• Journal of the Korean Society of Industry Convergence
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• v.25 no.4_1
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• pp.493-504
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• 2022

Recently, as interest in eco-friendliness grows, the supply of hybrid electric vehicles and pure electric vehicles (EVs) for improving fuel efficiency of automobiles is rapidly expanding. The average daily energy consumption of electric vehicles is less than 20 [%] of the total ESS capacity of the vehicle, and research on additional functions using the ESS of the vehicle is urgently needed to expand the supply of electric vehicles. V2H(Vehicle to Home), like V2G(Vehicle to Grid), includes the concept of cooperating with system stabilization using ESS of electric vehicles. In addition, it includes various operations that can realize home welfare, such as uninterrupted power supply in case of power outage at home, and power supply for home DC devices. Therefore, in order to expand the supply of eco-friendly electric vehicles, it is urgently required to develop a V2H system with various functions that can realize home welfare. In this paper, we propose a V2H system with a CLLC resonant converter and a non-isolated step-up converter that can solve different impedance and resonant frequencies depending on the power transfer direction. The proposed V2H system is 6 [kVA] applicable to 150-450 [V], the voltage range that can use the ESS voltage for electric vehicles, and is designed with a capacity that can handle instantaneous electricity use at home. In addition, in order to verify the feasibility, an experiment by Psim simulation and prototype production was performed.

• Proceedings of the KIEE Conference
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• 2004.07c
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• pp.1778-1780
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• 2004

Microwave heating system of KSTAR consists of ECH and LHCD. ECH and LHCD offer the reliability of operation in the beginning of plasma formation and non-inductive current drive for long time steady state operation with maintaining MHD stability, respectively. LHCD demands 5 GHz of frequency and consists of c-band waveguide, 4-port circuitor, dry dummy load, dual directional coupler, E-bend, arc detector. Our system is a lineup type pulse modulator that has 45 kV of output pulse voltage, 90 A of pulse current, 4 us of pulse width. 1:4 step-up pulse transformer, 7 stages of PFN and thyratron tube (E2V, CX1191D) are used in this modulator. The purpose of this paper is to show the modulator design and experimental result.

• Journal of the Korean Society for Precision Engineering
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• v.27 no.1
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• pp.49-57
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• 2010

This paper describes the design, construction, and fundamental testing of a precision rotational device that utilizes piezoelectric elements as a source of driving force and impact drive mechanism as a driving principle. A novel device structure is designed and the numerical simulations about the static displacement, stress distribution, and mode shape of the designed structure are performed. A fabricated rotational device has been rotated successfully by applying saw-shaped voltages to the piezoelectric elements. The one-step rotational angle was $0.44{\times}10^{-3}$ rad at the applied voltages of 80V. The angular velocities of the device were revealed to be increased as the driving frequency and voltage were respectively increased and the preload was decreased. The device has a feature that it can be translated as well as rotated. An experimental result shows that the device was translated by ${\pm}4.56{\mu}m$ maximum when the 120V sinusoidal voltages with a phase difference of $180^{\circ}$ were respectively supplied to two piezoelectric elements.

• Proceedings of the KIPE Conference
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• 2001.10a
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• pp.271-275
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• 2001

In this paper, proposes a novel AC-DC converter of high power factor and high efficiency by partial resonant method. The input current waveform in proposed circuit is got to be a discontinuous sinusoidal form in proportion to magnitude of ac input voltage under the constant duty cycle switching. Thereupon, the input power factor is nearly unity and the control circuit is simple. Also the switching devices in a proposed circuit are operated with soft switching by the partial resonant method. The result is that the switching loss is very low and the efficiency of system is high. The partial resonant circuit makes use of a inductor using step up and $L^2SC$ (Loss-Less Snubber Condenser). The switching control technique of the converter is simplified for switches to drive in constant duty cycle. Some simulative results and experimental results are included to confirm the validity of the analytical results.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1025_1026
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• 2009

This paper introduces the test a rapid pulsed power charging system for pulsed power application. The charger is designed based on three-phase series resonant inverter followed by air cooled step-up transformers. It has many advantages of lower weight, small size and high efficiency compared with large bulky traditional pulse power charging system. To apply 150kJ pulsed power system, detail test was carried out at various condition and its results shows 90% efficiency at full load condition. And additional experiments such as short, open, and self discharging during charging status are performed to verify reliable operation at abnormal condition and it was confirmed that developed capacitor charger showed very reliable operation all over the tests.

• Journal of Power Electronics
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• v.13 no.5
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• pp.737-745
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• 2013

Offshore wind farms are rapidly growing owing to their comparatively more stable wind conditions than onshore and land-based wind farms. The power capacity of offshore wind turbines has been increased to 5MW in order to capture a larger amount of wind energy, which results in an increase of each component's size. Furthermore, the weight of the marine turbine components installed in the nacelle directly influences the total mechanical design, as well as the operation and maintenance (O&M) costs. A reduction in the weight of the nacelle allows for cost-effective tower and foundation structures. On the other hand, longer transmission distances from an offshore wind turbine to the load leads to higher energy losses. In this regard, DC transmission is more useful than AC transmission in terms of efficiency because no reactive power is generated/consumed by DC transmission cables. This paper describes some of the challenges and difficulties faced in designing high-power-density power conversion systems (HPDPCSs) for offshore wind turbines. A new approach for high gain/high voltage systems is introduced using transformerless power conversion technologies. Finally, the proposed converter is evaluated in terms of step-up conversion ratio, device number, modulation, and costs.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.17 no.5
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• pp.149-153
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• 2003

In this paper, a hexagon-type piezoelectric transformer was investigated to increase the output power. The length of its side was 14mm and 17.5[mm], respectively. The piezoelectric ceramics was composed to PZT-PMN-PSN. This composition showed the characteristics which had an about 1200 of the mechanical Q-factor, 0.55 of the electromechanical coupling coefficient, 320 x 10$\^$-12/ C/N of the piezoelectric constant d$\sub$33/, 0.3% of the dissipation factor, etc. The voltage step-up ratio increased with increasing the load resistance, Rt., so it reached 80 with R$\sub$L/ of l[M$\Omega$] and was proportion to the length of side of the hexagon-type piezoelectric transformer.

• Journal of Power Electronics
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• v.16 no.5
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• pp.1763-1772
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• 2016

To reduce system complexity and implementation costs, fully-controlled H-bridge (FHB) modules and diode H-bridge PFC (DHB) modules are cascaded to form a hybrid cascaded H-bridge rectifier (HCHR). In this paper, the advantages of such a HCHR over other cascaded rectifiers are analyzed depending on the numbers of FHB modules and DHB modules. Therefore, to assign proper numbers to these two kinds of modules for the HCHR, a configuration determination method is investigated under balanced and imbalanced loads. Three principles are also presented to guide the configuration determination for the HCHR. In addition, the constraints for selecting the step-up ratio and filter inductance are derived based on a phasor diagram analysis. The proposed configuration determination method is validated by simulations under three different conditions in the PSIM environment. Finally, experiments are carried out on a scaled-down prototype where the configuration can be easily adjusted. The feasibility of the proposed theory is then verified by experimental results.

• Journal of the Korean Society of Marine Environment & Safety
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• v.13 no.2 s.29
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• pp.169-172
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• 2007

This paper presents circuit models and control algorithms of distributed generation system(DGS) which consists of Z-type converter and PWM inverter. Z-type converter which employs both the L and C passive components and shoot-through zero vectors instead qf the conventional DC/DC converter in order to step up DC-link voltage. Discrete time sliding mode control with the asymptotic observer is used for current control. This system am be used for power conversion of DC renewable energy.

• Proceedings of the KIPE Conference
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• 2008.06a
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• pp.286-288
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• 2008

본 논문은 낮은 입력 DC전압에서 높은 음의 DC전압을 출력하는 높은 전환 비의 극성 반전 형 DC/DC 전력 변환 회로에 관한 것으로써, 하나의 스위치, 하나의 인덕터, 그리고 다수개의 캐패시터와 다이오드로 구성된다. 기존의 극성 반전 형 DC/DC 컨버터 회로와 비교하여, 고압 변환 트랜스포머 대신에 인덕터를 사용할 수 있어, 자기 소자의 부피 및 크기는 물론 원가저감이 가능하다. 또한 자려 발진(Self Oscillation) 방식을 사용하여 별도의 제어 IC가 필요 없으므로, 회로구성이 대단히 간단하고, 저가격의 전원 회로를 만들 수 있다. 또한 다이오드들의 전압 스트레스가 감소하여 저가격 고성능의 고압 변환장치 구현이 가능하다. 제안된 회로의 동작원리를 설명하고, 타당성을 Simulation 및 실험을 통하여 검증한다.