• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 제39회 하계학술대회
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• pp.1146-1147
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• 2008

PV Power Conditioning System (PCS) must have high conversion and low cost. Generally, PV PCS uses either a single converter or multilevel module integrated converter (MIC). Each of these approaches has both advantage and disadvantage. For a high conversion efficiency and low cost of PV module, this paper proposes series connection of module integrated DC-DC converter's output with PV panel. Output voltage of PV panel is connected to the output capacitor of flyback converter. Thus, converter's output voltage is added to the output voltage of PV panel. Isolated DC-DC converter generates only the difference voltage between the PV panel voltage and the required total output voltage. This method reduces power level of DC-DC converter and enhances the energy conversion efficiency compared with conventional DC-DC converter.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제54권12호
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• pp.616-621
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• 2005

We considered of the buck and half bridge series DC-DC converter. It has good applications in areas with low voltage/high current, wide input voltage. The buck converter ratings and the half bridge converter ratings are $36\~72V$ input and 22V/5A output, $19\~24V$ input and 3.3V/30A output, respectively. Developed the buck and half Bridge series DC-DC converter ratings are of $36\~72V$ input and 3.3V/30A output. The buck converter is operated with zero voltage switching process to reduce the switching losses. The $80.1\%\~97.6\%$ of the efficiency is measured at $18.4{\mu}H$ output filter inductance of buck converter. In the half bridge converter, the $86\%\~96.4\%$ efficiency is measured at 150kHz switching frequency with PQI core. In the case of synchronized the buck and half bridge DC-DC converter, the measured efficiency is higher than that of the unsynchronized converter. In the synchronized converter, the maximum efficiency is measured up to $92.3\%$ with PQI core at 150kHz. 7A output.

• 대한전자공학회논문지SD
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• 제45권6호
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• pp.1-9
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• 2008

본 논문에서는 temperature/voltage에 둔감한 triple-mode CMOS DC-DC Converter를 제안한다. 제안된 triple-mode DC-DC converter는 단일 배터리의 수명에 따른 전압변화(3.3-5.5V)로부터 일정 또는 다양한 출력전압(0.6-2.2V)을 생성한다. 제안된 triple-mode CMOS DC-DC converter는 Pulse Width Modulator(PWM) 모드, Pulse Frequency Modulator(PPM) 모드, 그리고 Low Drop-Out(LDO) 모드, 이렇게 세 가지 모드로 동작한다. 또한, 제안된 회로는 temperature/voltage 변화에 의한 칩의 오동작을 방지하기 위해 temperature/voltage 변화에 둔감한 저 전력 1MHz CMOS ring oscillator를 사용한다. 제안된 triple-mode DC-DC converter는 단일 입력 전원소스(3.3-5.5V)에서 출력 전압(0.6-2.2V)을 생성하며, 출력 전압 ripple은 PWM mode에서 10mv, PFM mode에서 15mV, 그리고 LDO mode에서는 4mV 이하이다. 또한, 제안된 회로의 효율은 PWM mode에서 93% 이상이며, $-25-80^{\circ}C$의 온도변화에도 각 모드에서의 출력 전압 레벨의 오차는 단지 0.8% 이하로 유지한다 제안된 회로의 검증을 위해 CMOS $0.35{\mu}m$ 공정을 이용한 시뮬레이션 및 칩 테스트를 수행하였다.

• 한국전기전자재료학회논문지
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• 제14권6호
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• pp.487-490
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• 2001

Residual DC voltage of the in-plane switching (IPS)-liquid crystal display(LCD) by voltage-transmittance (V-T) hysteresis method was studied. Several IPS-LCD which have different concentrations of cynao LCs and different resistivities of fluorine LCs were fabricated. We found that the residual DC voltage of the IPS-LCD was decreasing with increasing concentration of cyano LCs and increasing with decreasing specific resistivity of fluorine LC materials. The residual DC voltage property can be improved by low molecular weight and high polarity of cyano LC.

• 한국군사과학기술학회지
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• 제13권4호
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• pp.586-593
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• 2010

In this paper, I have proposed that the 1st and 2nd AC-DC transformation methods using multi-level pulsating currents and selection switches. Through making the rectified voltage of the proposed AC-DC translation which is similar to reference voltage by selecting from multi-level pulsating currents, the proposed translation has dramatically reduced the ripple voltage. I have compared the performance of the DC voltage, the ripple voltage and the peak to peak voltage of the proposed method with the conventional method. The simulation results show that the proposed 2nd method has the better performance than the 1st method in the point of average DC voltage drop and peak to peak voltage increase.

• 전력전자학회논문지
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• 제25권3호
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• pp.157-161
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• 2020

High voltage gain converters are essential for distributed power generation systems with renewable energy sources, such as fuel cells and solar cells, because of their low voltage characteristics. This paper introduces a novel nonisolated DC-DC converter topology developed by combining an inverting buck-boost converter and voltage multipliers. In the proposed converter, the input voltage is connected in series with the output, and the majority of the input power is directly delivered to the load. The voltage multipliers are stacked in series to achieve high step-up voltage gain. The voltage stress across all of the switches and capacitors can be significantly reduced. As a result, the switches with low voltage ratings can be used to achieve high efficiency and low cost. To verify the validity of the proposed topology, a 360-W prototype converter is built to obtain the experimental results.

• 전기학회논문지
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• 제63권5호
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• pp.713-718
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• 2014

DC urban railway power system consists of DC power network and AC power network. The DC power network supplies electric power to railway vehicles and the AC power network supplies electric power to station electric equipment. Recently, because of power consumption reduction and peak load shaving, intelligent measurement of regenerative energy and renewable energy adapted on DC urban railway is required. For this reason, DC smart metering system for DC power network shall be developed. Therefore, in this paper, DC voltage sensor, current sensor, and DC smart meter were developed and evaluated by performance test. DC voltage sensor was developed for measuring standard voltage range of DC urban railway, and DC current sensor was developed as hall effect split core type in order to install in existing system. DC smart meter possesses function of general intelligent electric power meter, such as measuring electricity and wireless communication etc. And, DC voltage sensor showed average 0.17% of measuring error for 2,000V/50mA, and current sensor showed average 0.21% of measuring error for ${\pm}2,000V/{\pm}4V$ in performance test. Also DC smart meter showed maximum 0.92% of measuring error for output of voltage sensor and current sensor. In similar environment for real DC power network, measuring error rate was under 0.5%. In conclusion, accuracy of DC smart metering system was confirmed by performance test, and more detailed performance will be verified by further real operation DC urban railway line test.

• 전력전자학회논문지
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• 제25권2호
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• pp.73-78
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• 2020

In this study, a novel reactive power control scheme is proposed to supply stable reactive power to the distribution line by compensating a ripple voltage of DC link. In a single-phase system, a magnitude of second harmonic is inevitably generated in the DC link voltage, and this phenomenon is further increased when the capacity of DC link capacitor decreases. Reactive power control was performed by controlling the d-axis current in the virtual synchronous reference frame, and the voltage control for maintaining the DC link voltage was implemented through the q-axis current control. The proposed method for compensating the ripple voltage was classified into three parts, which consist of the extraction unit of DC link voltage, high pass filter (HPF), and time delay unit. HPF removes an offset component of DC link voltage extracted from integral, and a time delay unit compensates the phase leading effect due to the HPF. The compensated DC voltage is used as feedback component of voltage control loop to supply stable reactive power. The performance of the proposed algorithm was verified through simulation and experiments. At DC link capacitance of 375 uF, the magnitude of ripple voltage decreased to 8 Vpp from 74 Vpp in the voltage control loop, and the total harmonic distortion of the current was improved.

• 전기학회논문지
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• 제64권5호
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• pp.680-688
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• 2015

Hybrid type combined transmission systems is being operated by AC and DC line at the same space will be expanded instead of the overhead line. However, such hybrid type combined system has problem like the arrangement selection of DC cable for effective system operation. In this paper, to select the proper arrangement of DC cable, induced voltage of DC cable influenced by AC cable was analyzed in case of several type arrangement of DC cable. Such induced voltage is in detailed analyzed not only in case of steady, but transient state. The arrangement which has the lowest induced voltage is selected as the proper one. EMTP/ATPDraw is used for modeling and analysis of hybrid type combined transmission system.

• 전기전자학회논문지
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• 제23권3호
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• pp.1054-1060
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• 2019

A extension of the high boost voltage-lift DC-DC converter with large conversion ratio has been proposed in this paper. The proposed extension is combined the switched-inductor cell (SL-cell) and modular voltage cell (MV-cell). The proposed structure can achieve the large voltage conversion without high duty-cycle and the low voltage of the components. Moreover, the PID controller for novel SL-MV voltage-lift DC-DC converter also introduces. This technique a good-performance output voltage can kept constant with an good transient performance when the output load is suddenly changed. In order to prove the theoretical analysis, the experimental setup has been built for the DC load of $150[{\Omega}]$ and $300[{\Omega}]$. In addition, the transient of output voltage has been tested to determine the controller. Experimental results validate the effectiveness of the theoretical analysis proving the satisfactory converter performance.