• Journal of Power Electronics
• /
• v.15 no.3
• /
• pp.796-805
• /
• 2015

New direct and indirect current control methods for a fault-tolerant active power filter topology are presented in this paper. Since a three-phase four-switch topology has a phase bridge current which cannot be directly controlled, a hysteresis control method in the α-β plane which controls the three-phase current in the two-phase stationary coordinate system is proposed. The improved SVPWM algorithm is able to eliminate the operation of the trigonometric functions in the traditional algorithm by rotating the α-β coordinates and alternating the sequence of the output vectors, which in turn simplifies the algorithm and reduces the switching frequency. The selection of the DC-side reference voltage and DC-side capacitor equalization strategy are also discussed. Simulation and experiments demonstrate that the proposed control method is correct and feasible.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2012.08a
• /
• pp.342-342
• /
• 2012

Resistance-change Random Access Memory (ReRAM), which utilizes electrochemical control of nanoscale quantities of metal in thin films of solid electrolyte, shows great promise as a future solid state memory. The technology utilizes the electrochemical formation and removal of metallic pathways in thin films of solid electrolyte. Key attributes are low voltage and current operation, excellent scalability, and a simple fabrication sequence. In this study, we investigated the nature of thin films formed by photo doping of Ag+ ions into chalcogenide materials for use in solid electrolyte of programmable metallization cell devices. We measured the I-V characteristics by field-effect of the device. The results imply that a Ag-rich phase separates owing to the reaction of Ag with free atoms from chalcogenide materials.

• Design & Manufacturing
• /
• v.2 no.5
• /
• pp.30-33
• /
• 2008

Injection Molding is the most effective process for mass production of plastic parts. The injection molding process is composed with several steps such as Filling, Packing, Holding, Cooling, Ejecting. Among them, filling and packing process should be considered carefully to improve accuracy of dimension, surface quality of plastic parts. Usually the quality above-mentioned is managed with weight of part after molding on the field. In this paper, a series of experiment for molding automotive front bumper was conducted with cavitity temperature sensor to optimize switch-over time(V-P switching), hot runner vale gate sequence time during filling and packing step for the purpose of uniform quality, weight at every molding. As a result, it was found that it is effective method to use temperature sensor in injection molding for quality control of plastic molding.

• Proceedings of the KIPE Conference
• /
• 2016.07a
• /
• pp.359-360
• /
• 2016

This paper presents a new predictive current control (PCC) method to achieve the coordinate control of power and current of the matrix converter under unbalanced input voltages. In order to control the power fluctuation in the input side, the flexible source current reference is generated based on the positive-negative sequence components of the input voltage. The optimal switching state to adjust source and load currents is selected by minimization the cost function which is obtained from the sum of the absolute errors between the current references and their predictive values. Simulation results are given to validate the effectiveness of the proposed PCC method.

• Journal of the Korean Institute of Telematics and Electronics B
• /
• v.33B no.5
• /
• pp.102-108
• /
• 1996

Adaptive resonance theory (ART2) characterized by its built-in mechanism of handling the stability-plasticity switching and by the adaptive learning without forgetting informations learned in the past, is based on an unsupervised template matching. We propose an improved tow-stage learning algorithm for aRT2: the original unsupervised learning followed by a new supervised learning. Each of the output nodes, after the unsupervised learning, is labeled according to the category informations to reinforce the template pattern associated with the target output node belonging to the same category some dominant classes from exhausting a finite number of template patterns in ART2 inefficiently. Experimental results on a set of 2545 FLIR images show that the ART2 trained by the two-stage learning algorithm yields better accuracy than the original ART2, regardless of th esize of the network and the methods of evaluating the accuracy. This improvement shows the effectiveness of the two-stage learning process.

• The Academic Congress of Korean Shoulder and Elbow Society
• /
• 2008.03a
• /
• pp.179-179
• /
• 2008

For a partial tear of the subscapularis tendon, the presenting technique requires only the anterior portal for preparing the footprint and suture management, as well as the subclavian portal for placing the suture anchor and suture hook without inserting a cannula. It provides both a good angle for anchor placement and sufficient space for managing the upper portion of a subscapularis tendon tear. A spinal needle was inserted through the subclavian portal in order to identify the appropriate angle for placing the suture anchor. A 3-mm incision was made for the subclavian portal and a biosuture anchor was placed on the footprint portion of the subscapularis tendon. In order to avoid crowding, each limb of both strands of the biosuture anchor were passed through the tendon- posteromedial side first, and anterolateral side second, using a switching technique with suture hook embedded with no.1 PDS. A suture tie was applied in a reverse sequence (the lateral strand first and the medial strand second) through the anterior cannula using a sliding technique.

• Proceedings of the KIEE Conference
• /
• 2011.07a
• /
• pp.1191-1192
• /
• 2011

We released new triple redundant digital excitation system with real time generator-turbine simulator. One of its great merits is the real time generator-turbine simulator when it was compared with the other products. If excitation system is tripped by unexpected faults, Maintenance man can do easily performance test of digital excitation control board, sequence relay and thyristor switching device of phase controlled rectifier without manufacturer's support. For the verification of this system, It was tested with an actual excitation system implemented on 5kVA M-G Set. After finishing the tests, the trial product will be installed and operated at a 500MW thermal power plant.

• Proceedings of the KIPE Conference
• /
• 2017.11a
• /
• pp.95-96
• /
• 2017

A three-level inverter is widely used thanks to its excellent performances, but the voltage may fluctuate at the neutral point of the split DC-Link. Neutral point voltage fluctuations cause inverter performance degradation and switching element damage, so the neutral point voltage control is essential. However, the neutral point control can be also limited by modulation index and power factor. This paper analyzes the limitation of the neutral point voltage control due to the limitation of zero-sequence voltage, and suggests a method to determine the region where the PWM has to be changed for a better neutral point control.

• Proceedings of the KIEE Conference
• /
• 2009.07a
• /
• pp.159_160
• /
• 2009

In this paper proposes a new algorithm of efficiency outage restoration using a outage load switching to a healthy MTR a fault occurrence at a MTR. In addtion, proposed algorithm includes a outage restoration method which keeps MTR optimal capacity with reorganization of distribution network in case it can not restore outage state loads caused by shortage of healthy MTR remain capacity. In case that proposed sequence still can not complete restoration, this paper suggests a efficiency outage restoration with objective function included priority in outage loads.

• Proceedings of the KIPE Conference
• /
• 2004.07a
• /
• pp.411-414
• /
• 2004

본 연구에서는 RPP(Randomized Pulse Position PWM)의 특징과 RSF(Random Switching Frequency PWM)의 특징을 모두 갖는 하이브리드 RPWM (Random PWM)기법을 제안하였다. 제안된 방법은 PRBS(Pseudo-Random Binary Sequence)로 동작하는 시프트 레지스터의 lead-lag 랜덤 비트를 사용한다는 점에서 종전의 방법과 동일하나, 이와 논리적인 비교를 위해 랜덤 주파수의 삼각파를 이용한다는 점에서 종전의 방법과 다르다. 본 연구의 타당성을 확인하기 위하여 인버터 기반의 3상 유도모터 구동시스템에 제안된 방법을 적용하였다. 그 결과 종전의 방법에 비하여 인버터 구동 유도모터의 전압 및 전류의 고조파 스펙트럼의 광 대역화에 탁월한 효과가 있음을 입증할 수 있었다.