• 한국산학기술학회논문지
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• 제14권9호
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• pp.4117-4123
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• 2013

본 연구에서는 해수용 열교환기의 코팅에 따른 해수 부식특성을 조사하기 위해 실험이 수행되었다. 코팅은 테플론, 전착, 세라믹+실리콘 3종을 선정하였고, 코팅되지 않은 알루미늄 부식과 비교하였다. 해수부식을 가속시키기 위하여 $70^{\circ}C$ 고온의 농도 3.5% 인공해수를 제작하여 9주 동안 침지부식을 시켰다. 침지기간에 따른 코팅의 부식특성 변화를 관찰하기 위하여 임피던스 분광법과 SEM을 이용하였다. Bode 선도에서 얻어진 분극저항으로부터 코팅재질의 내부식성을 확인하였다. 이중코팅은 4주 이후에도 코팅의 내부식성을 유지하였다. 또한 침지기간에 따라서 금속모재와 점착된 코팅면 사이에 블리스터가 발생할 수 있음을 확인하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1995년도 하계학술대회 논문집 C
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• pp.1108-1110
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• 1995

This paper presents a balanced CMOS complementary folded cascode OP-AMP topology that achieves improved DC gain using the gain boosting technique, a high unity-gain frequency and improved slew rate using the CMOS complementary cascode structure and a high PSRR using the balanced output stage. Bode-plot measurements of a balanced CMOS complementary folded cascode OP-AMP show a DC gain of 80dB, a unity-gain frequency of 110MHz and a slew rate of $274V/{\mu}s$(1pF load). This balanced CMOS complementary folded cascode OP-AMP is well suited for high frequency analog signal processing applications.

• 대한전기학회논문지:전력기술부문A
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• 제52권5호
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• pp.241-249
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• 2003

This paper describes a novel approach for performing eigenvalue analysis and frequency domain analysis of multi-machine power system. The salient feature of this approach is a direct approach for constructing the state matrix equations of linearized power systems about its operating point using modular technique. These state matrix equations are then used to obtain eigenvalues and mode shapes of the system, and frequency response, or Bode, plots of selected transfer functions. The proposed program provides a flexible tool for systematic analyses of tuning PSS's parameters. The paper also presents its application to the analyses of a single-machine infinite bus system and two-area system with 4 machines.

• 대한전기학회논문지:전력기술부문A
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• 제52권7호
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• pp.371-380
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• 2003

In this paper, a new design method of H$H_\infty$-Qn PSS using genetic algorithm(GA) is proposed to efficiently damp low frequency oscillations despite the uncertainties and various disturbances of power systems. The selection method of evaluation function is proposed for selecting the robust PSS parameters. All QFT boundaries are satisfied automatically and H$H_\infty$-norm is minimized simultaneously without trial and error procedure. The eigenvalues and the damping ratio of dominant oscillation mode are investigated to evaluate performance of designed controller for one machine infinite bus system. A disturbance attenuation performance is investigated through singular value bode diagram of the system. Dynamic characteristics are considered to verify robustness of the proposed PSS by means of nonlinear simulations under various disturbances for various operating conditions. The results show that the proposed PSS is more robust than conventional PSS.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제48권3호
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• pp.131-138
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• 1999

Generally, the digital controller has many advantages such as high precision, robustness to electrical noise, capability of flexible programming and fast response to the load variation. In this study, we have established proper mathematical equivalent model of Brushless DC (BLDC) motor and estimated the motor parameter by means of the back-emf measurement as being the step input to the controlled target BLDC motor. And the validity of proposed estimation method is confirmed by the test result of step response. As well, we have designed the reasonable digital controller as a consequence of the root locus method which is obtained from the open-loop transfer function of BLDC motor with hall sensor, and the determination of control gain for variable speed control. Here, revised Ziegler-Nichols tuning method is applied for the proper digital gain establishment, and the system stability is verified by the frequency domain analysis with Bode-plot and experimentation.

• 한국약용작물학회:학술대회논문집
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• 한국약용작물학회 2008년도 추계학술발표회
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• pp.447-448
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• 2008

• 전기학회논문지
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• 제63권7호
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• pp.883-888
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• 2014

The paper describes the parameter tuning of power system stabilizer (PSS) for a power plant based on hybrid system modeling. The existing tuning method based on bode plot and root locus is well applied to keep power system stable. However, due to linearization of power system and an assumption that the parameter ratio of the lead-lag compensator in PSS is fixed, the results cannot guarantee the optimal performances to damp out low-frequency oscillation. Therefore, in this paper, hybrid system modeling, which has a DAIS (differential-algebraic-impusive-switched) structure, is applied to conduct nonlinear modeling for power system and find optimal parameter set of the PSS. The performances of the proposed method are carried out by time domain simulation with a single machine connected to infinite bus (SMIB) system.

• Journal of Electrical Engineering and Technology
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• 제10권2호
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• pp.443-451
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• 2015

The stability of a multi-terminal direct current (MTDC) system is often influenced by its control strategy. To improve the stability of the MTDC system, the control strategy of the MTDC system must be appropriately adopted. This paper deals with estimating stability of a MTDC system based on the line-commutated converter based high voltage direct current (LCC HVDC) system with an inverter with constant extinction angle (CEA) control or a rectifier with constant ignition angle (CIA) control. In order to evaluate effects of two control strategies on stability, a MTDC system is tested on two conditions: initialization and changing DC power transfer. In order to compare the stability effects of the MTDC system according to each control strategy, a mathematical MTDC model is analyzed in frequency domain and time domain. In addition, Bode stability criterion and transient response are carried out to estimate its stability.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1995년도 추계학술대회 논문집
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• pp.454-457
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• 1995

In optical disc system, tracking actuator is consisted of coarse actuator and fine tracking actuator. This, two-stage actuator, requires many devices and two servos for large stroke and precisional displacement. These complicate configuration increases moving mass. So dynamic characteristics become bad, that is, sensitivity of high frequency gain decrease. In this paper, frequency performance is willing to be better as so one dimensional tracking actuator is designed. In order to investigate the performance of the proposed tracking actuator, the Bode diagram is plotted with Dynamic analyzer and friction characteristic is explained. Finally, tracking error performance is ins investigated into 0.1 .mu.m resolution with MATLAB simulation.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 춘계학술대회논문집
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• pp.46-50
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• 2007

The nuclear power plant's turbine-generator system had been suffered form some problems, such as high shaft vibration, generator casing crack, stator coil water leakage, high $H_2$ gas consumption rate. Those kinds of problems were related to high vibration. So nuclear plant decided to replace generator in order to reduce rotor high vibration and high thermal sensitivity. A series of effort to reduce turbine-generator vibration was carried out as followings, first of all, replacement of generator, analysis of turbine-generator vibration, LP B rotor shop balancing, improvement of LP B/Gen coupling run-out, improvement of Generator basement and field balancing. Finally the nuclear turbine-generator's shaft vibration was reduced below $60{\mu}m$ from over $200{\mu}m$ which is very excellent vibration in nuclear turbine-generator in Korea.