Power Swing Blocking Protection in Presence of Large Scale Grid Following PV Generation

Includes Bibliographic references.

PhD;2024;Electrical Engineering.

The increasing penetration of Inverter-Based Resources (IBRs) in power grids, driven by environmental concerns, has significantly altered the system's dynamic behavior. Unlike traditional Synchronous Generators (SGs), IBRs exhibit distinct fault characteristics and lack inherent inertia, posing challenges to existing protection schemes designed for SG-dominated systems. Power swings, both stable and unstable, induced by system disturbances can trigger undesired relay operations. Power Swing Blocking (PSB) and Out-of-Step Tripping (OST) techniques have been traditionally employed to mitigate these issues. This research delves into the impact of large-scale Grid-Following (GFOL) Photovoltaic (PV) generation on the efficacy of PSB protection. By examining a modified IEEE-39 bus system, it has been found that GFOL PV integration significantly distorts power swing impedance trajectories compared to SG-dominated systems. Consequently, the rate of change of impedance, represented by |dZ/dt|, is amplified, increasing the risk of PSB and OST maloperations. These findings underscore the urgent need for adaptive protection strategies to accommodate the growing presence of IBRs. The study further investigates the influence of Phase-Locked Loop (PLL) characteristics on impedance trajectories. Different PLL types and parameters, along with varying PV penetration levels and relay locations, were analyzed. Results indicate that PLL dynamics significantly impact PSB performance during power swings. Additionally, the interaction between dynamic voltage support, active power recovery rate, and power swing characteristics has been explored. The findings emphasize the complex interplay of these factors in determining PSB behavior. The impact of auto-recloser dead time on the severity of power swings has also been studied. Subsequently, a novel approach utilizing nodal inertia for re-evaluating blinder time settings has been proposed to address the limitations of existing impedance-based PSB methods. Simulation results demonstrate the effectiveness of this method in both SG-dominated and GFOL PV-integrated systems. This research contributes to a deeper understanding of the challenges posed by IBR integration on power system protection. The findings highlight the critical need for comprehensive power swing protection schemes that can adapt to the evolving grid landscape.