A nearest level PWM method for the MMC in DC distribution grids

Yi Wang, Can Hu, Ruoyu Ding, Lie Xu, Chao Fu, Erlin Yang

Research output: Contribution to journalArticle

11 Citations (Scopus)

Abstract

For modular multilevel converters (MMCs) applied to medium-voltage DC distribution grids, using the traditional Nearest Level Modulation (NLM) as in HVDC systems can lead to severe current distortion due to significantly reduced module number. This paper proposes a hybrid modulation method combining NLM and Pulse Width Modulation (PWM) where only one module per arm operates under PWM mode. The proposed Nearest Level PWM (NL-PWM) method not only significantly reduces the current distortion, but also avoids the complicated voltage balancing control in each module. The harmonic characteristics of NL-PWM are derived using double Fourier transform, which provides theoretical basis for selecting module number and switching frequency for medium-voltage application in accordance with grid harmonic requirements. Finally, the harmonic characteristics and feasibility of the proposed modulation method are validated by simulation and experimental studies on a MMC with 6 modules per arm. The simulated and experimental results reveal that NL-PWM has better voltage and current harmonic characteristics over NLM and CPS-PWM, thereby suiting the application of MMC with few models.
LanguageEnglish
Number of pages17
JournalIEEE Transactions on Power Electronics
Early online date11 Jan 2018
DOIs
Publication statusE-pub ahead of print - 11 Jan 2018

Fingerprint

Pulse width modulation
Modulation
Electric potential
Switching frequency
Fourier transforms

Keywords

  • harmonic analysis
  • pulse width modulation
  • voltage control
  • power system harmonics

Cite this

Wang, Yi ; Hu, Can ; Ding, Ruoyu ; Xu, Lie ; Fu, Chao ; Yang, Erlin . / A nearest level PWM method for the MMC in DC distribution grids. In: IEEE Transactions on Power Electronics. 2018.
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A nearest level PWM method for the MMC in DC distribution grids. / Wang, Yi; Hu, Can; Ding, Ruoyu ; Xu, Lie; Fu, Chao; Yang, Erlin .

In: IEEE Transactions on Power Electronics, 11.01.2018.

Research output: Contribution to journalArticle

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N1 - (c) 2018 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.

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