Single battery state monitoring and active equalization system

Abstract

A single battery state monitoring and active equalization system belongs to the field of lithium ion battery management systems. The problem that the accuracy of state monitoring and the high efficiency and safety of equalization control cannot be realized cooperatively in an existing single battery monitoring and equalization method is solved. Each active equalization module is electrically connected with a single battery, all the active equalization modules are electrically connected with one another through a shared energy bus, and a main control module establishes communication connection with all the active equalization modules; the active equalization module receives the state estimation value transmitted by the main control module, and calculates the instantaneous internal loss power of the corresponding single battery in combination with the load state dynamic complex impedance and the equalization current amplitude; and when the instantaneous internal loss power is not less than the loss power threshold, adjusting the amplitude of the energy scheduling signal to reduce the equalizing current until the instantaneous internal loss power returns to a safety range, thereby realizing dynamic thermal protection of the single battery. The method is mainly used for single battery state monitoring and active equalization.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery management systems. Background Technology

[0002] As the core energy storage unit of new energy systems, the consistency of individual lithium-ion batteries directly affects the safety performance and lifespan of the battery pack. Battery management systems (BMS) need to correct differences in the state of charge (SOC) between individual cells through active balancing technology, while relying on precise battery SOC parameters for charge and discharge control. Traditional SOC monitoring and balancing control suffer from systemic defects such as low technical coupling and sluggish dynamic response.

[0003] Impedance detection techniques based on balanced current often struggle to eliminate coupling interference from the main energy transfer path to weak diagnostic signals, resulting in nonlinear errors in the acquired impedance parameters caused by current steps. Detection modes that directly superimpose disturbance signals disrupt the main circuit's operating modes, reduce energy dispatch efficiency, and high-frequency disturbances can easily trigger electromagnetic compatibility issues.

[0004] Current fixed-frequency impedance sensing methods cannot adapt to the transient fluctuations of equalization currents. Data collected under different polarization states suffers from phase ambiguity, limiting the accuracy of dynamic parameter modeling. Battery equivalent circuit model parameters cannot be corrected online, and changes in polarization characteristics due to battery aging can lead to cumulative errors in state-of-charge estimation.

[0005] Passive balancing schemes cannot actively optimize battery performance, while active balancing systems lack dynamic thermal constraint mechanisms during high-voltage differential and high-current balancing, leading to abnormal local temperature rises. The centralized state estimation algorithm of the main control unit struggles to respond promptly to the dynamic characteristic differences among multiple individual cells, and the global balancing strategy has an adaptation deviation from the actual operating conditions of individual cells, affecting the safe operation of the system. Summary of the Invention

[0006] This invention addresses the problem that existing battery cell monitoring and balancing methods cannot simultaneously achieve the accuracy of state monitoring and the efficiency and safety of balancing control. It provides a single-cell battery state monitoring and active balancing system.

[0007] The single-cell state monitoring and active balancing system described in this application includes:

[0008] At least one active balancing module, a shared energy bus, and a main control module;

[0009] Each battery pack to be monitored contains multiple individual battery cells;

[0010] Each active balancing module is electrically connected to a single battery cell, and all active balancing modules are electrically connected to each other through a shared energy bus. The main control module establishes a communication connection with all active balancing modules.

[0011] The active balancing module collects the voltage and current responses of the corresponding individual cells in real time, and uses the voltage and current responses to calculate the load-state dynamic complex impedance and near-equilibrium-state complex impedance of the corresponding individual cells, and transmits the near-equilibrium-state complex impedance to the main control module.

[0012] The main control module has a pre-set second-order RC equivalent circuit model for characterizing the electrochemical properties of the battery.

[0013] The main control module receives the near-equilibrium complex impedance uploaded by the active balancing module, uses the near-equilibrium complex impedance as the target value for parameter identification, adjusts the model parameters of the second-order RC equivalent circuit model through a recursive least squares algorithm, estimates the state of charge and heat transfer health of the single cell based on the adjusted model parameters, and transmits the state estimate to the corresponding active balancing module.

[0014] The active balancing module also receives the state estimate transmitted by the main control module, extracts the real part of the complex impedance of the load-state dynamic complex impedance, and calculates the instantaneous internal power loss of the corresponding single cell by combining the synchronously acquired balancing current amplitude. The instantaneous internal power loss is compared with a preset power loss threshold in real time. When the instantaneous internal power loss is not less than the power loss threshold, the amplitude of the energy dispatch signal is adjusted to reduce the balancing current until the instantaneous internal power loss returns to a safe range, thereby achieving dynamic thermal protection for the single cell.

[0015] Furthermore, in this invention, the active balancing module includes a power topology unit, a synchronization sensing unit, and a local control unit;

[0016] The power topology unit is a bidirectional DC-DC converter, whose input is connected to the local control unit of the corresponding single battery cell, and whose output is connected to the shared energy bus to perform bidirectional energy transfer.

[0017] The synchronous sensing unit includes a function for synchronously acquiring the instantaneous terminal voltage and equalization current of a single battery cell, and generating the voltage response and current response.

[0018] The local control unit is a digital signal processor that generates a total pulse width modulation signal containing energy dispatch signals and diagnostic injection signals. It receives the voltage and current responses generated by the synchronous sensing unit, calculates the load-state dynamic complex impedance and near-equilibrium-state complex impedance of the corresponding single cell, and obtains the instantaneous internal power loss by combining the state estimation value transmitted by the main control module. The instantaneous internal power loss is compared with a preset power loss threshold in real time. When the instantaneous internal power loss is not less than the power loss threshold, the amplitude of the energy dispatch signal is adjusted by the power topology unit to reduce the equalization current until the instantaneous internal power loss returns to a safe range, thereby achieving dynamic thermal protection for the single cell.

[0019] Furthermore, in this invention, the synchronous sensing unit includes: a voltage sensor, a current sensor, and a high-speed analog-to-digital converter; the voltage sensor and the current sensor are used to collect the instantaneous terminal voltage and current of the battery cell, and the high-speed analog-to-digital converter is used to convert the current and voltage into digital signals and send them out.

[0020] Furthermore, in this invention, the active balancing module uses a digital lock-in amplifier algorithm to calculate the load-state dynamic complex impedance and near-equilibrium-state complex impedance of the individual battery cell.

[0021] Furthermore, in this invention, the specific process by which the active balancing module calculates the load-state dynamic complex impedance and near-equilibrium-state complex impedance of the corresponding single cell is as follows:

[0022] The local control unit generates a total pulse width modulation signal containing energy dispatch signals and diagnostic injection signals, and outputs it to the power topology unit. The power topology unit generates an equalization current, and dynamically divides one cycle of the equalization operation into a peak polarization stage and a near-equilibrium stage according to the amplitude of the equalization current. A first frequency diagnostic disturbance source is applied in the peak polarization stage, and a second frequency diagnostic disturbance source is applied in the near-equilibrium stage, and the signals are output to the battery cells.

[0023] The voltage and current responses of individual battery cells at the corresponding stage are collected synchronously by the synchronous sensing unit. The local control unit calculates the load-state dynamic complex impedance and near-equilibrium state complex impedance of the corresponding individual battery cell based on the voltage and current responses at the corresponding stage.

[0024] Furthermore, in this invention, the peak polarization stage is the time interval during which the absolute value of the equilibrium current is not less than the peak current threshold, and the near-equilibrium stage is the time interval during which the absolute value of the equilibrium current is not greater than the near-zero current threshold.

[0025] Furthermore, in this invention, the power topology unit adopts a topology group that includes either a flyback converter topology or a Cook converter topology.

[0026] Furthermore, in this invention, the local control unit is implemented using a microcontroller, a digital signal processor, or a field-programmable gate array.

[0027] This invention seamlessly integrates battery dynamic parameter acquisition during active balancing by synchronously executing energy scheduling and disturbance injection. The total pulse width modulation signal is generated by the linear superposition of the energy scheduling signal and the diagnostic injection signal. The diagnostic injection signal is gated based on the transient characteristics of the balancing current to avoid interfering with the main energy transfer process, while simultaneously acquiring multi-band impedance response data to maintain balancing efficiency. By dynamically dividing the peak polarization stage and the near-equilibrium stage of the balancing current, differentiated modal excitation and data decoupling are achieved in impedance detection. The diagnostic disturbance signal injects sinusoidal excitations of different frequencies in stages, and the voltage and current responses of the corresponding stages are obtained in combination with the synchronous acquisition circuit. The complex impedance parameters of the near-equilibrium state and the load state are calculated separately to eliminate cross-interference between transient current and steady-state excitation, providing high-precision dynamic parameters for state estimation. Multi-dimensional joint optimization is achieved by online correction of the state estimation model and closed-loop constraint balancing strength. The robustness of the state of charge estimation is improved by real-time recursive parameter identification based on the near-equilibrium state complex impedance, while an adaptive limiting mechanism for the balancing current is formed based on the instantaneous power loss monitoring of the load state complex impedance, establishing an optimal balance between energy transfer efficiency and battery operation safety. Attached Figure Description

[0028] Figure 1 This is a block diagram illustrating the system principle of the present invention.

[0029] Figure 2 This is a flowchart of the single-cell state monitoring and active balancing method in a specific embodiment. Detailed Implementation

[0030] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of the present invention can be combined with each other.

[0031] Specific Implementation Method 1: Combination Figure 1 This embodiment describes a single-cell state monitoring and active balancing system, which includes:

[0032] At least one active balancing module 30, a shared energy bus, and a main control module 40;

[0033] Each battery pack 20 to be monitored contains multiple individual cells;

[0034] Each active balancing module 30 is electrically connected to a single battery cell, and all active balancing modules 30 are electrically connected to each other through a shared energy bus. The main control module 40 establishes a communication connection with all active balancing modules 30.

[0035] The active balancing module 30 collects the voltage and current responses of the corresponding individual cells in real time, and uses the voltage and current responses to calculate the load-state dynamic complex impedance and near-equilibrium state complex impedance of the corresponding individual cells, and transmits the near-equilibrium state complex impedance to the main control module 40.

[0036] The main control module 40 has a pre-set second-order RC equivalent circuit model for characterizing the electrochemical properties of the battery.

[0037] The main control module 40 receives the near-equilibrium complex impedance uploaded by the active balancing module 30, uses the near-equilibrium complex impedance as the target value for parameter identification, adjusts the model parameters of the second-order RC equivalent circuit model through a recursive least squares algorithm, estimates the state of charge and heat transfer health of the single cell based on the adjusted model parameters, and transmits the state estimate to the corresponding active balancing module 30.

[0038] The active balancing module 30 also receives the state estimate value transmitted by the main control module 40, extracts the real part of the complex impedance of the load-state dynamic complex impedance, and calculates the instantaneous internal power loss of the corresponding single cell by combining the synchronously acquired balancing current amplitude. The instantaneous internal power loss is compared with a preset power loss threshold in real time. When the instantaneous internal power loss is not less than the power loss threshold, the amplitude of the energy dispatch signal is adjusted to reduce the balancing current until the instantaneous internal power loss returns to a safe range, thereby achieving dynamic thermal protection for the single cell.

[0039] Furthermore, in this invention, the active balancing module 30 includes a power topology unit 33, a synchronization sensing unit 31, and a local control unit 32;

[0040] The power topology unit 33 is a bidirectional DC-DC converter. Its input terminal is connected to the local control unit 32 of the corresponding single cell, and its output terminal is connected to the shared energy bus to perform bidirectional energy transfer.

[0041] The synchronous sensing unit 31 includes a function for synchronously acquiring the instantaneous terminal voltage and equalization current of a single battery cell, and generating the voltage response and current response.

[0042] The local control unit 32 is a digital signal processor that generates a total pulse width modulation signal containing an energy dispatch signal and a diagnostic injection signal. It receives the voltage response and current response generated by the synchronization sensing unit 31, calculates the load-state dynamic complex impedance and near-equilibrium-state complex impedance of the corresponding single cell, and obtains the instantaneous internal power loss by combining the state estimation value transmitted by the main control module. The instantaneous internal power loss is compared with a preset power loss threshold in real time. When the instantaneous internal power loss is not less than the power loss threshold, the amplitude of the energy dispatch signal is adjusted by the power topology unit 33 to reduce the balancing current until the instantaneous internal power loss returns to a safe range, thereby achieving dynamic thermal protection for the single cell.

[0043] Furthermore, in this invention, the synchronous sensing unit 31 includes: a voltage sensor, a current sensor, and a high-speed analog-to-digital converter; the voltage sensor and the current sensor are used to collect the instantaneous terminal voltage and current of the battery cell, and the high-speed analog-to-digital converter is used to convert the current and voltage into digital signals and send them out.

[0044] Furthermore, in this invention, the active balancing module 30 uses a digital lock-in amplifier algorithm to calculate the load-state dynamic complex impedance and near-equilibrium-state complex impedance of the individual battery cell.

[0045] Furthermore, in this invention, the active balancing module 30 calculates the load-state dynamic complex impedance and near-equilibrium-state complex impedance of the corresponding single cell as follows:

[0046] The local control unit 32 generates a total pulse width modulation signal containing energy dispatch signals and diagnostic injection signals, and outputs it to the power topology unit 33. The power topology unit 33 generates an equalization current and dynamically divides one cycle of the equalization operation into a peak polarization stage and a near-equilibrium stage according to the amplitude of the equalization current. A first frequency diagnostic disturbance source is applied in the peak polarization stage and a second frequency diagnostic disturbance source is applied in the near-equilibrium stage, and the signals are output to the battery cells.

[0047] The voltage and current responses of the battery cells at the corresponding stage are synchronously collected by the synchronous sensing unit 31, and the local control unit 32 calculates the load-state dynamic complex impedance and near-equilibrium state complex impedance of the corresponding battery cell based on the voltage and current responses at the corresponding stage.

[0048] Furthermore, in this invention, the peak polarization stage is the time interval during which the absolute value of the equilibrium current is not less than the peak current threshold, and the near-equilibrium stage is the time interval during which the absolute value of the equilibrium current is not greater than the near-zero current threshold.

[0049] Furthermore, in this invention, the power topology unit 33 adopts a topology group that includes either a flyback converter topology or a Cook converter topology.

[0050] Furthermore, in this invention, the local control unit 32 is implemented using a microcontroller, a digital signal processor, or a field-programmable gate array.

[0051] The active balancing module 30 of this invention performs dynamic characteristic diagnosis of individual battery cells simultaneously while executing energy scheduling. The active balancing module 30 generates a total pulse width modulation duty cycle signal, which is a linear superposition of an energy scheduling signal and a diagnostic injection signal. The energy scheduling signal is used to control the energy transfer between the active balancing module 30 and the shared energy bus, and the diagnostic injection signal is used to excite the impedance response of the individual battery cells.

[0052] The active balancing module 30 monitors the balancing current generated by the energy dispatch signal in real time. Based on the amplitude of the balancing current, the active balancing module 30 dynamically divides one cycle of the balancing operation into at least two transient phases: a peak polarization phase and a near-equilibrium phase. The peak polarization phase is defined as the time interval during which the absolute value of the balancing current is not less than a peak current threshold. The near-equilibrium phase is defined as the time interval during which the absolute value of the balancing current is not greater than a near-zero current threshold.

[0053] The diagnostic injection signal is synthesized from two independent diagnostic perturbation sources and a gating mechanism. The active equalization module 30 applies a first diagnostic perturbation source during the peak polarization phase and a second diagnostic perturbation source during the near-equilibrium phase. The first and second diagnostic perturbation sources have different diagnostic frequencies.

[0054] The synchronous sensing unit 31 inside the active balancing module 30 synchronously collects the instantaneous terminal voltage and instantaneous current of a single cell during the peak polarization stage and the near-equilibrium stage, respectively, to form a voltage and current response.

[0055] The local control unit 32 of the active balancing module 30 processes the acquired voltage and current responses. The local control unit 32 calculates a load-state dynamic complex impedance using the response acquired during the peak polarization phase and a near-equilibrium-state complex impedance using the response acquired during the near-equilibrium phase. In one embodiment, the calculations are performed using a digital lock-in amplifier algorithm.

[0056] The system and method provided by this invention utilize the two separate complex impedance parameters to perform a dual-loop control that integrates state estimation and transient constraints.

[0057] In the first loop (state monitoring loop), the active balancing module 30 uploads the calculated near-equilibrium complex impedance to the main control module 40. The main control module 40 uses this near-equilibrium complex impedance as a target value and, through a recursive least squares algorithm, adjusts the model parameters of a second-order RC equivalent circuit model within itself in real time. The updated model parameters are then used in a battery state estimation algorithm to estimate the state of charge and health of the individual battery cells.

[0058] In the second loop (transient constraint loop), the load-state dynamic complex impedance is used for local control of the active balancing module 30. The active balancing module 30 uses the real part of the load-state dynamic complex impedance and the amplitude of the balancing current to calculate an instantaneous internal power loss in real time. The active balancing module 30 compares the instantaneous internal power loss with a power loss threshold. When the instantaneous internal power loss is not less than the power loss threshold, the active balancing module 30 automatically adjusts the energy dispatch signal to reduce the amplitude of the balancing current, thereby forming a closed-loop constraint on the internal heat loss of a single battery cell during the balancing process.

[0059] In one embodiment, the local control unit 32 of the active equalization module 30 generates a total pulse width modulation duty cycle signal to control the power switch within the active equalization module 30. This signal is represented by the following formula:

[0060] ;

[0061] in: Indicates at time Total pulse width modulation duty cycle signal; This represents the energy dispatch signal, which is a reference duty cycle used to control the active equalization module 30 to perform macroscopic energy transfer. The amplitude and polarity of the signal determine the equalization current. Size and direction; This indicates a diagnostic injection signal, which is a perturbation signal used to excite the impedance response of a single cell.

[0062] Diagnostic injection signal The application of the equalizing current is subject to the action of the equalizing current. Gating control is determined by the transient characteristics of the signal. The active balancing module 30 monitors the balancing current in real time. The waveform is obtained, and based on the current amplitude, one cycle of the equalization operation is divided into at least two transient phases: a peak polarization phase. and a near-equilibrium phase .

[0063] Peak polarization phase Defined as equalization current The absolute value is not less than a peak current threshold. The time interval. Near-equilibrium phase. Defined as equalization current The absolute value is not greater than a near-zero current threshold. The time interval.

[0064] In one embodiment, diagnostic injection signal It is synthesized from two independent diagnostic disturbance sources and one gating mechanism. This synthesis process is represented by the following formula:

[0065] ;

[0066] in: . Indicates a diagnostic injection signal; This indicates the first diagnostic disturbance source; the signal is a frequency of... A sinusoidal signal; This indicates the second diagnostic disturbance source; the signal is a frequency of... A sinusoidal signal; Represents the first gating function, when time... In the peak polarization stage At one time, the function value is 1; at other times, the function value is 0. This represents the second gating function, when time... In near-equilibrium stage At a given time, the function value is 1; at other times, the function value is 0.

[0067] After performing the disturbance injection, the active equalization module 30, through the synchronous sensing unit 31 inside the active equalization module 30, during the peak polarization phase... and near-equilibrium phase Synchronous acquisition of instantaneous terminal voltage of individual cells and instantaneous current .

[0068] The active equalization module 30 uses the collected signals to achieve near-equilibrium phase. A near-equilibrium complex impedance is calculated. This complex impedance is expressed by the following formula:

[0069] ;

[0070] in: Indicates the frequency of diagnosis The near-equilibrium complex impedance measured below; Indicates the near-equilibrium stage Internally, due to diagnostic disturbances Caused by, in frequency Complex voltage response under these conditions; Indicates the near-equilibrium stage Internally, due to diagnostic disturbances Caused by, in frequency The complex current response under [condition].

[0071] Meanwhile, the active equalization module 30 utilizes the collected signal during the peak polarization phase. A dynamic complex impedance under load conditions is calculated. This complex impedance is expressed by the following formula:

[0072] ;

[0073] in: Indicates the frequency of diagnosis The dynamic complex impedance under load conditions measured below; Indicating peak polarization phase Internally, due to diagnostic disturbances Caused by, in frequency Complex voltage response under these conditions; Indicating peak polarization phase Internally, due to diagnostic disturbances Caused by, in frequency The complex current response under [condition].

[0074] The main control module 40 receives the data calculated and uploaded by the active equalization module 30. and .

[0075] The main control module 40 utilizes near-equilibrium complex impedance. The real and imaginary parts are updated in real time to update the parameters of the battery model inside the main control module 40, which is used to estimate the battery charging state and health state, and to correct parameter drift caused by battery aging or temperature changes.

[0076] The active balancing module 30 utilizes load-state dynamic complex impedance. The real part, i.e. A calculation model for instantaneous internal loss is established. This model is expressed by the following formula:

[0077] ;

[0078] in: Indicates at time Instantaneous internal power loss; Indicates at time The macroscopic equilibrium current amplitude; Represents the dynamic complex impedance under load conditions. The real part.

[0079] The active balancing module 30 calculates the instantaneous internal power loss. With a preset power loss threshold Compare. If Not less than The active equalization module 30 will immediately adjust the energy dispatch signal in the total pulse width modulation duty cycle signal formula. This reduces the balancing current. The amplitude, until Less than This mechanism forms a local feedback loop for constraining the equilibrium strength.

[0080] This invention provides a single-cell battery state monitoring and active balancing system 10. The active balancing system 10 includes a battery pack 20, one or more active balancing modules 30, a main control module 40, and a shared energy bus 50.

[0081] The battery pack 20 contains multiple individual battery cells.

[0082] The number of active balancing modules 30 in the active balancing system 10 corresponds to the number of individual cells in the battery pack 20. Each active balancing module 30 establishes an electrical connection with one individual cell in the battery pack 20.

[0083] Each active balancing module 30 is electrically connected to each other via a shared energy bus 50. The shared energy bus 50 is used to transfer energy between different active balancing modules 30.

[0084] The main control module 40 establishes a communication connection with each active balancing module 30. This communication connection is used for the main control module 40 to send control commands to the active balancing module 30, and for the active balancing module 30 to upload data to the main control module 40.

[0085] See attached document Figure 1 The active balancing module 30 includes a power topology unit 33, a local control unit 32, and a synchronous sensing unit 31.

[0086] Power topology unit 33 is a bidirectional DC-DC converter circuit. In one embodiment, this circuit employs a flyback converter topology. In another embodiment, this circuit employs a Cook converter topology. Power topology unit 33 includes power switching elements, inductor elements, and capacitor elements. One end of power topology unit 33 is connected to the electrode of a single battery cell, and the other end is connected to the shared power bus 50.

[0087] The local control unit 32 is a processing unit. In one embodiment, the processing unit is a microcontroller. In another embodiment, the processing unit is a digital signal processor. In yet another embodiment, the processing unit is a field-programmable gate array (FPGA). The local control unit 32 is connected to the control terminal of the power switching element of the power topology unit 33. The local control unit 32 is used to generate pulse-width modulated signals to drive the power switching element. The local control unit 32 is also used to execute algorithms for signal injection, data acquisition, and parameter demodulation.

[0088] The synchronous sensing unit 31 includes a current sensor and a voltage sensor. In one embodiment, the current sensor is a sampling resistor connected in series in the current path. In another embodiment, the voltage sensor includes an isolation amplifier.

[0089] The synchronous sensing unit 31 also includes an analog-to-digital converter. The input terminal of the synchronous sensing unit 31 is connected in parallel with the two ends of the individual battery cell to collect instantaneous terminal voltage. It is also connected in series with the current path of a single cell to collect instantaneous current. .

[0090] The output of the synchronous sensing unit 31 is connected to the local control unit 32 to provide digitized voltage and current data. The local control unit 32 controls the sampling time of the synchronous sensing unit 31, and this control operation realizes the synchronous acquisition of voltage and current data.

[0091] See attached document Figure 1 The main control module 40 is a central processing unit.

[0092] In one embodiment, the main control module 40 includes a processor, a storage unit, and a communication interface.

[0093] The main control module 40 is responsible for formulating a macro-level balancing strategy, which determines which individual cells need to receive energy and which individual cells need to provide energy.

[0094] The main control module 40 also includes functions such as running algorithms to estimate the battery's state of charge and health.

[0095] The main control module 40 receives and processes the near-equilibrium complex impedance data uploaded from each active equalization module 30. and load-state dynamic complex impedance data.

[0096] The main control module 40 generates control commands based on the results of the equilibrium strategy and state estimation algorithm.

[0097] The main control module 40 sends control commands to one or more designated active equalization modules 30 through its communication interface. In one embodiment, the communication interface is a controller area network bus transceiver.

[0098] See attached document Figure 1 In the active balancing system 10, each individual cell within the battery pack 20 is electrically connected to a corresponding active balancing module 30. This connection is used for energy transfer and signal application and acquisition.

[0099] All active balancing modules 30 within the active balancing system 10 are electrically connected to the shared energy bus 50. This connection is used to transfer balancing energy between different active balancing modules 30.

[0100] The main control module 40 establishes a communication connection with each active balancing module 30 in the active balancing system 10.

[0101] This communication connection is used for the main control module 40 to transmit control commands to the active equalization module 30, and for the active equalization module 30 to transmit data to the main control module 40, including near-equilibrium complex impedance. and load-state dynamic complex impedance .

[0102] See attached document Figure 2 , Figure 2 This is a flowchart of a single-cell state monitoring and active balancing method according to an embodiment of the present invention. The present invention provides a single-cell state monitoring and active balancing method. This method is an active balancing method that integrates transient synchronous diagnostics.

[0103] The core steps of this method include: the active equalization module 30 generating a total pulse width modulation duty cycle signal. This signal contains energy dispatch signals for macroscopic energy transfer. Diagnostic injection signal used to excite impedance response .

[0104] Next, the active balancing module 30 monitors the energy dispatch signal. The generated equalization current The waveform was used to identify the peak polarization phase of the equalization current. and near-equilibrium phase .

[0105] Active equalization module 30 during the identified peak polarization stage and near-equilibrium phase Diagnostic injection signals were applied synchronously, respectively. .

[0106] Then, the active balancing module 30 synchronously collects the voltage and current responses of individual cells and calculates two complex impedance parameters: one for the near-equilibrium stage. The obtained near-equilibrium complex impedance The other is during the peak polarization phase. The obtained load-state dynamic complex impedance .

[0107] Finally, the active balancing system 10 uses the two obtained complex impedance parameters to perform fusion control and state estimation. (Near-equilibrium complex impedance) Model parameters used to correct the battery state estimation algorithm in the main control module 40. Load-state dynamic complex impedance. Used to constrain the magnitude of the balancing current in real time in the active balancing module 30.

[0108] See attached document Figure 2 This invention provides a method for monitoring and actively balancing the state of a single battery cell, which includes the following steps:

[0109] Step S201: Generate a dual-mode pulse width modulation control signal. The local control unit 32 of the active equalization module 30 generates a total pulse width modulation duty cycle signal. This signal is generated by the energy dispatch signal. With diagnostic injection signal It is formed by linear superposition and conforms to the definition of the total pulse width modulation duty cycle signal formula mentioned above.

[0110] Step S202: Identify the transient phase of the balancing current. The local control unit 32 of the active balancing module 30 analyzes the balancing current collected by the synchronization sensing unit 31 in real time. The local control unit 32 will The absolute value of the peak current threshold and a near-zero current threshold By comparing the peak polarization stages, the peak polarization phase can be identified. and near-equilibrium stage .

[0111] Step S203: Perform transient synchronization disturbance injection. The local control unit 32 uses the phase information identified in step S202 to control the diagnostic injection signal. The application of [something] during the peak polarization phase. The first diagnostic disturbance source Injection. During the near-equilibrium phase. The second diagnostic disturbance source Injection. This process conforms to the definition of the aforementioned diagnostic injection signal formula.

[0112] Step S204: Demodulate and separate transient impedance parameters. The local control unit 32 of the active equalization module 30 processes the instantaneous terminal voltages synchronously acquired at different transient stages. and instantaneous current Local control units 32 pairs are in the near-equilibrium phase. The acquired data is digitally phase-locked demodulated to calculate the near-equilibrium complex impedance. This calculation conforms to the aforementioned near-equilibrium complex impedance formula. Local control unit 32 operates during the peak polarization phase. The acquired data is digitally phase-locked demodulated to calculate the dynamic complex impedance under load conditions. This calculation conforms to the aforementioned dynamic complex impedance formula under load conditions. After the calculation is completed, the active balancing module 30 uploads the two complex impedance parameters to the main control module 40.

[0113] Step S205: Perform fusion control and state estimation. This step includes two processing loops. First, the main control module 40 utilizes the received near-equilibrium complex impedance. The main control module 40 updates the model parameters of its internal battery state estimation algorithm online. Secondly, the local control unit 32 of the active balancing module 30 utilizes load-state dynamic complex impedance... The real part is used to calculate the instantaneous internal power loss. This calculation conforms to the aforementioned formula for calculating instantaneous internal losses. The local control unit 32 will... With a preset power loss threshold In comparison, when Not less than At that time, the energy dispatch signal is automatically adjusted. To limit the balancing current.

[0114] See attached document Figure 1 and attached Figure 2 This section details step S201: generating a dual-mode pulse width modulation control signal.

[0115] The local control unit 32 of the active balancing module 30 generates an energy dispatch signal based on the balancing command received from the main control module 40. The signal is a reference duty cycle. The amplitude and polarity of the signal determine the rate and direction at which the active equalization module 30 extracts or injects energy into a single cell, thereby controlling the equalization current. Macro-level behavior.

[0116] The local control unit 32 simultaneously generates a diagnostic injection signal. This signal is a high-frequency, small-amplitude disturbance signal. The application of this diagnostic injection signal is gate-controlled, and the gate signal originates from the equalization current. The identification results during the transient phase.

[0117] Inside the local control unit 32, the energy dispatch signal is processed through digital addition. With diagnostic injection signal The signals are superimposed to synthesize a total pulse width modulation duty cycle signal. This signal is ultimately sent to the pulse width modulation generator of the local control unit 32 to drive the power switching elements in the power topology unit 33. This synthesis relationship is expressed by the following formula:

[0118] ;

[0119] in: Indicates at time Total pulse width modulation duty cycle signal; This represents the energy dispatch signal, which is a reference duty cycle used to control the active equalization module 30 to perform macroscopic energy transfer. The amplitude and polarity of the signal determine the equalization current. Size and direction; This indicates a diagnostic injection signal, which is a perturbation signal used to excite the impedance response of a single cell.

[0120] See attached document Figure 2 This section details step S202: identifying the transient phase of the equalization current.

[0121] The local control unit 32 of the active balancing module 30 continuously receives and processes the balancing current from the synchronization sensing unit 31. Digital signals.

[0122] Local control unit 32 will balance the current The absolute value of the peak current threshold stored in the internal memory of the local control unit 32. Perform real-time comparison. When balancing current... The absolute value is not less than the peak current threshold. At that time, the local control unit 32 identifies the current time interval as the peak polarization phase. .

[0123] Local control unit 32 will balance the current The absolute value and a near-zero current threshold stored in the internal memory of the local control unit 32 Perform real-time comparison. When balancing current... The absolute value is not greater than the near-zero current threshold. At that time, the local control unit 32 identifies the current time interval as a near-equilibrium phase. .

[0124] In one embodiment, the local control unit 32 detects the equalization current by executing a digital signal processing algorithm. The peak points and zero-crossing points of the waveform. The time interval around the peak point is identified as the peak polarization phase. The time interval around the zero point is identified as the near-equilibrium phase. .

[0125] The local control unit 32 will identify the stage information, namely the peak polarization stage. and near-equilibrium stage Generate the corresponding gating signal for use in step S203.

[0126] See attached document Figure 2 This section details step S203: performing transient synchronization perturbation injection.

[0127] The local control unit 32 of the active equalization module 30 controls the injection of diagnostic disturbance sources using the gating signal generated in step S202. The local control unit 32 internally generates two independent diagnostic disturbance sources, namely the first diagnostic disturbance source. Second diagnostic disturbance source In one embodiment, both diagnostic disturbance sources are sinusoidal signals with frequencies of [missing information]. and .

[0128] The local control unit 32 performs a gated synthesis operation. When the stage identified in step S202 is the peak polarization stage... At that time, the local control unit 32 will diagnose the first disturbance source. As an injection signal. When the identified stage is near equilibrium. At that time, the local control unit 32 will identify the second diagnostic disturbance source. As an injection signal.

[0129] This gating synthesis operation is implemented in the local control unit 32 using the following formula, ultimately generating a diagnostic injection signal. .

[0130] ;

[0131] in: Indicates diagnostic injection signal; The first diagnostic disturbance source is indicated; this signal is a frequency of A sinusoidal signal; This indicates the second diagnostic disturbance source; this signal is a frequency of A sinusoidal signal; Represents the first gating function, when time... In the peak polarization stage At one time, the function value is 1; at other times, the function value is 0. This represents the second gating function, when time... In near-equilibrium stage At a given time, the function value is 1; at other times, the function value is 0.

[0132] Generated diagnostic injection signal It was subsequently used to synthesize the total pulse width modulation duty cycle signal. As shown in step S201.

[0133] See attached document Figure 1 and attached Figure 2 This section details the first stage of step S204: synchronous signal acquisition and preprocessing.

[0134] The local control unit 32 of the active equalization module 30 generates a synchronous sampling trigger signal based on its internal pulse width modulation timer. The time base of this synchronous sampling trigger signal is the same as the total pulse width modulation duty cycle signal generated in step S201. The time base is strictly synchronized.

[0135] This synchronous sampling trigger signal is sent to the synchronous sensing unit 31 inside the active equalization module 30. Upon receiving each synchronous sampling trigger signal, the synchronous sensing unit 31 uses its voltage and current sensors to measure the instantaneous terminal voltage of the individual battery cells. and instantaneous current Perform a synchronous sampling.

[0136] The analog-to-digital converter inside the synchronous sensing unit 31 will collect the instantaneous terminal voltage. and instantaneous current The analog values ​​are converted into digital data and transmitted to the local control unit 32.

[0137] After receiving the digital data streams of voltage and current, the local control unit 32 performs preprocessing on the data. The preprocessing includes a digital bandpass filter operation. The passband of this digital bandpass filter is set to the frequency surrounding the currently injected diagnostic disturbance source, i.e. or .

[0138] The purpose of this filtering operation is to separate the diagnostic injection signal from the acquired signal. The resulting small voltage and current response, while suppressing the energy dispatch signal The generated low-frequency large signal components and measurement noise are processed. The processed data is stored in the storage unit of the local control unit 32 for subsequent demodulation calculations.

[0139] See attached document Figure 1 and attached Figure 2 This section elaborates on the principle of the digital lock-in amplifier algorithm used in step S204 for demodulating and separating transient impedance parameters.

[0140] The local control unit 32 of the active equalization module 30 executes a digital lock-in amplifier algorithm to calculate the instantaneous terminal voltage that has been preprocessed in the aforementioned signal acquisition and preprocessing steps. and instantaneous current The complex representation of the data stream at a specified diagnostic frequency.

[0141] This algorithm is executed internally by the local control unit 32. First, the local control unit 32 generates two digital reference signals internally: one is a sinusoidal reference signal that is in phase and frequency with the source of the diagnostic disturbance. The other path is a cosine reference signal orthogonal to it. The frequency of the reference signal is ,this Corresponding to the peak polarization stage of Or near-equilibrium stage of .

[0142] Subsequently, the local control unit 32 multiplies the preprocessed input signal, i.e., the voltage response signal or the current response signal, with the sine reference signal and the cosine reference signal point by point.

[0143] Then, the local control unit 32 performs a low-pass filtering operation on each of the two resulting product signals. In one embodiment, this low-pass filtering operation is achieved by integration or summation averaging over one or more diagnostic signal periods. The purpose of this operation is to extract the DC component from the product signals.

[0144] The result of integration or summation averaging is two scalar values: the in-phase component X and the quadrature component Y. These two components correspond to the input signal at the diagnostic frequency, respectively. The real and imaginary parts of the complex number representation below. This process converts the voltage response signal... Convert to complex voltage and the current response signal Convert to complex current .

[0145] Finally, the local control unit 32 calculates the complex impedance by performing complex division. For example, for near-equilibrium complex impedance... The calculation process conforms to the aforementioned near-equilibrium state complex impedance formula. For the load-state dynamic complex impedance... The calculation process conforms to the aforementioned dynamic complex impedance formula under load conditions.

[0146] See attached document Figure 1 and attached Figure 2 This section details the core calculation and separation process of step S204.

[0147] The local control unit 32 of the active balancing module 30 performs separate complex impedance calculations on the voltage and current data collected and preprocessed at the corresponding stages, based on the different transient stages identified in step S202.

[0148] For the near-equilibrium stage The collected data is used by the local control unit 32 to call the digital lock-in amplifier algorithm. The algorithm uses a second diagnostic disturbance source. frequency As a reference frequency, the algorithm processes the voltage response signal during this stage to obtain the complex voltage. Simultaneously, the current response signal during this stage is processed to obtain the complex current. Subsequently, the local control unit 32 calculates the near-equilibrium complex impedance by performing complex division. This calculation process is represented by the following formula:

[0149] ;

[0150] in: Indicates the frequency of diagnosis The near-equilibrium complex impedance measured below; Indicates the near-equilibrium stage Internally, due to diagnostic disturbances Caused by, in frequency Complex voltage response under these conditions; Indicates the near-equilibrium stage Internally, due to diagnostic disturbances Caused by, in frequency The complex current response under [condition].

[0151] For the peak polarization phase The collected data is used by the local control unit 32 to call the digital lock-in amplifier algorithm. The algorithm uses the first diagnostic disturbance source. frequency As a reference frequency, the algorithm processes the voltage response signal during this stage to obtain the complex electrical signal. Simultaneously, the current response signal during this stage is processed to obtain the complex current. Subsequently, the local control unit 32 calculates the load-state dynamic complex impedance by performing complex division. This calculation process is represented by the following formula:

[0152] ;

[0153] in: Indicates the frequency of diagnosis The dynamic complex impedance under load conditions measured below; Indicating peak polarization phase Internally, due to diagnostic disturbances Caused by, in frequency Complex voltage response under these conditions; Indicating peak polarization phase Internally, due to diagnostic disturbances Caused by, in frequency The complex current response under [condition].

[0154] Due to near-equilibrium complex impedance With load-state dynamic complex impedance The calculations are performed in two time-separated windows ( and The diagnostics were performed within the specified timeframe and at independent diagnostic frequencies. and Therefore, the impedance parameters under two different states can be measured separately.

[0155] After the calculation is completed, the active balancing module 30 will have a near-equilibrium complex impedance. and load-state dynamic complex impedance The calculation results are uploaded to the main control module 40 via the communication interface.

[0156] See attached document Figure 1 and Figure 2 This section elaborates on step S205, based on the near-equilibrium complex impedance. The condition monitoring model corrects the loop.

[0157] The main control module 40 receives data uploaded by each active balancing module 30 during the near-balancing phase. Measured near-equilibrium complex impedance data.

[0158] The main control module 40 internally runs a battery state estimation algorithm, which calculates the battery state based on a battery equivalent circuit model. In one embodiment, this equivalent circuit model is a first-order RC model, and the theoretical complex impedance of this model is... The calculation method is as follows:

[0159] ;

[0160] in: Represents the equivalent circuit model at frequency Theoretical complex impedance; This represents the ohmic internal resistance of the model; This represents the polarization resistance of the model; Represents the polarization capacitance of the model; Indicates frequency; It represents the imaginary unit.

[0161] The main control module 40 executes a parameter identification process. During this process, the module will process the received measurement values... As the target value, the model parameters are adjusted using a parameter identification algorithm. , , The value makes the diagnostic frequency Theoretical complex impedance calculated below With measured value The error between them is minimized. This process enables online updates of the battery model parameters.

[0162] Updated model parameters , , The battery state estimation algorithm is applied in real time to the main control module 40. This operation enables the battery model used by the estimation algorithm to reflect the dynamic characteristics of individual cells caused by changes in temperature, aging, and state of charge, thereby improving the accuracy of battery state estimation.

[0163] See attached document Figure 1 and attached Figure 2 This section details step S205, based on the load-state dynamic complex impedance. The equilibrium transient constraint loop.

[0164] This transient constraint loop is executed independently by the local control unit 32 within the active balancing module 30, forming a real-time local protection and control function.

[0165] Local control unit 32 is used during peak polarization phase Measured load-state dynamic complex impedance and the equalization current collected in real time by the synchronous sensing unit 31. The amplitude is used to calculate the instantaneous internal power loss of a single cell during the equalization process. .

[0166] This instantaneous internal power loss The calculation is performed using the following formula:

[0167] ;

[0168] in: Indicates at time Instantaneous internal power loss; Indicates at time The macroscopic equilibrium current amplitude; This indicates taking the real part of a complex number; Indicates the frequency of diagnosis The dynamic complex impedance under load conditions was measured.

[0169] The local control unit 32 calculates the instantaneous internal power loss. With a power loss threshold preset in the memory of the local control unit 32 Perform continuous comparisons.

[0170] When the instantaneous internal power loss The value is not less than the power loss threshold. At that time, the local control unit 32 automatically adjusts the energy dispatch signal used to generate the equalization current. The specific adjustment involves reducing the energy dispatch signal. The amplitude of the equalization current is reduced. Until the instantaneous internal power loss The value is again less than the power loss threshold. This operation forms a closed loop to limit internal heat generation in the battery during transient high-current equalization processes.

[0171] The technical solution disclosed in this invention, by simultaneously injecting a diagnostic disturbance coupled to the transient phase of the equalization current during the active equalization process, achieves the extraction of two impedance parameters with different physical meanings from a single equalization operation. Near-equilibrium complex impedance Measured in the region where the equilibrium current is close to zero, this parameter reflects the electrochemical characteristics of a single cell under small-signal excitation. It is used to correct the battery state estimation algorithm model in the main control module 40, thereby improving the long-term tracking accuracy of state of charge and state of health. Load-state dynamic complex impedance Measured in the peak range of the equalization current, this parameter characterizes the dynamic response and internal loss characteristics of a single cell under high current impact, and is used for local real-time protection of the active equalization module 30 to prevent overheating caused by transient high current.

[0172] This technical solution forms a dual-loop fusion system. One loop is the state monitoring model correction loop located in the main control module 40, which utilizes... The data undergoes long-term adaptive adjustment of model parameters. Another loop is the equilibrium transient constraint loop located in the active equilibrium module 30, which utilizes... The data undergoes short-cycle real-time power limiting, forming a distributed, fast protection mechanism.

[0173] In one alternative implementation, the diagnostic disturbance source is used for injection. and This is not limited to single-frequency sine waves. These two diagnostic perturbation sources can be designed as a superposition of multi-frequency sinusoidal signals or a chirp signal. Using such broadband perturbation signals, combined with Fourier transform or other spectral analysis algorithms, the impedance spectrum of a single cell over a frequency range can be obtained in a single measurement window during a transient phase, thereby acquiring richer information about different electrochemical processes of the cell.

[0174] In an alternative implementation, the identification of the equilibrium transient phase, in addition to employing a current amplitude threshold-based approach, can also be used. and The comparison method can also be based on equalization current. Methods for detecting the rate of change. Calculated by the local control unit 32. time derivative When the absolute value of this derivative reaches a peak, it indicates that the current is in a rapid rising or falling phase; when the value of this derivative is close to zero, it indicates that the current is at a peak plateau or near-zero plateau. The local control unit 32 uses these derivative characteristics to delineate the peak polarization phase. and near-equilibrium stage .

[0175] In one alternative implementation, the loss power threshold is used to balance the transient constraint loop. It is not a fixed value. This threshold can be dynamically calculated by the main control module 40 based on the operating status of the entire battery pack 20 (e.g., average temperature, total current, operating mode), and sent in real time to the local control unit 32 of each active balancing module 30 via the communication bus. This method combines system-level thermal management strategies with localized transient protection.

[0176] In an alternative implementation, the control and measurement methods described in this invention are independent of a specific power topology. The power topology unit 33 in the active equalization module 30 can employ various DC / DC converter architectures, including but not limited to flyback converters, forward converters, or bidirectional Buck-Boost converters. The core of this invention lies in synthesizing the energy dispatch signal and the diagnostic injection signal at the duty cycle level; this principle is applicable to any power converter controlled by pulse width modulation.

[0177] While the invention has been described herein with reference to specific embodiments, it should be understood that these embodiments are merely examples of the principles and applications of the invention. Therefore, it should be understood that many modifications can be made to the exemplary embodiments, and other arrangements can be designed without departing from the spirit and scope of the invention as defined by the appended claims. It should be understood that different dependent claims and features described herein can be combined in ways different from those described in the original claims. It is also understood that features described in conjunction with individual embodiments can be used in other described embodiments.

Claims

1. A single-cell state monitoring and active balancing system, characterized in that, include: At least one active balancing module (30), a shared energy bus, and a main control module (40). Each battery pack (20) to be monitored contains multiple individual cells; Each active balancing module (30) is electrically connected to a single battery cell, and all active balancing modules (30) are electrically connected to each other through a shared energy bus. The main control module (40) establishes a communication connection with all active balancing modules (30). The active balancing module (30) collects the voltage response and current response of the corresponding single battery cell in real time, and uses the voltage response and current response to calculate the load-state dynamic complex impedance and near-equilibrium state complex impedance of the corresponding single battery cell, respectively, and transmits the near-equilibrium state complex impedance to the main control module (40). The main control module (40) has a second-order RC equivalent circuit model pre-set inside to characterize the electrochemical properties of the battery. The main control module (40) receives the near-equilibrium complex impedance uploaded by the active balancing module (30), uses the near-equilibrium complex impedance as the target value for parameter identification, adjusts the model parameters of the second-order RC equivalent circuit model through a recursive least squares algorithm, estimates the state of charge and heat transfer health of the single cell based on the adjusted model parameters, and transmits the state estimate to the corresponding active balancing module (30). The active balancing module (30) also receives the state estimate transmitted by the main control module (40), extracts the real part of the complex impedance of the load-state dynamic complex impedance, and calculates the instantaneous internal power loss of the corresponding single cell by combining the synchronously acquired balancing current amplitude; compares the instantaneous internal power loss with the preset power loss threshold in real time, and when the instantaneous internal power loss is not less than the power loss threshold, adjusts the amplitude of the energy dispatch signal to reduce the balancing current until the instantaneous internal power loss returns to the safe range, thereby realizing dynamic thermal protection for the single cell.

2. The single-cell state monitoring and active balancing system according to claim 1, characterized in that, The active balancing module (30) includes a power topology unit (33), a synchronous sensing unit (31), and a local control unit (32). The power topology unit (33) is a bidirectional DC-DC converter. Its input end is connected to the local control unit (32) of the corresponding single cell battery, and its output end is connected to the shared energy bus to perform bidirectional energy transfer. The synchronous sensing unit (31) includes a method for synchronously acquiring the instantaneous terminal voltage and equalization current of a single battery cell, and generating the voltage response and current response. The local control unit (32) is a digital signal processor that generates a total pulse width modulation signal containing energy dispatch signal and diagnostic injection signal. It receives the voltage response and current response generated by the synchronous sensing unit (31), calculates the load-state dynamic complex impedance and near-equilibrium state complex impedance of the corresponding single cell, and obtains the instantaneous internal power loss by combining the state estimation value transmitted by the main control module. It compares the instantaneous internal power loss with the preset power loss threshold in real time. When the instantaneous internal power loss is not less than the power loss threshold, it adjusts the amplitude of the energy dispatch signal through the power topology unit (33) to reduce the balancing current until the instantaneous internal power loss returns to the safe range, thereby realizing dynamic thermal protection for the single cell.

3. The single-cell state monitoring and active balancing system according to claim 1 or 2, characterized in that, The synchronous sensing unit (31) includes: a voltage sensor, a current sensor and a high-speed analog-to-digital converter; the voltage sensor and the current sensor are used to collect the instantaneous terminal voltage and current of the battery cell, and the high-speed analog-to-digital converter is used to convert the current and voltage into digital signals and send them out.

4. The single-cell state monitoring and active balancing system according to claim 2, characterized in that, The active balancing module (30) uses a digital lock-in amplifier algorithm to calculate the load-state dynamic complex impedance and near-equilibrium-state complex impedance of the single cell.

5. The single-cell state monitoring and active balancing system according to claim 2, characterized in that, The active balancing module (30) calculates the load-state dynamic complex impedance and near-equilibrium-state complex impedance of the corresponding single cell as follows: The local control unit (32) generates a total pulse width modulation signal containing energy dispatch signal and diagnostic injection signal, and outputs it to the power topology unit (33). The power topology unit (33) generates an equalization current and dynamically divides one cycle of the equalization operation into a peak polarization stage and a near-balance stage according to the amplitude of the equalization current. A first frequency diagnostic disturbance source is applied in the peak polarization stage and a second frequency diagnostic disturbance source is applied in the near-balance stage, and the output is sent to the battery cell. The voltage and current responses of the battery cells at the corresponding stage are synchronously collected by the synchronous sensing unit (31), and the local control unit (32) calculates the load-state dynamic complex impedance and near-equilibrium state complex impedance of the corresponding battery cells based on the voltage and current responses at the corresponding stage.

6. The single-cell state monitoring and active balancing system according to claim 2, 4 or 5, characterized in that, The peak polarization phase is the time interval during which the absolute value of the equilibrium current is not less than the peak current threshold, and the near-equilibrium phase is the time interval during which the absolute value of the equilibrium current is not greater than the near-zero current threshold.

7. The single-cell state monitoring and active balancing system according to claim 2, 4 or 5, characterized in that, The power topology unit (33) adopts a topology group that includes either a flyback converter topology or a Cook converter topology.

8. The single-cell state monitoring and active balancing system according to claim 2 or 4, characterized in that, The local control unit (32) is implemented using a microcontroller, digital signal processor or field programmable gate array.

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