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This paper presents a method of operating a zeroemission 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. 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 realtime hardware-in-loop simulator consisting of real control units and virtual power device models.

Abstract-Operability and dependability metrics can be a valuable tool in early ship design by providing a quantitative analysis of the robustness of the ship's integrated engineering plant (IEP). However, the use of these metrics involves large numbers of time domain simulations of the IEP. The simulation of such a complex system, which includes electrical and thermal subsystems, can be problematic in terms of computational efficiency. In this paper, a simplified modeling approach based on the fundamental power limitations is set forth. The power flow problem is posed as a linear programming problem which is solved using a simplex method.

Abstract-Medium voltage dc distribution systems are currently of interest for future naval warships. In order to provide hardware validation for research associated with the development of these systems, a low power Medium Voltage DC Testbed (MVDCT) is being constructed. This paper documents the system being constructed and provides some initial test results.

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