Ohm and polarization internal resistance identification system and method based on filter decomposition

Abstract

The invention relates to an ohm and polarization internal resistance identification system and method based on filter decomposition. A direct current discharge module applies instantaneous discharge current to a battery; the voltage response sampling module collects a battery end voltage waveform; the core is that a multi-frequency filtering decomposition module adopts a high-pass filter and a low-pass filter which are connected in parallel to decompose a voltage waveform into a rapid change component corresponding to ohmic internal resistance and a slow change component corresponding to polarization internal resistance, and an internal resistance calculation and output module calculates an ohmic internal resistance value and a polarization internal resistance value according to the rapid change component and the slow change component respectively; accurate and real-time separation monitoring of the internal resistance components of the battery is realized through the simple filter circuit, the problem of mixed identification of the internal resistance components in the prior art is solved, special equipment or complex operation is not needed, the cost is low, integration is easy, the accuracy and reliability of battery health state evaluation are remarkably improved, and the reliability of battery health state evaluation is improved. The method can be widely applied to battery management fields of electric automobiles, energy storage systems and the like.

Description

Technical Field

[0001] This invention relates to the field of battery monitoring technology, and in particular to an ohmic and polarization internal resistance identification system based on filter decomposition. Background Technology

[0002] Battery internal resistance is a key internal parameter characterizing battery performance, health status, and safety, directly affecting the battery's output power, energy efficiency, and thermal management characteristics. Battery internal resistance consists of two parts: ohmic internal resistance and polarization internal resistance. Ohmic internal resistance is mainly formed by the inherent ion and electron conduction resistance of electrode materials, electrolyte, separator, and current collector; its response speed is extremely fast, on the order of milliseconds. Polarization internal resistance, on the other hand, originates from the kinetic delay in the electrochemical reaction process, exhibiting different time constants and reaction rates. It can be further divided into electrochemical polarization internal resistance (charge transfer resistance, caused by the energy barrier of the charge transfer process, with a time constant typically between 10 and 100 milliseconds). The internal resistance components, such as the ohmic resistance (resistance to ion diffusion caused by the concentration gradient of reactants and products, with a time constant on the order of seconds or even longer), correspond to different physicochemical processes within the battery. Their changing trends can reflect different aging mechanisms. For example, an increase in ohmic resistance is often related to electrolyte drying and deterioration of the contact between the electrode active material and the current collector; while an increase in polarization resistance is more indicative of electrochemical kinetic degradation such as active material deactivation and SEI film thickening. Therefore, accurate and separate measurement of these internal resistance components is of vital importance for achieving precise battery health management, failure early warning, and thermal runaway prevention.

[0003] Currently, the main methods used to measure battery internal resistance include the DC discharge method, the AC impedance method, and the hybrid pulse power test method. The DC discharge method applies a sudden high-current discharge pulse to the battery and calculates the internal resistance using Ohm's law based on the instantaneous changes in voltage and current at the start or end of the pulse. This method has a simple circuit, but traditional circuits cannot capture the complete voltage response process when the sampling frequency is insufficient. The instrument sampling frequency is usually no more than 10Hz (sampling interval no less than 100ms). Within the sampling time interval, the polarization voltage corresponding to the electrochemical polarization process has decayed to a negligible level, making it difficult to separate the charge transfer internal resistance from the ohmic internal resistance. Therefore, in the DC pulse method test, the resistance calculated from the sudden voltage is generally composed of two parts: the ohmic internal resistance and the charge transfer internal resistance, and it is impossible to accurately identify the independent internal components. The AC impedance method involves injecting a small AC current signal of a specific frequency or multiple frequencies into the battery, measuring the voltage response and phase difference across the battery terminals, and obtaining the battery's impedance spectrum by scanning the frequency. Although this method can separate internal resistance components with different time constants through simulation, it requires expensive specialized equipment (such as an electrochemical workstation), has a slow measurement speed, and is complex in data processing, making it difficult to implement online applications in embedded scenarios such as vehicle battery management.

[0004] The existing technical solutions have the following main problems in achieving the separation of internal resistance components of batteries: (1) the accuracy of mixed identification of internal resistance components is limited; (2) large current discharge is required and must be carried out in a static or offline state, making it difficult to achieve online monitoring and failing to meet the real-time requirements of the battery management system. Summary of the Invention

[0005] In view of this, the present invention provides an ohmic and polarization internal resistance identification system and method based on filter decomposition. By decomposing the voltage waveform generated by DC discharge through filters of different frequencies, the system can accurately identify each internal resistance component, solving the problems of mixed identification of internal resistance components and low measurement accuracy in the prior art. This enables real-time, online, and accurate separation and measurement of battery ohmic and polarization internal resistance.

[0006] To achieve the above objectives, the present invention provides an ohmic and polarization internal resistance identification system based on filter decomposition, comprising a DC discharge module, a voltage response sampling module, a multi-frequency filter decomposition module, and an internal resistance calculation and output module. The DC discharge module includes a controllable load circuit and a current control unit, which applies a controllable DC discharge current pulse to the battery under test. The voltage response acquisition module is connected to the battery under test and includes a high-precision analog-to-digital converter (ADC) and a signal conditioning circuit. It acquires the voltage waveform across the battery under test during DC discharge. The signal conditioning circuit includes an anti-aliasing filter and an amplifier. The multi-frequency filtering decomposition module is connected to the voltage response acquisition module, and decomposes the acquired voltage waveform across the battery under test into signals with different frequency components. The multi-frequency filtering decomposition module includes at least one high-pass filter, one band-pass filter, and one low-pass filter. The high-pass filter extracts the rapidly changing component of the voltage waveform across the battery under test corresponding to the ohmic internal resistance. The band-pass filter extracts the mid-frequency changing component of the voltage waveform across the battery under test corresponding to the electrochemical polarization resistance. The low-pass filter extracts the slowly changing component of the voltage waveform across the battery under test corresponding to the concentration polarization internal resistance. The internal resistance calculation and output module is connected to the multi-frequency filtering and decomposition module. It calculates the ohmic internal resistance of the battery under test based on the voltage signal output by the high-pass filter, calculates the electrochemical polarization internal resistance of the battery under test based on the voltage signal output by the band-pass filter, and calculates the concentration polarization internal resistance of the battery under test based on the voltage signal output by the low-pass filter.

[0007] Preferably, the DC discharge module includes a constant current source and a switching device, wherein the switching device is a MOSFET or an IGBT, which controls the magnitude and duration of the discharge current pulse.

[0008] Preferably, the voltage response acquisition module has a sampling frequency of not less than 10 kHz.

[0009] Preferably, the cutoff frequency of the high-pass filter is set to 1kHz-10kHz, the cutoff frequency of the band-pass filter is set to 1Hz-1kHz, and the cutoff frequency of the low-pass filter is set to 0.1-1Hz. The multi-frequency filtering decomposition module also includes a bandpass filter, which separates the electrochemical polarization resistance and the concentration polarization resistance.

[0010] Preferably, the expressions for calculating the ohmic internal resistance, electrochemical polarization internal resistance, and concentration polarization internal resistance by the internal resistance calculation and output module are as follows: in, Indicates the internal resistance of the ohm. This represents the voltage change after passing through the high-pass filter. Indicates the electrochemical polarization internal resistance. Indicates polarization internal resistance. This indicates the change in discharge current. express , Voltage change at a given time point This represents the steady-state voltage change after 30 seconds of passing through a low-pass filter. This indicates the internal resistance of concentration polarization.

[0011] This invention also provides a method for identifying ohmic and polarization internal resistance based on filter decomposition, comprising the following steps: S1. Control the DC discharge control module to apply a DC discharge current pulse to the battery under test; S2. The voltage waveform across the battery under test is acquired by the voltage response acquisition module during the DC discharge current pulse. S3. Simultaneously input the acquired voltage waveform into a high-pass filter, a band-pass filter, and a low-pass filter for signal decomposition; S301. The high-pass filter extracts the rapidly changing components in the voltage waveform, corresponding to the voltage drop caused by the ohmic internal resistance. Based on the voltage signal output by the high-pass filter, the ohmic internal resistance of the battery under test is calculated using the following expression: in, Indicates the internal resistance of the ohm. This represents the voltage change after passing through the high-pass filter. This indicates the change in discharge current; S302. The low-pass filter extracts the slowly changing components in the voltage waveform, corresponding to the voltage drop caused by the polarization resistance. Based on the voltage signal output by the low-pass filter, the polarization resistance of the battery under test is calculated, expressed as: in, This represents the voltage change after passing through the low-pass filter. Indicates polarization resistance; S4. Output the values ​​of each internal resistance component of the battery under test to evaluate the battery health status.

[0012] Preferably, the acquired voltage waveform is input into a bandpass filter, and the electrochemical polarization resistance is calculated, expressed as: in, Indicates the electrochemical polarization internal resistance. This indicates the change in discharge current. express , Voltage change at a given time point; in, This indicates the internal resistance of concentration polarization.

[0013] Compared with the prior art, the beneficial effects of the present invention are: This invention is the first to separate DC discharge voltage signals by frequency components using filter decomposition technology, extracting the voltage signal components corresponding to ohmic internal resistance and polarization internal resistance respectively. This method fundamentally solves the industry problem of "mixed identification" of internal resistance in traditional DC discharge methods, and can accurately reflect different aging mechanisms inside the battery (such as increased ohmic internal resistance indicating connection deterioration, and increased polarization internal resistance indicating active material deactivation). It also avoids the complex phase detection and spectrum analysis required by AC impedance methods. At the same time, the entire measurement and calculation process can be completed in seconds, without the need for long-term charge and discharge rest, and supports online real-time monitoring, which greatly improves the instant response capability of the battery management system and realizes accurate and real-time separation and monitoring of internal resistance components. This invention designs a parallel multi-channel filtering architecture that can simultaneously acquire different frequency components of a voltage signal, achieving real-time separation and calculation of internal resistance components. The core functions can be implemented using conventional filters and electronic components (such as second-order active filters and MCUs), without relying on expensive dedicated equipment (such as electrochemical workstations and square wave generators), resulting in extremely low hardware costs. This is highly beneficial for large-scale promotion and application in scenarios such as electric vehicles and energy storage systems. In addition, the circuit system provided by this invention can be easily integrated into existing battery management systems (BMS) as a functional module without requiring major modifications to the existing architecture.

[0014] This invention utilizes battery characteristic adaptive filtering technology to automatically adjust filter parameters based on battery type and operating state, ensuring accurate separation of internal resistance components in different application scenarios. By separating different internal resistance components, mutual interference is avoided, thus improving measurement accuracy.

[0015] The circuit system provided by this invention is applicable to various types of batteries, including lithium-ion batteries, lead-acid batteries, nickel-metal hydride batteries, etc., and can also be applied to battery systems of different sizes, from small portable devices to large energy storage systems. Attached Figure Description

[0016] Figure 1 is a schematic diagram of the connection of the identification system modules of the present invention; Figure 2 This is a flowchart of the identification method of the present invention. Detailed Implementation

[0017] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structure, features and effects of the present invention, in conjunction with the accompanying drawings and preferred embodiments, is provided below.

[0018] This embodiment provides an ohmic and polarization internal resistance identification system based on filter decomposition, such as... Figure 1As shown, it includes a DC discharge module (101), a voltage response sampling module (102), a signal amplification circuit (103), a multi-frequency filtering decomposition module, and an internal resistance calculation and output module (107). The multi-frequency filtering decomposition module includes a high-pass filter (104), a band-pass filter (105), and a low-pass filter (106). The DC discharge module (101) includes a controllable load circuit and a current control unit. It applies a controllable DC discharge current pulse to the battery under test in a very short time (usually milliseconds). The DC discharge module controls the size and duration of the discharge current pulse through a MOSFET or IGBT switch to generate a small current discharge pulse with a duration of 10ms and an amplitude of 0.01C, ensuring that the battery under test can generate sufficient voltage response without affecting the battery performance. The voltage response acquisition module (102) is connected to the battery under test and includes a high-precision analog-to-digital converter (ADC) and a signal conditioning circuit. The battery voltage differential signal is converted into a DC voltage signal. The voltage change generated by the small current discharge is amplified without distortion through the 105 high-bandwidth and high-gain signal amplification circuit to ensure signal accuracy. The high-precision ADC has a sampling frequency of not less than 1KHz and is used to capture the instantaneous change of the voltage at the terminal of the battery under test during the discharge process. In this embodiment, the voltage sampling module adopts a 16-bit ADC with a sampling frequency of 10KHz to ensure the capture of detailed changes in the voltage signal and to acquire the voltage waveform at both ends of the battery under test during DC discharge. The signal conditioning circuit includes an anti-aliasing filter and an amplifier to ensure the fidelity of the voltage signal. The multi-frequency filtering decomposition module is connected to the voltage response acquisition module (102) to decompose the acquired voltage waveform across the battery under test into signals with different frequency components. The multi-frequency filtering decomposition module includes at least one high-pass filter and one low-pass filter. The cutoff frequency of the high-pass filter is set to 1kHz-10kHz, and it extracts the rapidly changing components of the voltage waveform across the battery under test corresponding to the ohmic internal resistance. The cutoff frequency of the low-pass filter is set to 0.1-1Hz, and it extracts the slowly changing components of the voltage waveform across the battery under test corresponding to the polarization internal resistance. The multi-frequency filtering decomposition module also includes a band-pass filter, which further separates the electrochemical polarization internal resistance and the concentration polarization internal resistance. The correspondence between the internal resistance components and the voltage response characteristics is shown in Table 1. Table 1 In this embodiment, the high-pass filter is a second-order active filter with a cutoff frequency of 100kHz, and the low-pass filter is also a second-order active filter with a cutoff frequency of 1Hz. The internal resistance calculation and output module (107) is connected to the multi-frequency filter decomposition module. It calculates the ohmic internal resistance of the battery under test based on the voltage signal output by the high-pass filter and the polarization internal resistance of the battery under test based on the voltage signal output by the low-pass filter. In this embodiment, the internal resistance calculation and output module adopts an embedded MCU. The expressions for calculating the ohmic internal resistance and polarization internal resistance by the internal resistance calculation and output module are as follows: in, Indicates the internal resistance of the ohm. This represents the voltage change after passing through the high-pass filter. This represents the voltage change after passing through the low-pass filter. This indicates the change in discharge current. This indicates the polarization resistance.

[0019] In this embodiment, temperature sensing and adaptive filtering functions are added to the basic configuration. The temperature sensor monitors the battery temperature, and the MCU dynamically adjusts the filter parameters according to temperature changes to adapt to changes in battery characteristics. The relationship between the filter parameters and battery temperature is shown in Table 2. Table 2 Furthermore, this embodiment also includes a bandpass filter to further separate the electrochemical polarization resistance and concentration polarization resistance. The acquired voltage waveform is input into the bandpass filter to calculate the electrochemical polarization resistance, expressed as: in, Indicates the electrochemical polarization internal resistance. This indicates the change in discharge current. express , Voltage change at a given time point.

[0020] In this embodiment, the filter design has the following characteristics: Adjustable cutoff frequency: The cutoff frequency of the filter can be adjusted according to the battery type and application scenario to adapt to the internal resistance characteristics of different battery chemical systems. For example, for lithium-ion batteries, the cutoff frequency of the high-pass filter can be set to about 500Hz, and the cutoff frequency of the low-pass filter can be set to about 1Hz. Phase preservation characteristics: The filter design takes into account the phase response to ensure time alignment of different frequency components and avoid internal resistance calculation errors caused by phase distortion; Adaptive filtering: The filter parameters can be dynamically adjusted according to ambient temperature, battery SOC (state of charge) and SOH (state of health) to adapt to changes in battery characteristics.

[0021] This embodiment also provides an internal resistance identification method using an ohmic and polarization internal resistance identification system based on filter decomposition, including the following steps: S1. The DC discharge control module applies an instantaneous DC discharge current pulse to the battery under test, typically lasting between 10 and 100 milliseconds. S2. The voltage waveform across the battery under test is acquired by the voltage response acquisition module during the DC discharge current pulse. S3. The acquired voltage waveform is simultaneously input into a high-pass filter and a low-pass filter for signal decomposition. S301. The high-pass filter extracts the rapidly changing components in the voltage waveform, corresponding to the voltage drop caused by the ohmic internal resistance. The ohmic internal resistance of the battery under test is calculated based on the voltage signal output by the high-pass filter, expressed as: in, Indicates the internal resistance of the ohm. This represents the voltage change after passing through the high-pass filter. This indicates the change in discharge current; S302. The low-pass filter extracts the slowly changing components in the voltage waveform, corresponding to the voltage drop caused by the polarization resistance. The polarization resistance of the battery under test is calculated based on the voltage signal output by the low-pass filter, expressed as: in, This represents the voltage change after passing through the low-pass filter. Indicates polarization resistance; The acquired voltage waveform is input into a bandpass filter, and the electrochemical polarization internal resistance is calculated. The expression is: in, Indicates the electrochemical polarization internal resistance. This indicates the change in discharge current. express , Voltage change at a given time point; The remaining portion of the polarization internal resistance is identified as the concentration polarization internal resistance, expressed as follows: in, This indicates the internal resistance of concentration polarization.

[0022] S4 outputs the internal resistance components of the battery under test, which are used to evaluate the battery health status and system control.

[0023] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. An ohmic and polarization internal resistance identification system based on filter decomposition, characterized in that, It includes a DC discharge module, a voltage response sampling module, a multi-frequency filter decomposition module, and an internal resistance calculation and output module; The DC discharge module includes a controllable load circuit and a current control unit, which applies a controllable DC discharge current pulse to the battery under test. The voltage response acquisition module is connected to the battery under test and includes a high-precision analog-to-digital converter (ADC) and a signal conditioning circuit. It acquires the voltage waveform across the battery under test during DC discharge. The signal conditioning circuit includes an anti-aliasing filter and an amplifier. The multi-frequency filtering decomposition module is connected to the voltage response acquisition module, and decomposes the acquired voltage waveform across the battery under test into signals with different frequency components. The multi-frequency filtering decomposition module includes at least one high-pass filter, one band-pass filter, and one low-pass filter. The high-pass filter extracts the rapidly changing component of the voltage waveform across the battery under test, corresponding to the ohmic internal resistance. The band-pass filter extracts the mid-frequency changing component of the voltage waveform across the battery under test, corresponding to the electrochemical polarization resistance. The low-pass filter extracts the slowly changing component of the voltage waveform across the battery under test, corresponding to the concentration polarization internal resistance. The internal resistance calculation and output module is connected to the multi-frequency filtering and decomposition module. It calculates the ohmic internal resistance of the battery under test based on the voltage signal output by the high-pass filter, calculates the electrochemical polarization internal resistance of the battery under test based on the voltage signal output by the band-pass filter, and calculates the concentration polarization internal resistance of the battery under test based on the voltage signal output by the low-pass filter.

2. The Ohmic and Polarization Internal Resistance Identification System Based on Filter Decomposition according to claim 1, characterized in that, The DC discharge module includes a constant current source and a switching device, wherein the switching device is a MOSFET or an IGBT, which controls the magnitude and duration of the discharge current pulse.

3. The Ohmic and Polarization Internal Resistance Identification System Based on Filter Decomposition according to claim 1, characterized in that, The voltage response acquisition module has a sampling frequency of not less than 10KHz.

4. The Ohmic and Polarization Internal Resistance Identification System Based on Filter Decomposition according to claim 1, characterized in that, The cutoff frequency of the high-pass filter is set to 1kHz-10kHz, the cutoff frequency of the band-pass filter is set to 1Hz-1kHz, and the cutoff frequency of the low-pass filter is set to 0.1-1Hz.

5. The Ohmic and Polarization Internal Resistance Identification System Based on Filter Decomposition according to claim 1, characterized in that, The expressions for calculating ohmic internal resistance, electrochemical polarization internal resistance, and concentration polarization internal resistance by the internal resistance calculation and output module are as follows: in, Indicates the internal resistance of the ohm. This represents the voltage change after passing through the high-pass filter. Indicates the electrochemical polarization internal resistance. Indicates polarization internal resistance. This indicates the change in discharge current. express , Voltage change at a given time point This represents the steady-state voltage change after 30 seconds of passing through a low-pass filter. This indicates the internal resistance of concentration polarization.

6. A method for identifying ohmic and polarization internal resistance based on filter decomposition, which applies the identification system described in claim 1 for internal resistance identification, characterized in that, Includes the following steps: S1. Control the DC discharge control module to apply a DC discharge current pulse to the battery under test; S2. The voltage waveform across the battery under test is acquired by the voltage response acquisition module during the DC discharge current pulse. S3. Simultaneously input the acquired voltage waveform into a high-pass filter, a band-pass filter, and a low-pass filter for signal decomposition; S301. The high-pass filter extracts the rapidly changing components in the voltage waveform, corresponding to the voltage drop caused by the ohmic internal resistance. Based on the voltage signal output by the high-pass filter, the ohmic internal resistance of the battery under test is calculated using the following expression: in, Indicates the internal resistance of the ohm. This represents the voltage change after passing through the high-pass filter. This indicates the change in discharge current; S302. The low-pass filter extracts the slowly changing components in the voltage waveform, corresponding to the voltage drop caused by the polarization resistance. Based on the voltage signal output by the low-pass filter, the polarization resistance of the battery under test is calculated, expressed as: in, This represents the voltage change after passing through the low-pass filter. Indicates polarization resistance; S4. Output the values ​​of each internal resistance component of the battery under test to evaluate the battery health status.

7. The method for identifying ohmic and polarization internal resistance based on filter decomposition according to claim 6, characterized in that, The acquired voltage waveform is input into a bandpass filter, and the electrochemical polarization resistance is calculated. The expression is: in, Indicates the electrochemical polarization internal resistance. This indicates the change in discharge current. express , Voltage change at a given time point; in, This indicates the internal resistance of concentration polarization.

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