• The Transactions of the Korean Institute of Power Electronics
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• v.5 no.4
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• pp.394-402
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• 2000

This paper proposes a bifurcation theory method applied for voltage stability analysis and shows the improvement of voltage stability by attaching the FACTS devices in the power system. A power system is generally expressed by a set of equations of highly nonlinear dynamical system which includes system parameters(real or reactive power). Sometimes variation of parameters in the system may result in complication behaviors which give rise to system instability. The addition of FACTS increases the range of voltage stability in the power system. The effect of FACTS which improves voltage stability are illustrated in the case studies by delaying of Unstable Hopf Bifurcation and Saddle Node Bifurcation.

• Journal of the Korean Society of Safety
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• v.33 no.1
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• pp.41-46
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• 2018

Experiments were carried out the phenomenal observation on effect of corona treated hotmelt laminating film in process of manufacture by 2 kinds of rolling speed and electric power variatons. Surface treatment by corona which is exposure of film surface to electron of ion bombardment, rather than mere exposure to active species, like atomic oxygen or ozone, can enhance adhesion by removing contaminant, electret, roughening surface, and introducing reactive chemical group. Reactive neutrals, ions, electron and photons generated during the corona treatment interact simultaneously with polymers to alter surface chemical composition, wettability, and thus film adhesion. However, it is highly recommended that extensive chains scission is avoided because it can lead to side-effect by forming sticky matter, resulting in dropouts. This paper reviews principles of surface preparation of polypropylene substrate by corona discharging. In addition, the experimental section provides a description of parameter optimization on corona discharging treatment and its side-effect. Experimental results are discussed in terms of surface wetting as determined by contact angle and SEM measurements. When the rolling speed of the film decreased from 1.666 [m / sec] to 0.083 [m / sec], contact angle decreased from $80[^{\circ}]$ to $64[^{\circ}]$, and the wettability was greatly improved. As the supply power increased from 0.4 [kVA] to 2 [kVA] at the corona discharge surface treatment, the contact angle decreased from $77[^{\circ}]$ to $65[^{\circ}]$, and the wettability was greatly improved.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.13 no.3
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• pp.124-128
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• 1999

The object of the present study is to obtain a 20[kHz], 10[kW] rating, high efficiency induction heating system by high frequency serises-resonant inverter. Proposed is a topology that minimize a reactive power, by which direct iOIrt voltage is variable corresponding to the variation of the load, heated-object, and by which the switching of inverter is forced to follow a resonant frequency. And assured that the power foctor of the inverter in a induction heating system is proper about O.96 through the simulation and results.esults.

• Proceedings of the KIPE Conference
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• 2009.11a
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• pp.126-129
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• 2009

두 대 이상의 전원이 부하를 분담하는 경우 전원간의 통신이 없다면 여러 가지의 오차요인으로 인하여 문제가 생길 수 있다. 그래서 기존의 발전기 시스템은 이런 문제를 해결하기 위하여 droop제어를 수행하고 있다. 이와 마찬가지로 분산전원의 용량이 커짐에 따라 2대 이상의 분산전원이 병렬운전하여 고립된 계통에서 부하를 분담해야하는 경우 이들 간 통신이 없다면 문제가 된다. 그러나 발전기와는 달리 분산전원은 저압선로에서 전력을 공급하기 때문에 선로의 임피던스 특성에 따른 유 무효전력의 변동에 대한 분석이 필요하다. 본 논문에서는 분산전원의 병렬운전 시의 오차요인 계산하고 선로에 임피던스에 따른 유 무효전력의 변동을 분석하여 이를 시뮬레이션을 통하여 확인하고 저압선로에서의 분산전원 droop제어 방법에 대해서 연구하였다.

• Proceedings of the KIPE Conference
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• 2004.07b
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• pp.494-497
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• 2004

계통연계형 태양광발전 시스템의 확대보급에 따라 단독운전 검출기법의 검출 성능에 대한 검증의 필요성이 대두되고 있다. 본 논문에서는 단독운전 검출기법의 대표적인 능동적 검출기법인 무효전력 변동기법 (reactive power variation method)과 주파수 쉬프트기법(active frequency drift method)을 IEEE Std 929-2000에서 명시된 단독운전검출 시험 방법을 이용하여 단독운전검출기법의 성능 및 불검출 영역(non-detection zone)에 대하여 비교 분석하였다.

• Proceedings of the KIEE Conference
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• 1999.07c
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• pp.1302-1304
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• 1999

This Paper Proposes the FACTS site selection method using subtransmission system reduction. A general method which uses the sensitivity of the variation in voltage and reactive Power has been used to determine the location of shunt type FACTS device, but there is a difficulty to find a proper location due to the overestimation of the effect of sub-transmission systems. Therefore, there is a need to reduce sub-transmission system for finding an effective location of shunt type FACTS devices such as SVC(Static Var Compensator), STATCOM(Static Synchronous Compesator), and so on.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.44 no.3
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• pp.270-273
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• 1995

This paper proposes an optimal load shedding algorithm by which the system loss can be minimized when the load shedding is unavoidable in case of severe contingency such as the outage of key generators or lines. Shedding load .DELTA.S = .DELTA.P + J.DELTA.Q(MVA) is performed on the weakest bus (on the view of voltage stability), step by step, by the priority of the I.DELTA. = SQRT(.lambda.$\_$P/$\^$2/ + .lambda.$\_$Q/$\^$2/) index given for each load bus, where .lambda.$\_$P/ and .lambda.$\_$Q/ are the sensitivity indices representing the system loss variation versus active and reactive power change of the bus load bus. All loads are assumed to be constant power loads for convenience. A 5 bus sample system proves the effectiveness of the algorithm proposed.

• Proceedings of the KIPE Conference
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• 2015.11a
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• pp.79-80
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• 2015

중요부하를 갖는 하이브리드 ESS에서는 계통이상시에도 중요부하에 끊김없고 안정적인 전원을 공급해야한다. 기존 직접 전류 제어 방식은 독립운전시 전압제어를, 계통연계시 전류제어를 하기 때문에 모드전환시 과도상태가 발생하고, 단독운전 검출전에도 부하의 전압과 주파수가 변동하여 중요부하에 심각한 영향을 줄 수 있다. 본 논문에서는 모드 전환시 과도상태를 최소화하면서 단독운전 검출전에도 부하 전압과 주파수를 일정하게 유지하는 간접전류제어 기반의 인버터에서 무효전력변동 기법을 이용한 새로운 단독운전방지 기법을 제안한다.

• Journal of Power Electronics
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• v.17 no.1
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• pp.212-221
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• 2017

Permanent-Magnet Synchronous Generators (PMSGs) are used widely in Wind Power Generation Systems (WPGSs), and the Vienna rectifier was recently proposed to be used as the generator-side converter to rectify the AC output voltage in PMSG-based WPGS. Compared to conventional six-switch two-level PWM (2L-PWM) converters, the Vienna rectifier has several advantages, such as higher efficiency, improved total harmonic distortion, etc. The motivation behind this paper is to verify the performance of direct-driven PMSG wind turbine system based-Vienna rectifier by using a simulated direct-driven PMSG WPGS. In addition, for the purpose of reducing the reactive power loss of PMSGs, this paper proposes an induced voltage sensing scheme which can make the stator current maintain accurate synchronization with the induced voltage. Meanwhile, considering the Neutral-Point Voltage (NPV) variation in the DC-side of the Vienna rectifier, a NPV balancing control strategy is added to the control system. In addition, both the effectiveness of the proposed method and the performance of the direct-driven PMSG based-Vienna rectifier are verified by simulation and experimental results.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.11
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• pp.1931-1936
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• 2016

In this paper, we analyzed causes of accidents that recently increased in the illegal and defective LED lamps. They were analyzed by the electrical characteristics calculation and reappearance experiments. The causes of the accidents were analyzed from the circuit affected by the variation of voltage, current and power by harmonics. We drew a conclusion for electrical safety in illegal or degraded LED lamps from the analysis result. The management factors for electrical safety in LED lamps were harmonics, reactive power and power factor. It is possible to secure the electrical safety through monitoring of power factor in failure products and available in smart meters or smart distribution boards.