DBS-less MMC-MTDC system integrating large-scale offshore wind power

Abstract

Offshore wind farm (OWF) integration projects often adopt point-to-point high voltage direct current (HVDC) transmission schemes, where offshore wind power is transmitted onshore and directly integrated into the local AC grid. As OWF continues to scale up, accommodating large-scale wind energy becomes increasingly challenging for local AC grids. To address these challenges, this paper proposes a DBS-less modular multilevel converter-based multi-terminal direct current (MMC-MTDC) system integrating large-scale offshore wind power. Where large-scale offshore wind power is directly transmitted to load centers through DC cables and overhead lines. This paper first outlines the topology, operating modes, and control strategies of the proposed integration system. Then, it introduces the DC and AC fault ride-through strategies, which eliminate the requirement for DC circuit breakers (DCCBs) and dynamic braking systems (DBSs) by adopting hybrid MMCs and rapidly enabling DC choppers inside wind turbines (WTs) to absorb the surplus wind power. Later, a comparison of the economic and technical aspects of the proposed scheme and other three schemes is made, validating the economic benefits and technical advantages of the proposed system. Finally, the proposed system model is developed in PSCAD/EMTDC, and simulations are conducted to validate its feasibility and fault ride-through performance.