• 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.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2007년도 추계학술대회 논문집
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• pp.225-229
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• 2007

The output voltage of a synchronous generator is regulated constantly by field current control of excitation system. Synchronous generator exciter has two type, first one is Drop control type by thyristor and second one is exciter current control type through power output by PWM control. Control method of the second one prevails, but when the power devices have a breakdown, output voltage of the generator rises rapidly. This exciter must have a protection circuit and system is complicated, so reliability is poor Excitation control type which is drop control type control only 10% of the power, so it can be improved precision. When a trouble come to the controller, output voltage of a generator don't rise excessively and the voltage rise about 10%, so it has a excellent reliability. This paper prove stability of the digital AVR.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 하계학술대회 논문집 F
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• pp.1974-1977
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• 1997

오늘날 철강 냉간압연의 응용분야에서는 고성능의 장력제어와 높은 신뢰도, 역률 개선, 공장의 생산성 향상 등을 요구하고 있다. 기존의 직류전동기를 대체하는 가변속 교류전동기 구동시스템과 고주파 PWM, 그리고 높은 역률을 보장하는 PWM 컨버터에 의해 이러한 요구사항들은 만족될 수 있다. 이 논문에서는 위에서 언급된 제어요건을 보장하는 철강 생산 설비용 1MVA급 압연시스템을 설명한다. 본 시스템은 하나의 ac/dc PWM 컨버터와 각각 700kw 유도전동기를 구동하는 두대의 PWM 인버터로 구성되어 있다. 제어 알고리듬은 TMS320C40 디지탈 신호처리 프로세서(이하 DSP) 시스템을 이용하여 구현하였다.

• 동아시아경상학회지
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• 제5권1호
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• pp.10-26
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• 2017

This paper explains the concept of Economic Value Added (EVA) that is gaining popularity in India. We also examine whether EVA is a superior performance measure, both for corporate disclosure and for internal governance. Of late, companies in India have started focusing on shareholders wealth creation by adopting value-based models for measuring shareholder value that helps to align managerial decision-making with the firm preferences. In recent years, the EVA framework is gradually replacing the 'traditional' measures of financial performance on account of its robustness and its immunity from 'creative' accounting. Even though some leading Indian companies have already joined the band wagon of their American counterparts in adapting the EVA-based corporate performance systems, many other are hesitating as there is no strong evidence that the EVA system works in India. Till now, EVA disclosures are "not mandatory for the Indian companies." Also, we examine the value-creation strategies of selected Indian companies by analyzing whether EVA better represents the market-value of these companies in comparison to conventional performance measures. The study indicates that "there is no strong evidence to support Stern Stewart's claim that EVA is superior to the traditional performance measures in its association with MVA." As part of this study, we have also extensively surveyed the EVA disclosures in the Annual Reports made by the same sample group of 500 corporations from India.

• Journal of Electrical Engineering and Technology
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• 제13권4호
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• pp.1425-1437
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• 2018

In this paper, a methodology was proposed to reduce the electrical level and spatial size of the smart grid with distributed generations (DGs) to a scale in which the electrical phenomena and control strategies for disturbances on the smart grid could be safely and freely experimented and observed. Based on the design methodology, a micro smart grid simulator with a substation transformer capacity of 190VA, voltage level of 19V, maximum breaking current of 20A and size of $2{\times}2m^2$ was designed by reducing the substation transformer capacity of 45MVA, voltage level of 23kV and area of $2{\times}2km^2$ of the smart grid to over one thousandth, and also reducing the maximum breaking current of 12kA of the smart grid to 1/600. It was verified that the proposed design methodology and designed micro smart grid simulator were very effective by identifying how all of the fault currents are limited to within the maximum breaking current of 20A, and by confirming that the maximum error between the fault currents obtained from the fault analysis method and the simulation method is within 1.8% through the EMTP-RV simulation results to the micro smart grid simulator model.

• Journal of Electrical Engineering and Technology
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• 제5권1호
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• pp.16-20
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• 2010

Recently, the smart grid has become a hot issue and interest in related power sources have increased accordingly. The implementation of a smart grid can enable many generation resources to be linked to the power system, including small-scale reactors for the purpose of co-generation. Research on small-scale reactors is being carried out all over the world. Similarly, Korea is also conducting research on multi-purpose regional energy systems using nuclear energy. This paper proposes a real-time data acquisition and analysis system for small-scale reactors, and is known as the REX-10 (Regional Energy rX 10 MVA). This analysis requires real-time simulations for the power system since it needs data communication with a remote REX-10. A RTDS (Real Time Digital Simulator) has been used for the simulation, and a SCADA/HMI system interfaced with the RTDS is proposed for the purpose of monitoring and control of the regional energy system.

• 융합경영연구
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• 제4권4호
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• pp.1-16
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• 2016

In today's knowledge-based economy, measurement and disclosure (M&D) of intellectual capital (IC) are crucial for enhancing business performance and competitiveness. In the global world, M&D of IC are useful means to keep investors well-informed and reduce information asymmetry. At present, very few leading corporations in India have disclosed IC information on a 'voluntary' basis. Traditional accounting practices, therefore, will need to assimilate innovations that seek to meaningfully represent the 'true-value' of the intangible assets of the company. This is an exploratory study of IC M&D by 8 Indian companies over 5-year period, using 'content' analysis and market-value-added (MVA) as research methodologies. The annual reports of companies were collected from their respective websites. As part of present study, various statistical techniques have been used to analyze the data. The findings show that the sample companies, on an average, reported a positive value of IC, along with wide-disparity, low-level of ICD. Unfortunately, the omission of IC information may adversely influence the quality of decisions made by shareholders, or lead to material misstatements. Finally, we recommend to "the international accounting bodies, to take the lead by establishing a harmonized ICD standard, and provide guidance to the big listed-companies for proper measurement and disclosure of IC, both for internal and external users."

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2004년도 ICCAS
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• pp.710-715
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• 2004

The design problem of manufacturing system is addressed, adopting the closed queueing network model with multiple loops and re-entrant flows. The entire design problem is divided into two hierarchical sub-problems of (1) determining the station configuration and (2) optimizing the lot constitution; then they are tackled by neighbor search algorithm (NSA) and greedy mean value analysis (GMVA), respectively. Unlike the conventional MVA concerning multi-class closed queueing networks, the GMVA doesn't stick to a fixed lot proportion; rather it tries to find the optimal balance. The NSA, on the other hand, improves the object function value by altering the station configuration successively with its superior neighbor. The moderate time complexity, presented in big-${o}$ notation, enables us to apply the method even to the large-size practical cases, and the CPU time of an enlarged problem can be approximated by the same equation. The validity of our analytic approach is backed up by simulation studies with a widespread simulation package.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2016년도 전력전자학술대회 논문집
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• pp.473-474
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• 2016

최근 신재생에너지의 보급 정책으로 인해 태양광 또는 풍력과 같은 신재생에너지가 전체 전력 계통에서 차지하는 비율이 증가되고 있는 실정이다. 그러나 신재생에너지는 변동 적이기 때문에 계통의 안정성을 저해하는 원인이 될 수 있다. 이에 따라 각 나라에서는 계통 안정성을 위한 기능들을 요구하고 있으며, 그 요구는 점차 강화되고 있다. 이와 같이 신재생에너지 비율의 증가로 인해 계통 안정성에 대한 문제가 강조되고 있지만, 태양광 분산 발전 시스템의 경우에는 일사량에 의존하여 운전하기 때문에 일사량이 낮거나 야간에는 계통 안정성을 위한 기능을 수행하지 못하는 단점이 있다. 본 논문에서는 일사량이 낮거나 야간에도 계통 안정화를 위해 무효전력 지원이 가능한 확장된 무효전력 운전(EF-RPO: Extended feed-in Reactive Power Operation)방법의 제어 전략을 제안하며, 제안한 방식은 1MVA 계통 연계형 인버터의 제작과 실험을 통해 검증하였다.

• 한국초전도ㆍ저온공학회논문지
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• 제5권1호
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• pp.107-110
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• 2003

High Temperature Superconductor (HTS) transmission cable can carry more than 2 to 5 times higher electricity and also obtain substantially lower transmission losses than conventional cables. Liquid nitrogen is to be used to cool the HTS power cable and its cost is much cheaper than the liquid helium used for the cooling of metal superconducting wire. In Korea the HTS power cable development project has been ongoing since July, 2001 with the basic specifications of 22.9kV, 50MVA and told dielectric type as the first 3-year stage. The cryogenic system of the HTS cable is composed of HTS cable cryostat termination and refrigeration system. Termination of HTS cable is a connecting part between copper electrical cable at room temperature and HTS cable at liquid nitrogen temperature. In order to design the termination cryostat, it is required that the conduction heat leak and Joule heating on the current lead be reduced, the cryostat be insulated electrically and good vacuum insulation be maintained during long time operation. Heat loads calculations on the copper current lead have been performed by analytical and numerical method and the feasibility study fer the other candidate materials has also been executed.