IEEE Electrification - September 2020 - 38

the time it ran in the maneuver, DP, and docking
modes, as depicted in Figure 12, which is a typical
profile for research, engineering, and service vessels.
The fuel consumption and savings breakdown at the
different operation modes for this specific mission
are shown in Figure 13. Compared with the ac bus
system, an average fuel savings of 6% was achieved
throughout the entire mission. While negligible fuel

savings were achieved in cruising mode, more than
5%, 6%, and 9% fuel consumption reductions were
achieved in the maneuver, DP, and docking modes,
respectively. The significant fuel savings from the
maneuver, DP, and docking modes demonstrate the
high suitability of dc bus IEP systems for research,
service, and engineering ships used for more versatile duties, as well as ferries used for short distances with frequent docking and
undocking events.

ac Bus IEP System (Shen Kuo Vessel as an Example)
Side
Propulsion

ac-dc

dc-ac Side Propulsion Tx

ac-dc

dc-ac Main Propulsion Tx

Switchboard

M
G

M
Hotel Load Tx

Main Propulsion

G

Switchboard

Hotel Load Tx

G
Main Propulsion ac-dc

Main
dc-ac Propulsion Tx
G

M
(a)

dc Bus IEP System (Shen Kuo Vessel as an Example)
Integrated dc Bus and Converters
M
G
M

Hotel Load Tx

G

Integrated dc Bus and Converters
Hotel Load Tx
G

G
M
(b)

Figure 10. A comparison of system schematics between the (a) ac bus and (b) dc bus IEP systems. Tx: transmission.

38

I E E E E l e c t r i f i cati o n M agaz ine / SEPTEMBER 2020

Technology Acceptance
by the China Classification
Society
The China Classification Society
(CCS), which provides classification
services to ships in accordance
with international conventions
and the related rules and regulations, is technically involved in
promoting dc bus IEP systems. The
main challenge of the CCS certifying the dc bus system is the protection behavior of the dc bus
short circuit. For example, the calculation of different types of dc
bus systems, selection of parameters for components of simulation
modeling, and selective overcurrent protection for dc electrical
systems. Given that ship owners
and operators are reluctant to perform the destructive short circuit
test onboard, the CCS has proposed an innovative method by
using comprehensive software
simulations and full-power offland test validations to assess and
approve the short-circuit protection of dc bus systems.
The CCS has produced the draft
"Guidelines for the dc Bus System"
to standardize the approval method.
Moreover, due to its high technical
compatibility with the energy-storage systems (ESS), such as batteries
and super capacitors, the dc bus
system has been regarded as a
promising technical candidate in
vessels equipped with the ESS, and
has been accepted as one of the
standard topologies in the 2018
"Guidelines for the Hybrid-Powered
Ships" and the 2019 "Guidelines for
the Pure Battery-Powered Ships"
published by the CCS.
IEEE Electrification - September 2020

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