Partially Rated DC/DC Converter for Aircraft Battery Weight Reduction
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Solution Overview
Problem
Aircraft electric propulsion systems face challenges with high-voltage rated converters, which increase weight, conduction and switching losses, and prevent high-frequency operation, making it desirable to minimize weight and energy consumption.
Innovation Solution
Implementing a partially rated DC/DC converter in the electrical energy storage system, where the converter is rated less than the output voltage level, allowing for a reduction in weight by using a controller to adjust the output voltage and maintain a specified level across nodes, thereby reducing the overall weight of the system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a high voltage rated converter is used, then the converter can handle maximum battery voltage, but the weight of the converter increases
Solution Approach 1:
The battery system is segmented into two separate series-connected sets, each operating at a lower voltage than the total system voltage. The converter only needs to handle the voltage of one set rather than the full system voltage, reducing converter weight while maintaining system functionality through series connection of both sets.
Solution Approach 2:
A DC/DC converter acts as an intermediary between the two battery sets, enabling power transfer from one set to the other. This intermediary device operates at lower voltage levels than the total system, avoiding the need for a heavy high-voltage rated converter while still achieving the desired voltage and power management.
2Reliability
If a high voltage rated converter is used, then the converter can operate at system voltage, but conduction and switching losses increase
Solution Approach 1:
By segmenting the battery system into two series sets and using a DC/DC converter to transfer power between them, the converter operates at lower voltage levels. This segmentation reduces the voltage stress on the converter, thereby reducing conduction and switching losses compared to using a high-voltage rated converter for the full system voltage.
3Reliability
If a high voltage rated converter is used, then the converter can handle maximum voltage, but switching energy increases and high frequency operation is prevented
Solution Approach 1:
The battery system is divided into two series-connected sets, allowing the DC/DC converter to operate at the lower voltage of one set rather than the full system voltage. This voltage reduction enables higher switching frequencies with lower switching energy requirements, improving overall system efficiency and performance.
Solution Approach 2:
The system dynamically manages power between the two battery sets through the DC/DC converter, allowing flexible operation at optimized voltage levels. This dynamic power transfer capability enables the converter to operate at lower voltages and higher frequencies, reducing switching energy consumption.
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 reduces the weight of the electrical energy storage system, enhancing the aircraft's range and payload capacity while minimizing energy consumption and losses.
Implementation Method 1
a power converter (e.g., a DC/DC power converter) that converts DC electrical energy sourced from the plurality of batteries in series into DC electrical energy (e.g., at a different voltage) for output onto a DC electrical bus
Data Source
AI summary
An example system includes an electrical energy storage system (ESS) comprising: an upper node and a lower node; a first set of battery modules that are connected in series; a second set of battery modules that are connected in series; a DC/DC converter electrically in series with the first set of battery modules between the upper node and the lower node, wherein the DC/DC converter sources electrical energy from the second set of battery modules; and a controller configured to adjust an output voltage of the DC/DC converter such that a voltage across the upper node and the lower node is maintained at a specified output voltage level.