JP3849431B2 - Abnormality detection device for battery pack - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an abnormality detection apparatus for an assembled battery that detects when an abnormality occurs in a unit battery in the assembled battery.
[0002]
[Prior art]
When an abnormality occurs in a unit battery, the voltage differs from other unit batteries. By utilizing this fact, the abnormal unit battery in the assembled battery can be detected by comparing the voltage of each unit battery with a set threshold value.
Conventionally, the threshold value is set by, for example, obtaining a voltage average value Vmean and a standard deviation σ with respect to the voltage of each unit battery constituting the assembled battery, and using the obtained voltage average value Vmean and standard deviation σ, for example, Vmean + 20 × σ is calculated, and the calculated value is set as a threshold value.
The threshold value thus obtained changes according to the variation of the unit cells constituting the assembled battery, and the voltage of each unit cell is compared with this threshold value, for example, a unit of voltage higher than the threshold value. When a battery is detected, it is determined and detected as an abnormal unit battery.
[0003]
[Problems to be solved by the invention]
However, in the calculation of the threshold value, the voltage of each unit battery is used to calculate the voltage average value Vmean and the standard deviation σ. If there is an abnormal unit battery, the voltage of the abnormal unit battery is naturally determined. It is an operation including. As a result, an error occurs in the calculated values of Vmean and σ, and the error of σ is further enlarged by threshold calculation, and the calculated threshold becomes low in accuracy. As a result, there is a problem that the abnormal unit battery that should be detected may leak and become undetectable.
The present invention has been made in view of the above-described conventional problems, and an object of the present invention is to provide a battery pack abnormality detection device that can reliably detect abnormal unit batteries.
[0004]
[Means for Solving the Problems]
For this reason, the invention described in claim 1 is an assembled battery abnormality detection device comprising a plurality of unit cells, wherein the voltage detection means for detecting the voltage of each unit cell and the voltage of all unit cells are A first standard deviation calculating means for calculating one standard deviation, and a second standard for a voltage obtained by removing the maximum value or the minimum value from the voltages used in the calculation by the first standard deviation calculating means. A second standard deviation calculating means for calculating a deviation; a difference value calculating means for calculating a difference value between the first standard deviation and the second standard deviation; a determination reference value setting means for setting a determination reference value; When the calculated difference value is compared with the determination reference value, and the difference value is larger than the determination reference value, the second standard deviation is set as a new second standard deviation, and the second standard deviation is calculated. The voltage obtained by removing the maximum value or the minimum value from the new standard deviation calculation unit As a calculation target, a difference value comparison unit that repeats a difference value calculation between a new first standard deviation and a second standard deviation, and a second value calculated immediately before the difference value is equal to or less than a determination reference value. Threshold value calculation means for calculating a threshold value based on the standard deviation and abnormal unit battery detection means for detecting an abnormal unit battery by comparing the voltage of each unit battery with the threshold value .
[0005]
In the invention according to claim 2, the determination reference value setting means detects the charging rate of the assembled battery , and sets the determination reference value based on the detected charging rate .
[0006]
【The invention's effect】
In the first aspect of the present invention, since the unit battery abnormality occurs indicates a larger or smaller voltage than any unit cell of another, by excluding at least the maximum or minimum value from the voltage of each unit cell, in particular The threshold value can be calculated without the influence of the unit battery having a large degree of abnormality . As a result, the accuracy of the threshold is increased, and an abnormal unit battery can be reliably detected.
Further, by removing at least the maximum value or the minimum value from the voltage of each unit battery, a second standard deviation that eliminates the influence of the unit battery having a particularly high degree of abnormality is calculated, and a threshold value is calculated based on the standard deviation. Since the threshold value can be increased, the threshold suitable for the degree of variation of the unit battery can be obtained according to the assembled battery. An abnormal unit battery can be detected.
If the difference value between the first standard deviation and the second standard deviation with respect to the voltage of all unit batteries is larger than the determination reference value, the second standard deviation is set as a new first standard deviation, and the maximum It repeats making the thing remove | excluding the value or minimum value become the object of a new 2nd standard deviation. By sequentially removing the maximum value or the minimum value, both the first standard deviation and the second standard deviation are reduced as compared with the previous time, and at the same time, the difference value is reduced.
Since a highly accurate threshold value is calculated based on the second standard deviation when the difference value is equal to or less than the determination reference value, even when many abnormal unit batteries are generated, it is surely detected. Can do.
[0007]
According to the second aspect of the present invention , since the determination reference value is set corresponding to the charging rate of the assembled battery, the second standard deviation is calculated in correspondence with the charging rate of the assembled battery. As a result, a threshold value that varies according to the charging rate of the assembled battery can be obtained, and an abnormal unit battery can be reliably detected regardless of the usage state of the assembled battery.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Next, as an embodiment of the present invention, an abnormality detection device for a unit battery (hereinafter referred to as a cell) in an assembled battery used as a drive source for an electric vehicle will be described.
FIG. 1 is a schematic view showing a use state of the assembled battery.
The assembled battery C is configured by connecting n cells C1, C2,..., Cn in series. For example, n = 96 (pieces) is used as a drive source of the electric vehicle. The cells C1 to Cn are grouped in units of four to form modules M1, M2,. Cell controllers CC (CC1,..., CCm) are installed in each module M, and charge / discharge of cells is managed in module units .
[0009]
Cell controller CC has a voltage detection part and a discharge part, and is connected with battery controller BC by the communication line.
The assembled battery C is connected to the inverter IB and drives a drive motor M connected to a drive system.
Control ends of the battery controller BC and the inverter IB are connected to the vehicle controller BB.
The vehicle controller BB receives information such as an operation command and controls the inverter IB and the battery controller BB to perform vehicle control.
[0010]
When the assembled battery C is charged, the cell controller CC detects the voltage of each cell, and discharges the cell whose charging progresses quickly based on the charging information transmitted from the battery controller BC. Thereby, each cell is charged at substantially the same charging rate, and early deterioration of the cell due to overcharge or the like is prevented. The battery controller BC further has a function of detecting whether or not each cell has an abnormality.
[0011]
Detection of abnormal cells in the battery controller BC is executed according to the flowchart shown in FIG.
That is, when a vehicle activation or charging start signal such as ignition on is input from the vehicle controller BB, in step 101, the voltage of each cell in an unloaded state is input and stored from each cell controller CC.
[0012]
In step 102, the voltage average value Vmean1 of the voltages of all the cells is calculated as the first voltage average value.
In step 103, the standard deviation σ1 of the voltages of all cells is calculated as the first standard deviation.
[0013]
In step 104, the total voltage, which is the sum of the voltages of all cells, is calculated. In step 105, the correspondence relationship between the stored charge rate (SOC) and the total voltage is shown based on the calculated total voltage. Read the charge rate from the charge rate map.
FIG. 2 is a diagram showing a charging rate map.
According to this figure, the total voltage of the assembled battery C increases as the charging rate increases.
[0014]
Thereafter, in step 106, a determination reference value Vσ is calculated from the stored determination reference value map based on the read charging rate.
FIG. 3 is a diagram illustrating a determination reference value map.
Here, the determination reference value decreases as the charging rate (SOC) increases.
[0015]
In step 107, a cell for calculating the second standard deviation is set by removing the maximum value and the minimum value from the voltage obtained by calculating the first standard deviation.
For example, when the first standard deviation is calculated for 96 cells, the number of cells for calculating the second standard deviation is 94.
In step 108, the voltage average value Vmean2 is calculated as the second voltage average value using the cell voltage set in step 107.
In step 109, the standard deviation σ2 is calculated as the second standard deviation using the cell voltage set in step 107.
In step 110, a difference value Δσ between the first standard deviation σ1 and the second standard deviation σ2 is calculated.
[0016]
In step 111, the calculated difference value Δσ is compared with the determination reference value Vσ. If Δσ is larger than Vσ, the process proceeds to step 112, where the second standard deviation σ2 is set as the first standard deviation σ2. The deviation σ1 is set, the second voltage average value Vmean2 is set as the first voltage average value Vmean1, and the process returns to step 107.
In step 107 again, the maximum value and the minimum value are removed from the voltages obtained by calculating the previous second standard deviation. In steps 108 and 109, the second voltage average value Vmean2 and the second standard deviation σ2 are obtained. It is newly calculated. By repeating the above process, the difference between the second standard deviation and the first standard deviation becomes smaller.
[0017]
That is, when the assembled battery is not used for a long time, the voltage variation of the unit battery is widened. Since the variation changes in use in this way, for example, when the standard deviation is calculated in a state where the variation is small, the value becomes small. On the other hand, when the standard deviation is obtained in a state where the variation is large, the value becomes large. Therefore, the standard deviation well represents whether there is variation, that is, whether there is an abnormal cell. Therefore, if the parameter is reduced except for the maximum and minimum values of both extremes, the standard deviation is reduced and the difference value is also reduced. Therefore, if the difference value reaches a predetermined criterion value, abnormal cells are eliminated. Can be judged.
[0018]
If it is determined in step 111 that the difference value Δσ is equal to or smaller than the determination reference value Vσ, the process proceeds to step 113.
Thus, by using the determination reference value Vσ corresponding to the charging rate, the second standard deviation in which the difference value is equal to or less than the determination reference value is obtained, thereby obtaining the second standard deviation excluding the abnormal cell. .
In step 113, the threshold value Vs is calculated from the second standard deviation σ2 calculated this time and the second voltage average value Vmean2. The threshold value Vs is, for example, as follows:
Vs = Vmean2 + 20 × σ2
It can be calculated with.
[0019]
Thereafter, in step 114, the voltage of each cell is compared with the threshold value Vs, and when a cell having a voltage equal to or higher than the threshold value is detected, a command is output to alarm the vehicle controller BB in step 115. As a result, the vehicle controller BB controls the connected display Ds and buzzer Pz so as to give an alarm. A driver or the like can know the occurrence of an abnormal cell by an alarm.
In step 114, if the voltages of all the cells are smaller than the threshold value, it is determined that there is no abnormal cell in the assembled battery, and the determination is terminated.
[0020]
In the present embodiment, step 101 described above constitutes the voltage detection means of the invention, and step 114 constitutes the abnormal unit battery detection means.
In particular, Steps 102 and 103 constitute first standard deviation computing means, Steps 104 to 106 are judgment reference value setting means, Steps 107 to 109 are second standard deviation computing means, and Step 110 is differential value computation. Steps 111 and 112 constitute difference value comparison means, and step 113 constitutes threshold value calculation means.
[0021]
As described above, in the present embodiment, the difference value between the first standard deviation and the second standard deviation is calculated, and the difference value is compared with the determination reference value. Since the standard deviation and the second standard deviation are newly calculated by removing the maximum value and the minimum value from the previously calculated voltage, abnormal cells are eliminated in the process and are not affected by the abnormal cells. Standard deviation can be determined.
[0022]
The criterion value decreases as the charging rate increases. When the charging rate with small variation is high, a small criterion value is set. Conversely, when the charging rate with large variation is low, a large criterion value is set. Therefore, abnormal cells can be eliminated in response to changes in variation. Thereby, an abnormal cell can be detected regardless of the state of charge of the assembled battery.
In the above-described embodiment, the maximum value and the minimum value are excluded in step 107. However, even if either one is excluded, the same effect is obtained.
[Brief description of the drawings]
FIG. 1 is a schematic view showing a use state of an assembled battery in an embodiment.
FIG. 2 is a flowchart for detecting an abnormal cell.
FIG. 3 is a charge rate map showing the correspondence between total voltage and charge rate.
FIG. 4 is a determination reference value map showing a correspondence relationship between a charging rate and a determination reference value.
[Explanation of symbols]
C assembled battery C1 ... Cn cell CC1 ... CCm cell controller BC battery controller BB vehicle controller IB inverter M drive motor Ds display Pz buzzer

Claims (2)

An assembled battery abnormality detection device comprising a plurality of unit batteries,
Voltage detection means for detecting the voltage of each unit battery;
First standard deviation computing means for computing a first standard deviation for all unit cell voltages;
Second standard deviation calculating means for calculating a second standard deviation with respect to a voltage excluding the maximum value or the minimum value from among the voltages used for the calculation in the first standard deviation calculating means;
Difference value calculating means for calculating a difference value between the first standard deviation and the second standard deviation;
A determination reference value setting means for setting a determination reference value;
The calculated difference value is compared with a determination reference value, and when the difference value is larger than the determination reference value, the second standard deviation is set as a new first standard deviation, and the second standard deviation is calculated. The voltage obtained by subtracting the maximum value or the minimum value from the voltage to be calculated is used as a new calculation target of the second standard deviation calculation unit, and the difference value calculation between the new first standard deviation and the second standard deviation is repeated. Difference value comparison means;
Threshold value calculating means for calculating a threshold value based on the second standard deviation calculated immediately before when the difference value is equal to or less than the determination reference value;
An abnormality detection apparatus for an assembled battery, comprising: an abnormal unit battery detection unit that detects an abnormal unit battery by comparing the voltage of each unit battery with the threshold value. 2. The assembled battery abnormality according to claim 1, wherein the determination reference value setting unit detects a charging rate of the assembled battery and sets the determination reference value based on the detected charging rate. Detection device.

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