A method and system for distributing charging current in a multi-leg battery system

Abstract

The application discloses a charging current distribution method and system of a multi-branch battery system, and the method comprises the following steps: after a battery management system enters a charging mode, firstly, the maximum output capacity of a charging pile is identified; if the capacity is sufficient to cover the total charging demand of the battery system, the distribution strategy is to fully meet the requested current of each branch; if the charging pile capacity is insufficient, a priority-based decision logic is started, and the priority determination depends on the SOC state of each branch and the size of the requested current, so that the optimized distribution of the charging power is realized. The method can not only preferentially make full use of the available power of the charging pile, thereby maximizing the charging speed, but also effectively reduce the SOC difference between each branch, thereby improving the overall balance and operation efficiency of the system.

Description

Technical Field

[0001] This invention relates to the field of battery management system technology, and in particular to a charging current distribution method and system for a multi-branch battery system. Background Technology

[0002] In the fields of new energy commercial vehicles and new energy construction machinery, to achieve long driving range requirements, battery systems typically employ a configuration of multiple battery packs connected in parallel. In battery systems where the battery packs in each branch are directly connected in parallel, circulating and bias current phenomena are prone to occur between the branches. As usage time increases, the consistency differences between the cells gradually widen, affecting the overall system performance and lifespan. To solve this problem, the industry currently commonly adopts a solution where a DC / DC converter is connected to each battery branch before parallel connection, enabling independent control of each branch.

[0003] In such parallel battery systems with multiple branches combined with DC / DC converters, the Major Battery Management Unit (MBMU) needs to undertake two key functions: First, it needs to accurately estimate the output capacity of the charging station and, based on this, coordinate and control the current requests of each branch battery pack to avoid imbalance in the current distribution of each branch due to the total requested current exceeding the power supply capacity of the charging station. Second, the MBMU also needs to monitor the state of charge (SOC) of each branch in real time and reduce the SOC difference between branches by dynamically adjusting the charging current requests of each branch to prevent excessive accumulation of inconsistencies.

[0004] In the charging control of parallel battery systems with multiple branches combined with DC / DC, the commonly used charging current coordination control scheme is to directly and proportionally distribute power based on the initial state of charge of each battery branch.

[0005] When one or more branches with lower State of Charge (SOC) have a theoretical charging current calculated based on their SOC ratio that exceeds the maximum acceptable charging current that the branch can safely withstand in its current state, the system will forcibly limit the charging current of that branch to its upper limit to protect the battery. Because some branches have reached their current limits, the total power actually obtained by the battery system from the charging station will be lower than the maximum power the charging station can provide. At this point, although other branches with higher SOC still have charging capacity margin, they cannot obtain more current due to the limitations of the initial allocation logic. This results in the total charging power of the entire battery system not reaching its maximum value, wasting the charging station's charging capacity and extending the system charging time. Summary of the Invention

[0006] The purpose of this invention is to propose a charging current distribution method and system for a multi-branch battery system. On one hand, this invention estimates the output capacity of the charging pile and, based on this, coordinates and controls the current requests of each branch battery pack to avoid imbalance in current distribution due to the total requested current exceeding the charging pile's power supply capacity. On the other hand, the MBMU also needs to monitor the state of charge (SOC) of each branch in real time and dynamically adjust the charging current requests of each branch to reduce the SOC difference between branches and prevent excessive accumulation of inconsistencies. This method not only prioritizes the full utilization of the available power of the charging pile to maximize charging speed but also effectively reduces the SOC difference between branches, improving the overall system balance and operating efficiency.

[0007] To achieve the above objectives, the present invention employs the following technical solution:

[0008] This invention provides a charging current distribution method for a multi-branch battery system, comprising:

[0009] The battery management system enters charging mode, and the battery system management unit requests charging from the DC / DC converter according to the maximum allowable charging current of each branch.

[0010] Assess the maximum charging capacity of the charging pile. If the current charging current is stable and the charging capacity of the charging pile is sufficient, then allocate the charging current according to the maximum allowable charging current of each branch.

[0011] If the charging capacity of the charging pile is insufficient, a collaborative decision is made based on the SOC difference between each branch to determine the charging current distribution for each branch.

[0012] Preferably, the battery system management unit requests charging from the DC / DC converter according to the maximum allowable charging current of each branch, and further includes:

[0013] After the waiting time reaches the set time threshold t1, determine whether the current charging current is stable. The stability determination condition is:

[0014] If each branch road If the calibrated value is met and the duration threshold t2 is reached, then the current charging current is considered stable.

[0015] in branch road Bus current, branch road The average current calculated from the current moment back 5 seconds, This represents the number of battery branches.

[0016] Preferably, if the current charging current is unstable, the charging current will be allocated based on the charging capacity of the charging pile after the duration reaches the set time threshold t3.

[0017] Preferably, the time threshold t1 is set to 10s;

[0018] The time threshold t2 is set to 5s;

[0019] The time threshold t3 is set to 20s.

[0020] Preferably, the evaluation of the maximum charging capacity of the charging pile includes:

[0021] ,

[0022] In the formula, The maximum charging capacity of the charging station being evaluated.

[0023] Preferably, the method for determining that the charging pile has sufficient charging capacity is as follows:

[0024] If the following formula is satisfied, then the charging station has sufficient charging capacity:

[0025] ,

[0026] in, branch road The charging request current, The threshold value is used.

[0027] Preferably, if the charging capacity of the charging pile is insufficient, a collaborative decision is made based on the SOC difference between each branch, including:

[0028] Determine the SOC difference between the current branches. If the SOC difference between all branches is greater than or equal to the first SOC threshold, the battery system management unit will allocate the charging current according to the SOC sorting.

[0029] If the SOC difference between current branches is less than the first SOC threshold, the battery system management unit allocates charging current according to the charging request current limit value of each branch, where the charging request current limit value refers to the maximum allowable charging current.

[0030] Preferably, the battery system management unit allocates charging current according to SOC (State of Charge), as follows:

[0031] ,

[0032] in, For the primary battery branch Sorted battery branches The charging distribution current, The battery branch SOCs are numbered from low to high. For the primary battery branch number, For the primary battery branch Sorted battery branches The charging request current, For battery branch The charging request current.

[0033] Preferably, the battery system management unit allocates charging current according to the charging request current limit values ​​of each branch, as shown below:

[0034] ,

[0035] in, For the primary battery branch Sorted battery branches The charging distribution current, The current limit values ​​requested for charging the battery branch are numbered from low to high. For the primary battery branch number, For the primary battery branch Sorted battery branches The charging request current limit value, For battery branch The charging request current limit value.

[0036] Preferably, the first SOC threshold is set to 5%.

[0037] Preferably, after distributing the charging current, the method further includes:

[0038] If the sum of the charging request currents of each branch increases, and the sum of the charging request currents of each branch exceeds the current assessed maximum charging capacity of the charging pile, then the battery system management unit will request charging from the DC / DC converter again according to the maximum allowable charging current of each branch.

[0039] The present invention also provides a charging current distribution system for a multi-branch battery system, used to implement the above-described charging current distribution method for a multi-branch battery system, the system comprising:

[0040] A battery pack controller, configured in each battery branch, is used to estimate the maximum allowable charging current of the branch in real time;

[0041] The battery system management unit is used to collect the maximum allowable charging current reported by all battery pack controllers, evaluate the maximum charging capacity of the charging pile, and if the current charging current is stable and the charging capacity of the charging pile is sufficient, the charging current is allocated according to the maximum allowable charging current of each branch; if the charging capacity of the charging pile is insufficient, the charging current allocation of each branch is determined by combining the SOC difference between each branch.

[0042] The beneficial effects of the technical solution of this invention are as follows:

[0043] This invention can dynamically evaluate the maximum output capacity of a charging pile. Based on this evaluation result, a charging current allocation strategy is implemented in conjunction with the charging pile's charging capacity: if the charging pile's charging capacity is sufficient to cover the total charging demand of the battery system, a "power maximization" mode is adopted, allocating current according to the real-time charging current limit of each branch to fully utilize the charging pile's capacity and improve the overall charging speed; if the charging pile's charging capacity is insufficient, a "balance priority" mode is switched to, calculating priority weights based on the SOC or current limit of each branch for optimized allocation. Its core objective is to prioritize ensuring the balance and consistency of the SOC of each branch under power-constrained conditions. This invention not only prioritizes the full utilization of the charging pile's available power to maximize charging speed, but also effectively reduces the SOC difference between branches, improving the overall system balance and operating efficiency. Attached Figure Description

[0044] Figure 1 This is a control system architecture diagram of the battery pack controller (SBMU) and battery system management unit (MBMU) proposed in this invention;

[0045] Figure 2 This is a schematic flowchart of a charging current distribution method for a multi-branch battery system provided in an embodiment of the present invention. Detailed Implementation

[0046] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the embodiments and accompanying drawings. Here, the illustrative embodiments and descriptions of this invention are used to explain the invention, but are not intended to limit the invention.

[0047] It should also be noted that, in order to avoid obscuring the invention with unnecessary details, only the structures and / or processing steps closely related to the solution according to the invention are shown in the accompanying drawings, while other details that are not closely related to the invention are omitted.

[0048] It should be emphasized that the term "including / comprises" as used herein refers to the presence of a feature, element, step, or component, but does not exclude the presence or addition of one or more other features, elements, steps, or components.

[0049] It should also be noted that, unless otherwise specified, the term "connection" in this article can refer not only to a direct connection, but also to an indirect connection involving an intermediary.

[0050] In the following description, embodiments of the invention will be illustrated with reference to the accompanying drawings. In the drawings, the same reference numerals represent the same or similar parts, or the same or similar steps.

[0051] It should be emphasized here that the step markers mentioned below are not a limitation on the order of the steps, but should be understood as meaning that the steps can be executed in the order mentioned in the embodiments, or in a different order than in the embodiments, or several steps can be executed simultaneously.

[0052] This invention provides a charging current allocation method for a multi-branch battery system. The core of this strategy lies in: first, identifying the maximum output capacity of the charging station. If this capacity is sufficient to cover the total charging demand of the battery system, the control strategy is to fully satisfy the requested current of each branch. If the charging station's capacity is insufficient, a priority-based decision-making logic is initiated. The priority determination depends on the SOC state of each branch and the magnitude of its requested current, thereby achieving optimized allocation of charging power. The total charging request current is then sent to the charging station.

[0053] Furthermore, this invention implements the aforementioned control strategy based on a three-tier architecture of a battery management system. Each battery branch is equipped with a battery pack controller (SBMU, Secondary Battery Management Unit), responsible for estimating the maximum allowable charging current for that branch in real time; the entire battery system is managed uniformly by a system-level controller (MBMU). The MBMU collects the maximum allowable charging current data reported by all SBMUs and, based on this, makes collaborative decisions in conjunction with an assessment of the charging station's capabilities. Ultimately, it sends the optimized charging current commands for each branch to the corresponding DC / DC converters as their set limits for charging current.

[0054] Figure 1 This is a control system architecture diagram for the Battery Pack Controller (SBMU) and the Battery System Management Unit (MBMU).

[0055] Based on the above control system architecture and control strategy, an embodiment of the present invention provides a charging current distribution method for a multi-branch battery system, such as... Figure 2 As shown, it includes the following steps:

[0056] Step 1: When the battery pack is in charging mode, the MBMU requests charging from the DC / DC converter according to the maximum allowable charging current of each branch.

[0057] Step 2: After the waiting time reaches the set time threshold t1, execute steps 2.1 to 2.2 in sequence;

[0058] Step 2.1: Determine whether the current charging current is stable. The criterion for stability is:

[0059] If each branch road If the calibrated value is found and the duration threshold t2 is reached, then the current charging current is considered stable, and the process proceeds to step 3. branch road Bus current, branch road Historical 5-second average current The number of battery branches; historical 5s refers to 5 seconds before the current moment.

[0060] Step 2.2: If the current charging current is unstable and the duration reaches the set time threshold t3, then proceed to step 3.

[0061] In this step, the preferred time threshold t1 is set to 10s, the preferred time threshold t2 is set to 5s, and the preferred time threshold t3 is set to 20s.

[0062] Step 3: MBMU assesses the maximum charging capacity of the charging station. The assessment method is as follows:

[0063] In the formula, This represents the maximum charging capacity of the charging station estimated by MBMU.

[0064] Perform steps 3.1 through 3.4 in sequence.

[0065] Step 3.1: Determine if the charging station has sufficient charging capacity. The determination method is as follows:

[0066] If the following formula is satisfied, the charging pile has sufficient charging capacity, then proceed to step 3.2; otherwise, proceed to step 4.

[0067] ,

[0068] In the formula, branch road Bus current, branch road The charging request current refers to the maximum allowable charging current in step 1. The threshold value is used.

[0069] In this step, the preferred threshold is... It is 5A*n.

[0070] Step 3.2: The MBMU requests charging from the charging station based on the sum of the maximum allowable charging currents of each branch, i.e., the MBMU charging request current is... The MBMU sends the current distribution values ​​of each branch to the DC / DC converter. Then proceed to step 3.3;

[0071] Step 3.3: If the sum of the charging request currents of each branch increases, and the sum of the charging request currents of each branch exceeds the maximum charging capacity of the charging station estimated by the current MBMU. If the condition is met, proceed to step 1; otherwise, proceed to step 3 or 4.

[0072] Step 3.4: If charging is complete, end the process; otherwise, return to step 3.1.

[0073] Step 4: If the sum of the charging request currents of each branch increases, and the sum of the charging request currents of each branch exceeds the maximum charging capacity of the charging station estimated by the current MBMU. If the condition is met, proceed to step 1; otherwise, proceed to step 5.

[0074] Step 5: Determine the SOC difference between the current branches. If the SOC difference between all branches is greater than or equal to the first SOC threshold, the MBMU will allocate current to each DC / DC converter according to the SOC. Otherwise, proceed to step 6.

[0075] In this step, the charging current distribution logic for each branch is as follows:

[0076] First, the charging stations are sorted by State of Charge (SOC) from low to high, prioritizing full-power charging for branches with lower SOCs. The remaining capacity of the charging stations is then allocated accordingly. This approach aims to minimize the SOC differences between branches while maximizing the utilization of the charging station's capacity. This can be represented as:

[0077] ,

[0078] In the formula, The branch SOCs are numbered in ascending order. Number the branch roads branch road (After sorting the branch SOC from low to high, it becomes the number) The charging distribution current of each branch.

[0079] In this step, the preferred first SOC threshold is set to 5%.

[0080] Step 6: If the SOC difference between branches is less than the first SOC threshold, the MBMU allocates charging current to each DC / DC converter according to the charging request current limit value of each branch, as shown below:

[0081] ,

[0082] In the formula, The charging request current limit values ​​for each branch are sorted and numbered from low to high. Number the branch roads branch road (Branch charging request current limit values ​​sorted from low to high) The charging distribution current of each branch.

[0083] Step 7: If charging is complete, end the process; otherwise, return to step 4.

[0084] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for distributing charging current in a multi-branch battery system, characterized in that, include: The battery management system enters charging mode, and the battery system management unit requests charging from the DC / DC converter according to the maximum allowable charging current of each branch. After the waiting time reaches the set time threshold t1, determine whether the current charging current is stable. The stability determination condition is: If each branch road If the calibrated value is met and the duration threshold t2 is reached, then the current charging current is considered stable. in branch road Bus current, branch road The average current calculated from the current moment back 5 seconds, The number of battery branches; Assess the maximum charging capacity of the charging station. include: ， In the formula, The maximum charging capacity of the charging station being evaluated; If the current charging current is stable and the charging pile has sufficient charging capacity, then the charging current is allocated according to the maximum allowable charging current of each branch; the method for determining whether the charging pile has sufficient charging capacity is as follows: If the following formula is satisfied, then the charging station has sufficient charging capacity: ， in, branch road The charging request current, For the threshold; If the charging capacity of the charging pile is insufficient, a collaborative decision is made based on the SOC difference between each branch to determine the charging current allocation for each branch, including: Determine the SOC difference between the current branches. If the SOC difference between all branches is greater than or equal to the first SOC threshold, the battery system management unit will allocate the charging current according to the SOC sorting. If the SOC difference between current branches is less than the first SOC threshold, the battery system management unit allocates charging current according to the charging request current limit value of each branch, where the charging request current limit value refers to the maximum allowable charging current.

2. The charging current distribution method for a multi-branch battery system according to claim 1, characterized in that, If the current charging current is unstable, the charging current will be allocated based on the charging capacity of the charging pile after the duration reaches the set time threshold t3.

3. The charging current distribution method for a multi-branch battery system according to claim 1, characterized in that, The time threshold t1 is set to 10s; The time threshold t2 is set to 5s; The time threshold t3 is set to 20s.

4. The charging current distribution method for a multi-branch battery system according to claim 1, characterized in that, The battery system management unit allocates charging current according to SOC (State of Charge), as follows: ， in, For the primary battery branch Sorted battery branches The charging distribution current, The battery branch SOCs are numbered from low to high. For the primary battery branch number, For the primary battery branch Sorted battery branches The charging request current, For battery branch The charging request current.

5. The charging current distribution method for a multi-branch battery system according to claim 1, characterized in that, The battery system management unit allocates charging current according to the charging request current limit values ​​of each branch, as follows: ， in, For the primary battery branch Sorted battery branches The charging distribution current, The current limit values ​​requested for charging the battery branch are numbered from low to high. For the primary battery branch number, For the primary battery branch Sorted battery branches The charging request current limit value, For battery branch The charging request current limit value.

6. The charging current distribution method for a multi-branch battery system according to claim 1, characterized in that, The first SOC threshold is set to 5%.

7. The charging current distribution method for a multi-branch battery system according to claim 1, characterized in that, After distributing the charging current, it also includes: If the sum of the charging request currents of each branch increases, and the sum of the charging request currents of each branch exceeds the current assessed maximum charging capacity of the charging pile, then the battery system management unit will request charging from the DC / DC converter again according to the maximum allowable charging current of each branch.

8. A charging current distribution system for a multi-branch battery system, characterized in that, A method for distributing charging current in a multi-branch battery system according to any one of claims 1 to 7, the system comprising: A battery pack controller, configured in each battery branch, is used to estimate the maximum allowable charging current of the branch in real time; The battery system management unit is used to collect the maximum allowable charging current reported by all battery pack controllers, evaluate the maximum charging capacity of the charging pile, and if the current charging current is stable and the charging capacity of the charging pile is sufficient, the charging current is allocated according to the maximum allowable charging current of each branch; if the charging capacity of the charging pile is insufficient, the charging current allocation of each branch is determined by combining the SOC difference between each branch.

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