In this paper, two cascaded voltage source grid-connected inverters (VSI) with Quadratic boost converter (QBC) has been described and simulated as more attractive for a grid to interface with the PV system. The simulation is carried out by using the open loop control method to synchronize the grid with the photovoltaic system and these two inverters are controlled with the Sinusoidal Pulse Width Modulation (SPWM) approach and SV Pulse Width Modulation (SVPWM) skill technique for dynamic behavior. These two inverters individually operate as two-level inverters and after cascading with the transformer will get the three-level output voltage and it is interfaced to a three-phase ac grid. To interface PV system with Grid here using a two-stage method which includes DC to DC converter, three-phase voltage source inverters and cascaded transformer for analyzing dc output voltage, active power and harmonic distortion of current. The Quadratic Boost Converter (QBC) is used to convert from DC to DC for injecting DC supply voltage into the cascading three-phase inverters. In this paper, the entire system is carried out by using with QBC and without QBC and compares the output voltages and total harmonic distortion of current at the grid side.