AC ship microgrids: control and power management optimization

At sea, the electrical power system of a ship can be considered as an islanded microgrid. When connected to shore power at berth, the same power system acts as a grid connected microgrid or an extension of the grid. Therefore, ship microgrids show some resemblance to terrestrial microgrids. Nevertheless, due to the presence of large dynamic loads, such as electric propulsion loads, keeping the voltage and frequency within a permissible range and ensuring the continuity of supply are more challenging in ship microgrids. Moreover, with the growing demand for emission reductions and fuel efficiency improvements, alternative energy sources and energy storage technologies are becoming popular in ship microgrids. In this context, the integration of multiple energy sources and storage systems in ship microgrids requires an efficient power management system (PMS). These challenging environments and trends demand advanced control and power management solutions that are customized for ship microgrids. This paper presents a review on recent developments of control technologies and power management strategies proposed for AC ship microgrids

Grey wolf optimization-based optimum energy-management and battery-sizing method for grid-connected microgrids

In the revolution of green energy development, microgrids with renewable energy sources such as solar, wind and fuel cells are becoming a popular and effective way of controlling and managing these sources. On the other hand, owing to the intermittency and wide range of dynamic responses of renewable energy sources, battery energy-storage systems have become an integral feature of microgrids. Intelligent energy management and battery sizing are essential requirements in the microgrids to ensure the optimal use of the renewable sources and reduce conventional fuel utilization in such complex systems. This paper presents a novel approach to meet these requirements by using the grey wolf optimization (GWO) technique. The proposed algorithm is implemented for different scenarios, and the numerical simulation results are compared with other optimization methods including the genetic algorithm (GA), particle swarm optimization (PSO), the Bat algorithm (BA), and the improved bat algorithm (IBA). The proposed method (GWO) shows outstanding results and superior performance compared with other algorithms in terms of solution quality and computational efficiency. The numerical results show that the GWO with a smart utilization of battery energy storage (BES) helped to minimize the operational costs of microgrid by 33.185% in comparison with GA, PSO, BA and IBA

Techno-economic feasibility study of battery-powered ferries

The move towards incorporating more-electric solutions inthe transportation sector has gained increased momentum during thelast decade. Cost of fossil fuels and environmental impacts of emissionsare the main driving factors behind this growing trend. Nevertheless,advancements in battery technologies are the key enablers for the widespreadapplication of electric alternatives in a more realistic manner.This paper looks into this trend from electric ferries perspective andpresents a technical and economic feasibility assessment. The technicalstudy includes sizing of the battery storage system based on Depth-of-Discharge (DOD) and maximum load scenario. The proposed sizing isvalidated against the measured load profile. The economic studyincludes initial investment, operational cost and maintenance cost of abattery powered electric ferry. The economic analysis considered thepayback period (PBP) and battery lifecycles as assessment factors. Thetechnical assessment results revealed that the proposed battery systemcan efficiently power the ferry within the stipulated DOD range. Themaximum DOD achieved is 70 %, which provided a reasonable lifetimeof 10.7 years. The economic analysis revealed that the battery’s DODhas significant effects on the investment cost of the system and the PBP.The PBP is found to be 6.7 years which is 37 % less than the lifetime ofthe battery. Overall, the battery-powered ferry is found to be feasiblewith 51.3% operational costs saving compared to the diesel-electricalternative