Hierarchical Coordinated Control Strategy for Wind–BESS Primary Frequency Regulation Considering RoCoF-Triggered Dynamic Switching and SOC-Adaptive Power Allocation

The increasing penetration of wind power has made coordinated support from wind generation and battery energy storage systems (BESSs) increasingly important for maintaining frequency stability in low-inertia power systems. However, existing wind–BESS primary-frequency-regulation methods often rely on fixed participation factors or frequency-deviation-based power sharing, without considering different support requirements during rapid frequency decline and recovery. This may underutilize the rapid response capability of the BESS during high-RoCoF periods and lead to poorly coordinated wind-storage support, thereby limiting RoCoF suppression and frequency-nadir improvement. To address this issue, this paper proposes a hierarchical coordinated control strategy considering a rate-of-change-of-frequency (RoCoF) triggering mechanism. The strategy consists of an upper-layer coordination controller and lower-layer wind- and BESS-side controllers. The upper layer determines the total regulation demand and temporarily increases the BESS share when the direction-aware RoCoF activation condition is satisfied. The lower layer tracks allocated commands through wind-side virtual inertia and droop control and BESS-side deadband, SOC correction, and power limiting. This coordinated allocation combines rapid BESS support with sustained wind-power support. Simulations under different wind-power penetration levels and load disturbances demonstrate improved RoCoF suppression, frequency nadir, and recovery performance. At 25% wind penetration and a 0.10 p.u. load disturbance, the nadir increases from 49.62 to 49.77 Hz and recovery time decreases from 5.0 to 2.1 s.