Multiport Multilevel Converter With Integrated Storage for AC/DC Microgrids
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Solution Overview
Problem
Existing power converter solutions are not versatile enough to address a wide range of use scenarios, including both high power DC charging and AC microgrid applications.
Innovation Solution
A multiport multilevel power converter arrangement with a first AC port, a second AC port, a DC port, and a DC bus, featuring a unidirectional AC/DC stage, a multilevel converter with parallel converter legs, and controller circuitry for controlling semiconductor switches to manage DC bus voltage, energy storage element voltages, and AC port voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If separate converter arrangements are used for AC microgrid and DC charging applications, then each application can be optimized independently, but the overall system complexity and space requirements increase
Solution Approach 1:
The patent implements a universal power converter arrangement that can operate in multiple modes: AC microgrid formation, AC microgrid feeding, and DC charging. The same converter hardware with its multilevel topology and energy storage elements can be controlled to perform different functions, eliminating the need for separate dedicated converters for each application while maintaining optimization for each mode through controller configuration
2Adaptability or versatility
If traditional converter topologies are used, then the design is simpler, but they lack energy storage capability and versatility for multiple operating modes
Solution Approach 1:
The patent merges the energy storage function directly into the converter topology by integrating energy storage elements (capacitors and/or batteries) as integral parts of the converter cells. This combination allows the converter to inherently provide both power conversion and energy storage functions, enabling versatile operating modes including grid forming, grid feeding, and stand-alone operation without requiring additional separate energy storage systems
Solution Approach 2:
The converter is divided into multiple independent converter legs, each comprising several converter cells with energy storage elements. This segmented modular structure allows each cell to function independently while contributing to the overall converter performance, enabling flexible configuration and scaling while maintaining manageable complexity through standardized cell designs
3Reliability
If multiple separate converters are deployed for different functions, then each converter can be optimized for its specific function, but the total device footprint and cost increase
Solution Approach 1:
The patent designs a single multiport converter arrangement that consolidates multiple functions (AC-AC conversion, AC-DC conversion, energy storage) into one unified device. The converter can be configured to operate in different modes by controlling the semiconductor switches and energy storage elements, providing the functional performance of multiple separate converters while occupying significantly less space and reducing overall system cost
Data Source
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AI summary
A power converter arrangement comprising a first AC port, a second AC port, a DC port, a DC bus, an AC/DC stage arranged in between the first AC port and the DC port, a multilevel converter comprising at least two converter legs, wherein each converter leg comprises two converter arms connected in series at a middle point, wherein each converter arm comprises a plurality of series connected converter cells, each converter cell comprising at least one energy storage element for storing energy, and semiconductor switches for connecting the energy storage element to the rest of the converter arm, and a controller circuitry for controlling at least one of the DC bus voltage, one or more of the voltages of the plurality of energy storage elements, and the second voltage.