AC Fault Ride-Through Method of HVDC Interconnector for Islanded AC Grid With Offshore Wind Farm and Loads

Abstract

This paper proposes an ac fault ride-through (FRT) method for high-voltage dc (HVDC) transmission systems that serve as an interconnector between the onshore ac grid and an islanded offshore ac grid. The conventional HVDC system for offshore wind farms has realized its FRT by consuming excess power by a braking resistor. However, the same method cannot be applied if the offshore ac grid includes not only wind farms but also various loads, which are recently envisioned in multipurpose interconnectors or energy islands. In this article, a novel FRT method based on voltage control for HVDC interconnectors operating with bidirectional power flow is proposed. The proposed method curtails the ac voltage formed by the offshore converter according to the converter's dc current and voltage. The effectiveness of the proposed FRT method is established through experiments on a mini model.INDEX TERMS Deloading, islanding, HVDC transmission, fault ride-through (FRT), voltage control.