Small-Signal Stability Optimization of Power System Dominated by Variable Renewables with Virtual Inertia Control and Droop Control

Variable renewable generation (VRG) may replace conventional synchronous generators, which could result in a lack of system inertia and problems with frequency stability. To address this issue, virtual inertia control and droop control of VRG can be used to enhance system frequency stability. However, this may bring significant impact on small-signal angle stability among synchronous generators. This study looks into how VRG's virtual inertia control and droop control, which effectively affect the VRG's small-signal angle stability when a considerable amount of variable renewable energy sources are present. At the system's equilibrium point, a small-signal model, which is based on state space equation, is built to see if the system complies with the safety requirements for small-signal stability of VRG. To improve the VRG's small-signal stability, an optimization model for small-signal model is put forth in this study. The aim of optimization is how to reduce the variation of each state variable's damping ratio. Furthermore, using Particle Swarm Optimization, the virtual inertia parameters of each VRG and the equivalent damping to the grid are optimized. Finally, the proposed optimization method is validated through time-domain simulations, demonstrating its effectiveness and reliability.