• Proceedings of the KIEE Conference
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• 1994.11a
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• pp.172-174
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• 1994

Due to the environmental considerations and the energy crisis, there has been a revival of electric vehicles since 1960s. Research and development work concerning with electric vehicles (EVs) was becoming more intense in last decade. As compared with conventional internal combustion engine (ICE) cars, EVs have the advantages of clean, quiet, better energy efficiency, less maintenance and improving the load factor of electric power systems. However, EVs usually have a snort running range, bad acceleration performance and high initial cost. The main reason for these shortcomings is the low figure of energy density and the high per energy cost of battery at present technology state. So it is very important to optimize the overall drive system design with respect to the maximum utilization of battery, energy, motor torque and inverter power. This paper describes a demonstration model of electric car which is driven by 4-wheel direct method using the vector control.

• Proceedings of the KIEE Conference
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• 2005.10c
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• pp.198-201
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• 2005

The paper is proposed maximum torque control of IPMSM drive using adaptive learning mechanism-fuzzy neural network (ALM-FNN) controller and artificial neural network(ANN). The control method is applicable over the entire speed range and considered the limits of the inverter's current and voltage rated value. For each control mode, a condition that determines the optimal d-axis current $^i_d$ for maximum torque operation is derived. The proposed control algorithm is applied to IPMSM drive system controlled ALM-FNN and ANN controller, the operating characteristics controlled by maximum torque control are examined in detail. Also, this paper is proposed the analysis results to verily the effectiveness of the ALM-FNN and ANN controller.

• Proceedings of the KIEE Conference
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• 2005.07b
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• pp.1771-1774
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• 2005

가변속 직접 구동형 영구자석 농기발전기와 감속기(38:1)를 2 MW의 유도전동기축에 직결로 결합하여 유도전동기의 속도제어 통하여 발전기 단자전압을 인버터의 출력으로 계통에 전력을 전송하는 시험을 전기연구원에서 수행하였다. 인버터 출력 60 Hz의 상용전원으로 계통과 연계되는 동기발전기의 정격출력은 800 kW이며, 손실분을 제외한 인버터의 정격출력은 750 kW이다. 동기발전기는 속도 9 rpm에서 발전을 시작하여 정격속도인 25 rpm에서 정상적인 출력을 내도록 되어있다. 시험은 유도전동기 속도를 가변으로 각각의 속도에서 발전기 단자전압과 토오크를 측정하고, 정격속도에서 토오크 제어를 통한 최대전력을 측정하였다. 본 논문에서는 시험결과 분석 및 계통사고, 발전기 단락사고와 같은 극한상황에서 전력변환 장치를 보호하기 위한 보호시스템에 대한 국내 규정에 준하는 시험에 대한 결과를 보이고자 한다.

• Proceedings of the KIEE Conference
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• 2005.07b
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• pp.1705-1707
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• 2005

This paper proposes a novel active frequency drift(AFD) method for the islanding prevention of grid-connected photovoltaic inverter. To detect the islanding phenomenon of grid-connected photovoltaic(PV) inverters concerning about the safety hazards and the damage to other electric equipments, many kinds of anti-islanding methods have been presented. Among them, AFD method using chopping fraction(cf) enables the islanding detection to drift up(or down) the frequency of the voltage during the islanding situation. However, the performance of the conventional AFD methods, which have a certain value of cf only, is inefficient and difficult to design the appropriate cf value analytically to meet the limit of harmonics. In this paper, the periodic chopping fraction based on an AFD method is proposed. This proposed method shows the analytical design value of cf to meet the test procedure of IEEE Std. 929-2000 with the power quality and islanding detection time. To verify the validation of the proposed method, the islanding test results are presented. It is confirmed that the proposed method has not only less harmonic distortion but also good performance of islanding detection compare with the conventional AFD method.

• Proceedings of the KIPE Conference
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• 2016.11a
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• pp.73-74
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• 2016

본 논문은 포워드-플라이백 컨버터와 태양광 단일 전원 비대칭 다단식 H-bridge 다중 레벨 인버터를 적용한 태양광 전력 조절 시스템에 관한 논문이다. 이는 기존에 연구되었던 대칭형 다단식 H-Brdige 다중 레벨 인버터나 플라이백 컨버터를 사용한 태양광 전력 조절 시스템의 단점을 보완 한 것이다. 대칭형 다단식 멀티 레벨 인버터는 각 H-Bridge 구조 마다 독립된 전원이 필요하지만, 포워드-플라이백(Foward-Flyback) 컨버터를 접목시켜 단일 태양광 전원으로 하나의 다단식 H-Brdige 인버터를 구성 할 수 있고, 또한 기존의 플라이백 컨버터를 포워드-플라이백 컨버터로 대체 하면서 기존 대비 대용량 설비가 용이하고 효율적인 태양광 전력 조절 시스템을 설계 할 수 있다. 제안한 시스템의 가능성을 확인하기 위하여, PSIM 시뮬레이션을 통해 계통 연계형 1kW급 태양광 시스템의 최대 전력 추종 제어(Maximum Power Point Tracking)와 인버터의 $V_{dc}$ 전압 제어를 확인하였다.

• Proceedings of the KIPE Conference
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• 2015.11a
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• pp.95-96
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• 2015

In this paper, a single-sourced PV PCS using the trinary asymmetric MLI with a single-ended pre-regulator is proposed. Trinary based asymmetric CHB inverters provide higher output levels for the same number of cells compared to other CHB inverters. However, there is an issue of regeneration with trinary asymmetric inverters and this complicates the system with requirement of bi-directional converters at the input. Modified commutation strategies have been used to remove the regeneration issue with compromise in THD. The single-ended pre-regulator provides the isolated dc-link voltage for the individual H-bridge cells with the advantage of having a single switch and magnetic component. This implementation increases the magnetic utilization of the inductor core and reduces the switching loss in the pre-regulator and also the reduced parts count contributes to the cost competiveness of the proposed PCS. The proposed PV PCS has been verified using simulation results in this paper.

• Journal of Power Electronics
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• v.18 no.6
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• pp.1780-1790
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• 2018

Voltage feed-forward control (VFFC) is widely used in LCL-type grid-tied inverters due to its advantages in terms of disturbance rejection performance and fast dynamic response. However, VFFC may worsen the stability of inverters under weak grid conditions. It is revealed in this paper that a large phase-lag in the low-frequency range is introduced by VFFC, which reduces the phase margin significantly and leads to instability. To address this problem, a novel virtual-impedance-based control, where a phase-lead is introduced into the low-frequency area to compensate for the phase lag caused by VFFC, is proposed to improve system stability. The proposed control is realized with a high-pass filter, without high-order-derivative components. It features easy implementation and good noise immunity. A detailed design procedure for the virtual impedance control is presented. Both theoretical analysis and experimental results verify the effectiveness of the control proposed.

• Proceedings of the KIPE Conference
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• 2010.11a
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• pp.343-344
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• 2010

화석연료의 고갈로 인하여 친환경 자동차에 대한 연구와 상용화가 급속도로 진행되면서 점점 대형 차종으로 그 범위가 넓어지고 있다. 대형 차종에 적용되는 전기동력 시스템의 MCU(Motor Control Unit), GCU(Generator Control Unit), DC/DC 컨버터 등과 같은 전장품도 그 용량이 커지면서 상용화를 위해 효율적인 측면도 많이 부각되지만 스위칭 소자, 변압기, 초크, 다이오드 등에서 동작으로 인해 열이 발생하고 제품의 구조상 밀폐된 공간에 장착이 되기 때문에 발열로 인한 동작의 신뢰성과 제품의 내구성에 큰 영향을 미치게 된다. 그중 가장 발열이 심한 IGBT(Insulated Gate Bipolar Transistor) 등과 같은 스위칭 소자에서 발생하는 열을 효과적으로 냉각시키기 위해 수냉구조가 필수적이며 동일한 조건의 수압, 유량에 보다 높은 방열특성을 가지기 위해 냉각구조에 대한 해석이 제품을 개발 전에 선행되어야 한다. 본 논문에서는 유로의 냉각핀 형상과 유로 구조에 따라 방열특성이 어떠한 차이가 있는지 시뮬레이션 프로그램을 통하여 비교하고, 모사발열체를 이용한 방열부의 냉각 성능 시험과 다이나모 환경의 최대 출력 시험을 통하여 방열 특성을 확인하였다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2010.10a
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• pp.771-772
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• 2010

X-ray equipment used to diagnose a patient has a big defect of a patient's exposure to radiation caused in irradiating X-ray to the human body, ICRP restricts the permissible exposure dose of the human body. A number of studies has been proceeded to reduce these exposures. In this study the high voltage generator with inverter system, which is possible to increase the generation efficiency of X-ray and to control the precise output power was produced. Also, to minimize the ripple which is possible to occur in the direct voltage that is applied to X-ray tube the propagation rectification method was applied and the radiation reproducibility and properties were evaluated to use this for the diagnosis of patient.

• Journal of the Korean Institute of Intelligent Systems
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• v.8 no.2
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• pp.43-49
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• 1998

This paper describes a phase-shift pulse-width modulation and pulse-frequency modulation seriesresonant high-frequency inverter using IGBT for the power control of high-frequency inductionheating using fuzzy, which is practically applied for 2 0- 5~0 0~~ ~in 1d uction-heating and meltingpov~er supply in industrial fields. The adaptive frequency tracking based phase-shifting PWMregillation scheme is presented in order to minimize switching losses. The trially-producedbreadboards using IGBT are succesfully demostrated and discussed.discussed.