CN117368767B - Lithium battery state of charge estimation method and system based on ampere-hour integration method - Google Patents
Lithium battery state of charge estimation method and system based on ampere-hour integration method Download PDFInfo
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- CN117368767B CN117368767B CN202311289373.0A CN202311289373A CN117368767B CN 117368767 B CN117368767 B CN 117368767B CN 202311289373 A CN202311289373 A CN 202311289373A CN 117368767 B CN117368767 B CN 117368767B
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- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 title claims abstract description 170
- 229910052744 lithium Inorganic materials 0.000 title claims abstract description 170
- 238000000034 method Methods 0.000 title claims abstract description 91
- 230000010354 integration Effects 0.000 title claims abstract description 44
- 238000007599 discharging Methods 0.000 claims description 14
- 230000002159 abnormal effect Effects 0.000 claims description 6
- 238000004364 calculation method Methods 0.000 description 12
- 238000010586 diagram Methods 0.000 description 12
- 238000012544 monitoring process Methods 0.000 description 9
- 238000012545 processing Methods 0.000 description 9
- 238000004458 analytical method Methods 0.000 description 8
- 230000008569 process Effects 0.000 description 7
- 238000001514 detection method Methods 0.000 description 4
- 238000001914 filtration Methods 0.000 description 4
- 238000009499 grossing Methods 0.000 description 4
- 230000036541 health Effects 0.000 description 4
- 230000000977 initiatory effect Effects 0.000 description 3
- 230000009471 action Effects 0.000 description 2
- 230000001364 causal effect Effects 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 description 2
- 230000007246 mechanism Effects 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000007704 transition Effects 0.000 description 2
- 230000032683 aging Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 238000006731 degradation reaction Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 238000012827 research and development Methods 0.000 description 1
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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
- G01R31/388—Determining ampere-hour charge capacity or SoC involving voltage measurements
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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]
- G01R31/367—Software therefor, e.g. for battery testing using modelling or look-up tables
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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]
- G01R31/392—Determining battery ageing or deterioration, e.g. state of health
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R35/00—Testing or calibrating of apparatus covered by the other groups of this subclass
- G01R35/005—Calibrating; Standards or reference devices, e.g. voltage or resistance standards, "golden" references
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Abstract
The invention relates to the technical field of lithium battery state of charge estimation, in particular to a lithium battery state of charge estimation method and a system based on an ampere-hour integration method, which are used for acquiring and storing lithium battery data information; estimating the charge state of the current lithium battery by utilizing an ampere-hour integration method and judging whether the current lithium battery is in a normal range or not; for the battery with normal running state, judging whether the requirements of available capacity calibration and residual capacity calibration are met, carrying out available capacity calibration and residual capacity calibration on the battery meeting the calibration requirements, and respectively judging the effectiveness of the available capacity calibration and the residual capacity calibration; the state of charge estimation of the lithium battery has very important significance for the use of the lithium battery, the state of charge estimation is carried out by an ampere-hour integration method, and the state parameters required by the battery operation can be known and the accuracy of the state of charge estimation can be improved by correcting the available capacity calibration and the residual capacity calibration of the battery respectively.
Description
Technical Field
The invention relates to the technical field of lithium battery state of charge estimation, in particular to a lithium battery state of charge estimation method and system based on an ampere-hour integration method.
Background
In recent years, environmental problems and energy problems are becoming serious, and the daily life of people is already affected. Electric vehicles require a safe, efficient battery as a power source. The lithium battery is used as an ideal power source of a new generation of electric vehicles because of the advantages of stable working voltage, high energy density and charging efficiency, low self-discharge rate, no memory, long service life and the like.
At present, the state of charge of a lithium battery is one of important parameters of a battery management system, and in research and development of an electric vehicle, accurately predicting the state of charge of the battery plays a vital role in playing the best performance of the electric vehicle and predicting the driving range of the electric vehicle, and has important significance in improving the service life of the battery and improving the safety performance. However, the state of charge of a lithium battery cannot be directly measured, and is affected by many factors such as the rate of charge and discharge, the aging degree of the battery, the internal resistance of the battery and the like, so that accurate and rapid measurement is difficult. How to realize accurate estimation of the remaining capacity of the battery becomes a difficulty to be overcome in the prior art to improve the maximum utilization rate of the lithium battery and continuously optimize the battery technology.
Therefore, a method and a system for estimating the state of charge of a lithium battery based on an ampere-hour integration method are needed to solve the above problems.
Disclosure of Invention
The invention aims to provide a lithium battery state of charge estimation method and system based on an ampere-hour integration method, so as to solve the problems in the background technology.
In order to solve the technical problems, the invention provides the following technical scheme: a lithium battery state of charge estimation system based on an ampere-hour integration method, the system comprising: the system comprises a data acquisition module, a database, a state of charge estimation module and a calibration module.
The output end of the data acquisition module is connected with the input end of the database; the output end of the database is connected with the input end of the state of charge estimation module; the output end of the state of charge is connected with the input end of the calibration module;
The data acquisition module is used for acquiring data information of the lithium battery;
the database is used for storing and managing all acquired data;
The state of charge estimation module is used for analyzing the running state of the lithium battery according to the acquired information, estimating the state of charge of the lithium battery and judging whether the state of charge of the lithium battery is in a normal range;
The calibration module is used for carrying out available capacity calibration and residual capacity calibration on the lithium battery and judging the effectiveness of the calibration.
Further, the data acquisition module comprises a lithium battery data acquisition unit and a monitoring data acquisition unit; the output ends of the data acquisition unit and the monitoring data acquisition unit are connected with the input end of the database; the lithium battery data acquisition unit is used for acquiring factory information of the lithium battery; the monitoring data acquisition unit is used for acquiring data information of the lithium battery in detection.
Further, the state of charge estimation module comprises a state analysis unit, a state of charge estimation unit and a range judgment unit; the output end of the database is connected with the input end of the state analysis unit; the output end of the state analysis unit is connected with the input end of the state of charge estimation unit; the output end of the charge state estimation unit is connected with the input end of the range judgment unit; the state analysis unit is used for analyzing the running state of the lithium battery according to the detection data and judging the running state of the current lithium battery; the charge state estimating unit is used for estimating the charge state of the current lithium battery by adopting an ampere-hour integration method according to the condition of the lithium battery; the range judging unit is used for analyzing the charge state of the normal lithium battery and judging whether the charge state of the current lithium battery is in the normal range.
Further, the calibration module comprises a lithium battery calibration start judging unit, an available capacity calibration judging unit, a residual capacity calibration judging unit and a residual capacity calibration judging unit; the output end of the range judging unit is connected with the input end of the calibration starting judging unit, and the calibration starting judging unit judges whether available capacity calibration or residual capacity calibration is required to be started or not; for determining whether an available capacity calibration or a remaining capacity calibration needs to be started; the output end of the calibration start judging unit is connected with the input end of the available capacity calibration unit and the input end of the residual capacity calibration unit, and is used for calibrating the available capacity and the residual capacity respectively, the available capacity calibration unit is used for carrying out calibration calculation on the available capacity, and the residual capacity calibration unit is used for carrying out calibration calculation on the residual capacity; the output end of the available capacity calibration unit is connected with the input end of the available capacity calibration judging unit, and the available capacity calibration judging unit is used for judging whether the available capacity calibration is successful or not; the output end of the residual capacity calibration unit is connected with the input end of the residual capacity calibration judging unit, and the residual capacity calibration judging unit is used for judging whether the residual capacity calibration is successful or not.
A lithium battery state of charge estimation method based on an ampere-hour integration method comprises the following steps:
z1: collecting and storing lithium battery data information;
z2: estimating the charge state of the current lithium battery by utilizing an ampere-hour integration method and judging whether the current lithium battery is in a normal range or not;
z3: and judging whether the requirements of the available capacity calibration and the residual capacity calibration are met for the battery which runs normally, carrying out the available capacity calibration and the residual capacity calibration on the battery which meets the requirements of the calibration, and respectively judging the validity of the available capacity calibration and the residual capacity calibration.
Further, step Z2 includes: and electrifying the lithium battery, measuring the voltage to obtain a linear relation between the voltage and time, and judging whether the current operation state of the lithium battery is normal or not based on the linear relation. The method comprises the steps of electrifying a lithium battery and measuring voltage to obtain a line diagram of the voltage and time, wherein if the line diagram has stable trend, the current lithium battery has good running state; if the line graph is in a descending trend, the current lithium battery running state is problematic, and measures such as replacement of the lithium battery are needed. Under the condition that the lithium battery is electrified, the voltage of the lithium battery is monitored in real time, whether the current running state of the lithium battery is good or not is judged through the linear relation between the voltage and time, the health state of the battery can be mastered in real time, and if the problem is found, the lithium battery can be replaced in time, so that the problem of the running state of the lithium battery is prevented from influencing the normal running of equipment.
Further, in step Z2: extracting information in a database, obtaining an initial state B0 of lithium battery charging, and calculating a current state of charge B of the lithium battery according to the following formula:
Wherein, C E represents the rated capacity of the lithium battery, I represents the current of the lithium battery (the current is negative during charging and the current is positive during discharging), eta represents the charging efficiency, the current state of charge of the lithium battery is estimated by utilizing an ampere-hour integrating method, the ampere-hour integrating method does not consider the action mechanism inside the battery, the total capacity of the inflow and outflow battery is calculated by integrating the time and the current according to certain external characteristics of the system, such as current, time, temperature compensation and the like, and certain compensation coefficients are added, the ampere-hour integrating method is widely applied in a battery management system at present, and the ampere-hour integrating method has the advantages of being relatively less limited by the condition of the battery, and is simple and reliable in calculation method and capable of estimating the state of charge of the battery in real time. The main problem is that accumulated errors cannot be eliminated, if effective calibration is lacking, the errors are larger and larger, so the invention further provides a method for calibrating the ampere-hour integration method aiming at the defects of the ampere-hour integration method, thereby reducing the errors brought by the ampere-hour integration method.
Extracting the state of charge of the normal lithium battery with the same charge and discharge times stored in the database, obtaining a set D= { D 1,D2,...,Dn } of the state of charge of the normal lithium battery with n times, and comparing to obtain a minimum value D min and a maximum value D max of the state of charge of the lithium battery, wherein the range of the state of charge of the normal lithium battery with the same charge and discharge times stored in the database is [ D min,Dmax ]; if B is in the range of [ D min,Dmax ], judging that the current state of charge of the lithium battery is normal and the battery state is good; if B is not in the range of [ D min,Dmax ], judging that the current lithium battery charge state is abnormal, and reporting a fault to process. And judging whether the current state of charge of the lithium battery is abnormal or not by determining the range of the value of the state of charge of the normal lithium battery with the same condition stored in the previous database, so that the judging result is more effective, the calculation time of the system is reduced, and the running efficiency of the system is improved.
In the present invention, the calibration of the system is divided into two types, namely, remaining capacity calibration and usable capacity calibration, and the calibration is performed with respect to the numerator (remaining capacity) and denominator (usable capacity) in the SOC calculation, respectively.
The two kinds of calibration are performed based on charge-discharge SOC curve inflection points of the lithium iron phosphate system battery cell, and are called a calibration point A (SOC A) and a calibration point B (SOC B) in the invention, wherein the calibration point A is a point with larger SOC. The standard for identifying whether the battery reaches two calibration points is the SOC determined by a cell voltage method, and the calibration false start and calibration deviation caused by an ampere-hour integration method error are avoided.
Available capacity and residual capacity calibration initiation determination:
When it is recognized that the battery has completed a complete charge or discharge from calibration point a to calibration point B (or vice versa) (denoted as a standard condition), at the end of the calibration (i.e., at calibration point a or B), the available capacity calibration requirement is deemed satisfied, and the available capacity calibration is initiated; residual capacity calibration is initiated when the battery is charged in the [1, SOC A ] interval and a switch from charging to discharging of the battery is detected, or when the battery is discharged in the [ SOC B, 0] interval and a transition from discharging to charging of the battery is detected, the residual capacity calibration requirement is considered to be satisfied. In the remaining capacity calibration, the available capacity of the battery is required, but the value is not forced to be a calibrated value, that is, the calibration of the remaining capacity and the available capacity has no causal relationship, and the respective starting requirements are met to perform the respective calibration.
Available capacity calibration:
When the system is in charge-discharge operation between the AB points, the system performs accumulated calculation of the SOC and the charge-discharge capacity based on an ampere-hour integration method due to the flat section of the SOC. When the system SOC completes a complete condition from calibration point A to calibration point B (or vice versa), it is noted as a calibration condition. At the end of the calibration regime (i.e., at calibration points a or B), the available capacity calibration requirement is deemed satisfied, and the available capacity calibration is initiated using the following equation:
Wherein E ch_A、Edisch_A is the system integrated charge capacity and integrated discharge capacity corresponding to the calibration point a, and E ch_B、Edisch_B is the system integrated charge capacity and integrated discharge capacity corresponding to the calibration point B. This data is accumulated in the BMS for computing system warranty. E avb is the calculated available capacity for calibration.
Available capacity calibration validity determination:
The calibration difference Δe avb of the available capacity is calculated using the following formula:
ΔEavb＝|Eavb_0-Eavb|
The calibration threshold Δe avb_eff for the available capacity is calculated using the following formula:
ΔEavb_eff＝10％*Eavb_0
If Δe avb＜ΔEavb_eff, the calibration is successful, using E avb to replace the available capacity E avb_0 of the battery before calibration; if Δe avb≥ΔEavb_eff fails the calibration, the available capacity E avb_0 of the battery before calibration is preserved.
Residual capacity calibration:
When the battery is operated to two intervals of [1, SOC A ] and [ SOC B, 0], voltage calibration and residual capacity calibration are performed. For the interval [1, SOC A ], when the system is charged, a traditional cell voltage calibration mode is adopted, the current measured highest single cell voltage of the battery is subjected to Kalman filtering through the SOC value obtained by looking up a table and the value integrated at ampere hour to obtain an actual SOC value, and smoothing processing is carried out to improve the use experience. In the prior art, a corresponding table of battery voltage and SOC already exists, and specific values of SOC corresponding to battery voltage are slightly different based on different battery factories, and a method of searching for corresponding values of battery voltage and SOC by looking up a table is simply referred to as a table look-up method. When the system is switched from charging to discharging, the actual SOC value SOC tabl of the battery is obtained through data processing according to the SOC value corresponding to the maximum cell voltage of the battery measured at the moment; and under other conditions (such as unchanged charge and discharge working conditions or discharge to charge, and no residual capacity calibration is performed). Similarly, for the interval [ SOC B, 0], when the system discharges, a traditional cell voltage calibration mode is adopted, the current measured lowest single cell voltage of the battery is subjected to Kalman filtering through the SOC value obtained by looking up a table and the value integrated at ampere time to obtain an actual SOC value, and smoothing processing is carried out to improve the use experience. When the system is converted from discharging to charging, the actual SOC value SOC ab2 of the battery is obtained through data processing according to the SOC value corresponding to the minimum cell voltage of the battery measured at the moment; under other conditions (such as unchanged charge and discharge conditions or charge-discharge, and no residual capacity calibration). The remaining capacity calibration value E rem is calculated using the battery usable capacity E avb_0 and the SOC tabl by the following formula:
Erem＝SOCtab*Eavb_0；
the value of the SOC tab is the SOC tabl or the SOC tab2;SOCtabl is the actual SOC value corresponding to the maximum cell voltage of the battery; SOC tab2 is the actual SOC value corresponding to the minimum cell voltage of the battery.
Residual capacity calibration validity determination:
The calibration difference Δe rem of the available capacity is calculated using the following formula:
ΔErem＝|Erem_0-Erem|
the calibration threshold Δe rem_eff for the available capacity is calculated using the following formula:
ΔErem_eff＝30％*Erem_0
If Δe rem＜ΔErem_eff, the calibration is successful, using E rem to replace the remaining capacity E rem_0 of the battery before calibration; if Δe rem≥ΔErem_eff fails the calibration, leaving the remaining capacity E rem_0 of the battery before calibration.
Compared with the prior art, the invention has the following beneficial effects:
According to the invention, the current lithium battery running state is judged through the linear relation between the voltage and time of the lithium battery, the health state of the battery can be mastered in real time, if the problem is found, the battery can be replaced in time, the problem of the state of the lithium battery is prevented from influencing the normal running of the equipment, if the running state is good, the state of charge of the lithium battery is estimated by using an ampere-hour integration method, the range of the state of charge of the normal lithium battery is obtained by using the state of charge of the normal lithium battery with the same charge and discharge times stored in a database, so that the current lithium battery is judged to be not required to be calibrated, the difference between the calibrated system capacity and the system actual capacity is calculated, the difference is compared with a calibration threshold value, and whether the calibration is successful is judged, thereby improving the running efficiency of the system and the utilization rate of the lithium battery.
Drawings
The accompanying drawings are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate the invention and together with the embodiments of the invention, serve to explain the invention. In the drawings:
FIG. 1 is a flow chart of estimating the state of charge of a lithium battery based on an ampere-hour integration method;
FIG. 2 is a diagram of a lithium battery state of charge estimation system based on an ampere-hour integration method according to the present invention;
FIG. 3 is a line drawing of a first embodiment of the present invention;
FIG. 4 is a line drawing of a second embodiment of the present invention;
fig. 5 is a line drawing in the fourth embodiment of the present invention.
Detailed Description
The preferred embodiments of the present invention will be described below with reference to the accompanying drawings, it being understood that the preferred embodiments described herein are for illustration and explanation of the present invention only, and are not intended to limit the present invention.
Referring to fig. 1-2, the present invention provides the following technical solutions: a lithium battery state of charge estimation system based on an ampere-hour integration method, the system comprising: the system comprises a data acquisition module, a database, a state of charge estimation module and a calibration module.
The output end of the data acquisition module is connected with the input end of the database; the output end of the database is connected with the input end of the state of charge estimation module; the output end of the charge state estimation module is connected with the input end of the calibration module;
The data acquisition module is used for acquiring data information of the lithium battery;
the database is used for storing and managing all acquired data;
The state of charge estimation module is used for analyzing the running state of the lithium battery according to the acquired information, estimating the state of charge of the lithium battery and judging whether the state of charge of the lithium battery is in a normal range;
The calibration module is used for carrying out available capacity calibration and residual capacity calibration on the lithium battery and respectively judging the validity of the available capacity calibration and the residual capacity calibration.
Further, the data acquisition module comprises a lithium battery data acquisition unit and a monitoring data acquisition unit; the output ends of the data acquisition unit and the monitoring data acquisition unit are connected with the input end of the database; the lithium battery data acquisition unit is used for acquiring factory information of the lithium battery; the monitoring data acquisition unit is used for acquiring data information of the lithium battery in detection.
Further, the state of charge estimation module comprises a state analysis unit, a state of charge estimation unit and a range judgment unit; the output end of the database is connected with the input end of the state analysis unit; the output end of the state analysis unit is connected with the input end of the state of charge estimation unit; the output end of the charge state estimation unit is connected with the input end of the range judgment unit; the state analysis unit is used for analyzing the running state of the lithium battery according to the detection data and judging the quality of the current state of the lithium battery; the charge state estimating unit is used for estimating the charge state of the current lithium battery by adopting an ampere-hour integration method according to the condition of the lithium battery; the range judging unit is used for analyzing the charge states of the normal lithium batteries under the same conditions and judging whether the charge states of the current lithium batteries are in the normal range.
Further, the calibration module comprises a lithium battery calibration start judging unit, an available capacity calibration judging unit, a residual capacity calibration judging unit and a residual capacity calibration judging unit; the output end of the range judging unit is connected with the input end of the calibration starting judging unit, and the calibration starting judging unit judges whether available capacity calibration or residual capacity calibration is required to be started or not; for determining whether an available capacity calibration or a remaining capacity calibration needs to be started; the output end of the calibration start judging unit is connected with the input end of the available capacity calibration unit and the input end of the residual capacity calibration unit, and is used for calibrating the available capacity and the residual capacity respectively, the available capacity calibration unit is used for carrying out calibration calculation on the available capacity, and the residual capacity calibration unit is used for carrying out calibration calculation on the residual capacity; the output end of the available capacity calibration unit is connected with the input end of the available capacity calibration judging unit, and the available capacity calibration judging unit is used for judging whether the available capacity calibration is successful or not; the output end of the residual capacity calibration unit is connected with the input end of the residual capacity calibration judging unit, and the residual capacity calibration judging unit is used for judging whether the residual capacity calibration is successful or not.
A lithium battery state of charge estimation method based on an ampere-hour integration method comprises the following steps:
z1: collecting and storing lithium battery data information;
z2: estimating the charge state of the current lithium battery by utilizing an ampere-hour integration method and judging whether the current lithium battery is in a normal range or not;
z3: and judging whether the requirements of the available capacity calibration and the residual capacity calibration are met for the battery which runs normally, carrying out the available capacity calibration and the residual capacity calibration on the battery which meets the requirements of the calibration, and respectively judging the validity of the available capacity calibration and the residual capacity calibration.
Step Z2 comprises: and electrifying the lithium battery, measuring the voltage to obtain a linear relation between the voltage and time, and judging whether the current operation state of the lithium battery is normal or not based on the linear relation. The method comprises the steps of electrifying a lithium battery and measuring voltage to obtain a line diagram of the voltage and time, wherein if the line diagram has stable trend, the current lithium battery is in a good state; if the line diagram is in a descending trend, the current lithium battery running state is indicated to have a problem, the lithium battery needs to be replaced, the voltage of the lithium battery is monitored in real time under the condition that the lithium battery is electrified, whether the current lithium battery running state is good or not is judged through the linear relation between the voltage and time, the health state of the battery can be mastered in real time, and if the problem is found, the lithium battery running state can be replaced in time, so that the normal running of equipment is prevented from being influenced due to the state problem of the lithium battery.
In step Z2: information in the database is extracted, the initial state B 0 of lithium battery charging is obtained, and the current state of charge B of the lithium battery is calculated according to the following formula:
Wherein, C E represents the rated capacity of the lithium battery, I represents the charging current of the lithium battery (the current is negative during charging and the current is positive during discharging), eta represents the charging efficiency, the current state of charge of the lithium battery is estimated by utilizing an ampere-hour integration method, the ampere-hour integration method does not consider the action mechanism inside the battery, the total capacity of the inflow and outflow battery is calculated by integrating the time and the current according to certain external characteristics of the system, such as current, time, temperature compensation and the like, and certain compensation coefficients are added, the ampere-hour integration method is widely applied in a battery management system at present, and the ampere-hour integration method has the advantages of being relatively less limited by the condition of the battery, and is simple and reliable in calculation method and capable of estimating the state of charge of the battery in real time. The main problem is that accumulated errors cannot be eliminated, if effective calibration is lacking, the errors are larger and larger, so the invention further provides a method for calibrating the ampere-hour integration method aiming at the defects of the ampere-hour integration method, thereby reducing the errors brought by the ampere-hour integration method.
Extracting the state of charge of the normal lithium battery with the same charge and discharge times stored in the database, obtaining a set D= { D 1,D2,...,Dn } of the state of charge of the normal lithium battery with n times, and comparing to obtain a minimum value D min and a maximum value D max of the state of charge of the lithium battery, wherein the range of the state of charge of the normal lithium battery with the same charge and discharge times stored in the database is [ D min,Dmax ]; if B is in the range of [ D min,Dmax ], judging that the current state of charge of the lithium battery is normal and the battery state is good; if B is not in the range of [ D min,Dmax ], judging that the current lithium battery charge state is abnormal, and reporting a fault to process. And judging whether the current state of charge of the lithium battery is abnormal or not by determining the range of the value of the state of charge of the normal lithium battery with the same condition stored in the previous database, so that the judging result is more effective, the calculation time of the system is reduced, and the running efficiency of the system is improved.
In the present invention, the calibration of the system is divided into two types, namely, remaining capacity calibration and usable capacity calibration, and the calibration is performed with respect to the numerator (remaining capacity) and denominator (usable capacity) in the SOC calculation, respectively.
The two kinds of calibration are performed based on charge-discharge SOC curve inflection points of the lithium iron phosphate system battery cell, and are called a calibration point A (SOC A) and a calibration point B (SOC B) in the invention, wherein the calibration point A is a point with larger SOC. The standard for identifying whether the battery reaches two calibration points is the SOC determined by a cell voltage method, and the calibration false start and calibration deviation caused by an ampere-hour integration method error are avoided.
Available capacity and residual capacity calibration initiation determination:
When it is recognized that the battery has completed a complete charge or discharge from calibration point a to calibration point B (or vice versa) (denoted as a calibration condition), at the end of the calibration condition (i.e., at calibration point a or B), the available capacity calibration requirement is deemed satisfied, and the available capacity calibration is initiated; residual capacity calibration is initiated when the battery is charged in the [1, SOC A ] interval and a switch from charging to discharging of the battery is detected, or when the battery is discharged in the [ SOC B, 0] interval and a transition from discharging to charging of the battery is detected, the residual capacity calibration requirement is considered to be satisfied.
Wherein the available capacity is calibrated:
When the system is in charge-discharge operation between the AB points, the system performs accumulated calculation of the SOC and the charge-discharge capacity based on an ampere-hour integration method due to the flat section of the SOC. When the system SOC completes a complete condition from calibration point A to calibration point B (or vice versa), it is noted as a calibration condition. At the end of the calibration regime (i.e., at calibration points a or B), the available capacity calibration requirement is deemed satisfied, and the available capacity calibration is initiated using the following equation:
Wherein E ch_A、Edisch_A is the system accumulated charge capacity and accumulated discharge capacity corresponding to calibration point A, and E ch_B、Edisch_B is the system accumulated charge capacity and accumulated discharge capacity corresponding to calibration point B. This data is accumulated in the BMS for computing system warranty. E avb is the calculated available capacity for calibration.
Available capacity calibration validity determination:
The calibration difference Δe avb of the available capacity is calculated using the following formula:
ΔEavb＝|Eavb_0-Eavb|
The calibration threshold Δe avb_eff for the available capacity is calculated using the following formula:
ΔEavb_eff＝10％*Eavb_0
If Δe avb＜ΔEavb_eff, is successful, using E avb to replace the available capacity E avb_0 of the battery prior to calibration; if Δe avb≥ΔEavb_eff fails the calibration, the available capacity E avb_0 of the battery before calibration is preserved.
Residual capacity calibration:
When the battery is operated to two intervals of [1, SOC A ] and [ SOC B, 0], voltage calibration and residual capacity calibration are performed. For the interval [1, SOC A ], when the system is charged, a traditional cell voltage calibration mode is adopted, the current measured highest single cell voltage of the battery is subjected to Kalman filtering through the SOC value obtained by looking up a table and the value integrated at ampere hour to obtain an actual SOC value, and smoothing processing is carried out to improve the use experience. In the prior art, a corresponding table of battery voltage and SOC already exists, and specific values of SOC corresponding to battery voltage are slightly different based on different battery factories, and a method of searching for corresponding values of battery voltage and SOC by looking up a table is simply referred to as a table look-up method. When the system is switched from charging to discharging, the actual SOC value SOC tab1 of the battery is obtained through data processing according to the SOC value corresponding to the maximum cell voltage of the battery measured at the moment; and under other conditions (such as unchanged charge and discharge working conditions or discharge to charge, and no residual capacity calibration is performed). Similarly, for the interval [ SOC B, 0], when the system discharges, a traditional cell voltage calibration mode is adopted, the current measured lowest single cell voltage of the battery is subjected to Kalman filtering through the SOC value obtained by looking up a table and the value integrated at ampere time to obtain an actual SOC value, and smoothing processing is carried out to improve the use experience. When the system is converted from discharging to charging, the actual SOC value SOC ab2 of the battery is obtained through data processing according to the SOC value corresponding to the minimum cell voltage of the battery measured at the moment; under other conditions (such as unchanged charge and discharge conditions or charge-discharge, and no residual capacity calibration). The remaining capacity calibration value E rem is calculated using the battery usable capacity E avb_0 and the SOC tab1 by the following formula:
Erem＝SOCtab*Eavb_0；
The value of the SOC tab is the SOC tab1 or the SOC tab2;SOCtab1 is the actual SOC value corresponding to the maximum cell voltage of the battery; SOC tab2 is the actual SOC value corresponding to the minimum cell voltage of the battery.
Residual capacity calibration validity determination:
The calibration difference Δe rem of the available capacity is calculated using the following formula:
ΔErem＝|Erem_0-Erem|
the calibration threshold Δe rem_eff for the available capacity is calculated using the following formula:
ΔErem_eff＝30％*Erem_0
If Δe rem＜ΔErem_eff, the calibration is successful, using E rem to replace the remaining capacity E avb_0 of the battery before calibration; if Δe rem≥ΔErem_eff fails the calibration, leaving the remaining capacity E rem_0 of the battery before calibration.
Embodiment one: the lithium battery is electrified, the voltage is measured, a line diagram of the voltage and the time is obtained, and referring to fig. 3, the line diagram shows a descending trend, and the current lithium battery running state is problematic, so that the lithium battery needs to be replaced.
Embodiment two: electrifying the lithium battery, measuring the voltage to obtain a line diagram of the voltage and the time, referring to fig. 4, if the line diagram has stable trend, the running state of the current lithium battery is good; under the condition that the lithium battery is electrified, the voltage of the lithium battery is monitored in real time, whether the current running state of the lithium battery is good or not is judged through a voltage and time line diagram, the health state of the battery can be mastered in real time, if the problem is found, the lithium battery can be replaced in time, and the problem of the running state of the lithium battery is prevented from influencing the normal running of equipment.
Embodiment III: information in the database is extracted, the initial state B 0 =48% of the lithium battery is obtained, the rated capacity C E of the lithium battery is 3, the charging current I of the lithium battery is-2, the charging efficiency eta is 0.5, and the method is based on the following stepsAnd calculating to obtain the current charge state B of the lithium battery as 81%.
Extracting the charge states of the normal lithium batteries with the same charge and discharge times stored in the database, obtaining a set D= {81.5%,81.53%,81.55%,81.59% and 81.53% } of the charge states of the normal lithium batteries with the same charge and discharge times, and comparing to obtain a minimum value D min of 81.5% and a maximum value D max of 81.59% of the charge states of the lithium batteries, wherein the range of the charge states of the normal lithium batteries with the same charge and discharge times stored in the database is [81.5% and 81.59% ]; and the current state of charge B of the lithium battery is 81 percent and is not within the range of 81.5 percent and 81.59 percent, so that the current state of charge B of the lithium battery is judged to be abnormal, and the fault is reported for processing.
Embodiment four: and electrifying the lithium battery, measuring the voltage to obtain a voltage and time line diagram, monitoring that the charging process of the battery passes through 88% and 10% of SOC monitoring points after no fault is found, and turning to discharging after the battery is fully charged to 100%, wherein the charging process is finished, and the calibration requirement is met by referring to FIG. 5. The available capacity calibration is started first. By means ofThe available capacity after calibration is 197.07Ah, the calibration difference Δe avb is 2.34Ah by Δe avb＝|Eavb_0-Eavb |= |199.41-197.07 |=2.34 Ah, and the calibration threshold Δe avb_eff is 19.94Ah by Δe avb_eff＝10％*Eavb_0 =10% > 199.41=19.94 Ah:2.34Ah < 19.94Ah, Then the calibration is judged to be successful and 197.07Ah obtained by the calibration is used to replace 199.41Ah as the new available capacity of the battery. Further, it is determined whether or not to perform remaining capacity calibration. Firstly, the charging process of the battery is monitored to exceed the monitoring point 88% of the SOC, and the charging process is switched to the discharging working condition after the charging process is full, so that the requirement for starting the residual capacity calibration is met. The remaining capacity was 197.07Ah calculated using E rem＝SOCtab*Eavb_0 = 100% = 197.07 = 197.07Ah. Wherein. The available capacity is calibrated E avb_0, but whether the actual E avb_0 is calibrated does not affect the initiation of the remaining capacity calibration. That is, in the remaining capacity calibration, the available capacity of the battery is required, but the value of the available capacity may be calibrated or not, that is, the remaining capacity and the available capacity may be calibrated without causal relationship, so long as the respective starting requirements are satisfied. Using Δe rem＝|Erem_0-Erem |= |197.07-199.48 |=2.41 Ah gave a calibration difference Δe rem of 2.41Ah, and by Δe rem_eff＝30％*Erem_0 =30% > 199.48 =59.84 Ah gave a calibration threshold Δe rem_eff of 59.84Ah:2.41Ah < 59.84Ah, And judging that the calibration is successful, and using 197.07Ah obtained by the calibration to replace the original 199.48Ah as the new residual capacity of the battery.
The available capacity and the residual capacity of the system are calibrated respectively to obtain a difference value before calibration and a difference value after calibration, a calibration threshold value is calculated according to the actual available capacity and the residual capacity of the current system, the value after calibration is compared with the threshold value to judge whether the calibration is successful, the battery state is calibrated, the durability of the lithium battery is improved, the information of the lithium battery is more accurate, and the fault reason and the degradation degree of the lithium battery are judged.
Finally, it should be noted that: the foregoing is merely a preferred example of the present invention, and the present invention is not limited thereto, but it is to be understood that modifications and equivalents of some of the technical features described in the foregoing embodiments may be made by those skilled in the art, although the present invention has been described in detail with reference to the foregoing embodiments. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (9)
1. A lithium battery state of charge estimation method based on an ampere-hour integration method is characterized by comprising the following steps of: the method comprises the following steps:
z1: collecting and storing lithium battery data information;
z2: estimating the charge state of the current lithium battery by utilizing an ampere-hour integration method and judging whether the current lithium battery is in a normal range or not;
Z3: for the battery with normal running state, judging whether the requirements of available capacity calibration and residual capacity calibration are met, carrying out available capacity calibration and residual capacity calibration on the battery meeting the calibration requirements, and respectively judging the effectiveness of the available capacity calibration and the residual capacity calibration;
in step Z3: when the battery is identified to finish a standard working condition, at a calibration point A or a calibration point B at the tail end of the calibration working condition, the battery is considered to meet the requirement of available capacity calibration, and the available capacity calibration is started; when the battery is charged in the [1, SOC A ] section and the battery is detected to switch from charging to discharging, or when the battery is discharged in the [ SOC B, 0] section and the battery is detected to switch from discharging to charging, the battery is considered to satisfy the requirement of the remaining capacity calibration, and the remaining capacity calibration is started.
2. The method for estimating the state of charge of a lithium battery based on the ampere-hour integration method according to claim 1, wherein the method comprises the following steps: step Z2 further comprises: and electrifying the lithium battery, measuring the voltage to obtain a linear relation between the voltage and time, and judging whether the current operation state of the lithium battery is normal or not based on the linear relation.
3. The method for estimating the state of charge of a lithium battery based on the ampere-hour integration method according to claim 1, wherein the method comprises the following steps: in step Z2: information in the database is extracted, the initial state B 0 of lithium battery charging is obtained, and the current state of charge B of the lithium battery is calculated according to the following formula:
Wherein, C E represents the rated capacity of the lithium battery, I represents the current of the lithium battery, and eta represents the charging efficiency.
4. The method for estimating the state of charge of a lithium battery based on the ampere-hour integration method according to claim 3, wherein the method comprises the following steps: in step Z2: extracting the charge states of the normal lithium batteries with the same charge and discharge times stored in the database, obtaining a set D= { D 1,D2,...,Dn } of the charge states of the n lithium batteries, and taking the minimum value D min and the maximum value D max thereof as the charge state range of the normal lithium batteries; if B is at
Judging that the current state of charge of the lithium battery is normal within the range of [ D min,Dmax ]; otherwise, judging that the current state of charge of the lithium battery is abnormal.
5. The method for estimating the state of charge of a lithium battery based on the ampere-hour integration method according to claim 1, wherein the method comprises the following steps: in step Z3, the available capacity calibration is performed using the following formula:
Wherein E ch_A、Edisch_A is the system accumulated charge capacity and accumulated discharge capacity corresponding to the calibration point A, E ch_B、Edisch_B is the system accumulated charge capacity and accumulated discharge capacity corresponding to the calibration point B; e avb is the calculated available capacity for calibration.
6. The method for estimating the state of charge of a lithium battery based on the ampere-hour integration method according to claim 5, wherein the method comprises the following steps: the validity of the available capacity calibration is judged as follows:
the calibration difference Δe avb of the available capacity was calculated using the following formula:
ΔEavb＝|Eavb_0-Eavb|；
Where E avb_0 is the available capacity before calibration;
the calibration threshold Δe avb_eff for the available capacity is calculated using the following formula:
ΔEavb_eff＝10％*Eavb_0；
If Δe avb＜ΔEavb_eff, the calibration is successful, replacing the available capacity value E avb_0 before battery calibration with the value of E avb; if Δe avb≥ΔEavb_eff fails the calibration, the available capacity E avb_0 of the battery before calibration is preserved.
7. The method for estimating the state of charge of a lithium battery based on the ampere-hour integration method according to claim 6, wherein the method comprises the following steps: in step Z3, the remaining capacity calibration is performed using the following formula:
Erem＝SOCtab*Eavb_0；
The value of the SOC tab is the SOC tab1 or the SOC tab2;SOCtab1 is the actual SOC value corresponding to the maximum cell voltage of the battery; SOC tab2 is the actual SOC value corresponding to the minimum cell voltage of the battery.
8. The method for estimating the state of charge of a lithium battery based on the ampere-hour integration method according to claim 7, wherein the method comprises the following steps: the validity of the remaining capacity calibration is judged as follows:
The calibration difference Δe rem of the remaining capacity was calculated using the following formula:
ΔErem＝|Erem_0-Erem|；
The remaining capacity calibration threshold Δe rem_eff is calculated using the following formula:
ΔErem_eff＝30％*Erem_0；
If Δe rem＜ΔErem_eff, the calibration is successful, using E rem to replace the remaining capacity E rem_0 of the battery before calibration; if Δe rem≥ΔErem_eff fails the calibration, leaving the remaining capacity E rem_0 of the battery before calibration.
9. A lithium battery state of charge estimation system based on an ampere-hour integration method, the system being applied to the implementation of the lithium battery state of charge estimation method based on the ampere-hour integration method as set forth in any one of claims 1 to 8, and characterized in that: the system comprises: the system comprises a data acquisition module, a database, a state of charge estimation module and a calibration module;
the output end of the data acquisition module is connected with the input end of the database; the output end of the database is connected with the input end of the state of charge estimation module; the output end of the charge state estimation module is connected with the input end of the calibration module;
The data acquisition module is used for acquiring data information of the lithium battery;
the database is used for storing and managing all acquired data;
The state of charge estimation module is used for analyzing the running state of the lithium battery according to the acquired information, estimating the state of charge of the lithium battery and judging whether the state of charge of the lithium battery is in a normal range;
The calibration module is used for carrying out available capacity calibration and residual capacity calibration on the lithium battery and judging the effectiveness of the calibration.
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