• 제목/요약/키워드: transient information

검색결과 715건 처리시간 0.031초

송전계통 과도 안정도 향상을 위한 최적 순차 재폐로에 관한 연구 (A Study on Optimal Sequential Reclosing to Improve Transient Stability in Transmission System)

  • 권기현;오윤식;박지경;조규정;손승현;김철환
    • 전기학회논문지
    • /
    • 제62권10호
    • /
    • pp.1354-1360
    • /
    • 2013
  • In transmission system, reclosing scheme is very useful method to improve continuity of power supply and reliability of system. Especially, high speed reclosing which is used generally in transmission systems has a benefit improving transient stability. However, the reclosing can jeopardize the stability under the condition having high difference of voltage phase angle between both ends. Thus, this paper proposes optimal sequential reclosing scheme to improve transient stability due to reclosing operation. The optimal sequential reclosing is that each phase is closed sequentially considering transient energy. In this paper, 345kV and 154kV transmission system is modeled using EMTP (ElectroMagnetic Transient Program) to verify the performance and effectiveness of optimal sequential reclosing on transient stability. Also, Integral Square Error(ISE) method is used to assess the transient stability.

과도 안정도를 고려한 국내 송전선로 재폐로 방식 평가 (An Evaluation of Reclosing Schemes in Korean Transmission Systems Considering Transient Stability)

  • 오윤식;권기현;박지경;조규정;손승현;김철환;김완종
    • 전기학회논문지
    • /
    • 제62권6호
    • /
    • pp.731-736
    • /
    • 2013
  • Most of faults occurring in transmission lines are transient faults. For such faults, automatic reclosing is economic and effective method to improve the reliability and transient stability of power system. Many countries apply various reclosing schemes considering issues of their own systems such as transient stability, rate of success. Currently, different reclosing schemes are applied in Korean transmission systems according to a rated voltage. In this paper, we conduct an evaluation of reclosing schemes in Korean transmission systems considering transient stability. Computer simulations are performed by using ElectroMagnetic Transient Program (EMTP) and transmission system is modeled based on actual data of Korea.

Transient-Performance-Oriented Discrete-Time Design of Resonant Controller for Three-Phase Grid-Connected Converters

  • Song, Zhanfeng;Yu, Yun;Wang, Yaqi;Ma, Xiaohui
    • Journal of Power Electronics
    • /
    • 제19권4호
    • /
    • pp.1000-1010
    • /
    • 2019
  • The use of internal-model-based linear controller, such as resonant controller, is a well-established technique for the current control of grid-connected systems. Attractive properties for resonant controllers include their two-sequence tracking ability, the simple control structure, and the reduced computational burden. However, in the case of continuous-designed resonant controller, the transient performance is inevitably degraded at a low switching frequency. Moreover, available design methods for resonant controller is not able to realize the direct design of transient performances, and the anticipated transient performance is mainly achieved through trial and error. To address these problems, the zero-order-hold (ZOH) characteristic and inherent time delay in digital control systems are considered comprehensively in the design, and a corresponding hold-equivalent discrete model of the grid-connected converter is then established. The relationship between the placement of closed-loop poles and the corresponding transient performance is comprehensively investigated to realize the direct mapping relationship between the control gain and the transient response time. For the benefit of automatic tuning and real-time adaption, analytical expressions for controller gains are derived in detail using the required transient response time and system parameters. Simulation and experimental results demonstrate the validity of the proposed method.

봉상접지극의 과도임피던스 특성 (Transient Impedance Characteristics of Grounding Rods)

  • 김일권;김점식;송재용;길경석
    • 한국정보통신학회:학술대회논문집
    • /
    • 한국해양정보통신학회 2000년도 추계종합학술대회
    • /
    • pp.568-572
    • /
    • 2000
  • This paper describes the experimental results of a transient impedance characteristics of grounding rods to a square pulse and standard lightning impulse current. The test were performed on single grounding rod($\phi$ 10mm, 1m) and triple-grounding rods( $\phi$ 10mm, 1m) of equilateral triangles with 5m spacing. For measurements of transient impedance, a pulse generator which can produce square wave of 30ns rise time and 20U Pulse duration was designed and fabricated. In the experiment, transient impedance of the grounding systems have been investigated from the recorded potential and current waveforms. The results showed that the value of the transient impedance is quite higher than the stationary resistance, and provide useful information for the value of a grounding system considered transient characteristics under a high frequency condition such as lightning stokes and ground-fault.

  • PDF

LPC 켑스트럼 거리 기반의 천이구간 정보를 이용한 음성의 가변적인 시간축 변환 (Variable Time-Scale Modification of Speech Using Transient Information based on LPC Cepstral Distance)

  • 이성주;김희동;김형순
    • 음성과학
    • /
    • 제3권
    • /
    • pp.167-176
    • /
    • 1998
  • Conventional time-scale modification methods have the problem that as the modification rate gets higher the time-scale modified speech signal becomes less intelligible, because they ignore the effect of articulation rate on speech characteristics. Results of research on speech perception show that the timing information of transient portions of a speech signal plays an important role in discriminating among different speech sounds. Inspired by this fact, we propose a novel scheme for modifying the time-scale of speech. In the proposed scheme, the timing information of the transient portions of speech is preserved, while the steady portions of speech are compressed or expanded somewhat excessively for maintaining overall time-scale change. In order to identify the transient and steady portions of a speech signal, we employ a simple method using LPC cepstral distance between neighboring frames. The result of the subjective preference test indicates that the proposed method produces performance superior to that of the conventional SOLA method, especially for very fast playback case.

  • PDF

정규혼합모델을 이용한 수중 천이신호 식별 (Classification of Underwater Transient Signals Using Gaussian Mixture Model)

  • 오상환;배건성
    • 한국정보통신학회논문지
    • /
    • 제16권9호
    • /
    • pp.1870-1877
    • /
    • 2012
  • 천이신호는 지속시간이 짧으면서 길이의 변화가 크고, 시변성 및 비정재성 특성을 갖는다. 이러한 천이신호의 식별에는 분석 프레임 단위로 참조신호에 대한 기준패턴을 만들어 입력신호와의 유사도를 비교하는 방법이 효과적일 수 있다. 본 연구에서는 참조신호의 기준패턴으로 프레임 기반의 특징벡터들에 대해 확률통계 모형인 정규혼합모델을 적용하는 방법을 제안하고, 다양한 수중 천이신호에 대한 식별 실험을 통해 제안한 방법의 타당성을 검증하였다.

멀티미디어 학습에서 일시적 정보효과가 학습효율성에 미치는 영향 (The impact of the transient information effect on multimedia learning efficiency)

  • 시지현
    • 컴퓨터교육학회논문지
    • /
    • 제19권2호
    • /
    • pp.99-114
    • /
    • 2016
  • 일시적 정보효과는 멀티미디어 학습 환경에서 길고 복잡한 청각적 정보의 일시성으로 인해 학습에 가해지는 부정적인 효과를 말한다. 본 연구는 인지부하이론의 틀에서 멀티미디어 학습에서 일시적 정보효과가 학습에 미치는 영향을 살펴보고, 또한 일시적 정보효과를 극복하는 방법인 것으로 생각되는 분절화(long vs. short)와 학습자료 제시 조절방법(system-paced vs. learner-paced)이 일시적 정보효과에 어떤 영향을 미치는 지 살펴보고자 하였다. 연구결과에 의하면 멀티미디어 학습 환경에서 길고 복잡한 학습자료를 학습자에게 제시할 경우에는 시각적으로만 제시하는 것이 시청각적으로 제시하는 것보다 학습효율성이 보다 높은 것(높은 성취와 낮은 인지부하 투입)으로 드러났다. 또한 시청각적으로 자료를 제시해야 하는 경우는 청각적 학습 자료를 분절화해서 제시하거나, 학습자료 제시를 학습자가 조절하는 방법으로 멀티미디어 학습 환경을 설계하는 것이 학습 효율성을 높이는 방안인 것으로 드러났다.

Study of transient response in dielectric microstrip line with opto-microwave pulses

  • Wang, Xue;Kim, Ji-Hyoung;Yun, Ji-Hun
    • 한국정보전자통신기술학회논문지
    • /
    • 제2권2호
    • /
    • pp.63-68
    • /
    • 2009
  • We study on the transient response in non-uniform microstrip lines with optically controlled microwave pulses. The transient response of the microwave pulses in plasma layer has been evaluated by reflection function of dielectric microstrip lines. The variation of characteristic response in plasma layer with localized pulses has been evaluated analytically. Reflection the change of the reflection amplitude has been observed.

  • PDF

Transient Improvement Algorithm in Digital Images

  • 권지용;장준영;이민석;강문기
    • 한국방송∙미디어공학회:학술대회논문집
    • /
    • 한국방송공학회 2010년도 하계학술대회
    • /
    • pp.74-76
    • /
    • 2010
  • Digital images or videos are used in modern digital devices. The resolution of HDTV in digital broadcasting system is higher than that of previous analog systems. Also, mobile phone with 3G can provide images as well as video streaming services in realtime. In these circumstances, the visual quality of images has become an important factor. We can make image clear by transient improvement process that reduces transient in edges. In this paper, we present an transient improvement algorithm. The proposed algorithm improves edges by making smooth edge to steep edge. Before performing transient improvement algorithm, edge detection algorithm should be operated. Laplacian operator is used in edge detection, and the absolute value of it is used to calculate gain value. Then, local maximum and minimum values are computed to discriminate current pixel value to raise up or pull down. Compensating value that gain value multiplies with the difference between maximum (or minimum) value and current pixel value adds (or subtracts) to current pixel value. That is, improved signal is generated by making the narrow transient of edge. The advantage of proposed algorithm is that it doesn't produce shooting problem like overshoot or undershoot.

  • PDF

Step Response of RF Plasma in Carbon Tetrafluoride($CF_4$)

  • So, Soon-Youl;Akinori Oda;Hirotake Sugawara;Yosuke Sakai
    • 한국전기전자재료학회:학술대회논문집
    • /
    • 한국전기전자재료학회 2000년도 하계학술대회 논문집
    • /
    • pp.930-933
    • /
    • 2000
  • To understand the behavior of electron, ions and radicals on radio-frequency non-equilibrium plasma, it is necessary to know the basic information about its fundamental properties and reactions. Especially, the transient response of radio-frequency plasma has an important means of controlling selective etch rates and investigating the stability of a plasma chemical process. In this paper, we present the results of periodic steady-state behavior and transient behavior carbon Tetrafluoride(CF$_4$) discharge at 0.2 Torr in a 2 cm gap parallel-plate. After the number densities of charged particles became steady-state, the applied voltage was increased or decreased in an instant and the transient behavior of charged particles and radicals was investigated from one steady-state to the next steady state.

  • PDF