Important Issues and Economic Study of Ship DC Distribution System with Variable-Speed Diesel Generator

In a traditional AC distribution system, the synchronous frequencies of the generators are coupled with the system frequency, and thus the diesel engines are kept at a constant speed. In a Dynamic Positioning (DP) vessel such as a Platform Supply Vessel (PSV), the diesel engines sometimes work at the partial load condition. The efficiency of constant-speed diesel engines during partial load condition is lower than that during full load condition. This dropped efficiency can be improved by the variable-speed operation of diesel engines. At the request of Damen Shipyards Group, a new onboard DC distribution system is designed in this thesis to achieve the efficiency improvement in the PSVs. In a DC distribution system, the variable-speed operation of diesel engines becomes feasible because of the frequency decoupling between the generators. The Power Management System (PMS) of the proposed DC system is designed as well to achieve the system voltage stability, improve the quality of power supply and enhance the system survivability. After the economic comparative studies are conducted between the DC and AC onboard distribution systems, it can be concluded that the DC distribution system has a better economic performance with a higher efficiency, especially in DP partial load situations.(EPS) Electrical Power Systems(ESE) Electrical Sustainable EnergyElectrical Engineering, Mathematics and Computer Scienc