An integrated topology and control method for battery balancing and AC self-heating based on electromagnetic induction.

Abstract

This invention relates to the field of battery management systems, specifically disclosing an integrated topology and control method for battery balancing and AC self-heating based on electromagnetic induction. The topology includes a battery pack, a switch array, a multi-winding transformer, a signal acquisition and processing module, a control unit, and a drive circuit. Energy balancing within and between battery modules is achieved through the multi-winding transformer, and battery self-heating is achieved by generating AC current at low frequency using the same transformer winding. The control method dynamically switches between balancing and heating modes based on battery voltage and temperature information, and flexibly controls the heating rate and balancing speed by adjusting PWM parameters. This invention features high integration, requires no external power supply, and has strong scalability, making it suitable for efficient thermal management and state balancing of various lithium-ion battery systems in low-temperature environments.

Description

Technical Field

[0001] This invention relates to the field of battery management system technology, and in particular to an integrated topology and control method for battery balancing and AC self-heating based on electromagnetic induction. Background Technology

[0002] Lithium-ion batteries experience severe performance degradation in cold climates, resulting in reduced usable capacity and difficulties in charging and discharging. Internally, this manifests as slower electrode charge transfer and electrochemical reaction rates, leading to increased polarization; externally, it results in decreased output power. Furthermore, low-temperature charging easily induces lithium deposition, hindering lithium intercalation and causing irreversible capacity loss. To address the challenges of low-temperature operation, battery heating technology has emerged. Depending on the heat source, it can be categorized into external heating and internal heating. External heating relies on an external power source or heating medium, achieved through heat conduction or convection, but suffers from slow heating rates, low energy utilization, and the need for additional equipment. Internal heating utilizes the internal resistance of the battery during charging and discharging, offering advantages such as rapid temperature rise, high energy utilization, and uniform temperature distribution. Internal heating can be further divided into DC discharge heating and AC heating. AC heating, due to its rapid alternation between charging and discharging, effectively prevents side reactions and lithium deposition, making it safer and more efficient.

[0003] On the other hand, due to differences in manufacturing processes, material aging, and usage conditions, inconsistencies inevitably exist between individual battery cells and modules, leading to a "weakest link effect" that affects the overall system performance and lifespan. Battery balancing technology is key to mitigating these inconsistencies and is mainly divided into passive balancing and active balancing. Passive balancing dissipates excess energy through resistors, a simple method but with the risk of energy waste and thermal runaway. Active balancing, on the other hand, redistributes energy among batteries using energy storage components such as capacitors, inductors, or transformers, resulting in higher efficiency. Among these, transformer-based topologies have attracted attention due to their advantages such as fast balancing speed, high efficiency, and good electrical isolation.

[0004] Currently, heating and equalization systems are typically designed and installed independently, leading to hardware duplication, increased costs, bulky size, and the inability to share energy paths, resulting in complex control. Existing solutions, such as the system proposed in application number 202410267300.X, can achieve heating and equalization, but the equalization process still relies on resistive energy consumption, resulting in energy waste, slow heating speed, and poor temperature uniformity. Furthermore, existing heating solutions mostly operate in fixed modes, making it difficult to adjust heating power and rate in real time through simple control variables; while most active equalization topologies are complex with a large number of components, making it difficult to flexibly support energy transfer along arbitrary paths within and between modules, resulting in poor scalability and an inability to simultaneously support low-temperature heating functions.

[0005] In summary, in cold-region applications, battery thermal management and state equalization are complementary. Rapidly and uniformly raising the battery temperature to the ideal operating range, while simultaneously achieving efficient and flexible state equalization, is crucial for improving the overall performance of the battery system, extending its lifespan, and ensuring safety. Therefore, there is an urgent need to develop an integrated topology and intelligent control method that deeply integrates AC self-heating and efficient active equalization functions to achieve device sharing, cost reduction, simplified control, and meet the requirements of high efficiency and high speed. Summary of the Invention

[0006] The purpose of this invention is to solve the problems existing in the prior art and to propose an integrated topology and control method for battery equalization and AC self-heating based on electromagnetic induction. Through the coordinated work of multi-winding transformers and switch arrays, energy equalization and low-frequency AC self-heating between battery cells / modules are achieved. It has the advantages of high integration, strong scalability and flexible control.

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

[0008] A battery balancing-AC self-heating integrated topology based on electromagnetic induction includes:

[0009] The battery pack consists of m battery modules connected in series, and each battery module contains n battery cells connected in series.

[0010] The switching array consists of multiple MOSFET pairs, with each battery cell corresponding to a pair of MOSFETs, and the sources of the two MOSFETs in the MOSFET pair are interconnected.

[0011] A multi-winding transformer includes m primary windings and one secondary winding. Each primary winding is connected to a corresponding battery module. The polarity of each primary winding is the same and opposite to that of the secondary winding connected to both ends of the entire battery module. Energy transfer between different battery modules and within the modules is achieved through magnetic coupling.

[0012] The signal acquisition and processing module is used to acquire the voltage and temperature signals of individual battery cells and the current signals flowing through each winding of the multi-winding transformer, and convert them into digital signals.

[0013] The control unit receives the digital signal and outputs a PWM control signal to the switch array to realize the selection and switching of equalization and heating modes;

[0014] A driving circuit is used to amplify and isolate the PWM control signal to drive the MOSFETs in the switching array.

[0015] As a further technical solution of the present invention, the MOSFET pairs in the switch array are grouped by function, with odd-numbered battery cells connected to the top and bottom MOSFET groups, and even-numbered battery cells connected to the middle MOSFET group.

[0016] As a further technical solution of the present invention, each primary winding of the multi-winding transformer and its corresponding battery module constitute an independent electrical port. By controlling the conduction and cutoff of specific MOSFET pairs in the switching array, any single battery cell or any battery module in the battery pack can be connected to the primary winding corresponding to its electrical port.

[0017] A control method for an integrated battery equalization-AC self-heating topology based on electromagnetic induction, characterized in that, for controlling an integrated battery equalization-AC self-heating topology based on electromagnetic induction, the method includes the following steps:

[0018] S1. The voltage and temperature signals of each battery cell are periodically acquired through the signal acquisition and processing module;

[0019] S2. The control unit determines whether the battery voltage difference exceeds the set range based on the voltage signal. If it does, it executes the equalization control mode; otherwise, it executes the temperature judgment.

[0020] S3. If the battery voltage difference is within the set range, the control unit determines whether the battery temperature difference exceeds the set range based on the temperature signal. If it exceeds the set range, it performs self-heating control on the low-temperature cell; otherwise, it performs self-heating control on the entire battery module and generates a second set of PWM signals.

[0021] S4. In the equalization control mode, the control unit selects the energy transfer path according to the voltage difference and outputs the corresponding first group of PWM signals to drive the switch array, so that the high-energy battery transfers energy to the low-energy battery.

[0022] S5. In the self-heating control mode, the control unit adjusts the carrier frequency and duty cycle of the second set of PWM signals, and controls the switch array to form an alternating current between the battery or module and the transformer winding to achieve low-frequency AC self-heating.

[0023] As a further technical solution of the present invention, in S4, the control unit identifies the highest voltage cell and the lowest voltage cell based on the voltage signal, and selects one from multiple energy transfer paths according to the relationship between the cells and the battery modules to which they belong, thereby generating a first set of PWM signals with a first frequency and a first duty cycle.

[0024] As a further technical solution of the present invention, the multiple energy transfer paths include: transfer from the first cell to the second cell within the same battery module, transfer from the battery cell to the entire battery module to which it belongs, transfer from the battery module to a certain cell within it, transfer from one battery module to the entire battery pack, transfer from the entire battery pack to a certain battery module, and transfer from the first battery module to the second battery module.

[0025] As a further technical solution of the present invention, in S4, the first group of PWM signals is amplified by the driving circuit and controls the on / off sequence of the corresponding MOSFET pairs in the switch array, so that energy is transferred from the battery cell or battery module with higher voltage to the battery cell or battery module with lower voltage through the multi-winding transformer.

[0026] As a further technical solution of the present invention, in S5, the control unit dynamically adjusts the carrier frequency and duty cycle of the second PWM according to the temperature signal, the preset target temperature value and the ambient temperature parameters.

[0027] As a further technical solution of the present invention, in S5, after the second group of PWM signals is amplified by the driving circuit, it controls the on / off sequence of the corresponding MOSFET pairs in the switch array, so that a periodic alternating charging and discharging current loop is formed between the target heating battery module and the corresponding winding of the multi-winding transformer.

[0028] A battery management system, characterized in that it comprises:

[0029] A battery balancing-AC self-heating integrated topology based on electromagnetic induction;

[0030] And a control unit and related software program configured to execute a control method based on an electromagnetic induction-based battery balancing-AC self-heating integrated topology.

[0031] The beneficial effects of this invention are as follows:

[0032] 1. Highly integrated functions: Through a single multi-winding transformer topology, high-frequency active balancing within / between battery modules and low-frequency AC self-heating of individual battery cells / modules are simultaneously achieved without the need for an external power supply, deeply integrating the functions of two independent systems into a single hardware.

[0033] 2. Modularity and Scalability: The topology is highly modular. Heating and equalization of all cells within the battery pack share only one transformer winding; when the system scales up, only a pair of MOSFET switches need to be added to the new battery cells, without changing the core topology or adding extra functional modules, which greatly reduces the cost and complexity of expansion.

[0034] 3. Adjustable intelligent control: By adjusting the frequency and duty cycle of the control signal, the effective value of the AC heating current and the rate of equalization energy transfer can be directly and linearly adjusted. This allows for real-time and dynamic control of heating power and equalization speed based on battery status and ambient temperature, achieving intelligent thermal management and precise equalization.

[0035] 4. Wide applicability and non-invasiveness: This solution does not change the internal structure of the battery, does not require an external heating power source or additional heating film, and can work solely through the battery's own energy and an external electromagnetic induction circuit. It is suitable for a variety of application scenarios, from small battery packs to large series battery systems, and has strong versatility. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the battery pack equalization-heating topology according to Embodiment 1 of the present invention;

[0037] Figure 2 This is a schematic diagram illustrating the heating principle of a single cell within the battery pack according to Embodiment 1 of the present invention.

[0038] Figure 3 This is a schematic diagram of the overall heating working principle of the battery pack according to Embodiment 1 of the present invention;

[0039] Figure 4 This is a schematic diagram of the single-cell battery equalization working principle in Embodiment 1 of the present invention;

[0040] Figure 5 This is a schematic diagram of the battery module equalization working principle according to Embodiment 1 of the present invention;

[0041] Figure 6 This is a schematic diagram of the battery pack equalization heating control process according to Embodiment 2 of the present invention;

[0042] Figure 7 This is a waveform diagram of the battery pack heating current in Embodiment 3 of the present invention;

[0043] Figure 8 This is a cell-to-cell current waveform result diagram of Embodiment 3 of the present invention;

[0044] Figure 9 This is a diagram showing the cell-to-cell voltage balancing results of Embodiment 3 of the present invention;

[0045] Figure 10 This is a graph showing the heating temperature results of a single cell in Embodiment 3 of the present invention. Detailed Implementation

[0046] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below in conjunction with specific embodiments.

[0047] Example 1

[0048] Please see the appendix Figure 1 A battery equalization-AC self-heating integrated topology based on electromagnetic induction includes: a battery pack consisting of m battery modules (Pack1, Pack2, ..., Pack...). m The battery module is composed of n battery cells connected in series. Each battery module is further composed of n individual battery cells (e.g., B). 11 B 12 ,…,B 1n It is composed of multiple interconnected components. This structure can adapt to different application scenarios, ranging from portable devices to large-scale energy storage power stations.

[0049] Switch array: Each battery cell (e.g., B) 11 Each corresponds to a pair of source-connected MOSFETs (such as Q). 11 and Q 12 This back-to-back connection eliminates the unidirectional conduction effect of the MOSFET's internal diode, achieving true bidirectional current control and the ability to withstand AC current, enabling forward and reverse heating current control, and also providing safe isolation for the high-voltage battery module. The switch array employs a grouped design to optimize wiring: the entire battery module shares 6 pairs of MOSFETs. Within a battery module, odd-numbered individual cells (such as B...) 11 B 13 ) connect to the shared top (Q 123 Q 124 ) and bottom (Q) 117 Q 118 MOSFET pairs; even-numbered cell units (e.g., B) 12 B 14 Then it is connected to the middle MOSFET pair (such as Q). 119 Q 120 (etc.). The switching array selectively connects to the multi-winding transformer based on the PWM signal output by the control unit. The switching array is the core of realizing flexible switching of energy paths.

[0050] Multi-winding transformer (T1): A key energy conversion device integrating equalization and heating functions. The transformer contains m primary windings (Lp1, Lp2, ..., Lp...). m A primary winding (Ls) and a secondary winding (Ps). The two ends of each primary winding are connected to the total positive (P) of the corresponding battery module (e.g., Pack1). 1+ ) and total negative (P 1- The two ends of the secondary winding are connected to the total positive (P) of the entire battery pack. + ) and total negative (P -All primary windings have the same winding direction (polarity), while the secondary windings have the opposite winding direction. Energy can be transferred between any two windings through magnetic coupling. The multi-winding transformer structure allows for flexible expansion of the battery pack capacity and integrates both functions without the need for additional heating devices. The primary excitation inductance is approximately 7.9uH, the secondary excitation inductance is 129uH, and the turns ratio is set to 1:4.

[0051] Signal acquisition and processing module: Used for real-time monitoring of system status, including acquiring the voltage and temperature of each battery cell, as well as the current flowing through each winding of the transformer, and monitoring the battery temperature in real time to ensure that the heating rate is within a safe range. This module filters and amplifies the acquired analog signals, converts them into digital signals that can be processed by the microcontroller through an analog-to-digital converter (ADC), and transmits them to the control unit via SPI communication.

[0052] The control unit (such as an MCU) receives digital signals from the signal acquisition and processing module, executes the core control algorithm, and determines whether to execute the equalization mode or the heating mode based on the battery voltage inconsistency and temperature distribution, and selects the specific energy transfer path. The control unit outputs multiple pulse width modulation (PWM) signals to precisely control the turn-on and turn-off timing, frequency, and duty cycle of each MOSFET in the switching array; it also sets the maximum duty cycle upper limit of the PWM signal to ensure that the transformer is completely demagnetized in each switching cycle, prevents core saturation, and ensures long-term reliable operation of the system.

[0053] Drive circuit: Receives low-voltage PWM signal from control unit and converts it into high-level, high-current gate drive signal required to safely and reliably drive high-voltage side MOSFET. At the same time, it realizes electrical isolation between control circuit and power circuit, ensuring reliable operation of switch array during low-frequency heating and high-frequency equalization.

[0054] Fault detection and response: The main controller monitors the output voltage of the MOSFET drive circuit in real time, and collects the transformer winding current and battery temperature in real time. If the current, battery temperature, or drive voltage exceeds the upper limit, all MOSFETs will be immediately turned off and enter a safe state.

[0055] This system establishes a specific connection between the battery and the multi-winding transformer by controlling the switch array, thereby realizing two main functions on the same hardware platform: low-frequency AC self-heating and high-frequency active equalization.

[0056] A. AC self-heating working mode: The heating principle is based on the fact that the battery's internal resistance generates Joule heat under low-frequency AC excitation. The system can heat a single battery cell or the entire battery module.

[0057] A1. Battery cell AC self-heating (using heating B) 11 (For example)

[0058] Mode I (discharge stage): such as Figure 2 As shown in (a), the control unit closes MOSFET Q. 123 Q 124 Q 118 Q 117 Q 14 Q 13 Disconnect the remaining MOSFET switches. At this time, battery B... 11 Through its corresponding switch pair (Q) 11 Q 12 Although not directly connected, the path has been established) Discharge to the primary winding Lp1 of the transformer. The winding current rises linearly from zero to its maximum value, and the electrical energy is converted into magnetic energy and stored in the transformer.

[0059] Mode II (charging phase): such as Figure 2 As shown in (b), the switch state is switched, and the switch transistor Q is closed. 115 Q 12 Q 11 Q 13 Q 14 Q 119 Q 120 Turn off the remaining MOSFET switches (pay special attention to Q). 116 (Keep it off to effectively prevent the reverse flow of energy from the battery to the inductor during this process). At this time, the magnetic energy stored in the transformer is released, affecting battery B. 11 Reverse charging occurs, and the winding current drops from its peak to zero. The alternation of Mode I and Mode II, i.e., the mutual charging and discharging between the inductor and the battery, occurs at battery B. 11 An internal low-frequency alternating current is generated, thus achieving self-heating without the need for external power.

[0060] Mode III (Demagnetization Stage): In this stage, the switching state is consistent with that of Mode II, ensuring that the residual energy in the winding is completely released, ensuring that the equalization circuit operates in discontinuous conduction mode (DCM), and ensuring that the transformer is completely demagnetized within one equalization cycle, preparing for the next cycle.

[0061] A2. Battery module AC self-heating (taking Heating Pack 1 as an example):

[0062] Modal I: such as Figure 3 As shown in (a), the closed switch transistor Q 123 Q 124 Q 114 Q 113The remaining MOSFETs are disconnected. During this process, the entire battery module Pack1 discharges to winding Lp1, and the induced current increases from 0 to its maximum value.

[0063] Mode II: such as Figure 3 As shown in (b), the closed switch transistor Q 115 Q 12 Q 11 Q 125 Q 126 The remaining MOSFETs are disconnected. During this process, winding Lp1 releases the energy stored in mode I into battery module Pack1, thereby charging the entire battery module Pack1 (where Q... 116 (Always kept off to prevent reverse energy flow). During the heating process, the AC excitation is generated by the battery module itself, requiring no external power supply.

[0064] Mode III: This stage maintains the Mode II state, ensuring complete energy release in the inductor windings, ensuring the equalization circuit operates in DCM mode, and guaranteeing complete demagnetization of the transformer within one equalization cycle. This process generates alternating current in all series-connected cells of Pack1, achieving uniform heating of the entire module.

[0065] B. Active Balancing Mode: The balancing principle is based on flyback energy transfer using a multi-winding transformer. The system supports highly flexible energy paths, including intra-module and inter-module balancing.

[0066] B1. Intra-module inter-unit balancing (Cell to Cell, assuming B) 11 High battery level, B 12 Low battery, use B 11 To B 12 Transfer energy to achieve battery B 11 For battery B 12 (Taking charging equalization as an example)

[0067] Mode I (energy storage): such as Figure 4 As shown in (a), the closed switch transistor Q 11 Q 12 Q 122 Q 118 Q 117 Q 14 Q 13 The remaining MOSFETs are turned off. High-capacity battery B 11 When winding Lp1 is charged, the induced current increases from 0 to its maximum value.

[0068] Mode II (energy release): such as Figure 4 As shown in (b), the closed switch transistor Q 15 Q 16 Q122 Q 118 Q 117 Q 14 Q 13 The remaining MOSFETs are turned off. Winding Lp1 supplies power to the low-charge battery B. 12 During discharge, the induced current decreases from its maximum value to 0 (Q during this stage). 122 Always keep it off to prevent the reverse flow of energy.

[0069] Mode III (Demagnetization): This stage maintains the Mode II state, ensuring the circuit always operates in discontinuous mode and that the transformer is completely demagnetized after one equalization cycle. Energy is directly transferred from B. 11 Transfer to B 12 High efficiency.

[0070] B2. Intra-module and inter-module balancing (Cell to Pack, assuming B) 11 High battery level, with B 11 (Taking the transfer of energy to the entire battery module Pack1 to achieve discharge balancing as an example)

[0071] Modal I: such as Figure 5 As shown in (a), the closed switch transistor Q 11 Q 12 Q 122 Q 118 Q 117 Q 14 Q 13 The remaining MOSFETs are turned off. Single cell B 11 When the winding coil Lp1 is charged, the induced current increases from 0 to its maximum value.

[0072] Mode II: such as Figure 5 As shown in (b), the closed switch transistor Q 11 Q 12 Q 125 Q 126 Q 115 The remaining MOSFETs are turned off. The winding coil Lp1 releases energy to the entire battery module Pack1, and the induced current decreases from its maximum value to 0 (Q during this stage). 116 Always keep it off to prevent the reverse flow of energy.

[0073] Mode III: The switching state is the same as in Mode II. This mode allows the circuit to always operate in DCM mode, ensuring that the transformer is completely demagnetized after one equalization cycle. Similarly, Pack-to-Cell equalization can be achieved.

[0074] During the battery module balancing process, if B 11Low battery level, enabling the entire battery module to control individual battery cells B 11 The charging equalization process is similar to the discharging process, and will not be listed here.

[0075] B3. Pack to Pack Balancing: By controlling the switch array connected to the primary windings of two different modules, energy can be transferred directly from one module (such as Pack1) to another module (such as Pack2) via transformer magnetic coupling, or transferred through the secondary winding (System).

[0076] Equalization-AC self-heating integrated topology modeling analysis, taking the cell-to-cell equalization working mode as an example, the voltage V across the primary side inductor coil in mode I. L1 for:

[0077] ,

[0078] Where: i1 is the current in the discharge circuit of mode I, L p It is the magnetizing inductance of the primary side coil.

[0079] From Kirchhoff's laws:

[0080] ,

[0081] Where: i1(0) = 0, that is, the current is 0 at the initial moment; R p V is the equivalent resistance in the primary side circuit. Bi For a single-cell discharge battery, by solving the differential equation, we obtain:

[0082] ,

[0083] Substitute this formula into V L1 Zhongde:

[0084] ,

[0085] In mode II, the voltage V across the primary coil is... L1 for:

[0086] ,

[0087] Where: i2 is the current in the charging circuit of mode II, which, according to Kirchhoff's laws, is:

[0088] ,

[0089] Where: V Bi For a single rechargeable battery cell, i2(t0) = i1(t1) = i s By solving the differential equation, we obtain:

[0090] ,

[0091] Where: i2 is from the maximum value i s It begins to gradually decrease, after The formula for reducing it to 0 is as follows:

[0092] ,

[0093] ,

[0094] In Cell-to-cell equilibrium mode III, the following must be satisfied:

[0095] ,

[0096] Where: R s and L s For the secondary side resistance and magnetizing inductance, i p and i s t1 represents the equalization current on the primary and secondary sides, t2 represents the duration of mode II, t3 represents the end of mode I, t2 represents the end of mode II, and t3 represents the end of the entire equalization cycle.

[0097] Ensure the circuit operates in DCM discontinuous operation mode, so that the energy stored in the transformer windings is fully released within one equalization cycle.

[0098] Battery rapid heating modeling analysis:

[0099] In cold climates, when a battery is self-heated, the battery thermal model derived from Newton's law of cooling can be expressed as:

[0100] ,

[0101] Where m, c, s, and h represent the individual cell, specific heat capacity, surface area, and heat transfer coefficient of the battery, respectively; these parameters are determined by the battery itself and the environment. T, T0, and t represent the battery temperature, initial battery temperature, and time, respectively. P T The thermal power of a battery can be calculated using the following equation:

[0102] ,

[0103] Where: R b I is the internal resistance of the battery. rms Let be the effective value of the current. Substituting this into the above equation, we obtain the following expression for the battery temperature:

[0104] ,

[0105] The above equation is also the electrothermal model of the battery. From the equation, it can be seen that the battery temperature is greatly affected by the current; therefore, it can be adjusted by changing I. rms To adjust the heating speed.

[0106] Example 2

[0107] Please see the appendix Figure 6 A control method based on an integrated topology of battery equalization and AC self-heating based on electromagnetic induction is proposed. The control flow follows logical judgment and priority processing, and the specific steps are as follows:

[0108] S1. System Initialization and Signal Acquisition: After power-on, the system initializes all modules, and the signal acquisition and processing module begins to continuously acquire the voltage V of all battery cells. cell and temperature T cell And then send the data to the control unit.

[0109] S2. Voltage Consistency Judgment: The control unit calculates the maximum difference in voltage across all individual cells.

[0110] ΔV max Determine ΔV max Is it greater than the preset voltage equalization threshold V? th If the voltage is greater than the specified value, it is determined to be a voltage imbalance, and the balancing control in step S4 is executed first; if the voltage is not greater than the specified value, the temperature judgment in step S3 is performed. This step ensures the priority of power balancing and avoids exacerbating inconsistencies by heating when the power difference is too large. This invention prioritizes voltage imbalance over temperature imbalance as the control target, which not only conforms to the basic principles of battery safety and life protection, but also facilitates the synergistic realization of balancing and AC self-heating functions, thereby improving the overall system stability, energy utilization rate, and engineering practicality.

[0111] S3. Temperature Uniformity Assessment: The control unit calculates the maximum temperature difference among all individual units.

[0112] ΔT max Determine ΔT max Is it greater than the preset temperature equalization threshold T? th If the temperature is greater than the specified value, it is determined that the temperature is uneven. The battery cell with the lowest temperature is selected as the heating target, and step S5 is executed for directional heating. If the temperature is not greater than the specified value, it is determined that the battery pack temperature is uniform but the overall temperature may be low. The entire battery module that needs to be heated is selected as the heating target, and step S5 is executed.

[0113] S4. Balanced Control Execution: Based on voltage data, the control unit identifies the highest voltage cell (energy source) and the lowest voltage cell (energy receiver), and determines the optimal energy transfer path based on their locations. eq(e.g., Cell to Cell). Subsequently, a set of high-frequency PWM signals is generated. eq (For example, 50kHz), its duty cycle can be adjusted according to the voltage difference. PWM eq The switch array is controlled by the drive circuit to follow the selected path. eq The mode sequence switching achieves energy transfer. This process repeats until ΔV max Decrease to V th the following.

[0114] S5. Heating Control Execution: The control unit determines the heating strategy based on the selected heating target (individual unit or module) and the ambient temperature, and generates a set of low-frequency PWM signals. heat (e.g., 10-20kHz). By adjusting the PWM heat The frequency and duty cycle can control the effective value I of the heating current. rms This allows for direct adjustment of the heating power P. T (P) T = I rms 2 *R b ) PWM heat The control switch array enables the formation of an AC charging and discharging circuit between the heating target and the corresponding transformer winding. loop An alternating current is generated to heat the material until the target temperature is reached.

[0115] S6. Introduction of Intermediate Transition Mode: When switching from equalization mode to heating mode, the control unit first fixes the current PWM duty cycle and gradually reduces the equalization operating frequency over multiple control cycles, so that the transformer magnetizing current gradually decreases, avoiding core saturation or sudden energy release. By introducing a transition mode between equalization mode and AC self-heating mode, and adopting PWM duty cycle ramp adjustment, frequency gradual switching and current feedback constraint mechanism, this invention achieves smooth transition under multi-mode operation, effectively avoids sudden current and voltage changes, and improves the stability and reliability of system operation.

[0116] Table 1. Example of PWM parameter switching

[0117] Battery status PWM frequency PWM duty cycle Control Target <![CDATA[ΔV max >ΔV th T<T th ]]> 50kHz 50% Balanced priority <![CDATA[ΔV max <ΔV th T<T th ]]> 20kHz 80% decrease Rapid heating <![CDATA[ΔV max >ΔV th T>T th ]]> \ \ Protection shutdown

[0118] Example 3

[0119] To verify the effectiveness of the present invention, detailed simulation experiments were conducted.

[0120] I. Current waveform verification:

[0121] The battery used in the simulation has a nominal voltage of 3.65V, a rated capacity of 2.4Ah, an upper limit cutoff voltage of 5V, a nominal discharge current of 6.5A, a thermal internal resistance of 10C / W, and a buffer resistor of 10KΩ for the MOSFET used.

[0122] The initial temperature of the individual battery cell is set to -20℃, and the nominal ambient temperature is -20℃.

[0123] The transformer with a primary excitation inductance of 7.6uH was used. The control signal PWM frequency for the single-cell heating experiment was set to 20kHz with a duty cycle of 50%.

[0124] The parameters used in the experiment, such as inductance, battery terminal voltage, battery capacity, internal resistance of each circuit component, PWM signal frequency, and duty cycle, were input into the model. The simulated single-cell heating current waveform is shown below. Figure 7 As shown, the peak current is 7.6A. Among them, Figure 7 In the diagram, (a) represents the PWM waveform. Figure 7 In the diagram, (b) represents the corresponding current waveform.

[0125] The cell-to-cell equalization experiment was conducted with a PWM control signal frequency of 50kHz and a duty cycle of 50%. The simulated cell-to-cell equalization current waveform is shown below. Figure 8 As shown, the peak current is 4.4A. Among them, Figure 8 In the diagram, (a) represents the PWM waveform. Figure 8 In the diagram, (b) represents the corresponding current waveform.

[0126] The simulation experiments are used to analyze and predict the current variation and amplitude during the heating and equalization process, supporting the development of heating strategies.

[0127] II. Verification of Equalized Voltage Waveform:

[0128] In this embodiment, to verify the effectiveness of the proposed cell-to-cell energy balancing topology based on a multi-winding transformer, a battery pack balancing simulation experiment consisting of four series of lithium-ion batteries was conducted. The battery pack is composed of four individual cells connected in series, with initial voltages of 3.079V, 3.047V, 3.046V, and 3.021V, respectively. The maximum single-cell voltage difference is 58mV, and the initial total voltage of the battery pack is 12.193V.

[0129] Based on the initial state, it is known that there is a significant deviation in the consistency of individual cells within the battery pack. In particular, there is a significant voltage difference between the lowest voltage cell and the highest voltage cell. If this is not addressed, it will directly affect the battery pack's capacity utilization and charging / discharging safety.

[0130] During the simulation, the cell-to-cell (direct energy transfer) balancing mode proposed in this invention is adopted, which realizes the direct transfer of energy from high-voltage cells to low-voltage cells through the magnetic coupling path of multi-winding transformers. The control unit automatically selects the energy flow direction based on the cell voltage deviation and generates corresponding PWM drive signals based on the voltage difference and balancing strategy to drive the source-connected MOSFET switches of each cell, thereby gradually reducing the battery voltage difference.

[0131] During the balancing process, the flyback energy transfer process of each winding alternates, allowing the charge of the high-energy cells to be uniformly transferred to the low-energy cells in a distributed manner. Simulation results are as follows: Figure 9 As shown, as the equalization operation continues, the voltages of the four individual cells gradually become consistent, and the maximum voltage difference decreases continuously from the initial 58mV to eventually stabilize at around 1mV, thus achieving complete equalization.

[0132] Throughout the equalization process, the average voltage of the battery pack remained stable without significant fluctuations, indicating that the energy transfer process was smooth and reliable, without introducing significant additional ripple or surge current.

[0133] III. Verification of the effect of frequency on heating effect:

[0134] To investigate the influence of PWM frequency on the temperature rise characteristics of a battery during AC self-heating, this invention conducted experiments at an ambient temperature of -20℃. The battery was heated from -20℃ to 0℃, and the PWM drive signal frequencies were set to 10kHz, 20kHz, and 30kHz, respectively, while maintaining a consistent duty cycle. The experimental results of the battery temperature rise curves under each frequency condition are shown below. Figure 10 As shown.

[0135] Experimental results show that, within the tested frequency range, the battery's temperature rise rate is negatively correlated with the PWM frequency. At lower PWM frequencies, the amplitude of the AC excitation current generated inside the battery is larger, resulting in higher equivalent heating power and a faster temperature rise. Conversely, as the PWM frequency increases, the effective current in the battery heating coil decreases, leading to reduced heating efficiency and a slower temperature rise. Under the premise of ensuring system safety and device thermal stability, using a lower PWM frequency for AC self-heating can effectively improve the temperature rise rate of individual cells, allowing the battery to reach its suitable operating temperature range more quickly.

[0136] As can be seen from the above description, the embodiments of the present invention achieve the following technical effects:

[0137] This invention employs a multi-winding transformer to simultaneously address the imbalances within and between battery packs caused by battery inconsistencies, as well as the performance degradation of batteries at low temperatures. Without utilizing an external power source, it provides AC self-heating to the individual battery cells and the battery pack, rapidly bringing them to their normal operating temperature range while simultaneously performing a balancing function, thereby improving the energy utilization rate and power density of the battery pack.

[0138] This invention is small in size and low in cost. Heating each individual battery cell and the entire battery pack requires only one transformer winding; for additional battery cells, only a pair of MOSFETs needs to be added. This achieves self-heating and energy equalization of the entire battery pack and all battery cells. Heating of each battery cell and the overall battery pack can be achieved through a single transformer winding, eliminating the need for a separate heating module for each cell. When the number of battery cells increases or new battery cells are added, only a pair of MOSFETs needs to be added to the new cells, seamlessly expanding the system scale and achieving a low-cost, modular expansion method. Because no additional equalization circuit or heating structure is required, this invention has significant advantages in terms of material cost, PCB area, system weight, and wiring complexity, making it suitable for widespread application in various scenarios such as power batteries, energy storage power stations, and power tool batteries.

[0139] This invention enables AC self-heating of low-temperature batteries without an external power source, making it easy to integrate into battery packs. Furthermore, it achieves rapid heating and energy equalization of the battery pack without altering its internal structure or electrolyte. The system utilizes a multi-winding transformer and a switch array to circulate the stored energy within the battery cells in a controlled manner, generating an alternating current to achieve electromagnetic induction heating. This allows for rapid temperature rise even at -20°C or lower. The process requires no modification to the existing battery's internal structure, electrode materials, or electrolyte composition, and eliminates the need for additional components such as heating films or metal heating elements. Therefore, it is non-invasive and easily integrated into existing battery pack systems.

[0140] This invention allows for online adjustment of the heating rate by regulating the frequency and duty cycle of the control signal, making it suitable for various low-temperature environments. The control unit adaptively adjusts the drive signal parameters based on information such as the current battery temperature, ambient temperature, heating stage, and battery state estimation results, enabling precise controllability of the AC self-heating process. During the low-temperature start-up phase, a lower PWM frequency or a larger duty cycle can be used to obtain higher electromagnetic induction power, thereby rapidly increasing the battery temperature. When the battery temperature approaches the target range, the frequency can be increased or the duty cycle decreased to reduce the heating rate, achieving a smooth transition and avoiding overheating. Furthermore, both the frequency and duty cycle can be adjusted online, adapting to heating needs in different regions, seasons, and even extreme low-temperature environments without changing the hardware structure, significantly enhancing the system's environmental adaptability and flexibility.

[0141] This invention is applicable to various types and sizes of battery modules, and has high versatility and practicality: because the solution is based on a multi-winding transformer structure and modular switch array design, the functions of each winding do not interfere with each other, and the number of windings can be flexibly increased or decreased according to actual needs, thereby adapting to small-capacity single-cell batteries, small portable battery packs composed of several cells, to large power battery systems composed of dozens or even hundreds of cells connected in series and parallel.

[0142] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention is limited to these examples; within the framework of the invention, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of the different aspects of the invention as described above, which are not provided in detail for the sake of brevity.

[0143] This invention is intended to cover all such substitutions, modifications, and variations that fall within the broad scope of this specification. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A battery equalization-AC self-heating integrated topology based on electromagnetic induction, characterized in that, include: The battery pack consists of m battery modules connected in series, and each battery module contains n battery cells connected in series. The switching array consists of multiple MOSFET pairs, with each battery cell corresponding to a pair of MOSFETs, and the sources of the two MOSFETs in the MOSFET pair are interconnected. A multi-winding transformer includes m primary windings and one secondary winding. Each primary winding is connected to a corresponding battery module. The polarity of each primary winding is the same and opposite to that of the secondary winding connected to both ends of the entire battery module. The signal acquisition and processing module is used to acquire the voltage and temperature signals of individual battery cells and the current signals flowing through each winding of the multi-winding transformer, and convert them into digital signals. The control unit receives the digital signal and outputs a PWM control signal to the switch array to realize the selection and switching of equalization and heating modes; The driving circuit is used to amplify and isolate the PWM control signal to drive the MOSFETs in the switching array; The MOSFET pairs in the switch array are grouped by function, with odd-numbered battery cells connected to the top and bottom MOSFET groups, and even-numbered battery cells connected to the middle MOSFET group. Each primary winding of the multi-winding transformer and its corresponding battery module constitute an independent electrical port. By controlling the on and off of specific MOSFET pairs in the switching array, any single battery cell or any battery module in the battery pack can be connected to the primary winding corresponding to its electrical port. It also includes a control method for an integrated battery balancing-AC self-heating topology based on electromagnetic induction, used to control such a topology, comprising the following steps: The voltage and temperature signals of each battery cell are periodically acquired through the signal acquisition and processing module. The control unit determines whether the battery voltage difference exceeds the set range based on the voltage signal. If it does, it executes the equalization control mode; otherwise, it executes the temperature judgment. If the battery voltage difference is within the set range, the control unit determines whether the battery temperature difference exceeds the set range based on the temperature signal. If it does, it performs self-heating control on the low-temperature cell; otherwise, it performs self-heating control on the entire battery module and generates a second set of PWM signals. In the equalization control mode, the control unit selects the energy transfer path according to the voltage difference and outputs the corresponding first set of PWM signals to drive the switch array, so that the high-energy battery transfers energy to the low-energy battery. In the self-heating control mode, the control unit adjusts the carrier frequency and duty cycle of the second set of PWM signals, and controls the switch array to form an alternating current between the battery or module and the transformer winding, thereby achieving low-frequency AC self-heating.

2. A control method for an integrated topology of battery balancing and AC self-heating based on electromagnetic induction, characterized in that, The method for controlling the integrated topology of battery balancing and AC self-heating based on electromagnetic induction as described in claim 1 includes the following steps: The voltage and temperature signals of each battery cell are periodically acquired through the signal acquisition and processing module. The control unit determines whether the battery voltage difference exceeds the set range based on the voltage signal. If it does, it executes the equalization control mode; otherwise, it executes the temperature judgment. If the battery voltage difference is within the set range, the control unit determines whether the battery temperature difference exceeds the set range based on the temperature signal. If it does, it performs self-heating control on the low-temperature cell; otherwise, it performs self-heating control on the entire battery module and generates a second set of PWM signals. In the equalization control mode, the control unit selects the energy transfer path according to the voltage difference and outputs the corresponding first set of PWM signals to drive the switch array, so that the high-energy battery transfers energy to the low-energy battery. In the self-heating control mode, the control unit adjusts the carrier frequency and duty cycle of the second set of PWM signals, and controls the switch array to form an alternating current between the battery or module and the transformer winding, thereby achieving low-frequency AC self-heating.

3. The control method for an integrated topology of battery equalization-AC self-heating based on electromagnetic induction according to claim 2, characterized in that, The control unit identifies the highest voltage cell and the lowest voltage cell based on the voltage signal, and selects one from multiple energy transfer paths according to their relationship with the battery module, thereby generating a first set of PWM signals with a first frequency and a first duty cycle.

4. The control method for an integrated topology of battery equalization-AC self-heating based on electromagnetic induction according to claim 3, characterized in that, The various energy transfer paths include: transfer from the first cell to the second cell within the same battery module, transfer from the battery cell to the entire battery module to which it belongs, transfer from the battery module to a certain cell within it, transfer from one battery module to the entire battery pack, transfer from the entire battery pack to a certain battery module, and transfer from the first battery module to the second battery module.

5. The control method for an integrated topology of battery equalization-AC self-heating based on electromagnetic induction according to claim 4, characterized in that, After the first set of PWM signals is amplified by the drive circuit, it controls the on / off sequence of the corresponding MOSFET pairs in the switch array, so that energy is transferred from the battery cell or battery module with higher voltage to the battery cell or battery module with lower voltage through the multi-winding transformer.

6. The control method for an integrated topology of battery equalization-AC self-heating based on electromagnetic induction according to claim 4, characterized in that, The control unit dynamically adjusts the carrier frequency and duty cycle of the second PWM based on the temperature signal, the preset target temperature value, and the ambient temperature parameters.

7. The control method for an integrated topology of battery equalization-AC self-heating based on electromagnetic induction according to claim 4, characterized in that, After the second set of PWM signals is amplified by the drive circuit, it controls the on / off sequence of the corresponding MOSFET pairs in the switch array, so that a periodic alternating charging and discharging current loop is formed between the target heating battery module and the corresponding winding of the multi-winding transformer.

8. A battery management system, characterized in that, include: A battery balancing-AC self-heating integrated topology based on electromagnetic induction as described in claim 1; And a control unit and related software program configured to execute a control method based on an electromagnetic induction-based battery balancing-AC self-heating integrated topology as described in any one of claims 2-7.

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