• 전기학회논문지P
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• 제67권3호
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• pp.155-159
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• 2018

Recently, the expansion or establishment of facilities for the logistics system is increasing. Conveyor facilities play a major role in sorting and transporting logistics. Induction motors are widely used for the operation of these conveyor systems. In the logistics system, a large number of induction motors are used. These motors have a considerable distance from the power source side and have a low power factor. The installation position for the power factor compensation of the induction motor is very important. Since the voltage drop depends on the length of the line, it is an important parameter in capacitor capacity determination for power factor compensation. The capacity of the capacitors installed to compensate the power factor of the inductive load should be designed to the extent that self-excitation does not occur. In this study, we analyze the method of compensating the proper power factor considering the voltage drop and the installation position of the induction motor in the logistics system.

• 전기학회논문지
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• 제60권12호
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• pp.2206-2214
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• 2011

LDC(Line Drop Compensation) is widely used in controlling ULTC(Under Load Tap Changer) output voltage at distribution substation. However, LDC may experience some difficulties in voltage control due to renewable energy resources and distributed generations. Therefore, more advanced voltage control algorithm is necessary to deal with these problems. In this paper, a modified voltage control algorithm for ULTC and DG is suggested. ULTC is operated with the voltages measured at various points in distribution system and prevents overvoltage and undervoltage in the distribution feeders. Reactive power controller in DG compensates the voltage drop in each distribution feeders. By these algorithms, the voltage unbalance between feeders and voltage limit violation will be reduced and the voltage profile in each feeder will become more flat.

• Journal of Electrical Engineering and Technology
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• 제8권3호
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• pp.428-435
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• 2013

Flexible AC Transmission System (FACTS) application study on enhancing the flexibility of AC power system has continued to make progress. A thyristor-controlled series capacitor (TCSC) is a useful FACTS device that can control the power flow by adjusting line impedances and minimize the loss of power flow and voltage drop in a transmission system by adjusting line impedances. Reduced power flow loss leads to increased loadability, low system loss, and improved stability of the power system. This study proposes the optimal location and compensation rate method for TCSCs, by considering both the power system loss and voltage drop of transmission systems. The proposed method applies a multi-objective function consisting of a minimizing function for power flow loss and voltage drop. The effectiveness of the proposed method is demonstrated using IEEE 14- and a 30-bus system.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 하계학술대회 논문집 A
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• pp.289-291
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• 2001

This paper represents the application of the Static Var Compensator (SVC) on the electric railway power supply system to compensate for the voltage drop. The high reactance of line and a heavy train load consume a significant amount of the reactive power which results the voltage drop. This paper shows that the SVC is necessary for voltage compensation in the railway power supply system and verify effectiveness of the SVC through the simulation by using PSCAD/EMTDC. In this paper, the case studies were performed with the various line length and train loads.

• 전기학회논문지
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• 제58권4호
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• pp.763-769
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• 2009

A series voltage compensation(SVC) system is a power-electronics controller that can protect sensitive loads from disturbance in the supply system. Especially, voltage sags are considered the dominant disturbances affecting the power quality. This paper dealt with a system of off-line type voltage sag compensation by using a bi-directional DC/DC converter of environmentally friendly ultra-capacitor. This capacitor is attached to the DC link of SVC through the high-efficiency DC/DC converter in order to compensate the DC link voltage drop during short-term power interruption as voltage sags. Therefore, in this paper, a DC/DC converter to control high-efficiency energy of ultra-capacitor and voltage sag detection algorithm of off-line type SVC systems are newly introduced. According to the results of experimental of prototype system, it is verified that the proposed system has effectiveness of voltage sag compensation using an ultra-capacitor.

• 전기학회논문지
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• 제58권7호
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• pp.1263-1269
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• 2009

Stable and sustainable power supply means maintaining a certain level of power quality and service while securing energy resource and resolving environmental issues. Distributed generation (DG) has become an essential and indispensable element from environmental and energy security perspectives. It is known that voltage violation is the most important constraint for load variation and the maximum allowable DG. In distribution system, sending voltage from distribution substation is regulated by ULTC (Under Load Tap Changer) designed to maintain a predetermined voltage level. ULTC is controlled by LDC (Line Drop Compensation) method compensating line voltage drop for a varying load, and the sending voltage of ULTC calls for LDC parameters. The consequence is that the feasible LDC parameters considering variation of load and DG output are necessary. In this paper, we design each LDC parameters determining the sending voltage that can satisfy voltage level, decrease ULTC tap movement numbers, or increase DG introduction. Moreover, the maximum installable DG capacity based on each LDC parameters is estimated.

• 전력전자학회논문지
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• 제13권3호
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• pp.213-220
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• 2008

본 논문에서는 전압강하 보상모드를 갖는 직류 지하철 회생인버터 시스템을 제안하였다. 주 정류기에 고장이 발생하면 직류 지하철은 전원측으로부터 전력을 공급받지 못한다. 실제적으로 사고를 방지하기 위하여 변전소 측에 예비 정류기가 설치되어 있다. 이 논문에서는 전압강하 보상모드가 별도의 예비정류기를 대신하여 회생인버터에 부가된다. 제안된 인버터 시스템은 직류 가선 전압에서 발생한 회생에너지를 계통으로 반환한다. 부가하여, 인버터는 직류 지하철 시스템에서 사용된 전력변환장치에 의하여 야기된 고조파를 보상할 수 있다. 컴퓨터 시뮬레이션에 의해서 제안된 제어 알고리즘의 효용성을 설명하였다.

• 전기학회논문지
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• 제67권12호
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• pp.1723-1728
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• 2018

In order to investigate the voltage drop compensation effect of AT for domestic railway vehicle base, the parameters of AT voltage drop of railroad car base are Z3 (Impedance of feeder line), Xn ( Distance from railroad vehicle to AT to SS), and Dn (distance between both ATs of railway vehicle).In addition, when installed in a SSP for a railway vehicle base, there is no AT and feeder line in the railway vehicle base except for the SSP for the main line and the SSP for the railway vehicle base, so that if zero or ignored, the AC single-phase two- It can be confirmed that it becomes a form.

• Journal of Power Electronics
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• 제17권1호
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• pp.294-304
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• 2017

This paper proposes a point of common coupling (PCC) voltage compensation method for islanding microgrids using an improved power sharing control scheme among distributed generators (DGs) without communication. The PCC voltage compensation algorithm is implemented in the droop control scheme to reduce the PCC voltage deviation produced by the droop controller itself and the voltage drop on the line impedance. The control scheme of each individual DG unit is designed to use only locally measured feedback variables and an obtained line impedance to calculate the PCC voltage. Therefore, traditional voltage measurement devices installed at the PCC as well as communication between the PCC and the DGs are not required. The proposed control scheme can maintain the PCC voltage amplitude within an allowed range even to some extent assuming inaccurate line impedance parameters. In addition, it can achieve proper power sharing in islanding microgrids. Experimental results obtained under accurate and inaccurate line impedances are presented to show the performance of the proposed control scheme in islanding microgrids.

• Journal of Power Electronics
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• 제16권1호
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• pp.38-47
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• 2016

This paper presents DG based droop controlled parallel inverter systems with virtual impedance considering the unequal resistive-inductive combined line impedance condition. This causes a reactive power sharing error and dynamic performance degradation. Each of these drawbacks can be solved by adding the feedforward term of each line impedance voltage drop or injecting the virtual inductor. However, if the line impedances are high enough because of the long distance between the DG and the PCC or if the capacity of the system is large so that the output current is very large, this leads to a high virtual inductor voltage drop which causes reductions of the output voltage and power. Therefore, the line impedance voltage drops and the virtual inductor and resistor voltage drop compensation methods have been considered to solve these problems. The proposed method has been verified in comparison with the conventional droop method through PSIM simulation and low-scale experimental results.