• Journal of the Korean Physical Society
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• 제73권12호
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• pp.1889-1894
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• 2018

An innovative small-scale piezoelectric energy harvester has been proposed to gather wind energy. A conventional horizontal-axis wind power generation has a low generating efficiency at low wind speed. To overcome this weakness, we designed a piezoelectric windmill optimized at low-speed wind. A piezoelectric device having high energy conversion efficiency is used in a small windmill. The maximum output power of the windmill was about 3.14 mW when wind speed was 1.94 m/s. Finally, the output power and the efficiency of the system were compared with a conventional wind power system. This work will be beneficial for the piezoelectric energy harvesting technology to be applied to the real world such as wireless sensor networks (WSN).

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2012년도 춘계학술발표회 논문집
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• pp.227-228
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• 2012

In interfaces between carbon black or Pt and FTO glass in dye-sensitized solar cell counter electrodes, a marginal resistant channel for electrons, we tried to improve the connection by modifying the sintering process. A stepwise sintering process for carbon black and Pt counter electrodes was applied and its effect on power conversion efficiency was studied. Power conversion efficiencies of built-in DSSC made by a one-step sintering process with carbon black and Pt counter electrodes were about 5.01% and 5.02%, respectively. Cells made with the stepwise sintering process were 5.96% and 6.21%, respectively, indicating an 20% improvement. Fill factor (FF) increased, and it was them main reason for the power conversion efficiency improvement. Step wise sintering increased the adhesion of the interface and reduced the film thickness and surface roughness. As a result, the resistivity of the counter electrode and EIS impedance of DSSCs decreased.

• Journal of Power Electronics
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• 제16권2호
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• pp.414-424
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• 2016

This paper proposes a novel high-efficiency high-step-up interleaved converter with a voltage multiplier, which is suitable for electric vehicle power management applications. The proposed interleaved converter is capable of achieving high step-up conversion by employing a voltage-multiplier circuit. The proposed converter lowers the input-current ripple, which can extend the input source's lifetime, and reduces the voltage stress on the main switches. Hence, large voltage spikes across the main switches are alleviated and the efficiency is improved. Finally, a prototype circuit with an input voltage of 24 V, an output voltage of 380 V, and an output rated power of 1 kW is implemented and tested to demonstrate the functionality of the proposed converter. Moreover, satisfying experimental results are obtained and discussed in this paper. The measured full-load efficiency is 95.2%, and the highest measured efficiency of the proposed converter is 96.3%.

• Journal of Power Electronics
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• 제12권3호
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• pp.387-398
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• 2012

It is known that transformer based power supplies for ozone generators have low efficiency, high cost and exhibits a limited frequency range of operation. To overcome these disadvantages, this paper proposes a high frequency ozone generator with the absence of a transformer. The voltage step-up is achieved only by utilizing the resonant tank. This is made possible by a novel combination of ozone chamber materials that allow ozone to be generated at only 1.5 - 3.5 $kV_{p-p}$. The input to the resonant tank is driven by a PWM full bridge resonant inverter. Furthermore, zero-current zero-voltage switching (ZCZVS) operation is achieved by employing a duty factor of 25% between the switches of the full bridge. The advantages of the proposed system include high efficiency, low cost and the ability to control ozone production by varying the input voltage to the inverter. The prototype is verified by both simulation and experimental results.

• 전력전자학회논문지
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• 제21권6호
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• pp.525-529
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• 2016

In the case of a motor system that converts electrical energy into mechanical energy, the region of the motor and that of the generator coexists. In the case of an escalator, the ascending escalator is operated by the motor, whereas the descending escalator is operated by the generator according to the load. To evaluate the proposed method, this study reduces the power of the ascending escalator up to approximately 35% by sharing the regeneration power of the descending escalator. The loss of transfer power nearly exists in the case of the proposed method. Furthermore, the lifetime of the DC link condenser can be extended because it is connected in parallel, thus leading to a twofold increase in capacity.

• 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.

• Journal of Power Electronics
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• 제10권1호
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• pp.9-13
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• 2010

This paper proposes an input-series-output-parallel connected ZVS full bridge converter with interleaved control for photovoltaic power conditioning systems (PV PCS). The input-series connection enables a fully modular power-system architecture, where low voltage and standard power modules can be connected in any combination at the input and/or at the output, to realize any given specifications. Further, the input-series connection enables the use of low-voltage MOSFETs that are optimized for a very low RDSON, thus, resulting in lower conduction losses. The system costs decrease due to the reduced current, and the volumes of the output filters due to the interleaving technique. A topology for a photovoltaic (PV) dc/dc converter that can dramatically reduce the power rating and increase the efficiency of a PV system by analyzing the PV module characteristics is proposed. The control scheme, consisting of an output voltage loop, a current loop and input voltage balancing loops, is proposed to achieve input voltage sharing and output current sharing. The total PV system is implemented for a 10-kW PV power conditioning system (PCS). This system has a dc/dc converter with a 3.6-kW power rating. It is only one-third of the total PV PCS power. A 3.6-kW prototype PV dc/dc converter is introduced to experimentally verify the proposed topology. In addition, experimental results show that the proposed topology exhibits good performance.

• 한국전자파학회논문지
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• 제24권11호
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• pp.1091-1097
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• 2013

이 논문은 $0.11{\mu}m$ RF CMOS 공정에서 비대칭 몸체 바이어싱을 적용한 비교기를 사용한 정류기를 제안한다. 제안하는 정류기는 MOSFET와 두 개의 비교기로 이루어져 있다. 이 비교기는 부하 전압이 입력 전압보다 높을 때 생기는 역방향 누설 전류를 줄이는 데 사용한다. 비대칭 몸체 바이어싱을 사용함으로써 비교기의 High에서 Low 상태로 바꾸는 기준 전압을 높이고, 누설 전류가 흐르는 시간을 줄인다. 13.56 MHz의 2 Vpp 교류전압을 입력하고, $1k{\Omega}$의 저항과 1 nF의 커패시터를 부하에 연결한 환경에서 측정하였다. 시뮬레이션 결과, 전압 변환 효율은 87.5 %, 전력 변환 효율은 45 %이고, 측정한 전압 변환 효율은 85.215 %, 전력 변환 효율은 50 %이다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1998년도 하계종합학술대회논문집
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• pp.189-192
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• 1998

In this paper, we analyzed Microwave-DC conversion efficiency for the rectennas and it's position change. Rectenna consist of a two major parts, receiveing antenna and rectifying circuits. We made two types of 2.45C rectennas which the dipole and the patch antenna. Rectifying circuit is a GaAs-schottky diode with a large forward current and reverse breakdown voltage. The results of RF-DC conversion efficiency for two rectennas, patch type has 75.6% efficiency with 400$\Omega$ load resistor and dipole type has 69.75% efficiency with 360$\Omega$ load resistor. When the rectennas has optimal load resistor, Rectenna efficiency shows of $\pm10%$ at $70^{\circ}$~$110^{\circ}$ position.

• Journal of Power Electronics
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• 제9권6호
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• pp.866-873
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• 2009

In general, the output voltage level of a PV array varies widely at various irradiances and temperatures. The MPP (Maximum Power Point) range of a medium- or high-power PV PCS is normally 450~830Vdc or 300~600Vdc. This means the PV PCS should operate in a wide range of modulation indexes. The PV PCS should satisfy the harmonic current requirement that the TDD (Total demand distortion) shall not exceed 5%. This paper proposes a new PWM control method for a medium- or high-power PV PCS which increases the efficiency of power conversion in all operation ranges with acceptable harmonic ripple currents. This paper compares and analyzes appropriate PWM schemes for the PV PCS in the view points of conversion efficiency and current harmonics.