• Journal of international Conference on Electrical Machines and Systems
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• 제1권2호
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• pp.116-124
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• 2012

Wind is an abundant source of natural energy which can be utilized to generate power. Wind velocity does not remain constant, and as a result the output power of wind turbine generators (WTGs) fluctuates. To reduce the fluctuation, different approaches are already being proposed, such as energy storage devices, electric double layer capacitors, flywheels, and so on. These methods are effective but require a significant extra cost to installation and maintenance. This paper proposes to reduce output power fluctuation by controlling kinetic energy of a WTG system. A MW-class pitch-regulated permanent magnet synchronous generator (PMSG) is introduced to apply a power fluctuation reducing method. The major advantage of this proposed method is that, an additional energy storage system is not required to control the power fluctuation. Additionally, the proposed method can mitigate shaft stress of a WTG system. Which is reflected in an enhanced reliability of the wind turbine. Moreover, the proposed method can be changed to the maximum power point tracking (MPPT) control method by adjusting an averaging time. The proposed power smoothing control is compared with the MPPT control method and verified by using the MATLAB SIMULINK environment.

• 한국지능시스템학회논문지
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• 제22권6호
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• pp.780-785
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• 2012

최근 풍력발전은 전 세계적으로 전기의 생산을 위해 사용되는 신재생 에너지원 중 가장 빨리 성장하고 있는 분야이다. 일반적으로 풍력발전 시스템은 설치 후 약 20년 동안 사용될 수 있도록 설계되며 따라서 장기간 운전할 경우, 풍력 발전기에서의 고장은 필연적으로 발생하게 된다. 특히 풍력발전 시스템의 너셀 내부에는 로터샤프트, 기어박스 및 발전기 등이 설치되며 이들 요소의 정상적인 동작을 보장하기 위한 각종 냉각 시스템이 설치된다. 만일 이들 냉각 시스템에 고장이 발생된다면 전체 풍력발전시스템의 정상적인 동작을 보장하는 것이 불가능하다. 이에 본 연구에서는 풍력발전 시스템 너셀 내부에 설치되는 각종 냉각장치의 고장을 미연에 방지할 수 있게 하는 IR 카메라 기반의 풍력발전용 고장검출 시스템을 제안하고 실제 시스템의 구현을 통해 제안된 기법의 유용성을 확인하고자 한다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 하계학술대회 논문집 B
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• pp.1161-1164
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• 2002

The position information of the rotor are required while the SRG(Switched Reluctance Generator) is drived. The position information is generally provided by shaft encoder or resolver. But it is weak in the dusty, high temperator and EMI environment. Therefore, It is required for the sensor to be eliminated from SRG. In this paper, a estimation algorithm for the rotor position of the SRG is introducted and a constant DC-link voltage is controled by PID controller. The estimation algorithm is imple--mened by using the instantaneous flux profile, and the initial position is estimated by injecting high frequency pulse voltage. It is proved that the rotor position is esti--mated very well by the exeriments.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2009년도 춘계학술대회 논문집
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• pp.504-507
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• 2009

The purpose of this work is to predict the low frequency aero-acoustic noise generated from the horizontal axis wind turbine, NREL Phase VI using large eddy simulation and Ffowcs-Williams and Hawkings model provided in the commercial code, FLUENT. Calculated aerodynamic performances such as shaft torque and power are compared with experimentally measured value. Performance results show a good agreement with experimental data within about 0.8%. If the distance by two times is changed from 32D to 64D toward the downstream region, sound pressure level is reduced by about 6.4dB.

• International Journal of Control, Automation, and Systems
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• 제3권spc2호
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• pp.262-269
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• 2005

In this paper, a nonlinear robust control approach is applied to design a controller for the Static Synchronous Compensator (STATCOM). A robust control dynamic model of STATCOM in a one-machine, infinite-bus system is established with consideration of the torque disturbance acting on the rotating shaft of the generator set and the disturbance to the output voltage of STATCOM. A novel recursive approach is utilized to construct the energy storage function of the system such that the solution to the disturbance attenuation control problem is acquired, which avoids the difficulty involved in solving the Hamilton-Jacobi-Issacs (HJI) inequality. Sequentially, the nonlinear disturbance attenuation control strategy of STATCOM is obtained. Simulation results demonstrate that STATCOM with the proposed controller can more effectively improve the voltage stability, damp the oscillation, and enhance the transient stability of power systems compared to the conventional PI+PSS controller.

• 한국유체기계학회 논문집
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• 제8권5호
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• pp.13-21
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• 2005

This study aims to analyze operating performance of a micro gas turbine with the aid of detailed measurements of various system parameters. In addition to embedded measurements, parameters such as exhaust temperatures, engine inlet temperatures and fuel flow rates are measured. Variations in measured data and estimated performance parameters are analyzed. Those data are processed to calculate losses along the power transmission line and the net gas turbine performance (power and efficiency based on the gas turbine shaft end) is isolated from the overall system performance. A method to estimate characteristic parameters such as component efficiencies, based on the comparison between measured and predicted performance data, is suggested and exemplified for the full load condition.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 C
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• pp.1060-1062
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• 1999

This paper proposes a guideline of choosing the optimum stabilizer input considering the gain margin of power system stabilizer between the optimum stabilizer gain and the allowable maximum stabilizer gain in accordance with the five inputs, such as generator shaft speed, bus frequency, electrical power, accelerating power and bus terminal voltage. The local mode damping and exciter mode damping are considered with increasing the stabilizer gain to determine each gain margin of the inputs.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2010년도 하계학술대회 논문집
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• pp.321-321
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• 2010

In this paper, we propose a novel type shaft-less ring type ultrasonic motor. A traveling wave rotary type ultrasonic motor is selected as a base model. The newly designed stator has two piezoelectric ceramic rings which are bonded in sandwich shape as traveling wave generator. So, we can expect to produce higher torque. The proposed model has the rotor structure that coupled with the stator provokes the pressure, this model do not install the separate plate any spring device. We used the finite element method to verify the operation principle and to compute the vibration mode of proposed model.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2006년 제4회 한국유체공학학술대회 논문집
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• pp.287-290
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• 2006

Orbiter mechanism has been applied to vacuum pump design for small oxygen generator where low vacuum of about 200mmHg is required. Performance of the designed vacuum pump has been numerically investigated: calculated volumetric and adiabatic efficiencies were 69.7% and 83.9%, respectively for leakage clearance of $10{\mu}m$. Total efficiency of the orbiter vacuum pump was 77.5%. At the shaft speed of 1700 rpm suction displacement volume of 6.3cc provided discharge flow at the rate of 2.3 liter/min with power consumption of 10.1Watt. Torque variation of the orbiter pump was only about 20% of that of diaphragm pump.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2006년 제4회 한국유체공학학술대회 논문집
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• pp.157-160
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• 2006

A turbo-expander is developed for the regeneration in the expansion process. The turbo-expander operates in the partial admission and supersonic flow, and an axial-type single stage turbine is applied to the turbo-expander. Its outer diameter is 82mm and the operating gas is R134a. A 15kW reciprocating compressor is applied in this experiment and the turbo-expander is installed in the expansion process instead of the commonly using expansion valve. Two supersonic nozzles are applied for the expansion process. The high speed of R 134a after passing the supersonic nozzles gives the impulse force to the turbo-expander and some powers are generated on this process. A generator is installed at the end of the turbo-expander shaft. The generating output power from the turbo-expander is controlled by the power controller. Pressures and temperatures are measured on the lines for the performance investigation. More than 600W/(kg/sec) are generated in this experiment.