Electrochemical impedance spectroscopy measurement system for fuel cells and related measurement method

Abstract

The invention relates to an electrochemical impedance spectroscopy measurement system for a fuel cell, the measurement system being electrically connected to the fuel cell and comprising a fuel cell perturbation source that applies an alternating perturbation electrical signal to the fuel cell; a current sensing unit that senses an output current signal of the fuel cell; the blocking filter is connected to the current sensing unit and filters a direct current signal in the output current signal to obtain an alternating current component signal; a voltage sensing unit that senses an AC voltage signal of the fuel cell; and an electrochemical impedance spectroscopy analysis unit that calculates and analyzes an electrochemical impedance spectroscopy of the fuel cell based on the AC current component signal and the AC voltage signal. The invention also relates to an associated electrochemical impedance spectroscopy measurement method. By means of the electrochemical impedance spectroscopy measurement method and the related measurement system, the precision of ADC sampling when electrochemical impedance spectroscopy measurement is carried out on the fuel cell can be improved, and meanwhile the real-time performance and efficiency of ADC sampling are ensured.

Description

TECHNICAL FIELD

[0001] The present application relates generally to an electrochemical impedance spectroscopy measurement system for a fuel cell and a related measurement method. BACKGROUND

[0002] Fuel cells are a green and environmentally friendly new technology and are a research hotspot in the field of new energy today. Hydrogen fuel cells or other proton exchange membrane fuel cells are gradually becoming important as an important technical direction for new energy vehicles. Since the internal resistance comprehensively reflects the internal humidity, temperature, and health status of a hydrogen fuel cell, real-time monitoring of the internal resistance of a fuel cell is of great significance to ensure the safe and efficient operation of a hydrogen fuel cell. However, a hydrogen fuel cell is a nonlinear and time-varying system, and it is generally difficult to accurately measure the impedance parameters of the battery. In addition, the internal impedance of the battery is usually in the order of milliohms, which increases the difficulty of measuring the accuracy of the battery. In order to realize the detection of the internal resistance, the electrochemical (alternating current) impedance spectroscopy method is currently known, which uses a small amplitude current to perturb the fuel cell and test the internal resistance of the fuel cell to obtain impedance data.

[0003] Therefore, in order to implement the electrochemical impedance spectroscopy method, a sensing device is usually required to measure the response current and voltage caused by the fuel cell and use it for subsequent sampling such as ADC (analog-to-digital converter) sampling to analyze the obtained data, so as to obtain the impedance spectrum to analyze the internal situation of the battery. As mentioned above, the perturbation amplitude is very small, for example, it is usually only a small part of the direct current part (the direct current voltage and / or current generated by the battery itself), which is generally less than five percent of the direct current part, so it will limit the accuracy of subsequent sampling or measurement, especially ADC sampling, thereby increasing the error in the analysis process of the electrochemical impedance spectrum of the fuel cell.

[0004] For example, since the voltage selection of the ADC sampling chip port is 0-5Vdc (direct current voltage) and the current of the fuel cell can reach or exceed 600A. In this case, in order to ensure the operation of the ADC sampling chip, it is usually necessary to ensure that the port voltage ratio is at least 350V / A, so that for an alternating current with an amplitude of 5A, the alternating voltage signal amplitude is usually 14.28mV (taking the port voltage ratio as 350V / A). For a 12-bit ADC sampling chip, the quantization error is usually 0.6mV, resulting in a sampling error of no less than 4.2%. SUMMARY

[0005] The present application relates to an electrochemical impedance spectroscopy measurement system for a fuel cell, wherein the measurement system is electrically connected to the fuel cell and comprises: a fuel cell perturbation source configured to apply an alternating current perturbation electrical signal of a certain frequency to the fuel cell; a current sensing unit configured to sense an output current signal of the fuel cell; a DC blocking filter connected to the current sensing unit and configured to filter out a direct current signal in the output current signal sensed by the current sensing unit to obtain an alternating current component signal; a voltage sensing unit configured to sense an alternating current voltage signal of the fuel cell; and an electrochemical impedance spectroscopy analysis unit configured to calculate and analyze an electrochemical impedance spectroscopy of the fuel cell based on the alternating current component signal and the alternating current voltage signal.

[0006] The present application also relates to an electrochemical impedance spectroscopy measurement method for a fuel cell, wherein the method comprises: applying an alternating current perturbation electrical signal of a certain frequency to the fuel cell; sensing an output current signal of the fuel cell; filtering the sensed output current signal to filter out a component of a direct current signal therein to obtain an alternating current component signal; measuring an alternating current voltage signal of a voltage of the fuel cell; and performing an electrochemical impedance spectroscopy analysis on the fuel cell based at least in part on the alternating current component signal and the alternating current voltage signal to obtain an electrochemical impedance spectroscopy of the fuel cell.

[0007] By means of the electrochemical impedance spectroscopy measurement method for a fuel cell and the related measurement system of the present application, the accuracy of ADC sampling when performing electrochemical impedance spectroscopy measurement on a fuel cell can be improved, while ensuring the real-time and efficiency of ADC sampling. Furthermore, by means of the electrochemical impedance spectroscopy measurement method for a fuel cell and the related measurement system of the present application, error correction for current and / or voltage sensing can be implemented, thereby helping to improve the additional accuracy of ADC sampling. Further, simple improvements based on existing devices can also be implemented to achieve such accuracy improvement. BRIEF DESCRIPTION OF DRAWINGS

[0008] Other advantages and aspects of the present application will become more apparent upon consideration of the following detailed description, taken in conjunction with the accompanying drawings, in which:

[0009] Figure 1 An electrochemical impedance spectroscopy measurement system for a fuel cell is shown, according to one embodiment of the underlying application; and

[0010] Figure 2 A detailed schematic diagram of a current measurement branch of an electrochemical impedance spectroscopy measurement system for a fuel cell is shown, according to one embodiment of the underlying application; and

[0011] Figures 3A-3C A flowchart of an electrochemical impedance spectroscopy measurement method for a fuel cell is shown, according to different embodiments of the present application. DETAILED DESCRIPTION

[0012] In the context of the present application, identical reference signs designate identical or similar elements, parts or steps.

[0013] Figure 1 An electrochemical impedance spectroscopy measurement system for a fuel cell of one embodiment of the parent application is shown and Figure 2 A part of an electrochemical impedance spectroscopy measurement system for a fuel cell of an embodiment of the present application, in particular the current sensing branch, is shown, namely Figure 1 An additional possible detailed circuit schematic of the part shown in dashed box in Fig. 1. In this embodiment, the measurement object for which the measurement system is used, namely the fuel cell, is shown. It should be understood by the skilled person that although the measurement system is shown here to be used for a fuel cell, it should be understood that the measurement system can be used for one or more stacks in a fuel cell or can be used for more than one fuel cell or any other appropriate power source.

[0014] In the embodiment of Fig. 1, Figure 1 The measurement system 1 comprises a fuel cell perturbation source 10 configured to apply an alternating current perturbation electrical signal, such as an alternating current perturbation, to the fuel cell 20. The purpose of the perturbation electrical signal, such as the alternating current perturbation, is to enable the electrochemical impedance of the fuel cell to be detected or calculated. As will be understood by the skilled person, in the case of a perturbation alternating current, its amplitude is typically significantly smaller than the current output of the fuel cell. The purpose of this choice is to not unduly cause variations in the physical environment inside the fuel cell, such as temperature, etc. to ensure the accuracy of the impedance spectroscopy measurement as much as possible. Furthermore, it is noted that in the embodiments of the present application, in order to ensure the accuracy of the calculation of the electrochemical impedance, in the embodiments of the present application, a set of alternating current perturbation electrical signals, for example perturbation alternating currents, having different frequencies can be applied to the fuel cell and electrochemical impedance spectroscopy analysis is respectively performed based on the set of perturbation currents, thereby obtaining a more accurate final electrochemical impedance spectroscopy. Of course, it is envisaged that, for example, in the embodiments of the present application, the measurement system 1 comprises a plurality of fuel cell perturbation sources 10 to respectively apply a set of perturbation alternating currents having different frequencies to the fuel cell and electrochemical impedance spectroscopy analysis is respectively performed based on the set of perturbation currents. It is also envisaged that the measurement system 1 comprises a single fuel cell perturbation source 10 configured to apply a set of perturbation alternating currents having different frequencies in a time sequence and electrochemical impedance spectroscopy analysis is respectively performed based on the set of perturbation currents. It is also envisaged that the set of alternating current perturbation electrical signals having different frequencies can have the same amplitude. Of course, for specific cases, it is envisaged that the set of alternating current perturbation electrical signals having different frequencies can have different amplitudes.

[0015] Further, in the embodiment of Fig. 1, Figure 1In the embodiment of Fig. 1, the measurement system 1 further comprises a current sensing unit 12 configured to sense an output current signal of the fuel cell 20. Obviously, the output current comprises an alternating current component signal Iac (as will be described later) excited by a perturbation signal such as an alternating current perturbation. As an example, the sensing of the current of the fuel cell can be implemented by means of a sensing coil, which technique is well known to the skilled person and thus will not be described in more detail here. For the sake of completeness of the present application, the principle of a sensing coil known from the prior art will be described briefly here: the output line of the fuel cell passes through the center of the sensing coil, so that the sensing coil is in the electric field generated by the wire and the center of the coil substantially coincides with the center of the electric field. Thus, the sensing coil is able to generate different electric potentials based on the strength of the electric field caused by the current, so that the amplitude of the current can be expressed by means of this electric potential. Of course, the method of current sensing by means of a sensing coil is merely exemplary and not limiting. The skilled person is able to think of any known or future known technique for sensing the current of a fuel cell without departing from the scope of the present application.

[0016] Further, in the embodiment of Fig. 1, the measurement system 1 further comprises a voltage sensing unit 13 configured to sense an output voltage signal of the fuel cell 20. The output voltage signal of the fuel cell 20 is a DC voltage signal, which is the voltage across the fuel cell 20 when no perturbation signal is applied to the fuel cell 20. The output voltage signal of the fuel cell 20 is a measure of the fuel cell's 20 output power. The output voltage signal of the fuel cell 20 is a measure of the fuel cell's 20 output power. Figure 1In the embodiment of figure 1, the measuring system 1 further comprises a DC blocking filter 14 connected, in particular in series, to the current sensing unit 12 to filter out the direct current signal from the sensed current signal sensed by the current sensing unit 12 to obtain an alternating current component signal Iac. As will be understood by the skilled person, the alternating current component signal Iac is excited by a disturbance signal such as an alternating current disturbance. In the prior art, the alternating current component signal is obtained by means of a calculation of the component of the direct current signal from the current signal measured by the current sensing unit 12 by means of a processing program instead of filtering the measured current signal to filter out the component of the direct current signal therefrom. Obviously, the calculation of the component of the direct current signal by means of a processing program relies on the optimization and the fineness of the algorithm and not on the improvement of the measurement accuracy of the alternating current component signal itself. Obviously, the algorithm itself does not solve the error due to the measurement accuracy. Therefore, improving the measurement accuracy of the alternating current component signal would not lead to a significant technical effect for improving the measurement accuracy of the electrochemical impedance spectroscopy as would be unforeseeable for the skilled person. It is to be noted that although the DC blocking filter 14 is described herein as being connected to the current sensing unit 12 and configured to filter out the direct current signal from the current signal sensed by the current sensing unit 12 to obtain the alternating current component signal Iac, this is not limiting but can be varied. As an example, such as for certain non-sensing coil type current sensing units 12, it can be envisaged that the DC blocking filter 14 can be configured to be connected to the current sensing unit 12 and to filter out the direct current signal from the current signal to be sensed by the current sensing unit 12 so that the current sensing unit 12 is able to directly sense the alternating current component signal Iac. Indeed, the position of the DC blocking filter 14 is not limiting as long as it enables the filtering out of the direct current signal from the output current signal before the calculation of the electrochemical impedance spectroscopy is performed. Moreover, the connection of the DC blocking filter 14 to the current sensing unit 12 is to be understood as including a direct connection or an indirect connection.

[0017] Further, in Figure 1In one embodiment, the measurement system 1 further includes a voltage sensing unit 16 configured to measure the AC voltage signal Vac of the fuel cell. It should be understood that the AC voltage signal Vac typically represents the AC voltage signal component caused by an AC disturbance signal. Of course, in some cases, the AC voltage signal Vac may also represent the superposition of voltage changes caused by the applied AC disturbance signal and the voltage of the fuel cell itself. In one embodiment of this application, as will be understood, and in an alternative embodiment, the voltage signal of the fuel cell can be filtered first via another DC blocking filter (not shown) to remove the DC voltage signal, and then the voltage sensing unit 16 directly measures the AC voltage signal. In this case, the filtering process for the DC voltage component in the fuel cell voltage employs requirements similar to those for filtering the DC current signal component: it is necessary to ensure that the DC or near-DC voltage signal output by the fuel cell is filtered out as much as possible to ensure that the filtered AC voltage signal retains as much as possible the AC voltage signal caused by the applied disturbance AC current. Of course, any other method can be used to acquire the AC voltage signal without departing from the scope of this application. As an example and not a limitation, the voltage sensing unit 16 is able to directly measure the voltage of the fuel cell and obtain the corresponding AC voltage signal Vac by subtracting the DC voltage component therein through a processing program.

[0018] Furthermore, in Figure 1 In this embodiment, the measurement system 1 further includes an electrochemical impedance spectroscopy (EIS) analysis unit 18, which is configured to calculate the EIS of the fuel cell based on the obtained AC current component signal Iac and AC voltage signal Vac. Methods for obtaining the EIS of a fuel cell based on its AC current component signal and AC voltage signal are well known in the art and will not be elaborated further here. Further, as an example, EIS analysis of the fuel cell can be performed based on the measured AC current component signal and the measured AC voltage signal using FFT (Fast Fourier Transform) or DFT (Discrete Fourier Transform) methods.

[0019] Optionally or in combination, such as Figure 1 and 2As shown, the electrochemical impedance spectroscopy measurement of this application may further include a bias component unit 11, which is connected to a DC blocking filter 14 or a current sensing unit 12 (the connection method is not shown) and configured to apply a predetermined bias component to the obtained AC current component signal Iac such that the amplitude of the AC current component signal is positive; and / or an ADC sampling unit 13, which is connected to the bias component unit 13 and the voltage sensing unit 16 and configured to perform ADC sampling on the biased AC current component signal and the AC voltage signal respectively to obtain a first ADC sampling signal and a second ADC sampling signal. In this case, the electrochemical impedance spectroscopy analysis unit 18 is communicatively connected to the ADC sampling unit 13 and calculates the electrochemical impedance spectrum of the fuel cell based on the obtained first ADC sampling signal and second ADC sampling signal. Of course, as those skilled in the art can imagine, the ADC sampling unit 13 can be integrated into the electrochemical impedance spectroscopy analysis unit 18 so that the electrochemical impedance spectroscopy analysis unit 18 itself has the function of performing ADC sampling on the AC current component signal and the AC voltage signal. Conversely, these ADC sampling units 13 can be distributed with the electrochemical impedance spectroscopy analysis unit 18. In fact, any distribution arrangement of the ADC sampling units 13 and the electrochemical impedance spectroscopy analysis unit 18 is within the scope of this invention. Typically, the first ADC sampling signal and the second ADC sampling signal are acquired through the first and second ports of the ADC sampling unit 13, respectively.

[0020] Obviously, the ADC sampling unit 13 is helpful for electrochemical impedance spectroscopy analysis, and this ADC sampling technique is well known to those skilled in the art, so it will not be described in detail here.

[0021] Alternatively, or in combination, as shown in Figure 3. Figure 1 The electrochemical impedance spectroscopy measurement in one embodiment may further include an amplifier 15 connected to a bias component unit 11, which amplifies the biased AC current component signal obtained therefrom to obtain a high-resolution AC current component signal. In this case, an ADC sampling unit 13 is connected to the amplifier 15 and the voltage sensing unit 16 and is configured to perform ADC sampling on the high-resolution AC current component signal and the AC voltage signal respectively to obtain a third ADC sampling signal and a second ADC sampling signal. In this case, an electrochemical impedance spectroscopy analysis unit 18 is communicatively connected to the ADC sampling unit 13 and calculates the electrochemical impedance spectrum of the fuel cell based on the obtained third ADC sampling signal and second ADC sampling signal.

[0022] In embodiments of this application, the current sensing unit is configured as a sensing coil whose center passes through the output line of the fuel cell and thus measures the potential of the electric field of the output line of the fuel cell and thus determines the current value flowing through the output line.

[0023] As previously mentioned, by way of example, the DC blocking filter 14 is configured to filter the current sensed by or to be sensed by the current sensing unit 12 to filter out the DC current signal component from the current to obtain an AC current component signal. It is apparent that in the embodiments of the present application, the DC blocking filter 14 is configured to ensure that the DC or near-DC current signal generated by the fuel cell itself is filtered out as much as possible, so as to ensure that the filtered-out AC current component signal can as much as possible truly retain the AC current component signal caused by the applied perturbation AC current to the fuel cell. In the embodiments of the present application, the DC blocking filter 14 can be any suitable type of filter known to those skilled in the art without departing from the scope of the present application, as long as it can ensure that the electrical signal below the frequency of the applied perturbation AC current can be filtered out as much as possible. By way of example, the DC blocking filter 14 is configured as a capacitor or a combination of a capacitor and a resistor. In the embodiments of the present application, the DC blocking filter 14 can be selected according to the requirements and the type is not limited to Figure 2 As shown, but any DC blocking filter type known in the art or developed in the future can be adopted.

[0024] In the embodiments of the present application, Figure 2 The bias component unit 11 is connected to, in particular in series to, the DC blocking filter 14 to apply a predetermined bias component to the sensed obtained AC current component signal so that the amplitude of the AC current component signal is always positive. As those skilled in the art will understand, applying a bias component to the obtained AC current component signal Iac to ensure that it always remains at a positive value helps to achieve the acquisition processing of the AC current component signal using specific electronic devices, in particular the ADC sampling unit 13. Since the bias component is constant, the bias component only affects the amplitude of the AC current component signal and has no effect on other electrical characteristics such as frequency. Therefore, in the subsequent processing, the applied constant bias component is directly deducted (subtracted) to restore the original AC current component signal (including positive and negative values).

[0025] In the embodiments of the present application, the amplifier 15 is connected in series to the bias component unit 11 to amplify the biased AC current component signal to obtain a high-resolution AC current component signal. With this amplification processing, it is apparent that the measurement accuracy of the AC current component signal can be improved, thereby helping the analysis and measurement of the electrochemical impedance spectrum of the fuel cell. In the embodiments of the present application, the amplifier 15 can be connected to the circuit in positive or negative phase as required to achieve amplification processing and the type of amplifier is not limited to Figure 2 As shown, but any amplifier type known in the art or developed in the future can be adopted.

[0026] The ADC sampling unit 13 can be used for ADC sampling measurements of the alternating current component signal and the alternating voltage signal for analysis and calculation of the electrochemical impedance spectrum of the fuel cell. As shown, the ADC sampling unit 13 can be connected in series to the amplifier 15 and the voltage sensing unit 16 for ADC sampling of the high resolution alternating current component signal and the alternating voltage signal, respectively, to obtain a third ADC sampled signal and a second ADC sampled signal, respectively. Thanks to the application of the bias component, the high resolution alternating current component signal can be directly sampled by the ADC sampling unit, so that a relevant digital signal can be obtained for subsequent electrochemical impedance spectrum analysis. Figure 2

[0027] In an embodiment of the application, the electrochemical impedance spectrum analysis unit 18 is communicatively connected to the ADC sampling unit 13 and calculates the electrochemical impedance spectrum of the fuel cell based on the obtained third ADC sampled signal and second ADC sampled signal. The electrochemical impedance spectrum analysis unit can for example employ a FFT or DFT method. Figure 2 In an embodiment of the application, the electrochemical impedance spectrum analysis unit 18 is communicatively connected to the ADC sampling unit 13 and calculates the electrochemical impedance spectrum of the fuel cell based on the obtained third ADC sampled signal and second ADC sampled signal. The electrochemical impedance spectrum analysis unit can for example employ a FFT or DFT method.

[0028] Figure 2 In an embodiment of the application, the measurement system 1 further comprises a current sensing error determination circuit 17. In an embodiment of the application, the current sensing error determination circuit 17 is connected in series to the series circuit of the DC blocking filter 14, the bias component unit 11 and the amplifier 15 and also in series to the current sensing unit 12 to determine a sensing error ratio of the current sensing unit 12. Figure 1 Figure 2 In an embodiment of the application, the current sensing error determination circuit 17 is connected in series to the series circuit of the DC blocking filter 14, the bias component unit 11 and the amplifier 15 and also in series to the current sensing unit 12 to determine a sensing error ratio of the current sensing unit 12. In an embodiment of the application, the current sensing error determination circuit 17 is connected in series to the series circuit of the DC blocking filter 14, the bias component unit 11 and the amplifier 15 and also in series to the current sensing unit 12 to determine a sensing error ratio of the current sensing unit 12. 2

[0029] ​​​​In embodiments of the present application, the current sensing error determination circuit 17 is configured to apply a standard perturbation electrical signal, such as a standard perturbation current, to a standard current source generating a standard direct current signal in a case that the electrochemical impedance spectroscopy measurement system is coupled to the standard current source, and to sense the output current of the standard current source at this time. For the standard current source, since a high-precision response current can be generated, a theoretical measurement value of the sensed current of the standard current source under the standard perturbation current can be calculated or obtained through experiments in advance. Based on the theoretical measurement value and the actual measurement value Iac-cor of the sensed current, it is obvious that the sensing error ratio of the current sensing unit 12 itself can be determined by comparing the two values. Therefore, the sensing error ratio of the current sensing unit can be determined based on the comparison of the actually sensed current and the theoretical measurement value of the standard current source under the same condition, i.e. the sensing error ratio of the measurement value of the current sensing unit itself, for calibrating the measurement value of the current sensing unit. As an example, the sensing error ratio can be saved, for example, into the electrochemical impedance spectroscopy analysis unit 18 so that when the third or first ADC sampling signal is employed, especially in subsequent electrochemical impedance analysis calculation, the above-mentioned sensing error ratio can be fully considered and adopted to be applied to the first or third ADC sampling signal to obtain the calibrated first or third ADC sampling signal, thereby further improving the accuracy of the electrochemical impedance spectroscopy analysis. Obviously, after determining the sensing error ratio, the current sensing error determination circuit 17 is not used or does not output any sensing value in the subsequent use of the measurement system 1, which needs to be made clear here. It also needs to be noted here that the output current sensed by the current sensing error determination circuit 17 can also be input to the ADC sampling unit 13 to determine the sensing error ratio of the current sensing unit based on the ADC sampling signal.

[0030] In a case that the measurement system 1 further comprises the current sensing error determination circuit 17, the electrochemical impedance spectroscopy analysis unit 18 is communicatively connected to the ADC sampling unit and calculates the electrochemical impedance spectroscopy of the fuel cell based on the second ADC sampling signal, the sensing error ratio and the third ADC sampling signal or based on the second ADC sampling signal and the third ADC sampling signal calibrated via the sensing error ratio.

[0031] As mentioned previously, the DC blocking filter 14 is configured such that current signals with frequencies lower than the frequency of the applied AC perturbation current cannot pass through. However, it is appreciated by those skilled in the art that the applied AC perturbation current can also induce various interference signals such as parasitic currents with higher frequencies (significantly higher than the frequency of the applied AC current) in the fuel cell. These interference signals would obviously also adversely affect the analysis of the electrochemical impedance spectrum of the fuel cell. In order to remove these high frequency interference signals as much as possible, optionally, the measurement system further comprises a high frequency signal filtering circuit 19-1 connected in series to the AC current measurement circuit, e.g. after the amplifier, to filter out the high frequency interference signals, obviously with frequencies higher than the frequency of the applied AC perturbation current, immediately before the ADC sampling or before the input to the electrochemical impedance spectrum analysis unit 18. Of course, a similar high frequency signal filtering circuit 19-2 can also be connected in series to the current sensing error determination circuit 17 to improve the accuracy of the determination of the sensing error ratio.

[0032] Figure 1 A flow chart of the electrochemical impedance spectrum measurement method for a fuel cell according to the first embodiment of the present application is shown.

[0033] As Figure 3A shown, at step 300, in order to measure the electrochemical impedance spectrum of the fuel cell, an AC perturbation signal, such as an AC current perturbation, with a certain frequency is typically applied to the fuel cell. As would be appreciated by those skilled in the art, the amplitude of the perturbation AC current is typically significantly smaller than the current output of the fuel cell and the amplitude of the perturbation voltage due to the perturbation current passing through the internal resistance of the fuel cell is directly significantly smaller than the voltage output of the fuel cell. The purpose of this selection is to not unduly cause changes in the physical environment, such as temperature, etc. within the fuel cell to as much as possible ensure the accuracy of the impedance spectrum measurement.

[0034] Furthermore, it is noted that in the embodiments of the present application, in order to ensure the accuracy of the calculation of the electrochemical impedance, in the embodiments of the present application, a set of perturbation AC currents with different frequencies and / or different amplitudes can be applied to the fuel cell and the electrochemical impedance spectrum analysis is performed separately for each of the set of perturbation currents, thereby obtaining a more accurate final electrochemical impedance spectrum.

[0035] At step 302, the current of the fuel cell is sensed. As will be appreciated by those skilled in the art, the sensing of the current signal of the fuel cell can be achieved by means of a sensing coil. Such a technique is well known to those skilled in the art and as such will not be described herein again. However, in order to make the scheme of the present application complete, the principle of the sensing coil will be described herein briefly: the output line of the fuel cell passes through the center of the sensing coil, thus the sensing coil is in the electric field generated by the wire and the center of the coil coincides with the center of the electric field. Therefore, the sensing coil can generate different potentials based on the strength of the electric field caused by the current, thus the amplitude of the current can be expressed by means of such potentials. Of course, the method of current sensing by means of a sensing coil is merely exemplary and not limiting. Those skilled in the art can conceive of any known or future known technique for sensing the current of a fuel cell to achieve the sensing process without departing from the scope of the present application.

[0036] Due to the application of the perturbation alternating current as described before, the current and voltage output of the fuel cell will be obviously affected and thus generate corresponding fluctuations. The amplitude of these fluctuations is obviously corresponding to the perturbation alternating current and voltage and is proportional to the electrochemical impedance of the fuel cell.

[0037] In order to obtain the electrochemical impedance spectrum of the fuel cell, at step 304, the current is filtered to filter out the direct current signal component of the measured current to obtain an alternating current component signal. In some embodiments including the present embodiment, step 304 is achieved by means of a direct current blocking filter. In the prior art, there are direct subtraction of the direct current signal component of the measured current by means of a processing program instead of filtering the measured current to filter out the direct current signal component thereof, however the subtraction of the direct current signal component by means of a processing program depends on the optimization and refinement of the algorithm rather than on the improvement of the measurement accuracy of the alternating current component signal itself. Obviously, the algorithm itself cannot solve the errors caused by the measurement accuracy. Therefore, improving the measurement accuracy of the alternating current component signal will have an effect on improving the measurement accuracy of the electrochemical impedance spectrum which cannot be foreseen by those skilled in the art.

[0038] In fact, in the prior art, since the measurement of the electrochemical impedance spectrum needs to be achieved by means of subsequent processing programs, the subtraction of the direct current signal component integrated in the corresponding processing program can be beneficial to the adaptability of different fuel cells. However, as described before, such a processing program which does not depend on the improvement of the measurement accuracy itself cannot overcome the distortion caused by the measurement errors in the case of measurement system errors, thus the accurate measurement of the corresponding alternating current component signal before the measurement of the electrochemical impedance has obvious advantages for the subsequent analysis of the electrochemical impedance spectrum.

[0039] In the embodiments of the present application, in the filtering process at step 304, it is required to ensure that the direct current signal outputted by the fuel cell or the signal close to the direct current signal is filtered out as much as possible, so as to ensure that the alternating current component signal obtained after the filtering can retain the varying current signal caused by the applied perturbation alternating current as much as possible.

[0040] Further, in order to realize the analysis of the electrochemical impedance of the fuel cell, the alternating voltage signal caused by the applied perturbation alternating current to the fuel cell should also be accurately measured. For this purpose, at step 306, the alternating voltage signal in the voltage of the fuel cell is measured.

[0041] As will be understood and in the embodiments of the present application, it is contemplated that the voltage of the fuel cell is also filtered to filter out the direct voltage in the measured voltage so as to obtain the alternating voltage signal (alternating voltage component in the voltage) therein. It is contemplated that the filtering process for the direct voltage component in the voltage of the fuel cell adopts similar requirements as the filtering process for the component of the direct current signal: it is required to ensure that the direct voltage or the voltage close to the voltage outputted by the fuel cell is filtered out as much as possible, so as to ensure that the alternating voltage signal obtained after the filtering can retain the alternating voltage signal (alternating voltage component in the voltage) caused by the applied perturbation alternating current as much as possible. Of course, the obtaining of the alternating voltage signal can adopt any other method without departing from the scope of the present application.

[0042] At step 308, the electrochemical impedance spectroscopy of the fuel cell is analyzed based at least in part on the measured alternating current component signal and the measured alternating voltage signal to obtain the electrochemical impedance spectroscopy of the fuel cell. The method of obtaining the electrochemical impedance spectroscopy of the fuel cell based on the alternating current component signal and the alternating voltage signal of the fuel cell is well known in the art, and will not be described in additional details herein. Further, as an example, the electrochemical impedance spectroscopy of the fuel cell can be analyzed based on the measured alternating current component signal and the obtained alternating voltage signal based on FFT (Fast Fourier Transform) or DFT (Discrete Fourier Transform) method.

[0043] Figure 3A A flow chart of a method for electrochemical impedance spectroscopy measurement of a fuel cell according to a second embodiment of the present application is shown.

[0044] The method for electrochemical impedance spectroscopy measurement of a fuel cell of the second embodiment is generally the same as the first embodiment, except that additional processing is performed on the alternating current component signal to enable the electrochemical impedance spectroscopy measurement to be performed using an analog-to-digital conversion sampling device such as an ADC sampling chip. Thus, at step 306, the alternating voltage signal in the voltage of the fuel cell is measured, and at step 308, the electrochemical impedance spectroscopy of the fuel cell is analyzed based at least in part on the measured alternating current component signal and the measured alternating voltage signal to obtain the electrochemical impedance spectroscopy of the fuel cell. Figure 3BIn some embodiments, additionally or in combination, the electrochemical impedance spectroscopy measurement method for a fuel cell further comprises a step 310 of applying a constant bias component to the obtained alternating current component signal to ensure that the obtained biased alternating current component signal remains positive at all times. As will be appreciated by those skilled in the art, applying a bias component to the filtered obtained alternating current component signal to ensure that it remains positive at all times facilitates the measurement of the alternating current component signal using certain electronics. Since the bias component is constant, the bias component only affects the amplitude of the alternating current component signal and has no effect on other electrical characteristics such as frequency. Thus, the above steps 300-308 can be used in combination with certain electronics (such as an ADC chip) that measures positive values by directly subtracting (or deducting) the corresponding constant bias component in the processing routine. This combination process will be described in more detail below.

[0045] Based on step 310, the alternating current component signal can be further sampled using an ADC sampling chip and used for the electrochemical impedance spectroscopy measurement of the fuel cell. Thus, at step 312, the obtained biased alternating current component signal is sampled using an ADC sampling chip (e.g., by transmitting the biased alternating current component signal to a first port of the ADC sampling chip) to obtain a first sampled signal. The first sampled signal is a discrete digital signal representing the measured amplitude of the alternating current component signal.

[0046] Accordingly, at step 314, the obtained alternating voltage signal is sampled using an ADC sampling chip (e.g., by transmitting the alternating voltage signal to a second port of the ADC sampling chip) to obtain a second sampled signal. The second sampled signal is a discrete digital signal representing the measured amplitude of the alternating voltage signal.

[0047] Thus, the above electrochemical impedance spectroscopy analysis of the fuel cell based at least in part on the alternating current component signal and the alternating voltage signal of the fuel cell to obtain the electrochemical impedance spectroscopy of the fuel cell comprises electrochemical impedance spectroscopy analysis of the fuel cell based on the first sampled signal and the second sampled signal. Here, the electrochemical impedance spectroscopy analysis can also be based on FFT (Fast Fourier Transform) or DFT (Discrete Fourier Transform) methods based on the first and second sampled signals.

[0048] Figure 3BA flow chart of an electrochemical impedance spectroscopy measurement method for a fuel cell according to a third embodiment of the present application is shown. The electrochemical impedance spectroscopy measurement method for a fuel cell of the third embodiment is substantially the same as the second embodiment, except for the amplification of the biased AC current component signal. As previously mentioned, since the amplitude of the applied perturbation AC current is usually small and thus the resulting AC current component signal in the output current of the fuel cell is also usually small, in order to enlarge the measurement accuracy for the AC current component signal, according to the third embodiment of the present application, the biased AC current component signal is amplified at step 316 to obtain a high resolution AC current component signal. Of course, although described herein as the amplification being applied to the biased AC current component signal, it is appreciated that in this or other embodiments of the present application, the amplification can be applied directly to the filtered obtained AC current component signal. After the filtered obtained AC current component signal is amplified, the amplified AC current component signal can be applied with a constant bias component or directly used for electrochemical impedance spectroscopy analysis. Figure 3C The electrochemical impedance spectroscopy measurement method for a fuel cell according to the third embodiment of the present application further comprises an amplification process of the biased AC current component signal at step 316 to obtain a high resolution AC current component signal. Of course, although described herein as the amplification process being applied to the biased AC current component signal, it is appreciated that in this or other embodiments of the present application, the amplification process can be applied directly to the filtered obtained AC current component signal. After the filtered obtained AC current component signal is amplified, the amplified AC current component signal can be applied with a constant bias component or directly used for electrochemical impedance spectroscopy analysis.

[0049] At step 318, the high resolution AC current component signal obtained at step 316 is ADC sampled to obtain a third sampled signal (e.g. by transmitting the biased AC current component signal to a third port of an ADC sampling chip). Obviously, in this case, it is contemplated that step 312 in the second embodiment can be omitted. The third sampled signal is a discrete digital signal to represent the amplitude of the amplified AC current component signal. In this case, as mentioned above, the electrochemical impedance spectroscopy analysis of the fuel cell based at least in part on the AC current component signal and the AC voltage signal of the fuel cell to obtain the electrochemical impedance spectroscopy of the fuel cell comprises electrochemical impedance spectroscopy analysis of the fuel cell based on the third sampled signal and the second sampled signal. Here, the electrochemical impedance spectroscopy analysis based on the third and second sampled signals can also be based on FFT (Fast Fourier Transform) or DFT (Discrete Fourier Transform) methods.

[0050] In the above description of the present application Figure 3CIn the embodiments of the present application, the measurement error due to the hardware itself when measuring the AC current component signal of the fuel cell is also fully taken into account. In order to obtain the error of the hardware itself of the measurement, in the electrochemical impedance spectroscopy measurement method for the fuel cell of the first to third embodiments of the present application, a sensing error obtaining step is also selectively included: at step 320, the sensing part for sensing the current of the fuel cell is placed in a standard environment and connected to a standard current source, especially a standard fuel cell, and the standard current source is applied with a standard perturbation current. For the standard current source, since the current outputted therefrom is very high precision, the theoretical measurement value of the sensed current of the standard current source under the standard perturbation current can be calculated and obtained or obtained through experiments in advance. Based on the theoretical measurement value and the actual measurement value of the sensed current, it is obvious that the sensing error ratio of the sensing part for sensing the current can be determined by comparing the two values. That is, at step 320, the sensing error is determined based on the standard perturbation current and the standard current source which is configured to generate a standard direct current, after the standard perturbation current is applied to the standard current source, the current generated thereby is sensed and the sensed current is compared with the theoretical measurement value of the standard current source under the same condition to determine the sensing error ratio of the current sensing.

[0051] For the sensing error ratio obtained at step 320, it can be applied to one of the sensed current of the fuel cell or the AC current component signal obtained after filtering or the biased AC current after the AC current compensation or the amplified AC current component signal and the like to improve the accuracy of the final electrochemical impedance spectroscopy analysis. The above-mentioned step of applying the sensing error ratio obtained at step 320 is not explicitly shown in the embodiments of the present application, but it should be understood that the step of applying the sensing error ratio is also obviously optionally included in the scope of the present application. Figures 3A-3C

[0052] Although in the embodiments of the present application, the electrochemical impedance spectroscopy measurement method for the fuel cell is described in a specific order, it should be understood that one or more of the steps can be implemented in one step or one step can be implemented in multiple steps, or one or more of the steps can be executed simultaneously or in reverse order.

[0053] In addition, it should be noted that Figures 3A-3C Figure 2 The meanings of the symbols "GND" and "VDD" shown in the embodiments of the present application are explained as "ground" and "power terminal" as can be generally understood by those skilled in the art.

[0054] ​Those skilled in the art should also appreciate that, although in the above embodiments of the present application, only the measurement of the alternating current component signal is described, those skilled in the art should appreciate that the similar process described above can also be applied to the measurement process of the alternating voltage signal without departing from the scope of the present application. In fact, it is easy for those skilled in the art to consider that the process described above can be applied from the measurement of the alternating current component signal to the measurement of the alternating voltage signal, and therefore, the scope of protection of the present application actually covers the scope of the similar process for the measurement of the alternating voltage signal.

[0055] Although the specific embodiments of the present application are described in the above embodiments, those skilled in the art should appreciate that these are only exemplary.

Claims

1. An electrochemical impedance spectroscopy measurement system (1) for a fuel cell, wherein, The electrochemical impedance measurement system (1) is electrically connected to the fuel cell (20) and comprises: a fuel cell perturbation source (10) configured to apply an AC perturbation electrical signal of a certain frequency to the fuel cell; a current sensing unit (12) configured to sense an output current of the fuel cell (20); a DC blocking filter (14) connected to the current sensing unit (12) and configured to filter out a DC current signal from the output current sensed by the current sensing unit (12) to obtain an AC current component signal; a voltage sensing unit (16) configured to sense an AC voltage signal of the fuel cell (20); and an electrochemical impedance spectroscopy analysis unit (18) configured to calculate and analyze an electrochemical impedance spectrum of the fuel cell (20) based on the AC current component signal and the AC voltage signal.

2. The electrochemical impedance spectroscopy measurement system (1) for a fuel cell as claimed in claim 1, wherein, The electrochemical impedance spectroscopy measurement system (1) further comprises a bias component unit (11) configured to apply a predetermined bias component to the sensed obtained AC current component signal such that the magnitude of the AC current component signal is all positive.

3. The electrochemical impedance spectroscopy measurement system (1) for a fuel cell as claimed in claim 2, wherein, The electrochemical impedance spectroscopy measurement system (1) further comprises an ADC sampling unit (13) configured to perform ADC sampling on the biased AC current component signal to obtain a first sampling signal and perform ADC sampling on the AC voltage signal to obtain a second sampling signal, and wherein the electrochemical impedance spectroscopy analysis unit (18) is configured to calculate and analyze the electrochemical impedance spectrum of the fuel cell (20) based on the first sampling signal and the second sampling signal of the biased AC current component signal and the AC voltage signal.

4. The electrochemical impedance spectroscopy measurement system (1) for a fuel cell as claimed in claim 2, wherein, The electrochemical impedance spectroscopy measurement system (1) further comprises an amplifier (15) connected in series to the bias component unit (11) to amplify the biased AC current component signal to obtain a high resolution AC current component signal, and an ADC sampling unit (13) configured to perform ADC sampling on the high resolution AC current component signal and the AC voltage signal respectively to obtain a third sampling signal and a second sampling signal respectively; and wherein the electrochemical impedance spectroscopy analysis unit (18) is configured to calculate and analyze the electrochemical impedance spectrum of the fuel cell (20) based on the third sampling signal and the second sampling signal of the biased AC current component signal and the AC voltage signal.

5. The electrochemical impedance spectroscopy measurement system (1) for a fuel cell according to any one of claims 1-4, further comprising a current sensing error determination circuit (17) configured to be directly connected in series to the current sensing unit (12) and to directly obtain a directly sensed value of an output current of the fuel cell (20) by the current sensing unit (12), and configured to sense an output current of a standard current source generating a standard direct current and to determine a sensing error ratio of the current sensing unit (12) based on a comparison of the sensed output current and a theoretical measured value of the standard current source under the same conditions for calibrating the measurement of the current sensing unit based on a standard perturbation electrical signal applied to the standard current source.

6. The electrochemical impedance spectroscopy measurement system (1) for a fuel cell according to claim 3 or 4, wherein The DC blocking filter (14) is configured such that current signals below the frequency of the applied AC perturbation electrical signal cannot pass through, and / or wherein the electrochemical impedance spectroscopy measurement system (1) further comprises an additional signal filtering circuit to filter out high frequency interference signals immediately before the ADC sampling, the high frequency interference signals having a frequency higher than the frequency of the applied AC perturbation electrical signal.

7. An electrochemical impedance spectroscopy method for a fuel cell, wherein, The method comprises: applying an AC perturbation signal of a certain frequency to a fuel cell; sensing an output current signal of the fuel cell; filtering the sensed output current signal to filter out a direct current signal component therein to obtain an AC current component signal; measuring an AC voltage signal of a voltage of the fuel cell; performing electrochemical impedance spectroscopy analysis of the fuel cell based at least in part on the AC current component signal and the AC voltage signal to obtain an electrochemical impedance spectroscopy of the fuel cell.

8. The electrochemical impedance spectroscopy measurement method for a fuel cell as claimed in claim 7, wherein, applying a constant bias component to the obtained AC current component signal to obtain a biased AC current component signal such that the biased AC current component signal is always kept at a positive value, and / or wherein the method further comprises amplifying the biased AC current component signal to obtain a high resolution AC current component signal.

9. The electrochemical impedance spectroscopy measurement method for a fuel cell as claimed in claim 8, wherein, The method further comprises: ADC sampling the obtained high resolution AC current component signal to obtain a third sampling signal; ADC sampling the obtained AC voltage signal to obtain a second sampling signal, wherein performing electrochemical impedance spectroscopy analysis of the fuel cell based at least in part on the AC current component signal and the AC voltage signal of the fuel cell to obtain an electrochemical impedance spectroscopy of the fuel cell comprises performing electrochemical impedance spectroscopy analysis of the fuel cell based on the third sampling signal and the second sampling signal.

10. The electrochemical impedance spectroscopy measurement method for a fuel cell as claimed in claim 7, wherein, determining a sensing error ratio in sensing an output current of a fuel cell based on a standard perturbation current and a standard current source configured to generate a standard direct current, after applying the standard perturbation current to the standard current source, sensing an output current signal of the standard current source and determining a comparison of the sensed output current signal and a theoretical measured value of the standard current source under the same conditions to determine a sensing error ratio of the current sensing.

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