JP5262179B2 - Secondary battery charging rate estimation device and charging rate estimation method - Google Patents

Description

  The present invention relates to an apparatus and a method for estimating a charging rate of a secondary battery.

In Patent Document 1 below, an adaptive digital filter (hereinafter abbreviated as ADF) is used to estimate the charging rate (SOC: also referred to as the state of charge) of a secondary battery, and other conditions under which the estimation accuracy in ADF deteriorates. A technique for switching to an estimation method (for example, a charge rate estimation method by current integration) is disclosed.
JP 2006-105821 A

In the above prior art, when the estimation accuracy in ADF is deteriorated, the estimation method is switched to another estimation method. Therefore, a condition that the estimation accuracy in ADF is deteriorated must be estimated using some method. As such a method, for example, a method of detecting that there is no bias in the frequency distribution by performing input frequency analysis (FFT) is conceivable. However, there is a problem that it is very difficult to detect such a calculation in real time and at high speed with an in-vehicle controller having a small capacity.
The present invention solves the above-described problem, and a charging rate estimation device and a charging rate estimation for a secondary battery that can easily suppress a reduction in the accuracy of the charging rate estimation even in a state where the estimation accuracy of the ADF decreases. It aims to provide a method.

In order to achieve the above object, in the present invention, an adaptive digital filter is used to estimate the open circuit voltage from the charge / discharge current and terminal voltage of the secondary battery, and based on the relationship between the open circuit voltage and the charging rate obtained in advance. In the charging rate estimation device for estimating the charging rate of the secondary battery from the open circuit voltage, the upper limit value and the lower limit value of the charging rate change amount per predetermined time are calculated based on the charging / discharging current, and the estimated charging A final charge rate estimation value is calculated by limiting the change amount of the rate per predetermined time to be between the upper limit value and the lower limit value, and the upper limit value and lower limit value of the charge rate change amount are calculated. When calculating, the upper limit value and the lower limit value of the charging rate change amount are set based on the detection accuracy of the detection means for detecting the charge / discharge current .

  As described above, by adding a restriction corresponding to the charge / discharge current to the change in the charging rate estimated by the ADF, even if the estimation accuracy of the ADF deteriorates, the accuracy of the charging rate estimation is not degraded and the accuracy is high. Can be estimated. For example, as shown in FIG. 10, even when the estimation result of ADF fluctuates greatly and the estimation accuracy deteriorates, the change in the charging rate estimated value is limited, so that the deviation of the charging rate from the true value is reduced. I can keep it.

Example 1
FIG. 1 is a schematic configuration diagram of an entire system to which the present invention is applied, and shows an apparatus for driving an auxiliary machine such as an electric motor with a secondary battery.
In FIG. 1, a secondary battery 1 supplies electric power to an auxiliary machine 2 (such as an electric motor) and charges and accumulates electric power generated by the auxiliary machine 2. The charge / discharge current I of the secondary battery 1 is detected by the current sensor 5. The terminal voltage V is detected by the voltage sensor 4. These pieces of sensor information are input to the control device 3. The charge / discharge current I is, for example, a charge current when the value is positive, and a discharge current when the value is negative.

FIG. 2 is a functional block diagram showing an embodiment of the present invention, and shows a portion of a secondary battery charging rate estimation device provided in the control device 3 of FIG.
In FIG. 2, the open circuit voltage estimation means 2001 uses an adaptive digital filter (ADF) to calculate the open circuit voltage V ₀ (the terminal voltage when the energization is cut off) from the charge / discharge current I and the terminal voltage V. Estimated). The charge rate estimation means 2002 estimates the charge rate from the estimated open circuit voltage V _{0 based} on the relationship between the open circuit voltage and the charge rate obtained in advance. The charging rate limiting unit 2003 calculates a final charging rate by limiting the charging rate estimated value estimated by the charging rate estimating unit 2002 according to the charging / discharging current I (details will be described later).

  FIG. 3 is a diagram illustrating a calculation flow of the charging rate in the control device 2 of FIG. 1, and starts the processing at a predetermined cycle (for example, 0.01 [sec]). First, in step S101, the charge / discharge current I and the terminal voltage V are read. In step S102, an open circuit voltage estimation process (process in 2001) is performed. In step S103, a charge rate estimation process (process in 2002) is performed. The charge rate limiting process (the process in 2003) is performed.

FIG. 4 is a diagram showing a control flow of the open circuit voltage estimation process in step S102 of FIG.
As for an estimation calculation method of the open circuit voltage V ₀ using an adaptive digital filter (ADF), for example, Japanese Patent Application Laid-Open No. 2004-178848 (Japanese Patent Application No. 2002-340803, Patent) already patented in the prior application of the present applicant. No. 3714321) and the like are described in detail, and basic mathematical formulas and calculation processes are shown here.

In FIG. 4, first, in step S301, the charge / discharge current I and the terminal voltage V are read, and in step S302, internal parameters are estimated using ADF. In step S303, the open circuit voltage is estimated from the internal parameters.
The internal parameter estimation method using the ADF in step S302 is to sequentially estimate internal parameters using an equivalent circuit model of a secondary battery as shown in FIG. 6, and the battery model in FIG. It can be shown as follows.

ただし、Ｃ_１は電気二重層容量、Ｒ_１は電荷移動抵抗、Ｒ_２は純抵抗、Ｖは端子電圧、Ｉは充放電電流（正が充電、負が放電）、Ｖ_０が開路電圧、ｓはラプラス演算子である。
ここで、（数２）式とおくと、（数１）式は（数３）式のように表すことが出来る。

However, _{C 1} is an electric double layer capacitor, _{R 1} is the charge transfer resistance, _{R 2} is pure resistance, V is terminal voltage, I is the charging and discharging current (positive charge, a negative discharge), _{V 0} is the open circuit voltage, s Is a Laplace operator.
Here, if Equation (2) is set, Equation (1) can be expressed as Equation (3).

ここで端子電圧Ｖ、電流値Ｉのフィルタ出力Ｖ_１、Ｖ_２、Ｖ_３、Ｉ_１、Ｉ_２、Ｉ_３を（数４）式で示すように定義する。

Here, the filter outputs V ₁ , V ₂ , V ₃ , I ₁ , I ₂ , and I ₃ of the terminal voltage V and the current value I are defined as shown in the equation (4).

ただし、Ｇ_ｌｐ(ｓ）は観測ノイズを低減するために設けたローパスフィルタの特性を示す。
そしてＡＤＦの手法を用いて（数１）式の各定数を逐次推定する。この推定方法の詳細は前記特開２００４−１７８８４８号公報に記載されている。
ステップＳ３０３では、上記の推定した内部パラメータを用いて開路電圧Ｖ_０を推定すると、開路電圧Ｖ_０は（数５）式に示す関係となる。

Here, G _lp (s) indicates the characteristics of a low-pass filter provided for reducing the observation noise.
Then, using the ADF method, each constant in the formula (1) is estimated sequentially. The details of this estimation method are described in Japanese Patent Application Laid-Open No. 2004-178848.
In step S303, when the open circuit voltage V ₀ is estimated using the estimated internal parameter, the open circuit voltage V ₀ has a relationship represented by the formula (5).

上記のようにしてＡＤＦの手法を用いて推定した内部パラメータを用いて開路電圧Ｖ_０を推定することが出来る。

The open circuit voltage V ₀ can be estimated using the internal parameters estimated using the ADF technique as described above.

Figure 5 is a diagram showing an operation flow for estimating the charging rate from the open-circuit voltage V ₀ estimated above.
5, read the open-circuit voltage V ₀ at step S401, at step S402, the charging rate of the relationship between the open circuit voltage obtained in advance, obtains the charging rate corresponding to the open circuit voltage read. The relationship between the open circuit voltage and the charging rate has a characteristic as shown in FIG. 7, for example. By obtaining this characteristic in advance, the charging rate can be easily obtained from the estimated open circuit voltage.

Next, FIG. 8 is a flowchart showing an embodiment of calculation contents in the charging rate limiting means 2003, which is a feature of the present invention.
In FIG. 8, first, in step S501, the charging rate estimated by the charging / discharging current and ADF is read.
In step S502, an upper limit value and a lower limit value of the charging rate change amount are calculated from the charge / discharge current. The upper limit value and the lower limit value of the amount of change are characteristics in which, for example, the difference (width) between the upper limit and the lower limit increases as the charge / discharge current increases. For example, as will be described later (Embodiment 2), this characteristic has a large range of upper and lower limit values in the case of a current sensor with low accuracy, and upper and lower limits in the case of high accuracy, depending on the accuracy of the current sensor used. You may set so that the width | variety may be made small.

  In step S503, the value obtained by adding the upper limit value of the amount of change calculated in step S502 to the previous final charge rate estimated value (value after the restriction is added) is compared with the charge rate estimated value estimated by the current ADF. If the charging rate estimated value estimated by the current ADF is larger, that is, if the change amount is larger than the upper limit value, the process proceeds to step S504, and if not, the process proceeds to step S505.

  In step S505, the value obtained by adding the lower limit of the amount of change calculated in step S502 to the previous estimated final charge rate value is compared with the estimated charge rate value estimated by the current ADF, and estimated by the current ADF. If the estimated charge rate is smaller, that is, if the amount of change is smaller than the lower limit value, the process proceeds to step S506, and if not, the process proceeds to step S507.

In step S504, a value obtained by adding the upper limit value of the amount of change calculated in step S502 to the previous final charge rate estimated value is substituted as the current final charge rate estimated value.
In step S506, a value obtained by adding the lower limit value of the amount of change calculated in step S502 to the previous final charge rate estimated value is substituted as the current final charge rate estimated value.
In step S507, since the charge rate estimated value estimated by the current ADF is between the upper limit and the lower limit, the charge rate estimated by the current ADF is set as the final charge rate estimated value.
As described above, the amount of change in the estimated charge rate can be limited to a range between the upper limit value and the lower limit value obtained according to the charge / discharge current.

FIG. 9 is an explanatory diagram illustrating the restriction method.
In FIG. 9, the arrow (a) indicates the previous charging rate, and the upper and lower broken lines indicate the current upper limit value and the lower limit value. That is, in the final time one operation period T, the previous final charging rate estimated value A _H is the upper limit for the value of (a), A _L is the lower limit value, the A _H, the value of A _L charging Set according to the discharge current. For example, the value of “A _H − (a)” and the value of “(a) −A _L ” are set so as to increase as the charge / discharge current increases. If the current charging rate estimated by the ADF falls between the upper limit value and the lower limit value of the amount of change indicated by the broken line, the charging rate estimated by the current ADF is selected and When the estimated charging rate changes above the upper limit value of the change amount, the change in the charging rate is limited to the upper limit value of the charging rate change amount, and the charging rate estimated by the ADF this time as shown in FIG. When the change is less than the lower limit value, the control is performed so as to limit the change in the charging rate to the lower limit value of the change amount.
8 is repeated in a predetermined cycle, the amount of change at a predetermined cycle, that is, every predetermined time is limited to a range between the upper limit value and the lower limit value.

FIG. 10 is a characteristic diagram showing the effect of the present invention.
In FIG. 10, a thick solid line indicates a charging rate estimated by ADF, a thin solid line indicates a final charging rate estimated value of the present invention, and a broken line indicates a true charging rate (true value of charging rate).

As shown in FIG. 10, in the vicinity of time 20 to 30 [sec], the value of the internal parameter is greatly shifted immediately after the start of estimation by ADF, and the charging rate (thick solid line) estimated by ADF is the true charging rate (dashed line). ). However, in the characteristics of the present invention indicated by the thin solid line, since the amount of change in the charging rate is limited according to the charging / discharging current, even if the charging rate estimated by the ADF greatly deviates, the true charging rate It can be estimated without greatly deviating from.
When the internal parameter of the ADF converges to a true value from around time 80 [sec] and the charge rate estimated value approaches the true charge rate, the charge rate estimated value in which the change amount is limited by the charge / discharge current is also obtained. The charging rate estimated by the ADF approaches.

  As described above, in this embodiment, the upper and lower limits according to the charge / discharge current are provided for the amount of change in the charging rate, and the amount of change per predetermined time of the estimated charging rate by the ADF is limited. Even if the estimation accuracy due to is deteriorated, there is an effect that the estimation can be performed with high accuracy without degrading the accuracy of the charging rate estimation.

(Example 2)
In this embodiment, when setting the upper limit value and the lower limit value of the change rate of the charging rate, the determination is made taking into account the detection accuracy of the charge / discharge current detection means (current sensor). In other words, when using an inaccurate current sensor, if the upper and lower limits are set to be larger than the accuracy of the current sensor, the accuracy of the charge rate estimation value deteriorates due to the inaccuracy of the current sensor. The effect that it can prevent that will be acquired is acquired.

(Example 3)
When the estimation accuracy by ADF deteriorates, the final charging rate with a restriction according to the amount of current and the charging rate estimated by ADF are greatly different. Therefore, as the deviation between the charging rate estimated by the ADF and the final charging rate after the limit is increased, the difference between the upper limit value and the lower limit value of the charging rate change amount is reduced, that is, the change amount per predetermined time is reduced. If configured to do so, when the final charging rate is brought close to an ADF that is far away, the approaching rate is approached slowly, so that an effect can be obtained that accuracy can be estimated without degrading the accuracy of charging rate estimation. It is done.

1 is a schematic configuration diagram of an entire system to which the present invention is applied. The functional block diagram of one Example of this invention. The figure which shows the calculation flow of the charging rate in the control apparatus 2 of FIG. The figure which shows the control flow of the open circuit voltage estimation in step S102 of FIG. It shows an operation flow for estimating the charging rate from the open-circuit voltage V ₀ estimated. The circuit diagram which shows the equivalent circuit model of a secondary battery. The characteristic view which shows the relationship between an open circuit voltage and a charging rate. The flowchart which shows one Example of the calculation content in the charging rate restriction | limiting means 2003. FIG. Explanatory drawing which illustrated the limiting method of variation | change_quantity. The characteristic view which shows the effect of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Secondary battery 2 ... Auxiliary machine 3 ... Control apparatus 4 ... Voltage sensor 5 ... Current sensor 2001 ... Open circuit voltage estimation means 2002 ... Charge rate estimation means 2003 ... Charge rate restriction means

Claims (3)

A secondary battery,
Charge / discharge current detecting means for detecting charge / discharge current of the secondary battery;
Terminal voltage detecting means for detecting a terminal voltage of the secondary battery;
An open circuit voltage estimating means for estimating an open circuit voltage from the charge / discharge current and the terminal voltage using an adaptive digital filter;
Charge rate estimating means for estimating the charge rate of the secondary battery from the open circuit voltage based on the relationship between the open circuit voltage and the charge rate obtained in advance;
An upper limit value and a lower limit value of the charging rate change amount per predetermined time are calculated based on the charging / discharging current, and a change amount per predetermined time of the charging rate estimated by the charging rate estimation unit is the upper limit value and the lower limit value. Charging rate change amount limiting means for calculating a final charging rate estimated value by limiting to be between,
Equipped with a,
The charge rate change amount limiting means sets an upper limit value and a lower limit value of the charge rate change amount based on detection accuracy of the charge / discharge current detection means . The charging rate change amount limiting means is
As the deviation between the charging rate estimated by the charging rate estimating means and the final charging rate after being restricted by the charging rate change amount limiting means increases, the difference between the upper limit value and the lower limit value of the charging rate change amount is increased. The secondary battery charging rate estimation device according to claim 1 , wherein the secondary battery charging rate estimation device is smaller. The charge / discharge current and terminal voltage of the secondary battery are detected, an open circuit voltage is estimated from the charge / discharge current and the terminal voltage using an adaptive digital filter, and based on the relationship between the open circuit voltage and the charge rate obtained in advance. In the charging rate estimation method for estimating the charging rate of the secondary battery from the open circuit voltage,
An upper limit value and a lower limit value of the charging rate change amount per predetermined time are calculated based on the charge / discharge current, and the change amount of the estimated charging rate per predetermined time is between the upper limit value and the lower limit value. By calculating the final charge rate estimated value by limiting to
When calculating the upper limit value and the lower limit value of the charge rate change amount, setting the upper limit value and the lower limit value of the charge rate change amount based on the detection accuracy of the detection means for detecting the charge / discharge current. A charging rate estimation method for a secondary battery, which is characterized.

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