Fuel Cell Vehicle Shutdown Relay Protection
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Solution Overview
Problem
Existing methods for shutting down a fuel cell vehicle often result in relay damage and unnecessary hydrogen gas consumption due to high stack voltage maintenance and inrush currents during the shutdown process, which can lead to system delays and inefficiencies.
Innovation Solution
A method involving a controller-managed air blocking, voltage raising, and stack voltage blocking steps to prevent relay damage, combined with strategic use of resistor relays to consume remaining fuel cell stack voltage while maximizing high voltage battery charging, thereby controlling inrush currents and minimizing hydrogen gas usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the stack main relay is opened while maintaining high stack voltage during shutdown, then the shutdown process can proceed, but fusion damage of the stack main relay occurs due to current generation
Solution Approach 1:
The patent applies preliminary action by raising the voltage at the rear end of the stack main relay before opening the relay. This pre-conditioning ensures that when the relay opens, no current flows through it, preventing fusion damage. The controller increases the rear-end voltage to exceed the stack voltage, creating a voltage reversal that blocks current flow at the moment of relay opening.
Solution Approach 2:
The patent applies preliminary anti-action by creating a counter-voltage condition that prevents harmful current flow. By raising the rear-end voltage above the stack voltage before relay opening, the system creates an opposing electrical potential that actively prevents current generation, thereby protecting the relay from fusion damage during the shutdown process.
2Power
If the resistor relay is closed to consume stack voltage while hydrogen gas supply is maintained, then voltage consumption occurs, but unnecessary hydrogen gas consumption and heat generation occur
Solution Approach 1:
The patent applies dynamics by making the hydrogen gas supply conditional rather than static. The gas supply is dynamically controlled to be suspended when the resistor relay is activated for voltage consumption, and only restored when voltage consumption is complete. This dynamic adjustment eliminates unnecessary hydrogen consumption and associated heat generation during the voltage consumption phase.
Solution Approach 2:
The system uses the electrical energy already present in the stack to consume itself through the resistor relay, without requiring additional hydrogen gas input. The remaining electrical energy in the stack is discharged through the resistor, allowing the system to consume its own residual energy without needing to burn additional hydrogen, thereby improving efficiency.
3Productivity
If the stack main relay is opened while current is generated in the stack, then shutdown can proceed, but fusion damage of the stack main relay occurs
Solution Approach 1:
The patent applies preliminary action by raising the voltage at the rear end of the stack main relay before opening the relay. This pre-conditioning ensures that when the relay opens, no current flows through it, preventing fusion damage. The controller increases the rear-end voltage to exceed the stack voltage, creating a voltage reversal that blocks current flow at the moment of relay opening.
Solution Approach 2:
The patent converts the potentially harmful situation of high stack voltage into a beneficial protective mechanism. By deliberately raising the rear-end voltage above the stack voltage, the system creates a protective voltage reversal that prevents current flow and relay damage. The high voltage condition, which could be harmful, is transformed into a protective barrier that safeguards the relay during shutdown.
4Power
If resistor relays are switched during voltage consumption, then complete voltage consumption is achieved, but intermittent resistance relay damage occurs due to inrush current
Solution Approach 1:
The patent applies periodic action through a controlled sequence of resistor relay operations. The relays are switched in a specific periodic pattern with proper timing coordination, allowing complete voltage consumption while avoiding simultaneous switching that would cause inrush current. The controller manages the sequential activation and deactivation of resistor relays to prevent damage.
Solution Approach 2:
The patent uses feedback control to monitor stack voltage levels and adjust resistor relay operation accordingly. The controller continuously monitors the voltage consumption progress and adjusts the resistor relay switching timing based on real-time voltage conditions, preventing inrush current while ensuring complete voltage consumption. This feedback mechanism coordinates relay switching to avoid damage.
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 relay fusion and damage, improves fuel economy by maximizing battery charging, and minimizes hydrogen gas consumption during shutdown, ensuring efficient and safe system closure.
Implementation Method 1
a fuel cell vehicle receives power from two power supplying sources, namely a fuel cell stack and a high voltage battery
Implementation Method 2
energy used for consuming the remaining voltage of the stack is generated to heat by the resistor
Data Source
AI summary
A method of shutting down operation of a fuel cell vehicle includes: blocking, by a controller, an air supply to a fuel cell stack when an operation shutting down command of the fuel cell vehicle is applied; increasing, by the controller, a voltage at an rear end of a stack main relay connected to the fuel cell stack; and opening, by the controller, the stack main relay when the voltage at the rear end of the stack main relay is higher than a stack voltage by a predetermined voltage or more.