Fuel Cell Startup Load Switching for Smaller DC/DC Converters
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Solution Overview
Problem
Fuel cell systems face inefficiencies due to the need for oversized DC/DC converters to handle both open circuit and full load conditions, leading to poor power utilization and increased space requirements, as they must be dimensioned for both voltage and current, limiting the ability to stack more fuel cells in series.
Innovation Solution
Implementing a method where fuel cell stacks are initially connected to a local load during startup, allowing the output voltage to be higher, and only connecting to the main electrical system through a DC/DC converter when the voltage drops below rated levels, thereby reducing the need for additional converter hardware and optimizing space usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If fuel cell stacks are stacked in series to increase output voltage, then the voltage limitation prevents utilizing room height and more floor area is required, but stacking vertically would improve space utilization
Solution Approach 1:
The patent applies dynamics by enabling the fuel cell system to operate at different voltage levels dynamically. During startup, the system operates at higher voltage (utilizing vertical stacking), and during normal operation, it switches to regulated voltage mode. This dynamic operation allows vertical stacking to be feasible despite voltage concerns.
Solution Approach 2:
The patent changes the operating voltage parameter of the fuel cell system. By allowing the system to operate at higher voltages during startup and then regulating down to standard voltages during normal operation, it enables vertical stacking of fuel cells without exceeding voltage limits of connected equipment.
2Reliability
If DC/DC converters are dimensioned for both open circuit voltage and full load current, then voltage regulation is maintained, but power conversion capacity utilization becomes poor
Solution Approach 1:
The patent applies preliminary action by performing voltage regulation during the startup phase when the local load is connected. The DC/DC converter is pre-regulated to the appropriate voltage level before the main system operates, avoiding the need for continuous oversized conversion capacity.
Solution Approach 2:
The patent extracts the voltage regulation function to a separate startup phase with local load. By handling voltage regulation during startup rather than requiring continuous regulation capacity, the main DC/DC converter can be sized for normal operation only, improving utilization.
3Power
If more fuel cell stacks are connected in series to increase power output, then power capacity increases, but the amount of power converters and cabling increases
Solution Approach 1:
The patent merges multiple fuel cell stacks in series to achieve higher voltage and power output. By connecting stacks in series rather than parallel, the system achieves increased power capacity without proportionally increasing the number of converters and cabling required.
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 allows for more efficient packing of fuel cell stacks, reduces the amount of power converters and cabling, and enables better utilization of available space, while maintaining efficient voltage regulation and power delivery.
Implementation Method 1
The fuel cell system comprises one or more DC/DC converters connected to the voltage outputs of the fuel cell system
Implementation Method 2
The local load is adapted to draw power from the fuel cell system so as to decrease the voltage of the fuel cell system
Data Source
AI summary
A fuel cell power system and a method of starting a fuel cell power system. The fuel cell power system includes a fuel cell system having one or more voltage outputs, one or more DC/DC converters each having an output and an input, the input being connectable to the voltage outputs of the fuel cell system, a DC voltage link connectable to the output of the one or more DC/DC converters, and a local load connectable to the DC voltage link. In the system, the local load is adapted to draw power from the fuel cell system to decrease the voltage of the fuel cell system.