The growing integration of renewable energy sources (RESs), particularly inverter-based distributed generators (IBDGs), into modern power systems presents profound challenges to conventional grid protection and control schemes, thereby impacting overall grid resiliency. This monograph presents a comprehensive investigation into these challenges, aiming to develop and validate adaptive solutions for systems with high penetration of RESs. It commences with a detailed examination of the evolving concept of grid resiliency and analyses the complex fault response behaviours introduced by RESs, which often exhibit limited and controlled fault current contributions. This fundamental shift in fault characteristics highlights the inherent limitations of traditional protection schemes, especially distance relays, which were designed for grids dominated by synchronous generators and often fail to operate reliably in the presence of low-inertia, power-electronics-based RESs. The need for adaptive protection schemes and updated grid codes for modern distribution and transmission systems is thoroughly discussed.
The monograph also presents a detailed modelling of RESs, including solar photovoltaic, wind energy systems, and battery energy storage systems (BESS) with their necessary control schemes for effective grid integration. Major control techniques explored include grid-forming and grid-following inverter controls, droop control, virtual inertia emulation, and d-q current control. An in-depth analysis of proportional-integral and proportional-resonant controllers is provided to optimize inverter performance for enhanced grid stability. The performance degradation of conventional distance protection schemes in RES-dominated networks is analysed through simulation studies, revealing critical issues in fault detection, coordination, and isolation. To address these limitations, various adaptive distance protection techniques for RES-dominated grids are suggested. The comparative analysis of these adaptive and conventional distance protection techniques, simulated using RTDS and PSCAD/EMDC software, shows the efficacy of the adaptive methods.
Furthermore, the monograph explores the advanced methodologies for significantly improving overall grid resiliency, with a focus on the acceleration of second-zone protection of distance relays. Both theoretical analyses and simulation-based validations are presented to substantiate the effectiveness of these approaches in enhancing fault clearance times and system stability. It provides valuable insights and practical frameworks for developing coordinated protection and control strategies, which are indispensable for ensuring secure, reliable, and resilient grid operations amidst the escalating integration of RESs.
