IEEE Electrification Magazine - June 2016 - 46

pack together the distributed RESs and local electrical
loads as an independent and self-sustainable entity,
namely a microgrid. At present, research in the area of dc
microgrids has investigated and developed a series of
advanced methods in control, management, and objective-oriented optimization that would establish the technical interface enabling future applications in multiple
industrial areas, such as smart buildings, electric vehicles, aerospace/aircraft power systems, and maritime
power systems.
Maritime power systems can be traced back to the
1880s, starting with the earliest record of a dc-based
onboard power system on the SS Columbia, where Edison's
dc lighting system was first installed. In the last century,
maritime power systems have been greatly developed
along with the increasing demand of onboard electrical
loads. During this development, shipboard power transformed from Edison's dc power system into Tesla's ac
power system, as the use of electricity extended from the
initial lighting to almost every aspect aboard a vessel
where it was necessary to build upon the advances in the
ac distribution infrastructure. In recent years, government
regulation of emissions has become increasingly strict,
while customers' fuel-efficiency requirements have risen.
This has resulted in the current trend toward more efficient ships, the most emblematic of which is the all-electric ship (AES), which exploits an electrical propulsion
system instead of the conventional mechanical system.
One of the significant features of the AES is the concept of

Power Generation System

the integrated power system (IPS), which minimizes the
number of generators in a ship by incorporating intelligent methods for meeting load demands through multiple
paths and dynamically matching generational capability
to loading needs. In broad terms, the shipboard IPS can be
regarded as a large-scale, onboard microgrid with specific
requirements. In recent studies, the current IPS research
trend is turning to dc power distribution systems. This has
resulted in advanced research outcomes in the dc
microgrid field, especially in its advanced control, management, and optimization methods, all of which can be
attributed to a wide body of AES research.

DC Power Architecture
The Queen Elizabeth II, the world's first cruise vessel with
an electric propulsion system, is a high-profile example of
an existing ac shipboard power system. The power architecture of its shipboard power system is shown in Figure 1.
The vessel, originally steam powered, was built in 1968 and
was converted from steam to diesel-electric propulsion in
1987. The ship was refitted with nine diesel generator sets
rated 10.5 MW at 10 kV. The electric power plant is connected with the vessel's main bus, driving the two major
44-MW electric propulsion systems. The auxiliary loads
and the hotel service loads are powered through transformers and power electronic converters. The conversion
to a diesel-electric power system was expected to improve
fuel efficiency by up to 35% at the vessel's service speed of
28.5 kn and save £12 million a year in fuel costs. However,

Main Switchboard

Electric Propulsion System 1

G

Diesel Generator Set 1

Circuit
Breaker

Ship Service Load System
Low-Voltage Switchboard

G
Ship Service
Load

Diesel Generator Set 2

Electric Populsion System 2

G

Diesel Generator Set 9

Figure 1. The diesel-electric shipboard power system of the Queen Elizabeth II.

46

I E E E E l e c t r i f i c ati o n M agaz ine / j un e 2016



Table of Contents for the Digital Edition of IEEE Electrification Magazine - June 2016

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http://www.nxtbook.com/nxtbooks/pes/electrification_june2019
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http://www.nxtbook.com/nxtbooks/pes/electrification_december2018
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http://www.nxtbook.com/nxtbooks/pes/electrification_june2018
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http://www.nxtbook.com/nxtbooks/pes/electrification_september2017
http://www.nxtbook.com/nxtbooks/pes/electrification_march2018
http://www.nxtbook.com/nxtbooks/pes/electrification_june2017
http://www.nxtbook.com/nxtbooks/pes/electrification_march2017
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http://www.nxtbook.com/nxtbooks/pes/electrification_september2016
http://www.nxtbook.com/nxtbooks/pes/electrification_december2015
http://www.nxtbook.com/nxtbooks/pes/electrification_march2016
http://www.nxtbook.com/nxtbooks/pes/electrification_march2015
http://www.nxtbook.com/nxtbooks/pes/electrification_june2015
http://www.nxtbook.com/nxtbooks/pes/electrification_september2015
http://www.nxtbook.com/nxtbooks/pes/electrification_march2014
http://www.nxtbook.com/nxtbooks/pes/electrification_june2014
http://www.nxtbook.com/nxtbooks/pes/electrification_september2014
http://www.nxtbook.com/nxtbooks/pes/electrification_december2014
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