• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.22 no.10
• /
• pp.41-48
• /
• 2008

This paper proposes a three-phase Z-source dynamic voltage restorer (Z-DVR) to mitigate the voltage sag for the critical loads. The proposed system is composed of passive filter and Z-source topology inverter. As an ESS(Energy Storage System) of the proposed system is employed the Proton Exchange Membrane Fuel Cells (PEMFC). To calculate and control the harmonics and compensation voltage, $i_{d}-i_{q}$ theory in dq rotating reference frame and PI controller are used. In case that three-phase voltage sags occurred, a PSIM simulation was done for the performance comparison of the conventional method employed battery stacks and proposed method. As a result, considering the voltage compensation performance, each method was nearly similar. Also, the compensation performance and the %THD(%Total Harmonic Distortion) result under the various source voltage conditions (sag or swell) were presented and discussed to show the performance of the proposed system.

• KIEE International Transactions on Power Engineering
• /
• v.11A no.4
• /
• pp.1-8
• /
• 2001

This paper presents a discrete wavelet transform approach for detecting voltage sags initialized by fault conditions and starting of larger motors. The proposed technique is based on utilizing the summation value of D1(at scale 1) coefficients in multiresolution analysis(MRA) based on the discrete wavelet transform. In this paper, the proposed technique is tested under various cases of voltage sags. It is shown that the voltage sag detection technique based on the wavelet transform is a satisfactory and reliable method for detecting voltage sags in power quality disturbance analysis.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.62 no.11
• /
• pp.1505-1510
• /
• 2013

This paper presents a method for determining the optimal placement of distributed generation units considering voltage sags. In general, the existing methods for distributed generation placement do not consider power quality problems such as voltage sags. In this paper, a novel method based on both genetic algorithm and voltage sag assessment is proposed for determining the placement of distributed generation unit. In the proposed method, the optimal placement is determined to minimize voltage sag effects and system losses.

• Proceedings of the KIPE Conference
• /
• 2011.11a
• /
• pp.219-220
• /
• 2011

In this paper, 300[W] class boost type single phase inverter system which can compensate voltage sag was designed. If the voltage sag has appeared in input voltage, the boost converter would be operated to compensate it. The system is designed for that the THD of ouput voltage is below 5[%] and steady state error of output voltage is below 1[%]. The system was verified through experiments.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.29 no.1
• /
• pp.37-46
• /
• 2015

In order to charge EVs, they have to be connected to distribution system. Therefore, if unprecedented numbers of EVs are connected to power systems, it could result in deterioration of power quality, overload, and other system problems. In this paper, the effects of voltage sag on the distribution system due to the connection of EVs is evaluated by considering related field data of Republic of Korea such as the number of gasoline-fueled vehicles, seasonal load of power system and the monthly and daily real-time traffic volume. The distribution system and EVs are modeled using the Electro Magnetic Transients Program (EMTP).

• Proceedings of the KIPE Conference
• /
• 2001.10a
• /
• pp.502-507
• /
• 2001

This paper proposes a novel detection algorithm of faulted voltages under the unbalanced condition. To quantify the standard of unbalance under the faulted conditions, the 3-phase unbalanced voltages are decomposed into two balanced 3-phase symmetrical components of the positive and negative sequence voltages, which is defined by the magnitude factor (MF) and unbalance factor (MF). It is analyzed that MF and UF values are given as the dc constant values even though unbalance condition. This paper also proposes the control scheme of the instantaneous voltage sag corrector based on this detection algorithm. The validity of the proposed algorithm is verified through the EMTDC simulation and experiments.

• Proceedings of the KIEE Conference
• /
• 2011.07a
• /
• pp.1330-1331
• /
• 2011

The on-grid distributed power system operated antiislanding due to the momently voltage sag of the power system, fault and etc. According to the 'Dispersed Generations in Distribution Systems Connection Technology Standard', the utilizable time ratio of PCS is low because of being put into in the steady state of the power system after 5 minutes. In this paper, the output characteristic is optimized with the hybrid system consisting of the wind system and PV system. And energy of hybrid system is supplied to the power system. Also, DVR function was applied to PCS to compensate the voltage sag frequently happening for a power system. The control performance of the proposed hybrid PCS is analyzed and simulated using PSIM to validate the system performace.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
• /
• 2002.11a
• /
• pp.139-145
• /
• 2002

Recently, power-electronics equipments or machine that microprocessor is included and computers have been installed continuously in industrial process or region of electronics customer. So concern for power quality, especially sags has been increased. Because those equipments are very sensitive to sags. The sag is phenomenon that magnitude of load voltage temporarily decreases because of power system fault. If a certain equipment in industrial process have any trouble result from sag, it can cause utility to be charged for enormous economics loss. Therefore it need to analyze the characteristic of sag and then mitigation method for sags in distribution system in odor to increase reliability. This paper gives an overview of sags characteristic due to short circuit fault in distribution system and after a general discussion of the various forms mitigation, gives a sags mitigation method with concentrating on changing the distribution system like spot network, on-site generation.

• Proceedings of the KIPE Conference
• /
• 2009.11a
• /
• pp.290-292
• /
• 2009

본 연구에서는 배전계통의 전압 및 전류 품질을 통합적으로 개선할 수 있는 수동필터 연계형 Z-소스 전력품질 보상 시스템을 제안한다. 제안된 시스템의 주안점은 전압의 변동을 보상하는 직렬형 인버터와 고조파를 보상하는 병렬형 인버터에 각각 Z-소스 토폴로지를 적용하는 것이다. 전압 sag와 swell이 발생하는 과도상태에서 제안된 시스템의 성능을 검증하기 위하여 PSIM시뮬레이션을 하여 타당성을 입증하였다.

• Proceedings of the KIPE Conference
• /
• 2009.11a
• /
• pp.146-148
• /
• 2009

본 논문에서는 새로운 Quasi Z-소스 순간전압 Sag-Swell 보상기를 제안한다. 제안된 시스템은 Quasi Z-소스 교류-교류 컨버터를 기반으로 하며, 입력단과 출력단이 공통 접지이며, 연속적인 입력전류로 동작하는 특징을 가지고 있다. 또한 평균치 제어 기법의 단점을 보완하기 위한 방법으로 실시간 샘플링 검출기법을 이용한 알고리즘을 적용하여 샘플링 구간 동안 평균치 값을 계산해서 순간전압 변동을 검출해 내는 기법을 적용했다.