Opposing Switching Cells for Multilevel Converter Loss Reduction
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Solution Overview
Problem
Multilevel chain link converters face challenges in reducing conduction losses while maintaining harmonic performance, as reducing the number of switching units compromises the number of voltage levels.
Innovation Solution
A switching module comprising two identical switching cells connected in opposing directions, with specific terminal connections between the cells, allowing for a reduced number of switching units while maintaining a large number of voltage levels, and enabling the creation of a chain link with improved harmonic performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the number of switching units is reduced to lower conduction losses, then conduction losses are reduced, but the number of voltage levels decreases, affecting harmonic performance
Solution Approach 1:
The switching cell is divided into two independent half-bridges (first half-bridge with first and second switching units, second half-bridge with third and fourth switching units), each capable of operating autonomously to generate voltage levels. This segmentation allows reduction of switching units per half-bridge while maintaining overall voltage level diversity through coordinated operation of both half-bridges.
Solution Approach 2:
The patent introduces a temporal dimension by enabling independent switching control of the two half-bridges, where voltage levels are generated not only through spatial arrangement of switching units but also through time-coordinated switching sequences. This allows achieving multiple voltage levels with fewer simultaneous switching units.
2Loss of energy
If the number of switching cells is reduced to lower conduction losses, then conduction losses are reduced, but the harmonic performance of the converter deteriorates
Solution Approach 1:
Each switching cell is designed with universal half-bridge modules that can operate in multiple modes (different voltage level combinations) depending on switching states. The first and second half-bridges can each independently provide multiple voltage levels, and their coordinated operation enables the switching cell to achieve comprehensive voltage level coverage required for high harmonic performance with reduced component count.
3Adaptability or versatility
If more switching units are used to maintain voltage levels, then harmonic performance is maintained, but conduction losses increase
Solution Approach 1:
The patent extracts and eliminates redundant switching units from the conventional full-bridge configuration. By taking out unnecessary switching elements and replacing them with the optimized half-bridge structure, the design achieves the same voltage level generation capability with fewer components, thereby reducing conduction losses while maintaining harmonic performance.
Data Source
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AI summary
A switching cell (SC1, SC2) for a chain link is provided, which switchi ng cell (SC1, SC2) comprising a first side (S1 ) comprising a first terminal (T1 ) and a second terminal (T2), a second side (S2) comprising a third termi nal (T3) and a fourth terminal (T4), a first switchi ng unit (SU 1 ), a second switchi ng unit (SU2), and a first and a second capacitor unit (C1, C2). The first terminal (T1 ) is connected to the second termi nal (T2) via the first capacitor unit (C1 ), wherein the first capacitor unit (C1 ) has its positive side facing the first terminal (T1 ). The third termi nal (T3) is connected to the fourth terminal (T4) via the second capacitor unit (C2), wherei n the second capacitor has its positive side faci ng the fourth terminal (T4). The second terminal (T2) is connected to the fourth terminal (T4) via the second switching unit (SU2). The switchi ng cell also comprises a third capacitor unit (C3), and the first terminal (T1 ) is connected to the third terminal (T3) via a first series connection comprising the first switching unit (SU 1 ) and the third capacitor unit (C3), wherein the third capacitor unit (C3) has its positive side facing the third terminal (T3). A switchi ng module (SM) comprises at least one such switching cell (SC1, SC2). Preferably, the switching module (SM) comprises at least two such switching cells (SC1, SC2), wherein the first switchi ng cell (SC1 ) and the second switching cell (SC2) are connected i n series in opposing directions, wherein the second side (S21 ) of the first switching cell (SC1 ) is connected to the second side (S22) of the second switching cell (SC2). A chain link (CL) comprising a number of switching modules in serial connection is also provided.