JP2007265895A - Characteristic measuring device and method of fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a characteristic measuring device capable of measuring stably and at high speed electric characteristics of the fuel cell. <P>SOLUTION: The characteristic measuring part includes a load control part 301 for outputting current superimposing a prescribed AC component on a prescribed DC component; and a low frequency region impedance computing part 310 for measuring each output voltage value when output current having different two values is output from the fuel cell, finding the measured variation amount ▵i of output current two values and the measured variation amount ▵v of output voltage two values, and determining a ratio ▵v/▵i in the vicinity of OHz of the fuel cell in an impedance value. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an apparatus and a method for measuring characteristics of a fuel cell that are optimum for use in measuring electrical characteristics of the fuel cell.

  One of the methods for measuring the internal loss of the fuel cell is an AC impedance method (AC method) in which the loss is replaced with an impedance. In the alternating current impedance method, an internal impedance at each frequency is measured by superimposing a small alternating current as a load on an operating fuel cell using an electronic load device or a bipolar power source and observing the battery voltage at that time. Measurements are made while changing the alternating current frequency superimposed on the battery load current, and the internal impedance of the fuel cell equivalent circuit is divided into the real part and imaginary part, and the Cole-Cole Plot (Cole-Cole Plot) The characteristics inside the battery can be grasped quantitatively.

  For example, in the apparatus described in Patent Document 1, first, AC signals of predetermined measurement frequencies F1, F2, and F3 are applied to the fuel cell to measure impedance. Resistance values are acquired for these impedances obtained on the complex plane, and further, a deterioration diagnosis element is generated from these resistance values. The deterioration diagnosis element is defined as R1, R2-R1, and R3-2R2 + R1, assuming that the resistance values for the frequencies F1, F2, and F3 are R1, R2, and R3, respectively. The deterioration of the fuel cell is diagnosed by comparing it with the value of the deterioration diagnosis element obtained in (1).

Here, referring to FIG. 7, a conventional method for measuring the impedance of a fuel cell will be described in detail. In the conventional impedance measurement of a fuel cell, a direct current value Idc obtained by superimposing an alternating current of amplitude Iac and frequency f is applied to the fuel cell, and the frequency response (gain) of the terminal voltage of the fuel cell at that time is applied. , Phase). The impedance was measured sequentially while changing the frequency, and the response characteristic of the fuel cell terminal voltage with respect to the frequency of the superimposed alternating current was measured. Further, fitting to a fuel cell equivalent circuit model is performed from the response characteristics of the fuel cell terminal voltage, and the fuel cell is modeled with an equivalent circuit.
JP 2005-285614 A

  When measuring the above frequency characteristics, generally the response of the fuel cell terminal voltage is measured while decreasing the frequency from the high frequency to the low frequency direction, but in order to fit the equivalent circuit model, It is necessary to measure the response at a very low speed, for example, 1 Hz or less so that the capacitor component can be ignored. In this low frequency range, it may be close to the frequency band of the generated water generated by the power generation of the fuel cell, the gas flow path clogged by the generated water and the increase in pressure loss, temporary fuel shortage, oxidant shortage, etc. As a result, the terminal voltage becomes unstable, and as a result, errors and variations in impedance measurement increase and reproducibility also deteriorates. For this reason, in the equivalent circuit of the fuel cell, the accuracy of fitting of the DC resistance arranged in parallel with the capacitor has been lowered.

  Further, even if there is no power generation unstable element due to the generated water, it takes a very long test time to obtain the response characteristics up to a frequency of 1 Hz or less.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a fuel cell characteristic measuring apparatus and method capable of stably measuring the electric characteristics of a fuel cell at high speed. More specifically, a low-frequency impedance characteristic in impedance measurement, that is, a fuel that can ignore the capacitor component in the equivalent circuit, and can quickly and stably acquire the impedance characteristic in a region considered to be only DC resistance. An object of the present invention is to provide a battery characteristic measuring apparatus and method.

  In order to solve the above-mentioned problems, the invention according to claim 1 is an apparatus for measuring characteristics of a fuel cell, wherein a load control means for outputting a current obtained by superimposing a predetermined alternating current component on a predetermined direct current from the fuel cell; Measuring means for measuring each output voltage value when different binary output currents are output from the battery, and determining the measured output current binary change amount Δi and output voltage binary change amount Δv, and dividing them And determining means for determining the value Δv / Δi to be an impedance value in the vicinity of 0 Hz of the fuel cell.

  The invention according to claim 2 further includes impedance measuring means for measuring the impedance value of the fuel cell while changing the frequency of the superimposed alternating current component, and a predetermined value corresponding to the fuel cell based on the measured impedance value. Arithmetic means for obtaining a circuit constant of an equivalent circuit, in which the real part Z ′ of the impedance is the absolute value | Δv / Δi | of the division value and the imaginary part Z ″ is 0 as the impedance value in the vicinity of 0 Hz. The constraint condition is applied.

  According to a third aspect of the present invention, the impedance measuring means measures impedance while changing the frequency of the alternating current component from higher to lower, and the computing means is a circuit of an equivalent circuit every time the impedance value is measured. The calculation for obtaining the constant is performed, and further, it is determined whether or not the change amount of the equivalent circuit constant obtained by the calculation means is equal to or less than the set value. And determining means for determining circuit constants.

  According to a fourth aspect of the present invention, the amount of change in the equivalent circuit constant does not become a set value or less even when the determination means falls below a predetermined frequency, or the amount of change in the equivalent circuit constant tends to increase. If detected, the fact is output.

  According to a fifth aspect of the present invention, there is provided a method for measuring characteristics of a fuel cell, wherein a load control process for outputting a current obtained by superimposing a predetermined alternating current component on a predetermined direct current from the fuel cell, and different binary outputs from the fuel cell. A measurement process for measuring each output voltage value when the current is output, a change amount Δi of the measured output current binary value and a change amount Δv of the output voltage binary value are obtained, and the divided value Δv / Δi is calculated as And a determination process for determining an impedance value in the vicinity of 0 Hz of the fuel cell.

  According to a sixth aspect of the present invention, there is provided an apparatus for measuring characteristics of a fuel cell, which measures or calculates an open circuit voltage under the test conditions before measuring AC impedance, and measures current-voltage characteristics; Means for differentiating the current-voltage characteristic subtracted from the voltage with respect to the current change, and means for determining the result as an impedance value in the vicinity of 0 Hz of the fuel cell at the current value for impedance measurement. It is characterized by that.

  According to a seventh aspect of the present invention, there is provided a method for measuring characteristics of a fuel cell, in which an open circuit voltage is measured or calculated under the test conditions before measuring an AC impedance, and a current-voltage characteristic is measured. A process of differentiating a current-voltage characteristic subtracted from a voltage with respect to a current change, and a process of determining the result as an impedance value in the vicinity of 0 Hz of the fuel cell at a current value for impedance measurement. It is characterized by being.

  According to the present invention, it is not necessary to measure responsiveness to an AC signal in the vicinity of a frequency f≈0 Hz (low frequency region), and impedance characteristics can be measured using only a DC component, so that the measurement speed can be increased. In addition, since it is not necessary to measure the response to an AC signal, it is caused by a shortage of fuel gas or a shortage of oxidizing gas due to temporary blockage due to water generated by power generation of the fuel cell or an increase in pressure loss. It is possible to perform measurement without removing instability of fuel cell terminal voltage (variation in impedance measurement, cause of decrease in reproducibility). In other words, according to the present invention, low frequency impedance characteristics in impedance measurement, that is, capacitor components in the equivalent circuit can be ignored, and impedance characteristics in a region considered to be only DC resistance can be obtained quickly and stably. it can.

  Embodiments of a fuel cell characteristic measuring apparatus according to the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of the present embodiment. In FIG. 1, the fuel gas and oxidant gas supply and discharge systems for the fuel cell 100 are not shown.

  The characteristic measuring apparatus according to the present embodiment includes a fuel cell 100, an electronic load apparatus 200, and an impedance measuring instrument 300. The impedance measuring device 300 includes a storage device such as a CPU (Central Processing Unit), RAM, ROM, flash memory, and hard disk, and various input / output interfaces, and executes a predetermined program recorded in the flash memory or the like. Thus, control of each part and input / output of signals to / from an external device are performed. The fuel cell 100, the electronic load device 200, and the current measuring unit 302 are electrically connected in series by the connection 11. The voltage measuring unit 303 is connected in parallel to the fuel cell 100 by the connection 12 and measures the voltage at both ends (terminal voltage). The electronic load control unit 301 instructs / sets the direct current value and the amplitude and frequency of the superimposed alternating current to the electronic load device 200 to control the load on the fuel cell 100.

  In the impedance measuring instrument 300, the impedance measurement is performed by two different methods divided into a low frequency region and a high frequency region. In the low frequency region (frequency f≈0 Hz), first, the electronic load controller 200 is controlled by the electronic load control unit 301, and a current obtained by superimposing a predetermined AC component on a predetermined DC current Idc is supplied to the fuel cell 100 as a load current. The AC waveform measured by the current measuring unit 302 and the voltage measuring unit 303 is taken into the low frequency region impedance calculating unit 310. Next, the low frequency region impedance calculation unit 310 obtains each output voltage value when different binary output currents are output from the fuel cell 100 from the captured AC waveform, and changes in the obtained output current binary values. The division value Δv / Δi is obtained from the amount (deviation) Δi and the change amount (deviation) Δv of the output voltage binary value, and determined as the impedance value near the frequency 0 Hz of the fuel cell 100.

  Here, the impedance measurement in the low frequency region (frequency f≈0 Hz) will be described in detail with reference to FIG. FIG. 2 shows a current-voltage characteristic (broken line) of the fuel cell. In the present embodiment, impedance measurement in the low frequency region (frequency f≈0 Hz) is not obtained by measuring a voltage change with respect to a very slow current change, but Δi and Δv in the vicinity of a predetermined current Idc. It is obtained from the division value Δv / Δi. Actually, for example, the terminal voltage (V−) of the fuel cell at Idc−Iac and the terminal voltage (V +) at Idc + Iac are measured using the superimposed alternating current amplitude Iac in the impedance measurement as described with reference to FIG. The real part Z ′ and the imaginary part Z ″ of the impedance are determined by the following equations.

  On the other hand, the impedance in the high frequency region is measured by applying a load in which an alternating current is superimposed on the output current of the fuel cell 100 by the electronic load device 200 while changing the frequency, and at that time, the current measuring unit 302 and the voltage measuring unit The AC waveform measured at 303 is taken into the impedance measuring unit 304, and the gain and phase at the frequency f are obtained in the form of the response of the AC component of the voltage to the AC component of the current. At the time of impedance measurement in the high frequency region, the electronic load control unit 301 issues an instruction to discretely change the frequency with a plurality of predetermined values from a high frequency to a low frequency, and the impedance measurement unit 304 The measurement waveform of current and voltage is taken in at each frequency, and the impedance is obtained by calculation using Fourier calculation or the like. The alternating current impedance characteristic of the fuel cell 100 can be obtained by measuring the gain and phase sequentially by changing the frequency f. FIG. 3 shows an example of the measurement result obtained by expressing the obtained gain and phase results on a complex plane. In FIG. 3, circles (◯) indicate measurement values obtained by the impedance measurement technique in the high frequency region. In addition, the value indicated by an asterisk (*) is calculated by the impedance measurement method in the low frequency region.

  On the other hand, the equivalent circuit fitting unit 305 determines in advance based on a plurality of measurement results measured in the past when the set frequency is equal to or lower than the predetermined frequency fs in the measurement of impedance in the high frequency region. An operation for obtaining a circuit constant of a predetermined equivalent circuit is performed. At this time, the equivalent circuit fitting unit 305 sets the real part Z ′ of the impedance as the impedance value near the frequency of 0 Hz as the absolute value | Δv / Δi | of the division value determined by the low frequency region impedance calculation unit 310, and the imaginary number. The constraint condition where the part Z ″ is 0 is applied. That is, in the example shown in FIG. 3, a plurality of measured values (circles) in the high frequency region and calculated values (stars) in the low frequency region. Based on both, an arithmetic process for obtaining each circuit constant of the equivalent circuit is performed.

  FIG. 4 shows an example of an equivalent circuit of the fuel cell used in the present embodiment. The resistance Rm corresponds to the solution resistance, Ca and Cc correspond to the electric double layer capacitance, and Ra and Rc correspond to the reaction resistance, respectively. However, the equivalent circuit shown in FIG. 4 is an example of an equivalent circuit of a fuel cell, and the configuration of the equivalent circuit is not limited to this, and may be more complicated or simpler. In this case, the equivalent circuit fitting unit 305 generates an error between the impedance calculation result obtained from the model equation representing the equivalent circuit as shown in FIG. 4 and the impedance measurement value based on the plurality of measurement values of the impedance measurement result. Arithmetic processing for obtaining each circuit constant of the equivalent circuit is performed so as to be minimized. For example, a known method such as a least square method can be used.

  Whether the difference (amount of change in circuit constant) of the plurality of circuit constants obtained by the equivalent circuit fitting unit 305 is equal to or less than a predetermined set value based on a plurality of different measurement results by the impedance measurement unit 304. Determine whether or not. For example, each constant Rm, Ca, Cc, Ra, Rc is estimated based on a plurality of measurement results including a value estimated based on a plurality of previous measurement results and the latest measurement result. The difference between the two values is obtained, and it is determined whether or not the difference is not more than a predetermined value (for example, 0.01 mΩ or 0.1 F). Furthermore, when the determination result is equal to or less than the set value, the determination unit 306 outputs an instruction to end the impedance measurement and uses the latest measurement result (measurement result at the lowest frequency). A process for determining the final value of the measurement result is performed on the obtained circuit constant. The result is output to a predetermined output device (not shown).

  As shown in FIG. 3, the electronic load control unit 301 determines the direct current of the fuel cell 100 while decreasing the frequency in a predetermined step from a value close to infinity (∞) (actually, for example, 10 kHz). Current control is performed such that an alternating current component is superimposed on the output current, and the impedance measurement unit 304 measures impedance at each frequency. Then, when the frequency for the alternating current becomes equal to or less than the set value fs, the equivalent circuit fitting unit 304 starts an operation for obtaining the circuit constant of the equivalent circuit. After the equivalent circuit fitting unit 304 starts the calculation, the determination unit 306 starts determining the difference between the circuit constants, and measures each component such as the electronic load control unit 301 when the difference becomes a predetermined value or less. Outputs an instruction to end the process.

  Next, the processing of the impedance measuring device 300 of FIG. 1 will be described in detail with reference to FIG. In this example, values of a plurality of predetermined measurement frequencies are set in advance at frequencies f (i) (i = 0, 1, 2,...), And an equivalent circuit of the fuel cell 100 is shown in FIG. Assume that a model composed of a plurality of constants Rm, Ca, Cc, Ra, Rc is used. Further, it is assumed that the value Idc of the DC output current of the fuel cell 100 is set in another routine not shown.

  Assuming that a predetermined operator (not shown) is operated by the operator, the impedance measuring device 300 controls the direct current Idc to superimpose a predetermined amplitude Iac and an alternating current of the frequency as a load of the fuel cell 100. And the terminal voltage (V−) of the fuel cell at Idc−Iac and the terminal voltage (V +) at Idc + Iac are measured, and the real part Z ′ and the imaginary part Z ″ of the impedance are determined by the above formula (step S00). .

  Next, the impedance measuring device 300 initializes the frequency setting counter i and the fitting number counter j (i = 0, j = 0), and starts the measurement process (step S000). The impedance measuring device 300 measures the impedance of the target fuel cell 100 at the frequency f (i), and acquires the real part Z ′ (i) and the imaginary part Z ″ (i) of the impedance (step S001).

  Next, an equivalent circuit fitting start determination is performed (step S002). If the set frequency f (i) is equal to or lower than the predetermined frequency fs, the value calculated in step S00 and the measurement so far in step S001 are measured. Based on the measured value, fitting to the equivalent circuit model is performed (step S003). Otherwise, the counter i is incremented (i = i + 1), and impedance measurement is performed at the next set frequency (step). From S0021 to step S001).

  In step S003, the result of fitting to the equivalent circuit model is stored in the variable Res (j) (step S004). The variable Res (j) is a multidimensional array variable whose elements are estimated values Rm, Ra, Ca, Rc, and Cc of circuit constants obtained from a plurality of measurement results.

  Next, it is determined whether or not the fitting constant difference determination is started (step S005). When the counter j is larger than 1, an operation for comparing the fitting result is performed (step S006). In this case, the counter j is incremented (step S0051), and the processes of steps S0021 and steps S001 to S005 are repeated.

  In step S006, the difference between the fitting results Res (j) and Res (j-1) in the counters j and j-1 is obtained for comparison of the fitting results. Next, as a difference determination of the fitting result Res (j), the difference (variation amount) of each element (each circuit constant Rm, Ra, Ca, Rc, Cc) obtained in step S006 is equal to or less than a predetermined set value. Is determined (step S007). If the difference between the elements is equal to or less than the set value, the process of determining the fitting result Res (j) as an equivalent circuit model constant at the current value Idc is performed (step S008). If the difference value exceeds the set value, the counter j is incremented in step S0051, the counter i is incremented in step S0021, and impedance measurement, fitting, and determination processing of the result are performed at another frequency f (i). Is performed (steps S001 to S007).

  In the present embodiment, when the frequency becomes equal to or lower than the predetermined frequency fs, first, the circuit constant is obtained by fitting the AC impedance data up to the predetermined frequency fs to the equivalent circuit model, and thereafter the frequency is measured every time the frequency measurement is completed. Fitting is performed from the previous AC impedance data, and when the amount of change is below the set value, the circuit constant is determined and the measurement is terminated. According to this, since the measurement in the relatively low frequency region can be omitted in the impedance measurement in the high frequency region, the number of times of measurement is reduced, and further due to the electrochemical reaction in the measurement in the relatively low frequency region. It can be expected to reduce the influence of measurement variations. Furthermore, since the circuit constant is determined when the difference in the fitting result to the equivalent circuit model becomes equal to or less than a predetermined setting, it can be expected that the decrease in accuracy due to the reduction in the number of measurements can be suppressed to a certain range. That is, according to the present embodiment, it is possible to perform high-accuracy and short-time measurement, and it is possible to perform fuel cell characteristic measurement that eliminates the influence of measurement water on measurement variation. .

  As described above, according to the present embodiment, it is not necessary to measure responsiveness to an AC signal in a low frequency region (near f≈0 Hz), and impedance characteristics can be measured using only a DC component. High speed is possible. Also, fuel cell terminal voltage instability due to shortage of fuel gas due to temporary blockage of water generated by fuel cell power generation or increase in pressure loss, or instability of fuel cell terminal voltage due to lack of oxidizing gas (variation in impedance measurement). It is possible to measure without removing the reproducibility factor).

  As described above, in the present embodiment, at the beginning of the measurement of the impedance characteristics of the fuel cell, impedance measurement is performed at a low frequency (f≈0 Hz), and then impedance measurement is performed while changing the frequency (from a high frequency). To low frequency). Further, when entering a relatively low frequency region (designated before measurement) below the frequency fs, fitting to an equivalent circuit model is performed every time an impedance measurement result is obtained. At that time, if the constraint is applied with the value measured first as the real part Z ′ of the impedance at low frequency (f≈0 Hz) and the change in the constant of the equivalent circuit model is less than or equal to the set value, the convergence of the constant Judge and finish impedance measurement. According to this, it is not necessary to perform impedance measurement until the end of the low frequency and perform fitting to the equivalent circuit. It is possible to remove measurement variations and reproducibility degradation in the low frequency region due to the generated water.

  In the above configuration, the determination unit 306 in FIG. 1 does not reduce the amount of change in the equivalent circuit constant below the predetermined set value even when the frequency is equal to or lower than a predetermined frequency set in advance. When it is detected that there is an increasing trend, it is possible to add a function that outputs that fact. That is, in the fitting with the constraint condition of low frequency (f≈0), when the circuit constant does not converge or diverges, there is a problem such as flooding due to generated water. It is possible to perform a process such as displaying a message to that effect or automatically stopping the measurement. In this way, impedance measurement under environmental conditions that cause flooding or the like is eliminated.

  Next, another embodiment of the present invention will be described with reference to FIG. In the present embodiment, an impedance value in a low frequency region (f≈0) is calculated using a configuration similar to that in FIG.

  In the present embodiment, first, before measuring AC impedance, open circuit voltage Voc (dashed line) under the test conditions (environmental conditions where impedance measurement such as temperature, pressure, humidity, etc. is desired) is measured or calculated, Current-voltage characteristics (solid line) as shown in FIG. 6 are measured.

  Next, based on the equation (Equation (1)) representing the relationship between the resistance value R (i) of the fuel cell 100 and the voltage value Vx in consideration of the current dependency in the low frequency region (f≈0). A value obtained by subtracting the voltage Vx at each current obtained by measuring the current-voltage characteristic from the circuit voltage Voc is differentiated with respect to the current value Ix (formula (2)), and the result R (i) is obtained. The real part Z ′ of the impedance at a low frequency (f≈0) is assumed.

  Also in the present embodiment, the obtained impedance value is used as a constraint condition at the time of fitting, as in the above-described embodiment.

  That is, in the present embodiment, before the AC impedance is measured, the open circuit voltage under the test conditions (temperature, pressure, humidity, etc.) is measured or calculated, and the current-voltage characteristics are measured. And what subtracted the current-voltage characteristic from the open circuit voltage is differentiated with respect to the current change. The result is determined as the impedance value near 0 Hz of the fuel cell at the current value Ix for impedance measurement. This impedance value can be used as a constraint condition on the low frequency side at the current value for impedance measurement.

  According to this embodiment, the measurement in the low frequency region (f≈0) can be omitted as in the above-described embodiment, so that the effect of speeding up and stabilizing the measurement can be expected. In the current-voltage characteristic measurement, if the current pitch is made small, it is considered that the accuracy is improved as compared with the case where the voltage change Δv in the vicinity of the direct current Idc is set linear in the above embodiment. .

  The embodiment of the present invention is not limited to the above-described embodiment, and further modifications can be made. For example, in the determination process in step S007 of FIG. 4, it is possible to limit all circuit constants to specific circuit constants instead of performing comparison. When a difference (change amount) between specific circuit constants (for example, Ra alone or Rc alone) is within a predetermined range, all circuit constants are determined based on the values at that time.

  Moreover, the structure of this invention can be considered as what includes each structure shown in FIG. 1, what consists of structures other than the fuel cell 100, what consists only of the impedance measuring device 300, etc. FIG. Further, in the impedance measuring instrument 300, for example, the current measuring unit 302 and the voltage measuring unit 303 are constituted by general-purpose measuring instruments, and the electronic load control unit 301, the impedance measuring unit 304, the equivalent circuit fitting unit 305, the determining unit 306, and the low The frequency domain impedance calculation unit 310 can also be configured using a general-purpose computer. In this case, the configuration of the present invention includes an electronic load control unit 301, an impedance measurement unit 304, an equivalent circuit fitting unit 305, and a determination unit. 306 and the low frequency region impedance calculation unit 310, and the electronic load control unit 301, the impedance measurement unit 304, the equivalent circuit fitting unit 305, the determination unit 306, and the low frequency region impedance calculation unit 310. Functions Realized by a program, it is possible to sell the software program for realizing it as product. At that time, the program can be recorded on a computer-readable recording medium or distributed via a communication line.

The block diagram of embodiment of the characteristic measuring apparatus of the fuel cell of this invention. FIG. 2 is a current-voltage characteristic diagram used for explaining an example of an impedance measurement method having the configuration of FIG. 1. The complex top view for demonstrating an example of the impedance measurement method by the structure of FIG. The figure which shows an example of the equivalent circuit model of a fuel cell. The flowchart for demonstrating the function of FIG. The current-voltage characteristic view used in order to explain other embodiments of the fuel cell characteristic measuring device of the present invention. The figure for demonstrating the alternating current impedance measurement method of a fuel cell.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 ... Fuel cell, 200 ... Electronic load apparatus, 300 ... Impedance measuring device, 301 ... Electronic load control part (load control means), 302 ... Current measurement part (measurement means), 303 ... Voltage measurement part (measurement means), 304 ... impedance measurement unit (impedance measurement unit), 305 ... equivalent circuit fitting unit (calculation unit), 306 ... determination unit (determination unit), 310 ... low frequency region impedance calculation unit (measurement unit, determination unit)

Claims (7)

In an apparatus for measuring the characteristics of a fuel cell,
Load control means for outputting a current in which a predetermined alternating current component is superimposed on a predetermined direct current from the fuel cell;
Measuring means for measuring each output voltage value when different binary output currents are output from the fuel cell;
Determining means for obtaining a measured change amount Δi of the output current binary value and a change amount Δv of the output voltage binary value, and determining the divided value Δv / Δi as an impedance value in the vicinity of 0 Hz of the fuel cell; An apparatus for measuring the characteristics of a fuel cell. Furthermore, impedance measuring means for measuring the impedance value of the fuel cell while changing the frequency of the superimposed alternating current component;
Calculating means for obtaining a circuit constant of a predetermined equivalent circuit corresponding to the fuel cell based on the measured impedance value;
In the calculation means, as an impedance value in the vicinity of 0 Hz, a constraint condition is applied in which the real part Z ′ of impedance is the absolute value | Δv / Δi | of the division value and the imaginary part Z ″ is 0. Item 2. The fuel cell characteristic measuring device according to Item 1. The impedance measuring means measures impedance while changing the frequency of the AC component from high to low,
The calculation means performs a calculation to obtain a circuit constant of an equivalent circuit every time the impedance value is measured,
Further, it is determined whether or not the change amount of the equivalent circuit constant obtained by the calculation means is equal to or less than a set value, and when it is equal to or less than the set value, the impedance measurement is ended and the circuit constant is determined. The fuel cell characteristic measuring device according to claim 2, further comprising: means. If the determination means detects that the amount of change in the equivalent circuit constant does not become a set value or less even when the frequency falls below a predetermined frequency or that the amount of change in the equivalent circuit constant tends to increase. The fuel cell characteristic measuring device according to claim 3, wherein: In a method for measuring the characteristics of a fuel cell,
A load control process for outputting a current in which a predetermined AC component is superimposed on a predetermined DC current from the fuel cell;
A measurement process for measuring each output voltage value when different binary output currents are output from the fuel cell;
And determining a measured change amount Δi of the output current binary value and a change amount Δv of the output voltage binary value, and determining the divided value Δv / Δi as an impedance value in the vicinity of 0 Hz of the fuel cell. A method for measuring characteristics of a fuel cell. In an apparatus for measuring the characteristics of a fuel cell,
Means for measuring or calculating an open circuit voltage under the test conditions before measuring the AC impedance, and measuring a current-voltage characteristic;
Means for differentiating current-voltage characteristics from open circuit voltage with respect to current change;
And a means for determining the result as an impedance value in the vicinity of 0 Hz of the fuel cell at a current value for impedance measurement. In a method for measuring the characteristics of a fuel cell,
Measuring or calculating an open circuit voltage under the test conditions before measuring AC impedance, and measuring a current-voltage characteristic;
Differentiating the current-voltage characteristics from the open circuit voltage with respect to the current change,
And a step of determining the result as an impedance value in the vicinity of 0 Hz of the fuel cell at a current value for impedance measurement.

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