KR20150019190A - Method of Estimating Battery Stste-Of-Charge and Apparatus therefor the same - Google Patents

Abstract

The present invention relates to a method for estimating the state of charge (SOC) of a battery and a device for the same, which can estimate the accurate SOC of a battery by considering a real-time variable voltage, the steady state of the voltage, a temperature, etc. To achieve the objective of the present invention, the method for estimating the SOC of a battery according to an embodiment of the present invention comprises the steps of: measuring an instantaneous voltage, an instantaneous current, and a temperature; estimating an initial SOC (battery SOC); estimating a first SOC by integrating a current value inputted for a unit time based on the estimated initial SOC and dividing the integrated value by a total battery capacity value when the measured instantaneous current exceeds a first threshold, a current variation exceeds a second threshold range, or a voltage relaxation count is on; updating the internal resistance of a battery when the voltage relaxation count is off, the measured instantaneous current is less than or equal to the first threshold, and the current variation is less than or equal to the second threshold range, and estimating the open-circuit voltage (OCV) of the battery based on the updated internal resistance, the measured instantaneous voltage and instantaneous current; estimating a second SOC corresponding to the estimated OCV from a SOC-OCV table per temperature based on the measured temperature; and estimating a final SOC by combining the estimated first SOC and second SOC in a predetermined ratio.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method of estimating a state of charge of a battery,

The present invention relates to a battery charging state estimation method and apparatus therefor, and more particularly, to a battery charging state estimation method for accurately estimating a battery charging state (SOC) in consideration of a voltage, a stable state of a voltage, And to provide a device for such use.

Description of the Related Art [0002] Electric vehicles including a hybrid electric generator that performs power generation by driving or regeneration by an engine and a hybrid electric vehicle that operates by electric power from a battery to drive a drive wheel and a hybrid vehicle include a nickel- A secondary battery (i.e., battery) for driving a motor such as a battery is used.

When the SOC is 100% and the SOC is 0%, it indicates that the charged amount is in a zero state.

Also, the battery has a correspondence relationship between the open-circuit voltage (Vocv) and the SOC of 1: 1. Therefore, the open-circuit voltage (Vocv) of the battery can be measured or estimated, and the SOC corresponding to the open-circuit voltage (Vocv) can be obtained from the Vocv-SOC correlation.

The state of charge (SOC) of the battery described above varies depending on the running state of the vehicle (e.g., oscillation, normal running, acceleration, deceleration) or the vehicle load (stop lamp, head lamp, wiper, Therefore, it is necessary to estimate the SOC during use of the battery.

As a conventional SOC estimating device for a battery, an SOC estimating device for estimating the SOC by integrating the current (charge / discharge current) value of the battery is widely used.

For example, a method of estimating the initial SOC by obtaining the Vocv value through the measured open-circuit voltage, estimating the internal resistance from the voltage and the measured current from the next time, estimating the current therefrom, and continuously estimating the SOC through current integration have.

Although this method is a current integration method, it does not estimate the SOC at a measured current value sensed by an actual current sensor.

In addition, since the current value is estimated based on the battery internal resistance value and the current integration is applied based on the estimated current value, if the accurate internal resistance value can not be obtained, an incorrect SOC value can be estimated.

In addition, since the temperature variable is considered only when the current fluctuation is large, it is impossible to estimate the SOC according to the real-time temperature.

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above problems, and it is an object of the present invention to monitor the steady state of current and voltage which vary in real time, and to estimate an accurate SOC.

According to an aspect of the present invention, there is provided a battery state estimation method comprising: measuring an instantaneous voltage, an instantaneous current, and a temperature; estimating an initial SOC (battery charging state) Or integrates the current value inputted for a unit time based on the estimated initial SOC when the current change amount exceeds the second threshold value or when the voltage relaxation count is turned on and divides the integrated value by the total battery capacity value Estimates a first SOC, updates the internal resistance of the battery when the voltage relaxation count is off, the measured instantaneous current is less than or equal to the first threshold, and the current variation is less than or equal to the second threshold range , Estimating an open-circuit voltage (OCV) of the battery based on the updated internal resistance and the measured instantaneous voltage and instantaneous current, and based on the measured temperature Estimating a second SOC corresponding to the estimated open-circuit voltage (OCV) from the temperature-dependent SOC-OCV table, and combining the estimated first SOC and second SOC at a predetermined ratio to estimate a final SOC .

According to various embodiments of the present invention, there is an effect of accurately estimating the SOC in real time by monitoring the stable state of the current and voltage which vary in real time. In addition, the voltage relaxation count is applied so that the SOC can be more accurately estimated in a variable current range.

1 is a block diagram illustrating a process for estimating an SOC according to a preferred embodiment of the present invention.
2 is a graph showing an example of a dynamic model (a) and a static model (b) of a battery and a related circuit diagram thereof according to a preferred embodiment of the present invention.
FIG. 3 is a graph illustrating an SOC table for each OCV by interpolation according to a preferred embodiment of the present invention.
4 is a mapping table for performing a first SOC estimation operation and a second SOC estimation operation according to a voltage variation and a voltage variation according to a preferred embodiment of the present invention.
5 is a flowchart illustrating a process of estimating an SOC according to a preferred embodiment of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention and the manner of achieving them will become apparent with reference to the embodiments described in detail below with reference to the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Is provided to fully convey the scope of the invention to those skilled in the art, and the invention is only defined by the scope of the claims. It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. In the present specification, the singular form includes plural forms unless otherwise specified in the specification. As used herein, the terms " comprises, " and / or "comprising" refer to the presence or absence of one or more other components, steps, operations, and / Or additions.

The present invention is an algorithm for estimating the SOC of a battery pack for a vehicle, and uses the input current, temperature, and voltage at the time of charge / discharge of the battery to apply the SOC estimation calculation to estimate the final SOC.

1 is a block diagram illustrating a process for estimating an SOC according to a preferred embodiment of the present invention.

1, the controller 26 performs a first SOC estimation operation or a second SOC estimation operation according to a condition using a threshold value of an instantaneous current input from a current sensor, a change value of instantaneous currents, and a voltage relaxation count And selectively estimates the SOC.

The first SOC estimation operation estimates the SOC of the battery pack by integrating the input instantaneous current based on the initial SOC value to calculate the SOC of the battery pack. When the instantaneous current exceeds the first threshold value , Or estimates SOC by current integration when the amount of change in current exceeds the second threshold range.

Wherein the second SOC estimation operation is performed in the second SOC estimation operation in which the voltage relaxation count is off and the threshold current value (the instantaneous current is less than or equal to the first threshold value and the instantaneous current change amount is less than or equal to the second threshold value) Calculate the OCV value by calculating the internal resistance of the battery, and estimate the SOC using the 0CV table for each SOC by temperature.

To this end, the controller 26 receives the respective parameter input values from the temperature sensor 21, the voltage sensor 22, and the current sensor 23.

The controller 26 controls the first SOC estimation operation and the second SOC estimation operation described above to be performed according to the input condition based on the received parameter input value.

The first SOC estimation is expressed by Equation (1).

[Equation 1]

I indicates input current A, t indicates time s, and C indicates battery capacity (Ah = 3600 As).

That is, a value obtained by integrating a current value input by a unit time and dividing by the total battery capacity represents an SOC value fluctuated during a unit time. Therefore, if the instantaneous change SOC value is added to the (n-1) th SOC (n-1), the nth SOC value is estimated.

2 is a graph showing an example of a dynamic model (a) and a static model (b) of a battery and a related circuit diagram thereof according to a preferred embodiment of the present invention.

In Fig. 2, Rs denotes a battery series resistance, indicating electrode collector resistance + electrolyte resistance, and Rp indicates battery polarization resistance.

When the charging and discharging currents are applied and terminated in the battery, the IR voltage rise and drop due to the resistance is initially detected and a certain time is required until the voltage reaches the steady state. The voltage relaxation count considering this time is applied, And estimates the first SOC by the first SOC estimation calculation based on Equation (1).

The second SOC estimation operation is performed according to the following equation (2) and the detailed description thereof.

The internal resistance of the battery is calculated according to the Ohm's law as shown in Equation 2 below.

&Quot; (2) "

In Equation (2), the resistance is updated when the threshold value of the current is satisfied.

That is, the instantaneous current I (n) is less than or equal to the threshold current 1, and the change amount ΔI of the instantaneous currents is less than or equal to the threshold current 2 range.

The OCV value is calculated according to the following equation using the calculated internal resistance value.

&Quot; (3) "

ocv (n) = V (n) - I (n) * R

In the above equation, V (n) designates the instantaneous voltage of n time, I (n) designates the instantaneous current of n time, and R designates the battery internal resistance.

FIG. 3 is a graph illustrating an SOC table for each OCV by interpolation according to a preferred embodiment of the present invention.

Referring to FIG. 3, the controller 26 estimates a second SOC based on the second SOC estimation operation by converting the OCV calculated on the basis of the SOC-specific OCV-by-temperature table created by the interpolation method into the SOC.

4 is a mapping table for performing a first SOC estimation operation and a second SOC estimation operation according to a voltage variation and a voltage variation according to a preferred embodiment of the present invention.

In FIG. 4, a first SOC estimation or a second SOC estimation operation is performed according to the current value. The maximum value or the minimum value of the current value may vary according to the measured temperature.

5 is a flowchart illustrating a process of estimating an SOC according to a preferred embodiment of the present invention.

Referring to FIG. 5, a voltage sensor, a current sensor, and a temperature sensor measure an instantaneous voltage, an instantaneous current, and a temperature. (S10)

The initial SOC is calculated based on the measured instantaneous voltage, the instantaneous current, and the temperature. (S11) The initial SOC is calculated by referring to the SOC table for each initial voltage OCV. (S11)

Ten thousand and one, lI _n -I _{n -1} l is less than or equal to a critical current 1, lI l _n less than or equal to the threshold current 2, _n lI judges _-1 l is less than or equal to the second critical current. (S12), that is, whether the current change is less than or equal to the threshold current 1 range and whether the currents are less than or equal to the threshold current 2.

If the condition of S12 is satisfied, the resistance R is updated as follows. (S13)

&Quot; (4) "

R (resistance) = (V _n -V _{n -1} ) / (I _n -I _{n -1} )

When in the above S12 is lI _n -I _{n -1} l exceeds the critical current, or the first range lI l _n exceeds the second threshold current, or voltage relaxation (S14), the first SOC estimation operation when the count on To estimate the first SOC. (S15)

The first SOC estimation operation is performed according to the following equation (5) by a current integration method.

&Quot; (5) "

SOC (n) = SOC (n-1) + (I _n * time) / battery capacity

When the voltage relaxation count is off, the second SOC is estimated through a second SOC estimation operation using the internal resistance R calculated in S13. (S17)

The first SOC and the second SOC estimated using the first SOC estimation operation and the second SOC estimation operation are integrated based on FIG. 4 to estimate the final SOC.

&Quot; (6) "

Final SOC = 0.9 * SOC (n-1) + 0.1 * SOC (n)

FIG. 7 is a graph illustrating current values required by a battery pack according to a preferred embodiment of the present invention, and comparing battery charge / discharge data with simulated SOC algorithm of the present invention.

Referring to FIG. 7, a current value required in a battery pack is calculated on the basis of UDDS (Urban Dynamometer Driving Sehedule) proposed by the US Environmental Protection Agency, and the battery charge / discharge data and the SOC algorithm of the present invention are simulated As a result of simulating the UDDS pattern by applying the SOC algorithm, it is estimated that the SOC is calculated based on the data from the charge / discharge device and the error is less than 3%.

The embodiments of the present invention described above are not only implemented by the apparatus and method but may be implemented through a program for realizing the function corresponding to the configuration of the embodiment of the present invention or a recording medium on which the program is recorded, The embodiments can be easily implemented by those skilled in the art from the description of the embodiments described above.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. The present invention is not limited to the drawings, and all or some of the embodiments may be selectively combined so that various modifications may be made.

10: BMA (battery module)
20: Battery Management System (BMS)
21: Temperature sensor
22: Voltage sensor
23: Current sensor
24: first SOC estimation operation section
25: second SOC estimation calculating section
26:

Claims (8)

Measuring an instantaneous voltage, an instantaneous current, and a temperature;
Estimating an initial SOC (battery charging state);
Integrating a current value inputted for a unit time based on the estimated initial SOC when the measured instantaneous current exceeds a first threshold value, a current variation amount exceeds a second threshold value range, or a voltage relaxation count is turned on, Estimating a first SOC by dividing the integral value by the total battery capacity value;
Updating the internal resistance of the battery when the voltage relaxation count is off and the measured instantaneous current is less than or equal to the first threshold and the current variation is less than or equal to the second threshold range, Estimating an open circuit voltage (OCV) of the battery based on the measured instantaneous voltage and instantaneous current;
Estimating a second SOC corresponding to the estimated open-circuit voltage (OCV) from the temperature-dependent SOC-OCV table based on the measured temperature;
And estimating a final SOC by combining the estimated first SOC and second SOC at a predetermined ratio. The method of claim 1, wherein the open-
V (n) denotes an instantaneous voltage of n time, I (n) denotes an instantaneous current of n time, V (n) And R denotes the measured internal resistance of the battery. The method of claim 1, wherein the SOC is estimated by referring to a SOC table for each initial voltage OCV. The method according to claim 1, wherein the final SOC is obtained by a formula in the final SOC = 0.9 * SOC (n-1) + 0.1 * SOC (n). A battery module for supplying power to the vehicle;
At least one sensor for measuring an instantaneous voltage, an instantaneous current, and a temperature;
Estimating an initial SOC (battery charge state) of the battery; estimating an initial SOC (battery charge state) of the battery when the measured instantaneous current exceeds a first threshold, a current change amount exceeds a second threshold value range, Estimates a first SOC by integrating a current value input for a unit time based on the integrated current value, dividing the integrated current value by the total battery capacity value, turns off the voltage relaxation count, and determines that the measured instantaneous current is smaller than the first threshold And updates the internal resistance of the battery when the current change amount is smaller than or equal to the second threshold value range and estimates the open-circuit voltage (OCV) of the battery based on the updated internal resistance and the measured instantaneous current and instantaneous current , Estimating a second SOC corresponding to the estimated open-circuit voltage (OCV) from the temperature-dependent SOC-OCV table based on the measured temperature, Battery charging state estimating device being configured to include a battery module system of claim 2 SOC (Battery Management System) for estimating a final SOC in combination at a predetermined ratio. 6. The method of claim 5, wherein the open-
V (n) denotes an instantaneous voltage of n time, I (n) denotes an instantaneous current of n time, V (n) And R denotes the measured internal resistance of the battery. 6. The apparatus of claim 5, wherein the SOC is estimated by referring to an SOC table for each initial voltage OCV. 6. The apparatus for estimating charged state of a battery according to claim 5, wherein the final SOC is obtained by a formula in a final SOC = 0.9 * SOC (n-1) + 0.1 * SOC (n).

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