Reduced switching-frequency modulation and circulating current suppression for modular multilevel converters

Qingrui Tu, Zheng Xu, Lie Xu

Research output: Contribution to journalArticle

888 Citations (Scopus)

Abstract

This paper describes a modified phase-shifted carrier-based pulsewidth-modulation (PSC-PWM) scheme for modular multilevel converters (MMC). In order to reduce the average device switching frequency, a reduced switching-frequency (RSF) voltage balancing algorithm is developed. This paper also proposes a circulating current suppressing controller (CCSC) to minimize the inner circulating current in an MMC. Based on the double line-frequency, negative-sequence rotational frame, the three-phase alternative circulating currents are decomposed into two dc components and are minimized by a pair of proportional integral controllers. Simulation results based on a detailed PSCAD/EMTDC model prove the effectiveness of the modified PSC-PWM method and the RSF voltage-balancing algorithm. The proposed CCSC not only eliminates the inner circulating current but also improves the quality of the converter ac output voltage. A simple loss evaluation demonstrates that the RSF voltage-balancing algorithm and the CCSC reduce the converter power losses.
LanguageEnglish
Pages2009-2017
Number of pages9
JournalIEEE Transactions on Power Delivery
Volume26
Issue number3
DOIs
Publication statusPublished - Jul 2011

Fingerprint

Frequency modulation
Switching frequency
Controllers
Electric potential
Modulation
Power converters

Keywords

  • switching-frequency modulation
  • circulating current suppression
  • modular multilevel converters
  • switching frequency
  • voltage control
  • capacitors
  • converters
  • pulse width modulation
  • switches

Cite this

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title = "Reduced switching-frequency modulation and circulating current suppression for modular multilevel converters",
abstract = "This paper describes a modified phase-shifted carrier-based pulsewidth-modulation (PSC-PWM) scheme for modular multilevel converters (MMC). In order to reduce the average device switching frequency, a reduced switching-frequency (RSF) voltage balancing algorithm is developed. This paper also proposes a circulating current suppressing controller (CCSC) to minimize the inner circulating current in an MMC. Based on the double line-frequency, negative-sequence rotational frame, the three-phase alternative circulating currents are decomposed into two dc components and are minimized by a pair of proportional integral controllers. Simulation results based on a detailed PSCAD/EMTDC model prove the effectiveness of the modified PSC-PWM method and the RSF voltage-balancing algorithm. The proposed CCSC not only eliminates the inner circulating current but also improves the quality of the converter ac output voltage. A simple loss evaluation demonstrates that the RSF voltage-balancing algorithm and the CCSC reduce the converter power losses.",
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Reduced switching-frequency modulation and circulating current suppression for modular multilevel converters. / Tu, Qingrui; Xu, Zheng; Xu, Lie.

In: IEEE Transactions on Power Delivery, Vol. 26, No. 3, 07.2011, p. 2009-2017.

Research output: Contribution to journalArticle

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KW - switching-frequency modulation

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KW - voltage control

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KW - pulse width modulation

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