The fluctuation in the output of new energy sources can increase the operational risks of the new type of power system. To address the issue of negative values that arise when using the A?type gram?charlier series expansion to fit probability density functions, in probabilistic power flow calculations for electrical systems with wind and photovoltaic integration, the Latin hypercube sampling (LHS) technique and the C?type Gram?Charlier (CGC) series expansion method are introduced. Then a power system probabilistic power flow calculation method is proposed based on the LHS?CGC approach. Taking the calculation results of the monte?carlo method as the reference, the probability density distribution of various system state variables and output variables is verified in three operational modes: summer peak load, winter off?peak load, and high penetration of new energy sources, using the improved IEEE 30 test system. This validates the accuracy and effectiveness of the method proposed in this paper, which also exhibited a high computational speed. Through comparative analysis of probabilistic power flow calculation results under different operational modes, it is found that the system branch currents and voltage exceedance risks increase during high penetration of new energy sources. Therefore, in grid planning and dispatching, special attention needs to be given to the impact of seasonal variations in wind and photovoltaic output on the operational risks of the system.