Modular Power Electronic Transformer for Low-Voltage DC Joint Supply
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Solution Overview
Problem
The existing power distribution networks face challenges with voltage withstand levels of switching devices due to high common DC bus voltages, limiting their flexibility and scalability, especially when connecting large power DC loads and distributed renewable energy sources.
Innovation Solution
A power electronic transformer with a modular design, featuring multiple submodules with cascaded full bridge power conversion units, allows for flexible interconnection of AC feeder lines and joint supply to low voltage DC buses, thereby overcoming voltage limitations and enhancing network flexibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a common DC bus is formed using small power single phase converters in a multiple medium voltage AC port solid state transformer, then joint supply to low voltage DC users can be achieved, but the DC bus voltage reaches 2500V which exceeds the voltage withstand level of conventional IGBT devices (600V-1700V)
Solution Approach 1:
The patent divides the single high-voltage DC bus into multiple isolated DC-DC converter modules, each handling a portion of the power conversion. This segmentation allows each module to operate at manageable voltage levels while collectively achieving the joint supply function. The modular architecture enables independent voltage management for each converter unit.
Solution Approach 2:
The patent introduces isolated DC-DC converters as intermediary devices between the medium voltage AC ports and the low voltage DC bus. These converters act as voltage transformation mediators, stepping down the high voltage from the DC bus to the lower voltage required by the load, thereby protecting the switching devices from exceeding their voltage withstand limits.
2Ease of manufacture
If the DC bus voltage is reduced to match conventional IGBT voltage withstand levels, then device selection is improved, but the capability to support large power DC loads and high voltage level power distribution networks is limited
Solution Approach 1:
The patent segments the high power transmission task across multiple isolated DC-DC converter modules. Each module operates at a lower voltage level compatible with conventional IGBTs, but the aggregate power capacity of all modules combined enables support for large power DC loads. This segmentation allows both affordable device selection and high power capability.
Solution Approach 2:
The patent combines multiple isolated DC-DC converter modules in parallel to achieve the required total power capacity. By merging the capabilities of individual modules, each using affordable conventional IGBTs, the system collectively delivers high power distribution capability suitable for large power DC loads and high voltage level networks.
3Productivity
If multiple AC feeder lines are interconnected to achieve joint supply, then utilization rate of equipment and feeder lines improves, but the voltage level management becomes complex
Solution Approach 1:
The patent employs isolated DC-DC converters as intermediary voltage management devices that simplify the interconnection of multiple AC feeder lines. Each converter independently manages its voltage transformation, acting as a mediator that isolates voltage level variations between different feeder lines and the common DC bus, thereby reducing overall system complexity.
Solution Approach 2:
The patent segments the voltage management function into independent isolated DC-DC converter modules, each handling a specific AC feeder line connection. This segmentation allows each module to manage its own voltage transformation independently, simplifying the overall voltage level management while enabling efficient utilization of multiple feeder lines through modular scalability.
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 effectively addresses the voltage withstand limitations of switching devices, enabling efficient operation and expansion of power distribution networks, while improving the reliability of low voltage DC power distribution and supporting higher voltage level applications.
Implementation Method 1
a first submodule including a first input port and N output ports, where N is an integer greater than 0; a second submodule including a first input port and M output ports
Data Source
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AI summary
A power electronic transformer (10; 20; 30) includes three modules, the three modules each including: a first submodule (11;21;31); a second submodule (12;22;32); and a third submodule including a first power conversion module (131, 231, 331) including N first power conversion units having input ports connected to the N output ports of the first submodule (11;21;31) in one-to-one correspondence, and a second power conversion module (132, 232, 332) including M first power conversion units having input ports connected to the M output ports of the second submodule (12;22;32) in one-to-one correspondence, the first input port of the first submodule (11;21;31) of the three modules has one terminal (P1) connected to three phases of a first three-phase alternating current in one-to-one correspondence, and the other terminal (P2) connected to three phases of a second three-phase alternating current in one-to-one correspondence, output ports of the N first power conversion units are connected in parallel to output ports of the M first power conversion units.