Fuel Cell Current Control via Oxidant Flow Feedback
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Solution Overview
Problem
Fuel cell systems in vehicles experience fluctuations in driving torque due to variations in current output from the fuel cell, which are caused by periodic fluctuations in the flow of oxidant gas, leading to unstable vehicle performance.
Innovation Solution
A fuel cell system with a controller that measures the flow amount of oxidant gas and adjusts the current output to maintain an acceptable current value, incorporating a changing-suppression processing to reduce the fluctuation width of the current during specific conditions, ensuring stable torque delivery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the supply amount of oxidant gas is controlled to converge toward a target value, then the flow amount control precision is improved, but the current output fluctuates due to periodic variations in flow amount
Solution Approach 1:
The patent implements feedback control by measuring the actual flow amount of oxidant gas and adjusting the supply amount to converge toward a target value. The controller uses the measured flow amount to determine an acceptable current value and restricts the fuel cell current output accordingly, creating a closed-loop control system that maintains stability despite periodic fluctuations.
Solution Approach 2:
The patent changes the parameter used for current control from directly controlling current to controlling based on flow amount measurements. By determining an acceptable current value based on the measured flow amount and using this as the control parameter, the system adapts to flow variations while maintaining stable current output.
2Measurement precision
If the acceptable current value is determined based on measured flow amount, then the current control accuracy is improved, but the changing width of current value increases during transient conditions
Solution Approach 1:
The patent applies preliminary action by determining the acceptable current value in advance based on the measured flow amount before actual current control. The controller calculates what the current value should be based on flow conditions, then restricts the actual current to this pre-determined acceptable value, preventing excessive fluctuations before they occur.
Solution Approach 2:
The patent provides beforehand cushioning by establishing an acceptable current value range based on flow measurements. This pre-established limit acts as a cushion that absorbs potential current fluctuations, restricting the current to stay within acceptable bounds even during transient conditions where the changing width might otherwise increase.
3Measurement precision
If feed-back control is applied to converge flow amount to target value, then the flow control precision is improved, but the driving torque fluctuates due to current variations
Solution Approach 1:
The patent uses feedback control to measure the flow amount of oxidant gas and adjust the supply to converge toward the target value. This closed-loop feedback system maintains precise flow control while the controller simultaneously uses the measured flow amount to determine acceptable current values, ensuring stable current output and thereby stable driving torque despite flow variations.
Solution Approach 2:
The patent changes the control approach by determining current limits based on measured flow parameters rather than using fixed current targets. By adapting the acceptable current value to the actual flow conditions through parameter changes, the system maintains both precise flow control and stable torque output.
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
The system effectively reduces the fluctuation in driving torque by controlling the current output based on measured flow amounts, enhancing vehicle stability and performance by maintaining a consistent torque level during predetermined conditions.
Implementation Method 1
The fuel cell generates electric power by a chemical reaction between hydrogen as fuel and air containing oxygen as oxidant and drives a motor
Implementation Method 2
a flow-amount measurement unit that measures a flow amount of the oxidant gas from the supply unit
Implementation Method 3
a controller that feed-back controls the supply unit such that a measured flow-amount value of the flow-amount measurement unit converges toward a target flow-amount value
Implementation Method 4
the controller restricts the current output by the fuel cell to the acceptable current value or less, and controls the current in accordance with a requested current value of the fuel cell
Data Source
AI summary
A fuel cell system includes: a fuel cell outputting a current; a supply unit supplying oxidant gas; a flow-amount measurement unit measuring a flow amount of the oxidant gas; and a controller that feed-back controls the supply unit such that a measured flow-amount value converges toward a target flow-amount value, wherein the controller determines an acceptable current value in accordance with the measured flow-amount value, restricts the current to the acceptable current value or less, controls the current in accordance with a requested current value of the fuel cell; and performs a changing-suppression processing, when a condition continues for a predetermined period, the condition including that a changing width of the requested current value is equal to or less than a first value and a difference between the requested current value and the acceptable current value is equal to or less than a second value.