• Journal of Power Electronics
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• v.19 no.6
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• pp.1575-1581
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• 2019

Due to the mismatched line impedance among distributed generation units (DGs) and uncontrolled harmonic current, the droop controller has a number of problems such as inaccurate reactive power sharing and voltage distortion at the point of common coupling (PCC). To solve these problems, this paper proposes a resistive-capacitive virtual impedance control method. The proposed control method modifies the DG output impedance at the fundamental and harmonic frequencies to compensate the mismatched line impedance among DGs and to regulate the harmonic current. Finally, reactive power sharing is accurately achieved, and the PCC voltage distortion is compensated. In addition, adaptively controlling the virtual impedance guarantees compensation performance in spite of load changes. The effectiveness of the proposed control method was verified by experimental results.

• Journal of Veterinary Clinics
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• v.36 no.1
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• pp.85-87
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• 2019

Eight-week-old Spot-billed duck were presented with visible drooping of both of wings. On physical examination, the Spot-billed ducks revealed valgus deformity of the carpal joint resulting in the primary flight feathers protruding dorsally. The bird was in good body condition and there was no loss of motion in any of the joints in the wings. The bird was fed chicken pellet with 18.5% of protein level and reared in a cage. Based on the clinical presentation and physical examination 'angel wing' was diagnosed. Wing bandage and nutritional change to lower-protein diet with fresh vegetables were applied simultaneously. And duck was transferred to wider outside pen with small pond. Four-week afterward clinical signs of angel wing were improved.

• Proceedings of the KIPE Conference
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• 2019.07a
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• pp.115-117
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• 2019

In this paper, an intelligent control scheme based on Fuzzy PID controller is proposed for accurate power sharing in DC Microgrid. The proposed Fuzzy PID controller is designed with the aid of a closed loop control based on per unit power of each distributed generator (DG), and accurate power sharing is successfully realized in proportional to each DG's power rating regardless of the line resistance difference or the load change. Thanks to Fuzzy PID controller, the dynamic response becomes faster and the stability of the microgrid system are improved in comparison to conventional PID controller. The superiority of the proposed method is analyzed and verified by simulation in Matlab and Simulink.

• Proceedings of the KIPE Conference
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• 2019.07a
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• pp.370-371
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• 2019

태양광 및 풍력과 같은 신 재생에너지원을 바탕으로 하는 분산 발전이 증가함에 따라 대용량의 PCS가 요구된다. 대용량의 PCS를 제어하기 위해서는 병렬운전이 바탕이 되어야 한다. 본 논문에서는 통신 없이 제어가 가능한 기존의 드룹 제어의 장점을 살리면서 전력 편차가 적은 마스터 슬레이브 제어의 장점을 결합한 병렬운전 제어 방식을 제안하고 시뮬레이션을 통해 제어 알고리즘의 타당성을 검증하고자 한다.

• The Transactions of the Korean Institute of Power Electronics
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• v.24 no.5
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• pp.334-341
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• 2019

This study proposes the control strategy for the seamless mode transfer of indirect current controlled parallel grid-connected inverters. Under the abnormal grid condition, the grid-connected inverter can convert the operation mode from grid-connected to stand-alone mode to supply power to the local load. For a seamless mode transfer, the time delay problems caused by the accumulated control variable error must be solved, and the indirect current control method has been applied as one of the solutions. In this study, the design of control parameters for the proportional-resonant-based triple-loop indirect current controller and the control strategy for the seamless mode transfer of parallel grid-connected inverters are described and analyzed. The validity of the proposed mode transfer method is verified by the PSiM simulation results.

• The Transactions of the Korean Institute of Power Electronics
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• v.24 no.3
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• pp.191-200
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• 2019

This study proposes a hardware-in-the-loop simulation (HILS) system based on National Instruments' PXI platform to test power management and operation strategies for DC microgrids (MGs). The HILS system is developed based on the controller HIL prototype, which involves testing the controller board in hardware with a real-time simulation model of the plant in a real-time digital simulator. The system provides an economical and effective testing function for research on MG systems. The decentralized power management strategy based on the DC bus signaling method for DC MGs has been developed and implemented on the HILS platform. HILS results are determined to be similar to those of the off-line simulation in PSIM software.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.6C
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• pp.777-784
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• 2004

In this paper, a new filter structure to improve frequency response characteristics in decimation filter using CIC(Cascaded Integrator-Comb) filters and half band filters is proposed. Conventional filters improve only passband characteristics, but we propose a new filter which can improve stop band and pass band characteristics simultaneously. Since proposed filter needs only two multiplication, additional implementation cost is not much. And overall linear phase characteristics are maintained since the proposed filter is also linear phase. Finally, filter coefficients quantization effects ate discussed after Verilog-HDL coding.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.40 no.3
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• pp.189-198
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• 2003

Videooculography (VOG) is one of the eye-movement measurement methods used for objective evaluation of vestibule -ocular reflex. A key feature of VOG is to estimate accurately the center of pupil and ocular torsion with being less influenced by the upper eyelid droop, eyelashes, corneal reflection, and eye blinks. Especially, it Is important to find the accurate center of the pupil in 3-D VOG because the inaccurate pupil center causes significant errors on measuring torsional eye movement. A new algorithm was proposed to find the center of pupil which is a little influenced by factors mentioned above. In this study, real time three-dimensional VOG which can measure horizontal, vortical, torsional eye movements, and the diameter of pupil was implemented using the proposed method.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.356-356
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• 2012

InGaN/GaN LEDs는 1993년에 처음 소개 된 이래로, 성장, 제품 면에서 끊임없는 발전을 이루어 왔다. 따라서 GaN 기반의 LED는 조명, 디스플레이 그리고 후광 발광판 등 다양한 분야에서 사용되고 있다. 현재 GaN 기반의 LED는 낮은 작동전류에서 높은 내부, 외부 효율을 보인다고 알려져 있다. 그러나 LED는 보통 높은 작동 전류에서 사용하고 있는데 이 전류 값에서 'Efficiency Droop'이라 하는 효율 저하가 나타난다. 이 현상의 원인으로는 결함, Auger 영향, 캐리어 누설, 격자 불일치로 인한 내부 장 효과, 그리고 온도의 영향 등이 이 효율저하를 일으키는 주된 원인으로 생각되고 있다. 하지만 최근 효율저하의 원인에 대하여 결함, 그리고 온도 변화의 실험 등을 통하여 실험적으로 Auger 영향은 효율 저하의 원인으로 가능성이 매우 낮고 누설 전류가 효율저하의 주된 원인의 가능성이 높다고 많은 그룹에서 문제제기를 하고 있는 추세이다. 이 연구에서, 효율저하의 특성을 분석하기 위하여 GaN 기반의 EBL이 있는 LED와 없는 LED를 이용하였다. I-V 곡선, 주입 전류에 따른 반치폭의 변화와 스펙트럼의 변화, 그리고 외부 효율 등의 비교 분석을 통하여 효율 저하의 원인이 누설 전류에 의함이라고 분석을 할 수 있었다.

• Advances in aircraft and spacecraft science
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• v.4 no.1
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• pp.81-91
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• 2017

The performances of lifting surfaces are particularly critical in specific flight conditions like takeoff and landing. Different systems can be used to increase the lift and drag coefficients in such conditions like slat, flap or ailerons. Nevertheless they increase the losses and make difficult the mechanical design of wing structures. Morphing surfaces are a compromise between a right increase in lift and a reduction of parts movements involved in the actuation. Furthermore these systems are suitable for more than one flight condition with low inertia problems. So, flap and slats can be easily substituted by the corresponding morphing shapes. This paper deals with a genetic optimization of an airfoil with morphing flap with an already optimized nose. Indeed, two different codes are used to solve the equations, a finite volume code suitable for structured grids named ZEN and the EulerBoundary Layer Drela's code MSES. First a number of different preliminary design tests were done considering a specific set of design variables in order to restrict the design region. Then a RANS optimization with a single design point related to the take-off flight condition has been carried out in order to refine the previous design. Results are shown using the characteristic curves of the best and of the baseline reported to outline the computed performances enhancements. They reveal how the contemporary use of a morphing acting on the nose of the main component and the trailing edge of the flap drive towards a total not negligible increment in lift.