• Journal of Energy Engineering
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• v.11 no.4
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• pp.291-298
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• 2002

This paper presents a practical methodology that can analysis power flow and marginal factors based on optimal power flow (OPF) of power systems under restructuring environment. First of all, to evaluate useful marginal factors, nonlinear optimization problems of minimum fuel cost and minimum transmission loss are formulated and solved by nonlinear primal-dual interior point method. Here, physical constraints considered in the optimization problems are the limits of bus voltage. line overloading, and real & reactive power generation. Also, an evaluation method of marginal price and marginal transmission loss is presented based on sensitivities calculated by the two OPF problems. Especially, to reflect the cost related to transmission losses in the competitive electricity market, an analysis method of MLF (marginal loss factor) is pro-posed. Numerical results on IEEE RTS 24 show that the proposed algorithm is effective and useful for analysis of power market price.

• Journal of Electrical Engineering and Technology
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• v.2 no.4
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• pp.413-419
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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, it has been intensively studied and widely used in power system operation and planning. In the past few decades, many stochastic optimization methods such as Genetic Algorithm (GA), Evolutionary Programming (EP), and Particle Swarm Optimization (PSO) have been applied to solve the OPF problem. In particular, PSO is a newly proposed population based stochastic optimization algorithm. The main idea behind it is based on the food-searching behavior of birds and fish. Compared with other stochastic optimization methods, PSO has comparable or even superior search performance for some hard optimization problems in real power systems. Nowadays, some modifications such as breeding and selection operators are considered to make the PSO superior and robust. In this paper, we propose the Modified PSO (MPSO), in which the mutation operator of GA is incorporated into the conventional PSO to improve the search performance. To verify the optimal solution searching ability, the proposed approach has been evaluated on an IEEE 3D-bus test system. The results showed that performance of the proposed approach is better than that of the standard PSO.

• Proceedings of the KIEE Conference
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• 1998.07c
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• pp.926-928
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• 1998

A fast optimization algorithm has been evolved from a simple two stage optimal power flow(OPF) algorithm for constrained power economic dispatch. In the proposed algorithm, we consider various constraints such as power balance, generation capacity, transmission line capacity, transmission losses, security equality, and security inequality constraints. The proposed algorithm consists of four stages. At the first stage, we solve the aggregated problem that is the crude classical economic dispatch problem without considering transmission losses. An initial solution is obtained by the aggregation concept in which the solution satisfies the power balance equations and generation capacity constraints. Then, after load flow analysis, the transmission losses of an initial generation setting are matched by the slack bus generator that produces power with the cheapest cost. At the second stage we consider transmission losses. Formulation of the second stage becomes classical economic dispatch problem involving the transmission losses, which are distributed to all generators. Once a feasible solution is obtained from the second stage, transmission capacity and other violations are checked and corrected locally and quickly at the third stage. The fourth stage fine tunes the solution of the third stage to reach a real minimum. The proposed approach speeds up the coupled LP based OPF method to an average gain of 53.13 for IEEE 30, 57, and 118 bus systems and EPRI Scenario systems A through D testings.

• KIEE International Transactions on Power Engineering
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• v.4A no.4
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• pp.262-267
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• 2004

With the advent of electric power systems moving from a vertically integrated structure to a deregulated environment, calculating reactive power service charges has become a new and challenging theme for market operators. This paper examines various methods for reactive power management adopted throughout various deregulated foreign and domestic markets and then proposes an innovative method to calculate reactive power service charges using a reactive power market in a wholesale electricity market. The reactive power market is operated based on bids from the generating sources and it settles on uniform prices by running the reactive OPF programs of the day-ahead electricity market. The proposed method takes into account recovering not only the costs of installed capacity but also the lost opportunity costs incurred by reducing active power output to increase reactive power production. Based on the result of the reactive OPF program, the generators that produce reactive power within the obligatory range do not make payments whereas the generators producing reactive power beyond the obligatory range receive compensation by the price determined in the market. A numerical sample study is carried out to illustrate the processes and appropriateness of the proposed method.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.50 no.3
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• pp.120-130
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• 2001

We present an approach to parallelizing optimal power flow that is suitable for distributed implementation and is applicable to very large interconnected power systems. This approach can be used by utilities to optimize economy interchange without disclosing details of their operating costs to competitors. Recently, it is becoming necessary to incorporate contingency constraints into the formulation, and more rapid updates of telemetered data and faster solution time are becoming important to better track changes in the system. This concern led to a research to develop an efficient algorithm for a distributed optimal power flow based on the Auxiliary Problem Principle and to study the convergence rate improvement of the distributed algorithm. The objective of this paper is to find a set of control parameters with which the Auxiliary Problem Principle (Algorithm - APP) can be best implemented in solving optimal power flow problems. We employed several IEEE Reliability Test Systems, and Korea Power System to demonstrate the alternative parameter sets.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.240-241
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• 2011

풍력발전단지가 급속히 증가함에 따라 풍력발전단지의 제어를 통한 계통 규정 참여가 중요해지고 있다. 본 논문에서는 풍력발전단지 내에서의 송전손실을 최소화하기 위한 풍력발전기의 제어 방식을 제안한다. 모의 계통은 덴마크 해상풍력단지 Horns Rev를 본떴으며 풍력발전기 별로 적용되는 풍속도 Wake Effect를 고려한 실제 데이터를 사용하였다. 손실 최소화를 위해 Linear Programming(LP)에 기반을 둔Optimal Power Flow(OPF)를 사용하였다.

• Journal of Electrical Engineering and Technology
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• v.2 no.3
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• pp.335-341
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• 2007

In this study, we present an approach to parallelizing OPF that is suitable for distributed implementation and is applicable to very large inter-connected power systems. The approach could be used by utilities for optimal economy interchange without disclosing details of their operating costs to competitors. It could also be used to solve several other computational tasks, such as state estimation and power flow, in a distributed manner. The proposed algorithm was demonstrated with several case study systems.

• Proceedings of the KIEE Conference
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• 2008.11a
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• pp.444-446
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• 2008

논문에서는 전력시장 및 계통의 운영에 따라서 발생될 수 있는 시장참여자들의 편익을 정의하고 최적조류재산(OPF)을 이용하여 편익을 산정할 수 있는 방법을 제시하였으며, 이를 이용하여 송전선 투자에 따른 효과를 분석하고, 도매전력시장의 구조에 따른 투자효과를 비교분석 하였다.

• Proceedings of the KIEE Conference
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• 2000.07a
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• pp.52-54
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• 2000

Almost traditional ELD(Economic Load Dispatch) is hard to apply to power system directly and also OPF(Optimal Power Flow) is not easy to solve the problem. This paper deals with the practical application of ELD with considering power equation.

• Proceedings of the KIEE Conference
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• 1989.11a
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• pp.176-179
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• 1989

Newton's OPF algorithm, for each iteration, solves with second order approximation of Lagraqngian function and sparse matrix technique. When load model is applied to this technique, load voltages have tendency to be fixed at lower limit. It makes the solution inadequte. In this paper, reference bus voltage specification technique suggested to make adequate load voltage. This method is verified useful 6-bus Ward-Hale sample system.