KR101097956B1 - Apparatus and method for calculating state of charge - Google Patents

Abstract

PURPOSE: A charge state computation apparatus and method are provided to efficiently manage a battery and to monitor a user by being applied to the battery indicator of a small system. CONSTITUTION: A charge state computation apparatus comprises a detection unit(10), a first output unit(20), a second output unit(30), a controller(40), and a storage unit(60). The detection unit detects the voltage and current of a battery. The storage unit stores coefficient and degree information of a charge state function. The stores coefficient and degree information of the charge state function are calculated from a high level polynomial which is formed using Hermite interpolation and show correlation of the voltage of the battery and a charge state. The first output unit calculates the charge state according to voltage using charge state function information. The controller determines whether a current is flowing or not through the detection of the current and determines the charging and discharging of the battery.

Description

Apparatus and Method for calculating state of charge}

The present invention relates to charging and discharging of a battery, and more particularly, to an apparatus and a method for calculating a state of charge of a battery.

Today, the advancement of IT technology and the emergence of secondary batteries have created the ubiquitous era, and the rapid increase in the use of mobile devices such as notebooks, mobile phones, camcorders, PDAs, etc. has a strong demand for the rapid development of unprecedented battery technology. come. In particular, the development of secondary batteries such as lithium ion (Lithium Ion) battery or lithium polymer (Lithium Polymer) battery, which is light in weight and excellent in energy efficiency, is easy to use in mobile devices. Therefore, mobile devices have a great need for battery management including charge control, battery capacity monitoring, available time, compensation for battery capacity and available time caused by the influence of the environment. In addition, as the secondary battery is applied to an electric vehicle or a hybrid electric vehicle, the importance of battery management is also highlighted in this field.

In such battery management, the most important core technology is a technique for estimating the correct state of charge (SOC). If the state of charge of the battery is not known in the discharged state, the discharged out of the operating period of the battery due to the continuous discharge, the system is stopped or the life of the battery shortens due to the characteristics of the battery. In addition, when the state of charge is incorrectly charged in a situation where no charge is required, the battery may be wasted and cumbersome, and the battery life may be shortened. Therefore, in order to avoid such a problem, it is necessary to accurately estimate the state of charge of the battery, which is applied to a battery indicator of a small system or a battery management system (BMS) of a medium and large system. The accuracy of the estimation is determined by the state estimation method.

Batteries are devices that generate electrical energy by chemical reactions and have a non-linear characteristic that reacts sensitively to ambient temperature, internal resistance, and battery capacity. Thus, the state of charge of the battery is estimated in an indirect manner.

In the conventional method of estimating the state of charge, a method of estimating the state of charge by measuring a change in internal impedance according to charge and discharge of a battery using electro-chemical impedance spectroscopy (EIS), and a mathematical method such as a Kalman filter There is a charging state estimation method. However, the method using the internal impedance has a disadvantage in that impedance measurement is difficult and temperature sensitive in a state where the cells of the battery are chemically reacted. In addition, the method using the Kalman filter has a disadvantage in that it is difficult to apply practically due to the computation of complex parameters and the complexity of an algorithm.

In addition, conventional charging state estimation methods include a current integrating method called "Coulomb Counting" or "Ampere-Hour Counting" and an open circuit voltage (OCV) method. The current integration method is a method of integrating the actual charge / discharge current to subtract or subtract the initial charge state value (that is, the initial remaining capacity). The current integration method fails to estimate the initial state of charge and accumulates leakage current and current sensing error over time, making it impossible to accurately estimate the state of charge. On the other hand, the OCV method of estimating the state of charge by measuring the open voltage of the battery is very accurate and very suitable for estimating the initial state of charge. It is the most used at present because of its convenient advantages. However, since the OCV method depends on the accuracy of the correlation function of the state of charge with respect to the measured open voltage, the accuracy of the estimation of the state of charge varies according to the accuracy of the correlation function. Currently, the Boltzmann equation is most commonly used as a representative OCV method. The Boltzmann equation differs from the actual voltage measurement due to charging and discharging, which makes it impossible to accurately estimate the state of charge.

In addition, a conventional method of estimating a state of charge uses a method of using an electromotive force (EMF) of a battery instead of an open voltage. The EMF method is a method of estimating the state of charge using linear interpolation or linear extrapolation. Like other conventional methods, the EMF method has a problem in that due to the complexity of the algorithm, the implementation is complicated or the estimation of the inaccurate state of charge causes a large difference from the actual remaining capacity of the battery.

This conventional method of estimating the state of charge is suitable when a low current (100 mA or less: 0.1 to 0.2 C-rate (charge / discharge rate: A)) of a solar cell or the like is used or the discharge current consumed is larger than the charge current. (No design case), there is a problem that it is impossible to estimate the state of charge accurately.

The present invention estimates the state of charge of a battery through a high order polynomial implemented using Hermite Interpolation.

According to an aspect of the present invention, an apparatus for calculating a state of charge of a battery in a system equipped with a battery is disclosed.

An apparatus for calculating a state of charge according to an embodiment of the present invention includes a detector for detecting a voltage of the battery and a state of charge for the battery calculated from a high order polynomial implemented using Hermite Interpolation. A storage unit storing information, a first calculating unit calculating a state of charge according to the voltage using the state of charge function information, and determining whether the battery is charged or discharged based on detection of the voltage, And a controller configured to control the first calculator to calculate the state of charge.

The higher-order polynomial is a state-of-charge polynomial of order N, and the state of charge polynomial includes a parameter (K) representing a curve slope of the state of charge polynomial and a correction coefficient set such that the state of charge polynomial always has an inflection point, and the state of charge The function is calculated by calculating the correction coefficient and the K according to the NK value preset in the state of charge polynomial using the inflection point and the inclination of the inflection point calculated from measured data measured the state of charge with respect to the voltage of the battery. .

The state of charge polynomial (P _SOC (x)) is represented by the following equation.

은 계수, V_b는 배터리 전압이고, V_c는 배터리의 충전 종지 전압이고, V_d는 배터리의 방전 종지 전압임here,

Is the coefficient, V _b is the battery voltage, V _c is the end-of-charge voltage of the battery, and V _d is the end-of-discharge voltage of the battery

The state of charge polynomial and the coefficient are represented by the following equations for charge and discharge, respectively.

):State of charge polynomial (P _SOC (x) _C ) and coefficient (

):

):State of charge polynomial at discharge (P _SOC (x) _D ) and coefficient (

):

The state of charge polynomial and the coefficient to which the correction coefficient C _NK is applied are represented by the following equations in the case of charging and discharging, respectively.

):State of charge polynomial (P _SOC (x) _C ) and coefficient (

):

):State of charge polynomial at discharge (P _SOC (x) _D ) and coefficient (

):

The correction coefficient is calculated using the following equation when the inflection point calculated from the measured data is (ζ, SOC _C (ζ)) at the time of charging and (ζ, SOC _D (ζ)) at the time of discharge.

The slope at the inflection point is calculated using the following equation.

When the average curve slopes at the inflection points ζ, SOC _C (ζ) and (ζ, SOC _D (ζ)) obtained from the measured data are Slop _C and Slop _D , respectively, the correction coefficient C _NK , the N and K are determined using the following equation.

The apparatus may further include a second calculator configured to calculate a state of charge according to the open circuit voltage of the battery, wherein the controller controls the second calculator to calculate the state of charge when the battery is not charged or discharged.

According to another aspect of the present invention, a method of calculating a state of charge of a battery is disclosed by a state of charge calculating device provided in a system equipped with a battery.

According to an embodiment of the present invention, a method of calculating a charge state may include determining whether the battery is charged or discharged, detecting a voltage of the battery when the battery is charged or discharged, using Hermite Interpolation. Calculating a state of charge according to the voltage using the state of charge function information of the battery calculated from the implemented high order polynomial, and outputting the state of charge calculated.

The higher-order polynomial is a state-of-charge polynomial of order N, and the state of charge polynomial includes a parameter (K) representing a curve slope of the state of charge polynomial and a correction coefficient set such that the state of charge polynomial always has an inflection point, and the state of charge The function is calculated by calculating the correction coefficient and the K according to the NK value preset in the state of charge polynomial using the inflection point and the inclination of the inflection point calculated from measured data measured the state of charge with respect to the voltage of the battery. .

The state of charge polynomial (P _SOC (x)) is represented by the following equation.

은 계수, V_b는 배터리 전압이고, V_c는 배터리의 충전 종지 전압이고, V_d는 배터리의 방전 종지 전압임here,

Is the coefficient, V _b is the battery voltage, V _c is the end-of-charge voltage of the battery, and V _d is the end-of-discharge voltage of the battery

The state of charge polynomial and the coefficient are represented by the following equations for charge and discharge, respectively.

):State of charge polynomial (P _SOC (x) _C ) and coefficient (

):

):State of charge polynomial at discharge (P _SOC (x) _D ) and coefficient (

):

The state of charge polynomial and the coefficient to which the correction coefficient C _NK is applied are represented by the following equations in the case of charging and discharging, respectively.

):State of charge polynomial (P _SOC (x) _C ) and coefficient (

):

):State of charge polynomial at discharge (P _SOC (x) _D ) and coefficient (

):

The correction coefficient is calculated using the following equation when the inflection point calculated from the measured data is (ζ, SOC _C (ζ)) at the time of charging and (ζ, SOC _D (ζ)) at the time of discharge.

The slope at the inflection point is calculated using the following equation.

When the mean curve slopes at the inflection points ζ, SOC _C (ζ) and (ζ, SOC _D (ζ)) obtained from the measured data are Slop _C and Slop _D , respectively, the correction coefficient (C _{N -K} ) , N and K are determined using the following equation.

If the battery is not charged or discharged, the method may further include calculating a state of charge according to the open circuit voltage of the battery.

The present invention can estimate the state of charge of a battery through a higher-order polynomial implemented using Hermit interpolation.

In addition, the present invention can be applied to the battery indicator of a small system can be performed for efficient management of the battery and user monitoring.

In addition, the present invention can be applied to the battery management system of the medium-large system to estimate the state of charge during system operation or charging and discharging in real time.

1 is a flowchart illustrating a method of calculating a state of charge.
2 and 3 are graphs showing the characteristic graph of the Hermit interpolation state of charge polynomial according to the charge.
4 is a graph showing the characteristics of the modified Hermit interpolation state of charge polynomial according to the charge.
5 is a graph showing a characteristic graph of a modified Hermit interpolation state of charge polynomial according to discharge.
6 is a graph showing a state of charge and a state of charge measured using a Hermit interpolation state of charge polynomial;
7 is a configuration diagram schematically illustrating a configuration of an apparatus for calculating a state of charge.

The present invention may be variously modified and have various embodiments, and specific embodiments will be illustrated in the drawings and described in detail with reference to the accompanying drawings. However, this is not intended to limit the present invention to specific embodiments, it should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention.

In describing the present invention, when it is determined that the detailed description of the related known technology may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted. In addition, numerals (eg, first, second, etc.) used in the description process of the present specification are merely identification symbols for distinguishing one component from another component.

In addition, in the present specification, when one component is referred to as "connected" or "connected" with another component, the one component may be directly connected or directly connected to the other component, but in particular It is to be understood that, unless there is an opposite substrate, it may be connected or connected via another component in the middle.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description of the present invention, the same reference numerals will be used for the same means regardless of the reference numerals in order to facilitate the overall understanding.

1 is a flowchart illustrating a method of calculating a state of charge.

In step S110, a system equipped with a battery is operated. Accordingly, the state of charge calculation device provided in the system operates. Here, the battery may be, for example, a secondary battery such as a lithium ion battery, a lithium polymer battery, or the like. The apparatus for calculating a state of charge may be, for example, a battery indicator applied to a small system, a battery management system (BMS) applied to a medium to large system, and the like.

In operation S120, the charging state calculator determines whether the battery is charged or discharged. For example, the apparatus for calculating a state of charge may include a sensor for measuring current or voltage, and may determine whether the current flows through the sensor to determine whether the battery is charged or discharged. Charging may be performed through a charger or a solar cell, and the discharge may be a case where a current flows due to a phone call in the case of a mobile communication terminal.

In operation S130, when the battery is not charged or discharged, the charging state calculating device calculates and outputs the charging state according to the open circuit voltage of the battery. For example, the apparatus for calculating a state of charge may store the correlation of the state of charge with respect to the open circuit voltage in advance, and calculate the state of charge using the same.

In operation S140, the charging state calculating device detects a battery voltage when the battery is charged or discharged. For example, the state of charge calculator may detect the voltage of the battery through a sensor that measures the voltage.

In operation S150, the charging state calculating apparatus calculates the charging state according to the detected voltage of the battery using the charging state function. For example, the charging state calculating device calculates the charging state using the current integration method in the case of charging through the charger, and in the case of charging through the solar cell or in the case of general discharge (for example, the mobile communication terminal makes a phone call. Due to the current flowing through the Hermitite interpolation (Hermite Interpolation) using the high order polynomial implemented by using a high order polynomial (charge) state can be calculated.

Hereinafter, it is assumed that the state of charge calculating device calculates the state of charge for the battery being charged and discharged by using the state of charge function calculated from the Hermit interpolation polynomial. This will be described later in detail with reference to FIGS. 2 to 6.

In operation S160, the state of charge calculating device outputs the calculated state of charge.

In operation S170, the apparatus for calculating a state of charge determines whether the system is stopped. When the system is stopped, the state of charge calculation device enters step S120. That is, the charging state calculating device may calculate the charging state of the battery in real time by periodically detecting the battery voltage during charging and discharging, and calculating the charging state according to the detected battery voltage.

2 and 3 are graphs showing a characteristic graph of a Hermit interpolation state of charge polynomial according to charging, and FIG. 4 is a diagram showing a characteristic graph of a modified Hermit interpolation state of charge polynomial according to charging, and FIG. FIG. 6 is a diagram illustrating a characteristic graph of the modified Hermit interpolation state of charge polynomial, and FIG. 6 is a graph illustrating a comparison between the state of charge and the state of charge measured using the Hermit interpolation state of charge polynomial. Hereinafter, the Hermit interpolation polynomial is calculated using the Hermit interpolation polynomial, and the charging state function is calculated from the Hermit interpolation state of the polynomial, and the reference is made to FIGS. 2 to 6.

The calculation of the state of charge function can be achieved by deriving the Hermit interpolation state of charge polynomial of order N-K from the measured data obtained through the charge and discharge experiments. At this time, the Hermit interpolation polynomial showing the S-shape is derived to derive the Hermit interpolation state of charge polynomial, and a parameter for determining the slope of the curve is defined.

을 가지는 N차수 고차 다항식으로 나타낼 수 있다.In general, the state of charge polynomial (P _SOC (x)) having an S-shaped curve slope response characteristic has a real coefficient as shown in Equation 1 below.

It can be represented by the N-order higher order polynomial with.

[Equation 1]

Where V _b is the battery voltage, V _c is the end-of-charge voltage of the battery, and V _d is the end-of-discharge voltage of the battery. In this case, x has a range of 0 or more and 1 or less (x∈ [0, 1]), and the state of charge polynomial (P _SOC (x) _C ) during charging has a graph characteristic as follows.

P _SOC (x) _C having zeros of order K at x = 0

P _SOC (x) _C -1 having zeros of order N-K + 1 at x = 1

This is a special case with the "Hermite Interpolation problem", and the state of charge polynomial (P _SOC (x) _C ) at the time of charging can be represented by the following equation (2) using the Newton interpolation method.

[Equation 2]

Here, K is a parameter representing the degree of flatness of P _SOC (x) _{C and} the degree of curve inclination between (0, 1) when x = 0 and x = 1, and d _n is represented by Equation 3 below. .

&Quot; (3) "

) 공식은 다음 수학식 4와 같다.At this time, the real coefficient of the state of charge polynomial (P _SOC (x))

) Is the same as Equation 4.

&Quot; (4) "

During discharge, the state of charge polynomial (P _SOC (x) _D ) has the following graph characteristics and may be expressed as Equation 5 below.

P _SOC (x) _D having zeros of order K at x = 1

P _SOC (x) _D -1 having zeros of order N-K + 1 at x = 0

[Equation 5]

) 공식은 다음 수학식 6과 같다.At this time, the real coefficient of the state of charge polynomial (P _SOC (x))

) Formula is as shown in Equation 6 below.

&Quot; (6) "

As such, the state of charge polynomial can be easily implemented from the real coefficient formula of Equation 4 and Equation 6 using Hermit interpolation, and the real coefficient is determined by two parameters (N and K), Graph characteristics can be determined by N and K.

For example, in the case of the state of charge polynomial during charging in Equation 2, P _SOC (x) _C may be expressed as a function of K when NK or N is set. 2 and 3, each graph shown in FIGS. 2 and 3 shows a response characteristic of P _SOC (x) _C according to the value of (N, K). That is, FIG. 2 shows response characteristics of P _SOC (x) _C according to an increase in K value when NK = 3 (N = K + 3), and FIG. 3 shows P according to an increase in K value when N = 8. The response characteristic of _SOC (x) _C is shown. 2 and 3, as the K value increases, the slope of the curve increases, and the degree of flatness increases at x = 0. In addition, the slope change rate according to the increase of the K value increases more rapidly when N is set than when NK is set.

Therefore, in order to calculate the state of charge polynomial having the same curve characteristics as the state of charge graph based on the measured data, the K value must be determined for the set NK. However, P _SOC (x) _C in FIGS. 2 and 3 has unlimited K polynomials with different curve slopes for the set NK. In addition, since P _SOC (x) _C in FIGS. 2 and 3 cannot estimate the slope at a critical inflection point having a steep slope, there is a difficulty in determining the K value corresponding to the required curve slope.

Therefore, in the present specification, the correction coefficient C _NK is applied to the state of charge polynomials of Equations 2 and 5. The charging state polynomials during charging and discharging to which the correction factor is applied may be represented by Equations 7 and 8, respectively.

[Equation 7]

[Equation 8]

Here, the correction coefficient C _NK is a parameter for determining the S-shaped slope characteristic of the state of charge polynomial, which is given according to the physical capacity, characteristics, and environment of the battery so that the state of charge graph always has a significant inflection point regardless of the N and K values. It can be determined by inherent measurements.

)는 다음의 수학식 9 및 수학식 10과 같이 나타낼 수 있다.Actual coefficient with correction factor C _NK

) Can be expressed as Equation 9 and Equation 10 below.

[Equation 9]

[Equation 10]

The correction coefficient C _{N -K} may be calculated assuming that the inflection point (x = ζ) of the steep slope obtained from the measured data and the curve inflection point of the state of charge polynomials of Equations 7 and 8 are the same. That is, assuming that the important inflection points obtained from the measured data are (ζ, SOC _C (ζ)) at the time of charging and (ζ, SOC _D (ζ)) at the discharge, the correction coefficients C _NK for charging and discharging are respectively Equations 11 and 12 may be represented as follows.

[Equation 11]

[Equation 12]

At this time, the correction coefficient C _NK is a flat condition of the charging and discharging end voltage of the equation (2) and (5) has a range as shown in the following equation (13).

[Equation 13]

4 and 5 are diagrams showing the state of charge according to the N value and the K value (N, K) using the measured data for the charge and discharge, respectively. As shown in Figs. 4 and 5, the measured inflection points are (0.369, 0.29289) during charging and (0.369, 0.70711) during discharge. In other words, the state of charge graph always passes by x = 0.369. Therefore, by determining the N value and the K value having the same characteristics as the state of charge graph obtained from the measured data using the curve slope at the inflection point, the state of charge function can be calculated.

In order to determine the N and K values having the same characteristics as the state of charge graph obtained from the measured data in the state of charge polynomials of Equations 2, 5, 7 and 8, (ζ, SOC _C (ζ)) or The slope at (ζ, SOC _D (ζ)) is used. In the state of charge polynomials of the equations (2), (5), (7) and (8), the instantaneous slope (first derivative) when x = ζ may be expressed as in Equations 13 to 16, respectively.

[Equation 13]

[Equation 14]

[Equation 15]

[Equation 16]

Assuming that the mean curve slopes at the inflection points (ζ, SOC _C (ζ)) and (ζ, SOC _D (ζ)) obtained from the measured data are Slop _C and Slop _D , respectively, And (18).

[Equation 17]

Equation 18

Therefore, the correction coefficients C _NK , N values and K values can be calculated using Equations 17 and 18.

In order to confirm the accuracy of the state of charge polynomial with respect to Equation 15, a charging experiment of the battery was performed. As the measurement equipment for the experiment, Wonatech's WBCS3000 Automatic Battery Cycler was used, and the battery used was a lithium ion polymer battery of a commercially available S company's mobile phone. The battery has a capacity of 820mAh, and the battery in the pack form was disassembled and applied to the charging experiment in the form of a cell. Voltage range of the battery is 3.2V, depending on the charge-discharge experiments were set to:: (V _c charge voltage) (discharge end voltage V _d) ~ 4.2V. As a charging method, a constant current / constant voltage (CC-CV) method was used. In this case, a low current of 0.1 A, which is required for low power charging such as a solar cell, was applied. Through experiments, about 33,000 data were obtained with the battery open circuit voltage V _b (3.2≤V _b ≤4.2) over time, and 19 sample data extracted at 0.05V intervals were used as actual charging state. It became. The solid curve shown in FIG. 6 represents a real SOC graph shown using data extracted from the experiment. Referring to the measured state of charge graph of FIG. 6, the slope of the S-shaped curve increases rapidly in the range of 3.7 <V _b <3.75. Therefore, the important inflection points ζ and SOC _C (ζ) of P _SOC (x) _C approximated to the measured state of charge graph exist in the range of 0.5 <ζ <0.55. Using this inflection point, C _NK , N value and K value can be calculated. For example, assuming that (ζ, SOC _C (ζ)) exists at ζ = 0.525 which is intermediate at 0.5 <ζ <0.55, the measured mean slope is Slop _C = 3.169.

In addition, the instantaneous slope at (ζ, SOC _C (ζ)) = (0.525, 0.314) of the state of charge polynomial may be calculated as shown in Equation 19 according to Equation 15.

[Equation 19]

C _NK according to various K values satisfying Equation 13 may be calculated with respect to the set _NK, and C _NK and K values satisfying Equation 17 may be determined with respect to Equation 19. Experimental results When (N, K) = (11, 7) and C ₄ = 174.59, the instantaneous slope was calculated as shown in the following equation (20).

[Equation 20]

This value was analyzed to be the most similar to the measured mean slope (Slop _C = 3.169). The slight difference between the calculated slope and the actual slope is an error that occurs because the K value is expressed as a positive integer.

When (N, K) = (11, 7) and C ₄ = 174.59 determined in this way are substituted into Equation 9, which is a real coefficient formula, a polynomial coefficient as shown in Table 1 below is calculated.

0 0 One 0 2 0 3 0 4 0 5 0 6 0 7 112.58952 8 -495.35809 9 823.53714 10 -614.35809 11 174.58952

Using the calculated polynomial coefficients, the state of charge function may be calculated from the Hermit interpolation state of charge polynomial as shown in Equation 21 below.

[Equation 21]

Referring to FIG. 6, FIG. 6 shows a measured state of charge graph and a graph according to the state of charge function of Equation 21. It can be seen that the state of charge function using the Hermit interpolation method is approximated by a very accurate curve slope.

7 is a configuration diagram schematically illustrating a configuration of an apparatus for calculating a state of charge.

Referring to FIG. 7, the apparatus for calculating a state of charge includes a detector 10, a first calculator 20, a second calculator 30, a controller 40, an output unit 50, and a storage unit 60. do.

The detector 10 detects the battery voltage. For example, the detector 10 may detect the voltage of the battery through a sensor that measures the voltage.

When the battery is not charged or discharged, the first calculator 20 calculates the state of charge according to the open circuit voltage of the battery under the control of the controller 40. For example, the first calculator 20 may calculate the state of charge by using a correlation of the state of charge with respect to an open circuit voltage stored in advance.

When the battery is charged and discharged, the second calculator 30 calculates the charged state according to the detected voltage of the battery by using the charged state function under the control of the controller 40. For example, the second calculator 30 calculates the state of charge by using the current integration method in the case of charging through the charger, and in the case of charging through the solar cell or in the case of general discharge (for example, the mobile communication terminal). The charge state can be calculated using a high order polynomial implemented using Hermite Interpolation in the case where current flows due to the telephone call. That is, the second calculator 30 may calculate the state of charge using the state of charge function described above with reference to FIGS. 2 to 6.

The controller 40 controls each component of the state of charge calculating device (detector 10, first calculator 20, second calculator 30, output unit 50, and storage unit 60). .

The controller 40 determines whether the battery is charged or discharged through the detector 10, and controls the first calculator 20 or the second calculator 30 to calculate the state of charge of the battery according to whether the battery is charged or discharged. . In addition, the controller 40 controls the output unit 50 to output the calculated state of charge.

The output unit 50 outputs the state of charge calculated by the control of the control unit 40.

The storage unit 60 stores information necessary for calculating the state of charge. For example, the storage unit 60 may store the correlation information of the state of charge with respect to the open circuit voltage of the battery. In addition, the storage unit 60 may store the charging state function information. In this case, the storage unit 60 may store the order information and the coefficient information of the state of charge function as a table.

On the other hand, the method of calculating the state of charge according to an embodiment of the present invention may be implemented in the form of program instructions that can be executed through various electronic means for processing information may be recorded in the storage medium. The storage medium may include program instructions, data files, data structures, etc. alone or in combination.

Program instructions to be recorded on the storage medium may be those specially designed and constructed for the present invention or may be available to those skilled in the art of software. Examples of storage media include magnetic media such as hard disks, floppy disks and magnetic tape, optical media such as CD-ROMs, DVDs, and magnetic-optical media such as floppy disks. hardware devices specifically configured to store and execute program instructions such as magneto-optical media and ROM, RAM, flash memory, and the like. In addition, the above-described medium may be a transmission medium such as an optical or metal wire, a waveguide, or the like including a carrier wave for transmitting a signal specifying a program command, a data structure, and the like. Examples of program instructions include not only machine code generated by a compiler, but also devices that process information electronically using an interpreter, for example, high-level language code that can be executed by a computer.

The hardware device described above may be configured to operate as one or more software modules to perform the operations of the present invention, and vice versa.

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 as defined in the appended claims. It will be understood that the invention may be varied and varied without departing from the scope of the invention.

Claims (18)

An apparatus for calculating a state of charge of a battery in a system equipped with a battery,
A detector for detecting a voltage and a current of the battery;
A storage unit calculated from a high order polynomial implemented using Hermite Interpolation, and storing coefficient and order information of a state of charge function indicating a correlation between the voltage of the battery and the state of charge;
A first calculator configured to calculate a state of charge according to the voltage using the state of charge function information; And
A control unit configured to determine whether the current flows through the detection of the current to determine whether the battery is charged or discharged, and to control the first calculator to calculate the state of charge when the current flows. But
The higher-order polynomial is a state-of-charge polynomial of order N, wherein the state of charge polynomial includes a parameter (K) indicating a curve slope of the state of charge polynomial and a correction coefficient set such that the state of charge polynomial always has an inflection point,
The state of charge polynomial (P _SOC (x)) is represented by the following equation,

here,

Is the coefficient, V _b is the battery voltage, V _c is the end-of-charge voltage of the battery, and V _d is the end-of-discharge voltage of the battery
The state of charge polynomial and the coefficient are represented by the following equations for charge and discharge, respectively,
State of charge polynomial (P _SOC (x) _C ) and coefficient (

):

State of charge polynomial at discharge (P _SOC (x) _D ) and coefficient (

):

The state of charge polynomial and the coefficient to which the correction coefficient C _NK is applied are represented by the following equations for charge and discharge, respectively,
State of charge polynomial (P _SOC (x) _C ) and coefficient (

):

State of charge polynomial at discharge (P _SOC (x) _D ) and coefficient (

):

The state of charge function is calculated by calculating the correction coefficient and K in the state of charge polynomial using the inflection point and the inclination of the inflection point calculated from measured data measured the state of charge with respect to the voltage of the battery. Charge state calculation device.
delete delete delete delete The method of claim 1,
The correction coefficient is calculated when the inflection point calculated from the measured data is (ζ, SOC _C (ζ)) at the time of charging and (ζ, SOC _D (ζ)) at the discharge. Charge state calculating device.

The method of claim 6,
The slope at the inflection point is calculated using the following equation.

The method of claim 7, wherein
When the mean curve slopes at the inflection points ζ, SOC _C (ζ) and (ζ, SOC _D (ζ)) obtained from the measured data are Slop _C and Slop _D , respectively, the correction coefficient (C _{N -K} ) And N and K are determined using the following equation.

The method of claim 1,
A second calculation unit for calculating a state of charge according to the voltage using a correlation of the state of charge with respect to the open circuit voltage of the battery,
The storage unit further stores a correlation of the state of charge with respect to the open circuit voltage of the battery,
And the controller controls the second calculator to calculate the state of charge when the current is not generated and the battery is not charged or discharged.
In the method for calculating the state of charge of the battery by the state of charge calculation device provided in the system equipped with a battery (Battery),
Judging whether the current flows through the detection of the current of the battery to determine whether the battery is charged or discharged;
Detecting a voltage of the battery when the current flows to charge and discharge the battery;
Calculating the state of charge according to the voltage using a state of charge function calculated from a high order polynomial implemented using Hermite Interpolation and correlating the state of the battery with the state of charge step; And
Outputting the calculated state of charge,
The higher-order polynomial is a state-of-charge polynomial of order N, wherein the state of charge polynomial includes a parameter (K) indicating a curve slope of the state of charge polynomial and a correction coefficient set such that the state of charge polynomial always has an inflection point,
The state of charge polynomial (P _SOC (x)) is represented by the following equation,

here,

Is the coefficient, V _b is the battery voltage, V _c is the end-of-charge voltage of the battery, and V _d is the end-of-discharge voltage of the battery
The state of charge polynomial and the coefficient are represented by the following equations for charge and discharge, respectively,
State of charge polynomial (P _SOC (x) _C ) and coefficient (

):

State of charge polynomial at discharge (P _SOC (x) _D ) and coefficient (

):

The state of charge polynomial and the coefficient to which the correction coefficient C _NK is applied are represented by the following equations for charge and discharge, respectively,
State of charge polynomial (P _SOC (x) _C ) and coefficient (

):

State of charge polynomial at discharge (P _SOC (x) _D ) and coefficient (

):

The state of charge function is calculated by calculating the correction coefficient and K in the state of charge polynomial using the inflection point and the inclination of the inflection point calculated from measured data measured the state of charge with respect to the voltage of the battery. How to calculate the state of charge.
delete delete delete delete The method of claim 10,
The correction coefficient is calculated when the inflection point calculated from the measured data is (ζ, SOC _C (ζ)) at the time of charging and (ζ, SOC _D (ζ)) at the discharge. Charge state calculation method.

16. The method of claim 15,
The slope at the inflection point is calculated using the following equation.

The method of claim 16,
When the mean curve slopes at the inflection points ζ, SOC _C (ζ) and (ζ, SOC _D (ζ)) obtained from the measured data are Slop _C and Slop _D , respectively, the correction coefficient (C _{N -K} ) And N and K are determined using the following equation.

The method of claim 10,
Calculating a state of charge according to the open circuit voltage of the battery using the correlation of the state of charge with respect to the open circuit voltage of the battery when the current does not flow and thus the battery is not charged or discharged. Charge state calculation method made.

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