Transition of AC to DC Power Supply on Cruise Vessels with Load Sharing of Parallel Infeeds Using the Droop Control Approach

Abstract

The deployment of DC grids on ships promises to simplify the integration of renewable generation and improve transmission efficiency by minimizing conversion losses. As voltage is the only direct indicator of grid stability in a DC grid, there are challenges in terms of load flow control and grid stabilization. This paper investigates voltage regulation in a dc-based grid within the fire zone of a cruise vessel with two voltage sources connected in parallel. In addition to voltage regulation, load sharing between the feeding converters is to be achieved. Here, the concept of model-based control design is applied. First, a suitable control system is simulatively tested within the electrical replica of a fire zone and then transferred to real laboratory hardware using the power hardware-in-the-loop (PHIL) concept. It is shown that a characteristic-based droop control is suitable for voltage regulation and power sharing within a DC-based power system. By introducing a secondary control level, the grid can be operated at nominal voltage levels even under varying load situations.