• Proceedings of the KIPE Conference
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• 2009.11a
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• pp.209-211
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• 2009

A digital grid synchronization technique is needed for distributed generation system to make output current sinusoidal even if the grid voltage is distorted by harmonics. In this paper, a digital grid synchronization technique based on adaptive notch filter is proposed. The analysis of proposed technique is performed through the consideration of grid synchronization technique based on PLL and FLL, and the validity of the proposed method was confirmed by simulation results.

• Proceedings of the KIPE Conference
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• 2004.07a
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• pp.101-104
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• 2004

대체에너지 시스템에서 필수적인 계통연계형 인버터는 LC필터를 거친 정현전압 출력에 계통과 연계용 인덕터를 연결하여 사용하여 왔으나, 최근 들어 인버터와 계통을 LC필터 없이 인덕터로만 계통과 연결하여 직접 전류를 제어하는 형태가 적용되고 있다. 또한 출력에 절연 변압기를 사용하던 기존방식과 달리 변압기가 없는 비절연형 인버터는 전류제어를 통해 계통과 직접연결하고, 부피감소와 원가절감을 이룰 수 있다. 본 논문에서는 저주파 절연변압기가 없는 3kW급의 태양광 발전시스템 시제품을 소개하고 단상계통과 연계한 전류제어 알고리즘의 실험결과를 통해 순시전류제어의 타당성을 확인한다.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.52 no.12
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• pp.608-615
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• 2003

This paper describes an implementation of a DSP (Digital Signal Processor) controlled random carrier frequency modulation for the PWM inverter for acoustic noise reduction of induction motors. Real-time generation of the random variable and RPWM(Random PWM) along with the speed control was achieved by DSP TMS320C31. The experimental results show that the voltage and current harmonics are spread to a wide band area and the power spectrum of the acoustic switching noise was spread to create a more appealing, less annoying sound. Also, the speed response of the implemented method and the conventional method is nearly similar to each other from the viewpoint of the v/f constant control.

• Proceedings of the KIEE Conference
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• 1999.11c
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• pp.582-584
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• 1999

Generator has synchronized with power Network after build-up output voltage. In order to prevent a current surge when synchronizing, the conditions such as identical no-load voltages identical no-load frequencies and identical phase positions must be met between generator voltage and network voltage. Hydro-Pump generators or Gas-turbine generators, Co-generation Generators that serve peak load of network are synchronized many times. So, Automatic Synchronizing Circuits are very important service. This report apply Diagnosis methods the Automatic Synchronizing Circuits(Device) by developing simulator.

• Proceedings of the Korea Water Resources Association Conference
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• 2005.09b
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• pp.1355-1355
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• 2005

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.21 no.10
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• pp.950-953
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• 2008

YBCO coated conductor called the second-generation superconducting tapes have resistance increase significantly more than BSCCO tapes in terms of the speed or amount when quench occurs, they may have different ranges of application. Such characteristics are thought to get different properties by selection of stabilizing materials in manufacturing superconducting tapes. It is important in selecting superconducting tapes which will be applied to power devices in the future. In this study, one kind of BSCCO tapes and two kinds of YBCO CC with different stabilizing materials and one kind of YBCO CC with non stabilizing materials were used to compare and examine transport characteristics in flux-flow state and quench state with each tape joint of HTS tapes.

• Journal of The Korean Astronomical Society
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• v.29 no.spc1
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• pp.155-158
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• 1996

Magnetic fields correlated on several kiloparsec scales are seen in spiral galaxies. Their origin could be due to the winding up of a primordial cosmological field or due to amplification of a small seed field by a turbulent galactic dynamo. Both options have difficulties: There is no known battery mechanism for producing the required primordial field. Equally the turbulent dynamo may self destruct before being able to produce the large scale field, due to excess generation of small scale power. The current status of these difficulties is discussed. The resolution could depend on the nature of the saturated field produced by the small scale dynamo. We argue that the small scale fields do not fill most of the volume of the fluid and instead concentrate into intermittent ropes, with their peak value of order equipartition fields, and radii much smaller than their lengths. In this case these fields neither drain significant energy from the turbulence nor convert eddy motion of the turbulence on the outer scale to wave like motion. This preserves the diffusive effects needed for the large scale dynamo operation.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2000.02a
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• pp.185-188
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• 2000

The voltage induced in the superconducting background magnet system is analyzed according to the calculation of self inductance and mutual inductance. The voltage induced by blip and compensation coils of the background magnet system is about 6.4V. In order to charge the main background magnet, the power supply must provide the minimum voltage of 1.1 kV. the compensation coils have an influence on the field distribution. The compensation coils result in the decreasing center field about 2.67%. It can remarkably decrease the ac losses and the voltage on the current leads of the background magnet.

• Proceedings of the KIPE Conference
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• 2010.07a
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• pp.176-177
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• 2010

현재 학계에서는 신재생 에너지에 관한 연구가 활발히 진행되고 있으며, 그 중 태양광과 풍력이 큰 비중을 차지하고 있다. 본 논문에서는 Push-Pull 컨버터를 기초한 전류형 PWM 인버터를 제안하고 계통 연계가 가능한 회로로의 타당성을 검증하였다. 스위칭 소자 중 Push-Pull컨버터부의 두 개의 스위치만 PWM(Pulse Width Modulation)을 행하고 계통과 연결된 Full-Bridge의 스위치는 계통의 극성을 판단하여 Auto-ZCS (Zero Current Switching)가 가능하도록 설계하였다.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.55 no.12
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• pp.596-607
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• 2006

This paper presents Single Phase Switched Reluctance Motor (SPSRM) optimum design for vacuum cleaners using Response Surface Methodology (RSM) to determine geometric parameters, and the 2-D Finite Element Method (FEM) has been coupled with the circuit equations of the driving converter. Additionally, an optimum process for SPSRM has been proposed and peformed with geometric and electric parameters thereby influencing the inductance variation and effective torque generation as design variables. SPSRM performances have also been analyzed to determine an optimal design model for maximized efficiency at high power factor. In order to confirm the propriety of the Finite Element Method and motor performance calculation, simulation waveform and experiment waveform for motor voltage and current were compared.