With the growing awareness in a sustainable environment, more electricity customers are becoming energy conscious. This leads to the increase of installation of grid-connected photovoltaic (PV) panels for small scale electricity generation. Nature of intermittent power generated by PV cells and the interconnection between PV panels and the network through DC-AC converter affect the quality of the electrical supply and these issues are as important as the environmental issues. Various studies observing the impact of (increasing) penetration of PV systems at the distribution level and the methods to mitigate this impact have been conducted by many parties, including academia, network operators, even PV inverter manufacturers. The model created for each inverter is then validated in a simulation using MATLAB Simulink. An aggregation of multiple inverters is modelled by paralleling the output impedances and summing in phasor the harmonic currents of the inverters. This book gives complete analysis and modelling regarding the impact of PV System integration on the grid in terms of harmonics.