JP2014039434A - Soc estimation device and soc estimation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately estimate an SOC (State Of Charge) of a secondary battery capable of being charged/discharged and reduce time required for estimating the SOC, with regard to an SOC estimation device and an SOC estimation method for estimating the SOC.SOLUTION: A measurement unit 1-1 measures a value of OCV of each of cells C1 to C5 at outflow start time of bypass current flowing in bypass circuits B1 to B5 and outflow time of the bypass current. A fluctuation transition estimation unit 1-2 estimates transition of fluctuation in the value of OCV of the cell after the outflow start of the bypass current on the basis of known SOC-OCV characteristic information showing relation between an SOC and OCV of a cell and the value of OCV at the outflow start time of the bypass current. An OCV value estimation unit 1-3 estimates a value of OCV in the case of outflow suspension of the bypass current on the basis of the transition of the fluctuation in the value of OCV. SOC value estimation means 1-4 estimates a value of SOC in the case of the outflow suspension of the bypass current from the value of OCV estimated by the OCV value estimation unit 1-3, on the basis of the SOC-OCV characteristic information.

Description

  The present invention relates to an SOC estimation device and an SOC estimation method for estimating an SOC (State Of Charge) of a secondary battery that can be charged and discharged.

  A battery (assembled battery) in which a plurality of cells (single cells) are connected in series may cause a difference in the SOC of each cell during charging / discharging or standing, and a resistor is connected to a cell having a high voltage. The cell balance control is performed so that the SOC of all the cells is uniform by supplying a bypass current (see, for example, Patent Documents 1 and 2 below).

  FIG. 6 shows a configuration example of a cell balance circuit by a bypass circuit using a resistor. In each of the cells C1 to C5, bypass circuits B1 to B5 in which resistors R1 to R5 and switching elements Sw1 to Sw5 are connected in series are connected in parallel, the switching elements Sw1 to Sw5 are closed, and the resistors R1 to R5 are closed. The charges of the cells C1 to C5 are discharged through R5.

  In performing the cell balance control, the SOC of each of the cells C1 to C5 is determined in order to appropriately determine the closing time of the switching elements Sw1 to Sw5 and efficiently perform the cell balance control, or to properly manage the charge / discharge state. Must be estimated in a short time.

  As a method of estimating the SOC of each of the cells C1 to C5, a method of estimating the SOC by integrating the charge / discharge current, or a correspondence relationship between the OCV (Open Circuit Voltage) of the cell and the SOC in advance (SOC-OCV characteristics) ), The SOC-OCV characteristic information in which the correspondence is mapped is stored in the memory, the OCV of each cell is measured, and the SOC is estimated by referring to the SOC-OCV characteristic information from the value of the OCV A technique is known (see, for example, Patent Document 3 below).

JP 2009-038876 A JP 2011-234506 A JP 2012-026771 A

  The method of estimating the SOC of a cell by integrating the charge / discharge current of the cell is difficult to determine the SOC reference point when the cell is unlikely to be fully charged or completely discharged, and the current accumulation error is accumulated. However, it is difficult to perform highly accurate estimation.

  In addition, when the SOC is estimated using OCV, even if cell balancing is interrupted, the bypass current is set to zero, and the OCV is measured with respect to the cell being cell-balanced, the voltage of the cell is CCV ( It takes a certain amount of time to converge from the closed circuit voltage to the OCV, and the SOC cannot be estimated immediately.

  FIG. 7 shows an example of cell voltage fluctuations during cell balancing. In FIG. 7, the horizontal axis indicates the elapsed time from the start of cell balance, and the vertical axis indicates the cell voltage. A solid line 7-1 represents the cell voltage (CCV) during the cell balance and the actual cell voltage after the cell balance is interrupted.

  During cell balancing, the CCV is always lower than the OCV due to the effects of cell internal resistance and polarization. Even if the cell balancing is interrupted and the cell terminal is opened, the cell voltage does not immediately converge to the OCV, and a certain amount of time tw is required for depolarization. It is necessary to wait for a predetermined time tw until becomes a converged OCV. For this reason, it has been difficult to immediately estimate the SOC of the cell in use by measuring the OCV.

  In view of the above problems, the present invention provides an SOC estimation apparatus and an SOC estimation method that can accurately estimate an SOC and reduce the time required for the estimation.

  An SOC estimation apparatus according to an embodiment of the present invention is connected to a bypass circuit having a known resistance value, and a state of charge (SOC) of a secondary battery (cell) that performs cell balancing by flowing a bypass current to the bypass circuit. An SOC estimation device for estimating the cell open circuit voltage (OCV) value and the bypass current outflow time at the start of the bypass current outflow, and the SOC and OCV of the cell. Based on the SOC-OCV characteristic information indicating the correspondence relationship between the current and the OCV value at the start of outflow of the bypass current, the change in the OCV value of the cell after the start of outflow of the bypass current is estimated. From the fluctuation transition estimation means, the OCV value at the start of bypass current flow measured by the measurement means, and the bypass current flow time, the fluctuation of the OCV value estimated by the fluctuation transition estimation means OCV value estimating means for estimating the OCV value after the outflow time of the bypass current based on the shift, and the OCV value estimated by the OCV value estimating means, based on the SOC-OCV characteristic information, SOC value estimating means for estimating the SOC value after the outflow time of the bypass current.

With this configuration, after the cell balance is performed, it is possible to estimate the OCV value during the cell balance and obtain the SOC immediately using the estimated OCV value.
Further, the SOC estimation apparatus according to another embodiment includes a measuring unit that measures a value of the open circuit voltage (OCV) of the cell at the start of outflow of the bypass current and an outflow time of the bypass current, and the SOC of the cell. Based on the SOC-OCV characteristic information indicating the correspondence with the OCV and the OCV value at the start of the bypass current outflow, the transition of the OCV value fluctuation of the cell after the start of the bypass current outflow is estimated. Fluctuation transition estimating means for estimating the transition value of the bypass current from the OCV value of the cell estimated by the fluctuation transition estimating means, and integrating the value of the bypass current, An SOC value estimator for subtracting the integrated value accumulated by the current accumulated value estimating means from the SOC value of the cell at the start of the bypass current outflow to estimate the SOC value after the bypass current outflow time. When, those having a.

  With this configuration, after the cell balance is performed, the OCV value during the cell balance is estimated and obtained, and the current that has flowed out as a bypass current from the estimated OCV value is integrated. By subtracting from the SOC value at the start, the SOC estimation can be performed immediately.

  Further, the variation transition estimation means, the correlation between the OCV value after the bypass current starts to flow out and the outflow time of the bypass current from the fully charged state to the fully discharged state of the cell, The OCV mapping information mapped in advance is read from the memory, and the transition of the fluctuation of the OCV value of the cell is estimated.

  With this configuration, it is possible to estimate the transition of the fluctuation in the OCV value after the start of the outflow of the bypass current in a short time by referring to the OCV mapping information stored in the memory.

  According to the present invention, after the cell balance or the like is performed, the fluctuation of the OCV value during the outflow of the bypass current is estimated and obtained, and the SOC estimation is performed using the OCV value obtained by the estimation. Even when the implementation is interrupted, it is possible to immediately perform the SOC estimation without waiting for a certain amount of time for eliminating the polarization, and it is possible to perform the accurate SOC estimation in a short time.

It is a figure which shows the structural example of the SOC estimation apparatus of the 1st Embodiment of this invention. It is a figure which shows an example of the fluctuation | variation of OCV by SOC variation (DELTA) SOC. It is a figure which shows an example of transition of the fluctuation | variation of the value of OCV estimated based on the SOC-OCV characteristic. It is a figure which shows an example of transition of the fluctuation | variation of a bypass current, and consumption SOC. It is a figure which shows the structural example of the SOC estimation apparatus of the 2nd Embodiment of this invention. It is a figure which shows the structural example of the cell balance circuit by the bypass circuit using resistance. It is a figure which shows an example of the fluctuation | variation of the voltage of the cell at the time of cell balance implementation.

  Hereinafter, embodiments will be described in detail with reference to the drawings. FIG. 1 shows a configuration example of the SOC estimation apparatus. In FIG. 1, the configuration and operation of the bypass circuit by each switching element are the same as the configuration and operation described with reference to FIG.

  Cells C1 to C5 that are targets of SOC estimation by the SOC estimation apparatus of the present invention are cells to which bypass circuits B1 to B5 that allow a bypass current to flow out through resistors R1 to R5 having known resistance values are connected. In the illustrated example, a configuration example in which five cells C1 to C5 are connected in series is shown, but the present invention is not limited to this, and the number of cells is arbitrary.

  The cell SOC estimation apparatus 1 of the present invention includes a measurement unit 1-1, a fluctuation transition estimation unit 1-2, an OCV value estimation unit 1-3, and an SOC estimation unit 1-4. The measuring unit 1-1 measures the OCV value of each of the cells C1 to C5 at the start of outflow of the bypass current flowing through the bypass circuits B1 to B5 and the outflow time of the bypass current.

  The fluctuation transition estimation unit 1-2 includes known SOC-OCV characteristic information indicating the correspondence relationship between the SOCs and the OCVs of the cells C1 to C5, and the OCV at the start of the outflow of the bypass current measured by the measurement unit 1-1. Based on the value, the transition of the fluctuation of the OCV value of the cell after the start of the outflow of the bypass current is estimated.

  The OCV value estimator 1-3 determines the value of the OCV estimated by the change transition estimator 1-2 from the value of the OCV at the start of the outflow of the bypass current measured by the measuring unit 1-1 and the outflow time of the bypass current. The OCV value after the outflow time of the bypass current (when the cell balance is interrupted or at the end of the cell balance) is estimated based on the transition of the fluctuations of. The SOC value estimation means 1-4 estimates the SOC value after the outflow time of the bypass current based on the aforementioned SOC-OCV characteristic information from the OCV value estimated by the OCV value estimation unit 1-3.

Here, the operation of estimating the change of the OCV value of the cell after the start of outflow of the bypass current by the above-described change transition estimation unit 1-2 will be described in detail. The value of the resistor R1~R5 of the bypass circuit B1 to B5 R, A value of the OCV of the outflow starting cell bypass current to _{V 1,} the bypass current _{I 1} at this _time, at I 1 _{= V} 1 / R is there. Thus, the variation [Delta] SOC ₁ of SOC of the cell when the bypass current _{I 1} was short time _{t 1} sink _is estimated as _{(V 1 / R) · t} 1.

The manner in which the OCV is estimated based on the SOC change ΔSOC will be described with reference to FIG. FIG. 2 shows an example of a known SOC relationship (SOC-OCV characteristic) with respect to the OCV. As shown in FIG. 2, based on the SOC-OCV characteristic, it is estimated that the value of OCV becomes V ₂ due to a change in ΔSOC ₁ .

Similarly, when the value of the OCV is _{V 2,} the bypass current _{I 2} is _I 2 _{= V} 2 / Since R is, the SOC change amount in the cell [Delta] SOC ₂ when the bypass current _{I 2} was short time _{t 2} flow Is estimated as (V ₂ / R) · t ₂ . Based on the SOC-OCV characteristic, it is estimated that the value of OCV becomes V ₃ due to a change in ΔSOC ₂ .

Similarly, from the OCV value V ₁ of the cell at the start of bypass current outflow and the elapsed time t from the start of bypass current outflow, the OCV value V _n is calculated based on the SOC-OCV characteristics. Can be estimated. Note that the above-described minute times t ₁ , t ₂ ,... Are minute time widths in which the known SOC-OCV characteristics are linearly approximated.

FIG. 3 shows an example of changes in the OCV value estimated by the above-described method. In FIG. 3, a curve 3-1 shows the transition of the estimated OCV value variation, and a curve 7-1 shows the actual voltage (CCV) described in FIG. 7 for reference. As shown in FIG. 3, for example, it starts the cell balance at time T _1, and the value of OCV at that time was V _1. Then, the interrupted cell balance at time T _2, after the time t elapsed from the start time T ₁ of the cell balance. Then, the OCV value V _n at the time of cell balance interruption is estimated from the OCV value V ₁ at the start of cell balance and the cell balance execution time t by the above calculation.

Note that when estimating the value _{V n} of the OCV, by calculation based on the SOC-OCV characteristics as described above, instead of the configuration for estimating the value _{V n} of the OCV, based on pre-SOC-OCV characteristics, Mitsuru The correspondence (OCV-time characteristic) between the cell balance execution time and the OCV from the charge state to the complete discharge state is calculated in advance by the above calculation, and the correspondence is mapped and stored in the memory. Can be read to obtain the OCV value.

  Based on the OCV value obtained after the cell balance execution time obtained from the OCV value at the start of cell balance and the cell balance execution time, immediately after the cell balance is executed with reference to the known SOC-OCV characteristics. It is possible to estimate the SOC. In the above description, the influence of the internal resistance of the cell has been omitted for the sake of simplicity. However, when the OCV is estimated with higher accuracy, the value of the internal resistance of the cell is added as the above-described resistance value R. Value.

  Further, another embodiment will be described with reference to FIG. As described above, there is a relationship of I = V / R between the bypass current I, the OCV value V, and the known resistance value R. Therefore, similarly to the estimation of the OCV when the cell balance is performed, the variation of the bypass current I when the cell balance is performed can be estimated using this relational expression. FIG. 4A shows an example of the transition of the fluctuation of the bypass current I when the cell balance is performed by a curve 4-1.

Start the cell balance at time T _1, if at time T _2, the implementation of the cell balance is interrupted, the bypass current I ₁ at time T _1, the bypass current I at time T _2, after the lapse of the cell balance the operating time t Until _n , the bypass current that has been energized is integrated with reference to the estimated bypass current-time variation characteristic 4-1. In FIG. 4A, the integrated current is shown with a sand pattern. Figure 4 current value _{I 1,} I 2 of (a), ··· _{I n} the voltage value _{V 1,} V 2 of FIG. 3, a current value corresponding to · · · _{V n.}

  Since the integrated current corresponds to the consumed SOC, it is possible to estimate the SOC consumed by performing the cell balance from the integrated current. Therefore, as shown in FIG. 4 (b), by subtracting the consumed SOC (sand pattern portion in FIG. 4 (b)) estimated by the current integration from the SOC value of the cell before cell balancing, The SOC value at the time of cell balance interruption can be estimated.

  FIG. 5 shows a configuration example of the SOC estimation apparatus of the second embodiment that estimates the SOC by integrating the bypass current described above. The SOC estimation apparatus 2 of this embodiment includes a measurement unit 1-1, a fluctuation transition estimation unit 1-2, a current integration estimation unit 2-1, and an SOC estimation unit 2-2. The measurement unit 1-1 and the change transition estimation unit 1-2 are the same as those in FIG.

  The current integrated value estimation unit 2-1 determines the OCV value at the start of outflow of the bypass current measured by the measurement unit 1-1 and the transition of the fluctuation of the OCV value estimated by the variation transition estimation unit 1-2. Based on the relationship of I = V / R, the fluctuation of the bypass current after the bypass current flows out is estimated, and the energized bypass current after the cell balance execution time t has elapsed is integrated to estimate the consumed SOC.

Specifically, when the value of the OCV of the cell of the outflow start bypass current to _{V 1,} the bypass current _{I 1} at this time _is I 1 _{= V} 1 / R. Thus, the variation [Delta] SOC ₁ of SOC of the cell when the bypass current _{I 1} Features small time _{t 1} sink _is estimated as I 1 · _{t 1.} As shown in FIG. 2, based on the SOC-OCV characteristic, it is estimated that the value of OCV becomes V ₂ due to a change in ΔSOC ₁ .

Similarly, when the value of the OCV is _{V 2,} the bypass current _{I 2} is _I 2 _{= V} 2 / Since R is, the SOC change amount in the cell [Delta] SOC ₂ when the bypass current _{I 2} was short time _{t 2} flow Is estimated as I ₂ · t ₂ .

In the same manner, the amount of change ΔSOC ₁ , ΔSOC ₂ ,.
The SOC estimation unit 2-2 obtains the SOC value at the start of the cell balance from the OCV value at the start of the cell balance based on the known SOC-OCV characteristic information, and calculates the SOC at the start of the cell balance. The consumption SOC is subtracted from the value, and the SOC value after the outflow time of the bypass current is estimated.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to embodiment described above, In the range which does not deviate from the summary of this invention, a various structure or embodiment is taken. be able to.

DESCRIPTION OF SYMBOLS 1, 2 SOC estimation apparatus 1-1 Measurement part 1-2 Fluctuation transition estimation part 1-3 OCV value estimation part 1-4 SOC estimation part 2-1 Current integrated value estimation part 2-2 SOC estimation part

Claims (6)

SOC estimation for estimating a state of charge (hereinafter referred to as “SOC”) of a secondary battery (hereinafter referred to as “cell”) which is connected to a bypass circuit having a known resistance value and flows a bypass current to the bypass circuit to perform cell balancing. A device,
Measuring means for measuring the open circuit voltage (hereinafter referred to as “OCV”) of the cell at the start of the bypass current flow and the flow time of the bypass current;
Based on the SOC-OCV characteristic information indicating the correspondence between the SOC and OCV of the cell, and the OCV value at the start of the bypass current outflow, the OCV value of the cell after the bypass current outflow start is calculated. A fluctuation transition estimating means for estimating a transition of fluctuation;
Based on the transition of fluctuation of the OCV value estimated by the fluctuation transition estimation means from the OCV value at the start of the bypass current flow measured by the measuring means and the outflow time of the bypass current, the outflow of the bypass current OCV value estimation means for estimating the OCV value after time;
SOC value estimating means for estimating the SOC value after the outflow time of the bypass current based on the SOC-OCV characteristic information from the OCV value estimated by the OCV value estimating means;
An SOC estimation apparatus comprising: SOC estimation for estimating a state of charge (hereinafter referred to as “SOC”) of a secondary battery (hereinafter referred to as “cell”) which is connected to a bypass circuit having a known resistance value and flows a bypass current to the bypass circuit to perform cell balancing. A device,
Measuring means for measuring the open circuit voltage (hereinafter referred to as “OCV”) of the cell at the start of the bypass current flow and the flow time of the bypass current;
Based on the SOC-OCV characteristic information indicating the correspondence between the SOC and OCV of the cell, and the OCV value at the start of the bypass current outflow, the OCV value of the cell after the bypass current outflow start is calculated. A fluctuation transition estimating means for estimating a transition of fluctuation;
Current accumulated value estimating means for estimating the transition of the bypass current value from the OCV value of the cell estimated by the fluctuation transition estimating means, and integrating the bypass current value;
An SOC value estimating means for subtracting the integrated value integrated by the current integrated value estimating means from the SOC value of the cell at the start of the bypass current outflow to estimate the SOC value after the bypass current outflow time. When,
An SOC estimation apparatus comprising:   The fluctuation transition estimation means maps in advance the correspondence between the OCV value after the bypass current starts to flow and the flow time of the bypass current from the fully charged state to the fully discharged state of the cell. 3. The SOC estimation apparatus according to claim 1, wherein the OCV mapping information that has been read is read out from a memory, and a transition of a change in the OCV value of the cell is estimated. SOC estimation for estimating a state of charge (hereinafter referred to as “SOC”) of a secondary battery (hereinafter referred to as “cell”) which is connected to a bypass circuit having a known resistance value and flows a bypass current to the bypass circuit to perform cell balancing. A method,
A first step of measuring a value of an open circuit voltage (hereinafter referred to as “OCV”) of the cell at the start of the flow of the bypass current and a flow time of the bypass current;
Based on the SOC-OCV characteristic information indicating the correspondence between the SOC and OCV of the cell, and the OCV value at the start of the bypass current outflow, the OCV value of the cell after the bypass current outflow start is calculated. A second step of estimating the transition of the change;
Based on the change in the OCV value estimated in the second step from the OCV value at the start of the bypass current flow measured in the first step and the outflow time of the bypass current, the bypass current A third step of estimating the value of OCV after the outflow time of
A fourth step of estimating an SOC value after the outflow time of the bypass current based on the SOC-OCV characteristic information from the OCV value estimated in the third step;
SOC estimation method characterized by including. SOC estimation for estimating a state of charge (hereinafter referred to as “SOC”) of a secondary battery (hereinafter referred to as “cell”) which is connected to a bypass circuit having a known resistance value and flows a bypass current to the bypass circuit to perform cell balancing. A method,
A first step of measuring a value of an open circuit voltage (hereinafter referred to as “OCV”) of the cell at the start of the flow of the bypass current and a flow time of the bypass current;
Based on the SOC-OCV characteristic information indicating the correspondence relationship between the SOC and OCV of the cell, and the OCV value at the start of the bypass current outflow, the OCV of the cell after the bypass current outflow starts. A second step of estimating the transition of value fluctuations;
A third step of estimating a transition of the bypass current value from the OCV value of the cell estimated in the second step, and integrating the bypass current value;
A fourth step of subtracting the integrated value integrated in the third step from the SOC value of the cell at the start of outflow of the bypass current to estimate the SOC value after the bypass current outflow time; ,
SOC estimation method characterized by including.   In the second step, the correspondence between the OCV value after the bypass current starts to flow and the bypass current flow time is mapped in advance from the fully charged state to the fully discharged state of the cell. 6. The SOC estimation method according to claim 4, wherein the OCV mapping information is read from the memory, and the transition of the fluctuation of the OCV value of the cell is estimated.

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