Photovoltaic energy systems: Considerations for grid interconnection

The sun is a primary power source that can be turned into electricity by means of PMW or multilevel inverters. Despite the actual higher cost-effectiveness of other power sources, approximately around +14-15%, even including the plant losses (cables, inverters, transformers etc.), sunlight is a free and unlimited source which cost-effectiveness can be improved up to 22% [1]. The paper drives the attention on the major issues in the converting process of sunlight into electrical energy, particularly when connected to weak electric grids where voltage variations, distortions of voltage wave form (THDv) and fundamental frequency variations can be mostly found.