Online Estimation of Area-Level Inertia Considering Inter-Area Equivalent Frequency Dynamics

Online estimation of area-level inertia is important for frequency stability control in low-inertia power systems. This paper proposes an area-level inertia online estimation method considering inter-area equivalent frequency dynamics. Traditional methods require monitoring the frequency and active power of all the boundary buses and tie-lines, while the proposed method only needs one PMU placed at any bus within each area. The inter-area equivalent frequency dynamics model for the multi-area power system is developed, which is employed to estimate area-level inertia under ambient conditions. Then, the area-level inertia estimation model boils down to a nonlinear parameter identification problem. The other boundary conditions of the proposed method are derived by parameter identifiability. Simulation results carried out on the modified IEEE 39- bus system show that the proposed method can accurately estimate the area-level inertia using the bus frequency measurement. The proposed method is also effective under different PMU placements, time-varying virtual inertia, different system partitioning, system partitioning variation conditions, and different field conditions.