Design of Bypass Branch for Hybrid MMC Rapid Fault Ride‐Through
Wu Fangjie, Xu Ying, Hao Zhiyuan, Wang Ling, Gao Zijian, Huang MiaoqiABSTRACT
Ultra‐long DC transmission lines increase the difficulty of fault ride‐through (FRT) in hybrid modular multilevel converters (MMCs) because of their large stored electromagnetic energy. This paper proposes a passive bypass branch connected in parallel with the converter DC terminals, comprising a diode valve, a capacitor bank and an energy‐dissipation resistor. By sequentially transferring the fault current and dissipating the residual line energy, the branch decouples converter isolation from subsequent energy dissipation. Analytical models and parameter‐design criteria are developed for the fault‐isolation and energy‐dissipation stages. Simulation and real‐time results show that the proposed scheme effectively reduces FBSM capacitor‐voltage stress under near‐end faults and accelerates fault‐current clearance under remote‐end faults.