• Journal of Power Electronics
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• 제13권3호
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• pp.339-348
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• 2013

Multiphase dc-dc converters are widely used in modern power electronics applications due to their advantages over single-phase converters. Such advantages include reduced current stress in both the switching devices and passive elements, reduced output current ripple, and so on. Although the output current ripple of a converter can be significantly reduced by virtue of the interleaving effect, the inductor current ripple cannot be reduced even with the interleaving PWM method. One way to solve this problem is to use a coupled inductor. However, care must be taken in designing the coupled inductor to maximize its performances. In this paper, a detailed analysis of a coupled inductor is conducted and the effect of a coupled inductor on current ripple reduction is investigated extensively. From this analysis, a UU core based coupled inductor structure is proposed to maximize the performance of the coupled inductor.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2012년도 전력전자학술대회 논문집
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• pp.379-380
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• 2012

A bidirectional full-bridge CLLC resonant converter using a digital control method is proposed for a LVDC power distribution system. This converter can operate under high power conversion efficiency since the CLLC resonant network has soft switching capability for primary switches and output rectifiers. In addition, the power conversion efficiency of any directions is exactly the same as each other because of the symmetric structure of the converter. Intelligent digital control methods are proposed to regulate output voltage under any power flow directions. A 5kW prototype converter was designed for a high-frequency galvanic isolation of 380V dc buses using a digital signal processor to verify the performance of the proposed topology and algorithms.

• Journal of Power Electronics
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• 제12권4호
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• pp.587-594
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• 2012

When a PWM rectifier has a low DC-link voltage during startup, the output voltage vector cannot be high enough to regulate the input current. This lack of a PWM rectifier output voltage vector can cause an unregulated inrush current when the rectifier operation starts. This paper presents a PWM rectifier start-up current control algorithm for when it starts operation with a lower DC-link voltage than unloaded condition case. To avoid the unregulated inrush current caused by a lack of DC-link voltage, the proposed control scheme regulates the one phase current with one switch chopping and it generates the current command considering the uncontrolled current magnitude information, which is calculated in advance. Simulation and experiment results support the validity of the proposed method.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2018년도 전력전자학술대회
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• pp.382-383
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• 2018

To increase the efficiency of a wind energy conversion system (WECS), the maximum power point tracking (MPPT) algorithm is usually employed. This paper proposes an optimal MPPT algorithm which tracks a sudden wind speed change condition fast. The proposed method can be implemented without the prior information on the wind turbine parameters, generator parameters, air density or wind speed. By investigating the directions of changes of the mechanical output power in wind turbine and rotor speed of the generator, the proposed MPPT algorithm is able to determine an optimal speed to achieve the maximum power point. Then, this optimal speed is set to the reference of the speed control loop. As a result, the proposed MPPT algorithm forces the system to operate at the maximum power point by using a three-phase converter. The simulation results based on the PSIM are given to prove the effectiveness of the proposed method.

• 전력전자학회논문지
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• 제14권3호
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• pp.228-234
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• 2009

본 논문에서는 위상제어방식 풀브릿지 컨버터의 회로방식에 대한 전력손실과 전력변환 효율특성을 빠르고 효과적인 분석 방법에 대해 보고한 것이다. 위상제어방식 풀브릿지 컨버터의 회로 구성 소자 중에서 내부 기생저항만을 고려한 등가회로를 유도하고 이상적인 동작 파형을 이용하여 전류의 실효값과 전도손실을 유도하였다. 해석을 간단하게 하기 위해서 정상상태 결과로부터 코어 손실은 무시하였으며, 동기정류기 손실과 전도손실 만을 고려하였다. 해석결과의 타당성을 검토하기 위해서 시험용 위상제어방식 풀브릿지 컨버터를 구성하여 검증하였다. 입력전압 400V, 출력전압 12V, 최대전력 720W의 조건에서 실험결과와 해석결과와 비교적 잘 일치한다는 것을 본 논문에서 확인 하였다.

• Journal of Power Electronics
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• 제2권2호
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• pp.77-87
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• 2002

The purpose of this paper is to improve power conversion efficiency of three-phase soft-switching voltage-source inverter with an auxiliary resonant dc link (ARDCL) snubber circuit. Firstly, the operation principle of ARDCL snubber circuit is described. Secondly, this paper proposes an effictive generation method of zero voltage vector for three-phase voltage-source soft-switching inverter in power losses in which power losses in the ARDCL snubber circuit can be reduced. In particular, zero voltage holding interval in the inverter DC busline can be controlled due to the new generation scheme of zero voltage vector. Thirdly, a simulator for power loss analysis for power loss characteristics based on actual system, is developed. the validity of developed. The validity of developed simulator of proved with experimental results. Finally, power efficency of three-phase inverter is estimated according to high carrier frequency by using the simulatior.

• 한국인터넷방송통신학회논문지
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• 제10권4호
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• pp.105-113
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• 2010

240 GHz 대역의 캐리어 주파수를 이용하여 1.485 Gbps 비디오 전송 시스템을 설계 및 시뮬레이션 하였다. 송수신기는 Schottky Barrier 다이오드 기반의 Sub-harmonic 믹서를 이용하였으며 특히, 수신기는 Heterodyne 및 Direct Detection 두 가지 방식을 적용하여 각각의 성능을 시뮬레이션 하였다. 변조방식은 ASK이며, 수신기에서는 Envelop 검출 방식을 사용하였다. 송신기 시뮬레이션 결과 Sub-harmonic 믹서의 LO 전력 7 dBm(5 mW)에서 IF 입력 전력 -3 dBm(0.5 mW)일 때 RF 출력 전력은 -11.4 dBm($73{\mu}W$)이었으며, SSB(Single Side Band) Conversion Loss는 8.4 dB이다. VDI사의 상용모델 WR3.4SHM(220~325 GHz)의 240 GHz에서의 Conversion loss 8.0 dB(SSB)와 근접한 결과를 얻었다. 1.485 Gbps NRZ 신호전송 시뮬레이션 결과 전송신호와 동일한 수신 파형을 얻었다.

• 전력전자학회논문지
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• 제23권4호
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• pp.281-285
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• 2018

An isolated feedback method for measuring the inverter DC-link voltage is proposed. This method provides a simple and economical solution to inverter control systems that use a flyback converter as a controller power supply. In the proposed method, data on the DC-link voltage are acquired when the primary side voltage appears on the secondary side of the flyback transformer, thereby eliminating the need to adopt an extra signal isolation method. To solve the non-synchronization problem between the flyback converter switching and main controller sampling, the external interrupt function of the micro-controller is used as a trigger signal for the A/D conversion.

• 전력전자학회:학술대회논문집
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• 전력전자학회 1998년도 Proceedings ICPE 98 1998 International Conference on Power Electronics
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• pp.938-943
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• 1998

The induction motor of the electric vehicles is controlled based on the vector control method to obtain good torque control characteristics. In the conventional vector control system, the field exciting current should be kept on a constant value to keep a stable flux level. This method has a liability that core loss becomes increasing at the light load region. To solve this liability, the efficiency maximizing control method of the vector controlled induction motor is proposed in thid paper. We developed light weight water cooled 60kW induction motor drive system which adopts our method and fabricated a conversion electric car for actual vehicle test. We demonstrate the usefulness of drive system by comparing its driving mode with conventional field oriented system and an efficiency maximizing controlled induction motor.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2009년도 정기총회 및 추계학술대회 논문집
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• pp.135-138
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• 2009

In this paper, a novel maximum power point tracking (MPPT) for a PMSG-based variable speed wind power system is proposed using the fuzzy logic algorithm. The control algorithm is developed based on the normal hill climb searching (HCS) method, commonly used in wind energy conversion systems (WECS). The inputs of fuzzy-based controller are the derivations of DC output power and the step size of DC/DC converter duty cycles. The main advantages of the proposed MPPT method are no need to measure the wind velocity and the generator rotational speed. As such, the control algorithm is independent of turbine characteristics, achieving the fast dynamic responses with non-linear fuzzy systems. The effectiveness of the proposed MPPT strategy has been verified through the simulated results.