CN116879776A - SOC estimation method for lithium iron phosphate battery energy storage system - Google Patents
SOC estimation method for lithium iron phosphate battery energy storage system Download PDFInfo
- Publication number
- CN116879776A CN116879776A CN202310843128.3A CN202310843128A CN116879776A CN 116879776 A CN116879776 A CN 116879776A CN 202310843128 A CN202310843128 A CN 202310843128A CN 116879776 A CN116879776 A CN 116879776A
- Authority
- CN
- China
- Prior art keywords
- battery
- soc
- energy storage
- iron phosphate
- storage system
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
Classifications
-
- 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
-
- 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]
- G01R31/374—Arrangements for testing, measuring or monitoring the electrical condition of accumulators or electric batteries, e.g. capacity or state of charge [SoC] with means for correcting the measurement for temperature or ageing
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/36—Arrangements for testing, measuring or monitoring the electrical condition of accumulators or electric batteries, e.g. capacity or state of charge [SoC]
- G01R31/389—Measuring internal impedance, internal conductance or related variables
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Secondary Cells (AREA)
Abstract
The invention discloses a lithium iron phosphate battery energy storage system SOC estimation method, which comprises the following steps of S1: through carrying out discharge test on the lithium iron phosphate battery, estimating an initial value of the SOC by using an open circuit voltage method; s2: taking the influence of battery aging factors and temperature factors into consideration, and predicting the SOC change by using a corrected ampere-hour integration method; s3: combining the estimation methods of the step S1 and the step S2, and comprehensively estimating the SOC value of the energy storage system; comprehensively considering the influence of battery aging factors and temperature factors, and providing a corrected ampere-hour integration method to estimate the SOC of the battery; when the system is in a standby state, determining an initial SOC value of the system according to an open circuit voltage method; when the system is in a working state, the SOC value of the battery is estimated in real time by utilizing a corrected ampere-hour integration method; therefore, the SOC value of the battery can be estimated more accurately, and the safety of the battery is guaranteed.
Description
Technical Field
The invention belongs to the technical field of new energy and energy conservation, and particularly relates to an SOC estimation method of a lithium iron phosphate battery energy storage system.
Background
At present, the capacity of the energy storage market in China is steadily increased, the electrochemical energy storage share is obviously increased, and the energy storage scale of the lithium battery is over nine times. The advantages of the lithium battery are obvious, the energy density and the efficiency are high, the response is quick, but the current cost is high, along with the rapid reduction of the manufacturing cost of the lithium battery, the electrochemical energy storage requirement is also continuously increased, and the lithium battery is expected to gradually replace the market share of pumped storage. This requires the battery management system to accurately perform SOC estimation, and if the SOC estimation deviation is too large, it may cause the battery to be overcharged or overdischarged, which not only affects the life of the battery, but also presents a safety risk.
Disclosure of Invention
The invention aims to provide an SOC estimation method for an energy storage system of a lithium iron phosphate battery, which aims to solve the problems in the background technology.
In order to achieve the above purpose, the present invention provides the following technical solutions: the SOC estimation method of the lithium iron phosphate battery energy storage system comprises the following steps:
s1: through carrying out discharge test on the lithium iron phosphate battery, estimating an initial value of the SOC by using an open circuit voltage method;
s2: taking the influence of battery aging factors and temperature factors into consideration, and predicting the SOC change by using a corrected ampere-hour integration method;
s3: and (3) combining the estimation methods of the step S1 and the step S2, and comprehensively estimating the SOC value of the energy storage system.
Preferably, in step S1, the battery is placed in a constant temperature environment at 25 ℃, and is kept stand for 30 minutes before constant current discharge, the discharge process is divided into 50 sections, the discharge electric quantity is 0.02 times of the battery limit capacity each time, and is kept stand for 30 minutes after each discharge, and an open circuit voltage value is recorded after the voltage is stable; discrete data obtained by a high-order polynomial fitting experiment are utilized to obtain a functional relation between open-circuit voltage and SOC;
the higher order polynomial formula is:
U＝A 0 ·SOC n +A 1 ·SOC n-1 +A 2 ·SOC n-2 +…++A n-1 ·SOC+A n (n≥5)。
preferably, in step S2, the ampere-hour integration method does not consider the influence of other factors, and only considers the input and output of the battery, and the expression is as follows:
in the above formula, I (t) is an instantaneous current of current charge and discharge, and is greater than 0 when discharging and less than 0 when charging.
Preferably, in step S2, the aging factor is corrected:
the aging coefficient k of the battery is estimated by utilizing the internal resistance change rule, and the expression is as follows:
wherein R is 0 Is the initial internal resistance of the battery, R is the real-time internal resistance of the battery, R t Is the aging internal resistance of the battery;
the ampere-hour integral formula after the aging correction is:
preferably, in step S2, the temperature factor is corrected;
the empirical formula of battery temperature and battery capacity is as follows:
Q T ＝Q 25 ·[1+m T ·(T-25)]
wherein Q is T For the corresponding battery capacity at temperature T, Q 25 For battery capacity at a temperature of 25 ℃, i.e. rated capacity, m T For the temperature coefficient, generally 0.006-0.008 is adopted.
Let k T ＝[1+m T ·(T-25)] -1 The final corrected SOC estimation formula is:
preferably, in step S3, when the system is in a standby state, determining an initial SOC value of the system according to an open circuit voltage method, and measuring parameters such as internal resistance of the battery; when the system is in a working state, the SOC value of the battery is estimated in real time by using the corrected ampere-hour integration method.
Compared with the prior art, the invention has the beneficial effects that: comprehensively considering the influence of battery aging factors and temperature factors, and providing a corrected ampere-hour integration method to estimate the SOC of the battery;
when the system is in a standby state, determining an initial SOC value of the system according to an open circuit voltage method; when the system is in a working state, the SOC value of the battery is estimated in real time by utilizing a corrected ampere-hour integration method; therefore, the SOC value of the battery can be estimated more accurately, and the safety of the battery is guaranteed.
Drawings
FIG. 1 is a flow chart of SOC estimation according to the present invention;
FIG. 2 is a polynomial fit plot of a certain SOC-U curve 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.
Referring to fig. 1 to 2, the present invention provides a technical solution: the SOC estimation method of the lithium iron phosphate battery energy storage system comprises the following steps:
s1: through carrying out discharge test on the lithium iron phosphate battery, estimating an initial value of the SOC by using an open circuit voltage method;
in this embodiment, preferably, in step S1, the battery is placed in a constant temperature environment at 25 ℃, and is kept stand for 30 minutes before constant current discharge, the discharge process is divided into 50 segments, the discharge electric quantity is 0.02 times of the battery limit capacity each time, and is kept stand for 30 minutes after each discharge, and the open circuit voltage value is recorded after the voltage is stable. And obtaining a functional relation between the open-circuit voltage and the SOC by utilizing discrete data obtained by a high-order polynomial fitting experiment.
The higher order polynomial formula is:
U＝A 0 ·SOC n +A 1 ·SOC n-1 +A 2 ·SOC n-2 +…++A n-1 ·SOC+A n (n≥5)
as shown in fig. 2, a polynomial fitting of a certain SOC-U curve is adopted, and by comparing several fitting curves, the one with better fitting degree can be obtained, so that the accuracy of SOC initial value estimation can be improved to a certain extent;
ambient temperature has less effect on the SOC-U curve and is therefore negligible in engineering applications. The open-circuit voltage of the battery under any SOC can be calculated through the corresponding relation of the SOC-U function, an SOC-U two-dimensional corresponding table is manufactured, and the static SOC value of the battery is determined according to the voltage lookup table;
s2: taking the influence of battery aging factors and temperature factors into consideration, and predicting the SOC change by using a corrected ampere-hour integration method;
in step S2, the conventional ampere-hour integration method does not consider the influence of other factors, only considers the input and output of the battery, and its expression is:
in the above formula, I (t) is an instantaneous current of current charge and discharge, and is greater than 0 when discharging and less than 0 when charging. The method only considers the current magnitude, and does not consider the influence of external environment change and working state change on SOC estimation.
In the use process of the battery, the battery is aged gradually along with the increase of the use time and the cycle times, the rated capacity is smaller and smaller, and if the battery is estimated according to the constant capacity, the estimation error of the SOC is larger and larger. In addition, temperature affects the electrochemical reaction process, and the charge-discharge process of the battery is actually an electrochemical reaction of the materials inside the battery, so that a change in temperature also affects the actual usable capacity of the battery. Therefore, in order to reduce the estimation error, the influence of these aspects needs to be taken into consideration, thereby correcting the algorithm.
(1) And (3) ageing degree factor correction:
with the use of batteries, aging of the batteries is unavoidable and irreversible. Aging of the battery affects estimation of the battery SOC, and therefore correction of the aging coefficient k is required at the time of SOC estimation.
Research shows that as a lithium battery ages, the internal resistance of the lithium battery also changes regularly, so that the aging coefficient k of the battery can be estimated by utilizing the rule, and the expression is as follows:
wherein R is 0 Is the initial internal resistance of the battery, R is the real-time internal resistance of the battery, R t Is the aging internal resistance of the battery. All three parameters can be measured by experiments, but the real-time internal resistance can only be measured when the battery is in a static state, and the measurement error is large during working.
The ampere-hour integral formula after the aging correction is:
(2) Temperature factor correction:
ambient temperature has a large influence on SOC estimation, and the activity of the internal materials of the battery changes with temperature, thereby affecting the migration of ions inside the battery and the capacity of the battery. The empirical formula describing battery temperature and battery capacity is shown below:
Q T ＝Q 25 ·[1+m T ·(T-25)]
wherein Q is T For the corresponding battery capacity at temperature T, Q 25 For battery capacity at a temperature of 25 ℃, i.e. rated capacity, m T For the temperature coefficient, generally 0.006-0.008 is adopted.
Order theThe final corrected SOC estimation formula is:
s3: combining the estimation methods of the step S1 and the step S2, and comprehensively estimating the SOC value of the energy storage system;
in this embodiment, preferably, in step S3, the integrated estimation flow of the battery SOC is shown in fig. 1, and when the system is in a standby state, an initial SOC value of the system is determined according to an open circuit voltage method, and parameters such as internal resistance of the battery are measured; when the system is in a working state, the SOC value of the battery is estimated in real time by using the corrected ampere-hour integration method.
Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made therein without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.
Claims (6)
1. The SOC estimation method for the lithium iron phosphate battery energy storage system is characterized by comprising the following steps of: the method comprises the following steps:
s1: through carrying out discharge test on the lithium iron phosphate battery, estimating an initial value of the SOC by using an open circuit voltage method;
s2: taking the influence of battery aging factors and temperature factors into consideration, and predicting the SOC change by using a corrected ampere-hour integration method;
s3: and (3) combining the estimation methods of the step S1 and the step S2, and comprehensively estimating the SOC value of the energy storage system.
2. The method for estimating SOC of a lithium iron phosphate battery energy storage system according to claim 1, wherein: in the step S1, the battery is placed in a constant temperature environment at 25 ℃, kept stand for 30 minutes before constant current discharge, the discharge process is divided into 50 sections, the discharge electric quantity is 0.02 times of the battery limit capacity each time, kept stand for 30 minutes after each discharge, and the open circuit voltage value is recorded after the voltage is stable; discrete data obtained by a high-order polynomial fitting experiment are utilized to obtain a functional relation between open-circuit voltage and SOC;
the higher order polynomial formula is:
U＝A 0 ·SOC n +A 1 ·SOC n-1 +A 2 ·SOC n-2 +…++A n-1 ·SOC+A n (n≥5)。
3. the method for estimating SOC of a lithium iron phosphate battery energy storage system according to claim 1, wherein: in step S2, the ampere-hour integration method does not consider the influence of other factors, and when only the input and output of the battery are considered, the expression is as follows:
in the above formula, I (t) is an instantaneous current of current charge and discharge, and is greater than 0 when discharging and less than 0 when charging.
4. The method for estimating SOC of a lithium iron phosphate battery energy storage system according to claim 3, wherein: in step S2, the aging factor is corrected:
the aging coefficient k of the battery is estimated by utilizing the internal resistance change rule, and the expression is as follows:
wherein R is 0 Is the initial internal resistance of the battery, R is the real-time internal resistance of the battery, R t Is the aging internal resistance of the battery;
the ampere-hour integral formula after the aging correction is:
5. the method for estimating SOC of a lithium iron phosphate battery energy storage system according to claim 4, wherein: in step S2, temperature factor correction is performed;
the empirical formula of battery temperature and battery capacity is as follows:
Q T ＝Q 25 ·[1+m T ·(T-25)]
wherein Q is T For the corresponding battery capacity at temperature T, Q 25 Corresponding to a temperature of 25 DEG CBattery capacity, i.e. rated capacity, m T For the temperature coefficient, generally 0.006-0.008 is adopted.
Let k T ＝[1+m T ·(T-25)] -1 The final corrected SOC estimation formula is:
6. the method for estimating SOC of a lithium iron phosphate battery energy storage system according to claim 5, wherein: in step S3, when the system is in a standby state, determining an initial SOC value of the system according to an open-circuit voltage method, and measuring parameters such as internal resistance of a battery; when the system is in a working state, the SOC value of the battery is estimated in real time by using the corrected ampere-hour integration method.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202310843128.3A CN116879776A (en) | 2023-07-11 | 2023-07-11 | SOC estimation method for lithium iron phosphate battery energy storage system |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202310843128.3A CN116879776A (en) | 2023-07-11 | 2023-07-11 | SOC estimation method for lithium iron phosphate battery energy storage system |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN116879776A true CN116879776A (en) | 2023-10-13 |
Family
ID=88267453
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202310843128.3A Withdrawn CN116879776A (en) | 2023-07-11 | 2023-07-11 | SOC estimation method for lithium iron phosphate battery energy storage system |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN116879776A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN117783907A (en) * | 2023-12-29 | 2024-03-29 | 河北工程大学 | An electric vehicle power lithium battery SOC estimation method and system |
-
2023
- 2023-07-11 CN CN202310843128.3A patent/CN116879776A/en not_active Withdrawn
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN117783907A (en) * | 2023-12-29 | 2024-03-29 | 河北工程大学 | An electric vehicle power lithium battery SOC estimation method and system |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN109856559B (en) | A method for predicting the cycle life of lithium batteries | |
| US10353009B2 (en) | Secondary battery capacity measuring system and secondary battery capacity measuring method | |
| CN109143102B (en) | Method for estimating SOC (state of charge) of lithium battery through ampere-hour integration | |
| CN107991623A (en) | It is a kind of to consider temperature and the battery ampere-hour integration SOC methods of estimation of degree of aging | |
| CN107196371B (en) | Battery charging method, device, equipment and storage medium | |
| CN110967637B (en) | Method, device, system and storage medium for estimating allowable power of battery | |
| CN104849675A (en) | Method for obtaining electrochemical and thermal coupling models of lithium ion battery | |
| CN112415411A (en) | Method and apparatus for estimating SOC of battery, vehicle, and storage medium | |
| CN112816893B (en) | Method for rapidly estimating capacity of battery pack based on residual charging capacity of battery pack monomer | |
| CN112213659B (en) | Battery capacity correction method and test system | |
| CN110794314A (en) | Method for improving lithium ion battery capacity test accuracy | |
| CN105807168A (en) | Method for correcting supercapacitor SOC estimation | |
| CN107843847A (en) | A kind of battery SOC estimation online methods based on EKF algorithms | |
| CN104051810A (en) | Rapid correction method for SOC (state of charge) estimation of energy storage lithium ion battery system | |
| CN107817448B (en) | Method for online real-time monitoring of battery electric quantity suitable for complex working conditions | |
| CN113777501A (en) | SOH estimation method of battery module | |
| CN110133510B (en) | A Hybrid Estimation Method for State of Charge (SOC) of Li-ion Batteries | |
| CN112986828A (en) | Method for estimating health degree of battery | |
| CN118226262A (en) | Battery state of charge estimation method and device, energy storage power station and storage medium | |
| CN116879776A (en) | SOC estimation method for lithium iron phosphate battery energy storage system | |
| CN113075558B (en) | Battery SOC estimation method, device and system | |
| CN115480164A (en) | Module capacity prediction method, device, equipment and medium for matching battery cells | |
| CN114879053A (en) | Method for predicting service life of energy storage lithium iron phosphate battery | |
| CN115201700A (en) | Method and system for measuring battery entropy thermal coefficient | |
| CN113836471B (en) | Method and system for estimating maximum dischargeable capacity of lithium ion battery |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| WW01 | Invention patent application withdrawn after publication | ||
| WW01 | Invention patent application withdrawn after publication |
Application publication date: 20231013 |