Improved Variable DC Approach to Minimize Drivetrain Losses in Fuel Cell Marine Power Systems

This paper proposes a novel approach for operating hybrid fuel cell and battery power systems in marine vessels. The target of the approach is to reduce energy losses in drivetrain devices. In the proposed approach, the DC bus voltage of the hybrid power system is adjusted according to fuel cell operating points, which enables operation in Freewheel mode, and thus significantly reducing power conversion losses. Feasibility of the proposed approach is verified using a real-time hardware-in-loop simulation setup consisting of pre-validated virtual models and real industrial power converter controllers. The results presented in the work illustrate that the Variable DC Approach enables significant improvements in drivetrain efficiencies, and thus providing significant savings for vessel operators. Additionally, Variable DC Approach is shown to eliminate high frequency current ripple at the fuel cell terminals, which can further improve the efficiency and the lifetime of the fuel cells.