Fuel Cell Stack Fault Diagnosis Using THDA and EIS
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Solution Overview
Problem
Current methods for diagnosing faults in fuel cell stacks, such as THDA and EIS, struggle to quantitatively measure the cause of a drop in cell voltage, requiring additional apparatus and failing to accurately diagnose performance deterioration.
Innovation Solution
A method and apparatus that supply alternating currents with different frequency combinations to a fuel cell stack, measuring distortion rates and impedance to select optimal frequencies for diagnosing voltage drops and quantitatively determining the cause, using THDA and EIS for simultaneous diagnosis of voltage drops and their causes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If THDA method is used to diagnose cell voltage by calculating distortion rate through frequency analysis, then cell voltage drop can be easily detected, but it is substantially difficult to quantitatively measure the cause of the voltage drop
Solution Approach 1:
The diagnosis process is segmented into two distinct parts: first using THDA to detect voltage drop, then using EIS to identify the cause. This segmentation allows each method to specialize in what it does best while together providing complete diagnostic information.
Solution Approach 2:
Impedance measurement acts as an intermediary that bridges the gap between voltage drop detection and cause identification. The impedance data provides additional information about the fuel cell's internal state that helps interpret the voltage drop cause.
2Measurement precision
If EIS method is used to measure impedance by supplying sinusoidal current or voltage, then humidification state can be diagnosed, but it does not diagnose the drop in cell voltage and requires separate apparatus such as SVM or CVM
Solution Approach 1:
The patent merges THDA and EIS methods into a single integrated diagnostic system. By combining the voltage drop detection capability of THDA with the humidification diagnosis capability of EIS, the system achieves comprehensive diagnosis without requiring separate SVM or CVM apparatus.
Solution Approach 2:
The diagnostic system is designed to perform multiple functions: it can detect cell voltage drop, diagnose humidification state, and identify performance deterioration causes all through a single integrated platform that combines THDA and EIS measurements.
3Measurement precision
If separate apparatus such as SVM or CVM is used to diagnose cell voltage drop, then voltage diagnosis is possible, but the apparatus size and production costs increase
Solution Approach 1:
The patent merges the voltage diagnosis function into the existing EIS measurement system by incorporating THDA analysis. This eliminates the need for separate SVM or CVM apparatus, reducing overall system size and cost while maintaining diagnostic accuracy.
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 simultaneous measurement of voltage drops and their causes in fuel cell stacks, reducing apparatus size and production costs while improving diagnostic accuracy.
Implementation Method 1
A fuel cell is a type of battery that directly converts chemical energy generated by oxidation of fuel to electrical energy
Implementation Method 2
a fuel cell is identical to a chemical cell in that it uses an oxidation and reduction reaction to produce energy
Implementation Method 3
measuring impedance of the fuel cell stack using an electrochemical impedance spectroscopy (EIS). This method supplies a current or voltage as a sinusoidal waveform to the fuel cell stack and then measures a current (I) and voltage (V) of the fuel cell stack and calculates impedance based on the measured current (I) and voltage (V)
Data Source
AI summary
To diagnose a fault of a fuel cell stack, an alternating current having a first optimal frequency of a first frequency domain to diagnose a drop in cell voltage and an alternating current having a second optimal frequency of a second frequency domain to diagnose a cause of the drop in cell voltage are supplied to the fuel cell stack are provided. A distortion rate is then calculated based on voltage of the fuel cell stack according to the alternating current of the first optimal frequency, and the drop in cell voltage is diagnosed based on the calculated distortion rate. Also, impedance is calculated based on voltage and a current of the fuel cell stack according to the alternating current of the second optimal frequency and amount of water is calculated based on the calculated in the fuel cell stack, and the cause of the drop in cell voltage is diagnosed based on the calculated impedance and amount of water.