Rail Vehicle Fuel Cell Power Pack With Multi-Voltage DC/DC Conversion
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Solution Overview
Problem
Existing rail vehicle drive trains are inflexible due to voltage levels that are not suitable for all components, leading to inefficient energy distribution and operational limitations.
Innovation Solution
A rail vehicle design featuring a first energy supply unit with multiple fuel cells, DC/DC converters, and a DC/AC converter, along with a redundant second energy supply unit, allowing for adaptable voltage management and independent operation of the power pack, ensuring energy distribution across different components and maintaining operational safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single voltage level is used in the drive train, then the system structure is simplified, but the voltage is not suitable for all components leading to inflexible operation
Solution Approach 1:
The drive train is segmented into multiple independent voltage domains, each with its own DC/DC converter. The fuel cell system is divided into multiple strings (e.g., String 1, String 2) where each string can operate at different voltage levels (e.g., 700V, 1500V) according to the specific requirements of connected components, eliminating the need for a single universal voltage level
Solution Approach 2:
The system dynamically adapts voltage levels through controllable DC/DC converters that can adjust output voltage based on component requirements. Each converter can independently regulate voltage to match the needs of different components, enabling flexible and adaptable power distribution throughout the drive train
2Reliability
If the voltage level is dominated by the battery, then the battery operates optimally, but the voltage is unsuitable for other powertrain components
Solution Approach 1:
DC/DC converters serve as intermediary devices between the battery and other powertrain components. These converters isolate the battery's optimal voltage level from other components, allowing the battery to operate at its ideal voltage while the converters transform the voltage to suit different components' requirements, thus maintaining both battery reliability and component compatibility
3Power
If high voltage is used for high power transmission, then power capability is improved, but voltage suitability for various components is reduced
Solution Approach 1:
The system employs dynamic voltage transformation through DC/DC converters that can adaptively adjust voltage levels. High voltage (e.g., 1500V) can be transmitted for high power applications, while the converters dynamically transform this to lower voltages (e.g., 700V) for components that require it, thus maintaining both high power capability and voltage range compatibility across different components
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 solution enables optimal voltage utilization for various components, enhances operational safety by allowing continued operation even if one energy supply unit fails, and facilitates efficient energy distribution, improving overall performance and weight distribution within the rail vehicle.
Implementation Method 1
a first energy supply unit with at least one, preferably at least two fuel cells
Implementation Method 2
The DC/DC converters can have outputs connected in parallel. A DC/DC converter is a DC-DC converter that converts a DC electrical voltage supplied at the input into a DC electrical voltage with a higher voltage level or into a DC electrical voltage with a lower DC voltage level at the output
Data Source
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AI summary
The invention relates to a rail vehicle (1) comprising a first power supply unit (5). The first power supply unit (5) comprises at least two fuel cells (7), at least one fuel storage device (8), and a first fuel cell power converter (10). The first fuel cell power converter (10) has a DC/DC converter (12) for each fuel cell (7) of the first power supply unit (5). The DC/DC converters (12) can have outputs that are connected in parallel. The first power supply unit (5) can be arranged in a power pack (2). The invention also relates to a method for operating a rail vehicle (1) and the use of a traction battery (21) for starting a fuel cell (7).