Oscillation-Stability-Constrained Coordinated Optimal Operation of Grid-Forming Energy Storage for Dynamic Support

The high penetration of grid-following (GFL) renewable energy integrated into weak grids may induce small-signal synchronous oscillations due to the coupling between phase-locked loop (PLL) dynamics and network impedance, thereby limiting renewable energy accommodation and the flexible operation of energy storage. To address the insufficient consideration of dynamic support feasibility in existing optimization methods with oscillation stability constraints, this paper proposes a coordinated optimal operation method for grid-forming (GFM) battery–supercapacitor hybrid energy storage systems (HESSs) considering small-signal synchronous stability constraints. First, based on the critical oscillation modes of multiple GFL converters and the equivalent admittance model of GFM units, an oscillation stability constraint is established by incorporating renewable energy output, spatial participation factors, and grid-forming control parameters. Second, the dynamic support required by GFM virtual inertia and damping is mapped into constraints on the battery–supercapacitor power margins, short-term energy margins, and converter capacity, thereby forming a feasible region of the J–D parameters considering the support capability of HESSs. On this basis, a coordinated optimization model for GFM-HESSs is developed, which simultaneously accounts for oscillation stability, frequency security, renewable energy accommodation, and battery degradation costs. Simulation results on a modified IEEE 39-bus system show that the proposed method can adaptively adjust grid-forming parameters according to operating conditions and allocate fast dynamic power to supercapacitors, thereby reducing high-frequency stress on batteries. Under the constraints of oscillation stability and frequency security, the proposed method reduces the total operating cost and wind curtailment rate by 11.23% and 37.37%, respectively, compared with the fixed large-parameter Case and by 1.58% and 18.01%, respectively, compared with the battery-only GFM energy storage Case. These results verify the effectiveness of the proposed method in improving the feasibility of stability support, operational economy, and renewable energy accommodation capability.