Abstract
In this paper, previous contributions of the past 40 years in the area of distribution expansion planning are categorically analyzed. The primary focus would be the multistage formulations. Shortcomings form a practical point of view, for the techniques and solutions in each category are identified and discussed. Significant shortcomings are summarized and tabulated to serve as goals for future research.
Key words: Power system planning, Distribution expansion, shortcomings, future directions.
Introduction
While growth of electric energy demand has recently slowed, there will continue to be a need to expand facilities for the foreseeable future. Various plans to timely meet this demand growth, are continually studied for all major components of the electrical systems namely, generation, transmission, and finally distribution. In general, the primary goal in any system expansion is to timely meet the growth of demand in the most economical, reliable, and safe manner possible. Of course, safety and reliability introduce certain operational regulations and constraints that are different in distribution systems than other systems, and therefore must be considered in the expansion plans.
This general description of the expansion problems is somewhat independent of many other issues facing the both the suppliers and the users of electrical energy. For example, consider the deregulation issue, which is an attempt to promote better competition among the suppliers by giving more choices to the users. Although deregulation will impact the supplies' planning strategies, it cannot however, contain or limit the growth in demand or the system expansion in the global sense.
To correctly formulate any problem, a precise problem definition is necessary. In fact, solution set for the
problem is greatly reduced and the search algorithm to find it is more intelligently directed once the problem is clearly understood. Design criteria, and assumption statements are equally important element of a good formulation. Once the problem is clearly defined, design criteria has been set, and proper assumptions made, then a choice of an appropriate model, and application to a solution procedure would be in order.
The first paper about distribution planning optimization is attributed to [1] in 1960. Since this paper, there have been numerous publications in this area. References [2-56] are some selected examples of the significant published contributions. We begin with a systematic categorization and identification of common terminology among all previous research. Then, the shortcomings are identified and analyzed which subsequently narrows the focus to a smaller class for consideration. For the sake of completeness, we find it necessary to categorize the previous work along two lines. The first will be based on the optimization methods used, and the second will be based the application for example, the different approaches in problem identification and objectives. Some subdivision in each class will be done as needed to narrow the focus to the particular area of interest.
I - Categorization based on Optimization Methods
In so far as the distribution system expansion is concerned, optimization methods used may be divided in
to two distinct categories.
1 – Mathematical programming methods
2 – Heuristic methods, including expert systems and evolutionary algorithms
It is interesting to note that nearly all of the earlier research (1970s and 1980s) utilized mathematical programming algorithms, where as, almost all of the more recent work has been centered around the heuristic techniques, predominantly the Genetic Algorithms (GA) [13-26].
MOHAMMAD VAZIRI KEVIN TOMSOVIC TURAN GÖNEN
Department of EECS Department of EECS Department of EEE
Washington State University Washington State University California State University
Pullman WA 99163 USA Pullman WA 99163 USA Sacramento CA 95826 USA
mvaziri@eecs.wsu.edu tomsovic@eecs.wsu.edu gonen@ecs.csus.edu
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