Energy Management System in DC Micro-Grids of Smart Ships: Main Gen-Set Fuel Consumption Minimization and Fault Compensation

This paper proposes an energy management system (EMS) of the electrical system of a luxury ship (yacht). Starting from the analysis of the current configuration of the electric system, it proposes some solutions for its improvement, aiming at the reduction of the fuel consumption of the diesel engine (DE) driven permanent magnet synchronous generators (PMSG) and, therefore, at the reduction of the related ship polluting emissions. From the architectural side, a dc electrical distribution on-board has been adopted in place of the existing ac. Moreover, the dc micro-grid has been integrated with renewable energy sources (RES) based generators, as well as an energy storage system (ESS). From the management point of view, the proposed EMS governs the ship electric system in three working conditions: 1) regular operation; 2) DE driven PMSG fault/outage; 3) overload. During regular operation, the EMS implements the variable speed paradigm of the DE driven PMSGs on-board, permitting a reduction of the fuel consumption, and the related polluting emissions. In this phase, the ESS is exploited to minimize the speed and power transients of the DE. In case of a fault of one of the DE driven PMSGs, the ESS compensates the power missing for the entire duration of the cold start up of the auxiliary generator. In case of big overload, the ESS provides the exceeding power with respect to the rated one, thus avoiding potential micro-grid instability problems. This paper proposes also a stability analysis of the entire on-board dc micro-grid.