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- Title
Analysis and compensation of circulating currents errors in modular multilevel converters in low-frequency operation.
- Authors
Al Sabbagh, Muneer; Pan, Jianyu; Ke, Ziwei; Na, Risha; Xu, Longya
- Abstract
Errors in the injected high-frequency circulating currents are originally investigated for modular multilevel converters (MMCs) in low-speed drive operation. The mathematical analysis reveals that the magnitude and phase errors in the injected circulating currents cause serious energy imbalance in the MMC arms, resulting in large voltage fluctuations in the submodules. Furthermore, these fluctuations get larger when the circulating currents are injected at higher frequencies, which reduces the drive system stability and damages the submodule capacitors. A remedy approach is proposed to minimise the error effects by adjusting the circulating current command. A full-scale system comprising a 1 MVA MMC and a 1 MW induction machine is simulated to verify the theoretical analysis. The experimental investigation of a down-scale MMC feeding an inductor is also conducted to validate the theoretical results.
- Subjects
POWER capacitors; WAGES; MATHEMATICAL analysis; VARIABLE speed drives; ELECTRIC currents
- Publication
IET Power Electronics (Wiley-Blackwell), 2020, Vol 13, Issue 9, p1756
- ISSN
1755-4535
- Publication type
Article
- DOI
10.1049/iet-pel.2019.0872