Kenichi Aoki

Bio: Kenichi Aoki is an academic researcher from Hiroshima University. The author has contributed to research in topics: Linear programming & Electric power system. The author has an hindex of 14, co-authored 44 publications receiving 1338 citations.

Optimal VAr planning by approximation method for recursive mixed-integer linear programming

Abstract: The authors propose an algorithm for solving reactive power planning problems. The optimization approach is based on a recursive mixed-integer programming technique using an approximation method. A fundamental feature of this algorithm is that the number of capacitor or reactor units can be treated as a discrete variable in solving large-scale VAr (volt-ampere reactive) planning problems. Numerical results have verified the validity and efficiency of the algorithm. >

A new algorithm for service restoration in distribution systems

Abstract: This paper proposes a new algorithm to quickly. restore the deenergized loads in a distribution system by using the sectionalizing switches. The computational burden and the solution accuracy of the algorithm is improved by using the concept of the dual effective gradient method. Test results on practical system are given to demonstrate that the algorithm can be used in actual, large scale urban distribution system applications.

New approximate optimization method for distribution system planning

Abstract: An algorithm to obtain an approximate optimal solution to the problem of large-scale radial distribution system planning is proposed. The distribution planning problem is formulated as a MIP (mixed integer programming) problem. The set of constraints is reduced to a set of continuous variable linear equations by using the fact that the basis of the simplex tableau consists of the power flow variables of radial branch. This linear problem is solved by pivot operations which correspond to a branch-exchange of the radial network. Numerical examples are presented to demonstrate the validity and effectiveness of the algorithm. >

Normal State Optimal Load Allocation in Distribution Systems

Abstract: This paper addresses a subproblem related to distribution automation. It outlines an algorithm and presents computer results for minimizing the losses in a loop distribution system based on the remote operation of sectionalizing switches on feeders interconnecting different substations. The minimization is carried out subject to the voltage-drop, line-capacity and substation-capacity constraints. Computational experience with a system of realistic size indicates that the procedure proposed here is valid and effective in practical operations.

An efficient algorithm for load balancing of transformers and feeders by switch operation in large scale distribution systems

Abstract: A systematic and practical algorithm for load balancing of transformers and feeders by automatic sectionalizing of switch operation in large-scale distribution systems of the radial type is discussed. The algorithm is developed by extending an approximation for load transfer of the desired two transformers. The algorithm is applicable to operations not only in the normal state, but also in the scheduled and failure outage states. Computational experience on a real large-scale system has indicated that the algorithm is valid and effective for practical operations. >

Network reconfiguration in distribution systems for loss reduction and load balancing

Abstract: A general formulation of the feeder reconfiguration problem for loss reduction and load balancing is given, and a novel solution method is presented. The solution uses a search over different radial configurations created by considering switchings of the branch exchange type. To guide the search, two different power flow approximation methods with varying degrees of accuracy have been developed and tested. The methods are used to calculate the new power flow in the system after a branch exchange and they make use of the power flow equations developed for radial distribution systems. Both accuracy analysis and the test results show that estimation methods can be used in searches to reconfigure a given system even if the system is not well compensated and reconfiguring involves load transfer between different substations. For load balancing, a load balance index is defined and it is shown that the search and power flow estimation methods developed for power loss reduction can also be used for load balancing since the two problems are similar. >

Distribution feeder reconfiguration for loss reduction

Abstract: Feeder reconfiguration is defined as altering the topological structures of distribution feeders by changing the open/closed states of the sectionalizing and tie switches. A scheme is presented that utilizes feeder reconfiguration as a planning and/or real-time control tool to restructure the primary feeder for loss reduction. The mathematical foundation of the scheme is given. The solution is illustrated on simple examples. >

A genetic algorithm solution to the unit commitment problem

Abstract: This paper presents a genetic algorithm (GA) solution to the unit commitment problem. GAs are general purpose optimization techniques based on principles inspired from the biological evolution using metaphors of mechanisms such as natural selection, genetic recombination and survival of the fittest. A simple GA algorithm implementation using the standard crossover and mutation operators could locate near optimal solutions but in most cases failed to converge to the optimal solution. However, using the varying quality function technique and adding problem specific operators, satisfactory solutions to the unit commitment problem were obtained. Test results for power systems of up to 100 units and comparisons with results obtained using Lagrangian relaxation and dynamic programming are also reported.

Reconfiguration of electric distribution networks for resistive line losses reduction

Abstract: The authors describe a heuristic method for the reconfiguration of distribution networks in order to reduce their resistive line losses under normal operating conditions. The proposed approach is characterized by convergence to the optimum or a near-optimum solution and the independence of the final solution from the initial status of the network switches. The methodology has been implemented in a production-grade computer program, DISTOP (Distribution Network Optimization). The compensation-based power flow technique developed at Pacific Gas and Electric Company for the efficient solution of weakly meshed distribution networks is an essential part of this loss reduction methodology. Important implementation aspects of the methodology and the results of its application to several realistic distribution networks are presented. Numerous test results have indicated that the proposed technique is computationally robust and efficient and, hence, suitable for both planning and operations studies. >