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

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. In conventional HVDC systems for offshore wind farms FRT is realized by consuming excess power with braking resistors. However, the same method cannot be applied if the offshore ac grid includes not only wind farms but also various loads, which are being considered for integration into 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.