JP2010019595A - Residual capacity calculating apparatus of storage device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately calculate a residual capacity even if a large current is charged and discharged. <P>SOLUTION: When the residual capacity SOC of a battery is obtained, the residual capacity SOCc based on a current accumulation and the residual capacity SOCv based on an open voltage are weighted and combined. When the residual capacity SOCv is obtained, an impedance is obtained from an equivalent model of the battery. The open voltage of the battery is estimated by using the impedance. Since the equivalent model is determined by assuming a minute current and does not consider a continuous large current, the estimation accuracy of the open voltage is degraded and the residual capacity SOCv is highly calculated in comparison with an actual value when the battery is rapidly charged and discharged. The residual capacity SOC is subtracted from the residual capacity SOCv so as to calculate a capacity difference ΔSOC (S14). If the capacity difference ΔSOC exceeds a predetermined value V1 (S15), a weight w is corrected so as to decrease a weight of the residual capacity SOCv when it is weighted and combined (S18). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a remaining capacity computing device for an electricity storage device that computes the remaining capacity of an electricity storage device.

In recent years, power storage devices such as lithium ion secondary batteries have been reduced in size and weight and have increased energy density, and are used as power sources for portable devices, electric vehicles, hybrid vehicles, and the like. In order to effectively use this power storage device, it is important to accurately grasp the remaining capacity of the power storage device, and a technique for obtaining the remaining capacity by integrating the charge / discharge current of the power storage device (e.g., patent document) 1) and a technique for obtaining the remaining capacity based on the open circuit voltage of the power storage device (for example, see Patent Document 2). However, the calculation method using current integration is resistant to load fluctuations such as inrush current, but has a problem that errors are likely to accumulate. In the calculation method using open-circuit voltage, However, it has a problem that it is weak against load fluctuations such as an inrush current. Therefore, a technique has been proposed in which the remaining capacity based on the current integration and the remaining capacity based on the open circuit voltage are combined according to the charge / discharge status of the power storage device to improve the calculation accuracy of the remaining capacity (for example, (See Patent Documents 3 and 4).
JP-A-11-103505 JP 2002-189066 A JP 2002-222668 A JP 2002-305039 A

  By the way, when calculating the remaining capacity based on the open circuit voltage, it is necessary to estimate the open circuit voltage of the electricity storage device, but in order to estimate the open circuit voltage, in addition to the current and terminal voltage of the electricity storage device, internal resistance (impedance) is required. This internal resistance can be calculated using the equivalent circuit model of the electricity storage device, but the equivalent circuit model of the electricity storage device is determined with a minute current supplied, and a large current is continuously supplied. It is not an equivalent circuit model that takes into account the situation. Therefore, when a large current is continuously supplied by rapid charging or the like, the open circuit voltage of the power storage device is estimated to be higher than the actual value, and thus the remaining capacity based on the open circuit voltage is calculated to be higher than the actual value. In this way, calculating the remaining capacity high during rapid charging is a cause of terminating rapid charging before reaching the actual full charge state, and fully utilizing the capacity of the electricity storage device Was difficult. Especially for lithium-ion secondary batteries whose overcharged state will deteriorate, the remaining capacity in the vicinity of the fully charged state is calculated accurately and charged to the fully charged state without causing the overcharged state. It is desirable to implement.

  An object of the present invention is to accurately calculate the remaining capacity of an electricity storage device even when charging and discharging with a large current are continuously performed.

  The remaining capacity computing device for an electricity storage device according to the present invention comprises: first element computing means for computing a first remaining capacity element of the electricity storage device based on an integrated value of charge / discharge current of the electricity storage device; and an impedance of the electricity storage device. Second element calculation means for calculating a second remaining capacity element of the power storage device based on the estimated open circuit voltage, and weight setting for setting a weight of the remaining capacity element based on the charge / discharge status of the power storage device Means, a weight remaining combination of the first remaining capacity element and the second remaining capacity element using the weight, and a remaining capacity calculating means for calculating a remaining capacity of the power storage device, and the remaining capacity and the second remaining capacity Weight correction means for correcting the weight so as to increase the weight of the first remaining capacity element when the difference from the capacity element exceeds a predetermined value. The features.

  In the power storage device remaining capacity calculation device of the present invention, the weight correction unit is configured such that the state where the difference between the remaining capacity and the second remaining capacity element exceeds a predetermined value is continued for a predetermined time. Weight correction is performed.

  In the storage device remaining capacity calculation device according to the present invention, the weight correction unit determines a difference between the remaining capacity and the second remaining capacity element under a state in which the remaining capacity exceeds a predetermined capacity, and the weight Correction is performed.

  In the power storage device remaining capacity calculation device of the present invention, the weight correction unit determines a difference between the remaining capacity and the second remaining capacity element in consideration of the temperature of the power storage device, and executes the correction of the weight. It is characterized by doing.

  The remaining capacity computing device for an electricity storage device according to the present invention is characterized in that the weight setting means sets the weight based on a rate of change of the charge / discharge current that has been subjected to a moving average process.

  According to the present invention, the first remaining capacity element based on the integrated value of the charge / discharge current and the second remaining capacity element based on the open circuit voltage are weighted and combined using the weights to calculate the remaining capacity of the electricity storage device. Yes. When the difference between the remaining capacity and the second remaining capacity element exceeds a predetermined value, the weight is corrected so as to increase the weight of the first remaining capacity element. The remaining capacity can be calculated without receiving it, and the calculation accuracy of the remaining capacity can be improved.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic diagram showing an electric vehicle 10 to which an electric storage device remaining capacity calculation device according to an embodiment of the present invention is applied. As shown in FIG. 1, an electric vehicle 10 is equipped with a motor generator 12 that drives wheels 11. In order to supply electric power to the motor generator 12, the electric vehicle 10 is equipped with a battery 13 such as a lithium ion secondary battery as an electricity storage device. An inverter 14 is provided between the motor generator 12 and the battery 13, and the battery 13 and the inverter 14 are connected via energizing cables 15 and 16. The direct current supplied from the battery 13 is converted into an alternating current via the inverter 14 and then supplied to the motor generator 12.

  A battery control unit (BCU) 20 is connected to the battery 13 in order to calculate the remaining capacity SOC of the battery 13 and to control the charge / discharge state of the battery 13. Further, a vehicle control unit (EVCU) 22 is provided in the electric vehicle 10 in order to control the driving state of the inverter 14 and the operating state of the main relay 21. The battery control unit 20, the vehicle control unit 22, the inverter 14, and the like are connected to each other via a communication network 23. The battery control unit 20 and the vehicle control unit 22 include a CPU that calculates control signals and the like, and also includes a ROM that stores control programs, table data, and the like, and a RAM that temporarily stores data.

  Further, in order to enable quick charging of the battery 13, a power receiving side connector 24 for quick charging is installed on the vehicle body. The power receiving side connector 24 has a pair of connection terminals 25, 26. One connection terminal 25 is connected to the energization cable 15, and the other connection terminal 26 is connected to the energization cable 16. When the battery 13 is rapidly charged, a power supply side connector 28 extending from the quick charger 27 is connected to the power receiving side connector 24 of the vehicle body at a power supply station where the quick charger 27 is installed. Thereby, the low voltage (for example, 200V) alternating current supplied from the alternating current power source to the quick charger 27 is converted into the high voltage (for example, 400V) direct current corresponding to the battery 13, and then supplied to the battery 13. Is done. The battery control unit 20 and the quick charger 27 are connected via the communication network 23, and the operating state of the quick charger 27 is controlled based on the remaining capacity SOC output from the battery control unit 20. . In addition, you may charge the battery 13 using a household power supply by mounting a vehicle-mounted charger with respect to the electric vehicle 10. In this case, a high-voltage (for example, 400 V) direct current is generated from a low-voltage (for example, 100 V) alternating current by the in-vehicle charger.

  Next, the remaining capacity SOC calculation process executed by the battery control unit 20 will be described. FIG. 2 is a system configuration diagram of the battery control unit 20, FIG. 3 is a block diagram showing a calculation algorithm of the remaining capacity SOC, and FIG. 4 is a circuit diagram showing an equivalent circuit model of the battery 13. First, as shown in FIG. 2, the battery control unit 20 includes a voltage sensor 30 that detects a terminal voltage V of the battery 13, a current sensor 31 that detects a charge / discharge current I of the battery 13, and a cell temperature T of the battery 13. A temperature sensor 32 to be detected is connected. Further, the battery control unit 20 is provided with a calculation unit 33 configured by a microcomputer or the like. The computing unit 33 computes the remaining capacity SOC (t) every predetermined time t based on the terminal voltage V, current I, and temperature T input from the various sensors 30 to 32. This remaining capacity SOC (t) is not only used as basic data for controlling the charge / discharge state of the battery 13, but is also output from the battery control unit 20 to the vehicle control unit 22 for basic vehicle control. It is used as data and display data for the remaining battery level. As will be described later, the remaining capacity SOC (t) is also used as the remaining capacity SOC (t−1) one period before in the periodic calculation.

The calculation process of the remaining capacity SOC by the calculation unit 33 is executed according to the calculation algorithm shown in FIG. In this calculation algorithm, the terminal voltage V, current I, and temperature T of the battery 13 are used, and the remaining capacity SOCc as the first remaining capacity element based on the integrated value of the charge / discharge current and the estimated open circuit voltage Vo of the battery 13 are calculated. The remaining capacity SOCv as the second remaining capacity element is calculated in parallel. Incidentally, the remaining capacity SOCc based on current integration is resistant to load fluctuations such as inrush current, but has a characteristic that errors are likely to accumulate. The remaining capacity SOCv based on the open circuit voltage Vo is stable in current. While effective in the region, it has a characteristic that it is vulnerable to load fluctuations such as inrush current. Therefore, the battery control unit 20 sets a weight w that is a weighting coefficient in accordance with the charge / discharge status of the battery 13, and weights and combines the remaining capacities SOCc and SOCv using the weight w, whereby the remaining capacity of the battery 13 is set. The SOC is calculated. The weight w is set between 0 and 1, and the final remaining capacity SOC after synthesis is given by the following equation (1). As a result, the disadvantages of the remaining capacities SOCc and SOCv can be canceled to maximize the mutual advantages, and the calculation accuracy of the remaining capacities SOC can be improved. Thus, the battery control unit 20 functions as a first element calculation means, a second element calculation means, a weight setting means, and a remaining capacity calculation means.
SOC (t) = w.SOCc (t) + (1-w) .SOCv (1)

  Hereinafter, a method of calculating the remaining capacity SOCc based on current integration, the remaining capacity SOCv based on the open circuit voltage Vo, and the weight w set according to the charge / discharge status will be described in detail.

The remaining capacity SOCc (t) obtained by integrating the current is determined by using a remaining capacity SOC (t−1) synthesized using the weight w as a reference value as shown in the following formula (2). It is calculated by accumulating the current I every time. In Equation (2), η is current efficiency, Ah is current capacity (variable depending on temperature), and SD is self-discharge rate.
SOCc (t) = SOC (t−1) −∫ [(100ηI / Ah) + SD] dt / 3600 (2)

In this formula (2), the current efficiency η and the self-discharge rate SD can be regarded as constants (for example, η = 1, SD = 0), but the current capacity Ah depends on the temperature. It is a variable that changes. Therefore, as the current capacity Ah used for calculating the remaining capacity SOCc (t), the current capacity obtained by functioning the variation of the cell capacity due to the temperature T is used. Further, the calculation of the remaining capacity SOCc (t) is processed in discrete time by the calculation unit 33, and the remaining capacity SOC (t−1) one cycle before is used as a reference value for current integration (delay calculation shown in FIG. 3). Child Z- ¹ ). As a result, the error does not accumulate or diverge, so even if the initial value of the remaining capacity SOCc (t) is significantly different from the true value, after a predetermined time (for example, after several minutes) ) Can converge to a true value.

  Next, a method for calculating the remaining capacity SOCv using the open circuit voltage Vo will be described. When the remaining capacity SOCv is obtained based on the estimated open circuit voltage Vo, the impedance Z of the battery 13 is obtained by using the equivalent circuit model of FIG. 4 in order to estimate the open circuit voltage Vo from the terminal voltage V. This equivalent circuit model is an equivalent circuit model in which respective parameters of resistance components R1 to R3 and capacitance components C1, CPE1, and CPE2 (where CPE1 and CPE2 are double layer capacitance components) are combined in series and in parallel. Each parameter of the equivalent circuit model is determined by curve fitting a known Cole-Cole plot in the AC impedance method.

The impedance Z obtained from these parameters varies greatly depending on the temperature T of the battery 13, the electrochemical reaction rate, and the frequency component of the current I. Therefore, as a parameter for determining the impedance Z, the moving average value of the current change rate ΔI / Δt is replaced with a frequency component, and impedance measurement is performed with the moving average value of the current change rate ΔI / Δt and the temperature T as conditions. After accumulating data, the impedance Z table (impedance table in FIG. 7 described later) is created based on the moving average value of the current change rate ΔI / Δt and the temperature T. Then, from the impedance Z obtained from the impedance table, the measured terminal voltage V, and the measured current I, the open circuit voltage Vo is estimated using the following equation (3). Since the impedance Z of the battery 13 increases and the current change rate ΔI / Δt decreases as the temperature of the battery 13 decreases, the moving average value of the current I is calculated when determining the impedance Z, as will be described later. The corrected current change rate (change rate) KΔI / Δt obtained by correcting the temperature is used.
V = Vo−I × Z (3)

After the open circuit voltage Vo is estimated, the remaining capacity SOCv is calculated based on the electrochemical relationship in the battery 13. By applying the well-known Nernst equation describing the relationship between the electrode potential and the ion activity in the equilibrium state, the following equation (4) is obtained when the relationship between the open circuit voltage Vo and the remaining capacity SOCv is expressed. be able to. Here, E is a standard electrode potential (E = 3.745 V in the lithium ion secondary battery of this embodiment), and Rg is a gas constant (8.314 J / mol · K). T is a temperature (absolute temperature K), Ne is an ionic valence (Ne = 1 in the lithium ion secondary battery of this embodiment), and F is a Faraday constant (96485 C / mol). Note that Y in equation (4) is a correction term, which expresses the voltage-SOC characteristic at normal temperature as a function of SOC. If SOCv = X, it can be expressed by a cubic function of SOC as shown in the following equation (5).
Vo = E + [(Rg · T / Ne · F) × lnSOCv / (100−SOCv)] + Y (4)
Y = −10 ⁻⁶ X ³ + 9 · 10 ⁻⁵ X ² + 0.013X−0.7311 (5)

  When calculating the remaining capacity SOCv, it is possible to directly calculate the remaining capacity SOCv based on the equation (4) using the open-circuit voltage Vo and the temperature T as parameters. It is necessary to consider specific charge / discharge characteristics and use conditions. Therefore, in order to grasp the actual charge / discharge characteristics, etc. from the relationship of the above equation (4), charge / discharge tests or simulations at each temperature range are performed on the basis of the SOC-Vo characteristics at room temperature, and measured data is accumulated. To do. Then, a table of remaining capacity SOCv (remaining capacity table in FIG. 8 described later) that parameters open circuit voltage Vo and temperature T is created from the accumulated measured data, and the remaining capacity SOCv is obtained using this table. I have to.

  Next, a method for calculating the weight w will be described. The weight w needs to be determined using a parameter that can accurately represent the current charge / discharge status of the battery 13. As this parameter, the change rate of the current I per unit time, the deviation between the remaining capacities SOCc and SOCv, and the like can be used. The current change rate per unit time directly reflects the load fluctuation of the battery 13, but the mere current change rate is affected by a sudden change in current that occurs in a spike manner.

  Therefore, in this embodiment, in order to prevent the influence of a change in current that starts instantaneously, a current change rate obtained by performing processing such as a simple average, a moving average, a weighted average, or the like of a predetermined number of samplings is used. In particular, when considering a delay in current, the weight w is determined using a moving average that can appropriately reflect the past history without excessively changing the charging / discharging state of the battery 13. I am doing so.

  In this way, the weight w is determined by moving average processing of the current change rate, so that the weight w is raised when the current change rate is large, and the weight w is lowered when the current change rate is small. As a result, when the load variation is large and the current change rate is large, the weight of the remaining capacity SOCc based on the current integration is increased, while the weight of the remaining capacity SOCv based on the open circuit voltage Vo is decreased, The remaining capacity SOC can be accurately reflected, and the influence of the oscillating open-circuit voltage Vo can be avoided. Conversely, when the load fluctuation is small and the current change rate is small, the weight of the remaining capacity SOCc based on the current integration is reduced, while the weight of the remaining capacity SOCv based on the open circuit voltage Vo is increased to accumulate errors during current integration. Thus, the accurate remaining capacity SOC can be calculated from the open-circuit voltage Vo that is accurately estimated.

  In other words, the moving average process for the current change rate becomes a low-pass filter for the high-frequency component of the current, and this filtering can remove the spike component of the current that occurs due to load fluctuations during traveling without promoting the delay component. . As a result, the charge / discharge status of the battery 13 can be more accurately grasped, the disadvantages of both the remaining capacities SOCc and SOCv are canceled out, and the mutual advantages are maximized, and the estimation accuracy of the remaining capacities SOC is greatly improved. It becomes possible to make it.

  Next, a method for calculating the remaining capacity SOC of the battery 13 will be described in detail. Here, FIG. 5 is a flowchart showing a calculation procedure of the remaining capacity SOC, FIG. 6 is an explanatory diagram showing a current capacity table, and FIG. 7 is an explanatory diagram showing an impedance table. FIG. 8 is an explanatory diagram showing a remaining capacity table, and FIG. 9 is an explanatory diagram showing a weight table. In the flowchart of FIG. 5, for convenience of explanation, the remaining capacity SOCc based on the open circuit voltage Vo is calculated after calculating the remaining capacity SOCc based on the current integration. SOCc and SOCv are calculated in parallel. Further, the flowchart of FIG. 5 is executed at predetermined time intervals so as to update the remaining capacity SOC at predetermined time intervals (for example, every 0.1 second). 7 and 8 show the data within the range used for the description, and the description of the data in other ranges is omitted.

  As shown in FIG. 5, in step S1, it is determined whether or not the terminal voltage V, current I, temperature T, and the previous remaining capacity SOC (t-1) are input. Note that, for the terminal voltage V and the current I, for example, new data is acquired every 0.1 seconds, and for the temperature T, new data is acquired every 10 seconds, for example. If it is determined in step S1 that various data has not been input, the routine exits the routine as it is. If it is determined that various data has been input, the process proceeds to step S2 where the current capacity of the battery 13 is determined. Ah is calculated.

  In step S2, the current capacity Ah of the battery 13 is calculated by referring to the current capacity table shown in FIG. This current capacity table stores a capacity ratio Ah 'with respect to a predetermined rated current capacity as a reference, with the temperature T as a parameter. The standard rated current capacity is the current capacity of the battery 13 at room temperature (25 ° C.), and is obtained in advance by a charge / discharge test, simulation, or the like. As shown in FIG. 6, since the current capacity Ah of the battery 13 decreases as the temperature T decreases with respect to the capacity ratio Ah ′ (= 1.00) at room temperature (25 ° C.), the value of the capacity ratio Ah ′. Is set to be large. The current capacity Ah at the measured temperature T is calculated by dividing the rated current capacity by the capacity ratio Ah ′ referred to from the current capacity table.

  Subsequently, the process proceeds to step S3, and the remaining capacity SOCc (t) based on the current integration is calculated according to the above equation (2) using the current capacity Ah, the current I, and the remaining capacity SOC (t-1). Next, the process proceeds to step S4, and the current change rate ΔI / Δt per unit time subjected to the moving average process is calculated. For example, when the current I is sampled every 0.1 seconds and the current integration is calculated every 0.5 seconds, five pieces of current change rate data are subjected to moving average processing. In the subsequent step S5, a corrected current change rate KΔI / Δt obtained by temperature-correcting the current change rate ΔI / Δt is calculated.

  Subsequently, in step S6, the impedance Z of the battery 13 is calculated by referring to the impedance table of FIG. 7 based on the temperature T and the corrected current change rate KΔI / Δt. This impedance table stores the impedance Z of the equivalent circuit model using the temperature T and the corrected current change rate KΔI / Δt as parameters, and roughly, when the corrected current change rate KΔI / Δt is the same. The impedance Z increases as the temperature T decreases, and when the temperature T is the same, the impedance Z tends to increase as the corrected current change rate KΔI / Δt decreases. In the subsequent step S7, the open-circuit voltage Vo of the battery 13 is estimated based on the impedance Z, the terminal voltage V, and the current I by using the above-described equation (3).

  Subsequently, in step S8, the remaining capacity SOCv is calculated by referring to the remaining capacity table of FIG. 8 based on the temperature T and the open circuit voltage Vo. As described above, this remaining capacity table is a table created by grasping the electrochemical state in the battery 13 based on the Nernst equation. In general, the temperature T and the open circuit voltage Vo are lowered. As the remaining capacity SOCv decreases, the remaining capacity SOCv tends to increase as the temperature T and the open circuit voltage Vo increase.

  Subsequently, in step S9, based on the corrected current change rate KΔI / Δt, the weight w used when combining the remaining capacity SOCc and the remaining capacity SOCv is calculated by referring to the weight table of FIG. The This weight table is a one-dimensional table using the corrected current change rate KΔI / Δt as a parameter. In general, the smaller the corrected current change rate KΔI / Δt is, that is, the load fluctuation of the battery 13 is smaller. As shown, the weight w tends to be reduced to reduce the weight of the remaining capacity SOCc by current integration. In step S10, the remaining capacity SOCc and the remaining capacity SOCv are weighted and synthesized by using the above-described equation (1), and the final remaining capacity SOC of the battery 13 is calculated.

  In the above description, the impedance Z is obtained from the equivalent circuit model when the open circuit voltage Vo of the battery 13 is estimated. However, the equivalent circuit model of the battery 13 is determined in a state where a minute current is supplied. There is no equivalent circuit model that takes into account the situation where a large current is continuously supplied. That is, under a situation where a large current is continuously supplied by rapid charging or the like, it is difficult to accurately obtain the impedance Z, the open voltage Vo of the battery 13 is estimated to be high, and this open circuit The remaining capacity SOCv based on the voltage Vo may be calculated high.

  As described above, if the remaining capacity SOCv calculated to be higher than the actual value is used, it is erroneously determined that the battery 13 is fully charged before the battery 13 actually reaches the fully charged state. It becomes impossible to charge to a charged state. In particular, in the battery 13 that is rapidly charged, even if the terminal voltage V is high immediately after charging, the terminal voltage V decreases to an actual value as time passes (voltage hysteresis). It is important to calculate the capacity SOC with high accuracy. Therefore, the remaining capacity calculation device of the present invention is weighted so that the final remaining capacity SOC is appropriately weighted and synthesized under the situation where the remaining capacity SOCv based on the open circuit voltage Vo is calculated to be higher than actual. The correction processing of the weight w used in the above is executed.

  Hereinafter, the correction process of the weight w executed at the time of quick charging or the like will be described. FIG. 10 is a flowchart illustrating an example of an execution procedure of the weight correction process. This weight correction process is executed by the battery control unit 20 functioning as weight correction means.

  As shown in FIG. 10, in step S11, it is determined whether or not the remaining capacity SOC is input. If it is determined in step S11 that the remaining capacity SOC has not been input, the routine is directly exited. On the other hand, if it is determined that the remaining capacity SOC has been input, the process proceeds to step S12 and the remaining capacity SOC is determined. Is 95% (predetermined capacity) or more. If it is determined in step S12 that the remaining capacity SOC is less than 95%, the routine is directly exited. On the other hand, if it is determined that the remaining capacity SOC is 95% or more, the process proceeds to step S13 to reset the timer. Processing is executed. If it is determined that the remaining capacity SOC is less than 95%, even if the remaining capacity SOCv is calculated to be high due to rapid charging or the like, there is a margin until the battery 13 is fully charged, so the weight w is corrected. Without leaving the routine. On the other hand, when it is determined that the remaining capacity SOC is 95% or more, since the battery 13 is nearly fully charged, the remaining capacity SOC is accurately calculated by correcting the weight w in step S13 and subsequent steps. I am doing so.

  Next, in step S14, the final remaining capacity SOC is subtracted from the remaining capacity SOCv based on the open circuit voltage Vo, and a capacity difference ΔSOC that is the difference between the remaining capacity SOCv and the remaining capacity SOC is calculated. In the subsequent step S15, it is determined whether or not the capacity difference ΔSOC is equal to or greater than a predetermined value V1. If it is determined in step S15 that the capacity difference ΔSOC is equal to or greater than the predetermined value V1, the remaining capacity SOCv based on the open circuit voltage Vo is being calculated to be high, and thus the process proceeds to step S16 and the timer count process is performed. Executed. In a succeeding step S17, it is determined whether or not the timer Ti is equal to or longer than a predetermined time T1. If it is determined in step S17 that the timer Ti is equal to or longer than the predetermined time T1, the process proceeds to step S18, and an increase correction process for the weight w is executed. On the other hand, if it is determined in step S17 that the timer Ti has not reached the predetermined time T1, the capacity difference ΔSOC is calculated again in step S14, and whether or not the capacity difference ΔSOC is greater than or equal to the predetermined value V1 in step S15. Is determined.

  On the other hand, if it is determined in step S15 that the capacity difference ΔSOC is less than the predetermined value V1, the process proceeds to step S19, and it is determined whether or not the capacity difference ΔSOC is equal to or less than a predetermined value V2 lower than the predetermined value V1. The If it is determined in step S19 that the capacity difference ΔSOC is equal to or smaller than the predetermined value V2, the process proceeds to step S20, where the normal calculation processing of the weight w is executed, and the weight w obtained from the weight table in FIG. Used. On the other hand, if the capacity difference ΔSOC exceeds the predetermined value V2 in step S19, the routine is directly exited.

  Here, FIG. 11 is an explanatory diagram showing each variation state of the capacity difference ΔSOC, the weight w, and the remaining capacity SOC. As shown in FIG. 11, when the large capacity difference ΔSOC continues (references α1, α2), the weight w is corrected to increase so as to increase the weight of the remaining capacity SOCc (references β1, β2). As a result, the remaining capacity SOC (one-dot chain line) is calculated so as to approach the remaining capacity SOCc, not the remaining capacity SOCv whose calculation accuracy decreases due to charging and discharging with a large current. On the other hand, when the weight w is simply set according to the current change rate or the like without considering the capacity difference ΔSOC as in the past (signs γ1, γ2), the remaining capacity SOC is separated from the remaining capacity SOCc. (Two-dot chain line) will be calculated.

  As described above, when the state in which the capacity difference ΔSOC is equal to or greater than the predetermined value V1 is continued for the predetermined time T1, the remaining capacity SOCv is calculated to be high, and thus the remaining capacity The weight w is corrected to increase so as to increase the weight of the SOCc, and the weight of the remaining capacity SOCv when the remaining capacity SOC is combined is reduced. Thus, the remaining capacity SOC can be calculated with high accuracy without being affected by the remaining capacity SOCv calculated unnecessarily high. Thereby, when performing a quick charge etc., since the battery 13 can be charged to a full charge state, avoiding an overcharge state, it becomes possible to utilize the performance of the battery 13 to the maximum.

In the above description, the weight w increase correction process is executed when the capacity difference ΔSOC exceeds the predetermined value V1, but the sensitivity when the increase correction process is executed based on the temperature T of the battery 13 is increased. It may be changed. Here, FIG. 12 is an explanatory diagram showing a temperature correction coefficient table. As shown in FIG. 12, the temperature correction coefficient table stores the temperature correction coefficient k multiplied by the capacity difference ΔSOC, and the temperature correction coefficient k tends to increase as the temperature T decreases. . That is, when the temperature T of the battery 13 is low, the corrected capacity difference ΔSOC _R (= ΔSOC × k) is set large, so that the weight w increase correction process is executed early. When the temperature T of the battery 13 is decreasing, the open circuit voltage Vo tends to be largely estimated. Therefore, the remaining capacity SOC is calculated with high accuracy by executing the weight w increase correction process early. It becomes possible.

In addition to changing the sensitivity when increasing correction weights w based on the temperature T of the battery 13, based on the duration Ta of capacitance difference [Delta] SOC _R is greater than or equal to a predetermined value V1, when the increasing correction weights w You may make it change the sensitivity of. Here, FIG. 13 is an explanatory diagram showing a weight correction coefficient table. As shown in FIG. 13, the weight correction coefficient table stores the weight correction coefficient g to be multiplied by the weight w, and the weight correction coefficient g tends to increase as the duration time Ta increases. Yes. That is, a situation where the capacitance difference [Delta] SOC _R greater than or equal to a predetermined value V1, when it is continued for a long time, since the weights w (= w × g) is largely corrected, the remaining capacity based on current integration SOCc The weight of will increase. The case where the large capacity difference ΔSOCR _R continues for a long time is a situation in which the remaining capacity SOCv is calculated to be unnecessarily high. Therefore, by increasing the weight of the remaining capacity SOCc based on the current integration, the remaining capacity SOCc is increased. The capacity SOC can be calculated with high accuracy.

  The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the invention. For example, in the illustrated case, the present invention is applied to the battery 13 mounted on the electric vehicle 10, but the present invention is not limited to this, and the battery mounted on a hybrid vehicle, a portable device, etc. The present invention may be applied. Further, the power storage device is not limited to the above-described lithium ion secondary battery, and the present invention may be applied to other types of batteries and capacitors.

  In the above description, rapid charging is cited as a situation where a large current is supplied to the battery 13. However, the present invention is not limited to this, and a large current is generated from the battery 13 by continuously performing rapid acceleration. Needless to say, the battery may be in a state where it is released, or may be in a state where a large current is supplied to the battery 13 by continuously performing rapid deceleration. Further, as shown in the flowchart of FIG. 10, in steps S11 and S12, the remaining capacity SOC of the battery 13 is determined before the weight correction. However, the weight correction process is performed without determining the remaining capacity SOC of the battery 13. You may make it do.

It is the schematic which shows the electric vehicle with which the remaining capacity calculating apparatus of the electrical storage device which is one embodiment of this invention is applied. It is a system block diagram of a battery control unit. It is a block diagram which shows the calculation algorithm of remaining capacity SOC. It is a circuit diagram which shows the equivalent circuit model of a battery. It is a flowchart which shows the calculation procedure of remaining capacity SOC. It is explanatory drawing which shows a current capacity table. It is explanatory drawing which shows an impedance table. It is explanatory drawing which shows a remaining capacity table. It is explanatory drawing which shows a weight table. It is a flowchart which shows an example of the execution procedure of a weight correction process. It is explanatory drawing which shows each fluctuation condition of capacity | capacitance difference (DELTA) SOC, weight w, and remaining capacity SOC. It is explanatory drawing which shows a temperature correction coefficient table. It is explanatory drawing which shows a weight correction coefficient table.

Explanation of symbols

13 Battery (electric storage device)
20 Battery control unit (first element calculation means, second element calculation means, weight setting means, remaining capacity calculation means, weight correction means)
SOCc remaining capacity (first remaining capacity element)
SOCv remaining capacity (second remaining capacity element)
SOC remaining capacity ΔSOC capacity difference (difference)
I charge / discharge current Z impedance Vo open voltage w weight V1 predetermined value T1 predetermined time KΔI / Δt corrected current change rate (change rate)

Claims (5)

First element computing means for computing a first remaining capacity element of the electricity storage device based on an integrated value of charge / discharge current of the electricity storage device;
Second element calculation means for calculating a second remaining capacity element of the power storage device based on an open circuit voltage estimated from the impedance of the power storage device;
Based on the charge / discharge status of the electricity storage device, weight setting means for setting the weight of the remaining capacity element;
A remaining capacity calculating means for calculating a remaining capacity of the power storage device by weighting and combining the first remaining capacity element and the second remaining capacity element using the weight;
And weight correction means for correcting the weight so as to increase the weight of the first remaining capacity element when the difference between the remaining capacity and the second remaining capacity element exceeds a predetermined value. Device remaining capacity calculator. The apparatus for calculating a remaining capacity of an electricity storage device according to claim 1,
The weight correction unit executes the correction of the weight when a state where a difference between the remaining capacity and the second remaining capacity element exceeds a predetermined value is continued for a predetermined time. Device remaining capacity calculator. The remaining capacity computing device for an electricity storage device according to claim 1 or 2,
The weight correction unit determines a difference between the remaining capacity and the second remaining capacity element under a state in which the remaining capacity exceeds a predetermined capacity, and executes the correction of the weight. Remaining capacity calculation device. The remaining capacity calculation device for an electricity storage device according to any one of claims 1 to 3,
The weight correction means determines the difference between the remaining capacity and the second remaining capacity element in consideration of the temperature of the power storage device, and executes the correction of the weight. apparatus. In the remaining capacity calculation apparatus of the electrical storage device of any one of Claims 1-4,
The said weight setting means sets the said weight based on the change rate which carried out the moving average process of the said charging / discharging electric current, The remaining capacity calculating apparatus of the electrical storage device characterized by the above-mentioned.

Images