A fault judgment method and system based on single cell voltage consistency monitoring

Abstract

The present invention provides a fault judgment method and system based on single cell voltage consistency monitoring, the method comprising the following steps: charging state and SOC screening: when all single cells are in a charging state and the SOC is in a preset interval, outlier analysis is performed; outlier calculation and marking: the outlier of all single cell voltages is calculated, and if the outlier of a single cell exceeds a preset threshold, the single cell is marked as abnormal; abnormal accumulation judgment and fault alarm: the above steps are executed cyclically, and for cells whose outliers have not been restored in multiple consecutive rounds, the abnormal counts are accumulated and the fault alarm is triggered according to the counts. By calculating the outlier of the single cell voltage, real-time monitoring of the consistency deviation of the single cell and early warning of faults are achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of vehicle batteries, and in particular relates to a fault judgment method and system based on single cell voltage consistency monitoring. Background Art

[0002] With the mass production and application of new energy vehicles, the battery management system (BMS) has become a core component to ensure battery safety and performance. At present, BMS mainly sets alarm thresholds for faults such as cell pressure difference, cell undervoltage and cell overvoltage in terms of single cell monitoring. For example:

[0003] Large pressure difference fault: When the cell voltage difference (taking lithium iron phosphate battery as an example) is ≥0.8V and lasts for 5 seconds, the large pressure difference alarm is triggered.

[0004] Single cell overvoltage fault: When the single cell voltage is ≥3.67V and lasts for 5 seconds, the overvoltage alarm is triggered.

[0005] Single cell undervoltage fault: When the single cell voltage is ≤2.7V and lasts for 30 seconds, the undervoltage alarm is triggered.

[0006] Although the above alarm mechanism can preliminarily determine the abnormal situation of a single cell, there are still the following problems and limitations in practical applications:

[0007] The threshold of the large pressure difference fault alarm is high, and it is impossible to give early warning: The current threshold of the large pressure difference alarm (such as 0.8V) is set relatively high, and it is only triggered when the abnormality of the battery cell is already serious, lacking the ability to perceive the early stage of the fault in advance. In addition, the reasons for the large pressure difference are diverse, including sampling errors, unbalanced battery modules, and long-term battery undervoltage, which may trigger the large pressure difference alarm, but it is impossible to accurately locate the specific battery cell safety problem.

[0008] Single cell undervoltage and overvoltage faults cannot accurately monitor consistency: Undervoltage and overvoltage alarms rely on fixed voltage thresholds (such as 2.7V for undervoltage and 3.67V for overvoltage), and fail to fully consider the consistency changes between single cells. During battery operation, some single cells may deviate from the overall trend due to self-discharge, aging and other problems. Such consistency problems cannot be identified in time through fixed threshold monitoring.

[0009] It is difficult to locate the safety hazards of battery cells in a timely manner: the current fault mechanism lacks monitoring of the continuity and trend of faults, and it is difficult to effectively judge the potential safety hazards of single battery cells by relying only on fixed time and threshold triggers. The fault alarm range is relatively wide, and it is impossible to accurately locate the problem of the battery cell itself, which increases the complexity of fault handling. Summary of the invention

[0010] The purpose of the present invention is to address the deficiencies of the above-mentioned background technology and to provide a fault judgment method and system based on single cell voltage consistency monitoring, which can realize real-time monitoring of single cell consistency deviation and early warning of faults by calculating the outlier degree of single cell voltage.

[0011] The technical solution adopted by the present invention is: a fault judgment method based on single cell voltage consistency monitoring, comprising the following steps:

[0012] Charging state and SOC screening: When all single cells are in the charging state and the SOC is in the preset range, outlier analysis is performed;

[0013] Outlier calculation and marking: Calculate the outlier of all cell voltages. If the outlier of a cell exceeds the preset threshold, mark the cell as abnormal.

[0014] Abnormal accumulation judgment and fault alarm: The above steps are executed repeatedly. For the cells whose outliers have not been restored in multiple consecutive rounds, the abnormal counts are accumulated and the fault alarm is triggered according to the counts.

[0015] In the above technical solution, the process of accumulating abnormality counts includes: for any single cell, if the outlier degree is not restored in two consecutive rounds marked as abnormal, the abnormality count of the single cell is increased by 1.

[0016] In the above technical solution, the process of triggering a fault alarm according to the count includes: if the abnormal count of any single battery cell reaches a preset value, it is determined that the single battery cell has a fault and a corresponding fault alarm is triggered.

[0017] In the above technical solution, if a single cell is marked as abnormal in two consecutive rounds, and the outlier degree of the latter round is greater than or equal to the outlier degree of the previous round, it is determined that the outlier degree of the single cell has not recovered.

[0018] In the above technical solution, the absolute value of the difference between the mean of multiple frames of voltage data of any single cell within a certain SOC range and the mean of all cell voltages is calculated as the outlier degree of the single cell.

[0019] In the above technical solution, if the outlier degree of any single cell is greater than 3 times the standard deviation of the single cell voltage, the single cell is marked as abnormal.

[0020] The above technical solution also includes the following steps: monitoring the voltage, SOC and charge and discharge status of all single cells, and performing the charge status and SOC screening steps after cleaning invalid data.

[0021] In the above technical solution, if the abnormal count of any single battery cell reaches 3 times, it is determined that the single battery cell has a fault and a corresponding fault alarm is triggered.

[0022] In the above technical solution, the SOC preset interval is [60%, 70%].

[0023] The present invention also provides a fault judgment system based on single cell voltage consistency monitoring, which is used in the method described in the above technical solution, including:

[0024] The charging state and SOC screening module is used to perform outlier analysis when all single cells are in the charging state and the SOC is in the preset range;

[0025] The outlier calculation and marking module is used to calculate the outlier degree of all single cell voltages. If the outlier degree of a single cell exceeds a preset threshold, the single cell is marked as abnormal.

[0026] The abnormal accumulation judgment and fault alarm module is used to accumulate abnormal counts and trigger fault alarms according to the counts for the cells whose outliers have not been restored in multiple consecutive rounds.

[0027] The beneficial effects of the present invention are as follows: by calculating the outlier degree of the voltage of a single cell and the overall mean, the present invention can accurately locate the voltage abnormality of a single cell and reduce the interference of sampling error or module unbalanced judgment on the judgment by combining statistical principles. The dynamic monitoring of the outlier degree of the present invention avoids the limitation of relying solely on a fixed threshold value and improves the sensitivity and accuracy of abnormal judgment. On the basis of outlier degree monitoring, the present invention adopts a multi-round abnormal accumulation judgment mechanism with increasing discreteness, which better locates the problem of rapid self-discharge of the single cell. For continuous or trending faults (such as accelerated self-discharge, cell aging, etc.), early warning can be achieved through abnormal counting. The cumulative judgment mechanism of the present invention avoids the problem of misjudgment of a single fluctuation and can effectively identify long-standing hidden faults. Compared with the broad alarm of the prior art, the present invention combines consistency monitoring, outlier degree analysis and dynamic accumulation mechanism to accurately locate the abnormality of a specific single cell, significantly improving the efficiency and safety of fault handling.

[0028] Furthermore, the process of accumulating abnormality counts in the present invention can accurately monitor abnormal trends, use continuity judgment to avoid misjudgment due to single fluctuations, and ensure that the accumulated counts only reflect the real abnormal trends; at the same time, reduce false alarms and misjudgments: accumulate abnormalities whose outliers have not recovered, rather than independently judge each round, to avoid false alarms caused by instantaneous sampling errors or short-term fluctuations; and when abnormal trends appear, it can promptly reflect the severity of the problem and achieve early warning.

[0029] Furthermore, the fault alarm trigger mechanism of the present invention can dynamically adapt to the fault threshold: the abnormality count is based on multiple rounds of abnormality accumulation, allowing flexible fault thresholds to be set to adapt to different safety standards and application scenarios; at the same time, accurate alarms reduce interference, and alarms are only triggered after the abnormality count reaches a preset value, avoiding unnecessary alarms due to single or a few abnormal events; the present invention can dynamically judge the fault level according to the degree of abnormality accumulation, effectively improving the accuracy of fault alarms.

[0030] Furthermore, the present invention explicitly uses the change in outlier degree as a judgment criterion, and identifies the persistence or deterioration trend of the abnormality by monitoring the outlier degree that has not recovered; the outlier degree is counted as a persistent abnormality only when it has not recovered (or deteriorated), to avoid the misjudgment of a briefly recovered cell as a problem cell; by monitoring the outlier trend, the problem cell can be accurately identified rather than the misjudgment of the entire module.

[0031] Furthermore, the present invention adopts the mean difference of battery cell voltage as the outlier calculation index, which can dynamically adapt to the operating state of the battery system without the need for a fixed voltage threshold; the outlier calculation based on the overall mean reduces the direct impact of external conditions (such as temperature, current, etc.) on the voltage of the single battery cell; through the calculation of the absolute value of the difference, it can accurately reflect the degree of deviation of the single battery cell from the overall level and accurately identify the battery cell consistency problem.

[0032] Furthermore, the statistical method of the present invention improves the reliability of judgment: the 3σ principle is adopted to make the outlier judgment more scientific and accurate, reducing the error caused by artificial threshold setting; the standard deviation is dynamically calculated based on the current operating data and can adapt to the characteristics of different battery systems; the 3σ principle can make a quick judgment on extreme deviations, which helps to discover potential safety hazards in advance.

[0033] Furthermore, the data cleaning process of the present invention (such as removing abnormal data points) can effectively reduce misjudgment caused by sampling errors or noise; through charging state and SOC screening, it is ensured that the outlier analysis is only performed within a reasonable operating range (such as SOC60%-70%) to reduce the interference of abnormal environment; the monitoring of multiple parameters such as voltage, SOC, charging and discharging state, etc., provides a more comprehensive evaluation of the battery cell operating state. The present invention monitors the battery state in real time, and can provide early warning before the battery fails, reducing the occurrence of related safety problems.

[0034] Furthermore, the present invention triggers an alarm after the abnormal count reaches a threshold, so that the alarm mechanism has a hierarchy, avoiding frequent alarm triggering due to a few fluctuations; taking into account the timeliness and accuracy of fault warning, it can balance the risks of misjudgment and missed judgment; cumulative counting avoids false alarms caused by a single abnormality, and improves the credibility of the alarm.

[0035] Furthermore, the present invention ensures the stability of monitoring data: the cell voltage changes relatively smoothly within the 60%-70% SOC range, reducing the interference of extreme SOC on the judgment result; the middle range of SOC is selected for monitoring, which can better reflect the consistency of the actual operating state of the battery; and the influence of nonlinear characteristics (such as undervoltage or fully charged state) when the SOC is too high or too low on the outlier judgment is avoided. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 Schematic diagram of the method of the present invention. DETAILED DESCRIPTION

[0037] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments to facilitate a clear understanding of the present invention, but they do not constitute a limitation on the present invention.

[0038] Example 1

[0039] like Figure 1 As shown, the present invention provides a fault judgment method based on single cell voltage consistency monitoring, comprising the following steps:

[0040] Charging state and SOC screening: When all single cells are in the charging state and the SOC is in the preset range, outlier analysis is performed;

[0041] Outlier calculation and marking: Calculate the outlier of all cell voltages. If the outlier of a cell exceeds the preset threshold, mark the cell as abnormal.

[0042] Abnormal accumulation judgment and fault alarm: The above steps are executed repeatedly. For the cells whose outliers have not been restored in multiple consecutive rounds, the abnormal counts are accumulated and the fault alarm is triggered according to the counts.

[0043] The process of accumulating abnormality counts includes: for any single cell, if the outlier degree is not restored in two consecutive rounds marked as abnormal, the abnormality count of the single cell is increased by 1.

[0044] Specifically, the process of triggering a fault alarm according to the count includes: if the abnormal count of any single battery cell reaches a preset value, it is determined that the single battery cell has a fault, and a corresponding fault alarm is triggered.

[0045] Specifically, if, in two consecutive rounds in which a certain single cell is marked as abnormal, the outlier degree of the latter round is greater than or equal to the outlier degree of the previous round, it is determined that the outlier degree of the single cell has not recovered.

[0046] Specifically, the absolute value of the difference between the mean value of multiple frames of voltage data of any single cell within a certain SOC range and the mean value of all cell voltages is calculated as the outlier degree of the single cell.

[0047] Specifically, if the outlier degree of any single cell is greater than 3 times the standard deviation of the single cell voltage, the single cell is marked as abnormal.

[0048] Specifically, the method further includes the following steps: monitoring the voltage, SOC and charge and discharge status of all single cells, and performing a charge status and SOC screening step after cleaning invalid data.

[0049] Specifically, if the abnormal count of any single battery cell reaches 3 times, it is determined that the single battery cell has a fault, and a corresponding fault alarm is triggered.

[0050] Specifically, the SOC preset interval is [60%, 70%].

[0051] Example 2

[0052] The present invention further provides a fault judgment system based on single cell voltage consistency monitoring, which is used in the method described in Example 1, and includes:

[0053] The charging state and SOC screening module is used to perform outlier analysis when all single cells are in the charging state and the SOC is in the preset range;

[0054] The outlier calculation and marking module is used to calculate the outlier degree of all single cell voltages. If the outlier degree of a single cell exceeds a preset threshold, the single cell is marked as abnormal.

[0055] The abnormal accumulation judgment and fault alarm module is used to accumulate abnormal counts and trigger fault alarms according to the counts for the cells whose outliers have not been restored in multiple consecutive rounds.

[0056] Example 3

[0057] The present invention implements the method described in Example 1 based on the system provided in Example 2, which specifically includes the following steps:

[0058] In the first step, data processing module is used for data collection and cleaning.

[0059] Data collection:

[0060] The battery module's single cells are monitored in real time, with 10 frames of data collected each time. The battery module contains 5 single cells.

[0061] Assuming the monitored SOC range is [60%, 70%], the sampling data is shown in Table 1 (unit: V):

[0062] Table 1 Sampling data

[0063] Round Frame number Battery 1 Battery 2 Battery 3 Battery 4 Battery 5 1 1 3.65 3.8 3.68 3.7 3.72 1 2 3.66 3.82 3.69 3.71 3.73 ... ... ... ... ... ... ...

[0064] Data cleaning:

[0065] Eliminate invalid frames (such as V i,j =255V). Only the data with SOC in the range of [60%, 70%] are retained. After data cleaning, the remaining valid frames are all the data in the above table.

[0066] In the second step, the charging state and SOC screening module is used to determine whether to proceed to the subsequent steps: when all single cells are in the charging state and the SOC is in the preset range, outlier analysis is performed.

[0067] The third step is to use the outlier calculation and marking module to calculate the mean voltage of the single cell:

[0068] Calculate the mean of multiple frames of data for each cell i in the kth round:

[0069]

[0070] Assume that the multi-frame mean calculation results of each battery cell in the first round are as shown in Table 2:

[0071] Table 2 Average cell voltage

[0072] Cell number Multi-frame voltage average (V) 1 3.65 2 3.8 3 3.68 4 3.7 5 3.72

[0073] Module mean calculation:

[0074] Calculate the module mean of all cell voltages in the kth round:

[0075]

[0076] Average value of modules in round 1:

[0077]

[0078] The fourth step is to use the outlier calculation and marking module to calculate the outlier degree and abnormality judgment.

[0079] Outlier calculation:

[0080] Calculate the outlier degree for each cell:

[0081]

[0082] The calculation results of the outlier degree in the first round are shown in Table 3:

[0083] Table 3 Cell outlier degree

[0084]

[0085]

[0086] Abnormal judgment rules: If Xi,k >3σ, it is marked as abnormal. Assuming 3σ1=0.05, then cell 2: X 2,1 =0.09>3σ1, marked as abnormal.

[0087] The fifth step is to use the outlier calculation and marking module to perform abnormal marking and baseline value update.

[0088] Baseline value update rule: If abnormal, the current outlier degree X i,k as a baseline value.

[0089] Assuming 3σ1=0.05, then cell 2: X 2,1 =0.09>3σ1, marked as abnormal, reference value Y i Update to X 2,1 =0.09V.

[0090] Other cells do not exceed 3σ1, are not marked as abnormal, and no baseline value is updated.

[0091] So in the first round, the No. 2 battery cell is abnormal, and the reference value is Y i Updated to: X 2,1 =0.09. No reference value is set for the remaining cells.

[0092] Step 6: cyclically execute steps 1 to 4, and use the abnormal accumulation judgment and fault alarm module to perform abnormal accumulation and fault alarm.

[0093] Cumulative counting rules:

[0094] If X i,k >3σ and X i,k ≥Y i , the abnormal count is increased by 1 and the reference value Y is updated i ;

[0095] If X i,k >3σ and X i,k <Y i , or X i,k >3σ and no benchmark value was set in the previous round, the count remains unchanged but the benchmark value is updated.

[0096] Examples of multiple rounds of changes are shown in Table 4:

[0097] Table 4 Change data of each round

[0098]

[0099]

[0100] Step 5: Fault alarm: If the abnormal count of any single cell reaches 3 times, the single cell is judged to be faulty and the corresponding fault alarm is triggered.

[0101] When the abnormal count in the 5th round reaches 3 times, the fault alarm of battery cell No. 2 is triggered.

[0102] Example 4

[0103] The present invention provides a computer-readable storage medium having a computer program stored thereon. When the computer program is executed by a processor, the fault judgment method based on single cell voltage consistency monitoring described in the above technical solution is implemented.

[0104] Example 5

[0105] The present invention provides an electronic device, comprising: a memory and a processor, wherein the memory and the processor are connected to each other for communication, the memory stores computer instructions, and the processor executes the computer instructions to execute the fault judgment method based on single cell voltage consistency monitoring described in the above technical solution.

[0106] Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0107] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0108] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0109] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0110] The embodiments of the present invention are described above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned specific implementation modes, which are merely illustrative rather than restrictive. Under the guidance of the present invention, ordinary technicians in this field can also make many forms without departing from the scope of protection of the present invention and the claims, all of which are within the protection of the present invention.

[0111] The contents not described in detail in this specification belong to the prior art known to professional and technical personnel in this field.

Claims

1. A fault judgment method based on single cell voltage consistency monitoring, characterized in that: The following steps are involved: Charging state and SOC screening: When all single cells are in the charging state and the SOC is in the preset range, outlier analysis is performed; Outlier calculation and marking: Calculate the outlier of all cell voltages. If the outlier of a cell exceeds the preset threshold, mark the cell as abnormal. Abnormal accumulation judgment and fault alarm: The above steps are executed repeatedly. For the cells whose outliers have not been restored in multiple consecutive rounds, the abnormal counts are accumulated and the fault alarm is triggered according to the counts.

2. A method according to claim 1, characterized in that: The process of accumulating abnormality counts includes: for any single cell, if the outlier degree is not restored in two consecutive rounds marked as abnormal, the abnormality count of the single cell is increased by 1.

3. A method according to claim 2, characterized in that: The process of triggering a fault alarm according to the count includes: if the abnormal count of any single battery cell reaches a preset value, it is determined that the single battery cell has a fault and a corresponding fault alarm is triggered.

4. A method according to claim 2, characterized in that: If a single cell is marked as abnormal in two consecutive rounds, and the outlier degree of the latter round is greater than or equal to the outlier degree of the previous round, it is determined that the outlier degree of the single cell has not recovered.

5. A method according to claim 1, characterized in that: The absolute value of the difference between the voltage of any single cell and the mean voltage of all cells is calculated as the outlier degree of the single cell.

6. A method according to claim 1, characterized in that: If the outlier of any single cell is greater than 3 times the standard deviation of the cell voltage, the single cell is marked as abnormal.

7. A method according to claim 1, characterized in that: The following steps are also included: Monitor the voltage, SOC and charge and discharge status of all single cells, and perform charge status and SOC screening steps after cleaning invalid data.

8. A method according to claim 3, characterized in that: If the abnormal count of any single cell reaches 3 times, the single cell is determined to be faulty and the corresponding fault alarm is triggered.

9. A method according to claim 1, characterized in that: The SOC preset interval is [60%, 70%].

10. A fault diagnosis system based on single cell voltage consistency monitoring, used to implement the method according to any one of claims 1 to 9, characterized in that: include: The charging state and SOC screening module is used to perform outlier analysis when all single cells are in the charging state and the SOC is in the preset range; The outlier calculation and marking module is used to calculate the outlier degree of all single cell voltages. If the outlier degree of a single cell exceeds a preset threshold, the single cell is marked as abnormal. The abnormal accumulation judgment and fault alarm module is used to accumulate abnormal counts and trigger fault alarms according to the counts for the cells whose outliers have not been restored in multiple consecutive rounds.

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