Lithium ion battery on-line impedance spectrum detection system and method for cascade energy storage system

Abstract

The application discloses a lithium ion battery online impedance spectrum detection system and method of a cascade energy storage system, and the system comprises a plurality of energy storage battery clusters and a plurality of online impedance spectrum detection modules. The online impedance spectrum detection module comprises an impedance spectrum calculation module, an excitation current generation unit and an alternating current response acquisition module. The impedance spectrum calculation module is used for generating a control signal and calculating impedance spectrum data. The excitation current generation unit is used for injecting a sinusoidal excitation current into the energy storage battery cluster according to the control signal. The alternating current response acquisition module is used for synchronously acquiring an alternating current response voltage. The excitation current acquisition module is used for synchronously acquiring an alternating current excitation current. The excitation generation unit scheme of the isolation type DC-DC converter and the pulse power storage module is adopted, an independent excitation source is provided through the pulse power storage module, the purity and stability of the excitation current are ensured, electrical isolation is realized, and the system safety is ensured.

Description

Technical Field

[0001] This application relates to the field of energy storage, specifically to an online impedance spectroscopy detection system and method for lithium-ion batteries in cascaded energy storage systems. Background Technology

[0002] With the continuous expansion of renewable energy grid connection, the importance of medium- and high-voltage large-capacity energy storage systems is becoming increasingly prominent. Unlike centralized energy storage systems that are connected to the grid through step-up transformers, cascaded energy storage systems achieve medium- and high-voltage grid connection without the need for power frequency transformers by connecting the output terminals of multiple H-bridge modules in series. They have advantages such as high system efficiency, good output waveform quality, and large single-unit capacity, and have become an important development direction for current energy storage technology.

[0003] Lithium-ion batteries, due to their high energy density, high power density, and long cycle life, are suitable as core components in the aforementioned cascaded energy storage systems. However, lithium-ion batteries exhibit strong nonlinearity, time-varying characteristics, and environmental sensitivity. Relying solely on external parameters such as battery terminal voltage, current, and surface temperature makes it difficult to accurately estimate their internal state and provide early warning of faults. The internal state can include the state of charge (SOC) and state of health (SOH).

[0004] Electrochemical impedance spectroscopy (EIS) technology obtains the impedance characteristics of a battery at different frequencies by injecting a series of small-amplitude AC excitation signals into the battery and measuring its voltage / current response. Impedance spectroscopy contains rich information about the internal electrochemical processes of the battery, which can be used to achieve accurate estimation and non-destructive diagnosis of the battery's internal state.

[0005] Therefore, applying EIS online detection technology to cascaded energy storage systems to achieve online monitoring of battery status is of great significance for ensuring the safe, stable, and long-life operation of large-scale energy storage systems. However, the special topology of this system presents challenges for online impedance spectroscopy detection: Currently, mainstream online EIS (Electronic Information System) monitoring solutions typically utilize the converter itself connected to the battery management system to apply the excitation signal. However, in a cascaded H-bridge system, the AC sides of each H-bridge module are directly connected in series to form a unified whole for interaction with the power grid. This topology makes it difficult for any single H-bridge module to independently apply controllable AC excitation to its DC-side battery modules, as this would disrupt the overall power output balance and grid-connected current quality of the system. Furthermore, the series-connected battery modules in the system have DC potentials of hundreds to thousands of volts relative to ground, making it difficult to safely connect monitoring equipment directly to the ground.

[0006] In summary, traditional approaches lack a systematic solution that can adapt to the unique topology of cascaded energy storage systems and achieve safe and accurate online impedance spectrum detection without relying on excitation from the converter. Summary of the Invention

[0007] To address the aforementioned issues, this application proposes an online impedance spectroscopy detection system for lithium-ion batteries in a cascaded energy storage system, comprising: multiple energy storage battery clusters and multiple online impedance spectroscopy detection modules; The number of energy storage battery clusters and the number of online impedance spectrum detection modules are the same, and they correspond one-to-one; The energy storage battery cluster comprises multiple battery cells connected in series; The online impedance spectrum detection module includes an impedance spectrum calculation module, an excitation current generation unit, an AC response acquisition module, and an excitation current acquisition module. The impedance spectrum calculation module is used to receive online impedance spectrum detection commands and generate control signals, as well as to calculate and upload impedance spectrum data. The excitation current generating unit is connected to the corresponding energy storage battery cluster and is used to inject a sinusoidal excitation current of a specified frequency and amplitude into the energy storage battery cluster according to the control signal. The AC response acquisition module is used to synchronously acquire the AC response voltage of each cell in the corresponding energy storage battery cluster under the sinusoidal excitation current, and upload it to the impedance spectrum calculation module. The excitation current acquisition module is used to synchronously acquire the AC excitation current of the corresponding energy storage battery cluster and upload it to the impedance spectrum calculation module.

[0008] In one example, the excitation current generating unit includes an isolated bidirectional DC-DC converter, a pulse power energy storage module, and a power control module; The low-voltage side of the isolated bidirectional DC-DC converter is connected to the pulse power energy storage module, and the high-voltage side is connected to the energy storage battery cluster. The low-voltage side and the high-voltage side are coupled through a high-frequency transformer. The power control module is used to control the switching on and off of the isolated bidirectional DC-DC converter.

[0009] In one example, the power control module is used to control the isolated bidirectional DC-DC converter to charge the pulse power storage module in a constant current mode until the voltage of the pulse power storage module reaches a preset value. It is also used to control the isolated bidirectional DC-DC converter, so that it adjusts its output current according to a preset sine wave reference signal, thereby injecting the sinusoidal excitation current of the corresponding frequency and amplitude into the energy storage battery cluster.

[0010] In one example, the pulse power storage module is a supercapacitor module or a lithium capacitor module.

[0011] In one example, the isolated bidirectional DC-DC converter is a two-phase Boost integrated dual active bridge topology.

[0012] In one example, the impedance spectrum calculation module calculates the AC impedance of the individual cells in the corresponding energy storage battery cluster at different frequencies based on the AC response voltage and the AC excitation current, and generates an impedance spectrum.

[0013] In one example, the AC response acquisition module and the excitation current acquisition module achieve synchronous acquisition control through a hardware synchronization signal line.

[0014] On the other hand, an online impedance spectrum detection method for lithium-ion batteries in a cascaded energy storage system is also proposed. The detection is performed using an online impedance spectrum detection system for lithium-ion batteries in a cascaded energy storage system as described in any of the above examples. This system includes multiple energy storage battery clusters and multiple online impedance spectrum detection modules. Each online impedance spectrum detection module includes an impedance spectrum calculation module, an excitation current generation unit, an AC response acquisition module, and an excitation current acquisition module. The excitation current generation unit includes an isolated bidirectional DC-DC converter, a pulsed power energy storage module, and a power control module. The method includes: Initialize the power control module, the AC response acquisition module, and the excitation current acquisition module; The impedance spectrum calculation module receives online impedance spectrum detection commands and generates control signals, and the power control module charges the pulse power energy storage module. The impedance spectrum calculation module sends out the specified frequency and amplitude of the sinusoidal excitation current. The excitation current generating unit generates a corresponding sinusoidal excitation current based on the specified frequency and the specified amplitude. The AC response acquisition module and the excitation current acquisition module are used to acquire the AC response voltage of each battery cell in the energy storage battery cluster under the sinusoidal excitation current, and the AC excitation current of the energy storage battery cluster, respectively, and upload them to the impedance spectrum calculation module. The impedance spectrum calculation module calculates impedance spectrum data based on the AC response voltage and the AC excitation current.

[0015] In one example, the low-voltage side of the isolated bidirectional DC-DC converter is connected to the pulse power energy storage module through a low-voltage side contactor, and the high-voltage side is connected to the energy storage battery cluster through a high-voltage side contactor. The low-voltage side and the high-voltage side are coupled through a high-frequency transformer. The low-voltage side contactor includes a first low-voltage side contactor that is directly set and a second low-voltage side contactor that is set with a series resistor. Charging the pulse power storage module via the power control module specifically includes: The power control module issues closing commands to the second low-voltage side contactor and the high-voltage side contactor. By changing the duty cycle and phase of the switching signals of the switching transistors on the low-voltage side and the high-voltage side of the high-frequency transformer, the power is controlled to move from the high-voltage side to the low-voltage side, thereby charging the pulse power energy storage module.

[0016] In one example, the method further includes: Once it is determined that the impedance spectrum data corresponding to the current sinusoidal excitation current has been calculated, the sinusoidal excitation current is updated through the excitation current generating unit until the impedance spectrum data corresponding to all preset sinusoidal excitation currents has been calculated. Upload the impedance spectrum data corresponding to all sinusoidal excitation currents.

[0017] The online impedance spectroscopy detection system for lithium-ion batteries in cascaded energy storage systems proposed in this application can bring the following benefits: 1. Addressing the challenges posed by the unique topology of cascaded H-bridge systems, the traditional approach of "applying excitation through a converter" was abandoned. Instead, an excitation generation unit scheme combining an isolated DC-DC converter and a pulsed power storage module was adopted. This unit provides an independent excitation source through the pulsed power storage module, ensuring the purity and stability of the excitation current. Furthermore, the isolated DC-DC converter provides electrical isolation, guaranteeing system safety. Together, these two components fundamentally solve the core challenge of safely and accurately applying online excitation signals in cascaded energy storage systems.

[0018] 2. The system highly integrates excitation, acquisition, calculation, and control functions, completing impedance spectrum scanning across the entire frequency band through a pre-set automated process. The impedance spectrum calculation module not only outputs raw impedance spectrum data but also provides direct and rich data interfaces for subsequent accurate estimation of battery status based on impedance characteristics (such as SOH, SOC, internal temperature, etc.) and early safety warnings, enhancing the intelligence level and proactive safety management capabilities of the battery management system.

[0019] 3. It adopts a modular design with a compact structure, which can be quickly adapted to cascaded energy storage systems of different voltage levels and capacity scales. It has strong versatility and is easy to scale up and apply in cascaded energy storage systems. Attached Figure Description

[0020] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings: Figure 1 This is a schematic diagram of the architecture of the online impedance spectroscopy detection system for the lithium-ion battery in the cascaded energy storage system in this application embodiment; Figure 2 This is a schematic diagram of the structure of the online impedance spectrum detection module in one scenario of this application embodiment; Figure 3 This is a flowchart illustrating the online impedance spectroscopy detection method for lithium-ion batteries in a cascaded energy storage system, as described in this application. Figure 4 This is a detailed flowchart illustrating an online impedance spectroscopy detection method for lithium-ion batteries in a cascaded energy storage system, as described in one embodiment of this application. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0022] The technical solutions provided by the various embodiments of this application are described in detail below with reference to the accompanying drawings.

[0023] like Figure 1 As shown in the embodiment of this application, an online impedance spectroscopy detection system for lithium-ion batteries in a cascaded energy storage system is provided, comprising: multiple energy storage battery clusters and multiple online impedance spectroscopy detection modules. The number of energy storage battery clusters and online impedance spectroscopy detection modules are the same, and they correspond one-to-one.

[0024] like Figure 1 As shown, there are n energy storage battery clusters and n online impedance spectroscopy detection modules, namely online impedance spectroscopy detection module 1 to online impedance spectroscopy detection module n. Each online impedance spectroscopy detection module is connected in parallel with its corresponding energy storage battery cluster, and the energy storage battery clusters are cascaded with each other.

[0025] An energy storage battery cluster comprises multiple battery cells connected in series. Energy storage battery cluster 1 contains n battery cells connected in series, from aBT1 to aBTn; energy storage battery cluster 2 contains n battery cells connected in series, from bBT1 to bBTn; and so on. It should be noted that the number of battery cells n in a single energy storage battery cluster and the number of energy storage battery clusters n both indicate multiples, but do not necessarily mean that the two numbers are the same.

[0026] In a cascaded H-bridge system, each H-bridge module has a corresponding energy storage battery cluster on its DC side, while the AC side (Uac) is directly connected in series to form a whole for interaction with the power grid. Each H-bridge module has a corresponding H-bridge structure; for example, H-bridge module 1 has four semiconductor switches QM1a to QM4a, H-bridge module 2 has four semiconductor switches QM1b to QM4b, and so on. Adjacent H-bridge modules are connected to form a cascaded H-bridge system.

[0027] like Figure 2 As shown, the online impedance spectrum detection module includes an impedance spectrum calculation module, an excitation current generation unit, an AC response acquisition module, and an excitation current acquisition module.

[0028] The impedance spectrum calculation module receives online impedance spectrum detection commands, generates control signals, and calculates and uploads impedance spectrum data. It connects to the AC response acquisition module and the excitation current acquisition module, generating control signals to control the startup of these modules, receive corresponding data, calculate impedance spectrum data, and upload it to the host computer.

[0029] The excitation current generating unit is connected to the corresponding energy storage battery cluster and is used to inject a sinusoidal excitation current of a specified frequency and amplitude into the energy storage battery cluster according to the control signal. The purpose of this sinusoidal excitation current is to excite the electrochemical response inside the battery so that impedance information can be obtained by detecting changes in voltage and current.

[0030] The AC response acquisition module is used to synchronously acquire the AC response voltage of each cell in the corresponding energy storage battery cluster under a sinusoidal excitation current and upload it to the impedance spectrum calculation module. In one implementation, this module can be implemented by connecting a high-precision differential voltage sampling circuit in parallel across the positive and negative terminals of each cell.

[0031] The excitation current acquisition module is used to synchronously acquire the AC excitation current of the corresponding energy storage battery cluster and upload it to the impedance spectrum calculation module. In one implementation, the excitation current acquisition module can be implemented using a high-precision current sensor, which is connected in series with the energy storage battery cluster. This sensor can capture the AC excitation current signal flowing through the battery cluster in real time and convert it into an electrical signal that can be processed by the impedance spectrum calculation module.

[0032] The AC response acquisition module and the excitation current acquisition module achieve synchronous acquisition and control through a hardware synchronization signal line.

[0033] In one embodiment, such as Figure 2 As shown, the excitation current generating unit includes an isolated bidirectional DC-DC converter, a pulse power energy storage module, and a power control module.

[0034] The low-voltage side of the isolated bidirectional DC-DC converter is connected to the pulse power storage module, and the high-voltage side is connected to the energy storage battery cluster. The low-voltage and high-voltage sides are coupled through a high-frequency transformer. The isolated bidirectional DC-DC converter features wide voltage gain and bidirectional energy flow, and is used to realize bidirectional energy flow between batteries and capacitors. It can be configured as a two-phase Boost integrated dual active bridge topology.

[0035] like Figure 2 As shown, the isolated bidirectional DC-DC converter has power switching transistors (Q1, Q2, Q3, Q4) on the low-voltage side, forming a switching network for a two-phase Boost circuit, enabling voltage boosting and bidirectional energy flow control; energy storage inductors (L1, L2) are used for energy storage and voltage boosting, improving the converter's power density and dynamic response speed; filter capacitors (Cm) are used to smooth voltage fluctuations on the low-voltage side and stabilize the DC bus voltage; pulse power energy storage modules (SC1, SC2...SCn) are used to provide high power density energy support to meet the dynamic requirements of the excitation current; current sampling resistors (R1, R2) collect the current signal on the low-voltage side for closed-loop control and fault protection.

[0036] The isolated bidirectional DC-DC converter is equipped with a high-frequency transformer (T1) to achieve electrical isolation between the high and low voltage sides. By adjusting the turns ratio, the voltage gain can be adapted to battery clusters of different voltage levels, while simultaneously transmitting high-frequency AC energy.

[0037] The isolated bidirectional DC-DC converter has power switching transistors (S1, S2, S3, S4) on the high-voltage side, forming a dual active bridge high-voltage side full-bridge circuit, which converts the high-frequency AC energy transmitted by the transformer into DC, or transmits energy in the reverse direction, realizing bidirectional energy flow; bus interfaces (BUS+, BUS-): connected to the cascaded H-bridge battery cluster, serving as the output port of the excitation current.

[0038] The power control module is used to control the switching on and off of the isolated bidirectional DC-DC converter, enabling bidirectional energy flow and electrical isolation.

[0039] The power control module controls the isolated bidirectional DC-DC converter to charge the pulse power storage module in a constant current mode until the voltage of the pulse power storage module reaches a preset value. It also controls the isolated bidirectional DC-DC converter to adjust its output current according to a preset sinusoidal reference signal, thereby injecting a sinusoidal excitation current of corresponding frequency and amplitude into the energy storage battery cluster.

[0040] Pulse power storage modules (SC1, SC2...SCn) are characterized by high power density, and can provide the power required to excite battery clusters at the module level, for example, by setting them up as supercapacitor modules or lithium capacitor modules.

[0041] In one embodiment, the impedance spectrum calculation module calculates the AC impedance of individual cells in the corresponding energy storage battery cluster at different frequencies based on the AC response voltage and AC excitation current, and generates an impedance spectrum. The impedance spectrum can be used for accurate estimation of battery state and performance analysis. When calculating the impedance spectrum, the total AC response voltage of the battery cluster is theoretically equal to the sum of the voltages of each individual cell; therefore, the impedance spectrum of the battery cluster is the ratio of its total AC response voltage to its AC excitation current. Since the individual cells are connected in series, their corresponding AC excitation currents are the same; therefore, the impedance spectrum of each individual cell is the ratio of its respective AC response voltage to its AC excitation current.

[0042] like Figure 3 and Figure 4 As shown, this application also provides an online impedance spectrum detection method for lithium-ion batteries in a cascaded energy storage system. The detection is performed using an online impedance spectrum detection system for lithium-ion batteries in a cascaded energy storage system as described in any of the above embodiments. The online impedance spectrum detection system for lithium-ion batteries in a cascaded energy storage system includes multiple energy storage battery clusters and multiple online impedance spectrum detection modules. Each online impedance spectrum detection module includes an impedance spectrum calculation module, an excitation current generation unit, an AC response acquisition module, and an excitation current acquisition module. The excitation current generation unit includes an isolated bidirectional DC-DC converter, a pulse power energy storage module, and a power control module. This part has been described above and will not be repeated here.

[0043] like Figure 3 and Figure 4 As shown, the method includes: S301: Initialize the power control module, the AC response acquisition module, and the excitation current acquisition module.

[0044] Specifically, the initialization process may include configuring the communication interfaces, sampling parameters (e.g., sampling frequency, sampling accuracy), and control logic parameters (e.g., PWM switching frequency, protection threshold) of each module to ensure that each module is in a ready-to-operate state. Simultaneously, an initial state check is performed on the pulse power storage module to confirm whether its voltage, capacity, and other parameters meet the subsequent charging and discharging requirements.

[0045] S302: The impedance spectrum calculation module receives the online impedance spectrum detection command and generates a control signal, and the power control module charges the pulse power storage module.

[0046] Online impedance spectroscopy detection commands can be generated by the host computer and sent to the impedance spectroscopy calculation module based on user-issued commands.

[0047] like Figure 3 As shown, the low-voltage side of the isolated bidirectional DC-DC converter is connected to the pulse power energy storage module through low-voltage side contactors (including the first low-voltage side contactor KN1 directly set and the second low-voltage side contactor KN2 set in series resistance), and the high-voltage side is connected to the energy storage battery cluster through high-voltage side contactors (KQ1 and KQ2). The low-voltage side and the high-voltage side are coupled through a high-frequency transformer (T1).

[0048] Based on this, when charging the pulse power energy storage module, the power control module issues closing commands for the second low-voltage side contactor (KN2) and the high-voltage side contactors (KQ1 and KQ2).

[0049] By changing the duty cycle Dk and phase φk of the switching signals of the switching transistors on the low-voltage and high-voltage sides of the high-frequency transformer, the power is controlled to move from the high-voltage side to the low-voltage side (that is, from the energy storage battery cluster side to the pulse power energy storage module side), thus charging the pulse power energy storage module. The switching transistors on the low-voltage side include Q1, Q2, Q3, and Q4, while the switching transistors on the high-voltage side include S1, S2, S3, and S4.

[0050] After the pulse power energy storage module has finished charging, the power control module issues a command to open the second low-voltage side contactor KN2 buffer switch and a command to close the first low-voltage side contactor KN1 contactor, and sends a start-up completion command back to the impedance spectrum calculation module.

[0051] S303: The impedance spectrum calculation module sends out the specified frequency and specified amplitude corresponding to the sinusoidal excitation current.

[0052] After receiving the command indicating that the impedance spectrum calculation module has completed its startup, the module sends the specified excitation current frequency fc and specified amplitude Vc to the power control module, AC response acquisition module, and excitation current acquisition module, respectively. The specified frequency and amplitude can be flexibly set according to the battery type, aging level, and testing requirements. For example, for new batteries, a wider frequency range (e.g., 0.01Hz - 10kHz) can be selected to comprehensively acquire their impedance characteristics; for aged batteries, specific frequency bands (e.g., low-frequency diffusion impedance information) can be focused on to assess their degradation status.

[0053] S304: The excitation current generating unit generates a corresponding sinusoidal excitation current according to the specified frequency and the specified amplitude.

[0054] After receiving the excitation current parameters, the power control module adjusts the controller's preset parameters and starts outputting a sinusoidal excitation current, and generates the corresponding sinusoidal excitation current through the excitation current generation unit.

[0055] Specifically, the power control module generates a corresponding sinusoidal reference signal based on the received specified frequency fc and specified amplitude Vc. This reference signal serves as the current command for the isolated bidirectional DC-DC converter. Subsequently, the power control module adjusts the converter's output current by controlling the on / off timing and duty cycle of the low-voltage and high-voltage side power switches (Q1-Q4 and S1-S4) in the isolated bidirectional DC-DC converter. At this time, the pulse power storage module, acting as an energy source, converts the stored energy into a sinusoidal alternating current conforming to the specified frequency and amplitude requirements through the isolated bidirectional DC-DC converter, and injects it into the corresponding energy storage battery cluster through the high-voltage side contactors (KQ1 and KQ2). In this process, the isolated bidirectional DC-DC converter not only provides a bidirectional energy flow path, but its high-frequency transformer (T1) also achieves electrical isolation between the pulse power storage module and the high-voltage energy storage battery cluster, effectively solving the high-voltage safety access problem and ensuring that the detection system can operate safely without affecting the original high-voltage structure and insulation performance of the cascaded H-bridge system.

[0056] S305: The AC response acquisition module and the excitation current acquisition module are used to acquire the AC response voltage of each battery cell in the energy storage battery cluster under the sinusoidal excitation current, and the AC excitation current of the energy storage battery cluster, respectively, and upload them to the impedance spectrum calculation module.

[0057] After receiving the excitation current parameters, the AC response acquisition module and the excitation current acquisition module determine the sampling frequency fs and perform sampling. The sampling frequency can be set based on Shannon's sampling theorem, and is typically set to at least 10 times the specified frequency fc to ensure accurate reproduction of the AC signal waveform characteristics. For example, when the specified frequency fc is 1kHz, the sampling frequency fs can be set to 10kHz, meaning 10 data points are collected per cycle.

[0058] Once the number of sampling points reaches the predetermined value, the AC response acquisition module and the excitation current acquisition module send back the acquisition completion command and acquisition data to the impedance spectrum calculation module.

[0059] S306: The impedance spectrum calculation module calculates impedance spectrum data based on the AC response voltage and the AC excitation current.

[0060] After receiving the acquisition completion command, the impedance spectrum calculation module sends a stop excitation command to the power control module, and calculates the AC impedance Zk of each cell at frequency fc based on the acquired data, thus obtaining the impedance spectrum data. The calculation process of AC impedance has been described above and will not be repeated here.

[0061] Furthermore, once it is confirmed that the impedance spectrum data corresponding to the current sinusoidal excitation current has been calculated, the sinusoidal excitation current is updated through the excitation current generation unit until the impedance spectrum data corresponding to all preset sinusoidal excitation currents has been calculated. After the current impedance spectrum data has been calculated, the excitation current frequency fc can be changed, and the above steps S303~S306 can be repeated until all preset frequency points are completed. The preset frequency points can be flexibly configured according to the battery's electrochemical characteristics and detection requirements. For example, a logarithmically uniform distribution can be used to cover a wide frequency band from low frequency (e.g., 0.01Hz) to high frequency (e.g., 10kHz) to comprehensively reflect the battery's impedance characteristics in different reaction processes, including key information such as ohmic impedance, charge transfer impedance, and diffusion impedance.

[0062] The impedance spectrum calculation module sends disconnection commands to the first low-voltage side contactor (KN1) and the high-voltage side contactors (KQ1, KQ2) to the power control module, thus ending the impedance spectrum data detection process.

[0063] The impedance spectrum data corresponding to all sinusoidal excitation currents are uploaded to the host computer for user reference and judgment.

[0064] In addition, such as Figure 4 As shown, when there are multiple acquisition modules (including AC response acquisition module and excitation current acquisition module), in Figure 4When the acquisition modules are represented as acquisition modules 1 to n, the corresponding control signals can be transmitted sequentially through synchronization commands between the acquisition modules, thereby acquiring and transmitting impedance data (including sinusoidal excitation current and AC response voltage).

[0065] 1. Addressing the challenges posed by the unique topology of cascaded H-bridge systems, the traditional approach of "applying excitation through a converter" was abandoned. Instead, an excitation generation unit scheme combining an isolated DC-DC converter and a pulsed power storage module was adopted. This unit provides an independent excitation source through the pulsed power storage module, ensuring the purity and stability of the excitation current. Furthermore, the isolated DC-DC converter provides electrical isolation, guaranteeing system safety. Together, these two components fundamentally solve the core challenge of safely and accurately applying online excitation signals in cascaded energy storage systems.

[0066] 2. The system highly integrates excitation, acquisition, calculation, and control functions, completing impedance spectrum scanning across the entire frequency band through a pre-set automated process. The impedance spectrum calculation module not only outputs raw impedance spectrum data but also provides direct and rich data interfaces for subsequent accurate estimation of battery status based on impedance characteristics (such as SOH, SOC, internal temperature, etc.) and early safety warnings, enhancing the intelligence level and proactive safety management capabilities of the battery management system.

[0067] 3. It adopts a modular design with a compact structure, which can be quickly adapted to cascaded energy storage systems of different voltage levels and capacity scales. It has strong versatility and is easy to scale up and apply in cascaded energy storage systems.

[0068] The above description is merely an embodiment of this application and is not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of the claims of this application.

Claims

1. An online impedance spectroscopy detection system for lithium-ion batteries in a cascaded energy storage system, characterized in that, include: Multiple energy storage battery clusters and multiple online impedance spectroscopy detection modules; The number of energy storage battery clusters and the number of online impedance spectrum detection modules are the same, and they correspond one-to-one; The energy storage battery cluster comprises multiple battery cells connected in series; The online impedance spectrum detection module includes an impedance spectrum calculation module, an excitation current generation unit, an AC response acquisition module, and an excitation current acquisition module. The impedance spectrum calculation module is used to receive online impedance spectrum detection commands and generate control signals, as well as to calculate and upload impedance spectrum data. The excitation current generating unit is connected to the corresponding energy storage battery cluster and is used to inject a sinusoidal excitation current of a specified frequency and amplitude into the energy storage battery cluster according to the control signal. The AC response acquisition module is used to synchronously acquire the AC response voltage of each cell in the corresponding energy storage battery cluster under the sinusoidal excitation current, and upload it to the impedance spectrum calculation module. The excitation current acquisition module is used to synchronously acquire the AC excitation current of the corresponding energy storage battery cluster and upload it to the impedance spectrum calculation module.

2. The online impedance spectroscopy detection system for lithium-ion batteries in a cascaded energy storage system according to claim 1, characterized in that, The excitation current generating unit includes an isolated bidirectional DC-DC converter, a pulse power energy storage module, and a power control module; The low-voltage side of the isolated bidirectional DC-DC converter is connected to the pulse power energy storage module, and the high-voltage side is connected to the energy storage battery cluster. The low-voltage side and the high-voltage side are coupled through a high-frequency transformer. The power control module is used to control the switching on and off of the isolated bidirectional DC-DC converter.

3. The online impedance spectroscopy detection system for lithium-ion batteries in a cascaded energy storage system according to claim 2, characterized in that, The power control module is used to control the isolated bidirectional DC-DC converter to charge the pulse power energy storage module in a constant current mode until the voltage of the pulse power energy storage module reaches a preset value. It is also used to control the isolated bidirectional DC-DC converter, so that it adjusts its output current according to a preset sine wave reference signal, thereby injecting the sinusoidal excitation current of the corresponding frequency and amplitude into the energy storage battery cluster.

4. The online impedance spectroscopy detection system for lithium-ion batteries in a cascaded energy storage system according to claim 2, characterized in that, The pulse power energy storage module is a supercapacitor module or a lithium capacitor module.

5. The online impedance spectroscopy detection system for lithium-ion batteries in a cascaded energy storage system according to claim 2, characterized in that, The isolated bidirectional DC-DC converter is a two-phase Boost integrated dual active bridge topology.

6. The online impedance spectroscopy detection system for lithium-ion batteries in a cascaded energy storage system according to claim 1, characterized in that, The impedance spectrum calculation module calculates the AC impedance of the individual cells in the corresponding energy storage battery cluster at different frequencies based on the AC response voltage and the AC excitation current, and generates an impedance spectrum.

7. The online impedance spectroscopy detection system for lithium-ion batteries in a cascaded energy storage system according to claim 1, characterized in that, The AC response acquisition module and the excitation current acquisition module achieve synchronous acquisition and control through a hardware synchronization signal line.

8. A method for online impedance spectroscopy detection of lithium-ion batteries in a cascaded energy storage system, characterized in that, The detection is performed using the online impedance spectroscopy detection system for lithium-ion batteries in the cascaded energy storage system as described in any one of claims 1 to 7, wherein the online impedance spectroscopy detection system for lithium-ion batteries in the cascaded energy storage system includes multiple energy storage battery clusters and multiple online impedance spectroscopy detection modules; the online impedance spectroscopy detection module includes an impedance spectrum calculation module, an excitation current generation unit, an AC response acquisition module, and an excitation current acquisition module; the excitation current generation unit includes an isolated bidirectional DC-DC converter, a pulse power energy storage module, and a power control module; The method includes: Initialize the power control module, the AC response acquisition module, and the excitation current acquisition module; The impedance spectrum calculation module receives online impedance spectrum detection commands and generates control signals, and the power control module charges the pulse power energy storage module. The impedance spectrum calculation module sends out the specified frequency and amplitude of the sinusoidal excitation current. The excitation current generating unit generates a corresponding sinusoidal excitation current based on the specified frequency and the specified amplitude. The AC response acquisition module and the excitation current acquisition module are used to acquire the AC response voltage of each battery cell in the energy storage battery cluster under the sinusoidal excitation current, and the AC excitation current of the energy storage battery cluster, respectively, and upload them to the impedance spectrum calculation module. The impedance spectrum calculation module calculates impedance spectrum data based on the AC response voltage and the AC excitation current.

9. The online impedance spectroscopy detection method for lithium-ion batteries in a cascaded energy storage system according to claim 8, characterized in that, The low-voltage side of the isolated bidirectional DC-DC converter is connected to the pulse power energy storage module through a low-voltage side contactor, and the high-voltage side is connected to the energy storage battery cluster through a high-voltage side contactor. The low-voltage side and the high-voltage side are coupled through a high-frequency transformer. The low-voltage side contactor includes a first low-voltage side contactor that is directly set and a second low-voltage side contactor that is set with a series resistor. Charging the pulse power storage module via the power control module specifically includes: The power control module issues closing commands to the second low-voltage side contactor and the high-voltage side contactor. By changing the duty cycle and phase of the switching signals of the switching transistors on the low-voltage side and the high-voltage side of the high-frequency transformer, the power is controlled to move from the high-voltage side to the low-voltage side, thereby charging the pulse power energy storage module.

10. The method for online impedance spectroscopy detection of lithium-ion batteries in a cascaded energy storage system according to claim 8, characterized in that, The method further includes: Once it is determined that the impedance spectrum data corresponding to the current sinusoidal excitation current has been calculated, the sinusoidal excitation current is updated through the excitation current generating unit until the impedance spectrum data corresponding to all preset sinusoidal excitation currents has been calculated. Upload the impedance spectrum data corresponding to all sinusoidal excitation currents.

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