• 한국태양에너지학회 논문집
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• 제29권6호
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• pp.62-68
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• 2009

There has been a continuous increase in the utilization and utility value of renewable energy such as wind power generation in modem society. Wind condition is the absolute variable to the energy volume in the case of a wind power generation system. For this reason, wind power generators have already been installed in areas where wind velocity is high and the possibility of danger is very low. In other words, instability is likely if the wind velocity in an area is high and where a wind power generation system can be built. On the contrary, low wind velocity is possible in an area with high stability. Therefore, the design and manufacture of a wind power generation system should be carried out in a more complicated topography in order to secure a bigger market. This study examines and suggest how topography affects wind shear by analyzing the measured data in order to predict wind power generation more reliably.

• 전력전자학회논문지
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• 제23권2호
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• pp.101-105
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• 2018

Shortage of electric power occurs frequently along with increased electric power demand. ESS is a precaution to solve this issue. Household ESS has a capacity of approximately 3 kW/7 kWh. Household ESS batteries are typically designed with nominal voltages between 40 and 50 V. To connect household ESS with a 220 V AC system, low battery voltages in power conditioning system (PCS) should be boosted. To boost low battery voltage and match it with AC grid voltage, the use of a transformer for a commercial frequency can be considered. To attenuate switching harmonics of the household single-phase ESS-PCS, LC filter can be installed in two positions: on the primary side or on the secondary side of a transformer. A method has been used generally in single-phase inverters for the ESS-PCS. In another method, however, the output efficiency of the ESS-PCS may be decreased. Parasitic components of the transformer can affect voltage losses, when the square wave with the switching frequency in the ESS-PCS is passed through the transformer windings. In this work, the characteristics of the transformer according to the position of an LC filter are investigated for household single-phase ESS-PCS.

• Journal of Power Electronics
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• 제15권1호
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• pp.86-95
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• 2015

An active clamp high step-up boost converter with a coupled inductor is proposed in this paper. In the proposed strategy, a coupled inductor is adopted to achieve a high voltage gain. The clamp circuit is included to achieve the zero-voltage-switching (ZVS) condition for both the main and clamp switches. A rectifier composed of a capacitor and a diode is added to reduce the voltage stress of the output rectifier diode. As a result, diodes with a low reverse-recovery time and forward voltage-drop can be utilized. Since the voltage stresses of the main and clamp switches are far below the output voltage, low-voltage-rated MOSFETs can be adopted to reduce conduction losses. Moreover, the reverse-recovery losses of the diodes are reduced due to the inherent leakage inductance of the coupled inductor. Therefore, high efficiency can be expected. Firstly, the derivation of the proposed converter is given and the operation analysis is described. Then, a steady-state performance analysis of the proposed converter is analyzed in detail. Finally, a 250 W prototype is built to verify the analysis. The measured maximum efficiency of the prototype is 95%.

• 조명전기설비학회논문지
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• 제25권6호
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• pp.9-17
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• 2011

The high-power LED (Light Emitting Diode) which is recently gaining popularity as a digital light source has such advantages as low power consumption, long life, fast switching speed, and high efficiency. Thus, many efforts are being made to use the high-power LEDs for general lighting. This paper proposes LED driving circuit uses a DC/DC converter that can recover energy to compensate for the current variations caused by changes in LED equivalent resistance following a temperature change instead of serial resistance. The maximum input voltage of this DC/DC converter has low voltage variations by temperature change when the rated current is formed. In order to return current to the input side, we need a high boosting at low power. Thus, to improve the low efficiency of power converter, the power converter can be configured in such a way to gather the powers of low-capacity DC/DC converters and return the total power. Experiments showed that the proposed system improved efficiency compared to the conventional LED drive using the existing DC/DC converter.

• Journal of Power Electronics
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• 제16권6호
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• pp.2306-2314
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• 2016

Design and implementation of a low cost grid-connected 5kVA solar photovoltaic (PV) system is proposed in this paper. Since the inverter is a major component of the PV system, the B4 inverter used in this paper reduces the total cost of the PV system. In order to eliminate the massive transformer, the PV system is connected to the grid through IGBT switches. In addition to injection of active power into the grid, the B4 inverter can compensate reactive power and reduce harmonics of the nonlinear loads. A TMS320F28335 DSP processor is used for effective control of the B4 inverter. Various features of this processor enable the implementation of the necessary control algorithms. As a first step, the PV system is simulated and evaluated in Matlab/Simulink. In the second step, hardware circuits are designed and implemented based on the simulation results. The operation of the PV system has been evaluated under balanced, unbalanced, linear and nonlinear loads which proves its accuracy and efficiency.

• 전력전자학회논문지
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• 제17권1호
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• pp.27-33
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• 2012

Internet Data Centers (IDC), as essential facilities for modern IT industry, typically have scores of MW of concentrated electric loads. Uninterruptible Power Supplies (UPS) are necessary for the power feed system of IDCs because of stable power requirement. Thus, conventional AC power feed systems of IDCs have three cascaded power conversion stages such as (AC-DC), (DC-AC), and (AC-DC), which results in very low conversion efficiency. On the contrary, DC power feed systems need just a single power conversion stage (AC-DC) supplying AC mains power to DC server loads, which gives comparatively high conversion efficiency and reliability. This paper compares the efficiencies between 220V AC power feed system and 300V DC power feed system on equal load conditions which were established in Mok-Dong IDC of Korea Telecom company (KT). Experimental results show that the total operation efficiency of the 300V DC power feed system is around 15% higher than that of the 220V AC power feed system.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 심포지엄 논문집 정보 및 제어부문
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• pp.156-158
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• 2006

A super-regenerative receiver is designed and tested at 433 MHz ISM band, The designed receiver has the data rate of up to 200 kbps and a power consumption of 10 mW. We carried out the system performance test for the TX power of 0.1 mW and 1 m distance. The result of the bit-error rate test shows one bit error among the 4000 bits.

• 한국농공학회:학술대회논문집
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• 한국농공학회 2003년도 학술발표논문집
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• pp.491-494
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• 2003

An Automatic Water Level Measurement System has been developed in this study. It has the characteristics that it use lower power and solar power and it has the ability of sending data and remote-controlled by wireless MODEM this system was set up in the experimental site and was tested. Also, the management system for the water level data has been developed and will be used by instruments administrating reservoirs.

• 대한전기학회논문지:전력기술부문A
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• 제50권11호
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• pp.497-505
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• 2001

The power system stabilizer(PSS) is important for the suppression of low-frequency oscillation and the improvement of system stability. In this paper, An Adaptive Neurofuzzy-based Power System Stabilizer(ANF PSS) is proposed as the new PSS type. The proposed PSS employs a multi-layer adaptive network. The network is trained directly from the input and the output of the generating unit. The algorithm combines the advantages of the Artificial Neural Network(ANN) and Fuzzy Logic Control(FLC) schemes. Studies show that the proposed ANF PSS can provide good damping of the power system over the wide range of operating conditions and improve the dynamic performance of the system.

• 정보과학회 논문지
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• 제43권1호
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• pp.126-134
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• 2016

OLED 디스플레이는 빠른 응답속도, 전력 효율성 등 여러 장점 때문에 점차 사용이 증가하고 있는 추세이다. 뛰어난 전력 효율성에도 불구하고 메신저, 게임 등의 사용자와의 상호작용 기반의 어플리케이션 사용의 증가로 OLED에 의한 전력 소모 비중이 여전히 크게 나타나고 있다. OLED에서는 출력하는 영상에 따라 소모 전력이 크게 달라지기 때문에 저전력 색 변환 기법이 대표적인 전력 절감 기법이다. 기존의 저전력 색 변환 기법들은 색 변환 시 인간 시각 시스템의 만족에 대한 엄밀한 연구가 없으며, 시각 만족도와 소모 전력을 동시에 최적으로 고려하는 연구가 부재했다. 본 연구에서는 기존 기법들의 문제점을 보완한 새로운 저전력 색변환 기법을 제안한다. 실험 결과를 통해서 제안 기법이 기존 기법보다 시각 만족도 측면에서 더 인간 시각 시스템을 만족하며 또 전력절감 측면에서도 색 변환거리에 따라 기존 기법보다 평균 13.4% 및 22.4% 향상된 전력 절감이 가능한 것으로 나타났다.