Notional System Models

The objective of this report is to set forth a group of time-domain models for the earlydesign stage study of shipboard power systems. These models are highly simplified abstractions of shipboard power system components. The motivation for the simplification is two-fold. First, at an early design stage it is doubtful if the parameters needed for a more detailed system representation would be available. A highly detailed simulation would be based on many
assumptions leading to results which are no more indicative of actual performance than a highly simplified simulation. The second reason for the creation of highly simplified model is for the sake of computational speed, so that system simulations based on the component models will run at speeds compatible with the needs imposed by exploring the system behavior under a large variety of conditions.

The types of model simplifications used are three-fold. First, throughout this report average-value models are used. In particular, the switching of the power semiconductors is only represented on an average-value basis. Secondly, reduced-order models are typically used. Thus, high-frequency dynamics have been neglected. Simulation based on these models cannot be used to predict behaviors such as the initial response to a fault. In general, temporal predictions of features on a time scale of ~100 ms or less will not be reliable. The third simplification that has been made is that many components are represented in the abstract based on the operation goals of the component rather than on the details of what might physically be present.

The set of models provided herein is fairly extensive and adequate to serve as a basis for studying a variety of power system architectures. In particular, the set of models is currently being used to study a notional medium voltage ac shipboard power system, a notional highfrequency ac shipboard power system, and a notional dc shipboard power system. In order to support these studies, the models set forth include: turbines, turbine governors, wound-rotor
synchronous machine based ac generators, generator paralleling controls, rectified wound-rotor synchronous machine based dc generation systems, ac input permanent magnet synchronous machine based propulsion drives, dc input permanent magnet synchronous machine based propulsion drives, hydrodynamic models, ac and dc pulsed load models, isolated dc/dc conversion models, dc loads, non-isolated dc/ac inverter modules, ac loads, active zonal rectifiers, circuit breakers and controls, as well as a variety of supporting components.

For the purposes of brevity and because of the resources available, model validation results are not presented herein. However, comments on model maturity have been included with each component to provide the reader with a sense of the degree of model confidence for each component.

Finally, the reader should be aware that a follow-on report will be delivered in the January 2014 time frame. This report will include an update of the models presented herein, but also include examples of their application in the simulation of notional medium voltage ac, highfrequency ac, and dc shipboard power distribution systems.