JP2019016528A - Evaluation device for storage battery equivalent circuit model - Google Patents

Abstract

To provide an evaluation device capable of appropriately evaluating an equivalent circuit model for estimating SOC.SOLUTION: A control unit 25 for evaluating an equivalent circuit model of a storage battery 2 used for SOC estimation processing of the storage battery 2 includes an evaluation processing unit 25c that performs processing relating to evaluation of the equivalent circuit model on the basis of the AC impedance of the equivalent circuit model in a specific frequency band corresponding to a current charged and discharged from the storage battery 2.SELECTED DRAWING: Figure 6

Description

  The present invention relates to an evaluation device for evaluating an equivalent circuit model used for estimating the remaining amount of electricity stored in a storage battery such as a lithium ion storage battery.

In recent years, with the increase of vehicles using electric power such as electric vehicles and hybrid vehicles, and the spread of solar power generation, the importance of storage batteries for storing electric energy is increasing.
Since a storage battery is required to stably supply power to various devices in which the storage battery is incorporated, it is necessary to manage its state.
The state to be managed in the storage battery includes the temperature of the storage battery, the remaining amount of storage (storage rate), the deterioration state, etc. Among these, the storage rate (SOC: State of Charge) is particularly the state of the storage battery. A high accuracy is required for the estimation.

  For this reason, estimation methods such as an output voltage method, an internal resistance method, and a current integration method have been conventionally proposed as a method for estimating the SOC of a storage battery. In order to realize more accurate SOC estimation, an extended Kalman filter is used. The method of estimating the SOC of the storage battery using the battery may be employed (see, for example, Patent Document 1).

Japanese Patent Laid-Open No. 2006-99123

  In the SOC estimation method using the extended Kalman filter, an equivalent circuit model that models the target storage battery is constructed, and the state of the storage battery is estimated using the constructed equivalent circuit model.

  Here, in an estimation method using an equivalent circuit model, such as an SOC estimation method using an extended Kalman filter, the equivalent circuit model used for estimation may affect the estimation accuracy of the SOC.

  The present invention has been made in view of such circumstances, and an object thereof is to provide an evaluation apparatus that can appropriately evaluate an equivalent circuit model for estimating SOC.

(1) The present invention is an evaluation device that evaluates an equivalent circuit model of the storage battery used for the estimation process of the remaining amount of storage of the storage battery, and the equivalent circuit in a frequency band corresponding to a current charged / discharged from the storage battery An evaluation processing unit that performs processing related to the evaluation of the equivalent circuit model based on the AC impedance of the model is provided.

  According to the evaluation apparatus configured as described above, the equivalent circuit model is evaluated based on the AC impedance of the equivalent circuit model in the frequency band corresponding to the current charged / discharged from the storage battery. Evaluation can be made.

(2) In the evaluation device, the evaluation processing unit compares the measured value of the AC impedance of the storage battery in the frequency band with the AC impedance of the equivalent circuit model to thereby store the remaining power of the equivalent circuit model. It is preferable to perform processing related to estimation accuracy estimation.
In this case, since the actual measured value of the AC impedance of the storage battery and the AC impedance of the equivalent circuit model are compared and evaluated, more appropriate evaluation can be performed.

(3) Moreover, the said evaluation apparatus may further be provided with the switch part which performs the switch regarding the said estimation process based on the evaluation result by the said evaluation process.

(4) In the evaluation apparatus, the switching related to the estimation process may be a process of switching the equivalent circuit model to another equivalent circuit model different from the equivalent circuit model.

(5) Further, the switching related to the estimation process may be a process of switching the estimation process to another estimation process different from the estimation process.

  According to the present invention, an equivalent circuit model for estimating the SOC can be appropriately evaluated.

It is a block diagram which shows an example of a storage battery system. It is a block diagram which shows an example of a structure of a control part. It is a block diagram which shows an example of a structure of a 1st estimation part. It is a figure which shows an example of the 1st equivalent circuit model of the storage battery used in order that a 1st estimation part calculates | requires a SOC estimated value. It is a flowchart which shows an example of the 1st estimation process which a 1st estimation part performs. It is a block diagram which shows an example of a structure of a control part. It is a flowchart which shows an example of the switching process which a control part performs. It is a flowchart which shows an example of the evaluation process in FIG. (A) is a graph which shows an example of the time-dependent change of the input current value of the storage battery 2, (b) is an example of the result of converting the time-dependent change of the input current value of the storage battery 2 shown in FIG. 9 (a) into the frequency domain. It is a graph which shows. It is a figure which shows an example of a measured value database. It is a figure which shows the Cole-Cole plot which showed an example of the relationship between the measured value of the alternating current impedance of a storage battery, and the alternating current impedance of a 1st equivalent circuit model.

Hereinafter, preferred embodiments will be described with reference to the drawings.
[System configuration]
FIG. 1 is a block diagram illustrating an example of a storage battery system. In the figure, the storage battery system 1 includes a storage battery 2 and a storage battery management device 3.

  The storage battery 2 is composed of a single unit or a plurality of unit cells of a lithium ion battery. The storage battery 2 stores DC power by connecting a charger (not shown) to both end terminals 4 and charges the both end terminals 4. The stored DC power is discharged to the load by connecting a load (not shown) instead of the battery.

  The storage battery management device 3 is a current sensor 5 for measuring a current inputted to and outputted from the storage battery 2, a voltage sensor 6 for measuring a voltage between terminals of the storage battery 2, and an environmental temperature of the storage battery 2. The temperature sensor 7, the control apparatus 8 which performs the process which estimates the electrical storage residual amount of the storage battery 2, and the output device 9 for outputting the estimation result of the electrical storage residual amount of the storage battery 2 are provided.

The current sensor 5 measures the current input to and output from the storage battery 2 and gives a signal indicating the measurement result to the control device 8.
The voltage sensor 6 measures the voltage value between the terminals when the storage battery 2 is charged and discharged, and gives a signal indicating the measurement result to the control device 8.
The temperature sensor 7 measures the current temperature of the storage battery 2 and gives a signal indicating the measurement result to the control device 8.
In addition, in this embodiment, although the case where the temperature sensor 7 was comprised so that the environmental temperature of the storage battery 2 was measured was illustrated, you may comprise so that the surface temperature of the storage battery 2 may be measured.

  The control device 8 receives signals given from the sensors 5, 6 and 7, and based on these signals, sets the current value of the current input to and output from the storage battery 2, the voltage between the terminals of the storage battery 2, and the temperature of the storage battery 2, respectively. Obtain as information. The control device 8 estimates the remaining amount of power stored in the storage battery 2 using these pieces of information, and outputs the estimation result through the output device 9.

FIG. 2 is a block diagram illustrating an example of the configuration of the control device 8.
As shown in FIG. 2, the control device 8 includes a processing device 20 including a CPU (Central Processing Unit) and a storage device 21 including a ROM, a RAM, a hard disk, and the like, and is configured by a microcomputer.
The storage device 21 stores various computer programs for realizing the functions of the control device 8 in addition to an operating system necessary for operating the control device 8.
Further, the storage device 21 stores a measurement value database 22 used for evaluation processing described later.
The processing device 20 stores each piece of information acquired by signals given from the sensors 5, 6 and 7 in the storage device 21 and uses it for various processes.
The processing device 20 implements the following functions by executing a computer program stored in the storage device 21.

As illustrated in FIG. 2, the processing device 20 functionally includes a first estimation unit 23, a second estimation unit 24, and a control unit 25.
The first estimation unit 23 and the second estimation unit 24 have a function for executing a process for estimating the remaining amount of power stored in the storage battery 2. The first estimation unit 23 and the second estimation unit 24 acquire the state of the storage battery 2 based on the signals from both the sensors 5 and 6, and the storage rate (hereinafter simply referred to as the SOC) that is a value indicating the remaining storage amount of the storage battery 2. The estimated value is also obtained.

Based on the SOC estimated value obtained by the first estimating unit 23 or the second estimating unit 24 and each information acquired from the signals from the sensors 5, 6 and 7, the control unit 25 The 2nd estimation part 24 has a function which performs the process regarding evaluation of the equivalent circuit model of the storage battery 2 used for estimation of SOC.
The control unit 25 also has a function of performing switching related to an estimation process for obtaining the SOC estimated value of the storage battery 2 based on the evaluation of the equivalent circuit model.

[About the first estimation unit and the second estimation unit]
FIG. 3 is a block diagram illustrating an example of the configuration of the first estimation unit 23. In the following description, the first estimation unit 23 will be mainly described. However, in the present embodiment, the second estimation unit 24 has the same configuration as the first estimation unit 23.
As shown in FIG. 3, the first estimation unit 23 functionally includes a parameter estimation unit 23a and a remaining power storage estimation unit 23b.

The 1st estimation part 23 calculates | requires a SOC estimated value using the equivalent circuit model which modeled the storage battery 2 as mentioned above.
The parameter estimation unit 23a has a function of obtaining an estimated value for a model parameter included in the equivalent circuit model.
The remaining power storage estimation unit 23b has a function of obtaining the estimated SOC value of the storage battery 2 using the extended Kalman filter based on the equivalent circuit model to which the estimated value of the model parameter obtained by the parameter estimation unit 23a is given. .

FIG. 4 is a diagram illustrating an example of a first equivalent circuit model of the storage battery 2 used by the first estimation unit 23 to obtain the SOC estimation value.
In FIG. 4, the first equivalent circuit model 30 includes a power supply 31, a resistance element 32, and an RC circuit 33.
The power supply 31 is composed of an ideal power supply and represents an open circuit voltage (OCV: Open Circuit Voltage, hereinafter simply referred to as OCV) that is a voltage of the storage battery 2 in a no-load state. OCV is a nonlinear function of SOC, and is an internal voltage source that cannot be directly measured when the storage battery 2 is loaded.

A function OCV (SOC) indicating the relationship between the OCV and the SOC is stored in the storage device 21. The function OCV (SOC) is recursively obtained from a measured value indicating the relationship between the SOC and the OCV obtained by an experiment using the storage battery 2.
The first estimation unit 23 refers to the function OCV (SOC) stored in the storage device 21 as necessary.

The resistance element 32 is a resistance against the mass transfer of lithium ions in the electrolyte, and represents the internal resistance of the storage battery 2.
The RC circuit 33 is configured by connecting a resistance element 33a and a capacitor 33b in parallel. The RC circuit 33 represents an interface charge transfer resistance in the storage battery 2.
The resistance value _{R 0} of the resistor element 32, the resistance value _{R 1} of the resistance element 33a, the capacitance _{C 1} of capacitor 33b constitute the model parameters included in the first equivalent circuit model 30.

  Similarly to the first estimation unit 23, the second estimation unit 24 also obtains the estimated SOC value using an equivalent circuit model that models the storage battery 2. The second equivalent circuit model 40 of the storage battery 2 used by the second estimation unit 24 for obtaining the SOC estimation value has the same configuration as the first equivalent circuit model 30 shown in FIG. 4, and includes a power source 41, a resistance element 42, and the like. And an RC circuit 43 including a resistance element 43a and a capacitor 43b.

[SOC estimation by extended Kalman filter]
The remaining power storage estimation unit 23 b of the first estimation unit 23 performs a process of obtaining the SOC estimation value of the storage battery 2 using the extended Kalman filter based on the first equivalent circuit model 30.
Hereinafter, the process which calculates | requires the SOC estimated value of the storage battery 2 using the extended Kalman filter which the electrical storage residual amount estimation part 23b performs is demonstrated.
When the voltage u ₁ across the RC circuit 33 is expressed by a differential equation, the following equation (1) is obtained.
Further, the voltage across U _L of the storage battery 2, which is represented by the first equivalent circuit model 30 can be represented by the following equation (2).

In the above equations (1) and (2), i represents the input current value of the first equivalent circuit model 30. When the storage battery 2 is charged, the input current value i is a positive value, and when the storage battery 2 is discharged to the outside, the input current value i is a negative value. In Expression (2), OCV (SOC) is a function indicating the relationship between the above-described OCV and SOC.
Further, based on the concept of current integration, the SOC is expressed by the following equation.

  Furthermore, it is expressed as the following formula (3).

In the above equation (3), FCC is a full charge capacity.
When the above equations (1) and (3) are discretized with the sample period Δt by Euler approximation, the following equations (4) and (5) are obtained.

In the above formulas (4) and (5), k represents an index (discrete time) that increases every sample period Δt.
Here, if x _k = (SOC _k , u _1k , R _0k ) ^T , and the inter-terminal voltage y _k = u _Lk that is an observation value by the voltage sensor 6, equations (2), (4), ( Collecting 5), the discrete time state space model shown in the following formulas (6) and (7) is obtained.

Note that w _k is system noise, v _k is observation noise, and F _k , G _k , and h (x _k , i _k ) are as follows.

The remaining power storage estimation unit 23b acquires an inter-terminal voltage y _k and an input current value i _k representing a current value charged / discharged from the storage battery 2 from the current value and the voltage value obtained from the current sensor 5 and the voltage sensor 6. , The discrete-time state space model represented by the above equations (6) and (7) is sequentially updated by applying an extended Kalman filter, and each of the SOC, the both-end voltage u ₁ , and the resistance value R ₀ of the resistance element 32 is obtained. The estimated value is obtained sequentially.

[Estimation of model parameters by successive least squares estimation]
Model parameters included in the first equivalent circuit model 30 (the resistance value _{R 0} of the resistor element 32, the resistance value _{R 1} of the resistance element 33a, and the capacitance _{C 1} of the capacitor 33b) varies depending on the SOC and temperature.
On the other hand, the parameter estimation unit 23a of the first estimation unit 23 obtains the estimated value of each fluctuating model parameter and the estimated value of the OCV sequentially by the least square method.

  The linear regression model used in the sequential least square method is obtained from the above formulas (2), (4), and (5). That is, since the OCV change is sufficiently slow with respect to the sample period, assuming that the OCV does not change during one sample period, substituting the expression (2) into the expression (4), the following expression (8) is obtained. can get.

Here, the observation vector ψ _k including the inter-terminal voltage y _k and the input current value i _k is set as in the following formula (9).

  From the above equations (8) and (9), the following equation (10) is obtained as a linear regression model.

Here, in the above equation (10), _ek is an error term, and the parameter vector θ is as follows.

At this time, the parameter vector θ = (a ₁ , b ₀ , b ₁ , f) and (R ₀ , R ₁ , C ₁ , OCV) correspond to each other, and (a ₁ , b ₀ , b _1). , F), model parameters (R ₀ , R ₁ , C ₁ , OCV) can be obtained as shown in the following equation.

As described above, the problem of estimating each model parameter can be reduced to the problem of estimating the parameter vector θ.
Therefore, as shown in the following formula (11), sequentially calculates an estimate of the parameter vector theta _k capable of a square sum _{J RLS} to minimum error _{e k} in the formula (10).
In the above equation (11), λ is a forgetting factor, and is set to a value satisfying 0 <λ ≦ 1.

The parameter estimation unit 23a acquires the input current value i _k and the inter-terminal voltage y _k from the current value and the voltage value obtained from the current sensor 5 and the voltage sensor 6, and estimates the parameter vector θ by the above equation (11). And the estimated value of each model parameter and the estimated value of OCV are sequentially obtained by the least square method.

[About the first estimation process performed by the first estimation unit]
The 1st estimation part 23 has a function which performs the 1st estimation process for calculating | requiring the SOC estimated value of the storage battery 2. FIG.
FIG. 5 is a flowchart illustrating an example of the first estimation process performed by the first estimation unit 23.
The first estimating unit 23 first determines an initial value required when the parameter estimating unit 23a sequentially estimates each model parameter by the least-squares method, and a stored power remaining amount estimating unit 23b obtains an SOC estimated value by the extended Kalman filter. Necessary initial values are set (step S1). The first estimating unit 23 sets the discrete time k to “0” (step S1).

Next, the first estimation unit 23 adds “1” to the discrete time k (step S2), and acquires observation values (terminal voltage y _k and input current value i _k ) by the current sensor 5 and the voltage sensor 6 ( Step S3).
The 1st estimation part 23 which acquired the observed value gives the acquired observed value to the parameter estimation part 23a, and makes the said parameter estimation part 23a obtain | require the estimated value of each model parameter (step S4).

  When the parameter estimation unit 23a determines the estimated value of each model parameter, the first estimation unit 23 causes the remaining power storage estimation unit 23b to determine the SOC estimation value of the storage battery 2 (step S5). The remaining power storage estimation unit 23b obtains the estimated SOC value of the storage battery 2 based on the first equivalent circuit model 30 including the estimated value of the model parameter obtained by the parameter estimation unit 23a.

When the remaining power storage estimation unit 23b obtains the estimated SOC value of the storage battery 2, the first estimation unit 23 returns to step S2 again and repeats the same processing.
Thereby, the 1st estimation part 23 calculates | requires the estimated value of the model parameter in each discrete time, and the SOC estimated value of the storage battery 2. FIG.

Similarly to the first estimation unit 23, the second estimation unit 24 also includes a parameter estimation unit that obtains an estimated value of a model parameter and a remaining power storage amount estimation unit that obtains an SOC estimated value of the storage battery 2. The first estimation unit 23 has a function of performing a second estimation process for obtaining the SOC estimation value of the storage battery 2 by the same method.
However, the model parameters included in the first equivalent circuit model 30 used by the first estimation unit 23 and the model parameters included in the second equivalent circuit model 40 used by the second estimation unit 24 are set to different values. Yes.
Therefore, the 1st estimation part 23 and the 2nd estimation part 24 require | calculate the SOC estimated value of the storage battery 2 using the mutually different equivalent circuit model (The 1st equivalent circuit model 30 and the 2nd equivalent circuit model 40).
Further, both the first estimation unit 23 and the second estimation unit 24 are configured to perform the first estimation process and the second estimation process in parallel at the same discrete time k.

[About switching processing]
The control unit 25 of the control device 8 performs a switching process for switching the output source of the SOC estimated value of the storage battery 2 to be output from the output device 9 to either the first estimation unit 23 or the second estimation unit 24.
FIG. 6 is a block diagram illustrating an example of the configuration of the control unit 25.
The control unit 25 includes the temperature of the storage battery 2 by the temperature sensor 7, the SOC estimation value obtained by the first estimation unit 23 or the second estimation unit 24, the parameter estimation unit 23 a of the first estimation unit 23, or the second estimation unit 24. The estimated value of the model parameter obtained by the parameter estimation unit and the input current value of the storage battery 2 by the current sensor 5 are given.
Further, the control unit 25 refers to information registered in the measurement value database 22. The control unit 25 performs switching processing based on these pieces of information.

As shown in FIG. 6, the control unit 25 includes a specifying unit 25a, an evaluation processing unit 25b, and a switching unit 25c.
The specifying unit 25a has a function of specifying a frequency band corresponding to the current charged / discharged from the storage battery 2 by converting the time-dependent change of the current charged / discharged from the storage battery 2 (input current value i _k ) into the frequency domain. Have.
The evaluation processing unit 25b has a function of performing processing related to the evaluation of the SOC estimation accuracy of the first equivalent circuit model 30 based on the AC impedance of the first equivalent circuit model 30 in the frequency band specified by the specifying unit 25a. .
The switching unit 25c has a function of performing switching related to the estimation process for obtaining the SOC estimated value of the storage battery 2 based on the evaluation result of the evaluation process. More specifically, the switching unit 25 c has a function of switching the output source of the SOC estimation value of the storage battery 2 to be output from the output device 9 to one of the first estimation unit 23 and the second estimation unit 24. .

FIG. 7 is a flowchart illustrating an example of the switching process performed by the control unit 25.
When the state of the storage battery 2 is started, the switching unit 25c of the control unit 25 first selects the first estimation unit 23 as an output source of the SOC estimation value of the storage battery 2, and outputs the SOC estimation value to the first estimation unit 23 as an output device. 9 through step 9 (step S11).

  Next, the control unit 25 determines whether or not a certain period has elapsed since the output of the SOC estimation value of the first estimation unit 23 is started (step S12). When the control unit 25 determines that the certain period has not elapsed, the control unit 25 performs the determination in step S12 again. Therefore, the control unit 25 repeats the determination in step S12 until a certain period elapses.

  When it is determined that a certain period has elapsed since the start of the output of the SOC estimation value of the first estimation unit 23 (step S12), the control unit 25 causes the specifying unit 25a and the evaluation processing unit 25b to execute an evaluation process (step S12). S13). The specifying unit 25a and the evaluation processing unit 25b determine the validity of the first equivalent circuit model 30 of the first estimation unit 23 and the validity of the second equivalent circuit model 40 of the second estimation unit 24 by the evaluation process. The evaluation process will be described in detail later.

When the evaluation process ends, the control unit 25 causes the switching unit 25c to determine whether the determination result of the first equivalent circuit model 30 in the evaluation process is “valid” or “invalid” (step S14).
When determining that the determination result of the first equivalent circuit model 30 is “valid” (step S14), the switching unit 25c returns to step S11. Therefore, in this case, when the first estimating unit 23 is selected as the output source of the SOC estimated value of the storage battery 2 at the current stage, the switching unit 25c is the first estimating unit 23 as the output source of the SOC estimated value of the storage battery 2. And when the second estimation unit 24 is selected as the output source of the SOC estimation value of the storage battery 2, the first estimation unit 23 is switched to.
Thereafter, when a certain period of time elapses (step S12), the control unit 25 causes the specifying unit 25a and the evaluation processing unit 25b to execute the evaluation process again (step S13).

  On the other hand, if it is determined that the determination result of the first equivalent circuit model 30 in the evaluation process is “invalid” (step S14), the switching unit 25c proceeds to step S15 and determines the second equivalent circuit model 40 in the evaluation process. It is determined whether the result is “valid” or “invalid” (step S15).

If the switching unit 25c determines that the determination result of the second equivalent circuit model 40 is “valid” (step S15), the process proceeds to step S17.
When proceeding to step S17, the switching unit 25c selects the second estimation unit 24 as the output source of the SOC estimation value of the storage battery 2, and causes the second estimation unit 24 to output the SOC estimation value through the output device 9 (step S17). Return to step S12. Therefore, in this case, when the first estimation unit 23 is selected as the output source of the SOC estimated value of the storage battery 2 at the current stage, the switching unit 25c determines the output source of the SOC estimated value of the storage battery 2 as the first estimation unit 23. If the second estimation unit 24 is selected as the output source of the SOC estimated value of the storage battery 2, the second estimation unit 24 is maintained as the output source of the SOC estimated value of the storage battery 2.
Thereafter, when a certain period of time elapses (step S12), the control unit 25 causes the specifying unit 25a and the evaluation processing unit 25b to execute the evaluation process again (step S13).

  If it is determined that the determination result of the second equivalent circuit model 40 is “invalid” (step S15), the switching unit 25c proceeds to step S16, and the error E in the first equivalent circuit model 30 obtained in the evaluation process is It is determined whether or not the error E is smaller than the error E in the second equivalent circuit model 40 obtained in the evaluation process (step S16).

Here, the error E in the first equivalent circuit model 30 (second equivalent circuit model 40) is a value calculated in an evaluation process to be described later, and the acquired measured value of the AC impedance of the storage battery 2 and the current SOC. Is the average value of the difference between the first equivalent circuit model 30 (second equivalent circuit model 40) and the AC impedance used for the estimation of.
As will be described later, the error E indicates that the smaller the error E, the higher the SOC estimation accuracy.

  Therefore, when the switching unit 25c determines in step S16 that the error E in the first equivalent circuit model 30 is smaller than the error E in the second equivalent circuit model 40 (step S16), the process returns to step S11. Therefore, in this case, the switching unit 25c selects the first estimation unit 23 as the output source of the SOC estimation value of the storage battery 2, and causes the first estimation unit 23 to output the SOC estimation value.

  On the other hand, if it is determined in step S16 that the error E in the first equivalent circuit model 30 is not smaller than the error E in the second equivalent circuit model 40 (step S16), the process proceeds to step S17. In this case, the switching unit 25c selects the second estimation unit 24 as an output source of the SOC estimation value of the storage battery 2, causes the second estimation unit 24 to output the SOC estimation value, and returns to Step S12.

  Accordingly, the switching unit 25c selects an equivalent circuit model with a small error E among the first estimation unit 23 and the second estimation unit 24 even if the determination results of both models 30 and 40 are both “invalid”. By selecting the estimation unit to be used, the accuracy of the SOC estimation value is maintained as much as possible.

As described above, the control unit 25 performs the evaluation process at regular intervals during the switching process, and based on the evaluation result, the output source of the SOC estimated value of the storage battery 2 to be output from the output device 9 is the first. One of the estimation unit 23 and the second estimation unit 24 is selected and switched.
In addition, the fixed period in step S12 is set so that it may become a fixed frequency according to the necessity of evaluation of both models 30 and 40 at the time of calculating | requiring the SOC estimated value of the storage battery 2. FIG.

[Evaluation process]
FIG. 8 is a flowchart showing an example of the evaluation process in FIG. FIG. 8 illustrates the case where the first equivalent circuit model 30 used by the first estimation unit 23 is evaluated, but the same applies to the evaluation of the second equivalent circuit model 40 used by the second estimation unit 24.

  First, the control unit 25 acquires the temperature of the storage battery 2, the current SOC estimated value obtained by the first estimating unit 23, and the estimated value of the model parameter used for obtaining the SOC estimated value (step S21).

Next, the control unit 25 causes the specifying unit 25a to specify the frequency band corresponding to the current charged / discharged from the storage battery 2 by converting the change over time of the input current value of the storage battery 2 into the frequency domain (step S22). .
For example, the specifying unit 25a performs fast Fourier transform on the measurement data indicating the input current value of the storage battery 2 in a past fixed period, and converts the change over time of the input current value of the storage battery 2 into the frequency domain.

  FIG. 9A is a graph showing an example of a change with time of the input current value of the storage battery 2. In FIG. 9A, the vertical axis indicates the input current value of the storage battery 2. The input current value on the vertical axis indicates minus. That is, FIG. 9A shows the input current value during discharge. The horizontal axis indicates time.

FIG.9 (b) is a graph which shows an example of the result of having changed the time-dependent change of the input current value of the storage battery 2 shown to Fig.9 (a) to the frequency domain.
As shown in FIG. 9B, large peaks exist at 0.03 Hz and 0.07 Hz. As a result, the frequency components in the time-dependent change of the input current value of the storage battery 2 shown in FIG. 9A include more frequency components near 0.03 Hz and 0.07 Hz than other frequency components. You can see that

The specifying unit 25a discharges from the storage battery 2 a frequency component band that is higher than a preset threshold value among the frequency components when the time-dependent change of the input current value of the storage battery 2 is converted into the frequency domain. It is specified as a frequency band corresponding to the generated current (hereinafter also referred to as a specific frequency band).
For example, if the threshold value is set to “500” and the result shown in FIG. 9B is obtained, the specifying unit 25a includes the first band h1 (about 0. 03 Hz to 0.04 Hz) and the second band h2 (about 0.06 Hz to 0.08 Hz) are specified as specific frequency bands.

  The threshold value for specifying the specific frequency band is, for example, the frequency component when the change in the input current value of the storage battery 2 with time is converted into the frequency domain, the component of the specific frequency band is more than the component of the other frequency band. Is set to a value that can be judged to be clearly included.

  9A and 9B show the case where the specific frequency region is specified by converting the time-dependent change of the input current value of the storage battery 2 at the time of discharging into the frequency region. The change with time of the input current value of the storage battery 2 at the time of charging is similarly converted to the frequency domain, and the specific frequency band corresponding to the current charged in the storage battery 2 is specified.

  Returning to FIG. 8, when the specifying unit 25 a specifies the specific frequency band, the control unit 25 causes the evaluation processing unit 25 b to refer to the measurement value database 22 and measures the AC impedance registered in the measurement value database 22. A necessary measurement value of the AC impedance is acquired from the values (step S23).

FIG. 10 is a diagram illustrating an example of the measurement value database 22.
In the measurement value database 22, the measurement value of the AC impedance of the storage battery 2 actually measured by the AC impedance method is registered.
As shown in FIG. 10, a plurality of AC impedance measurement values are registered in the measurement value database 22 in association with the SOC, the temperature of the storage battery, and the frequency of the AC signal applied in the AC impedance method.
For the SOC, for example, values of 11 levels are set every 10%, such as 0%, 10%, 20%... 100%.
About the temperature of the storage battery 2, a value of 10 levels is set every 5 degrees, for example, 0 degree, 5 degrees, 10 degrees,... 45 degrees.
About the frequency of the alternating current signal applied in the case of measurement of alternating current impedance, the value of a predetermined number level is set between 0.01 Hz and 3000 Hz.

  The AC impedance means the impedance when an AC signal is applied by an AC impedance method or the like. In this embodiment, the storage battery 2 indicates an impedance when an AC signal having a predetermined frequency is applied so as to charge or discharge current.

The evaluation processing unit 25b refers to the measurement value database 22 and specifies a measurement value of AC impedance corresponding to the current temperature of the storage battery 2 and the estimated SOC value. If there is no value in the measured value database 22 that matches the current temperature and SOC estimated value of the storage battery 2, the measured value of the AC impedance associated with the closest value is specified.
Further, the evaluation processing unit 25b determines that the frequency of the applied AC signal (applied AC signal) is within a specific frequency band among the measured values of the AC impedance corresponding to the specified current temperature and SOC estimated value of the storage battery 2. A measurement value of a certain AC impedance is acquired (step S23).
When there are a plurality of AC impedance measurement values in which the frequency of the applied AC signal is within the specific frequency band (the first band h1 and the second band h2), the evaluation processing unit 25b acquires all of them.

  Returning to FIG. 8, the evaluation processing unit 25 b that has acquired the necessary AC impedance measurement value uses the acquired AC impedance measurement value of the storage battery 2 and the current SOC estimation based on the following equation (12). An error E with the AC impedance of the first equivalent circuit model 30 is calculated (step S24).

In the above equation (12), ω ₁ , ω ₂ ,... Ω _p indicate the frequency of the applied AC signal corresponding to each of the measured values of the AC impedance of the storage battery 2 acquired in step S23.
Z (ω _k ) represents a measured value of AC impedance when the frequency of the applied AC signal is ω _k . That is, Z (ω ₁ ), Z (ω ₂ ),... Z (ω _p ) indicate the measured values of the AC impedance of the storage battery 2 acquired in step S23.
Z _estimated (ω _k ) represents the AC impedance of the first equivalent circuit model 30 when the frequency of the applied AC signal is ω _k . The evaluation processing unit 25b obtains the AC impedance of the first equivalent circuit model 30 using the current model parameter.

  Therefore, the evaluation processing unit 25b calculates the AC impedance of the storage battery 2 and the AC impedance of the first equivalent circuit model 30 at the same frequency as the frequency of the applied AC signal corresponding to the AC impedance measurement of the storage battery 2. A plurality of differences are obtained, and an average of the plurality of differences is obtained as an error E.

FIG. 11 is a diagram showing a Cole-Cole plot showing an example of the relationship between the measured value of the AC impedance of the storage battery 2 and the AC impedance of the first equivalent circuit model 30.
In FIG. 11, the horizontal axis indicates the real component of the impedance, and the vertical axis indicates the imaginary component of the impedance.
In FIG. 11, the measured value of the alternating current impedance in the storage battery 2 in which the SOC is 50% and the temperature is about 25 degrees is indicated by a plurality of black circles and solid lines. The measured values of AC impedance indicated by a plurality of black circles 8 correspond to different frequencies of applied AC signals.
Here, the sample period Δt when processing is performed by the first estimation unit 23, the second estimation unit 24, and the control unit 25 is set to 1 second, for example.

In FIG. 11, the broken line indicates the AC impedance of the first equivalent circuit model 30 used by the first estimation unit 23 in the first estimation process. The AC impedance of the first equivalent circuit model 30 is represented by a continuous curve corresponding to a change in frequency.
Further, in FIG. 11, the alternate long and short dash line indicates the AC impedance of the first equivalent circuit model 30 used by the first estimation unit 23 in the process using the fixed value as the model parameter (comparison estimation process).

A white circle on each diagram indicates the value of AC impedance when the frequency of the applied AC signal is 0.08 Hz. For example, when the specific frequency band is the band shown in FIG. 9, a white circle indicates a value near the specific frequency band.
Moreover, the cross mark on each diagram shows the value of the AC impedance when the frequency of the applied AC signal in each diagram is 0.5 Hz (Nyquist frequency at the sample frequency).

  In FIG. 11, if the white circle 52 on the broken line representing the AC impedance of the first equivalent circuit model 30 used in the first estimation process approximates the white circle 51 on the solid line representing the measurement value of the AC impedance. It can be determined that the model parameters in the specific frequency band are estimated with higher accuracy and the estimation accuracy of the SOC is higher.

In the comparative estimation process, since a fixed value is used for the model parameter, the estimation accuracy of the SOC appears lower than that in the first estimation process in which the SOC is estimated while sequentially estimating the model parameter by the least square method.
Here, in FIG. 11, the relationship between the values between the white circle 53 and the white circle 51 on the alternate long and short dash line representing the AC impedance of the first equivalent circuit model 30 used in the comparison estimation process, and the white circle Comparing the relationship of the values between the mark 52 and the white circle 51, the value relationship between the white circle 52 and the white circle 51 is more in both the real component and the imaginary component. It is more approximate than the relationship of values between the white circle 53 and the white circle 51.

  This is because the difference between the measured value of the AC impedance of the storage battery 2 and the AC impedance of the first equivalent circuit model 30 at the same frequency as the frequency of the applied AC signal corresponding to the measured value of the AC impedance of the storage battery 2. If it is smaller, it indicates that the estimation accuracy of the SOC becomes higher.

From the above, it can be seen that the difference between the measured value of the AC impedance of the storage battery 2 and the AC impedance of the first equivalent circuit model 30 can be used for evaluating the estimation accuracy of the SOC.
Therefore, the evaluation processing unit 25b calculates a difference between the measured value of the AC impedance of the storage battery 2 and the AC impedance of the first equivalent circuit model 30, and calculates the average of these differences as the error E.

Returning to FIG. 8, when the error E is obtained, the evaluation processing unit 25b determines whether or not the error E is smaller than a preset threshold value δ (step S25).
When determining that the error E is smaller than the threshold δ, the evaluation processing unit 25b sets the evaluation result of the first equivalent circuit model 30 currently used for the estimation of the SOC to be “valid” and ends the process (step S26).
On the other hand, when determining that the error E is equal to or greater than the threshold δ, the evaluation processing unit 25b sets the evaluation result of the first equivalent circuit model 30 currently used for the estimation of the SOC to be “invalid” and ends the process (step S27).

  As described above, the difference between the AC impedance measurement value of the storage battery 2 and the AC impedance of the first equivalent circuit model 30 at the same frequency as the frequency of the applied AC signal corresponding to the AC impedance measurement value of the storage battery 2. Thus, the estimation accuracy of the SOC can be evaluated. Therefore, the threshold δ is set to a value that can maintain the SOC estimation accuracy within an allowable range, for example. Accordingly, when the estimation accuracy of the SOC can be maintained within the allowable range, the evaluation processing unit 25b sets the evaluation result of the first equivalent circuit model 30 to “valid” and cannot maintain the SOC estimation accuracy within the allowable range. In this case, the evaluation result of the first equivalent circuit model 30 can be “invalid”.

  As described above, the evaluation processing unit 25b uses the alternating current of the first equivalent circuit model 30 at the same frequency as the measured value of the alternating current impedance of the storage battery 2 and the frequency of the applied alternating current signal corresponding to the measured value of the alternating current impedance of the storage battery 2. The SOC estimation accuracy of the first equivalent circuit model 30 is evaluated by comparing with the impedance.

  Based on the AC impedance of the first equivalent circuit model 30 (second equivalent circuit model 40) in the specific frequency band corresponding to the current charged / discharged from the storage battery 2, Evaluation that evaluates the first equivalent circuit model 30 (second equivalent circuit model 40) of the storage battery 2 by including an evaluation processing unit 25b that performs processing related to the evaluation of the first equivalent circuit model 30 (second equivalent circuit model 40). Configure the device.

According to the present embodiment, the evaluation processing unit 25b uses the first equivalent circuit model 30 based on the AC impedance of the first equivalent circuit model 30 (second equivalent circuit model 40) in the frequency band corresponding to the current charged / discharged from the storage battery 2. Since the model 30 (second equivalent circuit model 40) is evaluated, it is possible to perform an appropriate evaluation in accordance with the output characteristics of the storage battery 2.
Moreover, since the evaluation process part 25b compares and evaluates the actual measured value of the alternating current impedance of the storage battery 2, and the alternating current impedance of the 1st equivalent circuit model 30, it can perform more suitable evaluation.

[Others]
The present invention is not limited to the above embodiment. For example, although the case where the lithium ion battery was used as the storage battery 2 was shown in the said embodiment, the storage battery management apparatus 3 of this embodiment is applicable also to another kind of storage battery.

Moreover, in the said embodiment, the evaluation process part 25b is the 1st equivalent circuit model 30 in the same frequency as the frequency of the applied AC signal corresponding to the measured value of the alternating current impedance of the storage battery 2, and the measured value of the alternating current impedance of the said storage battery 2. A case is illustrated in which a plurality of differences with respect to the AC impedance of the first equivalent circuit model 30 are evaluated and the first equivalent circuit model 30 is evaluated based on an error E that is an average of the plurality of differences.
In contrast, for example, between the measured value of the AC impedance of the storage battery 2 and the AC impedance of the first equivalent circuit model 30 at the same frequency as the frequency of the applied AC signal corresponding to the measured value of the AC impedance of the storage battery 2. May be obtained, and the first equivalent circuit model 30 may be evaluated based on this difference.

  Moreover, in the said embodiment, among the frequency components when the time-dependent change of the input current value of the storage battery 2 is converted into the frequency domain, the frequency component band having a value higher than a preset threshold is set to the specific frequency. The specific frequency band may include a plurality of bands as illustrated in FIG. 9 or may include only one band. Furthermore, the specific frequency band may include only one frequency.

  Moreover, in the said embodiment, although the case where the measured value of the alternating current impedance of the storage battery 2 and the alternating current impedance of the 1st equivalent circuit model 30 were compared and evaluated was illustrated, for example, the alternating current impedance of the 1st equivalent circuit model 30 and The AC impedance of the second equivalent circuit model 40 may be compared and evaluated. In this case, the evaluation can be performed based on which one of the AC impedance of the first equivalent circuit model 30 and the AC impedance of the second equivalent circuit model 40 is approximated to a predetermined reference value.

Moreover, in the said embodiment, the 1st estimation part 23 and the 2nd estimation part 24 perform a 1st estimation process and a 2nd estimation process using the mutually equivalent mutually equivalent circuit model, and according to evaluation of an equivalent circuit model Then, the case where the switching unit 25c is configured to switch the output source of the SOC estimation value of the storage battery 2 to be output from the output device 9 to either the first estimation unit 23 or the second estimation unit 24 is illustrated.
On the other hand, you may comprise so that many estimation parts may perform the estimation process of SOC in parallel, and it switches to either of them.
Further, only the first estimation unit 23 executes the SOC estimation process, and the first equivalent circuit model 30 used by the first estimation unit 23 is replaced with another equivalent circuit model according to the evaluation of the equivalent circuit model. May be.

  In the above embodiment, the first equivalent circuit model 30 and the second equivalent circuit model 40 have different model parameters, but the configuration of the elements constituting the model is the same. The equivalent circuit model may be configured similarly to the first equivalent circuit model 30, and the other equivalent circuit model may be configured such that two additional RC circuits are connected in series.

  Moreover, in the said embodiment, according to evaluation of an equivalent circuit model, the case where it comprised so that the equivalent circuit model used for calculating | requiring the SOC estimated value of the storage battery 2 until then may be switched to another equivalent circuit model is illustrated. However, for example, between the first estimation process (estimation process using the sequential least square method and the extended Kalman filter) performed by the first estimation unit 23 and another SOC estimation process different from the first estimation process. You may comprise so that it may switch. In addition, as an SOC estimation process different from the first estimation process, a current integration method, an output voltage method, an internal resistance method, or the like can be employed.

DESCRIPTION OF SYMBOLS 1 Storage battery system 2 Storage battery 3 Storage battery management apparatus 4 Both-ends terminal 5 Current sensor 6 Voltage sensor 7 Temperature sensor 8 Control apparatus 9 Output device 20 Processing apparatus 21 Memory | storage device 22 Measurement value database 23 1st estimation part 23a Parameter estimation part 23b Remaining power storage Estimation unit 24 Second estimation unit 25 Control unit 25a Identification unit 25b Evaluation processing unit 25c Switching unit 30 First equivalent circuit model 31 Power source 32 Resistive element 33 RC circuit 33a Resistive element 33b Capacitor 40 Second equivalent circuit model 41 Power source 42 Resistive element 43 RC circuit 43a Resistance element 43b Capacitor

Claims (5)

An evaluation apparatus for evaluating an equivalent circuit model of the storage battery used for estimation processing of a remaining storage capacity of the storage battery,
An evaluation apparatus comprising an evaluation processing unit that performs processing related to evaluation of the equivalent circuit model based on an AC impedance of the equivalent circuit model in a frequency band corresponding to a current charged and discharged from the storage battery. The evaluation processing unit performs a process related to evaluation of the remaining power estimation accuracy of the equivalent circuit model by comparing the measured value of the AC impedance of the storage battery in the frequency band with the AC impedance of the equivalent circuit model. The evaluation apparatus according to claim 1. The evaluation apparatus according to claim 1, further comprising a switching unit that performs switching related to the estimation process based on an evaluation result obtained by the evaluation process. The evaluation apparatus according to claim 3, wherein the switching related to the estimation process is a process of switching the equivalent circuit model to another equivalent circuit model different from the equivalent circuit model. The evaluation apparatus according to claim 3, wherein the switching related to the estimation process is a process of switching the estimation process to another estimation process different from the estimation process.