DC fault analysis of MMC based HVDC system for large offshore wind farm integration

Abstract

This paper analyzes the behaviour of a modular multilevel converter (MMC) based HVDC system under DC cable fault conditions. The behaviour of the HVDC system during a permanent line-to-line fault is analyzed in details at each stage of the fault timeline. Operation of the proposed system under a specific earthing configuration i.e. converter unearthed /AC transformer secondary side and DC cable solidly earthed, is also analyzed. Simulation studies are provided to assist the analytical analysis. It is observed that both faults leads to substantial AC and DC over-current and result in DC side oscillations

Design and control of all-DC offshore wind power plant with MMC-based DC/DC high-power converters

“…Modular multilevel converters (MMCs) have become popular for HVDC transmission applications, due to their modular design, scalability and a multilevel architecture that enables low harmonic distortion and low voltage and current variations across submodules, thus reducing switching losses [10,11].…”