Excitation source quality control device and method for online impedance measurement

Abstract

The invention relates to the technical field of fuel cells, and discloses an excitation source quality control device and method for fuel cell on-line impedance measurement, a signal compensation module is used for carrying out quality control on an excitation source for alternating current impedance on-line test, and a controller carries out harmonic component analysis on a fuel cell response output signal obtained after a disturbance signal is injected; and if the corresponding harmonic component is greater than a preset threshold value, the controller calculates a compensation component according to the harmonic component deviation, integrates all the compensation components and outputs the integrated compensation components to the signal compensation module, and the signal compensation module compensates the excitation source for the AC impedance online test according to the integrated compensation components, so that the accuracy of the excitation waveform is ensured. Experiments prove that according to the fuel cell alternating current impedance online test system, the frequency output precision is within 0.1%, the phase difference between alternating current voltage and current signals is smaller than 0.1 degree, sine wave waveform distortion is smaller than 1%, and the high-precision alternating current impedance test requirement is met.

Description

Technical Field

[0001] The invention relates to the technical field of fuel cells, and in particular to an excitation source quality control device and method for online impedance measurement of fuel cells. Background Art

[0002] As an efficient energy conversion technology, the performance and life of fuel cells are affected by many factors. Online impedance measurement is crucial for real-time monitoring of the operating status of fuel cells. It can provide direct information on the internal resistance and polarization loss of the battery, helping researchers optimize battery design and improve energy conversion efficiency. In addition, by analyzing the impedance spectrum, faults and degradation inside the battery can be discovered in a timely manner, so that preventive measures can be taken to extend the service life of the battery. Therefore, online impedance measurement technology is of great significance for the commercialization and large-scale application of fuel cells. The existing online measurement method of electrochemical impedance spectroscopy of membrane fuel cells can be found in the Chinese invention patent application with publication number CN118011256A. Summary of the invention

[0003] The purpose of the present invention is to provide a method for controlling the quality of an excitation source for online impedance measurement that ensures the accuracy and stability of the excitation signal, and to at least provide a beneficial option or create conditions for solving one or more technical problems existing in the prior art.

[0004] To achieve the above objectives, the present invention adopts the following technical solutions.

[0005] A fuel cell AC impedance online testing method uses a signal compensation module to perform quality control on an excitation source for the AC impedance online testing. A controller performs harmonic component analysis on a fuel cell response output signal obtained after a disturbance signal is injected. If the corresponding harmonic component is greater than a preset threshold, the controller calculates a compensation component based on the harmonic component deviation and integrates all the compensation components to output to the signal compensation module. The signal compensation module compensates the excitation source for the AC impedance online testing based on the integrated compensation component, thereby ensuring the accuracy of the excitation waveform.

[0006] More preferably, the harmonic component analysis includes phase synchronization analysis, and the controller performs phase difference analysis on the response output signal. If the phase difference is greater than a preset phase difference threshold, the controller calculates the compensation phase in real time to perform online compensation.

[0007] More preferably, the harmonic component analysis includes waveform integrity analysis, and the controller performs waveform distortion analysis on the response output signal. If the waveform distortion is greater than a preset waveform distortion threshold, the controller calculates a corresponding compensation waveform and performs online compensation.

[0008] On the other hand, the present invention also provides an online testing system for the AC impedance of a fuel cell, which includes an AC current excitation signal module, a fuel cell stack, a signal acquisition module, a signal compensation module and a controller. The disturbance signal generated by the AC current excitation signal module is injected into the fuel cell stack, and the signal acquisition module acquires the response output signal of the fuel cell stack after the disturbance signal is injected. The controller performs an online Fourier transform on the acquired response output signal, and calculates the AC impedance of the fuel cell in real time. The controller also performs a harmonic component analysis on the response output signal. If the corresponding harmonic component is greater than a preset threshold, the controller calculates the compensation component based on the harmonic component deviation, and integrates the compensation component and outputs it to the signal compensation module. The signal compensation module compensates the AC current excitation signal module according to the integrated compensation component, thereby ensuring the accuracy of the excitation waveform.

[0009] More preferably, the AC current excitation signal module includes a DDS signal generator, an amplifier circuit, a filter circuit and a power amplifier module, the filter circuit is a second-order active low-pass filter, the amplifier circuit is a two-stage differential instrument amplifier circuit, the power amplifier module is a Class A power amplifier circuit, and the frequency range generated by the DDS signal generator is 1Hz~100kHz and the maximum amplitude is 30A.

[0010] The frequency, amplitude and phase controllable sinusoidal AC current signal generated by the DDS signal generator is first amplified by a two-stage differential instrument amplifier circuit, then filtered out by a second-order active low-pass filter to remove high-order harmonic interference, and finally amplified by a power amplifier module to obtain an AC current excitation signal.

[0011] More preferably, the DDS signal generator includes a phase accumulator, a sine lookup table, a digital-to-analog converter and a low-pass filter circuit. The phase accumulator performs phase accumulation with the chip system clock as the reference frequency under the control of the frequency control word to generate a series of discrete phase sequences, and also outputs the address code of the sine lookup table. By looking up the sine table, a digital sequence corresponding to the signal is generated. The digital sequence is D / A converted by the digital-to-analog converter to obtain a stepped analog voltage signal waveform. The analog voltage signal is output after passing through the low-pass filter circuit to obtain a smooth analog signal.

[0012] More preferably, the signal compensation module includes a DC generating module and an AC generating module, the DC generating module is used to generate a DC current signal, and the AC generating module is used to generate an AC current signal.

[0013] More preferably, the signal acquisition module includes a DC current signal acquisition module, an AC current signal acquisition module and an AC voltage signal acquisition module, and the controller is an STM32F4 microcontroller, which has its own AD acquisition; the controller is also connected to a host computer through an embedded Ethernet module, and the operating status of the fuel cell is monitored and judged through the host computer.

[0014] Compared with the prior art, the present invention has at least the following beneficial effects.

[0015] The present invention utilizes a signal compensation module to perform quality control on an excitation source for online testing of AC impedance. A controller performs harmonic component analysis on a response output signal of a fuel cell obtained after injecting a disturbance signal. If the corresponding harmonic component is greater than a preset threshold, the controller calculates a compensation component based on the harmonic component deviation, and integrates all compensation components and outputs them to the signal compensation module. The signal compensation module compensates the excitation source for online testing of AC impedance based on the integrated compensation component. The excitation source outputs a high-quality waveform, which can ensure the accuracy of the excitation waveform, thereby ensuring the accuracy and stability of the excitation signal.

[0016] Experimental verification shows that the fuel cell AC impedance online testing system provided by the present invention has a frequency output accuracy within 0.1%, a phase difference between the AC voltage and current signals less than 0.1 degrees, and a sinusoidal waveform distortion less than 1%, meeting the requirements for high-precision AC impedance testing. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Schematic diagram of the structure of the fuel cell AC impedance online testing system in an embodiment of the present invention.

[0018] Figure 2 : is the waveform output by the AC current excitation signal module in the embodiment of the present invention.

[0019] Figure 3 FIG. 4 is another waveform diagram output by the AC current excitation signal module in an embodiment of the present invention. DETAILED DESCRIPTION

[0020] The following is a further description of the specific implementation of the present invention in conjunction with the drawings of the specification, so that the technical solution and its beneficial effects of the present invention are clearer and more explicit. The following description of the embodiments with reference to the drawings is exemplary and intended to explain the present invention, but cannot be understood as limiting the present invention.

[0021] Additional aspects and advantages of the present invention will become apparent from the following description or may be learned by practice of the present invention.

[0022] See also Figure 1As shown, a fuel cell AC impedance online testing system includes an AC current excitation signal module, a fuel cell stack, a signal acquisition module, a signal compensation module and a controller. The AC current excitation signal (disturbance signal) generated by the AC current excitation signal module is injected into the fuel cell stack. The signal acquisition module acquires the response output signal of the fuel cell stack after the AC current excitation signal is injected. The controller performs online Fourier transform on the acquired response output signal and calculates the fuel cell AC impedance in real time. The controller also performs harmonic component analysis on the response output signal. If the corresponding harmonic component is greater than a preset threshold, the controller calculates the compensation component according to the harmonic component deviation, and integrates the compensation component and outputs it to the signal compensation module. The signal compensation module compensates the AC current excitation signal module according to the integrated compensation component, thereby ensuring the accuracy of the excitation waveform.

[0023] In the AC impedance measurement of fuel cells, the frequency and sine waveform of the excitation signal will directly affect the accuracy of the impedance test results. The present invention provides a fuel cell AC impedance online test system, which can effectively ensure the accuracy and stability of the excitation signal by setting a compensation module and controlling the compensation module to compensate the AC current excitation signal module according to the harmonic component analysis result obtained by analyzing the response output signal.

[0024] In this embodiment, the AC current excitation signal module includes a DDS signal generator, an amplifier circuit, a filter circuit and a power amplifier module, wherein the filter circuit is a second-order active low-pass filter, the amplifier circuit is a two-stage differential instrument amplifier circuit, the power amplifier module is a Class A power amplifier circuit, and the DDS signal generator generates a frequency range of 1Hz~100kHz and a maximum amplitude of 30A. The sinusoidal AC current signal with controllable frequency, amplitude and phase generated by the DDS signal generator first passes through a two-stage differential instrument amplifier circuit to amplify the signal amplitude, then passes through a second-order active low-pass filter to filter out high-order harmonic interference, and finally passes through the power amplifier module to amplify the signal to obtain an AC current excitation signal.

[0025] In this embodiment, the more mature direct digital frequency synthesis technology (DDS) is used, and the DDS chip AD9852 with a 48-bit frequency control word is selected to design the AC current excitation signal module. The DDS signal generator includes a phase accumulator, a sine lookup table, a digital-to-analog converter DAC, and a low-pass filter circuit. Under the control of the frequency control word (FCW), the phase accumulator performs phase accumulation with the chip system clock as the reference frequency to generate a series of discrete phase sequences, and also outputs the address code of the sine lookup table. After searching the sine table ROM, a digital sequence corresponding to the signal is generated. The sequence is converted by the digital-to-analog converter to obtain a step-like analog voltage signal waveform, and finally the signal is output after passing through the low-pass filter circuit to obtain a smooth analog signal.

[0026] In this embodiment, the signal acquisition module includes a DC current signal acquisition module, an AC current signal acquisition module and an AC voltage signal acquisition module. The controller is preferably an STM32F4 microcontroller. The STM32F4 microcontroller has built-in AD acquisition, high performance, good compatibility, and is easy to expand or upgrade.

[0027] In this embodiment, the signal compensation module includes: a DC generation module for generating a DC current signal; an AC generation module for generating an AC current signal. The excitation source (AC current excitation signal module) is compensated by these signals to ensure the quality of the excitation source.

[0028] In this embodiment, the harmonic component analysis includes phase synchronization analysis and waveform integrity analysis. The controller performs phase difference analysis on the response output signal. If the phase difference is greater than the preset phase difference threshold, the controller calculates the compensation phase in real time for online compensation to ensure that the phase of the disturbance signal current and voltage are accurately synchronized. The controller performs waveform distortion degree analysis on the response output signal. If the waveform distortion is greater than the preset waveform distortion threshold, the controller calculates the corresponding compensation component and performs real-time online compensation to ensure that the waveform of the disturbance sine wave signal is complete. The phase difference threshold and the waveform distortion threshold are empirical values ​​or experimental values.

[0029] Figure 2 , Figure 3 The waveforms output by the AC current excitation signal module in two different embodiments of the present invention are 50Hz and 200KHz sine wave outputs respectively. Figure 2 , Figure 3 It can be seen that the waveform quality of the excitation source (AC current excitation signal module) is good when the output frequency is 50Hz and 200KHz, the internal signal frequency output accuracy is within 0.1%, the phase difference between the AC voltage and current signals is less than 0.1 degrees, and the sine wave waveform distortion is less than 1%, which meets the needs of high-precision AC impedance testing.

[0030] It should be noted that the controller is also connected to the host computer through an embedded Ethernet module, so that the user can monitor and determine the operating status of the fuel cell through the host computer.

[0031] It should also be noted that in the description of this specification, any process or method description in the flowchart or otherwise described herein may be understood to represent a module, fragment or portion of a code comprising one or more executable instructions for implementing steps of a specific logical function or process, and the scope of the preferred embodiments of the present invention includes alternative implementations, in which functions may not be performed in the order shown or discussed, including performing functions in a substantially simultaneous manner or in reverse order depending on the functions involved, which should be understood by technicians in the technical field to which the embodiments of the present invention belong.

[0032] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as an ordered list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by an instruction execution system, device or apparatus (such as a computer-based system, a system including a processor, or other system that can fetch instructions from an instruction execution system, device or apparatus and execute the instructions), or in combination with these instruction execution systems, devices or apparatuses. For the purpose of this specification, "computer-readable medium" can be any device that can contain, store, communicate, propagate or transmit a program for use by an instruction execution system, device or apparatus, or in combination with these instruction execution systems, devices or apparatuses. More specific examples of computer-readable media (a non-exhaustive list) include the following: an electrical connection with one or more wires (electronic device), a portable computer disk box (magnetic device), a random access memory (RAM), a read-only memory (ROM), an erasable and programmable read-only memory (EPROM or flash memory), a fiber optic device, and a portable compact disk read-only memory (CDROM). In addition, the computer-readable medium may even be paper or other suitable medium on which the program is printed, since the program may be obtained electronically, for example, by optically scanning the paper or other medium and then editing, interpreting or processing in other suitable ways if necessary, and then stored in a computer memory.

[0033] It should be understood that the various parts of the present invention can be implemented by hardware, software, firmware or a combination thereof. In the above-mentioned embodiments, a plurality of steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, it can be implemented by any one of the following technologies known in the art or their combination: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0034] A person skilled in the art may understand that all or part of the steps in the method for implementing the above-mentioned embodiment may be completed by instructing related hardware through a program, and the program may be stored in a computer-readable storage medium, which, when executed, includes one or a combination of the steps of the method embodiment.

[0035] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0036] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A fuel cell AC impedance online testing method, characterized in that: The signal compensation module is used to control the quality of the excitation source for the online test of AC impedance. The controller performs harmonic component analysis on the fuel cell response output signal obtained after the disturbance signal is injected. If the corresponding harmonic component is greater than the preset threshold, the controller calculates the compensation component based on the harmonic component deviation and integrates all the compensation components to output to the signal compensation module. The signal compensation module compensates the excitation source for the online test of AC impedance according to the integrated compensation component, thereby ensuring the accuracy of the excitation waveform.

2. A fuel cell AC impedance online testing method according to claim 1, characterized in that: The harmonic component analysis includes phase synchronization analysis. The controller performs phase difference analysis on the response output signal. If the phase difference is greater than a preset phase difference threshold, the controller calculates the compensation phase in real time to perform online compensation.

3. A fuel cell AC impedance online testing method according to claim 1, characterized in that: The harmonic component analysis includes waveform integrity analysis. The controller performs waveform distortion analysis on the response output signal. If the waveform distortion is greater than a preset waveform distortion threshold, the controller calculates a corresponding compensation waveform and performs online compensation.

4. A fuel cell AC impedance online testing system, characterized in that: It includes an AC current excitation signal module, a fuel cell stack, a signal acquisition module, a signal compensation module and a controller. The disturbance signal generated by the AC current excitation signal module is injected into the fuel cell stack. The signal acquisition module acquires the response output signal of the fuel cell stack after the disturbance signal is injected. The controller performs online Fourier transform on the acquired response output signal and calculates the AC impedance of the fuel cell in real time. The controller also performs harmonic component analysis on the response output signal. If the corresponding harmonic component is greater than a preset threshold, the controller calculates the compensation component according to the harmonic component deviation, and integrates the compensation component and outputs it to the signal compensation module. The signal compensation module compensates the AC current excitation signal module according to the integrated compensation component, thereby ensuring the accuracy of the excitation waveform.

5. A fuel cell AC impedance online testing system according to claim 4, characterized in that: The AC current excitation signal module includes a DDS signal generator, an amplifier circuit, a filter circuit and a power amplifier module, wherein the filter circuit is a second-order active low-pass filter, the amplifier circuit is a two-stage differential instrument amplifier circuit, the power amplifier module is a Class A power amplifier circuit, and the frequency range generated by the DDS signal generator is 1Hz~100kHz, and the maximum amplitude is 30A; The frequency, amplitude and phase controllable sinusoidal AC current signal generated by the DDS signal generator is first amplified by a two-stage differential instrument amplifier circuit, then filtered out by a second-order active low-pass filter to remove high-order harmonic interference, and finally amplified by a power amplifier module to obtain an AC current excitation signal.

6. A fuel cell AC impedance online testing system according to claim 5, characterized in that: The DDS signal generator includes a phase accumulator, a sine lookup table, a digital-to-analog converter and a low-pass filter circuit. The phase accumulator performs phase accumulation with the chip system clock as the reference frequency under the control of the frequency control word to generate a series of discrete phase sequences, and also outputs the address code of the sine lookup table. After looking up the sine table, a digital sequence corresponding to the signal is generated. The digital sequence is D / A converted by the digital-to-analog converter to obtain a stepped analog voltage signal waveform. The analog voltage signal is output after passing through the low-pass filter circuit to obtain a smooth analog signal.

7. A fuel cell AC impedance online testing system according to claim 4, characterized in that: The signal compensation module includes a direct current generation module and an alternating current generation module. The direct current generation module is used to generate a direct current signal, and the alternating current generation module is used to generate an alternating current signal.

8. A fuel cell AC impedance online testing system according to claim 4, characterized in that: The harmonic component analysis includes phase synchronization analysis. The controller performs phase difference analysis on the response output signal. If the phase difference is greater than a preset phase difference threshold, the controller calculates the compensation phase in real time to perform online compensation.

9. A fuel cell AC impedance online testing system according to claim 4, characterized in that: The harmonic component analysis includes waveform integrity analysis. The controller performs waveform distortion analysis on the response output signal. If the waveform distortion is greater than a preset waveform distortion threshold, the controller calculates the corresponding compensation component and performs real-time online compensation.

10. The fuel cell AC impedance online testing system according to claim 4, characterized in that: The signal acquisition module includes a DC current signal acquisition module, an AC current signal acquisition module and an AC voltage signal acquisition module. The controller is an STM32F4 microcontroller, which has its own AD acquisition function. The controller is also connected to a host computer through an embedded Ethernet module, and the operating status of the fuel cell is monitored and determined through the host computer.

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