• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.955_956
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• 2009

계통의 전력품질을 향상시키기 위해서는 비선형부하로 인해 발생되는 무효전력을 보상해야 한다. 이러한 무효전력을 보상하는 알고리즘에서 지령치를 생성하기 위해 평균전력 또는 순시전력을 이용한다. 평균전력을 이용하는 방법은 매 한주기마다 평균전력을 계산하여 지령치를 생성하는 방법으로 필연적으로 지연시간이 발생하게 된다. 이에 반해 순시전력을 이용하는 방법은 매 스위칭 순간에 무효전력을 보상할 수 있어 시스템 응답속도가 빠른 장점을 가진다. 또한 유효전력과 무효전력을 계산하기 위해 디지털 필터를 이용하게 되면 회로구성이 간편하고 제어가 용이한 장점이 있다. 본 논문에서는 계통의 전력품질을 개선시키기 위해 1개의 LPF(Low Pass Filter)와 2개의 곱셈블럭으로 구성되는 디지털 필터를 사용하였다. 이의 유용성을 확인하기 위해 단상 능동전력 필터(active power filter)에 적용하여 시뮬레이션을 수행하였다.

• Proceedings of the KIEE Conference
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• 2003.11c
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• pp.890-893
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• 2003

In this paper, we have designed the fractional-N frequency synthesizer for bluetooth system using 0.35-um CMOS technology and 3.3-V single power supply. The designed synthesizer consist of phase-frequency detector (PFD), charge pump, loop filter, voltage controlled oscillator (VCO), frequency divider, and sigma-delta modulator. A dead zone free PFD is used and a modified charge pump having active cascode transistors is used. A Multi-modulus prescaler having CML D flip-flop is used and VCO having a tuning range from 746 MHz to 2.632 GHz at 3.3 V power supply is used. Total power dissipation is 32 mW and phase noise is -118 dBc/Hz at 1 MHz offset.

• Proceedings of the KIEE Conference
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• 2003.04a
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• pp.281-284
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• 2003

본 논문에서는 비선형 단상부하에 의해 발생하는 전류 고조파를 보상하기 위한 단상능동전력필터의 제어방법을 제안한다. 정규의 단상에 시간지연을 주어 가상의 두 번째 상을 만들어 단상시스템을 두 축을 갖는 직교 좌표로 변환시킬 수 있다. 두 개의 상은 3상 2상 변환에서 사용하는 것과 같이 직교 좌표 시스템을 만들 수 있다. 이 것은 순시 무효전력을 계산하는 방법인 복소계산을 가능하게 한다. 고정 좌표계에서 순시무효전력이론을 적용한 기존의 방법 대신, 본 논문에서는 수정된 동기 좌표계를 이용하여 정상분과 역상분을 계산하여 보상전류 지령치를 결정하였다. 제안된 방법은 고조파저감과 PF개선에 있어 우수한 성능을 보여준다. 시뮬레이션 패키지(PSIM)를 사용하여 모의실험을 하였으며, 제안된 방법의 유효성을 입증하였다.

• Proceedings of the KIPE Conference
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• 2004.07a
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• pp.475-478
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• 2004

본 논문에서는 부하단에서 발생하는 고조파를 검지하는 방법으로 순시 무효전력 방법(IRPM: Instantaneous Reactive Power Method)을 사용하였다. 이 방식은 DQ변환을 통해 순시 무효 전력을 사용하여 고조파를 검지하는 방식이다. 그러나 순시 무효전력 방식은 3상 인버터를 기반으로 하는 DQ변환 방식을 이용하기 때문에 단상 시스템에는 적용될 수 없다. 본 논문에서는 단상에서도 임의의 가상축을 만들어 DQ변환을 수행할 수 있도록 함으로써 순시무효전력 보상 방식을 단상 능동 전력 필터 시스템에도 적용될 수 있는 방안을 제시하였다. 또한 검지된 고조파를 효과적으로 보상할 수 있는 3레벨 NPC 타입 멀티레벨 인버터를 사용하여 고전력 능동 필터를 구성할 수 있도록 하였다.

• Proceedings of the KIPE Conference
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• 1999.07a
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• pp.323-326
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• 1999

For decrease the harmonic current components of the power source, a first method is insert the choke coil that used the choke input type rectifier, the booster chopper circuit and buck chopper circuit. And the several method are studying like as the PWM(Pulse Width Modulation) converter and the active filter type which is used the high frequency switching and the sinusoidal wave formed input current. In this type, there are many problem as a low efficiency, increased the noise, the high leakage current and cost up by the high frequency switching. For improve this problems, the partial resonan method is used on the booster inducter and lossles snubber condenser. This method decreased the distortion factor has lower harmonic components than the hard switching and there is no switching loss by the ZCS(Zero Current Switching) at switch turn-on and the ZVS(Zero Voltage Swithcing) at switch turn-off

• Proceedings of the KIEE Conference
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• 2003.07e
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• pp.46-48
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• 2003

A single phase voltage-controlled active power filter(APF) is introduced to improve power quality and to reduce harmonic generated from nolinear loads. Real and reactive power control scheme was addressed using a new power circuit model. By analyzing the reactive power, a unit power factor control scheme was proposed. Simulation and experiment results using a nonlinear diode rectifier showed that the voltage-controlled APF, unlike the current-controlled APF, can reduce the voltage harmonics as well as current harmonics. Also the results showed that the input power factor was greatly improved.

• The Bulletin of The Korean Astronomical Society
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• v.44 no.1
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• pp.71.3-71.3
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• 2019

For slitless spectroscopy, we have installed the Volume Phase Holographic (VPH) gratings in the filter wheel of the SQUEAN on the 2.1m telescope at McDonald Observatory in Texas, United States. This system can effectively take spectra and monitor the variabilities of many sources, such as quasi-stellar objects, supernovae, and active galactic nuclei. On the single image frame, there are many spectra of the point sources. Therefore, a target extraction needs to trace along the tilted dispersion and to minimize the confusions by other sources. We present a real-time reduction software that has the functions with spectra extraction and wavelength calibration.

• Proceedings of the KIPE Conference
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• 2001.10a
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• pp.484-488
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• 2001

The grid voltage of commercial utility power source hi Japan and USA is 100rms, but in China and European countries, it is 200rms. In recent years, In Japan 200Vrms out putted single phase three wire system begins to be used for high power applications. In 100Vrms utility AC power applications and systems, an active voltage clamped quasi-resonant Inverter circuit topology using IGBTs has been effectively used so far for the consumer microwave oven. In this paper, presented is a half bridge type voltage-clamped high-frequency Inverter type AC-DC converter using which is designed for consumer magnetron drive used as the consumer microwave oven in 200V utility AC power system. This zero voltage soft switching Inverter can use the same power rated switching semiconductor devices and three-winding high frequency transformer as those of the active voltage clamped quasi-resonant Inverter using the IGBTs that has already been used for 100V utility AC power source. The operating performances of the voltage source single ended push pull type Inverter are evaluated and discussed for consumer microwave oven. The harmonic line current components In the utility AC power side of the AC-DC power converter operating at ZVS­PWM strategy reduced and improved on the basis of sine wave like pulse frequency modulation and sine wave like pulse width modulation for the utility AC voltage source.

• Journal of Electrical Engineering and Technology
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• v.10 no.1
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• pp.195-204
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• 2015

In this paper, the development of a cost-effective active power filter/uninterruptible power supply (APF/UPS) system with seamless mode transfer is described. The proposed scheme employs a pulse-width-modulation (PWM) voltage-source inverter and has two operational modes. First, when the source voltage is normal, the system operates as an APF, which compensates for the harmonics and power factor while boosting the DC-link voltage to be ready for the disturbance, without an additional DC charging circuit. A simple algorithm to detect the load current harmonics is also proposed. Second, when the source voltage is out of the normal range (owing to sag, swell, or outage), it operates a UPS, which controls the output voltage constantly by discharging the DC-link capacitor. Furthermore, a seamless transfer method for the single-phase inverter between the APF mode and the UPS mode is also proposed, in which an IGBT switch with diodes is used as a static bypass switch. Dissimilar to a conventional SCR switch, the IGBT switch can implement a seamless mode transfer. During the UPS operation, when the source voltage returns to the normal range, the system operates as an APF. The proposed system has good transient and steady-state response characteristics. The APF, charging circuit, and UPS systems are implemented in one inverter system. Finally, the validity of the proposed scheme is investigated with simulated and experimental results for a prototype APF/UPS system rated at 3 kVA.

• Proceedings of the IEEK Conference
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• 2002.07b
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• pp.1312-1315
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• 2002

This research describes the design of a fully integrated fractional-N frequency synthesizer intended for the local oscillator in IMT-2000 system using 0.18-$\mu\textrm{m}$ CMOS technology and 1.8-V single power supply. The designed fractional-N synthesizer contains following components. Modified charge pump uses active cascode transistors to achieve the high output impedance. A multi-modulus prescaler has modified ECL-like D flip-flop with additional diode-connected transistors for short transient time and high frequency operation. And phase-frequency detector, integrated passive loop filter, LC-tuned VCO having a tuning range from 1.584 to 2.4 ㎓ at 1.8-V power supply, and higher-order sigma-delta modulator are contained. Finally, designed frequency synthesizer provides 5 ㎒ channel spacing with -122.6 dBc/Hz at 1 ㎒ in the WCDMA band and total output power is 28 mW.