JP3864590B2 - Battery charge state detection device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a battery charge state detection device that detects a state of charge of a battery (hereinafter referred to as SOC), and more particularly to a device that detects SOC based on both battery current and battery voltage.
[0002]
[Prior art]
Conventionally, a state of charge (SOC) detection device for detecting a state of charge of a battery is known. For example, an SOC detection apparatus for a battery of an electric vehicle normally detects the SOC by integrating current (charge / discharge current) of the battery. In an electric vehicle, charging by regenerative braking can be expected, but the battery is basically discharged during traveling. And when not driving | running | working, a charging state is recovered by fully charging a battery with a charger. Therefore, the SOC detector basically integrates the discharge current from full charge and detects the SOC. The same applies to various devices such as portable personal computers, and the SOC of the battery is detected by integrating the amount of discharge from full charge.
[0003]
[Problems to be solved by the invention]
Even in a hybrid vehicle equipped with an engine generator, battery current integration is often used to detect the SOC of the battery. However, in a hybrid vehicle, charging / discharging is controlled so that the battery SOC is maintained at about 50%. Accordingly, the battery is not fully charged for a long time, and the charge / discharge current of the battery is integrated for a long time to detect the SOC. Although the accuracy of detection of the charge / discharge current is not so bad, if the detection of the charge / discharge current is repeated for a long time, the error becomes considerably large.
[0004]
The present invention has been made in view of the above problems, and it is an object of the present invention to provide a battery state-of-charge detection device capable of performing more accurate SOC detection by correcting SOC detection by current integration with simple means. And
[0005]
[Means for Solving the Problems]
The present invention relates to a battery charge state detection device for detecting a charge state (hereinafter referred to as SOC) of a battery, an integrated SOC detection means for obtaining an integrated SOC by integrating a charge / discharge current of the battery, a charge / discharge current of the battery, and a voltage of the battery with detected on the basis of these seek electromotive voltage V ₀ which batteries and a real SOC detection means for determining an actual SOC based on the electromotive voltage -SOC characteristic stored in advance with the obtained electromotive voltage V _0, prompted was by correcting the integration SOC and the integration SOC based on the actual SOC difference [Delta] SOC, possess a SOC calculation unit that calculates a SOC of the battery, and the SOC calculation unit, the integration SOC and the actual SOC difference [Delta] SOC When the predetermined value γ is exceeded, the integrated SOC is brought close to the actual SOC by a predetermined amount that is smaller than the predetermined value γ. In and calculates the SOC of the battery.
[0006]
Thus, in the present invention, the integrated SOC is detected by integrating the charge / discharge current of the battery. On the other hand, we obtain the voltage and electromotive voltage of the battery from the current of the battery, determining the electromotive voltage caused previously stores a voltage -SOC characteristics or RaMinoru SO C. The actual SOC is obtained from the current voltage at that time. The error is large, but no error is accumulated. On the other hand, the accumulated SOC has high accuracy but accumulates errors.
[0007]
Therefore, when the difference between the two becomes large, it is determined that the accumulated SOC error has been accumulated, and the accumulated SOC is brought close to the actual SOC. As a result, a large error in the integrated SOC can be eliminated. By using the integrated SOC as the detected SOC, suitable SOC detection can be performed.
[0008]
Alternatively, the electromotive voltage V _0SOC corresponding to the integrated SOC may be obtained, and the integrated SOC may be corrected by β when the difference between the electromotive voltage V _0SOC and the electromotive voltage V ₀ exceeds a predetermined value α.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention (hereinafter referred to as embodiments) will be described with reference to the drawings.
[0010]
FIG. 1 is a block diagram showing the configuration of a system in which the battery charge state detection device of the present invention is applied to a hybrid vehicle. The battery 10 includes a large number of battery cells. In this embodiment, this battery 10 is a nickel metal hydride battery, and 20 battery cells are grouped as one block, and 12 of these blocks are connected. Therefore, it has an output voltage of about 300V in which 240 battery cells are connected in series.
[0011]
The voltage of the battery 10 is measured by the voltage detector 12 and supplied to the battery ECU 14. The battery ECU 14 is also connected to a current sensor 16 that detects a battery current, and the battery current is supplied to the battery ECU 14.
[0012]
The battery ECU 14 detects the state of charge (SOC) of the battery 10 based on various supplied data, and supplies this to the HVECU 18.
[0013]
The HVECU 18 determines a torque command based on information such as the accelerator opening, the brake depression amount, the vehicle speed, and performs control so that the output of the motor generator 22 matches the torque command. That is, HVECU 18 controls switching in inverter 20 so that the output of motor generator 22 matches the torque command.
[0014]
Further, the HVECU 18 controls the output of the engine 24 to some extent according to the SOC supplied from the battery ECU 14, thereby controlling the SOC of the battery 10 to a target value (for example, 50%). For example, when the output of the engine 24 is larger than the output of the motor generator 22, electric power is output from the inverter 20 toward the battery 10 and the battery 10 is charged. On the other hand, when the output of engine 24 is smaller than motor generator 22, electric power is supplied from inverter 20 to motor generator 22, and battery 10 is discharged.
[0015]
Therefore, the SOC of the battery 10 can be controlled by controlling the output of the engine 24 in accordance with the charge request (or discharge request). However, this control does not control the output torque as in an engine-driven vehicle according to the torque command, but changes it within a predetermined range. The actual change in the output of the motor generator 22 is large, and discharging is performed even when a charging request is made, and charging is performed even when a discharging request is made.
[0016]
Next, SOC detection of the battery 10 in the battery ECU 14 will be described with reference to FIG.
[0017]
First, the battery ECU 12 integrates the charging / discharging current of the battery 10 that is the detection value of the current sensor 16, and detects the integrated SOC (S11). This integrated SOC is calculated by adding the current amount to the previous integrated SOC. For example, when the measured current is I and the time from the previous time to this time is t (usually the time of one cycle of the control loop),
Accumulated SOC ← Integrated SOC + I × t
Ask for.
[0018]
Here, the integrated SOC is reset by the IV determination when the SOC of the battery 10 reaches a predetermined value of 20% close to complete discharge or 80% close to full charge. That is, in a state close to full discharge or full charge, a considerable correlation appears between the battery current and the battery voltage, and SOC 20% or 80% can be determined from the relationship between the current voltage. Therefore, when the SOC can be detected by such IV determination, the SOC is replaced with the value and the integration is reset.
[0019]
Next, the electromotive voltage V ₀ of the battery 10 is calculated from the current-voltage characteristics (S12). The electromotive voltage V ₀ means a voltage obtained by subtracting the voltage drop caused by the internal resistance R in the battery 10 from the output voltage of the battery 10 and eliminating the influence of the battery current at that time. That is, as shown in FIG. 3, the battery voltage V decreases as the current increases. This increase / decrease is a voltage drop due to the internal resistance determined by the battery internal resistance R × current I, and the slope of the battery voltage V with respect to the current I is equal to the internal resistance value R. The battery voltage when the battery current is 0 is referred to as an electromotive voltage V ₀ . Therefore, the electromotive voltage can be calculated by V ₀ = V + RI. Since the internal resistance R varies depending on the temperature, the temperature of the battery 10 may be detected and corrected.
[0020]
Next, the corresponding electromotive voltage V _0SOC is calculated based on the integrated SOC obtained in S11 (S13). In the nickel metal hydride battery, the relationship between the SOC and the electromotive voltage is as shown in FIG. 4, and when the SOC is a value near the middle, the change in the electromotive voltage due to the change in the SOC is not so large. However, there is a temporary relationship, and the battery ECU 14 of the present embodiment has this relationship as a map. Therefore, V _0SOC corresponding to the integrated SOC is calculated based on this map.
[0021]
Next, a difference ΔV ₀ = V ₀ −V _0SOC between the electromotive voltages V ₀ and V _0SOC obtained in S12 and S13 is calculated (S14). Then, it is determined whether this ΔV ₀ is larger than a predetermined value α (S15). If it is larger, the predetermined value β is subtracted from the integrated SOC to correct the integrated SOC (S16). As a result, the integrated SOC is brought close to the SOC determined from the current-voltage characteristics by a predetermined value β.
[0022]
That is, as shown in FIG. 5, when the difference ΔV ₀ between the electromotive voltage V _OSOC corresponding to the integrated SOC and the electromotive voltage V ₀ obtained from the current-voltage characteristics is larger than a predetermined value α, the integrated SOC is increased by a predetermined value β. Is brought close to the SOC (referred to as the actual SOC) obtained from the current-voltage characteristics.
[0023]
In the case of NO step S15, the difference [Delta] V ₀ of the electromotive voltage V ₀ is determined whether a predetermined value -α smaller (S17), the integration SOC by adding a predetermined value β from integration SOC when smaller Is corrected (S18). This also brings the integrated SOC closer to the SOC determined from the current-voltage characteristics by a predetermined value β. When the difference ΔV ₀ is within the range of ± α, the integrated SOC is not corrected.
[0024]
If the integrated SOC is correct, and if the electromotive voltage obtained from the current-voltage characteristics at that time and the electromotive voltage obtained from the integrated SOC are also correct, they should be equal. Both of the obtained two electromotive voltages include errors, but if the difference between the two is too large, it is considered that either or both are wrong. Although the electromotive voltage obtained from the current-voltage characteristics has an error, the error is not accumulated. On the other hand, in the accumulated SOC, the error is accumulated, and the error may be large. Therefore, in this embodiment, when the difference between the two becomes very large, this is corrected.
[0025]
In the nickel metal hydride battery, there is a phenomenon called a memory effect in which the electromotive voltage of the battery decreases even when the SOC is the same while the battery is repeatedly charged and discharged. The battery voltage varies depending on the polarization in the electrode active material. That is, even with the same SOC, the electromotive voltage varies depending on whether it was discharged or charged before that time. For example, if the charging is continued, the electromotive voltage increases due to polarization, and the electromotive voltage decreases by leaving it to stand after that. On the contrary, if the discharge is continued, the electromotive voltage is lowered due to the polarization, and the electromotive voltage is increased by leaving it alone.
[0026]
Therefore, it is preferable to set the predetermined value α (for example, a value of about 10V with respect to 240V) larger than these sums in consideration of the voltage generated by the memory effect and polarization.
[0027]
Further, it is preferable that the correction value β for correcting the integrated SOC is smaller than the SOC difference corresponding to the voltage difference α as shown in FIG. 5 (for example, if it is shifted by 10%, it is shifted by 5%). This is because the nickel metal hydride battery is affected by the memory effect and polarization as described above, and the change in electromotive voltage with respect to the change in SOC is not so large as shown in FIG. This is because the electromotive voltage V ₀ also has a considerable error.
[0028]
In the above example, the integrated SOC is corrected from the difference ΔV _{0 in} electromotive voltage. However, in the processing of the present embodiment, there is a one-to-one relationship between the electromotive voltage V ₀ and the actual SOC, and there is a one-to-one relationship between the electromotive voltage V _0SOC and the integrated SOC. Therefore, even if the actual SOC is calculated based on the electromotive voltage V ₀ calculated from the current-voltage characteristics and the difference between the actual SOC and the accumulated SOC exceeds a predetermined value, the accumulated SOC is substantially corrected. The same processing can be performed. This process is shown in FIG.
[0029]
Thus, after calculating the electromotive voltage V ₀ from the current-voltage characteristics in S12, the actual SOC is calculated from the electromotive voltage V ₀ (S23), and the difference in SOC is calculated by ΔSOC = integrated SOC−actual SOC ( S24). Then, it is determined whether or not the difference ΔSOC is larger than a predetermined value γ (the difference in SOC corresponding to the electromotive voltage difference α) (S25). If so, β is subtracted from the integrated SOC, and the integrated SOC is reduced by β. It approaches the actual SOC (S16).
[0030]
In S25, if NO, it is determined whether ΔSOC is smaller than −γ (S27). If it is smaller, β is added to the integrated SOC, and the integrated SOC is brought closer to the actual SOC by β (S18). If ΔSOC is within the range of ± γ, the integrated SOC is not corrected.
[0031]
【The invention's effect】
As described above, according to the present invention, more accurate SOC detection can be performed by correcting SOC detection by current integration based on the electromotive voltage.
[Brief description of the drawings]
FIG. 1 is a block diagram showing the configuration of a system in which a battery charge state detection device of the present invention is applied to a hybrid electric vehicle.
FIG. 2 is a flowchart showing an operation.
FIG. 3 is a diagram illustrating an electromotive voltage.
FIG. 4 is a diagram showing a relationship between SOC and electromotive voltage.
FIG. 5 is a diagram illustrating SOC correction.
FIG. 6 is a flowchart showing another operation.
[Explanation of symbols]
10 battery, 12 voltage detector, 14 battery ECU, 16 current sensor, 18 HVECU, 20 inverter, 22 motor generator, 24 engine.

Claims (2)

In a battery charge state detection device that detects a state of charge of a battery (hereinafter referred to as SOC),
Integrated SOC detection means for determining integrated SOC by integrating the charge / discharge current of the battery;
Detecting the discharge current and battery voltage of the battery together with obtaining the electromotive voltage V ₀ which battery on the basis of these, the actual SOC based on the electromotive voltage -SOC characteristic stored in advance with the electromotive voltage V ₀ obtained The actual SOC detection means to be obtained;
By correcting the integration SOC based on the obtained integration SOC and the actual SOC difference [Delta] SOC, and SOC calculating means for calculating the SOC of the battery,
I have a,
When the difference ΔSOC between the accumulated SOC and the actual SOC exceeds a predetermined value γ, the SOC calculating means brings the accumulated SOC closer to the actual SOC by a predetermined amount that is smaller than the predetermined value γ. The battery state of charge detection device characterized by calculating SOC of a battery by this. In a battery charge state detection device that detects a state of charge of a battery (hereinafter referred to as SOC),
Integrated SOC detection means for determining integrated SOC by integrating the charge / discharge current of the battery;
Wherein the integration SOC integration is detected by the detection means SOC, and stored in advance based on the electromotive voltage -SOC characteristics are, electromotive voltage V _0SOC calculating means for calculating the electromotive voltage V _0SOC corresponding to the integrated SOC,
An electromotive voltage V ₀ detecting means for detecting a charge / discharge current of the battery and a voltage of the battery and obtaining an electromotive voltage V _{0 of the} battery based on the detected current ,
SOC calculating means for calculating the SOC of the battery by correcting the integrated SOC based on the difference ΔV ₀ between the obtained electromotive voltages V _0SOC and V ₀ ;
Have
When the difference between the electromotive voltage V _0SOC and the electromotive voltage V ₀ exceeds a predetermined value α, the SOC calculating means calculates the integrated SOC by a predetermined amount, and the SOC of the SOC corresponding to the predetermined value α. A battery state-of-charge detection device characterized in that the SOC is calculated by approaching the actual SOC by an amount β smaller than the difference γ .

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