JP2010217079A - Device for estimation of total capacity of secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device for estimation of total capacity of a secondary battery capable of estimating total capacity even during charging or discharging, and stably estimating the total capacity irrespective of magnitude of current. <P>SOLUTION: The device for estimation of total capacity of a secondary battery includes a parameter identifier for modeling transfer characteristics to terminal voltage V from charge and discharge current I of a secondary battery and open-circuit voltage V0, further modeling the open-circuit voltage as a value of integration of the current multiplied by a variable parameter h and sequentially identifying respective coefficients of the modeled transfer function and the variable parameter h, and a state estimator for sequentially estimating a charging ratio or the open-circuit voltage as a quantity of state. The total capacity is estimated from a charging ratio estimation value SOC or a ratio of inclination of the open-circuit voltage V0 for the charging ratio SOC at an open-circuit voltage estimation value V0 for a parameter estimation value. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a total capacity estimation device for a secondary battery capable of charging and discharging a plurality of batteries such as a lithium ion battery.

  As a conventional estimation device for the total capacity (full charge capacity) of a secondary battery, the open circuit voltage-charge rate characteristic of the secondary battery whose total capacity is to be detected is measured in advance, and before and after the start of charging or discharging By measuring the open circuit voltage later, the amount of change in the charge rate is obtained using the open circuit voltage-charge rate characteristic, and the total capacity is estimated from the amount of change in the charge rate and the amount of electricity supplied during charging and discharging. The thing of a structure is known (for example, refer patent document 1).

  In the secondary battery total capacity estimation device disclosed in Patent Document 1, an error (zero-point offset or measurement) is detected in the current sensor measurement value when the amount of electricity supplied during charge / discharge is obtained by integrating the charge / discharge current measurement value. If there is non-linearity in the output of the device, the measurement error accumulates in the quantity of electricity, so that the total capacity estimate becomes true over time as shown in prior art 1 (represented by black circles) shown in FIG. There is a problem of deviating from the value.

  Moreover, in the total capacity estimation apparatus of the secondary battery disclosed in Patent Document 1, when determining the change in the charging rate, an open circuit voltage of the charging / discharging rate is required, so the total capacity is estimated during charging / discharging. There is a problem that you can not.

Furthermore, in the secondary battery total capacity estimation device disclosed in Patent Document 1, the total capacity estimation value Cap is actually calculated by changing the charging / discharging current integrated value as shown in the following equation (1). It is calculated as a divided value, but in this equation (1), when the denominator or numerator is close to zero, it is easily affected by current measurement error, charge rate estimation error, and phase difference between the two. There is a problem that the total capacity cannot be calculated accurately. This means that in order to estimate with high accuracy, it is necessary to estimate the total capacity after the charge rate has changed to some extent and the denominator / numerator of Equation (1) has a value. However, this requires simultaneous calculation of the amount of electricity by long-time current integration, and as described above, accumulation of current measurement errors leads to deterioration in estimation accuracy.

As another device for estimating the total capacity of the secondary battery, the total capacity is calculated based on the following formula (2) from the ratio between the current I (t) measured on the heavy pole and the time differential value of the charge rate estimated value SOC. The thing of the structure to presume is known (for example, refer patent document 2). This technique solves the problem that the total capacity cannot be estimated during charge / discharge, which is also a problem of the secondary battery total capacity estimation apparatus disclosed in Patent Document 1 described above.

  However, in the secondary battery total capacity estimation device disclosed in Patent Document 2, although it is possible to estimate the total capacity based on the above formula (2) even during charging and discharging, the formula (2) When the charge / discharge current corresponding to the right side numerator is close to zero, the time rate of change of the charge rate corresponding to the right side denominator of Equation (2) is also small, so the current measurement error, the charge rate estimation error, There is a problem that the total capacity estimation value cannot be obtained stably due to the influence of the phase difference between them.

JP 2001-231179 A JP 2006-292492 A

  Therefore, the present invention has been devised by paying attention to the above-mentioned problems, and the object of the present invention is to estimate the total capacity even during charging and discharging, and the magnitude of the current. It is an object of the present invention to provide a secondary battery total capacity estimation device capable of stably estimating the total capacity regardless of the above.

（ただし、ｓはラプラス演算子であり、Ｇ１（ｓ）およびＧ２（ｓ）は任意のプロパーな伝達関数、ｈは未知パラメータ） A feature of the present invention is that the charge / discharge current I of the secondary battery and the transfer characteristics from the open circuit voltage V ₀ to the terminal voltage V are modeled (equation 3), and the open circuit voltage is a value obtained by multiplying the integral of the current by the variable parameter h. (Equation 4)

(Where s is a Laplace operator, G1 (s) and G2 (s) are arbitrary proper transfer functions, and h is an unknown parameter)

A total capacity estimation device for a secondary battery comprising a parameter identifier for sequentially identifying each coefficient of a modeled transfer function and a variable parameter h, and a state estimator for sequentially estimating the charging rate or open circuit voltage as a state quantity. Thus, the total capacity (full charge capacity) is calculated from the ratio of the slope (gradient, differential value) of the open circuit voltage V _{0 to} the charge rate SOC in the charge rate estimated value SOC (or the open circuit voltage estimated value V ₀ ) and the parameter estimated value h. The gist of this is to estimate.

  Here, since the total capacity is calculated using the parameters and states identified sequentially, it is possible to estimate the total capacity even during charging and discharging. Moreover, in general, the charging rate does not become zero, and the parameter h in (Equation 5) also has a positive value, so that the total capacity can be stably estimated regardless of the magnitude of the current. Become.

  In addition, since the open circuit voltage or charging rate is used as the state quantity and it is obtained without integrating the current, and this is used to estimate the total capacity, the total capacity even if there is a steady offset error in the current measurement value The estimated value can be accurately obtained without drifting with time.

  The secondary battery total capacity estimation device may be configured to include a phase compensator that matches the phase of the parameter estimation value with the phase of the open circuit voltage or the charge rate estimation value.

  Since the phase of the parameter estimation value output from the parameter identifier and the phase of the open circuit voltage or charging rate output from the state estimator can be matched, the estimation accuracy of the total capacity is improved.

  Further, in the above-described total capacity estimation device for the secondary battery, it is determined that the identification error in the parameter identifier (the difference between the battery model output inside the parameter identifier and the actual battery output) is within a preset range. The total capacity may be calculated only when the total capacity is calculated, and the estimated total capacity value may be updated using the calculated value.

  By doing so, since the total capacity is not estimated while the parameter identifier cannot accurately estimate the parameters immediately after startup or at the time of sudden battery parameter change, erroneous estimation of the total capacity can be avoided.

  Further, in the total capacity estimation device for the secondary battery, only in a charge rate region in which it is known in advance that the second-order differential value (that is, the rate of change in slope) of the open circuit voltage with respect to the charge rate is within a predetermined range. The total capacity may be estimated (see the hatched area in FIG. 2).

  In designing a parameter identifier, an approximation that the change rate of a parameter to be identified is generally zero is used. Therefore, the identification accuracy improves as the change rate of the parameter is closer to zero. On the other hand, the parameter h corresponds to the slope of the open circuit voltage-charging rate characteristic, and the rate of change generally differs depending on the charging rate region. Therefore, by calculating the total capacity only when the change rate of the slope of the open-circuit voltage-charge rate characteristic (that is, the change rate of the parameter h) is in an area that can be regarded as substantially equal to zero, it is possible to identify the parameter with high accuracy. As a result, it is possible to estimate the total capacity with high accuracy.

  Further, in the above-described total capacity estimation device for the secondary battery, the total capacity is obtained only in the charge rate region in which the slope of the open circuit voltage (gradient, first-order differential value) with respect to the charge rate is known in advance. May be estimated (see FIG. 2).

  By doing so, since the slope of the open-circuit voltage-charge rate characteristic measured in advance corresponds to the parameter h, both the denominator and the numerator in the total capacity calculation formula become small and the estimation accuracy deteriorates in a region where this is small. Can be avoided.

  Further, in the total capacity estimating device for the secondary battery, the value after the low-pass filter is applied to the total capacity estimated value is set as a definite value of the total capacity estimated value, and the time constant of the low-pass filter is variable. When an operating condition in which battery capacity deterioration is expected to proceed rapidly is detected, the time constant may be set to be short.

  By doing this, the deterioration rate of the total capacity is usually very slow, so that only the frequency component can be extracted by performing the low-pass filter process. By making the time constant of the low-pass filter variable according to the battery operating conditions, the estimated speed can be increased under operating conditions in which the deterioration of the battery proceeds rapidly.

  In this case, it is preferable to set the time constant of the low-pass filter short for a predetermined time after detecting battery replacement. Thereby, the response speed of the estimated total capacity can be increased with respect to a sudden change in the total capacity due to battery replacement.

It is a schematic block diagram of the total capacity estimation apparatus of the secondary battery which concerns on embodiment of this invention. It is a figure which shows the relationship between an open circuit voltage and a charging rate. It is a block diagram of total capacity estimated value calculation. It is a flowchart of the total capacity estimated value calculation performed with the total capacity estimation apparatus of a secondary battery in embodiment of this invention. It is a figure which confirms the problem of a prior art and the effect of this invention by simulation.

  Hereinafter, a secondary battery total capacity estimating apparatus according to an embodiment of the present invention will be described with reference to FIGS.

  FIG. 1 is a configuration diagram of a secondary battery total capacity estimating apparatus according to an embodiment of the present invention. In this embodiment, a secondary battery (hereinafter also simply referred to as “battery”) is used to drive a load such as a motor, or the secondary battery is charged with electric power generated by an alternator using a motor regeneration or engine as a power source. This is an example in which a secondary battery total capacity estimation device is attached to the system. This system includes a secondary battery 10, a load 20 such as a motor, and an electronic control unit 30 that estimates an internal state such as a charging rate of the secondary battery. The electronic control unit 30 includes a CPU that calculates a program, a microcomputer that includes a program and ROM and RAM that stores calculation results, an electronic circuit, and the like. The system also includes an ammeter 40 that detects a charge / discharge current (also simply referred to as “current”) to the secondary battery 10, and a voltmeter 50 that detects battery terminal voltage (also simply referred to as “voltage”). And each is connected to the electronic control unit 30.

FIG. 3 is a block diagram showing a configuration for performing the total capacity estimation calculation performed by the electronic control unit 38. As shown in FIG. 3, charging / discharging current detecting means 100 for periodically detecting the current charged / discharged to the secondary battery, terminal voltage detecting means 101 for periodically detecting the terminal voltage of the secondary battery, and measurement Parameter calculation for identifying a parameter representing the internal state of the battery using the filter calculation means 102 for performing a filter calculation on the charged / discharge current I (k) and the terminal voltage V (k), and the output of the filter calculation means 102 State estimation in which the open circuit voltage V ₀ (k) or the charging rate SOC (k) is estimated as a state quantity using the means 103, the output of the filter calculation means 102, and the battery parameter estimated value calculated by the parameter identification means 103 The total capacity for estimating the total capacity by using the parameters identified by the means 104, the parameter identifying means 103, and the state quantity estimated by the state estimating means 104 It consists of estimating means 105.

The relationship between the charge / discharge current I, the terminal voltage V, and the open circuit voltage V ₀ of the secondary battery is modeled using arbitrary transfer functions G ₁ (s) and G ₂ (s).

Here, the transfer functions G ₁ (s) and G ₂ (s) are defined and described as the following expressions (6) and (7), respectively, as an example. However, in the present invention, the transfer functions G ₁ ( The method of selecting s) and G ₂ (s) is not limited to this.

Here, s is a Laplace operator, and k, T ₁ and T ₂ are unknown parameters. The open circuit voltage V ₀ is considered to be obtained by integrating the current I multiplied by the variable efficiency h from a certain initial state, and is described by the following equation (8).

Substituting equations (6) to (8) into equation (5) yields equation (9) below.

Multiplying both sides of equation (9) by a stable low-pass filter G _LPF (s)
10).

Here, a value obtained by applying a low-pass filter or a band-pass filter to the current I detected by the charge / discharge current detecting means 100 or the terminal voltage V detected by the terminal voltage detecting means 101 is defined as the following expression (11), This is calculated by the filter calculation means 102.

In the present embodiment, as an example of a stable low-pass filter G _LPF (s),
Although it is set as the following Formula (12), how to select is not limited to this.

Note that p is a time constant of the filter. Further, the preprocessing filter calculation means 102 actually calculates using the recurrence formula obtained by discretizing the above formula (12) and the following formula (13) by Tustin approximation or the like.
If formula (10) is rewritten using formula (11) and rearranged with respect to V ₂ (t), the following formula (13) is obtained.

The above equation (13) is obtained by measuring values (I ₁ (t), I ₂ (t), I ₃ (t), V ₂ (t), V ₃ (t)) and unknown parameters (T ₁ , T ₂ , K, h), which is the same as the standard form of the general adaptive digital filter (the following expression (14)).

However, y, w ^T , and θ ^T are as in the following formula (15).

Therefore, by using the output signals (I ₁ (t), I ₂ (t), I ₃ (t), V ₂ (t), V ₃ (t)) of the filter calculation means 102 for the adaptive digital filter calculation, An unknown parameter vector θ composed of parameters K, T ₁ , T ₂ , h representing the transfer characteristics of the secondary battery can be collectively estimated.

In the present embodiment, a “dual trace” that improves the logical disadvantage of the simple “least-squares adaptive filter” (because once the estimated value converges, accurate estimation cannot be performed again even if the parameter changes thereafter). "Gain method" is used. Based on the above equation (14), algorithms for estimating the unknown parameter vector θ by the adaptive digital filter are the following equations (16) to (20). However, the battery parameter estimated value at time k is assumed to be θ ^ (t).

In the above formulas (16) to (20), the following formula (21) is applied.

Trace {Q (k)} means a trace (sum of diagonal elements) of the matrix Q (k). Λ ₁ , λ ₃ , γ _U , and γ _L are design parameters, and 0 <λ ₁ and 0 <λ ₃ <∞. lambda ₃ is a constant (adjustment gain) for setting the estimated speed of the adaptive digital filter, but the estimated speed is faster by increasing the value becomes susceptible to the contrary noise. γ _U and γ _L are parameters that define the upper and lower limits of the trace of the matrix Q (k), and are set such that 0 <γ _L <γ _U. Further, P (0) is a sufficiently large value, and θ ^ (0) is a non-zero sufficiently small value as an initial value.

  The above is one embodiment of the battery parameter identification method using the adaptive digital filter performed in the parameter identification means 103.

Next, an open circuit voltage estimation method in the state quantity estimation unit 104 shown in FIG. 3 will be described. The formula (5) by substituting the equation (6) above formula (7), the following equation is rearranged with respect to the open circuit voltage _{V 0} (22).

A change in the open circuit voltage V ₀ is considered to be gentle, and a value obtained by multiplying both sides by the low-pass filter G _LPF (s) of the above equation (22) is estimated by the following equation (23) as an open circuit voltage estimated value V ₀ .

したがって、上記式（２４）にパラメータ同定手段で推定した電池パラメータ推定値（Ｔ_１、Ｔ_２、Ｋ）とフィルタ演算手段１０２の出力（Ｉ_１（ｋ）、Ｉ_２（ｋ）、Ｖ１（ｋ）、Ｖ_２（ｋ））を代入することで開路電圧推定値Ｖ_０が演算できる。 Substituting the above equation (11) into the above equation 23 yields the following equation (24).

Therefore, the battery parameter estimation values (T ₁ , T ₂ , K) estimated by the parameter identification means and the outputs (I ₁ (k), I ₂ (k), V1 (k) ), V ₂ (k)) is substituted, the open circuit voltage estimated value V ₀ can be calculated.

  The formulation for estimating the open circuit voltage as described above is an example, and the present invention is not limited to this method. In order to estimate the charging rate from the open circuit voltage estimated by the above equation (24), the charge rate may be converted from the open circuit voltage using the previously measured open circuit voltage-charging rate characteristic. The above is one embodiment of the method for estimating the open circuit voltage and the charging rate in the state quantity estimating means 104.

  Next, the total capacity estimation method performed in the total capacity estimation means 105 shown in FIG. 3 will be described.

上記式（２５）の右辺において、総容量に対する電流の積算値の比は充電率に相当することから、下式（２６）であることを用いると下式（２７）となる。

When the above equation (8) is rewritten in the time domain and both sides are divided by the total capacity Cap, the following equation (25) is obtained.

In the right side of the above equation (25), the ratio of the integrated value of the current to the total capacity corresponds to the charging rate. Therefore, using the following equation (26), the following equation (27) is obtained.

When this is arranged with respect to the total capacity Cap, the total capacity can be estimated by the following equation (28) using the slope of the open circuit voltage V0 with respect to the charging rate SOC and the parameter estimated value. This may be the mathematically equivalent expression (29).

ただし、Ｇ_LPF（ｓ）特性は上記式（１２）で表される。 Here, as is apparent from the above equation (23), in the present embodiment, the phase of the open circuit voltage estimated value V ^ _{0 and} the phase of the charging rate estimated value SOC are low pass filters with respect to the phase of the parameter estimated value? Delayed by G _LPF (s). Therefore, in order to match both phases, the phase of the parameter estimation value? Is delayed by a phase compensator having the characteristic of G _LPF (s) (the following equation (30)).
. Actually, the calculation is performed using a recurrence formula obtained by discretizing G _LPF (s) by Tustin approximation or the like.

However, the G _LPF (s) characteristic is expressed by the above formula (12).

Therefore, the total capacity estimating means 105 stores in advance characteristics related to the inclination based on the open circuit voltage-charge rate characteristics acquired in advance, and the open circuit voltage estimated value estimated by the state estimating means 104 based on this characteristic. The slope at V ^ ₀ or the estimated charge rate SOC is calculated. Then, using this slope and the output? ^* Of the phase compensator (the above formula (30)), the total capacity is estimated by the following formula (31) or formula (32).

The charging rate estimation method described above will be described with reference to the flowchart of FIG. 4 showing processing performed by the electronic control unit 30 shown in FIG. Note that the process of FIG. 4 is performed every fixed period T ₀ (for example, 100 ms). In the following description, I (k) is the current I value in the current execution cycle, I (k−1) is the current value in the previous calculation cycle, and values other than the current are also expressed in the same manner. To do.

  As shown in FIG. 4, first, the charge / discharge current I (k) is measured based on the signal from the ammeter, and the terminal voltage V (k) of the secondary battery is measured based on the signal from the voltmeter (step S1). ).

For the current value I (k) and voltage value V (k) measured in step S1, filter processing whose characteristics in the continuous time relation are the above expressions (11) and (12) is Tustin approximation or the like. Is used to calculate I ₁ (k), I ₂ (k), I ₃ (k), V ₁ (k), V ₂ (k), and V ₃ (k) (step S2). .

Next, using the above formula (1) using I ₁ (k), I ₂ (k), I ₃ (k), V ₁ (k), V ₂ (k), and V ₃ (k) calculated in step S2. The parameter vector θ ^ (k) is calculated using the adaptive digital filters represented by 16) to (20) (step S3).

Then, parameters of the battery model identified in step S3 and _{(T ^ 1, K ^ ·} T ^ 2, K ^), the calculated filter output values in step _{S2 (I 1 (k),} I 2 (k) , V ₁ (k), V ₂ (k)), the open circuit voltage estimated value V ^ ₀ (k) is calculated from the above equation (23) (step S4).

And using the map which memorize | stored the inclination of the open circuit voltage-charging rate characteristic of the said battery measured beforehand, the open circuit voltage V ₀ with respect to the charging rate SOC in the open circuit voltage estimated value V ^ ₀ (k) calculated in said step S4 The inclination is calculated (step S5).

  Next, with respect to the parameters of the battery model identified in step S3, the filtering process of the above expression 30 in which the characteristic in the continuous time relation is expressed by the above expression (12) is expressed in a discrete time system by Tustin approximation or the like. Then, phase compensation is performed (step S6).

  Then, it is determined whether or not the estimation error e (k) (see the above equation (17)) in the parameter identification process performed in step S3 is continuously within a predetermined range for a predetermined time. If it is determined that the estimation error e (k) is within the preset range, the process proceeds to step S8 described later. If it is determined that the estimation error e (k) is not within the range, the total capacity estimation value is not calculated and the previous time is calculated. The total capacity estimation process is terminated (step S7).

Then, using the relation between the charging rate SOC and the open circuit voltage V ₀ measured in advance in step S8, determine the charging rate estimate from the open circuit voltage estimated value V _{0 (k)} calculated in step S4, which is set in advance It is determined whether it is within the range of the area. If the determination result is true, the process proceeds to step S9. If the determination result is false, the total capacity estimation value is not calculated and the previous calculation result is maintained, and the total capacity estimation process is terminated.

Using the parameter estimated value calculated in step S3 and the slope of the open circuit voltage V ₀ with respect to the charging rate SOC calculated in step S5, the total capacity is estimated by the above equation (28) or equation (29) (step S9). .

Low-pass filter processing is performed on the total capacity estimated value Cap calculated in step S9 (step S10). In this low-pass filter, for example, the transfer characteristic in a continuous system is represented by the following equation (33).

  Here, the time constant t is changed under preset conditions according to the operating state of the battery. Specifically, when a large current is output when the absolute value of the charge / discharge current is equal to or higher than a predetermined value with respect to the nominal set value, or when the battery temperature is equal to or higher than a predetermined value, the predetermined time is decreased by a predetermined time. For example, when battery replacement is detected by a method such as reading a serial number uniquely set for each battery when the system is activated, the time constant t is decreased by a predetermined time at a predetermined ratio.

  FIG. 5 shows the result of verifying the effect of the present invention by simulation using a battery model. In this simulation, the characteristics of the secondary battery were assumed to be in the form shown by the above formula 9. In addition, observation noise and quantization error were set for the charge / discharge current measurement value and the terminal voltage measurement value, and a measurement offset of +3 [A] was set for the current. In FIG. 5, charging and discharging current, terminal voltage, charging rate estimated value and true value, estimated value and true value of parameter h, total capacity estimated value and true value are shown in the graph of parameter and charging rate from the top. , The true value is indicated by a solid line, the estimated value is indicated by a chain line, and in the graph of the total capacity, the estimated value according to the prior art 2 is indicated by a dotted line, and the estimated value by the present invention is indicated by a chain line. In the prior art 1, the total capacity cannot actually be calculated during charging / discharging, but the estimated total capacity calculated when it is assumed that the open circuit voltage is measured by cutting off the current at each time is shown in FIG. Filled in with ●.

  In FIG. 5, the estimated value of the total capacity according to the prior art 1 drifts with time. In addition, although the estimated total capacity according to the conventional technique 2 does not drift with the passage of time, it is averaged with respect to the true value under the influence of the current measurement offset of +3 [A] set as the simulation condition. Is greatly estimated. Moreover, since the denominator and numerator of the estimation formula (the above formula (2)) may be zero, the total capacity estimation value vibrates violently and the total capacity cannot be estimated stably.

  On the other hand, according to the present invention, although the parameter estimation accuracy is slightly deteriorated due to the current measurement offset, the total capacity estimation value can be stably and highly accurately estimated without drifting over time. is there.

Although the present embodiment has been described above, in the present embodiment, a parameter identifier that sequentially identifies each coefficient and variable parameter h of the modeled transfer function, and a charging rate or an open circuit voltage are sequentially estimated as state quantities. It consists of a state estimator, and the charging rate estimated value SOC (or
The total capacity (also referred to as the full charge capacity) can be estimated from the ratio of the slope (gradient, differential value) of the open circuit voltage V _{0 to} the charge rate SOC in the open circuit voltage estimated value V ₀ ) and the parameter estimated value h.

  Here, since the total capacity is calculated using the parameters and states identified sequentially, it is possible to estimate the total capacity even during charging and discharging. In addition, the charging rate generally does not become zero, and the parameter h in the above equation (5) also has a positive value, so that the total capacity can be stably estimated regardless of the magnitude of the current. It becomes.

  In addition, since the open circuit voltage or charging rate is used as the state quantity and it is obtained without integrating the current and this is used to estimate the total capacity, the total capacity is even if there is a steady offset error in the current measurement value. The estimated value can be accurately obtained without drifting with time.

  In addition, a phase compensator that matches the phase of the parameter estimation value with the phase of the open circuit voltage or charging rate estimation value may be installed. The phase of the parameter estimation value output from the parameter identifier and the output from the state estimator Since the phase of the open circuit voltage or the charging rate can be matched, the estimation accuracy of the total capacity is improved.

  In the secondary battery total capacity estimating apparatus according to the present embodiment, the identification error in the parameter identifier (difference between the output of the battery model inside the parameter identifier and the output of the actual battery) is within a preset range. The total capacity may be calculated only when it is determined that the total capacity is estimated, and the total capacity estimation value may be updated using the calculated value. In this case, since the total capacity is not estimated while the parameter identifier cannot accurately estimate the parameters immediately after startup or at the time of sudden battery parameter change, erroneous estimation of the total capacity can be avoided.

  Furthermore, in the total capacity estimation device for secondary batteries according to the present embodiment, it is known in advance that the second-order differential value (that is, the rate of change in slope) of the open circuit voltage with respect to the charging rate is within a predetermined range. The total capacity may be estimated only in the charge rate region (see FIG. 2).

  In designing a parameter identifier, an approximation that the change rate of a parameter to be identified is generally zero is used. Therefore, the identification accuracy improves as the change rate of the parameter is closer to zero. On the other hand, the parameter h corresponds to the slope of the open circuit voltage-charging rate characteristic, and the rate of change generally differs depending on the charging rate region. Therefore, by calculating the total capacity only when the change rate of the slope of the open-circuit voltage-charge rate characteristic (that is, the change rate of the parameter h) is in an area that can be regarded as substantially equal to zero, it is possible to identify the parameter with high accuracy. As a result, it is possible to estimate the total capacity with high accuracy.

  Further, in the secondary battery total capacity estimating apparatus according to the present embodiment, the charging rate region in which the slope (gradient, first-order differential value) of the open circuit voltage with respect to the charging rate is within a predetermined range is known in advance. Only in this case, the total capacity may be estimated. In this case, since the slope of the open-circuit voltage-charge rate characteristic measured in advance corresponds to the parameter h, in a region where this is small, both the denominator and the numerator in the total capacity calculation formula are reduced, and the estimation accuracy is prevented from deteriorating. Can do.

Furthermore, in the total capacity estimation device for a secondary battery according to the present embodiment, the total capacity estimation value is subjected to a low-pass filter, and the value after the low-pass filter is used as a final value of the total capacity estimation value. The time constant may be variable, and when an operating condition in which battery capacity deterioration is expected to proceed rapidly is detected, the time constant may be set to be short. In this case, since the degradation rate of the total capacity is usually very slow, only the frequency component can be extracted by performing the low-pass filter process. By making the time constant of the low-pass filter variable according to the battery operating conditions, the estimated speed can be increased under operating conditions in which the deterioration of the battery proceeds rapidly.

  In addition, it is preferable to set the time constant of the low-pass filter short for a predetermined time after detecting battery replacement. Thereby, the response speed of the estimated total capacity can be increased with respect to a sudden change in the total capacity due to battery replacement.

  The present invention can be used in a manufacturing industry such as a vehicle in which a secondary battery is used.

DESCRIPTION OF SYMBOLS 10 ... Secondary battery 20 ... Load 30 ... Electronic control unit 40 ... Ammeter 50 ... Voltmeter 100 ... Charge / discharge current detection means 101 ... Terminal voltage detection means 102 ... Filter calculation means 103 ... Parameter identification means 104 ... State estimation means 105 ... Total capacity estimation means

Claims (7)

The transfer characteristics from the charge / discharge current I and the open circuit voltage V0 to the terminal voltage V of the secondary battery are modeled as in the following expression (A), and the open circuit voltage is calculated by multiplying the current integral by the variable parameter h. The model is configured as shown in (B), and includes a parameter identifier that sequentially identifies each coefficient of the modeled transfer function and the variable parameter h, and a state estimator that sequentially estimates the charging rate or open circuit voltage as a state quantity. ,

(Where s is a Laplace operator, G1 (s) and G2 (s) are arbitrary proper transfer functions, and h is an unknown parameter)
Charging rate estimated value ■ Total capacity of the secondary battery characterized by estimating the total capacity from the ratio of OC or the slope of the open circuit voltage V0 to the charging rate SOC at the open circuit voltage estimated value V0 and the parameter estimated value? Estimating device.   The total capacity estimating apparatus for a secondary battery according to claim 1, further comprising a phase compensator that matches the phase of the parameter estimated value with the phase of the open circuit voltage or the charging rate estimated value.   2. The total capacity is calculated only when an identification error in the parameter identifier is determined to be within a preset range, and the total capacity estimated value is updated using the calculated value. The total capacity estimation apparatus of the secondary battery as described in.   2. The secondary battery according to claim 1, wherein the total capacity is estimated only in a charge rate region in which it is known in advance that a second-order differential value of the open circuit voltage with respect to a charge rate falls within a predetermined range. Total capacity estimation device.   2. The total capacity estimation device for a secondary battery according to claim 1, wherein the total capacity is estimated only in a charge rate region in which it is known in advance that the slope of the open circuit voltage with respect to the charge rate falls within a predetermined range. .   The value after the low-pass filter is applied to the total capacity estimation value is set to be the final value of the total capacity estimation value. Further, the time constant of the low-pass filter is variable, and the battery capacity rapidly deteriorates. 6. The secondary battery total capacity estimating apparatus according to claim 1, wherein when the operating condition expected to be detected is detected, the time constant is shortened.   7. The secondary battery total capacity estimating apparatus according to claim 6, wherein the time constant of the low-pass filter is set short for a predetermined time after detecting battery replacement.

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