JP5995050B2 - Battery charge / discharge control device - Google Patents

Description

  The present invention relates to a battery charge / discharge control device for performing charge / discharge while suppressing a voltage drop due to concentration polarization in a battery.

  When the secondary battery is pulse-charged with a large current, a shared voltage that gradually increases as the concentration polarization progresses when the pulse is applied, and a shared voltage that gradually decreases as the concentration polarization disappears when the pulse application ends. When at least one of the values is read and the value becomes equal to or greater than a predetermined threshold value, it is determined that there is a possibility that the concentration polarization due to overcharging may occur and the battery is deteriorated, and the pulse charging is terminated. Is known.

JP 2008-181866 A

  However, since the conventional one applies the same single pulse and determines the occurrence of concentration polarization from the behavior of the voltage, it cannot be determined unless the concentration polarization is in a considerably advanced state. In addition to the possibility of delaying the battery timing and causing deterioration of the battery, accurate determination may be difficult in a system that performs complex input / output such as an electric vehicle or a hybrid vehicle.

  The present invention has been made in view of the above circumstances, and an object thereof is to monitor a load applied to a battery and prevent a voltage drop due to the concentration polarization described above in advance.

  In order to achieve the above object, according to the first aspect of the present invention, a current control unit that limits a current for charging / discharging the battery to a maximum current value or less and a concentration polarization calculation for calculating the concentration polarization of the battery Unit, an average concentration polarization calculating unit that calculates an average concentration polarization that is an average value per unit time of the concentration polarization, and a continuous charge / discharge time that calculates a continuous charge / discharge time during which the battery is continuously charged / discharged A calculation unit; a concentration polarization reduction necessity determination unit that determines necessity of concentration polarization reduction based on the average concentration polarization and the continuous charge / discharge time; and the maximum current based on determination of necessity of concentration polarization reduction. A battery charge / discharge control device comprising a maximum current value setting unit for setting a value is proposed.

  According to the invention described in claim 2, in addition to the configuration of claim 1, the average concentration polarization when the maximum current value is the first current value is a predetermined value or more, and the continuous When the charge / discharge time is equal to or longer than a predetermined time, the concentration polarization reduction necessity determination unit determines that concentration polarization reduction is necessary, and the maximum current value setting unit determines the maximum current value as the first current value. A charging / discharging control device for a battery is proposed in which the second current value is set to be smaller than that.

  According to the invention described in claim 3, in addition to the configuration of claim 2, the maximum current value setting unit sets the second current value based on the temperature of the battery, and A battery charge / discharge control device is proposed in which a higher value is set as the temperature is higher.

  According to the invention described in claim 4, in addition to the configuration of claim 2, the maximum current value setting unit further sets an allowable charge / discharge time that can be charged / discharged by the second current value. A battery charge / discharge control device is proposed.

According to the invention described in claim 5, in addition to the configuration according to claim 4, wherein the maximum current value setting section, the allowable charge that can be charged and discharged by the second current value and the second current value current value shows the relationship between the discharge charging time - permissible charging and discharging time with the map, the current value - permissible charging and discharging time map as the permissible charging and discharging time the larger the second current value is shortened A battery charge / discharge control device characterized by being set is proposed.

  According to the invention described in claim 6, in addition to the configuration of claim 2, the concentration polarization reduction necessity determination unit is configured to determine an average concentration polarization indicating a relationship between the average concentration polarization and the continuous charge / discharge time. -Comprising a continuous charge / discharge time map, wherein the average concentration polarization-continuous charge / discharge time map is set such that the average concentration polarization that can be tolerated becomes smaller as the continuous charge / discharge time is longer, and the maximum current value setting unit is A battery charge / discharge control device is proposed, which determines whether or not to set the second current value based on an average concentration polarization-continuous charge / discharge time map.

  The timer 25 of the embodiment corresponds to the continuous charge / discharge time calculation unit of the present invention.

  According to the configuration of claim 1, the concentration polarization calculation unit calculates the concentration polarization of the battery, the average concentration polarization calculation unit calculates the average concentration polarization that is an average value per unit time of the concentration polarization, and the continuous charge / discharge time. The calculation unit calculates the continuous charge / discharge time during which the battery is continuously charged / discharged, and the concentration polarization reduction necessity determination unit determines the necessity of concentration polarization reduction based on the average concentration polarization and the continuous charge / discharge time, The maximum current value setting unit sets the maximum current value based on whether or not concentration polarization reduction is necessary, and the current control unit limits the current to charge / discharge the battery to the maximum current value or less. Current can be reduced before concentration polarization increases due to charge / discharge, and voltage drop due to increase in internal resistance can be minimized. Furthermore, unlike the case where the same single pulse is applied to determine the occurrence of concentration polarization from the voltage behavior, the concentration polarization of the battery can be accurately detected even in a system with complicated input / output such as an electric vehicle or a hybrid vehicle. Can be determined.

  According to the second aspect of the present invention, the concentration polarization is reduced when the average concentration polarization when the maximum current value is the first current value is a predetermined value or more and the continuous charge / discharge time is a predetermined time or more. Since the necessity determination unit determines that concentration polarization reduction is necessary, it can accurately determine whether concentration polarization reduction is necessary. Moreover, since the maximum current value setting unit sets the maximum current value to the second current value smaller than the first current value, it is possible to prevent the concentration polarization from increasing due to charging / discharging with an excessive current. .

  According to the third aspect of the present invention, the maximum current value setting unit sets the second current value to a higher value as the battery temperature is higher, so that the battery is hot and concentration polarization hardly occurs (resolves). When the second current value is set to a high value, the battery performance can be maximized by avoiding an unnecessary current limit.

  According to the configuration of claim 4, the maximum current value setting unit sets the allowable charge / discharge time that can be charged / discharged by the second current value in addition to the second current value that is the maximum current value. Even when the charging / discharging current temporarily exceeds the second current value due to a sensor error or the like, unnecessary current limitation can be prevented each time.

According to the configuration of claim 5, the maximum current value setting unit current value shows the relationship between the allowable charging and discharging time to charging and discharging at a second current value and the second current value - allowable charge-discharge time includes a map, since the map is set such that the allowable charging and discharging time larger the second current value becomes shorter, depending on the occurrence tendency of concentration polarization, for example, a current value as a hybrid vehicle is high charge If discharge charging time is short and the current value as an electric vehicle is low but as the case long charge-discharge time can be set to a combination of the current value and the allowable charge-discharge time flexibility.

  Further, according to the configuration of claim 6, the concentration polarization reduction necessity determination unit includes an average concentration polarization-continuous charge / discharge time map set so that an allowable average concentration polarization becomes smaller as the continuous charge / discharge time is longer, Based on this map, it is determined whether or not the maximum current value setting unit sets the second current value. Therefore, the necessity of current limitation is flexibly determined based on two parameters, average concentration polarization and continuous charge / discharge time. be able to.

The block diagram which shows the whole structure of the charging / discharging control apparatus of a battery. The flowchart of a main routine. The flowchart of the subroutine of step S1 of the main routine. The flowchart of the subroutine of step S2 of the main routine. The flowchart of the subroutine of step S3 of the main routine. The flowchart of the subroutine of step S6 of the main routine. This map searches for the transient resistance increase rate from the average concentration polarization and continuous charge / discharge time. Explanatory drawing of the method of calculating the average concentration polarization upper limit value for the average concentration polarization and continuous charge / discharge time not exceeding a control intervention line. The second current value and the map to find the combination of allowable charging and discharging time from the average concentration polarization limit.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS.

  As shown in FIG. 1, an electric vehicle or a hybrid vehicle includes a battery 11 formed of a lithium ion battery that can be charged and discharged. The battery 11 is connected to a motor / generator (not shown). The battery 11 supplies electric power to the motor / generator to generate running torque and torque for assisting the engine. At the same time, the battery 11 uses electric power generated by the motor / generator by regenerative braking. Charged. A battery ECU 12 that controls charging / discharging of the battery 11 includes a battery temperature sensor 13 that detects the temperature of the battery 11, a battery current sensor 14 that detects the current of the battery 11, and a battery voltage sensor 15 that detects the voltage of the battery 11. The maximum current value capable of charging / discharging the battery 11 is calculated based on the signal from. The current control unit 16 connected to the battery ECU 12 controls charging / discharging of the battery 11 based on the maximum current value.

  The battery ECU 12 includes an SOC calculation unit 21, an SOC-OCV map 22, a resistance calculation unit 23, a concentration polarization calculation unit 24, a timer 25, an average concentration polarization calculation unit 26, and a concentration polarization reduction necessity determination unit 27. And a maximum current value setting unit 28. SOC: State of Charge is the remaining capacity of the battery 11, and OCV: Open Circuit Voltage is the open voltage of the battery 11.

  Next, the outline of the charge / discharge control of the battery 11 will be described based on the block diagram of FIG. 1 and the flowcharts of FIGS.

  First, in step S1 of the flowchart of the main routine of FIG. 2, the concentration polarization of the battery 11 is calculated by the concentration polarization calculation unit 24. When the current is taken out from the battery, the terminal voltage of the battery becomes smaller than the electromotive force. This phenomenon is called polarization, or the amount of decrease in battery terminal voltage caused by this phenomenon is called polarization. Concentration polarization is a kind of polarization described above. For example, in a lithium ion battery, the lithium ion concentration in the electrolyte is decreased on the positive electrode side and increased on the negative electrode side due to charge / discharge at a high rate, so that the internal resistance of the battery increases. As a result, the terminal voltage decreases.

  The flowchart of FIG. 3 shows the subroutine of step S1. First, the OCV of the battery 11 is acquired in step S11. That is, the SOC calculation unit 21 calculates the SOC from the battery current detected by the battery current sensor 14, and calculates the OCV by applying the SOC and the battery temperature detected by the battery temperature sensor 13 to the SOC-OCV map 22. . The SOC calculation unit 21 calculates the accumulated charge amount and the accumulated discharge amount by integrating the battery current detected by the battery current sensor 14 every predetermined time, and calculates the accumulated charge amount and the accumulated discharge amount in the initial state or immediately before the start of charge / discharge. The SOC is calculated by adding or subtracting to the SOC (initial SOC). Further, the OCV can be calculated with higher accuracy by changing the SOC-OCV map 22 according to the battery temperature.

  The OCV corresponds to the terminal voltage when the battery 11 is not charging / discharging. Therefore, when the battery 11 is not charging / discharging, the value detected by the battery voltage sensor 15 is the terminal voltage at that time. It can be used as OCV.

  In subsequent step S12, the instantaneous resistance R1 of the battery 11 is acquired by the resistance calculation unit 23. In other words, the battery instantaneous resistance R1 is calculated by applying statistical processing such as a least square method to the amount of change in the battery voltage detected by the battery voltage sensor 15 and the amount of change in the battery current detected by the battery current sensor 14. . In subsequent step S13, the concentration polarization Vc of the battery 11 is calculated by Vc = OCV−V−I * R1. Here, V is the battery voltage detected by the battery voltage sensor 15, and I is the battery current detected by the battery current sensor 14. At this time, if the battery temperature detected by the battery temperature sensor 13 is taken into consideration, the concentration polarization Vc can be calculated with higher accuracy.

  Returning to the main routine of FIG. 2, the average concentration polarization of the battery 11 is acquired by the average concentration polarization calculator 26 in step S <b> 2.

  The flowchart of FIG. 4 shows the subroutine of step S2. First, in step S21, the concentration polarization Vc of the battery 11 is acquired from the concentration polarization calculation unit 24. In step S22, the concentration polarization Vc is converted into an absolute value, and then in step S23, the integrated concentration polarization ∫Vc (k + 1) of the battery 11 is calculated by に よ り Vc (k + 1) = Vc + ∫Vc (k). That is, by adding the concentration polarization Vc of the current loop to the integrated concentration polarization ∫Vc (k) of the previous loop, the integrated concentration polarization ∫Vc (k + 1) of the current loop is calculated. In subsequent step S24, the continuous charge / discharge time t during which the battery current is flowing is measured by the timer 25, and in step S25, the average concentration polarization calculation unit 26 calculates the average concentration polarization AVE. Vc, AVE. Vc = [∫Vc (k + 1)] / t. The reason why the concentration polarization Vc is converted to an absolute value in the step S22 is that the sign of the concentration polarization Vc is different between positive and negative at the time of charging and discharging. AVE. This is because Vc cannot be calculated correctly.

  Returning to the main routine of FIG. 2, in step S3, the concentration polarization reduction necessity determination unit 27 causes the average concentration polarization AVE. It is determined whether control for reducing Vc is necessary.

  The flowchart of FIG. 5 shows the subroutine of step S3. First, in step S31, the average concentration polarization AVE. Obtain Vc. In subsequent step S32, the timer 25 counts the continuous charge / discharge time t during which the battery current flows, and in step S33, the average concentration polarization-AVE is stored in the average concentration polarization-continuous charge / discharge time map stored in the concentration polarization reduction necessity determination unit 27. . Vc and continuous charge / discharge time t are applied. The average concentration polarization-continuous charge / discharge time map shows the average concentration polarization AVE. Vc is taken and a horizontal charging / discharging time t is taken on the horizontal axis, and a control intervention line and an input / output inhibition line are set there.

  The control intervention line and the input / output inhibition line indicate that the average concentration polarization AVE. Vc decreases, and conversely, the average concentration polarization AVE. It is set so that the continuous charge / discharge time t decreases as Vc increases. And average concentration polarization AVE. When the point indicated by Vc and the continuous charge / discharge time t crosses the control intervention line from the origin side to the non-origin side, it is determined that there may be a temporary increase in resistance due to concentration polarization in the battery 11. In order to suppress the occurrence of polarization, the maximum charge / discharge current value is suppressed. Control for suppressing the maximum charge / discharge current value is executed in a region sandwiched between the control intervention line and the input / output inhibition line, and the average concentration polarization AVE. When the point indicated by Vc and the continuous charge / discharge time t crosses the input / output inhibition line from the origin side to the non-origin side, it is determined that a temporary increase in resistance has already occurred in the battery 11 and the battery 11 is charged. Discharge is prohibited.

  Returning to the main routine of FIG. 2, in step S4, the average concentration polarization AVE. When Vc is less than the threshold value or the continuous charge / discharge time t is less than the threshold value, that is, the average concentration polarization AVE. If the point indicated by Vc and the continuous charge / discharge time t is on the origin side of the control intervention line, it is determined that there is no possibility that the battery 11 will temporarily increase in resistance due to concentration polarization, and charging is performed in step S5. The discharge current is limited to the maximum value in the normal control, that is, the first current value corresponding to the SOC of the battery 11.

  On the other hand, in step S4, the average concentration polarization AVE. When Vc is equal to or greater than the threshold and the continuous charge / discharge time t is equal to or greater than the threshold, that is, the average concentration polarization AVE. If the point indicated by Vc and the continuous charge / discharge time t is on the opposite side of the control intervention line, it is determined that there may be a temporary increase in resistance due to concentration polarization in the battery 11, and in step S6 A second current value that is the maximum current value for eliminating the concentration polarization is set.

  The flowchart of FIG. 6 shows the subroutine of step S6. First, in step S61, the average concentration polarization AVE. An average concentration polarization upper limit value Vc (DOWN) for maintaining Vc and continuous charge / discharge time t closer to the origin side than the control intervention line is acquired. The map of FIG. 7 shows the average concentration polarization AVE. Vc is taken and the horizontal axis indicates the continuous charge / discharge time t. The average concentration polarization AVE. It shows that the transient internal resistance of the battery 11 increases due to concentration polarization as Vc increases or as the continuous charge / discharge time t increases. As shown by the broken line in FIG. 7, if the limit of the maximum current value for eliminating the concentration polarization is not executed, the average concentration polarization AVE. It can be seen that the transient resistance increase rate gradually increases as Vc and the continuous charge / discharge time t increase.

  In FIG. 8, the average concentration polarization AVE. When Vc and continuous charge / discharge time t change along the broken line, it is assumed that the control intervention line crosses from the origin side to the non-origin side at point A. A point where a line extending in parallel with the horizontal axis through point A intersects with the input / output inhibition line is designated as B point, and a point where a line extending through point B in parallel with the vertical axis intersects with the control intervention line is designated as point C. When the average concentration polarization AVE. If Vc is decreased at a predetermined decrease rate, the average concentration polarization AVE. Vc can be maintained closer to the origin than the control intervention area.

  The time at point A is a, the time at points B and C is b, and the average concentration polarization AVE. Vc is c, and average concentration polarization AVE. When Vc is d, the concentration polarization at point A (ie time a) is given by d × a, and the concentration polarization at point C (ie time b) is given by c × b. Average concentration polarization AVE. Time change rate ΔAVE. Of average concentration polarization for changing Vc from point A to point C Vc is calculated by dividing the difference obtained by subtracting the concentration polarization at point A (ie, d × a) from the concentration polarization at point C (ie, c × b) by the time ba from point A to point B. The

ΔAVE. Vc = {(c × b) − (d × a)} / (b−a)
In the above formula, for example, if a = 60 min, b = 120 min, c = 60 mV, d = 80 mV,
ΔAVE. Vc = {(60 × 120) − (80 × 60)} / (120-60)
= 40 (mV / min)
And the time change rate ΔAVE. Vc is defined as the average concentration polarization upper limit value Vc (DOWN). Therefore, the average concentration polarization AVE. With the average concentration polarization upper limit Vc (DOWN). If Vc is reduced, the average concentration polarization AVE. Vc and continuous charge / discharge time t can be maintained closer to the origin than the control intervention line.

Get the battery temperature by the battery temperature sensor 13 in subsequent step S62, the current value set for each battery temperature in step S63 - calculating a maximum current value and the allowable charging and discharging time of the allowable charge and discharge time map. Map of FIG. 9, which has taken the allowable charge-discharge time on the horizontal axis represents the current value on the vertical axis, there is an average of the battery temperature 25 ° C Concentration polarization limit Vc (DOWN) is 40m line A 50 mV line and a normal use line are shown. It means that the concentration polarization limit Vc (DOWN) is small, in order to eliminate the concentration polarization, and smaller the maximum current value of the charge and discharge, and that it requires a shorter allowable charge-discharge time Therefore, the characteristic line approaches the origin. Further, since the concentration polarization is easily eliminated when the battery temperature is high, for example, the 40 mV line at 30 ° C. moves to the opposite origin side than when the battery temperature is 25 ° C.

When the average concentration polarization limit Vc at the battery temperature 25 ° C (DOWN) is 40 mV, the allowable charge-discharge time when the current value of the charge and discharge is high I1 becomes short t1, the current value of the charging and discharging moderate if I2 permissible charging and discharging time becomes t2 moderate, allowable charge-discharge time becomes long t3 if I3 current value of charge and discharge is low. Therefore, the maximum current value and the allowable charge-discharge time supplied to the battery 11, the current value - cross lines of average given in permissive charge and discharge time map concentration polarization limit Vc (DOWN) so as not to exceed the opposite home side By controlling in relation to the above, it is possible to reliably suppress the concentration polarization of the battery 11 and prevent a sudden voltage drop.

  As described above, according to the present embodiment, the average concentration polarization AVE., Which is the average value per unit time of the concentration polarization Vc of the battery 11. It is determined that concentration polarization reduction is necessary when Vc is equal to or greater than a predetermined value and the continuous charge / discharge time t during which the battery 11 is continuously charged / discharged is a predetermined value, and the maximum current for charging / discharging the battery 11 Since the value is reduced from the first current value to a current value of 2 smaller than the first current value, the current is reduced before the battery 11 is charged / discharged with an excessive current and the concentration polarization is increased, and the internal resistance of the battery 11 is reduced. The voltage drop due to the increase can be minimized. In addition, unlike the case where the same single pulse is applied to determine the occurrence of concentration polarization from the behavior of voltage, the concentration polarization of the battery 11 is accurately determined even in a system that performs complex input / output such as an electric vehicle or a hybrid vehicle. Can be determined.

  Further, the average concentration polarization-continuous charge / discharge time map of the concentration polarization reduction necessity determination unit 27 indicates that the average concentration polarization AVE. Since Vc is set to be small, when determining whether or not the maximum current value setting unit 28 sets the second current value based on this map, the average concentration polarization AVE. The necessity of current limitation can be flexibly determined by two parameters, Vc and continuous charge / discharge time t.

  Further, since the maximum current value setting unit 28 sets the second current value to a higher value as the battery temperature is higher, the second current value is increased when the battery 11 is at a high temperature and concentration polarization is easily eliminated. By setting the value, unnecessary current limitation can be avoided and the performance of the battery 11 can be maximized.

The maximum current value setting unit 28 sets an allowable charge / discharge time that can be charged / discharged with the second current value in addition to the second current value that is the maximum current value with which the battery 11 can be charged / discharged. Even if the current for charging / discharging the current temporarily exceeds the second current value due to a sensor error or the like, unnecessary current limitation can be prevented each time. Moreover the current value of the maximum current value setting section 28 - permissible charging and discharging time map, so as allowable charging and discharging time is greater second current value is set to be shorter, for example, a current value as a hybrid vehicle high but or short aspects charging and discharging time, even if the current value as an electric vehicle is lesser to use battery 11 with long aspects charging and discharging time, the current value and the allowable charge-discharge time combination Can be set flexibly.

  The embodiments of the present invention have been described above, but various design changes can be made without departing from the scope of the present invention.

  For example, the battery of the present invention is not limited to a lithium ion battery, and its use is not limited to an electric vehicle and a hybrid vehicle.

11 Battery 16 Current control unit 24 Concentration polarization calculation unit 25 Timer (continuous charge / discharge time calculation unit)
26 Average concentration polarization calculation unit 27 Concentration polarization reduction necessity determination unit 28 Maximum current value setting unit

Claims (6)

A current control unit (16) for limiting a current for charging / discharging the battery (11) to a maximum current value or less;
A concentration polarization calculator (24) for calculating the concentration polarization of the battery (11);
An average concentration polarization calculating section (26) for calculating an average concentration polarization which is an average value per unit time of the concentration polarization;
A continuous charge / discharge time calculating unit (25) for calculating a continuous charge / discharge time during which the battery (11) is continuously charged / discharged;
A concentration polarization reduction necessity determination unit (27) for determining whether concentration polarization reduction is necessary based on the average concentration polarization and the continuous charge / discharge time;
A maximum current value setting unit (28) for setting the maximum current value based on the determination of whether or not concentration polarization reduction is necessary;
A charge / discharge control device for a battery, comprising:   When the average concentration polarization when the maximum current value is the first current value is a predetermined value or more and the continuous charge / discharge time is a predetermined time or more, the concentration polarization reduction necessity determination unit (27 ) Determines that concentration polarization reduction is necessary, and the maximum current value setting unit (28) sets the maximum current value to a second current value smaller than the first current value. The charge / discharge control device for a battery according to claim 1.   The maximum current value setting unit (28) sets the second current value based on the temperature of the battery (11), and sets the second current value to a higher value as the temperature of the battery (11) is higher. The charge / discharge control device for a battery according to claim 2.   The charge / discharge control apparatus for a battery according to claim 2, wherein the maximum current value setting unit (28) further sets an allowable charge / discharge time that can be charged / discharged with the second current value. The maximum current value setting unit (28), said second current value and the current value indicating the relationship between the allowable charging and discharging time can be charged and discharged at a current value of the second - with the allowable charge-discharge time map the current value - permissible charging and discharging time map is characterized by being configured as the permissible charging and discharging time large the second current value is reduced, the charging and discharging of the battery according to claim 4 Control device.   The concentration polarization reduction necessity determination unit (27) includes an average concentration polarization-continuous charge / discharge time map indicating a relationship between the average concentration polarization and the continuous charge / discharge time, and the average concentration polarization-continuous charge / discharge time map. Is set so that the allowable average concentration polarization becomes smaller as the continuous charge / discharge time becomes longer, and the maximum current value setting unit (28) sets the second current based on the average concentration polarization-continuous charge / discharge time map. The battery charge / discharge control device according to claim 2, wherein it is determined whether or not the current value is set.

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