Number Of Distributed Systems Research Articles

A simple heuristics for optimisation of unbalanced multistage supply chain logistics associated with fixed charges

This paper presents a mathematical model and a simple heuristics-based solution procedure for the multistage supply chain logistics associated with the fixed charges. The objective of this paper is to select the optimum set of suppliers, plants, distribution centres (DC) to be opened and determine the quantities to be supplied to satisfy the customer demand with minimum distribution cost. Fixed charge problems arise in a large number of distribution systems. In many distribution problems, the transportation cost consists of fixed charges, which are independent of the amount transported and variable costs, which are proportional to the amount shipped. The problem chosen goes beyond the traditional mathematical programming and it becomes a non-polynomial (NP) hard while considering the fixed charges. We present a simple heuristics for optimisation of unbalanced multistage logistics system and compared it in terms of distribution cost with spanning tree-based genetic algorithm (st-GA) and improved Prufer number encoding-based genetic algorithm (IPE-GA). The comparison reveals that the proposed heuristics is capable of providing better solutions.

Explicit loss formula, voltage formula and current flow formula for large-scale unbalanced distribution systems

Explicit formulas for determining system loss, current flows and voltages in terms of system and network data are developed for large-scale unbalanced distribution systems. The three-phase formulas consider multi-phase grounded or ungrounded loads and lines, cogenerators, multi-phase shunt elements and transformers of different connections all of which exist in large-scale unbalanced distribution systems. Test results on a number of distribution systems, including an actual 394-bus distribution network, are included to illustrate the accuracy and speed of the proposed formula for real-time analysis and control of distribution systems. It is shown numerically that the results given by these closed-form formulas are very close to those obtained by rigorous three-phase power flow methods. Applications of the explicit expressions to real-time control of distribution systems are also identified. Also, some features of the explicit formulas which are not possible with traditional power flow studies are discussed.