Research on Multi-Objective Optimization Strategy of Capacity Configuration for Ship Composite Energy Storage Systems

Composite energy storage system (CESS) provides an efficient and environmentally friendly energy utilization solution for green ships. However, due to the diversity of goals in shipbuilding and operation process, how to design the capacity of CESS with different energy storage units is a complex optimization problem. In this article, a CESS model composed of lithium-ion batteries (LBs) and ultracapacitors (UCs) is established, and a multi-objective optimization model is built considering both the life cycle cost (LCC) and the LB performance degradation of CESS. In the model, several key indicators are taken into account, including energy efficiency, cost-effectiveness, carbon emission, battery life, and so on, and constraints related to ship safety and stability are set. Then, an intelligent frequency division framework is introduced with support vector machine and filtering algorithms to deal with the allocation schemes of power outputs for different energy storage units. Besides, non-dominated sorting genetic algorithm II (NSGA-II) is utilized to search for the Pareto front and pseudo weight vector method is introduced for decision making. By comparing and analyzing the simulation results, optimal multi-objective configuration schemes for ship's CESS are derived, which effectively improve the economical and environmental performances of the ship's power system.