JP2012063244A - Charging rate estimation device of battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a charging rate estimation device of a battery for obtaining more accurate charging rate whether a charge and discharge current is constant current or open-circuit voltage changes.SOLUTION: The battery charging rate estimation device includes: an open-circuit voltage estimation means 4 for obtaining an open-circuit voltage estimation value OCV^ from a charge and discharge current value I and a terminal voltage value V on the basis of a battery equivalent circuit model 4A comprising a resistor and an open-circuit voltage generation part capacitor; a charging rate calculation means 5 for calculating charging rate SOC from the open-circuit voltage estimation value on the basis of relation data between the open-circuit voltage value and the charging rate; a delay means 6 for obtaining an open-circuit voltage estimation value OCV^obtained at the last sampling of the obtained open-circuit voltage estimation value; and an open-circuit voltage generation part capacitor capacity calculation means for calculating a capacity COCV of the open-circuit voltage generation part capacitor by using the open-circuit voltage estimation value at the time of the last sampling. The open-circuit voltage estimation means 4 uses the open-circuit voltage generation part capacitor capacity to estimate an open-circuit voltage estimation value of a battery.

Description

  The present invention relates to a battery charge rate estimation device that estimates a battery charge rate of an electric vehicle or the like.

  For example, in an electric vehicle or a hybrid electric vehicle, electric power is supplied (discharged) to an electric motor used to drive these vehicles, or an electric motor that causes braking energy to function as a generator or on the ground. A rechargeable battery (secondary battery) is used to store electric energy by charging from an installed power source.

  In this case, in order to keep the battery in an optimum state for a long period of time, it is necessary to perform battery management by constantly monitoring the state of the battery, particularly the state of charge (SOC). However, when a battery is used, the charge / discharge / storage is due to chemical action, so the state of the battery must be estimated indirectly. In this case, the influence of the temperature change is large, and the state of the battery constantly changes depending on the usage environment and usage history. Therefore, various methods for estimating the charging rate of various batteries have been proposed.

  The conventional battery charge rate estimation device measures the battery current value and the terminal voltage value, and uses these adaptive values to calculate the parameters of the battery equivalent circuit model consisting of a resistor and a capacitor using an adaptive digital filter. The circuit voltage value (open circuit voltage value) is obtained by estimation, and the charging rate is estimated from the circuit voltage value based on the relationship between the previously obtained circuit voltage value and the charging rate (for example, Patent Documents). 1).

  Another conventional battery charge rate estimation device measures a battery current value and a terminal voltage value, and uses a Kalman filter from these measured values to form a battery equivalent circuit model composed of a resistor and a capacitor. The open-circuit voltage value is estimated based on the above, and the charge rate is estimated based on the relationship between the circuit voltage value obtained in advance and the charge rate (see, for example, Non-Patent Document 1).

JP 2001-384606 A

Gregory L. Plett "Extended Kalman filtering for battery management systems of LiPB-based HEV battery packs" Journal of Power Sources 134 (2004) 252-261

However, the above-described conventional battery charge rate estimation apparatus has problems as described below.
First, in the former conventional battery charge rate estimation device, the parameter estimation accuracy of the equivalent circuit model by the adaptive digital filter differs depending on the characteristics of the charge / discharge current, and generally the estimation accuracy for a constant current Will fall. If the parameter estimation accuracy decreases in this manner, the calculation accuracy of the open circuit voltage value also decreases, so that there is a problem that the estimation accuracy of the charging rate determined based on this value also deteriorates.

  Further, in the latter conventional battery charge rate estimation device, the open-circuit voltage is estimated by a Kalman filter based on a battery equivalent circuit model represented by a capacitor as an open-circuit voltage generation unit of the battery equivalent circuit. At this time, the estimation calculation is performed with the value of the open-circuit voltage generator capacitor as a constant value. However, since the value of the open-circuit voltage generation unit capacitor varies depending on the open-circuit voltage value, there is a problem that when the open-circuit voltage value changes, the calculation accuracy of the charging rate also deteriorates.

  The present invention has been made paying attention to the above-mentioned problems, and the object of the present invention is to provide more accurate in any case even when the charge / discharge current is a constant current or the open-circuit voltage changes. An object of the present invention is to provide a battery charge rate estimation device capable of obtaining a high charge rate.

For this purpose, the battery charging rate estimation device according to the present invention is:
Charge / discharge current detection means for detecting a charge / discharge current value of the battery;
Terminal voltage detection means for detecting the terminal voltage value of the battery;
Based on the battery equivalent circuit model of the battery consisting of a resistor and an open-circuit voltage generator capacitor, the estimated open-circuit voltage of the battery from the charge / discharge current value detected by the charge / discharge current detection means and the terminal voltage value detected by the terminal voltage detection means An open-circuit voltage estimating means for estimating
From the open circuit voltage estimated value estimated by the open circuit voltage estimating means, the charge rate calculating means for calculating the charge rate based on the relationship data between the open circuit voltage value and the battery charge rate,
Delay means for obtaining an open-circuit voltage estimated value obtained at the time of sampling immediately before the open-circuit voltage estimated value obtained by the open-circuit voltage estimating means;
An open-circuit voltage generating unit capacitor capacity calculating means for calculating the capacity of the open-circuit voltage generating unit capacitor using the open-circuit voltage estimated value obtained at the time of the previous sampling;
With
The open-circuit voltage estimating means estimates the open-circuit voltage estimated value of the battery using the open-circuit voltage generating section capacitor capacity obtained by the open-circuit voltage generating section capacitor capacity calculating means for the battery equivalent circuit model of the battery.

  In the battery charging rate estimation device of the present invention, the capacity of the open-circuit voltage generation unit capacitor of the battery equivalent circuit model of the battery was obtained at the time of the previous sampling calculated by the open-circuit voltage generation unit capacitor capacity calculation means. Using the open-circuit voltage generation unit capacitor capacity obtained from the open-circuit voltage estimated value, it was made variable according to the open-circuit voltage generation unit capacitor capacity of the battery equivalent circuit model that originally changes sequentially. Even if the current is constant or the open-circuit voltage changes, a charging rate with higher accuracy than that of the prior art can be obtained.

It is a block diagram which shows the structure of the charging rate estimation apparatus of the battery which concerns on Example 1 of this invention. It is a figure of the battery equivalent circuit model used with the charging rate estimation apparatus of the battery of Example 1. It is a graph which shows the relationship between the open circuit voltage of a battery, and a charging rate. It is a block diagram which shows the structure of the open circuit voltage estimation part which comprises the charging rate estimation apparatus of the battery of Example 1. FIG. FIG. 5 is a block diagram illustrating a configuration of a Kalman gain calculation unit of the open circuit voltage estimation unit of FIG. 4. It is a block diagram which shows the structure of the state quantity estimation part of the open circuit voltage estimation part of FIG. It is a block diagram for open circuit voltage calculation based on the property of a battery utilized with the open circuit voltage generation part capacitor capacity calculation method. It is a block diagram for open circuit voltage calculation based on a battery equivalent circuit model used with the open circuit voltage generation part capacitor capacity calculation method. It is a block diagram which shows the structure of an open circuit voltage generation part capacitor | condenser capacity | capacitance part. It is a figure which shows the input input into the charging rate estimation apparatus of the battery of Example 1, (a) is a figure which shows the charging / discharging current of a battery, (b) is a figure which shows the terminal voltage of a battery. 10 is a diagram illustrating an output of the battery charging rate estimation apparatus according to the first embodiment with respect to the input of FIG. 10, in which (a) is a diagram illustrating a battery charging rate estimation value, and (b) is a diagram illustrating a charging rate estimation error at that time; FIG. It is.

  Hereinafter, embodiments of the present invention will be described in detail based on examples shown in the drawings.

FIG. 1 shows a configuration relationship of the charging rate estimation device for the battery 1 and the battery 1 to which the device is connected and the flow of signals thereof according to the first embodiment.
The charging rate estimation device for the battery 1 according to the first embodiment is used for vehicles such as electric vehicles and hybrid electric vehicles. Such a vehicle is equipped with an electric motor (not shown) that drives the vehicle, a battery 1, and a controller (not shown), and when the vehicle is driven, power is supplied (discharged) from the battery 1 to the electric motor, or braking is performed. Sometimes, the electric motor functions as a generator, and the braking energy obtained at that time is collected (charged) into the battery 1 as electric energy, or the battery 1 is charged from a power supply installed on the ground. The charging / discharging current of the battery 1 is monitored by a charging rate estimation device of the battery 1 to estimate the charging rate which is one of the states of the battery 1.

First, the overall configuration of the charging rate estimation device for the battery 1 will be described.
As shown in FIG. 1, the battery 1 charging rate estimation apparatus according to the first embodiment includes a voltage sensor 2, a current sensor 3, an open-circuit voltage estimation unit 4, a charging rate calculation unit 5, a delay device 6, and an open-circuit voltage generation unit capacitor. It has a capacity calculation unit 7 and is connected to the battery 1 via the voltage sensor 2 and the current sensor 3. The open-circuit voltage estimation unit 4, the charging rate calculation unit 5, the delay device 6, and the open-circuit voltage generation unit capacitor capacity calculation unit 7 are configured by an on-vehicle microcomputer.

  In this embodiment, the battery 1 uses a rechargeable battery, for example, a lithium ion battery, but is not limited to this, and other types of batteries such as a nickel-hydrogen battery may be used. Needless to say.

The current sensor 2 collects a part of the braking energy by charging the electric power facility on the ground by making the electric motor function as a generator during braking when the electric power is supplied from the battery 1 to the electric motor or the like. For example, the current value I flowing in the battery 1 is detected using a shunt resistor or the like. The detected charge / discharge current value I is input to the open-circuit voltage estimation unit 4 as an input signal.
The voltage sensor 3 detects the voltage between the terminals of the battery 1, and the detected terminal voltage value V is input to the open circuit voltage estimation unit 4.
Note that the current sensor 2 and the voltage sensor 3 can appropriately adopt ones having various structures and formats, and correspond to the charge / discharge current detection means and the terminal voltage detection means of the present invention, respectively.

  The open-circuit voltage estimation unit 4 includes a battery equivalent circuit model 4A, a state quantity estimation unit 4B, and a Kalman gain calculation unit 4C. The charge / discharge current value I detected by the current sensor 2 and the terminal voltage detected by the voltage sensor 3 The parameter of the battery equivalent circuit model 4A is estimated from the value V, and the open circuit voltage OCV ^ that is the state quantity is obtained. The open-circuit voltage estimation unit 4 corresponds to open-circuit voltage estimation detection means of the present invention.

A battery equivalent circuit model 4A used in the present embodiment is shown in FIG. As this equivalent circuit model 4A, a Foster-type RC ladder circuit (however, only one stage) shown in FIG. 2 is used in this embodiment. That is, in this circuit, a resistance (R ₁ : Faraday impedance) is set in a basque resistance (R ₀ ) for setting a direct current component such as an ohmic resistance due to the electrolyte resistance and connection of the battery 1. A parallel circuit of a capacitor (set as a reaction resistance representing dynamic behavior) and a capacitor (C ₁ : set as a non-Faraday impedance and representing an electric double layer) is connected. Further, in the figure, the open-circuit voltage value of the open voltage unit capacitor representing the open circuit voltage unit (C _OCV) OCV, the terminal voltage value V, to display each overvoltage value generated by the parallel circuit with V ₁ is there. Terminal voltage value V is equal to the sum of the open circuit voltage value OCV and overvoltage value V _1. R ₀ and R ₁ represent resistance values of the respective resistors, and C ₁ and C _OCV represent capacitances of the respective capacitors.

  In this embodiment, the state quantity estimation unit 4B estimates this state quantity based on the battery equivalent circuit model 4A using a Kalman filter. That is, the state quantity estimation unit 4B uses the state equation (discretized) of the battery equivalent circuit model 4A to estimate the charge / discharge current value I for the input, the terminal voltage value V ^ for the output, and the open circuit voltage for the state quantity. As the value OCV ^, the error ε between the estimated output value V ^ of the battery equivalent circuit model 4A for the same input and the actual output value V of the battery 1 is multiplied by the Kalman gain L calculated by the Kalman gain calculator 4C. The battery equivalent circuit model 4A is corrected so that the error is minimized by feeding back the parameters, and the parameters at that time are obtained. This detailed configuration will be described later. The open-circuit voltage estimated value OCV ^ estimated by the state quantity estimating unit 4B is input to the charging rate calculating unit 5 and the delay device 6, respectively. Note that the symbol ^ represents estimation, but is shifted to the right for convenience in the specification, unlike the symbol in the figure.

  The Kalman gain calculation unit 4C is a Kalman gain that is used to weight the error ε between the estimated output (voltage estimated value V ^) of the battery equivalent circuit model 4A and the output of the battery 1 (terminal voltage V). This is for determining L, and its detailed configuration will be described later.

  The charging rate calculation unit 5 stores relational data between the open-circuit voltage value (OCV) and the charging rate (SOC) for storing relational data between the open-circuit voltage value OCV and the charging rate SOC measured in advance for each type of battery. It has a relational data storage unit 5A for storing. An example of this relationship data is shown in FIG. Therefore, if the open circuit voltage of the battery 1 is estimated, the charge rate SOC can be obtained from the estimated value OCV ^ based on the relational data. This charge rate SOC is used for battery management.

The delay unit 6 uses 1 / z (z indicates z conversion) to the kth open-circuit voltage estimated value OCV ^ obtained by the state quantity estimation unit 4B using the discrete state equation of the battery equivalent circuit model 4A. To obtain the (k-1) th open circuit voltage estimated value OCV ^ ^- , which is the previous one of the kth. The immediately previous k−1th open circuit voltage estimated value OCV ^ ⁻ is input to the open circuit voltage section capacitor capacity calculation section 7. The delay device 6 corresponds to the delay means of the present invention.

In the open-circuit voltage section capacitor capacity calculation section 7, the capacity C _OCV of the open-circuit voltage section capacitor is calculated from the inputted (k−1) th open-circuit voltage estimated value OCV ^ ^−, and is input to the open-circuit voltage estimation section 4 for battery equivalent The capacitance C _OCV of the open circuit voltage capacitor in the circuit model 4A is continuously updated.

  The above is the main configuration of the battery charging rate estimation apparatus of the present embodiment. Next, the concept of applying the Kalman filter to the open-circuit voltage estimation unit 4 will be described below.

First, in designing the Kalman filter, the system to be estimated must be expressed by the following equation of state.
dx / dt = Ax + Bu (Formula 1)
y = Cx + Du (Formula 2)
Here, x is a system state vector (representing a state quantity as a parameter), u is an input vector to the system, y is an output vector, and A, B, C, and D are matrices describing system dynamics. Are a system matrix, an input matrix, an output matrix, and a transfer matrix, respectively, and d / dt is a time derivative.

ただし、状態ベクトルｘ＝［過電圧値 開放電圧値］^Ｔ、入力は充放電電流検出値Ｉ（充電をプラス、放電をマイナスにとる）、出力は端子電圧値Ｖである。なお、上記式中、行列の右上の添え字Ｔは、その行列の転置を意味する。 In the battery equivalent circuit model 4A shown in FIG. 2, the values of the matrices A, B, C, and D in the above (Expression 1) and (Expression 2) are as follows.

However, the state vector x = [overvoltage value, open-circuit voltage value] ^T , the input is the charge / discharge current detection value I (plus charge and minus minus discharge), and the output is the terminal voltage value V. In the above formula, the subscript T on the upper right of the matrix means transposition of the matrix.

Here, since (Equation 1) and (Equation 2) of the above state equation are described in a continuous system, they are discretized with a 0th-order hold with sampling time T as follows.
In the following equations, the subscript k is a sampling of the order of numbers, u _k is inputted in the k-th data (detected current value I in this embodiment), y _k guess the output data (the example in the k-th terminal voltage V ^), sigma ^ x ^~, k is the estimated error covariance value of the k-th, L _k is the Kalman gain in the k-th, sigma _V process noise, sigma _W is measurement noise, ^ is the estimated value, _ Represents the pre-time estimation, + represents the post-time estimation, and ε _k represents the difference between the detected output and the estimated output at the k-th (that is, the difference between the terminal voltage detected value and the terminal voltage predicted value in this embodiment). However, when using the Kalman filter, it is assumed that ε _k is an average value of 0, normal white noise, and that process noise and observation noise are independent of each other. In addition, in the above symbols, the symbols ^, ^˜ , _, + are described at the positions shifted to the right in the description, unlike the use in the drawings.

The state equation of the discrete Kalman filter can be expressed as follows.

なお、上記（式５）、（式６）中におけるｅ^ＡＴは、状態遷移マトリクスである。ここで、ｅは自然数、Ｔは入出力信号のサンプリング周期（行列やベクトルの転置を表す上付き添え字Ｔとは異なる）となる番号である。 A _k , B _k , C _k , and D _k in the above (Formula 3) and (Formula 4) are as follows.

The above equation (5), ^{e AT} in the equation (6) is a state transition matrix. Here, e is a natural number, and T is a number that is a sampling period of the input / output signal (different from the superscript T representing the transposition of a matrix or a vector).

これらの式(式９)〜(式1２)は状態量を推定するための式である。
これらの式により、カルマン・フィルタを用いる開放電圧推定部４は、図４のブロック線図にて表わすことができる。このブロック線図については後で説明する。 Therefore, the state equation of the Kalman filter is expressed as follows.

These equations (Equation 9) to (Equation 12) are equations for estimating the state quantity.
From these equations, the open-circuit voltage estimation unit 4 using the Kalman filter can be represented by the block diagram of FIG. This block diagram will be described later.

これらの式（式13）〜(式15)により、カルマン・ゲイン算出部４Ｃのブロック線図は、図５のように表すことができる。このブロック線図については後で説明する。 At this time, the estimation error covariance value and the Kalman gain in the k-th prior estimation and post-estimation are expressed by the following equations.

From these equations (Equation 13) to (Equation 15), the block diagram of the Kalman gain calculator 4C can be expressed as shown in FIG. This block diagram will be described later.

As described above, the estimation of the state quantity using the Kalman filter KF is performed by the state quantity calculation unit 4B according to (Formula 9) to (Formula 15) and the state equation (Formula 2) of the battery equivalent model 4A of FIG. This is performed by the Kalman gain calculation unit 4C.
As shown in FIG. 4, the state quantity estimation unit 4B receives the charge / discharge current value I measured by the current sensor 3 and the open-circuit voltage unit capacitor capacity COCV calculated by the open-circuit voltage unit capacitor capacity calculation unit 7. The open circuit voltage estimated value OCV ^ and the terminal voltage estimated value V ^ are output as state quantities in the battery equivalent circuit model 4A by calculation described later. The terminal voltage estimated value V ^ is input to the subtractor 109, where the error ε is obtained by subtracting from the terminal voltage knowledge value V of the battery 1 measured by the voltage sensor 3. .
The error ε is multiplied by the Kalman gain L calculated by the Kalman gain calculation unit 4C by the multiplier 108, and the multiplication value L · ε is fed back to the state quantity estimation unit 4B.

Next, the estimation of the Kalman gain L in the Kalman gain calculation unit 4C is performed by (Expression 13) to (Expression 15), and a block diagram thereof is shown in FIG.
As shown in the figure, the adder 110 includes the process noise Σ _V and the kth previous (k−1) th estimated error covariance value Σ _x ^˜ _{, k,} which is the output of the delay unit 112. A value _obtained by multiplying ₋₁ ⁺ by coefficient multipliers 113 and 114 by A _k and A _k ^T is added and output as estimated error covariance values Σ _x ^to _{, k} ⁻ as the k-th previous estimation ( Equation 13).

In the multiplier 111, the estimated error output from the adder 110 is subtracted from the subtracted value obtained by subtracting the accumulated value _obtained by multiplying the Kalman gain L _k by the matrix C _k from the charge / discharge current detection value I. The variance values Σ _x ^˜ _{, k} ⁻ are multiplied to obtain an estimation error covariance value Σ _x ^˜ _{, k} ⁺ as a k-th post-estimation (Equation 14). The estimated error covariance value sigma _x ^~, _k ⁺ is (multiplied by Z ^-1) delay unit 12 by Z conversion k-th previous (k-1 th) estimation error covariance value sigma _x ^~ _{a, k-1} ⁻ is obtained. The estimated error covariance values Σ _x ^˜ _{, k−1} ⁻ are multiplied by the matrix A _k and the transposed matrix A _k ^T respectively by the coefficient multipliers 113 and 114 as described above, and then the multiplied value is added. Input to the device 110.

On the other hand, the estimation error covariance values Σ _x ^˜ _{, k} ⁻ as the k-th pre-estimation output from the adder 110 are multiplied by the transpose matrix C _k ^T by the coefficient multiplier 116 and input to the divider 117. In addition, an integrated value obtained by multiplying the matrix C _k by the coefficient multiplier 118 is input to the adder 119. The integrated value are summed and observation noise sigma _W by the adder 119, the added value is inputted to the divider 117. The divider 117 divides the output from the coefficient multiplier 116 by the output from the adder 119 and outputs the result as a Kalman gain L _k (Equation 15). The Kalman gain L _k is multiplied by the matrix C _k by the coefficient multiplier 120 and input to the subtractor 115 as described above.

Next, the state quantity calculation in the state quantity calculation unit 4A is performed by the state quantities (Equation 9) to (Equation 12), and a block diagram thereof is shown in FIG.
In the figure, an input u _k (= charge / discharge current detection value I) is multiplied by Z ⁻¹ by a delay unit 122 based on Z conversion, whereby the (k−1) th previous input _{k k. -1} is obtained. The input u _k−1 is input to the multiplier 123, where the input u _k−1 is multiplied by the matrix B _k to obtain B _k u _k−1 . This B _k u _k−1 is input to the adder 124.

The adder 124 further receives and adds the estimated value A _k x _k−1 ^ ^+, which is the output from the coefficient multiplier 126, and obtains the _k- th pre-estimated state quantity x _k ^ ⁻ ( Formula 9). The estimated value A _k x _k−1 ^ ⁺ is converted into the k-th post-estimated state quantity x _k ^ ⁺ (= open-circuit voltage estimated value OCV ^) output from the adder 127 by the delay unit 125. It is obtained by multiplying the previous state quantity x _k-1 ^ ⁺ obtained by multiplying by ⁻¹ by the matrix A _k by the coefficient multiplier 126 as described above.

The estimated state quantity x _k ^ ⁻ in the adder 124 is added to the accumulated value L _k · ε _k obtained by the Kalman gain calculation unit 4B and the multiplier 108 in the adder 127, and the estimated state quantity x _k ^ ⁺ (= open-circuit voltage estimated value OCV ^) is obtained (Equation 10). This open-circuit voltage estimated value OCV ^ is input to the charging rate calculation unit 5 and the delay unit 6.

On the other hand, the output x _k ^ ⁻ from the adder 124 is also input to the coefficient multiplier 128 and multiplied by the matrix C _k to obtain C _k x _k ^ ⁻ . This C _k x _k ^ ⁻ is input to the adder 130. Further, D _k u _k obtained by multiplying the input u _k (= charge / discharge current detection value I) by the matrix D _k by the coefficient multiplier 129 is input to the adder 130 and added, and the state quantity C _k x _k ^ ⁻ + D _k u _k , that is, y _k ^ (= terminal voltage estimated value V ^) is obtained (formula 12). This terminal voltage estimated value V ^ is input to the subtractor 109 in FIG. 4, where the terminal voltage estimated value V ^ is subtracted from the terminal voltage detection value V to obtain a terminal voltage difference εk.

  The open-circuit voltage estimation unit 4 is configured as described above. Next, the calculation method of the open-circuit voltage unit capacitor capacity in the open-circuit voltage unit capacitor capacity calculation unit 7 will be described below with reference to the schematic diagrams of FIGS. explain.

The open-circuit voltage unit capacitor capacity calculation unit 7 uses the open-circuit voltage value OCV ⁻ obtained at the time of the previous sampling estimated and uses the open-circuit voltage equation based on the characteristics of the battery 1 and the battery equivalent circuit model 4A. Therefore, the open circuit voltage capacitor capacitance COCV is derived as follows.

  As shown in FIG. 7, the open-circuit voltage OCV1 calculated based on the properties of the battery 1 is obtained by first integrating the charge / discharge current I with time and dividing the integrated value by the design capacity FCC of the battery 1 and then by percentage ( %) To calculate the charge rate SOC. From this charge rate SOC, the open circuit voltage OCV1 is estimated based on the charge rate-open circuit voltage relationship data stored in the relationship data storage unit 5A.

  Since the open circuit voltage OCV2 calculated using the battery equivalent circuit model 4A is the voltage of the open circuit voltage section capacitor, the integrated value (corresponding to the charge amount) obtained by integrating the charge / discharge current value I is used as the open circuit voltage section capacitor. It is obtained by dividing by the capacity COCV.

Since these open-circuit voltages OCV1 and OCV2 are equivalent, the following relational expression is obtained from both equations for obtaining them.
COCV = FCC / {100 × (inclination SL of open-circuit voltage with respect to charge / discharge rate when open-circuit voltage value OCV ⁻ obtained at the previous sampling)}

From this equation, a block diagram of the open-circuit voltage section capacitor capacity calculation section 7 is as shown in FIG.
That is, the open circuit voltage value OCV ⁻ obtained at the previous sampling is input, and the open circuit voltage OCV−SL (the open circuit voltage obtained at the previous sampling is measured in advance from the open circuit voltage value OCV ⁻ ). voltage OCV ^- when the, on the basis of the relationship data of the slope) of the open circuit voltage for the charge and discharge rate, to obtain the slope SL. This slope SL is multiplied by 100 by a multiplier, and the open circuit voltage section capacitor capacity COCV is calculated by dividing the design capacity of the battery 1 by a value of 100 × SL by a divider.

  With respect to the charging rate estimation device of the present embodiment configured as described above, the experimental results of estimating the charging rate using the input data of the charge / discharge current value I and the terminal voltage value V of the battery 1 will be described.

FIG. 10 shows the charge / discharge current I and the voltage value V input to the battery 1 and the charging rate estimation apparatus of this embodiment. FIG. 10 (a) shows time on the horizontal axis and charge / discharge current on the vertical axis. In the figure, (b) shows time on the horizontal axis and terminal voltage V on the vertical axis. These inputs are the first conventional example using the adaptive digital filter mentioned above, the second conventional example using the Kalman filter in the battery equivalent circuit model with a constant open-circuit voltage section capacitor capacity, and the charging of this embodiment. Each was put in a rate estimation device, and the charging rates obtained at that time were compared.
In order to know the true value of the charging rate, in this experiment, the charge / discharge current of the battery 1 is measured using a current sensor that is too expensive to mount on the vehicle but has very high measurement accuracy, and the Coulomb count method (current The charging rate was estimated by a method of calculating the charging rate by dividing the integrated value and dividing the integrated value by the full charging capacity, and this was taken as the true value of the charging rate.

The result of this experiment is shown in FIG. FIG. 11 (a) shows a charge rate estimated value (indicated by a dotted line) in the present embodiment for the true value of the charge rate (indicated by a solid line), and charging in a first conventional example (indicated as conventional example 1 in the figure). A rate estimation value (indicated by a chain line) and a charge rate estimation value (indicated by a one-dot chain line) in a second conventional example (denoted as conventional example 2 in the figure) are shown.
FIG. 11B shows the charging rate estimation error in this embodiment (shown by a dotted line), the charging rate estimation error in the first conventional example (shown by a chain line), and the charging rate estimation in the second conventional example. An error (indicated by a dashed line) is shown.

  As can be seen from FIG. 11, in the first conventional example, the change of the input current I is reduced, the interval of about 5,000 seconds to about 10,000 seconds, the interval of about 15,000 seconds to about 20,000 seconds, and about 25,000 seconds to about 30,000 seconds. It can be seen that the accuracy of the charge rate estimation is worse in the section of, compared with the charge rate estimation value in the other sections where the change in the input current is large.

  In the second conventional example, the capacity of the open-circuit voltage section capacitor of the battery equivalent circuit model is regarded as constant. Therefore, in the input current section where the open-circuit voltage largely does not meet this assumption, the charge rate estimation is performed. It turns out that the accuracy is not good.

  Thus, from FIG. 11, compared with these conventional examples, in the battery charge rate estimation device of this embodiment, even when the input current is a constant current, the open-circuit voltage of the battery 1 also changes. It can be seen that the charging rate of the battery 1 can be detected with higher accuracy.

As described above, the following effects can be obtained in the first embodiment.
(1) Since the battery charging rate estimation apparatus of the first embodiment approaches the characteristics of the actual battery by changing the capacitance COCV of the open-circuit voltage section capacitor of the battery equivalent circuit model 4A, the input current is a constant current. However, even if the open circuit voltage of the battery 1 changes, the charging rate of the battery 1 can be detected with higher accuracy.

(2) Also, the open-circuit voltage generation unit capacitor capacity obtained from the open-circuit voltage estimated value OCV ^ ⁻ obtained at the previous sampling calculated by the open-circuit voltage generation unit capacitor capacity calculation unit 7 Therefore, the open-circuit voltage section capacitor capacitance COCV can be obtained easily and accurately.

(3) Since a Kalman filter is used for the open-circuit voltage estimation unit 4, the open-circuit voltage at that time can be estimated easily and accurately, and higher charge rate estimation accuracy can be obtained.

  Although the present invention has been described based on each of the above embodiments, the present invention is not limited to these embodiments, and even if there is a design change or the like without departing from the gist of the present invention, it is included in the present invention.

  For example, the battery equivalent circuit model is not limited to the model of the embodiment as long as it uses a capacitor in the open-circuit portion, and the Foster RC ladder circuit represents the dynamic behavior in the diffusion process. A parallel circuit in which a plurality of stages are connected in series may be used. Alternatively, a battery equivalent circuit model different from the Foster type RC ladder circuit, for example, a Cowell type ladder circuit may be used.

  The open-circuit voltage estimation in open-circuit voltage estimation unit 4 is not limited to the Kalman filter, and other methods such as a sequential least square method may be used.

  In addition, the battery charge rate estimation device of the present invention is not limited to a lithium ion battery, and can also be applied to other types of batteries, and the battery is not limited to vehicles such as electric vehicles and hybrid electric vehicles. It can also be used to estimate the charging rate of batteries used on the ground and structures.

1 battery 2 current sensor (charge / discharge current detection means)
3 Voltage sensor (terminal voltage detection means)
4 Open-circuit voltage estimation unit (open-circuit voltage estimation means)
4A Battery equivalent circuit model 4B State quantity estimation unit 4C Kalman gain calculation unit 5 Charging rate calculation unit 5A Charging rate-open voltage relationship data storage unit 6 Delay device 7 Open voltage generator capacitor 108, 111, 123 Multiplier 109, 115 Subtractor 110, 119, 124, 127, 130 Adder 112, 122, 125 Delay device 117 Divider 113, 114, 116, 118, 120, 126, 128, 129 Coefficient multiplier

Claims (2)

Charge / discharge current detection means for detecting a charge / discharge current value of the battery;
Terminal voltage detection means for detecting a terminal voltage value of the battery;
Based on the battery equivalent circuit model of the battery, which is composed of a resistor and an open-circuit voltage generating capacitor, the charge / discharge current value detected by the charge / discharge current detection means and the terminal voltage value detected by the terminal voltage detection means An open-circuit voltage estimating means for estimating an open-circuit voltage estimated value;
A charging rate calculating means for calculating a charging rate based on the relationship between the open voltage value and the charging rate of the battery from the open voltage estimated value estimated by the open voltage estimating means;
Delay means for obtaining an open-circuit voltage estimated value obtained at the time of sampling immediately before the open-circuit voltage estimated value obtained by the open-circuit voltage estimating means;
An open-circuit voltage generation unit capacitor capacity calculation unit for calculating the capacitance of the open-circuit voltage generation unit capacitor using the open-circuit voltage estimation value obtained at the time of the previous sampling by the delay unit;
With
The open-circuit voltage estimating means estimates the open-circuit voltage estimated value of the battery using the open-circuit voltage generating section capacitor capacity obtained by the open-circuit voltage generating section capacitor capacity calculating means in the battery equivalent circuit model of the battery;
An apparatus for estimating a charging rate of a battery. The battery charge rate estimation apparatus according to claim 1,
The open-circuit voltage estimation means is a Kalman filter.
An apparatus for estimating a charging rate of a battery.

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