• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 추계학술대회 논문집 전력기술부문
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• pp.251-254
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• 2003

A voltage stability assessment consists of the contingency screening, voltage stability analysis, and counter measures. A widely used index for the voltage stability assessment of power system is the reactive power margin. It shows some factors of voluntariness as following the status of power system and load levels for the target analyzing area. Therefore, it has a demerit that the absolute amounts of reactive power margin is not to be applied by the quantized margin criterion. This paper selects a vulnerable area by assigning the voltage instability for the particular contingency for the selection of vulnerable area in the respect of the investigation of reactive power margin or VQVI as an index of V-Q margin sensitivity in order to overcome the demerit. This will be able to grasp the V-Q margin sensitivity for the target analyzing area by presenting the ratio of power margin between the margin before and after contingency as following the calculation of reactive power margin. The presented method is applied to the voltage stability assessment for the Metropolitan area of 2003 KEPCO summer peak system.

• 전기학회논문지P
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• 제66권4호
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• pp.206-212
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• 2017

In this paper, using the power system information obtained from real-time monitoring device, to analyze the voltage stability margin index and described the voltage stability control scheme for voltage stability enhancement. Based on the utilization of the voltage stability monitoring index based on local information provided by the PMU(Phasor Measurement Unit), the purpose of the plan is to control the system stably in real time. In order to apply the load control scheme, the voltage stability margin is calculated using the data acquired through the PMU installed in each load bus. If the voltage drops below a certain level, load control is performed for each. The effectiveness of the voltage stability control measures is applied to the actual KEPCO system to analyze the effectiveness.

• KIEE International Transactions on Power Engineering
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• 제4A권3호
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• pp.141-145
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• 2004

FACTS devices, such as the Thyristor Controlled Series Compensator (TCSC) and Static Var Compensators (SVC), can help increase system load margin to improve static voltage stability. In power systems, because of the high cost and the effect value, the optimal placement for FACTS devices must be determined. This paper investigates the use of the series device (SVC) and the parallel device (TCSC) from the point of load margin to increase voltage stability. It considers the sensitivity of load margin to the line reactance and eigenvector of the collapse. The study has been carried out on the IEEE 14 Bus Test System to verify the validity and efficiency of the method. It reveals that incorporation of FACTS devices significantly enhance load margin as well as system stability.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1993년도 하계학술대회 논문집 A
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• pp.33-35
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• 1993

This paper presents a new optimal VAR planning algorithm considering voltage stability margin. The characteristic of this method is to make it possible to formulate VAR planning for the dual purpose of maintaining voltage profiles within specified limits, and increasing the voltage stability margin of anticipated operating conditions with respect to voltage collapse. The IEEE-30 bus system is used to demonstrate the capability of the proposed algorithm.

• 전기학회논문지P
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• 제63권1호
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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.

• 대한전기학회논문지:전력기술부문A
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• 제55권12호
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• pp.536-543
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• 2006

This paper uses Monte Carlo technique, which is one of probabilistic methods of estimating the economical quantity of electric power generation in consideration of voltage stability in the aspect of power generation companies. In the power exchange system in Korea, when power generation companies participate in tenders for power generation capacity at the power exchange, they need to determine their power supply capacity considering the stability of electric power system. Thus, we purposed to propose an algorithm for estimating economical power generation capacity in theaspect of power generation companies, through which we can estimate the margin for voltage stability through P-V curve analysis by capacity according to the change of power generation capacity in a simulated system and to conduct Monte Carlo simulation in consideration of the margin

• JSTS:Journal of Semiconductor Technology and Science
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• 제10권2호
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• pp.118-129
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• 2010

A lower-threshold-voltage (LVth) SRAM cell with an elevated cell biasing scheme, which enables to reduce the random threshold-voltage (Vth) variation and to alleviate the stability-degradation caused by word-line (WL) and cell power line (VDDM) disturbed accesses in row and column directions, has been proposed. The random Vth variation (${\sigma}Vth$) is suppressed by the proposed LVth cell. As a result, the LVth cell reduces the variation of static noise margin (SNM) for the data retention, which enables to maintain a higher SNM over a larger memory size, compared with a conventionally being used higher Vth (HVth) cell. An elevated cell biasing scheme cancels the substantial trade-off relationship between SNM and the write margin (WRTM) in an SRAM cell. Obtained simulation results with a 45-nm CMOS technology model demonstrate that the proposed techniques allow sufficient stability margins to be maintained up to $6{\sigma}$ level with a 0.5-V data retention voltage and a 0.7-V logic bias voltage.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 하계학술대회 논문집 A
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• pp.19-23
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• 2003

This paper presents a new concept of reactive reserve based contingency constrained optimal power flow (RCCOPF) for voltage stability enhancement. This concept is based on the fact that increase in reactive reserves is effective for enhancement of voltage stability margins of post-contingent states, in this paper, the proposed algorithm is applied to voltage stability margin of interface flow. Interface flow limit, in the open access environment, can be a main drawback. RCCOPF for enhancement of interface flow margin is composed of two modules, modified continuation power flow (MCPF) and optimal power flow (OPF). These modules art recursively perform ed until satisfying the required margin of interface flow in the given voltage stability criteria.

• KIEE International Transactions on Power Engineering
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• 제5A권2호
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• pp.152-158
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• 2005

This paper describes a reactive optimal power flow incorporating margin enhancement constraints. Margin sensitivity at a steady-state voltage instability point is calculated using invariant space parametric sensitivity, and it can provide valuable information for selection of effective control parameters. However, the weakest buses in neighboring regions have high margin sensitivities within a certain range. Hence, the control determination using only the sensitivity information might cause violation of operational limits of the base operating point, at which the control is applied to enhance voltage stability margin in the direction of parameter increase. This paper applies an interior point method (IPM) to solve the optimal power flow formulation with the margin enhancement constraints, and shunt capacitances are mainly considered as control variables. In addition, nonlinearity of margin enhancement with respect to control of shunt capacitance is considered for speed-up control determination in the numerical example using the IEEE 118-bus test system.

• 조명전기설비학회논문지
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• 제17권3호
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• pp.18-24
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• 2003

전력산업구조 개편 시 변화된 전력계통 환경하에서 효율적인 계통운용 및 계획을 위해서는 계통의 수송능력(Power Transfer Capability)을 산정하는 작업이 필수적이다. 또한 송전망의 자유로운 접근(Open Access)과 같은 전력정책의 변화로 인하여 전력계통은 더욱더 고부하상태에서 운전될 가능성이 높아지게 되었다. 전력계통의 부하가 증가하면 전압안정도 여유가 감소하므로 전력계통은 전압붕괴와 같은 전압안정도 문제를 야기시킬 수 있다. 본 연구에서는 전력계통의 수송능력 산정문제에 대해 전압안정도여유 제약을 고려 할 수 있는 수송능력산정 알고리즘 개발에 연구의 목적을 두고 있다. 이를 위해 본 연구에서는 전압안정도 여유제약식을 정식화한 다음 이를 수송능력 산정문제에 반영할 수 있는 방법을 제안하였다. 그리고 이를 시험계통에 적용하여 본 연구의 타당성을 검증하고 유응한 정보를 도출하였다.