Four-Transistor Bipolar Series-Parallel Module Structure for Cascaded Bridge and Modular Multilevel Circuits

Fuente: arXiv
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Autori principali: Zhang, Jinshui, Goetz, Stefan M
Natura: Preprint
Pubblicazione: 2025
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author Zhang, Jinshui
Goetz, Stefan M
author_facet Zhang, Jinshui
Goetz, Stefan M
contents With their great scalability and flexibility, cascaded-bridge and modular multilevel converters have enabled a variety of energy applications, such as offshore wind power, high-voltage dc power transmission, power-quality management, and cutting-edge medical instrumentation. The incorporation of parallel connectivity between modules equips systems with advantages such as sensorless balancing, switched-capacitor energy exchange, and reduced impedance. However, existing topologies require many individual switches -- eight transistors per module. Efforts to use fewer switches, instead, have previously compromised their functionality. We propose a new module topology, named the direction-selective parallel (DiSeP) structure, which requires only four transistors per module -- the same as an H bridge -- but can achieve bidirectional equilibration, bipolar module output, and inter-module switched-capacitor features. This topology is highly attractive for existing converters with cascaded bridge elements, as the addition of only four diodes enables key features such as sensorless balancing and inter-module energy exchange. Thus, the module can outcompete H bridges in their applications, as it adds parallel modes without any additional transistors. Compared to double-H bridges (CH2B), it saves as many as half of the transistors. We elaborate on its working principles and key design considerations. We validate our theories on an experimental prototype with six modules. This prototype attains a total voltage harmonic distortion plus noise (THD+N) of 10.3% and a peak efficiency of 96.3%. Furthermore, the modules achieve autonomous sensorless balancing under open-loop control.
format Preprint
id arxiv_https___arxiv_org_abs_2509_19516
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Four-Transistor Bipolar Series-Parallel Module Structure for Cascaded Bridge and Modular Multilevel Circuits
Zhang, Jinshui
Goetz, Stefan M
Systems and Control
With their great scalability and flexibility, cascaded-bridge and modular multilevel converters have enabled a variety of energy applications, such as offshore wind power, high-voltage dc power transmission, power-quality management, and cutting-edge medical instrumentation. The incorporation of parallel connectivity between modules equips systems with advantages such as sensorless balancing, switched-capacitor energy exchange, and reduced impedance. However, existing topologies require many individual switches -- eight transistors per module. Efforts to use fewer switches, instead, have previously compromised their functionality. We propose a new module topology, named the direction-selective parallel (DiSeP) structure, which requires only four transistors per module -- the same as an H bridge -- but can achieve bidirectional equilibration, bipolar module output, and inter-module switched-capacitor features. This topology is highly attractive for existing converters with cascaded bridge elements, as the addition of only four diodes enables key features such as sensorless balancing and inter-module energy exchange. Thus, the module can outcompete H bridges in their applications, as it adds parallel modes without any additional transistors. Compared to double-H bridges (CH2B), it saves as many as half of the transistors. We elaborate on its working principles and key design considerations. We validate our theories on an experimental prototype with six modules. This prototype attains a total voltage harmonic distortion plus noise (THD+N) of 10.3% and a peak efficiency of 96.3%. Furthermore, the modules achieve autonomous sensorless balancing under open-loop control.
title Four-Transistor Bipolar Series-Parallel Module Structure for Cascaded Bridge and Modular Multilevel Circuits
topic Systems and Control
url https://arxiv.org/abs/2509.19516