lithium-ion battery monomer ohmic internal resistance, R1 And R2For lithium-ion battery monomer polarization resistance, C1And C2For lithium-ion battery monomer polarization capacity, I is lithium-ion battery monomer Operating current, VocvFor the open-circuit voltage of lithium-ion battery monomer, U is lithium-ion battery monomer end voltage；
Step 2.2: sampling period τ, τ are the time interval at t-1 moment and t moment, are carried out at discretization to formula (5) Reason, can obtain state space equation, as follows:
In formula, state vectorut-1For the input vector at t-1 moment, ut-1=It-1, yt-1 For the output vector at t-1 moment, yt-1=Ut-1, t and t-1 respectively indicate t moment and t-1 moment, wt-1And vt-1It respectively represented The noise and measurement noise at journey t-1 moment, wt-1And vt-1Covariance be respectively QwAnd Qv, Qw=E (w × wT), Qv=E (v × vT),
Step 2.3: setting parameter vector θ=[R0 C1 R1 C2 R2 Vocv]T, the equation of the dynamic characteristic of the parameter is described such as Under:
In formula,Using a random small vector rt-1Carry out the time-varying of characterising parameter θ Characteristic, et-1For evaluated error, rt-1And et-1Covariance be respectively QrAnd Qe,Qr=E (r × rT)Qe=E (e × eT), t and t-1 Respectively indicate t moment and t-1 moment；
Step 3: on the basis of state space equation, estimating that several lithium-ion battery monomers exist respectively with DEKF algorithm Total internal resistance R at t-1 momentt-1；
Step 4: by the total internal resistance R of several lithium-ion battery monomers obtained in step 3t-1Bring recurrence formula (4) into respectively In, obtain the temperature T of several lithium-ion battery monomers of t momentt, compared with given preset value and according to different comparison results To adjust the intensity of cooling of battery cooling system.
The control strategy that the present invention uses is by estimation subsequent time lithium ion battery temperature, so as to improve temperature control Hysteresis avoids lithium-ion battery systems operating temperature that from may influencing performance and security situation generation when being more than normal range (NR).Its In, the internal resistance of several lithium-ion battery monomers can be accurately estimated with DEKF algorithm, and then can accurately estimate lithium ion battery Monomer temperature.
Further, step 3 is as follows:
Step 3.1: initialization sets initial state vector x0|0, initial parameter vector θ0|0And the association side of process noise Poor Qw, measurement noise covariance Qv, parameter vector covariance QrWith estimation error covariance QeInitial value；
Step 3.2: according to state vector xt-1, process noise covariance Qw, measurement noise covariance QvAcquisition state Prior estimate x of the vector x in t momentt|t-1:
xt|t-1=At-1xt-1|t-1+Bt-1ut-1 (9)
In formula, xt-1|t-1For the Posterior estimator of t-1 moment x；
Step 3.3: according to the covariance Q of the prior estimate determination process noise of acquisitionwIn the prior uncertainty association side of t moment Poor Pt|t-1:
Pt|t-1=At-1Pt-1|t-1At-1 T+Qw (10)
In formula, Pt-1|t-1For the posteriori error covariance at t-1 moment；
Step 3.4: according to the prior uncertainty covariance P of acquisitiont|t-1Obtain kalman gain Kt:
In formula,ForTransposed matrix,
Step 3.5: according to prior estimate xt|t-1With the kalman gain K of acquisitiont, determine state vector xtIn t moment Posterior estimator xt|t:
Step 3.6: according to the Posterior estimator x of acquisitiont|tThe covariance Q of renewal process noisewIn the posteriori error of t moment Covariance Pt|tAre as follows:
In formula, E is unit matrix；
Step 3.7: get parms vector θ t moment prior estimate θt|t-1:
θt|t-1=θt-1|t-1 (14)
In formula, under be designated as t-1 | t-1 is expressed as the Posterior estimator of t-1 moment θ；
Step 3.8: the covariance Q of parameter vector is determined according to the prior estimate of acquisitionrIn the prior uncertainty association side of t moment Difference
In formula, under be designated as t-1 | t-1 is expressed as t-1 moment posteriori error covariance；
Step 3.9: according toObtain parameter kalman gain
Step 3.10: according to prior estimate θt|t-1With the kalman gain of acquisitionDetermine state vector θtIn t moment Posterior estimator θt|t:
Step 3.11: according to the Posterior estimator θ of acquisitiont|tThe covariance Q of undated parameter vectorrIn the posteriori error of t moment CovarianceAre as follows:
Step 3.12: judging whether t moment is equal to n-hour, the n-hour is the temperature for needing to learn lithium-ion battery monomer At the time of spending, if so, obtaining the Posterior estimator x at t-1 moment according to step 3.2 to step 3.11t-1With Posterior estimator θt-1, And formula (6) are combined, lithium-ion battery monomer is obtained in the total internal resistance R of lithium-ion battery monomer at t-1 momentt-1。
Further, in the step 4, by the temperature T of several lithium-ion battery monomers of obtained t momenttIt is arranged Sequence chooses the temperature maximum T of the lithium-ion battery monomer in several lithium-ion battery monomer temperaturet,max, lithium ion battery list The temperature minimum value T of bodyt,minWith the temperature intermediate value T of lithium-ion battery monomert,mid, given preset value is Tpreset1With Tpreset2, wherein Tpreset1<Tpreset2If Tt,max<Tpreset1, then the battery cooling system does not work, if Tpreset1≤Tt,mid <Tt,max≤Tpreset2, then the battery cooling system is in tick-over, if Tpreset1≤Tt,mid≤Tpreset2<Tt,max, then institute It states battery cooling system and is in middling speed working condition, if Tt,min>Tpreset2, then the battery cooling system is in high speed operation.
Settable a variety of intensities of cooling according to demand can save energy under the premise of lithium-ion battery monomer works normally Consumption.
In the present invention, τ 0.03s.But not limited to this.
Further, the Temperature affection factor in step 1.2Acquisition methods it is as follows:
Lithium-ion battery monomer contains capacitance from 0 to 100%, is step-length with 10%, measures lithium ion under different temperatures T Battery cell corresponding open-circuit voltage V containing capacitanceocv, the current residual of fitting calculating lithium-ion battery monomer is containing capacitance value Lower VocvThe slope of T curve, and so on, obtain the current residual range containing capacity curve of full lithium-ion battery monomer Curve, and then the heat power for lithium-ion battery monomer being used for after curve progress piecewise fittingCalculation formula.
Further, the lithium-ion battery monomer in step 1.3 and the acquisition methods of fluid heat transfer coefficient h are as follows:
Lithium-ion battery monomer is put into experiment runner, a thin layer sheet metal is coated on its surface, using electric current to it Heating, the electric current and voltage drop for measuring sheet metal later can determine lithium-ion battery monomer surface heat flux, and measure lithium Ion battery monomer surface temperature calculates the size of the coefficient of heat transfer with Newtonian Cooling formula, by changing in experiment runner Fluid flow rate, can get it is different in flow rate under the coefficient of heat transfer, and tabulate, required h chooses from table, if actual flow velocity is not real Institute's velocity measurement is tested, then is calculated with interpolation method, to obtain the lithium-ion battery monomer under the flow velocity and air fluid heat transfer Coefficient h.
Further, battery cooling system is the air cooling system for including fan, adjusts wind by adjusting the revolving speed of fan Speed is so that battery cooling system is the working condition of low speed or midium speed or high speed.
Alternatively, battery cooling system is the liquid cooling system for including water pump, adjust flow velocity by adjusting pump power so that Battery cooling system is the working condition of low speed or midium speed or high speed.
In this method, the sequence of step 1 and step 2 be can be interchanged.

Claims (9)

1. a kind of temperature control strategy of lithium-ion battery systems Convective Heat Transfer, which comprises the steps of:
Step 1: according to the conservation of energy and battery heat dissipation equation, deriving several lithium-ion electrics in t moment lithium-ion battery systems The recurrence formula of the temperature Tt of pond monomer, as follows:
Step 1.1: the heat of lithium-ion battery monomer, radiation processes are the Unsteady Heat Transfers for typically having time-varying inner heat source Process, energy conservation equation are as follows:
In formula, mPFor the quality of lithium-ion battery monomer, cpFor the specific heat capacity of lithium-ion battery monomer, Tt is t moment lithium-ion electric The temperature of pond monomer,For t moment lithium-ion battery monomer heat power,For t moment lithium-ion battery monomer heat dissipation function Rate；
Step 1.2: not considering heat radiation and phase transformation heat production, the equation of lithium-ion battery monomer heat power are as follows:
In formula, ItFor t moment lithium-ion battery monomer operating current, RtFor the total internal resistance of t moment lithium-ion battery monomer,For temperature Degree influences coefficient；
Step 1.3: lithium-ion battery monomer radiating mode is heat convection, the equation of lithium-ion battery monomer heat radiation power are as follows:
In formula, h is lithium-ion battery monomer and fluid heat transfer coefficient, and A is lithium-ion battery monomer heat dissipation area, TA, tFor t moment Environment temperature；
Step 1.4: simultaneous formula (1), formula (2) and formula (3) estimate t moment with the t-1 moment, obtain t moment temperature Tt's Recurrence formula, as follows:
In formula, It-1For t-1 moment lithium-ion battery monomer operating current, Rt-1For the total internal resistance of t-1 moment lithium-ion battery monomer, TA, t-1For t-1 moment environment temperature；
Step 2: state space equation is established according to lithium-ion battery monomer second order equivalent-circuit model, as follows:
Step 2.1: lithium-ion battery monomer second order equivalent-circuit model has following equation:
The total internal resistance equation of t moment lithium-ion battery monomer are as follows:
In formula,WithFor lithium-ion battery monomer polarizing voltage, R0For lithium-ion battery monomer ohmic internal resistance, R1And R2For Lithium-ion battery monomer polarization resistance, C1And C2For lithium-ion battery monomer polarization capacity, I is lithium-ion battery monomer work electricity Stream, VocvFor the open-circuit voltage of lithium-ion battery monomer, U is lithium-ion battery monomer end voltage；
Step 2.2: sampling period τ, τ are the time interval at t-1 moment and t moment, carry out sliding-model control to formula (5), State space equation can be obtained, as follows:
In formula, state vectorut-1For the input vector at t-1 moment, ut-1=It-1, yt-1For t- The output vector at 1 moment, yt-1=ut-1, t and t-1 respectively indicate t moment and t-1 moment, wt-1And vt-1Respectively represent process t-1 The noise and measurement noise at moment, wt-1And vt-1Covariance be respectively QwAnd Qv, Qw=E (w × wT), Qv=E (v × vT),
Step 2.3: setting parameter vector θ=[R0 C1 R1 C2 R2 Vocv]T, the equation for describing the dynamic characteristic of the parameter is as follows:
In formula,Using a random small vector rt-1Carry out the time-varying characteristics of characterising parameter θ, et-1For evaluated error, rt-1And et-1Covariance be respectively QrAnd Qe, Qr=E (r × rT)Qe=E (e × eT), t and t-1 difference Indicate t moment and t-1 moment；
Step 3: on the basis of state space equation, estimating several lithium-ion battery monomers in t-1 respectively with DEKF algorithm Total internal resistance R at momentt-1；
Step 4: by the total internal resistance R of several lithium-ion battery monomers obtained in step 3t-1It brings into recurrence formula (4), obtains respectively To the temperature T of several lithium-ion battery monomers of t momentt, adjusted compared with given preset value and according to different comparison results The intensity of cooling of whole battery cooling system.
2. temperature control strategy according to claim 1, which is characterized in that the step 3 is as follows:
Step 3.1: initialization sets initial state vector x0|0, initial parameter vector θ0|0And the covariance Q of process noisew、 Measure the covariance Q of noisev, parameter vector covariance QrWith estimation error covariance QeInitial value；
Step 3.2: according to state vector xt-1, process noise covariance Qw, measurement noise covariance QvObtain state vector x In the prior estimate x of t momentt|t-1:
xt|t-1=At-1xt-1|t-1+Bt-1ut-1 (9)
In formula, xt-1|t-1For the Posterior estimator of t-1 moment x；
Step 3.3: according to the covariance Q of the prior estimate determination process noise of acquisitionwIn the prior uncertainty covariance of t moment Pt|t-1:
Pt|t-1=At-1Pt-1|t-1At-1 T+Qw (10)
In formula, Pt-l|t-1For the posteriori error covariance at t-1 moment；
Step 3.4: according to the prior uncertainty covariance P of acquisitiont|t-1Obtain kalman gain Kt:
In formula,ForTransposed matrix,
Step 3.5: according to prior estimate xt|t-1With the kalman gain K of acquisitiont, determine state vector xtEstimate in the posteriority of t moment Count xt|t:
Step 3.6: according to the Posterior estimator x of acquisitiont|tThe covariance Q of renewal process noisewIn the posteriori error covariance of t moment Pt|tAre as follows:
In formula, E is unit matrix；
Step 3.7: get parms vector θ t moment prior estimate θt|t-1:
θt|t-1=θt-1|t-1 (14)
In formula, under be designated as t-1 | t-1 is expressed as the Posterior estimator of t-1 moment θ；
Step 3.8: prior uncertainty covariance of the covariance Qr in t moment of parameter vector is determined according to the prior estimate of acquisition
In formula, under be designated as t-1 | t-1 is expressed as t-1 moment posteriori error covariance；
Step 3.9: according toObtain parameter kalman gain
Step 3.10: according to prior estimate θt|t-1With the kalman gain of acquisitionDetermine state vector θtIn the posteriority of t moment Estimate θt|t:
Step 3.11: according to the Posterior estimator θ of acquisitiont|tThe covariance Q of undated parameter vectorrIn the posteriori error association side of t moment DifferenceAre as follows:
Step 3.12: judging whether t moment is equal to n-hour, the n-hour is the temperature for needing to learn lithium-ion battery monomer Moment, if so, obtaining the Posterior estimator x at t-1 moment according to step 3.2 to step 3.11t-1With Posterior estimator θt-1, and tie It closes formula (6), obtains lithium-ion battery monomer in the total internal resistance R of lithium-ion battery monomer at t-1 momentt-1。
3. temperature control strategy according to claim 1, which is characterized in that in the step 4, by obtained t moment The temperature T of several lithium-ion battery monomerstIt is ranked up, chooses the lithium ion battery list in several lithium-ion battery monomer temperature The temperature maximum T of bodyT, max, lithium-ion battery monomer temperature minimum value TT, minWith the temperature intermediate value of lithium-ion battery monomer Tt,mid, given preset value is TpresetAnd Tpreset2, wherein Tpreset1< Tpreset2If TT, max< Tpreset1, then the electricity Pond cooling system does not work, if Tpreset1≤TT, mid< TT, max≤Tpreset2, then the battery cooling system is in tick-over, If Tpreset1TT, mid≤Tpreset2< TT, max, then the battery cooling system is in middling speed working condition, if TT, min> Tpreset2, Then the battery cooling system is in high speed operation.
4. temperature control strategy according to claim 1, which is characterized in that the τ is 0.03s.
5. temperature control strategy according to claim 1, which is characterized in that the Temperature affection factor in the step 1.2Acquisition methods it is as follows:
Lithium-ion battery monomer contains capacitance from 0 to 100%, is step-length with 10%, measures lithium ion battery under different temperatures T Monomer corresponding open-circuit voltage V containing capacitanceocv, the current residual of fitting calculating lithium-ion battery monomer is containing under capacitance value VocvThe slope of T curve, and so on, obtain the current residual range containing capacity curve of full lithium-ion battery monomerIt is bent Line, and then the heat power for lithium-ion battery monomer being used for after curve progress piecewise fittingCalculation formula.
6. temperature control strategy according to claim 1, which is characterized in that the lithium ion battery list in the step 1.3 Body and the acquisition methods of fluid heat transfer coefficient h are as follows:
Lithium-ion battery monomer is put into experiment runner, a thin layer sheet metal is coated on its surface, it is heated using electric current, The electric current and voltage drop for measuring sheet metal later can determine lithium-ion battery monomer surface heat flux, and measure lithium-ion electric Pond monomer surface temperature calculates the size of the coefficient of heat transfer with Newtonian Cooling formula, by changing the fluid stream in experiment runner Speed, can get it is different in flow rate under the coefficient of heat transfer, and tabulate, required h chooses from table, if actual flow velocity is not that experiment is surveyed Flow velocity is then calculated with interpolation method, to obtain the lithium-ion battery monomer under the flow velocity and air fluid coefficient of heat transfer h.
7. temperature control strategy according to claim 1, which is characterized in that the battery cooling system be include fan Air cooling system adjusts wind speed by adjusting the revolving speed of fan so that battery cooling system is low speed or midium speed or high speed Working condition.
8. temperature control strategy according to claim 1, which is characterized in that the battery cooling system be include water pump Liquid cooling system adjusts flow velocity by adjusting pump power so that battery cooling system is the work of low speed or midium speed or high speed Make state.
9. temperature control strategy according to claim 1, which is characterized in that the sequence of step 1 and step 2 can be interchanged.
CN201910441964.2A 2019-05-24 2019-05-24 A kind of temperature control strategy of lithium-ion battery systems Convective Heat Transfer Pending CN110265745A (en)

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