Bus voltage stability is a key issue in future medium-voltage DC (MVDC) power systems on ships. The presence of high-bandwidth controlled load converters (Constant Power Load, CPL) may induce voltage instabilities. A control design procedure is presented which starts at the modeling level and comes to control implementation. A control method based on a Linearization via State Feedback (LSF), is proposed to face the CPL destabilizing effect and to ensure the MVDC bus voltage stability. A multiconverter shipboard DC grid is analyzed by means of a new comprehensive model, which is able to capture the overall behavior in a second-order nonlinear differential equation. Exploiting DC–DC converters that interface power sources to the bus, LSF technique is able to compensate for system nonlinearities, obtaining a linear system. Then, traditional linear control techniques can be applied to obtain a desired pole placement. With reference to system parameters mismatch, LSF control design is verified by means of a sensitivity analysis, evaluating the possibility of an over-linearization strategy. Time-domain numerical simulations are used to validate the proposed control, in presence of relevant perturbations by means of a two-way comparison (average value model and detailed switching model).

In modern dc shipboard microgrid (SMG) systems, the propulsion motors and hotel loads are always supplied through tightly regulated point of load converters, which behave as constant power loads (CPLs). The negative incremental impedance due to CPL’s characteristics destabilizes the dc bus voltage of dc SMGs. Due to uncertain operating conditions of maritime ships on the sea, the dc bus voltage robust control is a crucial matter. Therefore, this paper presents a cutting-edge systematic review on advanced nonlinear control strategies to stabilize and control the CPLs in dc SMGs, such as sliding mode control, synergetic control, backstepping control, model predictive control, and passivity-based control. The latest stabilization techniques and the future trends towards an adaptive nonlinear control have been presented throughout this review. Several feedforward control-based observation and estimation techniques have been highlighted. The stability analysis and stability challenges of dc SMGs are also discussed.

This contribution starts with a review of the state of the art of existing high-voltage shore connection (HVSC) systems in terms of principles, rules, publications, technologies, and relevant installations. Then, tutorial sections present the main technical aspects of HVSC systems as ship-to-shore interface, shore equipment (transformers, converters, etc.), onboard devices (cubicles, shore switchboard, etc.), operating sequences, and feasibility aspects, for both commercial and military applications. Finally, some technical challenges are presented, concerning intentional/unintentional bonding, interactions between HVSC bonding and cathodic protection systems, bonding opportunity, and electrical safety aspects related to bonding issues in case of large earth fault currents in port facilities.

Nowadays, the Medium Voltage Direct Current (MVDC) technology represents a new possibility to renew the shipboard power system of large All Electric Ships (e.g. cruise liners or military vessels.). This new concept is capable of achieving valued advantages, such as simplified system integration, modularity and system efficiency, together with an expected reduction of the space devoted to technical system. For a shipyard interested in keeping a leading position in the market, such benefits will be the main strength points. Therefore, the MVDC Large Ship research program (presented in the paper) has been carried out trying to meet with the industrial needs of one of the partners, whose expertise deeply influenced the research and was deemed indispensable: Fincantieri Shipyard.

Ships have witnessed an astounding evolution in the last 200 years. The introduction of the combustion engine has started an ever-faster change, both in the performance and functionality given by the ships. From the steam-powered ships of the early 1800s to the modern diesel-electric ships, the improvements were significant and increasingly rapid. In particular, in the last 30 years, the design of ships has made a huge leap ahead, both in terms of efficiency of the entire vessel and new functions given to the owners. This is due to the progressive electrification that has occurred.

Voltage stability in Medium-Voltage DC (MVDC) power systems on ships is a key design goal. MVDC bus voltage stability can be impaired due to the presence of high-bandwidth controlled Constant Power Load (CPL) converters, which can induce negative incremental resistance instabilities. A linearization via state-feedback control is presented in this paper, to stabilize a MVDC bus voltage in presence of destabilizing CPLs. Once a linear control system is obtained, a traditional stable pole placement is operated. The control is designed to be implemented using the controlled DC/DC converters that interface the system power sources to the MVDC bus. The proposed control is verified by means of time-domain numeric simulations based on both an average state space model and a detailed power electronics circuit model, thus providing a two-way comparison.