KR-20260066470-A - Time/frequency based measurement method of internal impedance of battery and internal impedance time/frequency based measurement device using the same

Abstract

The time/frequency-based measurement method for the internal impedance of a battery according to the present invention comprises: a step of injecting an AC component during the charging and discharging process of the battery by setting a constant duty cycle and a duty cycle difference (ΔDuty Cycle) of a battery charging/discharging device associated with the battery; a step of processing the node current and node voltage between the battery charging/discharging device and the battery using a SOGI (Second-order Generalized Integrator) filter; a step of calculating the internal impedance of the battery through a time-domain-based impedance measurement method based on the output signal of the SOGI (Second-order Generalized Integrator) filter; and a step of calculating the internal impedance of the battery through a frequency-domain-based impedance measurement method based on the result of performing a Fast Fourier Transform (FFT) on the node current and node voltage between the battery charging/discharging device and the battery when the internal impedance calculated through the time-domain-based impedance measurement method deviates from a predetermined reference value.

Inventors

• 박화평
• 김성종

Assignees

• 국립금오공과대학교 산학협력단

Dates

Publication Date

20260512

Application Date

20241104

Claims (8)

1. A step of injecting an AC component during the charging and discharging process of the battery by setting a constant duty cycle and a duty cycle difference (ΔDuty Cycle) of a battery charging and discharging device associated with the battery; A step of processing the node current and node voltage between the battery charging/discharging device and the battery using a SOGI (Second-order Generalized Integrator) filter; A step of calculating the internal impedance of the battery through a time-domain-based impedance measurement method based on the output signal of the SOGI (Second-order Generalized Integrator) filter; and If the internal impedance calculated through the time-domain-based impedance measurement method deviates from a predetermined reference value, a step of calculating the internal impedance of the battery through a frequency-domain-based impedance measurement method based on the result of performing a Fast Fourier Transform (FFT) on the node current and node voltage between the battery charging/discharging device and the battery; A time/frequency-based measurement method for the internal impedance of a battery including
2. In measuring battery impedance by injecting an AC component during the charging and discharging process of the battery by setting a constant duty cycle and a duty cycle difference (ΔDuty Cycle) of a battery charging and discharging device associated with the battery, An internal impedance time/frequency-based measuring device characterized by measuring the internal impedance of the battery using a time-domain-based impedance measuring method or a frequency-domain-based impedance measuring method depending on the frequency band.
3. In paragraph 2, The above time-domain based impedance measurement method is, An internal impedance time/frequency-based measuring device characterized by using a SOGI (Second-order Generalized Integrator) filter including a band-pass filter and a low-pass filter.
4. In paragraph 2, The above frequency domain-based impedance measurement method is, An internal impedance time/frequency-based measuring device characterized by a Fast Fourier Transform (FFT)-based impedance measurement method.
5. Battery charging and discharging device connected to the battery; A signal generation unit that generates a PWM signal for injecting an AC component during the charging and discharging process of the battery by setting a constant duty cycle and a duty cycle difference (ΔDuty Cycle) of the battery charging and discharging device; A time-domain impedance processing unit that receives the node current and node voltage between the battery charging/discharging device and the battery and calculates the internal impedance of the battery; and A frequency domain impedance processing unit that receives the node current and node voltage between the battery charging/discharging device and the battery and calculates the internal impedance of the battery; An internal impedance time/frequency-based measuring device including
6. In paragraph 5, An internal impedance time/frequency-based measuring device characterized by further including a control unit that determines whether to process the time domain impedance processing unit or the frequency domain impedance processing unit according to the frequency band.
7. In paragraph 5, The above time-domain impedance processing unit is, A SOGI (Second-order Generalized Integrator) filter that receives the node current and node voltage between the battery charging/discharging device and the battery; and An internal impedance time/frequency-based measuring device characterized by including: a first impedance calculation unit that calculates the internal impedance of the battery based on the output signal of the SOGI (Second-order Generalized Integrator) filter.
8. In paragraph 5, The above frequency domain impedance processing unit is, A Fast Fourier Transform (FFT) receiving a node current and a node voltage between the battery charging/discharging device and the battery; and An internal impedance time/frequency-based measuring device characterized by including a second impedance calculation unit that calculates the internal impedance of the battery based on the output signal of the Fast Fourier Transform (FFT) unit.

Description

Time/frequency based measurement method of internal impedance of battery and internal impedance time/frequency based measurement device using the same The present invention relates to a method for measuring the internal impedance of a battery, and more specifically, to a time/frequency-based method for measuring the internal impedance of a battery and a time/frequency-based internal impedance measuring device using the same. Electrochemical Impedance Spectroscopy (EIS) is used to measure battery impedance, a critical factor in assessing battery condition. EIS offers the advantage of diagnosing battery status by measuring impedance at various frequencies. In the case of conventional battery measurement devices using EIS (Electrochemical Impedance Spectroscopy), AC voltage is injected into the battery from an external source, and the battery's impedance is calculated based on the magnitude and phase difference of the AC voltage and current. In other words, while measurement methods based on the Fast Fourier Transform (FFT) are generally used to implement Electrochemical Impedance Spectroscopy (EIS), performing the FFT in the low-frequency band consumes a significant amount of time, and time-domain based methods are vulnerable to disturbances in the relatively high-frequency band, leading to issues in the execution of EIS. Figure 1 is a diagram showing an EIS (Electrochemical Impedance Spectroscopy) graph and a battery internal impedance model. FIG. 2 is a configuration diagram of the internal impedance measurement system (1) of the present invention. FIG. 3 is a configuration diagram of the internal impedance time/frequency-based measuring device (200) of FIG. 2. FIG. 4 is a configuration diagram according to an embodiment of the internal impedance measurement system (1) of the present invention and a simulation of the measurement technique of the internal impedance time/frequency-based measurement device (200). FIG. 5 is a configuration diagram according to an embodiment of a time-domain impedance processing unit. FIG. 6 is a configuration diagram according to an embodiment of a frequency domain impedance processing unit. FIG. 7 is a flowchart of a battery impedance measurement technique according to an embodiment of the present invention. FIG. 8 is a diagram showing a system structure for measuring battery impedance according to an embodiment of the present invention. FIG. 9 is a drawing showing limitations according to the impedance calculation method. FIG. 10 is a diagram showing the proposed multi-sine wave perturbation. Figure 11 is a diagram showing the experimental verification of the designed perturbation signal. Figure 12 is a diagram showing the experimental verification of MSP through frequency spectrum analysis. Figure 13 is a diagram showing the experimental verification of the frequency sweep of a single sine wave perturbation (SSP). FIG. 14 is a diagram showing the change in perturbation mode between single sine wave operation and multiple sine wave operation. Figure 15 shows the experimental results of the battery AC resistance measurement. Hereinafter, in order to explain in detail enough for a person skilled in the art to easily implement the technical concept of the present invention, embodiments of the present invention will be described with reference to the attached drawings. Figure 1 is a diagram showing an Electrochemical Impedance Spectroscopy (EIS) graph and a battery internal impedance model. As shown in Fig. 1, the equivalent circuit of a battery can be represented by resistance, inductance, and capacitance. In addition, the battery impedance is divided into real and imaginary parts for the AC component, and as shown in Fig. 1, the value changes depending on the frequency. Conventionally, an external AC injection device is required to inject AC components into a battery, resulting in space and additional costs. However, the present invention measures battery impedance by injecting AC components during the charging and discharging process through setting a constant duty cycle and duty cycle difference (ΔDuty Cycle) of a battery charging/discharging device (DC/DC Converter). Fast Fourier Transform (FFT) and time-domain-based impedance measurement algorithms have already been developed as Electrochemical Impedance Spectroscopy (EIS) analysis techniques. While FFT-based impedance measurement techniques are widely used due to their ease of implementation, they have the disadvantage of consuming a significant amount of time for measurements in the low-frequency range due to the characteristics of the FFT. In addition, while time-domain based impedance measurement techniques enable real-time measurement, they have limitations due to their vulnerability to noise. To overcome these limitations, the present invention devised a time-domain based impedance measurement technique using a Second-order Generalized Integrator (SOGI) filter and proposed a hybrid battery impedance measurement techni