• Journal of Electrical Engineering and Technology
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• 제8권2호
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• pp.206-214
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• 2013

This paper proposes a new method for monitoring local voltage stability using the saddle node bifurcation set or loadability boundary in two dimensional power parameter space. The method includes three main steps. First step is to determine the critical buses and the second step is building the static voltage stability boundary or the saddle node bifurcation set. Final step is monitoring the voltage stability through the distance from current operating point to the boundary. Critical buses are defined through the right eigenvector by direct method. The boundary of the static voltage stability region is a quadratic curve that can be obtained by the proposed method that is combining a variation of standard direct method and Thevenin equivalent model of electric power system. And finally the distance is computed through the Euclid norm of normal vector of the boundary at the closest saddle node bifurcation point. The advantage of the proposed method is that it gets the advantages of both methods, the accuracy of the direct method and simple of Thevenin Equivalent model. Thus, the proposed method holds some promises in terms of performing the real-time voltage stability monitoring of power system. Test results of New England 39 bus system are presented to show the effectiveness of the proposed method.

• 한국융합학회논문지
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• 제11권6호
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• pp.7-14
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• 2020

본 논문에서는 확장 칼만 필터를 이용한 SOC 추정이 가능한 배터리 모니터링 시스템을 개발하였다. 배터리의 충·방전 상태를 정확하게 추정하기 위해 배터리 셀을 테브닌 모델로 모형화하고, 모델에 맞는 파라미터를 추출하였다. 이를 이용하여 확장 칼만 필터 알고리즘을 이용한 SOC 추정이 가능한 배터리 모니터링 디바이스를 제작하였으며, 다중 배터리 모니터링 디바이스 제어 및 배터리 상태 측정이 가능한 모니터링 서버를 제작하였다. 또한, 관리자가 실시간으로 상태를 확인하며 배터리 모니터링 디바이스 제어가 가능한 웹 서비스를 제작하였다. 특히, 배터리 SOC를 각각의 배터리 모니터링 디바이스에서 추정하고, 최종 결과만 모니터링 서버로 전달함으로써 서버의 계산량을 줄일 수 있다.

• 대한전기학회논문지
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• 제43권4호
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• pp.687-690
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• 1994

This paper presents a method of obtaining transmission network equivalents from the network's response to the pulse excitation signal. Proposed method is base on Prony signal analysis and jtransfer function identification technique. As a result Thevenin-type of discrete-time filter model can be generated. It can reproduce the driving point impedance characteristic of the network.

• 전자공학회논문지A
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• 제32A권12호
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• pp.209-219
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• 1995

As a new algorithm for RC tree delay estimation, we propose a $\tau$-model of the driver and a moment propagation method. The $\tau$-model represents the driver as a Thevenin equivalent circuit which has a one-time-constant voltage source and a linear resistor. The new driver model estimates the input voltage waveform applied to the RC more accurately than the k-factor model or the 2-piece waveform model. Compared with Elmore method, which is a lst-order approximation, the moment propagation method, which uses $\pi$-model loads to calculate the moments of the voltage waveform on each node of RC trees, gives more accurate results by performing higher-order approximations with the same simple tree walking algorithm. In addition, for the instability problem which is common to all the approximation methods using the moment matching technique, we propose a heuristic method which guarantees a stable and accureate 2nd order approximation. The proposed driver model and the moment propagation method give an accureacy close to SPICE results and more than 1000 times speedup over circuit level simulations for RC trees and FPGA interconnects in which the interconnect delay is dominant.

• KIEE International Transactions on Power Engineering
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• 제12A권1호
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• pp.6-14
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• 2002

In this paper, an EMM(Equivalent Mechanical Model) Is developed to explain the voltage collapse mechanism by reflecting the effects of reactive powers. The proposed EMM exactly represents the voltage instability mechanism described by the system equations. By the use of the EMM model, the voltage collapse mechanism has been illustrated by showing the exactness of the results. The stable region has been investigated with a reactive-power-controlled two-bus system, which shows that special alerts are required when the system operates with leading power factor. It is also discussed a system transform technique to eliminate the resistance component of the Thevenin equivalent impedance for practical applications. Finally, the results adopting the proposed method fur sample systems which were transformed are listed

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 하계학술대회 논문집 A
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• pp.171-174
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• 2001

In this paper, an EMM(Equivalent Mechanical Model) is developed to explain the voltage collapse mechanism by reflecting the effects of reactive powers. The proposed EMM exactly represents the voltage instability mechanism described by the system equations. By the use of the EMM model the voltage collapse mechanism has been illustrated by showing the exactness of the results. It is also discussed a system transform in technique to eliminate the resistance component of the Thevenin equivalent impedance for practical applications.

• 한국해양환경ㆍ에너지학회지
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• 제16권4호
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• pp.239-247
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• 2013

최근 화석연료의 고갈과 환경오염으로 인하여 해상풍력에너지와 같은 신재생 에너지에 대한 관심이 높아지고 있다. 본 연구에서는 범용 동역학해석 프로그램인 MSC.ADAMS를 이용하여 공력하중 및 전기 발전기 토오크를 결정하기 위한 테브난(Thevenin) 방정식이 고려된 해상풍력발전기의 다물체 동역학 해석 기법을 검토하였다. 해석대상으로 고려한 시스템은 5MW급 해상풍력발전기이며, 3개의 블레이드가 수평축 방향에서 역풍을 받아 전기를 생산하는 수평축 풍력발전 형태이다. 블레이드에 작용하는 공력하중은 블레이드 요소 모멘텀 이론을 기반으로 일반화된 동적 웨이크를 고려할 수 있도록 개발된 AeroDyn 프로그램으로부터 산출하였다. 해상풍력발전기의 주요 연결부에서의 동적하중과 토오크 특성이 실제 현상과 유사하게 산출될 수 있도록 하기 위하여, 다물체 동역학 모델 상에 블레이드와 타워는 실제 구조 특성치를 고려한 유연체 모델링을 적용하였다.

• 한국산학기술학회논문지
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• 제18권10호
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• pp.15-23
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• 2017

본 논문에서는 전기자동차용 배터리의 충방전 상태를 정확하게 추정하고 안정적으로 평가하기 위하여, 비선형성을 가지는 배터리의 출력특성을 단계마다 선형화시켜 상태를 평가하고, 실시간 구현 및 모델의 오차보정과 노이즈에 강인한 특성을 가지고 있는 확장칼만필터 알고리즘을 이용한 SOC 추정 방법을 제안한다. 확장칼만필터를 적용하기 위해 배터리를 1차 Thevenin 모델로 나타내고, SOC 추정을 위한 배터리 성능평가 시뮬레이터를 구현하여, 실험을 통해 확장칼만필터에 적용될 파라미터를 도출한다. 본 논문에 적용된 SOC 상태추정 전략에서는 기존 선행 연구들과 다르게 배터리에 명시되어 있는 정격용량을 최대 충전가능용량으로 대체함으로써, 배터리의 노화에 상관없이 언제나 0%~100%의 SOC를 가질 수 있도록 변경된 수법을 제안한다. 이를 통해, 고정밀 CT를 사용한 Ah counting에 의한 SOC 추정을 기준으로 하여 본 논문에서는 배터리의 비선형 구간에서도 오차를 줄일 수 있는 확장칼만필터 방법을 제안하고 시뮬레이션을 통해 배터리 전 SOC 영역에서 추정오차를 5% 미만으로 줄일 수 있음을 확인한다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2011년도 제42회 하계학술대회
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• pp.197-198
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• 2011

A technique to manage harmonic pollution at the point of common coupling (PCC) has been presented using a control chart. The recursive least-squares technique has been used to estimate the parameters of the Thevenin equivalent load model. With the estimated data from the measured voltage and current waveform at the PCC during certain period violating upper control limit, the individual contributions to the distortion of voltage waveform at an interested harmonic frequency have been calculated and shown by simple graph.

• 전기학회논문지
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• 제60권9호
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• pp.1639-1645
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• 2011

A technique to allocate responsibilities among the interested parties in electric power system with harmonic voltage distortion at the point of common coupling (PCC) has been presented. The recursive least-squares technique has been used to estimate the parameters of the Thevenin equivalent load model. The validity of the technique has been verified using a simulation which considered the voltage waveform distortion at the PCC between the utility and two industrial consumers. With the estimated data from the measured voltage and current waveform at the PCC, the individual contributions to the distortion of voltage waveform at an interested harmonic frequency have been calculated and could provide a flexible solution to identify the source of harmonic pollution in distribution systems.