A photovoltaic power generation system includes a photovoltaic power generation module, a capacitor, a DC/AC voltage converter, a filter, a relay, a PWM controller, a calculation module, a control module, and a grid. The control module traces the maximum power of the photovoltaic power generation module, and detects whether the grid is abnormal or not. Finally, the DC power outputted from the photovoltaic power generation module is transferred to the AC power and outputted to the grid via the DC/AC voltage converter by using the PWM controller.