• Journal of Electrical Engineering and Technology
• /
• 제13권4호
• /
• pp.1459-1473
• /
• 2018

This paper focuses on voltage control schemes for multi-terminal low-voltage direct current (LVDC) distribution systems. In a multi-terminal LVDC distribution system, there can be multiple AC/DC converters that connect the LVDC distribution system to the AC grids. This configuration can provide enhanced reliability, grid-supporting functionality, and higher efficiency. The main applications of multi-terminal LVDC distribution systems include flexible power exchange between multiple power grids and integration of distributed energy resources (DERs) using DC voltages such as photovoltaics (PVs) and battery energy storage systems (BESSs). In multi-terminal LVDC distribution systems, voltage regulation is one of the most important issues for maintaining the electric power balance between demand and supply and providing high power quality to end customers. This paper focuses on a voltage control method for multi-terminal LVDC distribution system that can efficiently coordinate multiple control units, such as AC/DC converters, PVs and BESSs. In this paper, a control hierarchy is defined for undervoltage (UV) and overvoltage (OV) problems in LVDC distribution systems based on the control priority between the control units. This paper also proposes methods to determine accurate control commands for AC/DC converters and DERs. By using the proposed method, we can effectively maintain the line voltages in multi-terminal LVDC distribution systems in the normal range. The performance of the proposed voltage control method is evaluated by case studies.

• 대한전자공학회:학술대회논문집
• /
• 대한전자공학회 2003년도 통신소사이어티 추계학술대회논문집
• /
• pp.153-156
• /
• 2003

In this paper, we propose QoS guarantee system fur multi-functional VoIP end Terminal. This system guarantees low delay of voice data for Internet telephony in VoIP end terminal that has various kinds of Internet dependant application. QoS system we propose support low delay transmission in VoIP terminal interface.

• 한국정보디스플레이학회:학술대회논문집
• /
• 한국정보디스플레이학회 2005년도 International Meeting on Information Displayvol.I
• /
• pp.464-467
• /
• 2005

In this paper, we present techniques to manufacture color electronic ink for multi-color electrophoretic display implementation. The charged color pigments have been prepared to have superior affinity for dielectric fluid. White $TiO_2$ nanoparticles were modified with poly(methyl methacrylate) copolymer for a microencapsulated electrophoretic display system, in order to reduce the density mismatch between nanoparticles and dielectric medium. These color balls and white pigment particle suspensions were microencapsulated through the typical microencapsulation technique. We fabricate the microcapsules to the single layer on flexible ITO substrate to test the multi-color electrophoretic display application.

• Journal of Power Electronics
• /
• 제18권2호
• /
• pp.467-481
• /
• 2018

Modular multilevel converter (MMC)-based high-voltage direct current (HVDC) presents attractive technical advantages and contributes to enhanced system operation and reduced oscillation damping in dynamic MMC-HVDC systems. We propose an advanced small-signal multi-terminal MMC-HVDC based on dynamic phasors and state space for power system stability analysis to enhance computational accuracy and reduce simulation time. In accordance with active and passive network control strategies for multi-terminal MMC-HVDC, the matchable small-signal stability models containing high harmonics and dynamics of internal variables are conducted, and a related theoretical derivation is carried out. The proposed advanced small-signal model is then compared with electromagnetic-transient and traditional small-signal state-space models by adopting a typical multi-terminal MMC-HVDC network with offshore wind generation. Simulation indicates that the advanced small-signal model can successfully follow the electromechanical transient response with small errors and can predict the damped oscillations. The validity and applicability of the proposed model are effectively confirmed.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1994년도 추계학술대회 논문집 학회본부
• /
• pp.30-32
• /
• 1994

This paper presents a new method for the computation of fault location in multi-terminal transmission lines. This technique based upon the distributed model of transmission lines to overcome the problems encountered in traditional approaches. This method uses, the magnitude of the differential currents at each terminal and also uses an algorithm an equivalent conversion from an multi-terminal to a 3 terminal system.

• 해양환경안전학회지
• /
• 제25권3호
• /
• pp.251-258
• /
• 2019

This study was conducted to propose an effective port operation method in terms of the design capacity of waiting anchorage by comparing the ratio and the number of waiting anchorage according to the port operation method of Busan New Port. For this, the Arena simulation program compared the rates of waiting vessels according to the application of the multi-user terminal, liner terminal and hybrid liner terminal operation methods. As a result, analysis suggested the necessary anchorage space can be reduced to about 18 % when using the multi-user terminal operation method and about 15.6 % when using the hybrid liner terminal operation method, as compared with the liner terminal operation method. Specifically, it was effective to apply the multi-user terminal operation method in terms of the anchorage capacity to be designated to Busan New Port. This study can apply to the designation of the new anchorage in the Busan New Port by reflecting the contents of the design of the anchorage in accordance with the port operation method.

• 중소기업융합학회논문지
• /
• 제2권1호
• /
• pp.19-24
• /
• 2012

본 논문에서는 네트워크 상황 정보를 이용한 다중 인터페이스 단말의 배터리 수명 연장 방법을 제안한다. 단말은 현재 접속 네트워크에 병목현상이 발생하는 경우, 다중 인터페이스를 이용하여 다중 경로로 데이터를 수신한다. 하지만 다중 인터페이스를 이용하는 경우 단말의 배터리 소모가 많아 단말의 배터리 수명이 짧아진다. 이러한 배터리 소모를 줄이기 위해 OLT를 통해 네트워크의 병목현상 유무를 판단하고 단말에게 네트워크 상황 정보를 전송한다. 단말은 네트워크 상황 정보를 통해 하나의 인터페이스를 비활성화 시켜 에너지 소비를 절감시킨다. 단일 인터페이스와 다중 인터페이스를 사용함에 따른 배터리 소비량을 계산하여 제안 방안의 효과를 확인하였다.

• 한국시뮬레이션학회논문지
• /
• 제28권3호
• /
• pp.25-40
• /
• 2019

오늘날 컨테이너 터미널은 증가하는 물동량을 유치하기 위하여 치열한 경쟁을 펼치고 있다. 이에 본 연구는 컨테이너 터미널의 생산성 향상을 위한 노력의 일환으로 두 가지 야드 트럭 우선순위 규칙(Dispatching rule)을 제안하였다. 첫 번째 Multi-attribute Dispatching은 컨테이너 터미널 생산성에 영향을 미치는 복수 요인들의 가중합으로 구성된 할당 방법이며, 선박의 체류시간을 감소시키기 위하여 안벽 크레인의 작업량을 고려하였다. 두 번째 Cycling Dispatching은 터미널 생산성 개선에 가장 큰 영향을 미치는 Double cycle횟수를 증가시키기 위한 할당 방법이다. 또한 본 연구는 풀링(Pooling)과 우선순위 규칙(Dispatching rule)이 터미널 생산성에 미치는 영향을 파악하기 위하여 풀링과 우선순위 규칙을 조합한 8가지 시나리오를 구성하였다. 실험은 실제 컨테이너 터미널의 데이터를 이용하여 시뮬레이션을 구현하였다. 실험 결과, 풀링과 우선순위 규칙 그리고 둘의 교호작용이 생산성에 영향을 미치는 것으로 나타났으며, 8가지 시나리오 중에서는 터미널 기준 풀링과 Multi-attribute Dispatching의 조합이 GCR, 선박 출항지연시간 등 KPI 지표에서 우수한 결과를 보임을 확인하였다.

• Journal of Power Electronics
• /
• 제14권1호
• /
• pp.143-155
• /
• 2014

The stability issues of a multi-module distributed DC power system without current-sharing loop are analyzed in this study. The physical understanding of the terminal characteristics of each sub-module is focused on. All the modules are divided into two groups based on the different terminal property types, namely, impedance (Z) and admittance (Y) types. The equivalent circuits of each group are established to analyze the stability issues, and the mathematical equations of the equivalent circuits are derived. A generalized criterion for multi-module distributed systems is proposed based on the stability criterion in a cascade system. The proposed criterion is independent of the power flow direction.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2015년도 제46회 하계학술대회
• /
• pp.151-152
• /
• 2015

Multi-terminal HVDC(MTDC) 시스템은 기존 전압형 HVDC 시스템이 갖는 능동적인 전력 조류 제어 및 불안정한 신재생에 너지원의 안정적 연계 기능을 극대화시킨 계통 구성 방식으로, 수퍼그리드의 구현에 가장 근접한 방식으로 각광받고 있다. 그러나 전압형 HVDC 시스템을 채택함으로써, 고장전류에 취약한 특징을 갖고 있으며 사고 구간의 분리를 위한 HVDC 차단기의 개발이 필수적으로 요구된다. 본 논문에서는, 추후 HVDC 차단기의 개발 및 적용을 위해 요구되는 MTDC시스템에서의 고장전류 특성 분석에 대한 내용을 기술하고 있다.