A.J. Urdaneta

Ant colony system algorithm for the planning of primary distribution circuits

The planning problem of electrical power distribution networks, stated as a mixed nonlinear integer optimization problem, is solved using the ant colony system algorithm (ACS). The behavior of real ants has inspired the development of the ACS algorithm, an improved version of the ant system (AS) algorithm, which reproduces the technique used by ants to construct their food recollection routes from their nest, and where a set of artificial ants cooperate to find the best solution through the interchange of the information contained in the pheromone deposits of the different trajectories. This metaheuristic approach has proven to be very robust when applied to global optimization problems of a combinatorial nature, such as the traveling salesman and the quadratic assignment problem, and is favorably compared to other solution approaches such as genetic algorithms (GAs) and simulated annealing techniques. In this work, the ACS methodology is coupled with a conventional distribution system load-flow algorithm and adapted to solve the primary distribution system planning problem. The application of the proposed methodology to two real cases is presented: a 34.5-kV system with 23 nodes from the oil industry and a more complex 10-kV electrical distribution system with 201 nodes that feeds an urban area. The performance of the proposed approach outstands positively when compared to GAs, obtaining improved results with significant reductions in the solution time. The technique is shown as a flexible and powerful tool for the distribution system planning engineers.

Integral planning of primary-secondary distribution systems using mixed integer linear programming

Important research effort has been devoted to the topic of optimal planning of distribution systems. However, in general it has been mostly referred to the design of the primary network, with very modest considerations to the effect of the secondary network in the planning and future operation of the complete grid. Relatively little attention has been paid to the optimization of the secondary grid and to its effect on the optimality of the design of the complete electrical system, although the investment and operation costs of the secondary grid represent an important portion of the total costs. Appropriate design procedures have been proposed separately for both the primary and the secondary grid; however, in general, both planning problems have been presented and treated as different-almost isolated-problems, setting aside with this approximation some important factors that couple both problems, such as the fact that they may share the right of way, use the same poles, etc., among other factors that strongly affect the calculation of the investment costs. The main purpose of this work is the development and initial testing of a model for the optimal planning of a distribution system that includes both the primary and the secondary grids, so that a single optimization problem is stated for the design of the integral primary-secondary distribution system that overcomes these simplifications. The mathematical model incorporates the variables that define both the primary as well as the secondary planning problems and consists of a mixed integer-linear programming problem that may be solved by means of any suitable algorithm. Results are presented of the application of the proposed integral design procedure using conventional mixed integer-linear programming techniques to a real case of a residential primary-secondary distribution system consisting of 75 electrical nodes.

A hybrid genetic algorithm for optimal reactive power planning based upon successive linear programming

A hybrid methodology is presented for the solution of the problem of the optimal allocation of reactive power sources. The technique is based upon a modified genetic algorithm, which is applied at an upper level stage, and a successive linear program at a lower level stage. The objective is the minimization of the total cost associated to the installation of the new sources. The genetic algorithm is devoted to defining the location of the new reactive power sources, and therefore to handle the combinatorial nature of the fixed costs problem. At the lower level, the variable cost problem is solved by calculating the magnitude of the sources to be installed at the previously determined locations by means of a linear program iterated successively with a fast decoupled load flow. Results are presented for the application of the proposed methodology when applied to the Venezuelan electric network.

Uniform marginal pricing for the remuneration of distribution networks

A new method for distribution access via uniform pricing for the remuneration of distribution networks is presented. The proposed approach merges in a unified framework the investments, the optimal network operation requirements, the effect of the price elasticity of demand, and the application of hourly pricing for demand side management purposes. Hourly uniform marginal prices-understood as tariffs of use of the network-are obtained from maximum social welfare condition sending efficient signals to the utility and consumers, related to the optimal operation of the grid and use of the energy at peak and valley hours. This method is used in the context of a Performance Based Ratemaking regulation to get model companies from operational optimized real networks. Capital fees are integrated in the marginal tariff of use, by means of the New Replacement Value concept, broadly used in yardstick competition. The model is stated as a mixed-integer linear optimization problem suitable to be solved through well-known linear programming tools. The methodology has been successfully tested in a 42-bus test distribution network.

A probabilistic methodology for distribution substation location

A probabilistic methodology is presented, conceived to assist the electric system planning engineers in the selection of the distribution substation locations, taking into account the hourly load changes or the daily load cycle. The hourly load centers, for each of the different hourly load scenarios, are calculated deterministically. These location points, properly weighted according to their correspondent load magnitude, are used to calculate the best fit probability distribution. This distribution is used to determine the maximum likelihood perimeter of the area where the substation should preferably be located by the planning engineers, taking into account, for example, the availability and the cost of the land lots, which are factors of special relevance in urban areas, as well as other obstacles that may be present in the final selection of the substation site. Results are presented and discussed for the application of the methodology to a real case, assuming three different bivariate probability distributions: the Gaussian distribution, a bivariate version of Freunds exponential distribution, and the Weibull probability distribution.

Tuning of power system stabilizers using optimization techniques

The application of a numerical optimization scheme to the tuning of power system stabilizers is studied. The scheme is based on minimax optimization techniques with multiple objectives given by relevant system perturbations, aggregated by means of a weighted sum. The large number of constraints is handled by separating the optimization and simulation in two levels which interchange limited information. Three different optimization techniques were tested with applications to the Venezuelan power system for the years 1989 and 2005. The overall method is shown to be accurate and reliable. >

Standard levels of energy losses in primary distribution circuits for SCADA application

The reduction of energy losses in distribution systems is an important issue during planning and operation with important technical and economical implications. The standard or normal level of energy losses in primary distribution circuits represents an important indicator for the planning and operation of electrical distribution circuits. It depends upon a number of parameters and variables such as the nominal circuit voltage, the installed transformer capacity, the number of transformation points, the load level, etc. In this article the application of a statistical procedure for the determination of the standard levels of energy losses in primary distribution circuits is proposed. The methodology is applied to a subset of 312 primary distribution circuits out of the total of 819 circuits of the electrical distribution network that serves the city of Caracas and its surroundings. The resultant standard upper and lower levels of energy losses are presented for the 15 different groups of circuits that were formed by the statistical procedure. These limits are used online for the identifleation of those distribution feeders with an operating level of energy losses out of the standard levels of its correspondent statistical group, as candidates for the application of energy losses reduction measures. The developed application software is presently running on-line at the distribution energy management system of the of C.A. La Electricidad de Caracas-AES Venezuela.

Application of adaptive reclosers to automatic distribution systems

This paper presents a discussion on several issues related to adaptive reclosers. It is shown, by using a realistic example, that adaptive reclosers should be installed in distribution systems with automatic switching capabilities in order to optimize their protective function. In particular, the case of primary circuits with automatic transfer systems is discussed. The conclusion is that the fuse-saving scheme normally implemented in primary-radial distribution systems can be automatically achieved for the different configurations of the primary circuit when adaptive reclosers are used. The paper also presents a brief discussion on the requirements that should be met by application programs for adaptive distribution protection.