Full Frequency Current Feature-Based Protection for Meshed Submarine MVDC Power Systems

Due to the high incidence of faults in submarine cables, the rapid and accurate fault line detection is crucial for ensuring the safety and reliable operation of submarine MVDC power systems. In this paper, considering the fault response of shore station MMC, the transient and steady-state fault characteristics of meshed submarine MVDC power systems are analyzed. It reveals the differences in the direction and amplitude of high frequency superimposed currents (HFSCs) and low frequency superimposed currents (LFSCs) at both ends of the fault and non-fault lines. Then, by extracting transient energy from HFSC and monitoring changing trend of LFSC, signed binary state direction features of full frequency current are derived. These features are used to construct the protection criteria, which are robust against the change of fault scenario, fault starting speed and sampling frequency. Localized feature processing renders the protection accuracy immune to communication delay and synchronization error. Furthermore, the low bandwidth fault data exchange demand between line terminals is ensured by combining the fast submarine cabled communication and flexible space-ground-sea integrated network. Finally, simulation results on the modified North East Pacific Time-Integrated Undersea Networked Experiments (NEPTUNE) power system validate the effectiveness of the proposed scheme under various fault scenarios.