A Two-Layer Energy Management Strategy of Fuel Cell Hybrid System in Electric Ships

Abstract

Hybrid ships, equipped with both fuel cells and lithium batteries, are recognized as a significant technological trend in electric ships. Due to the complex sailing states, ships experience significant fluctuations in load power, which poses challenges to the cooperation between fuel cells and lithium batteries. In this paper, a two-layer, multi-objective energy management strategy (EMS) based on the model predictive control (MPC) framework is proposed to achieve economical and efficient operation of hybrid ships. The upper layer EMS takes into account hydrogen consumption, power supplies degradation, adjusting the power output ratio between the fuel cell and lithium battery to minimize the comprehensive system costs. The lower layer EMS focuses on adjusting the output power of each power supply based on dynamic efficiency, aiming to maximize the system efficiency. Meanwhile, the topological characteristics of power converters are considered to ensure ship microgrid stability. The effectiveness of the proposed strategy is verified through MATLAB/Simulink and hardware-in-the-loop (HIL) experiments. The comparison results show that the EMS could coordinate control of different types of power supplies. It reduces equipment stress, alleviates the degradation of the fuel cell and the capacity loss of the lithium battery, and enhances the efficiency of the hybrid power system.