Considerations on the design of voltage control for multi-machine MVDC power systems on large ships

Medium Voltage Direct Current (MVDC) distribution is an enabling technology for future large ships, e.g. cruise liners or military vessels. In MVDC systems, shipboard loads are normally fed through power-converters directly connected to the MVDC bus. For such systems a key design goal is voltage stability, impaired by the presence of high-bandwidth controlled loads (Constant Power Loads, CPLs). The paper proposes an approach to stabilize the MVDC bus using the generating systems as sources of stabilizing power. Fast controlled DC/DC converters, interfacing generators to MVDC bus, are employed to control it in a stable way and to provide power sharing among the generators. To this aim, an Active Damping method is exploited. A supplementary Linearization via State Feedback control is utilized to stabilize DC/DC load converters feeding particularly impacting CPLs. Proposed controls are verified by means of time-domain numerical simulations. Shipboard feasibility and performance of the proposed control systems are most considered in the work as conclusions.