DC/DC-less Battery-Fuel Cell Coupling via Voltage Matching
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Solution Overview
Problem
Fuel cell vehicles require a supplemental power source and a bi-directional DC/DC converter to match battery voltage to the fuel cell stack voltage, which is costly, heavy, and prone to damage from large voltage swings.
Innovation Solution
A matched battery system that matches its voltage to the power bus line voltage, eliminating the need for a DC/DC converter, with a lithium ion battery design and additional components like diodes and switches to prevent over-discharge and over-charge, allowing the fuel cell stack to recharge the battery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a bi-directional DC/DC converter is used to match battery voltage to fuel cell stack voltage, then voltage matching is achieved, but the system becomes costly, heavy, and complex
Solution Approach 1:
The patent removes the DC/DC converter from the system entirely by selecting a battery with voltage characteristics that naturally match the fuel cell stack's operating voltage range. This extraction eliminates the complex voltage conversion device while maintaining proper voltage matching through careful battery selection and system design.
Solution Approach 2:
The patent changes the battery selection parameters to match the fuel cell stack's voltage characteristics. By selecting a specific battery type with appropriate voltage range and characteristics, the system achieves voltage compatibility without requiring active voltage conversion, thereby eliminating the DC/DC converter.
2Stability of the object's composition
If a DC/DC converter is used to handle voltage swings, then voltage stability is maintained, but the system cost and weight increase
Solution Approach 1:
The DC/DC converter is removed from the system by designing a battery-fuel cell interface that naturally handles voltage swings through proper battery selection and system architecture, eliminating the need for active voltage regulation hardware.
Solution Approach 2:
The battery is selected to inherently handle the voltage swings produced by the fuel cell stack through its natural voltage characteristics and operating range, without requiring external active regulation. The system uses the battery's inherent properties to self-regulate voltage compatibility.
3Device complexity
If the battery is designed to eliminate the DC/DC converter, then system complexity is reduced, but the battery may be damaged by large voltage swings
Solution Approach 1:
The system incorporates protective circuitry and control mechanisms that prevent the battery from being damaged by voltage swings, while still maintaining the simplified architecture without a DC/DC converter. This cushioning approach allows the battery to operate in the simplified system without exposing it to harmful voltage conditions.
Solution Approach 2:
The patent introduces intermediate protective elements or control mechanisms that mediate between the fuel cell stack and the battery, protecting the battery from damaging voltage swings while maintaining the overall simplified system architecture. This intermediary layer enables the DC/DC-less design to proceed safely.
4Device complexity
If a matched battery is used without a DC/DC converter, then cost and weight are reduced, but voltage and current matching becomes more difficult to control
Solution Approach 1:
The matched battery inherently provides voltage and current compatibility with the fuel cell stack through its selected characteristics, eliminating the need for complex active control systems. The system uses the battery's natural properties to self-regulate the voltage and current matching.
Solution Approach 2:
The patent carefully selects and designs the battery parameters (voltage range, capacity, internal resistance) to match the fuel cell stack's characteristics, thereby achieving proper voltage and current matching through parameter optimization rather than active control, reducing system cost while maintaining compatibility.
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
Enables efficient power delivery without a DC/DC converter, preventing battery damage from voltage swings and ensuring safe operation by matching battery characteristics to the fuel cell stack's voltage and current characteristics.
Implementation Method 1
A hydrogen fuel cell is an electrochemical device that includes an anode and a cathode with an electrolyte therebetween. The anode receives hydrogen gas and the cathode receives oxygen or air. The hydrogen gas is dissociated in the anode to generate free hydrogen protons and electrons.
Implementation Method 2
The system also includes a diode electrically coupled to the power bus line and a by-pass switch electrically coupled to the bus line in parallel with the diode.
Implementation Method 3
The by-pass switch is selectively opened and closed to allow the fuel cell stack to recharge the battery and prevent the battery from being overcharged.
Implementation Method 4
The hydrogen protons react with the oxygen and the electrons in the cathode to generate water. The electrons from the anode cannot pass through the electrolyte, and thus are directed through a load to perform work before being sent to the cathode.
Data Source
AI summary
A fuel cell system that employs a matched battery that matches the battery voltage to a fuel cell power bus voltage so as to eliminate the need for a DC/DC converter. The internal characteristics and parameters of the matched battery allow it to operate over the large load dependent voltage swing of the fuel cell, and prevent the battery state of charge from going below a damaging value. The battery type, number of battery cells and the battery internal impedance are selected to provide the desired matching. In one embodiment, the battery is a lithium ion battery. The system also includes a diode electrically coupled to the power bus line and a by-pass switch electrically coupled to the power bus line in parallel with the diode. The by-pass switch is selectively opened or closed to allow the fuel cell stack to recharge the battery and prevent the battery from being overcharged.