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Shipboard power systems that service large-scale dynamic loads and electric propulsion can significantly improve their performance by adding controllable energy storage. These systems require power management controls that consider dynamics like generator ramp rates, along with energy storage capacity and location. In the early-stage design process, many alternative designs are considered, and each requires a unique controller. This article describes a numerical optimization technique that establishes an upper bound performance criteria without manually designing controllers for each system. The solution is a best case performance that assumes perfect future knowledge of the time-varying load. While unrealistic in real-time, this technique yields a fair comparison between competing architectures without the variability of different control methods. To demonstrate the concept, a notional multi-bus power system architecture is evaluated on a representative set of operational duties to illustrate comparisons between system attributes like energy storage power and efficiency ratings. A design trade study shows that the success rate for a baseline ship can improve from under 60% to nearly 100% by increasing generator power by 10% and energy storage capacity by 100%. These automated architecture benchmarks fit into a broader total ship optimization process, or can be used in human-driven trade studies.

In present times, the concerns over severe environmental pollution, fluctuations, and fossil-fuel consumption caused by immensely dynamic loads (pulsed loads) have captured attention in shipboard microgrids. In order to make such power system stable and reliable, presently, more generators are kept online that operate much below their efficient point. Therefore, in order to boost the fuel efficiency of shipboard microgrids, the minimum generator operation with N-1 safety can be considered as a possible solution, which is a trade off between reliability and fuel economy. For that, one of the efficient solution is to interface an energy storage system (ESS) by removing the backup generator or removing one of generator and operate rest of the generators close to their efficient point. Energy storage devices that have been frequently in use in different applications consist of batteries, flywheel, ultra-capacitor, and fuel cell. Lithium-ion among the different type of batteries is one of the most used battery in fully electric zero-emission commercial ferries that sails on shorter routes. This paper therefore presents Lithium-ion based Battery Energy Storage System (BESS) as a feasible solution to the prior mentioned concerns. At first, in order to cater with the fluctuation caused by the propulsion motor with the varying sea conditions, BESS is interfaced without the use of buck-boost converter in parallel with the DC-link capacitor. Secondly, the same BESS is interfaced with the point of common coupling (PCC) in order to cater with pulsed loads. The proposed methodology is simulated and verified using MATLAB/SIMULINK software environment.

The article of record as published may be found at http://dx.doi.org/10.1109/TMAG.2006.887676 Part of the technical versatility of future all-electric ships is the potential ability to share large amounts of power among a variety of high-power loads. To help evaluate this potential and to provide information to help guide technology selection, a physics-based model of a power train for an electric ship has been developed and implemented on three modeling platforms. Using this model, three different investigations have been carried out to explore aspects of the behavior of a rotating machine power source for a shipboard rail launcher. These were: 1) influence of rapid charging of the rotating machine system on the ship power system; 2) use of the stored energy in the rotating machines to improve ship power quality; and 3) use of the stored energy in the rotating machines to power a pulsed free-electron laser. Each study highlighted different integration opportunities and challenges. The first showed that, because the charging of the rail launchers was through 5-MW motors, there could be a voltage sag for a few cycles, but this could easily be managed so that the sag could be reduced to an inconsequential level. The second study showed that, with appropriate power electronics, the stored energy in the rail launcher power supply can be used to correct power quality problems introduced by other ship systems. Finally, the stored energy in the launcher power supply can be used to fire a free electron laser for ship defense. This feature opens the possibility of routine operation of the entire ship at highest efficiency, i.e., with the smallest number of gas turbines operating near full power, while providing stored energy needed for ship defense. This work was supported by the Office of Naval Research.