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The benefits of using Power Electronics Based DC Distribution Systems in electrically propelled vessels are well known. However, some aspects must be deeply analyzed to guarantee a safe, robust and stable system by design. This paper presents a multivariable DC Distribution System mathematical model, where all the transmission lines and filters impedances are considered. The model has been tackled under a holistic approach in which the average small-signal model of the drives/converters can be easily added and 'connected' to the main grid model. The stability and power quality analysis, as well as the design and tuning of controls and active damping strategies can be conducted through this mathematical model at low computational cost. The usefulness of this model in the early design stages is thus presented in this paper through its application over a realistic design scenario and the performance of the proposed model is proven into a real test bench which presents a configuration and architecture quite close to the one used in a real vessel. The carried out tests prove the suitability of the proposed model, becoming a significant tool to get an improved design.

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Electric propulsion and integrated hybrid power systems can improve the energy efficiency and fuel consumption of different kinds of vessels. If the vessel power system is based on DC grid distribution, some benefits such as higher generator efficiency and lower volume and cost can be achieved. However, some challenges remain in terms of protection devices for this kind of DC grid-based power system. The absence of natural zero crossing in the DC current together with the fast and programmable breaking times required make it challenging. There are several papers related to DC breaker topologies and their role in DC grids; however, it is not easy to find comprehensive information about the design process of the DC breaker itself. In this paper, the basis for the design of a DC solid-state circuit breaker (SSCB) for low voltage vessel DC grids is presented. The proposed SSCB full-scale prototype detects and opens the fault in less than 3 µs. This paper includes theoretical analyses, design guidelines, modeling and simulation, and experimental results.