• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 춘계학술대회 논문집 전기설비전문위원
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• pp.51-56
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• 2006

저압 수용가에 적용되고 있는 3상 4선식 배전방식은 단상 및 3상 부하를 동시에 이용할 수 있는 장점이 있는 반면 부하의 불평형 운전에 의한 임피던스의 변화로 전압 불평형이 발생하게 된다. 이들 부하 중에서는 선형 및 비선형 부하가 사용될 경우 고조파의 발생으로 부하에 나쁜 영향을 미칠 수 있다. 그래서 본 논문에서는 전압 불평형율의 허용범위를 제한하기 위해 전압 불평형율에 대한 측정방법, 불평형율의 계산방법 그리고 현장 측정 등을 통해 도출된 결과들을 분석하여 가장 효과적인 허용범위를 제안하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 추계학술대회 논문집 전기설비전문위원
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• pp.33-36
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• 2004

단상 및 3상 부하를 동시에 공급할 수 있는 3강 4선식 배전시스템은 일반 수용가 및 상업용, 공장 등의 시설에 널리 적용되고 있다. 한대의 변압기로 전력을 공급할 수 있으므로 작은 공간과 시스템 구성의 간편함이 장점이지만, 부하 운전패턴의 다양화와 컴퓨터 및 가변속 드라이브와 같은 비선형부하의 사용 증가시 전압불평형에 의한 문제점 발생은 큰 문제가 되고 있다. 외국의 경우 전압불평형에 의한 영향을 줄이기 위해 전압별 또는 부하의 종류에 따라 전압불평형율에 대한 규정을 제시하고 있으나, 국내에서는 전기철도와 같은 대형 부하에서만 전압불평형율의 기준만 정립되어 있고, 선형 및 비선형부하에 대해서는 규정이 제시되어 있지 않아 점차 증가하는 다양한 부하의 종류에 효율적으로 대처하기가 매우 어렵다. 따라서 본 연구에서는 국내외 전압불평형율에 대한 기준의 비교와 측정방법에 대한 내용을 제시 하고자 한다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 제39회 하계학술대회
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• pp.824-825
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• 2008

This paper analyzes the stator winding currents of a three phase induction motor which is connected to the single phase supply. Two stator configurations, Steinmetz connection and modified Steinmetz connection, are respectively employed. In each case, the phase converter reactance at starting is determined using the condition of minimum voltage unbalance factor. By using this reactance, the stator winding currents of each connection are computed and compared with the results of three phase balanced operation.

• Journal of Power Electronics
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• 제19권5호
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• pp.1315-1325
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• 2019

Aiming at the negative sequence and harmonic problems in the operation of railway static power conditioners, an optimization compensation strategy for negative sequence and harmonics is studied in this paper. First, the hybrid RPC topology and compensation principle are analyzed to obtain different compensation zone states and current capacities. Second, in order to optimize the RPC capacity configuration, the minimum RPC compensation capacity is calculated according to constraint conditions, and the optimal compensation coefficient and compensation angle are obtained. In addition, the voltage unbalance ${\varepsilon}_U$ and power factor requirements are satisfied. A PSO (Particle Swarm Optimization) algorithm is used to calculate the three indexes for minimum compensating energy. The proposed method can precisely calculate the optimal compensation capacity in real time. Finally, MATLAB simulations and an experimental platform verify the effectiveness and economics of the proposed algorithm.

• 대한전기학회논문지
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• 제36권3호
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• pp.171-178
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• 1987

A study of two phase chopper system with four separate groups of DC motors in powering. A novel two phase chopper system with four separate groups of DC motors which applies the principles of two phase chopper with two separate groups of DC motors is dealt with this article. The main circuit consists of eight sets of chopping parts, four diodes and four separate groups of DC motors. Four groups of DC motors are driven through the series and parallel connections to each other in accordance with the operating conditions of the choppers. Although the proposed chopper circuit requires more circuit elements than the conventional two phase chopper system with combined output or two phase chopper system with two separate groups of DC motors, it has the following advantages` (1). It is possible to drive twice as much motors as conventional system does, using esisting receiving-and equipments and motors. (2). It is possible to control load voltage continuously from 0 to source voltage by changing time-ratio from 0 to 1. (3). Load current division becomes equalized. Therefore it is possible to drive not only series motors but also shunt and separately exited motors. (4). When smoothing reactor L is small, harmonic components of the proposed circuit is not so large. Therefore, the value of L can be determined from viewpoints of allowable value of ripple-ratio and current unbalance factor.

• Journal of Power Electronics
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• 제14권2호
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• pp.271-281
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• 2014

Fluctuating wind conditions necessitate the use of a variable speed wind turbine (VSWT) with a AC/DC/AC converter scheme in order to harvest the maximum power from the wind and to decouple the synchronous generator voltage and frequency from the grid voltage and frequency. In this paper, a combination of a three phase diode bridge rectifier (DBR) and a modified topology of the diode clamped multilevel inverter (DCMLI) has been considered as an AC/DC/AC converter. A control strategy has been proposed for the DCMLI to achieve the objective of grid interface of a wind power system together with local load compensation. A novel fixed frequency current control method is proposed for the DCMLI based on the level shifted multi carrier PWM for achieving the required control objectives with equal and uniform switching frequency operation for better control and thermal management with the modified DCMLI. The condition of the controller gain is derived to ensure the operation of the DCMLI at the fixed frequency of the carrier. The converter current injected into the distribution grid is controlled in accordance with the wind power availability. In addition, load compensation is performed as an added facility in order to free the source currents being fed from the grid of harmonic distortion, unbalance and a low power factor even though the load may be unbalanced, non-linear and of a poor power factor. The results are validated using PSCAD/EMTDC simulation studies.