• Journal of Industrial Technology
• /
• v.25 no.B
• /
• pp.195-202
• /
• 2005

The rectifier characteristics and the quality of the input current worsens with the increase of unbalances or harmonics of the supply voltages. Rectifier input current harmonics interfere with proper power system operation, reduce rectifier power factor, and limit the power available from a given source. It is of importance to select appropriately the rectifier's output filter inductance to determine the rectifier input current waveform, the input current harmonics, and the power factor. This paper presents a quantitative analysis of single and three phase rectifier input current harmonics, total harmonic distortion, and power factor as a function of the output filter inductance under balanced and unbalanced conditions. Also, its performance under the supply voltage including harmonics be investigated. These results provide a reference for selecting reasonable rectifier's output filter inductance for given harmonics or power factor criterion.

• Proceedings of the KIEE Conference
• /
• 2006.04b
• /
• pp.241-243
• /
• 2006

This paper describes experimental analysis of UPQC, which is composed of cascaded H-bridges and single-phase multi-winding transformers. The operational characteristic was analyzed through experimental works with a scaled model, and simulations with PSCAD/EMTDC. The UPQC proposed in this paper can be directly connected to the distribution line without series injection transformers. It has flexibility to expand the operation voltage by increasing the number of H-bridge modules. The analysis results can be utilized to design the actual UPQC system applicable for the actual distribution system.

• Proceedings of the KIEE Conference
• /
• 1996.07a
• /
• pp.255-258
• /
• 1996

A new low conduction loss, low cost zero-voltage-transition power factor correction circuit(PFC) is presented. Conventional PFC which consists of a bridge diode and a boost converter(one switch) always has three semiconductor conduction drops. Two switch type PFCs reduces conduction loss by reducing one conduction drop but the cost is increased because of increased number of active switches. The proposed PFC reduces conduction loss with one switch, which allows low cost. Conduction loss improvement is a little bit less than that of two switch type, but very close up. Operation and features are comparatively illustrated and verified by simulation and experimental results of 1 kW laboratory prototype.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2000.03b
• /
• pp.117-124
• /
• 2000

This paper presents the construction planning and the detail design of a 16.2 km long railroad tunnel in a mountainous area. Major design conditions for railroad are the single track, loop-typed alinement, and a maximum grade of 24.5$\textperthousand$. A underground station(double track) with a length of 1.1km is located in the middle of the line for train cross-passing. Tunnel is excavated in highly complex geological conditions including faulted areas, abandoned mine works areas, and various rock types such as sandstone, shale, limestone, and coal seam partly. Drilling and blasting method was adopted because it is more flexible than TBM(Tunnel Boring Machine) as a result of risk assessment for geological conditions in this area. Two working adits were planned to adjust the construction schedule and can be used for ventilation and maintenance in operation phase. New material and concept were introduced to the tunnel drain design. They are expected to improve tunnel drain condition and capability. Rational tunnel support design was tried to consider the various tunnel size and purpose and to use the geological investigation results.

• Progress in Superconductivity and Cryogenics
• /
• v.5 no.1
• /
• pp.56-59
• /
• 2003

As electric power systems grow to supply the increasing electric power demand short-circuit current tends to increase and impose a severe burden on circuit breakers and power system apparatuses. Thus, all electric equipment in a power system has to he designed to withstand the mechanical and thermal stresses of potential short-circuit currents. Among current limiting devices, Fault Current Limiter (FCL) is expected to reduce the short-circuit current. Especially, Superconducting Fault Current Limiters (SFCL) offer ideal performance: in normal operation the SFCL is in its superconducting state and has negligible impedance, in the event of a fault, the transition into the normal conducting state passively limits the current. The SFCL using high-temperature superconductors offers a positive resolution to controlling fault-current levels on utility distribution and transmission networks. This study contributes to the EMTDC based modeling and simulation method of DC Reactor type SFCL. Single and three phase faults in the utility system with DC reactor type SFCLs have been simulated using EMTDC in order to coordinate with other equipments, and the results are discussed in detail.

• 한국신재생에너지학회:학술대회논문집
• /
• 2005.11a
• /
• pp.677-679
• /
• 2005

최근 나노입자를 이용하는 광전 화학전지(PEC, Photoelectrochemical)인 염료감응형 태양전지(DSC)의 효율이 증가함에 따라 DSC 태양광 발전 시스템의 성능 개선 또한 요구되어진다. 본 연구에서는 Fly-Back DC-DC 컨버터(변화비율1:10)를 이용하여 DSC셀의 전압을 DC 300V로 승압시켰다. 또한 풀브릿지 인버터를 사용하여 AC 220V, 60Hz의 출력전압을 얻었다. 연구에서 제안한 회로는 높은 효율의 동작특성과 간단한 제작, 낮은 제조비용, 그리고 안정성을 추구한다. 또 다른 주요점은 부하단에서 Feed back을 받아 동작을 컨트롤하는 것이다. 부하단의 출력 전압과 전류를 Feed back 받아서 DSP320LF2406을 A/D기능을 사용하여 실시간으로 부하의 변화에 대처하여 컨버터와 인버터의 동작을 제어한다.

• Proceedings of the KIPE Conference
• /
• 2001.12a
• /
• pp.149-152
• /
• 2001

A Single-phase bi-directional inverter Using a diode bridge-type resonant circuit to implement ZVT(Zero Voltage Transition) switching is Presented. It is shown that the ZACE(Zero Average Current Error) algorithm based polarized ramptime current control can provide a suitable interface between diode bridge-type resonant circuit DC link and the inverter. The current control algorithm is analyzed about how to design the circuit with analyzed switch which m ZVT operation for the main power switch The simulation and experimental results would be shown to verify the proposed current algorithm, because the main power switch is turn on with ZVT and the bi-directional inverter is operated.

• Proceedings of the KIPE Conference
• /
• 2011.07a
• /
• pp.118-119
• /
• 2011

SVPWM 기반의 3상 전압형 PWM 컨버터는 DC-link전압을 이용하여 단상 교류부하에 전원을 공급할 경우, 컨버터 출력단에 단상 인버터를 추가적으로 필요로 한다. 이때 단상인버터의 스위칭에 의해 2차 고조파가 발생되며 DC-link에 저주파 전압 리플을 발생시킨다. 이 리플 성분에 의해 3상 입력전류의 불평형이 발생한다. 따라서 본 논문에서는 단상인버터 구동 시 발생되는 저주파 전압 리플을 필터링하기 위해 노치필터를 적용하였다. 전압 리플 분석 및 노치필터 설계에 관해 기술하고 시뮬레이션을 통하여 제안된 방법을 검증하였다.

• Proceedings of the KIEE Conference
• /
• 2009.07a
• /
• pp.762_763
• /
• 2009

본 논문에서는 영구자석형 동기전동기와 유도기 특성을 결합한 written-pole motor(WPM)의 운전특성을 다룬다. WPM은 회전자 표면의 자석을 운전 중 착자할 수 있도록 하는 exciter pole을 갖는 독특한 구조로서 유도기와 동기기의 특성을 동시에 나타낸다. WPM의 운전 원리를 설명하고 가전용으로 실제 설계, 제작된 WPM을 대상으로 실험을 통해 특성을 검증하였다.

• Journal of Electrical Engineering and Technology
• /
• v.10 no.4
• /
• pp.1552-1557
• /
• 2015

The paper unleashes a new idea to arrive at reduced switch count topological structures configured in the form of a matrix for a cascaded Multi level inverter (CMLI). The theory encircles to minimize the number of switches involved in the conduction path and there from acclaim reduced input current distortion, lower switching losses and electromagnetic interference. The focus extends to standardize the number of power devices required for reaching different levels of output voltage from the same architecture. It includes appropriate pulse width modulation (PWM) strategy to generate firing pulses and ensure the desired operation of the power modules. The investigative study carries with it MATLAB based simulation and experimental results obtained using suitable prototypes to illustrate the viability of the proposed concept. The promising nature of the performance projects a new dimension in the use of single phase MLIs for renewable energy related applications.