Current control method, current control system, vehicle and storage medium

Abstract

The invention relates to a current control method, a current control system, a vehicle and a storage medium. The method is applied to a battery parallel system comprising a plurality of branches connected in parallel. The method comprises the following steps: acquiring a reference branch current limiting value of each branch; determining a first total current limiting value based on the maximum allowable DCIR difference ratio between the branches, the number of the branches, and the reference branch current limiting value, such that when the actual maximum DCIR difference ratio between the branches is less than or equal to the maximum allowable DCIR difference ratio, no branch overcurrent warning occurs; and when the branch overcurrent warning occurs, setting the total current limiting value of the battery parallel system as a first total current limiting value.

Description

Technical Field

[0001] This disclosure relates to the field of battery management, and in particular, to a current control method, a current control system, a vehicle, and a storage medium. Background Technology

[0002] Batteries are widely used to provide power for the operation of devices such as vehicles.

[0003] In vehicles, for example, to provide the required power, a battery parallel system can be used, in which multiple branches are connected in parallel and each branch includes multiple battery packs.

[0004] Ideally, the battery packs in each branch have the same direct current internal resistance (DCIR), ensuring that the total system current is evenly distributed across the branches. However, in practical applications, due to various reasons such as differences in manufacturing processes of different battery packs, different aging conditions during use, or replacement or repair of some battery packs in a branch, the battery packs in each branch may have different DCIRs.

[0005] To ensure the stable and reliable operation of the battery system, the total current of the battery system needs to be monitored and controlled to ensure that the actual current flowing through each branch does not exceed the reference current limit of that branch. However, due to the different DCIRs of the battery packs in each branch, the actual DCIRs between branches vary, making the control of the total current of the battery system a challenging problem. Summary of the Invention

[0006] Therefore, it is necessary to provide a current control method, a current control system, a vehicle, and a storage medium to solve at least one problem existing in current battery parallel systems.

[0007] In a first aspect of this disclosure, a current control method is provided. This current control method can be applied to a battery parallel system. The battery parallel system includes a plurality of branches connected in parallel, each of the plurality of branches including one or more battery packs. The method includes: acquiring a reference branch current limit value for each of the plurality of branches; determining a first total current limit value for the plurality of branches based on a maximum permissible DC internal resistance (DCIR) difference ratio between the plurality of branches, the number of the plurality of branches, and the reference branch current limit value for each of the plurality of branches, wherein the first total current limit value is determined such that no branch overcurrent warning occurs when the actual maximum DCIR difference ratio between the plurality of branches is less than or equal to the maximum permissible DCIR difference ratio; and when a branch overcurrent warning occurs in the battery parallel system, setting the total current limit value of the battery parallel system from a default total current limit value to the first total current limit value; the branch overcurrent warning occurs when an actual current value of at least one of the plurality of branches is detected to exceed the reference branch current limit value.

[0008] In one embodiment, obtaining the reference branch current limit value may include obtaining the reference branch current limit value in the current direction. In one embodiment, setting the total current limit value of the battery parallel system as a first total current limit value may include setting the total current limit value of the battery parallel system in the current direction as the first total current limit value. The current direction of the system may include the charging direction or the discharging direction.

[0009] In one embodiment, the maximum permissible DCIR difference ratio between multiple branches can be predetermined.

[0010] In one embodiment, the maximum permissible DCIR difference ratio among the multiple branches can be determined based on one or more of the following: 1) State of Health (SOH) replacement threshold, where at least a portion of the battery pack of one of the multiple branches needs to be replaced when the actual SOH value of that branch is lower than the SOH replacement threshold; 2) Warranty period, where at least a portion of the battery pack of that branch is replaced free of charge or at a reduced price when it needs to be replaced during the warranty period; 3) Operating power requirements.

[0011] In one embodiment, the default total current limit value can be determined by multiplying the minimum current limit value among the reference current limit values ​​of the plurality of branches by the number of the plurality of branches.

[0012] In one embodiment, determining a first total current limit value for the plurality of branches based on the number of branches, the maximum permissible DCIR difference ratio, and a reference branch current limit value may include: making a first assumption: a first branch of the battery parallel system has the lowest internal resistance and is assigned a first allocated current limit value equal to the reference branch current limit value; making a second assumption: each of the remaining second branches in the battery parallel system, excluding the first branch, has an internal resistance higher than that of the first branch, such that the actual DCIR difference ratio between each second branch and the first branch is equal to the maximum permissible DCIR difference ratio; calculating a second allocated current limit value to be assigned to each second branch under the first and second assumptions; calculating the total allocated current limit value for the plurality of branches when the first branch is assigned a first allocated current limit value and each second branch is assigned a second allocated current limit value; and determining a first total current limit value based on the total allocated current limit value, wherein the first total current limit value is less than or equal to the total allocated current limit value.

[0013] In one embodiment, the first total rate limit is determined based on the total rate limit reduction factor and the default total rate limit.

[0014] In one embodiment, the total current limiting value reduction factor is based on the maximum permissible DCIR difference ratio between multiple branches, the number of multiple branches, and the reference branch current limiting value, which is predetermined.

[0015] In one embodiment, the total current limit reduction factor is a first ratio of a first total current limit to a default total current limit, and the first ratio decreases as the maximum allowable DCIR difference ratio increases.

[0016] In one embodiment, the total current limit reduction factor is a second ratio of the difference between the default total current limit and the first total current limit to the default total current limit, and the second ratio increases as the maximum allowable DCIR difference ratio increases.

[0017] In one embodiment, after setting the total current limit value of the battery parallel system to a first total current limit value, the method may further include: when a branch overcurrent warning occurs again in the battery parallel system, successively reducing the total current limit value of the battery parallel system by a predetermined current limit reduction amount until no more branch overcurrent warnings occur in the battery parallel system. In one embodiment, the predetermined current limit reduction amount is the amount by which the total current limit value is reduced each time. In one embodiment, the predetermined current limit reduction amount is in the range of 5% to 20% of the default total current limit value.

[0018] In one embodiment, during the process of successively reducing the total current limit of the battery parallel system, the total current limit of the battery parallel system can be limited to not less than a predetermined lower limit of total current. In one embodiment, the predetermined lower limit of total current is the lowest current limit that the total current limit of the battery parallel system is allowed to be. In one embodiment, the predetermined lower limit of total current is in the range of 40% to 60% of the default total current limit.

[0019] In one embodiment, after setting the total current limit value of the battery parallel system to a first total current limit value, the method may further include: when it is detected that the state in which the actual total current value of the battery parallel system is less than a predetermined proportion of the default total current limit value has lasted for a preset duration threshold, restoring the total current limit value of the battery parallel system to the default total current limit value. In one embodiment, the predetermined proportion is in the range of 60% to 80% of the default total current limit value.

[0020] In one embodiment, after setting the total current limit value of the battery parallel system as a first total current limit value, the method further includes the step of: setting a total current limit value in the reverse current direction opposite to the current current direction of the battery parallel system based on the actual SOC of each of the multiple branches. In one embodiment, the battery parallel system pre-stores multiple reference State of Charge (SOC) difference ranges higher than a SOC difference threshold, and multiple specified total current limit values ​​in the charging and discharging directions corresponding to the multiple SOC difference ranges, respectively. The step of setting the total current limit value in the reverse current direction based on the actual SOC of each of the multiple branches may include: monitoring the actual SOC of each of the multiple branches; and when the actual maximum SOC difference between the multiple branches in the current current direction changes from not exceeding the SOC difference threshold to exceeding the SOC difference threshold, marking the reverse current direction opposite to the current current direction as an effective current direction, and maintaining the marking of the effective current direction until the actual maximum SOC difference between the multiple branches in the current current direction changes from exceeding the SOC difference threshold. The OC difference threshold changes until it does not exceed the SOC difference threshold; during the period when the effective current direction marking is maintained, when the actual maximum SOC difference between the multiple branches in the current current direction falls within the first reference SOC difference range of the multiple reference SOC difference ranges, and when the reverse current direction opposite to the current current direction is the current direction marked as the effective current direction, the total current limit value of the battery parallel system in the reverse current direction is set to the first specified total current limit value in the reverse current direction corresponding to the first reference SOC difference range; when the reverse current direction is not the current direction marked as the effective current direction, setting the total current limit value in the reverse current direction to the first specified total current limit value is prohibited.

[0021] In one embodiment, after setting the total current limit value of the battery parallel system to a first specified total current limit value corresponding to a first reference SOC difference range, the method may further include: when it is detected that the actual maximum SOC difference between the plurality of branches changes to a second reference SOC difference range that is different from the first reference SOC difference range within the plurality of reference SOC difference ranges, setting the total current limit value of the battery parallel system in the reverse current direction to a second specified total current limit value in the reverse current direction corresponding to the second reference SOC difference range.

[0022] In one embodiment, after setting the total current limit value of the battery parallel system in the reverse current direction to a first specified total current limit value corresponding to a first reference SOC difference range, the method may further include: when it is detected that the actual maximum SOC difference between multiple branches has been changed to not greater than the SOC difference threshold and falls outside all of the multiple reference SOC difference ranges, restoring the total current limit value of the battery parallel system in the reverse current direction to the default total current limit value in the reverse current direction, and clearing the mark of the effective current direction.

[0023] In a second aspect of this disclosure, a current control system is provided. The current control system includes a battery management system. The battery management system is communicatively connected to a battery parallel system. The battery parallel system includes a plurality of branches connected in parallel, each of the plurality of branches including one or more battery packs. The battery management system includes a memory and a processor. The memory stores computer-readable instructions that, when executed by the processor, cause the processor to perform the following operations: acquire a reference branch current limit value for each of a plurality of branches; determine a first total current limit value based on the maximum permissible DC internal resistance (DCIR) difference ratio between the plurality of branches, the number of the plurality of branches, and the reference branch current limit value for each of the plurality of branches, wherein the first total current limit value is determined such that no branch overcurrent warning occurs when the actual maximum DCIR difference ratio between the plurality of branches is less than or equal to the maximum permissible DCIR difference ratio; and when a branch overcurrent warning occurs in the battery parallel system, set the total current limit value of the battery parallel system from a default total current limit value to the first total current limit value; the branch overcurrent warning occurs when the actual current value of at least one of the plurality of branches is detected to exceed the reference branch current limit value.

[0024] In one embodiment, the current control system may further include a battery parallel system.

[0025] In one embodiment, the battery management system may include: a plurality of parallel battery management units, each of which is communicatively connected to a corresponding branch in the plurality of branches, and configured to: determine a reference branch current limit value for the corresponding branch in the current current direction, monitor the actual current value of the corresponding branch, and initiate a branch overcurrent warning when the actual current value of the corresponding branch exceeds the reference branch current limit value in the current current direction; and a main battery management unit electrically connected to the plurality of parallel battery management units, and configured to: obtain the reference branch current limit value for each branch in the current current direction from the plurality of parallel battery management units, and set the total current limit value of the parallel battery system in the current current direction based on the obtained reference branch current limit value for each branch in the current current direction. A memory and a processor are included in the main battery management unit and / or the plurality of parallel battery management units.

[0026] In one embodiment, the current control system may further include: a plurality of current sensors, each of which is disposed in a corresponding branch of the plurality of branches and configured to detect the actual current value in the corresponding branch of the plurality of branches and transmit the detected actual current value to the battery management system.

[0027] In one embodiment, the current control system may further include: a plurality of relays, each of the plurality of relays being disposed in a corresponding branch of the plurality of branches and configured to turn on or off the corresponding branch of the plurality of branches in response to an instruction received from the battery management system.

[0028] In a third aspect of this disclosure, a vehicle is provided. The vehicle includes a vehicle control unit and the aforementioned current control system. A battery parallel system is installed in the vehicle and configured to provide power for the operation of the vehicle. A battery management system is communicatively connected to the vehicle control unit and configured to set a total current limit value for the battery parallel system in the current direction by sending a total current limit command to the vehicle control unit. This total current limit command instructs the vehicle control unit to limit the actual current between the vehicle and the battery parallel system in the current direction to not exceed the total current limit value in the current direction.

[0029] In a fourth aspect of this disclosure, a non-transitory computer-readable storage medium is provided. A computer program is stored on the non-transitory computer-readable storage medium. When the computer program is executed by a processor, it causes the processor to implement the aforementioned current control method. Attached Figure Description

[0030] Figure 1 This is a flowchart illustrating a current control method according to an embodiment of the present disclosure;

[0031] Figure 2 This is an example table illustrating a reference branch current limiting value table in the charging direction according to an embodiment of the present disclosure;

[0032] Figure 3 This is an example table illustrating a reference branch current limiting value table in the discharge direction according to an embodiment of the present disclosure;

[0033] Figure 4 This is a flowchart illustrating the process of determining a first total current limit value according to an embodiment of the present disclosure;

[0034] Figure 5 This is a table illustrating a specified total current limit value corresponding to different SOC differences according to embodiments of the present disclosure;

[0035] Figure 6 It is a table illustrating the setting of the total current limit value under different system states according to embodiments of the present disclosure;

[0036] Figure 7 This is a diagram illustrating the configuration of a current control system according to an embodiment of the present disclosure;

[0037] Figure 8 This is a diagram illustrating the configuration of a current control system according to an embodiment of the present disclosure;

[0038] Figure 9 This is a diagram illustrating the configuration of a current control system according to an embodiment of the present disclosure;

[0039] Figure 10 This is a diagram illustrating the configuration of a vehicle according to an embodiment of the present disclosure. Detailed Implementation

[0040] To make the foregoing objects, features, and advantages of this disclosure more apparent and understandable, specific embodiments of this disclosure will now be described in detail with reference to the accompanying drawings. Numerous specific details are set forth in the following description in order to provide a thorough understanding of this disclosure. However, this disclosure may be implemented in various ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this disclosure. Therefore, this disclosure is not limited to the specific embodiments disclosed below.

[0041] As discussed above, due to various reasons, in practical applications, the battery packs in each branch of a battery parallel system may have different DCIRs. To ensure the stable and reliable operation of the battery parallel system, it is necessary to control the total current of the battery parallel system composed of battery packs with different DCIRs in an appropriate manner.

[0042] In related technologies, the total current limit of a parallel battery system can be determined using the following formula based on the minimum reference current limit of each branch: Total current limit = Minimum reference current limit of each branch × Number of available branches. During actual operation, due to differences in the aging state and state of equilibrium (SOH) of each battery pack, the DCIR of the battery packs in each branch differs, resulting in uneven distribution of the total current across different branches. When the actual current of a branch exceeds its reference current limit, a branch overcurrent warning occurs. In this situation, the first method is to reduce the reference current limit of the branch that triggered the warning. While this method reduces the total current limit according to the formula, the uneven current distribution means the actual current of that branch may still exceed the reduced reference current limit, triggering another branch overcurrent warning. The second method is to directly disconnect the branch that triggered the warning. The second method recalculates the total current limit for the parallel battery system for the remaining connected branches. However, due to the uneven current distribution, the actual current in some of the remaining connected branches may still exceed their reference current limits, triggering another branch overcurrent warning. These repeated warnings and adjustments may affect the system's stable operation. Frequent warnings may also inconvenience users and negatively impact the user experience.

[0043] Based on this, the present disclosure provides a current control method, a current control system, a vehicle, and a storage medium that can more appropriately control the total current limit value of a battery parallel system.

[0044] In a first aspect of this disclosure, a current control method is provided. This current control method can be applied to a current control system, which will be described in more detail later. Typically, this current control method can be performed by a battery management system included in the current control system. The battery management system can apply this method to a battery parallel system to control the total current limit of the battery parallel system. A battery parallel system typically includes multiple branches connected in parallel, each of which can include one or more battery packs. The one or more battery packs in each branch can be connected in parallel, in series, or partially in parallel and partially in series. Each battery pack can consist of multiple modules connected in parallel and / or in series, and each battery module can also consist of multiple battery cells connected in parallel and / or in series.

[0045] During operation, the battery management system (BMS) acquires a reference branch current limit value for each of the multiple branches and monitors the current flowing through each branch. When the actual current value of at least one branch exceeds its reference branch current limit value, the BMS issues a branch overcurrent warning for the parallel battery system. Before a branch overcurrent warning occurs, i.e., when the parallel battery system is operating normally, the total current limit value for the parallel battery system can be set to a default total current limit value. The BMS can also determine a first total current limit value based on the maximum permissible DC-IR difference ratio between the multiple branches, the number of branches, and the reference branch current limit value. This first total current limit value is determined such that a branch overcurrent warning will not occur when the actual maximum DC-IR difference ratio between the multiple branches is less than or equal to the maximum permissible DC-IR difference ratio. The first total current limit value can be repeatedly determined and updated at predetermined time intervals throughout the system's operation so that the latest determined first total current limit value can be used to update the total current limit value of the parallel battery system should a warning occur. Alternatively, a first total current limit value can be determined in real time after a branch overcurrent warning occurs, and then the total current limit value can be updated using the determined first total current limit value. The battery management system monitors whether a branch overcurrent warning occurs, and when a branch overcurrent warning occurs for the parallel battery system, the battery management system sets the total current limit value of the parallel battery system from the default total current limit value to the first total current limit value, and the state of the battery management system switches from the normal state to the overcurrent warning state.

[0046] In the aforementioned current control method, the first total current limit is determined based on the maximum permissible DCIR difference ratio between branches. When a branch overcurrent warning occurs, the total current limit of the battery parallel system can be directly reduced from the default total current limit to the first total current limit. In this way, the total current limit can be reduced more efficiently, and as long as the actual maximum DCIR difference ratio between multiple branches is less than or equal to the maximum permissible DCIR difference ratio, branch overcurrent warnings will not easily occur again. This makes the system operation more stable and improves the user experience.

[0047] The monitoring and control of the current in a parallel battery system can be related to the direction of the current in the system. The direction of the current in a parallel battery system can be either the charging direction or the discharging direction. The charging direction refers to the direction of the current as the parallel battery system is charged using power from an external source. For example, when the parallel battery system is connected to an external power source and charged by that source, or when the parallel battery system is installed in a vehicle and regenerative braking is triggered by the user's braking, current flows into the parallel battery system from the outside, and therefore the current direction is the charging direction. On the other hand, the discharging direction refers to the direction of the current as the parallel battery system releases power to the outside. For example, when the parallel battery system is connected to a load (e.g., a vehicle) and supplies power to the load, current flows from the parallel battery system to the outside, and therefore the current direction is the discharging direction.

[0048] In some embodiments, the total current limit value of the battery parallel system in the charging direction and the total current limit value of the battery parallel system in the discharging direction are controlled independently of each other; this can be referred to as a bidirectional control configuration. In such an embodiment employing a bidirectional control configuration, reference branch current limit values ​​in the charging direction and reference branch current limit values ​​in the discharging direction for each branch can be pre-stored, and the step of obtaining the reference branch current limit value of a branch can include obtaining the pre-stored reference branch current limit value of that branch in the current current direction. Accordingly, the system can simultaneously maintain (i.e., continuously update and record) the reference branch current limit values ​​in the charging direction and the reference branch current limit values ​​in the discharging direction of the battery parallel system, and setting the total current limit value of the battery parallel system as a first total current limit value can include: setting the total current limit value of the battery parallel system in the current current direction as the first total current limit value.

[0049] In some embodiments, the total current limit value of the battery parallel system in the charging direction and the total current limit value of the battery parallel system in the discharging direction can be uniformly controlled, which can be referred to as a unidirectional control configuration. In this embodiment employing a unidirectional control configuration, a reference branch current limit value for each branch that can be used in both the charging and discharging directions can be pre-stored, and the step of obtaining the reference branch current limit value of a branch can include obtaining the pre-stored reference branch current limit value for that branch, regardless of the current direction. Accordingly, the system can maintain a reference branch current limit value for the battery parallel system, which is defaulted to a reference branch current limit value used to limit the current in the current current direction, and setting the total current limit value of the battery parallel system to a first total current limit value can include: setting the total current limit value of the battery parallel system (defaulted to the current current direction) to the first total current limit value.

[0050] The current control method provided in this disclosure can be applied to either the bidirectional control configuration or the unidirectional control configuration described above. In the following embodiments, the examples given are primarily for illustrating embodiments with a bidirectional control configuration (including expressions such as "in the current current direction / in that current current direction" as described). However, examples of embodiments with a unidirectional control configuration (where expressions such as "in the current current direction / in that current current direction" as described can be excluded) can be derived similarly from these examples by simply eliminating the distinction between the charging and discharging directions and uniformly using a single parameter for both the charging and discharging directions.

[0051] refer to Figure 1 In one embodiment of this disclosure, the current control method may include the following steps S110 to S130.

[0052] In step S110, a reference branch current limit value is obtained for each of the multiple branches (in the current current direction).

[0053] The reference branch current limit value indicates the current range within which the branch's current should be maintained to ensure stable operation without significant degradation. During operation, it is desirable to keep the actual current of a branch below its reference branch current limit value. Otherwise, if the actual current value of at least one branch is detected to exceed its reference branch current limit value, a branch overcurrent warning will occur to alert the system and / or the user to take measures to clear the warning.

[0054] Information used to obtain reference branch current limit values ​​in the charging direction and the discharging direction for each branch can be pre-stored in the battery management system. In some embodiments, the reference branch current limit value in the charging or discharging direction for each branch can vary depending on the branch's temperature and / or SOC. The SOC of the battery pack is the state of charge of the battery pack, which represents how much electrical energy remains in the battery pack. SOC can be expressed as a percentage from 0% to 100%, where 0% indicates that the battery pack is fully discharged and 100% indicates that the battery pack is fully charged. It should be noted that, in this disclosure, the SOC of a branch refers to the representative SOC of all battery packs in that branch, such as the average SOC of the battery packs in that branch. The system can maintain the SOC value of each branch by reading the SOC value of that branch stored in the system (e.g., in the system's EEPROM) when the system is powered on, and by correcting and updating the read SOC value at predetermined time intervals during operation. In this way, the system can obtain the SOC value of the maintained branch at any time when needed. In some embodiments, the reference branch current limit value for each branch in the charging or discharging direction can be obtained based on a reference branch current limit value table pre-stored by the system.

[0055] Figure 2 An example table of reference branch current limit values ​​in the charging direction is shown. Figure 3 An example of a reference branch current limit value table in the discharge direction is shown. By using the detected temperature and SOC of each branch, and referring to the reference branch current limit value table in the current current direction, the reference branch current limit value for each of the multiple branches in the current current direction can be determined in real time. A temperature sensor can be provided for each branch, and each temperature sensor detects the temperature value of its corresponding branch and transmits it to the battery management system 100. In this way, the battery management system 100 can obtain the detected temperature of each branch and use it in determining the reference branch current limit value. Alternatively, a temperature sensor can be provided for the entire parallel battery system, which can detect the temperature value of the entire parallel battery system and transmit it to the battery management system 100. Alternatively, the battery management system 100 can use the temperature value of the entire parallel battery system as the detected temperature of each branch. For example, if the current direction of the system is charging, the detection temperature of BR1 and BR2 is both 10℃, and the SOC of BR1 branch is 80% and the SOC of BR2 branch is 90%, then the reference branch current limit value for BR1 branch in the current current direction can be obtained as 42A, and the reference branch current limit value for BR2 branch in the current current direction can be obtained as 36A. It is worth noting that if the detected branch temperature and SOC values ​​are not exactly the same as any of the values ​​listed in the table, the reference branch current limit value for that branch in the current current direction can also be estimated based on the values ​​in the table, for example, using a linear interpolation method. In this way, N reference branch current limit values ​​in the current current direction can be obtained for N available branches in the system, where N represents a number and can be a positive integer. For example, N can be 2 or higher.

[0056] As mentioned earlier, before a branch overcurrent warning occurs, i.e. when the system is in normal condition, the total current limit value of the battery parallel system can be set to the default total current limit value.

[0057] In one embodiment, the default total current limit value in the current current direction can be determined by multiplying the minimum current limit value among the reference branch current limit values ​​of the plurality of branches in the current current direction by the number of the plurality of branches.

[0058] As described above, for N available branches in the system, N reference branch current limit values ​​can be obtained in the current direction. For example, if the system has N = 2 branches, and the minimum current limit value among the two reference branch current limit values ​​in the current direction is 83A, then the default total current limit value of the system in the current direction is 83A × 2 = 166A. Similarly, for a system with 3 available branches and a minimum current limit value of 83A, the default total current limit value is 83A × 3 = 249A; for a system with 5 available branches and a minimum current limit value of 83A, the default total current limit value is 83A × 5 = 415A.

[0059] In step S120, a first total current limit value for the plurality of branches in the current current direction is determined based on the ratio of the maximum permissible DC internal resistance (DCIR) difference between the plurality of branches, the number of the plurality of branches, and the reference branch current limit value of each of the plurality of branches in the current current direction.

[0060] As discussed above, a branch overcurrent warning will occur when the actual current value of a branch is detected to exceed the reference branch current limit for that branch. For example, if the actual current value of branch BR1 is detected to be 45A, which is higher than the reference branch current limit of 42A for branch BR1 in the current current direction, then branch BR1 will generate a branch overcurrent warning. In this step, a first overall current limit is determined such that no branch overcurrent warning will occur when the actual maximum DCIR difference ratio between the plurality of branches is less than or equal to the maximum permissible DCIR difference ratio.

[0061] It is worth noting that the DCIR of a branch in this disclosure refers to the representative DCIR of all battery packs in that branch, such as the average DCIR of all battery packs in that branch.

[0062] In this disclosure, when a parameter is prefixed with the word "actual," it means that the parameter prefixed with "actual" is the actual / true value of that parameter present during the operation of the battery parallel system in a real-world application. The true value of a parameter can be detected using a detector. For example, the actual DCIR difference ratio between multiple branches refers to the actual / true value of the DCIR difference ratio between multiple branches during the operation of the battery parallel system.

[0063] The DCIR difference ratio between two branches can refer to the ratio of the difference between the higher DCIR of one branch and the lower DCIR of the other branch to the lower DCIR of the other branch. Therefore, the maximum DCIR difference ratio among multiple branches can refer to the ratio of the difference between the highest and lowest DCIR of these branches to the lowest DCIR of these branches. Accordingly, the actual maximum DCIR difference ratio among multiple branches refers to the actual / true maximum value of the DCIR difference ratio among the multiple branches during the operation of the parallel battery system. The maximum permissible DCIR difference ratio among multiple branches refers to the highest value allowed for the actual maximum DCIR difference ratio among the multiple branches. In other words, it is desirable to limit the actual DCIR difference ratio among multiple branches to no greater than the maximum permissible DCIR difference ratio among the multiple branches. The maximum permissible DCIR difference ratio can be a predetermined expected or estimated value, for example, determined by the battery control system manufacturer's technicians and / or using a computer-implemented algorithm, taking into account various factors. The maximum permissible DCIR difference ratio can then be pre-stored in the system for later use. The maximum permissible DCIR difference ratio is preferably designed to be not too large, so that the first total current limit to be reduced will not be too low, thus excessively reducing the system's operating power and consequently excessively degrading the system's operating performance.

[0064] In one embodiment, the maximum permissible DCIR difference ratio among the plurality of branches can be determined based on one or more of the following factors: 1) State of Health (SOH) replacement threshold, where at least a portion of the battery pack in one of the plurality of branches needs to be replaced when the actual SOH value of that branch is below the SOH replacement threshold; 2) Warranty period, where at least a portion of the battery pack in that branch is replaced free of charge or at a reduced cost during the warranty period; and 3) Operating power requirements. The above factors can be considered, and the maximum permissible DCIR difference ratio can be determined based on historical data from a large number of battery parallel systems. For example, the maximum permissible DCIR difference ratio can be determined such that the total cost of providing free or reduced-cost battery pack replacement services during the warranty period is within budget, while ensuring the output power required for normal load operation. For example, the maximum permissible DCIR difference ratio for a battery parallel system is set to a value that keeps the SOH of each branch of the battery parallel system within the range of 80% to 100% during the warranty period.

[0065] For example, but not limited to, the maximum permissible DCIR difference ratio of a battery parallel system with two branches can be set to 100% (i.e., The maximum permissible DCIR difference ratio for a battery parallel system with three branches can be set to 80% (i.e., The maximum permissible DCIR difference ratio for a battery parallel system with 5 branches can be set to 60% (i.e., ),etc.

[0066] In one embodiment, reference Figure 4 Step S120 may include the following steps S121 to S125.

[0067] In step 121, a first assumption is given: a first branch of the battery parallel system has the lowest internal resistance and is assigned a first assigned current limit value equal to the reference branch current limit value in the current current direction.

[0068] In step 122, a second assumption is given: in the battery parallel system, each of the other second branches besides the first branch has a higher internal resistance than the first branch, such that the actual DCIR difference ratio between each second branch and the first branch is equal to the maximum allowable DCIR difference ratio.

[0069] In step 123, the second allocation current limit value that should be allocated to each second branch under the first and second assumptions is calculated.

[0070] In step 124, the total allocated current limit value of the plurality of branches is calculated when the first branch is allocated a first allocated current limit value and each second branch is allocated a second allocated current limit value.

[0071] In step 125, a first total current limit value in the current current direction is determined based on the total allocated current limit value. The determined first total current limit value in the current current direction is less than or equal to the total allocated current limit value. In one embodiment, the first total current limit value in the current current direction can be determined to be the total allocated current limit value. In this case, the determined first total current limit value in the current current direction will be equal to the total allocated current limit value. In another embodiment, the first total current limit value in the current current direction can be determined by subtracting a margin from the total allocated current limit value. In this case, the determined first total current limit value in the current current direction will be less than the total allocated current limit value.

[0072] In step S120, a reference branch current limit value in the current current direction is used to determine the first total current limit value. When multiple branches have multiple different reference branch current limit values ​​in the current current direction, a representative reference branch current limit value can be selected from the multiple reference branch current limit values. For example, the smallest reference branch current limit value can be selected from the multiple reference branch current limit values ​​in the current current direction.

[0073] The first total current limit is a parameter indicating the current limit to which the system should reduce when a branch overcurrent warning occurs. In practical use, it can be recorded in the system as a fixed value / magnitude of the current limit; however, this is not a limitation, and in some embodiments, it can be expressed in other forms.

[0074] In some embodiments, the first total current limit value in the current current direction can be represented by a total current limit reduction factor. The total current limit reduction factor is a parameter indicating the extent to which the first total current limit value in the current current direction is reduced from the default total current limit value in the current current direction; in other words, it is a parameter indicating the relationship between the default total current limit value in the current current direction and the reduced first total current limit value in the current current direction. By using the total current limit reduction factor, it is possible to better show how much the current limit value has been reduced from the default total current limit value. The first total current limit value can be determined based on the total current limit reduction factor and the default total current limit value.

[0075] In a specific example, and as will be used in subsequent embodiments, the total current limit reduction factor can be a first ratio of a first total current limit to a default total current limit, i.e., a proportion of the default total current limit, and this first ratio decreases as the maximum permissible DCIR difference ratio increases. In this case, the first total current limit can be determined by multiplying the default total current limit by the total current limit reduction factor. For example, for a system with two branches, if the default total current limit in the current current direction is 166A and the first total current limit in the current current direction is 116.2A, then the total current limit reduction factor can be denoted as 70%, which means that the first total current limit in the current current direction is 70% of the default total current limit in the current current direction. It is understood that the first ratio / proportion representing the first total current limit decreases as the maximum permissible DCIR difference ratio increases.

[0076] Alternatively, in another specific example, the total current limit reduction factor can be a second ratio of the difference between the default total current limit and the first total current limit to the default total current limit, i.e., a reduction percentage of the default total current limit. In this case, the first total current limit can be determined by subtracting the product of the default total current limit and the total current limit reduction factor from the default total current limit. For example, for the system with two branches described above, if the default total current limit in the current current direction is 166A and the first total current limit in the current current direction is 116.2A, then the total current limit reduction factor can be alternatively recorded as 30%, which means that the first total current limit in the current current direction is (1-30%) of the default total current limit in the current current direction. It is understood that the second ratio / reduction percentage increases with the increase of the maximum permissible DCIR difference ratio.

[0077] In some embodiments, in step S120, a first total current limit value for the plurality of branches in the current current direction is determined in real time based on a predetermined maximum allowable DCIR difference ratio, the number of the plurality of branches, and a reference branch current limit value for each of the plurality of branches acquired in real time in the current current direction. More specifically, in some further embodiments, step S120 may include performing the above steps S121 to S125 in real time.

[0078] For example, but not limited to, for a parallel battery system with two branches, when the current direction is charging, and the current limit value of a selected / acquired reference branch is 83A, assuming the maximum allowable DCIR difference ratio of the system is 100%, we can make a first assumption that one branch in the system has a lower internal resistance of 1R (i.e., the battery pack in that branch has less aging) and is allocated the 83A; we can make a second assumption that the remaining branch in the system has a higher internal resistance of 2R (i.e., the battery pack in that branch has more aging), and we can calculate that the remaining branch should be allocated 83A ÷ 2 = 41.5A, and the total allocated current limit value = 83A + 41.5A = 124.5A. Based on this, a first total current limit value in the charging direction can be determined by subtracting a margin from the total allocated current limit value. For example, the margin can be set to 6.77% of the original value (i.e., the total allocated current limit value). Therefore, the first total current limit in the charging direction = 124.5A - 124.5A × 6.67% ≈ 116.2A, which is slightly lower than 124.5A. The specific values ​​of the margin here, as well as those in other parts of this disclosure, can be appropriately preset according to actual needs. For example, the margin can also be set to a fixed 4.5A, then the first total current limit in the charging direction can be set to 120A, etc., as long as it does not exceed the total allocated current limit of 124.5A. Exemplarily, the value of each margin in this disclosure is limited to less than 10% or 5% of the original value, so that the final usage value calculated by subtracting the margin from the original value does not deviate too much from the original value. In another example, the first total current limit in the charging direction can be directly determined as the total allocated current limit = 124.5A, thus leaving no margin between the total allocated current limit and the first total current limit.

[0079] Similarly, for a parallel battery system with three branches, when the current direction is charging, and the current limit of a selected / acquired reference branch is 83A, assuming the maximum allowable DCIR difference ratio of the system is 80%, we can assume that one branch in the system has the lowest internal resistance of 1R (i.e., the battery pack in that branch has less aging) and is allocated the 83A. We can also assume that the other two branches each have the highest internal resistance of 1.8R (i.e., the battery pack in that branch has more aging). We can calculate that the other two branches should be allocated 83A ÷ 1.8 ≈ 46.1A, and the total allocated current limit ≈ 83A + 46.1A × 2 ≈ 175.2A. Based on this, the first total current limit in the charging direction can be set to 174.3A, which is slightly lower than 175.2A, leaving a margin.

[0080] Similarly, for a battery parallel system with 5 branches, with a selected / acquired reference branch current limit of 83A and the system's maximum allowable DCIR difference ratio of 60%, the total allocated current limit is approximately 83A + 51.9A × 4 ≈ 290.6A. Based on this, the first total current limit in the charging direction can be set to 290.5A, with a small margin.

[0081] However, the real-time determination of the first total current limit value can be time-consuming. In some other embodiments, some of the determination of the first total current limit value can be performed in advance to make the determination of the first total current limit value simpler and faster, which will be described below.

[0082] In some other embodiments where the first total current limit value in the current current direction is represented by a total current limit value reduction factor, step S120 may include: S127, determining the first total current limit value based on the total current limit value reduction factor and the default total current limit value in the current current direction obtained in real time; the total current limit value reduction factor is predetermined based on the maximum allowable DCIR difference ratio between the plurality of branches, the number of the plurality of branches, and the reference branch current limit value. More specifically, in further embodiments, step S120 may include: pre-determining the total current limit value reduction factor by performing the above steps S121 to S124 and the subsequent step S126 in advance, and determining the first total current limit value in real time by performing the above step S127 in real time. Wherein, S126 may include: determining the total current limit value reduction factor in the current current direction based on the total allocated current limit value, and the total current limit value reduction factor in the current current direction is determined to ensure that the corresponding first total current limit value is less than or equal to the total allocated current limit value. In other words, the above-mentioned S125 can also alternatively include the pre-performed step S126 and the real-time step S127.

[0083] When both the default total current limit value and the first total current limit value in the current current direction are determined based on the minimum reference current limit value in each branch, once the maximum allowable DCIR difference ratio is predetermined to a fixed value, the total current limit reduction factor, which represents the relationship between the default total current limit value and the first total current limit value in the current current direction, is also a fixed value. Therefore, in the above embodiment, since the system will always maintain the default total current limit value in the current current direction that is acquired in real time, it is not necessary to calculate the first total current limit value in the current current direction from the beginning. Instead, the first total current limit value in the current current direction can be calculated simply based on the total current limit reduction factor and the default total current limit value in the current current direction that is acquired in real time. For example, for the above system with two branches, the total current limit reduction factor as the first ratio can be predetermined by using steps S121 to S124 and step S126 in a manner similar to the example above. For example, in a parallel battery system with two branches, when the current direction is charging, we can assume a minimum reference branch current limit of I. Assuming the maximum allowable DCIR difference ratio of the system is 100%, we can make a first assumption that one branch in the system has a lower internal resistance of 1R (i.e., the battery pack in that branch has less aging) and is allocated the current limit of I. We can make a second assumption that the remaining branch in the system has a higher internal resistance of 2R (i.e., the battery pack in that branch has more aging). We can calculate that the remaining branch should be allocated I / 2, and the total allocated current limit = I + I / 2 = 3I / 2. Simultaneously, we can calculate the default total current limit of I × 2 = 2I. It can be seen that 3I / 2 ÷ 2I = 75%. Based on this, the total current limit reduction factor can be determined by subtracting a margin from the ratio of the total allocated current limit to the default total current limit. For example, the margin can be set to a fixed percentage of 5%. Therefore, the total current limit reduction factor = 75% - 5% = 70%, which is slightly lower than 75%. This predetermined total current limit reduction factor of 70% can then be pre-stored in the system. When a branch overcurrent warning occurs at time T1, and the first total current limit value in the current direction at time T1 needs to be calculated, it can be calculated simply by multiplying the default total current limit value in the current direction at time T1 by 70%. This is much more efficient than calculating the first total current limit value in the current direction at time T1 from the beginning using a predetermined maximum allowable DCIR difference ratio, the number of branches, and the reference branch current limit value of each of these branches in the current current direction obtained in real time.

[0084] In step S130, when a branch overcurrent warning occurs in the battery parallel system, the total current limit value of the battery parallel system in the current current direction is set from the default total current limit value to the first total current limit value in the current current direction.

[0085] As described above, when the battery parallel system is operating normally in both the charging and discharging directions, the total current limit value in the charging direction can be set to the default total current limit value in the charging direction, and the total current limit value in the discharging direction can also be set to the default total current limit value in the discharging direction. When a branch overcurrent warning occurs in the current current direction of the battery parallel system, and a first total current limit value in the current current direction is determined, the total current limit value in the current current direction can be reduced to the determined first total current limit value in the current current direction. For example, for the above-mentioned system with two branches, when the first total current limit value in the current current direction is determined to be 70% of the default total current limit value in the current current direction, and the current current direction is the charging direction, the total current limit value in the charging direction can be reduced to 70% of the default total current limit value in the charging direction.

[0086] When some battery packs in the system are replaced while others remain, DCIR differences may exist between branches. In this case, a branch overcurrent warning may be caused by these DCIR differences. When a branch overcurrent warning occurs, by using the method described above to reduce the total current limit in the charging direction to the first total current limit in the current direction, as long as the actual maximum DCIR difference ratio between multiple branches is less than or equal to the maximum allowable DCIR difference ratio, branch overcurrent warnings will not easily recur due to uneven distribution caused by DCIR differences. Furthermore, after the system has been operating in the same current direction for a long time, branches with lower DCIR will be allocated higher currents and age faster in the same current direction, thus gradually reducing the DCIR difference between branches and reducing the risk of branch overcurrent warnings caused by DCIR differences.

[0087] In some cases, such as when the actual maximum DCIR difference ratio between multiple branches has exceeded the maximum permissible DCIR difference ratio, a branch overcurrent warning may still occur again even when the total current limit value of the system in the charging direction has been reduced to a first total current limit value in the current current direction. In one embodiment, to address this situation, after setting the total current limit value of the battery parallel system in the current current direction from a default total current limit value to a first total current limit value in the current current direction, the method may further include: when a branch overcurrent warning occurs again in the battery parallel system, successively reducing the total current limit value of the battery parallel system in the current current direction by a predetermined current limit reduction amount until no more branch overcurrent warnings occur in the battery parallel system. The predetermined current limit reduction amount may be the amount by which the total current limit value is reduced each time, and may be expressed as an absolute value or a percentage. The value of the predetermined current limit reduction amount can be set according to actual needs. For example, the predetermined current limit reduction can be set to a value within the range of 5% to 20% of the default total current limit, such as 5%, 10%, 15%, or 20% of the default total current limit. For instance, when the predetermined current limit reduction is set to 10%, for a battery parallel system with two branches, when the first branch overcurrent warning occurs, the total current limit in the charging direction has been reduced to 70% of the default total current limit in the charging direction using the above method. Subsequently, when the second branch overcurrent warning occurs, with a predetermined current limit reduction of 10% of the default total current limit, the total current limit in the charging direction can be reduced to 60% of the default total current limit in the charging direction. Subsequently, when the third branch overcurrent warning occurs, the total current limit in the charging direction can be reduced to 50% of the default total current limit in the charging direction.

[0088] In the above embodiments, if the total current limit of the system has been reduced too low, the current supplied to the load (e.g., a vehicle) may be insufficient for the load to operate normally. In one embodiment, to address this situation, during the process of successively reducing the total current limit of the battery parallel system in the current current direction, the total current limit of the battery parallel system in the current current direction can be limited to no less than a predetermined lower limit of the total current in the current current direction. In other words, it is the lowest current limit that the total current limit of the battery parallel system in the current current direction is allowed to be. The predetermined lower limit of the total current can be set according to actual needs. For example, the predetermined lower limit of the total current can be set to a value within the range of 40% to 60% of the default total current limit, for example, set to 50%, 55%, or 60% of the default total current limit. For example, the predetermined lower limit of the total current in the current current direction can be set to 50% of the default total current limit in the current current direction, thereby limiting the total current limit of the battery parallel system in the current current direction to no less than 50% of the default total current limit in the current current direction. That is, once the total current limit in the current current direction is reduced to 50%, the total current limit in the current current direction will no longer decrease. Simulation tests have shown that when the total current limit is finally reduced to 50% of the default value in the current current direction, the system can operate stably and there will be no more branch overcurrent warnings due to uneven current distribution.

[0089] If the system remains at the reduced first total current limit value in the current current direction, the current output to the load is limited, potentially reducing the load's operating performance. Therefore, it is advantageous to restore the total current limit value so that the load can operate with higher performance when the risk of causing a warning decreases or is eliminated. In one embodiment, after setting the total current limit value of the battery parallel system in the current current direction from the default total current limit value in the current current direction to the first total current limit value in the current current direction, the method may further include: restoring the total current limit value of the battery parallel system in the current current direction to the default total current limit value in the current current direction when it is detected that the state of the actual total current value of the battery parallel system being less than a predetermined proportion of the default total current limit value in the current current direction has lasted for a preset duration threshold, the method may also include: restoring the total current limit value of the battery parallel system in the current current direction to the default total current limit value in the current current direction. The value of the predetermined proportion (i.e., percentage) can be set according to actual needs. For example, the predetermined proportion can be set to a value in the range of 60% to 80% of the default total current limit value, such as 60%, 65%, 70%, 75%, or 80% of the default total current limit value. For example, the predetermined ratio can be set to 70%, and the preset time threshold can be set to 5 minutes. In this way, when the actual total current value of the battery parallel system is detected to be less than 70% of the default total current limit value in the current current direction for 5 minutes, the system can return to the normal state and restore the total current limit value of the battery parallel system in the current current direction to the default total current limit value in the current current direction.

[0090] When the total current limit of the system in the current current direction has been reduced to the first total current limit in the current current direction, and the system maintains the same current current direction, branch overcurrent warnings are unlikely to occur again as long as the actual maximum DCIR difference ratio between multiple branches is less than or equal to the maximum allowable DCIR difference ratio. Furthermore, when the system maintains the same current current direction and no current direction change occurs, the SOC difference caused by the actual DCIR difference ratio between branches can also help reduce the actual current difference between branches. Therefore, when the system maintains the same current current direction, no additional current limiting based on the SOC difference is required. However, during operation, the system may suddenly switch from the current current direction to the reverse current direction (e.g., when a user suddenly applies the vehicle brakes, the system switches from the discharging direction to the charging direction). If the SOC difference between branches is high at the time of switching, another branch overcurrent warning may occur even if the actual maximum DCIR difference ratio between multiple branches is less than or equal to the maximum allowable DCIR difference ratio.

[0091] In one embodiment, to address the above situation, after setting the total current limit value of the battery parallel system as a first total current limit value, the method may further include the following step: based on the actual SOC of each of the multiple branches, setting a total current limit value in the reverse current direction opposite to the current current direction of the battery parallel system. Specifically, the battery parallel system pre-stores multiple reference state of charge (SOC) difference ranges higher than the SOC difference threshold, and multiple specified total current limit values ​​in the charging and discharging directions corresponding to the multiple SOC difference ranges, respectively. When the system is in an overcurrent warning state, and after setting the total current limit value of the battery parallel system in the current current direction from the default total current limit value in the current current direction to a first total current limit value in the current current direction, the method may further include: monitoring the actual SOC of each of the multiple branches; and when the actual maximum SOC difference between the multiple branches in the current current direction is detected to change from not exceeding the SOC difference threshold to exceeding the SOC difference threshold, marking the reverse current direction opposite to the current current direction as the effective current direction, and maintaining the marking of the effective current direction until the actual maximum SOC difference between the multiple branches in the current current direction is detected to change from exceeding the SOC difference threshold to not exceeding the SOC difference threshold. Optionally, the above-mentioned current current direction may also be marked as an invalid current direction, and maintained together with the marking and maintenance of the effective current direction. During the period when the markings for the effective current direction (and the markings for the ineffective current direction) are maintained, when the actual maximum SOC difference between the multiple branches in the current current direction falls within the first reference SOC difference range of multiple reference SOC difference ranges, and when the reverse current direction opposite to the current current direction is the current direction marked as the effective current direction, the total current limit value of the battery parallel system in the reverse current direction is set to the first specified total current limit value in the reverse current direction corresponding to the first reference SOC difference range; otherwise, when the reverse current direction is not the current direction marked as the effective current direction (i.e., it is marked as the ineffective current direction), setting the total current limit value in the reverse current direction to the first specified total current limit value is prohibited, so that the total current limit value of the battery parallel system in the reverse current direction remains unchanged.

[0092] The specified total current limit in the reverse current direction can be lower than the first total current limit in the reverse current direction. The first total current limit in the reverse current direction can be calculated using parameters in the reverse current direction in a similar manner to the first total current limit in the current direction. In this way, when the system is in an overcurrent warning state and the actual maximum SOC difference is detected to be higher than the SOC difference threshold, the total current limit in the reverse current direction is further reduced in advance. Therefore, even if the system suddenly switches to the reverse current direction, the likelihood of triggering another warning is reduced. For example, the SOC difference threshold could be 2%.

[0093] The SOC difference between two branches can refer to the difference between the higher SOC of one branch and the lower SOC of the other branch. Therefore, the maximum SOC difference among multiple branches can refer to the difference between the highest SOC and the lowest SOC among these branches. Correspondingly, the actual maximum SOC difference among multiple branches refers to the actual / true maximum value of the SOC difference among these branches during the operation of the parallel battery system. The SOC difference threshold is a threshold used to compare and determine whether the actual maximum SOC difference among multiple branches has exceeded a predetermined threshold.

[0094] Furthermore, in one embodiment, as the actual maximum SOC difference increases, the specified total current limit value in the reverse current direction can be set to a lower value.

[0095] In one embodiment, after setting the total current limit value of the battery parallel system in the reverse current direction to a first specified total current limit value corresponding to a first reference SOC difference range, the method may further include: when it is detected that the actual maximum SOC difference between the multiple branches changes to a second reference SOC difference range that is different from the first reference SOC difference range within the multiple reference SOC difference ranges, setting the total current limit value of the battery parallel system in the reverse current direction to a second specified total current limit value in the reverse current direction corresponding to the second reference SOC difference range.

[0096] In one embodiment, after setting the total current limit value of the battery parallel system in the reverse current direction to a first specified total current limit value corresponding to a first reference SOC difference range, the method may further include: when it is detected that the actual maximum SOC difference between multiple branches changes to no greater than the SOC difference threshold and falls outside all of the multiple reference SOC difference ranges, restoring the total current limit value of the battery parallel system in the reverse current direction to the default total current limit value in the reverse current direction, and clearing the mark of the effective current direction.

[0097] To further describe, when the actual maximum SOC difference between multiple branches is detected to change to no greater than the SOC difference threshold and fall outside the range of all the multiple reference SOC differences, regardless of whether the current current direction of the battery parallel system has switched to the reverse current direction, the total current limit value of the battery parallel system in the current current direction can be kept unchanged, while the total current limit value of the battery parallel system in the reverse current direction can be restored to the default total current limit value in the reverse current direction.

[0098] When the change in the actual maximum SOC difference between branches from no greater than the SOC difference threshold to greater than the SOC difference threshold occurs in a certain current direction, it is desirable only to further limit the current in the reverse current direction of that current direction to the specified total current limit value, and not to further limit the current in that current direction to the specified total current limit value. However, when the current current direction changes continuously multiple times, due to the change in the current current direction, the aforementioned original current direction may be regarded as the reverse current direction and limited to the specified total current limit value, which is undesirable.

[0099] Therefore, in the above-described scheme for setting the total current limit value based on SOC in this application, the current direction when the detected actual maximum SOC difference between branches changes from not exceeding the SOC difference threshold to exceeding the SOC difference threshold is marked as an invalid current direction, and the reverse current direction of this invalid current direction is marked as an effective current direction. Then, the total current limit value in the effective current direction is only allowed to be set to the specified total current limit value, and the total current limit value in the invalid current direction is not allowed to be set to the specified total current limit value (in other words, even if the current current direction has become an effective current direction, and the actual maximum SOC difference between branches in the current current direction remains higher than the SOC difference threshold, the system will not change the total current limit value in the invalid current direction, which is the current reverse current direction, to the specified total current limit value), until the actual maximum SOC difference between branches in the current current direction falls below the SOC difference threshold. When the actual maximum SOC difference between branches in the current current direction falls below the SOC difference threshold, the total current limit value in the effective current direction can be restored to the default total current limit value in the effective current direction. Once the invalid and valid current directions are marked, they will not change due to changes in the current current direction until the actual maximum SOC difference between branches in the current current direction falls below the SOC difference threshold. At this point, the markings for the invalid and valid current directions are cleared. During the period when the markings for the invalid and valid current directions are maintained, if the actual maximum SOC difference between branches in the current current direction is higher than the SOC difference threshold, the marking for the reverse current direction is checked. If the reverse current direction is a current direction marked as a valid current direction, the total current limit value in that reverse current direction is set to the corresponding specified total current limit value in the reverse current direction. If the reverse current direction is a current direction marked as an invalid current direction, the total current limit value in that reverse current direction remains unchanged and is not further set to the corresponding specified total current limit value in that reverse current direction.

[0100] This solution can be implemented, for example, by setting flag bits. Specifically, the system records flag bits for charging direction and discharging direction: i. When the actual maximum SOC difference between branches changes from not exceeding the SOC difference threshold to exceeding the SOC difference threshold in the charging direction, the discharging direction flag bit is set to valid, and the charging direction flag bit is set to invalid; ii. When the actual maximum SOC difference between branches changes from not exceeding the SOC difference threshold to exceeding the SOC difference threshold in the discharging direction, the charging direction flag bit is set to valid, and the discharging direction flag bit is set to invalid; iii. Only one flag bit is valid at any given time; iv. When the current power... When the flow direction changes, the validity / invalidity of the charging direction flag and the discharging direction flag remains unchanged; v. Only the total current limit value in the current direction with the valid flag can be additionally limited to the specified total current limit value, and the total current limit value in the current direction with the invalid flag will not be additionally limited to the specified total current limit value; vi. When the actual maximum SOC difference between branches in the current direction becomes no higher than the SOC difference threshold, the total current limit value in the current direction with the valid flag is restored to the default total current limit value in that current direction with the valid flag, and then both flags can be reset to 0. For example, when the discharge direction flag is set to valid and the charging direction flag is set to invalid, if the actual maximum SOC difference between branches in the charging direction (as the current current direction) is higher than the SOC difference threshold, and the discharge direction (as the reverse current direction) flag is found to be set to valid, then the total current limit value in the discharge direction is set to the corresponding specified total current limit value in the discharge direction. Conversely, if the current current direction is then switched to the discharge direction, if the actual maximum SOC difference between branches in the discharge direction (as the current current direction) is higher than the SOC difference threshold, and the charging direction (as the reverse current direction) flag is found to be set to invalid, then the total current limit value in the charging direction remains unchanged and is not further set to the corresponding specified total current limit value in the charging direction.

[0101] refer to Figure 5For example, a SOC difference range exceeding the 2% SOC difference threshold can be divided into four SOC difference ranges, each with a corresponding specified total current limit. When the actual maximum SOC difference between multiple branches falls within or changes to fall within any of the four SOC difference ranges, the system switches to an over-SOC difference state and updates the total current limit of the battery parallel system in the reverse current direction to the specified total current limit corresponding to that SOC difference range. When the actual maximum SOC difference between multiple branches is not greater than the 2% SOC difference threshold and therefore falls outside all four SOC difference ranges, the system switches to a non-over-SOC difference state and sets the total current limit of the battery parallel system in the reverse current direction to the first total current limit, or to the default total current limit (depending on the default total current limit set before setting the specified total current limit).

[0102] The above embodiments primarily consider how to adjust the overall current limit of the system when a branch overcurrent warning mainly occurs due to uneven current distribution caused by the DCIR difference between branches. In some cases, in addition to the DCIR difference, certain system errors or faults may also lead to more severe overcurrents. In the embodiments described below, different levels of overcurrent alerts (e.g., including branch overcurrent warnings, branch overcurrent alarms, and branch overcurrent faults described below) can occur, and different measures can be taken accordingly.

[0103] In some embodiments, a branch overcurrent warning occurs in the battery parallel system when the actual current value of at least one of the multiple branches is higher than the reference branch current limit value in its current current direction, but not higher than the reference branch current limit value in its current current direction multiplied by a first multiplier factor. When a branch overcurrent warning occurs, the system switches to an overcurrent warning state and sets the total current limit value in the current current direction to the aforementioned first total current limit value in the current current direction. For example, the first total current limit value in the current current direction determined in S120 above can be 70% of the default total current limit value in the current current direction.

[0104] In some embodiments, a branch overcurrent alarm occurs in the battery parallel system when the actual current value of at least one of the multiple branches is higher than the reference branch current limit value in its current current direction multiplied by a first multiplier factor, but not higher than the reference branch current limit value in its current current direction multiplied by a second multiplier factor higher than the first multiplier factor; the branch overcurrent alarm overrides the branch overcurrent warning. When a branch overcurrent alarm occurs, the system switches to overcurrent alarm state and sets the total current limit value in the current current direction to a second total current limit value in the current current direction that is lower than the first total current limit value in the current current direction. For example, the second total current limit value in the current current direction can be preset to 50% of the default total current limit value in the current current direction.

[0105] In some embodiments, a branch overcurrent fault occurs in the battery parallel system when the actual current value of at least one of the multiple branches is higher than the reference branch current limit value in its current current direction multiplied by a second multiplier factor; the branch overcurrent fault overrides the branch overcurrent alarm. When a branch overcurrent fault occurs, the system switches to an overcurrent fault state and sets the total current limit value in the current current direction to a third total current limit value in the current current direction that is lower than the second total current limit value in the current current direction. For example, the third total current limit value in the current current direction can be preset to 0% of the default total current limit value in the current current direction, that is, when a branch overcurrent fault occurs, the total current in the system in the current current direction is cut off.

[0106] The fact that a tributary overcurrent alarm covers a tributary overcurrent warning means that if both the conditions for triggering a tributary overcurrent warning and the conditions for triggering a tributary overcurrent alarm are met, the tributary overcurrent alarm has a higher triggering priority than the tributary overcurrent warning. Therefore, when both conditions for triggering a tributary overcurrent alarm and the conditions for triggering a tributary overcurrent warning are met simultaneously, the system will prioritize considering the system to be in an overcurrent alarm state rather than an overcurrent warning state, and will prioritize handling / taking measures under the tributary overcurrent alarm state rather than under the tributary overcurrent warning state. Similarly, the fact that a tributary overcurrent fault covers a tributary overcurrent alarm means that if both the conditions for triggering a tributary overcurrent fault and the conditions for triggering a tributary overcurrent alarm are met, the tributary overcurrent fault has a higher triggering priority than the tributary overcurrent alarm. Therefore, when both conditions for triggering a tributary overcurrent fault and the conditions for triggering a tributary overcurrent alarm are met simultaneously, the system will prioritize considering the system to be in an overcurrent fault state rather than an overcurrent alarm state, and will prioritize handling / taking measures under the tributary overcurrent fault state rather than under the tributary overcurrent alarm state. In other words, if the conditions for multiple occurrences of branch overcurrent alarm, branch overcurrent warning, and branch overcurrent fault are met, the system will process / take measures based on the one with the highest trigger priority.

[0107] For example, the first multiplier and the second multiplier can be 1.1 and 1.2, respectively. Correspondingly, when the actual current value of a branch is not greater than the reference branch current limit in the current current direction, no overcurrent warning will occur for that branch. When the actual current value of a branch is higher than the reference branch current limit in the current current direction, but not greater than 1.1 times the reference branch current limit in the current current direction, a branch overcurrent warning will occur, and the total current limit in the current current direction will be set to 70% of the default total current limit in the current current direction. When the actual current value of a branch is higher than 1.1 times the reference branch current limit in the current current direction, but not greater than 1.2 times the reference branch current limit in the current current direction, a branch overcurrent alarm will occur, and the total current limit in the current current direction will be set to 50% of the default total current limit in the current current direction. When the actual current value of a branch is higher than 1.2 times the reference branch current limit value in the current current direction, a branch overcurrent fault will occur, and the total current limit value in the current current direction will be set to 0% of the default total current limit value in the current current direction.

[0108] See Figure 6 In conjunction with the above embodiments, the setting of the total current limiting value in the current direction under different states is as follows: Figure 6 As shown. It is worth noting that, although Figure 6 In the system, when in an overcurrent warning state but not an over-SOC difference state, and when in an overcurrent alarm state or an overcurrent fault state, the system's total current limit in the reverse current direction is set to the default total current limit in the reverse current direction by default. However, the system's total current limit in the reverse current direction can also be set to other values ​​in these states. For example, in an alternative embodiment, when in an overcurrent warning state but not an over-SOC difference state, the system's total current limit in the reverse current direction is set to a first total current limit in the reverse current direction; when in an overcurrent alarm state, the system's total current limit in the reverse current direction is set to a second total current limit in the reverse current direction; and when in an overcurrent fault state, the system's total current limit in the reverse current direction is set to a third total current limit in the reverse current direction.

[0109] refer to Figure 7In a second aspect of this disclosure, a current control system 10 is provided. The current control system 10 can be used to implement the current control method described in any of the above embodiments. Specifically, the current control system 10 includes a battery management system 100. The battery management system 100 is communicatively connected to a battery parallel system 200. The battery parallel system 200 includes a plurality of branches 210 connected in parallel, each of the plurality of branches 210 including one or more battery packs 211. The one or more battery packs 211 in each branch 210 may be connected in parallel, in series, or partially in parallel and partially in series with each other. Each battery pack 211 may further consist of a plurality of battery cells connected in parallel and / or in series.

[0110] The battery management system 100 includes a memory 101 and a processor 102. The memory 101 stores computer-readable instructions. When the processor 102 executes the computer-readable instructions, it causes the processor 102 to operate to implement the current control method described in any of the above embodiments.

[0111] In one embodiment, the current control system 10 may further include a battery parallel system 200.

[0112] In one embodiment, see Figure 8 The battery management system 100 may include: a plurality of parallel battery management units 110, each of which is communicatively connected to a corresponding branch among the plurality of branches 210, and configured to: determine a reference branch current limiting value for the corresponding branch among the plurality of branches 210 in the current current direction, monitor the actual current value of the corresponding branch among the plurality of branches 210, and when the actual current value of the corresponding branch among the plurality of branches 210 is detected to exceed the reference branch current limiting value among the plurality of branches 210, the system will take appropriate action. When a branch reaches the reference branch current limit value in the current current direction, a branch overcurrent warning is initiated; and a main battery management unit 120, electrically connected to the plurality of parallel battery management units 110, is configured to obtain the reference branch current limit value of each branch 210 in the current current direction from the plurality of parallel battery management units 110, and set the total current limit value of the battery parallel system 200 in the current current direction based on the obtained reference branch current limit value of each branch 210 in the current current direction. A memory 101 and a processor 102 are included in the main battery management unit 120 and / or the plurality of parallel battery management units 110.

[0113] In one embodiment, reference Figure 9The current control system 10 may further include: a plurality of current sensors 212, each of the plurality of current sensors 212 being disposed in a corresponding branch of the plurality of branches 210 and configured to detect the actual current value in the corresponding branch of the plurality of branches 210 and transmit the detected actual current value to the battery management system 100.

[0114] In one embodiment, reference Figure 9 The current control system 10 may further include: a plurality of temperature detection devices 213, each of which is disposed at a corresponding branch of the plurality of branches 210 and configured to detect the temperature value of the corresponding branch and transmit the detected temperature value of the branch to the battery management system 100. In some embodiments, each branch temperature detection device 213 may include a temperature sensor configured to detect the temperature of all battery packs in the branch as the detection temperature of the branch. In some embodiments, each branch temperature detection device 213 may include n temperature sensors configured to detect the temperature of n battery packs in the branch in a one-to-one correspondence, and the average value of the n detected temperatures may be used as the detection temperature of the branch. In some embodiments, each battery pack temperature sensor may further include X sub-sensors configured to detect the temperature of X modules in the battery pack in a one-to-one correspondence, and the average value of the X detected temperatures may be used as the detection temperature of the battery pack.

[0115] In one embodiment, reference Figure 9 The current control system 10 may further include a plurality of relays 214, each of which is disposed in a corresponding branch of the plurality of branches 210 and configured to turn on or off the corresponding branch of the plurality of branches 210 in response to an instruction received from the battery management system 100.

[0116] refer to Figure 10In a third aspect of this disclosure, a vehicle 30 is provided. The vehicle 30 may be a wheeled or wheelless vehicle. The vehicle 30 includes a vehicle control unit 310 and the aforementioned current control system 10. A battery parallel system 200 is mounted on the vehicle 30 and configured to provide power for operation of the vehicle 30, such as driving. In some examples, the positive and negative terminals of the battery parallel system 200 are connected to the power distribution unit (PDU) of the vehicle 30 and supply power to the high-voltage system of the vehicle 30. A battery management system 100 is communicatively connected to the vehicle control unit 310 and configured to set a total current limit value for the battery parallel system 200 in the current current direction by sending a total current limit command to the vehicle control unit 310. This total current limit command instructs the vehicle control unit 310 to limit the actual current between the load of the vehicle 30 (e.g., various brakes) and the battery parallel system 200 in the current current direction to not exceed the total current limit value in the current current direction.

[0117] In a fourth aspect of this disclosure, a non-transitory computer-readable storage medium is provided. A computer program is stored on the non-transitory computer-readable storage medium. When the computer program is executed by a processor, the processor causes the processor to implement the current control method described in any of the above embodiments.

[0118] The technical features in the above embodiments can be combined arbitrarily. For the sake of brevity, not all possible combinations of technical features in the above embodiments are listed. However, as long as they do not conflict with each other, all combinations of technical features should be considered within the scope described in this specification.

[0119] The embodiments mentioned above merely describe several implementations of this disclosure. While the descriptions are specific and detailed, they should not be construed as limiting the scope of this disclosure. It is worth noting that those skilled in the art can make modifications and improvements without departing from the concept of this disclosure, and these all fall within the protection scope of this disclosure. Therefore, the protection scope of this disclosure should be determined by the scope of the appended claims.

Claims

1. A current control method applied to a battery parallel system, wherein, The battery parallel system includes multiple branches connected in parallel, each branch including one or more battery packs, and the method includes: Obtain the reference branch current limit value for each of the plurality of branches; A first total current limit is determined based on the maximum permissible DC-IR difference ratio among the plurality of branches, the number of the plurality of branches, and a reference branch current limit value for each of the plurality of branches, wherein the first total current limit is determined such that no branch overcurrent warning occurs when the actual maximum DCIR difference ratio among the plurality of branches is less than or equal to the maximum permissible DCIR difference ratio; and When the branch overcurrent warning occurs in the battery parallel system, the total current limit value of the battery parallel system is set from the default total current limit value to the first total current limit value; The branch overcurrent warning occurs when the actual current value of at least one of the plurality of branches exceeds the reference branch current limit value.

2. The method according to claim 1, wherein, Obtaining the reference branch current limit value includes obtaining the reference branch current limit value in the current direction. Setting the total current limit value of the battery parallel system to the first total current limit value includes: setting the total current limit value of the battery parallel system in the current current direction to the first total current limit value; and The direction of the current includes either the charging direction or the discharging direction.

3. The method according to claim 1, wherein, The maximum permissible DCIR difference ratio between the plurality of branches is determined in advance based on one or more of the following: State of Health (SOH) Replacement Threshold: When the actual SOH value of one of the plurality of branches is lower than the SOH Replacement Threshold, at least a portion of the battery pack of that one branch needs to be replaced.

4. The method according to claim 1, wherein, The default total current limit value is determined by multiplying the minimum current limit value among the reference current limit values ​​of the plurality of branches by the number of the plurality of branches.

5. The method according to claim 1, wherein, Determining the first total current limit value for the plurality of branches based on the number of the plurality of branches, the maximum allowable DCIR difference ratio, and the reference branch current limit value includes: The following assumptions are made: First, a first branch of the battery parallel system has the lowest internal resistance and is assigned a first current limit value equal to the reference branch current limit value; Second, each of the remaining second branches in the battery parallel system, excluding the first branch, has an internal resistance higher than that of the first branch, such that the actual DCIR difference ratio between each second branch and the first branch is equal to the maximum allowable DCIR difference ratio; Calculate the second current limit value that should be assigned to each second branch under the first and second assumptions. Calculate the total allocation current limit value for the plurality of branches, assuming the first branch is allocated the first allocation current limit value and each of the second branches is allocated the second allocation current limit value; and The first total rate limit is determined based on the total allocation rate limit, wherein the first total rate limit is less than or equal to the total allocation rate limit.

6. The method according to claim 1, wherein, The first total rate limit value is determined based on the total rate limit reduction coefficient and the default total rate limit value.

7. The method according to claim 6, wherein, The total current limiting value reduction factor is determined based on the maximum allowable DCIR difference ratio between the plurality of branches, the number of the plurality of branches, and the reference branch current limiting value, wherein: The total current limiting value reduction factor is a first ratio of the first total current limiting value to the default total current limiting value, and the first ratio decreases as the maximum allowable DCIR difference ratio increases; or The total current limiting value reduction factor is a second ratio of the difference between the default total current limiting value and the first total current limiting value to the default total current limiting value, and the second ratio increases as the maximum allowable DCIR difference ratio increases.

8. The method according to any one of claims 1 to 7, wherein, After setting the total current limit value of the battery parallel system to the first total current limit value, the method further includes: When the branch overcurrent warning occurs again in the battery parallel system, the total current limit value of the battery parallel system is continuously reduced by a predetermined current limit reduction until the branch overcurrent warning no longer occurs in the battery parallel system. The predetermined rate limit reduction is the amount by which the rate limit is reduced each time the total rate limit is lowered, and the predetermined rate limit reduction is within the range of 5% to 20% of the default total rate limit.

9. The method according to claim 8, wherein, During the process of continuously reducing the total current limit value of the battery parallel system, the total current limit value of the battery parallel system is limited to not less than a predetermined lower limit value of the total current. Wherein, the predetermined total current lower limit is the lowest current limit value that the total current limit value of the battery parallel system is allowed to be, and the predetermined total current lower limit value is in the range of 40% to 60% of the default total current limit value.

10. The method according to any one of claims 1 to 7, wherein, After setting the total current limit value of the battery parallel system to the first total current limit value, the method further includes: When it is detected that the actual total current value of the battery parallel system is less than a predetermined proportion of the default total current limit value for a period of time that has lasted for a preset time threshold, the total current limit value of the battery parallel system is restored to the default total current limit value. The predetermined ratio is within the range of 60% to 80% of the default total rate limit.

11. The method according to any one of claims 1 to 7, wherein, After setting the total current limit value of the battery parallel system to the first total current limit value, the method further includes the following step: based on the actual SOC of each of the plurality of branches, setting a total current limit value in the reverse current direction opposite to the current current direction of the battery parallel system. The battery parallel system pre-stores multiple reference state of charge (SOC) difference ranges higher than the SOC difference threshold, and multiple specified total current limit values ​​in the charging and discharging directions corresponding to the multiple SOC difference ranges, respectively. The step of setting the total current limit value in the reverse current direction based on the actual SOC of each of the multiple branches includes: Monitor the actual SOC of each of the multiple branches; and When the actual maximum SOC difference between the multiple branches in the current current direction changes from not exceeding the SOC difference threshold to exceeding the SOC difference threshold, the reverse current direction opposite to the current current direction is marked as the effective current direction, and the marking of the effective current direction is maintained until the actual maximum SOC difference between the multiple branches in the current current direction changes from exceeding the SOC difference threshold to not exceeding the SOC difference threshold. During the period in which the mark in the effective current direction is maintained, when the actual maximum SOC difference between the plurality of branches in the current current direction falls within the first reference SOC difference range of the plurality of reference SOC difference ranges, and When the reverse current direction, which is opposite to the current current direction, is the current direction marked as the effective current direction, the total current limit value of the battery parallel system in the reverse current direction is set to a first specified total current limit value in the reverse current direction corresponding to the first reference SOC difference range.

12. The method according to claim 11, wherein, During the period in which the mark of the effective current direction is maintained, when the actual maximum SOC difference between the plurality of branches in the current current direction falls within the first reference SOC difference range of the plurality of reference SOC difference ranges, the method further includes: prohibiting the setting of the total current limit value in the reverse current direction to the first specified total current limit value when the reverse current direction is not the current direction marked as the effective current direction; and / or After setting the total current limit value of the battery parallel system in the reverse current direction to the first specified total current limit value corresponding to the first reference SOC difference range, the method further includes: when it is detected that the actual maximum SOC difference between the plurality of branches changes to fall within a second reference SOC difference range that is different from the first reference SOC difference range, setting the total current limit value of the battery parallel system in the reverse current direction to a second specified total current limit value in the reverse current direction corresponding to the second reference SOC difference range; and / or After setting the total current limit value of the battery parallel system in the reverse current direction to the first specified total current limit value corresponding to the first reference SOC difference range, the method further includes: when it is detected that the actual maximum SOC difference between the plurality of branches changes to no greater than the SOC difference threshold and falls outside all of the plurality of reference SOC difference ranges, restoring the total current limit value of the battery parallel system in the reverse current direction to the default total current limit value in the reverse current direction, and clearing the mark of the effective current direction.

13. A current control system, the current control system comprising a battery management system, wherein, The battery management system is communicatively connected to a parallel battery system, the parallel battery system comprising multiple branches connected in parallel, each of the multiple branches comprising one or more battery packs, the battery management system comprising a memory and a processor, the memory storing computer-readable instructions, which, when executed by the processor, cause the processor to perform the method according to any one of claims 1 to 12, wherein... The current control system further includes the battery parallel system; and / or The battery management system includes multiple parallel battery management units, wherein each of the multiple parallel battery management units is communicatively connected to a corresponding branch among the multiple branches, and is configured to: determine a reference branch current limit value for the corresponding branch in the current current direction, monitor the actual current value of the corresponding branch among the multiple branches, and initiate a branch overcurrent when the actual current value of the corresponding branch among the multiple branches exceeds the reference branch current limit value for the corresponding branch in the current current direction. Warning; and a main battery management unit, electrically connected to the plurality of parallel battery management units, configured to obtain a reference branch current limit value for each branch in the current current direction from the plurality of parallel battery management units, and to set a total current limit value for the parallel battery system in the current current direction based on the obtained reference branch current limit values ​​for each branch in the current current direction; wherein the memory and the processor are included in the main battery management unit and / or the plurality of parallel battery management units; and / or The current control system further includes: a plurality of current sensors, wherein each of the plurality of current sensors is disposed in a corresponding branch of the plurality of branches and configured to detect the actual current value in the corresponding branch of the plurality of branches and transmit the detected actual current value to the battery management system.

14. A vehicle, the vehicle comprising a vehicle control unit and a current control system according to claim 13, wherein, The battery parallel system is installed on the vehicle and configured to provide power for the operation of the vehicle; The battery management system is communicatively connected to the vehicle control unit and configured to set the total current limit value of the battery parallel system in the current direction by sending a total current limit command to the vehicle control unit. The total current limit command is used to instruct the vehicle control unit to limit the actual current between the vehicle and the battery parallel system in the current current direction to not exceed the total current limit value in the current current direction.

15. A non-transitory computer-readable storage medium having a computer program stored thereon, wherein, When the computer program is executed by a processor, the processor causes the processor to implement the method according to any one of claims 1 to 12.

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