A review of modular multilevel converters for stationary applications

Yang Wang, Ahmet Aksoz, Thomas Geury, Salih Baris Ozturk, Omer Cihan Kivanc, Omar Hegazy*

*Corresponding author for this work

Research output: Contribution to journalReview articlepeer-review

41 Citations (Scopus)

Abstract

A modular multilevel converter (MMC) is an advanced voltage source converter applicable to a wide range of medium and high-voltage applications. It has competitive advantages such as quality output performance, high modularity, simple scalability, and low voltage and current rating demand for the power switches. Remarkable studies have been carried out regarding its topology, control, and operation. The main purpose of this review is to present the current state of the art of the MMC technology and to offer a better understanding of its operation and control for stationary applications. In this study, the MMC configuration is presented regarding its conventional and advanced submodule (SM) and overall topologies. The mathematical modeling, output voltage, and current control under different grid conditions, submodule balancing control, circulating current control, and modulation methods are discussed to provide the state of the MMC technology. The challenges linked to the MMC are associated with submodule balancing control, circulating current control, control complexity, and transient performance. Advanced nonlinear and predictable control strategies are expected to improve the MMC control and performance in comparison with conventional control methods. Finally, the power losses associated with the advanced wide bandgap (WBG) power devices (such as SiC, GaN) are explored by using different modulation schemes and switching frequencies. The results indicate that although the phase-shifted carrier-based pulse width modulation (PSC-PWM) has higher power losses, it outputs a better quality voltage with lower total harmonic distortion (THD) in comparison with phase-disposition pulse width modulation (PD-PWM) and sampled average modulation pulse width modulation (SAM-PWM). In addition, WBG switches such as silicon carbide (SiC) and gallium nitride (GaN) devices have lower power losses and higher efficiency, especially at high switching frequency in the MMC applications.

Original languageEnglish
Article number7719
Pages (from-to)1-36
Number of pages36
JournalApplied Sciences (Switzerland)
Volume10
Issue number21
DOIs
Publication statusPublished - 1 Nov 2020

Bibliographical note

Publisher Copyright:
© 2020 by the authors. Licensee MDPI, Basel, Switzerland.

Funding

This study was funded by China Scholarship Council (CSC). Yang Wang was sponsored by China Scholarship Council. The authors also acknowledge Flanders Make for the support of this research study.

FundersFunder number
China Scholarship Council

    Keywords

    • Battery inverters
    • Circulating current control
    • Grid applications
    • Modular multilevel converter (MMC)
    • Nonlinear and predictive control
    • Output voltage and current control
    • Power losses
    • Smart grid
    • Submodule balancing control
    • Submodule topology
    • WBG technology (SiC and GaN), MPC for MMC

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