• Geomechanics and Engineering
• /
• 제11권2호
• /
• pp.211-234
• /
• 2016

A total of 99 full-scale field load tests at 22 sites were compiled for this study to elucidate several issues related to the load-displacement behaviour of belled piers under axial uplift loading, including (1) interpretation criteria to define various elastic, inelastic, and "failure" states for each load test from the load-displacement curve; (2) generalized correlations among these states and determinations to the predicted ultimate uplift resistances; (3) uncertainty in the resistance model factor statistics required for reliability-based ultimate limit state (ULS) design; (4) uncertainty associated with the normalized load-displacement curves and the resulting model factor statistics required for reliability-based serviceability limit state (SLS) design; and (5) variations of the combined ULS and SLS model factor statistics for reliability-based limit state designs. The approaches discussed in this study are practical and grounded realistically on the load tests of belled piers with minimal assumptions. The results on the characterization and uncertainty of uplift load-displacement behaviour of belled piers could be served as to extend the early contributions for reliability-based ULS and SLS designs.

• Journal of Electrical Engineering and Technology
• /
• 제11권2호
• /
• pp.300-308
• /
• 2016

Application of demand-side resources to automatic generation control (AGC) has a great significance for improving the dynamic control performance of power system frequency regulation. This paper investigates the possibility of providing regulation services by demand-side energy storage in electric vehicle battery swapping stations (BSS). An interaction framework, namely station-to-grid (S2G), is presented to integrate BSS energy storage into power grid for giving benefits to frequency regulation. The BSS can be regarded as a lumped battery energy storage station through S2G framework. A supplementary AGC method using demand-side BSS energy storage is developed considering the vehicle user demand of battery swapping. The effects to the AGC performance are evaluated through simulations by using a two-area interconnected power grid model with step and random load disturbance. The results show that the demand-side BSS can significantly suppress the frequency deviation and tie-line power fluctuations.

• Journal of Electrical Engineering and Technology
• /
• 제8권6호
• /
• pp.1605-1614
• /
• 2013

This paper presents a probabilistic methodology for small signal stability analysis of power system with correlated wind sources. The approach considers not only the stochastic characteristics of wind speeds which are treated as random variables with Weibull distributions, while also the wind speed spatial correlations which are characterized by a correlation matrix. The approach based on the 2m+1 point estimate method and Cornish Fisher expansion, the orthogonal transformation technique is used to deal with the correlation of wind farms. A case study is carried out on IEEE New England system and the probabilistic indexes for eigenvalue analysis are computed from the statistical processing of the obtained results. The accuracy and efficiency of the proposed method are confirmed by comparing with the results of Monte Carlo simulation. The numerical results indicate that the proposed method can actually capture the probabilistic characteristics of mode properties of the power systems with correlated wind sources and the consideration of spatial correlation has influence on the probability of system small signal stability.

• Nuclear Engineering and Technology
• /
• 제52권8호
• /
• pp.1661-1668
• /
• 2020

A physical protection system (PPS) is used for the protection of critical facilities. This paper proposes a structure analytic hierarchy approach (SAHA) for the hierarchical evaluation of the PPS effectiveness in critical infrastructure. SAHA is based on the traditional analysis methods "estimate of adversary sequence interruption, EASI". A community algorithm is used in the building of the SAHA model. SAHA is applied to cluster the associated protection elements for the topological design of complicated PPS with graphical vertexes equivalent to protection elements.

• 천문학회보
• /
• 제36권2호
• /
• pp.102.1-102.1
• /
• 2011

In this study we use three-dimensional magnetohydrodynamic simulations to investigate how the dynamic state of emerging magnetic field is related to the twist of field lines. Emerging magnetic field forms a magnetic structure on the Sun where various kinds of activity such as solar flares, jets, and coronal mass ejections are observed. To understand the physical mechanism for producing such activity, we have to know the dynamic nature of this structure. Since flares are the manifestation of rapidly dissipating electric current in the corona, we also investigate the distribution of current density inside the structure and examine how it depends on the field-line twist. To demonstrate the dynamic structure of emerging magnetic field, we focus on the factors characterizing the geometric property and stratification of emerging magnetic field, such as the curvature of field line and the scale height of field strength. These two factors show that emerging field forms a two-part structure in which the central part is close to a force-free state while the outer marginal part is in a fairly dynamic state where magnetic pressure force is dominant. We discuss how the field-line twist affects the two-part structure and also explain a possible relation between electric current structure and sigmoid observed in a preflare phase.

• 전력전자학회논문지
• /
• 제12권4호
• /
• pp.324-331
• /
• 2007

본 연구에서는 슬라이딩 모드 관측기를 사용한 리튬 배터리의 충전량 예측방법에 대해서 논의한다. 배터리의 비선형 회로 모델링 기법이 소개되고 슬라이딩 모드 관측기를 사용한 충전량 예측기의 설계 방법이 논의된다. 기존의 복잡한 배터리 모델링 방법 대신, 단순화된 저항-커패시터 모델링 방법이 본 연구에서 사용되었다. 단순화된 모델에 의해 발생되는 오차나 불확실성은 슬라이딩 모드 관측기에 의해 보상되었다. 슬라이딩 모드 관측기의 구조는 단순하지만, 모델링 에러나 외란에 대해서 강인한 특성을 보여준다. 제안된 제어기의 수렴성은 등가제어 방법에 의해서 증명되었다. 제안된 시스템의 성능은 UDDS (Urban Dynamometer Driving Schedule) 시험에 의해서 증명되었다. 시험 결과 제안된 시스템은 실제 주행 환경에서도 우수한 추적 성능을 보여주었다.

• 로봇학회논문지
• /
• 제16권1호
• /
• pp.41-48
• /
• 2021

In this paper, we review papers which report to the all solid-state electroactive polymer-based tunable lens. Since electroactive polymer-based tunable lenses change their focal length by responding to electric stimuli, it can be minimized the size and weight of optical modules. Thus, it has been received attention in the robot, mobile device and display industry. The all solid-state electroactive polymer-based tunable lenses can be classified into two categories depending on the classification of materials: ionic electroactive polymer-based lenses and non-ionic electroactive polymer-based lenses. Most of the ionic electroactive polymer-based tunable lenses are fabricated with ionic polymer-metal composite. So, the ionic electroactive polymer-based tunable lenses can be operated under low electric voltage. But small force, slow recovery time and environmental limitation for operation has been pointed to the disadvantage of the lenses. The non-ionic electroactive polymer-based tunable lenses are classified again into two categories: dielectric polymer-based tunable lenses and polyvinylchloride gel-based tunable lenses. The advantage of the dielectric polymer-based tunable lenses is fast response to electric stimuli. But the essential flexible electrodes degrade performance of the lens. Polyvinylchloride gel-based tunable lens has reported impressive performance without flexible electrodes.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2011년도 제42회 하계학술대회
• /
• pp.728-729
• /
• 2011

Smart Power Grid (SPG) 분야 실증 플랜드 구축과제는 스마트그리드 플랫폼 기반에서 송전, 변전, 배전 분야의 전력기기와 운영 시스템을 통합해 전력망을 효율적, 지능적으로 운전할 수 있는지를 실증하는 프로젝트이다. 현재 스마트그리드 실증단지에는 송전계통의 무효전력관리시스템, 위성망을 이용한 전압위상관리시스템, 송전선로용 볼센서 등을 다루는 지능형 송전, IEC 61850 기반의 IED를 채용한 변전소 자동화, 전기품질 온라인 감시기능을 갖는 지능형 단말장치를 적용 및 변전소 SCADA 기능을 통합 구현하는 배전지능화가 설치되어 있다.

• Journal of Electrical Engineering and Technology
• /
• 제10권3호
• /
• pp.719-728
• /
• 2015

This paper presents the results of field tests on Voltage Management System (VMS) using hybrid voltage control, which utilizes coordinated controls of various reactive power resources such as generators, FACTS and switched shunt devices to regulate the pilot bus voltage in a voltage control area. It also includes the results of performance test on RTDS-based test bed in order to validate the VMS before installing it in Jeju power system. The main purpose of the system is adequately to regulate the reactive power reserve of key generators in a normal condition with coordination of discrete shunt devices such as condensers and reactors so that the reserves can avoid voltage collapse in emergency state in Jeju system. Field tests in the automatic mode of VMS operation are included in steady-states and transient states. Finally, by the successful operation of VMS in Jeju power system, the VMS is proved to effectively control system voltage profiles in steady-state condition, increase system MVAR reserves and improve system reliability for pre- and post-contingency.

• 한국산학기술학회논문지
• /
• 제12권11호
• /
• pp.5156-5163
• /
• 2011

전기 구동 이륜차는 우수한 연비 및 환경공해 능력 때문에 가장 유망한 미래 교통수단 중의 하나이다. 실제 전기 이륜차 시제품을 제작하기 전에 신뢰성이 확보된 시뮬레이션 프로그램을 통하여 전기 이륜차의 설계인자 최적화와 동력원의 능력을 평가할 필요가 있다. 이 같은 과정을 통하여 전기 이륜차 시스템 설계 과정에서의 소요비용을 줄일 수 있다. 본 논문에서는 수월하게 Simulink와 PSAT을 이용하여 구동 및 동력 시스템을 모델링할 수 있는 Matlab 기반의 전기 이륜차 해석 프로그램을 제시하였다. 전기 이륜차의 최대 출력, 에너지 능력, 충전 상태, 등판각도와 같은 설계 인자 해석을 실험과 시뮬레이션을 병행하였다. 본 연구에서 개발된 모델에 의해서 예측된 해석결과는 실험에 의해서 얻어진 결과와 양호하게 일치하였다.