Fuel Cell Vehicle Shutdown Sequence for Catalyst Protection
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Solution Overview
Problem
The existing fuel cell vehicle systems forcibly discharge electricity from fuel cells during power shutdown, leading to potential deterioration of catalysts and other components.
Innovation Solution
A fuel cell vehicle system with a controller-managed power stop sequence that shuts down the fuel cell system before discharging capacitors, maintaining the capacitor voltage higher than the fuel cell voltage to avoid forced discharge and minimize component damage, using relays to disconnect the boost converter from the inverter and battery, and employing capacitors and discharge resistances to manage voltage thresholds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the boost converter is activated to forcibly discharge remaining charges in the fuel cells, then the capacitor can be discharged, but the catalyst and other components of the fuel cells deteriorate
Solution Approach 1:
The fuel cell system is shut down before discharging the capacitor, allowing the fuel cell voltage to naturally decrease first. This preliminary shutdown prevents the harmful forced discharge current from flowing through the catalyst, while still enabling subsequent capacitor discharge through the inverter when fuel cell voltage is sufficient.
Solution Approach 2:
Instead of activating the boost converter to forcibly discharge the fuel cell as in conventional systems, this invention inverts the approach by allowing the fuel cell to naturally shut down and voltage to decrease first, then using the inverter to discharge the capacitor when conditions are favorable, avoiding damage to the fuel cell catalyst.
2Productivity
If the fuel cell system is shut down immediately, then the shutdown process is simplified, but the voltage difference between capacitor and fuel cell may cause harmful discharge
Solution Approach 1:
The controller continuously monitors the voltage of both the fuel cell and the capacitor, and dynamically controls the inverter operation based on the voltage difference. When the capacitor voltage exceeds the fuel cell voltage plus a predetermined threshold, the inverter is controlled to prevent harmful discharge, ensuring safe operation throughout the shutdown process.
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 prevents the forced discharge of fuel cells, thereby reducing the risk of catalyst and component damage during power shutdown, ensuring a more gradual and natural voltage decrease and maintaining capacitor voltage above the fuel cell voltage for controlled discharging.
Implementation Method 1
The fuel cell generates electricity by supplies of hydrogen fuel and oxygen
Implementation Method 2
The inverter converts DC power to AC power for driving the electric traction motor
Implementation Method 3
a boost converter which boosts an output voltage of a fuel cell
Implementation Method 4
A first capacitor is connected between a positive terminal and a negative terminal of the first high voltage terminals
Data Source
AI summary
A fuel cell vehicle may include: an electric traction motor; an inverter; a fuel cell system; a first boost converter including first low voltage terminals connected to a fuel cell and first high voltage terminals connected to the inverter, the first boost converter including a first capacitor connected between positive and negative terminals of the first high voltage terminals; a first relay connected between the first boost converter and the inverter; and a controller, wherein the controller is configured to: shut down the fuel cell system; while a voltage of the fuel cell is higher than a voltage threshold, discharge the first capacitor and maintain a voltage thereof higher than the voltage of the fuel cell; and when the voltage of the fuel cell becomes lower than the voltage threshold, stop discharging the first capacitor and disconnect the first boost converter from the inverter by opening the first relay.