Branch imbalance fault identification method and cloud platform for multi-branch battery system

Abstract

The present invention relates to a method and cloud platform for identifying branch imbalance faults in a multi-branch battery system, and belongs to the technical field of battery systems. The identification method includes: obtaining the highest cell voltage of the power battery during the rest stage after charging is completed, and the initial voltage value of the cell corresponding to the highest cell voltage; the rest stage is a static process between the completion of charging and the start of active discharge, and there is no secondary charging in this process; if the highest cell voltage is greater than a voltage threshold and the highest cell voltage is greater than the initial voltage value, it is determined to be a branch imbalance fault. The present invention analyzes the highest cell voltage of the power battery during the rest stage without secondary charging. If the highest cell voltage is greater than the voltage threshold and the highest cell voltage is greater than the initial voltage value, it indicates that the cell voltage has risen and is overcharged, and an imbalance fault has occurred. The present invention can determine whether an imbalance fault has occurred only by using the extreme value data of the cell voltage, which greatly improves the efficiency of fault identification.

Description

Technical Field

[0001] The present invention relates to a method for identifying branch imbalance faults in a multi-branch battery system and a cloud platform, belonging to the technical field of battery systems. Background Art

[0002] At present, the battery warranty requirements for new energy vehicles are becoming increasingly higher, generally requiring more than 8 years; in the context of increasingly higher requirements, electric vehicles need to increase the battery capacity when equipping battery designs so that the number of battery cycles is lower under the same mileage and age conditions.

[0003] For this reason, the application scope of multi-branch battery systems is becoming wider and wider. However, due to differences in branch capacity attenuation, battery cell internal resistance, connection resistance between battery cells, and branch harness internal resistance, the battery system has inconsistent current during the charging process, resulting in differences in the cumulative total voltage of branch cells and branch SOC. As a result, after the external charging is completed, charging and discharging between branches brings the risk of overcharging of single cells and the phenomenon of multi-branch imbalance, which has a serious impact on the battery life and safety.

[0004] As the number of vehicles increases and safety issues become increasingly serious, it is necessary to centrally manage vehicles and promptly detect vehicle imbalance faults. In order to monitor multi-branch imbalance phenomena of multiple vehicles in the existing technology, the power battery system of each vehicle sends the collected information to the cloud platform, and the cloud platform analyzes the faults.

[0005] However, if the vehicle sends all the collected information to the cloud platform, it will overburden the cloud platform and reduce the efficiency of fault identification. Summary of the Invention

[0006] The purpose of this application is to provide a multi-branch battery system branch imbalance fault identification method and cloud platform to solve the problem of high cost of existing imbalance fault identification.

[0007] To achieve the above objectives, the present application proposes a technical solution for a method for identifying branch imbalance faults in a multi-branch battery system, comprising the following steps:

[0008] 1) Obtaining the highest cell voltage of the power battery during a rest phase after charging is completed, as well as the initial cell voltage value corresponding to the highest cell voltage; the rest phase is a static process between the completion of charging and the start of active discharge, and no secondary charging occurs during this process;

[0009] 2) If the highest cell voltage is greater than the voltage threshold and the highest cell voltage is greater than the initial voltage value, it is determined to be a branch unbalance fault.

[0010] The beneficial effect of the technical solution of the multi-branch battery system branch imbalance fault identification method of the present invention is that, because secondary charging can affect the accuracy of fault diagnosis, the present invention analyzes the highest cell voltage during the power battery's idle phase (without secondary charging) to determine whether an imbalance fault exists. If the highest cell voltage is greater than a voltage threshold and greater than an initial voltage value, it indicates that the cell voltage has increased and is overcharged, indicating an imbalance fault. The present invention can determine whether an imbalance fault has occurred solely based on the extreme cell voltage data, greatly improving the efficiency of fault identification.

[0011] Furthermore, in order to accurately determine the secondary charge, the steps of determining the secondary charge include:

[0012] a. Obtain the total voltage at each moment during the shelf phase;

[0013] b. If the total voltage at a certain moment is greater than the reference voltage at that moment, or the difference between the total voltage at a certain moment and the lowest total voltage before that moment is greater than the difference threshold, it is secondary charging;

[0014] The reference voltage is a voltage on a reference curve of time-total voltage, and the reference curve is a straight line connecting an initial total voltage and a terminal total voltage in the rest phase.

[0015] Furthermore, in order to more accurately determine the shelving stage, the moment when charging is completed is the moment when the highest single cell voltage is greater than the full-charge voltage and 0≤total current≤high current value; the moment when active discharge starts is later than the moment when charging is completed and the total current is greater than the high current value or the total current is less than the low current value.

[0016] Furthermore, due to the characteristics of the battery material, the voltage threshold during overcharging is different, so the voltage threshold is set according to the battery material.

[0017] In addition, the present application also proposes a technical solution for a cloud platform, including a processor, a memory, and a computer program stored in the memory and executable on the processor, wherein the processor implements the following steps when executing the computer program:

[0018] 1) Obtaining the highest cell voltage of the power battery during a rest phase after charging is completed, as well as the initial cell voltage value corresponding to the highest cell voltage; the rest phase is a static process between the completion of charging and the start of active discharge, and no secondary charging occurs during this process;

[0019] 2) If the highest cell voltage is greater than the voltage threshold and the highest cell voltage is greater than the initial voltage value, it is determined to be a branch unbalance fault.

[0020] The cloud platform's technical solution has the beneficial effect of determining whether an imbalance fault exists by analyzing the maximum cell voltage during a power battery's rest phase (without secondary charging) to determine if an imbalance fault exists. Because secondary charging can affect the accuracy of fault diagnosis, the present invention analyzes the maximum cell voltage during a power battery's rest phase (without secondary charging) to determine if an imbalance fault exists. If the maximum cell voltage exceeds both a voltage threshold and an initial voltage, this indicates a rise in cell voltage and overcharge, indicating an imbalance fault. The cloud platform only needs to receive cell voltage extreme value data uploaded by the vehicle to determine if an imbalance fault has occurred, significantly improving the efficiency of fault identification.

[0021] Furthermore, in order to accurately determine the secondary charge, the steps of determining the secondary charge include:

[0022] a. Obtain the total voltage at each moment during the shelf phase;

[0023] b. If the total voltage at a certain moment is greater than the reference voltage at that moment, or the difference between the total voltage at a certain moment and the lowest total voltage before that moment is greater than the difference threshold, it is secondary charging;

[0024] The reference voltage is a voltage on a reference curve of time-total voltage, and the reference curve is a straight line connecting an initial total voltage and a terminal total voltage in the rest phase.

[0025] Furthermore, in order to more accurately determine the shelving stage, the moment when charging is completed is the moment when the highest single cell voltage is greater than the full-charge voltage and 0≤total current≤high current value; the moment when active discharge starts is later than the moment when charging is completed and the total current is greater than the high current value or the total current is less than the low current value.

[0026] Furthermore, due to the characteristics of the battery material, the voltage threshold during overcharging is different, so the voltage threshold is set according to the battery material. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is a flow chart of a method for identifying branch imbalance faults in a multi-branch battery system according to the present invention;

[0028] Figure 2 This is a schematic diagram of the present invention in which secondary charging is determined by condition b during the shelving stage;

[0029] Figure 3 This is a schematic diagram of determining the occurrence of secondary charging according to condition c during the shelving phase of the present invention;

[0030] Figure 4 This is a curve diagram of the maximum voltage of a single cell and the total voltage in the shelving stage when an unbalanced fault occurs in the present invention;

[0031] Figure 5 Schematic diagram of the structure of the cloud platform of the present invention. DETAILED DESCRIPTION

[0032] Example of a method for identifying branch imbalance faults in a multi-branch battery system:

[0033] The main idea of ​​the present invention is to determine whether branch imbalance occurs based on the highest cell voltage in the shelving stage and the initial voltage value of the cell corresponding to the highest cell voltage in the absence of secondary charging: if the highest cell voltage is greater than the voltage threshold and the highest cell voltage is greater than the initial voltage value, it indicates that the cell is charged and overcharged, and therefore it is determined to be a branch imbalance fault.

[0034] Multi-branch battery system branch imbalance fault identification method, such as Figure 1 As shown, the following steps are included:

[0035] 1) Data extraction of power batteries.

[0036] The power battery proposed in this embodiment is a lithium iron phosphate battery (a type of lithium battery). As other implementation methods, the power battery can also be a lead-acid battery or a ternary battery among lithium batteries, etc. The present invention does not impose any restrictions on this, as long as it can serve as a power source for a pure electric vehicle and provide power for a pure electric vehicle.

[0037] The power battery is connected to the power battery management system (BMS). The BMS records data including the battery management system status, the highest cell voltage at each moment, the initial cell voltage corresponding to the highest cell voltage, the total voltage and total current of the power battery. To identify imbalance faults, the BMS typically records data for the past two days.

[0038] In this embodiment, branch imbalance fault identification is performed on the cloud platform. The cloud platform can identify faults for many vehicles, so the cloud platform needs to obtain the VIN codes of different vehicles to distinguish them. The cloud platform also needs to obtain data recorded by the BMS of each vehicle as the basis for fault identification.

[0039] 2) Segment the data in step 1).

[0040] The battery management system is segmented according to its status. The moment when the battery management system's status changes from "non-charging" to "charging" is defined as the end of the previous data segment and the beginning of the next data segment. That is, the start moment of the previous "charging" is regarded as the beginning of the previous data segment, and the start moment of the next "charging" is regarded as the end of the previous data segment.

[0041] In this step, in order to accurately identify the charging time, the charging time must be comprehensively judged in combination with current, SOC and other conditions to avoid misjudgment of secondary charging and resulting in segmentation errors.

[0042] 3) Group the data in a certain data segment and select the data at the end of charging and the rest stage. The rest stage here refers to the static process between the completion of charging and the start of active discharge.

[0043] Charging is completed when the highest cell voltage is greater than 3.5V (3.5V for lithium iron phosphate, 3.5V means the battery is fully charged), and 0≤total current I≤10A (that is, the battery management system state is "charging state", and taking into account that the current sensor may drift), which is also the earliest time when full charging is completed.

[0044] Active discharge begins when the end time is later than the completion time of charging and the total current I is greater than the high current value X1 or the low current value is less than X2. This end time is determined to eliminate the effects of secondary charging and active discharge on the calculation. In this embodiment, X1 = 10A and X2 = -5A.

[0045] 4) Determine whether the data of the shelving stage is continuous. If not, the data of this stage is unavailable and is replaced with data of other shelving stages. If continuous, proceed to step 5).

[0046] The data continuity is determined by the time intervals between adjacent data. In this embodiment, if the time interval between the set number of times is greater than or equal to the time threshold X7, the data is discontinuous. Here, the number of times is set to 2, and the time threshold X7 is 1 minute. In the actual program, whether the data is continuous corresponds to the identifier d, which is a cumulative value. If a time interval is greater than or equal to 1 minute, d is increased by 1; if all time intervals are less than 1 minute, d = 0. In this embodiment, if more than two time intervals are greater than or equal to 1 minute, that is, d < 2, the data is continuous and the data at this stage is usable.

[0047] Of course, the number of settings and time thresholds can be set as needed and are not limited here.

[0048] 5) Determine whether there is secondary charging during the shelving phase. If there is secondary charging, the data of this phase will affect the imbalance determination and the data is unavailable. If there is no secondary charging, proceed to step 6).

[0049] The data required to determine whether it is a secondary charge is: the total voltage at each moment during the standby phase. The judgment logic includes conditions b and c:

[0050] Condition b: if the total voltage at a certain moment is greater than the reference voltage at that moment, it is secondary charging; the reference voltage is the voltage on the reference curve of time-total voltage, and the reference curve is the straight line connecting the initial total voltage and the final total voltage in the shelving stage; in the actual program, condition b corresponds to identifier b, which is the cumulative value. If the total voltage at a certain moment is greater than the reference voltage at that moment, identifier b is increased by 1. If the total voltage at all moments in the shelving stage is less than or equal to the reference voltage at the corresponding moment, then b=0; that is, b≥1 represents that the external charging is secondary charging. Figure 2 As shown, the dotted line represents the reference curve, and the solid line is the total voltage. Figure 2 This is a schematic diagram of determining that it is secondary charging based on condition b.

[0051] Condition c, if the difference between the total voltage at a certain moment and the lowest total voltage Vmin before that moment is greater than the difference threshold X6, it is secondary charging; here X6 is defined as 0.2V, and the numerical setting of X6 is based on big data statistical analysis. If the value of X6 is greater than 0.2V, it indicates that there is external charging interference; in the actual program, condition c corresponds to identifier c, identifier c is the cumulative value, if the difference between the total voltage at a certain moment and Vmin before that moment is greater than 0.2, then identifier c is increased by 1, if in the shelving stage, the difference between the total voltage at all moments and Vmin before the corresponding moment is less than or equal to 0.2, then c=0, that is, c≥1 represents external charging as secondary charging. Figure 3 As shown, the dotted line represents the total voltage, and the solid line represents the highest single cell voltage. Figure 3 This is a schematic diagram of determining that the battery is being charged again based on condition c.

[0052] The size of the difference threshold can be set according to actual conditions and is not limited here.

[0053] Of the two conditions above, satisfying only one indicates the presence of secondary charging. Therefore, the conditions for determining non-secondary charging are b=0 and c=0.

[0054] 6) Determine whether a branch unbalance fault occurs based on the single cell voltage during the shelving stage.

[0055] like Figure 4 As shown, if the highest cell voltage in the shelving stage is greater than the voltage threshold X8 and the highest cell voltage is greater than the initial voltage value of the cell corresponding to the highest cell voltage (the initial voltage value is the voltage value corresponding to the starting moment of the shelving stage), it is determined to be a branch unbalanced fault.

[0056] The voltage threshold X8 varies for different batteries. In this embodiment, the voltage threshold X8 for lithium iron phosphate batteries is 3.7V, because exceeding 3.7V indicates that the battery is overcharged. Furthermore, if the voltage is greater than the initial voltage, it indicates that the voltage has rebounded and charging has occurred, thus indicating an imbalance fault.

[0057] Since the judgment of unbalanced fault is based on the single cell voltage, in order to avoid the phenomenon that the single cell voltage increases due to secondary charging, the secondary charging judgment is performed before the unbalanced fault judgment to ensure the accuracy of unbalanced fault identification.

[0058] In the above embodiment, the total voltage is used to determine whether secondary charging is required in step 5). In other implementations, since total voltage = average voltage * number of cells (number of individual cells), the average voltage is equivalent to the total voltage in determining whether secondary charging is required. Therefore, the average voltage can also be used to determine whether secondary charging is required. All subsequent judgment logic involving the total voltage can be replaced by the average voltage. Note: Almost all vehicles upload the total voltage, while only some upload the average voltage. Therefore, when the average voltage is uploaded, the average voltage judgment method can be used.

[0059] In the above embodiment, the number of data in the shelving stage is greater than 5, which ensures that the shelving stage is long enough to determine the imbalance fault.

[0060] When the vehicle of the present invention uploads data to the cloud platform, it does not upload all the data collected by the BMS, but only uploads the data required to identify branch imbalances, which greatly reduces the burden on the cloud platform, improves the recognition efficiency of the cloud platform, ensures timely identification of each faulty vehicle, and provides protection for vehicle safety.

[0061] Cloud platform implementation example:

[0062] Cloud platforms, such as Figure 5 As shown, it includes a processor, a memory, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements a method for identifying branch imbalance faults in a multi-branch battery system.

[0063] The specific implementation process and effect of the method for identifying branch imbalance faults in a multi-branch battery system are introduced in the above-mentioned embodiment of the method for identifying branch imbalance faults in a multi-branch battery system, and will not be repeated here.

[0064] That is, it should be understood that the method in the above embodiment of the method for identifying branch imbalance faults in a multi-branch battery system can be implemented by computer program instructions. These computer program instructions can be provided to a processor (such as a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device), so that the processor executes these instructions to generate the functions specified in the above method flow.

[0065] The processor referred to in this embodiment refers to a processing device such as a microprocessor MCU or a programmable logic device FPGA;

[0066] The memory referred to in this embodiment is used to store computer program instructions generated to implement the method for identifying branch imbalance faults in a multi-branch battery system, and includes a physical device for storing information, typically digitizing the information and then storing it in a medium utilizing electrical, magnetic, or optical means. Examples include various types of memory that use electrical energy to store information, such as RAM and ROM; various types of memory that use magnetic energy to store information, such as hard disks, floppy disks, magnetic tapes, magnetic core memories, bubble memories, and USB flash drives; and various types of memory that use optical means to store information, such as CDs or DVDs. Of course, other types of memory are also available, such as quantum memory and graphene memory.

[0067] The cloud platform is composed of a memory and a processor that stores computer program instructions for implementing the method for identifying branch imbalance faults in a multi-branch battery system. The computer executes corresponding program instructions by the processor. The computer can use a Windows operating system, a Linux system, or other operating systems, such as Android and iOS system programming languages, to implement the method on a smart terminal, as well as based on the processing logic of a quantum computer.

[0068] As another embodiment, the cloud platform may further include other processing hardware, such as a database or multi-level cache, a GPU, etc. The present invention does not specifically limit the structure of the cloud platform.

Claims

1. A method for identifying branch imbalance faults in a multi-branch battery system, characterized in that: The following steps are involved: 1) Obtain the highest cell voltage at each moment after the power battery is charged and during the rest phase, as well as the initial cell voltage corresponding to the highest cell voltage; The rest phase is a rest process between the completion of charging and the start of active discharge, and there is no secondary charging during this process; 2) If the highest cell voltage is greater than the voltage threshold and the highest cell voltage is greater than the initial voltage value, it is determined to be a branch unbalance fault; For different types of batteries, the voltage threshold is different. The voltage threshold is a voltage value used to measure whether a single cell is overcharged. A voltage greater than the voltage threshold indicates overcharge.

2. The method for identifying branch imbalance faults in a multi-branch battery system according to claim 1, wherein: The steps for determining secondary charging include: a. Obtain the total voltage at each moment during the shelf phase; b. If the total voltage at a certain moment is greater than the reference voltage at that moment, or the difference between the total voltage at a certain moment and the lowest total voltage before that moment is greater than the difference threshold, it is secondary charging; The reference voltage is a voltage on a reference curve of time-total voltage, and the reference curve is a straight line connecting an initial total voltage and a terminal total voltage in the rest phase.

3. The method for identifying branch imbalance faults in a multi-branch battery system according to claim 1, wherein: The moment when charging is completed is when the highest single cell voltage is greater than the full-charge voltage and 0≤total current≤high current value; the moment when active discharge starts is later than the moment when charging is completed and the total current is greater than the high current value or the total current is less than the low current value.

4. The method for identifying branch imbalance faults in a multi-branch battery system according to claim 1, wherein: The voltage threshold is set according to the battery material.

5. A cloud platform, characterized in that: The system comprises a processor, a memory, and a computer program stored in the memory and executable on the processor, wherein the processor implements the following steps when executing the computer program: 1) Obtain the highest cell voltage at each moment after the power battery is charged and during the rest phase, as well as the initial cell voltage corresponding to the highest cell voltage; The rest phase is a rest process between the completion of charging and the start of active discharge, and there is no secondary charging during this process; 2) If the highest cell voltage is greater than the voltage threshold and the highest cell voltage is greater than the initial voltage value, it is determined to be a branch unbalance fault; For different types of batteries, the voltage threshold is different. The voltage threshold is a voltage value used to measure whether a single cell is overcharged. A voltage greater than the voltage threshold indicates overcharge.

6. The cloud platform according to claim 5, characterized in that: The steps for determining secondary charging include: a. Obtain the total voltage at each moment during the shelf phase; b. If the total voltage at a certain moment is greater than the reference voltage at that moment, or the difference between the total voltage at a certain moment and the lowest total voltage before that moment is greater than the difference threshold, it is secondary charging; The reference voltage is a voltage on a reference curve of time-total voltage, and the reference curve is a straight line connecting an initial total voltage and a terminal total voltage in the rest phase.

7. The cloud platform according to claim 5, characterized in that: The moment when charging is completed is when the highest single cell voltage is greater than the full-charge voltage and 0≤total current≤high current value; the moment when active discharge starts is later than the moment when charging is completed and the total current is greater than the high current value or the total current is less than the low current value.

8. The cloud platform according to claim 5, characterized in that: The voltage threshold is set according to the battery material.

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