• 대한전기학회:학술대회논문집
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• 대한전기학회 1993년도 하계학술대회 논문집 A
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• pp.106-108
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• 1993

This paper gives derivations of voltage collapse conditions by using the Lyapunov function, which yields the exactly same results with the sensitivity analysis approach. On the other hand, the voltage collapse phenomenon is interpreted in the physical sense, and causes of the static voltage unstability and the dynamic voltage unstability are analyzed with the use of proposed Lyapunov function. In addition a new method is developed to calculate the power capacity limit of transmission lines with respect to voltage stability. This paper shows that it is able to analyze the voltage collapse with the Lyapunov direct method in the simple 2-bus system and proposes that the method works well by observing the variation of Lyapunov function as the load is increased in the system.

• Journal of Power Electronics
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• 제18권2호
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• pp.511-521
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• 2018

Proportional capacitor current feedback active damping (CCFAD) has a limited valid damping region in the discrete time domain as (0, $f_s/6$. However, the resonance frequency ($f_r$) of an LCL-type filter is usually designed to be less than half the sampling frequency ($f_s$) with the symmetry regular sampling method. Therefore, ($f_s/6$, $f_s/2$) becomes an invalid damping region. This paper proposes an improved CCFAD method to extend the valid damping region from (0, $f_s/6$ to (0, $f_s/2$), which covers all of the possible resonance frequencies in the design procedure. The full-valid damping region is obtained and the stability margin of the system is analyzed in the discrete time domain with the Nyquist criterion. Results show that the system can operate stably with the proposed CCFAD method when the resonance frequency is in the region (0, $f_s/2$). The performances at the steady and dynamic state are enhanced by the selected feedback coefficient H and controller gain $K_p$. Finally, the feasibility and effectiveness of the proposed CCFAD method are verified by simulation and experimental results.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 제37회 하계학술대회 논문집 A
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• pp.198-199
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• 2006

FACTS(Flexible AC Transmission System) 기기들은 전력계통의 경제적이고 안정적인 운용과 제어에 더 많은 유연성을 제공할 수 있다. 그러나 이러한 FACTS 기기들은 기존의 전력 계통 설비들과는 달리 그 특성이 매우 비선형적이고 복잡하기 때문에 기존 전력 계통의 동적 시뮬레이션 알고리즘에 적용시키는 것이 매우 어렵다. 이러한 어려움을 해결하기 위하여 전압원 인버터(Voltage Sourced Inverter) 형태의 FACTS 기기를 병렬 형태로 주입되는 전류로 등가화 하여 기존의 시뮬레이션 알고리즘에 적용하는 방법이 제안되었다. 본 논문에서는 이 전류 주입형 기법을 이용하여 다수의 FACTS 기기들이 설치된 계통의 동적 안정도 해석 방법을 제안한다. 제안된 방법은 서로 다른 형태의 FACTS 기기들이 설치된 경우에도 적용될 수 있으며 이를 이용하여 서로 다른 FACTS 모델들 간의 조합에 의한 계통의 안정도 변화를 사례연구를 통하여 보일 것이다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2007년도 하계학술대회 논문집
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• pp.421-423
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• 2007

In this paper, The authors apply a state feedback control using an optimal control theory to improve the stability of the control and the dynamic response of the DC-DC converter system with a number of different loads. To execute a this state feedback control, The authors present the pole placement technique using Linear Quadratic Regulator(LQR) to optimally control the system. An integrator can also be included in the open-loop path in order to minimize the steady-state error of the output voltage. To confirm the superiority of the controller, The simulation results are presented.

• Nuclear Engineering and Technology
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• 제38권7호
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• pp.657-664
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• 2006

The problem of reactivity oscillations for a point reactor constitutes an interesting aspect of nuclear reactor physics and its solution may give important information for dynamic and safety assessments. The present paper considers the problem of a reactivity oscillation for a source-driven system which involves some specific aspects that introduce significant differences with respect to the source-free situation. Assuming a square-wave shape for the reactivity insertion, the solution is derived by a fully analytical approach. The conditions for stability and instability can be identified in a straightforward way by directly studying the stationarity of the power response. Numerical results presented allow to discuss the role of the system kinetic parameters and of the time-shape of the reactivity wave.

• 한국항공운항학회지
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• 제19권2호
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• pp.1-9
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• 2011

Several studies on the development for solar powered uninhabited aerial vehicles(UAVs) are under way as the use of the renewable energy becomes more and more important these days. This paper is for the conceptual design by a discrete and iterative method. An initial design point with 1.5 meter wing span is determined in the global design, which deploys the mass and energy balances among each component of UAV including solar cells and airframe. Then, the iteration for subsystems is carried out with the help of Vortex Lattice Method(VLM) to optimize the aircraft configuration and the solar power system. It is demonstrated in simulations that the optimized design increases the flight time from 62 to 120 minutes when the solar power system is installed. Also, the associated dynamic analysis reveals that the designed small aircraft has the acceptable stability and controllability.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 E
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• pp.1840-1842
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• 1998

Gyroscope is a very important core sensor, as a rotation sensor in inertial space, in inertial guidance and navigation system on aeronautics, plane, vessel and so on for civilian and millitary applications. Mechnical gyroscopes, adopting a principle of spinning a top, have been used in many application system. These mechnical gyroscopes need high power consumption, long warming time and complicated peripheral devices. But fiber-optic gyroscopes, based on the Sagnac effect, have novel advantages as small volume. simple scheme, low power consumption and high reliability. So we have developed a Intermediate grade All-fiber Optic Gyroscope, which has open-loop and minimum reciprocal configuration scheme. We have designed feedback circuits for stability of amplitude and phase using four lock-in amplifier(LIA) circuits and also used for noise limitation. This paper describes the scheme of optical part and electronic part and also test results of this all-fiber optic gyroscope. The performance have been achieved as long-term bias drift of $9.54^{\circ}/h$, random walk of $0.0317^{\circ}/\sqrt{h}$ and dynamic range of ${\pm}150\;deg/s$.

• 한국산업융합학회 논문집
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• 제20권5호
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• pp.431-439
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• 2017

Since the power transmission line(PTL) passes through the high mountain and heavy snowfall region, it is necessary to keep the stability of the PTL. In this study, PTL is modeled as a mass-spring-damper system by using RecurDyn. The lumped mass model is verified by calculated from the simulation comparing the deflection analysis according to the sag and tension. In order to analyze the dynamic behavior of PTL, a damping coefficient for a multi-body model is derived by using the free vibration test and Rayleigh damping theory. Sleet jump simulation according to the region is performed. The maximum jump height, icing sag and amount of jump are confirmed. Also, the amount of jump and the reaction force at the supporting point according to the tension and load of ice are analyzed, respectively. As a result, it is noted that the amount of jump and reaction force are influenced more by the load of ice than by the tension of PTL.

• 조명전기설비학회논문지
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• 제14권3호
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• pp.49-58
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• 2000

본 논문에서는 FACTS(Flexible AC Transnission System)로 분류되는 여라 기기중 기존의 전압제어 및 무효 전력보상기들이 가지고 있는 바속응성과 불연속성 문제를 해결해줄 수 있는 정지형 무효전력 보상가(Static Var Compensator : SVC)를 포함한 전력계통에 신경회로망 제어기를 적용하여 안정화에 관하여 연구하였다. 제안된 신경회로망 제어기는 오차와 오차변화량을 입력하는 오차역전과 학습 알고리즘을 사용하고, 학습시간올 단축하기 위해 모멘텀 방법을 사용하였다. 제안된 방법의 강인섬을 입증하기 위해 중부하시 및 정상부하시에 초기 전력을 변동시킨 경우와 초기에 회천자각을 변동시킨 경우에 대하여 시스렘의 회전자각, 각속도 편차 특성 및 단 자전압의 동특성을 고찰하여 다른 시스템보다 응답특성이 우수합을 보였다.

• 한국전자파학회논문지
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• 제14권2호
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• pp.148-156
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• 2003

본 논문은 3 GPP 규격을 바탕으로 한 W-CDMA UE 시스템의 RF 성능관련 내용을 다루고 있으며 송수신 파라미터를 RF 성능관점에서 유출하였다. 최적의 UE성능을 얻기 위해 송신기에 대해서는 ACLR, EVM, 피크코드영역 에러, 스펙트럼 방사 마스크, 주파수 오차 안정도, 송신전력제어 범위와 같은 성능 요구사항을 고찰하였고 수신기에 대해서는 수신 감도, 블록킹 특성, 잡음지수, 인접채널 선택도, 수신 ACC 범위 등이 고려되었다. 요구된 파라미터들을 근거로 UE RF 트랜시버를 구현하였고 실제 측정 시나리오에 따라서 RF 성능평가를 수행하였다.