This paper presents a photo-voltaic generation system using a single-phase grid-connected quasi Z-source inverter (QZSI). The method to track the maximum power point of the PV array by adjusting the shoot-through time of the QZSI is suggested. The modified switching patterns for controlling effectively the shoot-through time while reducing the switching loss are applied. The ac grid current controller with a resonant controller is designed in order to eliminate the steady-state error at the grid frequency, 60Hz. To confirm the effectiveness of proposed methods, some simulation results are shown.