With the increasing penetration of PV stations, the connected grid’s fault characteristics are fundamentally changed. As a result, the equivalent model (both voltage source and reactance that are connected in series) of traditional generators cannot be applied for calculating the protection settings of a power grid with large-scale PV stations. It is of great significance to build the fault current calculation model of PV stations based on their fault characteristics. In this paper, the difference algorithms of different generation units’ fault characteristics are revealed in the PV stations. The main factors influencing the fault current contribution difference of the generation units are explored. A clustering method is proposed on the basis of the difference algorithms of the generation units’ transient control modes. Further, a unified model for calculating the current contribution from a PV station is deduced under symmetrical and asymmetrical faults. Finally, using practical PV stations’ operating data, both theoretical analysis calculation results and PSCAD/EMTDC electromagnetic transient simulation results are compared and analyzed. These results verify the correctness of the proposed fault current calculation model. The research will provide support for studying the protection setting calculation of power grid with PV station. This work is supported by the Science and Technology Project of the Headquarters of State Grid Corporation of China (No. 52170221000U) and the Science and Technology Project of Henan Electric Power Company (No. SGHADK00DWJS2000186).