• 전력전자학회:학술대회논문집
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• 전력전자학회 2019년도 전력전자학술대회
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• pp.334-335
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• 2019

본 논문은 전기철도용 전력보상장치로 사용되는 단상 3레벨 인버터를 제작하였으며, 단상 3레벨 인버터의 유 무효 전력제어기를 설계하였다. 단상 3레벨 인버터는 유 무효전력을 제어하기 위해 가상 동기좌표계 축 상에서 PI 제어기를 통해 전류제어를 수행한다. DC 링크 제어는 3레벨 인버터를 고려할 때 DC 링크 전압의 상단부와 하단부 전압의 평형상태를 유지하기 위해 제어하는 밸런싱 제어기를 포함한다. 10kVA 단상 3레벨 인버터 프로토타입을 설계하였으며, 안정한 유 무효전력제어 특성 실험 결과를 통해 단상 3레벨 인버터의 설계 및 제어 동작의 타당성을 검증하였다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2020년도 전력전자학술대회
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• pp.121-123
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• 2020

본 논문은 단상 3레벨 조건에서 unipolar 및 bipolar PWM의 구현 및 동작에 대해 서술하였으며, 교류전기철도용 전력보상장치의 병렬 운전 상황에서 unipolar PWM과 bipolar PWM에 따른 인터리빙 효과에 대해 비교하였다. 또한, unipolar PWM 조건에서 전력보상장치의 3병렬과 4병렬 시스템의 인터리빙 결과에 대해 비교하였다. 이를 통해 단상 unipolar PWM을 사용한 병렬 시스템의 인터리빙이라는 특수한 조건에서는 PWM 캐리어의 180° phase shift가 포함되는 2병렬 및 4병렬의 경우 마치 bipolar PWM처럼 동작하여 스위칭 리플의 저감효과가 기대한 결과보다 낮음을 확인하였다. 따라서 스위칭 리플의 저감 측면만을 고려한다면 전력보상장치의 병렬 시스템은 180° 캐리어가 포함된 4병렬 시스템보다 120° 캐리어를 사용하는 3병렬 시스템이 유리한 것을 확인하였다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2020년도 전력전자학술대회
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• pp.103-105
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• 2020

본 논문은 저압 배전선로의 전압 조정을 위해 상태관측기와 반복제어기를 적용한 무효전력 제어 알고리즘을 제안하였으며, 시뮬레이션 및 실험으로 이를 검증하였다. 무효전력 보상기는 단상 풀 브리지 인버터 구조이며 전압제어 시 DC 전압을 일정하게 유지하기 위한 전압 제어와 전류 제어기로 구성된다. DC 리플 보상방식은 상태관측기로 만들어낸 출력 값, DC 링크 리플 성분을 보상한 값을 전압제어기 피드백 성분으로 사용하여 전압을 일정하게 제어하였다. 무효전력을 안정하게 주입하기 위해 기본파 성분은 PI제어기로 제어하고 반복제어기를 PI제어기와 병렬로 연결하여 저차 고조파를 보상하였다. 반복 제어기는 동기 좌표계에서 구현됨에 따라 홀수파 고조파 성분을 제거하는 역할을 한다. 제안한 제어기법은 5kVar 단상 인버터 시스템으로 실험을 진행하였으며, 상태관측기와 반복제어기가 적용된 경우 THD가 9%에서 2%로 향상됨을 확인함으로써 제안한 알고리즘의 성능을 검증하였다.

• 전력전자학회논문지
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• 제22권1호
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• pp.82-88
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• 2017

This study proposes a new topology for the performance test of a valve consisting of a modular multilevel converter (MMC)-based static synchronous compensator (STATCOM). The conventional valve performance test equipment requires high-voltage AC source of several kV rating because the number of submodules to be tested in a valve should be at least six or eight. However, the power source of the proposed scheme is DC and not AC source. The DC power source voltage range of the proposed test circuit is from several volts to several tens of volts. Therefore, the size and cost for the performance test equipment can be reduced considerably compared with the conventional method. The proposed scheme satisfies the requirements of the IEC 62927 standard. Simulations are conducted for a valve of 50[MVA] MMC-based STATCOM. Experimental results with a scale-downed setup show the validity of the proposed performance test topology.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2001년도 추계학술대회 논문집
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• pp.97-101
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• 2001

Recently, as the development of industry, the nonlinear load becomes increased. Because of nonlinear load, the variation of source voltage is generated by the impedace of source side flowed harmonic currents. For blocking harmonic currents by nonlinear load, a series active power filter operates blocking resistance of harmonic currents. The value of blocking resistance shows ideal compensating characteristic out of theoretically infinite value. But the blocking resistance is limited by the problem of the system stability and the capacity of inverter. In this paper, the value of optimum blocking resistance is found by a simulation in the applied system. In the case of unbalanced source voltages, each relation of the blocking resistance is shown. It is proved that blocking resistance of series active power filter relates to a passive filter.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2004년도 전력전자학술대회 논문집(1)
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• pp.97-100
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• 2004

Our country has depended on fossil fuel very much according to the Increasing of the demand of the electric power. For instance, if the reduction and freezing caused by the warm gas in earth by the regulation of international environment happen in Korea it will bring about the result of weakness in industrial activity. As a result, it will cause many problems to compete an advanced country which wants to connect environment with the activity of industrial product in their country. The photovoltaic system outputs have peak about a half past 13 o'clock(before and after) mainly in a good weather. The output decreases rapidly from a half past 17 o'clock and PV output doesn't work at six o'clock before the sun rises. The outputs of PV system stops at that time. The frequent degree of harmonics in dwelling house which lots of people live has peak from 19 o'clock to 22 o'clock Harmonics mainly happens at least at night. In recent, many researches about power quality has been studying very hard in order to solve the question, the voltage fluctuating and harmonics as one compensator. In this paper, I suggest the algorithm which can increase the power quality as a rate of operation of this system. This algorithm proves to have effectiveness through computer simulation.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 하계학술대회 논문집 A
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• pp.25-27
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• 2002

This paper describes a new economical voltage sag and swell generator suitable to the evaluations of high power custom power devices such as DVR (Dynamic Voltage Restorer) and DSTATCOM (Distribution Static Compensator). This system was designed to generate the several power quality disturbances in MVA power ratings - voltage sag and swell, under voltage, over voltage and harmonic distortions. The basic idea for voltage sag and swell is to use the voltage drop across a reactor, while the voltage swell is to use the step-up transformer and the TCR(Thyristor Controlled Reactor). In this paper, two identical 3 phase TCRs and a step-up transformer with tap changer are used. Additional harmonic filters are added to reduce the voltage distortion when TCRs are operated. Simulation results are given for several cases of voltage sag and swell generations.

• 제어로봇시스템학회논문지
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• 제15권12호
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• pp.1163-1168
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• 2009

The power quality of wind energy becomes more and more important in connecting wind-farms to the grid, especially weak grid. This paper presents the simulation of a wind farm of a permanent magnet synchronous generator (PMSG) and a doubly fed induction generator (DFIG). Flicker mitigation is performed by using PMSG as a static synchronous compensator (STATCOM) to regulate the voltage at the point of common coupling (PCC). A benefit of the measure is that integrating two function of to control the active power flow and to reduce the voltage flicker in a wind farm. Simulation results show that controlling PMSG is an effective and economic measure in reducing the flicker during continuous operation of grid connected wind turbines regardless of short circuit capacity ratio, turbulence intensity and grid impedance angle.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 제39회 하계학술대회
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• pp.2251-2252
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• 2008

Recently, voltage sag from sudden increasing loads is also one of the major problems inside the utility network. In order to compensate the voltage sag problem, power compensation device systems could be a good solution method. In case of voltage sag, an energy source is needed to overcome the energy loss caused by the voltage sag. Superconducting Magnetic Energy Storage (SMES) is a very promising source of this energy due to its fast response of charging and discharging time. Before constructing the power electronic delivering system for the SMES, it is necessary to simulate the system to understand its behavior. Nowadays, a lot of devices have been developed to compensate voltage sag such as Dynamic Voltage Restorer (DVR), Distribution Static Compensator (D-STATCOM) and Uninterruptible Power Supply (UPS). In this paper, focus is given only on DVR system which will be simulated by using PSCAD/EMTDC software.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 제39회 하계학술대회
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• pp.83-84
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• 2008

Voltage fluctuation, also known as flicker, is a power quality problem caused by nonlinear loads like electric arc furnace. Since it is interpreted as a variation of the supplied electrical energy, it causes the residential customers to feel much annoyed visually through the lamps. Due to the statistical nature of IEC (International Electrotechnical Commission) short-term flicker severity index, Pst, it is not feasible to pre-evaluate the flicker level using the transient power system simulators such as Sim Power System in Matlab/Simulink. So this paper presents not only how to design the Matlab/Simulink IEC flickermeter to yield the Pst value, which considering electric distribution environments of South Korea, but also how to mitigate the voltage flicker at the Point of Common Coupling (PCC). In order to achieve this, the flicker mitigation efficiencies of various compensating devices, such as Static Var Compensator (SVC), STATCOM will be applied and compared. The simulated result demonstrates which compensating equipment is the most efficient method to mitigate the flicker phenomenon.