Cooperative Frequency Regulation for Thermal Power and Energy Storage Clusters via Hierarchical SOC Control

Abstract

Distributed energy storage is crucial for frequency stability in low-inertia grids. However, conventional lumped models mask unit heterogeneity, causing premature depletion of low-state of charge (SOC) units known as the “barrel principle”. To address this, a hierarchical cooperative control strategy for thermal energy storage systems (thermal power and energy storage) prioritizing SOC consistency is proposed. A discrete-time state-space model is constructed to capture heterogeneous dynamics. The proposed two-layer architecture features an upper layer discrete filter for spectral-based power allocation and a lower layer adaptive consistency algorithm. A non-linear power-exponent weighting mechanism dynamically recalibrates output weights based on real-time SOC deviations. The simulation results demonstrate that the strategy effectively suppresses frequency fluctuations and ensures rapid SOC convergence. By preventing overcharge or overdischarge of the individual unit, the approach significantly enhances the effective capacity and operational robustness of the joint system.