Fuel Cell Stage Impedance Measurement With Reference Error Correction
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Solution Overview
Problem
Current methods for determining the impedance of fuel cell stages, especially in operational hydrogen fuel cells, are inadequate as they often require laboratory instruments and cannot accurately measure impedance at specific frequencies necessary for assessing the state of health, particularly due to insufficient sampling frequency and lack of portability for embedded systems like mobile vehicles.
Innovation Solution
A device and method that apply an excitation signal to each fuel cell stage, measure response signals, and use an equivalent circuit with a reference impedance to calculate the impedance of each stage, allowing for precise determination of impedance and state of health, even in operational conditions, with a compact design suitable for integration into mobile systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If dedicated laboratory instruments are used to measure impedance, then measurement precision is improved, but device complexity and portability are worsened
Solution Approach 1:
The patent segments the measurement system into modular components: connection circuits for each stage, selection means for choosing which stage to measure, and a compact measurement system with excitation signal generation. This segmentation allows the complex measurement function to be distributed and integrated into the fuel cell system without requiring a single large laboratory instrument.
Solution Approach 2:
The measurement system is designed to measure impedance of multiple stages (first stage, second stage, etc.) using the same excitation system and selection means. This multi-functional approach allows a single compact device to perform measurements on different stages, replacing the need for separate dedicated instruments for each stage.
2Device complexity
If electronic components with standard sampling frequency are used, then device complexity is reduced, but measurement precision at 1 kHz is worsened
Solution Approach 1:
The patent specifically addresses the sampling frequency parameter by designing the measurement system to operate at 1 kHz, which is the required frequency for accurate impedance measurement. The excitation system generates signals and the measurement system samples at this specific frequency, ensuring measurement precision while maintaining reasonable device complexity through targeted parameter selection rather than overly complex hardware.
3Productivity
If impedance measurement is performed during cell operation, then productivity is improved, but measurement precision is worsened due to operational conditions
Solution Approach 1:
The patent implements preliminary action by performing impedance measurements during normal fuel cell operation rather than requiring separate testing. The measurement system is integrated into the operational system, allowing impedance data to be collected continuously or periodically while the cell is generating power, thus improving productivity by eliminating separate measurement steps.
Solution Approach 2:
The patent introduces connection circuits as intermediaries between the fuel cell stages and the measurement system. These connection circuits enable the measurement system to access stage voltages and apply excitation signals without disrupting normal cell operation, allowing precise measurements to be taken during operational conditions.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables accurate and portable measurement of fuel cell stage impedance, improving the estimation of the state of health by determining resistance variations in the electrolyte, thus enhancing the performance and longevity assessment of fuel cell membranes.
Implementation Method 1
measuring a response signal of the selected stage to the application of the excitation signal; determining an impedance of the selected stage
Data Source
Figure 1
Figure 2~3
AI summary
Impedance determination device for a plurality of stages (2) of a fuel cell (3), the device comprising a measurement system (11) having an excitation system (C1) common to the plurality of stages (2), an equivalent circuit (C2) having a reference impedance corresponding to that of a stage of the plurality of stages (2), and selection means (M+, M-) capable of selecting a stage (2) and the equivalent circuit (C2); the measurement system being configured to measure a response signal of a selected stage (2) and a response signal of the equivalent circuit (C2) to the application of an excitation signal; and to determine an impedance of the selected stage from the response signal of the selected stage and an impedance error calculated from the reference impedance and an impedance determined of the equivalent circuit from the response signal of the equivalent circuit (C2).