IEEE Electrification Magazine - June 2015 - 33

few seconds and the system eventually blacks out.
Figure 12(b) shows the experimental results of an active
power compensation with a 1,000-kW BESS. The BESS current increases, and the PCC frequency is maintained within
the normal deviation region specified as ±3% from the
nominal value, 60 Hz. The active AFE converter current
decreases during the generator trip mode because of the
BESS power support. A standby generator, LDG2, is brought
to the PCC after 120 s, which is the typical synchronizing
time of a cold standby generator. After discharging ends,
the BESS SOC and dc-link voltage are restored with the constant charging energy from the engine generators.
For future mission loads, a trapezoidal pulse load was activated, which consumes 5 MW during 200 ms: increasing in
20 ms and decreasing in 80 ms.The ship-service load consumes
1 MW and 250 kVAr, and the propulsion load consumes
2.17 MW. The total active load, including pulse load, demands
8.17 MW. This exceeds the total generation capacity, 7 MW,
resulting in an inevitable decrease in the PCC frequency.
Figure 13 shows the PHILS results against the pulse load. In
Figure 13(a), the pulse load without a compensation strategy is
shown, where the PCC line-to-line root-mean-square voltage
drops from 690 to 440 V and the PCC frequency drops from 61 to
58.3 Hz, violating the naval grid standard. Figure 13(b) shows the
situation with the compensation strategy where the PCC voltage deviation was suppressed to less than 10% and the frequency deviation reduced to 2.5% compared to 60 Hz. Thus,
both satisfy the naval grid standard. The active and reactive AFE
converter current was controlled to counteract the pulse load.
The pulse current shape is stable compared to before due to the
stabilized PCC voltage with the proposed algorithm. The transient from the pulse load is recovered in a short period of time.

Conclusion

This article examined the high-capacity onboard BESS design
and operation that enhances fuel efficiency, reliability, and
quality of power in naval IPSs. Despite all of the advantages of
IPSs, fuel consumption optimization remains a challenge for
naval ships because of the conflict between system reliability
and fuel efficiency. Onboard BESSs can be a practical solution,
but it is hard to find onboard BESS introductions to commercial and naval ships. This article proposed a methodology for
the design and operation of an onboard BESS as well as a BESS
capacity decision procedure based on operating the profile
and SFC of engine generators. A recently constructed naval
ship serves as an example that prioritizes the electric power
supply reliability. The actual BESS capacity depends on the
installation conditions (i.e., the weight of the system and the
investment costs) as well as the annual fuel savings. The BESS
circuit configuration that interfaces it to the dc-link of the AFE
converter and propulsion inverter without additional dc/dc
converters was suggested. The proposed structure has many
excellent features when taking the special characteristics of
naval ships into consideration. Moreover, many of the problems that arise from the deviation in the frequency and

voltage of the naval IPS can be actively compensated with the
help of the AFE converter and the BESS. The performance
against the grid abnormality, such as generator trip and pulse
load, was simulated through a real-time, small-scale PHILS.

Acknowledgment
This work was supported by the Power Generation and Electricity Delivery Core Technology Program of the Korea Institute of Energy Technology Evaluation and Planning (KETEP),
granted financial resource from the Ministry of Trade, Industry and Energy, Republic of Korea (No. 20141010502280).

For Further Reading
S. Y. Kim and S. K. Sul, "Integrated power system of high
speed destroyer for increased fuel-efficiency and powerreliability," in Proc. 2012 ASNE Electric Machines Technology
Symp. (EMTS), 23-24 May 2012, pp. 265-273.
S. Y. Kim, B. G. Cho, and S. K. Sul, "Feasibility study of
integrated power system with battery energy storage system for naval ships," in Proc. 2012 IEEE Vehicle Power and
Propulsion Conf. (VPPC), 9-12 Oct, pp. 532-537.
S. Y. Kim, B. G. Cho, and S. K. Sul, "Consideration of
active-front-end rectifier for electric propulsion navy
ship," in Proc. 2013 IEEE Energy Conversion Congress and
Exposition (ECCE), 15-19 Sept. 2013, pp. 13-19.
S. Y. Kim, S. Choe, S. Ko, S. Kim, and S. K. Sul, "Electric propulsion naval ship with energy storage modules through
AFE converters," J. Power Electron., vol. 14, no. 2, pp. 402-412,
Mar. 2014.
S. Y. Kim, "Design of shipboard energy storage system
and operation for voltage/frequency compensation in
naval integrated power system," Ph.D. thesis, Seoul
National Univ., 2014 (in Korean).
S. Choe, S. Ko, S.-Y. Kim, and S.-K. Sul, "Small scaled
power hardware-in-the loop and control method of ship
integrated power system with active front end converter
and battery energy storage system using low cost multicore DSP," in Proc. 2014 16th European Conf. Power Electronics
and Applications (EPE'14-ECCE Europe), pp. 1211-1220.

Biographies
So-Yeon Kim (ksy4rang@gmail.com) is an assistant professor in the Department of Electrical Engineering, Republic
of Korea Naval Academy.
Sehwa Choe (sehwa@eepel.snu.ac.kr) is a Ph.D. student
in the Department of Electrical and Computer Engineering, Seoul National University, Republic of Korea.
Sanggi Ko (sang-gi.ko@samsung.com) is an assistant
research engineer in the Central Research Institute of
Samsung Heavy Industries, Republic of Korea.
Seung-Ki Sul (sulsk@plaza.snu.ac.kr) is a professor in
the Department of Electrical and Computer Engineering,
Seoul National University, Republic of Korea. He is a Fellow
of the IEEE.

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