Battery pack active equalization method and system

Abstract

The invention discloses a battery pack active equalization method and system, and the system comprises a plurality of battery modules which are connected in series, and each battery module comprises a plurality of battery monomers which are connected in series. The switching-in and switching-out of the battery modules are controlled through a switch; and the switching-in and switching-out of the battery monomers in each battery module are also controlled through the switch. A two-layer topological structure based on flexible reconstruction is adopted, the battery pack is divided into a plurality of battery modules, the series connection modes of a plurality of single batteries in the battery modules and the series connection modes of a plurality of single batteries in the battery modules are the same, the single batteries and the single batteries are cut in and cut out through a single-pole double-throw switch, and fault single batteries or modules are isolated under the condition that the balance function is not affected in the later period; and a hardware basis is provided for improving equalization timeliness and equalization consistency.

Description

Technical Field

[0001] The present invention relates to the technical field of battery balancing, and in particular to a method and system for active balancing of a battery pack. Background Art

[0002] Factors such as battery material limitations, production processes, and environmental conditions can cause inconsistencies in battery packs. Using inconsistent battery cells can cause energy variations between cells, leading to local overcharge or over discharge, which can adversely affect system performance and increase safety risks. To address this issue, equalization technology has been developed to balance the energy of cells. This effectively extends the life of the battery pack and improves the overall performance of the system.

[0003] The current method to improve the energy consistency of battery packs mainly adopts active balancing technology. This method promotes energy transfer between battery cells by using energy storage devices such as inductors and transformers to make the charge state of each battery cell tend to be balanced. By improving the consistency of the battery pack, this method can make each cell reach the cut-off discharge condition as much as possible at the same time, thereby improving the capacity utilization of the battery pack. This active balancing technology helps to extend the service life of the battery pack and improve its overall performance. However, in order to achieve efficient and fast balancing management, it is necessary to design a complex balancing circuit. This not only increases the design cost, but also increases the complexity of control. In addition, most of the existing active balancing solutions are proposed for fixed topology battery systems and cannot cope with the balancing scenario of faulty batteries. In addition, in actual vehicles, battery packs are usually composed of thousands of batteries connected in series or in parallel. With the substantial increase in the number of batteries, the inconsistency problem between batteries in the battery pack will become more prominent, and the requirements for the balancing mechanism will also be higher. Due to the limitations of its adjustment ability, the traditional single-stage balancing mechanism will become slower and the balancing effect will be greatly reduced when dealing with a large number of batteries. Although the existing two-stage balancing mechanism is superior to the single-stage balancing mechanism to a certain extent, its efficiency still needs to be improved when facing large-scale battery packs. Summary of the invention

[0004] The technical problem to be solved by the present invention is how to actively balance the battery energy quickly and effectively when there are thousands of batteries and a single battery may fail.

[0005] The present invention solves the above technical problems through the following technical means: The battery pack includes a plurality of battery modules connected in series, each battery module includes a plurality of battery cells connected in series; the switching in and out of the battery modules is controlled by switches; the switching in and out of the battery cells in each battery module is also controlled by switches.

[0006] As an optimization of the above solution, the switch is a single-pole double-throw switch.

[0007] The present invention also provides a battery pack consistency active balancing method, which is applied to the above-mentioned battery pack and is characterized by comprising the following steps: S1. Collect the charge state of all battery cells in the battery pack; S2. Equivalently convert the connection topology of a single battery module and the connection topology of a battery pack composed of multiple battery modules into a directed graph, and calculate the edge weights of the directed graph; S3. According to the state of charge SOC of all cells in the battery pack and the edge weights of the directed graph, the shortest path and the longest path of energy flow between the battery modules and within the battery module are selected based on the graph theory traversal algorithm; S4. Determine the battery cells or battery modules selected in the two balancing stages, and realize active balancing of the battery pack by controlling the action of the switch network; S5. Repeat S1-S4 until the SOCs of all battery cells and battery modules in the battery pack are consistent.

[0008] As an optimization of the above solution, the directed graph edge weights in step S2 are w i，j The calculation formula is as follows:

[0009] in, α represents the weight value, n Represents the slave node i To Node j The number of switches experienced, q Represents the fraction of energy loss in a single switch, r i Represents the energy fraction of a monomer or module;

[0010] in, x i The SOC of the ith cell or module is the difference between the current state of the battery system and its fully charged state.

[0011] As an optimization of the above solution, the energy path method for calculating a battery cell or battery module is: Step 1: Determine the starting vertex of the directed graph V 0 and V n+1 , respectively represent the positive and negative electrodes of the battery pack; the starting vertex V 0 is put into the stack; Step 2: Access the starting vertex V0 at the top of the stack; Step 3: Identify the adjacent nodes that have not been traversed yet and place them in the stack; Step 4: If there are no adjacent nodes that have not been traversed, pop the node from the stack and repeat Step 3; Step 5: Target Node V n+1 is popped from the stack; Step 6: The nodes have been traversed V n All adjacent nodes are popped from the stack; Step 7: Node V i Direct access to the target node V n+1 ;in i Indicates i nodes; Step 8: Target Node V n+1 is popped from the stack; Step 9: The nodes have been traversed V i All adjacent nodes, it pops from the stack; Step 10: Repeat Step 7 to 9 to traverse all paths; Finally, the longest and shortest energy paths are screened out.

[0012] As an optimization of the above scheme, a logic control signal is output to the switch network for the shortest energy path scheme selected, and the battery pack is reorganized in series through the control of the switch network, and the balancing inductor is charged; a logic control signal is output to the switch network for the longest energy path scheme selected, and the battery pack is reorganized in series through the control of the switch network, and the selected battery is charged by the balancing inductor.

[0013] The present invention also provides a battery pack consistency active balancing system, characterized by comprising: Charge data acquisition module: collects the charge status of all battery cells in the battery pack; Directed graph construction module: The connection topology of a single battery module and the connection topology of a battery pack composed of multiple battery modules are equivalent to a directed graph, and the edge weights of the directed graph are calculated; Energy path calculation module: according to the state of charge SOC of all cells in the battery pack and the edge weights of the directed graph, the shortest path and the longest path of energy flow between the battery modules and within the battery module are selected based on the graph theory traversal algorithm; Active balancing module: determines the battery cells or battery modules selected in the two balancing stages, and realizes active balancing of the battery pack by controlling the action of the switch network; the operation is cyclic until the SOC of all battery cells and battery modules in the battery pack reaches consistency.

[0014] As an optimization of the above solution, the directed graph edge weights w i，j The calculation formula is as follows:

[0015] in, α represents the weight value, n Represents the slave node i To Node j The number of switches experienced, q Represents the fraction of energy loss in a single switch, r i Represents the energy fraction of a monomer or module;

[0016] in, x i The SOC of the ith cell or module is the difference between the current state of the battery system and its fully charged state.

[0017] As an optimization of the above solution, the energy path method for calculating a battery cell or battery module is: Step 1: Determine the starting vertex of the directed graph V 0 and V n+1 , respectively represent the positive and negative electrodes of the battery pack; the starting vertex V 0 is put into the stack; Step 2: Access the starting vertex V0 at the top of the stack; Step 3: Identify the adjacent nodes that have not been traversed yet and place them in the stack; Step 4: If there are no adjacent nodes that have not been traversed, pop the node from the stack and repeat Step 3; Step 5: Target Node V n+1 is popped from the stack; Step 6: The nodes have been traversed V n All adjacent nodes are popped from the stack; Step 7: Node V i Direct access to the target node V n+1 ;in i Indicates inodes; Step 8: Target Node V n+1 is popped from the stack; Step 9: The nodes have been traversed V i All adjacent nodes, it pops from the stack; Step 10: Repeat Step 7 to 9 to traverse all paths; Finally, the longest and shortest energy paths are screened out.

[0018] As an optimization of the above scheme, a logic control signal is output to the switch network for the shortest energy path scheme selected, and the battery pack is reorganized in series through the control of the switch network, and the balancing inductor is charged; a logic control signal is output to the switch network for the longest energy path scheme selected, and the battery pack is reorganized in series through the control of the switch network, and the selected battery is charged by the balancing inductor.

[0019] The advantages of the present invention are: The present invention adopts a two-layer topology structure based on flexible reconstruction to divide the battery pack into multiple battery modules, and the battery modules are connected in series in the same way as the multiple battery cells within the battery module, and are all switched in and out through single-pole double-throw switches, so as to isolate faulty cells or modules in the later stage without affecting the balancing function; and provide a hardware foundation for improving the timeliness and consistency of balancing.

[0020] The method of the present invention can realize active balancing and fault isolation within and between modules during the operation of the battery pack. Even if a battery cell fails, the present invention can cut off the faulty battery through a switch without affecting the overall balancing and operation of the battery pack.

[0021] The switch network reconstruction technology of the present invention can not only realize the energy transmission between battery cells, but also optimize the energy flow of the entire battery pack, reducing the time and energy loss in the balancing process. This mechanism plays a key role in improving the overall consistency of the battery pack, especially in the application of larger battery packs. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a flow chart of a battery pack active balancing method based on a graph theory traversal algorithm according to an embodiment of the present invention; Figure 2 is a schematic diagram of a battery pack topology according to an embodiment of the present invention; Figure 3 It is a schematic diagram of building a stack in Step 1 of solving the “energy path” of a battery pack based on a graph theory traversal algorithm according to an embodiment of the present invention; Figure 4It is a schematic diagram of building a stack in Step 2 of solving the “energy path” of a battery pack based on a graph theory traversal algorithm according to an embodiment of the present invention; Figure 5 It is a schematic diagram of building a stack in Step 3 of solving the “energy path” of a battery pack based on a graph theory traversal algorithm in an embodiment of the present invention; Figure 6 It is a schematic diagram of building a stack in Step 4 of solving the “energy path” of a battery pack based on a graph theory traversal algorithm according to an embodiment of the present invention; Figure 7 It is a schematic diagram of building a stack in Step 5 of solving the “energy path” of a battery pack based on a graph theory traversal algorithm in an embodiment of the present invention; Figure 8 It is a schematic diagram of building a stack in Step 6 of solving the “energy path” of a battery pack based on a graph theory traversal algorithm in an embodiment of the present invention; Fig. 9 It is a schematic diagram of building a stack in Step 7 of solving the “energy path” of a battery pack based on a graph theory traversal algorithm according to an embodiment of the present invention; Fig.10 It is a schematic diagram of building a stack in Step 8 of solving the “energy path” of a battery pack based on a graph theory traversal algorithm according to an embodiment of the present invention; Fig.11 It is a schematic diagram of building a stack in Step 9 of solving the “energy path” of a battery pack based on a graph theory traversal algorithm according to an embodiment of the present invention; Fig.12 It is a schematic diagram of building a stack in Step 10 of solving the “energy path” of a battery pack based on a graph theory traversal algorithm in an embodiment of the present invention; Fig.13 is a battery SOC curve diagram of an embodiment of the present invention.

[0023] Fig.14 It is a battery SOC curve diagram of the comparative experimental embodiment. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] This embodiment proposes a battery pack consistency active balancing solution based on a graph theory traversal algorithm, such as Figure 1 , including the following steps: Step 1: Collect the state of charge of all cells in the battery pack.

[0026] The state of charge (SOC) is obtained by the ampere-hour integration method.

[0027] Step 2: Equivalently transform the battery pack topology into a directed graph, and use the adjacency matrix to represent the edge weights of the directed graph:

[0028] The battery pack is a series structure such as Figure 2 As shown, the battery pack contains n Battery modules, each battery module M i ( i =1, 2, …, n ) by a single-pole double-throw switch K Control the switching in and out of the module. The battery cells inside the module have the same connection topology. Each battery module contains m A battery cell. n Each battery cell B in a module n，i ( i =1, 2, …, m ) by a single-pole double-throw switch k n，m Control the cutting in and out of the monomer.

[0029] The switch action logic principle is as follows:

[0030]

[0031] in, K i and k n，i The logic 1 indicates that the switch cuts the module or the single-pole double-throw switch into the circuit, and the logic 0 indicates that the switch cuts the module or the single-pole double-throw switch out of the circuit.

[0032] w i，j ( i =0, 1, 2, ..., n ; j =1, 2, …, n +1) is the edge weight of the directed graph, ∞ represents no energy flow between nodes, and the edge weight w i，j The calculation formula is as follows:

[0033] in, α represents the weight value, n Represents the slave node i To Node jThe number of switches experienced, q Represents the fraction of energy loss in a single switch, r i Represents the energy fraction of a monomer or module.

[0034] The method for calculating the energy score of the monomer or module is as follows:

[0035] in, x i The SOC of the ith cell or module is the difference between the current state of the battery system and its fully charged state.

[0036] Step 3: According to the state of charge SOC of all cells in the battery pack and the edge weights of the directed graph, the shortest path and the longest path of the energy flow of the battery system are selected based on the graph traversal algorithm. Specifically, the algorithm is used to solve the problem from the node V 0 to V n+1 All "energy paths" of the battery pack, where "energy path" refers to the path from the negative electrode to the positive electrode of the battery pack. The specific steps are as follows: Step 1: Determine the starting vertex of the directed graph V 0 and V n+1 , respectively represent the positive and negative electrodes of the battery pack, such as Figure 3 shown.

[0037] Step 2: Access the starting vertex V0 at the top of the stack, such as Figure 4 shown.

[0038] Step 3: Identify the adjacent nodes that have not been traversed yet and place them in the stack, such as Figure 5 shown.

[0039] Step 4: If there are no adjacent nodes that have not been traversed, pop the node from the stack and repeat Step 3, such as Figure 6 shown.

[0040] Step 5: Target Node V n+1 is popped from the stack, such as Figure 7 shown.

[0041] Step 6: The nodes have been traversed V n All adjacent nodes are popped from the stack, such as Figure 8 shown.

[0042] Step 7: Node V i Direct access to the target nodeV n+1 , i Indicates i Nodes, such as Fig. 9 As shown, V i for V 3.

[0043] Step 8: Target Node V n+1 is popped from the stack, such as Fig.10 shown.

[0044] Step 9: The nodes have been traversed V i All adjacent nodes are popped from the stack, such as Fig.11 shown.

[0045] Step 10: Repeat Step 7 to 9 to traverse all paths, such as Fig.12 shown.

[0046] Based on the calculated energy flow path, the shortest and longest "energy paths" that meet the application requirements are screened: specifically, the "energy path" schemes are screened, and the shortest and longest "energy path" schemes are selected; the shortest "energy path" is used to determine the battery that charges the balancing inductor, and the longest "energy path" is used to determine the battery that needs to be charged by the balancing inductor; Step 4: Determine the battery cells selected in the two stages of balancing, and realize active balancing of the battery pack by controlling the action of the switch network. Specifically, output a logic control signal to the switch network for the shortest "energy path" solution selected, and control the switch network to realize the series reorganization of the battery pack and charge the balancing inductor; output a logic control signal to the switch network for the longest "energy path" solution selected, and control the switch network to realize the series reorganization of the battery pack, and charge the selected battery by the balancing inductor. The switch network is realized by series and parallel connection of relays or MOS tubes, such as Figure 2 shown.

[0047] Step 5: Repeat all the above steps until the SOC of all battery cells and modules in the battery pack reaches consistency.

[0048] The technical solution of the present invention is further described below with reference to a specific application example.

[0049] The balancing experiment was conducted on a battery pack with 36 battery cells in series. The 36 batteries were divided into 6 modules, each module had 6 battery cells, and the initial voltage of the battery was shown in Table 1.

[0050] Table 1

[0051] Through the graph theory traversal algorithm, the shortest and longest "energy paths" are found to determine the battery cells or modules that charge the balancing inductor, as well as the battery cells or modules that are charged by the balancing inductor. Fig.13 The figure shows the change of battery pack SOC under the balancing of this solution. It can be seen that this solution can achieve SOC consistency between modules and within modules. Fig.14 The single-layer active balancing effect is demonstrated. From the overall convergence trend, the proposed two-level active balancing is significantly faster than the single-level balancing scheme. At 10,000s, the battery pack SOC range of the traditional scheme is 0.193, and the battery pack SOC of the proposed active balancing scheme basically converges together, with an SOC range of 0.0254, which is about 86.839% lower than the traditional one. In terms of balancing time, the battery pack SOC range of the traditional balancing scheme is 0.1609 at 14,400s. For the proposed balancing scheme, the SOC range converges to 0.1609 at 3,412s, and the balancing time is shortened by 10,988s compared to the traditional scheme.

[0052] Although this experiment was only conducted on a battery pack of 36 batteries, through in-depth analysis of the experimental results, it is possible to reasonably deduce the difference in time and effect between the technology of this application and the existing single-stage and two-stage balancing mechanisms for thousands of batteries in actual vehicles. In contrast, the two-stage balancing mechanism of this application has stronger adaptability and efficiency. In terms of balancing time, due to its unique two-stage collaborative working mode, a large number of batteries can be balanced and adjusted in a shorter time. As the number of batteries increases, this time advantage may become more obvious. For example, assuming that the balancing time is in a certain linear relationship with the number of batteries (the actual situation may be more complicated), then when processing thousands of batteries, the balancing mechanism of this application may shorten the balancing time by several times or even dozens of times compared to the traditional single-stage balancing mechanism. In terms of balancing effect, the two-stage balancing mechanism of this application can more accurately adjust the SOC of each battery, so that the consistency of the batteries in the battery pack is significantly improved. For actual vehicles, this means that the overall performance of the battery pack is optimized, the service life of the battery is extended, and the vehicle's cruising range and safety are also improved.

[0053] In summary, this embodiment proposes a battery pack consistency active balancing solution based on a graph theory traversal algorithm. The proposed solution adopts a two-layer topology structure based on flexible reconstruction, which can isolate faulty cells or modules without affecting the balancing function; and uses graph theory to improve the convenience of the balancing process. The proposed solution can achieve two-layer active balancing between modules and within modules, and has better balancing performance than a single-level balancing solution.

[0054] This embodiment adopts a double-layer topology structure and a graph traversal algorithm to perform efficient active balancing inside and outside the module. This method adapts to the balancing needs of large-scale battery packs by flexibly reconstructing the topology, significantly improving the balancing speed and accuracy. Compared with the existing single-stage balancing solution, the balancing time and effect of this embodiment are more significant, especially in the actual application of processing thousands of batteries, which can shorten the balancing time and greatly improve the balancing effect.

[0055] In this embodiment, the switch network realizes the series-parallel reconstruction of the battery pack through relays or MOS tubes, and uses graph theory traversal algorithms to optimize energy flow. Battery cells and modules use single-pole double-throw switches to control energy transfer and balance, and use switches to cut out fault circuits. The action of the switch is controlled by the SOC state of the battery pack to achieve balance inside and outside the battery module.

[0056] The switch network in this embodiment not only helps to realize energy transmission between battery cells, but also optimizes the energy flow of the entire battery pack. By optimizing the energy path through graph theory, the time and energy loss in the balancing process are reduced. This mechanism plays a key role in improving the overall consistency of the battery pack, especially in the application of larger battery packs.

[0057] In addition, in the existing active balancing mechanism, the battery pack topology is fixed, and energy interaction between batteries is achieved through a large number of capacitor and inductor hardware circuits outside the circuit. Once a battery fails, the entire battery system needs to stop running because the faulty battery cannot be isolated and removed. Although a large number of switches are used in this embodiment, the cost of switches is significantly lower than that of capacitors and inductors. And whether a single cell in the battery module fails or a battery module fails, the faulty single cell or module can be removed through the switch network without affecting the overall operation of the system, ensuring that the first and second level balancing continue.

[0058] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for active equalization of battery pack consistency, characterized in that: The battery pack includes a plurality of battery modules connected in series, and each battery module includes a plurality of battery cells connected in series; the switching in and out of the battery modules is controlled by switches between the battery modules; the switching in and out of the battery cells in each battery module is also controlled by switches between the battery cells; The active balancing methods for battery pack consistency include: S1. Collect the charge state of all battery cells in the battery pack; S2. Equivalently convert the connection topology of a single battery module and the connection topology of a battery pack composed of multiple battery modules into a directed graph, and calculate the edge weights of the directed graph; S3. According to the state of charge SOC of all cells in the battery pack and the edge weights of the directed graph, the shortest path and the longest path of energy flow between the battery modules and within the battery module are selected based on the graph theory traversal algorithm; S4. Determine the battery cells or battery modules selected in the two balancing stages, and realize active balancing of the battery pack by controlling the switch action; S5. Repeat S1-S4 until the SOCs of all battery cells and battery modules in the battery pack are consistent.

2. The method for active equalization of battery pack consistency according to claim 1, characterized in that: The switch is a single-pole double-throw switch.

3. The battery pack consistency equalization method according to claim 1, characterized in that: The directed graph edge weights in step S2 w i，j The calculation formula is as follows: in, α represents the weight value, n Represents the slave node i To Node j The number of switches experienced, q Represents the fraction of energy loss in a single switch, r i Represents the energy fraction of a monomer or module; in, x i For the i The SOC of a single cell or module is the difference between the current state of the battery pack and its fully charged state.

4. The method for active battery pack consistency balancing according to any one of claims 1 to 3, characterized in that: The method for calculating the energy path of a battery cell or battery module is: Step 1: Determine the starting vertex of the directed graph V 0 and V n+1 , respectively represent the positive and negative electrodes of the battery pack; the starting vertex V 0 is put into the stack; Step 2: Access the starting vertex V0 at the top of the stack; Step 3: Identify the adjacent nodes that have not been traversed yet and place them in the stack; Step 4: If there are no adjacent nodes that have not been traversed, pop the node from the stack and repeat Step 3; Step 5: Target Node V n+1 is popped from the stack; Step 6: The nodes have been traversed V n All adjacent nodes are popped from the stack; Step 7: Node V i Direct access to the target node V n+1 ;in i Indicates i nodes; Step 8: Target Node V n+1 is popped from the stack; Step 9: The nodes have been traversed V i All adjacent nodes, it pops from the stack; Step 10: Repeat Step 7 to 9 to traverse all paths; Finally, the longest and shortest energy paths are screened out.

5. The method for active equalization of battery pack consistency according to claim 4, characterized in that: The shortest energy path solution selected is output with a logic control signal to the switch network, and the battery pack is reorganized in series through the control of the switch network, and the balancing inductor is charged; the longest energy path solution selected is output with a logic control signal to the switch network, and the battery pack is reorganized in series through the control of the switch network, and the selected battery is charged by the balancing inductor. 6.Battery pack consistency active equalization system, characterized by: include: Charge data acquisition module: collects the charge status of all battery cells in the battery pack; Directed graph construction module: The connection topology of a single battery module and the connection topology of a battery pack composed of multiple battery modules are equivalent to a directed graph, and the edge weights of the directed graph are calculated; Energy path calculation module: according to the state of charge SOC of all cells in the battery pack and the edge weights of the directed graph, the shortest path and the longest path of energy flow between the battery modules and within the battery module are selected based on the graph theory traversal algorithm; Active balancing module: determines the battery cells or battery modules selected in the two balancing stages, and realizes active balancing of the battery pack by controlling the switch action; the cycle operation is performed until the SOC of all battery cells and battery modules in the battery pack reaches consistency.

7. The battery pack consistency active equalization system according to claim 6, characterized in that: The directed graph edge weight w i，j The calculation formula is as follows: in, α represents the weight value, n Represents the slave node i To Node j The number of switches experienced, q Represents the fraction of energy loss in a single switch, r i Represents the energy fraction of a monomer or module; in, x i For the i The SOC of a single cell or module is the difference between the current state of the battery system and its fully charged state.

8. The battery pack consistency active equalization system according to claim 6 or 7, characterized in that: The method for calculating the energy path of a battery cell or battery module is: Step 1: Determine the starting vertex of the directed graph V 0 and V n+1 , respectively represent the positive and negative electrodes of the battery pack; the starting vertex V 0 is put into the stack; Step 2: Access the starting vertex V0 at the top of the stack; Step 3: Identify the adjacent nodes that have not been traversed yet and place them in the stack; Step 4: If there are no adjacent nodes that have not been traversed, pop the node from the stack and repeat Step 3; Step 5: Target Node V n+1 is popped from the stack; Step 6: The nodes have been traversed V n All adjacent nodes are popped from the stack; Step 7: Node V i Direct access to the target node V n+1 ;in i Indicates i nodes; Step 8: Target Node V n+1 is popped from the stack; Step 9: The nodes have been traversed V i All adjacent nodes, it pops from the stack; Step 10: Repeat Step 7 to 9 to traverse all paths; Finally, the longest and shortest energy paths are screened out.

9. The battery pack consistency active equalization system according to claim 8, characterized in that: The shortest energy path solution selected is output with a logic control signal to the switch network, and the battery pack is reorganized in series through the control of the switch network, and the balancing inductor is charged; the longest energy path solution selected is output with a logic control signal to the switch network, and the battery pack is reorganized in series through the control of the switch network, and the selected battery is charged by the balancing inductor.

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