• Proceedings of the KIEE Conference
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• 2000.11a
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• pp.104-106
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• 2000

Transient Stability of a power systems is its ability to maintain synchronous operation of machine when subjected to a large disturbance. This paper presents a new methodology for speed-up transient stability evaluation in SIME. SIME is a hybrid direct method including time simulation to enhance flexibility. The First features of the proposed method are that generator grouping can be performed even in very stable cases and that the stability of a contingency can be evaluated from a short period of time simulation results. The second features of the proposed method are that using power-angle trajectory and subdividing contingency classification have improved the screening capability.

• Journal of KIEE
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• v.11 no.1
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• pp.55-61
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• 2001

SIME(Single Machine Equivalent) method has been recognized as a useful tool to determine transient stability of power system. In this paper, SIME method is used to develop the KEPCO transient stability assessment (TSA) tool. A new screening algorithm that can be generators are identified by a new index in the early stage of the time domain simulation. Thus, computational time require to find OMIB(One Machine Infinite Bus) can be reduced significantly. Second, clustering critical machines can be performed even in very stable cases. It enables to be avoid extra calculation of time trajectory that is needed in SIME for classifying the stable cases. This algorithm is applied to the fast TSA of the KEPCO system in the year of 2010.

• Journal of Electrical Engineering and Technology
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• v.5 no.2
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• pp.209-219
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• 2010

In this paper, a novel dynamic available transfer capability (DATC) has been computed for real time applications using three different intelligent techniques viz. i) back propagation algorithm (BPA), ii) radial basis function (RBF), and iii) adaptive neuro fuzzy inference system (ANFIS) for the first time. The conventional method of DATC is tedious and time consuming. DATC is concerned with calculating the maximum increase in point to point transfer such that the transient response remains stable and viable. The ATC information is to be continuously updated in real time and made available to market participants through an internet based Open Access Same time Information System (OASIS). The independent system operator (ISO) evaluates the transaction in real time on the basis of DATC information. The dynamic contingency screening method [1] has been utilized and critical contingencies are selected for the computation of DATC using the energy function based potential energy boundary surface (PEBS) method. The PEBS based DATC has been utilized to generate patterns for the intelligent techniques. The three different intelligent methods are tested on New England 68-bus 16 machine and 39-bus 10 machine systems and results are compared with the conventional PEBS method.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.9
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• pp.1658-1666
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• 2009

This paper proposes an approach of Mult_HPSO based on the PC cluster system to reduce or remove the stagnation on an early convergence effect of PSO, reduce an execution time and improve a search ability on an optimal solution. Hybrid PSO(HPSO) is combines the PSO(Particle Swarm Optimization) with the mutation of conventional GA(Genetic Algorithm). The conventional PSO has operated a search process in a single swarm. However, Multi_PSO operates a search process through multiple swarms, which increments diversity of expected solutions and reduces the execution time. Multiple Swarms are composed of unsynchronized PC clusters. We apply to SCED(security constrained economic dispatch) problem, a nonlinear optimization problem, which considers line flow constraints and N-1 line contingency constraints. To consider N-1 line contingency in power system, we have chosen critical line contingency through a process of Screening and Selection based on PI(performace Index). We have applied to IEEE 118 bus system for verifying a usefulness of the proposed approaches.

• Proceedings of the KIEE Conference
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• 2003.11a
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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.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.8
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• pp.1334-1341
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• 2008

This paper introduces an approach of Hybrid Particle Swarm Optimization(HPSO) for a security-constrained economic dispatch(SCED) with line flow constraints. To reduce a early convergence effect of PSO algorithm, we proposed HPSO algorithm considering a mutation characteristic of Genetic Algorithm(GA). In power system, for considering N-1 line contingency, we have chosen critical line contingency through a process of Screening and Selection based on PI(performance Index). To prove the ability of the proposed HPSO in solving nonlinear optimization problems, SCED problems with nonconvex solution spaces are considered and solved with three different approach(Conventional GA, PSO, HPSO). We have applied to IEEE 118 bus system for verifying a usefulness of the proposed algorithm.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.8
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• pp.1053-1058
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• 2013

Because of computational burden and complex topology of substation, a transmission overload relief using circuit-breaker switching was very complex and difficult. However, a on-line algorithm for reducing the overloads in transmission lines has made progress due to the advance of IT technology. This paper describes the methodology for alleviating the overloads in transmission lines by circuit-breaker switching. First, the severe contingency lists and substations were selected from the results of contingency analysis. Then the switch combinations are determined using circuit-breakers of the selected substation. The topology changes are limited to equipment outage, bus split, island split, bus merge and island merge. Finally, the fast screening and full analysis methods are used to analyze the overload in transmission lines. To verify the performance of the proposed methodology, we performed a comprehensive test for both test system and large-scale power systems. The results of these tests showed that the proposed methodology can accurately alleviate the overloads in transmission lines from online data and can be applied to on-line applications.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.51 no.6
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• pp.262-268
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• 2002

Preventive control has to solve two important problems. The first is fast and accurate severity assessment of instability originated from the occurrence of a dangerous contingency. The second is to choose an action able to stabilize it. In this paper we assess contingencies in power systems using PASF(Power Angle Shape Filtering) and control power systems by a generation rescheduling. The control action stabilize the whole set of harmful contingencies simultaneously. Note that conventional time-domain transient stability methods can hardly tackle preventive control. So, we study the preventive control using off-line method. The proposed method is applied to prevent and to correct loss of synchronism of all the generators in a operating systems data.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.54 no.6
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• pp.306-314
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• 2005

In this paper, a new approach that is based on EEAC & only with network solutions for CS&S in the transient stability assessment is developed. The proposed CS&S algorithm in conjunction with EEAC to include the capability of performing on-line TSA without TDS is used to calculate the critical clearing time for stability index. In this algorithm, all generators are represented by classical models and all loads are represented by constant impedance load models. The accelerating & synchronizing power coefficient as an index is determined at its disturbance through solving network equation directly. As mentioned above, a new index for generator is generally used to determine the critical generators group. The generator rotor angle is fixed for non-critical generators group, but has equal angle increments for critical generators group. Finally, the critical clearing time is calculated from the power-angle relationship of equivalent OMIB system. The proposed CS&S algorithm currently being implemented is applied to the KEPCO system. The CS&S result was remarkably similar to TSAT program and SIME. Therefore, it was found to be suitable for a fast & highly efficient CS&S algorithm in TSA. The time of CS&S for the 139 contingencies using proposed CS&S algorithm takes less than 3 seconds on Pentium 4, 3GHz Desktop.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.806-807
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• 2007

Systematic studies on the dispatch scheduling algorithm and related constraints can enhance the effectiveness of electricity market operation. When System Operator (SO) establishes a dispatch schedule, the bid information should be preserved in the schedule as much as possible. In this paper, we introduce a new type of sensitivity factor called Line Outage Impact Factor (LOIF) to screen a transmission line causing the most severe outage when scheduling the dispatch. This screening can assure the stable system operation and make an efficient feedback between the SO and market participants. We propose a transmission line contingency constrained Pre-dispatch algorithm using sensitivity indices in a suitable Pre-dispatch scheduling. The proposed algorithm has been tested on sample system and the results show more secure operation against critical contingencies.