A detailed simulation model of Photovoltaic (PV) generation system based on MATLAB/Simulink is established firstly, based on its detailed mathematical presentation. Its inverter-based simplified models, i.e. the switching-function equivalent model and average model, are proposed and simulated, overcoming the limits of traditional method in simulation speed and robustness. Quantitative comparisons are made between these methods from different aspects, including the simulation speed, accuracy as well as robustness to step-size. Besides, a novel phasor simulation model of the grid-tied PV generation system, which significantly improves the simulation speed and is suitable for the fast analysis of power flow and electromagnetic transient behavior, is proposed. The validity and utility of the proposed phasor model are assessed by comparing the steady-state performance with the detailed model. Finally, the applications of each method are proposed based on the aforementioned analysis.