Improved Fuel-Use Efficiency in Diesel–Electric Tugboats With an Asynchronous Power Generating Unit

High capacity diesel-electric tugboats are employed at every modernized harbor for assisting big marine vessels and other harbor applications. Contemporary tugboats use multiple power sources to meet their propulsion and auxiliary on-board load demands. The effective utilization of multiple power sources leads to better fuel use efficiency with reduced emissions, economic, and environmental benefits. This paper presents a simple optimization technique for scheduling available power sources of a diesel-electric tugboat diesel engine generators (DEGs) and batteries to meet its load demand with an objective to minimize fuel consumption. For this paper, a diesel-electric tugboat system of 1.1-MW capacity with different generating systems is considered: 1) fixed speed generating unit (2 × 550 kW fixed speed DEG employing synchronous generators) and 2) variable speed generating unit 1×1.1 MW variable speed DEG employing doubly fed induction generator (DFIG). From the optimized test results, it is inferred that the variable speed generating unit offers a fuel saving of 29.86% in comparison with diesel-mechanical propelled system and 2.9% in comparison with fixed speed diesel- electric system. The simulation of a 1.1-MW variable speed generating system is performed in MATLAB/Simulink 2014A environment, and experimental demonstration is performed through a 2.2-kW laboratory prototype.