Optimization Software for Distribution Systems Expansion Planning

The paper presents the main features of software under development for the optimized expansion planning of distribution systems. The software allows the planner to identify the best choices for future investments in such a way that the investments costs are minimized over the stages of the planning horizon. The software is based on the concept of object oriented programming (POO) and written in C/C++ language. It was designed for personal computers and the Windows operational system. A GUI (graphical user interface) was designed to allow an easy and intuitive interaction with the user. The visualization and graphical modules use standard functions from the OpenGL Library. In this way, substations, existing and future nodes and branches can be defined in a straightforward fashion using the available menus, icons and shortcuts. The optimization of the system expansion is based on a mathematical model which permits the inclusion of several planning stages and the consideration of a number of constraints, including node voltage limits and operating limits of all components. After the definition of the existing system topology, new nodes, branches and loads, a mixed integer programming optimization problem is automatically generated. The objective function to be minimized is the overall costs of the considered stages. The generated optimization problem is solved by an integrated optimization module (solver) which is based on GLPK (GNU linear programming kit), a free software package. After the solution is obtained, the optimized solution for each stage can be visualized using the visualization tools (feeder routes, plots, tables). The paper presents examples illustrating the application field and the software capabilities. The software proved to be very helpful in helping the system planner to undertake a system expansion at minimum costs leading to substantial savings