This article is structured to present an overview of a DC ship power system. The main DC grid configurations will be presented and a difference to the AC system configuration will be highlighted. Compared to the AC power system used on board ships, DC has some obvious benefits which will be explored in this paper. These benefits include: improvement of prime mover efficiency and reduction of fuel costs, weight and space savings, unity power factor operation of generators, lower transmission losses, faster and simpler parallel connection of generators and simpler implementation of energy storage. Finally, some of the challenges introduced with the DC technology will also be explored. These include: high short-circuit currents, DC protection concept and expensive and possibly non-profitable energy storage system solutions.

Various faults in ship’s electrical power system, primarily those connected with diesel-generators, governors and automatic voltage regulators, may lead to oscillations in generator load, voltage and frequency. If those transients are large enough, a partial or total blackout may occur. In order to prevent such events, it is very important to get an insight into dynamic behaviour of electrical energy sources on board vessel. In this paper, a dynamic model in the time domain of marine diesel-generator is presented. The model is realized in the MATLAB/SIMULINK environment and consists of three main parts: the synchronous generator model, diesel-engine governor model and voltage regulator model. Simulation of a sudden loss of one generator when two generators are running in parallel is performed. Simulation results show that the presented model is fully applicable for the purpose of analysis of the marine diesel-generator dynamic behaviour during transient periods.

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Blackout prevention on dynamically positioned vessels during closed bus bar operation, which allows more efficient and eco-friendly operation of main diesel generators, is the subject of numerous studies. Developed solutions rely mostly on the ability of propulsion frequency converters to limit the power flow from the grid to propulsion motors almost instantly, which reduces available torque until the power system is fully restored after failure. In this paper, a different approach is presented where large scale energy storage is used to take part of the load during the time interval from failure of one of the generators until the synchronization and loading of a stand-by generator. In order to analyze power system behavior during the worst case fault scenario and peak power situations, and to determine the required parameters of the energy storage system, a dynamic simulation model of a ship electrical power system is used. It is concluded that implementation of large scale energy storage can increase the stability and reliability of a vessel’s electrical power system without the need for the reduction of propulsion power during a fault. Based on parameters obtained from simulations, existing energy storage systems were evaluated, and the possibility of their implementation in the maritime transportation sector was considered. Finally, an evaluation model of energy storage implementation cost-effectiveness was presented.