JP2014062823A - Circuit and method for estimating internal resistance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a circuit and a method for estimating internal resistance, which improve accuracy of internal resistance estimation.SOLUTION: An internal resistance estimation circuit includes; a sorting section which sorts coordinate points representing measured voltage values and current values into a plurality of ranges using one or more threshold values representing predetermined current values; a formulation section which formulates an approximate equation that passes through an origin, at which voltage and current are not supplied to a battery and battery internal resistance is 0 ohm, for each of the sorted regions using the coordinate points therein; and an estimation section which obtains a slope of an approximate equation of each region, obtains a weighting coefficient for each region by referring to coefficient information containing weighting coefficients, recorded in association with respective regions, for correcting the slopes of the respective approximate equations, multiplies a slope of an approximate equation of each region by a corresponding weighting coefficient, and adds up the multiplied values of all regions to estimate internal resistance.

Description

  The present invention relates to an internal resistance estimation circuit and an internal resistance estimation method for estimating the internal resistance of a battery.

  It is known to use the value of internal resistance as an index representing the state of deterioration of a battery. The internal resistance of the battery in the closed circuit is, for example, measuring a plurality of battery voltages and currents to determine a plurality of coordinates, obtaining an approximate expression using those coordinates, and using the slope of the obtained approximate expression as the internal resistance. . However, since the measurement accuracy decreases as the current flowing through the battery increases compared to when the current flowing through the battery is low, the estimation accuracy of the internal resistance also decreases.

  As a related technique, there is a technique for calculating an internal resistance from the open circuit voltage OCV when the current is zero, the closed circuit voltage CCV when charging / discharging, and the current Ic. See, for example, US Pat.

JP 2009-052975 A

  The present invention has been made in view of the above circumstances, and an object thereof is to provide an internal resistance estimation circuit and an internal resistance estimation method that improve the estimation accuracy of internal resistance.

An internal resistance estimation circuit which is one aspect of the present invention includes a voltage measurement unit, a current measurement unit, a classification unit, a generation unit, and an estimation unit.
The voltage measuring unit measures the voltage of the battery, and the current measuring unit measures the current flowing through the battery.

The classification unit classifies coordinates determined by the measured voltage and current into a plurality of ranges using a threshold value indicating one or more determined current values.
The generation unit generates, for each range, an approximate expression that passes through the origin indicating that the internal resistance of the battery is 0 ohm when voltage and current are not supplied to the battery, using coordinates within the classified range. .

  The estimation unit acquires the slope of the approximate expression generated for each range. Subsequently, the weighting coefficient corresponding to the range is acquired with reference to coefficient information stored in association with each range and the weighting coefficient for correcting each inclination of the approximate expression. Then, the slope of the approximate expression corresponding to each range is multiplied by the weighting coefficient, and the value multiplied for each range is added to estimate the internal resistance.

  According to the present embodiment, there is an effect that the estimation accuracy of the internal resistance can be improved.

It is a figure which shows one Example of an internal resistance estimation circuit. It is a figure which shows one Example of a control part. It is a figure which shows one Example of the coordinate decided by a voltage and an electric current. It is a figure which shows one Example of the straight line corresponding to the approximate expression for every range. It is a figure which shows one Example of operation | movement of a control part. It is a figure which shows one Example of the data structure of classification information. It is a figure which shows one Example of the data structure of inclination information, coefficient information, and internal resistance information.

Hereinafter, embodiments will be described in detail based on the drawings.
FIG. 1 is a diagram illustrating an embodiment of an internal resistance estimation circuit. The internal resistance estimation circuit of FIG. 1 is a circuit that estimates the internal resistance of each of the batteries B1 to B8 of the battery block, and includes a control unit 1, a storage unit 2, a current measurement unit 3, and voltage measurement units 4a to 4h. Note that the number of batteries is not limited to eight.

  As the control unit 1 (computer), for example, a Central Processing Unit (CPU), a multi-core CPU, and a programmable device (Field Programmable Gate Array (FPGA), Programmable Logic Device (PLD), etc.) may be used. The control unit 1 may include a storage unit, or may be connected to a storage unit provided separately from the control unit 1.

  The storage unit 2, for example, a memory such as a read only memory (ROM) or a random access memory (RAM), a hard disk, or the like is conceivable. Data such as parameter values and variable values may be recorded in the storage unit 2 or may be used as a work area at the time of execution.

  The batteries B1 to B8 of the battery block are connected in series. The batteries B1 to B8 can be secondary batteries. As the secondary battery, for example, a lithium ion secondary battery, a nickel hydride secondary battery, or the like can be considered.

Moreover, the terminals P1 and P2 of the battery block are connected to a load or a power supply source, and the battery block is charged and discharged.
The current measuring unit 3 measures the current flowing through the battery. The data measured by the current measuring unit 3 is output to the control unit 1. The current measuring unit 3 may be an ammeter, for example.

  Voltage measuring units 4a to 4h measure the voltages of batteries B1 to B8. The data measured by the voltage measuring units 4 a to 4 h is output to the control unit 1. As the voltage measuring units 4a to 4h, for example, a voltmeter may be considered.

The control unit will be described.
FIG. 2 is a diagram illustrating an example of the control unit. For example, in the closed circuit of the charging device, the control unit 1 acquires the closed circuit voltage (CCV) of the batteries B1 to B8 measured by the voltage measuring units 4a to 4h and the current flowing through the battery measured by the current measuring unit 3. In addition, the control unit 1 includes a classification unit 201, a generation unit 202, an estimation unit 203, and the like which will be described later.

The classification unit 201 classifies a plurality of coordinates (current value, voltage value) determined by the measured voltage and current into a plurality of ranges using a threshold value indicating one or more determined current values.
The coordinates are points surrounded by a broken line 301 shown in FIG. 3 and are determined by the measured current value (X axis) and voltage value (Y axis).

  The threshold values Isa to Isd are values determined by battery characteristics or experiments. Further, when there is a current value mainly used, it is desirable to determine the threshold value so that the current value is at the center. The threshold values Isa to Isd may be determined in consideration of the measurement allowable range of the voltage measuring units 4a to 4h and the current measuring unit 3, the ambient temperature, and the like.

  The plurality of ranges are ranges Ira to Ird determined by threshold values Isa to Isd indicating current values shown in FIG. FIG. 3 is a diagram illustrating an example of coordinates determined by voltage and current. In FIG. 3, the ranges Ira to Ird are set continuously, but the ranges do not have to be continuous. For example, the range Ira and any of the ranges Irb, Irc, and Ird may be used in combination. In this example, four ranges are described, but the number is not limited to four.

  The generation unit 202 generates an approximate expression that passes through the origin for each of the ranges Ira, IRb, Irc, and Ird. That is, an approximate expression that passes through the origin using coordinates within the range is generated for each of the ranges Ira to Ird.

  Here, the origin is the coordinates (0, 0) shown in FIGS. That is, when the voltage and current are not supplied to the batteries B1 to B8, the internal resistance of the batteries B1 to B8 is 0 ohm. The approximate expression is a straight line represented by a linear function passing through the origin. For example, the slope at the intercept 0 is obtained by using regression analysis or the like. FIG. 4 is a diagram illustrating an example of a straight line corresponding to an approximate expression for each range. FIG. 4A shows a straight line 401 representing an approximate expression generated using coordinates and the origin in the range Ira. In FIG. 4B, a straight line 402 representing an approximate expression generated using the coordinates in the range Irb and the origin is shown. In FIG. 4C, a straight line 403 representing an approximate expression generated using the coordinates in the range Irc and the origin is shown. In FIG. 4D, a straight line 404 representing an approximate expression generated using the coordinates and the origin in the range Ird is shown.

  The estimation unit 203 acquires the slope of the approximate expression generated for each of the ranges Ira, Irb, Irc, and Ird. Subsequently, the estimation unit 203 refers to the coefficient information associated with the weighting coefficients for correcting the inclinations of the approximate expressions of the ranges Ira, Irb, Irc, and Ird, and acquires the weighting coefficient corresponding to each range. Thereafter, the slope of the approximate expression is multiplied by the weighting coefficient for each range. Then, the internal resistance is estimated by adding the values multiplied for each range.

  The weighting coefficient stored in the coefficient information is the slope of the approximate expression corresponding to the range Ira (first range) used for classification when the current is smaller than the smallest first threshold value Isa among the threshold values Isa to Isd. As a reference, the weight of the weighting coefficient associated with each range is increased as the range is closer to the range Ira. That is, the weight of the weighting coefficient is increased in the smaller current range. For example, when the weighting coefficient δ1 (= 1) of the range Ira, the weighting coefficient δ2 of the range Irb, the weighting coefficient δ3 of the range Irc, and the weighting coefficient δ4 of the range Ird, δ1 = 1 ≧ δ2 ≧ δ3 ≧ δ4> 0. . The weighting coefficients δ1, δ2, δ3, and δ4 are determined in consideration of battery characteristics, experiments, ambient environment, and the like.

The operation of the control unit will be described.
FIG. 5 is a diagram illustrating an example of the operation of the control unit. In step S <b> 501, the control unit 1 acquires a current value from the current measurement unit 3.

In step S502, the control unit 1 acquires the voltage values of the batteries B1 to B8 from the measurement units 4a to 4h, respectively.
In step S503, the voltage value and current value acquired by the control unit 1 are classified and stored in the storage unit 2. That is, the coordinates determined using the voltage value and current value measured for each of the batteries B <b> 1 to B <b> 8 are classified for each range based on the current value, and stored in the classification information 601 of the storage unit 2. FIG. 6 is a diagram illustrating an example of the data structure of the classification information. The classification information 601 includes information stored in “battery”, “voltage”, “range Ira”, “range Irb”, “range Irc”, and “range Ird”. “Battery” stores identification information for identifying the battery. In this example, “B1”, “B2”, “B3”,... Are stored as identification information.

  In the “voltage”, a closed circuit voltage value corresponding to each measured battery is stored. In this example, “VB11”, “VB12”, “VB13”, “VB14”, “VB15”, “VB16”, “VB17”,... Representing the measured voltage values related to the battery “B1” are stored in “voltage”. Yes. Further, “VB21”, “VB22”, “VB23”, “VB24”, “VB25”, “VB26”, “VB27”,... Representing the measured voltage values related to the battery “B2” are stored in “voltage”. Further, “VB31”, “VB32”, “VB33”, “VB34”, “VB35”, “VB36”, “VB37”,... Representing the measured voltage values related to the battery “B3” are stored in “voltage”.

  In “Range Ira”, “Range Irb”, “Range Irc”, and “Range Ird”, the measured current values flowing through the batteries are classified and stored for each range. In the “range Ira”, the current values of the coordinates classified into the range Ira shown in FIGS. 3 and 4 are stored in association with the voltage values stored in the “voltage”. In this example, the “range” associated with the voltage values “VB11”, “VB21”, “VB31”,... Stored in each “voltage” corresponding to the batteries “B1,” “B2,” “B3,”. “IB1” indicating a current value is stored in “Ira”.

  In “Range Irb”, the current values of the coordinates classified into the range Irb shown in FIGS. 3 and 4 are stored in association with the voltage values stored in “Voltage”. In this example, “IB2” “IB3” indicating current values in “range Irb” associated with voltage values “VB12”, “VB13”, and “VB15” stored in each “voltage” corresponding to battery “B1”. "IB5" is stored. “IB2”, “IB3”, “IB5” indicating current values in “range Irb” associated with voltage values “VB22”, “VB23”, “VB25” stored in each “voltage” corresponding to battery “B2” Is remembered. “IB2”, “IB3”, “IB5” indicating current values in “range Irb” associated with voltage values “VB32”, “VB33”, “VB35” stored in each “voltage” corresponding to battery “B3” Is remembered.

  In “Range Irc”, the current values of the coordinates classified in the range Irc shown in FIGS. 3 and 4 are stored in association with the voltage values stored in “Voltage”. In this example, “IB4” and “IB6” indicating current values are stored in the “range Irc” associated with the voltage values “VB14” and “VB16” stored in each “voltage” corresponding to the battery “B1”. Has been. In this example, “IB4” and “IB6” indicating current values are stored in the “range Irc” associated with the voltage values “VB24” and “VB26” stored in each “voltage” corresponding to the battery “B2”. Has been. In this example, “IB4” and “IB6” indicating current values are stored in the “range Ird” associated with the voltage values “VB34” and “VB36” stored in each “voltage” corresponding to the battery “B3”. Has been.

  In “Range Ird”, the current values of the coordinates classified into the range Ird shown in FIGS. 3 and 4 are stored in association with the voltage values stored in “Voltage”. In this example, the “range” associated with the voltage values “VB17”, “VB27”, “VB37”,... Stored in each “voltage” corresponding to the batteries “B1,” “B2,” “B3,”. “IB7” indicating the current value is stored in “Ird”.

  In step S504, the control unit 1 refers to the classification information and generates an approximate expression that passes through the origin for each battery range. For example, an approximate expression passing through the origin corresponding to the straight lines 401 to 404 shown in A to D of FIG.

  In step S505, the control unit 1 acquires the slope of the approximate expression for each battery range. For example, the battery identification number and the inclination of the approximate expression are stored in association with each other. FIG. 7 is a diagram illustrating an example of the data structure of the inclination information, coefficient information, and internal resistance information. 7 includes information stored in “battery”, “range Ira”, “range Irb”, “range Irc”, and “range Ird”. “Battery” stores identification information for identifying the battery. In this example, “B1”, “B2”, “B3”,... Are stored as identification information. In “Range Ira”, “Range Irb”, “Range Irc”, and “Range Ird”, the inclinations of the approximate expressions obtained in step S504 corresponding to the respective ranges of the batteries are stored. In this example, the “range Ira” representing the range Ira includes “B1”, “B2”, “B3”, “B4”, “B5”,... Corresponding to the batteries B1, B2, B3, B4, B5,. The gradients “RB11”, “RB21”, “RB31”, “RB41”, and “RB51” of the range Ira are stored in association with each other. “Range Irb” representing the range Irb is associated with “B1”, “B2”, “B3”, “B4”, “B5”,... Corresponding to the batteries B1, B2, B3, B4, B5,. In addition, inclinations “RB12”, “RB22”, “RB32”, “RB42”, and “RB52” of the range Irb are stored. “Range Irc” representing the range Irc is associated with “B1”, “B2”, “B3”, “B4”, “B5”,... Corresponding to the batteries B1, B2, B3, B4, B5,. In addition, inclinations “RB13”, “RB23”, “RB33”, “RB43”, and “RB53” of the range Irc are stored. “Range Ird” representing the range Ird is associated with “B1”, “B2”, “B3”, “B4”, “B5”,... Corresponding to the batteries B1, B2, B3, B4, B5,. In addition, the slopes “RB14”, “RB24”, “RB34”, “RB44”, and “RB54” of the range Ird are stored.

  In step S506, the control unit 1 acquires the weighting coefficient for each range from the storage unit 2 or the like. For example, the weighting coefficient associated with each range is acquired from the coefficient information 702. In this example, the coefficient information 702 includes information stored in “Range Ira”, “Range Irb”, “Range Irc”, and “Range Ird”. “Range 1ra” stores a weighting coefficient “δ1”, “Range Irb” stores a weighting coefficient “δ2”, and “Range Irc” stores a weighting coefficient “δ3”. “Range 4” stores “δ4” indicating a weighting coefficient.

  In addition, when the kind of battery differs, you may have coefficient information for every kind of battery. In addition, when it is known that the characteristics change due to the deterioration of the battery, coefficient information in consideration of the characteristics due to the deterioration may be stored, and the coefficient information may be switched when the deterioration is detected.

In step S507, the control unit 1 obtains the internal resistance of each battery. For example, the internal resistance RB1 of the battery B1 is obtained by calculating (R11 × δ1 + R12 × δ2 + R13 × δ3 + R14 × δ4) / (δ1 + δ2 + δ3 + δ4). The internal resistance RB2 of the battery B2 is obtained by calculating (R21 × δ1 + R22 × δ2 + R23 × δ3 + R24 × δ4) / (δ1 + δ2 + δ3 + δ4). The internal resistance RB3 of the battery B3 is obtained by calculating (R31 × δ1 + R32 × δ2 + R33 × δ3 + R34 × δ4) / (δ1 + δ2 + δ3 + δ4). The internal resistance RB4 of the battery B4 is obtained by calculating (R41 × δ1 + R42 × δ2 + R43 × δ3 + R44 × δ4) / (δ1 + δ2 + δ3 + δ4). The obtained internal resistance for each battery is stored in, for example, internal resistance information 703 in FIG. In this example, “RB1” indicates the internal resistance obtained in association with the identification information “B1”, “B2”, “B3”, “B4”, and “B5” for identifying the batteries B1, B2, B3, B4, B5. "RB2", "RB3", "RB4", "RB5",... Are stored. In other words, the internal resistance is estimated by multiplying the slope of the approximate expression in each range by the weighting coefficient and adding the values obtained by the multiplication. If the sum of the weighting coefficients (δ1 + δ2 + δ3 + δ4) is not 1, the value obtained by addition is divided by the sum of the weighting coefficients to estimate the internal resistance.
In addition, the weighting coefficients (δ1 to δ4) may be coefficients such that the sum is 1 so that it is not necessary to divide by the sum of the weighting coefficients. Even in this case, δ1 ≧ δ2 ≧ δ3 ≧ δ4 is set, and the weight of the weighting coefficient is increased in the smaller current range.

  In step S508, the control unit 1 determines whether or not to end the measurement. When the measurement is ended (Yes), the measurement is ended. When the measurement is continued (No), the process proceeds to step S501. Continue measuring.

According to the present embodiment, there is an effect that the estimation accuracy of the internal resistance can be improved by utilizing the fact that the influence of the polarization on the closed circuit voltage is small in the low current range.
The present invention is not limited to the above-described embodiment, and various improvements and modifications can be made without departing from the gist of the present invention.

1 control unit,
2 storage unit,
3 Current measurement unit,
4a, 4b, 4c, 4d, 4e, 4f, 4g, 4h Voltage measurement unit,
B1, B2, B3, B4 batteries,
201 classification part,
202 generator,
203 estimator,
601 classification information,
701 Tilt information,
702 coefficient information,
703 internal resistance information,

Claims (4)

A voltage measurement unit for measuring the voltage of the battery;
A current measuring unit for measuring a current flowing through the battery;
A classifying unit that classifies coordinates determined by the measured voltage and current into a plurality of ranges using a threshold value indicating one or more determined current values;
Using the classified coordinates within the range, an approximate expression passing through the origin indicating that the internal resistance of the battery is 0 ohm is generated for each range when voltage and current are not supplied to the battery. A generator,
The inclination of the approximate expression generated for each range is acquired, and each range is associated with a weighting coefficient that corrects each inclination of the approximate expression with reference to coefficient information stored in association with the range. Obtaining a corresponding weighting factor, multiplying the slope of the approximate expression corresponding to each range by a weighting factor, and adding an multiplied value for each range to estimate an internal resistance;
An internal resistance estimation circuit comprising: The weighting coefficient stored in the coefficient information is
2. The weight of a weighting coefficient corresponding to each of the ranges is increased as the distance is closer to the first range used for classification when the current is smaller than the smallest first threshold among the thresholds. The internal resistance estimation circuit described. A method for estimating the internal resistance of a charging device, comprising:
Computer
A voltage measuring unit that measures the voltage of the battery, a current measuring unit that measures the current flowing through the battery, and a coordinate that is determined by the voltage and current measured using a threshold value that indicates a current value that is one level higher Categorize into multiple ranges,
Using the classified coordinates within the range, an approximate expression that passes through the origin indicating that the internal resistance of the battery is 0 ohm when no voltage and current are supplied to the battery is generated for each range. ,
Obtain the slope of the approximate expression generated for each range,
Each of the ranges and a weighting coefficient for correcting each of the inclinations of the approximate expression are referred to and stored in association with the coefficient information to obtain a weighting coefficient corresponding to the range,
Multiply the slope of the approximate expression corresponding to each range by a weighting coefficient,
An internal resistance is estimated by adding a value multiplied for each range.
An internal resistance estimation method characterized by executing processing. The weighting coefficient stored in the coefficient information is
The weight of the weighting coefficient corresponding to each of the ranges is increased as the distance is closer to the first range used for classification when the current is smaller than the smallest first threshold among the thresholds. The internal resistance estimation method described.

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