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

Wang, Yi and Hu, Can and Ding, Ruoyu and Xu, Lie and Fu, Chao and Yang, Erlin (2018) A nearest level PWM method for the MMC in DC distribution grids. IEEE Transactions on Power Electronics. ISSN 0885-8993 (https://doi.org/10.1109/TPEL.2018.2792148)

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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.

ORCID iDs

Wang, Yi, Hu, Can, Ding, Ruoyu, Xu, Lie ORCID logoORCID: https://orcid.org/0000-0001-5633-7866, Fu, Chao and Yang, Erlin;
  • Item type:Article
    ID code:62874
    Dates:
    Date
    Event
    11 January 2018
    Published
    11 January 2018
    Published Online
    27 December 2017
    Accepted
    Notes:(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.
    Subjects:Technology > Electrical engineering. Electronics Nuclear engineering
    Department:Faculty of Engineering > Electronic and Electrical Engineering
    Depositing user: Pure Administrator
    Date deposited:15 Jan 2018 16:57
    Last modified:12 Nov 2024 03:08
    Related URLs:
    URI:https://strathprints.strath.ac.uk/id/eprint/62874
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