Optimum size and placement of distributed generators in microgrid based on reliability concept

Integration of various on-site distributed generators in a micorgrid, which can either be operated in grid-connected or islanded mode, helps to satisfy the local demand. The optimum sizing and placement with a techno-economical optimization of a microgrid is done with Particle Swarm Optimization (PSO). The problem of optimum placement and size is formulated as a nonlinear integer minimization problem which minimizes the sum of the total capital, operational, maintenance and replacement cost of Distributed Generators (DGs), subject to constraints such as voltage, energy limits of each DG, exchanged power with utility and the constraints of system reliability. The exchanged power with the main grid, economics of DG units and penalty for not supplying the loads are taken into consideration. In this paper, some notions of reliability indices are calculated in order to evaluate the performance of a microgrid in both grid-connected and islanded mode, and the effect of reliability on total cost of microgrid is evaluated. The uncertainty of PV output is also considered which plays an important role in optimization technique.