This book presents modeling, simulation and their performance enhancement methodologies for a grid-connected photovoltaic systems. Grid-connected photovoltaic system is one of the most emerging technologies for a developing country to meet energy demand. Inherent intermittent nature of the renewable energy resources introducing significant challenge to integrate them to utility grid. The rapid increase in grid-connected PV systems whose output can change extremely rapidly, resulting many issues like voltage fluctuation, harmonic distortion and poor power factor for sustainable power generation. The main objective of photovoltaic systems is to extract the maximum power from the photovoltaic array and inject it into the utility grid. Therefore, the Maximum Power Point Tracking (MPPT) of a uniformly irradiated PV array and the maximization of the conversion efficiency is the main design issues. However, when the photovoltaic plant is connected to the grid, special attention has to be paid to the reliability of the system, the power quality and the implementation of protection and grid synchronization functions. Modern power plants are required to maximize their energy product.