An Advanced Dual Energy Control with Energy Dissipation Strategy to Enhance Fault Ride-Through in Offshore Wind MMC-HVDC Systems

The Modular Multilevel Converter-based High-Voltage Direct Current (MMC-HVDC) system has emerged as a promising technology to integrate offshore wind farms (OWFs). However, onshore AC faults and resulting DC-link voltage escalation can challenge the reliability of MMC-HVDC systems. This paper proposes an integrated dual energy control with energy dissipation scheme (DEC-EDS) to improve the AC fault ride-through (FRT) in OWF MMC-HVDC systems. The proposed DEC-EDS scheme leverages the short-term overload capacity of MMC half-bridge submodule (SM) capacitors to store part of the surplus power during onshore AC faults while dissipating any excess power into a DC energy dissipation device (EDD). During fault conditions, the MMC SM capacitors and the DC EDD operate in parallel to manage surplus energy, with the capacitors providing temporary buffering and the EDD dissipating the excess power. The proposed scheme is tested on a ±320 kV/420 MW MMC-HVDC system. The results show that the proposed control scheme effectively maintains DC-link voltages, ensuring the connection of OWFs.