• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2001년도 추계학술대회 논문집 전기기기 및 에너지변환시스템부문
• /
• pp.208-211
• /
• 2001

This paper presents the considerations of the high frequency modulation method for the metal halide lamp electronic ballast. The acousitc resonance phenomenon is occurred, if the metal halide lamp is driven at constant high frequency. The frequency modulation method therefore, is used to avoid the acoustic resonance phenomenon, but the crest factor of lamp current is increased. In this paper, the driving characteristic of the metal halide lamp according to the waveshape and frequency variations of modulating signal is considered with a viewpoint of crest factor.

• Journal of Electrical Engineering and Technology
• /
• 제5권2호
• /
• pp.290-298
• /
• 2010

This paper proposes an adaptive carrier-based pulse width modulation (PWM) method for a four-switch three-phase (4S3P) inverter under dc-link voltage ripple conditions. The proposed method guarantees balanced output currents despite of the existence of the voltage oscillations across two dc-link capacitors. And also, this new approach achieves a linear over-modulation with calculation time reduction. Simulation and experimental results are given to validate the feasibility of the proposed method.

• 한국정보통신학회논문지
• /
• 제4권1호
• /
• pp.283-288
• /
• 2000

본 논문은 마이크로프로세서를 이용하여 구현하는 전파브리지 인버터의 새로운 PWM 제어 방법을 제안한다. 이 방법은 단방향 전파 브리지 인버터의 한 주기를 주파수 변조비로 등간격 분할하고 기준 기본파와 인버터의 출력 기본파의 진폭을 비교하는 PWM 제어 방법이다. 이 방법을 이용하면 각 간격의 turn-on time 계산이 매우 용이하여 마이크로프로세서 구현에 매우 적합하다. 그리고, 고조파 해석에 있어서 주파수 변조비가 크면 모든 고조파를 무시할 수 있음을 보여준다 시뮬레이션과 실험을 통하여 타당성을 입증하였다.

• 한국광학회:학술대회논문집
• /
• 한국광학회 1990년도 제5회 파동 및 레이저 학술발표회 5th Conference on Waves and lasers 논문집 - 한국광학회
• /
• pp.215-218
• /
• 1990

A method for optical representation and modulation of synaptic interconnections between neurons using photoanisotropic amorphous As2S3 thin film is discussed. Experimental results show that the proposed method can be used for the representation of not only excitatory synaptic connections but also inhibitory synaptic connections. Applications of the method to the implementation of optical learning machine is also discussed.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2001년도 하계학술대회 논문집 B
• /
• pp.1076-1078
• /
• 2001

In this paper, we studies PWM control method for 400kVA inverter. This method is compared with the conventional sinusoidal modulation method applying to the power converter with large capacity. The inverter controls a PWM modulation using a DSP processor.

• 한국산학기술학회논문지
• /
• 제14권7호
• /
• pp.3482-3486
• /
• 2013

페이딩 채널에서 야기되는 진폭 및 위상 왜곡을 예측하여 보상하는 PSAM(Pilot Symbol Assisted Modulation)방식의 경우에는 fast 페이딩 채널에서 도플러확산에 의해 심한 성능 저하를 갖는다. 이에 대한 문제점을 분석하고, 이를 개선하기 위한 페이딩 보상 방식을 제안한다. 도플러 확산은 BER 성능을 저하시키는 주된 원인이 된다. 기존의 PSAM 방식과 비교해 보면, 한 심벌 주기 이내의 지연파의 간섭이 있는 환경에서는 기존 PSAM 방식은 도플러확산에 의해 BER이 $10^{-1}$ 정도의 매우 심각한 성능저하를 보이지만 제안된 방식은 도플러 확산이 클수록 성능저하는 발생하지만 기존 방식에 비해 BER이 $10^{-2}$ 이하로 성능이 우수함을 알 수 있다.

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

• 전력전자학회논문지
• /
• 제21권6호
• /
• pp.530-537
• /
• 2016

This work deals with a switching method for minimizing overcurrent in a three-phase interleaved bidirectional DC-DC converter with frequency modulation. Generally, a three-phase interleaved DC-DC converter is used to reduce a current ripple component. The combined operation of three-phase and two-phase converters can significantly reduce the ripple component. However, the conventional PWM method cannot solve severe overcurrent during phase transfer or frequency variation for power control. To overcome this problem, this work proposes a new PWM switching method. A 3 kW DC-DC power converter is designed and implemented, and the converter is operated in discontinuous current mode with varying switching frequencies for power control. Simulation and experimental results show the validity of the proposed switching method. The proposed switching method can be widely used in the field of current ripple reduction for three-phase interleaved bidirectional DC-DC converters.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 1995년도 춘계학술대회 논문집
• /
• pp.90-95
• /
• 1995

This paper describes the highly-sensitive Si magnetic sensor using the amplitude modulation in order to real ice the integrated magnetic sensor which to sensor a weak magnetic field. Generally, the most important two parameters in Hall IC which degrade the ability of magnetic detection are the variation of offset according to the variation of temperature and the noise of amplifiers. In this paper, we use a Hall element and compensator to reduce the offset and the nouse of amplifiers by Using amplititude modulation method.

• 대한전자공학회:학술대회논문집
• /
• 대한전자공학회 2001년도 하계종합학술대회 논문집(1)
• /
• pp.117-120
• /
• 2001

In this paper, we propose a robust trellis coded modulation for a correlated Rayleigh fading channel. This method use only one transmit antenna, which can achieve superior performance compared to Space-Time Trellis Coded Modulation (STTC) over a wide channel correlation range among transmit antennas. The code is designed to have the largest Euclidean distance between faded signals at the receiver. Computer simulations are performed to evaluate the frame error rate (FER) performance and to compare the proposed code with the conventional one.