Hierarchical Protection Scheme for DC Marine Integrated Power Systems

DC marine integrated power system is widely used in the ships because of its high-power destiny, but the small feeder impedance leads to the similar fault currents at different locations. Hence, the existing protection schemes are difficult to ensure the protection selectivity. This paper proposes a hierarchical protection scheme for DC marine integrated power systems to realize the coordination between each protection action. The protection scheme for the pole-to-pole faults combines two different time-frame protection actions, including the fast action by DC circuit breakers for the bus separation and the slow action by high-speed fuses for the feeder separation. To effectively coordinate each protection action in the event of DC short-circuit faults, the influences of feeder impedance and DC-link capacitance are investigated. Initially, the DC circuit breakers activate to protect the healthy DC bus and quarantine the faulty one while the high-speed fuses quarantine the faulty feeder to minimum the power-off range. Based on the two-layer protection, the protection selectivity of the DC marine integrated power systems is realized. The proposed method is verified using MATLAB/Simulink, demonstrating that the short circuit faults can be isolated without causing false operations of other fuses.