• ETRI Journal
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• 제33권5호
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• pp.814-817
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• 2011

In this letter, the distributions of direct current (DC) coefficients for P-frames in H.264/AVC are analyzed, and the distortion model of the Gaussian source under the quantization of the dead-zone plus-uniform threshold quantization with uniform reconstruction quantizer is derived. Experimental results show that the DC coefficients of P-frames are best approximated by the Laplacian distribution and the Gaussian distribution at small quantization step sizes and at large quantization step sizes, respectively.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2008년도 추계학술대회 논문집
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• pp.202-207
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• 2008

This study provides review and improvement plans for the possible problems caused when the CV cable is used as a positive feeder line which supplies power from the DC HSCB (high-speed circuit breaker) to the catenariesin Seoul Metro which is using direct-current feeder method. In detail, this study contributes to stabilizing the power line by triggering a protective device by instantly detecting potential rise which happens when grounding fault occurs in non-grounding type CV cable shield.

• 조명전기설비학회논문지
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• 제29권1호
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• pp.121-127
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• 2015

Recently, LVDC(Low Voltage Direct Current) has been came into the newly spotlight with HVDC(High Voltage Direct Current) and as increasing digital load, DC power supply and high quality of demand is also getting extended. In accordance with the report of EPRI(Electric Power Research Institute), they expect digital load will grow to 50% of whole load in 2020. Subsequently, the use of DC equipment will grow dramatically. Therefore, the careful adoption of LVDC standardization policy is urgently required for the safety of people, prevention of confusion and occupancy of the market.

• Journal of Power Electronics
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• 제15권3호
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• pp.796-805
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• 2015

New direct and indirect current control methods for a fault-tolerant active power filter topology are presented in this paper. Since a three-phase four-switch topology has a phase bridge current which cannot be directly controlled, a hysteresis control method in the α-β plane which controls the three-phase current in the two-phase stationary coordinate system is proposed. The improved SVPWM algorithm is able to eliminate the operation of the trigonometric functions in the traditional algorithm by rotating the α-β coordinates and alternating the sequence of the output vectors, which in turn simplifies the algorithm and reduces the switching frequency. The selection of the DC-side reference voltage and DC-side capacitor equalization strategy are also discussed. Simulation and experiments demonstrate that the proposed control method is correct and feasible.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 하계학술대회 논문집 B
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• pp.1364-1366
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• 2004

When an underground pipeline runs parallel with DC-powered railways, it suffers from electrolytic corrosion caused by the stray current leaked from the railway negative returns. Perforation due to the electrolytic corrosion may bring about large-scale accidents even cathodically protected systems. Traditionally, bonding methods such as direct drainage, polarized drainage and forced drainage have been used in order to mitigate the damage on pipelines. In particular, the forced drainage method is widely adopted in Seoul. In this paper, we report the analysis of the stray current conditions in Seoul subway DC electrification system.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2007년도 춘계학술대회 논문집
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• pp.291-294
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• 2007

This paper preserts the characteristics of leakage currents flowing through 18 kV zinc oxide (ZnO) surge arrester under the mixed DC and AC voltages. The I-V curves of ZnO surge arrester were measured as a function of the voltage ratio K The I-V curves under the mixed DC and AC voltages lay between the pure DC and AC characteristics, and the cross-over phenomenon in I-V curves was observed at the low current region As a result, the increase of DC component to mixed voltages causes the increase of resistive component of total leakage current th ZnO surge arrester.

• 한국산학기술학회논문지
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• 제16권1호
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• pp.445-452
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• 2015

경두개직류전류자극(tDCS)은 낮은 직류 전류 강도를 사용하여 대뇌피질의 자발적인 신경학적 활동의 흥분성을 증가 또는 감소시키는 신경조절 기법이다. 본 연구의 목적은 tDCS를 적용한 후 다양한 감각 기능의 변화를 측정하는데 있다. tDCS의 효과를 측정하기 위해 CPT 검사를 50명의 건강한 대상자에게 단일 기간(8월4일에서 8월29일), 단일 공간, 단일 맹검법으로 무작위 배정하였다. 신경전도검사는 우세 손의 말초신경 병변을 구별하기 위해 정중 감각과 운동신경을 측정하였다. 대상자들은 각 25명 씩 대뇌피질의 DLPFC의 tDCS 자극군과 대뇌피질의 DLPFC의 tDCS 위자극군으로 2개의 다른 조건 아래서 1 mA의 전류강도로 15분씩 양극 tDCS로 적용하였다. 촉각, 빠른 통증과 느린 통증을 각각 평가하기 위해 우세한 제 2수지에 2000, 250, 그리고 5 Hz의 주파수로 CPT 검사인 Neurometer$^{(R)}$를 이용하여 수치들을 기록하였다. DLPFC의 양극 tDCS 자극군의 CPT 수치들에서는 250과 5 Hz에서 통계적으로 유의한 증가를 보였다. 양극 tDCS 위자극군의 모든 CPT 수치들은 감소하였다. 이러한 결과는 DLPFC의 양극 tDCS가 건강한 대상자들의 감각 지각과 통증 역치들을 조절할 수 있다는 것을 보여준다. 따라서 본 연구는 재활과 통증 치료 분야에서 유용한 치료 방법 중 하나로 제시할 수 있을 것으로 생각한다.

• 전력전자학회논문지
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• 제4권4호
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• pp.325-331
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• 1999

계통연계형 태양광발전시스템에서는 계통과 태양광시스템을 연계하기 위해 PWM 인버터가 이용된다. 인버터 시스템을 연속전류모드로 운전하면 맥동이 발생하게 되고, 직류전류의 맥동발생은 교류전류파형의 왜형을 가져온다. 본 연구에서는 직류입력전류의 맥동을 감소시키기 위하여 불연속모드 승강압초퍼로 인버터를 운전한다. 직류 전류에 포함된 고조파성분을 리플성분과 직류성분으로 분리하여 해석하고, 맥동이 없는 일정한 직류전류를 태양 전지로부터 인버터로 공급한다. 제안하는 인버터시스템은 단위 역률로 부하와 계통에 교류전류를 공급한다.

• Journal of Power Electronics
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• 제16권6호
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• pp.2315-2326
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• 2016

This paper discusses the elimination of DC voltage deviation and the enhancement of load current sharing accuracy in multi-terminal high voltage direct current (MT-HVDC) systems. In order to minimize the power line losses in different parallel network topologies and to insure the stable operation of systems, a decentralized control method based on a modified droop control is presented in this paper. Averaging the DC output voltage and averaging the output current of two neighboring converters are employed to reduce the congestion of the communication network in a control system, and the decentralized control method is implemented. By minimizing the power loss of the cable, the optimal load current sharing proportion is derived in order to achieve rational current sharing among different converters. The validity of the proposed method using a low bandwidth communication (LBC) network for different topologies is verified. The influence of the parameters of the power cable on the control system stability is analyzed in detail. Finally, transient response simulations and experiments are performed to demonstrate the feasibility of the proposed control strategy for a MT-HVDC system.

• JSTS:Journal of Semiconductor Technology and Science
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• 제16권6호
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• pp.825-831
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• 2016

In this paper, a transimpedance amplifier based on a new DC offset cancellation (DCOC) method is proposed for WCDMA/LTE applications. The proposed method applies a sample and hold mechanism to the conventional DCOC method with a DC feedback loop. It prevents the removal of information around the DC, so it avoids signal-to-noise ratio degradation. It also reduces area and power consumption. It was designed in a $0.13{\mu}m$ deep n-well CMOS technology and drew a maximum current of 1.58 mA from a 1.2 V supply voltage. It showed a transimpedance gain of $80dB{\Omega}$, an input-referred noise current lower than 0.9 pA/${\surd}$Hz, an out-of-band input-referred 3rd-order intercept point more than 9.5 dBm, and an output DC offset lower than 10 mV. Its area is $0.46mm{\times}0.48mm$.