• Journal of Electrochemical Science and Technology
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• v.14 no.1
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• pp.31-37
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• 2023

Owing to the rapid climate change, a high-performance energy storage system (ESS) for efficient energy consumption has been receiving considerable attention. ESS, such as capacitors, usually has issues with the ion diffusion of electrode materials, resulting in a decrease in their capacitance. Notably, appropriate pore diameter and large specific surface area (SSA) may result in an effective ion diffusion. Therefore, graphene and multi-walled carbon nanotube (graphene@MWCNT) hybrid nanomaterials, with covalent bonds between the graphene and MWCNT, were prepared via an edge-chemistry reaction. The properties of these materials, such as high porosity, large SSA, and high electroconductivity, make them suitable to be used as electrode materials for capacitors. The optimal ratio of graphene to MWCNT can affect the electrochemical performance of the electrode material based on its physical and electrochemical properties. The supercapacitor using optimal graphene-based hybrid electrode material exhibited highest specific capacitance value as 158 F/g and excellent cycle stability.

• Journal of the Korean Electrochemical Society
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• v.13 no.2
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• pp.103-109
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• 2010

$Li_4Mn_5O_{12}$ was synthesized by combustion method using $LiNO_3$, $Li(CH_3COO){\cdot}2H_2O$ and $Mn(CH_3COO)_2{\cdot}4H_2O$. $Li_4Mn_5O_{12}$ was obtained over $400^{\circ}C$, however, the sample calcined at $400^{\circ}C$ for any time was mixed phases of $Li_4Mn_5O_{12}$ and $Mn_2O_3$. $Li_4Mn_5O_{12}$ calcined at $400^{\circ}C$ for 5 h had larger first discharge capacity (41.5mAh/g) at 1C-rate for 3.7~4.4V than other calcined samples. Moreover, applying to hybrid capacitor, it had good discharge capacity (24.74 mAh/g or 10.46 mAh/cc) at 100 mA/g for 1~2.5 V and higher energy density (39Wh/kg or 16.49Wh/cc) at same condition.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.12
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• pp.1537-1542
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• 2011

This paper presents the power management strategies for a compound hybrid excavator. The compound hybrid excavator has been replaced the hydraulic swing motor to the electric swing motor. This excavator requires a proper control algorithm to regulate the energy flow between the mechanical coupling and the electric devices. The controller should improve fuel economy and maintain the super capacitor voltage within a proper range. A thermostat controller and ECMS controller are designed such that these objectives can be achieved. The thermostat controller regulates the power of the engine-assist motor on the basis of the super capacitor voltage, and the ECMS controller determines it using the real-time fuel minimization strategy based on the concept of equivalent fuel. Simulation results showed that by using the hybrid excavator, the fuel economy becomes about 20% higher than that obtained using the conventional excavator and that the ECMS controller outperforms the thermostat controller.

• 한국전기화학회:학술대회논문집
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• 2005.04a
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• pp.16-16
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• 2005

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.266-266
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• 2009

For the development of hybrid supercapacitor, increasing energy density is one of the most crucial matters. Since the energy density is the function of capacitance and voltage, it is necessary to enhance energy density for increasing capacitance or voltage. For the high working voltage, it was to enforce Li ion free-doping to activated carbon. As a result, initial capacitance has increased by 11% than raw cell. But capacitance has decreased by Li ion re-solution to electrolyte for increase the number of cycle.

• Journal of Electrical Engineering and Technology
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• v.11 no.2
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• pp.353-360
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• 2016

Series hybrid electric vehicles (SHEVs) having multiple power sources such as an engine- generator (EnGen), a battery, and an ultra-capacitor require a power control unit with high power density and reliable control operation. However, manufacturing using separate individual power converters has the disadvantage of low power density and requires a large number of power and signal cable wires. It is also difficult to implement the optimal power distribution and fault management algorithm because of the communication delay between the units. In order to address these concerns, this approach presents a design methodology and a power control algorithm of an integrated power converter for the SHEVs powered by multiple power sources. In this work, the design methodology of the integrated power control unit (IPCU) is firstly elaborately described, and then efficient and reliable power distribution algorithms are proposed. The design works are verified with product-level and vehicle-level performance experiments on a 10-ton SHEV.

• Proceedings of the KIPE Conference
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• 2004.07a
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• pp.346-349
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• 2004

The design of DC-DC converters for power electronic interfaces in power management systems for Hybrid Electric Vehicle (HEV) is a very challenging task. In this paper, the considered topology is the hi-directional buck-boost converter and inverter system. If we make the converter side DC link current the same as the inverter side DC link current in a converter-inverter system, no current will flow through the BC link capacitor and as a result, no DC link voltage variation occurs. This leads to the possibility of reducing small th size of DC link capacitors which are expensive, bulky. Therefore we propose the converter current controller which can manage to match inverter and converter current at the DC link.

• Proceedings of the KIPE Conference
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• 2008.06a
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• pp.7-11
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• 2008

This paper describes design procedure and control strategy of HDC(High side DC/DC Converter) and MCU(Motor Control Unit) for diesel hybrid electric vehicle. In designing HDC and MCU for HEV high power density and reliability is strongly needed to meet the demand of automotive industry. In order to achieve the high performance of a controller, MPC5554 based control board is developed. An optimized film capacitor and inductor are also developed for high efficiency driving. Skim 63 IGBT module of SEMIKRON for automotive is used for power switching device. The most efficient cooling model for optimal size and reliability were verified by simulation. These procedures are verified by bench or driving test and the results are present in this paper.

• Proceedings of the KIEE Conference
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• 2002.07c
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• pp.1919-1921
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• 2002

In this paper, we were designed the ferroelectric phase shifter using 3-dB, $90^{\circ}$ branch-line hybrid coupler with two ports terminated in symmetric phase-controllable reflective networks. The design of phase shifter is based on reflection theory of terminating circuits. In order to find the optimum conditions of reflect phase, the effect of a change of capacitance and transmission line connected with two coupled ports of a coupler have been investigated. To obtain more accurate design parameters, finite element method is applied. We were showed large phase variation with small capacitance variation in the parallel connection of capacitor and transmission line by using EM-simulation and circuit-simulation.

• Proceedings of the KIPE Conference
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• 2018.07a
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• pp.374-375
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• 2018

신재생에너지의 보급 확산과 전력수요의 증가에 따라 전력계통이 분산화되는 추세이며 이에 따라 배전계통의 안정화를 위한 전력계통 안정화 장치(Power System Stabilizer)로 그 사용이 확대되고 있는 추세이다. 따라서 대표적인 전력계통 안정화 장치인 정지형 무효전력보상장치(SVC: Staic Var Compensator)에 대한 다양한 토폴로지로 개발되고 있다. 또한 기술의 트랜드는 SVC에서 Statcom 기술 개발로 이어지고 있다. 최근 Statcom의 변환손실 및 경제적 단점을 극복하기 위해 Statcom과 SVC를 병렬로 사용하는 Hybrid 방식에 대한 연구가 활발히 진행되고 있다. 본 논문에서는 SVC 기능에서 TCC(Thyristor Controlled Capacitor)방식에서 문제가 되는 돌입전류 제한을 위한 새로운 Soft-Step Switching 방식을 제안한다. 또한 Statcom의 용량을 줄이기 위해 SVC용 무효전력 보상 리액터 및 콘덴서 군을 설계하였다.