Page 30 - Modern Control of DC-Based Power Systems

INTRODUCTION

Shipboard power systems present a special set of challenges related to sta-
bility. In this research work, the Integrated Shipboard Power Systems
(ISPSs) are the focus area. The US Navy is pushing Direct Current (DC)
as the distribution technology in their future ships, which include a DC
power system with multiple power elements.
The usage of DC in shipboards has certain advantages, such as the
reduction of up 27% of the fossil fuel consumption in the case of the
“Dina Star of Myklebusthaug Offshore” in comparison with Alternating
Current (AC). Likewise, DC technology enables an adjustment of the
motor speed and therefore maximum efficiency at every operating point.
The efficiency gains could also be observed in the dynamic position sys-
tem of a shipboard, where it maintains its position and has a high impact
on its fuel consumption.
The implementation of DC also results in a reduction of noise emis-
sions in the machine room as less vibration are present. A DC distribution
system is also advantageous for the usage of batteries or other energy stor-
age in shipboards which also contributes towards the increase in energy
efficiency and the reduction of CO 2 emissions.
According to Doerry [1] there are many reasons for employing an
MVDC System, including, but not limited to:
• “Power conversion equipment can operate at high frequencies, result-
ing in relatively smaller transformers and other electromagnetic
devices.”
• “Without the skin effect experienced in AC power transmission, the
full cross section of a DC conductor is effective in the transmission of
power. Additionally, the power factor does not apply to DC systems.
Depending on the voltage selection, cable weights may decrease for a
given power level.”
• “Paralleling power sources only require voltage matching and do not
require time-critical phase matching.”

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