JP7570970B2 - Acquisition processing device, processing method, processing program, and measurement system - Google Patents

Description

The present invention relates to an acquisition processing device, a processing method, a processing program, and a measurement system for measuring the impedance of an electricity storage device.

Patent document 1 discloses an equivalent circuit analysis device that measures a battery. This equivalent circuit analysis device performs equivalent circuit analysis using the equivalent circuit of a battery.

JP 2014-10037 A

When performing equivalent circuit analysis using a nonlinear algorithm on such a device, there is a risk that the results will vary depending on which parameters are fixed when fitting the characteristics. Therefore, even if the residual value is reduced, it cannot be proven that the value represents the battery characteristics.

The present invention was made in consideration of the above problems, and aims to make it possible to obtain measurement results that indicate the characteristics of the electricity storage device being measured.

An acquisition processing device according to one aspect of the present invention is an acquisition processing device that acquires and processes the impedance of an electric storage device. The acquisition processing device includes an acquisition means that acquires the impedance of a measurement target component measured at three or more frequencies using a measuring device in a predetermined frequency band. The acquisition processing device includes a determination means that determines the extreme values of the real or imaginary components of the impedance at the three or more points acquired by the acquisition means. The acquisition processing device includes a calculation means that calculates a predicted value of the measurement target component based on an approximation formula that represents the relationship between the real and imaginary components of the impedance at the three or more points. The acquisition processing device includes a determination means that, when the extreme value protrudes so as to be the same as the predicted value or closer to the impedance of the measurement target component than the predicted value, determines the extreme value as the measured value for the measurement target component.

In this embodiment, a predicted value of the component to be measured is calculated based on an approximation formula that expresses the relationship between the real and imaginary components of the impedance at three or more points obtained by measurement. Then, when the extreme values of the real or imaginary components at three or more points stand out so as to be the same as the predicted value based on the approximation formula or to be closer to the impedance of the component to be measured than the predicted value, the extreme values are determined as the measured value for the component to be measured.

This measurement value is determined based on an actual measurement, and this actual measurement value indicates the characteristics of the energy storage device.

Therefore, it is possible to obtain measurement results that indicate the characteristics of the energy storage device being measured as measured values.

FIG. 1 is a block diagram illustrating a measurement system according to one embodiment. FIG. 2 is a block diagram illustrating a measurement device of a measurement system according to an embodiment. FIG. 3 is a block diagram illustrating an acquisition processing device of a measurement system according to an embodiment. FIG. 4 is a functional block diagram illustrating an acquisition processing device according to an embodiment. FIG. 5 is an equivalent circuit showing a state in which the impedance of an electricity storage device is measured by a measurement system according to an embodiment. FIG. 6 is an explanatory diagram showing a Cole-Cole plot in which the impedance at each frequency of an electricity storage device measured by a measurement system according to one embodiment is plotted on a complex plane. FIG. 7 is an explanatory diagram showing a part of the solution resistance component in a Cole-Cole plot of an electricity storage device measured by a measurement system according to one embodiment. FIG. 8 is an explanatory diagram showing a portion of the electric double layer capacitance component in a Cole-Cole plot of an electricity storage device measured by a measurement system according to one embodiment. FIG. 9 is an explanatory diagram showing a reaction resistance component portion in a Cole-Cole plot of an electricity storage device measured by a measurement system according to one embodiment. FIG. 10 is a flowchart showing the operation of the measurement process according to an embodiment. FIG. 11 is an explanatory diagram showing how a predicted value is predicted in a measurement process according to an embodiment. FIG. 12 is a flowchart showing the operation of the frequency calculation process according to an embodiment.

Each embodiment of the present invention will be described below with reference to the attached drawings.

<Embodiment>
An embodiment will be described below with reference to the accompanying drawings. Fig. 1 is a block diagram showing a measurement system 10 according to an embodiment. Fig. 2 is a block diagram showing a measurement device 12 of the measurement system 10 according to an embodiment. Fig. 3 is a block diagram showing an acquisition processing device 14 of the measurement system 10 according to an embodiment.

As shown in FIG. 1, the measurement system 10 is a system that measures the impedance of the power storage device 16.

Here, the power storage device 16 is a storage battery configured to be capable of being charged and discharged, and includes a capacitor-type power storage element such as an electric double layer capacitor. The power storage device 16 may be a battery pack in which multiple cells are connected in parallel, series, or series-parallel, or may be a single cell. The power storage device 16 has an internal resistance and outputs a DC voltage through a chemical reaction.

(Hardware configuration)
The measurement system 10 is composed of a plurality of devices for measuring the impedance of the electricity storage device 16. Specifically, the measurement system 10 includes a measuring device 12 that measures the impedance of the electricity storage device 16, and an acquisition processing device 14 that uses the measurement results from the measuring device 12 to determine the impedance of the measurement target component.

The measuring device 12 measures the impedance of the power storage device 16. The acquisition processing device 14 processes the impedance measured by the measuring device 12 to determine the measurement value of the component to be measured.

Specifically, the acquisition processing device 14 plots the real and imaginary components of the impedance measured at each frequency in the measurement device 12 on a complex plane to form a Cole-Cole plot. In this way, the acquisition processing device 14 uses the measurement results from the measurement device 12 to determine the impedance of the component to be measured.

Examples of components to be measured include a solution resistance component that can detect the electrolyte resistance, and an electric double layer capacitance component that can detect the electric double layer capacitance.

[Measuring equipment]
The measuring device 12 shown in Fig. 2 includes the constant current source 20, the voltage detection unit 22, the processing unit 24, and the communication unit 26 shown in Fig. 1. The constant current source 20 includes an AC current supply unit and a current detection unit.

The communication unit 26 communicates with the acquisition processing device 14 and passes on the measurement conditions and other information received from the acquisition processing device 14 to the processing unit 24. The communication unit 26 also passes on the measurement results and other information received from the processing unit 24 to the acquisition processing device 14.

The processing unit 24 operates the AC current supply unit of the constant current source 20 according to the measurement conditions received from the communication unit 26. The processing unit 24 also receives the current value measured by the current detection unit of the constant current source 20.

The processing unit 24 also calculates the impedance based on the output from the AC current supply unit of the constant current source 20, the voltage change detected by the voltage detection unit 22, and the current value measured by the current detection unit. The processing unit 24 then outputs the imaginary and real components of the impedance to the communication unit 26 as the measurement results.

The AC current supply unit of the constant current source 20 generates an AC current with a magnitude and frequency according to the measurement conditions from the processing unit 24. The AC current supply unit of the constant current source 20 also applies the generated AC current to the positive terminal 16A and the negative terminal 16B of the power storage device 16. The current detection unit of the constant current source 20 detects the current flowing through the power storage device 16.

The voltage detection unit 22 detects the voltage generated at the positive terminal 16A and the negative terminal 16B of the power storage device 16 in response to the AC current supplied from the constant current source 20 to the power storage device 16. The voltage detection unit 22 also outputs the detected voltage to the processing unit 24.

[Acquisition and processing device]
3, the acquisition processing device 14 is configured with a processor 30 constituting a computer as a core component. A communication unit 32, a storage unit 34, an input unit 36, a display unit 38, a notification unit 40, a clock unit 42, and an external communication unit 44 are connected to the processor 30.

The communication unit 32 communicates with the communication unit 26 of the measuring device 12. The communication is performed by wired communication or wireless communication. The communication unit 32 transmits the measurement conditions and the like sent from the processor 30 to the communication unit 26 of the measuring device 12. The communication unit 32 also receives the measurement results and the like received from the communication unit 26 of the measuring device 12 and passes them over to the processor 30.

The memory unit 34 stores data so that it can be read by the processor 30. The memory unit 34 stores a processing program that controls the operation of the acquisition processing device 14. The memory unit 34 functions as a storage medium that stores a processing program that realizes the functions of the acquisition processing device 14.

The memory unit 34 is composed of non-volatile memory (ROM: Read Only Memory) and volatile memory (RAM: Random Access Memory), etc.

The memory unit 34 also stores data used by the processing program in a readable manner.

Specifically, the memory unit 34 stores information indicating the frequency band for measuring the impedance of the component to be measured. The memory unit 34 also temporarily stores the frequency input when starting the measurement of the component to be measured, and data used in the process of calculating the measurement value of the component to be measured. The memory unit 34 also stores the measurement results.

The input unit 36 sends data input by the user to the processor 30. The input unit 36 functions as an input interface that accepts input operations by the user. As an example, the input unit 36 is composed of a plurality of operation buttons and numeric buttons, or a touch panel.

The display unit 38 performs display according to data from the processor 30. As an example, the display unit 38 displays measurement results, etc. Furthermore, if the acquisition processing device 14 has a function of ranking the power storage device 16 based on the measurement results, the display unit 38 displays the ranked rank. The displayed rank may be good or bad, indicating whether the power storage device 16 is good or bad, or quality, for classifying the power storage device 16 according to its use.

The quality of the output characteristics of the power storage device 16 is determined based on the state of the internal impedance. Specifically, a device with an internal impedance lower than a predetermined standard is considered to be a good product.

The device constituting the display unit 38 may be a display panel such as a light-emitting diode or an LCD (Liquid Crystal Display). As an example, the display unit 38 in this embodiment is composed of a liquid crystal panel.

The notification unit 40 issues notifications according to data from the processor 30. The notification unit 40 notifies the user by sound, such as guidance or warning sounds. Examples of devices that notify by sound include a piezoelectric buzzer or a speaker. In this embodiment, the notification unit 40 is, as an example, configured with a speaker.

The clock unit 42 indicates the current date and time and measures time. The clock unit 42 outputs the current date and time to the processor 30. The date and time indicated by the clock unit 42 are stored in the memory unit 34, for example, in association with a value determined as the measurement value of the component to be measured.

The external communication unit 44 enables data transmission and reception between the processor 30 and an external device. The external communication unit 44 constitutes an interface for transmitting and receiving data. The external communication unit 44 is composed of hardware that performs communication using a USB (universal serial bus), Bluetooth (registered trademark), wireless LAN, etc.

When the above-mentioned processing program is supplied from an external device, the external communication unit 44 receives the processing program from the external device and sends it to the processor 30. The processor 30 stores the received processing program in the memory unit 34.

The processor 30 is, for example, configured with a central processing unit (CPU). The processor 30 reads a processing program stored in the memory unit 34 and operates according to the read processing program. In this way, the processor 30 controls each part of the acquisition processing device 14 to carry out the processing method.

The processor 30 also displays the measurement results, etc. on the display unit 38, notifies them from the notification unit 40, and transmits them to an external device via the external communication unit 44.

(Function block)
FIG. 4 is a functional block diagram showing the functional configuration of the acquisition processing device 14 according to an embodiment.

As shown in FIG. 4, the acquisition processing device 14 includes an acquisition unit 50, a determination unit 51, a calculation unit 52, and a confirmation unit 54. The functions of the units 50, 51, 52, and 54 in the acquisition processing device 14 are realized by the processor 30 executing a software program read from the storage unit 34 as a processing program.

[Acquisition Department]
The acquiring unit 50, which functions as an acquiring means, acquires impedance measured at three or more frequencies in a predetermined frequency band for measuring the impedance of the measurement target component from the measuring device 12. The measurement target component includes, as an example, a solution resistance component of the electricity storage device 16, and the measurement target component will be described in detail later.

The acquisition unit 50 also determines whether the predicted value of the target component predicted by the calculation unit 52 is closer to the impedance of the measurement target component than the extreme values of the real or imaginary components of the impedance at three or more points acquired by the measurement device 12. If the predicted value is closer to the impedance of the measurement target component than the extreme values, an additional impedance measured at a predicted frequency in the frequency band that corresponds to the predicted value is acquired.

In other words, the acquisition unit 50 determines whether the value acquired from the measuring device 12 is farther from the impedance of the measured component than the predicted value of the measured component predicted by the calculation unit 52. If the acquired value is farther from the impedance of the measured component, the acquisition unit 50 newly acquires, as the measurement result, an additional impedance measured at a predicted frequency that is a frequency in the above frequency band that corresponds to the predicted value.

The predicted frequency corresponding to the predicted value is calculated based on the real component frequency obtained from the real component of the predicted value and the imaginary component frequency obtained from the imaginary component of the predicted value.

As an example, this predicted frequency is a weighted average value obtained by weighting the real component frequency and the imaginary component frequency based on the difference between the maximum and minimum values of the real component and the difference between the maximum and minimum values of the imaginary component acquired by the acquisition unit 50.

Here, whether the value obtained from the measuring device 12 is farther from the impedance of the component being measured than the predicted value can be determined based on the component being measured.

To give a specific example, when the component to be measured is a solution resistance component that includes electrolyte resistance, the electrolyte resistance correlates with the smallest value among the real components of the measured impedance. It is known that the smallest value of the real component in the measured impedance indicates the electrolyte resistance.

Therefore, when the component to be measured is a solution resistance component including electrolyte resistance, if the real component of the measured impedance is larger than the real component of the predicted impedance, it can be determined that the extreme value, which is the measured value, is farther from the impedance of the component to be measured than the predicted value. Also, if the real component of the measured impedance is smaller than the real component of the predicted impedance, it can be determined that the extreme value, which is the measured value, is closer to the impedance of the component to be measured than the predicted value.

[Decision section]
The determination unit 51 functioning as a determination means determines extreme values of real or imaginary components of the impedance at three or more points acquired by the acquisition unit 50 .

Here, the extreme value refers to the value of the real or imaginary components of the impedance obtained at three or more points that is closest to the impedance of the component to be measured. Whether or not a value is close to the impedance of the component to be measured can be determined by the method described above.

In addition, when the real or imaginary components of impedance at three or more points are plotted on a complex plane to form a curve, the extreme value can be said to be the value located in the direction in which the curve protrudes most.

[Calculation section]
The calculation unit 52, which functions as a calculation means, calculates a predicted value of the measurement target component based on an approximation formula expressing the relationship between the real components and imaginary components of the impedance at three or more points acquired by the acquisition unit 50. As an example, when the measurement target component is a solution resistance component including an electrolyte resistance, the predicted value of the measurement target component is the value of the real component.

In addition, the calculation unit 52 calculates the apex of an approximation equation that expresses the relationship between the real and imaginary components of the impedance at three or more points as a quadratic function as a predicted value of the component to be measured.

Specifically, the calculation unit 52 calculates a quadratic curve from the real and imaginary components of the impedance acquired by the acquisition unit 50 using the least squares method, and determines a predicted value based on the inflection point where the quadratic curve is most prominent in the protruding direction.

When the acquisition unit 50 acquires an additional impedance, the calculation unit 52 obtains an approximation formula based on the real and imaginary components of the additional impedance and the real and imaginary components of the impedances at three or more points measured before the additional impedance. The acquisition unit 50 then calculates a new predicted value of the measurement target component based on the obtained approximation formula.

[Determined part]
The determination unit 54, which is a determination means, determines the extreme value as the measurement value for the measured component when the extreme value obtained by the decision unit 51 stands out so as to be the same as the predicted value or closer to the impedance of the measured component than the predicted value.

In other words, if the value closest to the measured component among the three or more real or imaginary component values is the same as the predicted value or is closer to the measured component than the predicted value, the determination unit 54 determines that value as the value related to the measured component, i.e., the final result.

As a result, the impedance of the component to be measured is determined based on the value measured on the energy storage device.

When a new predicted value of the component to be measured is calculated using the additional impedance acquired by the acquisition unit 50, the determination unit 54 determines the value related to the component to be measured as follows. That is, when the measured value closest to the component to be measured is the same as the predicted value newly calculated by the calculation unit 52 or is closer to the component to be measured than the predicted value, the determination unit 54 determines the measured value as the value related to the component to be measured.

Here, the measurement value closest to the component to be measured is the value that is closest to the impedance of the component to be measured among all values, including the additional impedance measured at the predicted frequency.

As an example, when the component to be measured is a solution resistance component including electrolyte resistance, the predicted value of the component to be measured is the value of the real component. In this case, the determination unit 54 determines the measured value as the value related to the component to be measured when the smallest value among the values of the three or more real components is the same as or smaller than the predicted value.

This allows the value indicating the solution resistance component, including the electrolyte resistance, to be determined as the value relating to the component being measured.

If the extreme value is farther from the impedance of the component being measured than the predicted value, the process of measuring the impedance, calculating the predicted value, and comparing the extreme value to which the measured value is added with the predicted value is repeated, but the number of repetitions can also be specified in advance.

(Equivalent circuit)
FIG. 5 is an equivalent circuit 60 illustrating a state in which the impedance of the power storage device 16 is measured by the measurement system 10 according to one embodiment.

The impedance of the energy storage device 16 when the cable of the measuring device 12 is connected to each terminal 16A, 16B of the energy storage device 16 can be represented by an equivalent circuit 60 in which a cable resistance component 62, a solution resistance component 64, and a reaction resistance component 66 are connected in series.

The cable resistance component 62 is represented by an inductance Li and a resistance Ri connected in parallel to each other. The inductance Li represents the inductance of the cable, and the resistance Ri represents the resistance of the cable.

The solution resistance component 64 represents the solution resistance of the electrolyte between the electrodes of the electricity storage device 16. The solution resistance component 64 has an electrolyte resistance Rsol consisting of the electrolyte resistance of the electricity storage device 16 and the welding resistance of the electrode tabs.

The reaction resistance component 66 is composed of a positive electrode reaction resistance 68 generated at the positive electrode and a negative electrode reaction resistance 70 generated at the negative electrode. The positive electrode reaction resistance 68 and the negative electrode reaction resistance 70 are connected in series in the equivalent circuit 60.

The positive electrode reaction resistor 68 has an electric double layer capacitance C1 and a reaction resistance R1 connected in parallel. The electric double layer capacitance C1 indicates the electric capacitance occurring between the positive electrode and the electrolytic solution, and the reaction resistance R1 indicates the charge transfer resistance occurring between the positive electrode and the electrolytic solution.

The negative electrode reaction resistor 70 has an electric double layer capacitance C2 and a reaction resistance R2 connected in parallel to each other. The electric double layer capacitance C2 indicates the electric capacitance occurring between the negative electrode and the electrolytic solution, and the reaction resistance R2 indicates the charge transfer resistance occurring between the negative electrode and the electrolytic solution.

Figure 6 is an explanatory diagram showing a Cole-Cole plot 80 in which the impedance at each frequency of the electricity storage device 16 measured by the measurement system 10 according to one embodiment is plotted on a complex plane. Figure 7 is an explanatory diagram showing the solution resistance component 64 in the Cole-Cole plot 80 of the electricity storage device 16 measured by the measurement system 10 according to one embodiment.

Figure 8 is an explanatory diagram showing the electric double layer capacitance component 72 in the Cole-Cole plot 80 of the power storage device 16 measured by the measurement system 10 according to one embodiment. Figure 9 is an explanatory diagram showing the reaction resistance component 74 in the Cole-Cole plot 80 of the power storage device 16 measured by the measurement system 10 according to one embodiment.

As shown in FIG. 6, a Cole-Cole plot 80 (also called a Nyquist plot) is a plot of the impedance of the power storage device 16 at each frequency on a complex plane. The horizontal axis (R) of the complex plane indicates the real component of the impedance, and the vertical axis (X) indicates the imaginary component of the impedance.

As shown in Figures 6 and 7, this Cole-Cole plot 80 has a region where electrolyte resistance Rsol is the main factor in impedance. The region where electrolyte resistance Rsol is the main factor in impedance appears in a first frequency band, and in the case of the electricity storage device 16 of this embodiment, the first frequency band is, for example, a band between several hundred Hz and several tens of kHz.

The Cole-Cole plot 80 also has an impedance region in which the effects of the electric double layer capacitances C1 and C2 appear, as shown in Figures 6 and 8. The impedance region in which the effects of the electric double layer capacitances C1 and C2 appear appears in the second frequency band, and in the case of the power storage device 16 of this embodiment, the second frequency band is, for example, a band of several tens of Hz or more and less than several hundreds of Hz.

Furthermore, as shown in Figures 6 and 9, the Cole-Cole plot 80 has regions of reaction resistances R1, R2 and the impedance of the diffusion region of the solution. The reaction resistances R1, R2 and the impedance region of the diffusion region appear in a third frequency band, and in the case of the power storage device 16 of this embodiment, the third frequency band is, for example, a band of 0.01 Hz or more and less than several tens of Hz.

In this embodiment, the components to be measured are the solution resistance component 64 indicating the electrolyte resistance Rsol and the electric double layer capacitance component 72 indicating the electric double layer capacitances C1 and C2.

Here, the quality of the reaction resistances R1, R2 and the diffusion region can be evaluated based on, for example, the impedance of the electrolyte resistance Rsol detected in the high frequency area and the impedance of the reaction resistances R1, R2 in the low frequency area. To be more specific, in the Cole-Cole plot, the quality can be evaluated based on the length of the straight line connecting the position of the impedance of the electrolyte resistance Rsol detected in the high frequency area and the position of the impedance of the reaction resistances R1, R2 in the low frequency area.

Therefore, the reaction resistances R1, R2 and the reaction resistance component 74 indicating the diffusion region can also be considered as the impedance of the component to be measured.

The first frequency band indicates a frequency band for measuring the electrolyte resistance Rsol, the second frequency band indicates a frequency band for measuring the electric double layer capacitances C1 and C2, and the third frequency band indicates a frequency band for measuring the reaction resistances R1 and R2 and the impedance of the diffusion region.

(Operation description)
Next, the operation of the acquisition processing device 14 will be described with reference to Figures 10 to 12 and in accordance with the processing procedure executed by the processor 30 of the acquisition processing device 14. Note that the measurement system 10 functions in conjunction with the operation of the acquisition processing device 14.

Figure 10 is a flowchart showing an example of the operation of the acquisition processing device 14. Figure 10 shows a measurement process for measuring the measurement target component of the impedance of the power storage device 16.

Before executing this measurement process, a setting process is performed to set the parameters required for the measurement process. In this setting process, the measurement target component to be measured in the power storage device 16 is selected by the user. In addition, in the setting process, it is assumed that the user inputs three frequencies in the frequency band corresponding to the selected measurement target component.

To explain by way of example, in the electricity storage device 16 according to this embodiment, the electrolyte resistance Rsol is selected as the component to be measured. In addition, three frequencies are input in the first frequency band (a band of several hundred Hz or more and less than several tens of kHz) as the frequencies to be measured. Here, since the component to be measured is the electrolyte resistance Rsol, the component to be measured is represented by the value of the real component of the impedance.

In this embodiment, the electrolyte resistance Rsol, which is the component to be measured, is measured using the measurement results at a frequency in the first frequency band, but this is not limited to the above. For example, other components to be measured can be measured by using the measurement results at each frequency in other frequency bands.

The processor 30 of the acquisition processing device 14 executes the measurement process of the processing program stored in the memory unit 34. The processor 30 then acquires impedances measured at three pre-input frequencies in the frequency band for measuring the measurement target components, and obtains the real and imaginary components of each acquired impedance (step S1).

Specifically, the processor 30 of the acquisition processing device 14 communicates with the measurement device 12 via the communication unit 32. Through this communication, the processor 30 causes the measurement device 12 to measure the impedance of the power storage device 16 at the three input frequencies, and acquires each measured impedance from the measurement device 12.

Then, the processor 30 acquires the real and imaginary components of each impedance from the measuring device 12 and stores them in the memory unit 34.

Here, in the embodiment, a case will be described in which the real and imaginary components of each measured impedance are acquired from the measuring device 12, but this is not limited to this. For example, the impedance output from the measuring device 12 may be decomposed into real and imaginary components by the processor 30 of the acquisition processing device 14, and the real and imaginary components may be stored in the memory unit 34.

Figure 11 is an explanatory diagram showing how a predicted value 102 is predicted in a measurement process according to one embodiment. In Figure 11, a first measured impedance 90, a second measured impedance 92, and a third measured impedance 94 are shown on a complex plane as impedances measured at three frequencies.

As shown in FIG. 10, the processor 30 determines the extreme value among the real and imaginary components of each measured impedance 90, 92, 94 that is closest to the component to be measured (step S2).

In this embodiment, the impedance of the component to be measured is the electrolyte resistance Rsol. Therefore, the processor 30 determines the real component of the second measured impedance 92, which has the smallest real component among the measured impedances 90, 92, and 94, as the extreme value.

Then, the processor 30 sets the "counter" preset in the memory unit 34 to "0" (step S2-1), and determines whether the "counter" is less than n (step S2-2). Note that n is a predetermined value, and is composed of a number such as "3". Also, as one example, this n may be predetermined by input from the input unit.

At this point, the "counter" is "0", so in step S2-2 it is determined that the "counter" is less than n, and the process moves to step S3.

In step S3, the processor 30 calculates a quadratic curve 100 from the acquired measured impedances 90, 92, and 94 (step S3). As a result, the relationship between the real and imaginary components of the measured impedances 90, 92, and 94 is expressed as a quadratic function.

Specifically, as shown in FIG. 11, the processor 30 calculates a quadratic function from each measured impedance 90, 92, 94 using, for example, the least squares method, and obtains the quadratic curve 100 represented by this quadratic function. Note that the function may be calculated using an approximation method other than the least squares method.

Then, the processor 30 calculates the predicted value 102 of the measurement target component from the acquired quadratic curve 100 (step S4). This quadratic curve 100 indicates an approximation formula representing a quadratic function, and the apex of the quadratic function is calculated as the predicted value 102. The apex of the quadratic function indicates the inflection point where the quadratic curve 100 is most prominent in the protruding direction, and the predicted value 102 is determined based on this inflection point.

More specifically, the quadratic curve 100 is expressed by the formula Y=aX ² +bX+c. This formula can be rearranged to give Y=F(x)=a(X+b/2a) ² +(-b ² +4ac)/4a.

In this embodiment, the electrolyte resistance Rsol is selected as the component to be measured. For this reason, for convenience, the quadratic curve 100 is expressed by an equation that shows a curve that is convex in the vertical axis direction, with the horizontal axis representing reactance and the vertical axis representing resistance.

From this transformed equation, the value Xt of the imaginary component of the predicted value 102 corresponding to the apex is Xt = (-b/2a). The value Rt of the real component is Rt = {(-b ² + 4ac)/4a}. The smallest value of the real components is {(-b ² + 4ac)/4a}. Since the smallest real component indicates the apex, this value can be used as the predicted value 102.

In this way, the predicted value 102 is determined based on the peak of the quadratic function F(x) with the imaginary component as a variable.

In this embodiment, a quadratic function is used as an example of an approximation equation, but the present invention is not limited to this. For example, when impedance is measured at four frequencies, two approximation equations are assumed, one of which shows a straight line connecting two adjacent points, and the other of which shows a straight line connecting two adjacent points. In this case, the point where the two straight lines intersect can be set as the predicted value 102.

Then, as shown in FIG. 10, the processor 30 judges whether the minimum value (extreme value: the same below) of each measured impedance 90, 92, 94 is greater than the predicted value 102 (step S5). If it is judged in step S5 that the minimum value of each measured impedance 90, 92, 94 is equal to or smaller than the predicted value 102, the processor 30 determines the minimum value of each measured impedance 90, 92, 94 as the measured value for the component to be measured (step S6). Then, the measurement process ends.

As a result, if the value closest to the impedance of the component to be measured among the real or imaginary components of the measured impedances 90, 92, and 94 acquired in step S1 is the same as the predicted value 102 or is closer to the component to be measured than the predicted value 102, the measured value is determined as the value related to the component to be measured.

Specifically, the component to be measured includes a solution resistance component 64, and the predicted value 102 of the component to be measured is a real component value. Therefore, when the smallest value among the real component values of each of the acquired actual impedances 90, 92, 94 is the same as or smaller than the predicted value 102, the measured value is determined as the value related to the component to be measured.

The components to be measured include the solution resistance component 64. Therefore, the measured value determined as the value related to the components to be measured indicates the impedance of the solution resistance component 64, which is the component to be measured.

In addition, the acquisition processing device 14 may display the determined impedance on the display unit 38 in other processing. In addition, the acquisition processing device 14 may transmit the determined impedance to another device via the external communication unit 44.

The acquisition processing device 14 may also use the determined impedance to evaluate the characteristics of the power storage device 16 in other processes. Specifically, the acquisition processing device 14 may rank the power storage device 16 based on the determined impedance and display the result on the display unit 38 or display the quality of the power storage device 16.

If in step S5 the processor 30 determines that the minimum value of each measured impedance 90, 92, 94 is greater than the predicted value 102, it executes a frequency calculation process (step S7).

This step S7 calculates the predicted frequency Fa of the predicted value 102 in order to verify whether the predicted value 102 obtained in step S4 is a minimum value or to use it for statistical processing such as confidence intervals.

Figure 12 is a flowchart showing the processing steps of the frequency calculation process according to one embodiment, and the operation of the frequency calculation process will be explained using Figure 12.

The frequency calculation process is a process for calculating the predicted frequency Fa of the predicted value 102. In the frequency calculation process, the processor 30 calculates a general polynomial based on the real component values R1, R2, R3 of the acquired measured impedances 90, 92, 94 and the frequencies F1, F2, F3 at which the values R1, R2, R3 were acquired. The processor 30 then sets the calculated polynomial as a real component polynomial (step SB1). Note that the degree of the real component polynomial is selectable.

Then, the processor 30 substitutes the real component value Rt determined in step S4 into the calculated real component polynomial to calculate the frequency Fr of the real component that results in the real component value Rt (step SB2).

The processor 30 also calculates a general polynomial using the imaginary component values X1, X2, and X3 of the acquired measured impedances 90, 92, and 94, and the frequencies F1, F2, and F3 at which the values X1, X2, and X3 were acquired. The processor 30 then sets the calculated polynomial as an imaginary component polynomial (step SB3). Note that the degree of the imaginary component polynomial is selectable.

Then, the processor 30 substitutes the imaginary component value Xt calculated in step S3 into the calculated imaginary component polynomial to calculate the frequency Fx of the imaginary component that results in the imaginary component value Xt (step SB4).

Next, the processor 30 subtracts the minimum value from the maximum value of the real component of each of the measured impedances 90, 92, and 94 to obtain the difference in the real components ΔR (step SB5). The processor 30 also subtracts the minimum value from the maximum value of the imaginary component of each of the measured impedances 90, 92, and 94 to obtain the difference in the imaginary components ΔX (step SB6).

Then, the processor 30 multiplies the frequency of the real component Fr by the difference ΔR between the real components (F'r = Fr x ΔR) to weight Fr (step SB7). The processor 30 also multiplies the frequency of the imaginary component Fx by the difference ΔX between the imaginary components (F'x = Fx x ΔX) to weight Fx (step SB8).

The processor 30 divides the sum of the weighted real component frequency F'r and the weighted imaginary component frequency F'x by the sum of the real component difference ΔR and the imaginary component difference ΔX to calculate the weighted average predicted frequency Fa (step SB9), and returns to the measurement process. The calculation formula for the predicted frequency Fa is as follows:

Fa=(F'r+F'x)/(ΔR+ΔX)

As a result, the predicted frequency Fa is calculated based on the frequency F'r of the real component calculated from the real component of the predicted value 102 and the frequency F'x of the imaginary component calculated from the imaginary component of the predicted value 102. Note that Fa may be the average value of Fx and Fr.

The predicted frequency Fa is a weighted average of the real component frequency F'r and the imaginary component frequency F'x, weighted based on the difference ΔR between the maximum and minimum real component values and the difference ΔX between the maximum and minimum imaginary component values obtained in step S1.

In the measurement process, as shown in FIG. 10, the processor 30 compares the frequency at the R value of the real component of the extreme value obtained in step S2 with the predicted frequency Fa processed by truncating the minimum resolution digits, etc., to determine whether or not it is actually measurable (step S8).

In the judgment of step S8, if the frequency at the R value of the real component of the extreme value obtained in step S2 is equal to the predicted frequency Fa processed by truncating the minimum resolution digits, etc., a new value cannot be obtained. Therefore, the minimum value of each of the currently measured impedances 90, 92, 94 is determined as the impedance of the component to be measured (step S6), and the measurement process ends.

In the judgment of step S8, if the frequency at the R value of the real component of the extreme value obtained in step S2 differs from the predicted frequency Fa processed by truncating the minimum resolution digits, etc., a new value can be obtained at the calculated predicted frequency Fa. Therefore, the power storage device 16 is measured again at the predicted frequency Fa to obtain additional impedance (step S9). The impedance is obtained using the same procedure as in step S1.

As a result, when the measured value is farther from the impedance of the component to be measured than the predicted value 102, the impedance measured at the predicted frequency Fa in the frequency band that corresponds to the predicted value 102 is obtained as the additional impedance.

Then, the processor 30 determines whether the minimum value of each measured impedance 90, 92, 94 is greater than the additional impedance measured at the predicted frequency Fa (step S10).

In step S10, if the processor 30 determines that the minimum value of each measured impedance 90, 92, 94 is equal to or smaller than the additional impedance acquired at the predicted frequency Fa, the processor 30 branches to step S6. In step S6, the processor 30 determines the minimum value of each measured impedance 90, 92, 94 as the measured value for the component to be measured, and ends the measurement process (step S6).

On the other hand, in step S10, if the processor 30 determines that the minimum value of each measured impedance 90, 92, 94 is greater than the additional impedance measured at the predicted frequency Fa, the additional impedance is set to the minimum value (step S11).

Then, the processor 30 adds "1" to the "counter" and proceeds to step S2-2.

In step S2-2, the processor 30 determines whether the "counter" is less than n (step S2-2). If the processor 30 determines in step S2-2 that the "counter" is n, it determines the minimum value of all the actual measured impedances at this point in time as the measured value for the component to be measured, and ends the measurement process (step S6).

This allows the number of repetitions of steps S3 to S12 to be limited to n.

On the other hand, if in step S2-2, the processor 30 determines that the "counter" is less than n, it proceeds to step S3.

In step S3, the processor 30 calculates a quadratic curve using the above-described method using the total measured impedance with the additional impedance added to each measured impedance 90, 92, 94 (step S3).

The processor 30 also calculates new predicted values of the components to be measured from the acquired quadratic curve (step S4).

This allows a quadratic curve, which is an approximation equation, to be calculated based on the real and imaginary components of the additional impedance and the real and imaginary components of each measured impedance 90, 92, and 94, and a new predicted value of the component to be measured is calculated based on this approximation equation.

Then, the processor 30 determines whether the minimum value of all measured impedances is greater than the newly calculated predicted value (step S5).

If it is determined in step S5 that the minimum value of all measured impedances is equal to or smaller than the newly calculated predicted value, the minimum value of all measured impedances is determined as the value related to the component to be measured, and the measurement process is terminated (step S6).

As a result, if the value closest to the component to be measured among all the measured impedances is the same as the predicted value newly calculated in step S4 or is closer to the impedance of the component to be measured than the predicted value, the measured value is determined as the value related to the component to be measured.

Also, if it is determined in step S5 that the minimum value of all measured impedances is greater than the newly calculated predicted value, the process proceeds to step S7, and each step is repeated until the impedance of the component to be measured is determined.

(Action and Effects)
Next, the effects of this embodiment will be described.

The acquisition processing device 14 in this embodiment is an acquisition processing device 14 that measures the impedance of the power storage device 16. The acquisition processing device 14 includes an acquisition unit 50 that acquires the impedance of the measurement target component measured at three or more frequencies using the measurement device 12 in a predetermined frequency band. The acquisition processing device 14 includes a determination unit 51 that determines an extreme value that is the minimum value of the real component or imaginary component of the impedance at three or more points acquired by the acquisition unit 50. The acquisition processing device 14 includes a calculation unit 52 that calculates a predicted value of the measurement target component based on an approximation formula that represents the relationship between the real component and the imaginary component of the impedance at three or more points. The acquisition processing device 14 includes a determination unit 54 that determines the extreme value as a measured value related to the measurement target component when the extreme value protrudes so as to be the same as the predicted value or closer to the impedance of the measurement target component than the predicted value.

According to this configuration, a predicted value of the component to be measured is calculated based on an approximation formula that expresses the relationship between the real and imaginary components of the impedance at three or more points obtained by measurement. Then, when the extreme values of the real or imaginary components at three or more points stand out so as to be the same as the predicted value based on the approximation formula or to be closer to the impedance of the component to be measured than the predicted value, the extreme values are determined as the measured value for the component to be measured.

This measurement value is determined based on an actual measurement, and this actual measurement value indicates the characteristics of the energy storage device.

Therefore, it is possible to obtain measurement results that indicate the characteristics of the energy storage device being measured as measured values.

To be more specific, when performing equivalent circuit analysis using a nonlinear algorithm, there is a risk that the results will change depending on which parameters are fixed when fitting the characteristics. Therefore, even if the residual value is reduced, it cannot be proven that the value represents the characteristics of the energy storage device.

However, in this embodiment, the actual measured value that is closer to the component to be measured than the predicted value 102 is determined as the measured value for the component to be measured. Therefore, the measured value for the component to be measured can be determined using the actually measured value.

In addition, according to this configuration, a predicted value 102 of the component to be measured is calculated based on an approximation formula that expresses the relationship between the real and imaginary components of the impedance at three or more points that have been acquired. Then, if the value closest to the component to be measured among the acquired real or imaginary components is the same as the predicted value 102 or is closer to the impedance of the component to be measured than the predicted value 102, the measured value is determined as the value related to the component to be measured.

As a result, the impedance of the component to be measured can be obtained by processing the impedance at at least three points. This reduces the burden of calculation processing on the processor 30 compared to when a large number of measurement results must be processed.

In addition, the measurement time can be shortened compared to when a large number of measurement results are required. Furthermore, the input process of the measurement results to the acquisition processing device 14 is reduced compared to when a large number of measurement results are required to be input. This allows values related to the components to be measured to be calculated efficiently.

In addition, unlike equivalent circuit analysis, there is no need to design an equivalent circuit or set initial parameter values, which require advanced techniques. This makes it possible to stably obtain values for the components to be measured, even if one does not require advanced skills.

The processing method of this embodiment is a processing method for measuring the impedance of the power storage device 16. The processing method includes an acquisition step of acquiring the impedance of the measurement target component measured at three or more frequencies in a predetermined frequency band. The processing method includes a determination step of determining the extreme values of the real or imaginary components of the impedance at three or more points acquired in the acquisition step. The processing method includes a calculation step of calculating a predicted value of the measurement target component based on an approximation formula expressing the relationship between the real and imaginary components of the impedance at three or more points. The processing method includes a determination step of determining the extreme value as the measured value for the measurement target component when the extreme value protrudes so as to be the same as the predicted value or closer to the impedance of the measurement target component than the predicted value.

Furthermore, the processing program of this embodiment causes the processor 30 to function as each of the units 50, 52, and 54, which are each means of the acquisition processing device 14.

The measurement system 10 of this embodiment is a measurement system having multiple devices for measuring the impedance of the power storage device 16. The measurement system 10 includes an acquisition unit 50 that acquires the impedance of the measurement target component measured at three or more frequencies in a predetermined frequency band, and a determination unit 51 that determines the extreme values of the real or imaginary components of the impedance at the three or more points acquired by the acquisition unit 50. The measurement system 10 includes a calculation unit 52 that calculates a predicted value of the measurement target component based on an approximation formula that represents the relationship between the real and imaginary components of the impedance at the three or more points. The measurement system 10 includes a determination unit 54 that determines the extreme value as the measured value for the measurement target component when the extreme value protrudes so as to be the same as the predicted value or closer to the impedance of the measurement target component than the predicted value.

These processing methods, processing programs, and measurement system 10 can also achieve the effects described above.

In addition, in the acquisition processing device 14 of this embodiment, the calculation unit 52, which is a calculation means, calculates the apex of an approximation equation that expresses the relationship between the real components and the imaginary components of the impedance at three or more points as a quadratic function as a predicted value 102.

With this configuration, the predicted value 102 can be calculated based on the vertex of the quadratic function. Therefore, the burden of calculation processing by the processor 30 can be further reduced compared to a case where the approximation formula must be repeatedly calculated until the predicted value 102 converges.

Furthermore, in the acquisition processing device 14 of this embodiment, the calculation unit 52, which is a calculation means, calculates a quadratic curve based on the values of the real components and imaginary components acquired by the acquisition unit 50, which is an acquisition means, and determines a predicted value 102 based on the inflection point where the quadratic curve protrudes most in the protruding direction.

With this configuration, by identifying the most prominent inflection point in the quadratic curve, it is possible to accurately determine the predicted value 102 with this function as the apex.

In addition, in the acquisition processing device 14 of this embodiment, the acquisition unit 50, which is an acquisition means, acquires the additional impedance measured at a predicted frequency in the frequency band corresponding to the predicted value 102 when the predicted value 102 protrudes closer to the impedance of the measurement target component than the extreme value. The calculation unit 52, which is a calculation means, finds an approximation formula based on the real and imaginary components of the additional impedance and the real and imaginary components of the impedance at three or more points, and calculates a new predicted value of the measurement target component based on the approximation formula. The determination unit 54, which is a determination means, determines the extreme value as the measured value when the extreme value closest to the impedance of the measurement target component is the same as the newly calculated predicted value by the calculation unit 52 or is closer to the impedance of the measurement target component than the predicted value.

With this configuration, if the measured value is farther from the impedance of the component to be measured than the predicted value 102, an additional impedance measured at the predicted frequency Fa corresponding to the predicted value 102 can be added to determine the value related to the component to be measured with the new predicted value 102.

In addition, in the acquisition processing device 14 of this embodiment, the acquisition unit 50, which is an acquisition means, calculates the predicted frequency Fa based on the real component frequency Fr obtained from the real component of the predicted value 102 and the imaginary component frequency Fx obtained from the imaginary component of the predicted value 102.

According to this configuration, the predicted frequency Fa is calculated using two frequencies: the real component frequency Fr calculated from the real component of the predicted value 102, and the imaginary component frequency Fx calculated from the imaginary component of the predicted value 102. Therefore, the error range of the predicted frequency Fa can be narrowed compared to when one frequency is used.

As a result, it is possible to bring the additional impedance measured at the predicted frequency Fa closer to the true value of the impedance of the component being measured.

Furthermore, in the acquisition processing device 14 of this embodiment, the predicted frequency Fa is a weighted average value of the real component frequency Fr and the imaginary component frequency Fx. The weighted average value is a value obtained by weighting the real component frequency Fr and the imaginary component frequency Fx based on the difference ΔR between the maximum and minimum values of the real component acquired by the acquisition unit 50, which is an acquisition means, and the difference ΔX between the maximum and minimum values of the imaginary component.

With this configuration, the predicted frequency Fa is calculated by taking into account the amount of change in the value of the real component and the amount of change in the value of the imaginary component at different frequencies, making it possible to reduce the effects of variability in the measured values from the measuring device 12.

To give an example, in the frequency band for calculating the electrolyte resistance, the difference ΔX of the imaginary components is larger than the difference ΔR of the real components. Therefore, it is highly likely that the value of the imaginary components is measured more accurately than the value of the real components. Therefore, by setting the predicted frequency Fa to the weighted average value described above, it is possible to suppress the effects of variability in the measured values by the measuring device 12.

In addition, in the acquisition processing device 14 of this embodiment, the measurement target component of the electricity storage device 16 includes a solution resistance component 64, and the predicted value 102 of the measurement target component is a real component value. When the smallest measurement value among the real component values of the impedance at three or more points is the same as or smaller than the predicted value 102, the determination unit 54, which is a determination means, determines the measurement value as the value related to the measurement target component.

This configuration allows the value of the solution resistance component 64 to be obtained with high accuracy.

The area where the solution resistance component 64 can be measured is less affected by adjacent circuit elements in the equivalent circuit that constitutes the electricity storage device 16 than other areas. Therefore, it is suitable for obtaining values related to the solution resistance component.

In addition, the measured value determined as the value related to the component to be measured is measured in the high frequency band. Therefore, the influence of the cable resistance component 62 and the reaction resistance component 66 on the measured value is relatively small. As a result, there is a high degree of certainty that the measured value determined as the value related to the component to be measured is the impedance of the solution resistance component 64.

This makes it possible to more accurately evaluate the uniformity of the electrolyte components and concentration of the electricity storage device 16, or to evaluate the welding of the electrode tabs of the electricity storage device 16.

Although the embodiments of the present invention have been described above, the above embodiments merely show some of the application examples of the present invention, and are not intended to limit the technical scope of the present invention to the specific configurations of the above embodiments.

REFERENCE SIGNS LIST 10 Measurement system 12 Measurement device 14 Acquisition processing device 16 Electricity storage device 30 Processor 34 Memory unit 50 Acquisition unit 52 Calculation unit 54 Determination unit 64 Solution resistance component 66 Reaction resistance component 72 Electric double layer capacitance component 92 Second measured impedance 100 Quadratic curve 102 Predicted value C1, C2 Electric double layer capacitance Fa Predicted frequency Rsol Electrolyte resistance ΔR, ΔX Difference

Claims (10)

An acquisition processing device that acquires and processes impedance of a power storage device,
An acquisition means for acquiring impedance of a measurement target component measured at three or more frequencies using a measurement device in a predetermined frequency band;
A determination means for determining an extreme value of a real component or an imaginary component of the impedance at the three or more points acquired by the acquisition means;
a calculation means for calculating a predicted value of the measurement target component based on an approximation formula expressing a relationship between real components and imaginary components of the impedance at the three or more points;
a determination means for determining, when the extreme value is equal to or closer to the impedance of the measured component than the predicted value, the extreme value as a measured value related to the measured component;
an acquisition processing device including: The acquisition processing device according to claim 1 ,
The calculation means calculates, as the predicted value, a peak of the approximation equation obtained by expressing a relationship between real components and imaginary components of the impedances at the three or more points acquired by the acquisition means as a quadratic function.
Acquisition processing device. The acquisition processing device according to claim 2 ,
The calculation means calculates a quadratic curve based on each value of a real component and an imaginary component of the impedance at the three or more points acquired by the acquisition means, and determines the predicted value based on a bending point at which the quadratic curve is most prominent in a protruding direction.
Acquisition processing device. The acquisition processing device according to any one of claims 1 to 3,
When the predicted value is closer to the impedance of the measurement target component than the extreme value, the acquisition means acquires an additional impedance measured at a predicted frequency corresponding to the predicted value within the frequency band;
the calculation means determines the approximation formula based on the real and imaginary components of the additional impedance and the real and imaginary components of the impedances at the three or more points, and newly calculates the predicted value of the measurement target component based on the approximation formula;
The determination means determines the extreme value as the measured value when the extreme value closest to the impedance of the measured component is the same as the predicted value newly calculated by the calculation means or is closer to the impedance of the measured component than the predicted value.
Acquisition processing device. The acquisition processing device according to claim 4 ,
the obtaining means calculates the predicted frequency based on a real component frequency obtained from a real component of the predicted value and an imaginary component frequency obtained from an imaginary component of the predicted value.
Acquisition processing device. The acquisition processing device according to claim 5 ,
The predicted frequency is a weighted average value obtained by weighting the real component frequency and the imaginary component frequency based on a difference between a maximum value and a minimum value of the real component of the impedance at the three or more points and a difference between a maximum value and a minimum value of the imaginary component.
Acquisition processing device. The acquisition processing device according to any one of claims 1 to 6,
The component to be measured includes a solution resistance component,
the predicted value of the measured component is the value of the real component;
the determination means determines the smallest value among the values of the real components of the three or more points as the extreme value, and determines the extreme value as the measurement value when the extreme value is equal to or smaller than the predicted value.
Acquisition processing device. A processing method for measuring impedance of a power storage device, comprising:
an acquisition step of acquiring impedance of a measurement target component measured at three or more frequencies in a predetermined frequency band;
a determination step of determining extreme values of real components or imaginary components of the impedances at the three or more points acquired in the acquisition step;
a calculation step of calculating a predicted value of the measurement target component based on an approximation formula expressing a relationship between real components and imaginary components of the impedance at the three or more points;
a determination step of determining, when the extreme value is the same as the predicted value or is closer to the impedance of the measured component than the predicted value, the extreme value as a measured value related to the measured component;
A processing method comprising: A processing program that causes a processor to function as each of the means of the acquisition processing device according to any one of claims 1 to 7. A measurement system having a plurality of devices for measuring impedance of a power storage device,
an acquisition unit that acquires impedance of a measurement target component measured at three or more frequencies in a predetermined frequency band;
A determination unit that determines extreme values of real components or imaginary components of the impedances at the three or more points acquired by the acquisition unit;
a calculation unit that calculates a predicted value of the measurement target component based on an approximation formula that represents a relationship between real components and imaginary components of the impedance at the three or more points;
a determination unit that determines the extreme value as a measurement value related to the measured component when the extreme value is the same as the predicted value or is closer to the impedance of the measured component than the predicted value;
A measurement system comprising:

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