Energy flow control and sizing of a hybrid battery/supercapacitor storage in MVDC shipboard power systems

Abstract

The propulsion system of a medium-voltage dc (MVDC) ship is subject to large thrust/torque variations due to interactions of the ship and the propeller with sea waves. These variations induce steep power fluctuations on the MVDC bus, adversely impacting the stability, efficiency and power quality. Hybrid energy storage system (HESS) is a promising solution for mitigating these power fluctuations. Dictating the energy that the HESS components must deliver/absorb, the energy management strategy (EMS) impacts the size/capacity of the energy storage system (ESS). Based on this consideration, sizing and EMS of a battery/supercapacitor (SC) HESS are jointly optimised by using a deep reinforcement learning-based method. The proposed method splits the power between the HESS components such that while the operational constraints are satisfied, energy storage size and losses are minimised. Its features are adaptability to varying sea states, real-time implementation feasibility, while obviating the requirement for knowledge of the ship propulsion power profile. The efficacy of the joint sizing/EMS on reducing the ESS size is validated by comparing the sizes when battery-only, SC-only and HESS are employed in the MVDC shipboard power system. Real-time implementation feasibility and adaptability to various ship propulsion power profiles is confirmed through real-time simulations.

A comprehensive state‐of‐the‐art review on reliability assessment and charging methodologies of grid‐integrated electric vehicles

“…Furthermore, since high-energy ESSs are needed, there will always be an increase in the need for high-density battery packs. High-density battery packs consequently experience thermal management issues as a result of heat generation during the charging/discharging operation [35,36].…”

Design and Evaluation Framework for Modular Hybrid Battery Energy Storage Systems in Full-Electric Marine Applications

“…For modelling the battery cell, a basic equivalent circuit model is used, where battery behavior is described using an ideal voltage source, whose purpose is to simulate the battery open-circuit voltage, and a resistor that considers the battery internal resistance due to the electrodes. This modelling approach is a common practice in battery sizing [15,17], and it has been experimentally validated in reference [18]. This study considers two mainstream battery types, high-energy NMC and one high-power LTO cell, for the evaluation of different HBESS topologies.…”

“…The total purchase cost of the HBESS based on the number of HE and HP modules and other common components can be calculated using the following equation Cost HESS = n HE × Cost module,HE + n HP × Cost module,HP + Cost other common components (15) where the cost of each module depends on the cost of cells, heat sink, power converter, and other components in the module that can be written as Cost module,HE/HP = Cost cell,HE/HP + Cost heatsink,HE/HP + Cost power converter (16) The cost of the cells depends on the number of HE and HP cells in each topology. As reported in Table 1, it is a cost of 150 EUR/kWh and 381 EUR/kWh, for NMC and LTO battery cells, respectively.…”

“…However, HBESSs have only been investigated in road transport applications and electric grid applications (including charging stations) [13,14], while there has been limited explorations in maritime applications [11,12]. Although the existing literature, such as [8,15,16], has proposed several hybrid battery energy storage systems (HBESSs), it remains unanalyzed which HBESS has an advantage due to the absence of a generic design and evaluation framework on maritime HBESS.…”

Design of a reliable and coordinated protection strategy for zonal shipboard power systems

“…In most cases, shipboard power systems utilise AC power, which is generated by the ship's generators and then distributed throughout the vessel through a network of transformers and distribution panels. However, the use of DC and hybrid AC/DC electrical systems is increasing in modern SPSs [9,10]. One important aspect of the SPS is the need for redundancy and backup power sources to ensure reliable operation.…”