Multi-agent hierarchical consensus framework for frequency and voltage regulation with cooperative battery storage units

High penetration of renewable resources reduces inertia and short-circuit strength in transmission networks. This loss of electromechanical stiffness directly compromises the ability of the system to withstand power imbalances. This paper proposes a hierarchical multi-agent control framework to coordinate distributed battery energy storage. The architecture integrates a fast local layer for sub-second voltage support and primary frequency response. A secondary layer employs dual-consensus algorithms to harmonize the state of charge and historical regulation effort over a communication graph. The adaptive active-power reference is computed through a multiplicative formulation. This law couples frequency deviation, area control error, and available capacity while strictly enforcing apparent-power constraints. Thus, the controller ensures capacity-aware dispatch, prevents overcompensation, and preserves P / Q limits. Validation was conducted on a modified IEEE 14-bus system with 47.8% non-synchronous generation. Scenarios included a 204% load step, a 25% renewable surge, and a three-phase fault. Results demonstrate enhanced scalability and resilience. For operational (non-fault) events, frequency deviations remain within ≤ ± 0 . 08 % and return to the NERC 20 – 36 mHz band within 2 s. Furthermore, bus voltages satisfy IEEE Std C84.1 limits ( 0 . 95 – 1 . 05 pu ), while state-of-charge dispersion falls below 0 . 05 pu .