• Journal of Electrical Engineering and Technology
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• 제2권4호
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• pp.420-427
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• 2007

This paper highlights the comparison of a proposed methods named adaptive undervoltage load shedding based PTSI techniques for undervoltage load shedding and two previous methods named Fixed Shed Fixed Delay (FSFD) and Variable Shed Variable Delay (VSVD) for avoiding voltage collapse. There are three main area considerations in load shedding schemes as the amount of load to be shed, the timing of load shedding event, and the location where load shed is to be shed. The proposed method, named as adaptive UVLS based PTSI seem to be most appropriate among the uncoordinated schemes. From the simulation result can be shown the Adaptive UVLS based PTSI give faster response, accurate and very sensitive control for the UVLS control technique. This technique is effectively when calculating the amount to be shed. Therefore, it is possible to bring the voltage to the threshold value in one step. Thus, the adaptive load shedding can effectively reduce the computational time for control strategy.

• 전기학회논문지
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• 제58권12호
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• pp.2335-2341
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• 2009

High technique growth of modem times and high industrial facility in consequence of buildings demand for electric power of an extensive scale with stability supply and maintenance of high quality. But, power system always have risk of network contingency. When power system break out disturbance, it circumstantially happen like uncontrolled loss of load developing from of cascading. Severely which would be raised wide area blackout, plan to prevent, which make stability through a little of load shedding and multi-level UnderVoltageLoadShdding should work. This paper presents target, sensitivity of bus voltage have choose appropriating load shedding location and load shedding decision making logic with considering rate of change of voltage have studied multi-level under voltage load shedding scheme. Calculation of rate of change of voltage applied method of least square. As a result, we are studied an dynamic analysis of 2008 summer peak data. We have been known that network analysis is a little development and developing UnderVoltageLoadShedding scheme.

• 정보처리학회논문지D
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• 제13D권6호
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• pp.755-764
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• 2006

근래 들어 유비쿼터스 컴퓨팅 및 센서 네트워크 환경 등과 같은 다양한 응용 분야에서 데이터 스트림 형태의 정보를 발생시키고 있으며, 이들 정보를 효율적으로 처리하기 위한 다양한 방법들이 활발히 제안되어 왔다. 대부분의 이들 방법들은 주로 처리 과정에서의 공간 사용량 및 데이터당 처리 시간을 줄이는데 초점을 맞추고 있다. 하지만 이들 방법들에서 데이터 발생량이 급격히 증가되는 경우 일부 데이터는 실시간으로 처리되지 못하며 해당 방법의 성능 저하를 초래한다. 따라서, 데이터 스트림 처리의 효율성을 높이기 위해서는 효율적인 과부하 처리 기법을 필요로 한다. 이를 위해서 본 논문에서는 발생빈도 예측법을 이용한 과부하 처리 기법을 제안한다. 즉, 해당 기법에서는 처리 대상 데이터의 현재 시점까지의 발생빈도를 고려하여 해당 데이터의 향후 발생 상황을 예측하며, 이를 통해서 해당 데이터 스트림에서 과부하가 발생했을 때 효율적으로 대처할 수 있도록 지원한다. 또한, 제안되는 방법에서는 데이터 스트림의 변화를 고려하여 튜플 선별을 위한 임계값을 적응적으로 조절함으로써 불필요한 과부하 처리 수행을 최소화한다.

• Journal of Electrical Engineering and Technology
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• 제8권3호
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• pp.446-452
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• 2013

Under frequency load shedding (UFLS) is an effective way to prevent system blackout after a serious disturbance occurs in a power system. A novel centralized adaptive under frequency load shedding (AUFLS) scheme using the synchronous phase measurement unit (PMU) is proposed in this paper. Two main stages are consisted of in the developed technique. In the first stage, the active power deficit is estimated by using the simplest expression of the generator swing equation and static load model since the frequency, voltages and their rate of change can be obtained by means of measurements in real-time from various devices such as phase measurement units. In the second stage, the UFLS schemes are adapted to the estimated magnitude based on the presented model. The effectiveness of the proposed AUFLS scheme is investigated simulating different disturbance in IEEE 10-generator 39-bus New England test system.

• 대한전기학회논문지
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• 제36권6호
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• pp.381-389
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• 1987

This paper presents a method for optimal load shedding in preserving a system security following abnormal condition as well as a sudden major supply outage. The method takes account of static characteristic of generators control and voltage and system frequency characteristic of loads. The optimization problem is solved by a gradient technique to get the maximal effect by the least quantity of load shedding considering line overloads as well as voltage disturbances and system frequency. The method is illustrated on a 8-bus system. It has been found that the use of the proposed algorithm for model systems alleviate the line overload more efficiently than the former method. It is believed that this method will be useful in security studies and operational planning.

• 대한전기학회논문지:전력기술부문A
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• 제49권2호
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• pp.56-61
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• 2000

In the paper, the system loss sensitivity index that implies the incremental system loss with respect to the change of bus power is derived using optimization technique. The index λ reaches $\infty$ at critical loading point and can be applied to actual power systems for following purposes. 1) Evaluation of system voltage stability 2)Optimal investment of reactive power focused on minimizing system loss and maximizing system voltage stability 3)Optimal re-location of reactive power focused on minimizing system loss and maximizing system voltage stability 4)Optimal load shedding in case of severe system contingency focused on minimizing system loss and maximizing system voltage stability. Case studies for each application have proved their effectiveness.

• 한국정보과학회논문지:데이타베이스
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• 제37권1호
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• pp.1-11
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• 2010

최근 다중 데이터 스트림에 대한 연속 질의 처리에 관한 연구가 활발하게 진행되고 있다. 데이터 스트림에서 튜플들의 도착 속도가 폭증하여 시스템의 메모리 용량을 초과하는 경우, 일부 튜플을 버림으로써 시스템이 과부하 상태가 되지 않도록 하는 기법을 부하 감소(load shedding)라 한다. 본 논문에서는 다중 데이터 스트림에 대한 다중 윈도우 조인을 위한 효과적인 부하 감소 기법을 제안한다. 기존의 부하 감소 기법들은 버릴 튜플을 선택하기 위해 튜플들의 조인 키 값을 이용하여 각 튜플이 생성할 조인 결자 개수(생산성)를 예측하고, 생산성이 최소가 되는 튜플을 버린다. 그러나 이러한 방법들은 조인 키 값이 다시 나타나지 않거나, 조인 키 값의 분포가 일정하게 유지되지 않는 경우 튜플들의 생산성을 올바르게 예측하기 어렵다. 본 논문은 이러한 경우를 위해 튜플들의 조인 키 값 대신, 튜플의 데이터 스트림에 대한 도착 순서를 사용하여 튜플들의 생산성을 예측하는 방법을 사용한다. 제안하는 방법은 조인 키 값으로 튜플들의 생산성을 예측하가 어려운 상황에서 튜플의 도착 순서를 통해 각 튜플의 생산성을 효과적으로 예측할 수 있도록 해준다. 다양한 실험과 분석을 통해 제안하는 새로운 부하 감소 기법이 기존 기법에 비해 더욱 효과적이고 효율적으로 부하를 감소시킬 수 있음을 보인다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2015년도 제46회 하계학술대회
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• pp.155-156
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• 2015

Recently, electricity consumption has rapidly increased along with economic growth. The operating strategy using emergency generator is aimed, to resolve a demand response management. For strategy of peak shedding using emergency generator, it is essential to introduce the fast transfer switching device. One of the most effective solutions is to use a static transfer switch (STS) based on thyristor. However, the characteristic of natural commutated SCR thyristor should anticipate short duration voltage sag. STS system thus requires more than a quarter cycle to successfully complete transfer process. This paper proposes the operation scheme of the STS system using the forced-commutation technique to mitigate instantaneous voltage sag during peak transfer process. Proposed STS system improved turn-off characteristic thus accomplishes the peak load shedding satisfied power quality. Performance of the proposed STS system is evaluated using electromagnetic transient program (EMTP) to confirm the effectiveness.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2001년도 ICCAS
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• pp.104.1-104
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• 2001

This paper presents a technique to development load control and management system in order to limits a maximum load demand and saves electric energy consumption. The computer programming proper load forecasting algorithm associated with programmable logic control and digital power meter through inform of multidrop network RS 485 over the twisted pair, over all are contained in this system. The digital power meter can measure a load data such as V, I, pf, P, Q, kWh, kVarh, etc., to be collected in statistics data convey to data base system on microcomputer and then analyzed a moving linear regression of load to forecast load demand Eventually, the result by forecasting are used for compost of load management and shedding for demand monitoring, Cycling on/off load control, Timer control, and Direct control. In this case can effectively reduce the electric energy consumption cost for 10% ...

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 C
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• pp.918-922
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• 1998

With the development of industry, the qualitical advancement of power is needed. Since it is placed in the end step of power system, the fault at the distribution system causes some users blackout directly. So if the fault occurs, quick restoration is very important subject and, for the reason, induction of the distribution automation system is now being progressed briskly. For the quick restoration of the faulted distribution system, the load shedding of the blackout-area must be followed, and the other problems like the shedded load, faulted voltage and the rest may cause other accident. Accordingly load shedding must be based on the precise calculation technique during the distribution system load flow(dist flow) calculation. In these days because of its superior convergence characteristic the Newton-Raphson method is most widely used. The number of buses in the distribution system amounts to thousands, and if the fault occurs at the distribution system, the speed for the dist flow calculation is to be improved to apply to the On-Line system. However, Newton-Raphson method takes much time relatively because it must calculate the Jacobian matrix and inverse matrix at every iteration, and in the case of huge load, the equation is hard to converge. In this thesis. matrix equation is used to make algebraical expression and then to solve load flow equation and to modify above defects. Then the complex matrix is divided into real part and imaginary part to keep sparcity. As a result time needed for calculation diminished. Application of mentioned algorithm to 302 bus, 700 bus, 1004 bus system led to almost identical result got by Newton-Raphson method and showed constant convergence characteristic. The effect of time reduction showed 88.2%, 86.4%, 85.1% at each case of 302 bus, 700 bus system 86.4%, and 1004 bus system.