CN112379291B - SOC estimation method and system for lithium battery system - Google Patents

SOC estimation method and system for lithium battery system Download PDF

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Publication number
CN112379291B
CN112379291B CN202011050276.2A CN202011050276A CN112379291B CN 112379291 B CN112379291 B CN 112379291B CN 202011050276 A CN202011050276 A CN 202011050276A CN 112379291 B CN112379291 B CN 112379291B
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charge
discharge
soc
curve
lithium battery
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CN112379291A (en
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黄汉川
陈冬
王羽平
相佳媛
陈建
吴贤章
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Zhejiang Narada Power Source Co Ltd
Hangzhou Nandu Power Technology Co Ltd
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Zhejiang Narada Power Source Co Ltd
Hangzhou Nandu Power Technology Co Ltd
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    • 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]
    • G01R31/385—Arrangements for measuring battery or accumulator variables
    • G01R31/387—Determining ampere-hour charge capacity or 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]
    • G01R31/367—Software therefor, e.g. for battery testing using modelling or look-up tables
    • 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]
    • G01R31/392—Determining battery ageing or deterioration, e.g. state of health
    • 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]
    • G01R31/396—Acquisition or processing of data for testing or for monitoring individual cells or groups of cells within a battery
    • 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
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/60—Other road transportation technologies with climate change mitigation effect
    • Y02T10/70—Energy storage systems for electromobility, e.g. batteries

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Secondary Cells (AREA)
  • Charge And Discharge Circuits For Batteries Or The Like (AREA)

Abstract

The invention provides an SOC estimation method and system of a lithium battery system, wherein the invention comprises the following steps: dividing a standard charge-discharge curve into a plurality of standard curve partitions according to the time point voltage difference between every two time points separated by a preset time interval of each single battery, and acquiring a charge-discharge capacity and a charge-discharge calibration formula of each standard curve partition; calculating a single body SOH estimated value by combining each single body voltage curve with a standard curve partition and a charge-discharge calibration formula corresponding to the standard curve partition; acquiring a system SOH predicted value of the lithium battery system according to the single SOH predicted value of each single battery; integrating the charge and discharge current and the charge and discharge time of the lithium battery system to obtain a charge and discharge capacity estimated value; acquiring a system SOC estimated value according to the system SOH estimated value and the charge-discharge capacity estimated value; and carrying out calibration operation on the system SOC estimated value by combining the corresponding system working condition. The invention has the beneficial effects that: SOH is accurately estimated so as to accurately estimate SOC.

Description

SOC estimation method and system for lithium battery system
Technical Field
The invention relates to the technical field of battery management, in particular to an SOC estimation method and system of a lithium battery system.
Background
The SOC estimation algorithm of the current battery system generally adopts an open-circuit voltage method, an ampere-hour integration method, a neural network method, a battery equivalent circuit model method and a Kalman filtering method; meanwhile, the electricity used by the battery control system of the lithium ion battery system is provided for the battery.
However, the current neural network method, the battery equivalent circuit model method and the Kalman filtering method all need a large amount of data for extracting the model, so that the current open-circuit voltage method and the ampere-hour integration method which are mainly applied to the SOC estimation of the battery system are adopted. Meanwhile, the control system of the current lithium ion battery system adopts electricity as a battery side.
In the prior art, the estimated SOH is mainly estimated by adopting a method that the cycle and the capacity decay are in a linear relation, but the service life decay of the lithium ion battery is not in positive correlation with the cycle, so that the error of the SOH continuously increases along with the increase of the cycle times; because the lithium iron phosphate battery is in a 10% -90% SOC state, the platform is stable, the relation between the SOC and the voltage is not obvious, the open circuit voltage method can cause the SOC state to be rapidly reduced from the 20% SOC to the 5% SOC, and the estimated error is very large in the 10% -90% SOC state; the SOC state is estimated by utilizing an ampere-hour integration method, SOH is cited as a denominator, and the estimated SOH error is large by the current method, so that the estimated SOH error is large; and the system SOC estimation method in the prior art cannot be compatible with batteries of different working conditions and different types. Powering the battery control system by the battery system will also affect the accuracy of the system SOC estimation.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides an SOC estimation method and system of a lithium battery system.
The specific technical scheme is as follows:
an SOC estimation method for a lithium battery system, comprising the steps of:
obtaining a standard charge-discharge curve of a lithium battery system, wherein the lithium battery system comprises a plurality of single batteries;
acquiring a time point voltage difference between every two time points separated by a preset time interval of each single battery, dividing a standard charge-discharge curve into a plurality of standard curve partitions according to the time point voltage difference, and acquiring a charge-discharge capacity and a charge-discharge calibration formula of each standard curve partition;
acquiring a single voltage curve of each single battery under a corresponding system working condition, and calculating a single SOH (state of charge) estimated value by combining each single voltage curve with each standard curve partition and a corresponding charge-discharge calibration formula between standard curve partitions;
acquiring a system SOH predicted value of the lithium battery system according to the single SOH predicted value of each single battery;
acquiring charge and discharge current and charge and discharge time of the lithium battery system in real time, and performing integral processing on the charge and discharge current and the charge and discharge time of the lithium battery system to obtain a charge and discharge capacity estimated value;
Acquiring a system SOC estimated value according to the system SOH estimated value and the charge-discharge capacity estimated value;
and carrying out corresponding calibration operation on the system SOC predicted value by combining the corresponding system working condition.
Preferably, the SOC estimation method of the lithium battery system, wherein the standard charge-discharge curve is a charge-discharge curve of 100% SOC-0% SOC of the single battery or the lithium battery system under the corresponding system working condition.
Preferably, the SOC estimation method of a lithium battery system, wherein, a time point voltage difference between every two time points separated by a preset time interval of each single battery is obtained, and a standard charge-discharge curve is divided into a plurality of standard curve partitions according to the time point voltage difference, and a charge-discharge capacity and a charge-discharge calibration formula between each standard curve partition are obtained, specifically including the following steps:
acquiring a time point voltage difference between every two time points separated by a preset time interval of the single battery;
dividing the monomer voltage where the time point voltage difference on the standard charge-discharge curve is located into a first standard curve partition when the time point voltage difference is smaller than or equal to a first time point voltage difference threshold; or (b)
Dividing the monomer voltage where the time point voltage difference on the standard charge-discharge curve is located into a second standard curve partition when the time point voltage difference is larger than the first time point voltage difference threshold and smaller than the second time point voltage difference threshold; or (b)
Dividing the monomer voltage where the time point voltage difference on the standard charge-discharge curve is located into a third standard curve partition when the time point voltage difference is greater than or equal to a second time point voltage difference threshold;
wherein the first time point voltage difference threshold is less than the second time point voltage difference threshold;
acquiring a charging interval of the first standard curve partition during charging and a discharging interval of the first standard curve partition during discharging, and calculating to obtain the charge and discharge capacity of the first standard curve partition according to the charging interval and the discharging interval of the first standard curve partition; and
acquiring a charging interval of the second standard curve partition during charging and a discharging interval of the second standard curve partition during discharging, and calculating to obtain the charge and discharge capacity of the second standard curve partition according to the charging interval and the discharging interval of the second standard curve partition; and
acquiring a charging interval of the third standard curve partition during charging and a discharging interval of the third standard curve partition during discharging, and calculating to obtain the charge and discharge capacity of the third standard curve partition according to the charging interval and the discharging interval of the third standard curve partition;
Respectively fitting a charge-discharge calibration formula among the first standard curve partition, the third standard curve partition and the second standard curve partition according to a least square method by adopting a linear model;
the charge-discharge calibration formula comprises a charge calibration formula under a charge state and a discharge calibration formula under a discharge state.
Preferably, the SOC estimation method of a lithium battery system, wherein, a single voltage curve of each single battery under a corresponding system working condition is obtained, and each single voltage curve is combined with each standard curve partition and a corresponding charge-discharge calibration formula between standard curve partitions to calculate and obtain a single SOH estimated value, includes the following steps:
acquiring a time point voltage difference between every two time points separated by a preset time interval under the corresponding system working condition of the single battery;
dividing the monomer voltage where the time point voltage difference on the monomer voltage curve is located into a first monomer curve partition when the time point voltage difference is smaller than or equal to a first time point voltage difference threshold; or (b)
Dividing the monomer voltage where the time point voltage difference on the monomer voltage curve is located into a second monomer curve partition when the time point voltage difference is larger than the first time point voltage difference threshold and smaller than the second time point voltage difference threshold; or (b)
Dividing the monomer voltage where the time point voltage difference on the monomer voltage curve is located into a third monomer curve partition when the time point voltage difference is greater than or equal to a second time point voltage difference threshold;
wherein the first time point voltage difference threshold is less than the second time point voltage difference threshold;
acquiring a curve equation between the first monomer curve partitions according to a charge-discharge calibration formula between the first standard curve partitions, and calculating to obtain a first effective time according to the curve equation between the first monomer curve partitions; and
acquiring a curve equation between the second monomer curve partitions of the monomer voltage curve according to a charge-discharge calibration formula between the second standard curve partitions, and calculating to obtain second effective time according to the curve equation between the second monomer curve partitions; and
taking the charge-discharge capacity between the third standard curve partitions as the third partition capacity between the third monomer curve partitions;
obtaining maximum exertion capacity according to the first effective time, the second effective time and the capacity between the third partitions;
and calculating according to the maximum exertion capacity and the rated capacity to obtain a monomer SOH estimated value.
Preferably, the SOC estimation method of a lithium battery system, wherein the system SOH estimated value of the lithium battery system is obtained according to the monomer SOH estimated value, specifically includes the following steps:
Obtaining the voltage of all the single batteries, and obtaining the voltage difference of the single batteries between the single batteries according to the difference between the maximum voltage and the minimum voltage;
judging whether the voltage difference of the single battery is larger than a preset voltage difference threshold value of the single battery or not;
if so, taking the single SOH predicted value of the single battery corresponding to the minimum voltage as a system SOH predicted value;
if not, carrying out average processing on the voltages of all the single batteries to obtain a system SOH estimated value.
Preferably, the SOC estimation method of the lithium battery system, wherein the charge and discharge capacity of the lithium battery system includes a charge capacity of the lithium battery system and a discharge capacity of the lithium battery system;
the charge-discharge capacity predicted value includes a charge-capacity predicted value of the lithium battery system and a discharge-capacity predicted value of the lithium battery system.
Preferably, the SOC estimation method of a lithium battery system, wherein the charge and discharge current and the charge and discharge time of the lithium battery system are obtained in real time, and the charge and discharge current and the charge and discharge time of the lithium battery system are subjected to integral processing to obtain a charge and discharge capacity estimated value, further specifically includes the following steps:
acquiring the charge capacity of the lithium battery system and the discharge capacity of the lithium battery system according to the charge and discharge capacity between standard curve partitions;
Integrating the charging capacity of the lithium battery system according to the following formula to obtain a charging capacity predicted value of the lithium battery system;
C CH ＝∫I c (dt c )；
wherein C is CH A charge capacity predictive value for representing the lithium battery system;
I c for representing a charging current of the lithium battery system;
t c for representing the lithium battery systemCharging time;
and
integrating the discharge current and the discharge time of the lithium battery system according to the following formula to obtain a discharge capacity estimated value of the lithium battery system;
C DCH ＝∫I f (dt f )；
wherein C is DCH A discharge capacity predictive value for representing the lithium battery system;
I f for representing a discharge current of the lithium battery system;
t f for indicating the discharge time of the lithium battery system.
Preferably, the SOC estimation method for a lithium battery system, wherein the system SOC estimation value is obtained according to the system SOH estimation value and the charge-discharge capacity estimation value, includes:
obtaining a system SOC estimated value according to the system SOH estimated value and the charging capacity estimated value, wherein the system SOC estimated value is obtained according to the following formula:
SOC＝SOC initial state ±C CH Xxi x 100%/(SOH x rated capacity);
obtaining a system SOC estimated value according to the system SOH estimated value and the discharge capacity estimated value, wherein the system SOC estimated value is obtained according to the following formula:
SOC＝SOC Initial state ±C DCH Xxi x 100%/(SOH x rated capacity);
wherein in the above formula, SOC Initial state Initial value for representing SOC, SOC Initial state ＝1-C DCH *100％/(C max )；
ζ is used to represent the ratio of full discharge to full charge of the battery cell.
Preferably, the system working conditions comprise a first system working condition, a second system working condition, a third system working condition and a fourth system working condition;
the charge state range of the first system working condition is 100% SOC-xSOC;
the charge state range of the working condition of the second system is ySOC-0%;
the charge state range of the third system working condition is mSOC-nSOC;
the charge state range of the fourth system working condition is 100% SOC-0% SOC;
wherein m is not equal to n,0 < x, y, m, n < 1; and/or
And carrying out corresponding calibration operation on the system SOC estimated value by combining corresponding system working conditions, wherein the method specifically comprises the following steps of:
when the system is in the first system working condition, the charged system SOC estimated value is calibrated to 100% SOC; and/or
When the system is in the second system working condition, the discharged system SOC estimated value is calibrated to 0% SOC; and/or
When the third system working condition is met, when the voltage charge protection of the single battery occurs, the system SOC estimated value is calibrated to 100% SOC, or when the voltage discharge protection of the single battery occurs, the system SOC estimated value is calibrated to 0% SOC; and/or
And when the system is in the fourth system working condition, the charged system SOC estimated value is calibrated to 100% SOC, or the discharged system SOC estimated value is calibrated to 0% SOC.
An SOC estimation system for a lithium battery system, wherein the SOC estimation method for any one of the above lithium battery systems is adopted.
The technical scheme has the following advantages or beneficial effects: calculating a single SOH (state of charge) predicted value of each single battery by combining a single voltage curve with a charge-discharge calibration formula corresponding to each standard curve partition and each standard curve partition, acquiring a system SOH predicted value according to all the single SOH predicted values, acquiring a system SOC predicted value according to the system SOH predicted value, and performing calibration operation on the system SOC predicted value to accurately estimate SOH and further accurately estimate SOC;
and calculating a single SOH estimated value of each single battery by combining the single voltage curve with each standard curve partition and a corresponding charge-discharge calibration formula between the standard curve partitions, so as to realize the estimation of the SOH of different working conditions and different batteries.
Drawings
Embodiments of the present invention will now be described more fully with reference to the accompanying drawings. The drawings, however, are for illustration and description only and are not intended as a definition of the limits of the invention.
FIG. 1 is a flow chart of an embodiment of a method for estimating SOC of a lithium battery system according to the present invention;
FIG. 2 is a discharge graph of an embodiment of a method for estimating SOC of a lithium battery system according to the present invention;
fig. 3 is a charge graph of an embodiment of an SOC estimation method of a lithium battery system of the present invention.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
It should be noted that, without conflict, the embodiments of the present invention and features of the embodiments may be combined with each other.
The invention is further described below with reference to the drawings and specific examples, which are not intended to be limiting.
The invention includes a method for estimating SOC of a lithium battery system, as shown in FIG. 1, comprising the following steps:
step S1, a standard charge-discharge curve of a lithium battery system is obtained, wherein the lithium battery system comprises a plurality of single batteries;
Step S2, obtaining a time point voltage difference of every two time points separated by a preset time interval of each single battery, dividing a standard charge-discharge curve into a plurality of standard curve partitions according to the time point voltage difference, and obtaining a charge-discharge capacity and a charge-discharge calibration formula of each standard curve partition;
at this time, the charge-discharge capacity and a charge-discharge calibration formula between each standard curve partition of each single battery are obtained;
step S3, obtaining a single voltage curve of each single battery under the working condition of the system, and calculating a single SOH estimated value by combining each single voltage curve with each standard curve partition and a corresponding charge-discharge calibration formula between standard curve partitions;
at this time, a single SOH estimated value of each single battery is obtained;
s4, acquiring a system SOH predicted value of the lithium battery system according to the single SOH predicted value of each single battery; and
acquiring charge and discharge current and charge and discharge time of the lithium battery system in real time, and performing integral processing on the charge and discharge current and the charge and discharge time of the lithium battery system to obtain a charge and discharge capacity estimated value;
s5, acquiring a system SOC estimated value according to the system SOH estimated value and the charge-discharge capacity estimated value;
And S6, carrying out corresponding calibration operation on the system SOC estimated value by combining the corresponding system working condition.
In the above embodiment, the single body SOH predicted value of each single battery is calculated by combining the single body voltage curve with the charge-discharge calibration formula corresponding to each standard curve partition and each standard curve partition, the system SOH predicted value is obtained according to all the single body SOH predicted values, the system SOC predicted value is obtained according to the system SOH predicted value, and the system SOC predicted value is calibrated, so that accurate estimation of SOH and thus accurate estimation of SOC can be achieved.
In the above embodiment, the SOC of each single battery is accurately estimated for different batteries and different working conditions by obtaining the single voltage curve of each single battery under the working condition of the system and calculating the single SOH estimated value of each single battery by combining the single voltage curve with each standard curve partition and the corresponding charge-discharge calibration formula between standard curve partitions.
In the above embodiment, the influence on the accuracy of SOC estimation of the battery system is avoided by the unit cells.
Further, in the above embodiment, the standard charge-discharge curve is a charge-discharge curve of 100% soc-0% soc of the unit cell or the lithium battery system under the corresponding system working conditions.
As a preferred embodiment, according to the type of lithium ion battery cell of the lithium battery system, a charge-discharge curve of 100% soc-0% soc of the unit battery under the corresponding system working condition may be used as a standard charge-discharge curve.
As a preferred embodiment, a charge-discharge curve of 100% soc-0% soc of the lithium battery system under the system condition may be directly used as the standard charge-discharge curve.
Further, in the above embodiment, as shown in fig. 2-3, the step S2 specifically includes the following steps:
step S21, obtaining a time point voltage difference between every two time points separated by a preset time interval under the working condition of a standard system of the single battery;
step S22, dividing the monomer voltage where the time point voltage difference on the standard charge-discharge curve is located into a first standard curve partition when the time point voltage difference is smaller than or equal to a first time point voltage difference threshold; or (b)
Dividing the monomer voltage where the time point voltage difference on the standard charge-discharge curve is located into a second standard curve partition when the time point voltage difference is larger than the first time point voltage difference threshold and smaller than the second time point voltage difference threshold; or (b)
Dividing the monomer voltage where the time point voltage difference on the standard charge-discharge curve is located into a third standard curve partition when the time point voltage difference is greater than or equal to a second time point voltage difference threshold;
Wherein the first time point voltage difference threshold is less than the second time point voltage difference threshold;
step S23, a charging interval of the first standard curve partition during charging and a discharging interval of the first standard curve partition during discharging are obtained, and the charging and discharging capacity of the first standard curve partition is obtained through calculation according to the charging interval and the discharging interval of the first standard curve partition; and
acquiring a charging interval of the second standard curve partition during charging and a discharging interval of the second standard curve partition during discharging, and calculating to obtain the charge and discharge capacity of the second standard curve partition according to the charging interval and the discharging interval of the second standard curve partition; and
acquiring a charging interval of the third standard curve partition during charging and a discharging interval of the third standard curve partition during discharging, and calculating to obtain the charge and discharge capacity of the third standard curve partition according to the charging interval and the discharging interval of the third standard curve partition;
step S24, adopting a linear model, and respectively combining charge and discharge capacities among the first standard curve partition, the second standard curve partition and the third standard curve partition according to a least square method to fit charge and discharge calibration formulas corresponding to the first standard curve partition, the second standard curve partition and the third standard curve partition;
The charge-discharge calibration formula comprises a charge calibration formula under a charge state and a discharge calibration formula under a discharge state.
As a preferred embodiment, the charge state range of the standard system working condition is 100% SOC-0% SOC;
firstly, obtaining the time point voltage difference of each two time points separated by a preset time interval under the working condition of a standard system,
the following formula is shown:
ΔV＝V t+Δt -V t ；(1)
wherein, in the above formula (1), Δv is used to represent the time-point voltage difference;
t is used to represent the time point;
Δt is used to represent a preset time interval;
wherein t is s,0 < Deltat < 3600, and the voltage of the single battery is mV;
then, dividing the monomer voltage where the time point voltage difference is located into corresponding standard curve partitions according to the relation between the time point voltage difference and the first time point voltage difference threshold value and/or the second time point voltage difference threshold value, wherein the standard curve partitions comprise a first standard curve partition, a second standard curve partition and a third standard curve partition;
dividing the monomer voltage where the time point voltage difference is located into a first standard curve partition area when the delta V is less than or equal to alpha;
dividing the monomer voltage where the voltage difference at the time point is positioned into a second standard curve partition area when alpha < |DeltaV| < beta;
Dividing the monomer voltage where the time point voltage difference is located into a third standard curve partition area when |DeltaV| is not less than beta;
wherein α is used to represent a first time point voltage difference threshold, and β is used to represent a second time point voltage difference threshold;
wherein, 0 < alpha, beta < 3600, alpha < beta;
then, the charging interval of the first standard curve partition during charging is obtained, and the charging interval of the first curve partition can be marked as A CH The discharge interval of the first standard curve partition during discharge is obtained and can be marked as A DCH ；
Calculating according to the charging interval and the discharging interval between the first standard curve partitions to obtain the charging and discharging capacity between the first standard curve partitions, and marking the charging and discharging capacity between the first standard curve partitions as C ACH &C ADCH I.e. the charge capacity between the partitions of the first standard curve is C ACH The discharge capacity between the first standard curve partitions is C ADCH The method comprises the steps of carrying out a first treatment on the surface of the And
the charging interval of the second standard curve partition during charging is obtained, and the charging interval of the second curve partition can be marked as B CH The discharge interval of the second standard curve partition during discharge is obtained and can be marked as B DCH ；
Calculating according to the charging interval and the discharging interval between the second standard curve partitions to obtain the charging and discharging capacity between the second standard curve partitions, and marking the charging and discharging capacity between the second standard curve partitions as C BCH &C BDCH I.e. the charge capacity between the second standard curve partitions is C BCH The discharge capacity between the second standard curve partitions is C BDCH The method comprises the steps of carrying out a first treatment on the surface of the And
the third standard curve can be divided into charging intervals when the third standard curve is divided into charging intervalsThe charging interval of the zone is marked as C CH The discharge interval of the third curve partition during discharge is obtained and can be marked as C DCH ；
Calculating according to the charging interval and the discharging interval of the third standard curve interval to obtain the charging and discharging capacity of the third standard curve interval, and marking the charging and discharging capacity of the third standard curve interval as C CCH &C CDCH I.e. the charge capacity between the third standard curve partitions is C CCH The discharge capacity between the third standard curve partitions is C CDCH ；
Then, the voltage boundary points between the first standard curve partition and the second standard curve partition during charging are obtained, and the voltage boundary points are marked as V αCH ；
Acquiring voltage boundary points between the second standard curve partition and the third standard curve partition during charging, and marking the voltage boundary points as V βCH The method comprises the steps of carrying out a first treatment on the surface of the And
acquiring voltage boundary points between the first standard curve partition and the second standard curve partition during discharge, and marking the voltage boundary points as V αDCH ；
Acquiring voltage boundary points between the second standard curve partition and the third standard curve partition during discharge, and marking the voltage boundary points as V βDCH ；
The junction point is only a curve intersection point, is used for calculating the length of a curve interval, and has no special effect;
then, a linear model is adopted during charging, and a charging calibration formula between the first standard curve partitions is fitted according to a least square method, wherein the charging calibration formula is shown in the following formula:
y 1 ′＝k A ′X+b A ′；(2)
wherein in the above formula (2), y 1 ' ordinate, voltage, used to represent the charge calibration formula between the first standard curve partitions;
k A ' the slope of the line used to represent the charge calibration formula between the first standard curve partitions;
x is used for representing the abscissa, namely time, of a charging calibration formula between the partitions of the first standard curve;
b A ' intercept of a straight line and an ordinate representing a charge calibration formula between the first standard curve partitions;
and during charging, a linear model is adopted, and a charging calibration formula between the second standard curve partitions is fitted according to a least square method, wherein the charging calibration formula is shown in the following formula:
y 2 ′＝k B ′X+b B ′；(3)
wherein in the above formula (3), y 2 ' ordinate, voltage, used to represent the charge calibration formula between the second standard curve partitions;
k B ' the slope of the line used to represent the charge calibration formula between the second standard curve partitions;
x is used for representing the abscissa, namely time, of a charging calibration formula between the second standard curve partitions;
b B ' intercept of straight line and ordinate of charge calibration formula used for representing second standard curve partition;
and
During discharging, a straight line model is adopted, and a discharging calibration formula between the first standard curve partitions is fitted according to a least square method, wherein the discharging calibration formula is shown as the following formula:
y 1 ″＝k A ″X+b A ″；(4)
wherein in the above formula (4), y 1 "ordinate used to represent the discharge calibration formula between the first standard curve partitions, i.e., voltage;
k A "the slope of the straight line used to represent the discharge calibration formula between the first standard curve partitions;
x is used for representing the abscissa, namely time, of a discharge calibration formula between the first standard curve partitions;
b A "intercept of straight line and ordinate for discharge calibration formula used for representing first standard curve partition;
and adopting a linear model during discharging, and respectively fitting a discharging calibration formula between the second standard curve partitions according to a least square method, wherein the discharging calibration formula is shown as the following formula:
y 2 ″＝k B ″X+b B ″；(5)
wherein in the above formula (5), y 2 "ordinate used to represent the discharge calibration formula between the second standard curve partitions, i.e., voltage;
k B "the slope of the straight line used to represent the discharge calibration formula between the second standard curve partitions;
x is used for representing the abscissa, namely time, of a discharge calibration formula between the second standard curve partitions;
b B "intercept of straight line and ordinate of discharge calibration formula used for representing second standard curve partition.
As shown in fig. 2, taking the 3.2v105ah lithium iron phosphate square battery as an example, the discharge rate of the 3.2v105ah lithium iron phosphate square battery at the 0.5C rate is changed with time, as shown in fig. 2, which is a discharge curve graph of the 3.2v105ah lithium iron phosphate square battery at the 0.5C rate discharge voltage.
Further, in the above embodiment, as shown in fig. 3, the step S3 includes the steps of:
step S31, obtaining a time point voltage difference between every two time points separated by a preset time interval under the corresponding system working condition of the single battery;
dividing the monomer voltage where the time point voltage difference on the monomer voltage curve is located into a first monomer curve partition when the time point voltage difference is smaller than or equal to a first time point voltage difference threshold; or (b)
Dividing the monomer voltage where the time point voltage difference on the monomer voltage curve is located into a second monomer curve partition when the time point voltage difference is larger than the first time point voltage difference threshold and smaller than the second time point voltage difference threshold; or (b)
Dividing the monomer voltage where the time point voltage difference on the monomer voltage curve is located into a third monomer curve partition when the time point voltage difference is greater than or equal to a second time point voltage difference threshold;
wherein the first time point voltage difference threshold is less than the second time point voltage difference threshold;
step S32, obtaining a curve equation between the first monomer curve partitions according to a charge-discharge calibration formula between the first standard curve partitions, and calculating to obtain a first effective time according to the curve equation between the first monomer curve partitions; and
acquiring a curve equation between the second monomer curve partitions of the monomer voltage curve according to a charge-discharge calibration formula between the second standard curve partitions, and calculating to obtain second effective time according to the curve equation between the second monomer curve partitions; and
taking the charge-discharge capacity between the third standard curve partitions as the third partition capacity between the third monomer curve partitions;
in this embodiment, the capacity between the third monomer curve segments is approximately considered to be unchanged in the cyclic estimation, so that no calibration can be performed on the third monomer curve segments, and the maximum capacity between the third monomer curve segments can be obtained according to the capacity estimation obtained between the initial third standard curve segments.
Step S33, obtaining the maximum exertion capacity according to the first effective time, the second effective time and the capacity between the third partitions;
and step S34, calculating to obtain a monomer SOH estimated value according to the maximum exertion capacity and the rated capacity.
As a preferred embodiment, a first monomer curve partition, a second monomer curve partition and a third monomer curve partition of the single battery under the corresponding system working conditions can be obtained;
acquiring a curve equation between the first monomer curve partitions according to a charge-discharge calibration formula between the first standard curve partitions, wherein the curve equation is shown in the following formula:
y 1 ＝k 1 X 1 +b 1 ；(6)
wherein in the above formula (6), y 1 The ordinate of the curve equation representing the first monomer curve segment, i.e. the voltage;
k 1 a slope of a line representing a curve equation between the first monomer curve segments;
X 1 the abscissa, i.e. time, of the curve equation representing the first monomer curve partition;
b 1 an intercept of a straight line and an ordinate representing a curve equation between the first monomer curve partitions;
and
Acquiring a curve equation between the second monomer curve partitions of the monomer voltage curve according to a charge-discharge calibration formula between the second standard curve partitions, wherein the curve equation is shown in the following formula:
y 2 ＝k 2 X 2 +b 2 ；(7)
Wherein in the above formula (7), y 2 An ordinate representing a curve equation representing the second monomer curve section, i.e., voltage;
k 2 a slope of a straight line representing a curve equation between the second monomer curve segments;
X 2 the abscissa, i.e. time, of the curve equation representing the second monomer curve partition;
b 2 an intercept of a straight line and an ordinate representing a curve equation between the second monomer curve partitions;
then, when the system working condition is charging, judging the slope of the curve equation between the first monomer curve partitions and the slope of the charging calibration formula between the first standard curve partitions, when k 1 ＞k A ' then set k 1 ≈k A ′，
Judging the slope of the curve equation between the second monomer curve partitions and the slope of the charging calibration formula between the second standard curve partitions, when k 2 ＞k B ' then set k 2 ≈k B ′；
And set y 1 ＝V αDCH And y 1 ＝y 2 Set y2=v βDCH And y 1 ＝y 2 ；
Wherein V is αDCH Voltage crossing between first and second standard curve partitions for representing chargingA boundary point;
V βDCH voltage boundary points between the second standard curve partition and the third standard curve partition used for representing charging;
next, a first effective time (X) is obtained according to the above formulas (6) - (7) 1 ) And a second effective time (X 2 )；
Then, obtaining the maximum exertion capacity according to the first effective time, the second effective time and the capacity between the third partitions;
specifically, as preferable: calculating to obtain a first inter-partition capacity and a second inter-partition capacity, and then adding the first inter-partition capacity, the second inter-partition capacity and the third inter-partition capacity to obtain a maximum exertion capacity;
for example, when the lithium battery system is in constant current mode;
first, the capacity between the first partition is obtained as shown in the following formula:
C 1 ＝I×X 1 ；(8)
in the above formula (8), C 1 For representing a first inter-partition capacity;
i is used for representing the current under the constant current working condition;
X 1 for representing a first validity time;
calculating to obtain second partition capacity according to the second effective time;
second, the capacity between the second partitions is obtained as shown in the following formula:
C 2 ＝I×X 2 ；(9)
in the above formula (9), C 2 For representing a second inter-partition capacity;
i is used for representing the current under the constant current working condition;
X 2 for representing a second effective time;
thirdly, adding the first partition capacity, the second partition capacity and the third partition capacity to obtain a maximum exertion capacity, wherein the maximum exertion capacity is shown in the following formula:
C max ＝C 1 +C 2 +C CDCH ；(10)
in the above formula (10), C max For indicating maximum capacity.
For example, when the lithium battery system is in a constant power condition;
first, the capacity between the first partition is obtained as shown in the following formula:
C 1 ′＝∫P/y(dX 1 )；(11)；
in the above formula (11), C 1 ' is used to represent the first inter-partition capacity;
p is used for representing the power under the constant power working condition;
y is used for representing the working voltage of the battery cell or the system under the constant power working condition;
X 1 for representing a first validity time;
second, the capacity between the second partitions is obtained as shown in the following formula:
C 2 ′＝∫P/y(dX 2 )；(12)
in the above formula (12), C 2 ' is used to represent the second inter-partition capacity;
p is used for representing the power under the constant power working condition;
y is used for representing the working voltage of the battery cell or the system under the constant power working condition;
X 2 for representing the second validity time.
Thirdly, adding the first partition capacity, the second partition capacity and the third partition capacity to obtain a maximum exertion capacity, wherein the maximum exertion capacity is shown in the following formula:
C max ＝C 1 ′+C 2 ′+C CDCH ；(13)
wherein in the above formula (13), C max For representing maximum exertion capacity;
in the above two embodiments, the first effective time and the second effective time may be calculated by obtaining the endpoints of the first effective time and the second effective time;
X 1 ＝t2-t1；(14)
X 2 ＝t3-t2；(15)
in the above formulas (14) - (15),
the interval of the obtained first effective time is { t1, t2} and the interval of the second effective interval is { t2, t3};
t1 is used for representing the abscissa starting point of the interval of the first effective time of y1 in the SOH estimation algorithm;
t2 is used for representing an abscissa end point of a section of a first effective time of y1 in the SOH estimation algorithm or an abscissa start point of a section of a second effective section of y2 in the SOH estimation algorithm;
t3 is used for representing the abscissa end point of the interval of the second effective interval of y2 in the SOH estimation algorithm.
And finally, calculating according to the maximum exertion capacity and the rated capacity to obtain a monomer SOH estimated value, wherein the estimated value is shown in the following formula:
SOH＝C max /C e *100％；(16)
wherein, in the above formula (16), C max For representing maximum exertion capacity;
C e for representing the rated capacity;
according to the embodiment, the monomer SOH predicted value when the system working condition is charging can be obtained;
similarly, when the working condition of the system is the voltage boundary point between the first standard curve partition and the second standard curve partition and the voltage boundary point between the second standard curve partition and the third standard curve partition during discharging, the voltage boundary points between the first standard curve partition and the second standard curve partition are obtained;
and calculating to obtain a monomer SOH estimated value when the system working condition is discharge.
Further, in the above embodiment, the system SOH predicted value of the lithium battery system is obtained according to the monomer SOH predicted value in step S4, which specifically includes the following steps:
Step S41, obtaining the voltages of all the single batteries, and obtaining the single battery voltage difference between the single batteries according to the difference between the maximum voltage and the minimum voltage;
step S42, judging whether the voltage difference of the single battery is larger than a preset voltage difference threshold value of the single battery;
if so, taking the single SOH predicted value of the single battery corresponding to the minimum voltage as a system SOH predicted value;
if not, carrying out average processing on the voltages of all the single batteries to obtain a system SOH estimated value.
In the above embodiment, when the voltage difference of the single battery is smaller than or equal to the preset voltage difference threshold of the single battery, it is indicated that the consistency of all the single batteries in the lithium battery system at this time is better, then only an average voltage difference curve is needed to be made for the total voltage of the system at this time, that is, the average voltage difference curve is processed for the voltages of all the single batteries, and then the average voltage difference curve is estimated according to the charge-discharge capacity and the charge-discharge calibration formula between each standard curve partition of the standard charge-discharge curve to obtain the system SOH predicted value.
Further, in the above-described embodiments, the charge-discharge capacity of the lithium battery system includes the charge capacity of the lithium battery system and the discharge capacity of the lithium battery system;
the charge-discharge capacity predicted value comprises a charge capacity predicted value of the lithium battery system and a discharge capacity predicted value of the lithium battery system;
In step S4, the charging current and the charging time of the lithium battery system are obtained in real time, and the charging current and the charging time of the lithium battery system are integrated to obtain a charge capacity predicted value, and the method specifically includes the following steps:
step S43, acquiring the charging current and the charging time of the lithium battery system in real time;
step S44, integrating the charging current and the charging time of the lithium battery system according to the following formula to obtain a charging capacity estimated value of the lithium battery system;
C CH ＝∫I c (dt c )；(17)
wherein in the above formula (17), C CH A charge capacity predictive value for representing a lithium battery system;
I c for representing the charging current;
t c for indicating the charging time;
in step S4, the discharge current and the discharge time of the lithium battery system are obtained in real time, and the discharge current and the discharge time of the lithium battery system are integrated to obtain a discharge capacity estimated value, and the method specifically includes the following steps:
step S45, obtaining the discharge current and the discharge time of the lithium battery system in real time;
step S46, carrying out integral processing on the discharge current and the discharge time of the lithium battery system according to the following formula to obtain a discharge capacity estimated value of the lithium battery system;
C DCH ＝∫I f (dt f )；(18)
Wherein, in the above formula (18), C DCH A discharge capacity predictive value for representing a lithium battery system;
I f for representing the discharge current;
t f for indicating the discharge time.
In the above embodiment, the charge and discharge capacity of the lithium battery system is estimated by the ampere-hour integration method, so as to increase the accuracy of the estimation.
Further, in the above embodiment, the system conditions include a first system condition, a second system condition, a third system condition, and a fourth system condition;
the charge state range of the first system working condition is 100% SOC-xSOC;
the charge state range of the working condition of the second system is ySOC-0%;
the charge state range of the third system working condition is mSOC-nSOC;
the charge state range of the fourth system working condition is 100% SOC-0% SOC;
wherein m is not equal to n,0 < x, y, m, n < 1;
m is used to represent a constant of 0-1;
n is used to represent a constant of 0-1;
x is used to represent a constant of 0-1;
y is used to represent a constant of 0-1.
Wherein, the factor for determining the charge state (SOC state) as 100% SOC is that the voltage charge protection of the single battery occurs;
the factor determining the state of charge (SOC) to be 0% SOC is that the battery cells are voltage discharge protected.
In the above embodiment, the charge-discharge capacity predicted value includes a charge-capacity predicted value and a discharge-capacity predicted value;
The system SOC estimated value is obtained according to the system SOH estimated value and the charge-discharge capacity estimated value, and the method comprises the following steps:
obtaining a system SOC estimated value according to the system SOH estimated value and the charging capacity estimated value, wherein the system SOC estimated value is obtained according to the following formula:
SOC＝SOC initial state ±C CH Xxi x 100%/(SOH x rated capacity); (19)
Acquiring a system SOC estimated value under a charging working condition through the formula (19);
obtaining a system SOC estimated value according to the system SOH estimated value and the discharge capacity estimated value, wherein the system SOC estimated value is obtained according to the following formula:
SOC＝SOC initial state ±C DCH Xxi x 100%/(SOH x rated capacity); (20)
Acquiring a system SOC estimated value under a discharging working condition through the formula (20);
wherein in the above formulas (19) and (20), SOC Initial state Initial value for representing SOC, SOC Initial state ＝1-C DCH *100％/(C max )；
ζ is used to represent the ratio of full discharge to full charge of the battery cell.
Further, in the above embodiment, the step S6 specifically includes the steps of:
when the system is in the first system working condition, the charged system SOC estimated value is calibrated to 100% SOC; and/or
When the system is in the second system working condition, the discharged system SOC estimated value is calibrated to 0% SOC; and/or
When the third system working condition is met, when the voltage charge protection of the single battery occurs, the system SOC estimated value is calibrated to 100% SOC, or when the voltage discharge protection of the single battery occurs, the system SOC estimated value is calibrated to 0% SOC; and/or
And when the system is in the fourth system working condition, the charged system SOC estimated value is calibrated to 100% SOC, or the discharged system SOC estimated value is calibrated to 0% SOC.
The invention also provides an SOC estimation system of the lithium battery system, wherein the SOC estimation method of any lithium battery system is adopted.
Specifically, as a preferred embodiment, the SOC estimation system employed in the present embodiment may be compared with the SOC estimation system in the related art as follows:
first, acquiring an SOC estimation system of a lithium battery system adopting the SOC estimation method of any one of the lithium battery systems, and recording the SOC estimation system as BMS0;
acquiring a BMS battery control system with SOC and SOH state evaluation in a market A in the prior art, and recording the BMS battery control system as BMS1, wherein the BMS1 adopts a method for estimating by adopting a method of linear relation between circulation and capacity fading in the background art;
acquiring a BMS battery control system with SOC and SOH state evaluation in a market B in the prior art, and recording the BMS battery control system as BMS2, wherein the BMS2 adopts a method for estimating by adopting a neural network in the background art;
secondly, connecting BMS0 with a first 256V250Ah lithium iron phosphate system of 2P 80S;
Connecting BMS1 with a second 256V250Ah lithium iron phosphate system of 2P 80S;
connecting BMS2 with a third 256V250Ah lithium iron phosphate system of 2P 80S;
third, setting comparison parameters, such as:
control environment: room temperature 25+ -2deg.C;
working power: 16kW constant power charging and discharging;
SOC working interval: 20% -80% psoc cycle; 248V-276V;
monomer voltage protection: discharge 2.5V and charge 3.7V.
Then, when the cycle is n (wherein n is the cycle number in the table), respectively reading SOC estimated values of BMS0/1/2 on the lithium iron phosphate system at the voltage of 250V;
carrying out working condition charging and discharging on the lithium iron phosphate system for 2 times by using charging and discharging equipment to obtain a charging and discharging curve of the lithium iron phosphate system, and solving an accurate SOC value (an average value of SOC values when charging and discharging are carried out for 2 times) of the lithium iron phosphate system;
the SOC estimate value is compared with the SOC accuracy value to obtain an SOC error value, as shown in table 1 below:
TABLE 1
In table 1 above, it is possible to obtain SOC errors obtained by BMS0 in each cycle that are smaller than those obtained by BMS1 and BMS2, so that the present invention can obtain an estimated value of SOC more accurately than the prior art.
The specific implementation manner of the SOC estimation system of the lithium battery system of the present invention is substantially the same as the above embodiments of the SOC estimation method of the lithium battery system, and will not be described herein.
The foregoing is merely illustrative of the preferred embodiments of the present invention and is not intended to limit the embodiments and scope of the present invention, and it should be appreciated by those skilled in the art that equivalent substitutions and obvious variations may be made using the description and illustrations of the present invention, and are intended to be included in the scope of the present invention.

Claims (10)

1. The SOC estimation method of the lithium battery system is characterized by comprising the following steps of:
obtaining a standard charge-discharge curve of a lithium battery system, wherein the lithium battery system comprises a plurality of single batteries;
acquiring a time point voltage difference between every two time points separated by a preset time interval of each single battery, dividing the standard charge-discharge curve into a plurality of standard curve partitions according to the time point voltage difference, and acquiring a charge-discharge capacity and a charge-discharge calibration formula of each standard curve partition;
acquiring a single voltage curve of each single battery under a corresponding system working condition, and calculating a single SOH (state of charge) estimated value by combining each single voltage curve with each standard curve partition and the corresponding charge-discharge calibration formula between the standard curve partitions;
Acquiring a system SOH predicted value of the lithium battery system according to the single SOH predicted value of each single battery;
acquiring charge and discharge current and charge and discharge time of the lithium battery system in real time, and performing integral processing on the charge and discharge current and the charge and discharge time of the lithium battery system to obtain a charge and discharge capacity estimated value;
acquiring a system SOC estimated value according to the system SOH estimated value and the charge-discharge capacity estimated value;
and carrying out corresponding calibration operation on the system SOC estimated value by combining the corresponding system working conditions.
2. The SOC estimation method of claim 1, wherein the standard charge-discharge curve is a charge-discharge curve of the single battery or the lithium battery system in a charge state range of 100% SOC-0% SOC under the system operating condition.
3. The SOC estimation method of claim 1, wherein the obtaining a time point voltage difference between every two time points separated by a preset time interval for each of the unit cells, dividing the standard charge-discharge curve into a plurality of standard curve partitions according to the time point voltage difference, and obtaining a charge-discharge capacity and a charge-discharge calibration formula between each of the standard curve partitions, comprises the steps of:
Acquiring a time point voltage difference between every two time points which are separated by a preset time interval under the standard system working condition of the single battery;
dividing the monomer voltage of the time point voltage difference on the standard charge-discharge curve into a first standard curve partition when the time point voltage difference is smaller than or equal to a first time point voltage difference threshold; or (b)
Dividing the monomer voltage of the time point voltage difference on the standard charge-discharge curve into a second standard curve partition section when the time point voltage difference is larger than a first time point voltage difference threshold and smaller than a second time point voltage difference threshold; or (b)
Dividing the monomer voltage of the time point voltage difference on the standard charge-discharge curve into a third standard curve partition when the time point voltage difference is greater than or equal to a second time point voltage difference threshold;
wherein the first time point voltage difference threshold is less than the second time point voltage difference threshold;
acquiring a charging interval of the first standard curve partition during charging and a discharging interval of the first standard curve partition during discharging, and calculating to obtain the charge and discharge capacity of the first standard curve partition according to the charging interval and the discharging interval of the first standard curve partition; and
Acquiring a charging interval of the second standard curve partition during charging and a discharging interval of the second standard curve partition during discharging, and calculating to obtain the charge and discharge capacity of the second standard curve partition according to the charging interval and the discharging interval of the second standard curve partition; and
acquiring a charging interval of the third standard curve partition during charging and a discharging interval of the third standard curve partition during discharging, and calculating to obtain the charge and discharge capacity of the third standard curve partition according to the charging interval and the discharging interval of the third standard curve partition;
fitting the charge-discharge calibration formulas corresponding to the first standard curve partition, the second standard curve partition and the third standard curve partition by adopting a linear model and respectively combining the charge-discharge capacities of the first standard curve partition, the second standard curve partition and the third standard curve partition according to a least square method;
the charge-discharge calibration formula comprises a charge calibration formula under a charge state and a discharge calibration formula under a discharge state.
4. The SOC estimation method of claim 3, wherein the step of obtaining a single voltage curve of each single battery under a corresponding system condition, and calculating a single SOH estimated value by combining each single voltage curve with each standard curve partition and the corresponding charge-discharge calibration formula between the standard curve partitions, includes the following steps:
acquiring a time point voltage difference between every two time points which are separated by a preset time interval under the working condition of the system of the single battery;
dividing the monomer voltage of the time point voltage difference on the monomer voltage curve into a first monomer curve partition when the time point voltage difference is smaller than or equal to a first time point voltage difference threshold; or (b)
Dividing the monomer voltage of the time point voltage difference on the monomer voltage curve into a second monomer curve partition when the time point voltage difference is larger than a first time point voltage difference threshold and smaller than a second time point voltage difference threshold; or (b)
Dividing the cell voltage of the cell voltage curve in which the time point voltage difference is located into a third cell curve partition when the time point voltage difference is greater than or equal to a second time point voltage difference threshold;
Wherein the first time point voltage difference threshold is less than the second time point voltage difference threshold;
acquiring a curve equation between the first monomer curve partitions according to the charge-discharge calibration formula between the first standard curve partitions, and calculating to acquire a first effective time according to the curve equation between the first monomer curve partitions; and
acquiring a curve equation between the second monomer curve partitions of the monomer voltage curve according to the charge-discharge calibration formula between the second standard curve partitions, and calculating to acquire second effective time according to the curve equation between the second monomer curve partitions; and
taking the charge-discharge capacity between the third standard curve partitions as a third partition capacity between the third monomer curve partitions;
obtaining maximum exertion capacity according to the first effective time, the second effective time and the third inter-partition capacity;
and calculating according to the maximum exertion capacity and the rated capacity to obtain the monomer SOH predicted value.
5. The SOC estimation method of claim 1, wherein the acquiring the system SOH estimated value of the lithium battery system according to the single SOH estimated value specifically includes the following steps:
Obtaining the voltages of all the single batteries, and obtaining the voltage difference of the single batteries between the single batteries according to the difference between the maximum voltage and the minimum voltage;
judging whether the voltage difference of the single battery is larger than a preset single battery voltage difference threshold value or not;
if so, taking the single SOH predicted value of the single battery corresponding to the minimum voltage as the system SOH predicted value;
if not, carrying out average processing on the voltages of all the single batteries to obtain the system SOH estimated value.
6. The SOC estimation method of the lithium battery system of claim 5, wherein the charge-discharge capacity of the lithium battery system includes a charge capacity of the lithium battery system and a discharge capacity of the lithium battery system;
the charge-discharge capacity predicted value includes a charge capacity predicted value of the lithium battery system and a discharge capacity predicted value of the lithium battery system.
7. The SOC estimation method of claim 6, wherein the acquiring charge-discharge current and charge-discharge time of the lithium battery system in real time and integrating the charge-discharge current and charge-discharge time of the lithium battery system to obtain the charge-discharge capacity estimated value further comprises the steps of:
Acquiring charging current and charging time of the lithium battery system in real time, and acquiring discharging current and discharging time of the lithium battery system;
integrating the charging current and the charging time of the lithium battery system according to the following formula to obtain a charging capacity estimated value of the lithium battery system;
C CH ＝∫I c (dt c )；
wherein C is CH A charge capacity predictive value for representing the lithium battery system;
I c for representing a charging current of the lithium battery system;
t c for representing a charge time of the lithium battery system;
and
integrating the discharge current and the discharge time of the lithium battery system according to the following formula to obtain a discharge capacity estimated value of the lithium battery system;
C DCH ＝∫I f (dt f )；
wherein C is DCH A discharge capacity predictive value for representing the lithium battery system;
I f for representing a discharge current of the lithium battery system;
t f for indicating the discharge time of the lithium battery system.
8. The method for estimating the SOC of a lithium battery system according to claim 7, wherein,
the system SOC estimated value is obtained according to the system SOH estimated value and the charge-discharge capacity estimated value, and the method comprises the following steps:
obtaining a system SOC estimated value according to the system SOH estimated value and the charging capacity estimated value, wherein the system SOC estimated value is obtained according to the following formula:
SOC＝SOC Initial state ±C CH Xxi x 100%/(SOH x rated capacity);
obtaining a system SOC estimated value according to the system SOH estimated value and the discharge capacity estimated value, wherein the system SOC estimated value is obtained according to the following formula:
SOC＝SOC initial state ±C DCH Xxi x 100%/(SOH x rated capacity);
wherein in the above formula, SOC Initial state Initial value for representing SOC, SOC Initial state ＝1-C DCH *100％/(C max )；
And xi is used to represent the ratio of full discharge to full charge of the single cell.
9. The SOC estimation method of a lithium battery system of claim 1, wherein the system operating conditions include a first system operating condition, a second system operating condition, a third system operating condition, and a fourth system operating condition;
the charge state range of the first system working condition is 100% SOC-xSOC;
the charge state range of the second system working condition is ySOC-0%;
the charge state range of the third system working condition is mSOC-nSOC;
the charge state range of the fourth system working condition is 100% SOC-0% SOC;
wherein m is not equal to n,0 < x, y, m, n < 1; and/or
The corresponding calibration operation is carried out on the system SOC estimated value by combining the corresponding system working conditions, and the method specifically comprises the following steps:
when the system is in the first system working condition, the charged system SOC estimated value is calibrated to 100% SOC; and/or
When the system is in the second system working condition, the discharged system SOC estimated value is calibrated to 0% SOC; and/or
When the third system working condition is met, when the single battery is subjected to voltage charging protection, the system SOC estimated value is calibrated to 100% SOC, or when the single battery is subjected to voltage discharging protection, the system SOC estimated value is calibrated to 0% SOC; and/or
And when the system is in the fourth system working condition, the charged system SOC estimated value is calibrated to 100% SOC, or the discharged system SOC estimated value is calibrated to 0% SOC.
10. An SOC estimation system of a lithium battery system, characterized in that the SOC estimation method of a lithium battery system according to any one of claims 1 to 9 is employed.
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