Fuel Cell Control Device for Battery Overcharge Prevention
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Solution Overview
Problem
During low efficiency power generation in fuel cell systems, the battery tends to become overcharged or overdischarged, leading to deterioration, especially in low temperature environments due to deviations in generated electric power from target values.
Innovation Solution
A fuel cell system with a control device that adjusts the flow rate of oxidizing agent gas to control the fuel cell's current and voltage within specific ranges, allowing for the battery to be repeatedly charged and discharged, thereby maintaining allowable charged and discharged powers and preventing overcharging or overdischarging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If low efficiency power generation is performed to rapidly warm up the fuel cell, then the fuel cell temperature increases quickly, but the battery becomes overcharged or overdischarged leading to deterioration
Solution Approach 1:
The control device causes the fuel cell voltage to repeatedly increase and decrease above and below the target voltage through periodic adjustments in oxidizing agent gas flow rate. This periodic action makes the generated electric power fluctuate around the target value, allowing the battery to be repeatedly charged and discharged in a controlled manner that prevents overcharging or overdischarging while maintaining rapid warm-up performance
2Loss of energy
If the air stoichiometric ratio is reduced to enable low efficiency power generation, then power generation loss increases, but voltage fluctuation becomes greater when the ratio deviates from target
Solution Approach 1:
The control device continuously monitors the fuel cell voltage and adjusts the oxidizing agent gas flow rate based on feedback from the actual voltage compared to the target voltage. This feedback control ensures that when the air stoichiometric ratio is reduced for low efficiency power generation, the voltage fluctuations are actively compensated, maintaining stability while achieving the desired power generation loss for rapid warm-up
3Power
If the generated electric power deviates greatly from target value, then battery charging/discharging power increases, but the battery becomes overcharged or overdischarged
Solution Approach 1:
The control device dynamically adjusts the oxidizing agent gas flow rate to make the generated electric power increase and decrease above and below the target value, rather than maintaining a fixed target. This dynamic control ensures that the battery charging and discharging powers remain within allowable ranges by continuously adapting the power output to prevent overcharging or overdischarging while still achieving rapid warm-up through low efficiency power generation
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 enables quick temperature increase of the battery, expanding its allowable power handling capabilities and preventing battery deterioration during low efficiency power generation.
Implementation Method 1
a fuel cell configured to generate electric power by electrochemical reactions between a fuel gas and oxidizing agent gas
Implementation Method 2
a rechargeable battery configured to be charged with excess electric power and discharge an insufficient amount of electric power
Data Source
AI summary
The low efficiency power generation part of a control device is provided with an operating point setting part setting a target current and a target voltage defining an operating point of the fuel cell at the time of low efficiency power generation and a generated electric power control part making the generated electric power of the fuel cell increase and decrease at the time of low efficiency power generation by controlling the current of the fuel cell to the target current while making the flow rate of feed of oxidizing agent gas supplied to the fuel cell fluctuate so that the voltage of the fuel cell increases and decreases above and below the target voltage within a range where the charged and discharged electric powers of the rechargeable battery do not become larger than the allowable charged and discharged electric powers.