• Journal of Advanced Information Technology and Convergence
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• v.9 no.2
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• pp.75-87
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• 2019

This paper presents a fully digital controlled power supply unit for the wireless controlled dimmable LED lighting system. The proposed power supply designed using a fly-back converter, which is directly controlled by a microprocessor. Although the proposed circuit does not sense the AC input current and has not AC input voltage feed-forward, it can achieve a high power factor. The proposed power supply directly regulates the output power for LED loads using the PWM and PFM control of the fly-back converter without additional regulator. For a wireless remote control function, the Zigbee modem is equipped in the proposed power supply. A prototype set-up has been built and tested. Through the experiment with a prototype set-up, the usefulness of the proposed power supply is verified.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.8
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• pp.1418-1423
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• 2007

The topology of LLC half bridge resonant converter provides ZVS characteristic. The voltage stress and current stress are smaller than that of the general resonant converters. So the LLC HB resonant converter can be considered as a optimal circuit for the notebook computer adapter. In the adapter design, we should consider the weight, the size and the overheat of the adapter. Thus the higher efficiency is an essential particular. First of all, the optimal design of transformer is the most important facts. Some parameters should be considered in order to get the highest efficiency. The adapter is designed through the considering of these parameters including the PFC circuit as the pre-regulator. It converts AC line input into about DC 390V link voltage of the LLC HB converter input and the converter has 16V/90W ratings. The efficiency measured is about up to 93%.

• Proceedings of the KIEE Conference
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• 1995.07c
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• pp.1365-1367
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• 1995

The PLS 2-GeV linac employs 11 units of high-power pulsed klystrons(80MW) as the main RF sources. The matching modulators of 200 MW(400kV, 500 A) can provide a flat-top pulse width of 4.4 ${\mu}s$ with a maximum pulse repetition rate of 120 Hz at the full power level. For a good stability of electron beams, the pulse-to-pulse flat-top voltage variation of a modulator requires less than 0.5%. In order to achieve this goal, we stabilized high voltage charging power supplies within 1% by a phase controlled SCR voltage regulator. In addition, we employed ac/dc feedback together with a resistive De-Q'ing system to achieve far less than 0.5% variation of the PFN charging voltage. This paper presents the main feature of the klystron-modulator system and the characteristics of the pulsed high-power RF system performance during the beam injection operation for the Pohang Light Source commissioning.

• Proceedings of the KIEE Conference
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• 2006.07b
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• pp.1039-1040
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• 2006

The resonant converters cause the high voltage stress according to the input voltage, which increases the conduction loss in converter power switches. The topology of LLC half bridge resonant converter provides ZVS characteristic and also the stress of voltage and current is not higher than that of the general resonant converters. So we can expect the higher efficiency. In this paper, the LLC resonant converter is designed for the notebook computer adapter. In the adapter design, we should consider the weight, the size and overheat of the adapter. Thus the higher efficiency is an essential particular. First of all, the optimal design of transformer is the most important facts. Some parameters should be considered in order to get the highest efficiency. The adapter is designed through the considering of these parameters including the PFC circuit of the pre-regulator. It converts AC line input into about $400V_{DC}$ Link voltage of the LLC converter input and the converter has $16V_{DC}/90W$ ratings. The efficiency measured is about up to 92%.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.5
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• pp.672-678
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• 2020

The parallel-feeding operation of an AC traction power supply system has the advantages of extending the power supply section and increasing the power supply capacity by reducing the voltage drop and peak demand caused by a train operation load. On the other hand, the parallel-feeding operation is restricted because of the circulating power flow induced from the phase difference between substations. Moreover, the power supply capacity is limited because of the unbalanced substation load depending on the trainload distribution, which can be changed by the train operation along the railway track. This paper suggests a Thyristor-controlled Phase Angle Regulator (TCPAR) to reduce the circulating power flow and the unbalanced substation load, which depends on the phase difference and the trainload distribution and provides a feasibility study. A dedicated control model of TCPAR is also provided, which uses substation power supplies as the input to control the circulating power flow and an unbalanced substation load depending on the phase difference and the trainload distribution. Simulation studies using PSCAD/EMTDC shows that the proposed TCPAR control model can reduce the circulating power flow and the unbalanced substation load depending on the phase difference and the trainload distribution. The proposed TCPAR can extend the parallel-feeding operation of an AC traction power system and increase the power supply capacity.

• Proceedings of the KIPE Conference
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• 2014.07a
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• pp.173-174
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• 2014

본 논문에서는 저 대기전력 구현이 가능하며 정확한 출력전압 제어가 가능한 SSR(Secondary Side Regulator) 플라이백 컨버터를 제안하였다. 제안 SSR 플라이백 컨버터는 2차 측에 control IC를 사용하여 별도의 제어기(TL431) 및 포토커플러를 제거하여 구조가 간단하고 대기모드 시 TL431의 바이어스 전류에 의한 전력소모를 줄일 수 있으므로 대기전력을 최소화 할 수 있으며 출력전압을 직접 검출하여 정확하게 출력을 제어할 수 있다. 한편 1차 측의 위치한 게이트 구동을 위해 절연된 1-2차 측간 신호를 전송하는 PET(Pulse Edge Transmitter)를 제안하였으며 제안 방식은 IC로의 직접화가 매우 용이하여 1-2차 측 IC와 제안 PET를 one-chip화 할 수 있다. 제안 회로의 타당성 검증을 위해 10W급 Adaptor의 시작품을 제작하였고, 이를 이용한 실험결과를 바탕으로 제안 시스템의 타당성을 검증한다.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.49 no.6
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• pp.272-279
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• 2000

This paper describes a controller design and dynamic performance analysis of UPFC based on 3-level inverters. Major attention is focused on the controller design for both shunt and series inverters, including regulator design for the dc link voltage sharing across the dc capacitors. An energy-based approach was investigated for effectively designing the controller. A detailed UPFC model has been developed with EMTP using 24-pulse 3-level inverters to verify this approach. Simulation results about dynamic performance of UPFC confirm effects for increasing transmission capacity and damping low-frequency oscillation. The developed simulation model would be very effective to analyze the dynamic performance of UPFC.

• Proceedings of the KIEE Conference
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• 1993.07a
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• pp.167-170
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• 1993

This paper deals with AVR(Automatic Voltage Regulator) control1or design of synchronous generator adapting AC indirect excitation system. The simulation results are presented in frequency and tine domain for two plants(A and B). Try and error method for compensator design is used.

• Journal of Electrical Engineering and Technology
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• v.5 no.1
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• pp.103-115
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• 2010

This paper discusses a DC distribution system which has been supplied by external AC systems as well as local microturbine distributed generation system in order to demonstrate an overall solution to power quality issue. Based on the dynamic model of the converter, a design procedure has been presented. In this paper, the power flow control in DC distribution system has been achieved by network converters. A suitable control strategy for these converters has been proposed, too. They have DC voltage droop regulator and novel instantaneous power regulation scheme. Also, a novel control system has been proposed for MT converter. Several case studies have been studied and the simulation results show that DC distribution system including microturbine unit can provide the premium power quality using proposed methods.

• Proceedings of the KIEE Conference
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• 1995.07a
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• pp.206-208
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• 1995

Recently according to the increasing critical loads such as communication and life support systems stable power supplying becomes more and more important. Therefore it is indespensable to stabilize power source using these instruments - AVR(Automatic Voltage Regulator) or UPS(Uninterrutible Power Supply). This paper deals with ON-LNE UPS which is composed of PWM converter for AC-DC conversion. Using a PWM converter have advantages of low current harmonics and high power factor. In this paper ON-LNE UPS using PWM converter is proposed and its characteristics are investigated.