Abstract: In order to solve the influence of distributed power sources such as wind and sunlight on the stability of the power system, and to deal with power system failures caused by distributed power output fluctuations, an affine mathematical theory method is used to establish an interval model of photovoltaic and wind turbine output uncertainty. The complex affine power flow algorithm is studied. Finally, the optimization of the maximum power supply capacity is performed in combination with the particle swarm optimization algorithm. The verification of a numerical example shows that the access of distributed power sources has a large impact on the power supply capacity of the power system. The complex affine power flow algorithm can give the system node voltage, load rate interval, and maximum power supply interval. This method provides a basis for quantitative analysis of the influence of distributed power grids on the power system.