JP2011122918A - Device for evaluating battery characteristics - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device for evaluating battery characteristics which can enhance accuracy of a circuit constant identification value in an equivalent circuit model of a battery, in consideration of Warburg impedance. <P>SOLUTION: The device for evaluating battery characteristics, so constituted as to identify a circuit constant for the equivalent circuit model on the basis of current-voltage characteristics of the battery, includes a current detecting part which detects rise and fall of a rectangular wave current and outputs the respective step functions thereof and a circuit constant optimizing part to which the step functions, a voltage measured value and equivalent circuit model data are input and which computes and outputs an optimized circuit constant of the equivalent circuit model. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a battery characteristic evaluation apparatus, and more particularly, to an increase in accuracy of a circuit constant identification value in an equivalent circuit model of a battery.

  FIG. 7 is a block diagram showing an example of a conventional circuit used for current and voltage measurement for evaluating battery characteristics. A load 2 and an ammeter 3 are connected in series with the battery 1 to be measured, and a voltmeter 4 is connected in parallel with the battery 1.

  The ammeter 3 measures the measured value of the rise and fall of the output current of the battery 1 that changes according to the on / off state of the load 2, and the voltmeter 4 indicates the state of the battery 1 that changes according to the on / off state of the load 2. Measure the measured value of the rise and fall of the output voltage. These specific measurement procedures are described in Patent Document 1.

  FIG. 8 is a block diagram showing a conventional example of a battery characteristic evaluation apparatus that performs battery characteristic evaluation based on the measurement result of FIG. The input unit 5 receives current actual value data IM from the ammeter 3, voltage actual value data VM from the voltmeter 4, and standard equivalent circuit model data EM of the battery 1 created in advance.

  The circuit constant optimization unit 6 includes a voltage calculation unit 6a and a determination unit 6b. The current measurement value data IM by the ammeter 3 input from the input unit 5, the voltage measurement value data VM by the voltmeter 4, and the equivalent Based on the circuit model data EM, the circuit constant of the equivalent circuit model of the battery 1 is optimized as the identification value FV, and the optimized circuit constant of the equivalent circuit model is output to the output unit 7.

  In the circuit constant optimization unit 6, the current calculation value data IM and the equivalent circuit model data EM from the ammeter 3 and the circuit constant CC candidates from the determination unit 6 b are input to the voltage calculation unit 6 a to calculate the voltage calculation value VC. Is output to the determination unit 6b.

  The voltage measurement value data VM obtained by the voltmeter 4 and the voltage calculation value VC calculated by the voltage calculation unit 6a are input to the determination unit 6b, and the voltage measurement value data VM and the voltage calculation value VC are compared to determine whether or not the value is an optimum value. Is determined. If it is not optimal, a new circuit constant CC is generated from the comparison result and input to the voltage calculation unit 6a to calculate the voltage again. The above processing is repeated until the circuit constant is determined to be the optimum value. Thus, the identification value FV optimized as the circuit constant of the equivalent circuit model is output to the output unit 7.

  The output unit 7 generates a characteristic curve of the battery 1 based on the identification value FV of the circuit constant of the equivalent circuit model optimized by the circuit constant calculation unit 6 and displays it on a display unit (not shown).

  FIG. 9 is an equivalent circuit diagram illustrating the characteristics of the battery 1. In the equivalent circuit of FIG. 9, a DC power source E, a resistor R1, a parallel circuit of a resistor R2 and a capacitor C1, and a parallel circuit of a resistor R3 and a capacitor C2 are connected in series.

  When circuit data as shown in FIG. 9 is input as the equivalent circuit model data EM, the circuit constant calculation unit 6 has resistance values R1, R2, and R3 of the resistors so that the difference between the calculated voltage value and the actually measured value becomes small. The capacitance values C1 and C2 of the capacitors are calculated.

Patent Document 1 describes a method and apparatus configuration for measuring the internal impedance of a battery.
Patent Document 2 describes a method for removing the influence of response voltage due to polarization when measuring the internal impedance of a battery.

Japanese Patent Laid-Open No. 2003-4780 Japanese Patent Laid-Open No. 2005-1000096

  By the way, in the low frequency region of the impedance of the battery 1, Warburg impedance is seen due to the influence of diffusion. Although the Warburg impedance can be obtained as the impedance in the frequency domain as shown in FIG. 10, it is difficult to convert it to the time domain. Therefore, the Warburg impedance in the conventional equivalent circuit is also expressed by a resistor, a capacitor, and an inductance.

  However, the voltage drop curve due to the Warburg impedance cannot be reproduced by a combination of a resistor and a capacitor. Nevertheless, if identification is performed using a DC power source, a resistor, and a capacitor, the resistance value of the resistor and the capacitance value of the capacitor become too large to be realistic as shown in FIG. Will not be done.

  The present invention solves such a problem, and an object of the present invention is to provide a battery characteristic evaluation device capable of increasing the accuracy of the circuit constant identification value in the equivalent circuit model of the battery in consideration of the Warburg impedance. There is.

In order to achieve such a problem, the invention according to claim 1 of the present invention is:
In the battery characteristic evaluation apparatus configured to identify the circuit constant for the equivalent circuit model based on the current-voltage characteristic of the battery,
A current detector that detects the rising and falling of the rectangular wave current and outputs each step function; and
A circuit constant optimization unit that inputs the step function, the voltage actual measurement value, and the equivalent circuit model data, and calculates and outputs the circuit constant of the optimized equivalent circuit model,
It is characterized by including.

The invention described in claim 2 is the battery characteristic evaluation apparatus according to claim 1,
The circuit constant optimization unit
A step response calculation unit that receives the rising and falling step functions and equivalent circuit model data output from the current detection unit, and calculates and outputs a step response voltage corresponding to the rising and falling step functions;
A voltage adder that adds a step response voltage calculated and output from the step response calculator and outputs a voltage calculation value; and
The calculated voltage value and the measured voltage value are input, and the measured voltage value and the calculated voltage value are compared to determine whether the value is an optimum value. A determination unit that inputs to each step response calculation unit and calculates the voltage again,
It is comprised by these.

The invention according to claim 3 is the battery characteristic evaluation apparatus according to claim 1 or 2,
Each of the equivalent circuit models includes a Warburg impedance.

  According to the battery characteristic evaluation apparatus of the present invention, the circuit constants in the equivalent circuit model of the battery can be identified with high accuracy in consideration of the Warburg impedance, and the battery characteristic can be evaluated with high accuracy.

It is a block diagram which shows one Example of this invention. It is an equivalent circuit example figure containing the Warburg impedance showing the characteristic of a battery. It is operation | movement explanatory drawing which decomposes | disassembles the electric current of a rectangular wave into a step function. It is explanatory drawing of the recombination by the superimposition of the step response in the circuit of FIG. 2 except a power supply part. It is a voltage response characteristic example figure of a battery. It is an equivalent circuit diagram in which the Warburg impedance W1 is independently connected in series. It is a block diagram which shows the example of the conventional circuit used for the electric current and voltage measurement for evaluating a battery characteristic. It is a block diagram which shows the prior art example of the battery characteristic evaluation apparatus which performs the characteristic evaluation of a battery based on the measurement result of FIG. It is an equivalent circuit example figure showing the characteristic of a battery. It is explanatory drawing of Warburg impedance. It is explanatory drawing of the example which approximated Warburg impedance with the resistance and the capacitor | condenser.

  Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of the present invention, and the same reference numerals are given to portions common to FIG.

  In FIG. 1, the current detection unit 8 detects the rise and fall of the current in the square wave current measurement value IM, and detects the step function “current p” corresponding to the rise of the current and the “current” corresponding to the fall of the current. n ”, and the two step functions“ current p ”and“ current n ”are input to the circuit constant calculation unit 6.

  In the circuit constant calculator 6, instead of the voltage calculator 6a of FIG. 8, two step response calculators 6c and 6d and a voltage addition for adding the response calculation results of the two step response calculators 6c and 6d A portion 6e is provided.

  The step function “current p” corresponding to the equivalent circuit model data EM, the candidate of the circuit constant CC from the determination unit 6b, and the rise of the current from the current detection unit 8 is input to the first step response calculation unit 6c. The “step response voltage p” for the current given as the function “current p” is calculated, and the calculation result “step response voltage p” is input to one input terminal of the voltage adder 6e.

  The step function “current n” corresponding to the equivalent circuit model data EM and the candidate of the circuit constant CC from the determination unit 6b and the current falling from the current detection unit 8 is input to the second step response calculation unit 6d. The “step response voltage n” for the current given as the step function “current n” is calculated, and the calculation result “step response voltage n” is input to the other input terminal of the voltage adder 6e.

  The voltage adding unit 6e adds the calculation result “step response voltage p” of the first step response calculation unit 6c and the calculation result “step response voltage n” of the second step response calculation unit 6d to obtain a voltage calculation value VC. The calculated and calculated voltage value VC is output to the determination unit 6b.

  The voltage measurement value data VM obtained by the voltmeter 4 and the voltage calculation value VC added by the voltage addition unit 6e are input to the determination unit 6b, and the voltage measurement value data VM and the voltage calculation value VC are compared to determine whether the value is an optimum value. Is determined. If it is not optimal, a new circuit constant CC is generated from the comparison result and input to the first step response calculation unit 6c and the second step response calculation unit 6d to calculate the voltage again. The above processing is repeated until the circuit constant is determined to be the optimum value. Thus, the identification value FV optimized as the circuit constant of the equivalent circuit model is output to the output unit 7.

  The output unit 7 generates a characteristic curve of the battery 1 based on the identification value FV of the circuit constant of the equivalent circuit model optimized by the circuit constant calculation unit 6 and displays it on a display unit (not shown).

  FIG. 2 is an example of an equivalent circuit including the Warburg impedance representing the characteristics of the battery. In FIG. 2, a DC power source E, a resistor R1, a parallel circuit of a resistor R2 and a capacitor C1, a series circuit of a resistor R3 and a Warburg impedance W1 representing material diffusion, and a parallel circuit of a capacitor C2 are connected in series.

  FIG. 3 is an operation explanatory diagram for decomposing a rectangular wave current into step functions. Since the current I (t) shown in (A) is a rectangular wave, it can be divided into two step functions, rising and falling, as shown in (B) and (C).

The current rectangular wave I (t) with the pulse width b is
I (t) = Io · u (t) −Io · u (t−b) = Ip + In (1)
Can be expressed. However, u (t) is a unit step function with an amplitude of 1.

The equation (1) is considered by dividing it into two time functions of Ip = Io · u (t) and In = −Io · u (t−b). In particular, for In, t ₁ = t−b, and a new time axis of t ₁ will be considered.
In (t ₁ ) = − Io · u (t ₁ ) (2)
U (t) is

Similarly, on the time axis of t ₁

It is.

Two time functions Ip (t) = Io · u (t) and In (t ₁ ) = − Io · u (t ₁ ) are obtained by performing Laplace transform, respectively.
Ip (s) = L (Io · u (t)) = Io · 1 / s
In (s) = L (−Io · u (t ₁ )) = − Io · 1 / s (3)
It is expressed as

Since these current signals flow into the impedance Z (s) and are converted into voltages, the voltages due to the respective currents are
Vp (s) = Z (s) · Io · 1 / s
Vn (s) = − Z (s) · Io · 1 / s (4)

Next, the voltage transient response signals Vp (t) and Vn (t ₁ ) when the step current flows through the impedance Z are obtained by inverse Laplace transform of the equation (4), and expressed by the following equation: Can do.
Vp (t) = L ⁻¹ (Vp (s)) = Io · L ⁻¹ (Z (s) · 1 / s)
Vn (t ₁ ) = − L ⁻¹ (Vn (s)) = − Io · L ⁻¹ (Z (s) · 1 / s) (5)

Therefore, by recombining the step current separated into two, the transient response voltage waveform V (t) when the rectangular wave current is passed through the impedance Z is
V (t) = Vp (t) + Vn (t−b) (6)
It can be expressed as

  FIG. 4 is an explanatory diagram of recombination by superimposing step responses in the circuit of FIG. 2 excluding the power supply unit. In FIG. 4, (A) represents the two step functions of the current, (B) represents the respective step responses, and (C) represents the superposition of the step responses.

  The voltage response characteristic of the battery is as shown in FIG. 5, and the voltage by the equivalent circuit including the Warburg impedance can be calculated with high accuracy. In FIG. 5, (A) shows actual measurement values when the current rises at time t1 and falls at time t2, and (B) shows the actual measurement values regarding the change in voltage accompanying the rise and fall of the current shown in (A). Is indicated by a solid line, and the calculated value is indicated by a broken line.

With this configuration, the Warburg impedance can be included in the equivalent circuit, the battery identification accuracy is increased, and the current-voltage characteristics can be made closer to reality.
Also, realistic values can be obtained for circuit constants other than Warburg impedance.

  In the above embodiment, the equivalent circuit model in which the Warburg impedance is connected in parallel has been described. However, as shown in FIG. 6, an equivalent circuit in which the Warburg impedance W1 is independently connected in series can also be implemented with easy calculation.

  In FIG. 6, the conventional method is applied to the voltage in the circuit block in which the RLC circuits are connected in series, and the method of the present invention is applied to the voltage in the Warburg impedance block.

In this case, the time domain voltage Vw of the Warburg impedance block W1 is
Vw = (δ√2t) × Ip / Γ (3/2) (7)
The calculation can be simplified. Here, σ is a constant representing diffusion, and Γ is a gamma function.

  The voltage of the entire equivalent circuit in FIG. 6 is obtained as the sum of the voltage in the block of the Warburg impedance W1 and the voltage in the block of the RLC circuit. Then, the voltage calculated by each method is evaluated in comparison with the actually measured voltage value.

  It should be noted that even if the current is not strictly a rectangular wave and has a certain degree of gradient rise, it can be calculated by approximating the rectangular wave. In this case, the error can be reduced if the rise of the current is sufficiently early with respect to the battery response.

  As described above, according to the present invention, in consideration of the Warburg impedance, it is possible to realize a battery characteristic evaluation apparatus that can identify a circuit constant in an equivalent circuit model of a battery with high accuracy and perform high-accuracy battery characteristic evaluation, It is suitable for efficient analysis of various parameters of the battery.

DESCRIPTION OF SYMBOLS 5 Input part 6 Circuit constant optimization part 6b Judgment part 6c 1st step response calculating part 6d 2nd step response calculating part 6e Voltage addition part 7 Output part 8 Current detection part

Claims (3)

In the battery characteristic evaluation apparatus configured to identify the circuit constant for the equivalent circuit model based on the current-voltage characteristic of the battery,
A current detector that detects the rising and falling of the rectangular wave current and outputs each step function; and
A circuit constant optimization unit that inputs the step function, the voltage actual measurement value, and the equivalent circuit model data, and calculates and outputs the circuit constant of the optimized equivalent circuit model,
The battery characteristic evaluation apparatus characterized by including. The circuit constant optimization unit
A step response calculation unit that receives the rising and falling step functions and equivalent circuit model data output from the current detection unit, and calculates and outputs a step response voltage corresponding to the rising and falling step functions;
A voltage adder that adds a step response voltage calculated and output from the step response calculator and outputs a voltage calculation value; and
The calculated voltage value and the measured voltage value are input, and the measured voltage value and the calculated voltage value are compared to determine whether the value is an optimum value. A determination unit that inputs to each step response calculation unit and calculates the voltage again,
The battery characteristic evaluation apparatus according to claim 1, comprising:   The battery characteristic evaluation apparatus according to claim 1, wherein each equivalent circuit model includes a Warburg impedance.

Images