Comprehensive Assessment of the Impact of Large-Scale Solar Power Plants with WECC Controllers on Inter-Area Oscillations in the Power Grid

The increasing integration of large-scale solar photovoltaic plant (LSSPP) into power grids introduces new system stability challenges, particularly low-frequency interarea oscillations. This paper comprehensively assesses the dynamic impact of solar photovoltaic plants equipped with Western Electricity Coordinating Council (WECC) on interarea oscillatory modes. A two-area system is considered, and small-signal stability analysis is conducted to evaluate the influence of varying photovoltaic (PV) penetration levels on critical electromechanical modes. The role of WECC PV controllers in shaping system dynamics is investigated through participation factor analysis and eigenvalue tracking. Simulation results under different fault scenarios provide insights into the damping performance and modal interactions introduced by inverter-based resources (IBR). The findings contribute to a better understanding of how utility-scale solar integration affects oscillatory behavior and highlight the importance of coordinated control strategies to maintain system stability.