Fuel Cell Warm-Up Control for Auxiliary Failure Stability
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Solution Overview
Problem
In fuel cell systems, the warm-up operation can lead to unstable output voltage and current when auxiliary machines fail, causing overcharging of secondary batteries and excessive reduction in air stoichiometric ratio, which affects fuel cell performance.
Innovation Solution
A fuel cell system with a target operating point determination unit, operation control unit, and failure state identification unit that adjusts the operating point to reduce the required electric power and heat generation during failures, maintaining stability by controlling output voltage and current within predetermined ranges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the required electric power amount during warm-up is reduced to avoid overcharging the secondary battery when auxiliary machines fail, then the air stoichiometric ratio is excessively lowered, but this causes the output voltage and output current of the fuel cell to become unstable
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the target operating point parameters (output voltage and/or output current) based on the failure state of auxiliary machines. When a failure is detected, the control unit selects a different target operating point that maintains stability in the voltage-current characteristic region, rather than simply reducing power output. This resolves the contradiction by changing the operational parameters to achieve both power reduction and stability maintenance.
Solution Approach 2:
The patent implements feedback control by continuously monitoring the operating state of auxiliary machines and adjusting the fuel cell's target operating point accordingly. The control unit receives information about auxiliary machine failures and modifies the warm-up control strategy in real-time, selecting appropriate target operating points from predefined sets based on the detected failure state. This feedback mechanism enables the system to maintain stability while adapting to changed conditions.
2Power
If the air stoichiometric ratio is excessively lowered during warm-up operation, then the required electric power amount is reduced, but this operates the fuel cell in a region where the change in output voltage with respect to change in air stoichiometric ratio is large
Solution Approach 1:
The patent changes the control parameter from directly controlling air stoichiometric ratio to controlling the target operating point (output voltage and/or current). By selecting target operating points in regions with favorable voltage-current characteristics, the system indirectly controls the air stoichiometric ratio in a way that avoids excessive sensitivity regions. This parameter transformation resolves the contradiction between power reduction and voltage stability.
3Reliability
If the fuel cell operates at an operating point with reduced required electric power amount during warm-up, then the secondary battery is protected from overcharging, but the output voltage and current become unstable due to high air stoichiometric ratio sensitivity
Solution Approach 1:
The patent applies dynamics by implementing a dynamic target operating point selection mechanism that adapts to the operational state. Instead of using a fixed reduced power operating point, the system dynamically selects from multiple predefined target operating points based on auxiliary machine failure detection. This dynamic adaptation maintains ease of operation by keeping the fuel cell in regions with favorable control characteristics while still achieving power reduction when needed.
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 approach stabilizes the output voltage and current during warm-up operations even when auxiliary machines fail, preventing overcharging and maintaining efficient fuel cell performance by adjusting the operating point to match the target values.
Implementation Method 1
a fuel cell that receives supply of air and fuel gas to generate electric power
Implementation Method 2
a warm-up operation is executed in which electric power is generated at a lower air stoichiometric ratio than when starting at room temperature while rotating a circulation pump to operate the fuel cell stack at a low efficiency and increase the amount of discharged heat
Data Source
AI summary
A fuel cell system includes: a fuel cell; a target operating point determination unit that determines a warm-up target operating point based on a required electric power amount during warm-up and a required heat generation amount during warm-up; an operation control unit; and a failure state identification unit that identifies whether an electric power consumption device that operates by consuming generated electric power generated by the fuel cell has failed. When a failure of the electric power consumption device is identified, the target operating point determination unit determines an operating point that satisfies a required electric power amount during a failure that is set to be smaller than the required electric power amount during the warm-up and a required heat generation amount during the failure that is set to be smaller than the required heat generation amount during the warm-up as a target operating point during the failure.