IEEE Electrification Magazine - June 2015 - 27

0
100
200
300
400
500
600
700
800
900
1,000
1,100
1,200
1,300
1,400
1,500
1,600
1,700
1,800
1,900
2,000

Weight of BESS (t)

Payback Period (Year)

0
100
200
300
400
500
600
700
800
900
1,000
1,100
1,200
1,300
1,400
1,500
1,600
1,700
1,800
1,900
2,000

Fuel Savings (US$)

Annual Fuel Consumption (t)

changes the total power LFsafe and
sustainable load in Table 1. As the
120,000
2,440
BESS capacitor increases, the allowed
types of combinations change and
90,000
2,400
their corresponding LFsafe changes.
The engine generator has a better
60,000
2,360
fuel efficiency at the higher load ratio
whose typical specific fuel consump30,000
2,320
tion (SFC) curve is shown in Figure 4,
0
2,280
and this is the same as the higher
LFsafe . Therefore, the saved fuel cost
can justify the additional BESS cost,
Power Capacity of the BESS (kW)
weight, and volume in certain cases.
The estimated annual fuel savings
based on the annual operating profile Figure 5. The annual fuel savings according to the capacity of the BESS.
of the naval ship depend on the BESS
capacity, as shown in Figure 5, as well
as the BESS payback period and
10
40
weight, as shown in Figure 6. In this
8
estimation, the cost and weight of
30
onboard BESSs are assumed to be
6
US$1,800/kWh and 60 kg/kWh. This is
20
4
approximately two and three times
larger, respectively, when compared
10
2
with those currently available in com0
0
mercial applications because of military specifications. The maximum
continuous discharging current of the
Power Capacity of the BESS (kW)
battery module is assumed to be
4C-rate. As the BESS capacity increases, the possible fuel savings increase Figure 6. The payback period and system weight for BESS installation according
to the capacity of the BESS.
as well, but the tendency is saturated
above a certain point. Based on the
Figure 7, eliminating the cost, weight, volume, and loss of
assumptions, 1,000 kW/250 kWh of the BESS might be
the dc/dc converter. At the same time, the 12 pulse diode
selected to have a reasonable payback time with an affordrectifiers with a bulky transformer in Figure 3 can be
able BESS weight. These resulting figures and selection may
replaced with an AFE converter, as shown in Figure 7. This
change as the specific configuration of the ship IPS and
can improve the harmonic characteristics and provide the
operating profile change. The saved fuel cost would be much
bidirectional power flow capability. The cost of this configularger for the IPS with the GT because of its poor fuel effiration is that the BESS voltage, which varies according to
ciency at lower loads.
the state of charge (SOC), should be accommodated by the
Circuit Configuration and Control Strategy of
propulsion inverter and the AFE converter. This would
Onboard BeSS: Direct Connect to the DC-Link
result in the oversizing of the inverter and AFE converter.

of the electric Propulsion System
There are a variety of circuit configurations and control
strategies of the BESS as used in widespread applications.
The circuit configurations have prime design factors such
as 1) node location where the BESS connected with, 2) (its)
hardware structure, and 3) the corresponding control method. They are subject to cost, space, efficiency, reliability, and
others. Many of the applications, which employ the BESS to
support grids similarly to our purpose, interfaced the BESS
with the PCC through its own power converter or placed
the BESS on the dc-link of the propulsion system through
the dc/dc converter. However, the BESS can be directly connected to the dc-link of the propulsion system, as shown in

M

PCC
Propulsion
Inverter

AFE +
Converter
BESS

Propulsion
Motor

-

Figure 7. A circuit configuration diagram of the BESS direct connection to the dc-link of the propulsion system.

IEEE Electrific ation Magazine / j une 2 0 1 5

27



Table of Contents for the Digital Edition of IEEE Electrification Magazine - June 2015

IEEE Electrification Magazine - June 2015 - Cover1
IEEE Electrification Magazine - June 2015 - Cover2
IEEE Electrification Magazine - June 2015 - 1
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IEEE Electrification Magazine - June 2015 - Cover3
IEEE Electrification Magazine - June 2015 - Cover4
https://www.nxtbook.com/nxtbooks/pes/electrification_december2022
https://www.nxtbook.com/nxtbooks/pes/electrification_september2022
https://www.nxtbook.com/nxtbooks/pes/electrification_june2022
https://www.nxtbook.com/nxtbooks/pes/electrification_march2022
https://www.nxtbook.com/nxtbooks/pes/electrification_december2021
https://www.nxtbook.com/nxtbooks/pes/electrification_september2021
https://www.nxtbook.com/nxtbooks/pes/electrification_june2021
https://www.nxtbook.com/nxtbooks/pes/electrification_march2021
https://www.nxtbook.com/nxtbooks/pes/electrification_december2020
https://www.nxtbook.com/nxtbooks/pes/electrification_september2020
https://www.nxtbook.com/nxtbooks/pes/electrification_june2020
https://www.nxtbook.com/nxtbooks/pes/electrification_march2020
https://www.nxtbook.com/nxtbooks/pes/electrification_december2019
https://www.nxtbook.com/nxtbooks/pes/electrification_september2019
https://www.nxtbook.com/nxtbooks/pes/electrification_june2019
https://www.nxtbook.com/nxtbooks/pes/electrification_march2019
https://www.nxtbook.com/nxtbooks/pes/electrification_december2018
https://www.nxtbook.com/nxtbooks/pes/electrification_september2018
https://www.nxtbook.com/nxtbooks/pes/electrification_june2018
https://www.nxtbook.com/nxtbooks/pes/electrification_december2017
https://www.nxtbook.com/nxtbooks/pes/electrification_september2017
https://www.nxtbook.com/nxtbooks/pes/electrification_march2018
https://www.nxtbook.com/nxtbooks/pes/electrification_june2017
https://www.nxtbook.com/nxtbooks/pes/electrification_march2017
https://www.nxtbook.com/nxtbooks/pes/electrification_june2016
https://www.nxtbook.com/nxtbooks/pes/electrification_december2016
https://www.nxtbook.com/nxtbooks/pes/electrification_september2016
https://www.nxtbook.com/nxtbooks/pes/electrification_december2015
https://www.nxtbook.com/nxtbooks/pes/electrification_march2016
https://www.nxtbook.com/nxtbooks/pes/electrification_march2015
https://www.nxtbook.com/nxtbooks/pes/electrification_june2015
https://www.nxtbook.com/nxtbooks/pes/electrification_september2015
https://www.nxtbook.com/nxtbooks/pes/electrification_march2014
https://www.nxtbook.com/nxtbooks/pes/electrification_june2014
https://www.nxtbook.com/nxtbooks/pes/electrification_september2014
https://www.nxtbook.com/nxtbooks/pes/electrification_december2014
https://www.nxtbook.com/nxtbooks/pes/electrification_december2013
https://www.nxtbook.com/nxtbooks/pes/electrification_september2013
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