A battery active balancing system

Abstract

This invention discloses a battery active balancing system, comprising: a monitoring module, a main controller, and a balancing module; the monitoring module is used to monitor battery information in real time; the main controller is used to make decisions and adjust the balancing module according to the battery information and real-time monitoring of battery SOC changes; the balancing module is used to achieve balancing between batteries according to the decision adjustment. This invention can effectively achieve multi-layer active balancing within and between battery modules, and can achieve balancing between any battery modules. It achieves constant balancing current output through precise PI control of the balancing current, thereby improving battery pack consistency, extending its service life, and enhancing system safety and reliability.

Description

Technical Field

[0001] This invention belongs to the field of battery balancing technology, and particularly relates to an active battery balancing system. Background Technology

[0002] With the rapid development of technology, lithium battery packs have been widely used in new energy vehicles, energy storage systems, and other fields. Battery packs are typically composed of multiple battery cells connected in series and parallel to achieve the required voltage and capacity. However, in actual use, due to differences in manufacturing processes and material properties, the charge / discharge capabilities and performance of each battery cell often vary; this difference is called battery cell inconsistency. If these imbalances are not effectively addressed, repeated charge / discharge cycles may lead to overcharging or over-discharging, thereby reducing cycle life, decreasing usable capacity, and potentially causing serious safety accidents.

[0003] Current battery balancing technologies are mainly divided into two types: passive balancing and active balancing. Energy dissipation balancing reduces the voltage of high-voltage battery cells by consuming excess electrical energy. Although it is simple to design and inexpensive, its energy utilization rate is low, and it easily causes thermal management problems. Active balancing transfers energy from the high-voltage battery to the low-voltage battery through inductors, capacitors, or transformers. It has high balancing efficiency, but its circuit design is complex, and the balancing process is limited by the magnitude of the voltage difference; when the voltage difference is small, the balancing speed is slow.

[0004] Furthermore, traditional equalization methods are typically limited to equalization within individual battery cells, and this only considers the equalization between adjacent cells, with little attention paid to the equalization between modules. Inconsistencies between modules can further amplify the deviation in the overall performance of the battery pack, affecting system reliability. Simultaneously, existing equalization methods lack precision in current control, making it difficult to achieve constant current output. Especially under dynamic operating conditions, the equalization current fluctuates significantly, and the equalization efficiency and stability fail to meet practical requirements.

[0005] In summary, an active battery balancing system is needed to address the shortcomings and deficiencies of existing technologies. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention proposes an active battery balancing system that can effectively achieve multi-layer balancing within and between battery modules. By precisely controlling the balancing current, it achieves stable constant current output, thereby improving the consistency of the battery pack, extending its service life, and enhancing the safety and reliability of the system.

[0007] This invention provides a battery active balancing system, comprising: a monitoring module, a main controller, and a balancing module;

[0008] The monitoring module is used to monitor battery information in real time;

[0009] The main controller is used to monitor changes in battery SOC in real time based on the battery information and make decisions to regulate the equalization module.

[0010] The equalization module is used to achieve equalization between batteries based on decision control.

[0011] Optionally, the main controller includes: a battery state assessment unit, a PI control unit, and an active balancing algorithm strategy unit;

[0012] The battery state assessment unit is used to estimate the SOC of the battery and module in real time using the extended Kalman filter algorithm based on the battery information.

[0013] The PI control unit is used to control the conduction of switches within and between modules;

[0014] The active balancing algorithm strategy unit is used to formulate corresponding balancing strategies and perform battery balancing based on the SOC values ​​of the battery and module.

[0015] Optionally, the battery information includes: battery voltage data, battery current data, and battery temperature data.

[0016] Optionally, the equalization module includes: an intra-module equalization unit and an inter-module equalization unit;

[0017] The module equalization unit is used to achieve equalization between batteries within the module;

[0018] The inter-module equalization unit is used to achieve equalization between batteries in the modules.

[0019] Optionally, achieving battery balancing within the module includes:

[0020] The module contains an even number of individual cells, M. The individual cells are simultaneously balanced in two stages. The first stage is the balancing between adjacent individual cells in the module, and the second stage is the balancing between the upper M / 2 cells and the lower M / 2 cells in the module.

[0021] The balancing between adjacent individual cells within the module includes: when the SOC difference between two adjacent cells exceeds a preset balancing start threshold, the main controller instructs the MOS switch of the adjacent cell with the higher SOC to turn on and discharge through the inductor. After the discharge ends, the MOS switch of the adjacent cell with the higher SOC turns off and the MOS switch of the adjacent cell with the lower SOC turns on and charges through the energy stored in the inductor until the SOC difference between the adjacent individual cells drops below the balancing threshold, at which point balancing stops.

[0022] The balancing of the upper M / 2 battery and the lower M / 2 battery within the module includes: when the SOC difference between the upper M / 2 battery and the lower M / 2 battery exceeds a preset balancing start threshold, the main controller commands the corresponding MOS to turn on, discharging through the inductor. After the discharge ends, the MOS is turned off, and the MOS with the lower SOC is turned on, charging through the energy stored in the inductor, until the SOC difference drops below the balancing threshold, at which point balancing stops.

[0023] Optionally, the switching MOSFET is controlled by a buck-boost converter to achieve energy balance among the batteries within the module.

[0024] Optionally, the buck-boost converter includes: an inductor, a resistor, a switching MOSFET, and a control chip, wherein:

[0025] The control chip is used to drive the operating state of the switching MOSFET;

[0026] The switching MOSFET controls the charging and discharging process of the inductor by turning it on and off;

[0027] The inductor is used to store and release energy;

[0028] The resistor, in conjunction with the inductor and the switching MOSFET, regulates the current and stabilizes the circuit operation. The inductor, resistor, and switching MOSFET together constitute a buck-boost energy conversion circuit.

[0029] Optionally, the inter-module equalization unit includes: a polarity selection switch MOS, a bidirectional flyback converter, and a battery selection switch MOS;

[0030] The polarity selection switch is used to adjust the positive and negative polarity matching of the battery. When different battery modules to be balanced are connected to the balancing unit, it ensures that the positive and negative polarities of the battery module voltage are consistent with the positive and negative polarities of the balancing unit.

[0031] The bidirectional flyback converter, as an energy converter, is used to realize bidirectional energy transmission in the battery active balancing system. It transfers energy from the battery module with a higher SOC to the battery module with a lower SOC through a high-frequency transformer.

[0032] The battery selection switch is used to activate the energy transfer circuits of the highest SOC battery and the lowest SOC battery during balancing.

[0033] Optionally, achieving battery balancing between modules includes:

[0034] Calculate the sum of the SOC of individual cells in each battery module to obtain the SOC of the battery module;

[0035] The two battery modules with the largest SOC range are selected for balancing.

[0036] Optionally, selecting the two battery modules with the largest SOC range for balancing includes:

[0037] Before equalization, determine whether the SOC range of the battery module meets the first threshold. If it does, perform battery module equalization.

[0038] In the initial stage of the equalization process, the module with the highest SOC and the module with the lowest SOC are locked as the initial equalization target modules, and energy transfer is continuously carried out while the dynamic ranking of the SOC of all modules is monitored in real time.

[0039] When the initial equalization target module is surpassed by other modules or surpasses other modules during the equalization process, the system maintains the original conduction state of the switch array until the SOC difference between the initial equalization target module and the new target module continuously exceeds the preset second threshold. At this time, the path of the initial equalization target module is cut off and the system switches to the new target module, starting the next stage of equalization with the new target module as the core. After each switch, the system re-establishes the difference monitoring system based on the current module with the largest range. Subsequent switches are triggered only when the difference between the SOC of the new benchmark module and the module with the SOC of its adjacent modules exceeds the second threshold again.

[0040] Compared with the prior art, the present invention has the following advantages and technical effects:

[0041] This invention employs a multi-layered structural design to achieve more precise and efficient energy transfer. It ensures efficient energy conversion between different levels, significantly improving overall balancing speed and greatly reducing balancing errors. The module utilizes a buck-boost converter, while bidirectional flyback converters are used between modules. This addresses the issue of small-scale individual battery capacity differences and balances large-scale inter-module battery deviations, ensuring efficient energy conversion between different levels, improving overall consistency, and optimizing energy conversion.

[0042] Improve balancing efficiency: By using a second balancing threshold, the number of switching actions is reduced, thereby reducing system conduction losses and filtering out invalid switching caused by brief fluctuations or minor crossovers between adjacent SOC battery modules, ensuring that each switching action leads to a better global balancing state.

[0043] Enhanced system stability: The system employs online parameter identification and extended Kalman filter algorithm to estimate the SOC value in real time, thereby improving the accuracy of equalization control and the stability of the system.

[0044] Flexible control strategy: The equalization current is dynamically adjusted according to the battery's operating status, which ensures equalization efficiency and avoids excessive rise in battery temperature.

[0045] Modular design: The system structure is modular. If the number of modules is to be expanded, only modules of the same type need to be connected, which is convenient for expansion and maintenance and can adapt to battery pack applications of different scales and needs. Attached Figure Description

[0046] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0047] Figure 1 This is a framework diagram of a battery active balancing system according to an embodiment of the present invention;

[0048] Figure 2 This is a PI constant current control diagram according to an embodiment of the present invention;

[0049] Figure 3 This is a diagram illustrating the discharge process of a high-energy battery within a module according to an embodiment of the present invention.

[0050] Figure 4 This is a diagram illustrating the charging process of the low-energy battery within the module according to an embodiment of the present invention.

[0051] Figure 5 This is a diagram illustrating the high-energy battery module discharge process between modules according to an embodiment of the present invention;

[0052] Figure 6 This is a diagram illustrating the charging process of low-energy battery modules between modules according to an embodiment of the present invention. Detailed Implementation

[0053] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0054] It should be noted that the steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and although a logical order is shown in the flowchart, in some cases the steps shown or described may be executed in a different order than that shown here.

[0055] This embodiment proposes an active battery balancing system, such as... Figure 1 As shown, it specifically includes: a monitoring module, a main controller, and a balancing module;

[0056] The monitoring module is used to monitor battery information in real time;

[0057] The main controller is used to monitor changes in battery SOC in real time based on the battery information and make decisions to regulate the equalization module.

[0058] The balancing module is used to achieve balancing between battery modules based on decision control.

[0059] Specifically, the entire equilibrium system in this implementation includes:

[0060] Battery monitoring module: Collects voltage information of each battery in real time and transmits the collected data to the main controller.

[0061] Main Controller Module: The main controller identifies battery parameters online and uses this parameter to perform real-time state-of-the-art (SOC) estimation of the battery using an extended Kalman filter algorithm, ensuring accurate control of the equalization process under different SOC and temperature conditions. Based on the SOC values ​​of each battery and module, the main controller formulates corresponding equalization algorithm strategies and performs battery equalization by controlling the switching MOS in the equalization module via PWM.

[0062] Equalization module: Includes intra-group equalization and inter-group equalization, and uses a switch matrix to select the battery equalization path.

[0063] Furthermore, the main controller includes: a battery state assessment unit, a PI control unit, and an active balancing algorithm strategy unit;

[0064] The battery state assessment unit is used to estimate the SOC of the battery and module in real time using the extended Kalman filter algorithm based on the battery information.

[0065] The PI control unit is used to control the conduction of switches within and between modules;

[0066] The active balancing algorithm strategy unit is used to formulate corresponding balancing strategies and perform battery balancing based on the SOC values ​​of the battery and module.

[0067] Furthermore, the battery information includes: battery voltage data, battery current data, and battery temperature data.

[0068] Furthermore, the equalization module includes: an intra-module equalization unit and an inter-module equalization unit;

[0069] The module equalization unit is used to achieve equalization between batteries within the module;

[0070] The inter-module equalization unit is used to achieve equalization between batteries in the modules.

[0071] Specifically, the active balancing circuit in this embodiment adopts a multi-layer balancing structure, including balancing between batteries within a module and balancing between modules:

[0072] Intra-module balancing: Used for balancing between batteries within a module. This layer uses a buck-boost converter as the core component, and achieves energy transfer between batteries by controlling the switching MOSFETs.

[0073] Inter-module balancing: Used for balancing between battery modules. This layer uses a bidirectional flyback converter as the energy converter, and achieves energy transfer between different battery modules by controlling the polarity switch and the battery selection switch.

[0074] Furthermore, achieving battery balancing within the module includes:

[0075] The module contains an even number of individual cells, M. The individual cells are simultaneously balanced in two stages. The first stage is the balancing between adjacent individual cells in the module, and the second stage is the balancing between the upper M / 2 cells and the lower M / 2 cells in the module.

[0076] like Figure 3-4 As shown, the balancing between adjacent individual cells in the module includes: when the SOC difference between two adjacent cells exceeds the preset balancing start threshold, the main controller instructs the MOS switch of the adjacent cell with the higher SOC to turn on and discharge through the inductor. After the discharge ends, the MOS switch of the adjacent cell with the higher SOC is turned off, and the MOS switch of the adjacent cell with the lower SOC is turned on and charged through the energy stored in the inductor until the SOC difference between the adjacent individual cells drops below the balancing threshold, and then the balancing stops.

[0077] The balancing of the upper M / 2 battery and the lower M / 2 battery within the module includes: when the SOC difference between the upper M / 2 battery and the lower M / 2 battery exceeds a preset balancing start threshold, the main controller commands the corresponding MOS to turn on, discharging through the inductor. After the discharge ends, the MOS is turned off, and the MOS with the lower SOC is turned on, charging through the energy stored in the inductor, until the SOC difference drops below the balancing threshold, at which point balancing stops.

[0078] Specifically, the control method involves using a PI controller to adjust the balancing current. A smaller balancing current is used when the battery is charging or discharging to prevent further temperature increases; a larger balancing current is used when the battery is idle to accelerate the balancing process.

[0079] Furthermore, the switching MOSFET is controlled by a buck-boost converter to realize the transfer of energy between adjacent batteries.

[0080] Furthermore, the buck-boost converter includes: an inductor, a resistor, a switching MOSFET, and a control chip, wherein:

[0081] The control chip is used to drive the operating state of the switching MOSFET;

[0082] The switching MOSFET controls the charging and discharging process of the inductor by turning it on and off;

[0083] The inductor is used to store and release energy;

[0084] The resistor, in conjunction with the inductor and the switching MOSFET, regulates the current and stabilizes the circuit operation. The inductor, resistor, and switching MOSFET together constitute a buck-boost energy conversion circuit.

[0085] Furthermore, the second equalization unit includes: a polarity selection switch MOS, a bidirectional flyback converter, and a battery selection switch MOS;

[0086] The polarity selection switch is used to adjust the positive and negative polarity matching of the battery. When different battery modules to be balanced are connected to the balancing unit, it ensures that the positive and negative polarities of the battery module voltage are consistent with the positive and negative polarities of the balancing unit.

[0087] The bidirectional flyback converter, as an energy converter, is used to realize bidirectional energy transmission in the battery active balancing system. It transfers energy from the battery module with a higher SOC to the battery module with a lower SOC through a high-frequency transformer.

[0088] The battery selection switch is used to activate the energy transfer circuits of the highest SOC battery and the lowest SOC battery during balancing.

[0089] Furthermore, achieving battery leveling between modules includes:

[0090] Calculate the sum of the SOC of individual cells in each battery module to obtain the SOC of the battery module;

[0091] The two battery modules with the largest SOC range are selected for balancing.

[0092] Furthermore, selecting the two battery modules with the largest SOC range for balancing includes:

[0093] Before equalization, determine whether the SOC range of the battery module meets the first threshold. If it does, perform battery module equalization.

[0094] In the initial stage of the equalization process, the module with the highest SOC and the module with the lowest SOC are locked as the initial equalization target modules, and energy transfer is continuously carried out while the dynamic ranking of the SOC of all modules is monitored in real time.

[0095] When the initial equalization target module is surpassed by other modules during the equalization process, or when it surpasses other modules, the system maintains the original on state of the switch array until the SOC difference between the initial equalization target module and the new target module continuously exceeds the preset second threshold. At this time, the path of the initial equalization target module is cut off and the system switches to the new target module, starting the next stage of equalization with the new target module as the core. After each switch, the system re-establishes the difference monitoring system based on the current module with the largest difference. Subsequent switches are triggered only when the difference between the new benchmark module and the battery module with the adjacent SOC exceeds the second threshold again.

[0096] Specifically, in the initial stage, the system locks the highest and lowest SOC modules as the primary balancing targets, continuously transferring energy and monitoring the dynamic SOC ranking of all modules in real time. When the initial target module is surpassed by other modules or surpasses other module batteries during the balancing process (e.g., the initial highest SOC module's SOC value drops to the second-highest or lower due to discharge, or the initial lowest SOC module's SOC value increases due to balancing charging), the system maintains the original switch array's conduction state until the SOC difference between that module and the newly emerging extreme value module (the current actual highest or lowest SOC module) continuously exceeds a preset second threshold. Only then is the original module's path cut off and the system switches to the new target module, initiating the next stage of balancing centered on the new extreme value pair. After each switch, the system re-establishes the difference monitoring system based on the current module with the largest difference, triggering subsequent switches only when the difference between the new benchmark module and its adjacent SOC battery modules again exceeds the second threshold. This achieves battery balancing between modules.

[0097] More specifically, the inter-module balancing circuit mainly adjusts the SOC difference between battery modules, solving the problem that traditional balancing circuits cannot achieve cross-module balancing. Its specific structure and working principle are as follows:

[0098] Bidirectional flyback converter: A bidirectional flyback converter is used as the energy converter. The input and output terminals of the flyback converter are formed by a polarity switch and a battery selection switch. The input terminal is connected to a battery module with a higher SOC, and the output terminal is connected to a battery module with a lower SOC.

[0099] Operating Mode: Operates in DCM (Discontinuous Current Mode), ensuring the flyback converter's transfer function contains no right-half-plane zeros, improving transient response speed and enhancing system stability. Simultaneously, the transformer does not generate residual magnetism in discontinuous mode, guaranteeing flux reset and improving system stability in harsh environments. The transformer's inductance is lower in discontinuous mode, reducing transformer size and facilitating system design and layout.

[0100] Energy transfer: The main controller commands the main power MOSFET and rectifier MOSFET of the high SOC module to turn on, realizing the transfer of energy from the high SOC module to the low SOC module.

[0101] The equalization process continues until the SOC difference between modules drops below the dual equalization threshold, at which point the equalization operation stops. Due to the addition of the RCD snubber circuit, any high-voltage spikes generated during the equalization process are absorbed promptly, preventing potential damage to the battery pack and electronic components from high-voltage pulses. When the switching MOSFET of the flyback converter is turned off, the leakage inductance of the transformer generates a reverse voltage spike. The RCD snubber circuit, connected in parallel with the switching transistor, quickly absorbs and dissipates this energy. The capacitor (C) absorbs energy, the diode (D) allows energy flow and prevents reverse current, while the resistor (R) converts excess energy into heat, thus preventing the voltage spike from affecting the switching transistor.

[0102] Control strategies such as Figure 2 As shown: A PI controller is used to adjust the balancing current. When the battery is charging or discharging, a smaller balancing current is used to prevent temperature rise; when the battery is idle, a larger balancing current is used to accelerate balancing. The balancing strategy calculates the sum of the SOC of individual cells in each module and compares it with the range of other modules. The two modules with the largest SOC range are selected for balancing, avoiding frequent switching and reducing conduction losses.

[0103] The following is a detailed description of this embodiment with reference to the accompanying drawings:

[0104] The active balancing circuit in this embodiment includes a two-layer balancing mechanism and a main controller. Each battery cell is equipped with an information acquisition unit for real-time acquisition of voltage information and transmission of the data to the main controller. The main controller uses online identification technology to estimate the SOC value of each battery in real time and formulates corresponding balancing strategies.

[0105] In-module equalization circuit:

[0106] The module contains two equalization layers. Both the first and second equalization circuits are buck-boost converters composed of inductors L, resistors R, and synchronous switching MOS (Q1, Q2, Q3, Q4, Q5, Q6).

[0107] like Figure 3-4 As shown, the specific operation process is as follows:

[0108] 1. Assume that the SOC of battery C1 is greater than that of C2, the SOC of battery C3 is greater than that of C4, and the SOC of battery C1+C2 is greater than that of battery C3+C4 and reaches the equilibrium threshold.

[0109] 2. The main controller sends PWM control signals to control Q1, Q3 and Q5 to turn on, so as to transfer energy from the high SOC battery to the inductor for storage. Then, Q1, Q3 and Q5 are turned off and Q2, Q4 and Q6 are turned on to transfer energy to the low SOC battery through the inductor.

[0110] 3. Switches Q1, Q3, Q5 and Q2, Q4, Q6 conduct complementaryly within one cycle. Equalization stops when the SOC difference falls below the equalization threshold. This achieves energy transfer from battery C1 to C2, energy transfer from C3 to C4, and energy transfer from C1 and C2 to C3 and C4, thus achieving battery equalization within the module.

[0111] like Figure 5-6 As shown, the inter-module equalization circuit:

[0112] The odd-numbered index switches on the charging and discharging sides are connected together, for example, S1 and S3 on the equalizing discharge side, and S5 and S7 on the equalizing charging side. The even-numbered index switches are connected together, with S2 and S4 on the equalizing discharge side, and S6 and S8 on the equalizing charging side.

[0113] The second-layer equalization circuit includes a synchronous flyback converter, equalization discharge-side polarity switches (T1, T2, T3, T4), equalization charging-side polarity switches (T5, T6, T7, T8), equalization discharge-side battery selection switches (S1, S2, S3, S4), equalization charging-side battery selection switches (S5, S6, S7, S8), and a pair of main power switches (Qp, Qs), and incorporates an RCD (Rsubp, Csubp, Dp, Rsubs, Csubs, Ds) absorption circuit. Its operation is as follows:

[0114] 1. The main controller detects that the SOC difference between modules is greater than the module balancing threshold. For example, if the SOC of battery module 3 is greater than the SOC of battery module 2 and also greater than the module balancing threshold.

[0115] 2. The main controller controls switches S1, S2, S6, S7, T1, T4, T5, and T8 to be fully turned on within one cycle, while Qp and Qs are complementary in one cycle, so that energy can be transferred from the high SOC battery module 3 to the low SOC battery module 2 through the flyback converter. During this period, only two switches on the charging side are strictly kept on, and the same applies to the discharging side, in order to prevent the positive and negative terminals of the module batteries from being short-circuited together.

[0116] 3. The system first selects the modules with the largest initial SOC difference, module 3 with the highest SOC and module 2 with the lowest SOC, as the balancing targets, and turns on the corresponding switches to transfer energy. As balancing progresses, the SOC of the highest-SOC battery module in the initial target module will decrease, and the SOC of the lowest-SOC battery module in the initial target module will increase. This causes the SOC values ​​of other modules to surpass or be surpassed by the initial target module during the balancing process (e.g., module 3 is surpassed by the adjacent higher-ranking module, or module 2 is surpassed by the adjacent lower-ranking module). At this time, the system still maintains the original switching state. Switching will only be triggered when the SOC difference between the newly emerging extreme value module and the initial target module exceeds a preset second threshold. Assuming that module 3 still has the highest SOC at this time, while module 2's SOC is higher than module 1's and the second equalization threshold during the equalization process, during switching, the system first completely disconnects all current switches, and then turns on the corresponding switches of the new target module (such as discharge side S1 / S2 / T1 / T4 and charging side S7 / S8 / T6 / T7) within one control cycle. The system also controls the power switches (Qp / Qs) through complementary PWM signals to ensure unidirectional energy transfer from the new target module with the highest SOC (such as battery module 3) to the new target module with the lowest SOC (such as battery module 1). At any given time, a maximum of two sets of switches are allowed to be on on the discharge or charging side to prevent battery short circuits. This second threshold is set to avoid frequent switching, which increases turn-on and turn-off losses and improves the converter's efficiency.

[0117] Control strategy:

[0118] The main controller identifies lithium-ion battery parameters online and estimates the battery's State of Charge (SOC) in real time using an extended Kalman filter algorithm as an active balancing variable. It then initiates and stops balancing based on the battery's SOC range and employs a PI (proportional-integral) controller to adjust the balancing current. When the battery is charging or discharging, a smaller, constant balancing current is used to avoid overheating and reduce battery load; when the battery is idle, a larger, constant balancing current is used to accelerate the balancing process.

[0119] This embodiment employs a multi-layered design and advanced control strategies. It uses online identification of lithium-ion battery parameters to estimate the battery's State of Charge (SOC) in real time as an active balancing variable. A multi-layered active balancing circuit structure with a switch array as the battery balancing path is used, and constant current control is employed to achieve active battery balancing. This significantly improves the consistency and safety of the battery pack and has broad application prospects.

[0120] The above are merely preferred embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A battery active balancing system, characterized in that, include: Monitoring module, main controller, and balancing module; The monitoring module is used to monitor battery information in real time; The main controller is used to monitor changes in battery SOC in real time based on the battery information and make decisions to regulate the equalization module. The main controller includes: a battery state assessment unit, a PI control unit, and an active balancing algorithm strategy unit; The battery state assessment unit is used to estimate the SOC of the battery and module in real time using the extended Kalman filter algorithm based on the battery information. The PI control unit is used to control the conduction of switches within and between modules; The active balancing algorithm strategy unit is used to formulate corresponding balancing strategies and perform battery balancing based on the SOC values ​​of the battery and the module. The equalization module is used to achieve equalization between batteries based on decision control. The equalization module includes: an intra-module equalization unit and an inter-module equalization unit; The module equalization unit is used to achieve equalization between batteries within the module; The inter-module equalization unit is used to achieve equalization between batteries in the inter-module; Achieving battery balancing within the module includes: The module contains an even number of individual cells, M. The individual cells are simultaneously balanced in two stages. The first stage is the balancing between adjacent individual cells in the module, and the second stage is the balancing between the upper M / 2 cells and the lower M / 2 cells in the module. The balancing between adjacent individual cells within the module includes: when the SOC difference between two adjacent cells exceeds a preset balancing start threshold, the main controller instructs the MOSFET of the adjacent individual cell with the higher SOC to turn on and discharge through an inductor. After the discharge ends, the MOSFET of the adjacent individual cell with the higher SOC is turned off, and the MOSFET of the adjacent individual cell with the lower SOC is turned on and charged through the energy stored in the inductor until the SOC difference between the adjacent individual cells drops below the balancing threshold, at which point balancing stops. The balancing of the upper M / 2 battery and the lower M / 2 battery in the module includes: when the difference between the SOC of the upper M / 2 battery and the SOC of the lower M / 2 battery exceeds the preset balancing start threshold, the main controller commands the corresponding MOS to turn on, discharge through the inductor, turn off the switching MOS transistor after the discharge ends, and turn on the switching MOS transistor with the lower SOC, charge through the energy stored in the inductor, until the SOC difference drops to within the balancing threshold, and then the balancing stops. The switching MOSFET is controlled by a buck-boost converter to achieve energy balance among the batteries in the module; The buck-boost converter includes: an inductor, a resistor, a switching MOSFET, and a control chip, wherein: The control chip is used to drive the operating state of the switching MOSFET; The switching MOSFET controls the charging and discharging process of the inductor by turning it on and off; The inductor is used to store and release energy; The resistor, in conjunction with the inductor and the switching MOSFET, regulates the current and stabilizes the circuit operation. The inductor, resistor, and switching MOSFET together constitute a buck-boost energy conversion circuit. The inter-module equalization unit includes: a polarity selection switch MOSFET, a bidirectional flyback converter, and a battery selection switch MOSFET; The polarity selection switch is used to adjust the positive and negative polarity matching of the battery. When different battery modules to be balanced are connected to the balancing unit, it ensures that the positive and negative polarities of the battery module voltage are consistent with the positive and negative polarities of the balancing unit. The bidirectional flyback converter, as an energy converter, is used to realize bidirectional energy transmission in the battery active balancing system. It transfers energy from the battery module with a higher SOC to the battery module with a lower SOC through a high-frequency transformer. The battery selection switch is used to open the energy transfer circuits of the highest SOC battery module and the lowest SOC battery module during balancing. Achieving battery balancing between modules includes: Calculate the sum of the SOC of individual cells in each battery module to obtain the SOC of the battery module; The two battery modules with the largest SOC range are selected for balancing operation. The equalization operation involves selecting the two battery modules with the largest SOC range from the battery modules and performing the following steps: Before equalization, determine whether the SOC range of the battery module meets the first threshold. If it does, perform battery module equalization. In the initial stage of the equalization process, the module with the highest SOC and the module with the lowest SOC are locked as the initial equalization target modules, and energy equalization is continuously performed while the dynamic ranking of the SOC of all modules is monitored in real time. When the initial equalization target module is surpassed by other modules or surpasses other modules during the equalization process, the system maintains the original conduction state of the switch array until the SOC difference between the initial equalization target module and the new target module continuously exceeds the preset second threshold. At this time, the path of the initial equalization target module is cut off and the system switches to the new target module, starting the next stage of equalization with the new target module as the core. After each switch, the system re-establishes the difference monitoring system based on the current module with the largest range. Subsequent switches are triggered only when the difference between the SOC of the new benchmark module and the module with the SOC of its adjacent modules exceeds the second threshold again.

2. The battery active balancing system according to claim 1, characterized in that, The battery information includes: battery voltage data, battery current data, and battery temperature data.

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