4) What are notable advantages of DC versus AC? Are there equipment footprint reductions if DC is chosen over AC?
DC power systems do not have the stability problems associated with AC systems. In addition, DC transmission incurs less losses than similar AC transmission systems. Similarly, maximum DC voltages are lower than comparable AC systems resulting in reduced insulation levels.
In AC based configurations, generator sets must work at a fixed speed and limit further improvement in fuel efficiency in ship design. Reactive power flow and power quality concerns due to system imbalances must be managed, transformers are larger in size consuming valuable footprint in AC designs, and system voltage and frequency deviations due to dynamic coupling between generation and load are a few notable disadvantages with AC based designs. Medium voltage DC solutions show promise in leading to reduced weight and, increased efficiency but challenges exist with short-circuit currents, interrupting DC circuits, and determining system standardization. The latter is a result of experience in DC – realize we have a little over a century of experience with AC globally.