Battery active equalization system

Abstract

The invention discloses a battery active equalization system, which comprises a monitoring module, a main controller and an equalization module, the monitoring module is used for monitoring battery information in real time; the main controller is used for monitoring the SOC change of the battery in real time according to the battery information and carrying out decision regulation and control on the equalization module; and the equalization module is used for realizing equalization between the batteries according to decision regulation and control. Multi-layer active equalization in the battery modules and between the battery modules can be effectively realized, equalization between any battery modules can be realized, and constant equalization current output is realized through accurate PI control equalization current, so that the consistency of the battery pack is improved, the service life of the battery pack is prolonged, and the safety and reliability of the system are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of battery balancing, and particularly relates to a battery active balancing system. Background Art

[0002] With the rapid development of technology, lithium battery packs have been widely used in new energy vehicles, energy storage systems and other fields. A battery pack is usually composed of multiple battery cells connected in series and parallel to achieve the required voltage and capacity in this way. However, in actual use, due to differences in production processes, material properties, etc., the charge and discharge capabilities and performance of each battery cell are often different, and this difference is called the inconsistency of battery cells. If these imbalance problems are not effectively solved, repeated charge and discharge cycles may lead to overcharge or over-discharge, thereby reducing the cycle life, reducing the available capacity, and may cause 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 its design is simple and the cost is low, the energy utilization rate is low, and it is easy to cause thermal management problems. Active balancing transfers the energy of high-voltage batteries to low-voltage batteries through inductors, capacitors or transformers. Its balancing efficiency is high, but the circuit design is complex, and the balancing process is limited by the size of the voltage difference. When the voltage difference is small, the balancing speed is slow.

[0004] In addition, traditional balancing methods are usually limited to the balancing within battery cells, and the balancing within battery cells only considers the balancing between adjacent battery cells, and less attention is paid to the balancing between modules. The inconsistency between modules will further amplify the deviation of the overall performance of the battery pack and affect the reliability of the system. At the same time, the existing balancing methods have insufficient accuracy in current control and are difficult to achieve constant current output. Especially under dynamic working conditions, the balancing current fluctuates greatly, and the balancing efficiency and stability are difficult to meet the actual requirements.

[0005] In summary, to solve the defects and deficiencies in the prior art, a battery active balancing system is needed. Summary of the Invention

[0006] To solve the above technical problems, the present invention proposes a battery active balancing system, which can effectively achieve multi-layer balancing within battery modules and between battery modules, and achieve stable constant current output by precisely controlling the balancing current, thereby improving the consistency of the battery pack, extending its service life, and improving the safety and reliability of the system.

[0007] The present invention provides a battery active balancing system, including: 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 make decision and regulation on the equalization module according to the real-time monitoring of the change of battery SOC based on the battery information;

[0010] The equalization module is used to achieve equalization between batteries according to the decision and regulation.

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

[0012] The battery state evaluation unit is used to use the extended Kalman filter algorithm to estimate the SOC of the battery and the module in real time according to the battery information;

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

[0014] The active equalization algorithm strategy unit is used to formulate corresponding equalization strategies and perform battery equalization according to the SOC values of the battery and the 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 intra-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 between modules.

[0019] Optionally, achieving equalization between batteries within the module includes:

[0020] The module contains M cells with an even number. Two-level equalization is performed on the cells simultaneously. Among them, the first-level equalization is the equalization between adjacent cells within the module, and the other level is the equalization between the upper M / 2 cells and the lower M / 2 cells within the module;

[0021] The equalization between adjacent cells within the module includes: when the SOC difference between two adjacent cells exceeds the preset equalization start threshold, the main controller commands the MOS switch of the cell with a higher SOC among the adjacent cells to conduct, and discharges through the inductor. After the discharge is completed, the MOS switch of the cell with a higher SOC is turned off, and the switch MOS of the cell with a lower SOC among the adjacent cells is turned on, and the energy stored in the inductor is used for charging until the SOC difference between the adjacent cells drops below the equalization threshold, and the equalization stops;

[0022] The balancing of the upper M / 2 batteries and the lower M / 2 batteries within the module includes: when the SOC difference between the upper M / 2 batteries and the lower M / 2 batteries exceeds a preset balancing start threshold, the main controller commands the corresponding MOS to conduct, discharges through the inductor, closes the switching MOS after the discharge ends, and opens the switching MOS with a lower SOC, and charges through the energy stored in the inductor until the SOC difference drops within the balancing threshold, and then stops the balancing.

[0023] Optionally, the switching MOS transistor is controlled by a buck-boost converter to achieve the balancing of energy among the batteries within the module.

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

[0025] The control chip is used to drive the working state of the switching MOS transistor;

[0026] The switching MOS transistor controls the charging and discharging process of the inductor through conduction and cutoff;

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

[0028] The resistor cooperates with the inductor and the switching MOS transistor to adjust the current and stabilize the operation of the circuit, and the inductor, resistor, and switching MOS transistor together constitute a buck-boost energy conversion circuit.

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

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

[0031] The bi-directional flyback converter, as an energy converter, is used to achieve bi-directional energy transfer in the battery active balancing system, and 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 be responsible for opening the energy transfer circuit between the battery with the highest SOC and the battery with the lowest SOC during balancing.

[0033] Optionally, achieving the balancing between the batteries among the modules includes:

[0034] Calculating the total SOC of the individual batteries within each battery module to obtain the SOC of the battery module;

[0035] Selecting the two battery modules with the largest SOC difference among the battery modules for balancing operations.

[0036] Optionally, selecting the two battery modules with the largest SOC difference in the battery module for the equalization operation includes:

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

[0038] At the initial stage of the equalization process, lock the highest SOC module and the lowest SOC module as the initial equalization target modules, continuously perform energy transfer, and monitor the dynamic sorting of the SOC of all modules 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 still maintains the conduction state of the original 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, cut off the path of the initial equalization target module and switch to the new target module, and start the next stage of equalization with the new target module as the core. Among them, after each switch, the system re-establishes a difference monitoring system based on the current module with the largest difference. Only when the SOC difference between the new reference module and the module with its adjacent SOC breaks through the second threshold again, trigger subsequent switches.

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

[0041] Through the multi-layer structure design, the present invention makes the energy transmission more accurate and efficient. Ensure the efficient conversion of energy between different levels, greatly improve the overall equalization speed and greatly reduce the equalization error. A buck-boost converter is adopted inside the module, and a bi-directional flyback converter is adopted between the modules, which solves the power difference of a small range of single cells and balances the battery deviation between a large range of modules, ensures the efficient conversion of energy between different levels, improves the overall consistency, and optimizes the energy conversion.

[0042] Improve the equalization efficiency: Use the second equalization threshold to reduce the number of switch tube actions, reduce the on-state loss of the system, and filter out the ineffective switches caused by short-term fluctuations or small intersections between adjacent SOC battery modules, ensuring that each switching action leads to a better global equalization state.

[0043] Enhance the system stability: Adopt the online parameter identification and extended Kalman filtering algorithm to estimate the SOC value in real time, improving the accuracy of the equalization control and the stability of the system.

[0044] Flexible control strategy: Dynamically adjust the equalization current according to the working state of the battery, which not only ensures the equalization efficiency but also avoids excessive increase in battery temperature.

[0045] Modular design: The system structure is modular. If the number of modules continues to expand, only modules of the same type need to be connected, which is convenient for expansion and maintenance and adapts to battery pack applications of different scales and requirements. Brief Description of the Drawings

[0046] The drawings forming a part of this application are used to provide a further understanding of this application. The schematic embodiments of this application and their descriptions are used to explain this application and do not constitute an improper limitation to this application. In the drawings:

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

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

[0049] Figure 3 is a diagram of the discharging process of high-energy batteries within a module according to an embodiment of the present invention;

[0050] Figure 4 is a diagram of the charging process of low-energy batteries within a module according to an embodiment of the present invention;

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

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

[0053] It should be noted that, without conflict, the embodiments in this application and the features in the embodiments can be combined with each other. The following will refer to the drawings and combine the embodiments to detail this application.

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

[0055] This embodiment proposes a battery active balancing system, as Figure 1 shown, specifically including: a monitoring module, a main controller, and an equalization module;

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

[0057] The main controller is used to make decision and regulation on the equalization module according to the real-time monitoring of the change of battery SOC based on the battery information;

[0058] The balancing module is used to achieve balancing between battery modules according to decision regulation.

[0059] Specifically, the entire balancing system in this embodiment specifically includes:

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

[0061] Main controller module: The main controller online identifies battery parameters, and uses the extended Kalman filter algorithm to estimate the real-time state of the battery's SOC based on these parameters, ensuring accurate control of the balancing process under different SOC and temperature conditions. According to the SOC values of each battery and module, the main controller formulates corresponding balancing algorithm strategies and controls the switching MOS in the balancing module through PWM to perform battery balancing.

[0062] Balancing module: It includes intra-group balancing and inter-group balancing, and a switching matrix is used to select the path for battery balancing.

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

[0064] The battery state evaluation unit is used to use the extended Kalman filter algorithm to estimate the SOC of the battery and module in real time according to the battery information;

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

[0066] The active balancing algorithm strategy unit is used to formulate corresponding balancing strategies and perform battery balancing according to 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 balancing module includes: an intra-module balancing unit and an inter-module balancing unit;

[0069] The intra-module balancing unit is used to achieve balancing between the batteries within the module;

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

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

[0072] Intra-module balancing: It is used for balancing between the batteries within the module. This layer uses a buck-boost converter as the core component, and realizes the energy transfer between the batteries by controlling the switching MOS transistor.

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

[0074] Furthermore, realizing the balancing between the batteries within a module includes:

[0075] The module contains M single cells with an even number. Two-stage balancing is performed on the single cells simultaneously. Among them, the first-stage balancing is the balancing between adjacent single cells within the module, and the other stage is the balancing between the upper M / 2 batteries and the lower M / 2 batteries within the module;

[0076] As Figure 3-4 shown, the balancing between adjacent single cells within the module includes: when the SOC difference between two adjacent batteries exceeds the preset balancing start threshold, the main controller commands the MOS of the battery with a higher SOC among the adjacent batteries to conduct, and discharges through the inductor. After the discharge ends, the MOS of the battery with a higher SOC is turned off, and the MOS of the adjacent battery with a lower SOC is turned on, and the energy stored in the inductor is used for charging until the SOC difference between the adjacent battery cells drops below the balancing threshold, and the balancing stops;

[0077] The balancing between the upper M / 2 batteries and the lower M / 2 batteries within the module includes: when the SOC difference between the upper M / 2 batteries and the lower M / 2 batteries exceeds the preset balancing start threshold, the main controller commands the corresponding MOS to conduct, and discharges through the inductor. After the discharge ends, the switch MOS is turned off, and the switch MOS with a lower SOC is turned on, and the energy stored in the inductor is used for charging until the SOC difference drops below the balancing threshold, and the balancing stops.

[0078] Specifically, the control method: a PI controller is used to adjust the magnitude of the balancing current. When the battery is in the charging and discharging state, a smaller balancing current is used to avoid further temperature rise; when the battery is stationary, a larger balancing current is used to accelerate the balancing process.

[0079] Furthermore, the switch MOS tube is controlled by a buck-boost converter to realize the energy transfer between adjacent batteries.

[0080] Furthermore, the buck-boost converter includes: an inductor, a resistor, a switch MOS tube and a control chip, where:

[0081] The control chip is used to drive the working state of the switch MOS tube;

[0082] The switch MOS tube controls the charging and discharging process of the inductor by conduction and turn-off;

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

[0084] The resistor cooperates with the inductor and the switching MOS transistor to regulate the current and stabilize the operation of the circuit. The inductor, resistor and switching MOS transistor together constitute a buck-boost energy conversion circuit.

[0085] Further, the second balancing unit includes: a polarity selection switch MOS, a bi-directional flyback converter, and a battery selection switch MOS;

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

[0087] The bi-directional flyback converter, as an energy converter, is used to achieve bi-directional energy transfer 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 be responsible for opening the energy transfer loop of the battery with the highest SOC and the battery with the lowest SOC during balancing.

[0089] Further, achieving the balance between the batteries among the modules includes:

[0090] Calculate the total SOC of the single batteries in each battery module to obtain the SOC of the battery module;

[0091] Select two battery modules with the largest SOC difference in the battery modules for balancing operation.

[0092] Further, selecting two battery modules with the largest SOC difference in the battery modules for balancing operation includes:

[0093] Before balancing, judge whether the SOC difference of the battery modules meets the first threshold. If it meets, perform battery module balancing;

[0094] At the initial stage of the balancing process, lock the battery module with the highest SOC and the battery module with the lowest SOC as the initial balancing target modules, continuously perform energy transfer and real-time monitor the dynamic sorting of the SOC of all modules;

[0095] When the initial equilibrium target module is surpassed by other modules or surpasses other modules during the equalization process, the system still maintains the conduction state of the original switch array until the SOC difference between the initial equilibrium target module and the new target module continuously exceeds a preset second threshold. At this time, the path of the initial equilibrium target module is cut off and switched to the new target module, and the next stage of equalization with the new target module as the core is started. Among them, after each switch, the system re-establishes a difference monitoring system based on the current maximum range module, and only triggers subsequent switches when the difference between the new reference module and the battery module with adjacent SOC breaks through the second threshold again.

[0096] Specifically, the system locks the highest SOC and lowest SOC modules as the main equalization targets in the initial stage, continuously performs energy transfer, and monitors the dynamic sorting of the SOC of all modules in real time. When the initial target module is surpassed by other modules or surpasses other module batteries during the equalization process (for example, the SOC value of the initial highest SOC module drops to the second place or lower due to discharge, and the SOC value of the initial lowest SOC module increases due to equalization charging), the system still maintains the conduction state of the original switch array until the SOC difference between this module and the newly emerged extreme value module (the current actual highest or lowest SOC module) continuously exceeds the preset second threshold. At this time, the path of the original module is cut off and switched to the new target module, and the next stage of equalization with the new extreme value pair as the core is started. After each switch, the system re-establishes a difference monitoring system based on the current maximum range module, and only triggers subsequent switches when the difference between the new reference module and the battery module with adjacent SOC breaks through the second threshold again. In this way, the battery equalization between modules is realized.

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

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

[0099] Working mode: It works in DCM (discontinuous current mode) to ensure that the transfer function of the flyback converter does not contain right-half plane zeros, improve the transient response speed, and enhance the system stability. At the same time, in the discontinuous mode, the transformer will not generate residual magnetism, ensuring flux reset and enhancing the system stability in harsh environments. In the discontinuous mode, the inductance value of the transformer is small, reducing the volume of the transformer 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 conduct, 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 the modules drops below the double equalization threshold, at which point the equalization operation stops. Due to the addition of the RCD absorption circuit, any high-voltage spikes generated during the equalization process are absorbed in a timely manner, avoiding potential damage to the battery pack and electronic components caused by 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 absorption circuit is connected in parallel with the switching transistor and quickly absorbs and dissipates this part of the energy. The capacitor (C) absorbs the energy, the diode (D) allows the energy to flow and prevents reverse current, while the resistor (R) is used to convert the excess energy into heat, thus avoiding the impact of voltage spikes on the switching transistor.

[0102] The control strategy is as Figure 2 shown: A PI controller is used to regulate the equalization current. When the battery is in the charging or discharging state, a smaller equalization current is used to prevent the temperature from rising; when the battery is stationary, a larger equalization current is used to accelerate the equalization. The equalization strategy calculates the sum of the SOC values of the individual cells in each module, compares the difference with other modules, and selects the two modules with the largest SOC difference for equalization operation, avoiding frequent switching and reducing conduction losses.

[0103] The following elaborates on this embodiment in conjunction with the attached drawings:

[0104] The active equalization circuit of this embodiment includes two layers of equalization mechanisms 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 values of each battery in real time and formulates corresponding equalization strategies.

[0105] Equalization circuit within the module:

[0106] There are two layers of equalization within the module. Both the first-layer equalization circuit and the second-layer equalization circuit are buck-boost converters composed of an inductor L, a resistor R, and synchronous switches MOS (Q1, Q2, Q3, Q4, Q5, Q6).

[0107] As Figure 3-4 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 equalization threshold.

[0109] 2. The main controller sends PWM control signals to control the conduction of Q1, Q3, and Q5 respectively, realizing the transfer of 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 controlled to conduct, using the inductor to transfer energy to the low-SOC battery.

[0110] 3. Switches Q1, Q3, Q5 and Q2, Q4, Q6 conduct complementarily within one cycle. The equalization stops until the SOC difference drops below the equalization threshold. In this way, the energy of battery C1 is transferred to C2, the energy of C3 is transferred to C4, and the energy of C1 and C2 is transferred to C3 and C4, realizing the equalization of the batteries within the module.

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

[0112] The odd-index switches of the selection switches on both the charge and discharge sides are connected together, such as S1 and S3 on the equalization discharge side, and S5 and S7 on the equalization charge side. The even-index switches S2 and S4 on the equalization discharge side are connected together, and S6 and S8 on the equalization charge side.

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

[0114] 1. The main controller detects that the SOC difference between modules is greater than the module equalization threshold. Suppose at this time, the SOC of battery module 3 is greater than that of battery module 2 and greater than the module equalization threshold.

[0115] 2. Then the main controller controls switches S1, S2, S6, S7, T1, T4, T5, and T8 to conduct fully within one cycle, while Qp and Qs conduct complementarily within one cycle, realizing the transfer of energy from the high-SOC battery module 3 to the low-SOC battery module 2 through the flyback converter. During this period, it is strictly ensured that there are exactly two switches conducting on the charge side, and the same for the discharge side, to prevent the positive and negative poles of the module batteries from being connected together and causing a short circuit.

[0116] 3. The system first selects the modules with the largest initial SOC difference, i.e., the module 3 with the highest SOC and the module 2 with the lowest SOC as the balancing targets, and turns on the corresponding switches to transfer energy. As the 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, resulting in the SOC values of other modules exceeding or being exceeded by the initial target module during the balancing process (e.g., module 3 is exceeded by the adjacent higher module, or module 2 is exceeded by the adjacent lower module). At this time, the system still maintains the original switch state. Only when the SOC difference between the newly emerged extreme value module and the initial target module exceeds the preset second threshold will the switching be triggered. Suppose the SOC of module 3 is still the largest at this time, and module 2 is greater than module 1 and greater than the second balancing threshold during the balancing process. During the switching, the system first completely disconnects all the current switches, and then turns on the corresponding switches of the new target module (such as S1 / S2 / T1 / T4 on the discharging side and S7 / S8 / T6 / T7 on the charging side) within one control cycle, and controls the power switches (Qp / Qs) through complementary PWM signals to ensure that the energy is unidirectionally transferred from the new target highest SOC module (such as battery module 3) to the new target lowest SOC module (such as battery module 1). At the same time, at most two groups of switches on the discharging side or the charging side are allowed to conduct to prevent battery short - circuit. The setting of this second threshold is to avoid the frequent conduction of switches, thereby increasing the conduction and turn - off losses and improving the working efficiency of the converter.

[0117] Control strategy:

[0118] The main controller online identifies the parameters of the lithium - ion battery and uses the extended Kalman filter algorithm to estimate the SOC of the battery in real - time as the active balancing variable. It starts and stops the balancing according to the SOC range of the battery, and uses a PI (Proportional - Integral) controller to adjust the magnitude of the balancing current. When the battery is in the charging and discharging state, a smaller constant balancing current is used to avoid over - high temperature and reduce the battery load; when the battery is stationary, a larger constant balancing current is used to accelerate the balancing process.

[0119] In this embodiment, through multi - layer design and advanced control strategies, the parameters of the lithium - ion battery are online identified to estimate the SOC of the battery in real - time as the active balancing variable, a multi - layer active balancing circuit structure with a switch array as the battery balancing path, and a constant - current output control is used to achieve battery active balancing. It significantly improves the consistency and safety of the battery pack and has broad application prospects.

[0120] The above is only the preferred specific embodiment of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed in the present application should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection 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 the battery SOC changes in real time according to the battery information to make decisions and regulate the balancing module; The balancing module is used to achieve balancing between batteries according to decision-making regulation.

2. The battery active equalization system according to claim 1, characterized in that: The main controller includes: a battery status evaluation unit, a PI control unit and an active balancing algorithm strategy unit; The battery state evaluation unit is used to estimate the SOC of the battery and the module in real time using an extended Kalman filter algorithm according to the battery information; The PI control unit is used to control the conduction of switches within the module and between modules; The active balancing algorithm strategy unit is used to formulate corresponding balancing strategies and perform battery balancing according to the SOC values ​​of the batteries and modules.

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

4. The battery active equalization system according to claim 1, characterized in that: The balancing module includes: an intra-module balancing unit and an inter-module balancing unit; The module internal balancing unit is used to achieve balancing between batteries in the module; The inter-module balancing unit is used to achieve balancing between batteries in the modules.

5. The battery active equalization system according to claim 1, characterized in that: Balancing between batteries in the module includes: The module contains an even number of single cells, M of which are used for balancing. Two levels of balancing are performed on the single cells simultaneously. One level of balancing is balancing between adjacent single cells in the module, and the other level of balancing is balancing between the upper M / 2 cells and the lower M / 2 cells in the module. The balancing between adjacent single cells in the module includes: when the SOC difference between two adjacent cells exceeds a preset balancing start threshold, the main controller instructs the battery switch MOS with a higher SOC in the adjacent single cells to turn on, discharge through the inductor, and turn off the battery switch MOS with a higher SOC after the discharge, and turn on the switch MOS with a lower SOC in the adjacent cell to charge through the energy stored in the inductor until the SOC difference between the adjacent battery cells drops to within the balancing threshold, and then stops balancing; The balancing of the upper M / 2 battery and the lower M / 2 battery in the module includes: when the SOC difference between the upper M / 2 battery and the lower M / 2 battery exceeds the preset balancing start threshold, the main controller instructs the corresponding MOS to turn on and discharge through the inductor. After the discharge is completed, the switch MOS is turned off and the switch MOS with a lower SOC is turned on to charge through the energy stored in the inductor until the SOC difference drops to within the balancing threshold, and the balancing is stopped.

6. The battery active equalization system according to claim 5, characterized in that: The switch MOS tube is controlled by a buck-boost converter to achieve energy balance among the batteries in the module.

7. The battery active equalization system according to claim 6, characterized in that: The buck-boost converter comprises: an inductor, a resistor, a switch MOS tube and a control chip, wherein: The control chip is used to drive the working state of the switch MOS tube; The switch MOS tube controls the charging and discharging process of the inductor by turning on and off; The inductor is used to store and release energy; The resistor cooperates with the inductor and the switch MOS tube to adjust the current and stabilize the circuit operation. The inductor, the resistor and the switch MOS tube together constitute a buck-boost energy conversion circuit.

8. The battery active equalization system according to claim 1, characterized in that: The inter-module balancing unit includes: a polarity selection switch MOS, a bidirectional flyback converter and a battery selection switch MOS; The polarity selection switch is used to adjust the positive and negative poles of the battery to match each other. When different battery modules to be balanced are connected to the balancing unit, it ensures that the positive and negative poles of the battery module voltage are consistent with the positive and negative poles 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, and it transfers energy from the battery module with higher SOC to the battery module with lower SOC through a high-frequency transformer; The battery selection switch is used to open the energy transfer circuit of the highest SOC battery module and the lowest SOC battery module during balancing.

9. The battery active equalization system according to claim 8, characterized in that: Balancing between batteries in modules includes: Calculate the sum of the SOCs of the single cells in each battery module to obtain the SOC of the battery module; The two battery modules having the largest SOC range difference among the battery modules are selected for balancing operation.

10. The battery active equalization system according to claim 9, characterized in that: Selecting two battery modules with the largest SOC range of the battery module to perform a balancing operation includes: Before balancing, determine whether the SOC range of the battery module meets the first threshold, and if so, perform battery module balancing; At the initial stage of the balancing process, the highest SOC module and the lowest SOC module are locked as the initial balancing target modules, and energy balancing is continuously performed and the SOC dynamic ranking of all modules is monitored in real time; When the initial balancing target module is surpassed by other modules or surpasses other modules during the balancing process, the system still maintains the conduction state of the original switch array until the SOC difference between the initial balancing target module and the new target module continues to exceed the preset second threshold value. At this time, the initial balancing target module path is cut off and switched to the new target module, and the next stage of balancing with the new target module as the core is started. After each switch, the system re-establishes the difference monitoring system based on the current maximum extreme difference module, and triggers subsequent switching only when the SOC difference between the new reference module and its adjacent SOC module exceeds the second threshold value again.

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