A variable DC approach to minimize drivetrain losses in fuel cell marine power systems

This paper presents a method of operating a zero-emission power system in marine vessels. The main goal of the proposed method is to reduce losses of drivetrain devices. The power sources considered in this work are proton exchange membrane fuel cell and lithium-ion battery while the main power consumers are induction motors driven propulsion system. Both sources and consumers are connected to a common DC bus through power conversion devices. In the proposed method, the DC bus voltage level is controlled according to the loading of the fuel cells. By controlling the DC bus voltage, it allows operation of fuel cell DC/DC converter in freewheeling mode which significantly reduces the converter losses. In addition, this approach is also expected to reduce the motor and battery drive losses. Feasibility of the proposed operation method and loss calculations are presented on a real-time hardware-in-loop simulator consisting of real control units and virtual power device models.