DC-grid system for ships: a study of benefits and technical considerations

ABSTRACT The primary electric power system of ships has been based on the alternating current (AC) system for a long time. However, marine engineers started to question the efficiency of the AC-grid system, which was previously taken for granted and attempted to find a more efficient and eco-friendly electric power distribution system. Following this trend in the marine industry, the direct current (DC) system was adopted for the electric distribution system in ships and combined with the AC-grid. In this regard, this paper presents the technical, economic, and environmental benefits of the DC-grid system for marine applications. Ships that have already applied or plan to apply the DC-grid system are categorized into several types. Additionally, some technical considerations focused on the fault protection topology, the power-sharing (balancing) topology, power quality/stability issues, power source control methods, DC arc flash hazard, and international regulations/standards regarding DC-grid ships are reviewed. Lastly, the prospects of the DC-grid system in ships are addressed with a conclusion.