Load-Independent Voltage Balancing of Multi-Level Flying Capacitor Converters in Quasi-2-Level Operation
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Date
2021-10
Publication Type
Journal Article
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yes
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Abstract
Quasi-2-level (Q2L) operation of multi-level bridge-legs, especially of flying-capacitor converters (FCC), is an interesting option for realizing single-cell power conversion in applications whose system voltages exceed the ratings of available power semiconductors. To ensure equal voltage sharing among a Q2L-FCC’s switches, the voltages of a Q2L-FCC’s minimized flying capacitors (FCs) must always be balanced. Thus, we propose a concept for load-independent FC voltage balancing: For non-zero load current, we use a model predictive control (MPC) approach to identify the commutation sequence of the individual switches within a Q2L transition that minimizes the FC or cell voltage errors. In case of zero load current, we employ a novel MPC-based approach using cell multiple switching (CMS), i.e., the insertion of additional zero-current commutations within a Q2L transition, to exchange charge between the FCs via the charging currents of the switches’ parasitic capacitances. Experiments with a 5-level FCC half-bridge demonstrator confirm the validity of the derived models and verify the performance of the proposed load-independent balancing concept.
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published
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Journal / series
Volume
10 (19)
Pages / Article No.
2414
Publisher
MDPI
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Edition / version
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Date collected
Date created
Subject
quasi-2-level (Q2L); flying capacitor converter (FCC); model predictive control (MPC); flying capacitor balancing; multi-level converter
Organisational unit
03573 - Kolar, Johann W. (emeritus) / Kolar, Johann W. (emeritus)