Algoritmo genetico

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Electric Power Systems Research 32 (1995) 81-87

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Genetic algorithm for open-loop distribution system design
Gregory Levitin, Shmuel Mazal-Tov, David Elmakis
Relicthility DcT~artment Research and Development Division, Israel Electric Corporation Ltd., Ha(/a, Israel
Received 6 August 1994

Abstract

To ensure a given level of reliability of energy supply, distributionnetworks should be configured in such a way that each load point may be supplied from alternative sources. The method proposed in this paper is aimed at designing such distribution systems with minimal feeder length, energy losses and load imbalance between transformers, subject to voltage drop and capacity constraints. The method is based on the biologically inspired genetic algorithm (GA). Basic GAprocedures adapted to the given problem are presented and five versions of the GA are compared. Test results are reported which demonstrate that the chosen version of the proposed algorithm outperforms a heuristic procedure proposed previously.

Keywords: Genetic algorithms; Distribution network design; Open-loop network configuration

I. Introduction

To provide a desired level ofserviceability in urban distribution systems an open-loop configuration should be used which ensures alternative feeding for each load point. This is achieved by planning tie lines connecting different feeders or substations. Each pair of connected feeders forms a loop which may be supplied from two different sources. Thus, an outage of any single section of a feeder does not cause an interruption of powerdelivery. Two levels of serviceability of energy distribution are distinguished. The feeder serviceability level maintains serviceability during a feeder segment outage. To achieve this level it is enough to connect both loop ends to the same substation (transformer). The transformer serviceability level ensures continuity of power delivery during a transformer outage. To provide this level eachloop should be closed through different substations. In both cases transformers and cables should be chosen which are able to supply simultaneously all customers belonging to the loop. When the open-loop system is planned the cost of capital investment is considered as well as the annual cost of power losses. The objective of the system design is to find the minimum cost network configurationwhich provides the desired reliability rate. During the decision-making process different substation siting and sizing schemes are considered. For each scheme an
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algorithm for an optimal loop network configuration should be applied. Several aspects of open-loop distribution system planning are ofinterest to researchers [1-6]. The most advanced algorithm was suggested by Glamocanin and Filipovic [7]. This algorithm is aimed at determining the open-loop distribution system's minimum cost configuration and is based on a two-stage constructive heuristic procedure. In this paper the same problem formulation is used, but the definition of the criteria is extended and a genetic algorithm basedprocedure for multiobjective network structure optimization is proposed.

2. Problem formulation

The distribution system development plan should provide a network configuration in which N, new (planned) load nodes are connected to different substations. Existing feeders may be extended t, reach the new nodes and new feeders may be laid.

2.1. Data requirements
To define the problem the coordinatesof substations and all load nodes (existing and new) should be specified, as well as load data (Pi). In the case when a lateral radial line is connected to a node, the total load of this line is considered to be concentrated at this node.

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G. Levitin et a l . / Electric Power Systems Research 32 (1995) 81-87

The definition of each existing feeder includes the ordered list of nodes...