Open AccessBifurcate modular multilevel converter for low‐modulation‐ratio applications
Author(s) -
Chang Yiran,
Cai Xu,
Zhang Jianwen,
Shi Gang
Publication year - 2016
Publication title -
iet power electronics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.637
H-Index - 77
eISSN - 1755-4543
pISSN - 1755-4535
DOI - 10.1049/iet-pel.2015.0387
Subject(s) - modulation (music) , topology (electrical circuits) , modular design , voltage , capacitance , control theory (sociology) , current (fluid) , low voltage , high voltage , computer science , electronic engineering , materials science , electrical engineering , engineering , physics , electrode , control (management) , acoustics , quantum mechanics , artificial intelligence , operating system
In this study, a novel modular multilevel converter (MMC) topology for low‐modulation applications is proposed. The proposed topology has two three‐phase AC ports and is characterised by its bifurcate arms and phase‐shifted connection on the AC side. Conventional MMCs have been widely used in high‐voltage direct current (HVDC) applications and are able to connect a low‐voltage AC source to a high‐voltage DC source, which makes them useful in applications such as DC/AC distribution systems and DC collection of renewable energy. However, high arm currents and high energy fluctuation caused by low‐modulation ratio will increase converter losses and submodule capacitance. In the proposed bifurcate MMC, each arm has three branches and the branch current is lower than the arm current of the conventional MMC, so the difficulty of designing an MMC with low‐modulation ratio is relieved to some extent. Theoretical analysis proves the stability of bifurcate MMCs and provides reference voltage solutions for each branch. A control scheme for a bifurcate MMC is also proposed, and further analysis shows that the circulating current is naturally suppressed under certain conditions. Detailed simulation is performed based on the RT‐LAB platform and confirms the analysis results.