JP6435866B2 - Secondary battery control device - Google Patents

Description

  The present invention relates to a control device for a secondary battery mounted on a vehicle using at least an electric motor as a drive source.

  As a vehicle using an electric motor as a drive source, for example, a hybrid vehicle and an electric vehicle are known. In these vehicles, charge / discharge control of the secondary battery is performed based on the state of charge (SOC) of the secondary battery. In the charge / discharge control, for example, to avoid overcharge and overdischarge of the secondary battery, the SOC value of the secondary battery is estimated, and the SOC value is controlled within a predetermined use SOC range. When the estimation accuracy of the SOC value is low, it is necessary to provide a certain degree of margin in the use SOC range. In order to provide a margin in the used SOC range, it is necessary to increase the battery capacity of the secondary battery, which increases the cost of the secondary battery. Therefore, if the SOC value can be estimated accurately, a reduction in cost due to a reduction in the battery capacity of the secondary battery can be expected. Under such circumstances, improvement in the accuracy of estimating the SOC value is required. Conventionally, as a method of improving the estimation accuracy of the SOC value, for example, there is a method described in Patent Document 1.

  The device described in Patent Literature 1 includes an equivalent circuit model, a parameter estimation unit, and an inverse logarithmic conversion unit. The equivalent circuit model is obtained by modeling a secondary battery using resistors and capacitors as characteristic parameters. The parameter estimation unit sequentially estimates logarithmic conversion parameter values from the state equation and the output equation based on the charge / discharge current detected by the sensor and the voltage across the terminals of the secondary battery. The logarithmic conversion parameter value is a value obtained by logarithmically converting the characteristic parameter of the equivalent circuit model. The inverse logarithm conversion unit calculates the characteristic parameter of the equivalent circuit model by inverse logarithmically transforming the logarithmic conversion parameter value estimated by the parameter estimation unit. The estimation device described in Patent Document 1 estimates an OCV (Open Circuit Voltage) value based on the characteristic parameter of the equivalent circuit model calculated by the inverse logarithmic conversion unit, and OCV− from the estimated OCV value. An SOC value is obtained based on the SOC characteristics.

JP 2014-74682 A

  By the way, in a hybrid vehicle, the driving mode is generally switched based on the SOC value. For example, when the SOC value is close to the upper limit value, that is, when the charge amount of the secondary battery is close to full charge, EV traveling using only the motor as the drive source is performed in the hybrid vehicle. When the SOC value decreases due to EV traveling and the SOC value falls below a predetermined threshold, the hybrid vehicle performs HV traveling using both the engine and the motor as drive sources. During HV traveling, the SOC value is maintained within a predetermined range by charge / discharge control of the secondary battery.

  Here, when estimating the characteristic parameters of the equivalent circuit model of the secondary battery during HV traveling, since the SOC value is maintained within a predetermined range, the charge / discharge current detected by the sensor and the terminal of the secondary battery The voltage contains almost no component with a large time constant. Therefore, there is a possibility that characteristic parameters having a large time constant in the equivalent circuit model cannot be estimated with high accuracy.

  On the other hand, since there is a possibility that long-time discharge is performed during EV traveling, the charge / discharge current detected by the sensor and the voltage between the terminals of the secondary battery may have a component with a large time constant. However, when the duration of EV travel is short, there is a possibility that the charge / discharge current detected by the sensor and the voltage between the terminals of the secondary battery hardly contain components having a large time constant. After all, even during EV travel, depending on the situation, there is a possibility that a characteristic parameter having a large time constant in the equivalent circuit model cannot be accurately estimated.

  If a characteristic parameter having a large time constant in the equivalent circuit model of the secondary battery cannot be accurately estimated, there is a concern that the OCV value estimation accuracy decreases, and as a result, the SOC value estimation accuracy decreases.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a secondary battery control device capable of improving the estimation accuracy of the characteristic parameters of the equivalent circuit model of the secondary battery. .

In order to solve the above problems, a control device (6) for a secondary battery (3) mounted on a vehicle (1) using at least an electric motor (2) as a drive source includes a current detection unit (4), a voltage detection A part (5) and a calculating part (60) are provided. The current detection unit detects a charge / discharge current of the secondary battery. A voltage detection part detects the voltage between terminals of a secondary battery. Calculation unit identifies the characteristic parameters of the secondary battery of the equivalent circuit model (M1, M2). The equivalent circuit model has a diffusion circuit (15) that includes an impedance circuit having a maximum time constant. When the constant current equivalent to the charge / discharge current immediately before the charge / discharge current becomes zero is used as the current initial value, the calculation unit calculates the current initial value based on the charge / discharge current detected by the current detection unit before the vehicle stops. And the initial voltage value of the impedance circuit is identified based on the voltage between the terminals detected by the voltage detection unit after the vehicle stops, and the characteristic parameter of the diffusion circuit is identified based on the initial current value and the initial voltage value. .

The charge / discharge current detected by the current detection unit before the vehicle stops and the terminal voltage detected by the voltage detection unit after the vehicle stops contain components having a large time constant. Therefore, according to the above configuration, it is possible to identify a characteristic parameter having a large time constant in the equivalent circuit model, and thus it is possible to improve the estimation accuracy of the characteristic parameter of the equivalent circuit model.

  ADVANTAGE OF THE INVENTION According to this invention, the estimation precision of the characteristic parameter of the equivalent circuit model of a secondary battery can be improved.

The block diagram which shows the schematic structure about one Embodiment of the control apparatus of a secondary battery. The circuit diagram which shows an example of the equivalent circuit model of a secondary battery about the control apparatus of the secondary battery of embodiment. (A), (b) is a timing chart which shows the transition example of the inter-terminal voltage Vt detected by the voltage detection part at the time of a vehicle stop, and the charging / discharging current It detected by a current detection part. The circuit diagram which shows an example of the equivalent circuit model of a secondary battery about the control apparatus of the secondary battery of embodiment. The graph which shows the transition example of an electric current. (A) ~ (c), the input current I of the RC parallel circuit, a graph showing a change in the current I _R flowing through the current flowing through the capacitor I _C, and a resistor. The flowchart which shows the procedure of the process performed by the control apparatus of the secondary battery of embodiment.

  Hereinafter, an embodiment of a control device for a secondary battery will be described. First, the outline | summary of the vehicle carrying the control apparatus of the secondary battery of this embodiment is demonstrated.

  As shown in FIG. 1, the vehicle 1 is a so-called hybrid vehicle having an electric motor 2 and an engine (not shown) as drive sources. The vehicle 1 has, as its travel mode, an EV travel mode that travels using only the electric motor 2 and an HV travel mode that travels using both the electric motor 2 and the engine.

  The electric motor 2 is driven based on electric power supplied from the secondary battery 3 mounted on the vehicle, and transmits power to driving wheels of the vehicle (not shown). Moreover, the electric motor 2 performs regenerative power generation based on the regenerative energy transmitted from the drive wheels. Electric power generated by regenerative power generation of the electric motor 2 is charged in the secondary battery 3. The secondary battery 3 is made of, for example, a lithium ion battery or a nickel cadmium battery. In the secondary battery 3, chemical reactions having different reaction rates occur in combination during charge and discharge. The difference in reaction rate between these chemical reactions becomes the time constant of charge / discharge of the secondary battery. In other words, the secondary battery is charged and discharged by simultaneously proceeding with a plurality of chemical reactions having different time constants.

The vehicle 1 includes a current detection unit 4, a voltage detection unit 5, and a control device 6.
The current detection unit 4 is connected in series to the secondary battery 3 and the electric motor 2. The current detection unit 4 detects the charging / discharging current It flowing through the secondary battery 3 during charging / discharging of the secondary battery 3 with a preset detection cycle (sampling cycle) T _s . The voltage detection unit 5 is connected in parallel to the secondary battery 3 and the electric motor 2. The voltage detector 5 detects the inter-terminal voltage Vt of the secondary battery 3 with a detection cycle T _s . Output signals from the detection units 4 and 5 are taken into the control device 6.

  The control device 6 is mainly composed of a microcomputer and has a CPU, a memory and the like. The control device 6 includes a calculation unit 60 and a control unit 61. The calculation unit 60 estimates the SOC value indicating the state of charge of the secondary battery 3 based on the charge / discharge current It and the terminal voltage Vt detected by the detection units 4 and 5. The control unit 61 performs charge / discharge control of the secondary battery 3 based on the SOC value calculated by the calculation unit 60.

Next, a method for estimating the SOC value by the calculation unit 60 will be described.
In the present embodiment, the secondary battery 3 is modeled by an equivalent circuit as shown in FIG. As shown in FIG. 2, the equivalent circuit model M1 of the secondary battery 3 includes impedance circuits 11 to 14 corresponding to a plurality of chemical reactions having different time constants, and an open circuit voltage source VS that generates an open circuit voltage OCV. have. The impedance circuits 11 to 14 and the open circuit voltage source VS are connected in series.

Impedance circuit 11 consists of resistors only the resistance value R _1. The impedance circuits 12 to 14 are so-called RC parallel circuits in which resistors having resistance values R _{2 to} R ₄ and capacitors having capacitances C _{2 to} C ₄ are respectively connected in parallel. The impedance circuit 11 is assumed to be an RC parallel circuit in which the capacitance is set to zero. Hereinafter, for the sake of convenience, the capacitance of a virtual capacitor in the impedance circuit 11 is represented as “C ₁ (= 0)”. The characteristics of the equivalent circuit model M1 are determined by the resistance values R _{1 to} R ₄ and the capacitances C _{1 to} C ₄ . Hereinafter, the resistance values R _{1 to} R ₄ and the capacitances C _{1 to} C ₄ are collectively expressed as characteristic parameters R _{1 to} R ₄ and C _{1 to} C ₄ .

The time constant τ ₁ of the impedance circuit 11 is set to zero. The time constant τ ₂ (= R ₂ C ₂ ) of the impedance circuit 12 is set to the order of 10 milliseconds (for example, 30 ms). The time constant τ ₃ (= R ₃ C ₃ ) of the impedance circuit 13 is set to the second order (for example, 3 s). The time constant τ ₄ (= R ₄ C ₄ ) of the impedance circuit 14 is set to the order of 10 seconds (for example, 30 s). That is, the time constant τ ₄ of the impedance circuit 14 is set to the maximum value. Since the impedance circuit 14 having the maximum time constant represents the diffusion resistance in the chemical reaction of the secondary battery 3 in terms of impedance, the impedance circuit 14 is also referred to as the diffusion circuit 14 for convenience in the following. The impedance circuits 12 and 13 represent the reaction resistance in the chemical reaction of the secondary battery 3 by impedance.

When the secondary battery 3 is represented by the equivalent circuit model M1 as shown in FIG. 2, the voltage Vt between the terminals detected by the voltage detector 5, the open circuit voltage OCV, and the impedance circuits 11 to 13 between both ends. The relationship represented by the following expression f1 is established between the voltage Vr and the voltage Vd across the diffusion circuit 14.

Further, the voltages v _i between both ends of the impedance circuits 11 to 13 and the diffusion circuit 14 are expressed by time t, resistance value R _i , capacitance C _i , and “t = 0” as shown in the following expression f2. Can be expressed as a function of the initial voltage value v _0i . However, “i = 1 to 4”.

That is, the voltage f (t) between both ends of the impedance circuits 11 to 14 obtained by adding the voltages v _i between both ends of the impedance circuits 11 to 13 and the diffusion circuit 14 can be expressed by the following expression f3.

The calculation unit 60 identifies the resistance value R _i and the capacitance C _i of the model function f (t) by the least square method using the inter-terminal voltage Vt detected by the voltage detection unit 5. In detail, the calculating part 60 calculates the measured value F (t) of the voltage between both ends of the impedance circuit 11-14 whole based on the following formula | equation f4. In Expression f4, “OCV _pre ” indicates the value of the open circuit voltage estimated previously.

The calculation unit 60 acquires the actual measurement value F (T) based on the inter-terminal voltage Vt detected by the voltage detection unit 5 for a plurality of times T. The calculation unit 60 uses the function f (t) defined by the expression f3 as a model function, and uses the residual “f” between the model function f (T) and the actual measurement value F (T) at the time T indicated by the following expression f5. The characteristic parameters R _i and C _i are identified so that the square sum δ1 of (T) −F (T) ”is minimized.

Note that the calculation unit 60 calculates the expression f5 at a time when the voltage initial values v _0i of the impedance circuits 11 to 14 are uniquely determined. As a result, the only variables to be varied to minimize the square sum δ1 are the resistance values R _{1 to} R ₄ and the capacitances C _{2 to} C ₄ except for the capacitance C ₁ set to zero. .

Calculation unit 60, the resistance value R ₁ to R ₄ and the capacitance C ₂ -C ₄ by varying the resistance value R ₁ to R ₄ and the capacitance C ₂ -C ₄ square sum δ1 is minimized Is identified. The arithmetic unit 60 determines the voltage across v _i of each impedance circuit 11 to 14 based on the identified resistance value R ₁ to R ₄ and the capacitance C ₂ -C _4. The calculation unit 60 calculates an estimated value of the open circuit voltage OCV based on the following equation f6 based on the determined voltage v _i between both ends and the terminal voltage Vt detected by the voltage detection unit 5.

  The calculation unit 60 calculates the open circuit voltage OCV by the above method while the vehicle is traveling, and estimates the SOC value from the calculated open circuit voltage OCV based on the OCV-SOC characteristic diagram. The OCV-SOC characteristic diagram is obtained in advance by experiments or the like and is stored in the memory of the control device 6.

By the way, when the vehicle is traveling in the HV traveling mode, the control device 6 keeps the SOC value within a predetermined range, so that the time-dependent change in the inter-terminal voltage Vt of the secondary battery 3 detected by the voltage detection unit 5. Is difficult to contain a component having a large time constant. More specifically, the time-dependent change in the inter-terminal voltage Vt of the secondary battery 3 is relatively easy to include components corresponding to the time constants τ _{1 to} τ ₃ of the impedance circuits 11 to 13. The component corresponding to τ ₄ is hardly included. Therefore, when the calculation unit 60 identifies the characteristic parameters R _i and C _i by the above method, it is difficult to ensure the estimation accuracy of the resistance value R ₄ and the capacitance C ₄ of the diffusion circuit 14.

Therefore, the calculation unit 60 of the present embodiment uses the charge / discharge current It and the inter-terminal voltage Vt detected by the current detection unit 4 and the voltage detection unit 5 when the vehicle is stopped, and the resistance value R of the diffusion circuit 14. ₄ and capacitance C ₄ are identified. Hereinafter, the method will be described in detail.

FIGS. 3A and 3B show the inter-terminal voltage when the vehicle stops at time t2 after the driver performs a brake operation at time t1 when the vehicle is running with the electric motor 2 as a power source. The transition of Vt and charging / discharging current It is illustrated. In this case, when the driver performs a braking operation at time t1, the regenerative power generated by the electric motor 2 is charged in the secondary battery 3, so that the voltage Vt between the terminals indicates a value corresponding to the regenerative power and the charging is performed. The discharge current It changes at a negative value. Thereafter, when the vehicle stops at time t2, the electric motor 2 and the engine are stopped, so that the charge / discharge current It becomes zero. The inter-terminal voltage Vt gradually changes from the voltage value Vt1 at the time t2 toward the open circuit voltage OCV. The calculation unit 60 identifies the voltage initial value v ₀₄ and the time constant τ ₄ of the diffusion circuit 14 based on the inter-terminal voltage Vt after time t2, that is, based on the inter-terminal voltage Vt after the vehicle 1 stops.

Next, a method for identifying the voltage initial value v ₀₄ and the time constant τ ₄ of the diffusion circuit 14 will be specifically described. Hereinafter, for the sake of simplicity, the equivalent circuit model M2 of the secondary battery 3 when the vehicle is stopped is represented as a series circuit of the open circuit voltage source VS and the diffusion circuit 14 as shown in FIG.

When the equivalent circuit model M2 of the secondary battery 3 is expressed as shown in FIG. 4, in the situation where the charge / discharge current It is zero, that is, in the situation where only the circulating current flows in the diffusion circuit 14, both ends of the diffusion circuit 14 The inter-voltage v ₄ (t) is expressed as a function of the initial voltage v ₀₄ at time t, angular velocity ω ₄ (= 1 / τ ₄ ), and “t = 0”, as shown in the following formula f7. Can do.

The calculation unit 60 identifies the voltage initial value v ₀₄ and the angular velocity ω ₄ of the voltage v ₄ (t) between both ends using the terminal voltage Vt detected by the voltage detection unit 5. Specifically, the calculation unit 60 calculates the measured value V ₄ (t) of the voltage across the terminals of the diffusion circuit 14 based on the following formula f8. In Expression f8, “OCV _pre ” indicates the value of the open circuit voltage estimated previously.

The calculation unit 60 acquires the measured value V ₄ (T) of the inter-terminal voltage of the diffusion circuit 14 based on the inter-terminal voltage Vt detected by the voltage detection unit 5 for a plurality of times T. The computing unit 60 identifies the voltage initial value v ₀₄ and the angular velocity ω ₄ by the nonlinear least square method using the function v ₄ (t) defined by the equation f7 as a model function. As the nonlinear least square method, for example, the LM (Levenberg-Marquardt) method can be used. Specifically, the arithmetic unit 60 calculates the residual “v ₄ (T) −V ₄ (T) between the model function v ₄ (T) and the actual measurement value V ₄ (T) at time T shown by the following expression f9. The initial voltage value v ₀₄ and the angular velocity ω ₄ are identified so that the square sum δ2 of “)” is minimized.

On the other hand, in the equivalent circuit model M2 shown in FIG. 4, the charge and discharge current It immediately before charge and discharge current It becomes zero and the constant value i _04, with respect to the time constant tau ₄ is and time is a fixed value i ₀₄ When C ₄ is fully charged and the current flowing in C ₄ is zero, the relationship of the following equation f10 is established between the voltage initial value v ₀₄ and the current value i ₀₄ . Hereinafter, for convenience, “i ₀₄ ” is referred to as an initial current value.

That is, if this equation f10 can be used, the resistance value R ₄ can be identified from the voltage initial value v ₀₄ and the current initial value i ₀₄ . However, as shown in FIG. 3B, since the charge / discharge current It before the charge / discharge current It becomes zero, that is, before the time t2, is not constant, the expression f10 cannot be used. Therefore, in the present embodiment, a constant current equivalent to the charge / discharge current It detected by the current detection unit 4 is calculated before time t2, that is, before the vehicle 1 stops, and the constant current is set as the current initial value i _04. Use.

Next, a method for calculating the current initial value i ₀₄ will be described.
For example, when the current I changes as shown in FIG. 5, the current initial value I ₀ at time ta is obtained. In this case, first, the waveform of the current I is decomposed into a pulse current signal at the detection period T _s of the current detection unit 4. At this time, the pulse current signals at the time ta are numbered as first, and are numbered in the order of second, third,... In order from the closest to the pulse current signal. When j is an integer equal to or greater than 1, as shown in FIG. _6A , when the pulse current signal of the _jth current I _j is input to the RC parallel circuit, the current I _C flowing through the capacitor and the resistance are The flowing current I _R changes as shown in FIGS. 6B and 6C. That is, the capacitor current I _C becomes “I _Rj ” at the time t11 after the time T _{s has} elapsed from the supply time t10 of the current I _j . This current I _Rj can be expressed by the following equation f11. “Ω” represents the angular velocity of the RC parallel circuit.

When the T _s period elapses and the current supplied from the outside becomes zero, the charge accumulated in the capacitor is discharged through a resistor connected in parallel to the capacitor, and a circulating current flows. The circulating current inside the RC parallel circuit shows a change in the exp curve. The magnitude I _0j of the circulating current after the time (j−1) × T _s has elapsed from the time tb after the generation of the j-th pulse current signal in FIG. Can be expressed as

The initial current value I _{0 at the} time ta can be expressed as the sum of innumerable pulse current signals expressed by Equation 12. That is, the current initial value I ₀ can be expressed as the following formula f13.

Therefore, the current initial value i ₀₄ of the diffusion circuit 14 can be obtained by the following equation f14 based on the charge / discharge current It detected by the current detector 4.

Thus, the current initial value i ₀₄ is an inner product of the current array and the exp weight array. As is apparent from the equation f14, the weighting coefficient “exp (−ω ₄ () is decreased as“ (j−1) × T _s ”representing the elapsed time from the detection timing of the charge / discharge current It _j to the vehicle stop timing is shorter. j-1) T _s) "increases. That is, the closer the detection timing of the charge / discharge current It _j is to the stop time of the vehicle, the larger the weighting coefficient of the charge / discharge current It _j becomes. Note that if exp = −ω ₄ t and t = 5τ ₄ , “exp (−ω ₄ t) ≈0.006738” and almost zero, so the weighting coefficient “exp (−ω ₄ (j−1) T _s) inner product period of "" (j-1) × T _s "can be said to be sufficient to ensure the 5τ _4.

  Next, referring to FIG. 7, the procedure of processing executed by the calculation unit 60 will be summarized. Note that the calculation unit 60 repeatedly executes the processing shown in FIG. 7 at a predetermined calculation cycle.

As shown in FIG. 7, the arithmetic unit 60 first determines the voltage initial value v _{04 of the} voltage v ₄ (t) across the diffusion circuit 14 based on the inter-terminal voltage Vt detected by the voltage detection unit 5. The angular velocity ω ₄ is identified (step S1). Specifically, the calculation unit 60 identifies the voltage initial value v ₀₄ and the angular velocity ω ₄ by the nonlinear least square method so that the square sum δ2 represented by the expression f9 is minimized.

The arithmetic unit 60 calculates the initial current value i ₀₄ based from charging and discharging current It is detected by the current detector 4 in formula f14 (step S2). Next, the computing unit 60 computes the resistance value R ₄ from the current initial value i ₀₄ and the voltage initial value v ₀₄ based on the following formula f15 obtained by modifying the formula f10 (step S3).

Further, the calculation unit 60 calculates the capacitance C ₄ from the calculated resistance value R ₄ and angular velocity ω ₄ based on the following formula f16 (step S4).

  According to the control device 6 of the secondary battery 3 of the present embodiment described above, the operations and effects shown in the following (1) and (2) can be obtained.

(1) Since the resistance value R ₄ and the capacitance C ₄ of the diffusion circuit 14 having a large time constant can be identified, the estimation accuracy of the characteristic parameters R _i and C _i of the equivalent circuit model M1 of the secondary battery 3 is increased. Can be improved.

(2) In calculating the current initial value i ₀₄ , the shorter the “(j−1) × T _s ” representing the elapsed time from the detection time of the charge / discharge current It _j to the vehicle stop time, that is, the current detection unit 4 detection timing of the charging and discharging current it _j by the closer the stop time of the vehicle, it was decided to increase the weighting factor of the charge and discharge current it _j. As a result, the calculation accuracy of the current initial value i ₀₄ can be improved, and as a result, the estimation accuracy of the resistance value R ₄ and the capacitance C ₄ of the diffusion circuit 14 can be improved.

In addition, the said embodiment can also be implemented with the following forms.
The order of the time constants of the impedance circuits 12 to 14 can be changed as appropriate according to the characteristics of the secondary battery 3.

  The diffusion circuit 14 is not limited to one RC parallel circuit, and may be configured by a plurality of RC parallel circuits connected in series.

  The equivalent circuit models M1 and M2 of the secondary battery 3 can be appropriately changed according to the characteristics of the secondary battery 3 mounted on the vehicle.

The calculation unit 60 uses the calculation according to the above embodiment, so that the current detection unit 4 and the voltage detection unit 5 detect the charge / discharge current It and the inter-terminal voltage Vt, respectively, when the vehicle stops. The characteristic parameters R _{1 to} R ₃ , C ₂ and C ₃ of the impedance circuits 11 to 13 may be identified. In short, the calculation unit 60 is a characteristic of the equivalent circuit model of the secondary battery 3 based on the charge / discharge current It and the inter-terminal voltage Vt detected by the current detection unit 4 and the voltage detection unit 5 when the vehicle is stopped. Anything that identifies a parameter may be used.

  -The structure of the said embodiment is applicable not only to a hybrid vehicle but to the control apparatus of the secondary battery mounted in the vehicle which uses an electric motor as a drive source at least, such as an electric vehicle, for example.

  -This invention is not limited to said specific example. That is, the above-described specific examples that are appropriately modified by those skilled in the art are also included in the scope of the present invention as long as they have the characteristics of the present invention. For example, the elements included in each of the specific examples described above, their arrangement, conditions, and the like are not limited to those illustrated, and can be changed as appropriate. Moreover, each element with which embodiment mentioned above is provided can be combined as long as it is technically possible, and the combination of these is also included in the scope of the present invention as long as it includes the features of the present invention.

M1, M2: Equivalent circuit model 1: Vehicle 2: Electric motor 3: Secondary battery 4: Current detector 5: Voltage detector 6: Controller 14: Diffusion circuit

Claims (4)

A control device (6) for a secondary battery (3) mounted on a vehicle (1) having at least an electric motor (2) as a drive source,
A current detector (4) for detecting a charge / discharge current of the secondary battery;
A voltage detector (5) for detecting a voltage between terminals of the secondary battery;
Calculation unit for identifying the characteristic parameters of the previous SL secondary battery equivalent circuit model (M1, M2) and (60), provided with,
The equivalent circuit model includes a diffusion circuit (14) including an impedance circuit having a maximum time constant,
When a constant current equivalent to the charge / discharge current immediately before the charge / discharge current becomes zero is used as the current initial value,
The computing unit is
While calculating the current initial value based on the charge and discharge current detected by the current detection unit before the vehicle stops,
Identifying an initial voltage value of the impedance circuit based on the voltage between the terminals detected by the voltage detection unit after the vehicle stops,
A control device for a secondary battery, wherein a characteristic parameter of the diffusion circuit is identified based on the initial current value and the initial voltage value . The computing unit is
Based on the weighting coefficient according to the elapsed time from the detection time of the charging / discharging current to the time of stopping of the vehicle, the charging / discharging current detected by the current detection unit is weighted,
The secondary battery control device according to claim 1 , wherein the current initial value is calculated based on the weighted charge / discharge current. The equivalent circuit model is composed of an impedance circuit composed of RC parallel circuits,
The computing unit is
Further identifying the reciprocal of the time constant of the RC parallel circuit based on the voltage between the terminals detected by the voltage detection unit after the vehicle stops,
3. The control of the secondary battery according to claim 2 , wherein the weighting coefficient is set based on an inverse of the time constant and an elapsed time from a detection timing of the charge / discharge current to a stop of the vehicle. apparatus. The equivalent circuit model is composed of an impedance circuit composed of RC parallel circuits,
The computing unit is
Identifying the voltage initial value of the RC parallel circuit and the inverse of the time constant based on the voltage between the terminals detected by the voltage detector after the vehicle stops,
Based on the initial voltage value and the initial current value, the resistance value of the diffusion circuit is identified as the characteristic parameter ,
Based on the reciprocal and the resistance value of the time constant, as the characteristic parameter, secondary battery according to any one of claims 1 to 3, wherein the identification of the capacitance of the diffusion circuit Control device.

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