• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 하계학술대회 논문집 D
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• pp.1133-1136
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• 1997

This study established AC-DC system model including DC Link, and then BC Link equation was derived from the model. The equation was included into the calculational algorithm of AC system and solved using fast decoupled method. To minimize the line loss of AC-DC system, optimum theory was applied to the equations.

• 전력전자학회논문지
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• 제7권4호
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• pp.322-331
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• 2002

본 논문은 단상 반파 PWM 정류기와 3상 2-leg 인버터를 결합한 단상-삼상 컨버터 회로에서 전원전압의 센서를 제거하여 3상 유도전동기를 저가형으로 구동하는 방법을 제안하고자 한다. 전원전압의 센서를 제거하기 위해 전원 전류의 실측치와 제어기 내의 모델전류가 일치하도록 관측기를 구성하여 전원전압을 추정한다. 본 논문에서 제안한 기법을 사용할 경우 스위칭 소자와 센서 수를 줄이면서 직류전압 일정제어, 입력전류의 정현제어 및 단위 역률 제어가 가능하고 VVVF 교류전압을 얻을 수 있다는 장점이 있다. 3[Hp]의 3상 유도전동기의 V/f 구동에 적용한 실험결과로 제시된 알고리즘의 타당성을 검증한다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 A
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• pp.259-261
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• 2000

UPFC(Unified Power Flow Controller) consists of two voltage sourced converter(VSC)s inserted into AC system through series and parallel coupling transformer, where two VSCs are linked by capacitor at DC-side. Since VSC acts as an AC voltage source behind a reactance, where both magnitude and phase angle of the source are controllable, UPFC can be represented by the equation related to input-output relation of two VSCs. Voltage control of DC-link capacitor provides the path of real power flow between two VSCs. While UPFC is controlled for maintaining the given reference value in steady state, it should be controlled for damping power oscillation in dynamics. For such a control objective, the control strategy based on the energy function was proposed and has been shown to be effect and robust for damping power oscillation of power system. In this paper, UPFC model based on the VSC was analysed and applied to power-flow control and stability analysis. The control strategy based on the energy function is adopted for damping power oscillation of power system. The effectiveness of proposed control strategy was verified by simulation study

• Journal of Power Electronics
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• 제15권4호
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• pp.1026-1034
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• 2015

In this paper, a unified control strategy using the current space vector modulation (CSVM) technique is proposed and applied to a bidirectional three-phase DC/AC converter. The operation of the converter changes with the direction of the power flow. In the charging mode, it works as a buck type rectifier; and during the discharging mode, it operates as a boost type inverter, which makes it suitable as an interface between high voltage AC grids and low voltage energy storage devices. This topology has the following advantages: high conversion efficiency, high power factor at the grid side, tight control of the charging current and fast transition between the charging and discharging modes. The operating principle of the mode analysis, the gate signal generation, the general control strategy and the transition from a constant current (CC) to a constant voltage (CV) in the charging mode are discussed. The proposed control strategy has been validated by simulations and experimental results obtained with a 1kW laboratory prototype using supercapacitors as an energy storage device.

• Journal of Electrical Engineering and Technology
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• 제9권4호
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• pp.1202-1209
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• 2014

A novel integrated optimization method is proposed to combine both generation and transmission line expansion problem considering bus voltage limit. Most of the existing researches on the combined generation and transmission expansion planning cannot consider bus voltages and reactive power flow limits because they are mostly based on the DC power flow model. In this paper the AC power flow model and nonlinear constraints related to reactive power are simplified and modified to improve the computation time and convergence. The proposed method has been successfully applied to Garver's six-bus system which is one of the most frequently used small scale sample systems to verify the transmission expansion method.

• Journal of Electrical Engineering and Technology
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• 제5권1호
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• pp.103-115
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• 2010

This paper discusses a DC distribution system which has been supplied by external AC systems as well as local microturbine distributed generation system in order to demonstrate an overall solution to power quality issue. Based on the dynamic model of the converter, a design procedure has been presented. In this paper, the power flow control in DC distribution system has been achieved by network converters. A suitable control strategy for these converters has been proposed, too. They have DC voltage droop regulator and novel instantaneous power regulation scheme. Also, a novel control system has been proposed for MT converter. Several case studies have been studied and the simulation results show that DC distribution system including microturbine unit can provide the premium power quality using proposed methods.

• 전력전자학회논문지
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• 제23권5호
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• pp.299-304
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• 2018

An ideal circuit breaker should supply electric power to loads without losses in a conduction state and completely isolate the load from the power source by providing insulation strength in a break state. Fault current is relatively easy to break in an Alternating Current (AC) circuit breaker because the AC current becomes zero at every half cycle. However, fault current in DC circuit breaker (DCCB) should be reduced by generating a high arc voltage at the breaker contact point. Large fire may occur if the DCCB does not take sufficient arc voltage and allows the continuous flow of the arc fault current with high temperature. A semiconductor circuit breaker with a power electronic device has many advantages. These advantages include quick breaking time, lack of arc generation, and lower noise than mechanical circuit breakers. However, a large load capacity cannot be applied because of large conduction loss. An extinguishing technology of DCCB with polymeric positive temperature coefficient (PPTC) device is proposed and evaluated through experiments in this study to take advantage of low conduction loss of mechanical circuit breaker and arcless breaking characteristic of semiconductor devices.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 추계학술대회 논문집 학회본부
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• pp.432-434
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• 1997

In order to find the steady-state operating condition of HVDC system interacting with AC power system, the load flow calculation of AC/HVDC system is performed. For the calculation, each generating unit is modeled by an equivalent voltage source and coupled impedance. The rectifier station is modeled by a controlled DC voltage source. EMTP simulation of the AC/HVDC system is also performed to verify the result of the load flow calculation.

• Journal of Electrical Engineering and Technology
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• 제8권4호
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• pp.760-765
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• 2013

An Interline Power Flow Controller (IPFC) is a converter based controller which compensates and balance the power flow among multi-lines within the same corridor of the multi-line subsystem. The Interline Power Flow Controller consists of a voltage source converter based Flexible AC Transmission System (FACTS) controller for series compensation. The reactive voltage injected by individual Voltage Source Converter (VSC) can be controlled to regulate active power flow in the respective line in which one VSC regulates the DC voltage, the other one controls the reactive power flows in the lines by injecting series active voltage. In this paper, a circuit model for IPFC is developed and simulation of interline power flow controller is done using the proposed circuit model. Simulation is done using MATLAB Simulink and PSPICE. The results obtained by MATLAB are compared with the results obtained by PSPICE and compared with theoretical values.

• 대한기계학회논문집B
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• 제34권6호
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• pp.623-628
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• 2010

본 논문은 풍력에 의해 구동되는 압전효과 기반의 무구속 휴대용 전원 장치를 제안한다. 기계적 에너지를 효율적으로 변환하는 메커니즘의 한가지로 기계적 에너지를 전기적 에너지로 변환하는 압전효과를 이용하는 방법이 있다. 압전효과는 주기적으로 변하는 응력을 필요로 하지만, 자연 바람은 거의 일정한 속도를 보이거나, 변화하더라도 매우 느리고 불규칙적인 주파수를 갖기 때문에, 효과적으로 전기적 에너지를 얻어내기 힘들다. 본 연구에서는 바람을 프로펠러에 통과시켜, 손쉽게 주기적으로 변하는 응력을 만들어내고, 이를 압전외팔보에 전달하여 효율적으로 에너지를 변환하였다. 본 연구결과는 유비쿼터스 센서네트워크 시스템에 대한 에너지 공급의 실질적인 해결책이 되리라고 기대된다.