When a large number of power electronic devices are connected to a system, this results in changes in their transient behavior and an increase in the order of the topological structure state variables in a new power system dominated by new energy. A grid-connected inverter model for photovoltaic generation systems incorporating energy storage based on droop control methodology is established, and its Lyapunov function is constructed using singular perturbation reduction theory and the variable gradient method. Then, the influence of energy storage system integration on the power angle stability of new energy systems is analyzed by combining the constructed Lyapunov function with the equal area criterion. Additionally, the capability of energy storage systems to support system output and suppress fluctuations in photovoltaic system output is verified. Finally, the characteristics of integrated energy storage in new energy systems are analyzed and validated based on Matlab simulation results.