Energy Management of Marine Hybrid Power System with Composite Energy Storage Devices for a Tugboat

Due to the intense variation of operational loads of tugboats, the hybrid power system structure with composite energy storage including prime movers, batteries, and super-capacitors is issued, and then combined with the rule-based power management strategy to evaluate the potential to improve the energy efficiency at a typical working scenario. Furthermore, to optimize the energy and emissions performance of this system at real sea conditions, the equivalent consumption minimization strategy is introduced as the constraint, which can attribute to the reduction of fuel consumption and emissions. The results show that fuel consumption and NOx emissions can be reduced by up to 9.24% and 44.6% respectively, by implementing the super-capacitor. At the same time, smoother load fluctuation and overall discharge rate of batteries can be obtained by using ECMS, which is advantageous in improving the cycle life and stability of the battery, and the reliability during the whole voyage.