• 전력전자학회:학술대회논문집
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• 전력전자학회 2010년도 추계학술대회
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• pp.194-195
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• 2010

This paper describers a bidirectional DC/DC converter for charging and discharging of a supercapacitor. Simulations are carried out to see the operation and performance of the 3kW-rated converter. Simulation results show that the charging/discharging characteristics is sufficient for the compensation of the response delay of a fuel cell.

• 한국정보전자통신기술학회논문지
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• 제10권1호
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• pp.23-30
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• 2017

현재는 도로조명의 경우 기존 메탈할라이드 램프 400W이하로 설치되어 있어 에너지절약형 조명으로 대체가 이루어지고 있으며, 무전극 램프는 터널조명과 고천정조명 적용분야를 타겟으로 더욱 활발한 교체가 이루어질 것으로 예상된다. 따라서 추가적으로 고효율, 고출력 무전극 램프 시스템 개발이 필요한 상황이다. 본 연구에서는 고출력 무전극 램프의 설계 및 제작을 진행하여 가스종류 및 가스압에 따른 비교 분석, 아말감 종류에 따른 특성 분석 등을 통한 무전극 램프 최적화를 진행하였다. 현재 고출력 무전극 램프 방전관 및 페라이트코어에 맞는 가스압 300~350[mmHg] 사이로 최적화 하였다. 인듐(In) 아말감을 적용한 무전극 램프로 점등회로 매칭을 완료하여 250W(정격${\pm}10%$)로 정격소비전력으로 최적화를 완료하였다.

• 비파괴검사학회지
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• 제33권4호
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• pp.323-329
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• 2013

위상잠금 적외선 열화상 기법을 이용하여 원전 배관의 결함 검출 및 각도별 결함 검출 조건에 관한 연구를 수행하였다. 결함의 가공은 감육 길이, 원주방향 각도, 감육 깊이를 변화시켜 결함조건을 가공하였다. 사용된 장비는 적외선 열화상 카메라와 1 kW용량의 halogen lamp 2개를 사용하였으며, halogen lamp와 대상 배관과의 거리는 2 m로 고정시켜 실험을 수행하였다. 실험결과의 분석을 위하여 온도분포, 위상 데이터를 확보하고, 이를 분석하여 결함 길이를 측정하였다. 이 연구를 통해 각도별로 나타나는 감육 결함의 검출 형태를 파악함으로서 실제 발전소의 배관에 나타나는 다양한 각도의 결함의 분석이 가능하다. 적외선 열화상 데이터보다 위상잠금 적외선 열화상 데이터가 측정 결과의 신뢰도가 높았다.

• 드라이브 ㆍ 컨트롤
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• 제15권1호
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• pp.28-37
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• 2018

When the wind speed rises above the rated wind speed, the produced power of the wind turbines exceeds the rated power. Even more, the excessive power results in the undesirable mechanical load and fatigue. A solution to this problem is pitch control of the wind turbines. This paper presents a systematic design method of a collective pitch controller for the wind turbines using a discrete fuzzy Proportional-Integral (PI) controller. Unlike conventional PI controllers, the fuzzy PI controller has variable gains according to its input variables. Generally, tuning the parameters of fuzzy PI controller is complex due to the presence of too many parameters strongly coupled. In this paper, a systematic method for the fuzzy PI controller is presented. First, we show the fact that the fuzzy PI controller is a superset of the PI controller in the discrete-time domain and the initial parameters of the fuzzy PI controller is selected by using this relationship. Second, for simplicity of the design, we use only four rules to construct nonlinear fuzzy control surface. The tuning parameters of the proposed fuzzy PI controller are also obtained by the aforementioned relationship between the PI controller and the fuzzy PI controller. As a result, unlike the PI controller, the proposed fuzzy PI controller has variable gains which allow the pitch control system to operate in broader operating regions. The effectiveness of the proposed controller is verified with computer simulations using FAST, a NREL's primary computer-aided engineering tool for horizontal axis wind turbines.

• Journal of Electrical Engineering and Technology
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• 제9권3호
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• pp.820-826
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• 2014

It is well known that energy generated by a wind generator (WG) depends on the wind resources at the installation site. In other words, a WG installed in a high wind speed area can produce more energy than that in a low wind speed area. However, a WG installed at a low wind site can produce a similar amount of energy to that produced by a WG installed at a high wind site if the WG is designed with a rated wind speed corresponding to the mean wind speed of the site. In this paper, we investigated the power curve of a WG suitable for Korea's southwestern coast with a low mean wind speed to achieve a high capacity factor (CF). We collected the power curves of the 11 WGs of the 6 WG manufacturers. The probability density function of the wind speed on Korea's southwestern coast was modeled using the Weibull distribution. The annual energy production by the WG was calculated and then the CFs of all of the WGs were estimated and compared. The results indicated that the WG installed on the Korea's southwestern coast could obtain a CF higher than 40 % if it was designed with the lower rated speed corresponding to the mean wind speed at the installation site.

• Journal of Power Electronics
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• 제5권2호
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• pp.99-103
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• 2005

In this paper, a novel circuit topology of a three-winding coupling inductor-assisting a high-frequency PWM boost chopper type DC-DC power converter with a high boost voltage conversion ratio and low switch voltage stress is proposed for the new energy interfaced DC power conditioner in solar photovoltaic and fuel cell generation systems. The operating principle in a steady state is described by using its equivalent circuits under the practical condition of energy processing of a lossless capacitive snubber. The newly-proposed power MOSFET boost chopper type DC-DC power converter with the three-winding coupled inductor type transformer and a single lossless capacitor snubber is built and tested for an output power of 500W. Utilizing the lower voltage and internal resistance power MOSFET switch in the proposed PWM boost chopper type DC-DC power converter can reduce the conduction losses of the active power switch compared to the conventional model. Therefore, the total actual power conversion efficiency under a condition of the nominal rated output power is estimated to be 81.1 ％, which is 3.7％ higher than the conventional PWM boost chopper DC power conversion circuit topology.

• 전기학회논문지
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• 제56권6호
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• pp.1064-1070
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• 2007

This paper presents a grid-interactive current controlled voltage source inverter (CCVSI) with uniterruptible power supply (UPS), which uses an inner current control loop (polarized ramp time (PRT)) and outer feedback control loops to improve grid power quality and UPS. To reduce the complexity, cost and number of power conversions, which results in higher efficiency, a single stage CCVSI is used. The operation of this system could be divided into the power quality control (PQC) state mode and the UPS state mode. In PQC mode, the system operated to compensate the reactive power demand by nonlinear load or variation in load. In UPS mode. the system is controlled to provide a sinusoidal voltage at the rated value for the load when the gird fail. To verify the proposed system, a comprehensive evaluation with theoretical analysis, simulation and experimental results for 1KVA load capacity is presented.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2011년도 제42회 하계학술대회
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• pp.1129-1130
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• 2011

The output of small hydro power plant was generated less than rated output under high temperature. We Installed the artificial ventilation that blow cold wind from water supply pipe tunnel to small hydro power plant. The temperature of small hydro power has been decreased. The output of small hydro power plant has been increased from 405kW to 445kW.

• 전기학회논문지
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• 제62권7호
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• pp.1027-1032
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• 2013

Induction generator is used primarily in small hydroelectric power station less than 1000kW recently. Unlike the synchronous generator, induction generator produces electricity when it is rotated above synchronous speed. In this study, we calculated the parameters of the induction generator with test reports presented by the manufacturer and analyzed that how much the induction generator has produced power near the rated speed. If we can use the test data to calculate the parameters, it is possible the output characteristics analysis of the induction generator. As a result of analysis, we concluded that output of induction generator varies sensitively for small changes in rotational speed in the near synchronous speed.

• Journal of Power Electronics
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• 제16권4호
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• pp.1612-1620
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• 2016

This paper presents the dynamic excitation control of a siphon-turbine coupled pico-hydro powered cage rotor induction generator and load matching for off-grid electricity generation. Through the proposed dual-role of the current-controlled voltage source converter (VSC), acting as static synchronous compensator and load controller, real and reactive power are dynamically controlled in a decoupled manner with a self supported DC-bus. The proposed scheme entails minimal computation for ensuring the rated (set) capacity of real power. The scheme also exhibits fault immunity for protection, thus enabling the effective handling of constant power electrical loads presented by base telecom station towers in remote locations. The performance of the system is evaluated under MATLAB/Simulink and is experimented through a developed hardware prototype. Simulation and experimental results show close conformity and validate the effectiveness of the proposed scheme.