Fuel Cell Stack Impedance Isolation in DC-DC Converter Systems
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Solution Overview
Problem
Existing methods for measuring the impedance of a fuel cell stack in vehicles fail to accurately isolate the impedance of the stack from other components, leading to incomplete analysis of the fuel cell's internal state and performance characteristics.
Innovation Solution
An apparatus and method utilizing a DC-DC converter and an impedance measurement device, controlled by a controller, which measures the impedance of a fuel cell stack by distinguishing between the stack's impedance and that of other components by drawing and stopping the output of the fuel cell stack, applying AC signals, and adjusting resistors to isolate the stack's impedance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If impedance measurement is performed in a fuel cell system with DC-DC converter and other components, then the measurement can be conducted in practical vehicle conditions, but the measured impedance includes contributions from other components (air compressor, cooling pump, etc.) making it difficult to isolate the fuel cell stack impedance
Solution Approach 1:
The patent segments the impedance measurement process into two distinct states: one where the fuel cell stack output is drawn and another where it is not drawn. By measuring impedance in both states and comparing the results, the contribution of the fuel cell stack can be isolated from other system components. This segmentation allows practical vehicle system measurement while achieving accurate stack-specific impedance data.
Solution Approach 2:
The patent extracts the fuel cell stack impedance from the total system impedance by performing differential measurement. The controller calculates the stack impedance by subtracting the impedance measured when the stack is not drawing output from the impedance measured when the stack is drawing output. This extraction method isolates the stack's contribution from other components like DC-DC converter, air compressor, and cooling pump.
2Productivity
If the output of the fuel cell stack is continuously drawn to maintain normal operation, then the vehicle power supply is ensured, but the impedance measurement cannot be performed without stopping the drawing
Solution Approach 1:
The patent implements periodic impedance measurement by temporarily pausing the fuel cell stack output drawing at predetermined intervals, performing the measurement during this brief pause, and then resuming normal operation. The controller is configured to perform measurement at predetermined periods or when specific conditions are met, allowing the system to maintain productivity while enabling operational measurement capability.
Solution Approach 2:
The patent performs preliminary control actions to prepare the system for measurement by stopping the drawing temporarily before the actual impedance measurement takes place. This preliminary pause ensures that the measurement conditions are met without requiring prolonged interruption of vehicle power supply, making the measurement process easier to operate while maintaining overall productivity.
3Measurement precision
If the drawing of fuel cell stack output is stopped to perform impedance measurement, then the impedance measurement can be performed, but the vehicle power supply may be affected and the measurement process becomes more complex
Solution Approach 1:
The patent employs feedback control where the controller continuously monitors the impedance measurement process and automatically adjusts the drawing control based on measurement results. The controller determines whether to continue, pause, or resume drawing based on real-time impedance data and system conditions, simplifying the overall control complexity by using feedback-driven decision-making rather than complex predetermined control sequences.
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
Accurately measures the impedance of the fuel cell stack, enabling precise analysis of its internal state, quantity, mass transfer loss characteristics, and activation losses, even in the presence of other components like air compressors and cooling pumps.
Implementation Method 1
an impedance measurement device that is provided in a fuel cell system to measure an impedance of an output terminal of a fuel cell stack
Data Source
AI summary
Disclosed are an apparatus for measuring an impedance of a fuel cell in a system to which a DC-DC converter is applied and a method thereof. The method includes calculating an impedance of a fuel cell stack based on an impedance of an output terminal of the fuel cell stack measured in a state in which the output of the fuel cell stack is drawn and the impedance of the output terminal of the fuel cell stack measured in a state in which the drawing of the output of the fuel cell stack is stopped.