JP5625244B2 - Secondary battery capacity estimation device - Google Patents

Description

  The present invention relates to a capacity estimation device for a secondary battery.

  As a secondary battery control device, parameters (internal resistance, time constant) in a given battery model formula are estimated using an adaptive digital filter, and the estimated parameters and measured values of secondary battery current and terminal voltage Therefore, a control device that estimates the open circuit voltage of a secondary battery and estimates the charge rate of the secondary battery using the estimated open circuit voltage and the relationship between the open circuit voltage and the charge rate obtained in advance through experiments or the like is known. (See Patent Document 1).

Japanese Patent No. 3714246

  However, in the above prior art, when the calculation is performed by the adaptive digital filter, the open circuit voltage estimation accuracy depends on the waveform of the current supplied to the secondary battery, and therefore the supplied current is almost constant. In addition, when current is supplied at a predetermined frequency, there is a problem that the total capacity (capacity at full charge) of the secondary battery cannot be estimated appropriately.

  The problem to be solved by the present invention is to provide a capacity estimation device for a secondary battery that can appropriately estimate the total capacity of the secondary battery.

The present invention superimposes a detection current of a predetermined pattern on the charging current, and uses the adaptive digital filter to calculate the secondary battery current from the measured values of the secondary battery current and the terminal voltage when the detection current is superimposed. The open circuit voltage and the charging rate are estimated, and based on this, the total capacity of the secondary battery is estimated . At this time, the amplitude of the detection current superimposed on the charging current is determined by the secondary battery at the start of charging. The above-described problem is solved by setting the charging rate, the temperature of the secondary battery, and at least one selected from the previous value of the total capacity estimated for the secondary battery .

  According to the present invention, the open circuit voltage and the charging rate of the secondary battery are estimated using the adaptive digital filter from the current and the terminal voltage of the secondary battery when the detection current of a predetermined pattern is superimposed on the charging current. Since the total capacity of the secondary battery is estimated based on this, the estimation accuracy of the total capacity of the secondary battery can be improved.

FIG. 1 is a diagram illustrating a configuration of a control system for a secondary battery according to the present embodiment. FIG. 2 is a functional block diagram of the electronic control unit 30 according to the first embodiment. FIG. 3 is a diagram showing an equivalent circuit model showing a battery model of the secondary battery. FIG. 4 is a diagram illustrating an example of an open circuit voltage-charge rate characteristic of the secondary battery. FIG. 5 is a time chart showing an example of a charging method of the secondary battery. FIG. 6 is a time chart showing another example of a secondary battery charging method. FIG. 7 is a diagram showing an example of a profile showing a change in current when a detection current pattern DI (k) is superimposed on a charging current and a profile showing a change in identification error of adaptive digital filter calculation. FIG. 8 is a flowchart showing a calculation processing method of the total capacity estimation value Cap ^ (k) in the first embodiment. FIG. 9 is a flowchart showing the charging rate calculation processing method. FIG. 10 is a diagram illustrating a simulation result of the estimation of the charging rate SOC in the first embodiment. FIG. 11 is a functional block diagram of the electronic control unit 30 according to the second embodiment. FIG. 12 is a flowchart illustrating a calculation processing method of the total capacity estimation value Cap ^ (k) in the second embodiment. FIG. 13 is a diagram illustrating simulation results of estimation of the charging rate SOC and estimation of the parameter d in the second embodiment.

<< First Embodiment >>
First, a first embodiment of the present invention will be described.
FIG. 1 is a diagram illustrating a configuration of a control system for a secondary battery according to the present embodiment. The control system shown in FIG. 1 connects, for example, an electric vehicle such as a plug-in HEV or an electric vehicle to the charging facility 20 and charges the secondary battery 10 provided in the electric vehicle. This is an example in which the capacity estimation device according to the present invention is applied to the secondary battery 10.

  As shown in FIG. 1, the secondary battery control system according to the present embodiment connects the secondary battery 10 mounted on the electric vehicle and the charging facility 20 to the secondary battery 10 by the charging facility 20. In addition to charging, the electronic control unit 30 provided in the charging facility 20 estimates the total capacity (capacity at full charge) of the secondary battery 10.

  The secondary battery 10 is formed by connecting a plurality of unit batteries in series. Examples of the unit battery constituting the secondary battery 10 include a lithium-based secondary battery such as a lithium ion secondary battery. It is done. Although not shown, a temperature sensor for measuring the temperature of the secondary battery 10 is provided in the vicinity of the secondary battery 10. The battery temperature measured by this temperature sensor is sent to the electronic control unit 30 of the charging facility 20.

  The charging facility 20 includes an electronic control unit 30, a power supply 40, an ammeter 50 and a voltmeter 60. The power supply 40 outputs a charging current based on a command from the electronic control unit 30 and supplies the charging current to the secondary battery 10. The ammeter 50 is a sensor that detects a charge / discharge current flowing through the secondary battery 10, and a signal detected by the ammeter 50 is sent to the electronic control unit 30. The voltmeter 60 is a sensor that detects the terminal voltage of the secondary battery 10, and the signal detected by the voltmeter 60 is sent to the electronic control unit 30.

  The electronic control unit 30 is a control unit that controls the charging facility 20 and includes a CPU that calculates a program, a microcomputer that includes a ROM and RAM that stores programs and calculation results, an electronic circuit, and the like. FIG. 2 shows a functional block diagram of the electronic control unit 30. As shown in FIG. 2, the electronic control unit 30 includes the secondary current based on signals from the charging current control unit 310 that controls the charging current supplied from the power source 40 to the secondary battery 10, and the ammeter 50 and the voltmeter 60. A total capacity estimation unit 320 that estimates the total capacity of the battery 10.

As illustrated in FIG. 2, the charging current control unit 310 includes a charging current setting unit 311 that sets a reference charging current setting value I _R (k) that is a current value of a charging current supplied from the power supply 40 to the secondary battery 10. A detection current superimposing unit 312 for sending a detection current pattern DI (k) for superimposing a detection current having a predetermined current pattern on a charging current supplied from the power source 40 to the secondary battery 10. . Then, the reference charging current setting value I _R (k) set by the charging current setting unit 311 is sent to the power supply 40, so that the power supply 40 has a predetermined value based on the reference charging current setting value I _R (k). A charging current is supplied to the secondary battery 10. When the detection current pattern DI (k) is sent out by the detection current superimposing unit 312, the detection current pattern DI (k) is added to the charging current supplied from the power supply 40 to the secondary battery 10. The detection current according to the above is superimposed and supplied to the secondary battery 10.

As shown in FIG. 2, the total capacity estimation unit 320 detects the terminal voltage V based on the signal from the voltmeter 60 and the current detection unit 321 that detects the charge / discharge current I based on the signal from the ammeter 50. The secondary battery 10 is charged by an adaptive digital filter from the voltage detection unit 322, the current measurement value I (k) detected by the current detection unit 321 and the voltage measurement value V (k) detected by the voltage detection unit 322. The adaptive digital filter calculation unit 323 that estimates the rate and calculates the charging rate estimated value SOC ^ (k) and the current measurement value I (k) detected by the current detection unit 321 are integrated, and the current integration value DQ ( k), the total capacity of the secondary battery 10 is estimated from the charging rate estimated value SOC ^ (k) and the current accumulated value DQ (k), and the total capacity estimated value Cap ^ (k) is calculated. Total capacity to be calculated It includes a section 325, a. In addition, "^" attached to the right shoulder in SOC ^ (k) and Cap ^ (k) indicates that each value is an estimated value. Further, in FIG. 2, the estimated value “^” is shown immediately above “S” of SOC (k) and “C” of Cap (k), but as shown in the following formula (1). In addition, these are synonymous with SOC ^ (k) and Cap ^ (k). _{Hereinafter, θ ^ (k), V} 0 ^ (t), Cap ^, SOC ^ A, SOC ^ B, d ^ is the same.

In such an electronic control unit 30 according to this embodiment, the charging current is supplied from the power source 40 to the secondary battery 10 based on the reference charging current setting value I _R (k) set by the charging current setting unit 311. Thus, when the secondary battery 10 is charged, the detection current superimposing unit 312 converts the charging current supplied from the power supply 40 to the secondary battery 10 at a predetermined timing into the detection current pattern DI (k). A detection current having a predetermined pattern is superimposed. Then, from the current measurement value I (k) and the voltage measurement value V (k) when the detection current based on the detection current pattern DI (k) is superimposed on the charging current by the adaptive digital filter calculation unit 323, The estimated charge rate SOC ^ (k) of the secondary battery 10 is calculated by the adaptive digital filter. Then, the total capacity estimation value SOC ^ (k) calculated by the total capacity calculation unit 325 and the current integration value DQ (k) integrated by the current integration unit 324 are used to estimate the total capacity of the secondary battery 10. The total capacity of the secondary battery 10 is estimated by calculating Cap ^ (k).

Here, a method of estimating the total capacity estimated value Cap ^ (k) of the secondary battery 10 by the total capacity calculation unit 325 will be described. First, since the charging rate SOC of the secondary battery 10 is a ratio of the current charge electricity amount to the total capacity Cap of the secondary battery 10, the charging rate SOC of the secondary battery 10 is expressed by the following formula (2). be able to. In the following formula, Q ₀ is the initial amount of electricity that has been charged in the secondary battery 10 in advance.

なお、上記式（３）において、ΔＳＯＣは、二次電池の充放電による充電率ＳＯＣの変化量であり、そのため、ΔＳＯＣは、所定時における充電率ＳＯＣ_１と、充電率ＳＯＣ_１の状態からさらに充放電を行った後の充電率ＳＯＣ_２との差分と等しくなる。 Further, when the above formula (2) is arranged for the total capacity Cap, the following formula (3) is obtained.

In the above equation (3), ΔSOC is the amount of change in the charge rate SOC due to charging / discharging of the secondary battery. Therefore, ΔSOC is further calculated from the state of the charge rate SOC ₁ and the charge rate SOC ₁ at a predetermined time. equal to the difference between the charging rate SOC ₂ after the charge and discharge.

In this embodiment, the numerator in the above equation (3), that is, the current integrated value is calculated by the current integrating unit 324, and the denominator in the above equation (3), that is, each of the charging rates SOC ₂ and SOC ₁ is adaptive digital. By calculating with the filter calculation unit 323 and using these results, the total capacity of the secondary battery 10 can be obtained.

ここで、モデル入力は電流Ｉ［Ａ］（正値は充電、負値は放電）、モデル出力は端子電圧Ｖ［Ｖ］であり、Ｒ_１〔Ω］は電荷移動抵抗、Ｒ_２［Ω］は純抵抗、Ｃ_１［Ｆ］は電気二重層容量、Ｖ_０［Ｖ］は開路電圧である。また、上記式中、ｓは微分オペレータである。なお、本実施形態に係る電池モデルは、正極、負極を特に分離していないリダクションモデル（一次）であるが、実際の電池の充放電特性を比較的正確に示すことが可能である。このように本実施形態においては、電池モデルの次数を１次にした構成を例として説明する。 Next, a method for calculating the estimated charging rate SOC ^ (k) of the secondary battery 10 by the adaptive digital filter calculation unit 323 will be described. First, the “battery model” used in the present embodiment will be described. FIG. 3 is an equivalent circuit model showing a battery model of the secondary battery 10, and the equivalent circuit model shown in FIG. 3 is expressed by the following equation (4).

Here, the model input is current I [A] (positive value is charging, negative value is discharging), model output is terminal voltage V [V], R ₁ [Ω] is charge transfer resistance, R ₂ [Ω] Is a pure resistance, C ₁ [F] is an electric double layer capacitance, and V ₀ [V] is an open circuit voltage. In the above formula, s is a differential operator. Note that the battery model according to the present embodiment is a reduction model (primary) in which the positive electrode and the negative electrode are not particularly separated, but the actual charge / discharge characteristics of the battery can be shown relatively accurately. As described above, in the present embodiment, a configuration in which the order of the battery model is first will be described as an example.

Here, when R ₁ , R ₂ , and C ₁ are represented by the following formula (5), the above formula (4) is represented by the following formula (6).

Next, a method for estimating battery parameters (K, T ₁ , T ₂ ) using an adaptive digital filter from the battery model represented by the above formula (6) will be described. Assuming that the open circuit voltage V ₀ (t) is obtained by integrating the current I (t) multiplied by the variable parameter d from an initial state, the open circuit voltage V ₀ (t) is expressed by the following equation (7). Can be represented.

When the above formula (7) is substituted into the above formula (6), the following formula (8) is obtained, and when this is arranged, the following formula (9) is obtained.

Furthermore, when the both sides of the above equation (9) are multiplied by a stable low-pass filter 1 / G _lp (s) and rearranged, the following equation (10) is obtained.

In the present embodiment, as the low-pass filter 1 / G _lp (s), the following equation (11) is used. However, the low-pass filter 1 / G _lp (s) is not limited to the following equation (11). In the following formula (11), τ is a time constant of the filter.

Here, a value obtained by applying a low-pass filter to the current measurement value I (t) measured by the current detection unit 321 and the voltage measurement value V (t) detected by the voltage detection unit 322 is defined by the following equation (12). .

When the above formula (10) is rewritten by the above formula (12) and arranged for V ₂ (t), the following formula (13) is obtained.

ただし、上記式（１４）中、ｙ＝Ｖ_２(ｔ）、 ω^Ｔ＝［Ｖ_３(ｔ），Ｉ_３(ｔ），Ｉ_２(ｔ），Ｉ_１(ｔ）］、θ＝［−Ｔ_１，Ｋ・Ｔ_２，Ｋ，ｄ］ である。 Then, 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, d), and therefore coincides with the following expression (14) which is a standard form of the adaptive digital filter.

In the above formula (14), y = V ₂ (t), ω ^T = [V ₃ (t), I ₃ (t), I ₂ (t), I ₁ (t)], θ = [− T ₁ , K · T ₂ , K, d].

Therefore, by using the signal obtained by filtering the current measurement value I (t) detected by the current detection unit 321 and the voltage measurement value V (t) detected by the voltage detection unit 322 in the adaptive digital filter calculation, An unknown parameter vector θ composed of an internal resistance K representing a state, time constants T ₁ and T ₂ , and a parameter d can be collectively estimated.

In this embodiment, the logical disadvantage of the simple “adaptive digital filter by the least squares method” (because once the estimated value converges, accurate estimation cannot be performed again even if the parameter changes) is improved. "Trace gain method" is used. That is, assuming the above equation (14), an algorithm for estimating the unknown parameter vector θ by the adaptive digital filter is the following equation (15). Here, it is assumed that the battery parameter estimated value at the time point k is θ ^ (k).

In the above equation (15), trace {Q (k)} means a trace (sum of diagonal elements) of the matrix Q (k). Also, λ ₁ , λ ₃ , γ _U , γ _L are design parameters, and 0 <λ ₁ <1, 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. Also, P (0) has a sufficiently large value as an initial value, and θ ^ (0) has a non-zero and sufficiently small value as an initial value. In this way, the adaptive digital filter calculation unit 323 estimates the battery parameters (T ₁ , T ₂ , K, d) using the adaptive digital filter.

The adaptive digital filter operation unit 323, as follows, from the battery parameter estimating, calculating the open-circuit voltage V ₀ which the secondary battery 10. First, when the above equation (6) is arranged for the open circuit voltage V ₀ , the following equation (16) is obtained.

Since the change in the open circuit voltage V ₀ (t) is relatively gentle, the both sides of the above equation (16) are multiplied by a stable low-pass filter 1 / G _lp (s) and 1 / G _lp (s). The obtained value is estimated as the open circuit voltage estimated value V ₀ ^ (t) by the following equation (17).

Then, when the above equation (12) is substituted into the above equation (17), the following equation (18) is obtained.

Therefore, the battery parameter estimated value (T ₁ , T ₂ , K) estimated using the adaptive digital filter and the output (I ₁ (k), I ₂ (k), V ₁ By substituting (k), V ₂ (k)), it is possible to estimate the open circuit voltage, and thereby, it is possible to obtain the open circuit voltage estimated value V ₀ ^ (t).

Then, using the obtained open circuit voltage estimated value V ₀ ^ (t), charging of the secondary battery 10 is performed based on the open circuit voltage-charge rate characteristic of the secondary battery 10 acquired in advance by the adaptive digital filter calculation unit 323. The rate can be estimated, whereby the charge rate estimated value SOC ^ (t) can be obtained. An example of the open circuit voltage-charge rate characteristic of the secondary battery 10 is shown in FIG. In the present embodiment, the open circuit voltage-charge rate characteristic of the secondary battery 10 is stored in advance in a RAM provided in the electronic control unit 30, and the open circuit voltage and the charge rate of the secondary battery 10 are previously determined through experiments or the like. It can obtain by calculating | requiring the relationship.

  Next, a method for setting the charging current supplied from the power supply 40 to the secondary battery 10 by the charging current control unit 310 will be described.

The charging current setting unit 311 sets a reference charging current setting value I _R (k) that is a predetermined charging current value for charging the secondary battery 10. The reference charging current set value I _R (k) is a value for setting a current for charging the secondary battery 10, and is generally set to a substantially constant value. As a method for setting such a reference charging current set value I _R (k), a generally used method may be employed, which depends on the charging rate of the secondary battery 10 and the specifications of the secondary battery 10. For example, as shown in FIG. 5, in a region where the charging rate of the secondary battery 10 is relatively low, constant current charging is performed, and then the terminal voltage of the secondary battery 10 is set to the target voltage. In the CC-CV charging method that shifts to constant voltage charging or in a region where the charging rate of the secondary battery 10 is relatively low as shown in FIG. There is a method of performing multi-stage constant current charging that shifts to constant current charging and gradually approaches the charging current to zero. A combination of these may also be used. Incidentally, FIG. 5, FIG. 6 is a time chart showing an example of a method of charging a secondary battery 10, FIG. 5, 6, and starts charging the secondary battery 10 at time T _1, then the time T change the charging control method in _2, and terminates the charging of the secondary battery 10 at time T _3.

On the other hand, the detection current superimposing unit 312 sends a predetermined detection current pattern DI (k) for a predetermined time at a predetermined timing, and the detection current superimposing unit 312 detects the charging current based on the reference charging current set value I _R (k). A detection current based on the current pattern DI (k) is superimposed. Specifically, when the detection current pattern DI (k) is sent out by the detection current superimposing unit 312, the detection current pattern DI (k) is changed from the power supply 40 to the charging current supplied to the secondary battery 10. The detection current according to the above is superimposed and supplied to the secondary battery 10. In the present embodiment, the timing of sending the detection current pattern DI (k) by the detection current superimposing unit 312 is not particularly limited, but at the start of charging (for example, time T ₁ in FIGS. 5 and 6), and after a predetermined time has elapsed from the start of charging, specifically, when the charging rate has risen sufficiently (e.g., 5 and 6, any time during of T ₃ from the time T ₂₎ be like it can.

In the present embodiment, the adaptive digital filter calculation by the adaptive digital filter calculation unit 323 is performed by using the detection current based on the detection current pattern DI (k) to the charging current based on the reference charging current setting value I _R (k). This is done when is superimposed. Specifically, the current measurement value I (k) and voltage when the detection current based on the detection current pattern DI (k) is superimposed on the charging current based on the reference charging current set value I _R (k). Based on the measured value V (k), the adaptive digital filter calculation unit 323 performs the above-described adaptive digital calculation, thereby calculating the estimated charge rate SOC ^ (k) of the secondary battery 10. Therefore, the detection current superimposing unit 312 sends a detection current pattern DI (k) for supplying the secondary battery 10 with a detection current used when the adaptive digital filter calculation unit 323 performs the adaptive digital filter calculation. To do. The detection current superimposing unit 312 also transmits a command for causing the adaptive digital filter calculation unit 323 to perform the adaptive digital filter calculation when the detection current pattern DI (k) is transmitted.

  The detection current pattern DI (k) sent out by the detection current superimposing unit 312 is not particularly limited as long as it is a predetermined current pattern. By supplying the detection current pattern DI (k), FIG. The current measurement value I (k) and voltage measurement value V (k) of the secondary battery 10 detected by the current detection unit 321 and the voltage detection unit 322 shown are suitable for the adaptive digital filter calculation by the adaptive digital filter calculation unit 323. What is necessary is just to set so that it may become a thing. Specifically, the detection current pattern DI (k) may be formed by superimposing a plurality of alternating currents having different frequencies from the viewpoint that the effect of improving the estimation accuracy in the adaptive digital filter calculation is high. Preferably, for example, such an alternating current includes an alternating current based on an M-sequence signal. Further, the amplitude of the detection current pattern DI (k) is not particularly limited, and the measured current value I (k) detected by the current detection unit 321, the temperature of the secondary battery 10, or the total capacity calculation unit 325. May be set based on any one selected from the total capacity estimated value Cap ^ (k) estimated last time or a combination thereof.

FIG. 7 shows an example in which the detection current based on the detection current pattern DI (k) is superimposed on the charging current. In FIG. 7, from time T ₄ to time T ₆ , the current pattern when the AC current based on the M-sequence signal as the detection current is superimposed on the charging current, and the adaptation when the detection current is superimposed The transition of the identification error in the adaptive digital filter calculation by the digital filter calculation unit 323 is shown.

Note that, as shown in FIG. 7, the time for which the detection current is superimposed on the charging current includes the calculation result by the adaptive digital filter calculation by the adaptive digital filter calculation unit 323 and the actual internal state of the secondary battery 10. It is assumed that the identification error as a difference is determined to have converged (time T ₅ shown in FIG. 7) to after a predetermined time has elapsed (time T ₆ shown in FIG. 7). By setting the detection current superposition time in this way, the estimation accuracy of the open-circuit voltage estimated value V ₀ ^ (k) by the adaptive digital filter calculation unit 323 without unnecessarily increasing the detection current superposition time. , And the estimation accuracy of the total capacity estimated value Cap ^ (k) by the total capacity calculating unit 325 can be improved.

Next, a calculation process of the total capacity estimated value Cap ^ (k) in the present embodiment will be described using the flowchart shown in FIG. Note that the processing shown in FIG. 8 is performed at regular intervals (in this embodiment, every 100 msec). In the following description, I (k) is a current value (current measurement value) of the current execution cycle, I (k−1) is a current value (previous measurement value) of the previous execution cycle, The same applies to values other than current. Further, in the present embodiment, the process shown in FIG. 8 is performed by setting the reference charging current set value I _R (k) set by the charging current setting unit 311 when a vehicle equipped with the secondary battery 10 is connected to the charging facility 20. Based on this, the supply of charging current from the power source 40 to the secondary battery 10 is started, and the processing described below is performed by the electronic control unit 30.

  First, in step S1, the charging rate of the secondary battery 10 before supplying the charging current at the start of charging is estimated. As a method for estimating the charging rate of the secondary battery 10, for example, the open circuit voltage of the secondary battery 10 at the time when a vehicle equipped with the secondary battery 10 is connected to the charging facility 20 is measured, and the measured open circuit voltage is used in advance. The method of calculating based on the open circuit voltage-charge rate characteristic of the acquired secondary battery 10 is mentioned. Alternatively, when the previous charging rate estimated value is obtained by the electronic control unit 30, it may be used.

  In step S2, the total capacity estimation value Cap ^ estimated during the previous process is read. The total capacity estimated value Cap ^ can be obtained by, for example, storing it in a RAM provided in the electronic control unit 30 and reading it out.

  In step S3, the temperature of the secondary battery 10 measured by a temperature sensor (not shown) provided in the vicinity of the secondary battery 10 is detected.

  In step S4, a charging rate estimation process is performed. FIG. 9 shows a flowchart of the charging rate estimation process in the present embodiment.

First, in step S41 shown in FIG. 9, the detection current superimposing unit 312 sets the amplitude of the detection current pattern I _R (k). Note that the amplitude of the detection current pattern I _R (k) is the charge rate of the secondary battery 10 at the start of charging acquired in Steps S1 to S3, the total capacity estimated value Cap ^ at the previous processing, and the secondary battery 10. It is set based on the temperature. For example, when the charging rate of the secondary battery 10 at the start of charging is high, it is expected that the change in the terminal voltage with respect to the same current amplitude becomes larger than when the charging rate is low. Therefore, when setting the amplitude of the detection current pattern I _R (k) by the detection current superimposing unit 312, the amplitude is set to be small at a predetermined ratio. Further, when the total capacity estimated value Cap ^ at the time of the previous process is decreased due to deterioration of the secondary battery 10 or when the temperature of the secondary battery 10 is lower than a preset threshold value, the same tendency is observed. Therefore, similarly, the amplitude is set small at a predetermined rate. The amplitude of the detection current pattern I _{R (k),} when the detection current based on the detection current pattern I _{R (k)} is superimposed on the charging current, so that current is not a discharge direction of the secondary battery 10 It is desirable to set within a range.

In step S42, the detection current superimposing unit 312 performs transmission of the detection current pattern I _{R (k),} the detection current based on the detection current pattern I _{R (k),} it is superimposed on the charging current. In this case, the amplitude set in step S41 is used as the amplitude of the detection current pattern I _R (k).

  In step S43, the current detector 321 detects the charge / discharge current I of the secondary battery 10 from the signal from the ammeter 50, whereby the current measurement value I (k) is acquired, and the acquired current measurement is performed. The value I (k) is transmitted to the adaptive digital filter calculation unit 323 and the current integration unit 324. Further, the voltage detection unit 322 detects the terminal voltage V of the secondary battery 10 from the signal from the voltmeter 60, whereby the voltage measurement value V (k) is acquired, and the acquired voltage measurement value V ( k) is transmitted to the adaptive digital filter calculation unit 323.

  In step S44, the adaptive digital filter calculation unit 323 performs the above-described method based on the current measurement value I (k) transmitted from the current detection unit 321 and the voltage measurement value V (k) transmitted from the voltage detection unit 322. Then, the charging rate of the secondary battery 10 is estimated by adaptive digital filter calculation, and the charging rate estimated value SOC ^ (k) is calculated.

In step S45, the adaptive digital filter calculation unit 323 converges the identification error that is the difference between the calculation result of the adaptive digital filter calculation in step S44 and the actual internal state of the secondary battery 10, and the identification error converges. and whether the predetermined time has elapsed since (i.e., either in the state at time T ₆ in FIG. 7) is a determination. If it is determined that the identification error has converged and a predetermined time has elapsed since the identification error has converged, the adaptive digital filter calculation unit 323 proceeds to step S46 and ends the superimposition of the detection table current. This completes the charging rate estimation process. Then, the process proceeds to step S5 shown in FIG. On the other hand, if it is determined that the identification error has not converged, or if the identification error has converged but the identification error has not converged, the process returns to step S43 to measure the current. The acquisition of the value I (k) and the voltage detection unit 322 and the adaptive digital filter calculation based on these are repeated at regular intervals (in this embodiment, every 100 msec).

In step S5, the total capacity calculating unit 325 acquires the charging rate estimated value SOC ^ (k) calculated in step S4 (step S44), and the acquired charging rate estimated value SOC ^ (k) is set to "SOC ^ _A "Is memorized.

  In step S6, the current integration unit 324 starts integration of the current integration value DQ (k) based on the current measurement value I (k) transmitted from the current detection unit 321.

In step S7, it is determined whether or not the charging rate of the secondary battery 10 has sufficiently increased. The determination as to whether the charging rate has sufficiently increased is made, for example, when the charging current setting unit 311 changes the reference charging current setting value I _p (k), that is, when the charging mode is changed (for example, FIG. 5, in the example shown in FIG. 6, it is determined that the charging rate has sufficiently increased at the time T ₂ when shifting from constant current charging to constant voltage charging or when shifting from constant power charging to multistage constant current charging). can do. Alternatively, in step S44, the amount of change in the charging rate of the secondary battery 10 is calculated based on the calculated charging rate estimated value SOC ^ (k) and the current integrated value DQ (k) integrated by the current integrating unit 324. Based on the estimation result, it can be determined whether or not the charging rate has sufficiently increased.

  If it is determined that the charging rate of the secondary battery 10 has sufficiently increased, the process proceeds to step S8, and the temperature of the secondary battery 10 measured by a temperature sensor (not shown) provided near the secondary battery 10 is measured. Then, the process proceeds to step S10, and the charging rate estimation process (steps S41 to S46 shown in FIG. 9) is performed according to the flowchart shown in FIG. 9 as in step S4.

  On the other hand, in step S9, since it is determined that the charging rate has not increased sufficiently, the current detection unit 321 continues to detect the charge / discharge current I of the secondary battery 10 from the signal from the ammeter 50, and the current measurement value I. (K) is acquired, and the current measurement value I (k) is transmitted to the current integration unit 324. Then, until it is determined in step S7 that the charging rate has sufficiently increased, the current measurement value I (k) is acquired and the current integration by the current integration unit 324 is performed at regular intervals (in this embodiment, every 100 msec). The integration of the value DQ (k) is repeated.

In step S11, the total capacity calculating unit 325 acquires the charging rate estimated value SOC ^ (k) calculated in step S8 (step S44), and the acquired charging rate estimated value SOC ^ (k) is set to "SOC ^ _B "Is memorized.

  In step S12, the integration of the current integration value DQ (k) performed by the current integration unit 324 is terminated, and the obtained current integration value DQ (k) is transmitted to the total capacity calculation unit 325.

なお、上記式（１９）は、上述した式（３）において、それぞれ、「Ｃａｐ」を「Ｃａｐ＾」とし、「ＳＯＣ_１」を「ＳＯＣ_Ａ＾」、「ＳＯＣ_２」を「ＳＯＣ_Ｂ＾」に置換することにより得られる式である。
本実施形態では、以上のようにして二次電池１０の総容量Ｃａｐの推定が行われる。 In step S13, the total capacity calculation unit 325 causes the charging rate estimated value “SOC ^ _A ” stored in step S5, the charging rate estimated value “SOC ^ _B ” stored in step S10, and the current integrated value received in step 11 to be stored. Based on DQ (k), the total capacity estimation value Cap ^ (k) is calculated. Specifically, since the current integrated value DQ (k) is obtained by integrating the current I (t), the total capacity estimated value Cap ^ (k) is calculated according to the following equation (19).

Note that the equation (19) is the same as the equation (3), in which “Cap” is “Cap ^”, “SOC ₁ ” is “SOC _A ^”, and “SOC ₂ ” is “SOC _B ^”. Is a formula obtained by substituting
In the present embodiment, the total capacity Cap of the secondary battery 10 is estimated as described above.

  FIG. 10 shows the result of verifying the effect of the present embodiment by simulation using a battery model. Here, in the simulation shown in FIG. 10, the observation noise and the quantization error are set for the current measurement value I (k) and the voltage measurement value V (k). Further, in the simulation shown in FIG. 10, the simulation results are shown in the case where the detection current pattern is superimposed and the adaptive digital filter calculation is performed at around 0 seconds and around 2500 seconds, respectively. In FIG. 10, the profile showing the change in current, the profile showing the change in voltage, and the estimated value of the charging rate SOC and the true value of the charging rate SOC are shown from the top.

  As shown in FIG. 10, by superimposing the detection current suitable for the adaptive digital filter calculation on the charging current, the charging rate estimated value is obtained by the adaptive digital filter calculation while continuing to charge the secondary battery 10. , Which can be close to the true value. Therefore, according to the present embodiment, the estimated value of the charging rate obtained by the adaptive digital filter calculation at the time of such superposition of the detection current is used in accordance with the above equations (3) and (19). By estimating the total capacity of the secondary battery 10, it is possible to estimate the total capacity of the secondary battery 10 with high accuracy while continuing to charge the secondary battery 10.

  Further, according to the present embodiment, the charge rate estimated value SOC ^ (k) of the secondary battery 10 is calculated by adaptive digital filter calculation, and based on this, the total capacity of the secondary battery 10 is estimated. Therefore, when estimating the total capacity of the secondary battery 10, it is not necessary to directly measure the open circuit voltage of the secondary battery 10. Therefore, the total capacity is estimated as compared with the case of directly measuring the open circuit voltage. Therefore, the time required for this can be shortened. Particularly, in the past, when estimating the total capacity of the secondary battery, in order to directly measure the open circuit voltage, the secondary battery is set to a dormant state in which charging / discharging is not performed, and the dormant state is set for a predetermined time or more. There is a problem that the time required for estimating the total capacity becomes long, and this embodiment effectively solves such a problem.

<< Second Embodiment >>
Next, a second embodiment of the present invention will be described.
The second embodiment is the same as the first embodiment except that the electronic control unit 30 has the configuration shown in the functional block diagram as shown in FIG. 11 and functions as described below.

  As shown in FIG. 11, the electronic control unit 30 according to the second embodiment includes a charging current control unit 310 that controls the charging current supplied from the power supply 40 to the secondary battery 10, and the current, as in the first embodiment. A total capacity estimating unit 320a for estimating the total capacity of the secondary battery 10 based on signals from the total 50 and the voltmeter 60.

  The charging current control unit 310 includes a charging current setting unit 311 and a detection current superimposing unit 312 as in the first embodiment, and these function in the same manner as in the first embodiment.

  The total capacity estimation unit 320 includes a current detection unit 321, a voltage detection unit 322, an adaptive digital filter calculation unit 323, and a total capacity calculation unit 325a. The current detection unit 321 and the voltage detection unit 322 function in the same manner as in the first embodiment except that the current detection unit 321 transmits the current measurement value I (k) only to the adaptive digital filter calculation unit 323a. The adaptive digital filter operation unit 323a transmits a parameter estimation value d ^ that is an estimation value of the parameter d to the total capacity calculation unit 325a in addition to the charging rate estimation value SOC ^ (k) calculated by the adaptive digital filter calculation. Functions in the same manner as in the first embodiment. The total capacity calculation unit 325a calculates the total capacity estimation value Cap ^ (k) of the secondary battery 10 based on the charging rate estimation value SOC ^ (k) and the parameter estimation value d ^.

  In the electronic control unit 30 of the second embodiment, as in the first embodiment, the detection current pattern DI (k) is superimposed on the charging current by the detection current superimposing unit 312 and the detection current pattern DI ( k) When the current measurement value I (k) and the voltage measurement value V (k) are superimposed, the adaptive digital filter calculation unit 323 performs the adaptive digital filter calculation to estimate the charging rate SOC of the secondary battery 10. ^ (K) and the parameter estimated value d ^ are calculated, and based on these, the total capacity calculation unit 325a calculates the total capacity estimated value Cap ^ (k).

Here, a method for estimating the total capacity estimated value Cap ^ (k) by the total capacity calculating unit 325a in the second embodiment will be described. First, the above formula (7) is rewritten in the time domain and divided by the total capacity Cap of the secondary battery 10, the following formula (20) is obtained.

In the right side of the above equation (20), the ratio of the current integrated value to the total capacity Cap corresponds to the change amount ΔSOC of the charging rate, and therefore the relationship of the following equation (21) holds, and the above equation (21) Formula (20) can be expressed as the following formula (22).

Then, from the formula (22), the total capacity estimate Cap ^, using a gradient of open circuit voltage _{V 0} with respect to the charging rate SOC, a parameter estimate d ^, can be calculated by the following equation (23). It can also be obtained by the following equation (24) equivalent to the following equation (23).

Next, the calculation process of the total capacity estimation value Cap ^ (k) performed by the electronic control unit 30 of the second embodiment will be described using the flowchart shown in FIG. Note that the processing shown in FIG. 12 is performed at regular intervals (in this embodiment, every 100 msec). In the second embodiment, as in the first embodiment, the process shown in FIG. 12 is performed by connecting a vehicle equipped with the secondary battery 10 to the charging facility 20 and setting the reference charging set by the charging current setting unit 311. It starts when supply of charging current from the power supply 40 to the secondary battery 10 is started based on the current set value I _R (k).

  First, in steps S101 to S103, as in steps S1 to S3 in the first embodiment, estimation of the charging rate of the secondary battery 10 before supplying the charging current at the start of charging, and the total capacity estimated in the previous processing Reading of the estimated value Cap ^ and detection of the temperature of the secondary battery 10 are performed.

Next, in step S104, a charging rate estimation process is performed. The charging rate estimation process in the second embodiment is performed according to the flowchart shown in FIG. 9 as in the first embodiment. That is, based on the charging rate of the secondary battery 10 at the start of charging acquired in steps S101 to S103, the estimated total capacity Cap ^ during the previous process, and the temperature of the secondary battery 10, the detection current pattern I _R ( k) setting of amplitude (step S41), start of superimposition of detection current based on detection current pattern I _R (k) (step S42), current measurement value I (k) and current measurement value I (k) Acquisition (step S43), estimation of charging rate estimated value SOC ^ (k) by adaptive digital filter calculation (step S44), identification error convergence determination (step S45), and termination of detection current superposition (step S46) Done.

Next, in step S105, the total capacity calculation unit 325a acquires the charging rate estimated value SOC ^ (k) and the parameter estimated value d ^ calculated in step S104 (step S44), and these charging rate estimated values SOC ^ Based on (k) and the parameter estimated value d ^, the total capacity estimated value Cap ^ (k) is calculated. Specifically, the total capacity calculation unit 325a calculates the total capacity estimation value Cap ^ (k) using the above formula (23) or (24).
In the second embodiment, the total capacity Cap of the secondary battery 10 is estimated as described above.

  FIG. 13 shows the result of verifying the effect of the present embodiment by simulation using a battery model. Here, in the simulation shown in FIG. 13, the observation noise and the quantization error are set to the current measurement value I (k) and the voltage measurement value V (k), and +3 [A] is further added to the current measurement value I (k). The measurement offset of was set. Further, in the simulation shown in FIG. 13, the simulation result in the case where the detection current pattern is superimposed and the adaptive digital filter calculation is executed in the vicinity of 0 second is shown. In FIG. 13, a profile indicating a change in current, a profile indicating a change in voltage, an estimated value and a true value of parameter d, and an estimated value and a true value of charge rate SOC are shown, respectively.

  As shown in FIG. 10, by superimposing the detection current pattern on the charging current, the charging rate estimated value is close to the true value by the adaptive digital filter calculation while continuing to charge the secondary battery 10. It can be said that. Therefore, according to the second embodiment, according to the above equation (23) or (24), using the estimated value of the charging rate obtained by the adaptive digital filter calculation when the detection current pattern is superimposed. By estimating the total capacity of the secondary battery 10, the total capacity can be estimated with high accuracy. Moreover, according to the second embodiment, since the estimation of the total capacity of the secondary battery 10 ends immediately after the charging facility 20 starts charging, the setting of the charging current by the charging facility 20 is performed based on the estimated total capacity. This can be used for quick charging. Note that such rapid charging is performed, for example, based on the charging rate estimated value SOC ^ (k) and the total capacity estimated value Cap ^ (k), and the amount of electricity required to bring the secondary battery 10 into a fully charged state. Can be calculated by determining a current value for performing quick charging based on the calculated amount of electricity.

  Further, according to the second embodiment, similarly to the first embodiment described above, the charging rate estimated values SOC ^ (k), d ^ of the secondary battery 10 are calculated by adaptive digital filter calculation, and based on this. Since the total capacity of the secondary battery 10 is estimated, there is no need to directly measure the open circuit voltage of the secondary battery 10 when the total capacity of the secondary battery 10 is estimated. Compared to direct measurement, the time required to estimate the total capacity can be shortened. In particular, conventionally, there has been a problem that the time required for estimating the total capacity becomes long, but such a problem can be effectively solved also in the second embodiment.

  In the above-described embodiment, the charging current setting unit 311 is the charging control unit of the present invention, the detection current superimposing unit is the detecting current superimposing unit of the present invention, and the current detecting unit 321 and the voltage detecting unit 322 are the present invention. The adaptive digital filter calculation unit 323 corresponds to the detection means, the charge rate estimation unit of the present invention, and the total capacity calculation unit corresponds to the capacity estimation unit of the present invention.

  As mentioned above, although embodiment of this invention was described, these embodiment was described in order to make an understanding of this invention easy, and was not described in order to limit this invention. Therefore, each element disclosed in the above embodiment is intended to include all design changes and equivalents belonging to the technical scope of the present invention.

  For example, in the above-described embodiment, the case where the electronic control unit 30, the power source 40, the ammeter 50, and the voltmeter 60 are provided in the charging facility 20, but some or all of these are provided. It is good also as a structure with which the vehicle carrying the secondary battery 10 is equipped.

DESCRIPTION OF SYMBOLS 10 ... Secondary battery 20 ... Charging equipment 30 ... Electronic control unit 310 ... Charging current control part 311 ... Charging current setting part 312 ... Current superimposition part 320,320a ... Total capacity estimation part 321 ... Current detection part 322 ... Voltage detection Unit 323 ... adaptive digital filter calculation unit 324 ... current integration unit 325, 325a ... total capacity calculation unit 40 ... power supply 50 ... ammeter 60 ... voltmeter

Claims (7)

Charging control means for supplying a charging current to the secondary battery;
Detection current superimposing means for superimposing a predetermined pattern of detection current on the charging current supplied to the secondary battery by the charge control means;
Detection means for detecting current and terminal voltage of the secondary battery,
From the measured values of the current and terminal voltage detected by the detection means, using an adaptive digital filter, the open circuit voltage of the secondary battery is estimated, and based on the relationship between the open circuit voltage and the charging rate obtained in advance, From the estimated open circuit voltage, charging rate estimating means for estimating the charging rate of the secondary battery,
Capacity estimation means for estimating the total capacity of the secondary battery based on the charge rate estimated by the charge rate estimation means,
The detection current superimposing means determines the amplitude of the detection current based on the charging rate of the secondary battery at the start of charging, the temperature of the secondary battery, and the total of the secondary batteries estimated by the capacity estimation means. Set based on at least one selected from the previous capacity value,
The charging rate estimation means estimates the charging rate using measured values of current and terminal voltage when the detection current is superimposed by the detection current superimposing means. Capacity estimation device.   The secondary battery capacity estimation apparatus according to claim 1, wherein the detection current is formed by superimposing a plurality of alternating currents having different frequencies. The detection current superposition means, supply start time T _A of the charging current to the secondary battery by the charge control _unit, and a predetermined time has elapsed after T _B from the supply start of the charging current to the secondary battery, capacity estimating device for a secondary battery according to claim 1 or 2, characterized in that to superimpose the detection current to the charging current. Using the measured value of the current and terminal voltage detected at the start of supply of the charging current T _A , let the estimated charging rate be SOC _A ^
Using the measurement value of the detected current and the terminal voltage at a predetermined time has elapsed after T _B from the time the start of the supply of the charging current, the estimated charging rate and SOC B _^,
Starting supply time T _A of the charging current, at each time during a predetermined time has elapsed after T _B from the supply start of the charging current, the measured value of the current detected by said detecting means and the I (t) In case,
4. The secondary battery capacity estimation apparatus according to claim 3 , wherein the capacity estimation means estimates Cap ^, which is an estimated value of the total capacity of the secondary battery, according to the following formula (I).

However, in SOC _A ^, SOC _B ^, and Cap ^, “^” means an estimated value. The detection current superimposing means superimposes the detection current on the charging current at an arbitrary time _Tc during the supply of the charging current to the secondary battery by the charge control means,
The charging rate estimating means uses the measured values of the current and the terminal voltage detected at an arbitrary time _Tc during the supply of the charging current, and the SOC ^ and parameters that are the estimated values of the charging rate of the secondary battery Estimate d ^ which is an estimate of d,
The capacity estimating means estimates Cap ^, which is an estimated value of the total capacity of the secondary battery, based on the estimated value SOC ^ of the charging rate and the estimated value d ^ of the parameter d according to the following formula (II). capacity estimating device for a secondary battery according to any one of claims 1 to 4, characterized in that.

However, in SOC ^, d ^, and Cap ^, "^" means an estimated value.
The parameter d is a variable that satisfies the following formula (III).

In the above formula (III), V ₀ is an open circuit voltage, I is a measured value of current, and s is a differential operator. The charge control means calculates the amount of electricity required to fully charge the secondary battery based on the charge rate estimated by the charge rate estimation means and the total capacity estimated by the capacity estimation means. calculated, based on the calculated amount of electricity, the capacitance estimating device for a secondary battery according to any one of claims 1 to 5, characterized in that controlling the charging current. After the detection current superimposing means starts superimposing the detection current, the identification error of the calculation result using the adaptive digital filter by the charging rate estimation means is determined to have converged after a predetermined time has elapsed, capacity estimating device for a secondary battery according to any one of claims 1 to 6, characterized in that to end the superimposition of the detection current.

Images