Impedance measuring device and impedance measuring method

Abstract

The present invention measures the impedance of an impedance element to be measured in a state in which a non-measured subject is connected in parallel to the subject to be measured via a connection line.　The present invention comprises: a measurement-current output unit 2 that supplies an AC current Im for measurement to electrochemical cells C in a state in which a power-supply device PD is connected in parallel via a connection line Lc to a subject DUT to be measured, which is formed by connecting the electrochemical cells in series; a voltage measurement unit 3 that measures a voltage value V at both ends of the electrochemical cells; a current sensor 4-1 that measures a supply current value of the AC current for measurement; and a processing unit 5 that calculates the impedance of the electrochemical cells on the basis of the voltage value V and the supply current value. The measurement-current output unit 2 supplies the AC current for measurement to measurement-current supply points Po1, Po2 prescribed so that one or more electrochemical cells are included in a current path IR2, and supplies the AC current for measurement to a portion of the plurality of electrochemical cells other than said one or more electrochemical cells, said portion serving as electrochemical cells to be measured.

Description

Impedance measuring device and impedance measuring method

[0001] The present invention relates to an impedance measuring device and an impedance measuring method that can measure the impedance of some of a plurality of impedance elements to be measured when a measurement object is configured by connecting a plurality of impedance elements in series and a non-measurement object is connected in parallel via a connection line to the measurement object.

[0002] The impedance measuring device disclosed in the following Patent Document is known as an impedance measuring device capable of measuring the impedance of a measurement object when the measurement object is connected in parallel with the non-measurement object via a connection line. This impedance measuring device is configured to measure the internal impedance of the measurement object when the non-measurement object is connected in parallel with the measurement object via a connection line. Specifically, this impedance measuring device is configured to include an AC current supply unit, an AC voltage detection unit, an AC current detection unit, an A / D conversion unit, and an arithmetic control unit. In this case, the AC current detection unit is configured to include a clamp-type current sensor.

[0003] When using this impedance measuring device to measure the internal impedance of a measurement object connected in parallel to a non-measurement object via a connection line, for example, the connection line is first inserted through the opening of the clamp-type current sensor in the AC current detection unit. In this state, the AC current supply unit supplies a measurement AC current to both ends of the measurement object. As a result, a portion of the measurement AC current flows through the measurement object, and the remaining portion of the measurement AC current flows through the non-measurement object. In this case, the current sensor in the AC current detection unit detects the AC current flowing through the power supply line passing through the opening and outputs a negative feedback current corresponding to the AC current value. At this time, the flow of the feedback current generates an AC voltage across the detection resistor. Next, the A / D conversion unit A / D converts the detected AC current data into AC current data indicating the AC current value and outputs the data to the calculation control unit. Furthermore, the AC voltage detection unit detects a voltage value across the measurement object and outputs AC voltage data indicating the voltage value to the calculation control unit. Next, the calculation control unit calculates the internal impedance of the measurement object based on the AC current value indicated by the input AC current data and the voltage value across the measurement object indicated by the input AC voltage data.

[0004] JP 2004-251625 A (pages 3-8, Figure 1)

[0005] However, the above-described impedance measurement device has the following problem. Specifically, an example will be described in which the internal impedance of a DUT under test is measured when a power supply device PD (hereinafter, also referred to as an "electrolysis device") is connected to the DUT under test via a connection line Lc. In this case, the DUT under test is configured by stacking electrochemical cells C1 to C10 (hereinafter, also referred to as "electrochemical cell C" when not distinguishing between them) as impedance elements. The measurement system in this case is conceptually shown in FIG. 4. As shown in the figure, in this measurement system, the power supply device PD is connected in parallel to the DUT under test via a connection line Lc that is connected to terminals T1 and T11 of the DUT under test. Furthermore, an AC current supply unit U1 is connected to terminals T1 and T11 of the DUT under test via a measurement current supply line Li, and an AC voltage detection unit U2 is connected to terminals T1 and T11. Further, the current sensor S outputs AC current data indicating the current value of the measurement AC current Im flowing through the DUT to the calculation control unit U3.

[0006] Therefore, when measuring the internal impedance of the DUT under test using this impedance measuring device 1X, the AC current supply unit U1 first outputs a measurement AC current Im with a current value I10 and supplies it to the DUT under test. In this state, the measurement AC current Im is divided into a measurement AC current Im with a current value I11 (part of the current value I10) flowing through a current path consisting of one terminal of the AC current supply unit U1, the measurement current supply line Li, terminal T1, the DUT under test, terminal T11, the measurement current supply line Li, and the other terminal of the AC current supply unit U1, and a measurement AC current Im with a current value I12 (the remaining part of the current value I10) flowing through a current path consisting of one terminal of the AC current supply unit U1, the measurement current supply line Li, terminal T1, the connection line Lc, the power supply device PD, the connection line Lc, terminal T11, the measurement current supply line Li, and the other terminal of the AC current supply unit U1.

[0007] At this time, the AC voltage detection unit U2 detects the voltage value across terminals T1 and T11 of the DUT under test and outputs the AC voltage data to the calculation control unit U3. Furthermore, the current sensor S outputs AC current data indicating the current value I11 of the measurement AC current Im flowing through the DUT under test to the calculation control unit U3. The calculation control unit U3 then calculates the internal impedance of the DUT under test based on the voltage value across the DUT under test indicated by the input AC voltage data and the current value I11 of the measurement AC current Im flowing through the DUT under test indicated by the input AC current data.

[0008] In this case, since the impedance of the power supply device PD is extremely small, the current value I12 of the measurement AC current Im that is shunted and flows through the power supply device PD becomes extremely large, while the current value I11 of the measurement AC current Im that is shunted and flows through the DUT becomes extremely small. Therefore, since the current value I11 of the measurement AC current detected by the current sensor S is extremely small, there is a problem in that it becomes extremely difficult for the calculation control unit U3 to measure the internal impedance of the DUT.

[0009] In some cases, it may be desired to measure the impedance of a portion of the electrochemical cells C (impedance elements to be measured) within the DUT. In this case, an AC voltage detector U2 is connected to both ends of the electrochemical cell C to be measured, and the voltage across the electrochemical cell C is measured. The calculation controller U3 then calculates the impedance of the electrochemical cell C based on the voltage across the electrochemical cell C indicated by the input AC voltage data and the current value I11 of the measurement AC current Im flowing through the DUT (electrochemical cell C to be measured) indicated by the input AC current data. However, even in this case, because the impedance of the power supply device PD is extremely small, the current value I12 of the measurement AC current Im shunted through the power supply device PD becomes extremely large, while the current value I11 of the measurement AC current Im shunted through the DUT (electrochemical cell C to be measured) becomes extremely small. Therefore, since the current value I11 of the measurement AC current Im detected by the current sensor S is extremely small, there is a problem that it becomes extremely difficult for the calculation control unit U3 to measure the impedance of the electrochemical cell C that is to be measured.

[0010] The present invention has been made in consideration of such problems, and its main object is to provide an impedance measuring device and an impedance measuring method that can reliably measure the impedance of an impedance element to be measured when an object to be measured is configured by connecting multiple impedance elements in series and a non-object to be measured is connected in parallel via a connection line.

[0011] In order to achieve the above object, the impedance measuring device according to the present invention is an impedance measuring device comprising: a measurement current supply unit that supplies a measurement current to a plurality of impedance elements in a state in which a measurement object configured by connecting a plurality of impedance elements in series and a non-measurement object are connected in parallel via a connection line to the plurality of impedance elements; a voltage measurement unit that measures a voltage value across both ends of the impedance elements when the measurement current is being supplied; a first current sensor that measures a supply current value of the measurement current being supplied to the impedance elements; and a processing unit that calculates the impedance of the impedance elements based on the measured voltage value across both ends and the supply current value. The measurement current supply unit supplies the measurement current to a pair of measurement current supply points that are defined so that one or more of the plurality of impedance elements are included in the current path through which the measurement current flows in the connection line, thereby supplying the measurement current to a portion of the plurality of impedance elements other than the one or more impedance elements as the impedance element to be measured, and the voltage measurement unit measures the voltage value across the impedance element to be measured, and the processing unit calculates the impedance of the impedance element to be measured based on the measured voltage value across both ends and the supply current value.

[0012] In addition, in order to achieve the above-mentioned object, the impedance measurement method of the present invention is an impedance measurement method in which a measurement object constituted by a plurality of impedance elements connected in series is connected in parallel to a non-measurement object via a connection line, and while supplying a measurement current to the plurality of impedance elements, the method measures the voltage value across both ends of the impedance element when the measurement current is being supplied and measures the supply current value of the measurement current being supplied to the impedance element using a first current sensor, and measures the impedance of the impedance element based on the measured voltage value across both ends and the supply current value, by supplying the measurement current to a pair of measurement current supply points defined so that one or more of the plurality of impedance elements are included in a current path through which the measurement current flows in the connection line, and supplies the measurement current to some of the plurality of impedance elements other than the one or more impedance elements, as the measurement object impedance element, measures the voltage value across the measurement object impedance element, and measures the impedance of the measurement object impedance element based on the measured voltage value across both ends and the supply current value.

[0013] In this impedance measuring device and impedance measuring method, a measurement AC current is supplied to a pair of measurement current supply points that are specified so that one or more impedance elements are included in the current path through which the measurement AC current flows in the connection line, and a portion of the multiple impedance elements excluding the one or more impedance elements is designated as the measurement target impedance element, the measurement AC current is supplied to the measurement target impedance element, the voltage value across both ends of the measurement target impedance element is measured, and the impedance of the measurement target impedance element is measured based on the measured voltage value across both ends and the supply current value.

[0014] Therefore, with this impedance measuring device and impedance measuring method, even when a measurement object configured by connecting multiple impedance elements in series is connected in parallel to a low-impedance non-measurement object, some of the multiple impedance elements can be used as the measurement object impedance element, and a measurement AC current of a sufficiently large current value can be supplied to that measurement object impedance element.As a result, it is possible to measure the voltage value across the measurement object impedance element when the measurement AC current is supplied to the measurement object impedance element, and the supply current value of the measurement AC current flowing through the measurement object impedance element, thereby enabling the impedance of the measurement object impedance element to be measured reliably.

[0015] In addition, in the impedance measuring device of the present invention, the measurement current supply unit supplies the measurement current to a pair of measurement current supply points that are defined at the same electrical positions as a pair of voltage measurement points that measure the voltage across the impedance element to be measured.

[0016] In addition, the impedance measuring method according to the present invention supplies the measurement current by defining the pair of measurement current supply points at the same electrically positions as the pair of voltage measurement points for measuring the voltage across the impedance element to be measured.

[0017] In this impedance measurement device and impedance measurement method, a pair of measurement current supply points are defined at the same electrical positions as a pair of voltage measurement points for measuring the voltage across the impedance element being measured, and a measurement AC current is supplied to the pair of measurement current supply points. This allows the largest number of impedance elements to be included in a current path that does not include the impedance element being measured, so that even if the impedance element being measured has a low impedance, the current path as a whole can have a sufficiently large impedance. Therefore, with this impedance measurement device and impedance measurement method, the current value of the measurement AC current that is shunted and flows through the connection line can be minimized, and the current value of the measurement AC current that is shunted and flows through the impedance element being measured can be maximized, resulting in a sufficiently large voltage across the impedance element being measured. As a result, with this impedance measurement device and impedance measurement method, the ratio (S / N) of the signal level (S) to the noise level (N) of the voltage across the measured end can be sufficiently increased, allowing the impedance of the impedance element being measured with sufficiently high accuracy.

[0018] In addition, the impedance measuring device of the present invention includes a second current sensor that measures the current value of the measurement current flowing through the connection line, and the processing unit calculates a new supply current value by subtracting the current value measured by the second current sensor from the supply current value measured by the first current sensor, and calculates the impedance of the impedance element to be measured based on the measured voltage value across both ends and the calculated new supply current value.

[0019] In addition, the impedance measurement method of the present invention measures the current value of the measurement current flowing through the connection line using a second current sensor, calculates a new supply current value by subtracting the current value measured by the second current sensor from the supply current value measured by the first current sensor, and measures the impedance of the impedance element to be measured based on the measured voltage value across both ends and the calculated new supply current value.

[0020] In this impedance measuring device and impedance measuring method, the current value of the measurement AC current flowing through the connection line is measured by a second current sensor, the current value measured by the second current sensor is subtracted from the current value measured by the first current sensor to calculate a new supply current value, and the impedance of the impedance element to be measured is measured based on the measured voltage value across both ends and the calculated new supply current value.

[0021] Therefore, according to this impedance measuring device and impedance measuring method, the supply current value of the measurement AC current flowing only through the impedance element to be measured is used for impedance calculation, so the impedance of the impedance element to be measured can be measured with extremely high accuracy.

[0022] In the impedance measuring device according to the present invention, the first current sensor is configured as a clamp-type non-contact current sensor that is configured to be openable and closable.

[0023] Furthermore, the impedance measuring method according to the present invention uses a clamp-type non-contact current sensor that is configured to be openable and closable as the first current sensor.

[0024] According to this impedance measuring device and impedance measuring method, by using a clamp-type non-contact current sensor that is configured to be able to open and close as the first current sensor, the current value of the measurement AC current supplied to the impedance element to be measured can be measured safely and easily.

[0025] In the impedance measuring device according to the present invention, the second current sensor is configured as a clamp-type non-contact current sensor that is configured to be openable and closable.

[0026] Furthermore, the impedance measuring method according to the present invention uses a clamp-type non-contact current sensor that is configured to be openable and closable as the second current sensor.

[0027] According to this impedance measuring device and impedance measuring method, by using a clamp-type non-contact current sensor that is configured to be able to open and close as the second current sensor, the current value of the measurement AC current flowing through the connection line can be measured safely and easily.

[0028] In addition, the impedance measuring device according to the present invention has one of an electrolyzer, a fuel cell, and a lithium ion battery as the measurement object, and some of the multiple impedance elements in the measurement object as the measurement object impedance elements.

[0029] In addition, the impedance measurement method according to the present invention has one of an electrolyzer, a fuel cell, and a lithium ion battery as the measurement object, and some of a plurality of impedance elements in the measurement object as the measurement object impedance elements.

[0030] According to this impedance measuring device and impedance measuring method, the impedance of the impedance element to be measured can be reliably measured when a non-measurement object with an extremely small output impedance is connected in parallel with the measurement object.

[0031] According to the impedance measuring device and impedance measuring method of the present invention, by supplying a measurement AC current to a pair of measurement current supply points that are specified so that one or more of the impedance elements to be measured are included in the current path through which the measurement AC current flows in the connection line, the measurement AC current can be supplied to the impedance element to be measured.As a result, the supply current value of the measurement AC current flowing through the impedance element to be measured and the voltage value across both ends of the impedance element to be measured can be measured, thereby enabling the impedance of the impedance element to be measured reliably.

[0032] Fig. 1 is an explanatory diagram illustrating an impedance measurement method using the impedance measurement device 1. Fig. 2 is another explanatory diagram illustrating an impedance measurement method using the impedance measurement device 1. Fig. 3 is an explanatory diagram illustrating an impedance measurement method using the impedance measurement device 1A. Fig. 4 is an explanatory diagram illustrating an impedance measurement method using a conventional impedance measurement device 1X.

[0033] Hereinafter, an embodiment of an impedance measuring device and an impedance measuring method using the impedance measuring device will be described with reference to the accompanying drawings.

[0034] The impedance measuring device 1 shown in Figure 1 is an example of an impedance device that performs an impedance measurement method, and is configured to be able to measure the impedance of a measurement target impedance element, some of the multiple impedance elements being measurement target impedance elements, in a state where a measurement target DUT consisting of multiple impedance elements connected in series is connected in parallel to a non-measurement target (in the same figure, a power supply device PD) via a connection line Lc.

[0035] In this case, the measurement target may be an electrolysis device (electrolysis device) in which multiple electrochemical cells (an example of an impedance element) are electrically connected in series to form a stack; an electrolysis-reduction device (electrolysis-reduction device) in which multiple electrolyte membranes (an example of an impedance element) are electrically connected in series to form a stack; an ion exchange membrane device in which multiple ion exchange membranes (an example of an impedance element) are electrically connected in series to form a stack; a fuel cell in which multiple power generation cells (an example of an impedance element) are electrically connected in series to form a stack; and a lithium ion battery or lead-acid battery in which multiple battery cells (an example of an impedance element) are electrically connected in series to form a stack. Furthermore, the non-measurement target may be a power supply device such as an inverter device or a converter device, various loads such as electronic devices, and various power generation devices such as fuel cells in operation or non-operation. Below, as an example, an example will be described in which an electrolysis device is the measurement target DUT and a power supply device PD that supplies power to the measurement target DUT is the non-measurement target.

[0036] First, the measurement target will be described. As shown in FIG. 1 , in this example, the measurement target DUT is an electrolysis device configured by electrically connecting multiple electrochemical cells C1 to C10 (hereinafter, also referred to as "electrochemical cells C" when not distinguishing between them) in a stacked configuration. Note that, while an electrolysis device is actually configured by connecting tens to hundreds of electrochemical cells C in series, in this example, for ease of understanding, the measurement target DUT is configured by electrically connecting 10 electrochemical cells C1 to C10 in series. In this case, the measurement target DUT is provided with a pair of terminals T1, T11 and terminals T2 to T10 (hereinafter, also referred to as "terminals T" when not distinguishing between the terminals T1 to T11) that are respectively connected to the connection points of the electrochemical cells C, C.

[0037] First Embodiment Next, we will explain the configuration of the impedance measuring device 1. As shown in Figure 1, the impedance measuring device 1 is configured to include a measurement current output unit 2, a voltage measurement unit 3, a current sensor 4-1, a processing unit 5, an output unit 6, voltage detection probes P1 and P2, and measurement current supply probes Pi1 and Pi2.

[0038] The measurement current output unit 2 functions as a measurement current supply unit that supplies a measurement AC current to a measurement target cell serving as a measurement target impedance element. In accordance with instructions from the processing unit 5, the measurement current output unit 2 generates and outputs a measurement AC current Im, which is a sinusoidal AC signal for measuring the impedance of the measurement target cell. A measurement current supply line Li is connected to one output terminal and the other output terminal of the measurement current output unit 2. Therefore, the measurement current output unit 2 outputs the measurement AC current Im to an electrochemical cell C serving as a measurement target impedance element (hereinafter, the measurement target electrochemical cell C will also be referred to as the "measurement target electrochemical cell C") via the measurement current supply lines Li and Li and the probes Pi1 and Pi2. The measurement current output unit 2 is configured to be able to vary the frequency of the measurement AC current Im, and sweeps (varies) the frequency of the measurement AC current Im and outputs it in accordance with a frequency control signal Sf output from the processing unit 5.

[0039] The voltage measurement unit 3 measures the voltage input via the pair of probes P1 and P2, and outputs voltage value data Dv indicating the measured value to the processing unit 5.

[0040] The current sensor 4-1 functions as a first current sensor and can be, for example, a current sensor such as that disclosed in Japanese Patent Application Laid-Open No. 2014-235045. It is configured as a clamp-type ammeter that can clamp a conductor such as a coated metal conductor in a non-contact manner. Specifically, the current sensor 4-1 is configured with two semicircular magnetic cores 4a and 4b and a magnetic detection element 4c formed, for example, by a Hall element or a fluxgate element. By operating an operating unit (not shown), the magnetic cores 4a and 4b are brought close to each other to form an annular opening 4d, through which the conductor can be clamped (inserted). By operating the operating unit to move the magnetic cores 4a and 4b apart from each other, the clamp on the clamped conductor can be released (opened and closed). The current sensor 4-1 functions as a clamp-type non-contact current sensor. In addition, in this current sensor 4-1, the magnetic detection element 4c detects the magnetic flux generated in the magnetic cores 4a and 4b when a current flows through the conductor inserted in the opening 4d, thereby measuring (detecting) the current value of the current flowing through the conductor in a frequency band ranging from direct current to high frequency, and outputs current value data Di1 indicating the measured current value. However, as the current sensor 4-1, a sensor of a type that can measure the current value of high-frequency signals other than direct current can also be used, and instead of a clamp-type current sensor, a current sensor that uses an annular core and is configured to be unable to be opened or closed can also be used.

[0041] The processing unit 5 is configured, for example, by a CPU, and performs overall control of the impedance measuring device 1. Specifically, during impedance measurement, the processing unit 5 controls the measurement current output unit 2 to generate and output a measurement AC current Im. Furthermore, as will be described later, during impedance measurement, the processing unit 5 measures (calculates) the impedance of the electrochemical cell C to be measured.

[0042] Specifically, the processing unit 5 controls the voltage measurement unit 3 to measure the voltage between the probes P1 and P2 and output the voltage value data Dv, and controls the current sensor 4-1 to measure the current flowing through the conductor (in this example, the measurement current supply line Li) inserted through the opening 4d of the current sensor 4-1 and output the current value data Di1. The processing unit 5 also receives the voltage value data Dv output from the voltage measurement unit 3 and the current value data Di1 output from the current sensor 4-1. The processing unit 5 also measures (calculates) the impedance of the target electrochemical cell C based on the input voltage value data Dv and current value data Di1. Specifically, the processing unit 5 calculates the AC voltage (voltage across both ends) at both ends of the target electrochemical cell C as a voltage value V (voltage across both ends) based on the amplitude of the AC voltage included in the voltage value data Dv, and calculates the current value I (supply current value) of the measurement AC current Im flowing through the target electrochemical cell C based on the amplitude of the AC current included in the current value data Di1. Furthermore, based on the voltage value data Dv and the current value data Di1, the processing unit 5 calculates the phase difference (θ) between the AC voltage and the AC current, i.e., the phase difference (θ) between the AC voltage generated across both ends of the measurement target electrochemical cell C and the AC current flowing through the measurement target electrochemical cell C. Based on the voltage value (V) of the AC voltage, the current value (I) of the measurement AC current Im, and the phase difference (θ) calculated in this manner, the processing unit 5 measures (calculates) the impedance of the measurement target electrochemical cell C (impedance Z=V / I, R=Z·cos θ, X=Z·sin θ).

[0043] In addition, the processing unit 5 outputs a frequency control signal Sf to the measurement current output unit 2 in accordance with instructions from an operation unit (not shown) to sweep the measurement AC current Im between the low frequency band and the high frequency band, and outputs display data Dd to the output unit 6 for displaying the measured impedance of the electrochemical cell C under test and the frequency characteristics of the impedance such as a Cole-Cole plot and a Bode diagram.

[0044] The output unit 6 is, for example, configured with a display device such as a liquid crystal panel or an organic EL panel, and receives the display data Dd output from the processing unit 5 to display on a screen the impedance and impedance frequency characteristics of the electrochemical cell C under measurement. Note that instead of a display device, the output unit 6 may be configured with an interface device that performs data communication with an external device, and may output impedance data indicating the impedance and impedance frequency characteristics of the electrochemical cell C under measurement to this external device.

[0045] The probes P1 and P2 are configured as contact-type probes whose tips are connected (contacted) to the terminals T of the DUT to be measured and measure an AC voltage as a voltage across the terminals T when a measurement AC current Im is supplied to the measurement electrochemical cell C. The probes Pi1 and Pi2 are also configured as contact-type probes whose tips are connected (contacted) to the terminals T of the DUT to be measured and supply the measurement AC current Im.

[0046] Next, an impedance measurement method for measuring (calculating) the impedance of an electrochemical cell C under measurement using the impedance measurement device 1 will be described with reference to the drawings. It is assumed that the power supply device PD is already connected in parallel to the DUT under measurement via a connection line Lc connected to terminals T1 and T11 of the DUT under measurement. Furthermore, the measurement method will be described for measuring the impedance between both ends of two electrochemical cells C4 and C5 within the DUT under measurement, which are designated as electrochemical cells C under measurement.

[0047] First, probes Pi1 and Pi2 are connected to a pair of terminals T and T. In this case, probes Pi1 and Pi2 are connected to a pair of measurement current supply points Po1 and Po2 that are defined so that one or more electrochemical cells C among a plurality of electrochemical cells C are included in a current path IR2 (described later) through which a measurement AC current Im having a current value I2 flows in connection line Lc. As shown in FIG. 1 , as an example, in this example, probes Pi1 and Pi2 are connected to terminals T3 and T8 of the DUT under test as a pair of measurement current supply points Po1 and Po2. Note that, as long as one or more electrochemical cells C among the plurality of electrochemical cells C are included in current path IR2, probe Pi1 can be connected to terminal T2 instead of terminal T3, and probe Pi2 can be connected to terminal T7 or terminals T9 to T10 instead of terminal T8. Furthermore, the probe Pi1 can be connected to the terminal T1 instead of the terminal T3, and the probe Pi2 can be connected to the terminal T7 or the terminals T9 to T10 instead of the terminal T8. That is, the probes Pi1 and Pi2 are connected to the terminals T, T such that one or more electrochemical cells C are included in either the current path IR2 (described later) connecting the probe Pi1 and the power supply device PD, or the current path IR2 connecting the probe Pi2 and the power supply device PD.

[0048] Next, some (in this example, electrochemical cells C4 and C5) of the plurality of impedance elements (in this example, electrochemical cells C3 to C7) excluding the one or more electrochemical cells C (in this example shown in FIG. 1, electrochemical cells C1, C2, C8 to C10) are designated as electrochemical cells C to be measured, and probes P1 and P2 are connected to a pair of terminals T4 and T6 functioning as a pair of voltage measurement points Po3 and Po4, respectively, to measure the voltage value V across the electrochemical cells C4 and C5 that are the electrochemical cells C to be measured.

[0049] Next, the current sensor 4-1 is placed on the measurement current supply line Li at a position between one output terminal of the measurement current output unit 2 and terminal T3 (the measurement current supply line Li is clamped by the current sensor 4-1). At this time, the operating unit (not shown) is operated to move the magnetic cores 4a and 4b of the current sensor 4-1 away from each other and open the opening 4d. Next, the measurement current supply line Li is inserted into the opening 4d of the current sensor 4-1. After that, the operating unit (not shown) is operated to move the magnetic cores 4a and 4b of the current sensor 4-1 closer to each other and close the opening 4d. This causes the measurement current supply line Li to be clamped by the current sensor 4-1.

[0050] Next, the measurement start switch (not shown) is operated, which causes the processing unit 5 to output a frequency control signal Sf to control the measurement current output unit 2 to output the measurement AC current Im. In this case, the measurement AC current Im of current value I0 output from the measurement current output unit 2 is branched into a measurement AC current Im of current value I1 flowing through a current path IR1 consisting of one output terminal of the measurement current output unit 2, the measurement current supply line Li, probe Pi1, terminal T3 of the DUT under test, electrochemical cells C3 to C7, terminal T8, probe Pi2, the measurement current supply line Li, and the other output terminal of the measurement current output unit 2, and a measurement AC current Im of current value I2 flowing through a current path IR2 consisting of one output terminal of the measurement current output unit 2, the measurement current supply line Li, probe Pi1, terminal T3 of the DUT under test, electrochemical cells C2 and C1, terminal T1 of the DUT under test, connection line Lc, power supply device PD, connection line Lc, terminal T11 of the DUT under test, electrochemical cells C10 to C8, terminal T8, probe Pi2, the measurement current supply line Li, and the other output terminal of the measurement current output unit 2. Furthermore, a direct current having a current value ID output from the power supply device PD flows through the DUT from the terminal T1 to the terminal T11 of the DUT. In other words, the connection line Lc is an active line through which a direct current flows.

[0051] In this state, the processing unit 5 controls the voltage measurement unit 3 to measure the voltage value V across the electrochemical cells C4 and C5 connected between the probes P1 and P2 and output voltage value data Dv. At this time, the voltage measurement unit 3 measures the voltage across the electrochemical cells C4 and C5 generated when the measurement AC current Im with a current value I1 flows through a current path IR1 including the electrochemical cells C3 to C7 inside the DUT, and outputs voltage value data Dv indicating the voltage value V to the processing unit 5.

[0052] The current sensor 4-1 measures the current value I0 of the measurement AC current Im flowing through the measurement current supply line Li inserted (clamped) in the opening 4d, and outputs current value data Di1. In this case, the current value I0 of the measurement AC current Im measured by the current sensor 4-1 is the sum of the current value I1 of the measurement AC current Im flowing through the current path IR1 and the current value I2 of the measurement AC current Im flowing through the current path IR2.

[0053] In this state, the number of electrochemical cells C included in the current path IR2 (eight in this example) is sufficiently greater than the number of electrochemical cells C included in the current path IR1 (two in this example). Therefore, the impedance of the current path IR2 with respect to the measurement AC current Im is sufficiently greater than the impedance of the current path IR1 with respect to the measurement AC current Im, and as a result, the current value I1 of the measurement AC current Im flowing through the current path IR1 is sufficiently greater than the current value I2 of the measurement AC current Im flowing through the current path IR2. In this case, the conventional impedance measuring device 1X is unable to sufficiently pass the measurement AC current Im through the electrochemical cell C under test, and therefore is unable to measure the voltage across the electrochemical cell C under test, and therefore is unable to measure the impedance of the electrochemical cell C under test. In contrast, the impedance measuring device 1 is able to sufficiently pass the measurement AC current Im through the electrochemical cell C under test, and therefore is able to reliably measure the voltage across the electrochemical cell C under test, and therefore is able to reliably measure the impedance of the electrochemical cell C under test.

[0054] Next, the processing unit 5 receives the voltage value data Dv output from the voltage measurement unit 3 and the current value data Di1 output from the current sensor 4-1. The processing unit 5 also measures (calculates) the impedances of the electrochemical cells C4 and C5 based on the received voltage value data Dv and current value data Di1.

[0055] Specifically, the processing unit 5 calculates the AC voltage, which is the voltage across the electrochemical cells C4 and C5, as a voltage value (V) based on the amplitude of the measurement AC current Im included in the voltage value data Dv. The processing unit 5 also calculates the current value (I) of the measurement AC current Im flowing through the electrochemical cells C4 and C5 based on the amplitude of the measurement AC current Im included in the corrected current value data Di1. The processing unit 5 also calculates the phase difference (θ) between the AC voltage and the AC current, i.e., the phase difference (θ) between the AC voltage generated across the electrochemical cells C4 and C5, which are the measurement target electrochemical cells C, and the AC current (measurement AC current Im) flowing through the measurement target electrochemical cells C4 and C5, based on the voltage value data Dv and the current value data Di1. Furthermore, the processing unit 5 measures (calculates) the impedances (impedance Z=V / I, R=Z·cos θ, X=Z·sin θ) of the electrochemical cells C4 and C5, which are the electrochemical cells C to be measured, based on the voltage value (V), current value (I), and phase difference (θ) calculated in this manner.

[0056] In this case, in impedance measurement by this impedance measuring device 1, the current value I1 of the measurement AC current Im flowing through the electrochemical cell C under measurement (electrochemical cells C4 to C5 in this example) increases, resulting in an increase in the voltage value V of the voltage across the electrochemical cell C under measurement. Therefore, the ratio (S / N) of the signal level (S) of the measurement AC current Im to the noise level (N) of the voltage value V of the voltage across both ends measured by the voltage measurement unit 3 increases, and the impedance of the electrochemical cell C under measurement is measured with high accuracy in the impedance calculation process performed by the processing unit 5.

[0057] The processing unit 5 also sweeps the frequency of the measurement AC current Im by outputting a frequency control signal Sf to the measurement current output unit 2. The processing unit 5 then measures (calculates) the impedances of the electrochemical cells C4 and C5, which are the electrochemical cells C to be measured, at multiple frequencies as described above. The processing unit 5 then acquires the frequency characteristics of the impedances of the electrochemical cells C4 and C5, which are the electrochemical cells C to be measured, at multiple frequencies. In this case, the processing unit 5 acquires, as the frequency characteristics, a Cole-Cole plot showing the impedance characteristics of the electrochemical cells C with respect to frequency, and a Bode plot showing the gain characteristics and phase characteristics with respect to frequency. The processing unit 5 then outputs display data Dd to the output unit 6, causing the display device of the output unit 6 to display the measured impedances of the electrochemical cells C4 and C5, as well as the acquired Cole-Cole plot and Bode plot. This completes the process of measuring the impedances of the electrochemical cells C4 and C5, which are the electrochemical cells C to be measured, by the processing unit 5.

[0058] In this way, in the impedance measuring device 1 and the impedance measuring method, the measurement AC current Im is supplied to a pair of measurement current supply points Po1, Po2 that are defined so that one or more of the multiple electrochemical cells C are included in the current path IR2 through which the measurement AC current Im flows in the connection line Lc. Some of the multiple electrochemical cells C other than the one or more electrochemical cells C are designated as measurement target electrochemical cells C (in this example, electrochemical cells C4, C5), and the measurement AC current Im is supplied to the measurement target electrochemical cell C, the voltage value V across both ends of the measurement target electrochemical cell C is measured, and the impedance of the measurement target electrochemical cell C is measured based on the measured voltage value V and the current value I0 of the measurement AC current Im being supplied to the measurement target electrochemical cell C.

[0059] Therefore, with this impedance measuring device 1 and impedance measuring method, even when a low-impedance non-measurement target (in this example, power supply device PD) is connected in parallel to a measurement target DUT configured by connecting multiple electrochemical cells C1 to C10 in series, it is possible to select some electrochemical cells C (in this example, electrochemical cells C4 and C5) of the multiple electrochemical cells C1 to C10 as the measurement target electrochemical cells C, and supply a measurement AC current Im of a sufficiently large current value I1 to the measurement target electrochemical cells C. As a result, it is possible to measure the voltage value V of the voltage across both ends of the measurement target electrochemical cell C when the measurement AC current Im is supplied to the measurement target electrochemical cell C, and the supply current value (current value I1 approximately equal to current value I0) of the measurement AC current Im flowing through the measurement target electrochemical cell C, and therefore the impedance of the measurement target electrochemical cell C can be reliably measured.

[0060] Furthermore, in reality, the DUT (in this example, the electrolysis device) is configured by connecting in series tens to hundreds of impedance elements (in this example, electrochemical cells C). Therefore, when measuring the impedance of a small number of electrochemical cells C (in this example, the electrochemical cells C) to be measured, the current value I2 of the measurement AC current Im flowing through the current path IR2, which includes a very large number of electrochemical cells C, is extremely small, and a large current value I1 for the measurement AC current Im, which is approximately equal to the current value I0, flows through the current path IR1, which is the measurement path. This makes it possible to measure the impedance of the electrochemical cells C to be measured more reliably and accurately.

[0061] Furthermore, according to this impedance measuring device 1 and impedance measuring method, by using a clamp-type non-contact current sensor configured to be able to open and close as the current sensor 4-1, it is possible to safely and easily measure the current value (supply current: current value I1 that is approximate to current value I0) of the measurement AC current Im supplied to the electrochemical cell C to be measured (in this example, electrochemical cells C4 and C5).

[0062] Furthermore, according to this impedance measuring device 1 and impedance measuring method, the DUT to be measured is either an electrolyzer, a fuel cell, or a lithium ion battery (in this example, an electrolyzer), and some of the multiple electrochemical cells C1 to C10 in the DUT to be measured (in this example, electrochemical cells C4 and C5) are used as the electrochemical cells to be measured C to measure the impedance. This makes it possible to reliably measure the impedance of the electrochemical cells to be measured C (in this example, electrochemical cells C4 and C5) when a non-measurement object (in this example, a power supply device PD) with an extremely small output impedance is connected in parallel with the DUT to be measured.

[0063] Furthermore, with this impedance measuring device 1 and impedance measuring method, the frequency characteristics of the impedance of the electrochemical cell C to be measured (in this example, electrochemical cells C4 and C5) at multiple frequencies can be obtained, thereby making it possible to determine the performance and deterioration of the electrochemical cell C to be measured.

[0064] Furthermore, according to this impedance measuring device 1 and impedance measuring method, by acquiring either a Cole-Cole plot or a Bode plot as the frequency characteristic, it is possible to determine the performance and degradation of the electrochemical cell C to be measured with high accuracy.

[0065] Second Example Next, another method for defining a pair of measurement current supply points Po1, Po2 will be described with reference to Fig. 2. Note that, with regard to the processing content and impedance measurement method by the impedance measuring device 1, duplicated explanations of the processing content and measurement method that are the same as those in the first example will be omitted.

[0066] With regard to the pair of measurement current supply points Po1, Po2, the pair of measurement current supply points Po1, Po2 can also be defined as being electrically at the same position as the pair of voltage measurement points Po3, Po4, as long as one or more electrochemical cells C among the plurality of electrochemical cells C are included in the current path IR2 through which the measurement AC current Im (in this example, the measurement AC current Im with a current value I2) flows in the connection line Lc.

[0067] 2, when the electrochemical cell C4 is the electrochemical cell C to be measured, two terminals T4 and T5 connected to both ends of the electrochemical cell C4 are used as a pair of voltage measurement points Po3 and Po4, and probes P1 and P2 are connected to them. Furthermore, the same electrical positions as the pair of voltage measurement points Po3 and Po4 are defined as a pair of measurement current supply points Po1 and Po2, and probes Pi1 and Pi2 are connected to the pair of measurement current supply points Po1 and Po2 (terminals T4 and T5 in this example). Next, as in the first embodiment, the measurement current supply line Li is clamped by a current sensor 4-1.

[0068] Next, the measurement start switch (not shown) is operated. As a result, in the same manner as in the first embodiment, the processing unit 5 executes the above process, and the measurement AC current Im having the current value I0 output from the measurement current output unit 2 is converted into the measurement AC current Im having the current value I3 flowing through a current path IR3 consisting of one output terminal of the measurement current output unit 2, the measurement current supply line Li, the probe Pi1, the terminal T4 (measurement current supply point Po1) of the DUT under test, the electrochemical cell C4, the terminal T5 (measurement current supply point Po2), the probe Pi2, the measurement current supply line Li, and the other output terminal of the measurement current output unit 2. , and a measurement AC current Im having a current value I4 flowing through a current path IR4 consisting of one output terminal of the measurement current output unit 2, the measurement current supply line Li, the probe Pi1, terminal T4 of the DUT under test (measurement current supply point Po1), electrochemical cells C3 to C1, terminal T1 of the DUT under test, connection line Lc, the power supply device PD, connection line Lc, terminal T11 of the DUT under test, electrochemical cells C10 to C5, terminal T5 (measurement current supply point Po2), the probe Pi2, the measurement current supply line Li, and the other output terminal of the measurement current output unit 2. In addition, a DC current having a current value ID output from the power supply device PD flows through the DUT under test D from terminal T1 to terminal T11.

[0069] In this state, the voltage measurement unit 3 measures the voltage value V of the voltage across the electrochemical cell C4 by causing a measurement AC current Im with a current value I3 to flow through a current path IR3 including the electrochemical cell C4, and outputs voltage value data Dv indicating the voltage value V to the processing unit 5. In addition, the current sensor 4-1 measures the current value I0 of the measurement AC current Im flowing through the measurement current supply line Li inserted (clamped) in the opening 4d, and outputs current value data Di1.

[0070] Next, the processing unit 5 inputs the voltage value data Dv output from the voltage measurement unit 3 and the current value data Di1 output from the current sensor 4-1. The processing unit 5 also measures (calculates) the impedance of the electrochemical cell C4 based on the input voltage value data Dv and current value data Di1. The processing unit 5 then outputs display data Dd to the output unit 6, causing the calculated impedance to be displayed on the display device of the output unit 6. This completes the process of measuring the impedance of the electrochemical cell C4, which is the electrochemical cell C to be measured, by the processing unit 5.

[0071] In this manner, the impedance measuring device 1 and the impedance measuring method supply the measurement AC current Im to a pair of measurement current supply points Po1, Po2 that are electrically positioned at the same positions as a pair of voltage measurement points Po3, Po4 that measure the voltage value V across the electrochemical cell C (in this example, electrochemical cell C4) to measure the voltage value V across the electrochemical cell C under measurement. This allows the current path IR4 that does not include the electrochemical cell C under measurement to include the largest number of electrochemical cells C. Therefore, even if the power supply device PD has a low impedance, the impedance of the current path IR4 as a whole can be made sufficiently large. Therefore, the impedance measuring device 1 and the impedance measuring method can minimize the current value I4 of the measurement AC current Im that is diverted from the measurement AC current Im having the current value I0 and flows through the connection line Lc, and can correspondingly maximize the current value I3 of the measurement AC current Im that is diverted from the measurement AC current Im having the current value I0 and flows through the electrochemical cell C under measurement (in this example, electrochemical cell C4). As a result, the voltage value V across the electrochemical cell C under measurement can be made sufficiently large. As a result, with this impedance measuring device 1 and impedance measuring method, the ratio (S / N) of the signal level (S) to the noise level (N) of the voltage across the two ends being measured can be sufficiently increased, and the impedance of the electrochemical cell C to be measured can be measured with sufficiently high accuracy.

[0072] Third Embodiment Next, an impedance measuring apparatus 1A will be described with reference to Fig. 3. Note that duplicated descriptions of components and operations similar to those of the impedance measuring apparatus 1 will be omitted.

[0073] In addition to the configuration of the impedance measuring device 1, the impedance measuring device 1A includes a current sensor 4-2 that functions as a second current sensor, and is configured to be able to measure the impedance of the electrochemical cell C to be measured with even higher accuracy than the measurement accuracy of the impedance measuring device 1. In this case, the current sensor 4-2 has the same configuration as the current sensor 4-1, and is configured as a clamp-type ammeter that can clamp a conductor such as a coated metal conductor in a non-contact manner.

[0074] When measuring the impedance of the electrochemical cell S under test, the processing unit 5 calculates the current value I1 of the measurement AC current Im flowing through the electrochemical cell C under test by subtracting the current value I2 of the measurement current Im after shunting, measured by the current sensor 4-2, from the current value I0 of the measurement current Im before shunting, measured by the current sensor 4-1. The processing unit 5 also calculates (measures) the impedance of the electrochemical cell C under test based on the voltage value V measured by the voltage measurement unit 3 and the calculated current value I1. Therefore, the impedance calculation uses the current value I1 of the measurement AC current Im flowing only through the electrochemical cells C4 and C5 under test, allowing for the most accurate calculation of the impedance.

[0075] Next, an impedance measurement method for measuring (calculating) the impedance of an electrochemical cell C under measurement using the impedance measurement device 1A will be described with reference to FIG. It is assumed that the power supply device PD is already connected in parallel to the DUT under measurement via a connection line Lc connected to terminals T1 and T11 of the DUT under measurement. As an example, the method will be described for measuring the impedance between both ends of two electrochemical cells C4 and C5 within the DUT under measurement, which are designated as electrochemical cells C under measurement.

[0076] First, as in the first embodiment, probes Pi1 and Pi2 are connected to a pair of terminals T3 and T8, respectively, and probes P1 and P2 are connected to a pair of terminals T4 and T6, respectively. In this case, as in the second embodiment, a pair of measurement current supply points Po1 and Po2 may be defined at the same electrical positions as the pair of voltage measurement points Po3 and Po4. Next, current sensor 4-1 is placed between one output terminal of measurement current output unit 2 and terminal T3 (the current sensor 4-1 clamps the measurement current supply line Li), and current sensor 4-2 is placed between terminal T1 of the DUT under test and one output terminal of power supply device PD (the current sensor 4-2 clamps the connection line Lc).

[0077] Next, a measurement start switch (not shown) is operated. This causes the processing unit 5 to output a frequency control signal Sf to control the measurement current output unit 2 to output a measurement AC current Im. At this time, the measurement AC current Im output from the measurement current output unit 2 is divided into a measurement AC current Im with a current value I1 flowing through a current path IR1 and a measurement AC current Im with a current value I2 flowing through a current path IR2. In addition, a DC current with a current value ID output from the power supply device PD flows through the DUT under test from terminal T1 to terminal T11 of the DUT under test.

[0078] In this state, the processing unit 5 controls the voltage measurement unit 3 to measure the voltage value V across the electrochemical cells C4 and C5 connected between the probes P1 and P2 and output voltage value data Dv. The current sensor 4-1 measures the current value I0 of the measurement AC current Im flowing through the measurement current supply line Li inserted (clamped) into the opening 4d and outputs current value data Di1. The current sensor 4-2 measures the current value I2 of the measurement AC current Im flowing through the connection line Lc inserted (clamped) into the opening 4d and outputs current value data Di2.

[0079] Next, the processing unit 5 receives the voltage value data Dv output from the voltage measurement unit 3, the current value data Di1 output from the current sensor 4-1, and the current value data Di2 output from the current sensor 4-2. The processing unit 5 also measures (calculates) the impedances of the electrochemical cells C4 and C5 based on the input voltage value data Dv and the current value data Di1 and Di2.

[0080] Specifically, first, the processing unit 5 corrects the current value indicated by the current value data Di2 by subtracting the current value ID of the DC current from data indicating the current value included in the current value data Di2 (the sum of the current value I2 of the measurement AC current Im and the current value ID of the DC current). As a result, the current value indicated by the corrected current value data Di2 is the current value I2 of the measurement AC current Im flowing through the current path IR2. Note that when no DC current is flowing through the DUT under measurement or when the current sensor 4-2 is a current sensor that does not detect DC current, the current value indicated by the current value data Di2 is only the current value I2 of the measurement AC current Im, and therefore the process of subtracting the current value ID of the DC current from the current value data Di2 to correct the current value is unnecessary.

[0081] Next, the processing unit 5 calculates a current value I1 as a new supply current value by subtracting the current value 2 of the measurement current Im after shunting, indicated by the current value data Di2, from the current value 10 of the measurement current Im before shunting, indicated by the current value data Di1. Next, the processing unit 5 calculates a voltage value (V) that is the AC voltage across the electrochemical cells C4 and C5, based on the amplitude of the measurement AC current Im included in the voltage value data Dv. The processing unit 5 also calculates a current value (I) of the measurement AC current Im flowing through the electrochemical cells C4 and C5, based on the amplitude of the calculated current value I1 of the measurement AC current Im. Furthermore, based on the voltage value data Dv and the calculated current value I1, the processing unit 5 calculates the phase difference (θ) between the AC voltage and the AC current, i.e., the phase difference (θ) between the AC voltage generated across both ends of electrochemical cells C4, C5, which are the measurement target electrochemical cells C, and the AC current (measurement AC current Im) flowing through electrochemical cells C4, C5, which are the measurement target electrochemical cells C. Based on the voltage value (V), current value (I) and phase difference (θ) calculated in this manner, the processing unit 5 also measures (calculates) the impedance (impedance Z=V / I, R=Z·cos θ, X=Z·sin θ) of electrochemical cells C4, C5, which are the measurement target electrochemical cells C.

[0082] In this case, the calculated current value I1 is the current value of the measurement AC current Im flowing only through the electrochemical cells C4 and C5 being measured. Therefore, in impedance measurement using this impedance measuring device 1A, the impedance of the electrochemical cell C being measured (in this example, electrochemical cells C4 to C5) is measured with the highest accuracy. This completes the process of measuring the impedance of the electrochemical cells C4 and C5 being the electrochemical cells C being measured by the processing unit 5.

[0083] In this way, in this impedance measuring device 1A and impedance measuring method, the current value I2 of the measurement AC current Im flowing through the connection line Lc is measured by the current sensor 4-2, the current value I2 measured by the current sensor 4-2 is subtracted from the current value I0 measured by the current sensor 4-1 to calculate a new supply current value (current value I1), and the impedance of the electrochemical cell C to be measured (in this example, electrochemical cells C4 and C5) is measured based on the measured voltage value V and the calculated current value I1.

[0084] Therefore, according to this impedance measuring device 1A and impedance measuring method, the current value I1 of the measurement AC current Im flowing only through the electrochemical cells C4 and C5 to be measured is used for impedance calculation, so the impedance of the electrochemical cell C to be measured can be measured with extremely high accuracy.

[0085] Furthermore, according to this impedance measuring device 1A and impedance measuring method, by using a clamp-type non-contact current sensor that is configured to be able to open and close as the current sensor 4-2, the current value I2 of the measurement AC current Im flowing through the connection line Lc can be measured safely and easily.

[0086] The present invention is not limited to the above-described embodiments and can be modified as appropriate. For example, in the above-described embodiments, an AC current is used as the measurement AC current Im. However, when no DC current flows between the DUT and the power supply device PD, a DC current can be used as the measurement current. Furthermore, in the above-described embodiments, the number of electrochemical cells C to be measured is one or two, but this is not limited to this, and the number can be three or more. Furthermore, in the above-described embodiments, an electrolysis device is used as the DUT to be measured. However, a fuel cell or lithium ion battery can also be used as the DUT to be measured, and a load can also be used as a non-measurement target.

[0087] Furthermore, although an example has been described in which the voltage measurement unit 3 outputs voltage value data Dv, it is also possible to adopt a configuration in which the voltage measurement unit 3 outputs a voltage measurement signal that is an analog signal, and the processing unit 5 measures (calculates) the impedance based on the input voltage measurement signal. Similarly, although an example has been described in which the current sensors 4-1, 4-2 output current value data Di1, Di2, it is also possible to adopt a configuration in which the current sensors 4-1, 4-2 output current measurement signals that are analog signals, and the processing unit 5 measures (calculates) the impedance based on the input current measurement signal.

[0088] According to the present invention, since it is possible to supply a measurement AC current to the impedance element under measurement, it is possible to measure the voltage value across the impedance element under measurement and the supply current value of the measurement AC current flowing through the impedance element under measurement, thereby enabling reliable measurement of the impedance of the impedance element under measurement. As a result, the present invention can be widely applied to impedance measurement devices and impedance measurement methods for such impedance measurements.

[0089] 1, 1A Impedance measuring device 2 Current output section 3 Voltage measuring section 4-1, 4-2 Current sensor 5 Processing section C1 to C10 Electrochemical cell Di1, Di2 Current value data Dv Voltage value data Lc Connection line Li Measurement current supply line DUT Measurement object P1, P2 Measurement current supply point P3, P4 Voltage measurement point PD Power supply device

Claims

1. An impedance measurement device comprising: a measurement current supply unit that supplies a measurement current to a plurality of impedance elements configured to be connected in series, in a state where a non-measured object is connected in parallel via a connection line to a measurement object configured by connecting the plurality of impedance elements in series; a voltage measurement unit that measures both-end voltage values at both ends of the impedance element when the measurement current is being supplied; a first current sensor that measures a supply current value of the measurement current supplied to the impedance element; and a processing unit that calculates the impedance of the impedance element based on the measured both-end voltage values and the supply current value, wherein the measurement current supply unit supplies the measurement current to a pair of measurement current supply points defined such that one or more of the plurality of impedance elements are included in a current path through which the measurement current flows in the connection line, so that a part of the plurality of impedance elements other than the one or more impedance elements is used as a measurement target impedance element, and the measurement current is supplied to the measurement target impedance element, the voltage measurement unit measures the both-end voltage value of the measurement target impedance element, and the processing unit calculates the impedance of the measurement target impedance element based on the measured both-end voltage value and the supply current value.

2. The impedance measurement device according to claim 1, wherein the measurement current supply unit supplies the measurement current to the pair of measurement current supply points defined at positions electrically the same as a pair of voltage measurement points that measure the both-end voltage of the measurement target impedance element.

3. The impedance measurement device according to claim 1, further comprising a second current sensor that measures a current value of the measurement current flowing through the connection line, wherein the processing unit calculates a new supply current value by subtracting the current value measured by the second current sensor from the supply current value measured by the first current sensor, and calculates the impedance of the measurement target impedance element based on the measured both-end voltage value and the calculated new supply current value.

4. The impedance measurement device according to claim 1, wherein the first current sensor is a clamp-type non-contact current sensor configured to be openable and closable.

5. The impedance measuring apparatus according to claim 3, wherein the second current sensor is a clamp-type non-contact current sensor configured to be openable and closable.

6. The impedance measuring apparatus according to any one of claims 1 to 5, wherein any one of an electrolysis apparatus, a fuel cell, and a lithium ion battery is the measurement target, and a part of a plurality of impedance elements in the measurement target is the measurement target impedance element.

7. An impedance measuring method for measuring the impedance of an impedance element based on the measured voltage value across both ends and the supply current value, wherein a measurement current is supplied to the impedance element while supplying a measurement current to a plurality of impedance elements configured to be connected in series, and measuring the voltage value across both ends at both ends of the impedance element when the measurement current is supplied, and measuring the supply current value of the measurement current supplied to the impedance element by a first current sensor. In the impedance measuring method, the measurement current is supplied to a pair of measurement current supply points defined such that one or more of the plurality of impedance elements are included in a current path through which the measurement current flows in the connection line, so that a part of the plurality of impedance elements other than the one or more impedance elements is used as a measurement target impedance element, and the measurement current is supplied to the measurement target impedance element, the voltage value across both ends of the measurement target impedance element is measured, and the impedance of the measurement target impedance element is measured based on the measured voltage value across both ends and the supply current value.

8. The impedance measuring method according to claim 7, wherein the measurement current is supplied by defining the pair of measurement current supply points at the same electrical position as a pair of voltage measurement points for measuring the voltage across both ends of the measurement target impedance element.

9. The current value of the measurement current flowing through the connection line is measured by a second current sensor, and a new supply current value is calculated by subtracting the current value measured by the second current sensor from the supply current value measured by the first current sensor. The impedance of the impedance element to be measured is measured based on the measured voltage value across both ends and the calculated new supply current value. The impedance measurement method according to claim 7.

10. The impedance measurement method according to claim 7, wherein a clamp-type non-contact current sensor configured to be openable and closable is used as the first current sensor.

11. The impedance measurement method according to claim 9, wherein a clamp-type non-contact current sensor configured to be openable and closable is used as the second current sensor.

12. The impedance measurement method according to any one of claims 7 to 11, wherein any one of an electrolysis device, a fuel cell, and a lithium ion battery is used as the measurement target, and a part of a plurality of impedance elements in the measurement target is used as the impedance element to be measured.

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