Inertia Estimation and Real-Time Assessment Method for Power Systems Considering Virtual Inertia of Renewable Energy

The large-scale integration of new energy sources into the power grid brings stability issues to the power system. Power system inertia is an important measure to evaluate the system's resistance to disturbances. In traditional power systems, inertia is provided by synchronous machines. However, new energy sources do not have physical inertia and provide virtual inertia through control strategies such as grid-forming and gridfollowing. The characteristics of virtual inertia vary under different control strategies. Deriving the equivalent inertia constants of different types of devices can greatly facilitate inertia assessment. Therefore, a method is proposed to evaluate the equivalent inertia of new energy power systems considering various control methods. Through theoretical derivation, a unified inertia analytical model for grid-forming, grid-following devices, and synchronous generators is established. Dynamic modeling based on the Extended Kalman Filter transforms inertia calculation into parameter identification. Using the Forgetting Factor Recursive Least Squares (FFRLS) algorithm to identify parameters in the model, and evaluating the system inertia level online based on the system's operating state. Simulation analysis is conducted on the IEEE 39-bus system, verifying the correctness of the theoretical analysis and the effectiveness of the identification method.