This paper is devoted to study the impact of the PV systems on electrical grids. This paper investigate the stability response of a Single Machine Infinite Bus (SMIB) system with a PV installation at the middle of the transmission. A mathematical model of a single-machine infinite-bus power system integrated with a PV power generation plant is established. Both the non-linear and linear dynamic model of synchronous generator, PV system and power conditioning unit that comprises of DC-DC converter, DC-link and DC-AC converter are developed. The system dynamics are investigated for various disturbance levels depending on the PV penetration amount and location.