Abstract
Shipboard microgrids (SMGs) are distinguished by the heavy propulsion system that can vary largely in a short time. Consequently, this variation shifts the optimum operating points of the diesel engines that leads to increase the overall emissions and operational costs. Moreover, power fluctuations caused by the dynamic loads such as propulsion motors along with the lack of cold-ironing facilities at both ends of seaports make it even worse. Therefore, the application of energy storage systems (ESSs) with proper coordination is becoming very popular for ships to improve the energy management, and thus decreases the fuel consumption. The aim of this paper is to firstly highlights different architectures of SMGs and the benefits the ESS can brings into them, then proposes an enhanced hierarchical control-based energy management scheme that is suitable for SMGs operations during an islanded and grid-connected operation. The proposed method based on the ESSs supports the diesel generators to enable them to operate in the optimum window recommended by the diesel engines company, which significantly decreases fuel consumption, operational costs, and emissions. Furthermore, to provide a linkage between SMG and the grid during port stays, conventional <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$P-f$ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$Q-V$ </tex-math></inline-formula> droop control strategy is adopted to import and export power to the seaport load or the grid for emergency purposes referred to in this study as Ship-to-X operation. The enhanced hierarchical control is capable of optimally shifting the modes for efficient and reliable operation and reducing specific fuel consumption. The performance of the proposed scheme is adopted and validated with satisfactory results of a practical hybrid SMG in a MATLAB/SIMULINK environment.
Highlights
HE varying fuel prices and strict regulations introduced by the international marine Organization have urged shipbuilders to move towards energy-efficient and greener resources following the footprints of the terrestrial energy sector, where an increased amount of integration of renewable energy sources (RES) helps in minimizing the emissions [1]
The primary layer includes power-sharing between diesel genera- tors (DG) and battery packs (BPs) during the islanded mode of operation whereas secondary control is responsible for voltage and frequency restoration, which helps for allelectric port operation (AEPO)
B) When the ship is running at a higher speed or during overloading conditions, which usually occurs due to the environmental changes in the sea, i.e., βPR, DGs will operate at the fixed frequency referred to as fη where the rest of the power will be supplied by the c) When the ship operates at a value greater than the minimum threshold limit and below a maximum threshold limit i.e., αPR ≤ PT L ≤ βPR, the ship operates in DG mode, and BP will share the least amount of power), referred to as fDG
Summary
HE varying fuel prices and strict regulations introduced by the international marine Organization have urged shipbuilders to move towards energy-efficient and greener resources following the footprints of the terrestrial energy sector, where an increased amount of integration of renewable energy sources (RES) helps in minimizing the emissions [1]. Quasi load leveling is defined here as, during low and overloading operations, BP will store and supply power respectively whereas, during operation of load between the minimum and the maximum threshold limit, BP will share the least amount of power It helps to achieve better fuel efficiency, reduction in the operational cost of DGs, and utilization of BPs. Further during long stays at the port, hierarchical control based on conventional P − f and Q − V droop control is adopted where secondary control is responsible for synchronization and export of power to the grid respectively.
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