• 대한전기학회논문지:전력기술부문A
• /
• 제52권12호
• /
• pp.705-712
• /
• 2003

In this paper, we propose new unified methodologies of reliability and its cost evaluation in power distribution systems. The unified method means that the proposed reliability approaches consider both conventional evaluation factor, i.e. sustained interruptions and additional ones, i.e. momentary interruptions and voltage sags. Because the three voltage quality phenomena generally originate from the outages on distribution systems, the basic and additional reliability indices are summarized considering the fault clearing mechanism. The proposed unified method is divided into the reliability evaluation for calculating the reliability indices and reliability cost evaluation for assessing the damage of customer. The analytic and probabilistic methodologies are presented for each unified reliability and its cost evaluation. The time sequential Monte Carlo technique is used for the probabilistic method. The proposed DVL(Demand Varying Load) model is added to the reliability cost evaluation substituting the average load model. The proposed methods are tested using the modified RBTS(Roy Billinton Test System) form and historical reliability data of KEPCO(Korea Electric Power Corporation) system. The daily load profile of the each customer type in domestic are gathered for the DVL model. Through the case studies, it is verified that the proposed methods can be effectively applied to the distribution systems for more detail reliability assessment than conventional approaches.

• 전기학회논문지
• /
• 제59권9호
• /
• pp.1523-1529
• /
• 2010

This paper describes the distribution power system econimical PQMS(Power quality monitoring system) of Utility. Recently, the korea power quality standard has been established based on the IEC Std. By IEC Std., the power quality assessment point is measured in PCC(Point of common coupling). In this case, the utility has to construct PQM system in all customer PCC point and the PQ meter cost would be very high in order to acquire the suitable data. Also the distribution system would be encounter the communication overload problem due to the huge data. Accordingly the utilities could not apply to PQM system in the distribution power system by the cost and communication problem. In this paper, the proposed economical PQMS has the voltage and current signal reiteration function and FFT operation function is transferred the server. Also the voltage and current measurement channels are minimized by a classified substation construction.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2011년도 제42회 하계학술대회
• /
• pp.418-419
• /
• 2011

Recently, the korea power quality standard has been established based on the IEC Std. By IEC Std., the power quality assessment point is measured in PCC. In this case, the utility has to construct PQM system in all customer PCC point and the PQ meter cost would be very high in order to acquire the suitable data. Accordingly the utilities could not apply to PQM system in the distribution power system by the cost and communication problem. In this paper, the proposed economical PQMS(Power quality monitoring system) of Utility.

• Journal of Electrical Engineering and Technology
• /
• 제10권3호
• /
• pp.1015-1024
• /
• 2015

This paper introduces a low cost, high efficiency, high performance three-phase unified power quality conditioner (UPQC) by using four-switch three-phase inverters (FSTPIs) and an extra capacitor in the shunt active power filter (APF) side of the UPQC. In the proposed UPQC, both shunt and series APFs are developed by using FSTPIs so that the number of switching devices is reduced from twelve to eight devices. In addition, by inserting an additional capacitor in series with the shunt APF, the DC-link voltage in the proposed UPQC can also be greatly reduced. As a result, the system cost and power loss of the proposed UPQC is significantly minimized thanks to the use of a smaller number of power switches with a lower rating voltage without degrading the compensation performance of the UPQC. Design of passive components for the proposed UPQC to achieve a good performance is presented in detail. In addition, comparisons on power loss, overall system efficiency, compensation performance between the proposed UPQC and the traditional one are also determined in this paper. Simulation and experimental studies are performed to verify the validity of the proposed topology.

• 예술인문사회 융합 멀티미디어 논문지
• /
• 제7권1호
• /
• pp.35-44
• /
• 2017

본 연구에서는 항공운송산업에서 기내서비스와 가성비가 고객의 만족과 추천에 미치는 영향에 있어서 대형항공사 브랜드 파워의 조절적인 영향을 살펴보고자 한다. 연구결과, 첫째, 고객만족에 있어서 브랜드 파워가 높은 대형항공사는 가성비뿐 아니라 다른 기내서비스 속성들도 모두 영향을 주는 것으로 나타났다. 그러나 브랜드 파워가 낮은 대형항공사는 다른 기내 서비스 속성에 비해 가성비의 영향이 무엇보다 더 큰 것으로 나타났다. 둘째, 고객의 추천에 있어서도 브랜드 파워가 높은 대형항공사들은 가성비뿐만 아니라 좌석이나 승무원서비스도 중요하게 고려하고 있는 반면에 브랜드 파워가 낮은 대형항공사들은 좌석이나 승무원서비스보다 가성비를 훨씬 더 중요하게 여기는 것으로 나타났다. 따라서 브랜드 파워가 낮은 대형항공사는 저가항공사의 저가격파괴 전략에 맞대응하는 노력이 필요하고, 브랜드 파워가 높은 대형항공사는 가성비뿐만 아니라 다양한 기내서비스 속성을 모두 향상시키는 존속적 혁신전략을 추구하는 것이 필요하다고 할 수 있다.

• 한국재료학회지
• /
• 제25권9호
• /
• pp.487-491
• /
• 2015

In photovoltaic power generation where minority carrier generation via light absorption is competing against minority carrier recombination, the substrate thickness and material quality are interdependent, and appropriate combination of the two variables is important in obtaining the maximum output power generation. Medici, a two-dimensional semiconductor device simulation tool, is used to investigate the interdependency in relation to the maximum power output in front-lit Si solar cells. Qualitatively, the results indicate that a high quality substrate must be thick and that a low quality substrate must be thin in order to achieve the maximum power generation in the respective materials. The dividing point is $70{\mu}m/5{\times}10^{-6}sec$. That is, for materials with a minority carrier recombination lifetime longer than $5{\times}10^{-6}sec$, the substrate must be thicker than $70{\mu}m$, while for materials with a lifetime shorter than $5{\times}10^{-6}sec$, the substrate must be thinner than $70{\mu}m$. In substrate fabrication, the thinner the wafer, the lower the cost of material, but the higher the cost of wafer fabrication. Thus, the optimum thickness/lifetime combinations are defined in this study along with the substrate cost considerations as part of the factors to be considered in material selection.

• 품질경영학회지
• /
• 제45권4호
• /
• pp.917-932
• /
• 2017

Purpose: This study aims to identify the most important quality construct among system quality, information quality, and service quality, which are integrated as the second-order construct; perceived quality, and to investigate the relationship between perceived quality, learner satisfaction, learner enjoyment, switching cost, and learner loyalty. Method: Data were collected from learners who had taken e-learning course, and the analysis was conducted in two phases. The first phase described demographic characteristics using SPSS23.0; the second phase involved the second order CFA of perceived quality and the analysis of measurement model and structural model through AMOS 23.0. Results: (1) The explanatory power of system quality, information quality, and service quality appears to be almost equal; (2) Perceived quality positively influences only both learner satisfaction and switching cost; (3) Only learner satisfaction positively influences learner loyalty and switching cost negatively influences learner loyalty. Conclusion: Learner enjoyment does not play an important role in this study, which could be extrapolated in regard to the characteristics of sample. The respondents are over high school students, who emphasize on the acquisition of knowledge rather than enjoyment. Additionally, the result implies that respondents show low loyalty in the high switching cost.

• Journal of Power Electronics
• /
• 제7권3호
• /
• pp.257-264
• /
• 2007

Active power filters can be cost-effective for use in practical systems with the insertion of a few passive elements in shunt or series configuration. The resulting hybrid filters can be designed to provide dominant lower order harmonic elimination and reactive power support by the passive elements so that the burden on the active filter counterpart is reduced. In this paper, the rate reduction in the shunt active filter is estimated when it is connected in parallel with suitable passive tuned harmonic filters. The active filtering system is based on an appropriate control scheme. The simulation and the experimental results of the shunt active filter, along with the estimated value of reduction in rating, show that the hybrid shunt filtering system is quite effective in compensating for the harmonics and reactive power, in addition to being cost-effective.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
• /
• 제5B권4호
• /
• pp.374-381
• /
• 2005

The ability to provide quality power has become a significant issue in power systems. The main causes of poor power quality are harmonic currents, poor power factor, supply-voltage variations, etc. A technique of achieving both active current distortion compensation, power factor correction and also mitigating the supply-voltage variation (sag or swell) at the load side is presented in this paper. The operation and rating issues of the proposed Single-phase Unified Power Quality Conditioner are also highlighted. To reduce the total cost while simultaneously increasing the performance, the system is fully digitally controlled using the fixed-point TMS320F240 digital signal processor. The performances of the UPQC, which is composed by shunt and series PWM controlled-converters, have been verified on a laboratory prototype.

• 대한전기학회논문지:전력기술부문A
• /
• 제52권1호
• /
• pp.9-16
• /
• 2003

In this paper, we propose a reliability evaluation method considering the momentary interruptions of power distribution systems. The results of research are concentrated on two parts. One is the analytic and probabilistic reliability evaluation of power distribution system considering the momentary interruptions and the other is the reliability cost evaluation that unifies the cost of sustained and momentary interruptions. This proposed reliability cost evaluation methodology is also divided into the analytic and probabilistic approach and the time sequential Monte Carlo method is used for the probabilistic method. The proposed methods are tested using the modified RBTS (Roy Billinton Test System) form and historical reliability data of KEPCO (Korea Electric Power Corporation) system. Through the case studies, it is verified that the proposed reliability evaluation and its cost/worth assessment methodologies can be applied to the actual reliability studies.