• 전기학회논문지
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• 제66권2호
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• pp.357-362
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• 2017

Among the lithium metal oxides for asymmetric hybrid supercapacitor, $Li_4Ti_5O_{12}(LTO)$ is an emerging electrode material as zero-stain material in volume change during the with the charging and discharging processes. The pulverized LTO powder was observed to show the enhanced capacity from 120 mAh/g to 156 mAh/g at C-rate (10, 100 C). Hybrid supercapacitor module(48V, 416F) was fabricated using an asymmetric hybrid capacitor with a capacitance of 7500F. As a result of the measurement of C-rate characteristics, the module shows that the discharge time is drastically reduced at more than 50C, and the ESR and voltage drop characteristics are increased. The energy density and power density were reduced under high C-rate conditions. When designing asymmetric hybrid supercapacitor module, the C-rate and ESR should be considered As a result of measuring the 5 kw UPS, it was discharged at the current of 116A~170A during the discharge in the voltage range of 48V~30V, and the compensation time at discharge was measured to be about 33.2s. Experimental results show that it can be applied to applications related to stabilization of power quality by applying hybrid supercapacitor module.

• Journal of Electrical Engineering and Technology
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• 제13권1호
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• pp.413-417
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• 2018

The $Li_4Ti_5O_{12}$ of anode material for the hybrid capacitor was coated using $CePO_4$, $M_3(PO_4)_2$ (M=Mg, Zn). The capacitance of phosphate coated $Li_4Ti_5O_{12}$ was found to be lower than that of $Li_4Ti_5O_{12}$, whereas the equivalent series resistance was higher than that of $Li_4Ti_5O_{12}$. With an increase in cycle number, the base of cylindrical cell exhibited swelling due to gas generated from the reaction between $Li_4Ti_5O_{12}$ and electrolyte. The swelling cycle number of phosphate coated $Li_4Ti_5O_{12}$ was higher than that of $Li_4Ti_5O_{12}$ due to improvement in electrochemical stability. Based on the results, it is proposed that phosphate coating can be employed as a barrier layer to control the gassing reaction by isolating the $Li_4Ti_5O_{12}$ particle from electrolyte solution.

• Journal of Electrochemical Science and Technology
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• 제4권1호
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• pp.19-26
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• 2013

Graphene/Ni-Al layered double hydroxide (LDH) hybrid materials were synthesized by a hydrothermal reaction. Hexagonal Ni-Al LDH particles nucleated and grew on graphene sheets, thus preventing restacking of the graphene sheets and aggregation of the Ni-Al LDH nanoparticles upon drying. Electrode made from the graphene/Ni-Al LDH hybrid materials showed a substantial improvement in electrochemical capacitance relative to those made with pure Ni-Al LDH nanoparticles. In addition, the graphene/Ni-Al LDH hybrid composite materials showed remarkable stability after 4000 cycles with over 100% capacitance retention. These materials are thus very promising for use in electrochemical capacitor electrodes.

• 한국정보통신학회논문지
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• 제20권9호
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• pp.1763-1770
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• 2016

본 논문에서는 넓은 출력 부하 전력에서도 동작하는 하이브리드 변환기를 제안했다. 스위치드 커패시터 변환기는 높은 부하 전력에서 효율이 낮고, 낮은 부하 전력에서는 효율이 높다. 반대로, 벅 변환기는 높은 부하 전력에서는 효율이 높고, 낮은 부하 전력에서는 효율이 낮다. 제안된 하이브리드 변환기는 스위치드 커패시터 변환기와 벅 변환기를 혼합했다. 낮은 부하 전력에서는 스위치드 커패시터 변환기를 동작시키고, 높은 부하에서는 벅 변환기를 동작시켜, 넓은 출력 부하 전력에서 전력 효율을 향상시켰다. 제안된 하이브리드 변환기는 $0.18{\mu}m$ CMOS 공정으로 구현되었다. 하이브리드 변환기의 출력 부하 전력 범위는 0.05~100mW 이며, 벅 변환기와 스위치드 커패시터 변환기에서 각각 93%와 77%의 최대 전력 효율을 가진다.

• Korean Chemical Engineering Research
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• 제51권3호
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• pp.308-312
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• 2013

NaOH 화학적 활성화법을 사용하여 야자각 차로부터 고 비표면적과 미세기공이 발달된 활성탄을 제조하였다. 활성탄제조 공정은 탄화과정에서 활성화 약품과 야자각 차의 비율과 불활성 기체 유량과 같은 실험변수들을 분석함으로서 수행되었다. 이와 같은 NaOH 화학적 활성화에 의한 2,481 $m^2/g$의 고 비표면적과 2.32 nm의 평균 기공크기를 갖는 활성탄이 얻어졌다. 양극으로 $LiMn_2O_4$, $LiCoO_2$와 음극으로 제조된 활성탄을 사용하여 하이브리드 커패시터의 전기화학적 성능을 조사하였다. $LiPF_6$, $TEABF_4$의 유기 전해질을 사용한 하이브리드 커패시터의 전기화학적 거동은 정전류 충방전, 순환 전류 전압법, 사이클과 누설전류 테스트에 의해 특성화 되었다. $LiMn_2O_4$/AC 전극을 사용한 하이브리드 커패시터가 다른 하이브리드 시스템 보다 더 좋은 충방전 성능을 보였으며, 출력밀도 1,448 W/kg와 131 Wh/kg의 고 에너지 밀도를 전달할 수 있다.

• Journal of Electrical Engineering and Technology
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• 제6권6호
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• pp.786-792
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• 2011

The present paper presents an optimal capacitor placement (OCP) algorithm for voltagestability enhancement. The OCP issue is represented using a mixed-integer problem and a highly nonlinear problem. The hybrid particle swarm optimization (HPSO) algorithm is proposed to solve the OCP problem. The HPSO algorithm combines the optimal power flow (OPF) with the primal-dual interior-point method (PDIPM) and ordinary PSO. It takes advantage of the global search ability of PSO and the very fast simulation running time of the OPF algorithm with PDIPM. In addition, OPF gives intelligence to PSO through the information provided by the dual variable of the OPF. Numerical results illustrate that the HPSO algorithm can improve the accuracy and reduce the simulation running time. Test results evaluated with the three-bus, New England 39-bus, and Korea Electric Power Corporation systems show the applicability of the proposed algorithm.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2018년도 전력전자학술대회
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• pp.105-107
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• 2018

This paper presents a new hybrid multilevel converter topology, which consists of a combination of the series connected switched capacitor units with boost ability, and an H-bridge with T-type bidirectional switches. The proposed converter boosts the input voltage without any bulky inductors, and has the small number of components, which can make the size and cost of a power converter greatly reduced. The output filter size and harmonics are also reduced by the high quality multilevel output. In addition, there is no need for complicated methods to balance the capacitor voltage. Simulation and experimental results with a nine-level converter system are presented to validate the proposed topology and modulation method.

• 전기화학회지
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• 제6권2호
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• pp.153-157
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• 2003

전기이중층 축전용량(electric double layer capacitance)과 유사축전용량(pseudo-capacitance)을 함께 갖는 하이브리드 전기화학 축전기에 대한 연구를 수행하였다. 양극은 $Ni(OH)_2$ 활성탄소가 복합된 전극을 사용하였으며 음극은 활성탄소를 활물질로 사용하므로써 비대칭 전극 구조를 갖는다. 셀 실험을 위하여 $5\times5cm^2$ 크기인 전극을 제작 사용하였다. Cyclic voltammetry측정 및 교류 임피던스 측정실험을 통하여 각각의 셀들이 갖는 전기화학적 거동을 조사하였고 충 방전 실험을 통하여 양극과 음극의 최적 질량비를 조사하였다.

• Journal of Power Electronics
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• 제17권1호
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• pp.96-105
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• 2017

In this paper, a hybrid modular multilevel converter (MMC) topology with an improved nearest level modulation method is proposed for medium-voltage high-power applications. The arm of the proposed topology contains N series connected half-bridge submodules (HBSMs), one full-bridge submodule (FBSM) and an inductor. By exploiting the FBSM, half-level voltages are obtained in the arm voltages. Therefore, an output voltage with a 2N+1 level number can be generated. Moreover, the total level number of the inserted submodules (SMs) is a constant. Thus, there is no pulse voltage across the arm inductors, and the SM capacitor voltage is rated. With the proposed voltage balancing method, the capacitor voltage of the HBSM is twice the voltage of the FBSM, and each IGBT of the FBSM has a relatively low switching frequency and an equalized conduction loss. The capacitor voltage balancing methods of the two kinds of SMs are implemented independently. As a result, the switching frequency of the HBSM is not increased compared to the conventional MMC. In addition, according to a theoretical calculation of the total harmonic distortion of the electromotive force (EMF), the voltage quality with the presented method can be significantly enhanced when the SM number is relatively small. Simulation and experimental results obtained with a MMC-based inverter verify the validity of the developed method.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 하계학술대회 논문집
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• pp.18-18
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• 2009

본 논문은 X8R 온도 특성을 가지는 유전체 원료를 이용하여 고용량이면서 고압화가 가능한 적층 칩 캐패시터를 제작하였다. 대형 고압용 적층 칩 캐패시터를 위한 내부 전극 설계 및 외부 전극 형성 방법에 대한 연구도 함께 진행하였다. 적층 칩 캐패시터를 하이브리드 자동차 및 산업용 인버터의 DC-Link으로 사용하기 적합한 모듈을 제작하였으며 모듈 설계시 고유전율의 에폭시-세라믹 필름을 하였다. 본 모듈을 평가한 결과 기존 캐패시터 모듈에 비하여 2/3 크기의 소형화를 얻을 수 있었으며 ripple 전류 및 발열 특성이 매우 우수함을 확인하였다.