CN115113063A - Method and device for predicting branch current balance in battery system - Google Patents
Method and device for predicting branch current balance in battery system Download PDFInfo
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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
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
- G01D21/00—Measuring or testing not otherwise provided for
- G01D21/02—Measuring two or more variables by means not covered by a single other subclass
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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]
- G01R31/389—Measuring internal impedance, internal conductance or related variables
Abstract
The invention provides a method and a device for predicting branch current balance in a battery system, wherein the prediction method at least comprises the following steps: firstly, acquiring the operation data of a current normally-operated battery system in a set time period; then obtaining the average direct current internal resistance of each battery pack in the battery system according to the operation data; and finally, analyzing according to the average direct current internal resistance of all battery packs in the battery system to obtain the balance prediction result of each branch current in the battery system. The invention can perform accurate pre-detection on whether the current of each branch in the battery system is balanced in advance, generate early warning when the current is unbalanced, and automatically output a maintenance scheme, thereby effectively saving the time and energy consumed by field investigation and test of after-sales personnel.
Description
Technical Field
The present invention relates to battery technologies, and in particular, to a method and an apparatus for predicting branch current balance in a battery system.
Background
After being grouped, the lithium ion battery cells are usually loaded in a vehicle or an energy storage system in a parallel or series-parallel mode, however, because of the temperature difference caused by the difference of the positions of different battery packs under the actual condition, or the battery cells of the battery cells inevitably have inconsistency to a certain extent during batch production, the internal resistance of different branches in the battery system is caused to be different, so that the current difference of different branches is large during working, and the service life of the whole battery system can be greatly reduced under the condition that the current difference of different branches is large for a long time.
The current difference of different branches in the battery system is too large and mainly caused by the internal resistance difference of battery packs of different branches, fault diagnosis needs to be carried out on the current difference, however, in the current method for determining the fault, after the fault occurs, after-sales personnel generally call the latest operation data of each battery pack after the fault of the system one by one on the site, the internal resistance difference of different branches is manually analyzed, and finally a solution is provided. This approach has certain limitations: (1) manual analysis is time-consuming and labor-consuming, and misjudgment is caused to a certain extent; (2) the failure can not be predicted in advance, thereby affecting the working efficiency of the battery system.
Disclosure of Invention
In view of the above-mentioned shortcomings of the prior art, an object of the present invention is to provide a method and an apparatus for predicting branch current balance in a battery system, which are used to solve the problem in the prior art that the risk cannot be predicted in advance by the post-failure judgment.
To achieve the above and other related objects, the present invention provides a method for predicting branch current balance in a battery system, the method at least comprising:
acquiring operation data of a current normally-operated battery system in a set time period; the operation data comprises the voltage and the temperature of the battery pack and the current of each branch circuit at each moment;
obtaining the average direct current internal resistance of each battery pack in the battery system according to the operation data;
and analyzing according to the average direct current internal resistance of all battery packs in the battery system to obtain the balance prediction result of each branch current in the battery system.
Preferably, the method for obtaining the average direct current internal resistance of each battery pack in the battery system according to the operation data comprises the following steps:
obtaining a plurality of current stabilization periods according to the operating data;
and processing the stable stage data of each current stable period to obtain the average direct current internal resistance of each battery pack.
Preferably, the current stabilization period refers to a first current stabilization variation period which meets a set condition after each shelving; the setting conditions are as follows:
(1) the difference between the starting time and the ending time of the first current stable change time period is less than or equal to a set threshold value;
(2) the absolute value of the change of the total branch current in the first current stable change period is greater than the set current value;
(3) the absolute value of the change of the branch voltage in the first current stable change period is greater than 0;
(4) the number ratio of the different sign points in the current change rate array in the first current stable change period is less than or equal to a set value; wherein the different sign points comprise positive number points and negative number points.
Preferably, the calculation mode of the different sign point is as follows:
wherein Np is the number of positive points, Nn is the number of negative points, and w is an element [0,1 ].
Preferably, deriving a plurality of current stabilization periods from the operational data comprises:
selecting a first current stable change time period after each time of shelving from operation data;
judging and processing the operation data of each primary current stable change time period according to set conditions to obtain a plurality of stable phase data;
and taking the time sequence corresponding to each stable phase data as a current stable time.
Preferably, the processing the stable period data of each current stable period to obtain the average dc internal resistance of each battery pack includes:
processing the stability phase data of each current stability time period to obtain the corresponding direct current internal resistance of each battery pack;
and obtaining the average direct current internal resistance of each battery pack according to the direct current internal resistances of all the battery packs.
Preferably, the result of the balance prediction of the current of each branch in the battery system obtained by analyzing the average direct current internal resistance of all the battery packs in the battery system is as follows:
and obtaining branch direct-current internal resistance range differences of all branches in the battery system and branch direct-current internal resistance standard differences of all branches in the battery system according to the average direct-current internal resistance of all battery packs in the battery system, and obtaining a balance prediction result of the current of each branch in the battery system according to the branch direct-current internal resistance range differences of all branches in the battery system and a first set threshold value or according to the branch direct-current internal resistance standard differences of all branches in the battery system and a second set threshold value.
Preferably, the method further comprises:
when the branch current balance prediction result is that the branch currents in the battery system are not balanced, rearranging and combining all battery packs in the battery system, and processing all permutation and combination to obtain a maintenance scheme; the maintenance scheme is a permutation and combination mode of exchanging the mutual positions of the battery packs in the battery system.
Preferably, the processing of all permutation and combination to obtain the maintenance scheme includes:
branch current balance judgment is carried out on each branch current of each permutation and combination;
and determining a maintenance scheme according to the branch current balance judgment result.
Preferably, the branch current balancing judgment of each branch current of each permutation and combination comprises:
processing the normalized average direct current internal resistance of each battery pack according to the average direct current internal resistance of all the battery packs in each branch;
obtaining the normalized branch direct-current internal resistance of each branch according to the normalized average direct-current internal resistance of all the battery packs in each branch;
obtaining the direct current internal resistance pole difference of the normalization branch circuits and the direct current internal resistance standard difference of the normalization branch circuits of the battery system according to the direct current internal resistance of the normalization branch circuits of each branch circuit;
and judging whether the branch current in the battery system is balanced according to the comparison result of the normalized branch direct-current internal resistance range of all branches in the battery system and a first set threshold or the comparison result of the normalized branch direct-current internal resistance standard difference and a second set threshold.
Preferably, the maintenance scheme is determined according to the branch current balance judgment result as follows:
and processing all arrangement combinations meeting the branch current balance according to the battery pack exchange times or/and the normalized branch direct current internal standard deviation to determine a maintenance scheme.
In order to achieve the above objects and other related objects, the present invention also provides a device for predicting branch current balance in a battery system, the device including a processor and a memory, the memory storing a computer program executable on the processor, the computer program, when executed by the processor, implementing the steps of the method for predicting branch current balance in a battery system.
As described above, the method and the device for predicting branch current balance in a battery system of the present invention have the following advantages:
the prediction method comprises the steps of firstly obtaining the operation data of the current normally-operated battery system in a set time period; then obtaining the average direct current internal resistance of each battery pack in the battery system according to the operation data; and finally, analyzing according to the average direct current internal resistance of all the battery packs in each branch circuit to obtain the balance prediction result of the current of each branch circuit in the battery system. The invention can perform accurate pre-detection on whether the current of each branch in the battery system is balanced in advance, generate early warning when the current is unbalanced, and automatically output a maintenance scheme, thereby effectively saving the time and energy consumed by field investigation and test of after-sales personnel. In addition, the maintenance scheme provided by the invention is specifically characterized in that the mutual positions of the battery packs are changed, so that the technical requirement on maintenance personnel is not high, professional after-sales personnel cannot be used, the maintenance can be realized only by field technical personnel, and the time cost and the economic cost caused by using the professional after-sales personnel are avoided.
Drawings
Fig. 1 is a schematic flow chart illustrating a method for predicting branch current balance in a battery system according to the present invention.
Fig. 2 is a schematic flow chart illustrating a method for predicting branch current balance in a battery system according to the present invention.
Fig. 3 is a schematic structural diagram of a prediction apparatus for branch current equalization in a battery system according to the present invention.
Detailed Description
The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention.
Please refer to fig. 1-3. It should be noted that the drawings provided in the present embodiment are only for illustrating the basic idea of the present invention, and the components related to the present invention are only shown in the drawings rather than drawn according to the number, shape and size of the components in actual implementation, and the type, quantity and proportion of the components in actual implementation may be changed freely, and the layout of the components may be more complicated.
The first embodiment of the method comprises the following steps:
the flow of the prediction of the branch current balance in the battery system is shown in fig. 1, and the technical scheme of the prediction method of the branch current balance in the battery system is described in detail according to fig. 1. The method for predicting the branch current balance in the battery system at least comprises the following steps:
s1, acquiring the operation data of the current normal operation battery system in a set time period;
in the embodiment of the invention, the battery system is or can also normally operate currently, and in order to predict whether the branch current in the battery branch is balanced, the operation data of the battery system in a set time period can be acquired when the battery system operates or the battery system is in a dormant state.
The operating data of the present invention includes the battery pack voltage, temperature and branch current at each time.
The battery system comprises p parallel branches, and each branch is provided with q battery packs, so that the voltage of each branch in parallel connection is the same, and the currents of the battery packs on the same branch are equal to the current of the branch. The acquisition of the battery system operation data can be directly obtained through measurement, or can be obtained through data stored in the platform, or the data of the battery pack can be obtained through calculation of related data of a single battery in the platform; wherein P and q are both positive integers greater than or equal to 2.
In the embodiment of the present invention, the set time period is 10 days, and as another embodiment, the set time period may be 15 days or 7 days; the set time cannot take operating data too long from the current time interval, considering that the current or subsequent operating safety is pre-checked.
S2, obtaining the branch direct current internal resistance of each branch in the battery system according to the operation data;
the step aims to process and analyze the operation data of the battery system to obtain the branch direct current internal resistance of each branch in the battery system, so that the branch direct current internal resistance of each branch can be used for pre-checking and judging whether the branch current is balanced.
The method for obtaining the average direct current internal resistance of each battery pack in the battery system according to the operation data comprises the following steps:
s21, obtaining a plurality of current stabilization periods according to the operation data;
in a vehicle or an energy storage system applied to a battery system, the vehicle or the energy storage system is parked after being used for a period of time and then restarted, and the vehicle or the energy storage system may need to be restarted every day or be restarted for a plurality of times every day.
Selecting a first current stable change time period after each standing from operation data, judging and processing the operation data of each first current stable change time period according to set conditions to obtain a plurality of stable stage data, and taking a time sequence corresponding to each stable stage data as a current stable time period.
The setting conditions of the invention are as follows:
(1) the difference between the starting time of the first current stable change period and the ending time of the current fluctuation stage before the first current stable change period is less than or equal to a set threshold value;
in the embodiment of the invention, after each shelving, the current firstly rises from 0, and the current is stabilized after a period of fluctuation, namely, the current enters a current stabilization change period after the shelving firstly passes through a current fluctuation stage. The set threshold in the embodiment of the invention is 1 min;
(2) the absolute value of the change of the total branch current in the first current stable change period is greater than the set current value; in the embodiment of the present invention, the current value is set to 10A;
the total branch current change absolute value is the absolute value of the difference value of the sum of all branch current values at the starting moment and the sum of all branch current values at the ending moment.
(3) The absolute value of the change of the branch voltage in the first current stable change period is greater than 0;
the absolute value of the change of the branch voltage is the absolute value of the difference value of all the branch voltages at the starting moment and the ending moment; and the branch voltage is the sum of the voltages of all the battery packs on the branch.
(4) The number ratio of the different sign points in the current change rate array in the first current stable change period is less than or equal to a set value; wherein the different sign points comprise positive number points and negative number points; in the present embodiment, the set value is 1/9.
The current change rate array of the invention is K ═ K 1 ,k 2 ,...k n-1 ]Wherein, in the process,
if K n If > 0, it is a positive number, if K n If < 0, it is a negative point.
The calculation mode of the unnumbered point w of the invention is as follows:
wherein Np is the number of positive points, Nn is the number of negative points, and w is [0,1 ].
In the embodiment of the present invention, if the positive number points in the current rate-of-change array are 9, and the negative number points in the current rate-of-change array are 1, w is 1/9, which meets the requirement.
The first current stable change time period after the first standing, namely the first current stable time period, obtained by judging and screening the operation data according to the set conditions is d 1 ＝[t 11 ,t 12 ,…]Correspondingly, the operation data corresponding to the first current stabilization period is defined as first stabilization period data; the first current stabilization period after the second settling, i.e., the second current stabilization period, is d 2 ＝[t 21 ,t 22 ,…]Correspondingly, the operation data corresponding to the second current stabilization period is defined as second stabilization period data; … …, wherein the first current stable change time after the mth resting, namely the mth current stable time is d m ＝[t m1 ,t m2 ,…,t mn ]Correspondingly, the operation data corresponding to the mth current stabilization periodDefined as the mth stable phase data.
S22, processing the stable phase data of each current stable time period to obtain the average direct current internal resistance of each battery pack;
the method for processing the stable stage data of each current stable period to obtain the average direct current internal resistance of each battery pack comprises the following steps:
s221, processing the stable stage data of each current stable time period to obtain the corresponding direct current internal resistance of each battery pack;
in the invention, the internal resistance of the battery pack at each current stabilization period is obtained for each battery pack voltage and corresponding branch current at each current stabilization period;
the determination mode of the internal resistance of the battery pack in each current stabilization period is as follows: and obtaining the direct current internal resistance of each battery pack in the current stabilization period according to the battery pack voltage at the last moment in the current stabilization period and the corresponding branch current.
In the formula, R kij The direct current internal resistance of the jth battery pack of the ith branch in the kth current stabilization period; u shape kij (T m ) The voltage of a battery pack at the last moment of the kth current stabilization period is used as the jth battery pack of the ith branch; I.C. A kij (T m ) The branch current of the jth battery pack of the ith branch at the last moment of the kth current stabilization period is obtained; u shape kij (T 1 ) The voltage of a battery pack at the starting moment of the kth current stabilization period of the jth battery pack of the ith branch is obtained; i is kij (T 1 ) The branch current of the jth battery pack of the ith branch at the starting moment of the kth current stabilization period; wherein k is less than or equal to m, i is less than or equal to p, and j is less than or equal to q; t is m At the end of the period for which the current is stable, T 1 Is the starting time of the current stabilization period.
And S222, obtaining the average direct current internal resistance of each battery pack in each branch circuit according to the direct current internal resistances of all the battery packs.
The method specifically comprises the steps of averaging the internal resistances of the battery packs of each battery pack in all current stabilization periods to obtain the average direct current internal resistance of each battery pack;
wherein the content of the first and second substances,
is the average direct current internal resistance of the jth battery pack of the ith branch.
And S3, analyzing according to the average direct current internal resistance of all battery packs in the battery system to obtain the balance prediction result of each branch current in the battery system.
And obtaining branch direct-current internal resistance range differences of all branches in the battery system and branch direct-current internal resistance standard differences of all branches in the battery system according to the average direct-current internal resistance of all battery packs in the battery system, and obtaining a balance prediction result of each branch current in the battery system according to the branch direct-current internal resistance range differences of all branches in the battery system and a first set threshold value or according to the comparison judgment of the branch direct-current internal resistance standard differences of all branches in the battery system and a second set threshold value.
In a preferred embodiment of the present invention, internal resistance analysis is performed according to comparison between the branch direct current internal resistance range S of all branches in the battery system and a first set threshold, and a balance prediction result of the branch current is obtained according to the internal resistance analysis result.
(1) Obtaining the branch direct-current internal resistance of each branch according to the average direct-current internal resistance of all the battery packs in each branch;
in the invention, the average direct current internal resistances of all the battery packs in each branch circuit are summed to obtain the branch circuit direct current internal resistances of the corresponding branch circuits.
Wherein the content of the first and second substances,
the direct current internal resistance of the branch circuit of the ith branch circuit.
(2) Obtaining branch direct current internal resistance pole differences of all branches in the battery system according to the branch direct current internal resistance of each branch;
the branch direct current internal resistance pole difference S in all the branches is as follows:
wherein the content of the first and second substances,
the maximum value of the direct current internal resistance of the branch circuit is obtained;
is the minimum value of the direct current internal resistance of the branch circuit.
(3) And judging whether the branch current in the battery system is balanced or not according to the branch direct current internal resistance pole differences of all the branches in the battery system and a first set threshold value.
The branch direct current internal resistance range of all branches in the battery system is larger than a first set threshold value, which indicates that the branch direct current internal resistance range of each branch is larger, and the branch current imbalance of the battery system is judged; otherwise, judging that the branch current in the battery system is balanced.
The embodiment is suitable for the case that P is greater than or equal to 2 in the battery system, and when the branch P is 2 in the battery system,
the branch direct current internal resistance is a larger value;
the smaller value of the direct current internal resistance of the branch circuit is.
In another preferred embodiment of the present invention, internal resistance analysis is performed according to comparison between the standard deviation σ of the branch direct current internal resistances of all the branches in the battery system and the second set threshold, and a balance prediction result of the branch current is obtained according to the internal resistance analysis result. (1) Obtaining the branch direct-current internal resistance of each branch according to the average direct-current internal resistance of all the battery packs in each branch;
in the invention, the average direct current internal resistances of all the battery packs in each branch circuit are summed to obtain the branch circuit direct current internal resistances of the corresponding branch circuits.
Wherein the content of the first and second substances,
the direct current internal resistance of the branch circuit of the ith branch circuit.
(2) Obtaining the standard deviation sigma of all the branches in the battery system according to the direct current internal resistance of the second branch of each branch;
wherein the content of the first and second substances,
the average value of the branch direct-current resistances of all the branches is obtained.
(3) And judging whether the branch current in the battery system is balanced or not according to the branch direct current internal resistance standard deviation of all branches in the battery system and a second set threshold.
The standard difference of the direct current internal resistances of the branches of all the branches in the battery system is smaller than a second set threshold value, which indicates that the difference of the direct current internal resistances of the branches is not large, namely the difference of the resistances of the branches is not large, and the branch current of the battery system is judged to be balanced; otherwise, the branch current in the battery system is judged to be unbalanced.
In the invention, the branch direct current internal resistance range of all branches in the battery system is preferentially selected to perform branch current balance judgment on the battery system with 2 parallel branches, because the battery system only comprises 2 branches, the calculation quantity is small, the branch direct current internal resistance range is simple to determine, and the accurate judgment on whether the branch current in the battery system is balanced can be realized through the judgment on the branch direct current internal resistance range.
The branch direct current internal resistance standard deviation of all branches in the battery system is preferably selected to perform branch current balance judgment on the battery systems with 3 or more parallel branches, and for the reason that more parallel branches are contained in the battery systems, the branch direct current internal resistance standard deviation can be adopted to realize more accurate judgment on whether the branch current in the battery systems is balanced or not integrally and globally.
After the balance prediction result of the branch current is obtained, after-sales personnel can analyze the branch current, so that the battery system can be managed and maintained before a fault occurs.
The second method embodiment:
as a preferable scheme, the invention can also provide a managed maintenance scheme according to the prediction result, so that after-sales personnel can maintain quickly, and the production efficiency of the battery system application is improved.
The flow of predicting the branch current balance in the battery system is shown in fig. 2, and the technical solution of the method for predicting the branch current balance in the battery system is described in detail according to fig. 2. The method at least comprises the following steps:
s1, acquiring the operation data of the current normal operation battery system in a set time period;
s2, obtaining the average direct current internal resistance of each battery pack in the battery system according to the operation data;
s3, analyzing according to the average direct current internal resistance of all battery packs in the battery system to obtain the balance prediction result of each branch current in the battery system;
s4, when the branch current balance prediction result is that the branch currents in the battery system are not balanced, rearranging and combining all battery packs in the battery system, and processing all the arranging and combining to obtain a maintenance scheme; the maintenance scheme is a permutation and combination mode of exchanging the mutual positions of the battery packs in the battery system.
The invention rearranges and combines the battery packs in the battery system, judges whether each permutation and combination mode meets the branch current balance, and takes the permutation and combination mode meeting the branch current balance as a maintenance scheme; and finally, after-sale personnel exchange the mutual positions of the battery packs in the existing battery system according to the arrangement and combination mode in the maintenance scheme, so that the branch current balance in the battery system is realized.
The contents of steps S1 to S3 in this embodiment have been described in detail in the method embodiment, and are not repeated in this embodiment to avoid repetition. Only the content of the step S4 for generating the maintenance plan will be described in detail in this embodiment.
In the embodiment of the invention, the direct current internal resistance of each battery pack is normalized by considering the weight of the temperature factor to obtain the normalized average direct current internal resistance of each battery pack; then calculating to obtain the direct current internal resistance of the normalized branch of each branch; then, calculating the pole difference or standard deviation of the normalized resistance value of each branch; and finally, realizing branch current balance prediction through the direct current internal resistance standard deviation of the normalization branch circuits or the direct current internal resistance standard deviation of the normalization branch circuits.
S41, obtaining all permutation and combination according to the number p of the branches in the battery system and the number q of the battery packs;
in the invention, the total quantity of all permutation and combination of the p branches of the battery system, each branch has q battery packs is (pq)! The total number of the permutation and combination of the branches is (pq)! /(p.q!).
S42, branch current balance judgment is carried out on each branch current of each permutation and combination;
the branch current balance judgment of each branch current of each permutation and combination comprises the following steps:
s421, processing the average direct current internal resistance of all the battery packs in each branch circuit to obtain the normalized average direct current internal resistance of each battery pack;
considering the temperature factors of the internal resistances of different battery packs, and calculating the average direct current internal resistance data of each battery pack
Carrying out normalization processing of the temperature factor weight:
wherein the content of the first and second substances,
is the average temperature of the jth battery pack of the ith branch, namely the average value (T) of the temperatures of the same battery pack at all times ij > 0)，μ ij Weighting the temperature factor of the jth battery pack of the ith branch; r ij And the normalized average direct current internal resistance of the jth battery pack of the ith branch is obtained.
S422, obtaining the normalized branch direct-current internal resistance of each branch according to the normalized average direct-current internal resistance of all the battery packs in each branch;
the normalized average direct current internal resistances of all the battery packs in each branch are summed to obtain the normalized branch direct current internal resistances of the corresponding branches.
Wherein R is i The normalized branch direct current internal resistance of the ith branch.
S423, obtaining the direct current internal resistance pole difference and the direct current internal resistance standard deviation of the normalization branch circuits of all the branch circuits in the battery system according to the direct current internal resistance of the normalization branch circuits of each branch circuit;
the calculation methods of the dc internal resistance pole difference of the normalization branches and the standard difference of the dc internal resistance of the normalization branches are the same as those in method embodiment 1, and are not described herein again.
And S424, judging whether the branch circuits in the battery system are all balanced according to the comparison result of the direct current internal resistance range of the normalization branch circuits of all the branch circuits in the battery system and a first set threshold value or the comparison result of the direct current internal resistance standard deviation of the normalization branch circuits and a second set threshold value.
The method for determining whether the branch current in the battery system is balanced according to the normalized branch direct-current internal resistance pole difference or the normalized branch direct-current internal resistance standard difference of all the branches is the same as that in method embodiment 1, and details are not repeated here.
S43, determining a maintenance scheme according to the branch current balance judgment result;
in the embodiment of the invention, a plurality of permutation and combination modes of branch current in the battery system meeting branch current balance can be used as maintenance schemes according to the balance judgment result. The arrangement and combination mode relates to the mutual position exchange of the battery packs in the current battery system.
In the preferred embodiment of the invention, considering that the permutation and combination modes meeting the branch current balance are more, the selection is inconvenient to carry out maintenance, or the selected maintenance scheme is not optimal, therefore, all permutation and combination meeting the branch current balance are processed according to the battery pack exchange times or/and the normalized branch direct current internal standard deviation to determine the maintenance scheme.
(1) Processing all arrangement modes meeting branch current balance according to the exchange times of the battery pack to determine a maintenance scheme;
specifically, the arrangement combination mode with the least number of times of battery pack replacement among all arrangement modes satisfying branch current balance is taken as a maintenance scheme, so that the workload of maintenance personnel can be reduced.
(2) Processing all arrangement modes meeting the branch current balance according to the normalized branch direct current internal resistance standard difference to determine a maintenance scheme;
specifically, the permutation and combination mode corresponding to the minimum value of the normalized branch direct-current internal resistance standard deviation in all the permutation modes meeting the branch current balance is used as a maintenance scheme, so that the optimal balance of the battery system can be integrally realized.
(3) Processing all arrangement modes meeting the branch circuit current balance according to the battery pack exchange times and the normalized branch circuit direct current internal resistance standard difference to determine a maintenance scheme;
specifically, if at least 2 to 3 permutation and combination modes with the minimum normalized branch direct current internal resistance standard deviation in all the permutation modes meeting the branch current balance or the minimum battery pack exchange frequency in all the permutation modes meeting the branch current balance exist, the permutation and combination mode with the minimum battery pack exchange frequency can be determined as a maintenance scheme in the permutation and combination modes with the minimum normalized branch direct current internal resistance standard deviation in all the permutation modes meeting the branch current balance, so that the workload of maintenance personnel is minimized on the basis of realizing the optimal balance of the whole battery system, and the efficiency is improved; the permutation and combination mode which determines the minimum value of the normalized branch direct current internal resistance standard deviation in the permutation and combination mode which has the minimum battery pack replacement times in the permutation and combination modes which meet the branch current balance can also be used as a maintenance scheme, so that the optimal balance can be realized on the premise of the minimum workload of maintenance personnel.
The invention can automatically output the maintenance scheme when the branch current in the battery system is unbalanced, and can effectively save the time and energy consumed by field investigation tests of after-sales personnel.
The embodiment of the device comprises:
the invention also provides a device for predicting branch current balance in a battery system, as shown in fig. 3, where the device includes a processor and a memory, where the memory stores a computer program that can be executed on the processor, and the computer program, when executed by the processor, implements the steps of the method for predicting branch current balance in a battery system.
Since the principle and steps of the prediction method for branch current equalization in the battery system are described in detail in the method embodiment, no further description is given in this embodiment.
In summary, according to the prediction method and the prediction device for branch current balance in the battery system provided by the invention, the prediction method firstly obtains the operation data of the current normally-operated battery system in a set time period; then obtaining the average direct current internal resistance of each battery pack in the battery system according to the operation data; and finally, analyzing according to the average direct current internal resistance of all the battery packs in each branch circuit to obtain the balance prediction result of the current of each branch circuit in the battery system. The invention can accurately pre-check whether the current of each branch in the battery system is balanced in advance, generate early warning when the current is unbalanced, and automatically output a maintenance scheme, thereby effectively saving the time and energy consumed by field investigation tests of after-sales personnel. Therefore, the invention effectively overcomes various defects in the prior art and has high industrial utilization value.
The foregoing embodiments are merely illustrative of the principles and utilities of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which may be accomplished by those skilled in the art without departing from the spirit and scope of the present invention as set forth in the appended claims.
Claims (12)
1. A method for predicting branch current balance in a battery system is characterized by at least comprising the following steps:
acquiring operation data of a current normally-operated battery system in a set time period; the operation data comprises the voltage and the temperature of the battery pack and the current of each branch circuit at each moment;
obtaining the average direct current internal resistance of each battery pack in the battery system according to the operation data;
and analyzing according to the average direct current internal resistance of all battery packs in the battery system to obtain the balance prediction result of each branch current in the battery system.
2. The method for predicting branch current balance in a battery system according to claim 1, wherein the method for obtaining the average direct current internal resistance of each battery pack in the battery system according to the operation data comprises:
obtaining a plurality of current stabilization periods according to the operating data;
and processing the stable stage data of each current stable period to obtain the average direct current internal resistance of each battery pack.
3. The method for predicting the branch current balance in the battery system according to claim 2, wherein the current stabilization period refers to a first current stabilization variation period that meets a set condition after each shelving; the setting conditions are as follows:
(1) the difference between the starting time and the ending time of the first current stable change period is less than or equal to a set threshold;
(2) the absolute value of the change of the total branch current in the first current stable change period is greater than the set current value;
(3) the absolute value of the change of the branch voltage in the first current stable change period is greater than 0;
(4) the number ratio of different sign points in the current change rate array in the first current stable change period is less than or equal to a set value; wherein the different sign points comprise positive number points and negative number points.
4. The method for predicting branch current balance in a battery system according to claim 3, wherein the calculation manner of the opposite sign point is as follows:
wherein Np is the number of positive points, Nn is the number of negative points, and w is an element [0,1 ].
5. The method of claim 3, wherein obtaining a plurality of current stabilization periods based on the operational data comprises:
selecting a first current stable change time period after each shelving from operation data;
judging and processing the operation data of each primary current stable change time period according to set conditions to obtain a plurality of stable phase data;
and taking the time sequence corresponding to each stable phase data as a current stable time.
6. The method for predicting branch current balance in a battery system according to claim 3, wherein the step of processing the stability phase data of each current stability period to obtain the average internal dc resistance of each battery pack comprises:
processing the stability phase data of each current stability time period to obtain the corresponding direct current internal resistance of each battery pack;
and obtaining the average direct current internal resistance of each battery pack according to the direct current internal resistances of all the battery packs.
7. The method for predicting the branch current balance in the battery system according to claim 1, wherein the balance prediction result of each branch current in the battery system obtained by analyzing the average direct current internal resistance of all battery packs in the battery system is as follows:
and obtaining branch direct-current internal resistance range differences of all branches in the battery system and branch direct-current internal resistance standard differences of all branches in the battery system according to the average direct-current internal resistance of all battery packs in the battery system, and obtaining a balance prediction result of the current of each branch in the battery system according to the branch direct-current internal resistance range differences of all branches in the battery system and a first set threshold value or according to the branch direct-current internal resistance standard differences of all branches in the battery system and a second set threshold value.
8. The method for predicting branch current balance in a battery system according to claim 1, wherein the method further comprises:
when the branch current balance prediction result is that the branch currents in the battery system are not balanced, rearranging and combining all battery packs in the battery system, and processing all the permutation and combination to obtain a maintenance scheme; the maintenance scheme is a permutation and combination mode of exchanging the mutual positions of the battery packs in the battery system.
9. The method for predicting branch current balance in a battery system according to claim 8, wherein the step of processing all permutation and combination to obtain a maintenance scheme comprises:
branch current balance judgment is carried out on each branch current of each permutation and combination;
and determining a maintenance scheme according to the branch current balance judgment result.
10. The method for predicting branch current balance in a battery system according to claim 9, wherein the branch current balance determination for each branch current of each permutation and combination comprises:
processing the average direct current internal resistance of all the battery packs in each branch circuit;
obtaining the normalized branch direct-current internal resistance of each branch according to the normalized average direct-current internal resistance of all the battery packs in each branch;
obtaining the direct current internal resistance pole difference of the normalization branch circuits and the direct current internal resistance standard difference of the normalization branch circuits of the battery system according to the direct current internal resistance of the normalization branch circuits of each branch circuit;
and judging whether the branch current in the battery system is balanced according to a comparison result of the normalized branch direct-current internal resistance range of all branches in the battery system and a first set threshold or a comparison result of the normalized branch direct-current internal resistance standard deviation and a second set threshold.
11. The method for predicting branch current balance in a battery system according to claim 9, wherein the maintenance scheme determined according to the branch current balance determination result is:
and processing all permutation and combination meeting the branch circuit current balance according to the battery pack exchange times or/and the normalized branch circuit direct current internal standard deviation to determine a maintenance scheme.
12. A prediction apparatus for branch current balancing in a battery system, the apparatus comprising a processor and a memory, the memory having stored thereon a computer program operable on the processor, the computer program, when executed by the processor, implementing the steps of the prediction method for branch current balancing in a battery system according to any one of claims 1 to 11.
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