• Title, Summary, Keyword: Voltage instability

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A Dynamic Simulation at Voltage Instability using EMTP (EMTP를 이용한 전압 불안정 현상의 동적 시뮬레이션)

  • Heo, J.Y.;Kwon, O.S.;Kim, C.H.
    • Proceedings of the KIEE Conference
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    • pp.131-133
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    • 2003
  • Voltage instability has been studied for some decade now. But, there is not generally accepted definition of voltage instability because of the complex phenomenon and the variety of ways in which it can manifest itself. Both IEEE and CIGRE have the respective definitions. The areas of voltage instability research arc the analysis, simulation and countermeasure of voltage instability. In this paper, we perform a dynamic simulation of voltage instability and voltage collapse using EMTP MODELS. The exponential load model is designed with MODELS and this load model is connected with test power system. The result shows the process of voltage change in time domain when the voltage instability or voltage collapse occurs.

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A Dynamic Simulation of Voltage Instability Using EMTP (EMTP를 이용한 전압 불안정 현상의 동적 시뮬레이션)

  • 허정용;김철환
    • The Transactions of the Korean Institute of Electrical Engineers A
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    • v.52 no.6
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    • pp.295-300
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    • 2003
  • Voltage instability has been studied for some decade now. But, There is not generally accepted definition of voltage instability because of the complex phenomenon and the variety of ways in which it can manifest itself. Both IEEE and CIGRE have the respective definitions. The areas of voltage instability research are the analysis, simulation and countermeasure of voltage instability. It needs to model the components of the power system to simulate the voltage instability and voltage collapse. At the beginning, the static simulation was used. This method provides the voltage stability indices and it requires less CPU resource and gives much insight into the voltage and power problem. However, it is less accurate than the dynamic simulation peformed in the time domain simulation. So, when it appears difficult to secure the voltage stability margin in a static stability, it is necessary to perform the dynamic simulation. To perform time-domain simulation, we have to model the dynamic component of the power system like a generator and a load. The dynamic simulation provides the accurate result of the voltage instability. But, it is not able to provide the sensitivity information or the degree of stability and it is time consuming and it needs much CPU resource. In this Paper, we perform a dynamic simulation of voltage instability and voltage collapse using EMTP MODELS. The exponential load model is designed with MODEIS and this load model is connected with test power system. The result shows the process of voltage change in time domain when the voltage instability or voltage collapse occurs.

Stability Index Based Voltage Collapse Prediction and Contingency Analysis

  • Subramani, C.;Dash, Subhransu Sekhar;Jagdeeshkumar, M.;Bhaskar, M. Arun
    • Journal of Electrical Engineering and Technology
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    • v.4 no.4
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    • pp.438-442
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    • 2009
  • Voltage instability is a phenomenon that could occur in power systems due to stressed conditions. The result would be an occurrence of voltage collapse leading to total blackout of the system. Therefore, voltage collapse prediction is an important part of power system planning and operation, and can help ensure that voltage collapse due to voltage instability is avoided. Line outages in power systems may also cause voltage collapse, thereby implying the contingency in the system. Contingency problems caused by line outages have been identified as one of the main causes of voltage instability in power systems. This paper presents a new technique for contingency ranking based on voltage stability conditions in power systems. A new line stability index was formulated and used to identify the critical line outages and sensitive lines in the system. Line outage contingency ranking was performed on several loading conditions in order to identify the effect of an increase in loading to critical line outages. Correlation studies on the results obtained from contingency ranking and voltage stability analysis were also conducted, and it was found that line outages in weak lines would cause voltage instability conditions in a system. Subsequently, using the results from the contingency ranking, weak areas in the system can be identified. The proposed contingency ranking technique was tested on the IEEE reliability test system.

Estimation of Voltage Instability Index Using RLS(Recursive Least Square) (RLS(Recursive Least Square)를 이용한 전압안정도 지수 평가)

  • Jeon, Woong-Jae;Lee, Byong-Jun
    • Proceedings of the KIEE Conference
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    • pp.279-281
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    • 2006
  • A Voltage Instability Predictor(VIP) estimates the proximity of a power system to voltage collapse in real time. Voltage Instability Index(Z-index) from VIP algorithm is estimated using LS(Least Square) method. But this method has oscillations and noise of result due to the system's changing conditions. To suppress oscillations, a larger data window needs to be used. In this paper. I propose the new other method which improves that weakness. It uses RLS(Recursive Least Square) to estimate voltage instability index without a large moving data window so this method is suitable for on-line monitor and control in real time. In order to verify effectiveness of the algorithm using RLS method, the method is tested on HydroQuebec system in real time digital simulator(HYPERSIM).

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A Study on Change of Static Voltage Instability Point Related to Load Model in the KEPCO System (부하모델에 따른 한전계통의 정적인 전압불안정점의 변화에 관한 연구)

  • Song, H.;Song, T.Y.;Jeong, M.G.;Lee, S.C.;Choi, G.S.;Choi, S.G.;Jo, Y.S.;Lee, B.;Kwon, S.H.
    • Proceedings of the KIEE Conference
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    • pp.319-321
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    • 2000
  • Today's power systems operate near their stability limit and numerous incidents closely related to voltage instability phenomena have been reported. In addition. a world-wide fashion towards restructuring in electricity industry can worsen the trend of voltage instability. In this environment, finding exact voltage instability points of practical power systems is a main concern of power system engineers. This paper reports change of static voltage instability point with respect to various load model in the KEPCO system.

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A Study on Decentralized under Voltage Load Shedding Scheme for Preventing Wide-area Black Out (광역정전 예방을 위한 분산형 부하 제어 방안에 대한 연구)

  • Lee, Yun-Hwan
    • The Transactions of the Korean Institute of Electrical Engineers P
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    • v.63 no.1
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    • pp.1-6
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    • 2014
  • An electric power system sometimes fails because of disturbances that occur unexpectedly, such as the uncontrolled loss of load that developed from cascading blackout. Which make stability through a little of under voltage load shedding should work. The development of phasor measurement unit(PMU) makes network supervision possible. The information obtained from PMU is synchronized by global positioning system(GPS). There are many real-time algorithms which are monitoring the voltage stability. This paper presents the study on the VILS(Voltage Instability Load Shedding) using PMU data. This algorithm computes Voltage Stability Margin Index(VSMI) continuously to track the voltage stability margin at local bus level. The VSMI is expressed as active and reactive power. The VSMI is used as an criterion for load shedding. In order to examine the algorithm is effective, applied to KEPCO system.

A Study on the Analysis and Control of Voltage Stability (전압안정성 분석 및 제어에 관한 연구)

  • 장수형;김규호;유석구
    • The Transactions of the Korean Institute of Electrical Engineers
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    • v.43 no.6
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    • pp.869-876
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    • 1994
  • This paper presents an efficient method to calculate voltage collapse point and to avoid voltage instability. To evaluate voltage stability in power systems, it is necessary to get critical loading points. For this purpose, this paper uses linear programming to calculate efficiently voltage collapse point. Also, if index value becomes larger than given threshold value, voltage stability is improved by compensation of reactive power at selected bus. This algorithm is verified by simulation on the IEEE 14-bus sample system.

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Operating Characteristic of a User Defined Distance Relay Model in PSS/E during Voltage Instability (전압 불안정시 PSS/E 사용자 정의모델로 구현된 거리계전기 응동 특성)

  • Lee, D.G.;Kang, S.H.;Yang, J.J.;Oh, H.W.;Jang, B.T.
    • Proceedings of the KIEE Conference
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    • pp.82-84
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    • 2003
  • This paper presented a method to develop a relay model by the user-written model function of PSS/E. As for the voltage instability, although generator current limiters, transformer's tap-changers and dynamic loads have been considered as the dominant components, the protection system is also very important because it may influence the system's dynamic behaviour. Hence a distance relay model implemented with the suggested method was added, and then the operating characteristics of the distance relay under the voltage instability condition were investigated.

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Utilizing Under Voltage Load Shedding Strategy to Prevent Delayed Voltage Recovery Problem in Korean Power System

  • Lee, Yun-Hwan;Oh, Seung-Chan;Lee, Hwan-Ik;Park, Sang-Geon;Lee, Byong-Jun
    • Journal of Electrical Engineering and Technology
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    • v.13 no.1
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    • pp.60-67
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    • 2018
  • The presence of induction motor loads in a power system may cause the phenomenon of delayed voltage recovery after the occurrence of a severe fault. A high proportion of induction motor loads in the power system can be a significant influence on the voltage stability of the system. This problem referred to as FIDVR(Fault Induced Delayed Voltage Recovery) is commonly caused by stall of small HVAC unit(Heating, Ventilation, and Air Conditioner) after transmission or distribution system failure. This delayed voltage recovery arises from the dynamic characteristics associated with the kinetic energy of the induction motor load. This paper proposes the UVLS (Under Voltage Load Shedding) control strategy for dealing with FIDVR. UVLS based schemes prevent voltage instability by shedding the load and can help avoid major economic losses due to wide-ranging cascading outages. This paper review recent topic about under voltage load shedding and compare decentralized load shedding scheme with conventional load shedding scheme. The load shedding strategy is applied to an actual system in order to verify the proposed FIDVR mitigation solution. Simulations demonstrate the effectiveness of the proposed method in resolving the problem of delayed voltage recovery in the Korean Power System.

A Study on Voltage Collapse Mechanism using Equivalent Mechanical Model

  • Kim, Do-Hyung;Ryu, Heon-Su;Lee, Jong-Gi;Moon, Young-Hyun
    • KIEE International Transactions on Power Engineering
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    • v.12A no.1
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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