JP2015105825A - State-of-charge estimation device and state-of-charge estimation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a state-of-charge estimation device and a state-of-charge estimation method capable of accurately estimating an SOC of a real battery in view of a slow response part of the actual battery.SOLUTION: In a state-of-charge estimation device including: a voltage sensor; a current sensor; a parameter sequential estimation unit sequentially estimating parameters relating to the actual battery based on charge/discharge currents and the battery voltage; an overvoltage calculation unit calculating an overvoltage on the basis of the parameters relating to the actual battery; a terminal-voltage calculation unit calculating a terminal voltage on the basis of the battery voltage and the overvoltage; and a charging-rate calculation unit calculating a charging rate on the basis of the terminal voltage and a relation between the terminal voltage and the charging rate prepared in advance, the relation between the terminal voltage and the charging rate prepared in advance is a relation determined from the terminal voltage measured in the actual battery left untreated for time corresponding to a highest time constant of parameters used by the overvoltage calculation unit when calculating the overvoltage.

Description

  The present invention relates to a charging rate estimation device and a charging rate estimation method capable of accurately estimating a charging rate of a real battery.

  Of the actual batteries, a rechargeable secondary actual battery is employed in, for example, an electric vehicle. In this case, it is necessary to know the distance that can be traveled by the actual battery, the current value that can be charged and discharged, and in order to grasp these, the charge rate of the actual battery (SOC: State of Charge) that is the internal state quantity of the actual battery. ) Must be detected. However, since these internal state quantities cannot be directly detected, a current integration method (also called a coulomb count method or a book keeping method) and an open-circuit voltage estimation method (sequential parameter method) are often used. In the current integration method, the internal state is estimated by detecting charge / discharge current values in time series. In addition, the open-circuit voltage estimation method constructs a real battery model, compares the input and output with the real battery, and reduces the difference between them with an adaptive filter such as a Kalman filter. The charging rate is estimated by estimating the open voltage of the actual battery (Patent Document 1).

  The secondary real battery charging rate estimation device described in Patent Document 1 monitors the current and voltage of the secondary real battery, uses the input to estimate the parameters by a parameter estimation unit such as a Kalman filter, and the like. OCV: Open Circuit Voltage) is calculated. And it is the structure which calculates | requires SOC from the calculated open circuit voltage and the SOC-OCV characteristic prepared beforehand (FIG. 10). The OCV is a terminal voltage when the current is zero and the actual battery is left for a long time to stabilize the inside. The SOC-OCV characteristic is created by measuring the terminal voltage after leaving for a long time for each SOC.

JP 2012-58089 A

  Here, due to the characteristics of the parameter estimation unit, there is an upper limit to the time constant that can be estimated, and it is difficult to estimate a parameter related to a long time constant. FIG. 11 is a conceptual diagram showing polarization relaxation of a real battery, and more specifically, is a graph showing the transition of the terminal voltage of the real battery after constant discharge. As shown in FIG. 11, during constant discharge, the terminal voltage decreases with time. After the discharge is stopped, the terminal voltage of the actual battery rises due to the influence of the early response part (the dynamic state region in FIG. 11). Thereafter, the terminal voltage of the actual battery further increases due to the influence of the slow response portion (the region in the static state in FIG. 11). Here, since the relaxation of polarization is completed after 24 hours, the voltage after 24 hours is OCV. The time at which the polarization relaxation ends differs depending on the characteristics of the actual battery.

  Here, the OCV obtained by the parameter estimation unit is a short time constant open-circuit voltage OCV (that is, a terminal voltage that has not yet reached the open-circuit voltage). FIG. 12 shows the relationship between the terminal voltage and SOC of the actual battery after being left for 1 minute, and the relationship between the terminal voltage and SOC of the actual battery after being left for 24 hours. As shown in FIG. 12, when compared at the same voltage, the difference between the SOCs is about 5%. Thus, if the charge rate SOC is obtained using the SOC-OCV characteristic based on the OCV obtained by the conventional parameter estimation unit, the accuracy of the SOC is lowered. There is also a method in which the parameter estimation unit directly estimates the state quantity, that is, the open circuit voltage. However, even in this case, as with the parameter estimation, it is difficult to estimate the state quantity related to the long time constant.

  Accordingly, an object of the present invention made in view of the above problems is to provide a charging rate estimation device and a charging rate estimation method capable of accurately estimating the SOC of a real battery in consideration of a slow response part of the real battery. Is to provide.

In order to solve the above problem, a charging rate estimation apparatus according to the first invention
A voltage sensor for measuring the battery voltage of the battery;
A current sensor for measuring the charge / discharge current of the battery;
A sequential parameter estimator for sequentially estimating parameters related to the battery based on the charge / discharge current and the battery voltage;
An overvoltage calculating unit for calculating an overvoltage based on a parameter relating to the battery;
A terminal voltage calculation unit that calculates a terminal voltage based on the battery voltage and the overvoltage;
Based on the terminal voltage and the relationship between the terminal voltage prepared in advance and the charging rate, a charging rate calculation unit for obtaining a charging rate;
In the charging rate estimation device having
The relationship between the terminal voltage prepared in advance and the charging rate is a relationship obtained from the terminal voltage measured from the battery left for a time corresponding to the longest time constant of the parameter used when the overvoltage calculation unit calculates the overvoltage. It is characterized by being.

The charging rate estimation device according to the second invention is
In the battery charge rate estimation apparatus according to the first invention,
A battery having a plurality of relationships between the terminal voltage and the charging rate for each time, and the charging rate calculating unit is left for a time corresponding to the longest time constant of the parameter used when the overvoltage calculating unit calculates the overvoltage The relationship obtained from the measured terminal voltage is selected and used.

Moreover, the charging rate estimation apparatus according to the third invention is:
In the charging rate estimation apparatus of the first or second invention,
The relationship between the terminal voltage prepared in advance and the charging rate is a relationship obtained from the terminal voltage measured from the battery left for a time corresponding to the longest time constant of the parameter sequentially estimated by the sequential parameter estimation unit. It is characterized by.

Moreover, the charging rate estimation device according to the fourth invention is:
In the charging rate estimation apparatus of the first or second invention,
The relationship between the terminal voltage prepared in advance and the charging rate is a relationship obtained from a terminal voltage measured from a battery left for a time corresponding to the longest time constant of a parameter obtained by experiment.

The charging rate estimation method according to the fifth invention is
A voltage measurement step for measuring the battery voltage of the actual battery;
A current measuring step for measuring a charge / discharge current of the actual battery;
Sequential parameter estimation step for sequentially estimating parameters related to the actual battery based on the charge / discharge current and the battery voltage;
An overvoltage calculating step of calculating an overvoltage based on the parameter relating to the actual battery;
A terminal voltage calculating step for calculating a terminal voltage based on the battery voltage and the overvoltage;
A charge rate calculation step for obtaining a charge rate based on the terminal voltage and a relationship between the terminal voltage and the charge rate prepared in advance,
In the charging rate estimation method having
The relationship between the terminal voltage prepared in advance and the charging rate was obtained from the terminal voltage measured from an actual battery left for a time corresponding to the longest time constant of the parameter used when calculating the overvoltage in the overvoltage calculation step. It is a relationship.

  According to the charging rate estimation device of the first invention, taking into account the slow response part of the real battery, measurement is performed from the real battery left for a time corresponding to the longest time constant of the parameter used when calculating the overvoltage. Since the SOC is calculated based on the relationship obtained from the terminal voltage, the SOC of the actual battery can be accurately estimated.

  Moreover, according to the charging rate estimation device according to the second aspect of the present invention, there are a plurality of relationships between the terminal voltage and the charging rate for each time, and the time corresponding to the longest time constant of the parameter used when calculating the overvoltage is obtained. Accordingly, since the relationship between the terminal voltage and the charging rate is selected (switched) and used, the SOC of the actual battery can be estimated more accurately.

  Further, according to the charging rate estimation device of the third invention, since the relationship between the terminal voltage and the charging rate corresponding to the longest time constant of the parameter sequentially estimated by the sequential parameter estimating unit is used, the SOC of the actual battery is used. Can be estimated more accurately.

  In addition, according to the charging rate estimation device according to the fourth aspect of the invention, since the relationship obtained from the terminal voltage measured from the actual battery left for a time corresponding to the longest time constant of the parameter obtained by experiment is used, Even with a long-time time constant that cannot be estimated by the estimation unit, the SOC of the actual battery can be accurately estimated.

  Further, according to the charging rate estimation method according to the fifth aspect of the present invention, considering the slow response part of the real battery, the real battery is left for a time corresponding to the longest time constant of the parameter used when calculating the overvoltage. Since the SOC is calculated based on the relationship obtained from the measured terminal voltage, the SOC of the actual battery can be accurately estimated.

It is a block diagram which shows the charging rate estimation apparatus which concerns on Embodiment 1. FIG. 3 is an example of an equivalent circuit model of an actual battery used in the sequential parameter estimation unit of the first embodiment. It is a figure which shows the look-up table used in the terminal voltage-SOC conversion part of Embodiment 1. 6 is an example of an equivalent circuit model of an actual battery used in the sequential parameter estimation unit of the second embodiment. It is a block diagram of the charging rate estimation apparatus which concerns on Embodiment 3. FIG. It is a figure which shows the real battery equivalent circuit model of the quick response part and late response part of a real battery which are used in the sequential parameter estimation part of Embodiment 3. It is a figure which shows the structure of the low pass filter which comprises the filter process part of Embodiment 3. It is a figure which shows the example of the look-up table of Embodiment 4. It is a figure which shows the experimental data of estimation of SOC by the charging rate estimation apparatus by this invention. It is a block diagram of the conventional charging rate estimation apparatus. It is a conceptual diagram which shows the polarization relaxation of a real battery. It is a figure which shows the relationship between the terminal voltage and SOC of the real battery left for a predetermined time.

  Embodiments of the present invention will be described below.

(Embodiment 1)
First, the overall configuration of the real battery charging rate estimation apparatus according to the first embodiment will be described. The real battery charging rate estimation apparatus according to the first embodiment is connected to a real battery (secondary real battery such as a lithium ion battery) 101 that is mounted on, for example, an electric vehicle and can supply power to a drive motor (not shown). ing. This charging rate estimation device includes a current sensor 102, a voltage sensor 103, a sequential parameter estimation unit 104, a multiplier 105, a subtractor 106, and a terminal voltage-charge rate conversion unit 107 (V _t -SOC conversion unit 107). ) And. The present invention is generally different from the prior art in that the SOC is estimated using the relationship between the terminal voltage and the SOC (V _t -SOC characteristics). Here, the terminal voltage (hereinafter also referred to as V _t ) is a value obtained by subtracting an overvoltage value (hereinafter also referred to as V ₀ ) from the voltage (hereinafter also referred to as V _a ) detected by the voltage sensor 103. , V _t = V _a −V ₀ .

The current sensor 102 detects the magnitude of the discharge current when power is supplied from the actual battery 101 to the drive motor or the like. The current sensor 102 detects the magnitude of the charging current when the electric motor is caused to function as a generator during vehicle braking and a part of braking energy is collected or charged from a power supply facility on the ground. The detected current value _Ia is output to the sequential parameter estimation unit 104 and the multiplier 105 as an input signal with + when charging and-when discharging. Note that current sensors 102 having various structures and types can be appropriately employed.

The voltage sensor 103 detects a voltage value (battery voltage, V _a ) between terminals of the actual battery 101, and the detected V _a is output to the sequential parameter estimation unit 104 and the subtractor 106, respectively. As the voltage sensor 103, those having various structures and formats can be appropriately employed.

The sequential parameter estimation unit 104 estimates parameters related to the actual battery based on the equivalent circuit model of the actual battery. FIG. 2 shows an example of an equivalent circuit model of the real battery according to the first embodiment. The equivalent circuit model of the real battery shown in FIG. 2 is composed of R ₀ , R ₁ , and C ₁ . The sequential parameter estimation unit 104 sequentially estimates the parameters of the state equation of the equivalent circuit model of the real battery using, for example, a Kalman filter, using the current values I _a and V _a as input signals. Details of parameter estimation by the Kalman filter are described in Japanese Patent Application No. 2011-007874 of the present applicant. Then, the sequential parameter estimation unit 104 outputs the estimated parameters (R ₀ , R ₁ , and C ₁ ) to the multiplier 105.

Further, the sequential parameter estimation unit 104 outputs the estimated parameter time constant to the V _t -SOC conversion unit 107.

The multiplier 105 multiplies the charge / discharge current value I _a detected by the current sensor 102 with the resistance value (R ₀ , R ₁ ) and the capacitor capacity (C ₁ ) estimated by the sequential parameter estimation unit 104. to give the overvoltage value _{V 0.} This overvoltage value V ₀ is output to the subtractor 106. The multiplier 105 corresponds to an overvoltage calculation unit of the present invention.

The subtractor 106 subtracts the overvoltage value V ₀ from V _a detected by the voltage sensor 103 to obtain a terminal voltage value (hereinafter referred to as V _t ). The subtractor 106 outputs this V _t to the V _t -SOC conversion unit 107. The subtractor 106 corresponds to a terminal voltage calculation unit of the present invention.

V _t -SOC converter 107 uses a time constant obtained from the sequential parameter estimation unit 104, and _{V t} obtained from the subtractor 106, and a look-up table representing a relationship between _{V t} and SOC To output the SOC. Note that the V _t -SOC conversion unit 107 corresponds to a charge rate calculation unit of the present invention.

Here, the look-up table is a table showing the relationship between V _t and the SOC. Look-up table has a plurality of relationships between V _t and the SOC for each standing elapsed time of the actual battery (for example, every 1 hour). The elapsed time of the actual battery represents the time that has elapsed with reference to the time when the discharge current of the actual battery is zero from a predetermined value. Look-up table is created based on the relationship between standing elapsed time and the SOC with previously measured V _t by experiment. Specifically, first, a constant discharge is performed for a predetermined time using a fully charged real battery, and the SOC is decreased by a predetermined value (for example, 2%). Thereafter, measuring the V _t of each standing elapsed time (e.g., every 1 hour). Thereafter, similarly measured V _t to polarization relaxation is completed time the terminal voltage becomes constant (e.g., 24 hours). And the standing time elapsed and _{V t,} associating the value (98%) obtained by subtracting a predetermined value from the SOC. Similarly gradually reduce the SOC by a predetermined value (96%, 94%, 92% ... 0%), measuring the _{V t} of each respective standing elapsed time (e.g., every 1 hour).

FIG. 3 shows an example of the look-up table created in this way. In FIG. 3, a three-axis (V _t , time, and SOC) three-dimensional graph (three-dimensional map) is shown. The look-up table is prepared by being stored in advance in a storage unit (not shown) of the charging rate estimation device. The V _t -SOC conversion unit 107 estimates the SOC based on V _t and the time constant by using the look-up table.

The V _t -SOC conversion unit 107 selects (switches) the relationship between V _t and SOC used according to the time constant in the look-up table shown in FIG. Specifically, the V _t -SOC conversion unit 107 selects the relationship between V _t and SOC in the neglected elapsed time corresponding to the longest time constant among the time constants obtained from the sequential parameter estimation unit 104. Then, the V _t -SOC conversion unit 107 calculates the SOC based on the relationship between the V _t and the SOC.

That relationship between V _t and SOC for use in the invention, a relationship determined from the longest when the terminal voltage measured from the actual battery was left for a time corresponding to the constant of the parameters used when calculating the overvoltage. Here, in the present embodiment, the parameter used when the multiplier 105 calculates the overvoltage is a parameter sequentially estimated by the sequential parameter estimation unit 104. That relationship between V _t and the SOC used in the present embodiment, the sequential parameter estimation unit 104 sequentially estimated parameters of the longest time was determined from the measured terminal voltage than the actual battery was left for a time corresponding to the constant relationship with It is.

  Here, the “time corresponding to the longest time constant” is preferably about 2τ to 3τ when the time constant is τ. The “time corresponding to the longest time constant” is not limited to this, and may be τ.

Next, the operation of the actual battery charging rate estimation apparatus of the first embodiment configured as described above will be described. The current sensor 102 detects _a charging / discharging current value Ia charged / discharged in the actual battery 101, and inputs this value to the sequential parameter estimation unit 104 and the multiplier 105, respectively. On the other hand, the voltage sensor 103 detects a battery voltage value _{V a} of the real cell 101, this value is inputted sequentially parameter estimation unit 104, and the subtractor 106.

The sequential parameter estimation unit 104 estimates each parameter (R ₀ , R ₁ , and C ₁ ) based on the input I _a and V _a using the equivalent circuit model and the Kalman filter shown in FIG. These resistance and capacitance is inputted to the multiplier 105 and is multiplied by the charge-discharge current value I _a that is input from the current sensor 102 is overvoltage value V ₀ is obtained. This overvoltage value V ₀ is input to the subtractor 106. The successive parameter estimation unit 104 also outputs the estimated parameter time constant to the V _t -SOC conversion unit 107.

A subtracter 106, from the battery voltage V _a that is input from the voltage sensor 103, by subtracting the overvoltage value V _0, to obtain a terminal voltage value V _t of the actual battery. This V _t is input to the V _t -SOC conversion unit 107.

V _t -SOC converter 107 uses a time constant obtained from the sequential parameter estimation unit 104, and _{V t} obtained from the subtractor 106, and a look-up table representing a relationship between _{V t} and SOC To output the SOC. More specifically, V _t -SOC conversion unit 107 outputs this charging rate SOC to a necessary calculation unit such as a travelable distance calculation unit (not shown).

As can be seen from the above description, in the real battery charging rate estimation apparatus according to the first embodiment, the sequential parameter estimation unit 104 calculates the time constant. Then, by selecting (switching) the relationship between V _t and SOC used by the V _t -SOC conversion unit 107 according to the time constant, the slow response part of the real battery is taken into account, and the SOC of the real battery is accurately estimated. can do.

(Embodiment 2)
The second embodiment of the present invention will be described below. The second embodiment is different from the first embodiment in the equivalent model used by the sequential parameter estimation unit 104. Further, the sequential parameter estimation unit 104 is different in that parameters are sequentially estimated based on UKF. Since other configurations are the same as those in the first embodiment, the same reference numerals as those in the first embodiment are used and will be described below.

FIG. 4 shows an example of an equivalent circuit model of an actual battery according to the second embodiment. FIG. 4 is composed of R ₀ , R ₁ , C ₁ , R ₂ , C ₂ , R ₃ , and C ₃ . However, it is assumed that there is a relationship of the following formulas (1) and (2) between these parameters.
C ₁ = C ₂ = C ₃ (1)
R ₃ = 9R ₂ = 25R ₁ (2)

The sequential parameter estimation unit 104 outputs the time constant related to R ₃ and C ₃ corresponding to the longest time constant to the V _t -SOC conversion unit 107. The V _t -SOC conversion unit 107 selects the relationship between V _t and SOC in the neglected elapsed time corresponding to the longest time constant among the time constants obtained from the sequential parameter estimation unit 104. Then, the V _t -SOC conversion unit 107 calculates the SOC based on the relationship between the V _t and the SOC.

As described above, the charging rate estimation apparatus according to the second embodiment also selects (switches) the relationship between V _t and SOC used by the V _t -SOC conversion unit 107 according to the time constant, as in the first embodiment. In consideration of the slow response part of the real battery, the SOC of the real battery can be accurately estimated.

(Embodiment 3)
The third embodiment of the present invention will be described below. FIG. 5 is a block diagram showing an overall configuration of the actual battery charging rate estimation apparatus according to the third embodiment. The real battery charge rate estimation apparatus according to the third embodiment is mounted on an actual battery (secondary real battery such as a lithium ion battery) 301 that is mounted on, for example, an electric vehicle and can supply power to a drive motor (not shown). It is connected. The charging rate estimation device includes a current sensor 302, a voltage sensor 303, a filter processing unit 304, a sequential parameter estimation unit 305, a first multiplier 306, a second multiplier 307, an adder 308, and a subtraction. 309, a V _t -SOC conversion unit 310, and a constant setting unit 311.

The current sensor 302 detects the magnitude of the discharge current when power is supplied from the actual battery 301 to the drive motor or the like. The current sensor 302 detects the magnitude of the charging current when the electric motor is caused to function as a generator during vehicle braking and a part of the braking energy is collected or charged from the power supply equipment on the ground. The detected current value _Ia is output to the filter processing unit 304 and the second multiplier 307 as input signals with + when charging and-when discharging. As the current sensor 302, those having various structures and types can be appropriately adopted.

The voltage sensor 303 detects _a voltage value (V _a ) between terminals of the actual battery 301, and the detected V _a is output to the filter processing unit 304 and the subtractor 309, respectively. As the voltage sensor 303, those having various structures and formats can be appropriately adopted.

The filter processing unit 304, the charge and discharge current _{I a} from the current sensor 302, the battery voltage value _{V a} from the voltage sensor 303, also a constant is input from the constant setting section 311. Then, the filter processing unit 304, a charge-discharge current value I _a and early response portion obtained by removing the slow response portion (diffusion resistance) from the respective battery voltage values V _a (connection resistance + electrolyte resistance + charge transfer resistance), The filtered current value _Ib and the filtered voltage value _Vb are sequentially input to the parameter estimation unit 305. The filter processing unit 304 will be described in more detail later.

The sequential parameter estimation unit 305 estimates the parameter of the fast response part from which the slow response part is removed from the equivalent circuit model of the real battery shown in FIG. In FIG. 6, the third to fifth resistance-capacitor parallel circuit portions (shaded portions in FIG. 6) composed of R ₃ and C ₃ , R ₄ and C ₄ , R ₅ and C ₅ have a slow response. A portion of the primary and secondary resistance-capacitor parallel circuit composed of R ₀ , R ₁ and C ₁ , R ₂ and C ₂ shows a fast response portion. Sequential parameter estimation unit 305, more specifically, a filtering current I _b and filtered voltage value V _b obtained from the filter processing unit 304 as an input signal, for example using a Kalman filter, the actual battery 301 The output value is compared with the output value of the early response part of the actual battery equivalent circuit model. Then, the sequential parameter estimation unit 305 estimates the parameter of the fast response part by sequentially adjusting the parameters of the state equation of the model so that the difference between the output values becomes small. Resistance values (R ₀ , R ₁ , R ₂ ) and capacitor capacities (C ₁ , C ₂ ), which are parameters estimated by the sequential parameter estimation unit 305, are output to the first multiplier 306.

The first multiplier 306 includes a charge / discharge current value I _a detected by the current sensor 302, a resistance value (R ₀ , R ₁ , R ₂ ) estimated by the sequential parameter estimation unit 305, and a capacitor capacity (C ₁ , C ₂ ) to obtain the first overvoltage value V ₀₁ . The first overvoltage value V ₀₁ is output to the adder 308.

The second multiplier 307 to obtain a second overvoltage value V ₀₂ of the slow part of the actual battery by multiplying the charge and discharge current value I _a obtained from the current sensor 302 to a constant obtained from the constant setting section 311. Then, the second multiplier 307 outputs the second overvoltage value V ₀₂ to the adder 308.

The adder 308 includes a first overvoltage value V ₀₁ of the fast response portion of the real battery obtained by the first multiplier 306 and a second overvoltage value V of the late response portion of the real battery obtained by the second multiplier 307. ₀₂ is added to obtain the overvoltage value V ₀ of the actual battery. Then, the adder 308 outputs this overvoltage value V ₀ to the subtracter 309. The adder 308 corresponds to an overvoltage calculation unit of the present invention.

Subtractor 309 obtains the subtraction to the actual battery terminal voltage overvoltage value _{V 0} obtained by the adder 308 from the detected battery voltage _{V a} by the voltage sensor 303 _{(V t).} Then, the subtracter 309 outputs the _{V t} to _V t -SOC converter 310. The subtractor 309 corresponds to a terminal voltage calculation unit of the present invention.

V _t -SOC conversion unit 310 uses the time constant obtained from the constant setting section 311, and _{V t} obtained from the subtractor 309, and a look-up table representing a relationship between _{V t} and SOC , Output SOC. The look-up table used by V _t -SOC conversion section 310 is the same as that in the first embodiment. Note that the V _t -SOC conversion unit 310 corresponds to a charge rate calculation unit of the present invention.

The V _t -SOC conversion unit 310 selects (switches) the relationship between V _t and SOC used according to the time constant in the look-up table shown in FIG. Specifically, the V _t -SOC conversion unit 107 selects the relationship between the V _t and the SOC at the neglected elapsed time corresponding to the longest time constant among the time constants obtained from the constant setting unit 311. Then, the V _t -SOC conversion unit 310 calculates the SOC based on the relationship between the V _t and the SOC. Here the relationship between the V _t and the SOC used in the present embodiment, the measurement from the actual battery was left only when constant, i.e. the time corresponding to the longest time constant of the parameters determined by experiments obtained from the constant setting portion 311 The relationship obtained from the terminal voltage obtained.

  Here, “the time corresponding to the longest time constant” preferably means about 2τ to 3τ, where τ is the time constant. The “time corresponding to the longest time constant” is not limited to this, and may be τ.

  The constant setting unit 311 sets a constant as an eigenvalue representing a slow response portion in the equivalent circuit model of the real battery 301, and outputs this constant to the filter processing unit 304 and the second multiplier 307, respectively. This eigenvalue, that is, the constant is peculiar to the actual battery 301, and this value is obtained by experiment.

Next, the filter processing unit 304 will be described in more detail with reference to FIGS. In the filter processing unit 304, the sequential parameter estimation unit 305 prevents the overvoltage portion from being overlapped between the fast response portion (connection resistance + electrolyte resistance + charge transfer resistance) and the slow response portion (diffusion resistance) of the actual battery. in order to be able to perform the parameter estimation, and performs filtering to charge and discharge current I _a and the battery voltage value V _a.

In this embodiment, performs filter processing using the value (constant) determined in advance experiments on charge and discharge current values I _a and the battery voltage value V _a before performing the parameter estimation successively with parameter estimation unit 305 . In this embodiment, as shown in FIG. 7, parameter estimation of the early response portion is performed using a signal obtained by removing the late response portion from the input signal, so that the overvoltage and the late response portion of the early response portion are obtained. Do not overlap with the overvoltage.

In this embodiment, the battery voltage value V _a, for example, low pass filter shown in FIG. 7 is used. In the figure, the low pass filter, the battery voltage value V _a, the charge-discharge current value the voltage value of the fast response portion by subtracting the voltage value V _c of a slow response portion obtained by calculation using the I _a By calculating the filter processing voltage value _Vb , the voltage component of the slow response portion is removed.

In FIG. 7, the transfer function 12 corresponding to the third order R ₃ and C ₃ , the transfer function 13 corresponding to the fourth order R ₄ and C ₄ , and the fifth order in the equivalent circuit model of the slow response portion of the real battery. The charge / discharge current value _Ia is input to the transfer function 14 corresponding to R ₅ and C ₅ , and respective overvoltage values are obtained. Then, the voltage value V _c of a slow response portion these overvoltage value is added by the adder 15 is obtained. Note that s in FIG. 7 is a variable of Laplace transform. Subtractor 16 obtains a voltage value V _b for fast response portion by subtracting the voltage value V _c of slow response portion from the terminal electric value voltage V _a.

On the other hand, with respect to current, filtering section 304 removes the slow response portion using high pass filter and inputs sequentially the parameter estimation unit 305 as the filter processing current value I _b, but the processing in filtering section 304 You may input into the parameter estimation part 305 as it is, without performing.

Next, the operation of the actual battery charging rate estimation apparatus of the third embodiment configured as described above will be described. The current sensor 302 detects _a charge / discharge current value Ia charged / discharged in the actual battery 301 and inputs this value to the filter processing unit 304 and the second multiplier 307. On the other hand, the voltage sensor 303 detects a battery voltage value _{V a} of the real cell 301, this value is inputted to the filter processing unit 304 and the subtractor 309.

Filtering section 304 uses the constants from the constant setting section 311, the charge-discharge current value I _a and the battery voltage value V _a minute slow response portion of the actual battery removed, respectively, filtering current I _b and the filter The processed voltage value _Vb is input to the sequential parameter estimation unit 305.

Sequential parameter estimation unit 305, based on the filtering current I _b and filtering the voltage value V _b which is input, a resistor R ₀ of the equivalent circuit model (Figure 6 the fast response part of the actual cell in FIG 6 the Using the first-order and second-order resistor-capacitor parallel circuits (R ₁ , C ₁ , R ₂ , C ₂ ) and the Kalman filter, the resistance values (R ₀ , R ₁ , R, which are parameters of the fast response part) ₂ ) and capacitor capacitances (C ₁ , C ₂ ), which are input to the first multiplier 306 and multiplied by the charge / discharge current value I _a input from the current sensor 302. Thus, a first overvoltage value V ₀₁ is obtained, and this first overvoltage value V ₀₁ is input to the adder 308.

On the other hand, the second multiplier 307 is input constant representing the resistance and capacitance of the slow part of the actual battery from the constant setting unit 311, the charge-discharge current value I _a that is input from the current sensor 302 in the constant multiplied Thus, the second overvoltage value V _{02 in} the slow response portion of the real battery is obtained. The second overvoltage value V ₀₂ is input to the adder 308.

The adder 308 adds the first overvoltage value V ₀₁ input from the first multiplier 306 and the second overvoltage value V ₀₂ input from the second multiplier 307 to obtain the overvoltage value V ₀ of the actual battery. . This overvoltage value V ₀ is input to the subtractor 309. A subtracter 309, from the battery voltage V _a that is input from the voltage sensor 303, by subtracting the overvoltage value V ₀ which is input from the adder 308 to obtain a terminal voltage value V _t of the actual battery. This V _t is input to the V _t -SOC conversion unit 310.

V _t -SOC conversion unit 310 uses the time constant obtained from the constant setting section 311, and _{V t} obtained from the subtractor 309, and a look-up table representing a relationship between _{V t} and SOC , Output SOC. More specifically, V _t -SOC conversion unit 310 outputs this charging rate SOC to a necessary calculation unit such as a travelable distance calculation unit (not shown).

As can be seen from the above description, the actual battery charging rate estimation apparatus of Embodiment 3 has the following effects. That is, the charging rate estimation device for a real battery according to the third embodiment uses the filtered current value _Ib and the filtered voltage value _Vb from which the slow response part is removed by the filter processing unit 304. Sequential parameter estimation is performed using an equivalent circuit model. The charging rate estimating apparatus obtains a first overvoltage value V ₀₁ is multiplied by the charge-discharge current value I _a to (resistance and capacitor fast response portion) parameters obtained by the sequential parameter estimation. Also, the slow response part of the actual battery, the charging rate estimating apparatus obtains the second overvoltage value V ₀₂ is multiplied by the charge-discharge current value I _a constant determined in advance through experiment (eigenvalues of actual battery). These first overvoltage value V ₀₁ accurately overvoltage value V ₀ which real battery by adding the second overvoltage value V _02, moreover it is possible to obtain easily. Therefore, it is possible to accurately estimate the internal state of the real battery in consideration of even the slow response part of the real battery, which is difficult with the sequential parameter method under the actual use environment of the real battery.

The charging rate of the actual battery, the charging rate estimating apparatus obtains a terminal voltage value V _t by subtracting the overvoltage value V ₀ from the battery voltage value V _a, the terminal voltage value by using the relationship data of V _t -SOC get the SOC corresponding to V _t. Therefore, by selecting the relationship between V _t and SOC used by the V _t -SOC conversion unit 310 according to the time constant, it is possible to accurately estimate the SOC of the real battery in consideration of the slow response part of the real battery. In addition, the filter processing unit 304 can prevent the overvoltage value in the early response portion and the overvoltage value in the late response portion of the actual battery from being calculated redundantly.

(Embodiment 4)
The fourth embodiment of the present invention will be described below. The fourth embodiment is different from the third embodiment in that the sequential parameter estimation unit 305 is not configured to output a time constant to the V _t -SOC conversion unit 310. Since other configurations are the same as those in the third embodiment, the same reference numerals as those in the third embodiment are used and will be described below.

Charging rate estimating apparatus according to the fourth embodiment, it is determined in advance the limit value of the time constant based on the equivalent circuit model of the real cell, using a relationship between V _t and the SOC corresponding to the time constant. Based on the equivalent circuit model shown in FIG. 6, the limit value of the time constant is about 800 seconds. In this case, therefore, the time constant of 800 seconds, left for elapsed time using the relationship between _{V t} and the SOC in the case of 800 seconds. Figure 8 shows the relationship of the relationship between V _t and the SOC corresponding to a predetermined time constant. The V _t -SOC conversion unit 310 estimates the SOC from the V _t -SOC characteristic of FIG. 8 based on V _t obtained from the subtractor 309. By doing so, the control of the V _t -SOC conversion unit 310 can be simplified to reduce the calculation cost, and the memory capacity required for the look-up table can be reduced.

FIG. 9 shows an experimental SOC value by the charging rate estimation apparatus according to Embodiment 4 of the present invention. Note that “After” in FIG. 9 represents the experimental value of SOC by the charging rate estimation apparatus according to Embodiment 4 of the present invention. “Before” in FIG. 9 indicates an experimental value when the SOC is obtained from the SOC-OCV characteristics prepared in advance instead of the V _t -SOC conversion unit 310. As shown in FIG. 9, it can be seen that the charging rate estimation apparatus according to the present invention has a smaller absolute value of error and can calculate a more accurate SOC.

  Although the present invention has been described based on the drawings and examples, it should be noted that those skilled in the art can easily make various modifications and corrections based on the present disclosure. Therefore, it should be noted that these variations and modifications are included in the scope of the present invention. For example, functions and the like included in each means and step can be rearranged so as not to be logically contradictory, and a plurality of means and steps can be combined into one or divided.

12, 13, 14 Transfer function 15 Adder 16 Subtractor 101, 301 Real battery 102, 302 Current sensor 103, 303 Voltage sensor 104, 305 Sequential parameter estimation unit 105, 308 Multiplier 106, 309 Subtractor 107 V _t -SOC Conversion unit 304 Filter processing unit 306 First multiplier 307 Second multiplier 310 V _t -SOC conversion unit 311 Constant setting unit

Claims (5)

A voltage sensor for measuring the battery voltage of the actual battery;
A current sensor for measuring the charge / discharge current of the actual battery;
A sequential parameter estimation unit that sequentially estimates parameters related to the actual battery based on the charge / discharge current and the battery voltage;
An overvoltage calculation unit for calculating an overvoltage based on a parameter relating to the actual battery;
A terminal voltage calculation unit that calculates a terminal voltage based on the battery voltage and the overvoltage;
Based on the terminal voltage and the relationship between the terminal voltage prepared in advance and the charging rate, a charging rate calculation unit for obtaining a charging rate;
In the charging rate estimation device having
The relationship between the terminal voltage prepared in advance and the charging rate was obtained from the terminal voltage measured from an actual battery left for a time corresponding to the longest time constant of the parameter used when the overvoltage calculation unit calculated the overvoltage. A charge rate estimation apparatus characterized by having a relationship. In the real battery charge rate estimation apparatus according to claim 1,
There are a plurality of relationships between the terminal voltage and the charging rate for each hour, and the charging rate calculation unit is left to stand for a time corresponding to the longest time constant of the parameter used when the overvoltage calculation unit calculates the overvoltage. A charging rate estimation device, wherein a relationship obtained from a terminal voltage measured from a battery is selected and used. In the charging rate estimation apparatus according to claim 1 or 2,
The relationship between the terminal voltage prepared in advance and the charging rate is a relationship obtained from a terminal voltage measured from an actual battery left for a time corresponding to the longest time constant of the parameter sequentially estimated by the sequential parameter estimation unit. The charge rate estimation apparatus characterized by the above-mentioned. In the charging rate estimation apparatus according to claim 1 or 2,
The relationship between the terminal voltage prepared in advance and the charging rate is a relationship obtained from a terminal voltage measured from an actual battery left for a time corresponding to the longest time constant of a parameter obtained by experiment. Rate estimation device. A voltage measurement step for measuring the battery voltage of the actual battery;
A current measuring step for measuring a charge / discharge current of the actual battery;
Sequential parameter estimation step for sequentially estimating parameters related to the actual battery based on the charge / discharge current and the battery voltage;
An overvoltage calculating step of calculating an overvoltage based on the parameter relating to the actual battery;
A terminal voltage calculating step for calculating a terminal voltage based on the battery voltage and the overvoltage;
A charge rate calculation step for obtaining a charge rate based on the terminal voltage and a relationship between the terminal voltage and the charge rate prepared in advance,
In the charging rate estimation method having
The relationship between the terminal voltage prepared in advance and the charging rate was obtained from the terminal voltage measured from an actual battery left for a time corresponding to the longest time constant of the parameter used when calculating the overvoltage in the overvoltage calculation step. A charging rate estimation method characterized by being a relationship.