In this paper, the phenomena that occurs when connecting a PV energized micro-grid to the public grid, is presented. A PV inverter system, for supplying the micro-grid, was designed and simulated using Matlab-Simulink. The simulations are done for three different power factors, showing in this way how the power factor can influence the behavior of the system, especially when the transitory regime occurs. A PI control strategy is used for controlling the PV inverter system. The PV inverter is driven by a PWM with unipolar voltage switching technique.