Battery management system and method of driving the same

1. A method of driving a battery management system that estimates an internal impedance of a battery including a plurality of cells, the method comprising:

generating a battery equivalent model of the battery;

receiving a terminal voltage signal and a charge and discharge current signal of the battery;

generating a first discrete signal corresponding to the terminal voltage signal of the battery;

generating a second discrete signal corresponding to the charge and discharge current signal of the battery;

estimating the internal impedance of the battery by filtering the first discrete signal and the second discrete signal according to a frequency range corresponding to the battery equivalent model; generating a third discrete signal by filtering the first discrete signal according to the frequency range corresponding to the battery equivalent model; and generating a fourth discrete signal by filtering the second discrete signal according to the frequency range corresponding to the battery equivalent model,

wherein the generating of the battery equivalent model comprises:

calculating a first parameter, which represents a resistance overvoltage corresponding to the internal impedance of the battery;

calculating a second parameter, which represents a charge transfer overvoltage;

calculating a third parameter, which represents a diffusion overvoltage; and

calculating a fourth parameter, which represents an open circuit voltage;

dividing the first to fourth parameters according to a frequency domain; and the estimating of the internal impedance of the battery further comprises:

filtering the first parameter by using a high-pass filter,

filtering the second parameter by using a band-pass filter, and

filtering the third and fourth parameters by using a low-pass filter.

2. The method of claim 1 , wherein the estimating of the internal impedance further comprises:

using a bilinear conversion method to generate the first to fourth discrete signals.

3. The method of claim 1 , wherein the battery equivalent model comprises:

a first capacitor and a first resistor connected in parallel to represent a charge transfer impedance of the battery;

a second capacitor and a second resistor connected in parallel to represent a diffusion impedance of the battery;

a third resistor to represent a series resistance impedance of the battery; and

an open circuit voltage component to represent an open circuit voltage of the battery.

4. The method of claim 1 , further comprising:

dividing the first to fourth parameters according to a frequency domain; and

estimating of the internal impedance further comprises:

filtering the first parameter by using a high-pass filter; and

filtering the second, third, and fourth parameters by using a low-pass filter.

5. The method of claim 1 , further comprising:

estimating the first to fourth parameters by using the third discrete signal and the fourth discrete signal; and

estimating a resistor and a capacitor that correspond to the internal impedance of the battery by using the first to fourth parameters.

6. The method of claim 5 , further comprising:

estimating the first to fourth parameters by using the third discrete signal and the fourth discrete signal by using a least square estimation method.

7. A battery management system that estimates an internal impedance of a battery including a plurality of cells, the system comprising:

an anti-aliasing low-pass filter that receives a battery terminal voltage signal and a battery terminal current signal and removes aliasing of the battery terminal voltage signal and the battery terminal current signal so as to generate a first signal and a second signal;

a continuous/discrete signal converter that converts the first signal and the second signal from the anti-aliasing low-pass filter into discrete signals according to a sampling time, and thereby generates a first discrete signal corresponding to the first signal and a second discrete signal corresponding to the second signal; and

an impedance estimating unit that estimates the internal impedance of the battery by filtering the first and the second discrete signals according to a frequency range corresponding to a battery equivalent model of the battery,

wherein the impedance estimating unit further:

generates a third discrete signal by filtering the first discrete signal and a fourth discrete signal by filtering the second discrete signal according to the frequency range corresponding to the battery equivalent model of the battery;

estimates the internal impedance of the battery by using a third discrete signal and a fourth discrete signal,

wherein the battery equivalent model includes four parameters, each of which corresponds to the internal impedance of the battery, the four parameters comprising:

a first parameter, which represents resistance overvoltage;

a second parameter, which represents a charge transfer overvoltage;

a third parameter, which represents a diffusion overvoltage; and

a fourth parameter, which represents an open circuit voltage; and

wherein the impedance estimating unit:

divides the four parameters according to a frequency domain; and

filters the first parameter by using a high-pass filter;

filters the second parameter by using a band-pass filter; and

filters the third and the fourth parameters by using a low-pass filter.

8. The system of claim 7 , wherein the impedance estimating unit further:

estimates the four parameters by using the third discrete signal and the fourth discrete signal; and

estimates a resistor and a capacitor that correspond to the internal impedance of the battery using the four parameters.