JP2007292666A - Device for estimating charged state of secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To precisely estimate a state of charge (SOC) of a battery on the basis of estimation of its open voltage considering a polarization electromotive voltage, based on detected state quantities (current, voltage, temperature, etc.) of the battery. <P>SOLUTION: At usual time excluding a period being in a small current state after the generation of a large current, a battery ECU estimates a polarization electromotive voltage reflecting a charge discharge history by serially using estimated polarization electromotive voltage values up to the present time (S260, S270). Meanwhile, in the period being in the small current state just after the generation of the large current, the polarization electromotive voltage is estimated on the basis of a battery current in the large current state, a battery temperature, and a present battery current without using, for calculation, estimated polarization electromotive voltage values in the past (S280). Thereby, the change speed of the polarization electromotive voltage becomes a rapid one unlike in a usual case, and generation of an SOC estimation error resulting from an error of estimation of the polarization electromotive voltage can be prevented, in the small current state just after the generation of the large current. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a state-of-charge estimation device for a secondary battery, and more specifically, based on an estimation of an open-circuit voltage in consideration of a polarization electromotive voltage inside the secondary battery, the state of charge of the secondary battery (hereinafter referred to as SOC: The present invention also relates to a secondary battery charge state estimation device that estimates a state of charge).

  2. Description of the Related Art Conventionally, a charging state estimation device that estimates a charging state (SOC) of a secondary battery (hereinafter also simply referred to as a battery) is known. This device generally employs a method of detecting SOC by integrating discharge currents from full charge. For example, in a hybrid vehicle equipped with a generator based on engine output, the SOC of the battery is maintained at about 50%. Therefore, the battery is not fully charged for a long period of time. As a result, the integration error may increase by integrating the charging / discharging current of the battery for a long period of time. For this reason, it is difficult to apply SOC estimation based only on current integration to a battery mounted on a hybrid vehicle in which charge / discharge control as described above is performed.

  On the other hand, the voltage drop inside the battery can be calculated by multiplying the charge / discharge current of the battery and the internal resistance, and the battery electromotive voltage can be detected by subtracting this voltage drop from the battery voltage. For this reason, the open circuit voltage (OCV) of the battery is accurately estimated based on the state quantity (typically, voltage, current, temperature) of the battery detected by the sensor, and the estimated open circuit voltage is used. A method of detecting the state of charge (SOC) of the battery is used.

  Here, in the battery, an electromotive force is generated by a change in each part of the electrode active material in each battery cell. However, the chemical reaction of the electrode active material is likely to occur near the surface, but the reaction inside the electrode is not diffused. Delay time occurs. Therefore, it is known that due to the imbalance (polarization) between the inside of the electrode and the surface portion, a difference in electromotive force occurs even with the same SOC. And the voltage change resulting from this polarization is a dynamic thing considered to be eliminated as time passes. Therefore, a configuration has been proposed in which the SOC estimation accuracy is improved by estimating the open circuit voltage of the battery in consideration of such a polarization electromotive voltage (for example, Patent Documents 1 to 4).

  In particular, in the charge state detection device disclosed in Patent Document 1 (Japanese Patent Laid-Open No. 2000-258514), the polarization value f {corresponding to the current battery current is based on the current dependency of the polarization electromotive voltage obtained in advance. i (t)} is sequentially obtained at each time point, and the polarization value Vdyn reflecting the past charge / discharge history is obtained by temporally integrating the sequentially obtained polarization value after attenuation in the time axis direction. Is calculated. The calculated polarization electromotive voltage Vdyn is used to estimate the open circuit voltage and the SOC.

Moreover, in the charge state detection apparatus disclosed in Patent Document 2 (Japanese Patent Laid-Open No. 2003-68370), the polarization value at each time point in Patent Document 1 is calculated based on the battery current and the battery temperature. It is disclosed.
JP 2000-258514 A JP 2003-68370 A JP 2004-93551 A JP 11-346444 A

  As described above, in the battery charge state detection devices disclosed in Patent Documents 1 and 2, the polarization value corresponding to the current battery state amount (current, temperature) is sequentially calculated, and the polarization value calculated at each time point is calculated. Is attenuated by a constant time constant, and time axis integration is performed to estimate the polarization electromotive voltage reflecting the past charge / discharge history. Generally, this time constant is obtained experimentally so as to correspond to the rate of change of the polarization electromotive voltage in an average current state. In particular, Patent Document 2 (Japanese Patent Application Laid-Open No. 2003-68370) discloses a time constant of decay when time-integrating the polarization value calculated at each time point in order to improve the estimation accuracy of the polarization electromotive voltage at a low battery temperature. It is disclosed that the estimation accuracy of the polarization electromotive force is improved by setting a plurality of each of the battery components and using the average value of the polarization electromotive force calculated according to the plurality of time constants.

  However, in the polarization electromotive force estimation disclosed in Patent Documents 1 and 2, a constant time constant is used for estimation calculation by time integration regardless of the current state. For this reason, it is difficult to reflect a sudden change in the polarization electromotive voltage at the time of sudden current change in the estimation calculation.

  In particular, in the small current state immediately after the end of the large current discharge, the change in the polarization electromotive voltage becomes more rapid than in the normal current state, whereas in the estimation calculation, the polarization electromotive voltage estimated during the large current discharge is the above-described value. It will affect the subsequent estimation of the polarization voltage according to a certain time constant. Therefore, in such a case, an estimation error due to time integration may cause an estimation error of the polarization electromotive voltage, which may reduce the accuracy of estimation of the open circuit voltage (OCV) and thus the state of charge (SOC).

  The present invention has been made to solve such problems, and an object of the present invention is to charge based on the detected state quantity (current, voltage, temperature, etc.) of the secondary battery (battery). The state (SOC) estimation is to prevent the occurrence of an SOC estimation error due to an estimation error of the polarization electromotive voltage immediately after the generation of a large current.

  The secondary battery state of charge estimation device according to the present invention comprises a state quantity acquisition means, a large current state detection means, a small current state detection means, a polarization induced voltage estimation means, an internal resistance estimation means, and an open circuit voltage detection means. And charging state estimation means. The state quantity acquisition unit is configured to acquire the current voltage, current, and temperature of the secondary battery. The large current state detection means is configured to detect a large current state where the current of the secondary battery is equal to or greater than a predetermined current. The small current state detection is configured to detect that a small current state in which the current is equal to or less than a predetermined value is detected immediately after the large current state. The polarization electromotive force estimation means is configured to estimate the polarization electromotive voltage of the secondary battery based on the charge / discharge history of the secondary battery up to the present time. The internal resistance estimation means is configured to estimate the internal resistance of the secondary battery based on at least the temperature acquired by the state quantity acquisition means. The open circuit voltage detection means is based on the voltage and current acquired by the state quantity acquisition means, the internal resistance estimated by the internal resistance estimation means, and the polarization induced voltage estimated by the polarization induced voltage estimation means. Configured to detect an open circuit voltage. The charge state estimation means is configured to estimate the charge state of the secondary battery using the open circuit voltage detected by the open circuit voltage detection means. The polarization electromotive force estimation means includes first estimation means, prohibition means, and second estimation means. The first estimating means sequentially estimates the current polarization electromotive voltage based on the estimated value of the polarization electromotive voltage up to the present time and at least the current of the state quantity obtained by the state quantity obtaining means. Composed. The prohibiting means is configured to prohibit the estimation of the polarization electromotive force by the first estimating means in the small current state immediately after the large current state. The second estimating means estimates the current polarization electromotive force based on the current in the large current state without using the estimated value of the polarization electromotive voltage up to the present time when the estimation by the first estimating means is prohibited. Composed.

  According to the state of charge estimation device for a secondary battery described above, in normal times, the polarization electromotive force reflecting the charge / discharge history is estimated by sequentially using the estimated value of polarization electromotive voltage up to the present time, while immediately after the large current state. In the small current state, the polarization electromotive force is estimated independently of the immediately preceding estimated value of the polarization electromotive voltage, which has changed greatly due to the large current. As a result, in the small current state immediately after the large current state, the change in the polarization induced voltage becomes abrupt than usual. By using the estimated value of the polarization induced voltage thus far, the estimation error of the polarization induced voltage increases. Can be prevented. As a result, it is possible to prevent the occurrence of an estimation error of the state of charge (SOC) due to the estimation error of the polarization electromotive voltage in the above case.

  Preferably, the prohibiting means performs the estimation by the first estimating means in response to the lapse of a predetermined time from the end of the small current state or the start of the small current state in the small current state immediately after the large current state. Configured to lift the prohibition.

  According to such a configuration, when the small current state immediately after the large current state ends or when such a small current state continues for a predetermined time or more, the rapid change of the polarization electromotive voltage is suppressed. Therefore, it is possible to resume the estimation of the polarization electromotive force by successively using the past estimated value of the polarization electromotive force by the first estimating means. Therefore, after the rapid change of the polarization electromotive voltage in the small current state immediately after the large current state is subsided, the polarization electromotive voltage can be estimated again with high accuracy.

  More preferably, the first estimating means, when the prohibition of the estimation by the prohibiting means is canceled, the estimated value of the polarization electromotive voltage by the second estimating means immediately before and the state quantity acquired by the state quantity acquiring means Is configured to estimate a current polarization electromotive voltage based on at least the current.

  According to such a configuration, since the initial value of the polarization electromotive voltage estimated value when the estimation by the first estimating means is resumed can be appropriately set, the subsequent polarization electromotive voltage is accurately estimated. be able to.

  Further preferably, the second estimating means is configured to estimate the current polarization electromotive voltage based on the current and temperature acquired by the state quantity acquiring means in addition to the current in the large current state.

  According to such a configuration, the polarization electromotive voltage in the small current state immediately after the large current state can be estimated with high accuracy based on the current in the large current state and the current current and temperature.

  Preferably, the predetermined current used by the high current state detecting means for detecting the large current state is variably set according to the temperature of the secondary battery so that the predetermined current is set to be relatively small at a low temperature of the secondary battery. .

  According to such a configuration, a rapid change in the polarization electromotive voltage in the small current state immediately after the large current state is relatively likely to occur at the low temperature of the secondary battery, that is, at the low temperature of the secondary battery, Considering that it is necessary to consider the current region relatively lower than that at room temperature as the above-mentioned large current state, the estimation error of the polarization electromotive voltage is reduced to the small current state immediately after the large current state at the low temperature of the secondary battery. Can be prevented from increasing.

  Preferably, in the secondary battery state of charge estimation apparatus, the secondary battery is constituted by a lithium ion battery.

  According to such a configuration, since the secondary battery is composed of a lithium ion battery having a high correlation between the state of charge (SOC) and the open circuit voltage, it is possible to improve the estimation accuracy of the circuit voltage by improving the estimation accuracy of the polarization electromotive voltage. The effect of improving the estimation accuracy of the state of charge (SOC) is high. That is, the state of charge estimation device for a secondary battery according to the present invention is suitable for application to a lithium ion battery.

  According to the state of charge estimation device for a secondary battery according to the present invention, in the state of charge (SOC) estimation based on the detected state quantity (current, voltage, temperature, etc.) of the secondary battery (battery), immediately after the occurrence of a large current It is possible to prevent the occurrence of an SOC estimation error due to the estimation error of the polarization electromotive voltage at.

  Embodiments of the present invention will be described below in detail with reference to the drawings. In the following, the same or corresponding parts in the drawings are denoted by the same reference numerals, and the description thereof will not be repeated in principle.

(Description of overall system configuration example)
FIG. 1 is a block diagram showing a configuration of a system in which a battery charge state estimation device according to an embodiment of the present invention is applied to a hybrid vehicle.

  The battery 10 includes a large number of battery cells. Typically, the battery 10 is composed of a lithium ion battery. As is well known, a lithium ion battery has a high correlation between the SOC and the open circuit voltage (OCV). Therefore, as shown in FIG. 2, by measuring the open circuit voltage Vocv with respect to the SOC in advance, based on the open circuit voltage Vocv estimated based on the state quantity (current, voltage, temperature, etc.) of the battery 10, Can be estimated. Thus, the battery state-of-charge estimation device according to the embodiment of the present invention is suitable for estimating the state of charge of a lithium ion battery having a high correlation between the SOC and the open circuit voltage. However, SOC estimation based on open circuit voltage (OCV) estimation including polarization electromotive voltage estimation is also applied to other types of batteries, such as nickel metal hydride batteries, where the correlation between SOC and open circuit voltage is not as high as that of a lithium ion battery. By combining with other SOC estimation methods such as SOC estimation based on charge / discharge current integration, it is possible to apply the battery charge state estimation device according to the embodiment of the present invention.

  The voltage for each block of the battery 10 and the overall voltage are measured by the voltage detector 12 and supplied to a battery ECU (Electronic Control Unit) 14. Hereinafter, this entire voltage Vb is referred to as a battery voltage Vb. The voltage for each block can also be used for detection of overdischarge in each battery cell.

  The battery ECU 14 is further connected with a temperature sensor 16 that detects the battery temperature Tb and a current detector 18 that detects the battery current Ib. The battery temperature Tb and the battery current Ib are also input to the battery ECU 14. In addition, about the battery temperature Tb, you may arrange | position the temperature sensor 16 in multiple places (for example, one or more arrangement | positioning for every block). The battery current Ib is defined as Ib> 0 during discharge and Ib <0 during discharge.

  The battery ECU 14 detects the state of charge (SOC) of the battery 10 on the basis of the battery voltage Vb, the battery current Ib, and the battery temperature Tb, which are battery state quantities input from the detectors and sensors, and sends this to the HVECU 20. Supply.

  The HVECU 20 controls the load 22 in accordance with a torque command determined based on information such as the accelerator opening, the brake depression amount, and the vehicle speed. The load 22 includes, for example, an inverter and a motor (not shown). In such a configuration, the DC power from the battery 10 is converted into AC power by the inverter to drive the motor. By controlling the operation of the inverter by the control signal from the HVECU 20, it is possible to output torque that matches the torque command from the motor. In particular, regenerative braking by the motor is also performed by controlling the switching of the inverter so that the motor outputs torque in the direction opposite to the current rotational direction by a control signal from the HVECU 20. The power generated by the regenerative braking of the motor can be converted into DC power by an inverter and used for charging the battery 10.

  Note that the hybrid vehicle equipped with the battery state of charge estimation device according to the present embodiment is equipped with an engine (not shown) and an engine-driven generator (not shown). While being able to charge, you may be comprised so that a motor output shaft can be rotated with an engine. Further, the motor and the generator may be configured as a motor generator.

  The HVECU 20 controls the motor output, the engine output, and the like according to the SOC value of the battery 10 supplied from the battery ECU 14 so that the SOC of the battery 10 is close to the target value. When overdischarge of the battery cell (or out of the lower limit range of SOC) is detected, discharge from the battery 10 is prohibited, and overcharge of the battery cell (or out of the upper limit range of SOC) is detected. If this happens, discharging to the battery 10 is prohibited. For example, as illustrated in FIG. 2, the SOC is controlled with SOC = 50% as a target value and SOC = 20% and 80% as a lower limit and an upper limit, respectively.

(Description of SOC estimation method)
Below, SOC estimation of the battery 10 by battery ECU14 is demonstrated.

  Here, the current / voltage characteristics of the battery 10 are expressed by the following equation (1) using the internal resistance R of the battery 10.

Vb = Vo−Ib · R (1)
In the formula (1), Vo represents an electromotive voltage in the battery. The electromotive voltage Vo corresponds to the battery voltage Vb when the battery current Ib = 0.

  Here, since the internal resistance R has temperature dependence, it is necessary to correct according to the change of the battery temperature Tb. For example, a change in the internal resistance R with respect to the battery temperature Tb is experimentally measured in advance, and a map of the internal resistance R based on the measurement result is stored in the battery ECU 14 in advance. Accordingly, the battery ECU 14 can obtain the current internal resistance R by referring to the map based on the battery temperature Tb detected by the temperature sensor 16. In the following, SOC estimation for the entire battery 10 will be described. Therefore, when the temperature sensors 16 are arranged at a plurality of locations, the battery temperature Tb is defined by the average value of the detected temperatures by the plurality of sensors. Is done.

  There is a relationship as shown in FIG. 2 between the SOC and the open circuit voltage Vocv. Here, the open circuit voltage Vocv is expressed by the following equation (2) using the electromotive voltage Vo and the polarization electromotive voltage Vdyn.

Vo = Vocv + Vdyn (2)
Therefore, the following expression (3) is obtained from the expressions (1) and (2).

Vocv = Vb + Ib · R−Vdyn (3)
As described above, in a lithium ion battery, Vocv is shown as a function of SOC. In a nickel metal hydride battery or the like, Vocv is a voltage that depends on the SOC and the battery temperature Tb. Therefore, the SOC can be estimated by estimating the open circuit voltage Vocv.

  The polarization electromotive voltage Vdyn in the equations (2) and (3) is a dynamic voltage fluctuation due to the charge / discharge history. As described above, the battery 10 generates an electromotive force due to the chemical change of the electrode active material in each battery cell. However, the chemical reaction of the electrode active material is likely to occur near the surface and diffuses in the reaction inside the electrode. Due to the delay time. Therefore, due to the imbalance (polarization) between the inside of the electrode and the surface portion, there is a difference in electromotive force even with the same SOC. And the voltage change resulting from this polarization is dynamic which is considered to be resolved with time.

  For example, when the battery current Ib changes as shown in FIG. 3A, as shown in FIG. 3B, the electromotive voltage Vdyn due to polarization changes in the negative voltage direction due to the continuation of discharge, and the charging continues. Changes in the positive voltage direction. That is, when the battery current Ib> 0 (during discharging), the change amount of the polarization electromotive voltage Vdyn at that time is basically negative, and when the battery current Ib <0 (during charging), The amount of change in the polarization electromotive voltage Vdyn at is basically positive. Further, if a sufficient time has passed while the battery current Ib is constant, the polarization electromotive voltage Vdyn converges to a constant value that depends on the battery current Ib. Further, when the battery current Ib changes, the polarization electromotive voltage Vdyn changes greatly.

  Thus, the magnitude of the polarization electromotive voltage Vdyn is considered to be determined according to the past charge / discharge history. Further, the closer the time is, the greater the influence, and the larger the charge or discharge current amount, the greater the influence. Therefore, in this embodiment, the polarization electromotive voltage Vdyn is obtained by the following equation (4).

  In the equation (4), Vdyn (to) represents a polarization electromotive voltage at time t = to, and τ represents a time constant. As described above, the time constant τ is experimentally determined so as to correspond to the rate of change of the polarization electromotive voltage in the average current state. Further, fdyn {st (t)} indicates the dependence of the polarization electromotive voltage on the battery state quantity obtained in advance. As will be described below, the battery state quantity here includes at least the battery current Ib, and preferably includes both the battery current Ib and the battery temperature Tb. As shown in FIG. 3 and Patent Documents 1 and 2, if the battery current Ib remains constant and the time elapses sufficiently, the polarization electromotive voltage Vdyn converges to a constant value that depends on the battery current Ib. That is, fdyn {st (t)} corresponds to the convergence value of the polarization electromotive voltage Vdyn when a sufficient amount of time has passed with the current battery state quantity (at least the battery current Ib) being constant. Hereinafter, this fdyn is also referred to as a polarization value.

  According to the equation (4), similarly to Patent Documents 1 and 2, the polarization value fdyn (corresponding to f {i (t)} in Patent Documents 1 and 2) is sequentially estimated based on the current battery state quantity. By integrating the estimated polarization value fdyn along the time axis direction with attenuation by the time constant τ, the polarization electromotive voltage Vdyn (t0) at an arbitrary time point to can be obtained.

  Further, similarly to Patent Documents 1 and 2, in order to sequentially estimate the polarization electromotive force Vdyn by discrete data processing for each predetermined period Δt by a computer, the following expression (5) is obtained by discretizing expression (4). Is obtained.

  According to equation (5), if the initial value of the polarization electromotive voltage Vdyn is set, then the current polarization value fdyn {st (t0)} and the previous estimated value of the polarization electromotive voltage Vdyn are used. The current polarization electromotive voltage Vdyn (t0) can be estimated sequentially.

  For the polarization value fdyn in the equations (4) and (5), a map for obtaining the polarization value fdyn based on the battery current Ib by performing in advance an experiment for measuring the polarization electromotive voltage with the battery current Ib kept constant. Can be created in advance. Moreover, even if the battery current Ib is the same, the battery temperature Tb affects the degree of occurrence of polarization. Therefore, it is preferable to estimate the polarization value fdyn based on the battery current Ib and the battery temperature Tb. In this case, a map based on the experimental result can be created in advance for the polarization value fdyn (Ib, Tb) with the battery current Ib and the battery temperature Tb as variables.

  FIG. 4 shows a map image of the polarization value fdyn (Ib, Tb). Basically, fdyn (Ib, Tb) <0 is set during discharging (Ib> 0), and fdyn (Ib, Tb)> 0 is set during charging (Ib <0). Note that the absolute value of the polarization value | fdyn (Ib, Tb) | is set to be relatively large as the current during discharging and charging increases. Regarding the temperature, as the battery temperature Tb is lower, the absolute value | fdyn (Ib, Tb) | of the polarization value is set to be relatively large. Then, at each time point when the SOC estimation is performed, based on the battery current Ib and the battery temperature Tb at that time point, the map is referred to and corresponds to fdyn {st (t0)} in the equation (5). The polarization value fdyn (Ib, Tb) is read out.

  As described above, the SOC estimation according to the embodiment of the present invention involves the estimation of the polarization electromotive voltage. As described above, the estimation of the polarization electromotive voltage is basically performed so as to reflect the charge / discharge history by sequentially using the estimated value of the polarization electromotive voltage up to the present time.

  FIG. 5 shows the battery voltage behavior at the time of sudden current change, particularly in the small current state immediately after the large current state.

  Referring to FIG. 5, discharging in a large current state in which battery current Ib is equal to or greater than a predetermined current Ilg is continued for a certain period of time, and discharging is terminated at time ta. After time ta, the battery current Ib is in a small current state that is equal to or less than a preset predetermined current Ism.

  In such a small current state immediately after the large current state, the polarization electromotive voltage that has greatly changed in the negative direction due to the large current discharge changes rapidly with the end of the discharge. At this time, when the polarization electromotive force is estimated using the estimated value of the polarization electromotive voltage up to the present time by the arithmetic processing according to the above formulas (4) and (5), the polarization electromotive voltage at the time of large current discharge according to the time constant. Therefore, it is difficult to follow a sudden change in the actual polarization voltage due to a sudden change in current. In addition, it has been confirmed by the inventor that such a rapid change in the polarization electromotive voltage is relatively likely to occur when the battery temperature is low.

  On the other hand, the behavior of the polarization electromotive voltage in the small current state immediately after the large current state can be ascertained through experiments, and the change in the polarization electromotive voltage converges as the fixed convergence time Tst elapses. The polarization induced voltage at the time of convergence depends on at least the battery current Ib in the large current state (hereinafter also referred to as the battery current Iblg), and further depends on the battery temperature Tb and the current (small current state) battery current. Dependent. Further, the convergence time Tst required for the polarization electromotive voltage change to converge also depends on the battery current Iblg, the battery temperature Tb, and the current (small current state) battery current.

  In the period (time ta to tb) until the change of the polarization electromotive force converges to the small current state immediately after the large current state, the estimation of the polarization electromotive voltage according to the above equations (4) and (5) If the estimated value of the polarization electromotive force is used for the calculation, an estimation error of the polarization electromotive voltage is generated instead. In particular, in consideration of the fact that the change in the polarization electromotive voltage during this period is abrupt due to a sudden change in current, rather than executing the polarization electromotive force estimation according to the equations (4) and (5), It is more likely that the estimation error can be suppressed by using the expected polarization electromotive voltage Vdyn # at the time of convergence as it is.

  Therefore, in the battery charge state estimation device according to the embodiment of the present invention, in order to suppress the estimation error of the polarization electromotive voltage in the small current state immediately after the large current state, the SOC estimation is performed according to the flowcharts shown in FIGS. Execute.

  Referring to FIG. 6, battery ECU 14 obtains battery voltage Vb, battery current Ib, and battery temperature Tb as battery state quantities from voltage detector 12, temperature sensor 16, and current detector 18 in step S110. Further, in step S120, battery ECU 14 determines whether or not absolute value | Ib | of battery current Ib is greater than or equal to predetermined current Ilg.

  If | Ib | ≧ Ilg (when YES is determined in step S120), battery ECU 14 determines that the state is “a large current state”, and “turns on” large current state flag FGl in step S130. In S135, the battery current Ib at this time is stored as the battery current Iblg in the large current state. Note that, as described above, when the battery temperature is low, the current level that causes such a rapid change in the polarization electromotive voltage is lowered, so it is necessary to relatively widen the detection range of the large current state. For this reason, it is preferable that the predetermined current Ilg, which is a threshold for detecting a large current state, be variably set according to the battery temperature Tb so as to be set to a relatively small value when the battery temperature is low.

  On the other hand, when | Ib | <Ilg (when NO is determined in step S120), battery ECU 14 makes a “small current state” in which absolute value | Ib | of battery current Ib is equal to or smaller than predetermined current Ism in step S140. Determine if it exists. When YES is determined in step S140, that is, when a small current state is detected, the battery ECU 14 determines whether the large current state flag FGl is “ON” in step S150.

  When YES is determined in step S150, that is, when the small current state is detected when the large current state flag FGl is “ON”, the battery ECU 14 determines that “the small current state has occurred immediately after the large current state. And the flag FGls is turned “ON”. Further, in step S170, the battery ECU 14 starts a timer (not shown) for measuring the elapsed time from the start point of the small current state immediately after the large current state (time ta in FIG. 5). A predetermined time Tth corresponding to the convergence time Tst shown in FIG. The predetermined time Tth may be a fixed value, but is based on at least one of the battery current Iblg, the battery temperature Tb, and the current (small current state) battery current Ib according to the characteristics of the convergence time Tst described above. Can be variably set. That is, steps S160 to S180 are executed at time ta in FIG.

  On the other hand, when NO is determined in step S150, that is, when the small current state is detected when the large current state flag FGl is “off”, the battery ECU 14 determines whether the flag FGls is “on” in step S190. Determine if. When the determination in step S190 is YES, that is, when the flag FGls is “ON”, the battery ECU determines that the small current state immediately after the large current state continues, and in step S200, in step S170. Counts up the timer value of the activated timer. Further, in step S210, battery ECU 14 determines whether the timer value has reached predetermined time Tth set in step S170. That is, steps S190 to S210 are executed at times ta to tb in FIG.

  When the determination in step S210 is YES, that is, when the duration of the small current state immediately after the large current state has reached the predetermined time Tth, the battery ECU 14 “turns off” the flag FGls in step S220. This process is executed at time tb in FIG.

  Battery ECU 14 executes step S220 for clearing flags FGl and FGls to “off” also at the time of NO determination at step S140 and NO determination at step S190.

  As a result of the processing in steps S120 to S220 described above, the battery ECU 14 turns on the flag FGls when the small current state occurs immediately after the large current state, and sets the large current state flag FGl once turned on. It can be “off” to prepare for the next detection of a large current state. On the other hand, the flag FGls is “off” except in a small current state immediately after the occurrence of a large current (that is, in a normal state). Then, the flag FGls that is once “on” is set until the end of the small current state (NO determination in S140) or until the low current state duration immediately after the large current state reaches the predetermined time Tth (NO in S190). At the time of determination) “on” is maintained, and “off” in response to the satisfaction of these conditions.

  Referring to FIG. 7, in step S250, battery ECU 14 determines whether flag FGls is “ON” or not. When the flag FGls is “OFF” (when NO is determined in S250), that is, in the normal time (period other than the times ta to tb in FIG. 5), the battery ECU 14 performs the above-described equation (4) according to steps S260 and S270. , (5), the polarization electromotive force is estimated using the past estimated value of polarization electromotive force in the calculation. Specifically, in step S260, the battery ECU refers to the map shown in FIG. 4 and the like, so that the polarization value fdyn (Ib, Tb) is based on the current battery state quantity (battery current Ib and battery temperature Tb). = Fdyn (t0) is estimated. Further, in step S270, the battery ECU 14 substitutes the current polarization value fdyn (t0) obtained in step S260 as fdyn {st (t0)} in the equation (5), so that the current polarization electromotive voltage is obtained. Vdyn (t0) = Vdyn is calculated.

  On the other hand, when the flag FGls is “ON” (YES in S250), that is, a small current state immediately after the large current state and the duration is shorter than the predetermined time Tth (that is, in FIG. 5). In the period between time ta and tb, the battery value ECU 14 refers to the map shown in FIG. 8 in step S280, and thereby the polarization electromotive voltage corresponding to the predicted convergence value in the small current state immediately after the large current state Vdyn # is obtained.

FIG. 8 shows a configuration image of the polarization electromotive voltage Vdyn # estimation map.
Referring to FIG. 8, as described above, polarization electromotive voltage Vdyn # is a convergence value when convergence time Tst has elapsed in a small current state immediately after a large current state, and can be obtained in advance by experiments. Polarization electromotive voltage Vdyn # is estimated based on at least battery current Iblg in a large current state. Basically, Vdyn # <0 is set after large current discharge (Iblg> 0), and Vdyn #> 0 is set after large current charge (Ib <0).

  More preferably, polarization electromotive voltage Vdyn # is further estimated based on battery temperature Tb and current (small current state) battery current Ib. Regarding the battery temperature Tb, the absolute value | Vdyn # | of the polarization electromotive voltage is set to be relatively higher as the temperature is lower. Regarding the battery current Ib, as the absolute value | Ib | increases, the absolute value | Vdyn # | of the polarization electromotive voltage is set to be relatively large.

  In this manner, in step S280, the battery ECU 14 separates the polarization electromotive voltage estimated up to the present time, and directly uses the polarization electromotive voltage Vdyn by referring to the map without using the past polarization electromotive voltage estimated value for the calculation. Estimate (Vdyn = Vdyn #).

  Thus, the battery ECU 14 switches the estimation method of the polarization electromotive voltage Vdyn between the normal time and the small current state immediately after the large current state according to the flag FGls. Since the polarization electromotive voltage does not increase to a certain extent, the absolute value | Vdyn | of the polarization electromotive voltage estimated in step S270 or S280 does not become excessively large within the range of the preset maximum value and minimum value. It is preferable to provide a guard that can estimate the polarization electromotive voltage Vdyn.

  When the flag FGls changes from “on” to “off”, the polarization electromotive voltage Vdyn estimated when the flag FGls is “on”, that is, the polarization electromotive voltage estimated based on the map of FIG. With Vdyn # as the previous value Vdyn (t0−Δt) in the equation (5), the estimation of the polarization electromotive voltage according to the equation (5) reflecting the polarization value fdyn (t0) at that time is resumed.

  Further, in step S290, battery ECU 14 estimates internal resistance R of battery 10 based at least on battery temperature Tb. Further, the battery ECU 14 determines that the battery voltage Vb and the battery current Ib acquired in step S100 in step S300, the internal resistance R estimated in step S210, and the polarization electromotive voltage Vdyn obtained in step S270 or S280 The open circuit voltage Vocv is calculated according to the equation (3).

  Battery ECU 14 further estimates the SOC of battery 10 using open circuit voltage Vocv in step S310.

  In step S310, as described above, in the lithium ion battery having a high correlation between the SOC and the open circuit voltage, the estimated SOC value of the battery 10 can be calculated based on the characteristics shown in FIG. Also, in other types of batteries, such as nickel metal hydride batteries, where the correlation between the SOC and the open circuit voltage is not as high as that of the lithium ion battery, the SOC estimation obtained by integrating the SOC change amount by integrating the battery current Ib and the SOC based on the open circuit voltage The process in step S310 may be executed in combination with estimation. The SOC estimation process in S310 can be executed based on an arbitrary estimation method in consideration of the characteristics of the battery 10 as long as it reflects the polarization electromotive voltage estimated as described above.

  As described above, according to the battery state-of-charge estimation device according to this embodiment, the estimation error of the polarization electromotive voltage increases in the small current state immediately after the generation of the large current, and the open circuit voltage (OCV) and the state of charge (SOC) are increased. ) Can be prevented from being degraded. As a result, it is possible to improve the estimation accuracy of the state of charge (SOC) based on the detected state quantity (current, voltage, temperature, etc.) of the battery.

  Further, in the present embodiment, the SOC estimation is performed for the entire battery 10, but the polarization electromotive force is generated using the battery current Ib common to each battery cell, the battery voltage and the battery temperature detected for each battery cell. It is also possible to adopt a control configuration in which estimation and open circuit voltage and SOC estimation are executed for each battery cell.

  Here, the correspondence relationship between the flowcharts shown in FIGS. 6 and 7 and the configuration of the present invention will be described. Step S110 corresponds to the “state quantity acquisition unit” in the present invention, and step S120 includes “large current state detection unit”. Steps S140 and S150 correspond to “small current state detection means” in the present invention. Further, the processing of steps S250 to S280 corresponds to “polarization electromotive voltage estimation means” in the present invention, and in particular, step S250 corresponds to “prohibition means”, and steps S260 and 270 correspond to “first estimation means”. Step S280 corresponds to “second estimation means”. Step S290 corresponds to “internal resistance estimation means” in the present invention, step S300 corresponds to “open circuit voltage detection means” in the present invention, and step S310 corresponds to “charge state estimation means” in the present invention. To do.

  As described above, in the present embodiment, the state of charge estimation device for estimating the state of charge (SOC) of the battery mounted on the hybrid vehicle has been described. However, the application of the present invention is limited to such a case. is not. That is, the present invention can be applied to a battery whose state of charge (SOC) is estimated with estimation of the polarization electromotive voltage without particularly limiting the use form of the battery, that is, the form of the load.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is a block diagram which shows the structure of the system which applied the battery charge condition estimation apparatus by embodiment of this invention to the hybrid vehicle. It is a graph which shows the example of a correspondence of SOC and open circuit voltage (OCV). It is a wave form diagram explaining the relationship between the change of a battery current, and the change of a polarization induced voltage. It is a conceptual diagram explaining the structure image of the map which calculates | requires a polarization value based on battery current and battery temperature. It is a wave form diagram explaining the battery voltage behavior in the small current state immediately after the large current state at the time of sudden current change. It is a 1st figure which shows the flowchart explaining SOC estimation in the battery charge condition estimation apparatus by embodiment of this invention. It is a 2nd figure which shows the flowchart explaining SOC estimation in the battery charge condition estimation apparatus by embodiment of this invention. It is a conceptual diagram explaining the structure image of the map for directly estimating the polarization electromotive voltage in the small current state immediately after the large current state.

Explanation of symbols

  10 battery, 14 battery ECU, 12 voltage detector, 16 temperature sensor, 18 current detector, 22 load, fdyn polarization value, FLG current continuation flag, Ib battery current, Iblg battery current (in high current state), Ilg predetermined current (For detecting a large current state), Ism predetermined current (for detecting a large current state), R battery internal resistance, Tb battery temperature, Tst polarization electromotive voltage convergence time (at a small current immediately after a large current), Vb battery voltage, Vdyn polarization Electromotive voltage, Vdyn # Polarization electromotive voltage convergence value (at a small current immediately after a large current), Vocv open circuit voltage, Δt SOC estimation period, τ time constant.

Claims (6)

State quantity acquisition means for acquiring the voltage, current and temperature of the secondary battery at the current time;
A large current state detection means for detecting a large current state in which the current of the secondary battery is equal to or greater than a predetermined current;
Immediately after the large current state, a small current state detection means for detecting that the current is in a small current state that is equal to or less than a predetermined value;
A polarization electromotive force estimation means for estimating a polarization electromotive force of the secondary battery based on a charge / discharge history of the secondary battery up to the present time;
Internal resistance estimation means for estimating internal resistance of the secondary battery based on at least the temperature acquired by the state quantity acquisition means;
Based on the voltage and current acquired by the state quantity acquisition unit, the internal resistance estimated by the internal resistance estimation unit, and the polarization induced voltage estimated by the polarization induced voltage estimation unit, the secondary An open circuit voltage detecting means for detecting an open circuit voltage of the battery;
Using the open circuit voltage detected by the open circuit voltage detection means, comprising a charge state estimation means for estimating the charge state of the secondary battery,
The polarization electromotive force estimation means includes
A first for sequentially estimating the current polarization electromotive voltage based on the estimated value of the polarization electromotive voltage up to the present time and at least the current of the state quantities acquired by the state quantity acquisition means. Means for estimating
A prohibiting means for prohibiting the estimation of the polarization electromotive force by the first estimating means in the small current state immediately after the large current state;
And a second estimation unit for estimating the current polarization electromotive voltage based on the current in the large current state when the estimation by the first estimation unit is prohibited. .   In the low current state immediately after the large current state, the prohibiting means responds to the end of the small current state or the elapse of a predetermined time from the start point of the small current state. The secondary battery charge state estimation apparatus according to claim 1, wherein the prohibition of estimation by the means is canceled.   The first estimating means, when the prohibition of estimation by the prohibiting means is released, the estimated value of the polarization electromotive voltage immediately before by the second estimating means and the state acquired by the state quantity acquiring means The state estimation device for a secondary battery according to claim 2, wherein the polarization electromotive voltage at the present time is estimated based on at least the current of the quantity.   The second estimation means estimates the current polarization electromotive voltage based on the current acquired by the state quantity acquisition means and the temperature in addition to the current in the large current state. The charge state estimation apparatus of the secondary battery as described.   The predetermined current used by the high current state detection means for detecting the high current state is variably set according to the temperature of the secondary battery so that the predetermined current is relatively small at a low temperature of the secondary battery. The charging state estimation device for a secondary battery according to claim 1.   The secondary battery charging state estimation device according to claim 1, wherein the secondary battery is configured by a lithium ion battery.

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