High efficiency Shaft Generator drive system design for Ro-Ro trailer-passenger ship application

This paper introduces a particular direct driven Shaft Generator (SG) system for implementation in an existing Ro-Ro (Roll on board-Roll off board) trailer-passenger ship. In a first step, both a high speed (1200rpm) Salient-Pole Synchronous Generator (SPSG) and a low speed (400rpm) direct driven Permanent Magnet Synchronous Generator (PMSG) of the same nominal power with the SG installed in the investigated ship are designed and geometrically optimized, based on the specified operating characteristics. The generators are quantitatively compared and assessed in terms of their torque capability, efficiency and produced power quality, illustrating that the low-speed PMSG constitutes a favorable option for SG applications. In a second step, assessing the benefits of the low speed PMSG, a drive system is designed for the implementation of PMSG in the ship´s electric grid. Appropriate converter topology and advanced generator control methodology are adopted enabling successful interconnection of the SG system with the electric grid as well as high quality electric power supply. Finally, the economic benefits of the operation of the proposed SG systems in terms of lower fuel consumption are investigated.