CN107576918B - Method and system for estimating residual electric quantity of lithium battery - Google Patents
Method and system for estimating residual electric quantity of lithium battery Download PDFInfo
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Abstract
The invention discloses a residual electric quantity of a lithium batteryThe method comprises the following steps: s1And judging the working mode of the lithium battery at regular time, and if the working mode is the charging mode, executing the step S21If the discharge mode is selected, step S is executed22；S21Judging whether the chargeable capacity change rate of the lithium battery reaches a wave crest or a wave trough, if so, executing the step S3If not, executing step S22；S22Calculating the current SOC value by adopting an ampere-hour integration method, and executing the step S4；S3Calculating the current SOC value by adopting an ampere-hour integration method, and using the SOCpCorrecting the value of the current SOC, SOCpThe SOC value of the extreme point corresponding to the chargeable capacity change rate of the lithium battery at the peak or the trough is obtained; s4And outputting the current SOC value. The method is simple and easy to implement, has small calculation amount, and can effectively improve the estimation precision of the SOC on the premise of not increasing the existing hardware condition.
Description
Technical Field
The invention relates to the technical field of battery management of lithium batteries for energy storage, in particular to a method and a system for estimating the residual electric quantity of a lithium battery.
Background
The BMS (Battery Management System) is used as key equipment in the energy storage System, can effectively avoid the influence of the problems of Battery overcharge, overdischarge, over-temperature, grouping inconsistency and the like on the safety and the service life of the Battery, fully exerts the energy storage performance of the lithium Battery and reduces the operation cost of energy storage. The SOC (State of Charge) as a representation of the remaining battery capacity is an important parameter of the control strategy of the battery management system, provides a judgment standard for the whole control strategy, and will directly affect the working performance of the battery. Accurate estimation and monitoring of the SOC are important from the viewpoint of safety and battery use efficiency. At present, SOC estimation at home and abroad is still in a development stage, a plurality of new methods are endless, and although estimation accuracy can be improved to a great extent, due to complex calculation, the high-accuracy estimation requirement of a lithium battery in real-time online states such as a charging and discharging state and the like is difficult to meet.
The lithium titanate battery is one of lithium ion batteries and has wide application in the field of energy storage. Due to the limitation of the hardware condition of the battery management system, the SOC estimation of the lithium titanate battery still adopts a mode of combining the Open Circuit Voltage (OCV) method and the ampere-hour integration method which are commonly used. The open circuit voltage method is to estimate SOC based on OCV-SOC curve, but requires the battery to be left for a long enough time to have a high accuracy after the battery reaches a steady state. The ampere-hour integration method is the most extensive and simple estimation method, and carries out integration operation on the charging and discharging current of the battery to time, and then dynamically estimates the SOC value of the battery. After the battery is operated for a long time, the SOC error accumulated by the ampere-hour integration method is large, and the SOC is usually corrected by using the open-circuit voltage after the battery is sufficiently stationary.
In the prior art, when a lithium titanate battery runs stably and has enough standing time, the SOC can be simply and effectively estimated. However, in the actual operation process, because the working condition of the energy storage lithium battery is complex and the lithium battery rarely has a long-time standing condition, the open-circuit voltage cannot be effectively utilized to correct the SOC calculation error accumulated by the ampere-hour integration method, so that the SOC estimation precision is greatly reduced, and the safe operation of the battery and even the whole energy storage system is influenced.
Disclosure of Invention
The invention aims to overcome the defect of low SOC estimation precision of a lithium battery for energy storage in real time online in the prior art, and provides a method and a system for estimating the residual electric quantity of the lithium battery, which can correct the accumulated error caused by long-time calculation of an ampere-hour integral method when the lithium battery is in a charging and discharging state so as to improve the SOC estimation precision of the lithium battery for energy storage in real time online.
The invention solves the technical problems through the following technical scheme:
the invention provides a method for estimating the residual electric quantity of a lithium battery, which is characterized by comprising the following steps of:
S1and judging the working mode of the lithium battery at regular time, and if the working mode is the charging mode, executing the step S21If the discharge mode is selected, step S is executed22；
S21Judging whether the chargeable capacity change rate of the lithium battery reaches a wave crest or a wave trough, if so, executing the step S3If not, executing step S22；
S22Calculating the current SOC value by adopting an ampere-hour integration method, and executing the step S4；
S3Calculating the current SOC value by adopting an ampere-hour integration method, and using the SOCpCorrecting the value of the current SOC, the SOCpThe SOC value of the extreme point corresponding to the chargeable capacity change rate of the lithium battery at the peak or the trough is obtained;
S4and outputting the current SOC value.
In the scheme, different SOC estimation methods are adopted to calculate the current SOC value according to different working modes of the lithium battery at regular time, so that the SOC estimation precision of the energy storage lithium battery in real time on line is improved. When the lithium battery is in a charging and discharging state, the accumulated error caused by long-time calculation of the ampere-hour integral method can be corrected. The scheme can adapt to SOC correction under complex working conditions of the lithium battery, and can quickly and accurately estimate the residual electric quantity of the battery under limited hardware conditions.
In the scheme, the SOC is corrected on line according to the SOC value of the extreme point when the lithium battery is selected to be in the charging mode, because the lithium battery is in a discharging state and is externally connected with various loads, the required discharging current of the lithium battery is large in change, the current of the lithium battery is not large in general change when the lithium battery is in the charging mode, and most of the lithium battery is in constant-current constant-voltage charging, so that the SOC correction in the charging mode can effectively improve the estimation accuracy of the SOC.
Preferably, the lithium battery is a lithium titanate battery.
Preferably, the value of the SOC of the extreme point is determined from historical data of the lithium battery.
In the scheme, the current charging quantity caused by the unit increment of the terminal voltage of the lithium titanate battery can reach peak values or valley values at certain SOC value points, so that the SOC value of the corresponding extreme point can be determined according to historical data after a large number of experimental tests are carried out on the lithium titanate battery.
Preferably, the chargeable capacity change rate is Δ SOC/Δ V, where Δ SOC/Δ V is an amount of electric current charged due to a unit increase in terminal voltage of the lithium battery.
Preferably, step S1When the working mode of the lithium battery is judged at medium timing, if the working mode is the standing mode, the step S is executed23；
S23Judging whether the standing time T of the lithium battery is greater than a first threshold value T or not0If yes, go to step S2301；
S2301Correcting the current SOC value by adopting an open circuit voltage method, and executing the step S4。
In the scheme, when the lithium battery is kept still for enough time, the SOC value is corrected by adopting an open-circuit voltage method so as to obtain a more accurate current SOC value.
Preferably, step S1Judging the working mode of the lithium battery at medium timing comprises judging the working mode of the lithium battery at intervals of a calculation period t;
S0setting the first cycle number n to 0, setting the second cycle number k to 0, and expressing the value of the current SOC as SOCn，SOCnIs represented as SOC value of the previous calculation cyclen-1N and k are natural numbers;
step S4Then also includes step S5；
S5N is n +1, step S is executed1；
Step S1Before also comprising a step S0；
Step S23Before the determining, setting T ═ T + T;
step S21Further comprising setting T ═ 0;
step S22Further comprising setting T ═ 0;
step S23If not, executing step S2302；
S2302And determining whether k × T is less than or equal to a second threshold value T1If yes, go to step S2303If not, executing step S2304；
S2303Setting k as k +1, setting SOCn＝SOCn-1Execute step S4；
S2304Setting k to 0, calculating SOCn＝SOCn-1+T/T0×(SOCOCV-SOCn-1) Wherein SOC isOCVFor the value of SOC obtained by open circuit voltage method, step S is executed4。
In the scheme, when the lithium battery is in the standing mode but the standing time does not reach the first threshold value, the relationship between the standing time and the second threshold value is further judged and the SOC is used as the basisOCVAnd SOCn-1The current SOC value is corrected, thereby further improving the estimation accuracy of the SOC.
Preferably, step S2301Wherein setting T ═ T is further included0。
Preferably, step S0Setting initial parameters of the lithium battery, wherein the initial parameters comprise the rated capacity C of the lithium batteryNThe calculation period T, the first threshold value T0The second threshold value T1And a value of the SOC at the extreme point; step S0Obtaining working parameters of the lithium battery, wherein the working parameters comprise the standing time T, the current I and/or the terminal voltage V;
the calculation formula of the ampere-hour integration method is SOCn＝SOCn-1+η×I×t/CNWhere η represents the charge-discharge efficiency.
In the scheme, an ampere-hour integration method is adopted to calculate the SOCnAnd then, according to the mode of the battery, the current I during charging and discharging is obtained again according to the requirement for calculation.
Preferably, the initialization isThe parameters further comprise a third threshold value, step S3The method comprises the following steps:
S31calculating the current SOC value SOC by adopting an ampere-hour integration methodn；
S32And determining | SOCn-SOCpIf | is greater than the third threshold, if yes, execute step S33If not, executing step S4；
S33Setting SOCn＝SOCpExecute step S4。
In this scheme, SOC is usedpWhen correcting the value of the current SOC, when the SOC is not in usenAnd SOCpWhen the difference between the values does not exceed a preset third threshold value, the SOC is not usedpAnd correcting, so setting makes the estimation of the SOC more scientific and reasonable.
Preferably, the OCV-SOC curve in the open circuit voltage method is obtained by fitting a Back Propagation (BP) neural network.
In the scheme, the functional relation between the open-circuit voltage OCV and the SOC adopted by the open-circuit voltage method is obtained by BP neural network fitting.
The invention also provides an estimation system of the residual electric quantity of the lithium battery, which is characterized by comprising a mode judgment module, an extreme value judgment module, a first calculation module, a second calculation module and an output module;
the mode judging module is used for regularly judging the working mode of the lithium battery, if the working mode is a charging mode, the extreme value judging module is called, and if the working mode is a discharging mode, the first calculating module is called;
the extreme value judging module is used for judging whether the chargeable capacity change rate of the lithium battery reaches a peak or a trough, if so, the second calculating module is called, and if not, the first calculating module is called;
the first calculation module is used for calculating the current SOC value by adopting an ampere-hour integration method and calling the output module;
the second calculation module is used for calculating the current SOC value by adopting an ampere-hour integration method and using the SOCpCorrection instituteThe value of the current SOC, the SOCpThe SOC value of the extreme point corresponding to the chargeable capacity change rate of the lithium battery at the peak or the trough is obtained;
the output module is used for outputting the value of the current SOC.
Preferably, the lithium battery is a lithium titanate battery.
Preferably, the value of the SOC of the extreme point is determined from historical data of the lithium battery.
Preferably, the chargeable capacity change rate is Δ SOC/Δ V, where Δ SOC/Δ V is an amount of electric current charged due to a unit increase in terminal voltage of the lithium battery.
Preferably, the estimation system further comprises a first time judgment module and a third calculation module;
the mode judging module is also used for calling the first time judging module when the working mode of the lithium battery is judged to be the standing mode at regular time;
the first time judgment module is used for judging whether the standing time T of the lithium battery is greater than a first threshold value T0If yes, calling the third calculation module;
and the third calculation module is used for correcting the current SOC value by adopting an open-circuit voltage method and calling the output module.
Preferably, the mode judging module is configured to judge the working mode of the lithium battery at regular time, including judging the working mode of the lithium battery every other calculation period t;
the estimation system also comprises a cycle execution module, a setting module, a second time judgment module, a fourth calculation module and a fifth calculation module;
the setting module is used for setting a first cycle number n to 0 and a second cycle number k to 0 before the mode judging module is called, and the value of the current SOC is represented as SOCn，SOCnIs represented as SOC value of the previous calculation cyclen-1N and k are natural numbers;
the output module is also used for calling the cycle execution module;
the loop execution module is used for setting n to n +1 and calling the mode judgment module;
the first time judgment module is further used for setting T to T + T before the judgment;
the extreme value judging module is also used for setting T to be 0;
the first calculation module is further configured to set T ═ 0;
the first time judgment module is also used for calling the second time judgment module if the first time judgment module is not used for calling the second time judgment module;
the second time judgment module is used for judging whether k × T is less than or equal to a second threshold value T1If yes, the fourth calculation module is called, and if not, the fifth calculation module is called;
the fourth calculation module is used for setting k to k +1 and setting SOCn＝SOCn-1Calling the output module;
the fifth calculation module is used for setting k to 0 and calculating the SOCn＝SOCn-1+T/T0×(SOCOCV-SOCn-1) Wherein SOC isOCVAnd calling the output module for the SOC value obtained by adopting an open-circuit voltage method.
Preferably, the third calculation module is further configured to set T ═ T0。
Preferably, the setting module is further configured to set an initial parameter of the lithium battery, where the initial parameter includes a rated capacity C of the lithium batteryNThe calculation period T, the first threshold value T0The second threshold value T1And a value of the SOC at the extreme point; the setting module is further used for obtaining working parameters of the lithium battery, wherein the working parameters comprise the standing time T, the current I and/or the terminal voltage V;
the calculation formula of the ampere-hour integration method is SOCn＝SOCn-1+η×I×t/CNWhere η represents the charge-discharge efficiency.
Preferably, the initial parameter further includes a third threshold, and the second calculation module includes a sixth calculation module, a modification judgment module, and a seventh calculation module;
the sixth calculation module is used for calculating the value SOC of the current SOC by adopting an ampere-hour integration methodnCalling the correction judgment module;
the correction judgment module is used for judging the | SOCn-SOCpIf l is larger than the third threshold, calling the seventh calculation module if l is larger than the third threshold, and otherwise calling the output module;
the seventh calculation module is used for setting the SOCn＝SOCpAnd calling the output module.
Preferably, the OCV-SOC curve in the open-circuit voltage method is obtained by fitting a BP neural network.
The positive progress effects of the invention are as follows: the method and the system for estimating the residual electric quantity of the lithium battery provided by the invention are combined with an ampere-hour integral method and an open-circuit voltage method, and can calculate the current SOC value by adopting different SOC estimation methods according to different working modes of the lithium battery at regular time. The method realizes the off-line and on-line correction of the SOC value of the lithium titanate battery by utilizing the characteristics of the lithium titanate battery, and ensures the real-time, quick and accurate estimation of the SOC of the lithium titanate battery under three working modes of standing, charging and discharging. The method is simple and easy to estimate the SOC of the lithium titanate battery, has small calculated amount, can effectively improve the estimation precision of the SOC on the premise of not increasing the existing hardware condition, fully considers the working mode of the battery, and corrects the SOC by adopting different modes.
Drawings
Fig. 1 is a flowchart of a method for estimating a remaining capacity of a lithium battery according to embodiment 1 of the present invention.
Fig. 2 is a schematic structural diagram of a system for estimating remaining capacity of a lithium battery according to embodiment 2 of the present invention.
Fig. 3 is a schematic structural diagram of a second computing module in embodiment 2 of the present invention.
Fig. 4 is a flowchart of an estimation method implemented based on embodiment 1.
FIG. 5 is a graph of a BP neural network fit OCV-SOC used in the present invention.
Detailed Description
The invention is further illustrated by the following examples, which are not intended to limit the scope of the invention.
Example 1
As shown in fig. 1, a method for estimating a remaining capacity of a lithium battery includes the steps of:
In this embodiment, the lithium battery is a lithium titanate battery. The calculation formula of the ampere-hour integration method adopts SOCn＝SOCn-1+η×I×t/CNη represents the charge and discharge efficiency, I represents the charge and discharge current, an OCV-SOC curve in the open circuit voltage method is obtained by BP neural network fitting, and the SOC value of an extreme point is determined by the historical data of the lithium battery.
In this embodiment, the working mode of the lithium titanate battery is determined every t times. And calculating the current SOC value by adopting different SOC estimation methods according to different modes. When the lithium battery is kept still for enough time, correcting the SOC value by adopting an open-circuit voltage method to obtain a more accurate current SOC value; when the lithium battery is in a standing mode but the standing time does not reach the first threshold value, further judging the relation between the standing time and the second threshold value and according to the SOCOCVAnd SOCn-1The current SOC value is corrected, thereby further improving the estimation accuracy of the SOC. When the lithium battery is selected to be in the charging mode, SOC online correction is carried out according to the SOC value of the extreme point, which is caused by the external negative pole when the lithium battery dischargesThe SOC correction method has the advantages that the SOC correction method is diversified in load, the discharge current of the required lithium battery is large in change, the current of the lithium battery is generally not large in change when the lithium battery is in the charging mode, and most of the lithium battery is charged in a constant current-constant voltage mode, so that the SOC correction can be performed in the charging mode, and the SOC estimation accuracy can be effectively improved. In addition, the current charging capacity caused by the unit increment of the terminal voltage of the lithium titanate battery can reach peak values or valley values at certain SOC value points, so that after a large number of experimental tests are carried out on the lithium titanate battery, the SOC value of the corresponding extreme point can be determined according to historical data. Using SOCpWhen correcting the value of the current SOC, when the SOC is not in usenAnd SOCpWhen the difference between the values does not exceed a preset third threshold value, the SOC is not usedpAnd correcting, so setting makes the estimation of the SOC more scientific and reasonable.
The method for estimating the remaining capacity of the lithium battery provided by the embodiment has the capability of correcting the SOC off-line and on-line, and not only can correct the remaining capacity of the lithium titanate battery when the lithium battery is in a standing state, but also can correct the accumulated error caused by long-time calculation of the ampere-hour integration method when the lithium battery is in a charging and discharging state. The method can adapt to SOC correction of the lithium titanate battery under complex working conditions, and can quickly and accurately estimate the residual capacity of the battery under limited hardware conditions.
Example 2
As shown in fig. 2, an estimation system for a remaining power of a lithium battery includes a setting module 1, a mode determining module 2, an extreme value determining module 3, a first calculating module 4, a second calculating module 5, a third calculating module 6, a fourth calculating module 7, a fifth calculating module 8, a first time determining module 9, a second time determining module 10, an output module 11, and a cycle executing module 12. The second calculating module 5 includes a sixth calculating module 501, a modification judging module 502 and a seventh calculating module 503.
The setting module 1 is configured to set the first cycle number n to 0 and the second cycle number k to 0 before the calling mode determining module 2, where a value of the current SOC is represented as the SOCn，SOCnIs represented as SOC value of the previous calculation cyclen-1N and k are natural numbers; the setting module 1 is further configured to set initial parameters of the lithium battery, the initial parameters including the lithium batteryRated capacity CNCalculating period T and first threshold value T0A second threshold value T1A third threshold value, and a value of the SOC at the extreme point.
The mode judging module 2 is used for judging the working mode of the lithium battery at intervals of a calculating period t, if the working mode is a charging mode, the extreme value judging module 3 is called, if the working mode is a discharging mode, the first calculating module 4 is called, and if the working mode is a standing mode, the first time judging module 9 is called.
The extreme value determining module 3 is configured to set T to 0, determine whether the chargeable capacity change rate of the lithium battery reaches a peak or a trough, call the second calculating module 5 if the chargeable capacity change rate of the lithium battery reaches the peak or the trough, and call the first calculating module 4 if the chargeable capacity change rate of the lithium battery does not reach the trough.
The first calculating module 4 is configured to set T to 0, calculate a current SOC value by using an ampere-hour integration method, and call the output module 11.
The second calculation module 5 is used for calculating the current SOC value by adopting an ampere-hour integration method and using the SOCpCorrecting the value of the current SOC, SOCpThe SOC value is the SOC value of the extreme point corresponding to the peak or trough of the chargeable capacity change rate of the lithium battery. The SOC value of the extreme point is determined by historical data of the lithium battery, the chargeable capacity change rate is recorded as delta SOC/delta V, and the delta SOC/delta V is the electric quantity charged by current caused by unit increase of the terminal voltage of the lithium battery.
The third calculation module 6 is used to set T ═ T0And correcting the current SOC value by adopting an open-circuit voltage method, and calling the output module 11.
The fourth calculation module 7 is configured to set k to k +1, and set the SOCn＝SOCn-1The output module 11 is called.
A fifth calculating module 8 is used for setting k to 0 and calculating SOCn＝SOCn-1+T/T0×(SOCOCV-SOCn-1) Wherein SOC isOCVThe output module 11 is called for the SOC value obtained by the open circuit voltage method.
The sixth calculating module 501 is configured to calculate the current SOC value SOC by using an ampere-hour integration methodnThe modification determination module 502 is invoked.
The correction judgment module 502 is used for judging the | SOCn-SOCpIf l is greater than the third threshold, if so, the seventh calculation module 503 is invoked, otherwise, the output module 11 is invoked.
The seventh calculation module 503 is used for setting the SOCn＝SOCpThe output module 11 is called.
The first time determination module 9 is configured to set T ═ T + T, and determine whether the standing time T of the lithium battery is greater than a first threshold T0If yes, the third calculation module 6 is called, and if not, the second time judgment module 10 is called.
The second time judgment module 10 is used for judging whether k × T is less than or equal to a second threshold T1If yes, the fourth calculation module 7 is called, otherwise, the fifth calculation module 8 is called.
The output module 11 is used for outputting the current SOC value and calling the loop execution module 12.
The loop execution module 12 is configured to set n to n +1, and call the mode determination module 2.
In this embodiment, the lithium battery is a lithium titanate battery; the calculation formula of the ampere-hour integration method adopts SOCn＝SOCn-1+η×I×t/CNWherein η represents the charge-discharge efficiency, I represents the charge-discharge current, and the OCV-SOC curve in the open-circuit voltage method is obtained by adopting BP neural network fitting.
The following further illustrates the technical solutions and effects of the present invention by means of specific examples.
As shown in fig. 3, the present example realizes estimation of SOC of a lithium titanate battery based on the estimation method of remaining capacity of a lithium battery provided in embodiment 1, and specifically includes the following steps:
(1) electrifying the battery, and setting initial parameters of SOC estimation of the lithium battery, including rated capacity CN20Ah (ampere hour), SOC calculation period T is 1s (second), and standing time is first threshold value T01h (hour), standing time second threshold value T115min (min), the SOC value corresponding to the Delta SOC/Delta V trough point is 60%, and the working parameters of the battery are obtained, including the current working mode of the battery, the standing time T of the battery, and the SOC at the last calculation periodn-1Current I, battery terminal voltage V.
(2) Set n to 0, k to 0, and initialize the SOC. At this time, the open-circuit voltage OCV is considered to be V, and referring to fig. 5, the initial SOC is directly obtained from the OCV-SOC function fitted by the neural network0And SOCn-1＝SOC0。
(3) Setting n to be n +1, judging the working mode of the lithium battery, if the working mode of the battery is standing, setting the standing time T to be T +1, and entering the step (4); if the working mode is discharging, setting the set standing time T to be 0, and entering the step (5); and if the working mode is charging, setting the set standing time T to be 0, and simultaneously judging whether the delta SOC/delta V reaches the valley point, if so, entering the step (6), otherwise, entering the step (5).
(4) Open circuit voltage OCV is equal to V, and whether the set time T is longer than the set time T is judged0. If T>T0If T is equal to T0Directly obtaining SOC according to OCV-SOC functional relation fitted by neural networknEntering the step (7); if T is less than or equal to T0And (k × T) is less than or equal to T1If k is k +1, and go to step (7); if T is less than or equal to T0And (k × t)>T1According to the previous time SOCn-1SOC obtained from OCV-SOC functional relationshipOCVAnd T, T0Calculating the current SOCnI.e. SOCn＝SOCn-1+T/T0×(SOCOCV-SOCn-1) K is 0 and proceeds to step (7).
(5) Calculate SOC as followsn，SOCn＝SOCn-1+η×I×t/CN。
(6) If SOCn-60％|>5% of the total SOC n60%, otherwise SOCnAnd (5) if the state is not changed, entering the step (7).
(7) And (4) outputting the SOC and continuing to operate in the step (3).
The method is simple and easy to estimate the SOC of the lithium titanate battery, has small calculated amount, can effectively improve the estimation precision of the SOC on the premise of not increasing the existing hardware condition, fully considers the working mode of the battery, corrects the SOC by adopting different modes, and is more scientific and reasonable.
While specific embodiments of the invention have been described above, it will be appreciated by those skilled in the art that this is by way of example only, and that the scope of the invention is defined by the appended claims. Various changes and modifications to these embodiments may be made by those skilled in the art without departing from the spirit and scope of the invention, and these changes and modifications are within the scope of the invention.
Claims (18)
1. A method for estimating the remaining capacity of a lithium battery is characterized by comprising the following steps:
S1judging the working mode of the lithium battery at regular time, and if the working mode is the charging mode, executing the step S21If the discharge mode is selected, step S is executed22；
S21Judging whether the chargeable capacity change rate of the lithium battery reaches a peak or a trough, if so, executing the step S3If not, executing step S22；
The chargeable capacity change rate is delta SOC/delta V, wherein the delta SOC/delta V is the electric quantity charged by current caused by unit increase of the terminal voltage of the lithium battery;
S22calculating the current SOC value by adopting an ampere-hour integration method, and executing the step S4；
S3Calculating the current SOC value by using an ampere-hour integration method, and using the SOCpCorrecting the value of the current SOC, the SOCpThe SOC value of the extreme point corresponding to the chargeable capacity change rate of the lithium battery at the peak or the trough is obtained;
S4outputting the value of the current SOC.
2. The method for estimating the remaining capacity of a lithium battery according to claim 1, wherein the lithium battery is a lithium titanate battery.
3. The method for estimating the remaining capacity of a lithium battery according to claim 1, wherein the value of the SOC at the extreme point is determined from historical data of the lithium battery.
4. The method for estimating remaining capacity of lithium battery as claimed in claim 1, wherein the step S1When the working mode of the lithium battery is judged at medium timing, if the working mode is the standing mode, the step S is executed23；
S23Judging whether the standing time T of the lithium battery is greater than a first threshold value T0If yes, go to step S2301；
S2301Correcting the current SOC value by adopting an open circuit voltage method, and executing the step S4。
5. The method of estimating the remaining capacity of a lithium battery according to claim 4,
step S1Judging the working mode of the lithium battery at medium timing comprises judging the working mode of the lithium battery at intervals of a calculation period t;
step S1Before also comprising a step S0；
S0Setting the first number of cycles n to 0 and the second number of cycles k to 0, the value of the current SOC being expressed as SOCn，SOCnIs represented as SOC value of the previous calculation cyclen-1N and k are natural numbers;
step S4Then also includes step S5；
S5N is n +1, step S is performed1；
Step S23Before the determining, setting T ═ T + T;
step S21Further comprising setting T ═ 0;
step S22Further comprising setting T ═ 0;
step S23If not, executing step S2302；
S2302Determine whether k × T is less than or equal to a second threshold value T1If yes, go to step S2303If not, executing step S2304；
S2303Is provided withSet k to k +1, set SOCn＝SOCn-1Execute step S4；
S2304Set k to 0, calculate SOCn＝SOCn-1+T/T0×(SOCOCV-SOCn-1) Wherein SOC isOCVFor the value of SOC obtained by open circuit voltage method, step S is executed4。
6. The method for estimating remaining capacity of lithium battery as claimed in claim 5, wherein the step S2301Wherein setting T ═ T is further included0。
7. The method of estimating the remaining capacity of a lithium battery according to claim 6,
step S0Setting initial parameters of the lithium battery, wherein the initial parameters comprise the rated capacity C of the lithium batteryNThe calculation period T, the first threshold value T0The second threshold value T1And a value of the SOC at the extreme point; step S0Obtaining working parameters of the lithium battery, wherein the working parameters comprise the standing time T, the current I and/or the terminal voltage V;
the calculation formula of the ampere-hour integration method is SOCn＝SOCn-1+η×I×t/CNWhere η represents the charge-discharge efficiency.
8. The method for estimating remaining capacity of lithium battery as claimed in claim 7, wherein the initial parameter further includes a third threshold value, step S3The method comprises the following steps:
S31calculating the current SOC value SOC by adopting an ampere-hour integration methodn；
S32Judge | SOCn-SOCpIf | is greater than the third threshold, if yes, execute step S33If not, executing step S4；
S33Setting SOCn＝SOCpExecute step S4。
9. The method for estimating the remaining capacity of a lithium battery according to any one of claims 4 to 8, wherein an OCV-SOC curve in the open circuit voltage method is fitted by a BP neural network.
10. The system for estimating the residual electric quantity of the lithium battery is characterized by comprising a mode judgment module, an extreme value judgment module, a first calculation module, a second calculation module and an output module;
the mode judging module is used for regularly judging the working mode of the lithium battery, if the working mode is a charging mode, the extreme value judging module is called, and if the working mode is a discharging mode, the first calculating module is called;
the extreme value judging module is used for judging whether the chargeable capacity change rate of the lithium battery reaches a peak or a trough, if so, the second calculating module is called, and if not, the first calculating module is called;
the chargeable capacity change rate is delta SOC/delta V, wherein the delta SOC/delta V is the electric quantity charged by current caused by unit increase of the terminal voltage of the lithium battery;
the first calculation module is used for calculating the current SOC value by adopting an ampere-hour integration method and calling the output module;
the second calculation module is used for calculating the current SOC value by adopting an ampere-hour integration method and using the SOCpCorrecting the value of the current SOC, the SOCpThe SOC value of the extreme point corresponding to the chargeable capacity change rate of the lithium battery at the peak or the trough is obtained;
the output module is used for outputting the value of the current SOC.
11. The system for estimating a remaining capacity of a lithium battery as claimed in claim 10, wherein the lithium battery is a lithium titanate battery.
12. The system for estimating a remaining capacity of a lithium battery as claimed in claim 10, wherein the value of the SOC at the extreme point is determined from historical data of the lithium battery.
13. The system for estimating a remaining capacity of a lithium battery as claimed in claim 10, further comprising a first time judgment module and a third calculation module;
the mode judging module is also used for calling the first time judging module when the working mode of the lithium battery is judged to be the standing mode at regular time;
the first time judgment module is used for judging whether the standing time T of the lithium battery is greater than a first threshold value T0If yes, calling the third calculation module;
and the third calculation module is used for correcting the current SOC value by adopting an open-circuit voltage method and calling the output module.
14. The system for estimating a remaining capacity of a lithium battery according to claim 13,
the mode judging module is used for judging the working mode of the lithium battery at regular time, and comprises the step of judging the working mode of the lithium battery at intervals of a calculation period t;
the estimation system also comprises a cycle execution module, a setting module, a second time judgment module, a fourth calculation module and a fifth calculation module;
the setting module is used for setting a first cycle number n to 0 and a second cycle number k to 0 before the mode judging module is called, and the value of the current SOC is represented as SOCn，SOCnIs represented as SOC value of the previous calculation cyclen-1N and k are natural numbers;
the output module is also used for calling the cycle execution module;
the loop execution module is used for setting n to n +1 and calling the mode judgment module;
the first time judgment module is further used for setting T to T + T before the judgment;
the extreme value judging module is also used for setting T to be 0;
the first calculation module is further configured to set T ═ 0;
the first time judgment module is also used for calling the second time judgment module if the first time judgment module is not used for calling the second time judgment module;
the second time judgment module is used for judging whether k × T is less than or equal to a second threshold value T1If yes, the fourth calculation module is called, and if not, the fifth calculation module is called;
the fourth calculation module is used for setting k to k +1 and setting SOCn＝SOCn-1Calling the output module;
the fifth calculation module is used for setting k to 0 and calculating the SOCn＝SOCn-1+T/T0×(SOCOCV-SOCn-1) Wherein SOC isOCVAnd calling the output module for the SOC value obtained by adopting an open-circuit voltage method.
15. The system for estimating remaining capacity of lithium battery as claimed in claim 14, wherein said third calculation module is further configured to set T-T0。
16. The system for estimating a remaining capacity of a lithium battery according to claim 15,
the setting module is further used for setting initial parameters of the lithium battery, and the initial parameters comprise the rated capacity C of the lithium batteryNThe calculation period T, the first threshold value T0The second threshold value T1And a value of the SOC at the extreme point; the setting module is further used for obtaining working parameters of the lithium battery, wherein the working parameters comprise the standing time T, the current I and/or the terminal voltage V;
the calculation formula of the ampere-hour integration method is SOCn＝SOCn-1+η×I×t/CNWhere η represents the charge-discharge efficiency.
17. The system for estimating a remaining capacity of a lithium battery as claimed in claim 16, wherein the initial parameter further includes a third threshold, and the second calculation module includes a sixth calculation module, a correction judgment module, and a seventh calculation module;
the sixth calculation module is used for calculating the value SOC of the current SOC by adopting an ampere-hour integration methodnCalling the correction judgment module;
the correction judgment module is used for judging the | SOCn-SOCpIf l is larger than the third threshold, calling the seventh calculation module if l is larger than the third threshold, and otherwise calling the output module;
the seventh calculation module is used for setting the SOCn＝SOCpAnd calling the output module.
18. The system for estimating a remaining capacity of a lithium battery according to any one of claims 13 to 17, wherein an OCV-SOC curve in the open circuit voltage method is fitted by a BP neural network.
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