• Title/Summary/Keyword: optimal power flow

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Optimal Design of the Hoist Hydraulic System Including the Counter Balance Valve and Differential Cylinder Circuit (카운터밸런스밸브와 차동실린더회로를 포함한 호이스트 유압장치의 최적설계)

  • Lee, S.R.
    • Transactions of The Korea Fluid Power Systems Society
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    • v.5 no.1
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    • pp.13-19
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    • 2008
  • The typical hydraulic system of hoist is composed of a hydraulic supply unit, a directional control valve, counter balance valve, and flow control valves. The flow capacity coefficients of flow control valves should be adjusted so that the hoist is operated at moderate speed and the hydraulic energy loss is minimized. However, it is difficult to adjust the flow coefficients of flow control valves by trial and error for optimal operation. Here, the steady state model of the hoist hydraulic system including the differential cylinder circuit is derived and the optimal flow capacity coefficients of flow control valves are obtained using the complex method that is one kind of constrained direct search method.

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Adaptive Firefly Algorithm based OPF for AC/DC Systems

  • Babu, B. Suresh;Palaniswami, S.
    • Journal of Electrical Engineering and Technology
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    • v.11 no.4
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    • pp.791-800
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    • 2016
  • Optimal Power Flow (OPF) is an important operational and planning problem in minimizing the chosen objective functions of the power systems. The recent developments in power electronics have enabled introduction of dc links in the AC power systems with a view of making the operation more flexible, secure and economical. This paper formulates a new OPF to embrace dc link equations and presents a heuristic optimization technique, inspired by the behavior of fireflies, for solving the problem. The solution process involves AC/DC power flow and uses a self adaptive technique so as to avoid landing at the suboptimal solutions. It presents simulation results of IEEE test systems with a view of demonstrating its effectiveness.

Security Cost Analysis with Linear Ramp Model using Contingency Constrained Optimal Power Flow

  • Lyu, Jae-kun;Kim, Mun-Kyeom;Park, Jong-Keun
    • Journal of Electrical Engineering and Technology
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    • v.4 no.3
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    • pp.353-359
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    • 2009
  • This paper proposes a novel technique for calculating the security costs that properly includes ramping constraints in the operation of a deregulated power system. The ramping process is modeled by a piecewise linear function with certain assumptions. During this process, a ramping cost is incurred if the permissible limits are exceeded. The optimal production costs of the power producers are calculated with the ramping cost included, considering a time horizon with N-1 contingency cases using contingency constrained optimal power flow (CCOPF), which is solved by the primal-dual interior point method (PDIPM). A contingency analysis is also performed taking into account the severity index of transmission line outages and its sensitivity analysis. The results from an illustrative case study based on the IEEE 30-bus system are analyzed. One attractive feature of the proposed approach is that an optimal solution is more realistic than the conventional approach because it satisfies physical constraints, such as the ramping constraint.

Multiobjective Optimal Reactive Power Flow Using Elitist Nondominated Sorting Genetic Algorithm: Comparison and Improvement

  • Li, Zhihuan;Li, Yinhong;Duan, Xianzhong
    • Journal of Electrical Engineering and Technology
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    • v.5 no.1
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    • pp.70-78
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    • 2010
  • Elitist nondominated sorting genetic algorithm (NSGA-II) is adopted and improved for multiobjective optimal reactive power flow (ORPF) problem. Multiobjective ORPF, formulated as a multiobjective mixed integer nonlinear optimization problem, minimizes real power loss and improves voltage profile of power grid by determining reactive power control variables. NSGA-II-based ORPF is tested on standard IEEE 30-bus test system and compared with four other state-of-the-art multiobjective evolutionary algorithms (MOEAs). Pareto front and outer solutions achieved by the five MOEAs are analyzed and compared. NSGA-II obtains the best control strategy for ORPF, but it suffers from the lower convergence speed at the early stage of the optimization. Several problem-specific local search strategies (LSSs) are incorporated into NSGA-II to promote algorithm's exploiting capability and then to speed up its convergence. This enhanced version of NSGA-II (ENSGA) is examined on IEEE 30 system. Experimental results show that the use of LSSs clearly improved the performance of NSGA-II. ENSGA shows the best search efficiency and is proved to be one of the efficient potential candidates in solving reactive power optimization in the real-time operation systems.

A Study on the Convergency Property of the Auxiliary Problem Principle

  • Kim, Balho-H.
    • Journal of Electrical Engineering and Technology
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    • v.1 no.4
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    • pp.455-460
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    • 2006
  • This paper presents the convergency property of the Auxiliary Problem Principle when it is applied to large-scale Optimal Power Flow problems with Distributed or Parallel computation features. The key features and factors affecting the convergence ratio and solution stability of APP are also analyzed.

Marginal Loss Factor using Optimal Power Flow in Power Market (최적조류계산을 이용한 한계손실계수의 전력시장 적용)

  • Ko, Young-Jun;Shin, Dong-Joon;Kim, Jin-O;Lee, Hyo-Sang
    • Proceedings of the KIEE Conference
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    • 2001.07a
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    • pp.509-511
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    • 2001
  • In the competitive electricity market, various pricing methods are developed and practiced in many countries. Among these pricing methods, marginal loss factor(MLF) can be applied to reflect the marginal cost of network losses. For the calculation of MLF, power flow method has been used. However, it shows some shortcomings such as necessity of regional reference node, and absence of an ability to consider network constraints. The former defect might affect adversely to the equity of market participants and the latter might generate an inappropriate price signal. To overcome these defects, the utilization of optimal power flow(OPF) is suggested in this paper. 30-bus system is used for the case study to compare the MLF by the power flow and the OPF method for 24-hour dispatching and pricing.

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A Framework for Determining Minimum Load Shedding for Restoring Solvability Using Outage Parameterization

  • Hwachang Song;Lee, Byongjun
    • KIEE International Transactions on Power Engineering
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    • v.4A no.2
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    • pp.73-78
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    • 2004
  • This paper proposes a framework for determining the minimum load shedding for restoring solvability. The framework includes a continuation power flow (CPF) and an optimal power flow (OPF). The CPF parameterizes a specified outage from a set of multiple contingencies causing unsolvable cases, and it traces the path of solutions with respect to the parameter variation. At the nose point of the path, sensitivity analysis is performed in order to achieve the most effective control location for load shedding. Using the control location information, the OPF for locating the minimum load shedding is executed in order to restore power flow solvability. It is highlighted that the framework systematically determines control locations and the proper amount of load shedding. In a numerical simulation, an illustrative example of the proposed framework is shown by applying it to the New England 39 bus system.

A Modified Particle Swarm Optimization for Optimal Power Flow

  • Kim, Jong-Yul;Lee, Hwa-Seok;Park, June-Ho
    • 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.

An Optimal Rescheduling of Power Generation to Constrain the EM Field Emitted from Power Transmission Lines (송전선로에서 발생하는 전자계 제약을 고려한 발전력의 최적 재분배)

  • Kim, Jong-Hyeong;Sin, Myeong-Cheol;Ra, Wan-Su;Park, Il-Han
    • The Transactions of the Korean Institute of Electrical Engineers A
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    • v.50 no.10
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    • pp.464-471
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    • 2001
  • Power utilities must satisfy both supplying high quality power economically and reducing EMF levels. In general, in order to reduce EMF levels from transmission line, it is effective to install shielding wires, configure wires with minimal space or modify structure of other conductors, etc., but these techniques require much cost and time. To some extent, the EMF levels associated with critical transmission lines can be reduced by redistributing the scheduled power generation, since it can change the power flows. There this technique can be readily applied without modifying other structures. This paper considers the OPF(Optimal Power Flow) with the EMF constraints in transmission lines to determine the power generation redistributions and demonstrates numerically the effectiveness of the approach.

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A New Dispatch Scheduling Algorithm Applicable to Interconnected Regional Systems with Distributed Inter-temporal Optimal Power Flow (분산처리 최적조류계산 기반 연계계통 급전계획 알고리즘 개발)

  • Chung, Koo-Hyung;Kang, Dong-Joo;Kim, Bal-Ho
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.56 no.10
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    • pp.1721-1730
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    • 2007
  • SThis paper proposes a new dispatch scheduling algorithm in interconnected regional system operations. The dispatch scheduling formulated as mixed integer non-linear programming (MINLP) problem can efficiently be computed by generalized Benders decomposition (GBD) algorithm. GBD guarantees adequate computation speed and solution convergency since it decomposes a primal problem into a master problem and subproblems for simplicity. In addition, the inter-temporal optimal power flow (OPF) subproblem of the dispatch scheduling problem is comprised of various variables and constraints considering time-continuity and it makes the inter-temporal OPF complex due to increased dimensions of the optimization problem. In this paper, regional decomposition technique based on auxiliary problem principle (APP) algorithm is introduced to obtain efficient inter-temporal OPF solution through the parallel implementation. In addition, it can find the most economic dispatch schedule incorporating power transaction without private information open. Therefore, it can be expanded as an efficient dispatch scheduling model for interconnected system operation.