Modular Multi-Level Converter Sub-Module With Bidirectional Switching
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Solution Overview
Problem
Existing multilevel converters face limitations in carrying peak currents and generating negative voltage levels, with voltage states often linked to the charge state of capacitors, leading to inefficiencies and increased control effort.
Innovation Solution
The design incorporates a sub-module with a half-bridge, series connection unit, and bidirectionally switchable switching device, allowing for independent current switching and freewheeling paths, enabling higher peak current handling and voltage modulation independent of capacitor charge states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If sub-modules use simple series connection of half and full bridges, then device complexity is reduced, but peak current handling capability is limited
Solution Approach 1:
The sub-module is divided into functionally independent units: half-bridge circuit, series connection unit with switching elements, and bidirectionally switchable switching device. Each unit can operate independently to handle different current directions and voltage levels, enabling the system to carry higher peak currents while maintaining manageable complexity through modular design.
2Ease of operation
If voltage states are linked to capacitor charge states, then control effort increases, but voltage level generation is simplified
Solution Approach 1:
The bidirectionally switchable switching device enables dynamic voltage level generation that is independent of capacitor charge states. The switching device can actively generate negative voltage levels and modulate voltage states regardless of capacitor charging status, reducing control effort by decoupling voltage state management from capacitor charge state dependency.
Solution Approach 2:
The invention changes the operational parameters by introducing bidirectional switching capability that allows voltage levels to be modulated independently of capacitor charge states. This parameter change enables the system to generate negative voltage levels and adjust voltage states without being constrained by capacitor charging conditions, thereby reducing control complexity.
3Adaptability or versatility
If sub-modules cannot generate negative voltage levels, then device structure is simpler, but application versatility is reduced
Solution Approach 1:
The bidirectionally switchable switching device provides multi-functionality by enabling both positive and negative voltage level generation within the same sub-module configuration. This universal switching capability allows the sub-module to adapt to various operating conditions and application requirements without requiring different hardware configurations, thereby increasing versatility while maintaining reasonable structural complexity.
Data Source
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AI summary
The invention relates to, inter alia, a modular multi-level converter having at least one sub-module series circuit (UE) comprising at least two sub-modules (T) connected in series and an inductance. According to the invention, at least one of the sub-modules (T) comprises: a half bridge (100) which forms an input connection (Et) of the sub-module (T) and has a first and a second half bridge output connection (101, 102); a series circuit unit (300) that is connected to the first half bridge output connection (101) by a first connection (301), and to the second half bridge output connection (102) by a second connection (302), wherein the series circuit unit (300) comprises a first and a second switch unit (310, 320) as well as a capacitor (C2), and the electrical connection point (V300) between the two switch units (310, 320) of the series circuit unit (300) forms an output connection (At) of the sub-module (T); and a bidirectionally switchable switch device (200) that can activate and deactivate current regardless of the current flow direction, and having a connection (A200) at the output connection (At) of the sub-module (T), and having another connection (E200) at the second half bridge output connection (102), and is thereby connected to the second connection (302) of the series circuit unit (300).