Open AccessA Study of Circulating Current in MMC based HVDC System under an Unbalanced Grid Condition
Author(s) -
Won-Seok Do,
Si-Hwan Kim,
TaeJin Kim,
Rae-Young Kim
Publication year - 2015
Publication title -
jeon-gi hakoe nonmunji/jeon'gi haghoe nonmunji
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.174
H-Index - 11
eISSN - 2287-4364
pISSN - 1975-8359
DOI - 10.5370/kiee.2015.64.8.1193
Subject(s) - ripple , current (fluid) , grid , modular design , hvdc converter station , electric power system , control theory (sociology) , power (physics) , high voltage direct current , reliability (semiconductor) , ac power , direct current , electronic engineering , engineering , computer science , voltage , electrical engineering , physics , mathematics , geometry , control (management) , quantum mechanics , artificial intelligence , operating system
This paper presents a study of circulating current of modular multi-level converter (MMC) based a high voltage direct current (HVDC) system under unbalanced grid conditions. Due to the connection of a dependent DC source in each phase, the MMC system inherently generates the power ripple of double-line-frequency components in the AC-side and as a result, the additional sinusoidal current named circulating current flows through the each arm. Reliability improvement of HVDC system under an unbalanced grid condition is one of the important criteria. Generally, the modeling of the circulating current is based on the power relation between DC-side and AC-side. However, the method is not perfectly matched in the
MMC system due to the difference of the structural characteristic. In this paper, improved modeling method of circulating current is proposed, which is based on the inner arm power. The proposed method is verified by several simulations to have good agreement of the circulating current components