Battery fault diagnosis method and system based on energy storage battery cluster SOC

Abstract

The invention belongs to the technical field of battery fault diagnosis, and provides a battery fault diagnosis method and system based on an energy storage battery cluster SOC. The battery fault diagnosis method comprises the following steps: estimating a battery cluster SOC on line; dynamically updating a safety early warning threshold value of the battery module based on the identification parameters of the equivalent circuit model of the battery module, the current current and temperature of the battery module and the online estimated SOC of the battery cluster; judging whether the battery module is a normal battery module or not based on the SOC deviation of each parallel branch of the battery module, the deviation of the battery module relative to the time differential and a corresponding threshold value; if the battery module is a fault battery module or a potential fault battery module, fault diagnosis of the next level is carried out, whether the battery module is a normal battery or not is judged according to the voltage deviation and the SOC deviation of the single batteries, the deviation of the single batteries about time differential and corresponding threshold values, and matching operation is executed according to the fault level of the battery module.

Description

Technical Field

[0001] The present invention belongs to the technical field of battery fault diagnosis, and in particular relates to a battery fault diagnosis method and system based on the SOC of an energy storage battery cluster. Background Art

[0002] The statements in this section merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] As the smallest battery unit connected to the energy storage inverter of the energy storage power station, the energy storage battery cluster is usually composed of multiple battery boxes, each of which is composed of multiple single cells connected in series and parallel. Lithium-ion batteries have become the preferred type of energy storage batteries due to their high energy density, long life, and high charging and discharging efficiency. In the actual application scenario of energy storage power stations, the energy storage battery cluster is essentially a large battery group. During the application process, the performance of the battery will deteriorate over time, and internal short circuits, external short circuits and other faults may occur. The above problems will not only reduce the efficiency of the energy storage system, but may also cause serious safety problems. Therefore, the development of reliable battery fault diagnosis technology is the key to ensuring the safe operation of the energy storage system.

[0004] Traditional battery cluster fault diagnosis methods mainly perform battery fault diagnosis based on characteristics such as voltage, voltage extreme difference, current, temperature, and temperature extreme difference. These methods are easily affected by factors such as noise and data acquisition time step in complex application scenarios of battery clusters, resulting in inaccurate fault diagnosis. At the same time, the battery current acquisition error is large, and the temperature acquisition inside the battery module is too small, which makes it difficult to use it for fault diagnosis. The state of charge (SOC) of the battery cluster is another important state parameter in its operation process. It can not only intuitively reflect the capacity storage state of the battery cluster, but also has a certain correlation with the battery fault behavior. Although the battery cluster SOC cannot be measured directly, it can be estimated online based on basic parameters. Common estimation methods include ampere-hour integration method and table lookup method. At present, due to the dynamic and nonlinear characteristics of the single cell during the charging and discharging process, the battery cluster SOC estimated by the traditional method has a large error. Especially when the performance of a single cell decreases, the accuracy of the battery cluster SOC estimation will be significantly reduced, making it very challenging to establish a reliable fault diagnosis method based on the battery cluster SOC. In addition, battery performance will decay as the battery is used for a longer time, which may make the previously set fault diagnosis threshold no longer applicable. Existing battery cluster management systems (BCMS) often lack sufficient adaptive capabilities and dynamic optimization mechanisms, making it difficult to adjust the fault diagnosis threshold in real time according to the degradation of battery performance. This limitation reduces the accuracy of fault diagnosis. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a battery fault diagnosis method and system based on the SOC of an energy storage battery cluster. The BCMS fault diagnosis method has the SOC adaptive adjustment capability, which can improve the estimation accuracy of the battery cluster SOC and utilize the changing characteristics of the SOC to achieve reliable diagnosis and early warning of battery cluster faults.

[0006] In order to achieve the above object, the present invention adopts the following technical solution:

[0007] A first aspect of the present invention provides a battery fault diagnosis method based on the SOC of an energy storage battery cluster.

[0008] In one or more embodiments, a battery fault diagnosis method based on the SOC of an energy storage battery cluster is provided, comprising:

[0009] Perform parameter identification on the equivalent circuit model of each parallel branch of each battery module, and estimate the battery cluster SOC online based on the current discharge capacity of each battery module;

[0010] Based on the identification parameters of the battery module equivalent circuit model, the current current and temperature of the battery module and the online estimated battery cluster SOC, the safety warning threshold of the battery module is dynamically updated; the safety warning threshold includes: the SOC deviation threshold of each parallel branch of the battery module and its deviation threshold with respect to time differential, and the voltage deviation threshold, SOC deviation threshold and its deviation threshold with respect to time differential of the single cell;

[0011] Based on the SOC deviation of each parallel branch of the battery module and its deviation with respect to time differential and the corresponding threshold, it is determined whether the battery module is a normal battery module. If so, it directly enters the charging and discharging process at the next moment;

[0012] If the battery module is a faulty battery module or a potential faulty battery module, the next level of fault diagnosis is performed, and the voltage deviation, SOC deviation and its deviation with respect to time differential of the single battery and the corresponding threshold are used to determine whether the battery module is a normal battery. If so, the charging and discharging process at the next moment is directly entered; otherwise, the fault level of the battery module is determined, and then matching operations are performed.

[0013] As an implementation mode, if the battery module is determined to be a primary fault battery or a secondary fault battery, the battery balancing control strategy is dynamically adjusted to reduce the battery fault level or eliminate the battery fault at the next moment;

[0014] If the battery module is determined to be a level 3 faulty battery, the single cells in the battery module will be further powered off for evaluation and maintenance to determine the type of battery fault.

[0015] As an implementation manner, when the SOC deviation of any parallel branch of the battery module is greater than or equal to the corresponding threshold value, the battery module is determined to be a faulty battery module.

[0016] As an implementation manner, if the SOC deviation of a parallel branch of the battery module is less than the corresponding threshold value, and the deviation of the SOC of a parallel branch of the battery module with respect to the time differential is greater than or equal to the corresponding threshold value, the battery module is determined to be a potential battery module.

[0017] As an implementation mode, when the battery module is a potential battery module, if the deviation of the SOC of the single battery with respect to the time differential is greater than or equal to the corresponding threshold, the battery module is judged to be a primary fault battery;

[0018] When the battery module is a potential battery module, if the deviation of the SOC of the single battery with respect to the time differential is less than the corresponding threshold, the battery module is determined to be a normal battery.

[0019] As an implementation manner, if the SOC deviation of a parallel branch of the battery module is less than a corresponding threshold value, and the deviation of the SOC of a parallel branch of the battery module with respect to the time differential is less than the corresponding threshold value, the battery module is determined to be a normal battery module.

[0020] As an implementation mode, if the voltage deviation of the single cell is greater than or equal to the corresponding threshold value, the single cell in the battery module is determined to be a level 3 fault cell;

[0021] If the voltage deviation of any single battery is less than the corresponding threshold value, and the SOC deviation of the single battery is greater than or equal to the corresponding threshold value, the battery module is determined to be a secondary fault battery;

[0022] If the voltage deviation of any single battery is less than the corresponding threshold, the SOC deviation of the single battery is less than the corresponding threshold, and the deviation of the SOC of the single battery with respect to the time differential is greater than or equal to the corresponding threshold, then the battery module is judged to be a primary fault battery;

[0023] If the voltage deviation of any single battery is less than the corresponding threshold, the SOC deviation of the single battery is less than the corresponding threshold, and the deviation of the SOC of the single battery with respect to the time differential is less than the corresponding threshold, the battery module is judged to be a normal battery.

[0024] A second aspect of the present invention provides a battery fault diagnosis system based on the SOC of an energy storage battery cluster.

[0025] In one or more embodiments, a battery fault diagnosis system based on the SOC of an energy storage battery cluster includes:

[0026] A battery cluster SOC estimation module is configured to: perform parameter identification on an equivalent circuit model of each parallel branch of each battery module, and estimate the battery cluster SOC online in combination with the current dischargeable capacity of each battery module;

[0027] A battery cluster fault diagnosis module is configured to:

[0028] Based on the identification parameters of the battery module equivalent circuit model, the current current and temperature of the battery module and the online estimated battery cluster SOC, the safety warning threshold of the battery module is dynamically updated; the safety warning threshold includes: the SOC deviation threshold of each parallel branch of the battery module and its deviation threshold with respect to time differential, and the voltage deviation threshold, SOC deviation threshold and its deviation threshold with respect to time differential of the single cell;

[0029] Based on the SOC deviation of each parallel branch of the battery module and its deviation with respect to time differential and the corresponding threshold, it is determined whether the battery module is a normal battery module. If so, it directly enters the charging and discharging process at the next moment;

[0030] If the battery module is a faulty battery module or a potential faulty battery module, the next level of fault diagnosis is performed, and the voltage deviation, SOC deviation and its deviation with respect to time differential of the single battery and the corresponding threshold are used to determine whether the battery module is a normal battery. If so, the charging and discharging process at the next moment is directly entered; otherwise, the fault level of the battery module is determined, and then matching operations are performed.

[0031] In some other embodiments, a battery fault diagnosis system based on the SOC of an energy storage battery cluster includes:

[0032] Data acquisition unit and battery cluster management system;

[0033] The data acquisition unit is used to collect the charge and discharge current of each branch of the battery module, the battery temperature and the charging capacity of the battery module in the previous complete charging process and transmit them to the battery cluster management system;

[0034] The battery cluster management system includes a battery cluster SOC estimation module and a battery cluster fault diagnosis module;

[0035] The battery cluster SOC estimation module is configured to: perform parameter identification on each parallel branch equivalent circuit model of each battery module, and estimate the battery cluster SOC online in combination with the current dischargeable capacity of each battery module;

[0036] The battery cluster fault diagnosis module is configured as follows:

[0037] Based on the identification parameters of the battery module equivalent circuit model, the current current and temperature of the battery module and the online estimated battery cluster SOC, the safety warning threshold of the battery module is dynamically updated; the safety warning threshold includes: the SOC deviation threshold of each parallel branch of the battery module and its deviation threshold with respect to time differential, and the voltage deviation threshold, SOC deviation threshold and its deviation threshold with respect to time differential of the single cell;

[0038] Based on the SOC deviation of each parallel branch of the battery module and its deviation with respect to time differential and the corresponding threshold, it is determined whether the battery module is a normal battery module. If so, it directly enters the charging and discharging process at the next moment;

[0039] If the battery module is a faulty battery module or a potential faulty battery module, the next level of fault diagnosis is performed, and the voltage deviation, SOC deviation and its deviation with respect to time differential of the single battery and the corresponding threshold are used to determine whether the battery module is a normal battery. If so, the charging and discharging process at the next moment is directly entered; otherwise, the fault level of the battery module is determined, and then matching operations are performed.

[0040] A third aspect of the present invention provides a computer-readable storage medium.

[0041] A computer-readable storage medium stores a computer program, which, when executed by a processor, implements the steps in the battery fault diagnosis method based on the SOC of an energy storage battery cluster as described above.

[0042] Compared with the prior art, the present invention has the following beneficial effects:

[0043] (1) The present invention dynamically adjusts and updates the battery fault warning threshold by online identification of battery internal resistance and online data collection (including battery temperature and operating current), so that the constructed battery fault diagnosis method has high adaptability throughout the life cycle of the battery cluster, thereby ensuring the timely discovery and processing of potential faults of the battery cluster.

[0044] (2) The present invention uses the deviation of the module branch SOC and its differential as the basis for fault judgment at the battery cluster module level. The battery SOC deviation is not limited by the sampling time interval of the battery management system. The SOC differential changes significantly in amplitude and does not change its sign when a fault such as an external short circuit occurs. The faulty module can be identified quickly and reliably, and the requirement for the sampling time interval is lower than that of the voltage-based fault diagnosis method. The faulty battery can be further accurately located at the battery level through the SOC deviation and its differential of the single cell, thereby improving the efficiency and positioning accuracy of fault detection and providing a faster response for the system.

[0045] (3) The present invention can effectively eliminate the impact of SOC imbalance and minor faults in the battery cluster by dynamically adjusting the battery balancing control strategy for two minor faults, namely, primary battery fault and secondary battery fault, thereby extending the service life of the battery cluster and reducing the probability of a minor fault in the battery cluster evolving into a serious fault (i.e., a third-level fault). At the same time, the proposed hierarchical fault diagnosis method using voltage deviation, SOC deviation, and SOC differential deviation significantly reduces the amount of calculation while ensuring the reliability of fault detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0047] Figure 1 A schematic diagram of a battery cluster structure and diagnostic classification according to an embodiment of the present invention;

[0048] Figure 2 A flow chart of a method for dynamic diagnosis of battery cluster faults according to an embodiment of the present invention;

[0049] Figure 3 This is a schematic diagram of an equivalent circuit model of a battery cluster branch according to an embodiment of the present invention;

[0050] Figure 4 The discharge current curve of the battery with two instantaneous external short circuits according to the embodiment of the present invention;

[0051] Figure 5 Comparison of discharge voltage curves of a normal battery and a faulty battery in an embodiment of the present invention;

[0052] Figure 6 Comparison of discharge voltage differential curves of a normal battery and a faulty battery in an embodiment of the present invention;

[0053] Figure 7 Comparison of SOC change curves of a normal battery and a faulty battery during discharge in an embodiment of the present invention;

[0054] Figure 8 The figure is a comparison of SOC differential curves of a normal battery and a faulty battery during the discharge process according to an embodiment of the present invention. DETAILED DESCRIPTION

[0055] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0056] It should be noted that the following detailed descriptions are all illustrative and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0057] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0058] The present invention divides the battery cluster into three levels according to its structure, such as Figure 1 As shown: the first level is the battery cluster, which is composed of multiple battery modules; the second level is the battery module, which is composed of multiple single cells connected in series and parallel; the third level is the single cell, which is commonly a square lithium iron phosphate battery.

[0059] In an optional embodiment, a first-order RC circuit model is selected to simulate the current of each parallel branch, and the battery module is formed by connecting multiple first-order RC equivalent circuit models of parallel branches in parallel, such as Figure 3 shown.

[0060] In another embodiment, other order RC circuit models may also be used to simulate the current of each parallel branch.

[0061] Combination Figure 2 The battery fault diagnosis method based on the energy storage battery cluster SOC in this embodiment may include:

[0062] Step 1: Perform parameter identification on the equivalent circuit model of each parallel branch of each battery module, and estimate the battery cluster SOC online based on the current discharge capacity of each battery module.

[0063] The open circuit voltage of the battery module is directly measured by constant SOC titration method, and each parallel branch of the battery module is an equivalent "large battery cell" whose voltage is the sum of the voltages of the series-connected single cells in each branch. Its ohmic resistance R o,i , polarization resistance R p,i and double layer capacitance C p,i The Forgetting factor recursive least squares (FFRLS) algorithm is used for online identification. The specific method is as follows:

[0064] The current branch current I collected by the battery cluster data acquisition unit i (The current of each branch of the battery module needs to be collected) and the battery temperature T m (Battery module typical site collection) as the model input parameter to monitor the battery module voltage U online m As the system output parameter, ignore the battery charging and discharging process U OCV_m-SOC relationship curve, and the model parameter R is derived according to the circuit principle o,i , R p,i and C p,i The calculation formula is used to realize the online identification of battery model parameters using the FFRLS algorithm.

[0065] This embodiment introduces a recursive least squares algorithm with a forgetting factor to update and accurately identify the parameters of the battery cluster module equivalent circuit model in real time, thereby improving the accurate estimation of the battery cluster SOC. At the same time, by identifying the parallel branch internal resistance in real time and collecting the battery module temperature and operating current, the battery fault warning threshold can be dynamically adjusted and updated, significantly improving the adaptability and accuracy of the fault warning method over the entire life cycle.

[0066] Finally, the Extended Kalman Filter (EKF) algorithm is used to estimate the SOC (i.e., S i ), where all parallel branches S in the battery cluster module i The lowest value among them is the SOC of the battery module (i.e.: S m ).

[0067] This embodiment uses an extended Kalman filter algorithm that takes battery degradation into consideration to dynamically estimate the SOC of the parallel branches of the battery cluster modules, effectively solving the problem of error accumulation caused by the traditional SOC estimation algorithm not taking into account battery aging and inconsistent charging and discharging of the parallel branches, thereby ensuring that the battery cluster SOC is highly accurate under all operating conditions throughout its service life cycle, laying the foundation for establishing a battery fault diagnosis method based on battery SOC.

[0068] Step 2: Based on the identification parameters of the battery module equivalent circuit model, the current current and temperature of the battery module, and the online estimated SOC of the battery cluster, the safety warning threshold of the battery module is dynamically updated; the safety warning threshold includes: the SOC deviation threshold of each parallel branch of the battery module and its deviation threshold with respect to time differential, and the voltage deviation threshold, SOC deviation threshold and its deviation threshold with respect to time differential of the single cell;

[0069] Based on the SOC deviation of each parallel branch of the battery module and its deviation with respect to time differential and the corresponding threshold, it is determined whether the battery module is a normal battery module. If so, it directly enters the charging and discharging process at the next moment;

[0070] If the battery module is a faulty battery module or a potential faulty battery module, the next level of fault diagnosis is performed, and the voltage deviation, SOC deviation and its deviation with respect to time differential of the single battery and the corresponding threshold are used to determine whether the battery module is a normal battery. If so, the charging and discharging process at the next moment is directly entered; otherwise, the fault level of the battery module is determined, and then matching operations are performed.

[0071] If the battery module is determined to be a primary fault battery or a secondary fault battery, the battery balancing control strategy is dynamically adjusted to reduce the battery fault level or eliminate the battery fault at the next moment;

[0072] If the battery module is determined to be a level 3 faulty battery, the single cells in the battery module will be further powered off for evaluation and maintenance to determine the type of battery fault.

[0073] When diagnosing battery failures in a battery cluster, the current internal resistance R of each parallel branch is first obtained based on the equivalent circuit model of the battery module. in,i (R o,i With R p,i The sum of the battery current I collected online i and temperature T m , the safety warning threshold of the battery module (ie: ε ms_max , ε dms_max , ε cv_max , ε cs_max and ε dcs_max ) is dynamically updated, where the above threshold is related to R in,i ,I i , T m The functional relationship between them can be determined in advance through experiments. Preferably, the present invention recommends using the following function form to determine the functional relationship between the battery fault warning threshold and the operating parameters:

[0074]

[0075] In the formula, ε max is the fault warning threshold at the current time under the current number of cycles (i.e.: ε ms_max , ε dms_max , ε cv_max , ε cs_max and ε dcs_max ), ε0 is the threshold value of the new battery when it is first cycled, I 1C is the battery 1C rate current, R in_0 is the internal resistance of the new battery, Ea is the activation energy, R is the gas constant (usually 8.314 J / (mol·K)), T ref is the reference temperature (usually 25°C). The above parameters can be determined in advance by experiments before the battery is used. ms_max , εdms_max , ε cv_max , ε cs_max and ε dcs_max Replace ε respectively max , the corresponding threshold can be obtained.

[0076] The charging capacity of the battery cluster module in the previous complete charging process C mch_N-1 , calculate the current discharge capacity C of the battery cluster module m_N , the calculation formula is as follows:

[0077]

[0078] In the formula, C mch_0 is the initial charging capacity after the battery cluster module is completely discharged, C m_1 The first discharge capacity of the fully charged battery cluster module. Preferably, the present invention recommends that the above capacity be tested under standard operating conditions. The current discharge capacity C of the battery cluster module m_N Dividing it by the number of parallel branches z contained in the battery module can approximately obtain the discharge capacity of the parallel branches of the battery cluster module under the current number of cycles, that is:

[0079] Subsequently, the present invention provides a faulty battery diagnosis method based on the SOC of the battery module and the single battery at two levels. First, based on the SOC deviation of each parallel branch of the battery module (i.e., S i -S m ) and its deviation with respect to the time derivative (i.e.: ), determine whether the battery module is a faulty module. If it is a normal battery module, directly enter the next moment of charging and discharging process;

[0080] If the battery is a faulty battery module or a potential faulty battery module, the next level of fault diagnosis is performed, using the voltage deviation of the single battery (i.e.: ), SOC deviation (ie: ) and its deviation with respect to the time derivative (i.e.: ) to determine whether a single cell in the battery module is a faulty cell.

[0081] If it is a normal battery, it will directly enter the charging and discharging process at the next moment; if it is determined to be a primary fault battery or a secondary fault battery, the battery balancing control strategy will be dynamically adjusted, for example, a PID controller (Proportion Integration Differentiation) will be used to reduce the battery fault level or eliminate the battery fault at the next moment; if it is determined to be a tertiary fault battery, the single battery in the battery module needs to be further powered off for evaluation and maintenance to determine the type of battery fault.

[0082] Specifically, when the SOC deviation of any parallel branch of the battery module is greater than or equal to the corresponding threshold (i.e., S i -S m ≥ε ms_max ), the battery module is determined to be a faulty battery module.

[0083] If the SOC deviation of a parallel branch of the battery module is less than the corresponding threshold (i.e. S i -S m <ε ms_max ), the deviation of the SOC of a parallel branch of the battery module with respect to the time differential is greater than or equal to the corresponding threshold (i.e. ), the battery module is judged to be a potential battery module.

[0084] When the battery module is a potential battery module, if the deviation of the SOC of the single battery with respect to the time differential is greater than or equal to the corresponding threshold (i.e. ), the battery module is judged to be a primary fault battery;

[0085] When the battery module is a potential battery module, if the deviation of the SOC of the single battery with respect to the time differential is less than the corresponding threshold (i.e. ), the battery module is judged to be a normal battery.

[0086] If the SOC deviation of a parallel branch of the battery module is less than the corresponding threshold (i.e. S i -S m <ε ms_max ), the deviation of the SOC of a parallel branch of the battery module with respect to the time differential is less than the corresponding threshold (i.e. ), then the battery module is judged to be a normal battery module.

[0087] If the voltage deviation of a single cell is greater than or equal to the corresponding threshold (i.e. The single cell in the battery module is determined to be a level 3 faulty cell;

[0088] If the voltage deviation of any single cell is less than the corresponding threshold (i.e. ), the SOC deviation of the single battery is greater than or equal to the corresponding threshold (i.e. ), the battery module is determined to be a secondary fault battery;

[0089] If the voltage deviation of any single cell is less than the corresponding threshold (i.e. ), the SOC deviation of the single battery is less than the corresponding threshold (i.e. ), the deviation of the SOC of the single battery with respect to the time differential is greater than or equal to the corresponding threshold (i.e. ), the battery module is judged to be a primary fault battery;

[0090] If the voltage deviation of any single cell is less than the corresponding threshold (i.e. ), the SOC deviation of the single battery is less than the corresponding threshold (i.e. ), the deviation of the SOC of the single battery with respect to the time differential is less than the corresponding threshold (i.e. ), the battery module is judged to be a normal battery.

[0091] The battery failure levels are ranked in descending order according to the severity of battery damage: level 3 failure battery > level 2 failure battery > level 1 failure battery. For batteries diagnosed as level 3 failure, the battery failure is more serious and the battery needs to be powered off for evaluation in order to further determine the specific failure type of the battery and perform maintenance or replacement according to the requirements of the OEM. For batteries diagnosed as level 1 failure or level 2 failure, the battery failure has less damage to the battery. For example, a PID controller can be used for balancing control to reduce the battery failure level or eliminate the battery failure during subsequent charging and discharging.

[0092] For battery cluster modules with primary or secondary fault batteries, a PID controller is used to adjust the charge and discharge power or balancing current of each module in the battery cluster in real time to balance the SOC differences between the individual batteries in the battery cluster and eliminate minor faults caused by imbalance; finally, through continuous monitoring and feedback adjustment, the battery cluster state balance is gradually achieved, the stability and reliability of the overall system are improved, and the battery fault level or battery fault is eliminated during the subsequent charging and discharging process. In practical applications, the proportional gain K of the PID controller can be adjusted according to the characteristics of the battery cluster, load conditions, and charging and discharging strategies. p , integral gain K i and differential gain K d The three parameters are automatically adjusted. The method is as follows: when the load changes significantly or the battery cluster enters a high-power discharge state, K is automatically increased. p and K d , so that the system responds faster; when the load is stable or the temperature changes slightly, reduce K i and K d , to maintain the stable operation of the energy storage battery cluster; considering the impact of battery degradation on the dynamic response of the battery cluster, as the battery ages, K is gradually reduced. p and K d , so that the system response is reduced to avoid oscillation caused by frequent adjustments, and K is appropriately increased i , reducing the long-term deviation of SOC between the parallel branches or single cells of the battery cluster module.

[0093] Transient external short circuit is a common fault in lithium-ion batteries during the charging and discharging process. Its possible causes include: (1) Damage, wear, looseness, or brief contact of external objects on the battery's external wires or connectors will cause the positive and negative electrodes of the battery to short-circuit, which may lead to a transient large current pulse, which may then return to normal or the current may be cut off due to a protection mechanism. Therefore, this external short circuit fault may only last for a few milliseconds to a few seconds; (2) The inductive elements in the energy storage battery and the external circuit (such as the inductance of the cable and battery pack) will temporarily store energy and release it at the moment of short circuit, forming a current pulse of a few milliseconds to a few seconds. This type of transient phenomenon may also be eliminated due to the inductive characteristics of the system and load changes. If the battery with an external short circuit fault is not discovered quickly and in time, it may cause a continuous short circuit and may even cause a safety accident. Therefore, it is crucial to accurately and quickly detect the transient external short circuit fault of the battery cluster to ensure its safe operation.

[0094] Taking a square lithium iron phosphate battery (width × thickness × height: 135 × 29 × 29 (mm); rated capacity 68Ah; rated voltage: 3.2V) as an example, the discharge process of the above battery with and without instantaneous short-circuit faults at an ambient temperature of 25°C is simulated by numerical simulation. The discharge current is 0.5C. The battery with instantaneous faults has a discharge current transiently changed to 10C within 999s to 1007s, and a discharge current transiently changed to 5C within 1509s from a few milliseconds to a few seconds. Figure 4 shown. Figure 5 The following is a comparison of the discharge voltage curves of a normal battery and a faulty battery. It can be seen from the figure that when a battery has a momentary short circuit, its discharge voltage has a downward spike during the duration of the momentary short circuit. Reliable monitoring of the voltage change characteristics under this fault requires that the voltage sampling time is less than the duration of the momentary pulse, otherwise the fault characteristics cannot be monitored. Figure 5 The sampling interval is 30s. Figure 6 The differential curves of the discharge voltage of a normal battery and a faulty battery with respect to time are shown in Figure 2. Since the battery voltage shows an instantaneous change rule of "first drop and then rise" after the current jumps, the discharge voltage time differential shows "positive and negative peaks" during the duration of the battery instantaneous short circuit, such as Figure 6 The red curve with a sampling interval of 1s is shown in the figure; if the sampling time is too long, the fault cannot be detected, such as Figure 6 As shown in the blue curve at a sampling interval of 30s, or an error feature is detected, such as Figure 6 As shown in the green curve with a sampling interval of 5s, the required time sampling interval is shorter than that of the voltage curve (it should be sampled at least 3 times during the instantaneous short circuit). Figure 7The SOC change curves of the normal battery and the faulty battery during the discharge process show that once an external short circuit occurs in the battery, the SOC will experience a certain degree of "sudden drop", and this feature is independent of the sampling time interval. Therefore, using the battery SOC to detect this fault is more reliable than using the voltage. Figure 8 The curves of SOC versus time differential during the discharge process of a normal battery and a faulty battery show that when a short circuit occurs, the SOC time differential only shows a "negative spike". Compared with the voltage differential curve, the sampling time interval requirement is reduced when the SOC time differential curve is used. Only one sampling is required during the instantaneous short circuit (e.g. Figure 8 Both 5s and 1s sampling intervals can detect battery short circuit faults). Figure 8 It can also be seen that the SOC time differential changes significantly when a short circuit fault occurs. For example, during the second short circuit (1509s-1514s), the SOC time differential jumps to 5 times its original value. Therefore, this feature can be used to further detect battery faults with less significant SOC changes.

[0095] Furthermore, a three-level fault diagnosis method is adopted at the battery level, which significantly reduces the amount of calculation while ensuring the reliability of fault detection, as follows:

[0096] Level 1: No additional calculation is required, and battery fault diagnosis is performed directly using the real-time collected single cell voltage. The battery is judged to be a level 3 fault battery; if Then enter the second level fault diagnosis.

[0097] Level 2: Estimate the SOC of the single battery for fault diagnosis. The battery is judged to be a secondary fault battery; if Then enter the third level fault diagnosis.

[0098] Level 3: Calculate the differential of the single battery SOC with respect to time for fault diagnosis. The battery is judged to be a primary fault battery; if The battery is determined to be a safe battery.

[0099] In one or more embodiments, a battery fault diagnosis system based on the SOC of an energy storage battery cluster includes:

[0100] A battery cluster SOC estimation module is configured to: perform parameter identification on an equivalent circuit model of each parallel branch of each battery module, and estimate the battery cluster SOC online in combination with the current dischargeable capacity of each battery module;

[0101] A battery cluster fault diagnosis module is configured to:

[0102] Based on the identification parameters of the battery module equivalent circuit model, the current current and temperature of the battery module and the online estimated battery cluster SOC, the safety warning threshold of the battery module is dynamically updated; the safety warning threshold includes: the SOC deviation threshold of each parallel branch of the battery module and its deviation threshold with respect to time differential, and the voltage deviation threshold, SOC deviation threshold and its deviation threshold with respect to time differential of the single cell;

[0103] Based on the SOC deviation of each parallel branch of the battery module and its deviation with respect to time differential and the corresponding threshold, it is determined whether the battery module is a normal battery module. If so, it directly enters the charging and discharging process at the next moment;

[0104] If the battery module is a faulty battery module or a potential faulty battery module, the next level of fault diagnosis is performed, and the voltage deviation, SOC deviation and its deviation with respect to time differential of the single battery and the corresponding threshold are used to determine whether the battery module is a normal battery. If so, the charging and discharging process at the next moment is directly entered; otherwise, the fault level of the battery module is determined, and then matching operations are performed.

[0105] In some other embodiments, a battery fault diagnosis system based on the SOC of an energy storage battery cluster includes:

[0106] Data acquisition unit and battery cluster management system;

[0107] The data acquisition unit is used to collect the charge and discharge current of each branch of the battery module, the battery temperature and the charging capacity of the battery module in the previous complete charging process and transmit them to the battery cluster management system;

[0108] The battery cluster management system includes a battery cluster SOC estimation module and a battery cluster fault diagnosis module;

[0109] The battery cluster SOC estimation module is configured to: perform parameter identification on each parallel branch equivalent circuit model of each battery module, and estimate the battery cluster SOC online in combination with the current dischargeable capacity of each battery module;

[0110] The battery cluster fault diagnosis module is configured as follows:

[0111] Based on the identification parameters of the battery module equivalent circuit model, the current current and temperature of the battery module and the online estimated battery cluster SOC, the safety warning threshold of the battery module is dynamically updated; the safety warning threshold includes: the SOC deviation threshold of each parallel branch of the battery module and its deviation threshold with respect to time differential, and the voltage deviation threshold, SOC deviation threshold and its deviation threshold with respect to time differential of the single cell;

[0112] Based on the SOC deviation of each parallel branch of the battery module and its deviation with respect to time differential and the corresponding threshold, it is determined whether the battery module is a normal battery module. If so, it directly enters the charging and discharging process at the next moment;

[0113] If the battery module is a faulty battery module or a potential faulty battery module, the next level of fault diagnosis is performed, and the voltage deviation, SOC deviation and its deviation with respect to time differential of the single battery and the corresponding threshold are used to determine whether the battery module is a normal battery. If so, the charging and discharging process at the next moment is directly entered; otherwise, the fault level of the battery module is determined, and then matching operations are performed.

[0114] Each module in the battery fault diagnosis system based on the energy storage battery cluster SOC corresponds one by one to each step in the above-mentioned battery fault diagnosis method based on the energy storage battery cluster SOC, and the specific implementation process is the same and will not be repeated here.

[0115] In particular, according to an embodiment of the present application, the process described above with reference to the flowchart can be implemented as a computer software program. For example, an embodiment of the present application includes a computer program product, which includes a computer program carried on a computer readable medium, the computer program including a computer program for executing Figure 1 In such an embodiment, the computer program can be downloaded and installed from a network through a communication part, and / or installed from a removable medium. When the computer program is executed by a central processing unit, various functions defined in the device of the present application are executed.

[0116] in, Figure 1 The computer program instructions corresponding to the method shown 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 a product including an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0117] A person skilled in the art can understand that all or part of the processes in the above-mentioned embodiments can be implemented by instructing the relevant hardware through a computer program, and the program can be stored in a computer-readable storage medium, and when the program is executed, it can include the processes of the embodiments of the above-mentioned methods. The storage medium can be a disk, an optical disk, a read-only memory (ROM) or a random access memory (RAM), etc.

[0118] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A battery fault diagnosis method based on the SOC of an energy storage battery cluster, characterized in that: include: Perform parameter identification on the equivalent circuit model of each parallel branch of each battery module, and estimate the battery cluster SOC online based on the current discharge capacity of each battery module; Dynamically update the safety warning threshold of the battery module based on the identification parameters of the battery module equivalent circuit model, the current current and temperature of the battery module, and the online estimated battery cluster SOC; The safety warning thresholds include: the SOC deviation threshold of each parallel branch of the battery module and its deviation threshold with respect to time differential, and the voltage deviation threshold, SOC deviation threshold and its deviation threshold with respect to time differential of the single battery; Based on the SOC deviation of each parallel branch of the battery module and its deviation with respect to time differential and the corresponding threshold, it is determined whether the battery module is a normal battery module. If so, it directly enters the charging and discharging process at the next moment; If the battery module is a faulty battery module or a potential faulty battery module, the next level of fault diagnosis is performed, and the voltage deviation, SOC deviation and its deviation with respect to time differential of the single battery and the corresponding threshold are used to determine whether the battery module is a normal battery. If so, the charging and discharging process at the next moment is directly entered; otherwise, the fault level of the battery module is determined, and then matching operations are performed.

2. The battery fault diagnosis method based on the SOC of the energy storage battery cluster according to claim 1, characterized in that: If the battery module is determined to be a primary fault battery or a secondary fault battery, the battery balancing control strategy is dynamically adjusted to reduce the battery fault level or eliminate the battery fault at the next moment; If the battery module is determined to be a level 3 faulty battery, the single cells in the battery module will be further powered off for evaluation and maintenance to determine the type of battery fault.

3. The battery fault diagnosis method based on the SOC of the energy storage battery cluster according to claim 1, characterized in that: When the SOC deviation of any parallel branch of the battery module is greater than or equal to the corresponding threshold, the battery module is determined to be a faulty battery module.

4. The battery fault diagnosis method based on the SOC of the energy storage battery cluster according to claim 1, characterized in that: If the SOC deviation of a parallel branch of the battery module is less than the corresponding threshold value, and the deviation of the SOC of a parallel branch of the battery module with respect to the time differential is greater than or equal to the corresponding threshold value, the battery module is determined to be a potential battery module.

5. The battery fault diagnosis method based on the SOC of the energy storage battery cluster according to claim 1, characterized in that: When the battery module is a potential battery module, if the deviation of the SOC of the single battery with respect to the time differential is greater than or equal to the corresponding threshold, the battery module is judged to be a primary fault battery; When the battery module is a potential battery module, if the deviation of the SOC of the single battery with respect to the time differential is less than the corresponding threshold, the battery module is determined to be a normal battery.

6. The battery fault diagnosis method based on the SOC of the energy storage battery cluster according to claim 1, characterized in that: If the SOC deviation of a parallel branch of the battery module is smaller than the corresponding threshold value, and the deviation of the SOC of a parallel branch of the battery module with respect to the time differential is smaller than the corresponding threshold value, the battery module is determined to be a normal battery module.

7. The battery fault diagnosis method based on the SOC of the energy storage battery cluster according to claim 1, characterized in that: If the voltage deviation of the single cell is greater than or equal to the corresponding threshold, the single cell in the battery module is determined to be a level 3 faulty cell; If the voltage deviation of any single battery is less than the corresponding threshold value, and the SOC deviation of the single battery is greater than or equal to the corresponding threshold value, the battery module is determined to be a secondary fault battery; If the voltage deviation of any single battery is less than the corresponding threshold, the SOC deviation of the single battery is less than the corresponding threshold, and the deviation of the SOC of the single battery with respect to the time differential is greater than or equal to the corresponding threshold, then the battery module is judged to be a primary fault battery; If the voltage deviation of any single battery is less than the corresponding threshold, the SOC deviation of the single battery is less than the corresponding threshold, and the deviation of the SOC of the single battery with respect to the time differential is less than the corresponding threshold, the battery module is judged to be a normal battery.

8. A battery fault diagnosis system based on energy storage battery cluster SOC, characterized in that: include: A battery cluster SOC estimation module is configured to: perform parameter identification on an equivalent circuit model of each parallel branch of each battery module, and estimate the battery cluster SOC online in combination with the current dischargeable capacity of each battery module; A battery cluster fault diagnosis module is configured to: Dynamically update the safety warning threshold of the battery module based on the identification parameters of the battery module equivalent circuit model, the current current and temperature of the battery module, and the online estimated battery cluster SOC; The safety warning thresholds include: the SOC deviation threshold of each parallel branch of the battery module and its deviation threshold with respect to time differential, and the voltage deviation threshold, SOC deviation threshold and its deviation threshold with respect to time differential of the single battery; Based on the SOC deviation of each parallel branch of the battery module and its deviation with respect to time differential and the corresponding threshold, it is determined whether the battery module is a normal battery module. If so, it directly enters the charging and discharging process at the next moment; If the battery module is a faulty battery module or a potential faulty battery module, the next level of fault diagnosis is performed, and the voltage deviation, SOC deviation and its deviation with respect to time differential of the single battery and the corresponding threshold are used to determine whether the battery module is a normal battery. If so, the charging and discharging process at the next moment is directly entered; otherwise, the fault level of the battery module is determined, and then matching operations are performed.

9. A battery fault diagnosis system based on energy storage battery cluster SOC, characterized in that: include: Data acquisition unit and battery cluster management system; The data acquisition unit is used to collect the charge and discharge current of each branch of the battery module, the battery temperature and the charging capacity of the battery module in the previous complete charging process and transmit them to the battery cluster management system; The battery cluster management system includes a battery cluster SOC estimation module and a battery cluster fault diagnosis module; The battery cluster SOC estimation module is configured to: perform parameter identification on each parallel branch equivalent circuit model of each battery module, and estimate the battery cluster SOC online in combination with the current dischargeable capacity of each battery module; The battery cluster fault diagnosis module is configured as follows: Dynamically update the safety warning threshold of the battery module based on the identification parameters of the battery module equivalent circuit model, the current current and temperature of the battery module, and the online estimated battery cluster SOC; The safety warning thresholds include: the SOC deviation threshold of each parallel branch of the battery module and its deviation threshold with respect to time differential, and the voltage deviation threshold, SOC deviation threshold and its deviation threshold with respect to time differential of the single battery; Based on the SOC deviation of each parallel branch of the battery module and its deviation with respect to time differential and the corresponding threshold, it is determined whether the battery module is a normal battery module. If so, it directly enters the charging and discharging process at the next moment; If the battery module is a faulty battery module or a potential faulty battery module, the next level of fault diagnosis is performed, and the voltage deviation, SOC deviation and its deviation with respect to time differential of the single battery and the corresponding threshold are used to determine whether the battery module is a normal battery. If so, the charging and discharging process at the next moment is directly entered; otherwise, the fault level of the battery module is determined, and then matching operations are performed.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the program is executed by a processor, the steps of the battery fault diagnosis method based on the SOC of the energy storage battery cluster as described in any one of claims 1 to 7 are implemented.

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