JP2012088157A - Control device of secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control device of a secondary battery for accurately grasping a full charge capacity.SOLUTION: A first SOC is calculated based on an accumulation value of a current, and a second SOC is calculated based on a voltage (S12 and S16). A difference of the first SOC and the second SOC is calculated as a SOC difference (S18). A point (correction point) is calculated by subjecting the SOC difference to an arithmetic operation with a prescribed conversion level according to the SOC difference (S20). The full charge capacity of the secondary battery is corrected based on the point (S26 and S30).

Description

  The present invention relates to a control device for a secondary battery, and more particularly to a technique for correcting a full charge capacity of a secondary battery.

It is an important technical problem to grasp the secular change (decrease) in the full charge capacity of a secondary battery in a vehicle that uses electricity as a power source, such as an electric vehicle, a hybrid vehicle equipped with an internal combustion engine and an electric motor.
If the full charge capacity of the secondary battery is not fully grasped, the vehicle will stop even though the battery capacity is sufficient, or conversely, the battery capacity is sufficient even though the battery capacity is insufficient This causes a problem that the secondary battery is over-discharged due to erroneous recognition.

In recent years, lithium ion secondary batteries and lithium polymer secondary batteries have been rapidly used especially for vehicles, but due to their nature, the full charge capacity of these secondary batteries decreases every time charging and discharging are repeated. It is known that the above problem is remarkable.
Therefore, in order to grasp the full charge capacity, for example, based on the SOC (State of Charge) which is the ratio of the battery capacity to the full charge capacity and the battery capacity (Ah) which is the integrated value of the current, A technique is known in which a full charge capacity is calculated and determined based on δSOC and δAh, which are differences in SOC (see Patent Document 1).

  Further, as a method for obtaining the SOC, there are known a method for obtaining the SOCc from the integrated value of the current and a method for obtaining the SOCv from the open circuit voltage (see Patent Document 2). In Patent Document 1, the SOCc is calculated from the integrated value of the current. Asking for.

JP 2008-241358 A JP 2005-201743 A

However, when the full charge capacity is calculated based on δSOC and δAh in the environment of the vehicle as in the technique described in Patent Document 1, a measurement error is largely included in obtaining δSOC and δAh. Therefore, there is a problem that the full charge capacity cannot be accurately grasped.
If the full charge capacity cannot be accurately grasped in this way, the full charge capacity must be estimated on the safe side, and the performance of the secondary battery cannot be fully exhibited, which is not preferable.

  The present invention has been made to solve such problems, and an object of the present invention is to provide a secondary battery control device capable of accurately grasping the full charge capacity.

  In order to achieve the above object, the secondary battery control device according to claim 1 is a secondary battery control device that corrects a full charge capacity of the secondary battery, and detects a charge / discharge current of the secondary battery. A current detection unit; a voltage detection unit that detects a voltage of the secondary battery; a first SOC calculation unit that obtains a first SOC based on an integrated value of the current detected by the current detection unit; and the voltage detection unit. Second SOC calculating means for obtaining a second SOC based on the voltage detected by the means, SOC difference calculating means for calculating a difference between the first SOC and the second SOC as an SOC difference, and the SOC A point calculation means for calculating a difference as a score converted at a predetermined conversion degree according to the SOC difference, and a correction means for correcting the full charge capacity of the secondary battery according to the score. To do.

The control apparatus for a secondary battery according to claim 2 is characterized in that, in claim 1, the predetermined degree of conversion in the score calculation means is smaller as the absolute value of the SOC difference is larger.
The control apparatus for a secondary battery according to claim 3 is characterized in that, in claim 1 or 2, the predetermined conversion degree in the score calculation means differs depending on whether the SOC difference is positive or negative. To do.

In a secondary battery control device according to a fourth aspect of the present invention, in any one of the first to third aspects, the score calculating means obtains the score a predetermined number of times at a predetermined time interval, and adds the scores obtained for the predetermined number of times. A sum value is obtained, and the correction means corrects a full charge capacity of the secondary battery according to the sum value.
The control device for a secondary battery according to claim 5 is characterized in that, in claim 4, the correction means corrects a full charge capacity of the secondary battery when the sum value exceeds a predetermined threshold value.

  According to the secondary battery control apparatus of the first aspect of the present invention, the first SOC and voltage detection obtained from the integrated value of the current detected by the current detection means when correcting the full charge capacity of the secondary battery. The difference from the second SOC obtained from the voltage detected by the means is calculated as the SOC difference, the score calculating means obtains a score converted with a predetermined conversion degree according to the SOC difference, and the difference is calculated according to the score. The full charge capacity of the secondary battery is corrected.

Therefore, once the SOC difference is converted into the number of points converted at a predetermined conversion degree, the measurement error in the integrated value of the current detected by the current detection unit and the measurement error of the voltage detected by the voltage detection unit are absorbed well. The full charge capacity can be appropriately corrected to be accurate.
According to the control device for a secondary battery of claim 2, by reducing the predetermined conversion degree as the absolute value of the SOC difference is increased, the correction sensitivity of the full charge capacity can be freely changed, and an abnormal value caused by erroneous detection is detected. The influence of an extremely large SOC difference as expected can be suppressed as much as possible.

  According to the secondary battery control device of the third aspect, the predetermined conversion degree is made different depending on whether the SOC difference is positive or negative, and therefore the SOC difference is positive or negative. Depending on the situation, the full charge capacity correction sensitivity can be changed freely.For example, in a situation where the full charge capacity is erroneously estimated to be larger than the actual full charge capacity, the full charge capacity can be made appropriate at an early stage. Can be prevented from becoming an overdischarged state.

According to the control device for a secondary battery of claim 4, the measurement in the integrated value of the current detected by the current detection means is performed by correcting the full charge capacity of the secondary battery according to the sum of the predetermined number of points. Errors can be absorbed better, and the full charge capacity can be made even more accurate.
According to the control device for a secondary battery of claim 5, since the full charge capacity of the secondary battery is corrected when the sum of the predetermined number of points exceeds a predetermined threshold, it seems to be an abnormal value due to erroneous detection. It is possible to satisfactorily suppress the influence of the SOC difference.

It is a whole block diagram of the control apparatus of the secondary battery in this invention. It is a map which shows standard full charge capacity. It is a flowchart which shows the full charge capacity correction control routine of a secondary battery. It is a figure which shows the relationship between the open circuit voltage of a secondary battery, and SOC [voltage]. It is a figure which shows the relationship between (delta) SOC and a correction point.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is an overall configuration diagram of a control apparatus for a secondary battery according to the present invention.
The secondary battery control device is a secondary battery control device that supplies power to a travel motor (not shown) mounted as a driving force source of a series hybrid vehicle, for example.
As shown in FIG. 1, the secondary battery control device is configured by connecting a battery management control unit 20 to a secondary battery 10 and a power line 11 extending from the secondary battery 10 to a travel motor or a charging plug.

The secondary battery 10 is, for example, a lithium ion secondary battery, and includes a battery pack 12 in which a plurality of battery modules 14 are connected in series. A battery management control unit 20 is provided for each battery pack 12.
Specifically, a voltage sensor (voltage detection means) 16 and a battery temperature sensor 17 for measuring a voltage are provided for each battery module 14 and are electrically connected to the battery management control unit 20. The power line 11 is provided with a current sensor (current detection means) 18 that detects a charge / discharge current, and is electrically connected to the battery management control unit 20.

  The battery management control unit 20 is provided with an SOC calculation unit (first SOC calculation means, second SOC calculation means) 21 for calculating an SOC (State of Charge) which is a ratio of the battery capacity to the full charge capacity. In addition, each voltage detected by the voltage sensor 16, that is, the voltage value of the battery pack 12 is supplied to the SOC calculation unit 21, and the current value of the charge / discharge current flowing through the power line 11 is supplied from the current sensor 18. The Specifically, the SOC calculation unit 21 calculates SOC [voltage] based on the voltage value, and calculates SOC [current] based on the integrated value of the current.

A full charge capacity correction section (correction means) 22 for correcting and calculating the full charge capacity of the secondary battery 10 is connected to the input section of the SOC calculation section 21.
On the other hand, a correction calculation section (SOC difference calculation means, score calculation means) 23 and a correction start / execution determination section 24 for calculating the correction amount of the full charge capacity are connected to the output section of the SOC calculation section 21. .

  The correction start / execution determination unit 24 is further connected to the battery temperature sensor 17 and the correction calculation unit 23, and the output unit of the correction calculation unit 23 is connected to the input unit of the full charge capacity correction unit 22 via the storage unit 25. It is connected. In the storage unit 25, as shown in FIG. 2, the reference value of the full charge capacity that decreases with the passage of time since the use of the secondary battery 10 is started, that is, the reference full charge capacity (Ahr) is an experiment or the like. Is stored as a map based on the above, and the updated full charge capacity correction value, that is, the full charge capacity correction value is stored.

The battery management control unit 20 is further connected with a vehicle control device 30 for displaying the SOC in addition to various vehicle controls. Specifically, the input unit of the vehicle control device 30 is connected to the correction calculation unit 23, and the output unit is connected to the correction start / execution determination unit 24. Specifically, the start of correction and the execution of correction are determined based on the running state, the charging state, and the like.
FIG. 3 is a flowchart showing a full charge capacity correction control routine of the secondary battery 10 executed in the secondary battery control device during the charging of the secondary battery according to the present invention. The full charge capacity correction control content according to the present invention will be described below.

  In step S10, the correction start / execution determination unit 24 determines whether correction control can be started. Specifically, the vehicle control device 30 is in a charged state, the current SOC [voltage] value calculated by the SOC calculation unit 21 is, for example, 50% or less, and is detected by the battery temperature sensor 17. It is determined whether or not the minimum temperature of each battery temperature is, for example, 10 ° C. or higher. Here, the reason why the current SOC [voltage] value is set to, for example, 50% or less as the requirement for whether or not to start correction control is that the SOC [voltage] is relatively stable, and the minimum temperature of each battery temperature is, for example, The reason why the temperature is set to 10 ° C. or higher is that when the battery temperature is lower than 10 ° C., for example, the performance of the secondary battery 10 is degraded and accurate correction control cannot be performed. If the determination result is false (No) and the current SOC [voltage] value is not 50% or less, or the battery temperature is not less than 10 ° C. Exit the routine.

On the other hand, the determination result of step S10 is true (Yes), the battery is in a charged state, the current SOC [voltage] value is, for example, 50% or less, and the lowest battery temperature detected by the battery temperature sensor 17 is reached. When it is determined that the temperature is 10 ° C. or higher, for example, correction control of the full charge capacity is started.
In step S12, the SOC [current] is calculated in the SOC calculation unit 21. Specifically, the SOC [current] is obtained by converting the integrated value of the charging current detected by the current sensor 18 into a reference full charge capacity and a full charge capacity correction value stored in the storage unit 25 in the full charge capacity correction unit 22. It is obtained by dividing by the corrected full charge capacity calculated based on the above.

  In step S14, the correction start / execution determination unit 24 determines whether or not correction control can be performed. Specifically, it is determined whether or not SOC [current] has reached a predetermined value and a predetermined time (for example, 5 to 15 minutes) has elapsed since the charging current was temporarily stopped. Here, the reason for waiting for the elapse of a predetermined time (for example, 5 to 15 minutes) after temporarily stopping the charging current is to obtain the SOC [voltage] from the open voltage of the secondary battery 10 in the next step S16. It is. If the determination result is false (No), and it is determined that the SOC [current] has not reached the predetermined value or that the predetermined time has not elapsed since the charging current was temporarily stopped, the routine is exited. .

On the other hand, if the determination result in step S10 is true (Yes), the SOC [current] reaches a predetermined value, and it is determined that the predetermined time has elapsed after the charging current is temporarily stopped, the full charge capacity Perform the correction.
In performing the correction of the full charge capacity, the SOC [voltage] is calculated in the SOC calculation unit 21 in step S16. Specifically, the SOC calculation unit 21 stores a relationship between the open circuit voltage of the secondary battery 10 and the SOC [voltage] as shown in FIG. 4 as a map through experiments or the like. ] Is read.

In step S18, the correction calculation unit 23 calculates a difference between the SOC [current] and the SOC [voltage] calculated as described above, that is, δSOC (SOC difference) (δSOC = SOC [current] −SOC [voltage]. ).
In step S20, a correction point (point) is calculated based on the positive or negative magnitude of δSOC calculated as described above. Specifically, the correction point is calculated based on the relationship between δSOC and the correction point as shown in FIG. That is, the magnitude of δSOC is once converted into a correction point with a predetermined conversion degree.

  As shown in FIG. 5, with regard to the predetermined conversion degree in the relationship between δSOC and the correction point, here, as the absolute value of δSOC increases, the correction point is increased or decreased stepwise, and further, the magnitude of δSOC is further increased. Accordingly, the correction points are weighted accordingly, and the degree of conversion is such that as the absolute value of δSOC increases, the amount of change in the correction points is suppressed.

Then, the operations of step S18 and step S20 are repeated n times (predetermined number of times, for example, 10 times) at a predetermined time interval, and the n correction points are added up.
In step S <b> 22, the total value of the n correction points added in this way is temporarily stored in the storage unit 25.
In step S24, the full charge capacity correction unit 22 determines whether or not the sum of the correction points is smaller than a predetermined negative threshold (predetermined threshold). When the determination result is true (Yes) and it is determined that the total value of the correction points is smaller than a predetermined negative threshold value, the process proceeds to step S26, and the full charge capacity is subtracted and corrected by a certain amount. That is, the situation where the sum of the correction points is a negative value and smaller than a predetermined negative threshold, that is, the situation where δSOC is negative and SOC [current] is smaller than SOC [voltage]. The actual full charge capacity is smaller than the corrected full charge capacity. In other words, the full charge capacity for calculating the SOC [current] is erroneously estimated to be larger than the actual full charge capacity. In this case, the full charge capacity is subtracted and corrected by a certain amount so that δSOC goes to a value of 0, that is, SOC [current] and SOC [voltage] match.

  On the other hand, if the determination result in step S24 is false (No) and the sum value of the correction points is not smaller than a predetermined negative threshold value, the process proceeds to step S28, and the sum value of the correction points is a predetermined positive threshold value (predetermined value). It is determined whether or not it is larger than (threshold). When the determination result is true (Yes) and it is determined that the total value of the correction points is greater than a predetermined positive threshold value, the process proceeds to step S30, and the full charge capacity correction unit 22 sets the full charge capacity to a certain amount. Only add correction. That is, the situation where the sum of the correction points is a positive value and is smaller than a predetermined positive threshold, that is, the situation where δSOC is positive and SOC [current] is greater than SOC [voltage]. The actual full charge capacity is larger than the corrected full charge capacity, in other words, the corrected full charge capacity for calculating the SOC [current] is erroneously estimated to be smaller than the actual full charge capacity. In this case, the full charge capacity is added and corrected by a certain amount so that δSOC goes to a value of 0, that is, SOC [current] and SOC [voltage] match.

After subtraction correction or addition correction of the full charge capacity in this way, the process proceeds to step S32, where the sum value of the n correction points stored in step S22 is reset, and thereafter, SOC [current] and SOC [voltage] are obtained. The routine is repeatedly executed so that they match.
As described above, in the secondary battery control device according to the present invention, paying attention to the difference between the SOC [current] and the SOC [voltage] due to the secular change of the secondary battery 10, the secondary battery The full charge capacity of the secondary battery 10 is corrected and controlled so that the SOC [current] and the SOC [voltage] coincide with each other while the battery 10 is being charged. At this time, the difference between the SOC [current] and the SOC [voltage], that is, δSOC is converted into a correction point, and as the δSOC increases to the positive side, the amount of the correction point increases stepwise to the positive side, or δSOC As the value is smaller on the negative side, the amount of correction points is gradually increased to the negative side to obtain a total value of n correction points, and the total value of the correction points is greater than a predetermined positive threshold or a predetermined negative value. When it becomes smaller than the threshold, the full charge capacity is subjected to subtraction correction or addition correction by a certain amount.

  Therefore, for example, if the full charge capacity is simply corrected according to the magnitude of the δSOC based on the instantaneous value of δSOC, it is particularly susceptible to the measurement error of the current sensor 18, and the full charge capacity is appropriately set. Although there is a possibility that the correction cannot be performed, δSOC is converted into a correction point, and as δSOC is larger on the positive side, the amount of correction point is increased stepwise toward the positive side, or as δSOC is smaller on the negative side, The amount is gradually increased to the negative side to obtain a total value of n correction points, and the full charge capacity is subtracted or added based on the total value of the correction points. Even if a measurement error occurs, the measurement error can be improved by converting the magnitude of δSOC into a correction point and by adding the correction points n times. Absorption can can be made accurate to properly correct the full charge capacity.

In particular, an abnormal value due to erroneous detection of the current sensor 18 by correcting the full charge capacity by subtraction correction or addition correction when the total value of the correction points is greater than a predetermined positive threshold value or smaller than a predetermined negative threshold value. It is possible to satisfactorily suppress the influence of the SOC difference that seems to be.
When the magnitude of δSOC is once converted into a correction point in this way, a predetermined conversion degree is set to a conversion degree that weights the correction point according to the magnitude of δSOC, thereby correcting the full charge capacity. Sensitivity can be changed freely.

For example, it is considered that the predetermined conversion degree is an abnormal value due to erroneous detection of the current sensor 18 by setting the conversion degree such that the change amount of the correction point is suppressed as the absolute value of δSOC is large as shown in FIG. The influence of such an extremely large δSOC can be minimized.
Also, for example, when δSOC is negative, it is considered that the corrected full charge capacity for calculating the SOC [current] is erroneously estimated to be larger than the actual full charge capacity. In this case, by making the amount of correction points for δSOC larger as a whole than when δSOC is on the positive side, subtraction correction of the full charge capacity can be performed early. Specifically, in FIG. 5, when δSOC is on the positive side, no correction point is assigned when δSOC is near the value 0, whereas when δSOC is on the negative side, the correction point is set even when δSOC is near the value 0. I try to put it on. As a result, the sensitivity of the subtraction correction of the full charge capacity can be particularly increased, and the SOC [current] and the SOC [voltage] can be made to coincide with each other quickly with the proper full charge capacity. It is possible to suitably prevent a situation in which the secondary battery 10 is overdischarged and the vehicle stops in the middle of traveling.

Although the description of the control apparatus for a secondary battery according to the present invention is finished as above, the present invention is not limited to the above embodiment.
For example, in the above embodiment, it is determined whether or not the sum of the correction points is smaller than a predetermined negative threshold or larger than a predetermined positive threshold in step S24 or step S28, and satisfied in step S26 or step S30. The charging capacity is added or subtracted by a fixed amount. However, a predetermined negative threshold and a predetermined positive threshold are provided in a plurality of stages, and the correction amount is not limited to a fixed amount. It may be made different for each threshold value or a predetermined positive threshold value.

  Moreover, in the said embodiment, although the secondary battery 10 was used as the lithium ion secondary battery, for example, it may be a secondary battery and may be a lithium polymer secondary battery.

10 Secondary battery 12 Battery pack 16 Voltage sensor (voltage detection means)
17 Battery temperature sensor 18 Current sensor (current detection means)
20 battery management control unit 21 SOC calculation unit (first SOC calculation means, second SOC calculation means)
22 Full charge capacity correction unit (correction means)
23 Correction calculation section (SOC difference calculation means, point calculation means)
24 correction start / execution determination unit 25 storage unit 30 vehicle control device

Claims (5)

A control device for a secondary battery that corrects the full charge capacity of the secondary battery,
Current detection means for detecting a charge / discharge current of the secondary battery;
Voltage detection means for detecting the voltage of the secondary battery;
First SOC calculation means for obtaining a first SOC based on an integrated value of the current detected by the current detection means;
Second SOC calculating means for obtaining a second SOC based on the voltage detected by the voltage detecting means;
SOC difference calculating means for calculating a difference between the first SOC and the second SOC as an SOC difference;
Point calculation means for calculating the SOC difference as a point converted with a predetermined conversion degree according to the SOC difference;
Correction means for correcting the full charge capacity of the secondary battery according to the score;
A control apparatus for a secondary battery, comprising:   The secondary battery control device according to claim 1, wherein the predetermined conversion degree in the point calculation means is smaller as the absolute value of the SOC difference is larger.   3. The secondary battery control device according to claim 1, wherein the predetermined degree of conversion in the point calculation means varies depending on whether the SOC difference is positive or negative. 4. The score calculation means calculates the score a predetermined number of times at a predetermined time interval, adds the scores determined for the predetermined number of times, and calculates a sum value.
4. The secondary battery control device according to claim 1, wherein the correction unit corrects a full charge capacity of the secondary battery according to the total value. 5.   The secondary battery control device according to claim 4, wherein the correction unit corrects a full charge capacity of the secondary battery when the total value exceeds a predetermined threshold value.

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