• The Transactions of the Korean Institute of Electrical Engineers A
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• v.49 no.7
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• pp.339-344
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• 2000

This paper presents an improved optimal power flow algorithm, which solves an optimization problem with equality constraints with converted inequality constraints. The standard OPF and the penalty function method should do reconstructing active constraints among the inequality constraints so that the activation of the inequality constraints has been imposing an additional burden to solve OPF problem efficiently. However the proposed algorithm converts active inequality constraints into the equality constraints in order to preclude us from reconstructing the procedures. The effectiveness of the new OPF algorithm is validated by applying the IEEE 14 bus system.

• Korean Chemical Engineering Research
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• v.51 no.4
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• pp.465-469
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• 2013

In this study, we investigated the feasibility of torrefied OPF (oil palm fronds) as the fuel. The torrefaction was performed at 200, 250, 300 and $350^{\circ}C$ during 1 and 2 hours, respectively. As raising the torrefaction temperature and increasing the processing time, the GHV (gross heating value) of torrefied OPFs was increased. Moreover, we found that the torrefaction temperature is more important factor than the processing time. However, the proper torrefaction temperature was asked because the higher torrefaction temperature leaded to the lower torrefied OPF yield. TGA (thermo-gravimetric analysis) data released that the torrefaction at $250^{\circ}C$ could significantly decompose the hemicellulose and the almost cellulose was decomposed at $300^{\circ}C$. In addition, the grindability of biomass was improved after torrefaction, so that it can reduce energy consumption in comminution.

• Journal of Electrical Engineering and Technology
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• v.12 no.6
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• pp.2187-2195
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• 2017

In order to solve the AC optimal power flow (OPF) problem considering the generators' on/off status, it is necessary to model the problem as mixed-integer nonlinear programming (MINLP). Because the computation time to find the optimal solution to the mixed-integer AC OPF problem increases significantly as the system becomes larger, most of the existing solutions simplify the problem either by deciding the on/off status of generators using a separate unit commitment algorithm or by ignoring the minimum output of the generators. Even though this kind of simplification may make the overall computation time tractable, the results can be significantly erroneous. This paper proposes a novel algorithm for the mixed-integer AC OPF problem, which can provide a near-optimal solution quickly and efficiently. The proposed method is based on a combination of the outer approximation method and the relaxed AC OPF theory. The method is applied to a real-scale power system that has 457 generators and 2132 buses, and the result is compared to the branch-and-bound (B&B) method and the genetic algorithm. The results of the proposed method are almost identical to those of the compared methods, but computation time is significantly shorter.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.10
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• pp.1699-1708
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• 2007

The optimal power flow(OPF) problem was introduced by Carpentier in 1962 as a network constrained economic dispatch problem. Since then, the OPF problem has been intensively studied and widely used in power system operation and planning. In these days, OPF is becoming more and more important in the deregulation environment of power pool and there is an urgent need of faster solution technique for on-line application. To solve OPF problem, many heuristic optimization methods have been developed, such as Genetic Algorithm(GA), Evolutionary Programming(EP), Evolution Strategies(ES), and Particle Swarm Optimization(PSO). Especially, PSO algorithm is a newly proposed population based heuristic optimization algorithm which was inspired by the social behaviors of animals. However, population based heuristic optimization methods require higher computing time to find optimal point. This shortcoming is overcome by a straightforward parallel processing of PSO algorithm. The developed parallel PSO algorithm is implemented on a PC cluster system with 6 Intel Pentium IV 2GHz processors. The proposed approach has been tested on the IEEE 30-bus system. The results showed that computing time of parallelized PSO algorithm can be reduced by parallel processing without losing the quality of solution.

• Proceedings of the KIEE Conference
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• 1992.07a
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• pp.214-217
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• 1992

This paper introduces a new methodology to apply the interpolation technique wi th optimum pattern to voltage-reactive power control of power system. The conventional tool for the optimal operation of power system is Optimal Power Flow(OPF) by standard optimization techniques. The achievement of solution through OPF programs has a defect of computation time, so that it is impossible to apply the OPF programs to the real-time control area. The proposed method presents a solution in a short period of time and an output with a good accuracy. The optimum pattern is a set of input-output pairs, where an input is a load level and a type of outage and an output is the result of OPF program corresponding to the input. The output in the OPF represents control variables of voltage-reactive power control. The interpolation technique is used to obtain the solution for an arbitrary input. As a result, the new technique helps operators in the process of the real-time voltage-reactive power control in both normal and emergency operating states.

• KIEE International Transactions on Power Engineering
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• v.5A no.4
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• pp.412-415
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• 2005

The recent requirement for faster and more frequent solutions has encouraged the consideration of parallel implementations using decentralized processors. Distributed multi-processor environments can potentially greatly increase the available computational capacity and decrease the communication burden, allowing for faster Optimal Power Flow (OPF) solutions. This paper presents a mathematical approach to implementing distributed OPF using the alternating direction method (ADM) to parallelize the OPF. Several IEEE Reliability Test Systems were adopted to demonstrate the proposed algorithm.

• Journal of Electrical Engineering and Technology
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• v.6 no.6
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• pp.786-792
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• 2011

The present paper presents an optimal capacitor placement (OCP) algorithm for voltagestability enhancement. The OCP issue is represented using a mixed-integer problem and a highly nonlinear problem. The hybrid particle swarm optimization (HPSO) algorithm is proposed to solve the OCP problem. The HPSO algorithm combines the optimal power flow (OPF) with the primal-dual interior-point method (PDIPM) and ordinary PSO. It takes advantage of the global search ability of PSO and the very fast simulation running time of the OPF algorithm with PDIPM. In addition, OPF gives intelligence to PSO through the information provided by the dual variable of the OPF. Numerical results illustrate that the HPSO algorithm can improve the accuracy and reduce the simulation running time. Test results evaluated with the three-bus, New England 39-bus, and Korea Electric Power Corporation systems show the applicability of the proposed algorithm.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.49 no.6
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• pp.298-304
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• 2000

In this paper, we propose that the SCOPF be solved in a decentralized framework, consisting of regions, using a price-based mechanism. We first solve the distributed OPF problem to determine the maximum secure simultaneous transfer capability of each tie-line between adjacent regions by taking only the security constraints imposed on the tie-lines into account. And then, the regional SCOPF is performed using the conventional LP approach. A description on the inclusion of security constraints with distributed OPF algorithm will be given, folowed by a case study for Korea power system.

• Proceedings of the KIEE Conference
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• 2002.11b
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• pp.372-374
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• 2002

The Optimal Power Flow(OPF) is the optimization model that has different constraints and the specified objective function, which is very useful tool for efficient system and market operation in the competitive electricity market. The existed OPF models focus on the minimization of generation fuel cost under informed demand values at each bus Recently, the studies of OPF model with demand function considering the response behavior of customers in the deregulated electricity market have been executed. This paper implements the OPF model using demand function with specified price elasticity, and provides the analysis of related results.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.49 no.12
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• pp.575-580
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• 2000

Switching of the transmission lines(T/L) is one of the ways for suppressing the short circuit capacity. This paper presents the extended optimal power flow(OPF) to the problem of selecting the T/Ls to be open. The constraints of the short circuit currents within limits are added to the inequalities of OPF. Also, the overload on the other lines due to switching of T/Ls is avoided by the linearized inequalities. The number of the open lines can be minimized by incorporating into the objective function of OPF in order to maintain reliability. The method of an effective calculation of the extended OPF is also proposed in this paper, which makes the two parts decoupled. The one concerning the generation dispatch is solved in the first place by the conventional method. Secondly, the other concerning the line-switching is optimized by the proposed formulation.