Fuel Cell Impedance Measurement Feedback Control
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Solution Overview
Problem
The existing impedance measuring devices for fuel cells face accuracy issues due to fluctuations in capacitance, leading to excessive amplification of AC signals and decreased measurement accuracy.
Innovation Solution
An impedance measuring device with a positive and negative output unit, a detection unit for AC potential differences, and adjustment units to converge detection signals to a predetermined value, utilizing in-phase and orthogonal component extraction to calculate resistance and capacitance components, ensuring accurate impedance measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the amplitude of the AC signal is adjusted using an out-of-phase potential difference signal, then the measurement range is extended, but the measurement accuracy decreases due to excessive amplification
Solution Approach 1:
The patent implements feedback control by detecting the potential difference signal, comparing its phase with the AC signal, and adjusting the AC signal amplitude accordingly. The detection unit monitors the potential difference between electrode terminals, and the adjustment unit modifies the AC signal amplitude to maintain the potential difference within a predetermined range, preventing excessive amplification while adapting to varying capacitance conditions
Solution Approach 2:
The patent changes the amplitude parameter of the AC signal dynamically based on the detected phase difference and potential difference magnitude. By adjusting this key parameter in response to capacitance fluctuations, the system maintains measurement accuracy across different operating conditions without requiring excessive signal amplification
2Adaptability or versatility
If capacitance components fluctuate significantly depending on operation state, then the fuel cell adapts to different operating conditions, but the potential difference signal becomes out of phase with the AC signal
Solution Approach 1:
The system continuously monitors the phase relationship between the AC signal and potential difference signal, and adjusts the AC signal amplitude in real-time based on detected phase deviations. This feedback mechanism compensates for phase shifts caused by capacitance fluctuations, maintaining signal coherence across different operation states
Solution Approach 2:
The patent employs dynamic adjustment of the AC signal amplitude rather than a fixed amplitude. The adjustment unit modifies the signal characteristics in real-time according to the instantaneous operation state and capacitance conditions, enabling the system to adapt to varying operating conditions while maintaining measurement precision
3Difficulty of detecting and measuring
If the amplitude of the AC signal is excessively amplified to compensate for low detection level, then the signal detection sensitivity is improved, but the impedance measurement accuracy decreases
Solution Approach 1:
The detection unit monitors the potential difference signal level and phase, and the adjustment unit provides feedback control to modify the AC signal amplitude. This feedback loop prevents excessive amplification by continuously adjusting the signal to maintain optimal detection levels without compromising measurement accuracy
Solution Approach 2:
Instead of excessively amplifying the AC signal, the patent applies partial adjustment - modifying the amplitude just enough to maintain the potential difference within the predetermined range. This avoids the harmful effects of excessive amplification while achieving sufficient detection sensitivity
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
This solution effectively suppresses the decrease in measurement accuracy by adjusting AC signal amplitudes based on vector values, maintaining precise impedance measurement despite capacitance fluctuations, thereby reducing current leakage to the load and enhancing measurement reliability.
Implementation Method 1
an in-phase signal being in phase with the AC signal having the predetermined frequency
Implementation Method 2
a phase of the orthogonal signal being orthogonal to a phase of the AC signal having the predetermined frequency
Data Source
Figure 1A~1B
Figure 2
Figure 3
AI summary
An impedance measuring device outputs an AC signal having a predetermined frequency to each of a positive electrode terminal and a negative electrode terminal of the fuel cell. The impedance measuring device includes a detection unit that detects an AC potential difference between the positive electrode terminal and a midpoint of the fuel cell, and an adjustment unit that adjusts an amplitude of the AC signal to adjust a detection signal to a predetermined value. The impedance measuring device includes an in-phase component extraction unit that multiplies the detection signal by an in-phase signal and extracts a resistance component of the detection signal, and a calculation unit that calculates a positive real axis impedance on the basis of the resistance component and the output signal. The impedance measuring device includes an orthogonal component extraction unit that multiplies the detection signal by an orthogonal signal and extracts a capacitance component of the detection signal, and a reproduction unit reproduces a vector value of the detection signal on the basis of the extracted capacitance component and resistance component. The adjustment unit adjusts the amplitude of the AC signal so that the reproduced vector value equals the predetermined value.