• The Journal of the Convergence on Culture Technology
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• v.5 no.2
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• pp.367-373
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• 2019

As the number of Battery Electric Vehicle (BEV) is increasing dramatically Vehicle-to-Grid (V2G) te chnology also has been spotlight from industry and academia recently. With help of V2G technology Battery of EV can play many important roles like as energy storage system (ESS) and electric energy resource in Smart Grid environment. This paper provides comprehensive review of Vehicle-to-Home(V2H), Vehicle-to-Building(V2B) and Vehicle-to-Grid(V2G) technologies. The economical analysis of these technologies is also discussed.

• Journal of the Korean Society of Industry Convergence
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• v.24 no.4_1
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• pp.387-395
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• 2021

Distributed resources such as renewable energy sources and ESS are connected to the low voltage direct current(LVDC) distribution network through the power conversion system(PCS). Control power is required for the operation of the PCS. In general, controller power is supplied from AC power or DC power through switch mode power supply(SMPS). However, the conventional SMPS has a low input voltage, so development and research on high input voltage self-power suitable for LVDC is insufficient. In this paper, to develop Self-Power that can be used for LVDC, the characteristics of the conventional topology are analyzed, and a series-input single-output flyback converter using a flux-sharing transformer for high voltage is designed. The high input voltage Self-Power was designed in the DCM(discontinuous current mode) to reduce the switching loss and solve the problem of current dissipation. In addition, since it operates even at low input voltage, it can be applied to many applications as well as LVDC. The validity of the proposed high input voltage self-power is verified through experiments.

• Prospectives of Industrial Chemistry
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• v.23 no.1
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• pp.3-17
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• 2020

리튬이온전지(LIB)는 기존의 다른 이차전지와 다른 확실한 몇 가지 장점이 있다. 높은 작동 전압과 높은 에너지 밀도, 긴 수명, 그리고 낮은 자체 방전 속도이다. 이러한 장점으로 모바일 제품에서부터 전기 자동차(battery electric vehicle, BEV), 최근에는 전기저장장치(energy storage system, ESS)까지 다양한 분야에서 사용되고 있다. 하지만 사용 범위가 증가함에 따라 높은 안정성을 가지며 더 큰 에너지 용량을 나타내는 리튬이온전지에 대한 요구가 점점 더 커지게 되었다. 리튬이온전지의 용량 증가는 전지의 설계보다는 양극 및 음극 재료, 분리막 및 전해질과 같은 주요 전지 재료의 기술적 진보에 달려 있다. 주요 전지 소재 중에 전지의 성능에 가장 큰 영향을 미치는 것은 전지 반응에 의한 과전압과 가격이 가장 비싼 양극이다. 본 기획 특집에서는 리튬이차전지의 성능에 가장 큰 영향을 미치는 양극 물질의 종류와 향후 연구동향에 대해서 소개하고자 한다. 양극 물질의 발전 방향, 안정성과 용량 증대를 위해서 최근 연구되고 있는 방향에 대해서 자세하게 소개한다.

• Journal of the Korean Society of Industry Convergence
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• v.26 no.6_3
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• pp.1259-1267
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• 2023

In recent years, as the demand for distributed power has increased, the need for microgrids connected to grid power and renewable power generation sources has emerged. In the case of DC microgrids, reactive power does not occur, and power conversion losses are reduced compared to AC when connecting to the load and power grid[2]. With the revitalization of the DC distribution network industry, various studies and demonstrations of DC microgrids have been carried out. In the case of the recent unit distribution, its stability and effectiveness have been verified through empirical and research analysis. However, there is a lack of empirical tests to prevent chain accidents for the protection of the power grid circuits and the misoperation of the distributed power system caused by individual accidents when connecting various distributed power sources and power grids. In this paper, the operation plan of a stable multi-circuit DC distribution connection for the demonstration site was verified through the protection cooperation and operation algorithm for the stable linkage management of the DC distribution network composed of such a multi-circuit.

• Transactions of the Korean hydrogen and new energy society
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• v.28 no.2
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• pp.156-165
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• 2017

This study quantitatively assessed the environmental impacts of fuel cell (FC) systems by performing life cycle assessment (LCA) and analyzed their energy efficiencies based on energy return on investment (EROI) and electrical energy stored on investment (ESOI). Molten carbonate fuel cell (MCFC) system and polymer electrolyte membrane fuel cell (PEMFC) system were selected as the fuel cell systems. Five different paths to produce hydrogen ($H_2$) as fuel such as natural gas steam reforming (NGSR), centralized naptha SR (NSR(C)), NSR station (NSR(S)), liquified petroleum gas SR (LPGSR), water electrolysis (WE) were each applied to the FCs. The environmental impacts and the energy efficiencies of the FCs were compared with rechargeable batteries such as $LiFePO_4$ (LFP) and Nickel-metal hydride (Ni-MH). The LCA results show that MCFC_NSR(C) and PEMFC_NSR(C) have the lowest global warming potential (GWP) with 6.23E-02 kg $CO_2$ eq./MJ electricity and 6.84E-02 kg $CO_2$ eq./MJ electricity, respectively. For the impact category of abiotic resource depletion potential (ADP), MCFC_NGSR(S) and PEMFC_NGSR(S) show the lowest impacts of 7.42E-01 g Sb eq./MJ electricity and 7.19E-01 g Sb eq./MJ electricity, respectively. And, the energy efficiencies of the FCs are higher than those of the rechargeable batteries except for the case of hydrogen produced by WE.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.10
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• pp.1390-1396
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• 2013

The paper estimated the reasonable market price of lead-acid battery energy storage system (BESS) intended for demand management of electricity customers. As time-of-use (TOU) tariffs have extended to a larger number of customers and gaps in the peak and off-peak rates have gradually risen, deployment of BESS has been highly needed. However, immature engineering techniques, lack of field experiences and high initial investment cost have been barriers to opening up ESS markets. This paper assessed electricity cost that BESS operation could save for customers and, based on the possible cost savings, estimated reasonable prices at which BESSs could become a more prospective option for demand management of customers. Battery scheduling was optimized to maximize the electricity cost savings that BESS would possibly achieve under TOU tariffs conditions. Basic economic factors such as payback period and return on investment were calculated to determine reasonable market prices. Actual load data of 12 industrial customers were used for case studies.

• International Journal of Computer Science & Network Security
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• v.22 no.3
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• pp.37-44
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• 2022

Plug-in Hybrid electric vehicles (PHEV) show great potential to reduce gas emission, improve fuel efficiency and offer more driving range flexibility. Moreover, PHEV help to preserve the eco-system, climate changes and reduce the high demand for fossil fuels. To address this; some basic components and energy resources have been used, such as batteries and proton exchange membrane (PEM) fuel cells (FCs). However, the FC remains unsatisfactory in terms of power density and response. In light of the above, an electric storage system (ESS) seems to be a promising solution to resolve this issue, especially when it comes to the transient phase. In addition to the FC, a storage system made-up of an ultra-battery UB is proposed within this paper. The association of the FC and the UB lead to the so-called Fuel Cell Battery Electric Vehicle (FCBEV). The energy consumption model of a FCBEV has been built considering the power losses of the fuel cell, electric motor, the state of charge (SOC) of the battery, and brakes. To do so, the implementing a reinforcement-learning energy management strategy (EMS) has been carried out and the fuel cell efficiency has been optimized while minimizing the hydrogen fuel consummation per 100km. Within this paper the adopted approach over numerous driving cycles of the FCBEV has shown promising results.

• Journal of Electrical Engineering and Technology
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• v.11 no.6
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• pp.1664-1673
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• 2016

Lithium rechargeable cells are used in many industrial applications, because they have high energy density and high power density. For an effective use of these lithium cells, it is essential to build a reliable battery management system (BMS). Therefore, the state of charge (SOC) estimation is one of the most important techniques used in the BMS. An appropriate modeling of the battery characteristics and an accurate algorithm to correct the modeling errors in accordance with the simplified model are required for practical SOC estimation. In order to implement these issues, this approach presents the comparative analysis of the SOC estimation performance using equivalent electrical circuit modeling (EECM) and noise suppression technique (NST) in three representative $LiCoO_2/LiFePO_4/LiNiMnCoO_2$ cells extensively applied in electric vehicles (EVs), hybrid electric vehicles (HEVs) and energy storage system (ESS) applications. Depending on the difference between some EECMs according to the number of RC-ladders and NST, the SOC estimation performances based on the extended Kalman filter (EKF) algorithm are compared. Additionally, in order to increase the accuracy of the EECM of the $LiFePO_4$ cell, a minor loop trajectory for proper OCV parameterization is applied to the SOC estimation for the comparison of the performances among the compared to SOC estimation performance.

• Journal of Korea Multimedia Society
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• v.4 no.1
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• pp.56-66
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• 2001

The spectral subtraction algorithm using a criterion based on the human perception has been recently developed. The speech processed with Virag's algorithm sounds more pleasant to a human listener than those obtained by the classical methods. However, Virag's algorithm requires a robust voice activity detector (VAD). In the ESS (extended spectral subtraction) algorithm without VAD, the residual noise becomes more noticeable as the SNR decrease. In this paper we propose a new speech enhancement method, the combination of Wiener filter and spectral subtraction based on noise masking characteristics in the human auditory system. There is no need of VAD because the noise can be successively updated even during speech activity using Wiener filter. The adjustment of the subtraction parameter based on the masking threshold makes the residual noise inaudible. The proposed method has been compared with conventional spectral subtraction algorithms. Objective and subjective evaluation of the proposed system is performed with several noise types having different time-frequency distributions. The application of objective measures, the study of the speech spectrograms, as well as subjective listening tests, confirm that the enhanced speech with proposed algorithm is more pleasant to a human listener.

• Journal of Korean Tunnelling and Underground Space Association
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• v.9 no.3
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• pp.219-228
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• 2007

Scaled model tests were performed to explore the influence of eccentric load and lateral earth pressure on tunnel behavior and their results were verified through numerical analyses. As a method for reducing the eccentric load acting on tunnel, an eccentric supporting system (ESS) was proposed and its applicability was investigated. Experimental results showed that displacement decreased overall and the load inducing initial cracks increased as the eccentric supporting system was applied. The maximum eccentric vertical load which impacted the stability of tunnel was also increased. The test results on the influence of lateral earth pressure on tunnel behavior showed that the general aspect of displacement and crack growth changed significantly depending on the coefficient of lateral earth pressure. In addition, the weak zone In view of stability varied as well.