Method for accurately identifying electric leakage position of battery pack

Abstract

The invention discloses a method and system for accurately identifying the electric leakage position of a battery pack, and is suitable for the technical field of battery insulation detection and protection. The core of the method is as follows: firstly, when a battery pack is in a stable working state, specific excitation voltage is injected between a high-voltage loop and a battery shell of the battery pack; secondly, acquiring battery voltage and injection point voltage by adopting a high-precision voltage acquisition circuit; then, by analyzing the relative relation of the voltage values of all the collection points, simulation calculation and comparison are carried out based on the established battery pack distributed equivalent circuit model; and finally, accurately positioning a specific module, a battery cell cluster and even a single battery cell with an insulation fault (electric leakage). The scheme is simple in structure, low in cost and simple in calculation. According to the invention, on-line and non-intrusive accurate positioning of the electric leakage position of the battery pack is realized, and the troubleshooting efficiency and the maintenance safety of the battery system are greatly improved.

Description

Technical Field

[0001] This invention relates to the field of battery management systems and safety testing technology, specifically to a method and system for detecting insulation faults and accurately identifying leakage locations in large battery packs such as those used in ships, energy storage power stations, and electric vehicles. Background Technology

[0002] With the widespread use of batteries, the safe operation of battery packs (or battery banks) composed of hundreds or thousands of cells connected in series and parallel is of paramount importance. Insulation failure (i.e., leakage) is one of the major faults in battery systems, which can lead to electric shock hazards, damage to electrical components, or even thermal runaway fires.

[0003] Currently, industry standard methods (such as GB / T 18384.1) mainly use the "insulation resistance detection method," which calculates the overall insulation resistance value by measuring the voltage of the battery's total positive and negative terminals to ground (vehicle body). This method has significant limitations: it can only determine whether the overall system has poor insulation, but it cannot pinpoint the fault location. For a battery pack containing dozens of modules, once an alarm is triggered, each module needs to be manually disconnected for troubleshooting, which is extremely inefficient and may affect the integrity of the system.

[0004] Therefore, there is an urgent need for a technology that can accurately identify the specific location of leakage without disassembling the battery system. Summary of the Invention

[0005] 1. Purpose of the invention

[0006] This invention aims to overcome the shortcomings of existing technologies and provide a method and system for online and precise location of leakage points inside battery packs, achieving a leap from "overall alarm" to "precise location", greatly improving maintenance efficiency and system safety.

[0007] 2. Technical Solution

[0008] To achieve the above objectives and accurately identify the location of battery pack leakage, this invention has the following features: active injection, synchronous measurement, and accurate positioning.

[0009] Active injection: The test circuit actively injects two voltages to obtain circuit parameters under two states. The conversion frequency and specific voltage value are determined by the test circuit and can be adjusted according to different system parameters. It is highly flexible and applicable to various systems and scenarios.

[0010] Synchronous measurement: During measurement, the normal operation of the battery is not affected, and the battery can be charged and discharged normally, truly achieving synchronous measurement.

[0011] Accurate location: This invention can accurately calculate the number of battery strings where the insulation fault point is located, with an error of no more than 1 string. The accurate location greatly reduces the workload for subsequent maintenance.

[0012] 3. Beneficial effects

[0013] Compared with the prior art, the present invention has the following significant advantages:

[0014] Precise location: It can pinpoint leakage faults to specific battery modules or cell clusters, greatly narrowing the scope of troubleshooting.

[0015] Online non-destructive testing: No need to disassemble the battery pack or disconnect electrical connections; testing can be completed quickly while the battery is idle or under maintenance.

[0016] High sensitivity: By employing the injection method and high-precision synchronous sampling, it can detect changes in insulation resistance and identify early insulation hazards.

[0017] Strong anti-interference capability: By selecting a specific frequency excitation signal and synchronous demodulation technology, the inherent DC bias and power frequency interference of the system are effectively suppressed.

[0018] Intelligent: By combining models and algorithms, it can achieve automatic diagnosis, historical trend analysis and remote early warning, providing data support for predictive maintenance. Attached Figure Description

[0019] Figure 1 Diagram of low-voltage injection insulation testing model;

[0020] Figure 2 Actual model diagram of battery pack and detection circuit;

[0021] Figure 3 Battery pack single-point failure model diagram;

[0022] Figure 4 Software flowchart. Detailed Implementation

[0023] The basic circuit is as shown above. Figure 1 As shown in the figure, the specific definitions of each point are as follows.

[0024] UB: DC system battery voltage

[0025] U1: Voltage at the sampling point relative to B- when the injected voltage US is applied.

[0026] U2: Voltage of the sampling point relative to B- when the injection voltage is 0V.

[0027] US: Injection voltage value

[0028] RXP, RXN: Sampling resistor values ​​in the voltage sampling circuit

[0029] RP, RN: Equivalent insulation resistance values ​​under a simplified model

[0030] In the simplified model, the parallel value of RP and RN

[0031] N: Total number of battery cells connected in series

[0032] according to Figure 1 As can be seen from the circuit structure, the entire measurement and driving circuit structure is very simple. In practical applications, it includes a voltage detection circuit, a voltage conversion circuit, and an injected voltage driving circuit.

[0033] For detailed principles and formula derivations, please refer to... Figure 1 The equivalent circuit model.

[0034] Given conditions:

[0035] Formula 1:

[0036] Formula 2:

[0037] Formula 3:

[0038] Formula 4:

[0039] From the above formulas, through mathematical derivation, the insulation resistances RP and RN in the simplified model can be obtained. The formulas are as follows:

[0040] Formula 5:

[0041] Formula 6:

[0042] Formula 7:

[0043] To facilitate calculations in embedded software and prevent overflow errors due to excessively large data, the formula is modified to obtain the following formula:

[0044] Formula 8:

[0045] Formula 9:

[0046] Formula 10:

[0047] The above measurements show the insulation resistance of the system under normal conditions. Battery system insulation faults fall into two main categories: one is caused by leakage due to prolonged use and aging, leading to a gradual decrease in insulation resistance; the other is caused by vibration or other factors, resulting in a short circuit between a cell and the casing, causing an insulation fault. In the first case, where the insulation resistance gradually decreases, the battery fault can be identified through calculations using a simplified model's RP and RN. This situation indicates battery aging, not a fault in a single cell; the entire battery pack's insulation weakens due to aging, and there's no need to pinpoint the specific cell. The second type of fault occurs within the battery's normal lifespan, where an insulation failure occurs in a cell due to vibration or other factors. In this case, it's necessary to locate and inspect the fault point.

[0048] For single-point insulation faults, such as Figure 2 As shown in the single-cell model, when the corresponding cell fails, the corresponding Rx resistance value will become close to 0Ω. At this time, when the injected voltage is 0V, the measured sampling point voltage U2 (FGND to B-) is the fault point voltage, and the corresponding faulty battery string location is:

[0049] Formula 11:

[0050] Round up to the nearest whole number; the result is the location of the faulty battery.

[0051] When the fault point is not completely short-circuited and the insulation resistance is not close to 0Ω, the insulation resistance of a normal battery is very large and can be ignored. In this case, the equivalent circuit is as follows: Figure 3 As shown.

[0052] At this time there is

[0053] Formula 12:

[0054] Formula 13:

[0055] Formula 14:

[0056] Solving equations 12-14 simultaneously yields:

[0057] Formula 15:

[0058] Formula 16:

[0059] Round up to the nearest whole number; the result is the location of the faulty battery.

[0060] Based on the above strategy, the actual measurement results are accurate, with a maximum error not exceeding one battery cell.

[0061] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for accurately identifying the location of leakage in a battery pack, characterized in that, Includes the following steps: S1: When the battery pack is in a stable working state, inject a DC excitation signal of US (usually 10~30V) between the total positive / total negative (B+ / B-) of the battery pack and the casing. S2: Using a high-precision voltage acquisition module, the voltage value signals at each detection point of the battery pack are acquired synchronously, including the battery voltage UB and the voltage U1 between sampling points B- (FGND to B-). S3: Set the injected signal voltage value to 0V. S4: Using a high-precision voltage detection circuit, the sampling point voltage U2 (FGND to B-) and the injected signal voltage US are collected; S5: Analyze the collected voltage signal with the excitation signal to obtain the amplitude difference of each state voltage and its relationship with the excitation signal; S6: Based on the topology of the battery pack, establish an equivalent circuit model of the battery pack including distributed insulation impedance, and input the measured voltage data of each point obtained in steps S2~S4 into the model for simulation calculation and reverse deduction. S7: By comparing simulation results with measured data, the battery locations where the insulation resistance is significantly lower than the preset threshold are identified.

2. The method according to claim 1, characterized in that, In step S1, the excitation signal switching frequency range is 1Hz - 1kHz, preferably 1Hz - 10Hz, to avoid power frequency interference and adapt to the capacitive reactance characteristics of the battery system.

3. The method according to claim 1, characterized in that, In step S2, the high-precision voltage detection circuit has an accuracy of not less than 0.1% FS to ensure accurate measurement of weak voltage signals.

4. The method according to claim 1, characterized in that, In step S6, when establishing the equivalent circuit model, each battery module or cell cluster is equivalent to a sub-circuit consisting of an ideal voltage source, internal resistance, and insulation resistance to be diagnosed connected in parallel. All sub-circuits are combined according to the actual electrical connection relationship.

5. The method according to claim 1, characterized in that, It also includes step S6: storing the location results, fault insulation resistance value, relevant data waveforms and timestamps, alarming and uploading them to the remote monitoring platform.

6. A battery pack leakage location accurate identification system for implementing the method of any one of claims 1-5, characterized in that, include: Signal injection unit: used to generate and inject the excitation signal; Acquisition unit: includes multiple high-precision voltage acquisition circuits, used to synchronously acquire voltage signals at each detection point; Signal processing and control unit: used to control the synchronization of signal injection and acquisition, and to filter, amplify and process the acquired signals; Analysis and localization unit: It contains the equivalent circuit model and localization algorithm, and is used to perform model simulation, data comparison and fault location calculation; Human-computer interaction and output unit: used to display positioning results, alarm information and historical data.

7. The system according to claim 6, characterized in that, The high-precision voltage acquisition module is non-invasively mounted on the dedicated grounding wire of each battery module or cell cluster.

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