JP2008180692A - Electromotive force computing device and charge state estimation device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce an error in an electromotive force Ve of a secondary battery which is calculated based on a polarized voltage Vp. <P>SOLUTION: A polarized voltage computing part 214 acquires over a predetermined period a plurality of data pairs of a current I flowing through the secondary battery and a terminal voltage V of the secondary battery with respect to the current I, calculates an integrated quantity Q by integrating the acquired current I over the predetermined period, computes the polarized voltage Vp of the secondary battery from the integrated quantity Q. A no-load voltage computing part 212 computes a no-load voltage V0 on the basis of the plurality of data pairs. A subtractor 216 computes the electromotive force Ve of the secondary battery by subtracting the polarized voltage Vp from the no-load voltage V0. An electromotive force correcting part 217 performs correction with respect to a presently computed electromotive force Ve so that a change amount between a previously computed electromotive force Veb and the presently computed electromotive force Ve does not exceed a predetermined limiting value Vt. Further, a SOC estimating part 230 estimates the charge state of the secondary battery from the post-correction electromotive force Ve'. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an electromotive force calculation device that calculates an electromotive force of a secondary battery, and a charge state estimation device that estimates a charge state of the secondary battery based on the electromotive force of the secondary battery calculated by the electromotive force calculation device.

  An electric vehicle such as an electric vehicle (PEV) or a hybrid vehicle (HEV) that obtains a vehicle driving force by an electric motor is equipped with a secondary battery, and the electric motor is driven by electric power stored in the secondary battery. Such an electric vehicle has a function of braking by regenerative braking, that is, by causing the motor to function as a generator during vehicle braking and converting the kinetic energy of the vehicle into electric energy. The converted electric energy is stored in the secondary battery and reused for acceleration.

  If the secondary battery is overdischarged or overcharged, the battery performance is deteriorated. Therefore, it is necessary to grasp the state of charge (SOC) of the secondary battery and adjust the charging or discharging. In particular, in a hybrid electric vehicle of a type that can generate electric power by driving a generator with an on-board heat engine and charge the secondary battery, so that the secondary battery can accept regenerative power, Also, in order to be able to supply electric power to the motor as soon as requested, the state of charge is approximately in the middle between the fully charged state (100%) and the state where no charge is stored (0%) (50 ˜60%). In this case, it is desired to detect the SOC of the secondary battery more accurately.

  In Patent Document 1, a charge / discharge current for a secondary battery is measured, and the current value (having a minus sign for charging and a plus sign for discharging) is multiplied by a predetermined charging efficiency η, and the multiplied value is obtained. A method is disclosed in which the integrated capacity is calculated by integrating over a period of time, and the SOC is estimated based on the integrated capacity.

  In Patent Document 1, the accuracy of the estimated SOC is improved by correcting the charging efficiency η according to the electromotive force Ve of the secondary battery, but the SOC of the SOC is corrected by correcting the charging efficiency η in this way. In order to improve the accuracy, it is important to accurately calculate the electromotive force Ve as a correction parameter for the charging efficiency η.

  The electromotive force Ve is obtained, for example, as follows. That is, a plurality of pair data of the terminal voltage V and the charge / discharge current I of the secondary battery are acquired and stored in a predetermined period (for example, 60 sec), and a first-order approximation straight line (voltage) is obtained from the pair data by regression analysis. V-current I approximate line) is obtained, and the V intercept of the VI approximate line is obtained as the no-load voltage V0. Further, the integrated capacity Q is calculated by integrating the current I for a predetermined period, and the polarization voltage Vp of the battery is obtained based on the change amount ΔQ of the integrated capacity Q and the battery temperature T in the predetermined period, and from the no-load voltage V0. The electromotive force Ve is obtained by subtracting the polarization voltage Vp (see Patent Document 2).

  As described above, by calculating the electromotive force Ve in consideration of the polarization voltage Vp, the accuracy of the calculated electromotive force Ve can be improved. However, as shown in FIG. 2 of Patent Document 2, the polarization voltage Vp changes with a delay of several tens of seconds from the change amount ΔQ of the integrated capacitance. This delay also causes a time lag in the relationship between the no-load voltage V0 and the polarization voltage Vp. Therefore, if this time lag is not taken into account, an error occurs in the electromotive force Ve obtained by subtracting the polarization voltage Vp from the no-load voltage V0.

  Therefore, Patent Documents 1 and 2 disclose performing a process of correcting the time delay on the polarization voltage Vp in the step of calculating the electromotive force Ve.

JP 2003-197272 A JP 2003-197275 A Japanese Patent Laid-Open No. 2005-65482 JP 2000-323183 A JP 2003-149307 A

  However, as in Patent Documents 1 and 2, even when processing for correcting the time delay is performed on the polarization voltage Vp when calculating the electromotive force Ve, the correction is not sufficient, and the calculated electromotive force is calculated. An error may occur in Ve.

  An object of the present invention is to reduce an error in an electromotive force Ve of a secondary battery obtained by calculation.

  The electromotive force calculation device according to the present invention is based on the no-load voltage V0 representing the terminal voltage of the secondary battery when the current flowing through the secondary battery is zero, and the polarization voltage Vp of the secondary battery, When the change amount of the electromotive force Ve calculated this time with respect to the electromotive force Veb calculated last time exceeds a predetermined limit value Vt, the change amount is calculated. And an electromotive force correction unit that corrects the electromotive force Ve so as not to exceed the limit value Vt.

  In one aspect of the electromotive force calculation device according to the present invention, the electromotive force calculation unit obtains a set data of a current I flowing through the secondary battery and a terminal voltage V of the secondary battery corresponding to the current I. A plurality of data is acquired over a predetermined period, and a no-load voltage calculation unit that calculates the no-load voltage V0 by statistical processing based on the acquired plurality of sets of data, and the current I is integrated over the predetermined period. And a polarization voltage calculating unit that calculates the integrated voltage Q and calculates the polarization voltage Vp based on an integrated capacity change amount ΔQ that is a difference from the previous integrated capacity Q.

  In one aspect of the electromotive force calculation device according to the present invention, the electromotive force correction unit corrects the secondary battery by adding the limit value Vt to the electromotive force Veb when the secondary battery is charged. Is corrected by subtracting the limit value Vt from the electromotive force Veb during discharge.

  In one aspect of the electromotive force calculation device according to the present invention, the electromotive force correction unit includes the electromotive force Veb, a change amount ΔQ of the accumulated capacity Q of the secondary battery in the predetermined period, and a battery temperature of the secondary battery. The limit value Vt is set using at least one of the charged states of the secondary battery as a parameter.

  An electromotive force calculation device according to the present invention is calculated last time with an electromotive force calculation unit that time-wise calculates an electromotive force of a secondary battery whose charge or discharge is controlled so as to maintain a charged state within a predetermined allowable range. The electromotive force correction unit that corrects the electromotive force Ve so that the amount of change of the electromotive force Ve calculated this time relative to the electromotive force Veb does not exceed the limit value Vt set according to the state of charge of the secondary battery. And.

  The charging state estimation device according to the present invention is a charging state estimation device that estimates the charging state of the secondary battery based on the electromotive force of the secondary battery acquired from the electromotive force calculation device, and the change in the electromotive force When the amount exceeds the limit value Vt, the state of charge of the secondary battery is estimated based on the corrected electromotive force Ve ′, and when the amount of change in the electromotive force is within the limit value Vt, the electromotive force Ve The charging state of the secondary battery is estimated based on the above.

  According to the present invention, it is possible to reduce the error of the electromotive force Ve of the secondary battery obtained by calculation.

  In addition, according to one aspect of the present invention, an electromotive force Ve calculated based on the no-load voltage V0 and the polarization voltage Vp does not exceed an allowable change amount based on the previous electromotive force Veb. Make corrections. Thereby, the error of the electromotive force Ve caused by the time lag between the no-load voltage V0 and the polarization voltage Vp can be suppressed.

  An embodiment specifically showing the best mode for carrying out the present invention will be described with reference to the drawings, taking a hybrid electric vehicle as an example. In addition, although this embodiment demonstrates the hybrid electric vehicle which is one of the electric vehicles as an example, this embodiment is applicable also to the other electric vehicle provided with a motor generator as a drive source.

  FIG. 1 is a diagram illustrating a schematic configuration of a hybrid electric vehicle according to the present embodiment. In FIG. 1, a battery electronic control unit (hereinafter referred to as a battery ECU) 20 receives information such as battery voltage and battery temperature from the secondary battery 10 to estimate the SOC of the secondary battery 10 in a timely manner. Information such as the SOC, battery voltage, and battery temperature transmitted to the hybrid electronic control unit (hereinafter referred to as HV-ECU) 40 is transmitted. The HV-ECU 40 controls the inverter 50, the driving force distribution mechanism 56, and the engine 60.

  The secondary battery 10 is configured by connecting a plurality of battery blocks in series. Each battery block is configured by electrically connecting two battery modules in series, and each battery module is configured by electrically connecting six unit cells in series. In addition, the number of battery blocks, battery modules, and single cells is not particularly limited. The configuration of the secondary battery is not limited to the above example. Specifically, the secondary battery 10 is a nickel metal hydride secondary battery, a lithium ion secondary battery, or the like.

  Secondary battery 10 is connected to motor generator (M / G) 52 via relay 38 and inverter 50. The motor generator 52 is connected to an engine (internal combustion engine) 60 via a driving force distribution mechanism 56 including a planetary gear mechanism.

  Further, the temperature sensor 32 is provided in at least one location of the secondary battery 10 and detects the battery temperature Tb of a predetermined portion of the secondary battery 10. In the case where a plurality of temperature sensors 32 are provided, the temperature sensors 32 are arranged, for example, one for each group with a plurality of battery blocks having relatively close temperatures as one group. Or you may arrange | position one for every battery block with a comparatively temperature difference. The grouping or selection of the battery blocks to be detected may be performed by measuring the temperature of each battery block by a prior experiment or the like.

  Moreover, the voltage sensor 34 is provided for every battery block, and detects the terminal voltage Vb of each battery block. Furthermore, the current sensor 36 detects the charge / discharge current I flowing through the secondary battery 10.

  The temperature data Tb (n), terminal voltage data Vb (n), and current data I (n) output from the temperature sensor 32, the voltage sensor 34, and the current sensor 36 are respectively stored at a predetermined sampling period (for example, 100 msec). Input to the ECU 20, the battery ECU 20 estimates the SOC of the secondary battery 10 based on each data input from each sensor.

  Next, the configuration of the battery ECU 20 in the present embodiment will be described using the functional block diagram shown in FIG.

  The voltage measuring unit 202 measures the terminal voltage Vb of each battery block detected by each voltage sensor 34 as terminal voltage data Vb (n) at a predetermined sampling period (for example, 100 msec), and the terminal voltage data of each battery block. The voltage data V (n) of the secondary battery 10 is measured by summing Vb (n). The current measurement unit 204 calculates the charge / discharge current of the secondary battery 10 detected by the current sensor 36 as current data I (n) (a sign indicates whether it is a charge direction or a discharge direction) at a predetermined sampling period (for example, 100 msec). ) To measure. The temperature measuring unit 206 measures a representative value (for example, an average value) of the temperature data Tb (n) detected by each temperature sensor 32 as the temperature data T (n) of the secondary battery 10.

  The electromotive force calculation unit 210 includes a set data selection unit 211 for calculating the no-load voltage V0, a no-load voltage calculation unit 212, and a no-load voltage determination unit 213, and further a polarization for calculating the polarization voltage Vp. A voltage calculation unit 214 is included.

  The voltage data V (n) from the voltage measurement unit 202 and the current data I (n) from the current measurement unit 204 are input to the set data selection unit 211 as set data. In the group data selection unit 211, as the selection condition, the value of the current data I (n) in the charging direction (−) and the discharging direction (+) is within a predetermined range (for example, ± 50 A), and the charging direction and the discharging direction. The number of current data I (n) at a predetermined number is greater than or equal to a predetermined number (for example, 10 out of 60 samples), and the amount of change ΔQ of the accumulated capacity during the acquisition of set data is within a predetermined range (for example, 0.3 Ah) If it is determined that the group data of the voltage data V (n) and the current data I (n) is valid, the group data S (V (n), I (n)) is selected by selecting them. Is output as

  The effective set data S (V (n), I (n)) output from the set data selection unit 211 is input to the no-load voltage calculation unit 212. In the no-load voltage calculation unit 212, as shown in FIG. 3, the primary voltage-current straight line is obtained from the effective set data S (V (n), I (n)) by statistical processing using the least square method. An (approximate straight line) is obtained, and a no-load voltage V0 that is a voltage value (voltage (V) intercept) when the current is zero is calculated.

  The no-load voltage V0 output from the no-load voltage calculation unit 212 is then input to the no-load voltage determination unit 213. In the no-load voltage determination unit 213, as a determination condition, a dispersion value of the set data S (V (n), I (n)) with respect to the approximate straight line is obtained, and the dispersion value is within a predetermined range or approximate. A correlation coefficient between the straight line and the set data S (V (n), I (n)) is obtained, and when the correlation coefficient is equal to or greater than a predetermined value, it is determined that the calculated no-load voltage V0 is valid. And output.

  In addition, the calculation method of the no-load voltage V0 in the no-load voltage calculation part 212 is not limited to said method.

  On the other hand, the polarization voltage calculation unit 214 calculates the polarization voltage Vp of the secondary battery 10. As shown in FIG. 4A, the polarization voltage Vp gradually increases, for example, when charging of the secondary battery 10 with a constant current is continued. Head to. That is, the polarization voltage Vp has a minus sign with respect to the polarization generation component Vpo that is a component from the start to the end of charging with a constant current and the polarization decay component Vpd that is a component after the stop of charging (the polarization generation component Vpo). ). In FIG. 4A, the voltage Vir indicates a voltage generated by the internal resistance of the secondary battery 10 when charging of the secondary battery 10 with a constant current is started. In addition, when the secondary battery 10 is continuously discharged with a constant current, the change with time of the voltage is substantially contrasted with respect to the horizontal axis of FIG.

  Therefore, for example, the polarization voltage calculation unit 214 calculates a polarization generation component Vpo and a polarization decay component Vpd, and calculates the polarization voltage Vp by adding them.

  The charge / discharge control of the secondary battery 10 mounted on the hybrid electric vehicle is not actually a constant current, but is repeatedly charged or discharged in a short time. Therefore, the polarization generating component Vpo is approximately within a certain time. Since the integration amount of the charge / discharge current I is multiplied by a coefficient h and limited by a certain value, the polarization voltage calculation unit 214 calculates the polarization generation component Vpo by the following equation (1).

Vpo = h × ∫I (1)
Here, h is a polarization voltage generation coefficient calculated based on a function f (T) obtained in advance by experiments or the like using the battery temperature as a parameter, and ∫I is a current integration of current data I (n). The value, that is, the integrated capacity Q is shown.

  In general, as shown in FIG. 4B, the polarization attenuation component Vpd of the battery includes n components (A1, A2,..., An) from a component that attenuates in a short period to a component that attenuates in a long period. It is synthesized. Here, since the polarization decay rate of each component is represented by exp (−t / Tn), the polarization decay rate of the polarization voltage obtained by synthesizing each component is represented by the following equation (2).

Polarization decay rate = A1 × exp (−t / T1) + A2 × exp (−t / T2) + A3 × exp (−t / T3) +... + Anex (−t / Tn) (2)
Here, (A1, A2,... ・ An)> 0 and A1 + A2 +... + An = 1. Further, A1 to An and T1 to Tn are values obtained in advance through experiments or the like based on battery characteristics. Furthermore, t indicates the elapsed time since the end of charging or discharging of the secondary battery 10.

  Since the polarization voltage attenuates with respect to the polarization voltage generated during charging or discharging, the polarization attenuation component Vpd can be calculated by the following equation (3).

  Vpd = Vpo × (A1 × exp (−t / T1) + A2 × exp (−t / T2) + A3 × exp (−t / T3) +... + Anexp (−t / Tn)) (3)

  As described above, the polarization voltage calculation unit 214 calculates the polarization generation component Vpo and the polarization decay component Vpd on the basis of the expressions (1) and (3), and then adds them to obtain the polarization voltage Vp ( = Vpo + Vpd).

  In addition to the above calculation method, the polarization voltage calculation unit 214 may calculate the polarization voltage Vp as follows, for example.

  That is, the polarization voltage calculation unit 214 calculates the current integrated capacity Q based on the current integration in a predetermined period (for example, 60 sec) of the current data I (n) input from the current measurement unit 204, and the previous predetermined period. A change amount ΔQ of the integrated capacity, which is a difference from the integrated capacity Q in (for example, 60 sec), is obtained. Next, the polarization voltage calculation unit 214 is based on the temperature data T (n) from the characteristic curve or expression of the polarization voltage Vp with respect to the change amount ΔQ of the integrated capacity, using the temperature as a parameter, which is stored in advance in the reference table (LUT). A polarization voltage Vp is calculated. FIG. 5 shows a characteristic curve of the polarization voltage Vp with respect to ΔQ when the temperature is 25 ° C. FIG. 5 shows only a characteristic curve at 25 ° C., but actually, for example, in the case of a hybrid electric vehicle application, there is a characteristic curve that can cover a range from −30 ° C. to + 60 ° C. It is stored in the LUT as reference data.

  In addition, the calculation method of the polarization voltage Vp in the polarization voltage calculating part 214 is not limited to said method.

  After calculating the polarization voltage Vp as described above, the polarization voltage calculation unit 214 performs time delay processing on the calculated polarization voltage Vp, performs timing adjustment with the no-load voltage V0, and then calculates the polarization voltage Vp. Output. As will be described later, in the present embodiment, when the time delay process is not sufficiently performed in the polarization voltage calculation unit 214 and a time lag occurs between the no-load voltage V0 and the polarization voltage Vp, the calculation is performed based on these. The error of the generated electromotive force Ve is suppressed.

  The subtractor 216 outputs an electromotive force Ve obtained by subtracting the polarization voltage Vp output from the polarization voltage calculation unit 214 from the no-load voltage V0 output from the no-load voltage determination unit 213. The electromotive force Ve output from the subtractor 216 is input to the electromotive force correction unit 217.

  The electromotive force correction unit 217 corrects the electromotive force Ve so as to suppress an error generated in the electromotive force Ve due to a time lag between the no-load voltage V0 and the polarization voltage Vp, and the corrected electromotive force Ve ′. Is output.

  FIG. 6 is a diagram showing the relationship between the SOC and the electromotive force Ve when a nickel metal hydride battery is used as the secondary battery 10. As shown in FIG. 6, the amount of change in electromotive force Ve depends on the amount of change in SOC. For example, in the case of a hybrid electric vehicle, the charging or discharging of the secondary battery 10 is controlled while maintaining the SOC in an intermediate region indicating a predetermined allowable range. As shown in FIG. Is small. Therefore, for example, although the SOC is around 50%, a sudden increase or decrease in electromotive force rarely occurs in normal control. Therefore, for example, even though the SOC is around 50%, the current electromotive force Ve calculated after a relatively short period (for example, 60 sec) is too large compared to the electromotive force Veb calculated last time. In other words, when the amount of change in electromotive force is too large, the calculated electromotive force Ve may contain a lot of errors.

  Therefore, in the present embodiment, in consideration of the relationship between the SOC and the electromotive force as described above, the electromotive force correction unit 217 includes the previous electromotive force Veb stored in the previous electromotive force storage unit 218 and the current electromotive force. Ve is compared, and if the change amount is larger than the predetermined change limit value Vt, the change amount from the previous electromotive force Veb is limited to the change limit value Vt.

  More specifically, on the charging side, if the absolute value (| Ve−Veb |) of the value obtained by subtracting the previous electromotive force Veb from the electromotive force Ve exceeds the change limit value Vt, the corrected electromotive force Ve ′. Is Veb + Vt. On the other hand, if the absolute value (| Ve−Veb |) exceeds the change limit value Vt on the discharge side, the corrected electromotive force Ve ′ is set to Veb−Vt. If | Ve−Veb |) is within the change limit value Vt, the corrected electromotive force Ve ′ is set to Ve as it is. Here, the determination of whether the secondary battery is on the charging side or the discharging side may be made based on the current data I (n). That is, if the sign of the integrated value of the current data I (n) measured between the time when the previous electromotive force Veb is calculated and the time when the current electromotive force Ve is calculated is negative, the charge side is positive. If there is, it may be determined as the discharge side.

  Since the amount of change from the previous electromotive force Veb only needs to be limited to the change limit value Vt, the corrected electromotive force Ve ′ is always set to Veb + Vt on the charging side and the corrected electromotive force Ve ′ on the discharging side. May not be Veb−Vt.

  The allowable amount of change in electromotive force varies depending on the SOC value of the secondary battery 10 and the amount of change in SOC. Further, the SOC value has a correlation with the electromotive force, and the change amount of the SOC has a correlation with the change amount ΔQ of the integrated capacity Q. That is, the allowable amount of change in electromotive force depends on the magnitude of the previous electromotive force Veb and the amount of change ΔQ of the accumulated capacity Q from the time when the previous electromotive force Veb is calculated until the time when the current electromotive force Ve is calculated. Different. For this reason, the change limit value Vt is preferably changed according to the previous electromotive force Veb and the change amount ΔQ of the integrated capacity Q.

  Therefore, in the present embodiment, the electromotive force correction unit 217 determines the change limit value Vt based on a reference table (LUT) illustrated in FIGS. 7A and 7B. FIG. 7A is a reference table that is referred to during discharging, and FIG. 7B is a reference table that is referred to during charging. As shown in FIGS. 7A and 7B, the change limit value Vt is obtained using the magnitude of the previous electromotive force Veb and the change amount ΔQ as parameters. For example, in FIG. 7A, if the magnitude of the previous electromotive force Veb is between V5 and V6 and the change amount ΔQ is between 1.5 Ah and 2.0 Ah, the change limit value Vt at this time is 0.02 V. It becomes.

  Further, the assumed amount of change in electromotive force varies depending on the battery temperature. For example, the amount of change in electromotive force when SOC is high at low temperatures (−30 ° C.) is larger than the amount of change in electromotive force at normal temperatures (25 ° C.). Therefore, it is preferable to change the change limit value Vt also depending on the battery temperature. Therefore, as shown in FIG. 8, the magnitude of the previous electromotive force Veb corresponding to each change limit value Vt may be changed depending on the battery temperature. For example, when the battery temperature is 0 ° C. or higher, V5 in the reference table shown in FIG. 7A or 7B is set to 16.0V, V6 is set to 16.2V, and the battery temperature is −15 ° C. or higher and lower than 0 ° C. In this case, V5 is set to 16.1 and V6 is set to 16.4.

  As described above, the electromotive force correction unit 217 corrects the electromotive force Ve, and even if a time lag between the no-load voltage V0 and the polarization voltage Vp occurs, it is calculated based on these. The error of the electromotive force Ve can be suppressed.

  As described above, the amount of change in electromotive force Ve depends on the amount of change in SOC. Therefore, for example, a reference table (LUT) indicating the correlation between the SOC and the change limit value Vt is prepared in advance, and the change limit value Vt is set according to the SOC size with reference to the reference table. It doesn't matter.

  As described above, the electromotive force Ve ′ corrected and output by the electromotive force correction unit 217 is input to the previous electromotive force storage unit 218 and to the current integration coefficient correction unit 220. When a new electromotive force Ve ′ is input, the previous electromotive force storage unit 218 rewrites the currently stored previous electromotive force Veb to the newly input electromotive force Ve ′. Further, the current integration coefficient correction unit 220 determines a correction amount α for the current integration coefficient k in accordance with the electromotive force Ve ′. The correction amount α for the electromotive force Ve ′ is expressed by a linear expression, which is determined in consideration of the convergence of the system. The correction amount α obtained by the current integration coefficient correction unit 220 is added, subtracted or multiplied by the charging efficiency η output from the charging efficiency calculation unit 222 and the adder 224 to obtain a current integration coefficient k.

  The current integration coefficient k from the adder 224 is input to the SOC estimation unit 230. In the SOC estimation unit 230, the current data I (n) from the current measurement unit 204 is multiplied by the current integration coefficient k, and the remaining capacity SOC is estimated by current integration in a predetermined period.

  The estimated SOC value is input to the charging efficiency calculation unit 222. The charging efficiency calculation unit 222 calculates the temperature from the characteristic curve of the charging efficiency η with respect to the estimated SOC value using the temperature as a parameter. Based on the temperature data T (n) measured by the measuring unit 206, the charging efficiency η is calculated. Note that when the secondary battery 10 is in a discharged state, the charging efficiency η is fixed to 1, and when the secondary battery 10 is in a charged state, the charging efficiency η calculated by the charging efficiency calculating unit 222 is used. .

  As described above, each unit provided in the battery ECU 20 executes the process, so that the battery ECU 20 has the temperature data Tb (n) and the terminal voltage output from the temperature sensor 32, the voltage sensor 34, and the current sensor 36. The SOC of the secondary battery 10 is estimated based on the data Vb (n) and the current data I (n).

  Next, a processing procedure when the battery ECU 20 configured as described above estimates the SOC of the secondary battery will be described with reference to the flowchart of FIG. 9.

  In FIG. 9, first, voltage data V (n) and current data I (n) are measured as set data (S100). Next, in order to check whether or not the set data of the voltage data V (n) and current data I (n) measured in step S100 is valid set data, they are subjected to the selection conditions as described above. It is determined whether or not it is satisfied (S102). If the selection condition is not satisfied in the determination in step S102 (the determination result in step S102 is negative “N”), the process returns to step S100, and the set data of the voltage data V (n) and the current data I (n) is again obtained. taking measurement. On the other hand, if the selection condition is satisfied in the determination in step S102 (the determination result in step S102 is affirmative “Y”), a plurality (for example, 10 in each of the 60 samples in the charge and discharge directions) valid set data. S (V (n), I (n)) is acquired (S104).

  Next, a primary approximate straight line (V-I straight line) is obtained from valid set data S (V (n), I (n)) by statistical processing using the least square method, and V of the approximate straight line is obtained. The intercept is calculated as no-load voltage V0 (S106). Next, in order to check whether or not the no-load voltage V0 is valid, it is determined whether or not the no-load voltage V0 satisfies the determination condition as described above (S108). If it is determined in step S108 that the determination condition is not satisfied (the determination result in step S108 is negative “N”), the process returns to step S104, and another plurality (for example, another 10 in 60 samples) is returned. Valid set data S (V (n), I (n)) is acquired, and steps S104 and S106 are repeated. On the other hand, if it is determined in step S108 that the calculated no-load voltage V0 satisfies the determination condition (the determination result in step S108 is affirmative “Y”), the calculated no-load voltage V0 is employed in the calculation of the electromotive force Ve.

  Next, the accumulated capacity Q in the past predetermined period (for example, 60 sec) is calculated from the current data I (n) measured in step S100, and the polarization voltage Vp is calculated based on the accumulated capacity Q as described above. (S110). Next, the electromotive force Ve is calculated by subtracting the polarization voltage Vp from the no-load voltage V0 (S112), and the electromotive force Ve is corrected (S114).

  Here, the procedure of the electromotive force Ve correction process will be further described with reference to the flowchart shown in FIG.

  First, it is determined whether or not the electromotive force Ve has been calculated by determining whether or not the Ve flag is on (S200). Here, the Ve flag is a flag that is turned on when the electromotive force Ve is calculated. As described above, in order to calculate the electromotive force Ve, it is necessary to calculate the no-load voltage V0. The no-load voltage V0 is obtained by statistical processing using pair data of a plurality of terminal voltages V and currents I. It is done. That is, the no-load voltage V0 is not always calculated. Therefore, first, it is determined whether or not the Ve flag is on. If the Ve flag is off (determination result in step S200 is negative “N”), the process ends.

  On the other hand, if the Ve flag is on (the determination result of step S200 is affirmative “Y”), then whether or not the electromotive force Ve to be corrected is the electromotive force calculated first after turning on the ignition switch. Is determined (S202). If it is the first as a result of the determination (the determination result in step S202 is affirmative “Y”), the previous electromotive force Ve does not exist, so the electromotive force Ve is not corrected (S214), and the process is terminated.

  On the other hand, if it is not the first (the determination result in step S202 is negative “N”), as described above, based on the magnitude of the previous electromotive force Veb, the change amount ΔQ of the integrated capacity Q, and the temperature data T (n), A change limit value Vt is set (S204).

  Next, it is determined whether or not the absolute value (| Ve−Veb |) of the value obtained by subtracting the previous electromotive force Veb from the electromotive force Ve exceeds the change limit value Vt (S206). The process is terminated without correcting the electromotive force Ve (S214).

  On the other hand, if the change limit value Vt is exceeded, the electromotive force Ve is determined whether the secondary battery 10 is calculated at the time of discharging or at the time of charging (S208). The electric power Ve ′ is set to Veb−Vt (S210). If it is during charging, the corrected electromotive force Ve ′ is set to Veb + Vt (S212).

  As described above, after obtaining the corrected electromotive force Ve ′, the previous electromotive force Veb stored in the previous electromotive force storage unit 218 is replaced with the corrected electromotive force Ve ′, thereby changing the previous electromotive force Veb. Update (S216), and the correction process of the electromotive force Ve ends.

  Returning to FIG. 9, after the electromotive force Ve correction processing is performed as described above, the correction amount α for the current integration coefficient k is calculated according to the electromotive force Ve ′ after correction (S116). Further, based on the measured temperature data T (n), the charging efficiency η is calculated from the currently estimated SOC estimated value (S118). Next, the current integration coefficient k is calculated by adding the correction amount α obtained in step S118 and the charging efficiency η obtained in step S120 (S120). Finally, the current integration coefficient k is multiplied by the current data I (n), and the SOC is estimated by current integration over a predetermined period (122).

  As described above, according to this embodiment, the electromotive force Ve obtained by subtracting the polarization voltage Vp from the no-load voltage V0 does not exceed an allowable change amount based on the previous electromotive force Veb. Make corrections. Thereby, the error of the electromotive force Ve caused by the time lag between the no-load voltage V0 and the polarization voltage Vp can be suppressed. Therefore, it is possible to improve the accuracy of the SOC estimated based on the electromotive force Ve.

  In the above-described embodiment, the case where the SOC is estimated based on the calculated electromotive force has been described as an example. However, the electromotive force may be used for purposes other than the parameters used when estimating the SOC.

It is a figure which shows schematic structure of the hybrid electric vehicle which concerns on this embodiment. It is a figure which shows the functional block of battery ECU which concerns on this embodiment. It is a figure which shows the set data of voltage data and current data in this embodiment, and the approximate straight line for calculating | requiring a no-load voltage by statistical processing from it. It is a figure for demonstrating the calculation method of the polarization voltage Vp of a secondary battery. It is a figure for demonstrating the calculation method of the polarization voltage Vp of a secondary battery. It is a figure which shows an example of the characteristic curve of the polarization voltage p with respect to variation | change_quantity (DELTA) Q which used temperature as the parameter in this embodiment. It is a figure which shows the relationship between the electromotive force of a secondary battery, and SOC. It is a figure which shows an example of the reference table at the time of the discharge referred when determining the change limiting value Vt. It is a figure which shows an example of the reference table at the time of charge referred when determining the change limiting value Vt. It is a figure which shows an example of the reference table referred when setting the magnitude | size of the last electromotive force Veb corresponding to each change limitation value Vt. In this embodiment, it is a flowchart which shows the process sequence performed when battery ECU estimates SOC of a secondary battery. In this embodiment, it is a flowchart which shows the process sequence performed when battery ECU correct | amends an electromotive force.

Explanation of symbols

  10 secondary battery, 20 battery ECU, 32 temperature sensor, 34 voltage sensor, 36 current sensor, 38 relay, 50 inverter, 52 motor generator, 56 driving force distribution mechanism, 60 engine, 202 voltage measurement unit, 204 current measurement unit, 206 Temperature measurement unit, 210 Electromotive force calculation unit, 211 Set data selection unit, 212 No load voltage calculation unit, 213 No load voltage determination unit, 214 Polarization voltage calculation unit, 216 Subtractor, 217 Electromotive force correction unit, 218 Power storage unit, 220 current integration coefficient correction unit, 222 charge efficiency calculation unit, 224 adder, 230 SOC estimation unit.

Claims (6)

Based on the no-load voltage V0 representing the terminal voltage of the secondary battery when the current flowing through the secondary battery is zero and the polarization voltage Vp of the secondary battery, the electromotive force of the secondary battery is measured in time. An electromotive force calculation unit to calculate,
When the change amount of the electromotive force Ve calculated this time with respect to the electromotive force Veb calculated last time exceeds a predetermined limit value Vt, the electromotive force Ve is corrected so that the change amount does not exceed the limit value Vt. A power correction unit;
An electromotive force calculation device comprising: In the electromotive force calculation apparatus according to claim 1,
The electromotive force calculator is
Statistical data based on the plurality of set data obtained by acquiring a plurality of set data of the current I flowing through the secondary battery and the terminal voltage V of the secondary battery corresponding to the current I over a predetermined period A no-load voltage calculation unit for calculating the no-load voltage V0 by:
A polarization voltage calculation unit that calculates the integrated capacity Q by integrating the current I over the predetermined period, and calculates the polarization voltage Vp based on an integrated capacity change amount ΔQ that is a difference from the previous integrated capacity Q; ,
An electromotive force calculation device comprising: In the electromotive force calculation apparatus according to claim 1 or 2,
The electromotive force correction unit is
When the secondary battery is charged, it is corrected by adding the limit value Vt to the electromotive force Veb,
When the secondary battery is discharged, correction is performed by subtracting the limit value Vt from the electromotive force Veb.
An electromotive force calculation apparatus characterized by that. In the electromotive force calculating device according to any one of claims 1 to 3,
The electromotive force correction unit is
The limit value Vt is set using at least one of the electromotive force Veb, the change amount ΔQ of the accumulated capacity Q of the secondary battery during the predetermined period, the battery temperature of the secondary battery, and the charge state of the secondary battery as parameters. To
An electromotive force calculation apparatus characterized by that. An electromotive force calculation unit that timely calculates an electromotive force of a secondary battery in which charging or discharging is controlled so as to maintain a charged state within a predetermined allowable range;
An electromotive force that corrects the electromotive force Ve so that a change amount of the electromotive force Ve calculated this time with respect to the electromotive force Veb calculated previously does not exceed a limit value Vt that is set according to a charge state of the secondary battery. A power correction unit;
An electromotive force calculation device comprising: A charging state estimation device that estimates a charging state of the secondary battery based on an electromotive force of the secondary battery acquired from the electromotive force calculation device according to any one of claims 1 to 5,
When the amount of change in the electromotive force exceeds the limit value Vt, the state of charge of the secondary battery is estimated based on the corrected electromotive force Ve ′,
When the amount of change in the electromotive force is within the limit value Vt, the state of charge of the secondary battery is estimated based on the electromotive force Ve.
The charge state estimation apparatus characterized by the above-mentioned.

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