Impedance measurement method

Abstract

To reliably measure the impedance of an object to be measured in a state where an object not to be measured is connected in parallel to the object to be measured via a connection line.SOLUTION: In this impedance measurement method, a load Ld is connected in parallel to a measurement object MT via a connection line Lc, a measurement AC current I0 is supplied to the measurement object MT via a measurement current supply line Li connected to a pair of measurement current supply points P1, P2, a current I1 of the measurement AC current I0 supplied to the measurement object MT is measured by a current sensor 4 in which the measurement current supply line Li is inserted into an opening 4d, and a voltage at both ends of the measurement object MT is measured, and the impedance of the measurement object MT is measured based on the measured current I1 and the voltage at both ends, and the current I1 is measured by the current sensor 4 with the measurement current supply line Li and the connection line Lc inserted into the opening 4d so that the directions of flow of the measurement AC current I0 are opposite to each other.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an impedance measuring method capable of measuring the impedance of an object to be measured in a state where an object not to be measured is connected in parallel to the object to be measured via a connection line. [Background technology]

[0002] As an impedance measuring device capable of executing this type of impedance measuring method, an impedance measuring device disclosed in the following patent document is known. This impedance measuring device is configured to be able to measure the internal impedance of a secondary battery in a state in which a load as a non-measurement object is connected in parallel to a secondary battery as a measurement object via a power supply line as 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 a calculation control unit. In this case, the AC current detection unit is configured to include a clamp-type current sensor.

[0003] When the internal impedance of a secondary battery is measured using this impedance measuring device, first, a power line is inserted into the opening of a clamp-type current sensor in the AC current detection unit. In this state, the AC current supply unit supplies a measurement AC current between the power lines. As a result, a part of the measurement AC current flows through the secondary battery. In addition, the remaining part of the measurement AC current flows through the load, and a DC current output from the secondary battery flows. In this case, the current sensor of the AC current detection unit detects the AC current flowing through the power line passing through the opening, and outputs a negative feedback current according to the AC current value of the AC current. At this time, an AC voltage is generated across the detection resistor due to the feedback current flowing. Next, the A / D conversion unit A / D converts the AC current data indicating the AC current value, and outputs it to the calculation control unit. In addition, the AC voltage detection unit detects the voltage across both ends of the secondary battery, and outputs AC voltage data indicating the voltage value across both ends to the calculation control unit. Next, the calculation control unit calculates the internal impedance of the secondary battery based on the AC current value indicated by the input AC current data and the voltage value across both ends indicated by the input AC voltage data. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2004-251625 A (pages 3-8, Figure 1) Summary of the Invention [Problem to be solved by the invention]

[0005] However, the above impedance measuring device has the following problem. Specifically, as conceptually shown in Fig. 2, the load Ld is connected in parallel to the secondary battery Bat via a power supply line Lp connected to the terminals T1, T2 of the secondary battery Bat. Therefore, when measuring the internal impedance of the secondary battery Bat using this impedance measuring device 1X, in a state in which the power supply line Lp is connected to the terminals T1, T2 of the secondary battery Bat, first, a measurement current supply line Li for supplying a measurement AC current I0 to the secondary battery Bat is connected to a pair of measurement current supply points P1, P2. In this state, the measurement AC current I0 is branched into a current I1 (part of the measurement AC current I0) flowing through a current path that flows through one terminal of the AC current supply unit PW, the measurement current supply line Li, the measurement current supply point P1, terminal T1, the secondary battery Bat, terminal T2, the measurement current supply point P2, the measurement current supply line Li, and the other terminal of the AC current supply unit PW, and a current I2 (part of the measurement AC current I0) flowing through a current path that flows through one terminal of the AC current supply unit PW, the measurement current supply line Li, the measurement current supply point P1, the power supply line Lp, the load Ld, the power supply line Lp, the measurement current supply point P2, the measurement current supply line Li, and the other terminal of the AC current supply unit PW.

[0006] In this case, in order to measure the internal impedance of the secondary battery Bat, the current I1 flowing only through the secondary battery Bat must be detected by the current sensor S. For this reason, it is necessary to insert a line between the measurement current supply point P1 and the terminal T1 into the current sensor S. When the current sensor S is disposed in such a state, in principle, by using the impedance measuring device 1X to cause the current sensor S to measure the current I1 flowing only through the secondary battery Bat and to cause the AC voltage detection unit DV to measure the AC voltage between the terminals T1 and T2 of the secondary battery Bat, the calculation control unit PRO can calculate (measure) the internal impedance of the secondary battery Bat based on the AC current value of the current I1 measured by the current sensor S and the voltage value across the secondary battery Bat measured by the AC voltage detection unit DV.

[0007] On the other hand, as shown in Fig. 3, in an actual circuit in which a load Ld is connected in parallel to a secondary battery Bat, the power supply line Lp is usually covered, so that the measurement current supply points P1, P2 cannot be defined on the power supply line Lp, and as a result, the measurement current supply points P1, P2 are defined at the terminals T1, T2. Therefore, in this state, the current sensor S cannot be placed on the line between the measurement current supply point P1 and the terminal T1, so the measurement current supply line Li is inserted into the current sensor S.

[0008] In such a state, the current sensor S measures the total current value of the shunted currents I1 and I2 (i.e., the current value of the measurement AC current I0), and is unable to detect the current value of the current I1 flowing only through the secondary battery Bat. As a result, the impedance measurement method using this impedance measuring device 1X has the problem that it is unable to measure the internal impedance of the secondary battery Bat in a state in which a load Ld (non-measurement object) is connected in parallel to the secondary battery Bat (measurement object) via a power supply line Lp (connection line).

[0009] The present invention has been made in consideration of the above-mentioned problems, and has as its main object to provide an impedance measurement method that can reliably measure the impedance of an object to be measured when an object to be measured is connected in parallel to the object to be measured via a connection line. [Means for solving the problem]

[0010] In order to achieve the above-mentioned object, the impedance measurement method of the present invention is an impedance measurement method in which, in a state in which a non-measurement object is connected in parallel to the measurement object via a connection line, a measurement current is supplied to the measurement object via a measurement current supply line connected to a pair of measurement current supply points defined at both ends of the measurement object, the supply current value of the measurement current supplied to the measurement object is measured by a non-contact current sensor in which the measurement current supply line is inserted into an opening, and the voltage at both ends of the measurement object is measured, and the impedance of the measurement object is measured based on the measured supply current value and the voltage at both ends, and the supply current value is measured by the current sensor with the measurement current supply line and the connection line inserted into the opening so that the directions in which the measurement current flows are opposite to each other.

[0011] According to this impedance measurement method, the current sensor measures the supply current value while inserting the measurement current supply line and the connection line into the opening so that the directions of the measurement current flow are opposite to each other, so that the current value of the measurement current measured by the current sensor can be made to be only the supply current flowing to the object to be measured, thereby enabling the impedance of the object to be measured reliably.

[0012] In addition, the impedance measuring method according to the present invention uses a clamp-type current sensor that is configured to be openable and closable as the current sensor.

[0013] According to this impedance measurement method, by using a clamp-type current sensor that is configured to be able to open and close, the current value of the measurement current being supplied to the object to be measured can be reliably and easily measured by clamping the connection line and the measurement current supply line while bringing the measurement current supply line close to the connection line.

[0014] Moreover, the impedance measuring method according to the present invention measures the impedance of any one of a lithium ion battery, a fuel cell, and an electrolysis device as the measurement object.

[0015] According to this impedance measurement method, when the measurement object is any of a lithium ion battery, a fuel cell, and an electrolyzer, the impedance of the measurement object can be reliably measured. Effect of the Invention

[0016] According to the impedance measurement method of the present invention, the measurement current supply line and the connection line are inserted into the opening of the current sensor so that the directions of the measurement current flow are opposite to each other, and the supply current value is measured by the current sensor. This makes it possible to ensure that the current value of the measurement current measured by the current sensor is only the supply current flowing to the object to be measured, thereby enabling the impedance of the object to be measured reliably. [Brief description of the drawings]

[0017] [Figure 1] FIG. 1 is an explanatory diagram illustrating an impedance measuring method using the impedance measuring device 1. [Diagram 2] FIG. 1 is an explanatory diagram illustrating a method of using a conventional impedance measuring device 1X. [Diagram 3] FIG. 11 is another explanatory diagram illustrating a method of using the conventional impedance measuring device 1X. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Hereinafter, an embodiment of an impedance measuring method will be described with reference to the accompanying drawings.

[0019] The impedance measuring device 1 shown in FIG. 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 object MT when a load Ld as a non-measurement object is connected in parallel to the measurement object MT via a connection line Lc.

[0020] In this case, the measurement target may be a lithium ion battery in which a plurality of battery cells are electrically connected in series to form a stack, a fuel cell in which a plurality of power generation cells are electrically connected in series to form a stack, or an electrolysis device in which a plurality of electrochemical cells are electrically connected in series to form a stack. Hereinafter, an example in which a lithium ion battery is used as the measurement target will be described. In addition, the load Ld may be various loads such as an electrolysis device and electronic devices in operation or non-operation, or various power generation devices such as a fuel cell in operation or non-operation. Hereinafter, an example in which a resistive load is used as the load Ld will be described.

[0021] First, a description will be given of the configuration of the impedance measuring device 1. As shown in Fig. 1, the impedance measuring device 1 is configured to include a current output section 2, a voltage measuring section 3, a current sensor 4, a processing section 5, an output section 6, and probes Pr1 to Pr4 (hereinafter, also referred to as "probes Pr" when no distinction is made).

[0022] The current output unit 2 functions as a measurement current supply unit and generates a measurement AC current I0 (one example of a measurement current) which is a sine wave AC signal for measuring the impedance of the measurement target MT according to an instruction from the processing unit 5. A measurement current supply line Li is connected to one output terminal and the other output terminal of the current output unit 2. Therefore, the current output unit 2 outputs the measurement AC current I0 via the measurement current supply line Li and the probes Pr1 and Pr2. The voltage measurement unit 3 measures the voltage generated between the probes Pr3 and Pr4 (the voltage across the measurement target) according to an instruction from the processing unit 5, and outputs voltage value data Dv indicating the measurement value to the processing unit 5.

[0023] The current sensor 4 may be, for example, a current sensor as disclosed in Japanese Patent Application Laid-Open No. 2014-235045, and is configured as a clamp-type ammeter capable of clamping a conductor such as a coated metal conductor in a non-contact manner. Specifically, the current sensor 4 is configured with magnetic cores 4a and 4b and a magnetic detection element 4c, for example, a Hall element or a fluxgate element, and functions as a clamp-type ammeter that can release (open and close) the clamp on the clamped conductor by operating an operation unit (not shown) to bring the magnetic cores 4a and 4b close to each other to form an annular opening 4d and clamp (insert) the conductor, and can operate the operation unit to move the magnetic cores 4a and 4b away from each other to release (open and close) the clamp on the clamped conductor. In addition, in this current sensor 4, the magnetic detection element 4c detects the magnetic flux generated in the magnetic cores 4a and 4b by the current flowing 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 from direct current to high frequency, and outputs current value data Di indicating the measured current value. However, instead of a clamp-type ammeter, the current sensor 4 can also be a current sensor that uses an annular core and is configured to be unopenable.

[0024] The processing unit 5 is configured by, for example, a CPU, and controls the impedance measuring device 1 in an overall manner. Specifically, during impedance measurement, the processing unit 5 controls the current output unit 2 to generate and output a measurement AC current I0. During impedance measurement, the processing unit 5 controls the voltage measurement unit 3 to measure the voltage between the probes Pr3 and Pr4 and output the voltage value data Dv, and controls the current sensor 4 to measure the current flowing through the conductor inserted into the opening 4d of the current sensor 4 and output the current value data Di. The processing unit 5 inputs the voltage value data Dv output from the voltage measurement unit 3 and the current value data Di output from the current sensor 4. The processing unit 5 measures (calculates) the impedance of the measurement target MT based on the input voltage value data Dv and current value data Di. Specifically, the processing unit 5 calculates the current value (I) of the measurement AC current I0 (current I1 described later) flowing through the measurement target MT based on the amplitude of the AC current included in the current value data Di, and calculates the AC voltage (voltage at both ends) between the probes Pr3 and Pr4 as a voltage value (V) based on the amplitude of the AC voltage included in the voltage value data Dv. The processing unit 5 also calculates the phase difference (θ) between the AC current and the AC voltage, that is, the phase difference (θ) between the AC current flowing through the measurement target MT and the AC voltage generated at both ends of the measurement target MT based on the current value (I) of the measurement AC current I0, the voltage value (V) of the AC voltage, and the phase difference (θ) calculated in this way, and measures (calculates) the impedance Z (Z=V / I, R=Z·cosθ, X=Z·sinθ) of the measurement target MT based on the current value (I) of the measurement AC current I0, the voltage value (V) of the AC voltage, and the phase difference (θ). The processing unit 5 also outputs display data Dd to the output unit 6 for displaying the measured impedance Z of the measurement target MT.

[0025] 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 the impedance Z of the measurement object MT on a screen. Note that the output unit 6 may be configured with an interface device that performs data communication with an external device instead of a display device, and may output impedance data indicating the impedance Z to the external device.

[0026] The probes Pr1 and Pr2 are contact-type probes whose tips are connected (contacted) to the terminals T1 and T2 of the measurement target MT, respectively, to supply the measurement AC current I0. The probes Pr3 and Pr4 are contact-type probes whose tips are connected (contacted) to the terminals T1 and T2 of the measurement target MT, respectively, to measure the AC voltage generated between the terminals T1 and T2 when the measurement AC current I0 is supplied to the measurement target MT.

[0027] Next, a method for measuring the impedance Z of the object to be measured MT by the impedance measuring device 1 will be described with reference to the attached drawings. It is assumed that the load Ld is already connected in parallel to the object to be measured MT via the connection line Lc that is connected to the terminals T1 and T2 of the object to be measured MT.

[0028] First, probes Pr1 and Pr2 are connected to a pair of measurement current supply points P1 and P2 that supply a measurement AC current I0 to the measurement target MT. In addition, probes Pr3 and Pr4 are connected to the measurement current supply points P1 and P2 that also function as a pair of voltage measurement points that measure the voltage across the measurement target MT.

[0029] Next, the measurement current supply line Li and the connection line Lc are clamped by the current sensor 4. At this time, the operation unit not shown is operated so that the magnetic cores 4a and 4b of the current sensor 4 are separated from each other and the opening 4d is in an open state. Next, the measurement current supply line Li and the connection line Lc are inserted into the opening 4d of the current sensor 4 so that the directions of the measurement AC current I0 (i.e., the measurement AC current I0 and the current I2) flowing through both lines Li and Lc are opposite to each other. In other words, both lines Li and Lc are inserted into the opening 4d of the current sensor 4 so that the direction of the measurement AC current I0 flowing through the measurement current supply line Li and the direction of the current I2 flowing through the connection line Lc, which is a branch current of the measurement AC current I0, are opposite to each other. After that, the operation unit not shown is operated so that the magnetic cores 4a and 4b of the current sensor 4 are brought close to each other and the opening 4d is in a closed state. As a result, the measurement current supply line Li and the connection line Lc are clamped by the current sensor 4.

[0030] Next, a measurement start switch (not shown) is operated, which causes the processing unit 5 to output a control signal to control the current output unit 2 to output the measurement AC current I0. At this time, the measurement AC current I0 output from the current output unit 2 is branched into a current I1 (supply current) flowing through a current path IR1 consisting of the current output unit 2, one output terminal of the current output unit 2, the measurement current supply line Li, probe Pr1, terminal T1 (measurement current supply point P1) of the object to be measured MT, the object to be measured MT, terminal T2 (measurement current supply point P2), probe Pr2, the measurement current supply line Li, and the other output terminal of the current output unit 2, and a current I2 flowing through a current path IR2 consisting of the current output unit 2, one output terminal of the current output unit 2, the measurement current supply line Li, probe Pr1, terminal T1 (measurement current supply point P1) of the object to be measured MT, the connection line Lc, the load Ld, the connection line Lc, the load Ld, terminal T2 (measurement current supply point P2) of the object to be measured MT, probe Pr2, the measurement current supply line Li, and the other output terminal of the current output unit 2. Moreover, a direct current I3 output from the object of measurement MT flows through the load Ld from the terminal T1 to the terminal T2 of the object of measurement MT. In other words, the connection line Lc is an active line through which a direct current flows.

[0031] In this state, the current sensor 4 measures the current flowing through the measurement current supply line Li and the connection line Lc inserted (clamped) in the opening 4d. In this example, since the direction of the measurement AC current I0 consisting of the currents I1 and I2 and the direction of the current I2 are opposite to each other, the current sensor 4 measures the current values ​​that are offset by canceling out the magnetic fluxes generated in the magnetic cores 4a and 4b due to the flow of the measurement AC currents I0 and I2, and outputs current value data Di indicating the current value to the processing unit 5. In this case, the current value measured by the current sensor 4 is ((current value of measurement AC current I0 (=current value of current I1 + current value of current I2) - current value of current I2 + current value of current I3 = current value of current I1 + current value of current I3). In addition, the processing unit 5 controls the voltage measurement unit 3 to measure the voltage across both ends of the measurement object MT connected between probes Pr3 and Pr4 and output voltage value data Dv. At this time, the voltage measurement unit 3 measures the voltage across both ends of the measurement object MT caused by the current I1 flowing through the current path IR1 including the measurement object MT, and outputs voltage value data Dv indicating the voltage value to the processing unit 5.

[0032] Next, the processing unit 5 inputs the voltage value data Dv output from the voltage measurement unit 3 and the current value data Di output from the current sensor 4. The processing unit 5 also measures (calculates) the impedance Z of the measurement target MT based on the input voltage value data Dv and current value data Di. Specifically, first, the processing unit 5 corrects the current value indicated by the current value data Di by subtracting the current value (current value of current I3) generated by the flow of the direct current I3 from the data indicating the current value (current value of current I1+current value of current I3) included in the current value data Di. As a result, the current value indicated by the corrected current value data Di is the current value (supply current value) of the current I1, which is an alternating current flowing only through the current path IR1. In other words, it is the current value of the current I1 flowing through the measurement target MT, which is the measurement target. In addition, when no DC current I3 flows from the measurement object MT to the load Ld, the current value indicated by the current value data Di is only the current value of the current I1, so there is no need to correct the current value indicated by the current value data Di by subtracting the current value of the current I3 from the data indicating the current value contained in the current value data Di (the current value of the current I1).

[0033] The processing unit 5 also calculates the current value (I) of the current I1 flowing through the measurement target MT based on the amplitude of the AC current included in the corrected current value data Di, and calculates the AC voltage, which is the voltage across the measurement target MT, as a voltage value (V) based on the amplitude of the AC voltage included in the voltage value data Dv. The processing unit 5 also calculates the phase difference (θ) between the AC current and the AC voltage, that is, the phase difference (θ) between the AC current flowing through the measurement target MT and the AC voltage generated across the measurement target MT, based on the corrected current value data Di and voltage value data Dv. The processing unit 5 also measures (calculates) the impedance Z (Z=V / I, R=Z·cosθ, X=Z·sinθ) of the measurement target MT based on the current value (I) of the current I1, the voltage value (V) of the AC voltage, and the phase difference (θ) calculated in this way. Thereafter, the processing unit 5 outputs the display data Dd to the output unit 6, and causes the display device of the output unit 6 to display the measured impedance Z. With the above, the measurement process of the impedance Z of the measurement object MT by the processing unit 5 is completed.

[0034] In this case, the current value of the measurement AC current I0 indicated by the current value data Di is the current value of the current I1 flowing through the measurement object MT only, so the processing unit 5 can reliably measure the impedance Z of the measurement object MT when a non-measurement object load Ld is connected in parallel to the measurement object MT via the connection line Lc.

[0035] Thereafter, the processing unit 5 outputs the display data Dd to the output unit 6, and causes the calculated impedance Z to be displayed on the display device of the output unit 6. With the above, the measurement process of the impedance Z of the measurement object MT by the processing unit 5 is completed.

[0036] In this way, according to the impedance measurement method, the current sensor 4 measures the supply current value (in this example, current value data Di) while the measurement current supply line Li and the connection line Lc are inserted into the opening 4d so that the directions of flow of the measurement AC current I0 (measurement AC current I0 and current I2) are opposite to each other, so that the current value of the measurement AC current I0 measured by the current sensor 4 can be made to be only the supply current (in this example, current I1) flowing to the measurement object MT, thereby making it possible to reliably and easily measure the impedance Z of the measurement object MT.

[0037] Furthermore, according to this impedance measurement method, by using a clamp-type current sensor 4 that is configured to be able to open and close, the current value of the measurement AC current I0 (supply current: in this example, current I1) supplied to the measurement object MT can be reliably and easily measured by clamping the connection line Lc and the measurement current supply line Li while bringing the measurement current supply line Li close to the connection line Lc.

[0038] Furthermore, according to this impedance measurement method, when the measurement object is any of a lithium ion battery, a fuel cell, and an electrolyzer, the impedance of the measurement object can be reliably measured.

[0039] The present invention is not limited to the above-mentioned embodiment, and can be modified as appropriate. For example, in the above-mentioned embodiment, an AC current is used as the measurement current, but when no DC current flows between the measurement object MT and the load Ld, a DC current can be used as the measurement current. In addition, in the above-mentioned embodiment, a lithium ion battery is used as the measurement object MT, but a fuel cell or an electrolysis device can be used as the measurement object MT.

[0040] Although an example has been described in which the current sensor 4 outputs the current value data Di, it is also possible to adopt a configuration in which the current sensor 4 outputs a current measurement signal that is an analog signal, and the processing unit 5 measures (calculates) the impedance based on the input current measurement signal. Similarly, 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. [Industrial Applicability]

[0041] According to the present invention, since the current value of the measurement current measured by the current sensor can be the only supply current flowing through the measurement object, the impedance of the measurement object can be reliably measured. As a result, the present invention can be widely applied to impedance measurement methods for such measurement objects. [Explanation of symbols]

[0042] 1. Impedance measuring device 2 Current output section 3. Voltage measurement section 4 Current Sensor 5 Processing section Di Current value data Dv Voltage value data Lc connection line Li measurement current supply line Ld load MT Measurement Target P1,P2 Measured current supply point

Claims

1. 1. An impedance measurement method for measuring an impedance of an object to be measured based on the measured supply current value and the voltage across both ends of the object to be measured, the method comprising the steps of: supplying a measurement current to the object to be measured through a measurement current supply line connected to a pair of measurement current supply points defined at both ends of the object to be measured, measuring a supply current value of the measurement current supplied to the object to be measured by a non-contact current sensor having the measurement current supply line inserted through an opening thereof, and measuring a voltage across both ends of the object to be measured, the method comprising the steps of: An impedance measuring method in which the measurement current supply line and the connection line are inserted into the opening so that the measurement currents flow in opposite directions to each other, and the supply current value is measured by the current sensor.

2. 2. The impedance measuring method according to claim 1, wherein the current sensor is a clamp-type current sensor that is configured to be openable and closable.

3. 3. The impedance measuring method according to claim 1, wherein the impedance is measured using any one of a lithium ion battery, a fuel cell, and an electrolysis device as the measurement object.

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