A vehicle battery system monitoring platform and power system branch circuit identification method

Abstract

The application relates to a vehicle battery system monitoring platform and a power supply system branch circuit identification method, and belongs to the technical field of power batteries for electric vehicles. The application does not require voltage data of each single battery, only requires extreme value data of the battery, accurately obtains the battery extreme value data of the battery which is normally charged, has a complete charging process and a charging duration reaching a set duration, and judges the branch circuit cut-off according to the relationship between the difference between the maximum value and the minimum value of the lowest single battery voltage in the flow reduction stage at the end of the charging and the minimum amplitude of the battery depolarization voltage fluctuation. The branch circuit identification method of the application requires small battery data, and the monitoring platform can process data of multiple vehicles simultaneously.

Description

Technical Field

[0001] This invention relates to a vehicle battery system monitoring platform and a method for identifying branch circuit breaks in the power system, belonging to the field of power battery technology for electric vehicles. Background Technology

[0002] Currently, commercial vehicle power systems use battery systems with significantly larger capacities than passenger vehicles. Although battery management systems monitor the voltage of all individual cells and the temperature of all sampling points, the data uploaded to the monitoring backend only includes the highest and lowest individual cell voltages, highest and lowest sampling temperatures. This data limitation means that some early warning algorithms applicable to passenger vehicles are unsuitable for commercial vehicles. Developing effective early warning algorithms using low-frequency extreme value data is a key challenge in the development of battery fault early warning systems for commercial vehicles. Summary of the Invention

[0003] The purpose of this invention is to provide a vehicle battery system monitoring platform and a method for identifying open circuits in power system branches, so as to solve the problem that current power system branch open circuit identification requires a large amount of data.

[0004] To solve the above-mentioned technical problems, the present invention provides a method for identifying open circuits in a power system branch, the method comprising the following steps:

[0005] 1) Sample and acquire extreme value data of the power supply system under test according to the set sampling interval. The extreme value data includes the lowest single cell voltage, the highest single cell voltage and the total current. Perform preliminary screening on the acquired data to ensure that the acquired data of the battery system is the data during charging.

[0006] 2) The data that was initially screened was screened again to ensure that the data obtained from the battery system is battery data that shows the battery is charging normally, the charging process is complete, and the charging time reaches the set time.

[0007] 3) Determine if the branch is open based on the extreme value data of the selected individual cell voltages. If both of the following conditions are met, it indicates that the branch containing the individual cell with the lowest individual voltage is open.

[0008] Condition 1: The highest single-cell voltage is greater than the voltage at which the constant current charging ends and the current-reducing charging begins, but less than the charging cutoff voltage;

[0009] Condition 2: The difference between the maximum and minimum values ​​of the lowest single-cell voltage is less than the minimum amplitude of the battery depolarization voltage fluctuation.

[0010] The present invention also provides a vehicle battery system monitoring platform, the monitoring platform including a processor and a memory, the processor executing a computer program stored in the memory to implement the power system branch open circuit identification method of the present invention as described above.

[0011] This invention does not require voltage data for each individual battery cell, but only extreme value data. By filtering the extreme value data, it accurately obtains the extreme value data of batteries that are charging normally, with a complete charging process, and a charging time that reaches the set duration. Branch circuit openness is determined based on the relationship between the difference between the maximum and minimum values ​​of the lowest single-cell voltage during the current-reducing phase at the end of charging and the minimum amplitude of the battery depolarization voltage fluctuation. This invention's branch circuit openness identification method requires a small amount of battery data, allowing the monitoring platform to process data from multiple vehicles simultaneously.

[0012] Furthermore, in order to ensure the integrity of the acquired charging data, the conditions that need to be met in the preliminary screening in step 1) are: the battery management system status is charging; the total current is less than 0; and the extreme value data is not empty.

[0013] Furthermore, in order to achieve accurate screening, the conditions to be met for the second screening in step 2) are: the lowest single cell voltage maximum value < the first threshold; the lowest single cell voltage maximum value > the second threshold; the highest single cell voltage maximum value > the third threshold; the highest single cell voltage maximum value < the fourth threshold; the minimum battery SOC value < the fifth threshold; wherein the first threshold, the second threshold, the third threshold and the fourth threshold are all determined according to the battery material system, and the fifth threshold is greater than or equal to 85%.

[0014] Furthermore, to ensure that the data is normal charging data and that the length of the collected data meets the requirements, the conditions to be met in step 2) are further filtered again: minimum current value < sixth threshold; number of data points > seventh threshold; the sixth threshold is a negative value, the purpose of which is to ensure that the battery is charging normally. Attached Figure Description

[0015] Figure 1 This is a flowchart of the power system branch circuit open circuit identification method of the present invention. Detailed Implementation

[0016] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings.

[0017] This invention targets batteries with large capacity systems. Because these batteries contain a large number of individual cells, uploading the voltage and current data of each cell would result in excessive data transmission. To reduce this, only extreme value data, such as the lowest and highest individual cell voltages, is transmitted at a time. Therefore, this invention proposes a method for identifying branch circuit breaks in a power system using only extreme value data. The implementation process of this method is as follows: Figure 1 As shown, the specific implementation steps are as follows.

[0018] 1. Obtain extreme value data from the battery system and perform preliminary screening.

[0019] First, the battery management system collects parameters of the battery system, including data such as voltage, current and temperature of individual cells. Then, it selects extreme values ​​and filters the selected data to ensure that the battery management status is charging, the battery is in the charging process, and the highest, lowest, and current values ​​of each individual cell are not empty. At the same time, it uses the battery system data of the vehicle for the current day, or it can use data from a previously set time, such as data from 24 hours or 12 hours ago.

[0020] 2. The preprocessed data is screened again to ensure that the acquired battery system data is battery data that shows the battery is charging normally, the charging process is complete, and the charging time is sufficient.

[0021] To ensure that the selected data meets the above conditions, the present invention specifies the following judgment criteria:

[0022] 1) The minimum single cell voltage is less than the first threshold. This is to rule out the problem of battery polarization. This is because the static full-charge voltage of a lithium battery generally does not exceed the first threshold. If the minimum single cell voltage exceeds the first threshold, it means that the lithium battery is polarized and has not been disconnected.

[0023] 2) The minimum single cell voltage is greater than the second threshold. This is to rule out the possibility of a damaged single cell. This is because the minimum voltage for normal use of a lithium battery is generally greater than the second threshold.

[0024] 3) To ensure that the power system was once fully charged, the maximum single-cell voltage is greater than the third threshold. This is because polarization occurs at the end of a full charge of a lithium battery, and the voltage will reach the third threshold.

[0025] 4) The maximum single-cell voltage is less than the fourth threshold, where the fourth threshold is the upper limit of the normal operating range of a certain type of lithium battery, which varies depending on the material system.

[0026] 5) The minimum battery SOC value is less than the fifth threshold (which can be set to 95%). The purpose is to exclude data with too short a charging time on that day, because too short a charging time will affect the accuracy of subsequent branch circuit breakage judgment.

[0027] 6) The minimum current value is less than the sixth threshold (the sixth threshold is a negative value, indicating charging, and can be set to -10A). The purpose is to ensure that the battery is charged normally, eliminate branch circuit repairs, and ensure a certain degree of polarization.

[0028] 7) The number of data points > the seventh threshold (can be set to 15) is used to exclude data with too short a charging time.

[0029] The first, second, third, and fourth thresholds are determined based on the battery's material system (different material systems result in different OCV curves). For lithium iron phosphate batteries, the first, second, third, and fourth thresholds can be set to 3.33V, 2.5V, 3.6V, and 4.0V, respectively.

[0030] 3. Determine if a branch circuit is open based on the extreme value data of the selected individual cell voltages.

[0031] The present invention provides two conditions for determining branch circuit openness, as follows:

[0032] 1) The highest single-cell voltage is greater than the eighth threshold and less than the ninth threshold;

[0033] 2) The difference between the maximum and minimum values ​​of the lowest single-cell voltage is less than the tenth threshold.

[0034] When both of the above conditions are met, an open circuit occurs in the branch containing the cell with the lowest individual voltage. The eighth, ninth, and tenth thresholds are determined based on the battery's material system. The eighth threshold is the voltage at which the battery begins current-reducing charging after constant current charging ends; the ninth threshold is the charging cutoff voltage; and the tenth threshold is the minimum amplitude of depolarization voltage fluctuation for a typical battery. For lithium iron phosphate batteries, the eighth, ninth, and tenth thresholds can be set to 3.55V, 3.7V, and 5mV, respectively. Condition 1 aims to ensure that it is the final current-reducing stage of charging. If the change in the lowest individual voltage is less than a certain threshold during this stage, it indicates that the individual cell represented by the lowest individual voltage has not undergone depolarization during the final current-reducing stage of charging. In this case, it indicates that an open circuit fault has occurred in the branch containing the individual cell represented by the lowest individual voltage.

[0035] In a lithium battery system containing 100 individual cells, if an open circuit occurs in the branch containing the second individual cell, neither charging nor discharging will affect the voltage or state of charge (SOC) of that cell. If the open circuit occurs in the branch containing the second individual cell when its SOC is 70%, its voltage and SOC will remain unaffected during the current charging process. However, towards the end of the charging process (during the transition from constant current charging to reduced current charging), the voltage of the cells in the normal branches will experience depolarization voltage fluctuations. Only the voltage of the second individual cell will not exhibit polarization. The maximum and minimum values ​​of the minimum individual cell voltage are both for the second individual cell. Therefore, the voltage change of the second individual cell during this reduced current charging process is very small; that is, the difference between the maximum and minimum values ​​of the minimum individual cell voltage is less than the minimum amplitude of the battery depolarization voltage fluctuation. This allows us to determine which branch experienced the open circuit.

[0036] Platform Implementation Examples

[0037] The vehicle battery system monitoring platform of the present invention is a cloud platform, including a processor and a memory. The processor executes a computer program stored in the memory to implement the method of the above-described method embodiments. That is, the method in the above method embodiments should be understood to be a flow of a power system branch open circuit identification method implemented by computer program instructions. These computer program instructions can be provided to the processor, causing the processor to execute these instructions to produce the functions specified for implementing the above-described method flow.

[0038] In this embodiment, the processor refers to a processing device such as a microprocessor (MCU) or a programmable logic device (FPGA); the memory refers to a physical device used to store information, which typically involves digitizing the information and then storing it using media that utilizes electrical, magnetic, or optical methods. Examples include: various types of memory that store information using electrical energy, such as RAM and ROM; various types of memory that store information using magnetic energy, such as hard disks, floppy disks, magnetic tapes, magnetic core memory, bubble memory, and USB flash drives; and various types of memory that store information using optical methods, such as CDs or DVDs. Of course, there are other types of memory, such as quantum memories and graphene memories.

[0039] The device consisting of the aforementioned memory, processor, and computer program is implemented in a computer by the processor executing the corresponding program instructions. The processor can run various operating systems, such as Windows, Linux, Android, and iOS.

[0040] As an alternative implementation, the device may also include a display for showing diagnostic results for staff reference.

Claims

1. A power system branch circuit break identification method, characterized by, The identification method comprises the following steps: 1) Obtain extreme value data in the power supply system to be measured according to a set sampling interval, the extreme value data comprising the lowest single battery voltage, the highest single battery voltage and the total current, and perform preliminary screening on the obtained data to ensure that the obtained data of the battery system is data during charging; 2) Perform re-screening on the preliminarily screened data to ensure that the obtained data of the battery system is battery data during normal charging, complete charging process and charging duration reaching a set duration; 3) Perform branch circuit breaking judgment according to the extreme value data of the screened single battery voltage, and if the following two conditions are both met, it is indicated that the branch circuit of the single battery with the lowest single battery voltage occurs breaking; Condition one: the highest single battery voltage is greater than the voltage at which the constant current charging of the battery ends and the current drops and is less than the charging cutoff voltage; Condition two: the difference between the maximum value and the minimum value of the lowest single battery voltage is less than the minimum amplitude of the battery depolarization voltage fluctuation.

2. The power system branch circuit identification method of claim 1, wherein, The conditions required to be met for the preliminary screening in the step 1) are: the state of the battery management system is charging; the total current is less than 0; and the extreme value data is not empty.

3. The power system branch circuit identification method of claim 1, wherein, The conditions required to be met for the re-screening in the step 2) are: the maximum value of the lowest single battery voltage < the first threshold value; the maximum value of the lowest single battery voltage > the second threshold value; the maximum value of the highest single battery voltage > the third threshold value; the maximum value of the highest single battery voltage < the fourth threshold value; and the minimum value of the battery SOC < the fifth threshold value; wherein the first threshold value, the second threshold value, the third threshold value and the fourth threshold value are determined according to the material system of the battery, and the fifth threshold value is greater than or equal to 85%.

4. The power system branch circuit identification method of claim 3, wherein, The conditions required to be met for the re-screening in the step 2) further comprise: the minimum value of the current < the sixth threshold value; and the number of data points > the seventh threshold value; the sixth threshold value is a negative value, and the purpose is to ensure normal charging of the battery.

5. A vehicle battery system monitoring platform in communication with each vehicle, the monitoring platform comprising: The monitoring platform comprises a processor and a memory, the processor executes a computer program stored by the memory to realize the power supply system branch circuit breaking identification method according to any one of claims 1-4.

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