• Journal of Electrical Engineering and Technology
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• 제12권3호
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• pp.1187-1194
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• 2017

In this paper, a high step-up DC-DC PWM converter with continuous input current and low voltage stress is presented for renewable energy application. The proposed converter is composed of a boost converter integrated with an auxiliary step-up circuit. The auxiliary circuit uses an additional coupled inductor and a balancing capacitor with voltage doubler and switching capacitor technique to achieve high step-up voltage gain with an appropriate switch duty cycle. The switched capacitors are charged in parallel and discharged in series by the coupled inductor, stacking on the output capacitor. In the proposed converter, the voltage stress on the main switch is clamped, so a low voltage switch with low ON resistance can be used to reduce the conduction loss which results in the efficiency improvement. A detailed discussion on the operating principle and steady-state analyses are presented in the paper. To justify the theoretical analysis, experimental results of a 200W 40/400V prototype is presented. In addition, the conducted electromagnetic emissions are measured which shows a good EMC performance.

• 한국산업융합학회 논문집
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• 제20권2호
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• pp.115-124
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• 2017

This paper aims to develop an SMPS topology for handling a high range of input voltages based on a DC-DC flyback converter circuit. For this purpose, 2 capacitors of the same specifications were serially connected on the input terminal side, with a flyback converter of the same circuit configuration serially connected to each of them, so as to achieve high input voltage and an effect of dividing input voltage. The serially connected flyback converters have the transformer turn ratio of 1:1, so that each coil is used for the winding of a single transformer, which is a characteristic of doubly-fed configuration and enables the correction of input capacitor voltage imbalance. In addition, a pulse transformer was designed and fabricated in a way that can achieve the isolation and noise robustness of the PWM output signal of the PWM controller that applies gate voltage to individual flyback converter switches. PSIM simulation was carried out to verify such a structure and confirm its feasibility, and a 100W class stack was fabricated and used to verify the feasibility of the proposed high voltage SMPS topology.

• Journal of Power Electronics
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• 제19권4호
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• pp.858-868
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• 2019

With the widespread use of modern clean energy, lithium-ion batteries have become essential as a more reliable energy storage component in the energy Internet. However, due to the difference in monomers, some of the battery over-charge or over-discharge in battery packs restrict their use. Therefore, a novel multiphase interleaved converter for reducing the inconsistencies of the individual cells in a battery pack is proposed in this paper. Based on the multiphase converter branches connected to each lithium battery, this circuit realizes energy transferred from any cell(s) to any other cell(s) complementarily. This flexible interlaced converter is composed of an improved bi-directional Buck-Boost circuit that is presented with its own available control method. A simulation model based on the PNGV model of fundamental equalization is built with four cells in PSIM. Simulation and experimental results demonstrate that converter and its control achieve simple and fast equalization. Furthermore, a comparison of traditional methods and the HNFABC equalization is provided to show the performance of the converter and the control of lithium-based battery stacks.

• 한국산업융합학회 논문집
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• 제26권6_2호
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• pp.1117-1125
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• 2023

The DC part of the DC microgrid power conversion system uses capacitors for buffers of charge and discharge energy for smoothing voltage and plays important roles such as high frequency component absorption, power balancing, and voltage ripple reduction. The capacitor uses an aluminum electrolytic capacitor, which has advantages of capacity, low price, and relatively fast charging/discharging characteristics. Aluminum electrolytic capacitors(AEC) have previous advantages, but over time, the capacity of the capacitors decreases due to deterioration and an increase in internal temperature, resulting in a decrease in use efficiency or an accident such as steam extraction due to electrolyte evaporation. It is necessary to take measures to prevent accidents because the failure diagnosis and detection of such capacitors are a very important part of the long-term operation, safety of use, and reliability of the power conversion system because the failure of the capacitor leads to not only a single problem but also a short circuit accident of the power conversion system.

• 전력전자학회논문지
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• 제26권2호
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• pp.82-89
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• 2021

This study proposes a DAB two-stage series structure with insulated bidirectional DC-DC converter for two-way power transfer between the renewable energy of high voltages (1 kV and above). The proposed circuit transforms the existing DAB converter into a two-stage series structure to reduce the pressure in the switch. The problem of power imbalance occurring in the design of the DAB converter second-stage series is improved by applying the cell balancing method circuit and the common mode coupled inductor using an external flying capacitor instead of reflecting the existing improvement measures, voltage balance control, and inductor current control. In addition, a no-load supercharging sequence is proposed in high voltages and high-speed switching by using the fixed duty output method. This study presents the analysis results through the structure of the proposed circuit, the principle of improving the power imbalance problem, and simulations. Prototypes were manufactured to meet the specifications of input/output voltage of 1700 V, maximum load of 65 kW, and switching frequency of 51kHz, and the validity of the topology was verified using the experimental results and efficiency data.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2016년도 전력전자학술대회 논문집
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• pp.305-306
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• 2016

본 논문은 선택적 전압 균일화 기법을 이용하여 직렬 연결된 리튬 이온 배터리의 빠른 전압 균일화를 위한 새로운 능동형 셀 밸런싱 회로를 제안하였다. 제안한 회로는 다권선 변압기를 사용한 전하 균일화 회로에 인덕터 1개, MOSFET 스위치 1개를 추가한 회로 구성을 가지며, 기존의 빠른 밸런싱을 위한 회로 대비 수 배 적은 소자로 구성이 가능하다. 추가된 인덕터는 직렬 연결된 배터리 전압을 통해 빠르게 저장된 에너지를, 낮은 전압의 배터리로 높은 밸런싱 전류를 전달함으로써 배터리 셀 간의 빠른 전압 밸런싱을 구현하였다. 제안한 회로의 밸런싱 속도에 대한 검증을 위해서, PSIM Simulation을 통해 기존 회로와 비교 검증 하였다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2011년도 전력전자학술대회
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• pp.222-223
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• 2011

최근 저전력 소모와 얇은 두께, 무 수은, 다양한 색 표현력, 빠른 응답 속도 등의 다양한 장점을 가진 LED(Light Emitting Diode)를 광원으로 이용하는 LCD(Liquid Crystal Display) TV가 큰 주목을 받고 있다. 이러한 LCD TV의 화면을 균등한 휘도로 표현하기 위해 기존의 구동회로는 다 채널의 LED를 정전류로 제어하는 DC/DC 컨버터가 채널마다 각각 적용되었고, 이는 원가 상승 및 효율 저하의 원인이 되었다. 이를 해결하기 위하여 본 논문에서는 각 LED 채널에 적용되는 DC/DC 컨버터 없이 트랜스포머, 커패시터, 다이오드를 이용하여 모든 LED 채널의 정전류 제어가 가능한 저가격형 구동회로를 제안한다. 이는 전력변환 효율과 전력밀도를 획기적으로 개선할 수 있고 수동소자만을 사용하므로 높은 신뢰성을 확보할 수 있다. 본 논문에서는 제안된 회로에 대한 이론적 해석과 실험을 통해 제안 회로의 타당성을 검증한다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2011년도 전력전자학술대회
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• pp.89-90
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• 2011

본 논문에서는 스마트그리드 시스템의 안정적인 운전을 위한 핵심적인 요소인 고압의 에너지저장장치를 충방전 할 수 있는 BESS 시스템을 제안한다. 제안한 BESS 시스템용 전력변환장치는 배터리 밸런싱 회로를 적용하여 저압의 배터리 모듈을 직렬로 구성하여 양방향 DC/DC 컨버터 없이 양방향 DC/AC 인버터만으로 BESS 시스템을 구성할 수 있다. 제안한 BESS 시스템의 충방전 시 특성을 살펴보고 50kW급 BESS 시스템을 통해 유용성을 확인한다.

• 산업공학
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• 제10권1호
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• pp.155-167
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• 1997

The purpose of this study is to develop the program for efficient operation of a multi-functional surface mounting device(SMD) which mount various components on a printed circuit board(PCB). These components are provided by diverse types of feeders such as cassette, stick and tray feeders. The SMD has one or two heads. In the SMD, the positions of PCB and feeders and fixed, and the head moves to pick up a component from a feeder and to mount it on the PCB. The number of lanes occupied by each feeder and the nozzle used for each component can be different. We develop an off-line program to minimize the cycle-time of the SMD by studying the optimal assignment of feeders and the optimal mounting sequence of components. Graphical User Interface(GUI) is also developed. Additionally, we consider the line balancing problem which appears when two SMDs are used sequentially.

• 조명전기설비학회논문지
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• 제26권9호
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• pp.8-17
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• 2012

This paper proposes high performance control of light emitting diode(LED) drive system for liquid crystal display(LCD) backlight. The CCFL(cold cathode fluorescent lamp)was used to a conventional LCD backlight. Due to improvement on luminous efficiency, long life and wide color gamut, LED has gradually substituted for CCFL as backlight. The backlight using LED is necessary to use many LED. For that reason, the LED backlight is using a lot of LED driving circuits. The many LED driving circuit is generated a current deviation between LED. Eventually, it is caused brightness deviation between LED. Therefore, this paper improves the current deviation using transformer and balancing capacitor to solve this problem. Also, for accurate and uniform brightness control, this paper is applied the artificial intelligent control to a dimming control. This paper is compared with conventional system, and validity of this paper proves through that result.