Series battery pack equalization system based on double-layer topology and control method

Abstract

The invention belongs to the technical field of battery equalization, and particularly relates to a series battery pack equalization system based on double-layer topology and a control method. The system is applied to at least two battery packs, each battery pack comprises a plurality of single batteries, and the system comprises at least two bottom layer equalization circuits which are respectively in one-to-one correspondence with the battery packs and are used for realizing equalization of the single batteries in the corresponding battery packs through inductors; and the top-layer equalization circuit is connected with each bottom-layer equalization circuit and is used for realizing inter-group equalization of each battery pack through a flyback transformer. The series battery pack equalization system provided by the invention has a flyback transformer-inductor double-layer battery equalization circuit structure, can directly realize energy transfer between and in each battery pack, shortens an equalization path, reduces resource loss caused by step-by-step energy transfer in an equalization process, and improves equalization efficiency; meanwhile, the size of the system is reduced, and the equalization cost is reduced.

Description

Technical Field

[0001] The present application belongs to the field of battery balancing technology, and in particular relates to a series battery pack balancing system and control method based on a double-layer topology. Background Art

[0002] At present, energy storage systems based on lithium batteries have become an indispensable part of smart grid construction. Among them, energy storage battery technology, as a key technology, has not only promoted the rapid development of electric vehicles, but also promoted the intelligence of large-scale distributed power grids.

[0003] To achieve voltage levels suitable for practical engineering applications, multiple single-cell lithium batteries are typically connected in series to achieve high voltage and large capacity. Due to factors such as manufacturing processes, materials, and degradation rates, variations in battery module capacity and impedance increase with charge and discharge time, reducing the usable capacity of the series battery pack and even creating safety hazards due to overcharge and over-discharge. Therefore, to improve the safety and reliability of energy storage modules and extend their cycle life, cell balancing, a key technology, is required to reduce these variations in battery packs.

[0004] Battery balancers can be divided into energy-consuming balancers and non-energy-consuming balancers. Among them, energy-consuming balancers consume excess energy in batteries with higher state of charge (SOC) by connecting resistors in parallel to single cells. They have a simple structure, low cost, and are easy to implement, but they have large losses, low efficiency, and a significant temperature rise in the circuit during the balancing process, which can easily cause safety hazards. Common structures in non-energy-consuming balancers include capacitors and their derivative topologies, inductors and their derivative topologies, transformers and their derivative topologies, etc. Among them, the balancing topology based on inductors or capacitors has a huge disadvantage. Energy cannot be directly transferred between single cells, and energy will cause excessive loss during step-by-step transmission. This disadvantage is particularly obvious for battery pack modules with too many cells in series. Although the transformer-based balancing method can shorten the balancing path and improve the balancing efficiency, since each battery requires a transformer, the system is bulky and the cost is high.

[0005] Therefore, how to improve the balancing efficiency of series-connected battery packs and reduce the balancing cost has become an urgent problem to be solved. Summary of the Invention

[0006] The present application provides a series battery pack balancing system and control method based on a double-layer topology, aiming to improve the balancing efficiency of the series battery pack and reduce the balancing cost.

[0007] In a first aspect, an embodiment of the present application provides a series battery pack balancing system based on a double-layer topology, characterized in that it is applied to at least two battery packs, each of which includes a plurality of single cells, and the system includes:

[0008] At least two bottom-level balancing circuits, corresponding one to each of the battery packs, for achieving balancing of the single cells in the corresponding battery packs through inductance;

[0009] The top-layer balancing circuit is connected to each of the bottom-layer balancing circuits and is used to achieve inter-group balancing of each of the battery groups through a flyback transformer.

[0010] In a possible implementation, the target underlying balancing circuit includes a plurality of inductors and a plurality of switch pairs, each of the switch pairs includes two switches, each of the inductors corresponds one-to-one to each of the switch pairs, and the target underlying balancing circuit is any of the underlying balancing circuits;

[0011] The target inductor is connected to the target single cell pair in the first target battery group through a target switch pair, the drain of the target switch pair is connected to the positive electrode of the target single cell pair, and the source is connected to the target inductor, the target inductor is any inductor in the target underlying balancing circuit, the target switch pair is a switch pair corresponding to the target inductor, the first target battery group is a battery group corresponding to the target underlying balancing circuit, and the target single cell pair includes at least two single cells in the first target battery group.

[0012] In a possible implementation, the target switch pair includes a first switch and a second switch, and the target single cell pair includes a first single cell and a second single cell;

[0013] One terminal of the target inductor is connected to the positive electrode of the first single battery through the first switch, and the other terminal is connected to the positive electrode of the second single battery through the second switch;

[0014] The drain of the first switch is connected to the positive electrode of the first battery, and the source is connected to one terminal of the target inductor;

[0015] The drain of the second switch is connected to the other terminal of the target inductor, the source is connected to the positive electrode of the second battery, and the negative electrode of the first battery and the negative electrode of the second battery are connected to a common node.

[0016] In a possible implementation, the target switch pair includes a third switch and a fourth switch, and the target single cell pair includes a first single cell, a second single cell, and a third single cell;

[0017] One terminal of the target inductor is connected to the positive electrode of the first single cell through a third switch, and the other terminal is connected to the positive electrode of the third single cell through a fourth switch;

[0018] The drain of the third switch is connected to the positive electrode of the first battery cell, and the source is connected to one terminal of the target inductor;

[0019] The drain of the fourth switch is connected to the other terminal of the target inductor, and the source is connected to the positive electrode of the third single cell. The first single cell and the second single cell are connected in series, and the negative electrodes of the second single cell and the third single cell are connected to a common node.

[0020] In one possible implementation, the top-level balancing circuit includes a flyback transformer, a plurality of bidirectional switches, and a unidirectional switch. The flyback transformer includes a primary winding and a plurality of secondary windings. Each of the secondary windings corresponds one-to-one to each of the battery packs, and each of the secondary windings corresponds one-to-one to each of the bidirectional switches.

[0021] The primary winding connects all the battery packs in series through the one-way switch, so that the primary winding, the one-way switch and all the battery packs form a loop;

[0022] Each of the secondary windings is connected to a corresponding battery pack via a corresponding bidirectional switch.

[0023] In one possible implementation, the battery packs are connected in series in sequence to form a series battery pack array, one terminal of the primary winding is connected to the positive electrode of the first battery pack in the series battery pack array, the other terminal is connected to the drain of the unidirectional switch, and the source of the unidirectional switch is connected to the negative electrode of the last battery pack in the series battery pack array.

[0024] In one possible implementation, one terminal of the target secondary winding is connected to the drain of the target bidirectional switch, and the other terminal is connected to the positive electrode of the second target battery pack. The source of the target bidirectional switch is connected to the negative electrode of the second target battery pack. The target secondary winding is any secondary winding in the flyback transformer, the target bidirectional switch is a bidirectional switch corresponding to the target secondary winding, and the second target battery pack is a battery pack corresponding to the target secondary winding.

[0025] In a second aspect, an embodiment of the present application provides a control method for a series battery pack balancing system based on a dual-layer topology, which is applied to the series battery pack balancing system as described in the first aspect or any one of the implementations thereof, including:

[0026] Obtain the state of charge value of each single battery in each battery pack;

[0027] Based on the state of charge value of each single battery in each battery pack, performing intra-group balancing on the single batteries in the corresponding battery pack through each bottom-layer balancing circuit;

[0028] Obtaining a state of charge value of each of the battery packs;

[0029] Based on the state of charge value of each battery pack, the battery packs are balanced among each other through the top-level balancing circuit.

[0030] In a possible implementation, based on the state of charge value of each single battery in each battery pack, performing intra-group balancing on the single batteries in the corresponding battery pack through each underlying balancing circuit includes:

[0031] Determining the single cells to be balanced based on the state of charge values ​​of the single cells in the target battery group, wherein the target battery group is any of the battery groups;

[0032] Determining a target single cell pair, a target switch pair, and a target inductor based on a target underlying balancing circuit and the single cell to be balanced, wherein the target underlying balancing circuit is a bottom-level balancing circuit corresponding to the target battery pack, and the target single cell pair includes the single cell to be balanced;

[0033] By controlling the state of each switch in the target switch pair, the target inductor is first charged by the other cells in the target cell pair except the cell to be balanced, and then the target inductor is discharged to the cell to be balanced.

[0034] In a possible implementation, performing inter-group balancing on each of the battery packs by a top-level balancing circuit based on the state of charge value of each of the battery packs includes:

[0035] Determining a battery group to be balanced based on the state of charge value of each of the battery groups;

[0036] Controlling the unidirectional switch in the top-level balancing circuit to be turned on so that all the battery packs charge the primary winding in the flyback transformer;

[0037] After charging is completed, the unidirectional switch in the top-level balancing circuit is controlled to be disconnected, and the bidirectional switch connected to the battery group to be balanced is controlled to be turned on, so that the flyback transformer charges the battery group to be balanced.

[0038] In a third aspect, an embodiment of the present application provides an electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the computer program, the method described in the second aspect or any one of the implementation methods thereof is implemented.

[0039] In a fourth aspect, an embodiment of the present application provides a computer-readable storage medium, wherein the computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, it implements the method described in the second aspect or any one of the implementation methods thereof.

[0040] In a fifth aspect, an embodiment of the present application provides a computer program product. When the computer program product is run on an electronic device, the electronic device executes the method described in the second aspect or any one of the implementation methods.

[0041] Compared with the prior art, the embodiments of the present application have the following advantages: the system has a double-layer battery balancing circuit structure of a flyback transformer-inductor, the bottom balancing circuit uses the inductor to achieve balancing of each single battery in the corresponding battery pack, and the top balancing circuit uses the flyback transformer to achieve inter-group balancing of each battery pack. Compared with battery pack balancing only through inductors, it can directly achieve energy transfer between and within each battery pack, shorten the balancing path, reduce the resource loss caused by step-by-step energy transmission during the balancing process, and improve the balancing efficiency; compared with battery pack balancing only through flyback transformers, the system volume is reduced and the balancing cost is reduced.

[0042] It can be understood that the control method, electronic device, computer-readable storage medium and computer program product of the series battery pack balancing system based on the double-layer topology provided in the embodiments of the present application have the same beneficial effects as the above-mentioned series battery pack balancing system based on the double-layer topology, and will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments or descriptions of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0044] Figure 1 A schematic diagram of the architecture of a series battery pack balancing system based on a double-layer topology provided in one embodiment of the present application;

[0045] Figure 2 A schematic structural diagram of a bottom-level balancing circuit in a series battery pack balancing system based on a double-layer topology provided in one embodiment of the present application;

[0046] Figure 3 A schematic structural diagram of a top-level balancing circuit in a series battery pack balancing system based on a double-layer topology provided in one embodiment of the present application;

[0047] Figure 4 A flowchart of a control method for a series battery pack balancing system based on a double-layer topology provided in one embodiment of the present application;

[0048] Figure 5A flowchart of an implementation of step S420 in a control method for a series battery pack balancing system based on a double-layer topology provided in an embodiment of the present application;

[0049] Figure 6 A flowchart of an implementation of step S440 in a control method for a series battery pack balancing system based on a double-layer topology provided in an embodiment of the present application;

[0050] Figure 7 A schematic diagram of the structure of an electronic device provided in one embodiment of the present application. DETAILED DESCRIPTION

[0051] In the following description, specific details such as specific system structures and techniques are provided for purposes of illustration rather than limitation to facilitate a thorough understanding of the embodiments of the present application. However, it will be apparent to those skilled in the art that the present application may be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to avoid obscuring the description of the present application with unnecessary detail.

[0052] It should be understood that when used in the present specification and the appended claims, the term "comprising" indicates the presence of described features, integers, steps, operations, elements and / or components, but does not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or collections thereof.

[0053] It will also be understood that the term "and / or" used in this specification and the appended claims refers to and includes any and all possible combinations of one or more of the associated listed items.

[0054] As used in this specification and the appended claims, the term "if" can be interpreted as "when" or "upon" or "in response to determining" or "in response to detecting," depending on the context. Similarly, the phrase "if it is determined" or "if [described condition or event] is detected" can be interpreted as meaning "upon determination" or "in response to determining" or "upon detection of [described condition or event]" or "in response to detecting [described condition or event]," depending on the context.

[0055] In addition, in the description of the present application specification and the appended claims, the terms "first", "second", "third", etc. are only used to distinguish the descriptions and cannot be understood as indicating or implying relative importance.

[0056] References to "one embodiment" or "some embodiments" in this specification mean that a particular feature, structure, or characteristic described in conjunction with that embodiment is included in one or more embodiments of the present application. Thus, phrases such as "in one embodiment," "in some embodiments," "in other embodiments," and "in other embodiments" appearing in various places in this specification do not necessarily refer to the same embodiment, but rather mean "one or more but not all embodiments," unless otherwise specifically emphasized. The terms "including," "comprising," "having," and variations thereof all mean "including but not limited to," unless otherwise specifically emphasized.

[0057] The inevitable inconsistency between individual cells can reduce the available capacity of a series battery pack and even pose a safety hazard due to overcharging and over-discharging. To address this issue, this application proposes a simple and efficient active balancing solution for series battery packs. This solution is based on a two-layer topology, using the battery SOC as the balancing variable. The bottom balancing circuit adopts a hierarchical balancing topology, while the top balancing circuit adopts a flyback transformer-based balancing topology. Overall balancing uses a modular balancing strategy, either intra-group balancing followed by inter-group balancing or inter-group balancing followed by intra-group balancing, to increase balancing speed.

[0058] For ease of understanding, the technical solution of this application will be described in detail below with reference to the accompanying drawings.

[0059] Figure 1 This is a schematic diagram of the architecture of a series battery pack balancing system based on a double-layer topology provided in one embodiment of the present application. Figure 1 For ease of explanation, only the parts related to this embodiment are shown. The system is applied to at least two battery packs, each battery pack including a plurality of single cells, including:

[0060] At least two bottom-level balancing circuits, one corresponding to each battery pack, for balancing each single battery in the corresponding battery pack through inductance;

[0061] The top-layer balancing circuit is connected to each bottom-layer balancing circuit and is used to achieve inter-group balancing of each battery group through a flyback transformer.

[0062] In a possible implementation, the target underlying balancing circuit includes several inductors and several switch pairs, each switch pair includes two switches, each inductor corresponds one-to-one to each switch pair, and the target underlying balancing circuit is any underlying balancing circuit.

[0063] The target inductor is connected to the target single cell pair in the first target battery group through the target switch pair, the drain of the target switch pair is connected to the positive electrode of the target single cell pair, and the source is connected to the target inductor, the target inductor is any inductor in the target underlying balancing circuit, the target switch pair is a switch pair corresponding to the target inductor, the first target battery group is a battery group corresponding to the target underlying balancing circuit, and the target single cell pair includes at least two single cells in the first target battery group.

[0064] As an example, the target switch pair includes a first switch and a second switch, and the target single cell pair includes a first single cell and a second single cell; one terminal of the target inductor is connected to the positive electrode of the first single cell through the first switch, and the other terminal is connected to the positive electrode of the second single cell through the second switch; the drain of the first switch is connected to the positive electrode of the first single cell, and the source is connected to one terminal of the target inductor; the drain of the second switch is connected to the other terminal of the target inductor, and the source is connected to the positive electrode of the second single cell, and the negative electrode of the first single cell and the negative electrode of the second single cell are connected to a common node.

[0065] As another example, the target switch pair includes a third switch and a fourth switch, and the target single cell pair includes a first single cell, a second single cell, and a third single cell; one terminal of the target inductor is connected to the positive electrode of the first single cell through the third switch, and the other terminal is connected to the positive electrode of the third single cell through the fourth switch; the drain of the third switch is connected to the positive electrode of the first single cell, and the source is connected to one terminal of the target inductor; the drain of the fourth switch is connected to the other terminal of the target inductor, and the source is connected to the positive electrode of the third single cell; the first single cell and the second single cell are connected in series, and the negative electrode of the second single cell and the negative electrode of the third single cell are connected to a common node.

[0066] For example, Figure 2 As shown, B1, B2, B3, and B4 are four single cells in a battery pack, L1, L2, and L3 are inductors, and S1, S2, S3, S4, S5, and S6 are MOS tube switches. Among them, the inductor L1 corresponds to the switch pair consisting of switches S1 and S2, and is used to achieve balancing of single cells B1 and B2; the inductor L2 corresponds to the switch pair consisting of switches S3 and S4, and is used to achieve balancing of single cells B1, B2, and B3; the inductor L3 corresponds to the switch pair consisting of switches S5 and S6, and is used to achieve balancing of single cells B1, B2, B3, and B4.

[0067] One terminal of inductor L1 is connected to the positive electrode of battery B1 via MOS switch S1, and the other terminal is connected to the positive electrode of battery B2 via MOS switch S2. The drain of switch S1 is connected to the positive electrode of battery B1, and the source of switch S1 is connected to one terminal of inductor L1. The drain of switch S2 is connected to the other terminal of inductor L1, and the source of switch S2 is connected to the positive electrode of battery B2. The negative terminals of B1 and B2 are typically connected to a common node (such as the negative terminal of the battery pack or a shared bus). This configuration forms a loop. When switch S1 is on and S2 is off, inductor L1 is charged by B1; when switch S1 is off and S2 is on, inductor L1 discharges to battery B2. For battery cell B3, MOS switches S3 and S4 control energy transfer. Switches S3 and S4 are connected to inductor L2 in a manner similar to the connection between switches S1 and S2 and inductor L1. The conduction condition for switch S3 or S4 depends on a comparison between the difference between battery cell B3's SOC and the average SOC of batteries B1 and B2, and a preset threshold value e. For battery cell B4, energy transfer is controlled via MOS switches S5 and S6. Switches S5 and S6 are connected to inductor L3 in a manner similar to the connection between switches S1 and S2 and inductor L1. The conduction condition for switch S5 or S6 depends on a comparison between the difference between battery cell B4's SOC and the average SOC of batteries B1, B2, and B3, and a preset threshold value e.

[0068] In one possible implementation, the top-level balancing circuit includes a flyback transformer, several bidirectional switches, and a unidirectional switch. The flyback transformer includes a primary winding and several secondary windings. Each secondary winding corresponds to each battery pack one-to-one, and each secondary winding corresponds to each bidirectional switch one-to-one. The primary winding connects all battery packs in series through the unidirectional switch, so that the primary winding, the unidirectional switch, and all battery packs form a loop. Each secondary winding is connected to the corresponding battery pack through the corresponding bidirectional switch.

[0069] As an example, the battery packs are connected in series in sequence to form a series battery pack array, one terminal of the primary winding is connected to the positive electrode of the first battery pack in the series battery pack array, the other terminal is connected to the drain of the one-way switch, and the source of the one-way switch is connected to the negative electrode of the last battery pack in the series battery pack array.

[0070] As an example, one terminal of the target secondary winding is connected to the drain of the target bidirectional switch, the other terminal is connected to the positive pole of the second target battery pack, the source of the target bidirectional switch is connected to the negative pole of the second target battery pack, the target secondary winding is any secondary winding in the flyback transformer, the target bidirectional switch is the bidirectional switch corresponding to the target secondary winding, and the second target battery pack is the battery pack corresponding to the target secondary winding.

[0071] For example, Figure 3 As shown, W1 is the primary winding of the flyback transformer, W2, W3...Wn+1 are the n secondary windings of the flyback transformer, M1, M2...Mn are MOS tube bidirectional switches, Mn+1 is a MOS tube unidirectional switch, battery pack 1, battery pack 2...battery pack n are connected in series in sequence to form a series battery pack array, and each secondary winding is connected to a battery pack through a bidirectional switch.

[0072] The primary winding W1 is connected in series with a unidirectional switch Mn+1. When the unidirectional switch Mn+1 is controlled to conduct, current is allowed to flow through the primary winding. The primary winding is connected to the entire battery pack (including all battery packs or modules). Specifically, one terminal of the primary winding is connected to the positive electrode of the series-connected battery pack array, the other terminal is connected to the drain of the unidirectional switch Mn+1, and the source of the unidirectional switch Mn+1 is connected to the negative electrode of the series-connected battery pack array, forming a complete charging circuit. Each secondary winding corresponds to a specific battery pack (e.g., battery pack 1, battery pack 2, etc.). Each secondary winding is connected in series with a bidirectional switch (typically a MOS transistor, such as the bidirectional switch M1 connected to the secondary winding W2 corresponding to battery pack 1). For example, the drain of the bidirectional switch M1 is connected to one terminal of the secondary winding W2, and the other terminal of the secondary winding W2 is connected to the positive electrode of the corresponding battery pack 1. The source of the bidirectional switch M1 is connected to the negative electrode of the corresponding battery pack 1. This configuration allows the energy stored in the transformer's magnetic field to be transferred to the corresponding target battery pack when the MOS tube bidirectional switch is turned on.

[0073] The technical solution provided by the present application is a system with a double-layer battery balancing circuit structure of a flyback transformer-inductor. The bottom balancing circuit uses the inductor to achieve balancing of each single battery in the corresponding battery pack, and the top balancing circuit uses the flyback transformer to achieve inter-group balancing of each battery pack. Compared with battery pack balancing only through inductors, it can directly achieve energy transfer between and within each battery pack, shorten the balancing path, reduce the resource loss caused by step-by-step energy transmission during the balancing process, and improve the balancing efficiency; compared with battery pack balancing only through flyback transformers, the system volume is reduced and the balancing cost is reduced.

[0074] Figure 4 A flow chart of a control method for a series battery pack balancing system based on a double-layer topology provided in one embodiment of the present application. Figure 4 As shown, based on the above embodiment, this embodiment further illustrates and optimizes the technical solution. Specifically, in this embodiment, the method is applied to Figure 1 The series battery pack balancing system based on the double-layer topology shown includes the following steps:

[0075] S410: Obtain the state of charge value of each single battery in each battery pack.

[0076] S420 , based on the state of charge value of each single battery in each battery pack, perform intra-group balancing on the single batteries in the corresponding battery pack through each bottom-layer balancing circuit.

[0077] In one possible implementation, step S420 may optionally include: determining a cell to be balanced based on the state of charge of each cell in a target battery pack, where the target battery pack is any battery pack; determining a target cell pair, a target switch pair, and a target inductor based on a target underlying balancing circuit and the cell to be balanced, where the target underlying balancing circuit is the underlying balancing circuit corresponding to the target battery pack, and the target cell pair includes the cell to be balanced; and controlling the state of each switch in the target switch pair to first charge the target inductor with the cells in the target cell pair except the cell to be balanced, and then causing the target inductor to discharge the cell to be balanced.

[0078] In the specific implementation, based on Figure 2 In the bottom-level balancing circuit shown, the SOC value of cell B1 is denoted as SOC1, and the SOC value of cell B2 is denoted as SOC2. When SOC1 - SOC2 > e, the cell to be balanced is B2, the target cell pair is B1 and B2, the target switch pair is S1 and S2, and the target inductor is L1. The control logic turns on switch S1, allowing inductor L1 to charge from cell B1 and absorb excess energy. After charging is complete, switch S1 is turned off and S2 is turned on, allowing inductor L1 to discharge into cell B2, transferring energy from cell B1 to B2. If SOC2 - SOC1 > e, the control process is reversed. Cell B1 is the cell to be balanced. Switch S2 is turned on first, allowing inductor L1 to charge from cell B2. After charging is complete, switch S2 is turned off and switch S1 is turned on, allowing inductor L1 to discharge into cell B1. For cells B3 and B4, the process is similar, and the control logic determines the direction of energy transfer by comparing their SOC with the average SOC of the previous cells.

[0079] As an example, Figure 5As shown, B1, B2, B3, and B4 are four battery cells, and SOC1, SOC2, SOC3, and SOC4 are the corresponding state of charge values ​​for each of the four cells. When an SOC imbalance occurs between the cells, a preset threshold e is used as the balancing initiation condition. For example, the absolute value of the difference between SOC1 and SOC2 is determined to be less than or equal to the preset threshold e. If so, switches S1 and S2 are turned off. Further determination is made as to whether the absolute value of the difference between the average of SOC1 and SOC2 and SOC3 is less than or equal to the preset threshold e. If not, the difference between SOC1 and SOC2 is determined. When SOC1 - SOC2 > e, energy from cell B1 is transferred to cell B2. First, logic switches S1 are turned on and S2 are turned off. B1 charges inductor L1, which absorbs excess energy from B1. Next, S1 is turned off and S2 is turned on, stopping charging B1 and causing inductor L1 to discharge B2, transferring energy from B1 to B2. This completes balancing. On the contrary, when SOC2-SOC1>e, the power transfer process is reversed. Similarly, the opening conditions of S3 and S4 are determined by judging the difference between SOC3 and the average SOC value of the two batteries B1 and B2 and the size of the preset threshold value e. When the absolute value of the difference between the average value of SOC1 and SOC2 and SOC3 is greater than the preset threshold value e, the size of the difference between the average value of SOC1 and SOC2 and SOC3 is further judged. If (SOC1+SOC2) / 2-SOC3>e, the single cell to be balanced is B3, the target single cell pair is B1, B2 and B3, the target switch pair is S3 and S4, and the target inductor is L2. First, S3 is controlled to be turned on and S4 is turned off. B1 and B2 charge the inductor L2. After charging is completed, S3 is controlled to be turned off and S4 is turned on. The inductor L2 discharges B3. When SO If C3-(SOC1+SOC2) / 2>e, the cells to be balanced are B1 and B2, the target cell pair is B1, B2, and B3, the target switch pair is S3 and S4, and the target inductor is L2. First, S3 is controlled to be off and S4 is controlled to be on, so that B3 charges inductor L2. After charging is completed, S3 is controlled to be on and S4 is controlled to be off, so that inductor L2 discharges B1 and B2. The opening condition of S5 and S6 is to determine the difference between SOC4 and the average SOC of B1, B2, and B3 and the preset threshold value e. For the specific operation steps, please refer to the above content. Finally, when the difference between the balanced SOC1, SOC2, SOC3, and SOC4 meets the error requirement, the balancing of the battery pack is completed.

[0080] S430: Obtain the state of charge value of each battery pack.

[0081] S440 , based on the state of charge value of each battery pack, perform inter-group balancing on each battery pack through a top-level balancing circuit.

[0082] In one possible implementation, step S440 may optionally include: determining a battery group to be balanced based on the state of charge value of each battery group; controlling a unidirectional switch in a top-level balancing circuit to be turned on so that all battery groups charge the primary winding of a flyback transformer; after charging is completed, controlling the unidirectional switch in the top-level balancing circuit to be turned off, and controlling a bidirectional switch connected to the battery group to be balanced to be turned on so that the flyback transformer charges the battery group to be balanced.

[0083] In the specific implementation, based on Figure 3 In the top-level balancing circuit shown, when the system identifies battery pack 1 as having the lowest SOC, it selects battery pack 1 as the battery pack to be balanced and controls MOSFET unidirectional switch Mn+1 to conduct, allowing all battery packs to charge primary winding W1. Subsequently, unidirectional switch Mn+1 is controlled to turn off, turning on the secondary MOSFET bidirectional switch M1 corresponding to battery pack 1, transferring energy from the primary winding to the secondary winding W2, and then to battery pack 1. This setup ensures that energy is transferred from the entire battery pack to the specific battery pack with the lowest SOC, achieving a "valley-filling" effect.

[0084] For example, Figure 6 As shown, the SOC values ​​of all battery packs are obtained, and the maximum and minimum values ​​are selected from them. When the difference between the maximum and minimum values ​​is greater than the preset threshold σ, the top-level balancing process is started, and the battery pack with the smallest SOC value is used as the battery pack to be balanced. First, the MOS tube unidirectional switch Mn+1 is controlled to be turned on, so that all battery packs charge the primary side w1 of the transformer. After charging is completed, the unidirectional switch Mn+1 is closed, and the bidirectional switch corresponding to the battery pack with the smallest SOC value is opened, so that the energy in the primary winding is transferred to the battery pack with the smallest SOC value, thereby charging the battery pack, realizing the transfer of energy from the entire battery pack to the low SOC battery pack. When the difference between the SOC values ​​of any two battery packs is less than or equal to the preset threshold σ, the top-level balancing is completed.

[0085] It should be noted that based on Figure 1 The series battery pack balancing system based on the double-layer topology shown can also first perform inter-group balancing of each battery pack based on the charge state value of each battery pack through the top-level balancing circuit, and then perform intra-group balancing of the single cells in the corresponding battery pack based on the charge state value of each single cell in each battery pack through each bottom-level balancing circuit. This application does not limit this.

[0086] In summary, the technical solution provided by the present application has the following advantages: ① Easy to expand. When the number of battery packs changes, you can choose to increase the switching tube in the corresponding battery pack or increase the secondary winding of the flyback transformer according to the number of added battery packs; ② Fast balancing speed. The double-layer balancing structure combining the flyback transformer and the inductor designed in the present application can effectively make up for the disadvantage that the energy in the inductor balancing circuit is only transferred between adjacent single cells, and effectively reduce the time required for balancing multiple single cells; ③ Simple control. The control signals required in the primary and secondary sides of the transformer and the inductor balancing circuit are simple.

[0087] Figure 7 This is a schematic diagram of the structure of an electronic device provided in one embodiment of the present application. Figure 7 As shown, the electronic device 7 of this embodiment includes: at least one processor 700 ( Figure 7 Only one is shown), a memory 701 and a computer program 702 stored in the memory 701 and executable on at least one processor 700, the computer program 702 being executed by the processor 700 to implement the above Figure 4 、 Figure 5 and Figure 6 Steps in a method embodiment.

[0088] The electronic device 7 may be a computing device such as a desktop computer, a notebook, a PDA, or a cloud server. The electronic device 7 may include but is not limited to a processor 700 and a memory 701. Those skilled in the art will appreciate that Figure 7 It is only an example of the electronic device 7 and does not constitute a limitation on the electronic device 7. It may include more or fewer components than shown in the figure, or a combination of certain components, or different components. For example, it may also include input and output devices, network access devices, etc.

[0089] The processor 700 may be a central processing unit (CPU), or other general-purpose processors, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), an off-the-shelf programmable gate array (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor may be a microprocessor or any conventional processor.

[0090] In some embodiments, the memory 701 may be an internal storage unit of the electronic device 7, such as a hard disk or memory of the electronic device 7. In other embodiments, the memory 701 may also be an external storage device of the electronic device 7, such as a plug-in hard disk equipped on the electronic device 7, a smart media card (SMC), a secure digital (SD) card, a flash memory card, etc. Furthermore, the memory 701 may include both an internal storage unit of the electronic device 7 and an external storage device. The memory 701 is used to store an operating system, application programs, a boot loader, data, and other programs, such as the program code of a computer program. The memory 701 may also be used to temporarily store data that has been output or is about to be output.

[0091] An embodiment of the present application further provides a computer-readable storage medium, which stores a computer program. When the computer program is executed by a processor, the steps in the above-mentioned method embodiments can be implemented.

[0092] If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the present application implements all or part of the processes in the above-mentioned embodiment method, which can be completed by instructing the relevant hardware through a computer program. The computer program can be stored in a computer-readable storage medium, and the computer program, when executed by the processor, can implement the steps of the above-mentioned various method embodiments. Wherein, the computer program includes computer program code, and the computer program code can be in source code form, object code form, executable file or some intermediate form. The computer-readable medium may include at least: any entity or device capable of carrying the computer program code to an electronic device, a recording medium, a computer memory, a read-only memory (ROM), a random access memory (RAM), an electric carrier signal, a telecommunication signal and a software distribution medium. For example, a USB flash drive, a mobile hard disk, a magnetic disk or an optical disk.

[0093] A computer-readable storage medium provided in an embodiment of the present application has the same beneficial effects as the above-mentioned series battery pack balancing system based on a double-layer topology.

[0094] An embodiment of the present application provides a computer program product, which includes a computer program. When the computer program is executed by a processor, it can implement the steps in the above-mentioned method embodiments.

[0095] A computer program product provided in an embodiment of the present application has the same beneficial effects as the above-mentioned series battery pack balancing system based on a double-layer topology.

[0096] In the above embodiments, the description of each embodiment has its own focus. For parts that are not described or recorded in detail in a certain embodiment, reference can be made to the relevant description of other embodiments.

[0097] Those skilled in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0098] In the embodiments provided in this application, it should be understood that the disclosed devices / equipment and methods can be implemented in other ways. For example, the device / equipment embodiments described above are merely schematic. For example, the division of the modules or units is merely a logical function division. In actual implementation, there may be other division methods, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms.

[0099] Units described as separate components may or may not be physically separate, and components shown as units may or may not be physical units, that is, they may be located in one place or distributed across multiple network units. Some or all of these units may be selected to achieve the purpose of this embodiment according to actual needs.

[0100] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. 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 various embodiments of the present application, and should all be included in the scope of protection of the present application.

Claims

1. A series battery pack balancing system based on a double-layer topology, characterized in that: Applicable to at least two battery packs, each of which includes a plurality of single cells, the system includes: At least two bottom-level balancing circuits, corresponding one to each of the battery packs, for achieving balancing of the single cells in the corresponding battery packs through inductance; The top-layer balancing circuit is connected to each of the bottom-layer balancing circuits and is used to achieve inter-group balancing of each of the battery groups through a flyback transformer.

2. The system according to claim 1, wherein: The target bottom-layer balancing circuit includes a plurality of inductors and a plurality of switch pairs, each of the switch pairs includes two switches, each of the inductors corresponds one-to-one to each of the switch pairs, and the target bottom-layer balancing circuit is any of the bottom-layer balancing circuits; The target inductor is connected to the target single cell pair in the first target battery group through a target switch pair, the drain of the target switch pair is connected to the positive electrode of the target single cell pair, and the source is connected to the target inductor, the target inductor is any inductor in the target underlying balancing circuit, the target switch pair is a switch pair corresponding to the target inductor, the first target battery group is a battery group corresponding to the target underlying balancing circuit, and the target single cell pair includes at least two single cells in the first target battery group.

3. The system according to claim 2, characterized in that The target switch pair includes a first switch and a second switch, and the target single cell pair includes a first single cell and a second single cell; One terminal of the target inductor is connected to the positive electrode of the first single battery through the first switch, and the other terminal is connected to the positive electrode of the second single battery through the second switch; The drain of the first switch is connected to the positive electrode of the first battery, and the source is connected to one terminal of the target inductor; The drain of the second switch is connected to the other terminal of the target inductor, the source is connected to the positive electrode of the second battery, and the negative electrode of the first battery and the negative electrode of the second battery are connected to a common node.

4. The system according to claim 2, wherein: The target switch pair includes a third switch and a fourth switch, and the target single cell pair includes a first single cell, a second single cell, and a third single cell; One terminal of the target inductor is connected to the positive electrode of the first single cell through a third switch, and the other terminal is connected to the positive electrode of the third single cell through a fourth switch; The drain of the third switch is connected to the positive electrode of the first battery cell, and the source is connected to one terminal of the target inductor; The drain of the fourth switch is connected to the other terminal of the target inductor, and the source is connected to the positive electrode of the third single cell. The first single cell and the second single cell are connected in series, and the negative electrodes of the second single cell and the third single cell are connected to a common node.

5. The system according to claim 1, wherein: The top-level balancing circuit includes a flyback transformer, a plurality of bidirectional switches, and a unidirectional switch. The flyback transformer includes a primary winding and a plurality of secondary windings. Each of the secondary windings corresponds to each of the battery packs, and each of the secondary windings corresponds to each of the bidirectional switches. The primary winding connects all the battery packs in series through the one-way switch, so that the primary winding, the one-way switch and all the battery packs form a loop; Each of the secondary windings is connected to a corresponding battery pack via a corresponding bidirectional switch.

6. The system according to claim 5, characterized in that Each of the battery packs is connected in series in sequence to form a series battery pack array, one terminal of the primary winding is connected to the positive electrode of the first battery pack in the series battery pack array, the other terminal is connected to the drain of the one-way switch, and the source of the one-way switch is connected to the negative electrode of the last battery pack in the series battery pack array.

7. The system according to claim 5, characterized in that One terminal of the target secondary winding is connected to the drain of the target bidirectional switch, and the other terminal is connected to the positive electrode of the second target battery group. The source of the target bidirectional switch is connected to the negative electrode of the second target battery group. The target secondary winding is any secondary winding in the flyback transformer. The target bidirectional switch is a bidirectional switch corresponding to the target secondary winding. The second target battery group is a battery group corresponding to the target secondary winding.

8. A control method for a series battery pack balancing system based on a double-layer topology, characterized in that: The series battery pack balancing system according to any one of claims 1 to 7 comprises: Obtain the state of charge value of each single battery in each battery pack; Based on the state of charge value of each single battery in each battery pack, performing intra-group balancing on the single batteries in the corresponding battery pack through each bottom-layer balancing circuit; Obtaining a state of charge value of each of the battery packs; Based on the state of charge value of each battery pack, the battery packs are balanced among each other through the top-level balancing circuit.

9. The method according to claim 8, characterized in that The method of performing intra-group balancing on the single cells in the corresponding battery pack based on the state of charge value of each single cell in each battery pack by each bottom-layer balancing circuit includes: Determining the single cells to be balanced based on the state of charge values ​​of the single cells in the target battery group, wherein the target battery group is any of the battery groups; Determining a target single cell pair, a target switch pair, and a target inductor based on a target underlying balancing circuit and the single cell to be balanced, wherein the target underlying balancing circuit is a bottom-level balancing circuit corresponding to the target battery pack, and the target single cell pair includes the single cell to be balanced; By controlling the state of each switch in the target switch pair, the target inductor is first charged by the other cells in the target cell pair except the cell to be balanced, and then the target inductor is discharged to the cell to be balanced.

10. The method according to claim 8, characterized in that The step of performing inter-group balancing on the battery packs by a top-level balancing circuit based on the state of charge value of each battery pack includes: Determining a battery group to be balanced based on the state of charge value of each of the battery groups; Controlling the unidirectional switch in the top-level balancing circuit to be turned on so that all the battery packs charge the primary winding in the flyback transformer; After charging is completed, the unidirectional switch in the top-level balancing circuit is controlled to be disconnected, and the bidirectional switch connected to the battery group to be balanced is controlled to be turned on, so that the flyback transformer charges the battery group to be balanced.

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