JP2013210206A - On-vehicle battery charge state estimation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an on-vehicle battery charge state estimation device that can quickly determine whether or not a state of a battery terminal voltage is required for an urgent action when the battery terminal voltage exceeds a predetermined overcharge voltage.SOLUTION: When a terminal voltage V of a battery 20 exceeds an overcharge voltage V, a charge state estimation unit 10 estimates whether or not there is a possibility of the terminal voltage V of the battery 20 exceeding a danger voltage Vwithin a predetermined count number Tc on the basis of a change amount α of an internal resistance of the battery 20. More particularly, when the change amount α of the internal resistance is larger than a first threshold value and smaller than a second threshold value, it is estimated that there is no possibility of the terminal voltage thereof exceeding the danger voltage Vwithin the predetermined count number Tc, and when the change amount α of the internal resistance is larger than the second threshold value and smaller than a third threshold value, it is estimated that there is a possibility of the terminal voltage thereof exceeding the danger voltage Vwithin the predetermined count number Tc, and when the change amount α of the internal resistance is larger than the third threshold value, it is estimated that the battery 20 is out of order.

Description

  The present invention relates to an on-vehicle battery charge state estimation device.

  An electric vehicle (EV vehicle) that travels by an electric motor and a plug-in hybrid vehicle (PHV vehicle) that travels by using an electric motor and a gasoline engine in combination have become widespread. These EV cars and PHV cars are equipped with a chargeable / dischargeable battery for storing electric power for driving the electric motor.

  During regenerative travel of EV cars and PHV cars, the battery is charged and the battery terminal voltage gradually rises, but the battery cannot store power even if it is charged further. There is a threshold called "overcharge voltage" that causes battery degradation. For this reason, the battery terminal voltage is usually monitored by a voltage sensor or the like, and the battery is protected by taking measures such as limiting the input current to the battery when the voltage exceeds a predetermined overcharge voltage. It has been broken. However, in the method of monitoring the terminal voltage of the battery with a voltage sensor or the like, a terminal voltage that temporarily exceeds the overcharge voltage may be observed temporarily due to the influence of measurement noise or the like even if the battery is not overcharged. possible. Therefore, Patent Document 1 does not immediately determine that the terminal is in an overcharged state even if a terminal voltage exceeding the overcharged voltage is observed, and waits for that state to continue for a predetermined time before the battery enters the overcharged state. Items that are judged to be present are described.

JP 2009-177937 A

  However, if the terminal voltage rises slowly after exceeding the overcharge voltage, the input current to the battery is limited by determining that it is in the overcharge state after waiting for the state to continue for a predetermined time. Although it is not slow even if measures such as this are taken, if the terminal voltage rises suddenly, the terminal voltage may rise further while waiting for that state to continue for a predetermined time, and the battery may be damaged. There is a possibility of exceeding the “dangerous voltage”. In addition, when the cause of the increase in the terminal voltage is a battery failure, the use of the battery must be stopped immediately. Therefore, as described in Patent Document 1, in the method of determining that the battery is in the overcharged state after waiting for the terminal voltage to exceed the overcharged state for a predetermined time, the terminal voltage rapidly increases. There is a problem that a prompt action cannot be taken in a situation where an urgent action is required such as when the battery is malfunctioning or when the battery is out of order.

  The present invention has been made to solve such a problem. When the battery terminal voltage exceeds a predetermined overcharge voltage, it is quickly determined whether or not the state requires urgent action. It is an object of the present invention to provide an in-vehicle battery charge state estimation device that can determine the above.

  In order to solve the above problems, an on-vehicle battery charge state estimation device according to the present invention includes a calculation unit that calculates a change amount of an internal resistance of a battery, and an estimation unit that estimates a charge state of the battery. When the battery terminal voltage exceeds a predetermined overcharge voltage, the means determines a predetermined dangerous voltage that is higher than the predetermined overcharge voltage by a predetermined count number based on the amount of change in the internal resistance. Estimate whether or not there is a possibility of exceeding.

  Preferably, when the change amount of the internal resistance is larger than the first threshold value and smaller than the second threshold value, the estimating means may cause the battery terminal voltage to exceed a predetermined dangerous voltage within a predetermined count number. If the change amount of the internal resistance is larger than the second threshold value and smaller than the third threshold value, it is estimated that the battery terminal voltage may exceed the predetermined dangerous voltage within the predetermined count number. If the change amount of the internal resistance is larger than the third threshold value, it is estimated that the battery has failed.

The estimation means is configured such that the battery terminal voltage is V, the input current is I, the internal resistance change amount is α, even if the change amount of the internal resistance is larger than the first threshold value and smaller than the second threshold value. When the dangerous voltage of V is _B
V> V _B + Iα
If the above relationship is satisfied, it may be estimated that the terminal voltage of the battery may exceed a predetermined dangerous voltage within a predetermined count number.

  Protecting means for protecting the battery is further provided. When it is estimated that there is no possibility that the terminal voltage of the battery exceeds the predetermined dangerous voltage within the predetermined count number, the protective means detects that the terminal voltage of the battery exceeds the predetermined overvoltage. Waiting for the state exceeding the charging voltage to continue for a predetermined count number, limiting the input current to the battery, and the battery terminal voltage may exceed the predetermined dangerous voltage within the predetermined count number If estimated, the input current to the battery is immediately limited, and if it is estimated that the battery has failed, the use of the battery may be stopped immediately.

  According to the on-vehicle battery charge state estimation device according to the present invention, when the battery terminal voltage exceeds a predetermined overcharge voltage, it is quickly determined whether or not the state requires urgent action. be able to.

It is a figure which shows the structure of the electric system of the electric vehicle carrying the charging condition estimation unit of the vehicle-mounted battery which concerns on embodiment of this invention. It is a flowchart which shows the estimation method of the charge condition of the battery by the charge condition estimation unit which concerns on embodiment of this invention. It is a figure which shows the charge condition of the battery which concerns on embodiment of this invention. It is a flowchart which shows the modification of the estimation method of the charge condition of the battery by the charge condition estimation unit which concerns on embodiment of this invention.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
Embodiment.
FIG. 1 shows a configuration of an electric system of an electric vehicle equipped with an in-vehicle battery charging state estimation unit 10 according to an embodiment of the present invention.
As shown in FIG. 1, an electric system of an electric vehicle includes a battery 20 that stores DC power, a power conversion unit 21 that can operate as an inverter and a converter, and a motor generator 22 that can operate as an electric motor and a generator. These are sequentially connected in series.

  During normal driving of the electric vehicle, the DC power supplied from the battery 20 is converted into AC power by the power conversion unit 21, and the motor generator 22 operates as an electric motor by this AC power to drive the wheels of the electric vehicle. . On the other hand, during regenerative travel of the electric vehicle, the motor generator 22 operates as a generator to generate AC power, and the AC power is converted into DC power by the power conversion unit 21 to charge the battery 20. .

  A voltage sensor 23 is attached to the terminal of the battery 20, and a current sensor 24 is attached in the middle of the wiring connecting the battery 20 and the power conversion unit 21. The terminal voltage V of the battery 20 and the value of the input current (output current at the time of discharging) I measured by the voltage sensor 23 and the current sensor 24 are input to the charging state estimation unit 10.

  The charging state estimation unit 10 is constituted by a microcomputer, and includes a calculation unit 11, an estimation unit 12, a protection unit 13, and a storage unit 14.

  The calculation means 11 reads the values of the terminal voltage V and the input current I of the battery 20 measured by the voltage sensor 23 and the current sensor 24, and calculates a change amount α of the internal resistance of the battery 20 described later based on these values. To do.

  The estimation unit 12 estimates the state of charge of the battery 20 based on the change amount α of the internal resistance of the battery 20 calculated by the calculation unit 11.

  The protection unit 13 protects the battery 20 by taking measures such as limiting the input current I to the battery 20 based on the state of charge of the battery 20 estimated by the estimation unit 12.

  The storage unit 14 stores the values of the terminal voltage V and the input current I of the battery 20 measured by the voltage sensor 23 and the current sensor 24, and the value of the change amount α of the internal resistance of the battery 20 calculated by the calculation unit 11. To do.

  Next, a method for estimating the state of charge of the battery 20 by the state of charge estimation unit 10 according to this embodiment will be described with reference to FIGS.

  During regenerative travel of the electric vehicle, the charging state estimation unit 10 repeatedly executes the processing routine shown in the flowchart of FIG. 2 at a time period of, for example, 10 ms.

  In this processing routine, first, the values of the terminal voltage V and the input current I of the battery 20 measured by the voltage sensor 23 and the current sensor 24 in step S 1 are stored in the storage unit 14, and the calculation unit 11 has the internal resistance of the battery 20. Is calculated according to the following equation.

    α (n) = | V (n) / I (n) −V (n−1) / I (n−1) |

  However, in the above equation, V (n) and I (n) are the values of the terminal voltage V and the input current I of the battery 20 measured during the current execution of the routine, and V (n−1) and I (n -1) are the values of the terminal voltage V and the input current I of the battery 20 measured during the previous routine execution. The calculation unit 11 reads out these values stored in the storage unit 14 to calculate the change amount α (n) of the internal resistance at the time of the current routine execution, and stores the calculated value in the storage unit 14.

Next, in step S2, the estimating means 12 checks whether or not the terminal voltage V of the battery 20 exceeds a predetermined overcharge voltage _VA . When the terminal voltage V is higher than the overcharge voltage _VA (step S2 = YES), the battery 20 may be in an overcharge state, and therefore the estimation unit 12 continues to perform the processes after step S3. On the other hand, when the terminal voltage V is lower than the overcharge voltage _VA (step S2 = NO), the battery 20 is considered not in an overcharge state, and thus the processing routine is ended (RET).

  In step S3, the estimating means 12 checks whether or not the change amount α (n) of the internal resistance calculated in step S1 satisfies the following conditions. If YES, the process proceeds to step S4, and if NO, the process proceeds to step S9.

    α (n−1) <α (n) <Cα (n−1); C> 1

In the above equation, α (n) is the amount of change in internal resistance calculated during the current routine execution, and α (n−1) is the amount of change in internal resistance calculated during the previous routine execution. is there. Next, in step S4, the terminal voltage V is checked whether below a predetermined danger voltage _{V B,} the YES if the step S5, the process proceeds to NO if step S10. Further, in step S5, it is checked whether or not the processing routine of steps S3 and S4 has been repeatedly executed, for example, three times. If YES, the process proceeds to step S6, and if NO, the process returns to step S3.

If YES is determined in step S5, that is, the amount of change α (n) of the internal resistance is larger than α (n−1) which is the first threshold and smaller than Cα (n−1) which is the second threshold. When the state continues three times, as shown by the solid line in FIG. 3, the estimating means 12 indicates that the battery 20 is in an overcharged state, but its internal resistance changes moderately, and the terminal voltage V is Is in a “moderate overcharge state” in which there is no possibility of exceeding the dangerous voltage V _B within a predetermined count number Tc (5 times in the example of this embodiment) required to reliably determine that the battery is in the overcharge state. (Step S6). When the terminal voltage V of the battery 20 exceeds the overcharge voltage _VA continues for a predetermined count number Tc = 5 times, and it is determined that the battery 20 is reliably overcharged (step S7 = (YES), the protection means 13 protects the battery 20 by limiting the input current I to the battery 20 (step S8).

  On the other hand, if NO is determined in step S3, the estimating means 12 checks whether or not the change amount α (n) of the internal resistance satisfies the following condition in step S9, and the condition is 3 in step S10. Check whether it is satisfied continuously.

    Cα (n−1) <α (n) <β

  However, in the above formula, β is selected to be larger than Cα (n−1).

If YES is determined in step S10, that is, the internal resistance change amount α (n) is larger than the second threshold value Cα (n−1) and is the third threshold value β (> Cα (n−1). When the state smaller than) continues three times, the estimation means 12 indicates that the battery 20 is in an overcharged state and the change in its internal resistance is abrupt, as shown by the one-dot broken line in FIG. It is estimated that the terminal voltage V is in the “rapid overcharge state” in which the terminal voltage V may exceed the dangerous voltage V _B within the predetermined count number Tc (step S11). At that time, the protection means 13 protects the battery 20 by immediately limiting the input current I to the battery 20 (step S12).

  If NO is determined in step S9, the estimating means 12 checks whether or not the determination is continuously performed three times in step S13.

If YES is determined in step S13, that is, if the state in which the amount of change α (n) of the internal resistance is greater than the third threshold value β continues three times, the estimating means 12 is shown in FIG. as indicated by the dashed line, is in the battery 20 is "failure state", the terminal voltage V is estimated that there is a possibility to exceed a dangerous voltage V _B within a predetermined count Tc (step S14). At that time, the protection means 13 protects the battery 20 by immediately stopping the use of the battery 20 (step S15).

As described above, the charging state estimation unit 10 according to this embodiment is based on the change amount α of the internal resistance of the battery 20 when the terminal voltage V of the battery 20 exceeds the overcharge voltage _VA . the terminal voltage V of the battery 20 is estimated whether there is a possibility to exceed a dangerous voltage V _B within a predetermined count number Tc. Thereby, when the terminal voltage V of the battery 20 exceeds the overcharge voltage _VA , it can be quickly determined whether or not the state requires urgent countermeasures. In the above embodiment, the first threshold value is α (n−1), the second threshold value is Cα (n−1), and the third threshold value is β (> Cα (n−1)). The method of determining each threshold value is not limited to these, and a range in which the terminal voltage V of the battery 20 is unlikely to exceed the dangerous voltage V _B within the predetermined count number Tc is determined by the first threshold value and the second threshold value. The range that may exceed the dangerous voltage V _B within the predetermined count number Tc may be determined by the second threshold and the third threshold.

Other embodiments.
In the embodiment, as shown in FIG. 4, in step S <b> 3, the change amount α (n) of the internal resistance is larger than α (n−1) which is the first threshold and Cα (n−) which is the second threshold. If smaller than 1), in step S216, V (n)> V _B + I (n) α (n)
Satisfied the relationship, if (step S10 = YES) that state continues for a certain number of times, even if the estimated terminal voltage of the battery 20 is likely to exceed the dangerous voltage V _B within a predetermined count number Tc Good.

10 Charge state estimation unit (charge state estimation device), 11 calculation means, 12 estimation means, 13 protection means, 20 battery, V terminal voltage, I input current, V _A overcharge voltage, V _B dangerous voltage, α of internal resistance Change amount, Tc Predetermined count number.

Claims (4)

In-vehicle battery charge state estimation device,
Calculating means for calculating the amount of change in the internal resistance of the battery;
An estimation means for estimating the state of charge of the battery,
When the battery terminal voltage exceeds a predetermined overcharge voltage, the estimating means determines that the battery terminal voltage is higher than the predetermined overcharge voltage based on the amount of change in the internal resistance. An in-vehicle battery state of charge estimation device that estimates whether or not a dangerous voltage may be exceeded within a predetermined count. The estimation means includes
When the change amount of the internal resistance is larger than the first threshold and smaller than the second threshold, it is estimated that there is no possibility that the terminal voltage of the battery exceeds the predetermined dangerous voltage within the predetermined count number. ,
When the amount of change in the internal resistance is larger than the second threshold and smaller than the third threshold, it is estimated that the terminal voltage of the battery may exceed the predetermined dangerous voltage within the predetermined count number. And
The in-vehicle battery charge state estimation device according to claim 1, wherein when the amount of change in the internal resistance is greater than the third threshold value, the battery is estimated to have failed. The estimation means is configured such that the battery terminal voltage is V, the input current is I, and the internal resistance is changed even when the change amount of the internal resistance is larger than the first threshold and smaller than the second threshold. When the amount of change is α and the predetermined dangerous voltage is V _B ,
V> V _B + Iα
The in-vehicle battery charge state estimation device according to claim 2, wherein when the relationship is satisfied, it is estimated that the terminal voltage of the battery may exceed the predetermined dangerous voltage within the predetermined count number. And further comprising protection means for protecting the battery,
The protective means is
When it is estimated that the terminal voltage of the battery is unlikely to exceed the predetermined dangerous voltage within the predetermined count number, a state where the terminal voltage of the battery exceeds the predetermined overcharge voltage is Wait for the count to continue, limit the input current to the battery,
If it is estimated that the terminal voltage of the battery may exceed the predetermined dangerous voltage within the predetermined count number, immediately limit the input current to the battery,
The in-vehicle battery charge state estimation device according to claim 2 or 3, wherein when it is estimated that the battery is out of order, use of the battery is immediately stopped.

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