• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.9 no.5
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• pp.57-63
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• 1995

In this paper, 3-Phase PWM AC/DC step up type converter that reduces the harmonics and reactive power of the distribution line is analyzed and the stable control method is proposed as controlling the sinusoidal phase current and phase voltage in phase. In implementation of controller, simple control algorithm is derived as the instantaneous voltage control methods without current sensor. The instantaneous voltage is controled by PWM method and the switching frequency is presented in low range 3 [kHz] for reducing the switching loss. In case of active load, four quadrants operation converter regenerate power from the load to the power source is conducted. Through the computer simulation and experimentation, the proposed control method is justified.

• Proceedings of the KIEE Conference
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• 1999.11a
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• pp.52-55
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• 1999

In recent years, much attention has been paid to the voltage collapse phenomena. There has been reported many cases about the voltage collapse in many countries. These voltage collapse phenomena are known as the event that can occur due to reactive power deficits. This paper proposes an efficient method that can pursue the reactive power loss changes and gives the simple voltage collapse proximity indicator(VCPI) based on the reactive power loss sensitivities using optimal techniques. By comparing reactive power loss sensitivity with active power loss sensitivity, it is also proved that VCPI based on reactive power loss sensitivities is more effective. The developed VCPI is derived from the Jacobian matrix of Load Flow and the computational burden is very low and on-line implementation is possible. The proposed method is applied to a IEEE-14 bus test system and reliable and promising results are obtained.

• Proceedings of the KIEE Conference
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• 2000.07a
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• pp.350-353
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• 2000

This paper presents an algorithm for Optimal Reactive Power Dispatch(ORPD) problem based on genetic algorithm. Optimal reactive power dispatch is particularized to the minimization of transmission line losses by suitable selection of generator reactive power outputs and transformer tap settings. To reduce system loss and improve voltage profile, two methods, Loss Re-Distribution Algorithm (LRDA) and Voltage Dependent Load Model (VDLM), are applied to ORPD. The proposed methods have been evaluated on the IEEE 30 bus system. Each of results have been compared with result of load flow.

• Proceedings of the KIEE Conference
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• 1999.11b
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• pp.190-192
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• 1999

This paper presents an algorithm for optimal reactive power dispatch problem based on genetic algorithm. Optimal reactive power dispatch is particularized to the minimization of transmission line losses by suitable selection of generator reactive power outputs and transformer tap settings. To attain for the objective, in this paper, loss re-distribution algorithm(LRDA) is applied to ORPD. The proposed method has been evaluated on the IEEE 30 bus system. Results of the application of the method are compared with a simple genetic algorithm.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.52 no.7
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• pp.429-436
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• 2003

This paper presents a new approach for evaluating the transmission marginal loss factors (MLFs) considering the reactive power. Generally, MLFs are represented as the sensitivity of transmission losses, which is computed from the change of the generation at reference bus by the change of the load at the arbitrary bus-i. The conventional evaluation method for MLFs uses the only H matrix, which is a part of jacobian matrix. Therefore, the MLFs computed by the existing method, don't consider the effect of the reactive power, although the transmission losses are a function of the reactive power as well as the active power. To compensate the limits of the existing method for evaluating MLFs, the power factor at the bus-i is introduced for reflecting the effect of the reactive power in the evaluation method of the MLFs. Also, MLFs calculated by the developed method are applied to energy spot markets to reflect the impacts of reactive power. This method is tested with the sample system with 5-bus, and analyzed how much MLFs have an effect on the bidding/offer price, market clearing price(MCP), and settlement in the competitive energy spot market. This paper compared the results of MLFs calculated by the existing and proposed method for the IEEE 14-bus system, and the KEPCO system.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.463-464
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• 2007

본 논문은 경제성 및 안정성을 유지하는 최적의 전압유지범위 설정을 위해 다양한 목적함수를 최적조류계산에 이용하였다. 경제성을 위해 융통전력 최대화와 유효전력 손실최소화를 목적함수로 하였고 안정성을 위해 무효전력예비력 최대화를 목적함수로 하였다. 또한 경제성과 안정성을 모두 반영하기 위해 다목적 함수를 구성하였다. 최적화기법을 실계통에 적용하였을 때 목적함수를 얼마나 잘 만족시킬 수 있는지 각종 지표를 통해 살펴보았다. 그리고 모니터링 모선의 전압 변동 추이를 살펴보고 이를 통해 경제성 및 안정성을 유지하는 최적의 전압유지 범위설정을 하는데 활용할 수 있도록 하였다.

• Proceedings of the KIEE Conference
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• 2003.11a
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• pp.41-44
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• 2003

본 논문에서는 부하의 상태에 따라 능동적으로 추종 및 보상기능을 갖으며, 에너지절약기능 및 고품질을 유지할 수 있는 소형이면서 가격도 저렴한 전력 품질보상장치의 Prototype을 구성하고져 한다. 최근 일반 주택이나 사무실내에 반도체소자 및 전력전자기기의 사용이 급증하면서 이들 기기에서 발생하는 고조파 및 무효전력량이 증가하여 주위의 환경과 전기적 손실이 심각한 문제를 발생한다. 이런 상황 하에서 전력품질에 민감한 부하들이 급증하고 부하의 민감도에 따라 다양한 전력품질을 요구하는 장치가 점점 필요로 하게 되었다. 지금까지 국내 외적으로 이런 문제를 보상하는 소형보상장치는 가전기기 즉 세탁기 냉장고등 각기 개개로 부착하고 있는 것들은 어느 정도 개발되어 사용되고 있으나, 가정용도로 사용하기 위하여 주택전체를 보상하는 기기는 개발이 되어있지 않은 상태에 있다. 따라서 현재까지 국내 외적으로 개발되어온 기기들은 가정용 소형 전력품질의 모니터링 수준이라고 할 수 있다. 따라서 본 논문에서는 기기의 최 말단 즉, 기기자체에 부착하여 사용하는 단순형 보상형태를 확장시켜 소형이면서 에너지 절약이 가능한 가정용으로 적합한 능동 추종형 전력품질 보상장치의 기술에 대한 연구를 하는 것이 목적이다.

• 전기의세계
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• v.28 no.10
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• pp.41-47
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• 1979

The paper develops a method of minimizing power transmission losses by optimum control of reactive power flow. In the past, because the optimizing method considers as the first step the minimization of node voltage deviations and as the second step the minimization of transmission losses within the system, the calculating procedure was more complex and difficult to handle. In this paper, a new computing method for real time control on a digital computer is described which aims at a coordinated use of reactive power sources and voltage regulating devices. The power transmission losses are minimized by a gradient method while satisfying the constrained system voltage conditions and sensitivity parameters are the basis of the method.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.7
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• pp.121-127
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• 2016

We propose a algorithm to calculate power factor of fundamental waveform in an environment where the voltage and current have been distorted by harmonics. In the proposed power factor computation algorithm, voltage and current are converted to rotating DQ reference frame, and power factor is calculated from active power and reactive power. We compare the proposed method with the conventional power factor measurement method as mathematically. In a condition that voltage and current are distorted by harmonics, the proposed method accurately measure the power factor of fundamental wave, and it is confirmed by simulation using MATLAB. If the proposed power factor measurement method is applied to an automatic power factor control system, a power factor compensation performance can be maximized in harmonic distortion environment. As a result, it is possible to reduce electricity prices, reduce line loss, increase load capacity, ensure the transmission margin capacity, and reduce the amount of power generation.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.16 no.5
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• pp.83-89
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• 2002

The purpose of this paper is to assess experimentally system stability of the 154［㎸］transmission system due to the current of the forthcoming AC High-Speed Railway (HSR) era. It introduces a simple method to evaluate the system stability. The proposed method also shows the relationship between stability and power losses, and the stability indices made by the numerical process proposed in this paper will be used to assess whether a system can be stabilized or not. This paper also presents the improvement of the stability via loss reduction using a shunt compensator. Reactive power compensation is often the most effective way to improve both power transfer capability and system stability. The suitable modeling of the traction power system should be applicable to the PSS/E. The proposed method is tested on a practical system which will be expected to accommodate the heavy HSR load.