JP2016014634A - Impedance measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an impedance measuring device capable of reducing the size of the device and suppressing manufacturing cost.SOLUTION: An impedance measuring device comprises: power supply means outputting an AC current to a positive electrode and a negative electrode of a stacked battery in which a plurality of battery cells is stacked; and detection means detecting at least one of an AC potential difference between the positive electrode and a midway point of the stacked battery and an AC potential difference between the negative electrode and the midway point. The impedance measuring device comprises: arithmetic means computing an impedance of the stacked battery on the basis of the AC potential difference detected by the detection means and the AC current output from the power supply means; and DC cutoff means cutting off a DC signal output from the stacked battery. Furthermore, the impedance measuring device comprises synthesis means synthesizing a different signal with a signal output to the stacked battery via the DC cutoff means.

Description

  The present invention relates to an impedance measuring device that measures the impedance of a laminated battery.

  Patent Document 1 proposes an apparatus for measuring the internal resistance of a laminated battery while power is supplied from the laminated battery to a load.

  This measuring device outputs an alternating current of the same frequency to each of the positive electrode terminal and the negative electrode terminal of the multilayer battery so that the current does not leak to the load connected to the multilayer battery. The measuring apparatus subtracted the potential of the halfway terminal from the potential of the positive terminal of the laminated battery, and the AC potential difference obtained by subtracting the potential of the halfway terminal located between the positive terminal and the negative terminal. AC potential difference is detected. Then, based on the detected AC potential difference and the AC current output from the measuring device, the internal resistance of the laminated battery is measured.

International Publication No. 2012/077450

  The measuring apparatus as described above is provided with a direct current cut-off unit composed of a capacitor or the like in order to cut off a direct-current voltage signal output from the laminated battery. Since the size of the DC blocking unit is determined by a signal output from the laminated battery or the measuring device, it is difficult to reduce the size of the DC blocking unit without changing the parameters of the output signal.

  The present invention has been made paying attention to such problems, and an object of the present invention is to provide an impedance measuring apparatus that reduces the size of the apparatus and suppresses the manufacturing cost.

  According to an aspect of the present invention, an impedance measuring apparatus includes: a power source that outputs an alternating current to a positive electrode and a negative electrode of a stacked battery in which a plurality of battery cells are stacked; and a midpoint between the positive electrode and the stacked battery. Detecting means for detecting at least one of the AC potential difference between the negative electrode and the AC potential difference between the negative electrode and the midpoint. The impedance measuring device outputs from the laminated battery, computing means for computing the impedance of the laminated battery based on the AC potential difference detected by the detecting means and the alternating current output from the power supply means. And DC blocking means for blocking the DC signal. Furthermore, the impedance measuring apparatus includes a combining unit that combines different signals with a signal output to the stacked battery via the DC blocking unit.

  According to this aspect, since a different signal is combined with the signal output to the DC cut-off means by the combining means, the potential difference generated at both ends of the DC cut-off means can be reduced. Thereby, since the size of the direct current interrupting portion can be reduced, the impedance measuring device can be reduced in size and the manufacturing cost can be suppressed.

FIG. 1A is a diagram illustrating an example of a laminated battery that is a measurement target of the impedance measuring apparatus according to the first embodiment of the present invention. FIG. 1B is an exploded view showing the structure of the battery cell formed in the laminated battery. FIG. 2 is a diagram illustrating a basic configuration of the impedance measuring apparatus according to the present embodiment. FIG. 3 is a diagram illustrating a configuration of a detection unit that detects an AC potential difference generated between the positive electrode terminal and the midpoint terminal of the stacked battery and an AC potential difference generated between the negative electrode terminal and the midpoint terminal of the stacked battery. is there. FIG. 4 is a diagram illustrating a configuration of a power supply unit that outputs an alternating current to the positive electrode terminal of the laminated battery. FIG. 5 is a diagram illustrating a configuration of an AC adjustment unit that adjusts the amplitude of the AC current output to each of the positive electrode terminal and the negative electrode terminal of the laminated battery. FIG. 6 is a diagram illustrating a configuration of a calculation unit that calculates the internal impedance of the laminated battery. FIG. 7 is a flowchart illustrating an example of an equipotential control method for matching the positive-side AC potential difference with the negative-side AC potential difference. FIG. 8 is a time chart showing an example when equipotential control is executed. FIG. 9 is a diagram illustrating potentials generated at the positive electrode and the negative electrode of the laminated battery by equipotential control. FIG. 10 is a configuration diagram showing a mixing circuit of an AC signal source in the first embodiment of the present invention. FIG. 11 is a conceptual diagram showing the waveform of the mixed signal generated by the mixing circuit. FIG. 12 is a diagram illustrating frequency components of the mixed signal. FIG. 13 is a diagram illustrating a configuration of a synchronous detection circuit that detects an AC potential difference of a mixed signal. FIG. 14 is a diagram illustrating a waveform of an AC signal generated in the synchronous detection circuit. FIG. 15 is a diagram showing a configuration of a mixing circuit in the second embodiment of the present invention. FIG. 16 is a conceptual diagram showing the waveform of the mixed signal generated by the mixing circuit. FIG. 17 is a diagram showing the configuration of the impedance measuring apparatus according to the third embodiment of the present invention. FIG. 18 is a diagram showing a configuration of an impedance measuring apparatus according to the fourth embodiment of the present invention.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

(First embodiment)
FIG. 1A is a diagram illustrating an example of a laminated battery that is a measurement target of the impedance measuring apparatus according to the first embodiment of the present invention. FIG. 1A shows an external perspective view of a fuel cell stack 1 in which a plurality of battery cells are stacked as an example of a stacked battery.

  As shown in FIG. 1A, the fuel cell stack 1 includes a plurality of power generation cells 10, a current collecting plate 20, an insulating plate 30, an end plate 40, and four tension rods 50.

  The power generation cell 10 is a so-called battery cell and indicates one of a plurality of fuel cells stacked on the fuel cell stack 1. The power generation cell 10 generates an electromotive voltage of about 1 V (volt), for example. The detailed configuration of the power generation cell 10 will be described later with reference to FIG. 1B.

  The current collecting plates 20 are respectively arranged outside the stacked power generation cells 10. The current collecting plate 20 is formed of a gas impermeable conductive member, for example, dense carbon. A current collecting plate 20 corresponding to a positive (positive) electrode (positive electrode) of the fuel cell stack 1 is provided with a positive electrode terminal 211, and a current collecting corresponding to a negative (minus) electrode (negative electrode) of the fuel cell stack 1. A negative electrode terminal 212 is provided on the plate 20. Note that electrons e − generated in the power generation cell 10 are taken out from the negative electrode terminal 212 to the outside.

  Further, a midpoint terminal 213 is provided in the power generation cell 10 that is midway between the positive terminal 211 and the negative terminal 212. In the present embodiment, the midpoint terminal 213 is provided in the power generation cell 10 located in the middle (midpoint) among the plurality of power generation cells 10 stacked from the positive electrode terminal 211 to the negative electrode terminal 212. Note that the midpoint terminal 213 may be provided at a position off the midpoint between the positive terminal 211 and the negative terminal 212.

  The insulating plates 30 are respectively arranged outside the current collecting plates 20. The insulating plate 30 is formed of an insulating member such as rubber.

  The end plate 40 is disposed outside the insulating plate 30. The end plate 40 is made of a rigid metal material such as steel.

  One end plate 40 (the left front end plate 40 in FIG. 1A) has an anode supply port 41a, an anode discharge port 41b, a cathode supply port 42a, a cathode discharge port 42b, and a cooling water supply port 43a. A cooling water discharge port 43b is provided. In the present embodiment, the anode discharge port 41b, the cooling water discharge port 43b, and the cathode supply port 42a are provided on the right side in the drawing. The cathode discharge port 42b, the cooling water supply port 43a, and the anode supply port 41a are provided on the left side in the drawing.

  The tension rods 50 are disposed near the four corners of the end plate 40, respectively. The fuel cell stack 1 has a hole (not shown) penetrating therethrough. The tension rod 50 is inserted through the through hole. The tension rod 50 is formed of a rigid metal material such as steel. The tension rod 50 is insulated on the surface in order to prevent an electrical short circuit between the power generation cells 10. A nut (not shown because it is in the back) is screwed into the tension rod 50. The tension rod 50 and the nut tighten the fuel cell stack 1 in the stacking direction.

  As a method of supplying hydrogen as anode gas to the anode supply port 41a, for example, there are a method of directly supplying hydrogen gas from a hydrogen storage device, a method of reforming and supplying hydrogen-containing fuel, and the like. Examples of the fuel containing hydrogen include natural gas, methanol, and gasoline. Air is generally used as the cathode gas supplied to the cathode supply port 42a.

  FIG. 1B is an exploded view showing the structure of the power generation cells 10 stacked on the fuel cell stack 1.

  As shown in FIG. 1B, in the power generation cell 10, an anode separator (anode bipolar plate) 12a and a cathode separator (cathode bipolar plate) 12b are arranged on both surfaces of a membrane electrode assembly (MEA) 11. Is the structure.

  In the MEA 11, electrode catalyst layers 112 are formed on both surfaces of an electrolyte membrane 111 made of an ion exchange membrane. A gas diffusion layer (GDL) 113 is formed on the electrode catalyst layer 112.

  The electrode catalyst layer 112 is formed of, for example, carbon black particles on which platinum is supported.

  The GDL 113 is formed of a member having sufficient gas diffusibility and conductivity, such as carbon fiber.

  The anode gas supplied from the anode supply port 41a flows through this GDL 113a, reacts with the anode electrode catalyst layer 112 (112a), and is discharged from the anode discharge port 41b.

  The cathode gas supplied from the cathode supply port 42a flows through this GDL 113b, reacts with the cathode electrode catalyst layer 112 (112b), and is discharged from the cathode discharge port 42b.

  The anode separator 12a is stacked on one side of the MEA 11 (back side in FIG. 1B) via the GDL 113a and the seal 14a. The cathode separator 12b is overlaid on one side (the surface in FIG. 1B) of the MEA 11 via the GDL 113b and the seal 14b. The anode separator 12a and the cathode separator 12b are formed by press-molding a metal separator base such as stainless steel so that a reaction gas channel is formed on one surface and alternately arranged with the reaction gas channel on the opposite surface. A cooling water flow path is formed. As shown in FIG. 1B, the anode separator 12a and the cathode separator 12b are overlapped to form a cooling water flow path.

  The MEA 11, the anode separator 12a, and the cathode separator 12b are respectively formed with holes 41a, 41b, 42a, 42b, 43a, 43b, which are stacked to be an anode supply port 41a, an anode discharge port 41b, and a cathode supply port. 42a, cathode discharge port 42b, cooling water supply port 43a and cooling water discharge port 43b are formed.

  FIG. 2 is a diagram showing a basic configuration of the impedance measuring apparatus 5 in the embodiment of the present invention.

  The fuel cell stack 1 is a stacked battery that is connected to the load 3 and supplies power to the load 3, and is mounted on a vehicle, for example. The fuel cell stack 1 has an impedance inside.

  The load 3 is an electric load such as an electric motor or an auxiliary machine used for power generation of the fuel cell stack 1. The auxiliary machine connected to the fuel cell stack 1 includes, for example, a compressor for supplying cathode gas to the fuel cell stack 1 and cooling water circulated to the fuel cell stack 1 when the fuel cell stack 1 is warmed up. For example, a heater for heating.

  The control unit (C / U) 6 controls the operation state of the fuel cell stack 1 such as the power generation state, the wet state, the internal pressure state, and the temperature state of the fuel cell stack 1 according to the operating state of the load 3. .

  For example, the control unit 6 controls the flow rate of the cathode gas and the anode gas supplied to the fuel cell stack 1 according to the generated power required from the load 3.

  Further, in the fuel cell stack 1, when the electrolyte membrane 111 is in a dry state, the power generation performance is degraded. As a countermeasure, the control unit 6 uses the internal resistance value of the fuel cell stack 1 correlated with the wetness of the electrolyte membrane 111 to prevent the electrolyte membrane 111 from being dried or excessively wet. Adjust.

  The impedance measuring device 5 measures the internal impedance of the fuel cell stack 1 in order to maintain the power generation performance of the fuel cell stack 1. In the present embodiment, the impedance measuring device 5 measures the internal resistance of the fuel cell stack 1 and transmits the measured value to the control unit 6.

  The impedance measuring device 5 includes a positive side DC cutoff unit 511, a negative side DC cutoff unit 512, a midpoint DC cutoff unit 513, a positive side detection unit 521, a negative side detection unit 522, and a positive side power supply unit 531. , A negative power supply unit 532, an AC adjustment unit 540, and a calculation unit 550.

  The positive-side DC blocking unit 511, the negative-side DC blocking unit 512, and the midpoint DC blocking unit 513 are DC blocking means that block the DC signal but pass the AC signal. Each of the DC blocking units 511 to 513 is realized by, for example, a capacitor or a transformer. In addition, about the halfway point DC interruption | blocking part 513 shown with the broken line, it is omissible.

  The positive electrode side detection unit 521 and the negative electrode side detection unit 522 are at least one of an AC potential difference generated between the positive electrode terminal 211 and the midpoint terminal 213 and an AC potential difference generated between the negative electrode terminal 212 and the midpoint terminal 213. Detection means for detecting the AC potential difference.

  The positive electrode side detection unit 521 has a potential difference (hereinafter referred to as “AC potential difference V1”) between an AC potential Va that is an AC component of the potential generated at the positive terminal 211 and an AC potential Vc that is an AC component of the potential generated at the midpoint terminal 213. ") Is detected.

  The positive electrode side detection unit 521 outputs a detection signal whose value changes according to the amplitude of the AC potential difference V1 to the AC adjustment unit 540 and the calculation unit 550. For example, the level of the detection signal increases as the AC potential difference V1 increases, and the level of the detection signal decreases as the AC potential difference V1 decreases.

  As for the positive electrode side detection unit 521, the first input terminal is connected to the positive electrode terminal 211 via the DC blocking unit 511, the second input terminal is grounded, and the output terminal is connected to each of the AC adjustment unit 540 and the calculation unit 550. Is done.

  The negative electrode side detection unit 522 has a potential difference (hereinafter referred to as “AC potential difference V2”) between an AC potential Vb that is an AC component of the potential generated at the negative terminal 212 and an AC potential Vc that is an AC component of the potential generated at the halfway point terminal 213. ) Is detected.

  The negative electrode side detection unit 522 outputs a detection signal whose value changes according to the amplitude of the AC potential difference V2 to the calculation unit 550. As for the negative electrode side detection unit 522, the first input terminal is connected to the negative electrode terminal 212 through the DC blocking unit 512, the second input terminal is grounded, and the output terminal is connected to each of the AC adjustment unit 540 and the calculation unit 550. Is done.

  Next, details of the positive-side DC blocking unit 511, the negative-side DC blocking unit 512, the midpoint DC blocking unit 513, the positive-side detection unit 521, and the negative-side detection unit 522 will be described with reference to FIG.

  Here, each of the positive-side DC blocking units 511 to 513 is realized by a capacitor.

  The positive-side DC blocking unit 511 is a second DC blocking unit that blocks a DC signal output from the positive terminal 211 of the fuel cell stack 1. One electrode of the capacitor constituting the positive side DC blocking unit 511 is connected to the positive terminal 211 of the fuel cell stack 1, and the other electrode is connected between the output terminal of the positive side power source unit 531.

  The negative electrode side DC blocking unit 512 is a third DC blocking unit that blocks a DC signal output from the negative electrode terminal 212 of the fuel cell stack 1. One electrode of the capacitor constituting the negative electrode side direct current blocking unit 512 is connected to the negative electrode terminal 212 of the fuel cell stack 1, and the other electrode is connected between the output terminal of the negative electrode side power supply unit 532.

  The midpoint DC cut-off unit 513 is a first DC cut-off unit that cuts off a DC signal output from the midpoint terminal 213 of the fuel cell stack 1. One electrode of the capacitor constituting the midpoint DC blocking unit 513 is connected to the midpoint terminal 213 of the fuel cell stack 1, and the other electrode together with the second input terminal of the positive electrode side detection unit 521 is the negative electrode side detection unit 522. To the second input terminal. Furthermore, the other electrode is connected to the ground line 533.

  The ground line 533 is a power supply line (power supply means) that is grounded (GND) so that the potential becomes 0 V (volt). Therefore, a ground signal (potential signal) of 0V is output to the ground line 533.

  The positive electrode side detection unit 521 includes a potential difference detection circuit 5211, a band pass filter (BPF) 5212, an amplification circuit 5213, and a synchronous detection circuit 5214.

  The potential difference detection circuit 5211 outputs a detection signal corresponding to the AC potential difference V1 obtained by subtracting the potential Vc from the AC potential Va. The AC potential Va is a signal component that passes through the positive-side DC cutoff unit 511 among the signals output from the positive terminal 211, and the potential Vc is the midpoint DC cutoff among signals output from the midpoint terminal 213. This is a signal component that passes through the unit 513. In this embodiment, the potential difference detection circuit 5211 is realized by a differential amplifier.

  Noise is mixed into the potential difference detection circuit 5211 from the load 3 through the positive electrode terminal 211. Regarding the noise from the load 3, the frequency distribution of the noise covers a wide range, and the noise level is about three orders of magnitude larger than the AC potential difference V1. For this reason, it is preferable to remove unnecessary signals from the load 3 included in the detection signal.

  The band-pass filter 5212 removes unnecessary signals included in the detection signal and passes only signal components in a frequency band necessary for detection. Specifically, the band-pass filter 5212 passes a signal component having the same frequency as the frequency of the alternating current I1 in the detection signal output from the potential difference detection circuit 5211, and removes signal components in other frequency bands. .

  The amplifier circuit 5213 amplifies the detection signal output from the band pass filter 5212 and outputs it. The amplification factor (gain) of the amplifier circuit 5213 is determined in consideration of the dynamic range of the impedance measuring device 5.

  The synchronous detection circuit 5214 extracts only the signal component having the same frequency as the alternating current I1 and the same phase as the alternating current I1, that is, the actual axis component of the detection signal, from the detection signal output from the amplification circuit 5213. This is an extraction circuit.

  Specifically, the synchronous detection circuit 5214 multiplies the detection signal by a signal having the same frequency fb as the alternating current I1 and having the same phase as that of the alternating current I1, and the multiplied alternating detection signal. Is converted into a DC detection signal V1. The smoothed detection signal V1 changes according to the amplitude of the AC potential difference V1.

  As described above, the positive electrode side detection unit 521 removes unnecessary signals by the band pass filter 5212 and the synchronous detection circuit 5214, and outputs the detection signal V1 proportional to the amplitude of the AC potential difference V1 to the AC adjustment unit 540 and the calculation unit 550. .

  The negative electrode side detection unit 522 includes a potential difference detection circuit 5221, a band pass filter (BPF) 5222, an amplification circuit 5223, and a synchronous detection circuit 5224. Since these configurations are basically the same as those of the positive electrode side detection unit 521, description thereof is omitted here.

  Next, the configuration of the positive power supply unit 531 and the negative power supply unit 532 will be described.

  The positive power supply unit 531 and the negative power supply unit 532 are power supply units that output an alternating current having the same frequency to each of the positive terminal 211 and the negative terminal 212 of the fuel cell stack 1.

  The positive power supply unit 531 outputs an alternating current I1 having a reference frequency fb determined for measuring the internal impedance of the fuel cell stack 1 to the positive terminal 211 via the positive DC blocking unit 511. The amplitude of the alternating current I1 output from the positive power supply unit 531 is controlled by the alternating current adjustment unit 540. The positive power supply unit 531 is realized by a voltage-current conversion circuit including an operational amplifier (OA), for example. Hereinafter, the reference frequency fb is referred to as “reference frequency fb”.

  The details of the positive power supply unit 531 will be described with reference to FIG.

  The positive power supply unit 531 includes a voltage / current conversion circuit 5311 and a synchronous detection circuit 5312.

  The voltage-current conversion circuit 5311 converts the alternating voltage Vi1 changing at the reference frequency fb into the alternating current I1, and outputs the alternating current I1 to the direct current cut-off unit 511. The AC voltage Vi1 is a current command signal output from the AC adjustment unit 540 to the positive power supply unit 531.

  The voltage-current conversion circuit 5311 adjusts the amplification factor of the alternating current I1 according to the operational amplifier OA1 that outputs the alternating current I1 based on the alternating voltage Vi1, the detection resistance element Rs, and the detection voltage Vi1s generated in the detection resistance element Rs. An operational amplifier OA2 and resistance elements R1 to R5 are included.

  The operational amplifier OA1 outputs an alternating current I1 that is proportional to the alternating voltage Vi1. The non-inverting input terminal (+) of the operational amplifier OA1 is connected to the positive terminal of the AC adjusting unit 540, and the inverting input terminal (−) is connected to the output terminal of the current adjusting operational amplifier OA2 via the resistor element R5. The The output terminal of the operational amplifier OA1 is grounded via the resistance element R2 and the resistance element R3.

  The detection resistance element Rs is a resistance element provided for detecting the magnitude of the alternating current I1 output from the operational amplifier OA1. One end of the detection resistance element Rs is connected to the output terminal of the operational amplifier OA1, and the other end of the detection resistance element Rs is connected to the inverting input terminal (−) of the operational amplifier OA2 and the positive-side DC blocking unit 511.

  The detection voltage Vi1s generated at both ends of the detection resistance element Rs is a value (I × R) obtained by multiplying the current value of the alternating current I1 and the resistance value of the detection resistance element Rs, and is proportional to the magnitude of the alternating current I1.

  The operational amplifier OA2 is a detection circuit that detects the magnitude of the detection voltage Vi1s generated in the detection resistance element Rs. The detection signal Vi1s output from the operational amplifier OA2 is fed back to the inverting input terminal (−) of the operational amplifier OA1. The operational amplifier OA1 increases or decreases the alternating current I1 according to the detection signal Vi1s. Thereby, the amplitude of the alternating current I1 is adjusted to be proportional to the amplitude of the alternating voltage Vi1.

  The resistance values of the resistance elements R1 to R5 are appropriately set according to the design of the impedance measuring device 5.

  In order to remove unnecessary signals from the detection signal Vi1s output from the operational amplifier OA2, the synchronous detection circuit 5312 extracts only the signal component having the same frequency fb and the same phase as the alternating current I1 from the detection signal Vis. Circuit. The configuration of the synchronous detection circuit 5312 is the same as that of the synchronous detection circuit 5214 shown in FIG.

  The synchronous detection circuit 5312 outputs the detection signal I1 from which the unnecessary signal is removed to the arithmetic unit 550. The detection signal I1 output from the synchronous detection circuit 5312 is a direct current signal proportional to the amplitude of the alternating current I1.

  In this way, the positive power supply unit 531 outputs the alternating current I1 based on the current command signal output from the alternating current adjustment unit 540. Further, the magnitude of the alternating current I1 is detected by the detection resistor element Rs and the operational amplifier OA2, and the detection signal I1 from which unnecessary signals are removed by the synchronous detection circuit 5312 is output to the arithmetic unit 550.

  The negative power supply unit 532 outputs an alternating current I2 having the same reference frequency fb as the alternating current I1 to the negative terminal 212 via the negative DC blocking unit 512. The amplitude of the alternating current I2 output from the negative power supply unit 532 is controlled by the alternating current adjustment unit 540. The configuration of the negative electrode side detection unit 522 is the same as that of the positive electrode side detection unit 521, and thus detailed description thereof is omitted here.

  Next, the configuration of the AC adjustment unit 540 will be described with reference to FIG.

  The AC adjustment unit 540 outputs AC from at least one of the positive power supply unit 531 and the negative power supply unit 532 so that the positive AC potential Va and the negative AC potential Vb coincide with each other. It is an adjusting means for adjusting the amplitude and phase of the current.

  In the present embodiment, the AC adjustment unit 540 adjusts the amplitude of the AC current I1 output from the positive power supply unit 531 and the amplitude of the AC current I2 output from the negative power supply unit 532. The AC adjustment unit 540 is realized by, for example, a PI (Proportional Integral) control circuit.

  The AC adjustment unit 540 includes a positive electrode side subtractor 5411, a positive electrode side integration circuit 5421, a positive electrode side multiplier 5431, a negative electrode side subtractor 5412, a negative electrode side integration circuit 5422, and a negative electrode side multiplier 5432. Further, the AC adjustment unit 540 includes a reference power source 545 and an AC signal source 546.

  The reference power source 545 outputs a voltage (hereinafter referred to as “reference voltage Vs”) set with 0 V (volt) as a reference in order to match the positive-side AC potential difference V1 with the negative-side AC potential difference V2. . The reference voltage Vs is set to a value determined by experiments or the like. Here, the reference power source 545 that outputs the reference voltage Vs to the positive side subtractor 5411 and the reference power source 545 that outputs the reference voltage Vs to the negative side subtractor 5412 are shown separately for convenience, but a common reference power source 545 is shown. May be output.

  The AC signal source 546 is an oscillation source that oscillates an AC signal including the reference frequency fb. The reference frequency fb is set to a predetermined value suitable for measuring the internal impedance of the fuel cell stack 1. The reference frequency fb is set to 1 kHz (kilohertz), for example.

  The signal output from the AC signal source 546 is output to the positive-side multiplier 5431 and the negative-side multiplier 5432, and is the same as the AC currents I1 and I2 with respect to the synchronous detection circuits 5214 and 5224 shown in FIG. It is output as a detection signal for detecting the frequency component.

  The positive-side subtractor 5411 outputs a difference signal proportional to the deviation width from the reference voltage Vs by subtracting the reference voltage Vs from the detection signal V1 output from the positive-side detection unit 521. For example, the difference signal level increases as the deviation width from the reference voltage Vs increases.

  The positive side integration circuit 5421 integrates the difference signal output from the positive side subtractor 5411 to average the difference signal or adjust the sensitivity. Then, the positive side integration circuit 5421 outputs the integrated difference signal to the positive side multiplier 5431.

  The positive-side multiplier 5431 generates an AC voltage Vi1 that converges the amplitude of the AC potential difference V1 to the reference voltage Vs by multiplying the AC signal output from the AC signal source 546 by the difference signal. For example, the amplitude of the AC voltage Vi1 increases as the level of the difference signal output from the subtractor 541 increases.

  The positive multiplier 5431 outputs the alternating voltage Vi1 to the positive power supply 531 as a command signal. The AC voltage Vi1 is converted into an AC current I1 by the positive power supply unit 531.

  Note that the negative-side subtractor 5412, the negative-side integrating circuit 5422, and the negative-side multiplier 5432 have the same configurations as the positive-side subtracter 5411, the positive-side integrating circuit 5421, and the positive-side multiplier 5431, respectively. The description about is omitted.

  As described above, the AC adjustment unit 540 adjusts the amplitude of the AC current I1 output from the positive power supply unit 531 so that the amplitude of the AC potential difference V1 becomes the reference voltage Vs. Similarly, the AC adjustment unit 540 adjusts the amplitude of the AC current I2 output from the negative power supply unit 532 so that the amplitude of the AC potential difference V2 becomes the reference voltage Vs.

  As a result, the AC potential Va and the AC potential Vb are controlled to the same level, so that the AC potential Va superimposed on the positive electrode terminal 211 and the AC potential Vb superimposed on the negative electrode terminal 212 coincide. For this reason, it is possible to suppress leakage of the alternating currents I1 and I2 output from the impedance measuring device 5 to the fuel cell stack 1 toward the load 3. In the following, controlling the positive power supply unit 531 and the negative power supply unit 532 so that the AC potential Va and the AC potential Vb are equal to each other is referred to as “equipotential control”.

  Next, the structure of the calculating part 550 is demonstrated with reference to FIG.

  The calculation unit 550 is a calculation unit that calculates the internal impedance of the fuel cell stack 1 based on the amplitudes of the alternating currents I1 and I2 adjusted by the AC adjustment unit 540 and the amplitudes of the AC potential differences V1 and V2.

  Detection signals indicating the amplitudes of the AC potential differences V1 and V2 are input to the arithmetic unit 550 from the positive electrode side detection unit 521 and the negative electrode side detection unit 522, respectively. A detection signal indicating the amplitude of the currents I1 and I2 is input.

  The arithmetic unit 550 includes an AD (Analog Digital) converter 551 and a microcomputer chip 552.

  The AD converter 551 converts the detection signals of the alternating currents I1 and I2 and the detection signals of the alternating potential differences V1 and V2 into digital numerical signals and transfers them to the microcomputer chip 552.

  The microcomputer chip 552 stores a program for calculating the internal resistance Rn of the fuel cell stack 1 and the internal resistance R of the entire fuel cell stack 1 in advance. The microcomputer chip 552 sequentially calculates the internal resistance R at predetermined minute time intervals, or calculates the internal resistance R in response to a request from the control unit 6 and outputs the calculation result to the control unit 6. The internal resistance Rn of the fuel cell stack 1 and the internal resistance R of the entire fuel cell stack 1 are calculated by the following equations.

  The calculation unit 550 is realized by an analog calculation circuit including an analog calculation IC, for example. By using the analog arithmetic circuit, it is possible to output a temporally continuous change in resistance value to the control unit 6.

  When the control unit 6 receives the internal resistance R output from the calculation unit 550, the control unit 6 controls the operation state of the fuel cell stack 1 according to the magnitude of the internal resistance R.

  For example, when the internal resistance R is high, the control unit 6 determines that the electrolyte membrane 111 of the fuel cell stack 1 is in a dry state, and reduces the flow rate of the cathode gas supplied to the fuel cell stack 1. Thereby, the amount of water taken out from the fuel cell stack 1 can be reduced.

  FIG. 7 is a flowchart illustrating an example of a control method when the control performed by the AC adjustment unit 540 is realized by a controller.

  In step S1, the controller determines whether or not the positive-side AC potential Va is greater than a predetermined value. If the determination result is negative, the controller proceeds to step S2, and if the determination result is positive, the controller proceeds to step S3.

  In step S2, the controller determines whether or not the positive-side AC potential Va is smaller than a predetermined value. If the determination result is negative, the controller proceeds to step S4, and if the determination result is positive, the controller proceeds to step S5.

  In step S <b> 3, the controller decreases the output of the positive power supply unit 531. That is, the controller decreases the amplitude of the alternating current I1. As a result, the positive AC potential Va decreases.

  In step S4, the controller maintains the output of the positive power supply unit 531. As a result, the positive AC potential Va is maintained.

  In step S5, the controller increases the output of the positive power supply unit 531. As a result, the positive AC potential Va increases.

  In step S6, the controller determines whether or not the negative AC potential Vb is larger than a predetermined value. If the determination result is negative, the controller proceeds to step S7, and if the determination result is positive, the controller proceeds to step S8.

  In step S7, the controller determines whether or not the negative AC potential Vb is smaller than a predetermined value. If the determination result is negative, the controller proceeds to step S9. If the determination result is positive, the controller proceeds to step S10.

  In step S <b> 8, the controller decreases the output of the negative power supply unit 532. As a result, the negative AC potential Vb decreases.

  In step S <b> 9, the controller maintains the output of the negative power supply unit 532. As a result, the negative AC potential Vb is maintained.

  In step S <b> 10, the controller increases the output of the negative power supply unit 532. This increases the negative AC potential Vb.

  In step S11, the controller determines whether or not the AC potential Va and the AC potential Vb are predetermined values. If the determination result is positive, the controller proceeds to step S12. If the determination result is negative, the controller exits the process.

  In step S12, the controller calculates the internal resistance value based on the above-described equations (5-1) and (5-2).

  FIG. 8 is a time chart when the controller executes control of the impedance measuring device 5. Note that step numbers are also shown so that the correspondence with the flowchart is easy to understand.

  In the initial stage of FIG. 8, the internal resistance value R1 on the positive electrode side is higher than the internal resistance value R2 on the negative electrode side (FIG. 8A). In this state, the controller starts control.

  At time t0, neither the positive AC potential Va nor the negative AC potential Vb has reached the control level (FIG. 8C). In this state, the controller repeats steps S1, S2, S5, S6, S7, S10, and S11. As a result, the positive-side AC current I1 and the negative-side AC current I2 increase (FIG. 8B).

  When the positive AC potential Va reaches the control level at time t1 (FIG. 8C), the controller repeats steps S1, S2, S4, S6, S7, S10, and S11. As a result, the positive side alternating current I1 is maintained and the negative side alternating current I2 increases (FIG. 8B).

  When the negative AC potential Vb reaches the control level at the time t2 and becomes the same level as the positive AC potential Va (FIG. 8C), the controller performs steps S1, S2, S4, S6, S7, S9, and S11. Process S12. As a result, the positive side alternating current I1 and the negative side alternating current I2 are maintained. Based on the equation (1-1), the internal resistance value R1 on the positive electrode side and the internal resistance value R2 on the negative electrode side are calculated. Then, the internal resistance value R1 on the positive electrode side and the internal resistance value R2 on the negative electrode side are added together to obtain the total internal resistance R.

  After time t3, the internal resistance value R2 on the negative electrode side increases due to the wet state of the fuel cell stack changing (FIG. 8A). In this case, the controller repeats steps S1, S2, S4, S6, S8, S11, and S12. By processing in this way, the negative side AC current I2 is lowered as the negative side internal resistance value R2 increases, so the negative side AC potential Vb is maintained at the same level as the positive side AC potential Va. Therefore, the internal resistance R is calculated even in this state.

  After time t4, the internal resistance value R2 on the negative electrode side coincides with the internal resistance value R1 on the positive electrode side (FIG. 8A). In this case, the controller repeats steps S1, S2, S4, S6, S7, S9, S11, and S12. By processing in this way, the positive side AC potential Va and the negative side AC potential Vb are maintained at the same level (FIG. 8C), and the internal resistance R is calculated.

  Next, the effect of the equipotential control by the impedance measuring device 5 will be described.

  FIG. 9 is a diagram illustrating a change in the positive electrode potential generated at the positive electrode terminal 211 of the fuel cell stack 1 and a change in the negative electrode potential generated at the negative electrode terminal 212.

  During output of the fuel cell stack 1, a DC voltage Vdc output from the fuel cell stack 1 to the load 3 is generated between the positive electrode terminal 211 and the negative electrode terminal 212. Before the impedance measuring device 5 is activated (ON), the positive electrode potential of the positive electrode terminal 211 and the negative electrode potential of the negative electrode terminal 212 are both constant as shown by the dotted line, which is a potential difference between the positive electrode potential and the negative electrode potential. A DC voltage Vdc is supplied to the load 3. After that, when the impedance measuring device 5 is activated and the alternating currents I1 and I2 are output from the positive power supply unit 531 and the negative power supply unit 532, the alternating current potential Va is superimposed on the positive potential and the alternating potential Vb is superimposed on the negative potential. Is done.

  The alternating current I1 output from the positive electrode side power supply unit 531 is output to the positive electrode terminal 211 of the fuel cell stack 1 through the positive electrode side direct current cut-off unit 511, and then passes through the intermediate point terminal 213 and the intermediate point direct current cut off unit 513. It is output to the positive electrode side detection unit 521. At this time, an AC potential difference V1 (= Va−Vc) is generated between the positive electrode terminal 211 and the midway terminal 213 due to a voltage drop at the internal resistance R1 by supplying the AC current I1 to the internal resistance R1. The AC potential difference V1 is detected by the positive electrode side detection unit 521.

  On the other hand, the alternating current I2 output from the negative electrode side power supply unit 532 is supplied to the negative electrode terminal 212 of the fuel cell stack 1 via the negative electrode side DC blocking unit 512 and passes through the halfway terminal 213 and the halfway DC blocking unit 513. And output to the negative electrode side detection unit 522. At this time, an AC potential difference V2 (= Vb−Vc) is generated between the negative electrode terminal 212 and the midway terminal 213 due to the voltage drop at the internal resistance R2 by supplying the AC current I2 to the internal resistance R2. The AC potential difference V2 is detected by the negative electrode side detection unit 522.

  The AC adjusting unit 540 always reduces the potential difference (V1−V2) between the AC potential difference V1 on the positive electrode side and the AC potential difference V2 on the negative electrode side, that is, the difference (Va−Vb) between the AC potential Va and the AC potential Vb. The negative-side power supply unit 532 is adjusted. As a result, the amplitude of the AC component Va having the positive potential is equal to the amplitude of the AC component Vb having the negative potential, so that the DC voltage Vdc is constant without fluctuation.

  Then, the calculation unit 550 converts the AC potential differences V1 and V2 output from the positive electrode side detection unit 521 and the negative electrode side detection unit 522 and the AC currents I1 and I2 output from the positive electrode side power supply unit 531 and the negative electrode side power supply unit 532. Apply Ohm's law based on. Thereby, the internal resistance R1 on the positive electrode side and the internal resistance R2 on the negative electrode side of the fuel cell stack 1 are calculated.

  Here, since the AC potentials of the positive electrode terminal 211 and the negative electrode terminal 212 have the same value, even if the load 3 such as a traveling motor is connected to the positive electrode terminal 211 and the negative electrode terminal 212, the AC current I1 or I2 can be prevented from leaking toward the load 3.

  Furthermore, the internal resistance R of the entire fuel cell stack 1 can be accurately measured based on the measured values of the internal resistances R1 and R2 of the operating fuel cell stack 1 regardless of the operating state of the load 3. Further, since the positive power supply unit 531 and the negative power supply unit 532 are used, the internal resistance R can be measured even when the fuel cell stack 1 is stopped.

  In such an impedance measuring apparatus, the size of the DC blocking units 511 to 513 is determined by the capacitance (capacitance) and the withstand voltage that form the DC blocking units 511 to 513. For this reason, the size of the capacitor can be reduced as the capacitance of the DC blocking units 511 to 513 is reduced.

  However, as shown in the following equation, for example, when the capacitance C of the DC blocking unit 511 is reduced, the voltage drop Vc generated in the DC blocking unit 511 due to the AC current I1 of the reference frequency fb increases.

  For this reason, when the AC current I1 is constant, the AC potential difference V1 generated by the internal resistance R1 of the fuel cell stack 1 is reduced by an amount corresponding to the increase in the voltage drop Vc, and the detection signal V1 output from the positive electrode side detection unit 521 is reduced. Lower. Therefore, the S / N ratio (Noise to Ratio) becomes worse.

  On the other hand, by increasing the reference frequency fb of the alternating currents I1 and I2, the voltage drop Vc at the DC blocking units 511 to 513 can be reduced. However, if the frequency of the alternating currents I1 and I2 is higher than the reference frequency fb, the internal resistance The accuracy of measuring R1 is reduced. Specifically, when the frequency of the alternating currents I1 and I2 is set to a frequency higher than the reference frequency fb, the level of the detection signal V1 varies depending on a component different from the internal resistance R1 correlated with the wetness of the electrolyte membrane 111. .

  Therefore, in the present embodiment, with respect to the alternating currents I1 and I2 having the reference frequency fb, the size of the direct current blocking units 511 to 533 is reduced without changing parameters such as the amplitudes of the alternating currents I1 and I2 and the reference frequency fb. An AC signal having a frequency higher than the reference frequency fb is synthesized.

  FIG. 10 is a diagram showing the configuration of the AC signal source 546 in the first embodiment of the present invention.

  The AC signal source 546 of the present embodiment is a combining unit that combines different AC signals with the AC currents I1 and I2 that are signals output to the DC blocking units 511 to 513.

  The AC signal source 546 includes a mixing circuit 546A, a reference pulse converter 5464, and a carrier pulse converter 5465.

  The mixing circuit 546A mixes an alternating current signal having a frequency fc higher than the reference frequency fb of the alternating currents I1 and I2 with the alternating currents I1 and I2 output from the positive power supply unit 531 and the negative power supply unit 532. To do. The mixing circuit 546A includes a reference signal generator 5461, a carrier signal generator 5462, and a multiplier 5463.

  The reference signal generator 5461 generates an AC signal that changes at the reference frequency fb. For example, the reference frequency fb is set to 1 kHz as described in FIG. The AC signal output from the reference signal generator 5461 is a signal for modulating the AC signal having the carrier frequency fc, and is hereinafter referred to as a “modulation signal”.

  The carrier wave signal generator 5462 generates an AC signal that changes at a carrier frequency fc higher than the reference frequency fb. For example, the carrier frequency fc is set to a value of 20 kHz or higher. The AC signal output from the carrier signal generator 5462 is hereinafter referred to as a “carrier signal”. The carrier signal is a signal different from the modulation signal of the reference frequency fb of the alternating currents I1 and I2.

  Multiplier 5463 multiplies a carrier signal having a frequency fc higher than reference frequency fb by a modulation signal having reference frequency fb. As a result, a mixed signal (fc ± fb) obtained by mixing the AC signal having the reference frequency fb and the AC signal having the carrier frequency fc is output from the multiplier 5463.

  FIG. 11 is a diagram illustrating a waveform of a mixed signal generated in the mixing circuit 546A.

  FIG. 11A is a diagram illustrating a waveform of a modulation signal having a reference frequency fb. FIG. 11B is a diagram illustrating a waveform of a carrier wave signal having a carrier frequency fc. FIG. 11C shows the waveform of the mixed signal output from the multiplier 5463. In each drawing from FIG. 11A to FIG. 11C, the vertical axis indicates amplitude and the horizontal axis indicates time.

  Multiplier 5463 combines modulated signal Sb (t) output from reference signal generator 5461 and carrier wave signal Sc (t) output from carrier wave signal generator 5462.

  As shown in FIG. 11C, the mixed signal Smix (t) output from the multiplier 5463 has an envelope of a waveform obtained by superposing an inverted signal obtained by shifting the modulation signal of the reference frequency fb by 180 degrees and the modulation signal. It becomes an AC signal having a carrier frequency fc as a line.

  Since the mixed signal Smix (t) is input to each of the positive-side multiplier 5431 and the negative-side multiplier 5432, the waveforms of the alternating currents I1 and I2 output from the positive-side power supply unit 531 and the negative-side power supply unit 532 are used. Also has the same waveform as the mixed signal output from the multiplier 5463.

  FIG. 12 is a diagram illustrating frequency components of the mixed signal Smix (t) output from the multiplier 5463.

  FIG. 12A is a diagram illustrating the relationship between the waveform of the mixed signal and the voltage drop Vc at the DC blockers 511 to 513. FIG. 12B is a diagram illustrating the frequency distribution of the mixed signal.

  As shown in FIG. 12A, the voltage drop Vc at the DC blockers 511 to 513 is determined by the maximum value of the modulation signal Sb (t) that forms the envelope of the mixed signal Smix (t). For this reason, the voltage drop Vc decreases as the amplitude of the modulation signal Sb (t) decreases.

  In FIG. 12B, the frequency component of the modulation signal Sb (t) having the reference frequency fb and the frequency component of the carrier signal Sc (t) having the carrier frequency fc are indicated by broken lines, and the modulation signal and the carrier signal are mixed. The frequency component of the mixed signal Smix (t) is indicated by a solid line.

  Here, the sinusoidal modulation signal Sb (t) output from the reference signal generator 5461 is expressed by the following equation.

  The sine wave carrier signal Sc (t) output from the carrier wave signal generator 5462 is expressed by the following equation.

  Then, the mixed signal Smix (t) obtained by multiplying the carrier signal Sc (t) by the modulation signal modulation signal Sb (t) by the multiplier 5463 is expressed by the following equation.

  Thus, the mixed signal Smix (t) has the sum signal component fa of the frequency (fb + fc) obtained by adding the carrier frequency fc and the reference frequency fb, and the frequency (fc−fb) obtained by subtracting the modulation frequency fb from the carrier frequency fc. ) Difference signal component fd.

  For example, when the reference frequency fb is set to 1 kHz and the carrier frequency fc is set to 20 kHz, the frequency (fc−fb) obtained by subtracting the frequency fb from the carrier frequency fc is 19 kHz, which is larger than the reference frequency fb. Become.

  Therefore, as shown in the equation (2), as the frequency f of the AC signals I1 and I2 increases, the voltage drop Vc at the DC cut-off parts 511 to 513 becomes small. The capacitances 511 to 513 can be reduced.

  Thus, the carrier frequency fc is a frequency (2 × fb) that is twice the reference frequency fb so that the frequency (fc−fb) of the difference signal among the frequency components included in the mixed signal is larger than the reference frequency fb. ) Is set to a larger value.

  Then, by multiplying the alternating currents I1 and I2 having the reference frequency fb by the carrier wave signal having the frequency fc higher than the reference frequency fb, the voltage drop Vc at the DC blocking units 511 to 513 is reduced. The size of the parts 511 to 513 can be reduced.

  Next, the configuration of the synchronous detection circuits 5214 and 5224 in this embodiment will be described. First, detection signals input to the synchronous detection circuits 5214 and 5224 will be described with reference to FIG.

  FIG. 10 shows a reference pulse converter 5464 and a carrier pulse converter 5465 as a configuration for generating a detection signal input to the synchronous detection circuits 5214 and 5224.

  The reference pulse converter 5464 converts the modulation signal having the reference frequency fb into a rectangular wave pulse signal Dm. For example, the reference pulse converter 5464 outputs the pulse signal Dm of “+1” while the modulation signal is larger than zero (0), and outputs the pulse signal Dm of “−1” while the modulation signal is smaller than zero. Output.

  The carrier pulse converter 5465 converts a carrier wave signal having a carrier frequency fc higher than the reference frequency fb into a rectangular wave pulse signal Dc. For example, the carrier pulse converter 5465 outputs a pulse signal Dc of “+1” while the carrier signal is larger than zero, and outputs a pulse signal Dc of “−1” while the carrier signal is smaller than zero.

  FIG. 13 is a diagram illustrating a configuration of the synchronous detection circuit 5214 and the synchronous detection circuit 5224 in the present embodiment.

  The synchronous detection circuit 5214 includes a carrier pulse multiplier 411, a modulation pulse multiplier 421, and a low pass filter (LPF) 431.

  The detection signal input from the amplifier circuit 5213 to the carrier pulse multiplier 411 has the same waveform as the mixed signal shown in FIG.

  The carrier pulse multiplier 411 multiplies the detection signal output from the amplifier circuit 5213 by the pulse signal Dc having the carrier frequency fc.

  Thereby, the mixed signal of the carrier frequency fc having the envelope of the AC signal having the same phase as the modulation signal of the reference frequency fb among the detection signals is processed so as to have a full-wave rectified waveform on the positive (plus) side. . Then, the mixed signal of the carrier frequency fc having the inverted signal whose phase is rotated by 180 degrees with respect to the modulation signal of the reference frequency fb is processed so as to be a full-wave rectified waveform on the negative (minus) side.

  That is, when the modulation signal is larger than zero, the mixed signal is processed so as to have a full-wave rectified waveform on the positive side, and when the modulation signal is smaller than zero, the mixed signal becomes a full-wave rectified waveform on the negative side. To be processed.

  The carrier pulse multiplier 411 outputs to the modulation pulse multiplier 421 a detection signal in which a positive full-wave rectified waveform and a negative full-wave rectified waveform are alternately formed.

  The modulation pulse multiplier 421 multiplies the detection signal output from the carrier pulse multiplier 411 by the pulse signal Dm having the reference frequency fb. As a result, the negative-side full-wave rectified waveform is inverted to the positive side, so that all of the detection signals become full-wave rectified waveforms on the positive side.

  The modulation pulse multiplier 421 outputs the detection signal subjected to the full-wave rectification waveform processing to the low-pass filter 431.

  The low-pass filter 431 removes high-frequency components from the detection signal output from the modulation pulse multiplier 421. As a result, the detection signal of the full-wave rectified waveform is smoothed and converted to a DC detection signal V1. The low-pass filter 431 is realized by, for example, a circuit configuration in which an end portion of a resistance element that outputs a detection signal is grounded via a capacitor.

  The low-pass filter 431 outputs the smoothed detection signal V1 to the AC adjustment unit 540. The level of the detection signal V1 is proportional to the amplitude of the alternating current I1, and the level of the detection signal V1 increases as the amplitude value of the envelope of the alternating current I1 increases.

  FIG. 14 is a diagram illustrating a waveform of a detection signal generated in the synchronous detection circuit 5214.

  FIG. 14A shows the waveform of the pulse signal Dm having the reference frequency fb. FIG. 14B shows a waveform of the pulse signal Dc having the carrier frequency fc.

  FIG. 14C is a diagram illustrating a waveform when the detection signal of the full-wave rectified waveform output from the modulation pulse multiplier 421 is converted into the DC signal V1 by the low-pass filter 431. In each of the drawings from FIG. 14A to FIG. 14C, the vertical axis indicates the amplitude, and the horizontal axis is a common time axis.

  When the pulse signal Dm is “+1” and the pulse signal Dc is set to “+1”, the positive half-wave sine wave of the detection signal is not inverted, and the pulse signal Dc is set to “−1”. Then, the negative half-wave sine wave of the detection signal is inverted to the positive side.

  On the other hand, when the pulse signal Dm is “−1” and the pulse signal Dc is set to “+1”, the negative half-wave sine wave of the detection signal is inverted to the positive side, and the pulse signal Dc becomes “ When set to “−1”, the positive half-wave sine wave of the detection signal is not inverted.

  Thus, by multiplying the detection signal by the pulse signal Dm generated based on the reference frequency fb and the pulse signal Dc generated based on the carrier frequency fc, as shown in FIG. The detection signal is processed so as to be a full-wave rectified waveform. Then, the low-pass filter 431 smoothes the detection signal that has been processed with the full-wave rectified waveform.

  As shown in FIG. 14C, since the envelope of the detection signal has the same waveform as the full-wave rectified waveform of the modulation signal Sb (t) of the reference frequency fb, the amplitude of the modulation signal of the reference frequency fb is large. The higher the level of the smoothed detection signal V1, the higher the level.

  Thus, the synchronous detection circuit 5214 has the same frequency as the AC current I1 based on the AC signal of the reference frequency fb and the AC signal of the frequency fc higher than the reference frequency fb among the detection signals output from the amplifier circuit 5213. Extract component signals.

  Similarly to the synchronous detection circuit 5214, the synchronous detection circuit 5224 includes a carrier pulse multiplier 412, a modulation pulse multiplier 422, and a low-pass filter (LPF) 432. These configurations are the same as the carrier pulse multiplier 411, the modulation pulse multiplier 421, and the low-pass filter 431, respectively. For this reason, the synchronous detection circuit 5224 has the same frequency as the AC current I2 based on the AC signal of the reference frequency fb and the AC signal of the frequency fc higher than the reference frequency fb among the detection signals output from the amplifier circuit 5223. Extract component signals.

  Thus, even if an alternating current signal having a frequency fc higher than the reference frequency fb is synthesized with the alternating currents I1 and I2 having the reference frequency fb, the synchronous detection circuits 5214 and 5224 can detect the positive electrode side detection unit 521 and the negative electrode side detection. The detection signal output from the unit 522 can be synchronously detected.

  According to the first embodiment of the present invention, the power source means configured by the positive power source unit 531 and the negative power source unit 532 is connected to the alternating currents I1 and I2 with respect to the positive terminal 211 and the negative terminal 212 of the fuel cell stack 1. Are output respectively. And the detection means comprised by at least one among the positive electrode side detection part 521 and the negative electrode side detection part 522 is the alternating current potential difference V1 between the positive electrode terminal 211 and the halfway point terminal 213, the negative electrode terminal 212, and the halfway point terminal 213. At least one of the AC potential differences V2 is detected. The calculation means configured by the calculation unit 550 calculates the impedance of the fuel cell stack 1 based on the AC potential difference detected by the detection means and the AC current output from the power supply means.

  Further, the DC blocking means configured by the DC blocking units 511 to 513 blocks the DC signal output from the positive terminal 211, the negative terminal 212, and the midway terminal 213 of the fuel cell stack 1. The synthesizing means constituted by the AC signal source 546 is a modulation signal for the modulation signals of the AC currents I1 and I2 output to the positive terminal 211 and the negative terminal 212 of the fuel cell stack 1 through the DC blocking means. A carrier signal different from the above is synthesized.

  As a result, as shown in the equation (2), even if the capacitance C of the DC blockers 511 to 513 is reduced, the reactance (1 / 2π (fc−fb) C) can be kept low. The potential difference Vc generated at both ends can be reduced. For this reason, the size of the DC blocking units 511 to 513 can be reduced. Therefore, the impedance measuring device 5 can be reduced in size and the manufacturing cost can be suppressed.

  In the present embodiment, the AC signal source 546 has an AC signal (carrier signal) having a frequency fc higher than the frequency fb serving as a reference for the AC currents I1 and I2 with respect to the AC currents I1 and I2 output from the power supply means. Mix. Thereby, the power supply means outputs AC currents I1 and I2 in which carrier signals having a frequency fc higher than the reference frequency fb are mixed to the DC blocking units 511 to 513.

  As a result, since the alternating currents I1 and I2 have signal components having a frequency higher than the reference frequency fb, as shown in the equation (2), the voltages at the capacitors constituting the direct current blocking units 511 to 513 The drop Vc can be reduced.

  In this embodiment, the synchronous detection circuit 5214 as an extraction circuit includes an AC signal having a reference frequency fb and an AC signal having a frequency fc higher than the reference frequency fb among the detection signals V1 output from the positive electrode side detection unit 521. Based on the above, the same frequency component as the alternating current I1 is extracted.

  Thereby, it becomes possible to synchronously detect the detection signal V1 of the AC potential difference generated in the internal resistance R1 of the fuel cell stack 1 by the AC current I1 mixed with the carrier wave signal having the frequency fc higher than the reference frequency fb. Similarly, in the synchronous detection circuit 5224, the detection signal V2 can be synchronously detected based on the AC signal having the reference frequency fb and the AC signal having a frequency fc higher than the reference frequency fb.

  In the present embodiment, the AC adjustment unit 540 matches the detection signal of the AC potential difference V1 detected by the positive electrode side detection unit 521 with the detection signal of the AC potential difference V2 detected by the negative electrode side detection unit 522. The amplitude of the envelopes of the alternating currents I1 and I2 is adjusted.

  As a result, the amplitudes of the alternating currents I1 and I2 on which the carrier signal having a frequency fc higher than the reference frequency fb is superimposed are adjusted, so that the alternating potential difference V1 and the alternating potential difference V2 can be matched. For this reason, even if the internal resistances R1 and R2 of the fuel cell stack 1 fluctuate, the measurement accuracy can be maintained.

(Second Embodiment)
FIG. 15 is a diagram illustrating a configuration of an AC signal source 546 according to the second embodiment of the present invention.

  The impedance measuring device of the present embodiment has basically the same configuration as the impedance measuring device 5 shown in FIG. For this reason, about the thing with the same structure as the impedance measuring apparatus 5, the same code | symbol is attached | subjected and description here is abbreviate | omitted.

  In the present embodiment, the AC signal source 546 includes a mixing circuit 546B instead of the mixing circuit 546A illustrated in FIG. The mixing circuit 546B performs amplitude modulation (AM) processing on the alternating currents I1 and I2. The mixing circuit 546B includes an adder 5466 between the reference signal generator 5461 and the multiplier 5463.

  The adder 5466 receives a level setting voltage Vh for setting the level (amplitude) of the carrier wave signal. The adder 5466 adds the level setting voltage Vh to the modulation signal output from the reference signal generator 5461 and outputs the modulation signal added with the level setting voltage Vh to the multiplier 5463.

  Multiplier 5463 multiplies the carrier wave signal output from carrier wave signal generator 5462 by the modulation signal added with level setting voltage Vh. As a result, a mixed signal (fc−fb, fc, fc + fb) in which the carrier wave signal is amplitude-modulated is output.

  FIG. 16 is a diagram relating to the mixed signal generated in the mixing circuit 546B in the present embodiment.

  FIG. 16A is a diagram illustrating a waveform of the mixed signal Smix (t) obtained by multiplying the modulated signal added with the level setting voltage Vh and the carrier wave signal. FIG. 16B is a diagram illustrating frequency components of the mixed signal Smix (t).

  The modulation signal Sm (t) to which the level setting voltage Vh is added is expressed by the following equation.

  Further, the carrier signal Sc (t) is expressed by the equation (4) as described above.

  A mixed signal Smix (t) obtained by multiplying the carrier signal Sc (t) by the modulation signal Sm (t) is expressed by the following equation.

  As described above, the mixed signal Smix (t) includes the carrier signal frequency fc, the sum signal component of the frequency (fb + fc) obtained by adding the carrier frequency fc and the reference frequency fb, and the frequency obtained by subtracting the modulation frequency fb from the carrier frequency fc ( fc−fb) difference signal component.

  For this reason, by setting the carrier frequency fc to a value larger than twice the reference frequency fb, the DC blocking units 511 to 513 are compared with the AC currents I1 and I2 having only the reference frequency fb as in the first embodiment. Voltage drop Vc can be reduced, and capacitance C can be reduced.

(Third embodiment)
FIG. 17 is a diagram showing the configuration of the impedance measuring apparatus according to the third embodiment of the present invention.

  The impedance measurement device of this embodiment includes a voltage dividing circuit 560 in addition to the configuration of the impedance measurement device 5 shown in FIG. The midpoint DC blocking unit 513, the positive DC blocking unit 511, and the negative DC blocking unit 512 can be referred to as a first DC blocking unit, a second DC blocking unit, and a third DC blocking unit, respectively.

  The voltage dividing circuit 560 is connected between the fuel cell stack 1 and the DC blocking units 511 to 513, and divides the DC voltage Vdc generated between the positive terminal 211 and the negative terminal 212. Then, the voltage dividing circuit 560 couples the divided signals Vb1 and Vb2 obtained by dividing the DC voltage Vdc to the 0 V potential (GND_C) that is a reference for the AC currents I1 and I2.

  In the present embodiment, the voltage dividing circuit 560 is connected to the signal line 501 that connects the positive terminal 211 and the positive side DC blocking unit 511 of the fuel cell stack 1, and the signal that connects the negative terminal 212 and the negative side DC blocking unit 512. Connected to the line 502.

  The voltage dividing circuit 560 is connected to the ground line 533. The ground line 533 is grounded (GND_C) and outputs a ground signal of 0V. The ground line 533 is a common ground line used by both the positive power supply unit 531 and the negative power supply unit 532.

  For example, the DC voltage Vdc is 300V to 600V (volts). Moreover, the positive electrode side voltage Vd1 generated between the positive electrode terminal 211 and the intermediate point terminal 213 and the negative electrode side voltage generated between the negative electrode terminal 212 and the intermediate point terminal 213 are 150V to 300V.

  The voltage dividing circuit 560 includes a resistance element 561 and a resistance element 562 connected in series with each other.

  The resistance element 561 and the resistance element 562 are voltage dividing elements for dividing the DC voltage Vdc. Both the resistance element 561 and the resistance element 562 have the same resistance value, and are set to a resistance value smaller than the minimum value of the insulation resistance of the DC blocking units 511 to 513, for example, 100 MΩ (mega ohms).

  One end of the resistance element 561 is connected to the signal line 501, the other end of the resistance element 561 is connected to one end of the resistance element 562, and the other end of the resistance element 562 is connected to the signal line 502. A contact ND between the resistance element 561 and the resistance element 562 is connected to the ground line 533.

  The voltage Vb1 generated at both ends of the resistance element 561 has the same voltage value as the voltage Vb2 generated at both ends of the resistance element 562, for example, 150 to 300V.

  Therefore, a voltage that is half (1/2) of the DC voltage Vdc is applied from the fuel cell stack 1 to each of the positive side DC cutoff unit 511 and the negative side DC cutoff unit 512. Therefore, the withstand voltages of the positive side DC cutoff unit 511 and the negative side DC cutoff unit 512 can be suppressed to half of the maximum value (upper limit value) of the DC voltage Vdc output from the fuel cell stack 1.

  Further, the negative electrode side voltage Vd2 is supplied to one electrode of the midpoint DC cut-off unit 513 from the midpoint terminal 213 of the fuel cell stack 1. The other electrode is supplied with a divided voltage ((Vd1 + Vd2) / 2) obtained by dividing the DC voltage Vdc in half from the contact ND of the voltage dividing circuit 560.

  Therefore, the voltage Vb3, which is the difference between the half voltage of the DC voltage Vdc and the negative side voltage Vd2 ((Vd2−Vd1) / 2), is applied to both electrodes of the midpoint DC blocking unit 513. Become. In other words, the halfway DC cut-off unit 513 is only applied with a voltage obtained by further halving the difference between the positive side voltage Vd1 and the negative side voltage Vd2.

  For example, in the case of the fuel cell stack 1 in which the voltage Vd1 and the voltage Vd2 are maintained in substantially the same state regardless of the power generation state of the fuel cell stack 1, the voltage applied to both electrodes of the halfway DC cut-off unit 513 is almost equal. It becomes zero. In such a case, a low withstand voltage capacitor may be used or omitted as the midpoint DC blocking unit 513.

  In this way, the voltage dividing circuit 560 grounds the voltage signal Vd1 output from the positive terminal 211 via one resistance element 561 and the voltage signal Vd2 output from the negative terminal 212 via the other resistance element 562. The potentials (0 V) of the line 533 are added together (combined).

  According to the second embodiment of the present invention, the voltage dividing circuit 560 is connected between the DC blocking units 511 to 513 and the electrode terminals 211 to 213 of the fuel cell stack 1, and is connected between the positive electrode terminal 211 and the negative electrode terminal 212. The DC voltage Vdc generated between the two is divided. The voltage dividing circuit 560 couples the divided voltage signals Vb1 and Vb2 obtained by dividing the DC voltage Vdc to the ground line 533 having a potential serving as a reference for the AC currents I1 and I2.

  As a result, the voltage applied to the DC blocking units 511 and 512 from the positive terminal 211 and the negative terminal 212 is reduced, so that the withstand voltage of the DC blocking units 511 and 512 can be lowered, and the DC blocking units 511 and 512 The size can be reduced.

  In the present embodiment, the voltage dividing circuit 560 is a resistor connected in series between the positive electrode terminal 211 and the negative electrode terminal 212 as a plurality of voltage dividing elements that divide the DC voltage Vdc output from the fuel cell stack 1. An element 561 and a resistance element 562 are included. A ground line 533 is connected to a contact ND between the resistance element 561 and the resistance element 562.

  Thus, the DC voltage Vd is divided in half by the resistance elements 561 and 562, and the divided voltage signals (divided signals) Vd1 and Vd2 are coupled at the ground line 533. The applied voltage can be reduced. For this reason, since the withstand voltage of the midpoint DC cutoff unit 513 can be reduced, the size of the midpoint DC cutoff unit 513 can be reduced.

  In addition to this, the DC voltage supplied from the positive terminal 211 to the positive DC blocking unit 511 and the DC voltage supplied from the negative terminal 212 to the negative DC blocking unit 512 are both halved. The sizes of the blocking unit 511 and the negative-side DC blocking unit 512 can also be reduced.

  In the present embodiment, the resistance value of the resistance element 561 connected between the positive electrode terminal 211 and the contact point ND and the resistance value of the resistance element 562 connected between the negative electrode terminal 212 and the contact point ND are mutually different. Set to the same value. Thereby, the voltage applied to both poles of the halfway DC cut-off unit 513 can be reduced.

  In the present embodiment, the example in which the resistance elements 561 and 562 are used as the voltage dividing element that divides the DC voltage Vdc has been described, but a capacitive element or the like may be used.

(Fourth embodiment)
FIG. 18 is a diagram showing a configuration of an impedance measuring apparatus according to the fourth embodiment of the present invention.

  The impedance measuring apparatus according to the present embodiment includes a midpoint DC cutoff unit 570 and a voltage divider circuit 580 instead of the midpoint DC cutoff unit 513 and the voltage divider circuit 560 shown in FIG. The configuration other than the halfway DC blocking unit 570 and the voltage dividing circuit 580 is the same as the configuration shown in FIG.

  The midpoint DC cut-off unit 570 is a DC cut-off means that cuts off a DC signal output from the midpoint terminal 213 of the fuel cell stack 1. Midpoint DC blocking unit 570 includes a capacitor 571 and a capacitor 572.

  The capacitor 571 is a first capacitor connected to the ground line (GND_A) of the positive power supply unit 531. One electrode of the capacitor 571 is connected to the midpoint terminal 213, and the other electrode is connected to the ground line 5331.

  The ground line 5331 is a first ground line that is grounded (GND_A) so that the potential is 0 V, and is common to the ground line (GND_A) used in the positive power supply unit 531.

  The capacitor 572 is a second capacitor connected to the ground line (GND_B) of the negative power supply unit 532. One electrode of the capacitor 572 is connected to the midpoint terminal 213 together with one electrode of the capacitor 571, and the other electrode is connected to the ground line 5332 insulated from the ground line 5331.

  The ground line 5332 is a ground line that is grounded (GND_B) so that the potential becomes 0 V, and is a second ground line that is independent of the ground line 5331. The ground line 5332 is the same as the ground line (GND_B) used in the negative power supply unit 532.

  The voltage dividing circuit 580 includes resistance elements 581 to 584 connected in series. Each of the resistance elements 581 to 584 has the same resistance value as the third embodiment.

  The resistance element 581 and the resistance element 582 are connected in series between the positive electrode terminal 211 and the halfway point terminal 213 of the fuel cell stack 1, and the resistance element 583 and the resistance element 584 are halfway with the negative electrode terminal 212 of the fuel cell stack 1. A point terminal 213 is connected in series.

  One end of the resistor element 581 is connected to the signal line 501, the other end of the resistor element 581 is connected to one end of the resistor element 582, and the other end of the resistor element 582 is connected to one end of the resistor element 583. The other end of the resistance element 583 is connected to one end of the resistance element 584, and the other end of the resistance element 584 is connected to the signal line 502.

  A contact ND1 between the resistance element 581 and the resistance element 582 adjacent to each other is connected to the ground line 5331, and a contact ND2 between the resistance element 583 and the resistance element 584 adjacent to each other is connected to the ground line 5332.

  Each of voltages Vb1 to Vb4 generated in resistance elements 581 to 584 has the same voltage value. That is, the direct current voltage Vdc is equally divided into four by the resistance elements 581 to 584. For example, if the DC voltage Vdc is 600V, each of the voltages Vb1 to Vb4 is 150V.

  The positive-side DC blocking unit 511 is only applied with a voltage that is 1/4 of the DC voltage Vdc from the positive-electrode terminal 211 of the fuel cell stack 1. Also for the negative-side DC blocking unit 512, only a voltage that is ¼ of the DC voltage Vdc is applied from the negative-electrode terminal 212 of the fuel cell stack 1. Therefore, the withstand voltages of the positive side DC cutoff unit 511 and the negative side DC cutoff unit 512 can be suppressed to ¼ of the maximum value of the DC voltage Vdc.

  Further, only the voltage Vb2, which is a divided voltage ((Vd1 + Vd2) / 4) obtained by dividing the DC voltage Vdc into four, is applied to both electrodes of the capacitor 571. The voltage Vb3, which is a divided voltage ((Vd1 + Vd2) / 4) obtained by dividing the DC voltage Vdc into four equal parts, is only applied to both electrodes of the capacitor 572. Therefore, the withstand voltages of the capacitor 571 and the capacitor 572 can be suppressed to ¼ of the maximum value of the DC voltage Vdc.

  According to the fourth embodiment of the present invention, the capacitor 571 for the positive electrode side detection unit 521 and the capacitor 572 for the negative electrode side detection unit 522 are separately provided instead of the midpoint DC blocking unit 513. A ground line 5331 common to the positive power supply unit 531 is connected to the capacitor 571, and a ground line 5332 common to the negative power supply unit 532 is connected to the capacitor 572.

  In addition, among the resistance elements 581 to 584 constituting the voltage dividing circuit 580, the resistance elements 581 and 582 connected in series between the positive electrode terminal 211 and the halfway point terminal 213 are a voltage dividing element group on the positive electrode side. Used. Further, the resistance elements 583 and 584 connected in series between the negative electrode terminal 212 and the halfway terminal 213 are used as a voltage dividing element group on the negative electrode side.

  A contact point ND1 between the resistance elements 581 and 582 which is one voltage dividing element group is connected to the first ground line 5331, and a contact point ND2 between the resistance elements 581 and 582 which is the other voltage dividing element group is the second ground. Connected to line 5332.

  As a result, the potential difference generated between the two poles of the capacitors 571 and 562 constituting the positive side DC cutoff unit 511, the negative side DC cutoff unit 512, and the midpoint DC cutoff unit 570 is suppressed to a voltage value that is 1/4 of the DC voltage Vc. be able to. Therefore, it is only necessary to prepare a capacitor whose withstand voltage is ¼ of the maximum value of the DC voltage Vc, so that the sizes of the DC blocking units 511 to 513 can be reduced.

  By combining the first to fourth embodiments, the capacitance of the DC blocking units 511 to 513 can be reduced by the mixing circuit 546A that mixes the carrier current signal with the AC currents I1 and I2, and the DC blocking unit 511 is reduced by the voltage dividing circuit 560. The withstand voltage of 513 can be reduced.

  Therefore, since the sizes of the DC blocking units 511 to 513 can be reduced, the configuration of the impedance measuring device 5 can be simplified and the manufacturing cost can be suppressed.

  The embodiment of the present invention has been described above. However, the above embodiment only shows a part of application examples of the present invention, and the technical scope of the present invention is limited to the specific configuration of the above embodiment. Absent.

  In the above embodiment, the synchronous detection circuit 5214 illustrated in FIG. 4 has described the example of extracting the real axis component of the detection signal. However, the sum of the square value of the real axis component and the square value of the imaginary axis component of the detection signal is described. The vector value may be obtained by calculating the square root of and output as the detection signal V1. The imaginary axis component of the detection signal is obtained by multiplying the detection signal by an orthogonal signal whose phase is orthogonal to the alternating current I1 and smoothing the detection signal. By using the vector value, the amplitude of the AC potential difference V1 or V2 can be accurately obtained, so that equipotential control can be appropriately performed.

  In the above embodiment, the calculation unit 550 has described an example in which the internal resistance of the fuel cell stack 1 is obtained. However, in addition to the internal resistance of the fuel cell stack 1, the calculation unit 550 is an imaginary axis of the AC potential differences V1 and V2. The electrostatic capacity of the fuel cell stack 1 may be calculated by obtaining the components.

  Moreover, although the said embodiment demonstrated the example which measures the internal impedance of the fuel cell stack 1 with the impedance measuring apparatus 5, the measurement object should just be a laminated battery by which the several battery cell was laminated, for example, a laminated type The lithium ion battery may be used.

  Further, the circuit configuration of the impedance measuring device 5 may be simplified as long as the internal resistance on the positive electrode side and the negative electrode side hardly changes. For example, the AC adjustment unit 540 is omitted, and the AC currents I1 and I2 whose amplitude and phase match are fixedly output from the power supply units 531 and 532. Also, one of the detection units 521 and 522 is omitted, and an AC potential difference (for example, AC potential difference V1) detected only by the other detection unit (for example, the positive electrode side detection unit 521) and an AC current (for example, AC current) that causes the AC potential difference. The internal resistance is calculated using the current I1). Even with such a circuit configuration, the same effect as in the above embodiment can be obtained.

  Further, in the present embodiment, the halfway point terminal 213 is provided in the middle of the fuel cell stack 1, and the AC currents I1 and I2 are set so that the AC adjustment unit 540 sets the AC potential differences V1 and V2 to the same reference value Vs. An example of controlling the amplitude has been described. However, the midpoint terminal 213 may be provided in the power generation cell 10 that is out of the power generation cell 10 located in the middle of the fuel cell stack 1. In this case as well, the AC potential Va generated at the positive terminal 211 and the AC potential Vb generated at the negative terminal need only coincide with each other, so that the internal resistance R1 and the internal resistance R2 depend on the position of the power generation cell 10 provided with the halfway terminal 213. And a reference value Vs of each amplitude of the AC potential differences V1 and V2 may be set in accordance with the resistance ratio.

  In addition, the said embodiment can be combined suitably.

Claims (8)

Power supply means for outputting an alternating current to a positive electrode and a negative electrode of a laminated battery in which a plurality of battery cells are laminated;
Detecting means for detecting an AC potential difference between at least one of the AC potential difference between the positive electrode and the middle point of the laminated battery and the AC potential difference between the negative electrode and the halfway point;
Calculation means for calculating the impedance of the laminated battery based on the AC potential difference detected by the detection means and the AC current output from the power supply means;
DC blocking means for blocking a DC signal output from the laminated battery;
Synthesizing means for synthesizing different signals with respect to signals output to the laminated battery via the DC blocking means;
An impedance measuring device comprising: The impedance measuring device according to claim 1,
The synthesizing unit includes a mixing circuit that mixes an alternating current signal output from the power supply unit with an alternating current signal having a frequency higher than a frequency serving as a reference for the alternating current
The power supply means outputs an alternating current mixed with an alternating current signal having a frequency higher than the reference frequency to the direct current blocking means.
Impedance measuring device. The impedance measuring device according to claim 2,
Of the detection signals output from the detection means, the frequency component of the mixed alternating current is extracted based on the alternating current signal having the reference frequency and the alternating current signal having a frequency higher than the reference frequency. Further including an extraction circuit to
Impedance measuring device. The impedance measuring device according to any one of claims 1 to 3, wherein
The power supply so that the detection signal detected by the detecting means detects an AC potential difference between the positive electrode and the midpoint and the detection signal detected an AC potential difference between the negative electrode and the midpoint. Adjusting means for adjusting the amplitude of the envelope of the alternating current output from the means to at least one of the positive electrode and the negative electrode;
Impedance measuring device. The impedance measuring device according to any one of claims 1 to 4, wherein
The synthesizing unit includes a voltage dividing circuit that is connected between the DC blocking unit and the stacked battery and divides a DC voltage generated between the positive electrode and the negative electrode, and is an AC current output from the power source unit A voltage-divided signal obtained by dividing the DC voltage by the voltage-dividing circuit is combined with a potential signal serving as a reference for
Impedance measuring device. The impedance measuring device according to claim 5,
The power supply means includes a ground line to which the reference potential signal is supplied,
The DC blocking means is
A first DC block connected between the ground line and the midpoint;
A second DC blocking unit connected to the positive electrode;
A third DC blocking unit connected to the negative electrode,
The voltage dividing circuit has a plurality of voltage dividing elements connected in series between the positive electrode and the negative electrode,
The contact between the voltage dividing elements is connected to the ground line,
The voltage dividing circuit combines a voltage dividing signal output from the positive electrode through one voltage dividing element and a voltage dividing signal output from the negative electrode through the other voltage dividing element through the ground line. Let
Impedance measuring device. The impedance measuring device according to claim 6,
The resistance value of the voltage dividing element connected between the positive electrode and the contact point and the resistance value of the voltage dividing element connected between the negative electrode and the contact point are set to the same value.
Impedance measuring device. The impedance measuring device according to claim 6,
The ground wire is
A grounded first ground wire;
A second ground line different from the first ground line,
The first DC blocking unit is
A first capacitor connected between the first ground line and the midpoint;
A second capacitor connected between the second ground line and the halfway point;
Of the plurality of voltage dividing elements, one voltage dividing element connected in series is connected between the positive electrode and the midpoint, and the other voltage dividing element connected in series is the negative electrode and the voltage dividing element. Connected between halfway points,
A contact point between the one voltage dividing elements is connected to the first ground line,
The contact between the other voltage dividing elements is connected to the second ground line.
Impedance measuring device.

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