Assessing Grid Stability with High Penetration of Renewable Energy Resources and Energy Storage for Stability Enhancement

The global transition to renewable energy sources (RESs), driven by environmental goals and net-zero initiatives, has significantly transformed power system dynamics. However, this transition introduces critical challenges for grid stability, particularly in weak and low-inertia grids. This thesis investigates the impacts of high RES penetration on voltage and frequency stability and proposes advanced strategies to ensure grid resilience under diminishing grid strength. A comprehensive framework is developed to address voltage stability challenges in weak grids, where reduced Available Fault Level (AFL) and diminished grid strength increase sensitivity to disturbances. Key factors, such as grid impedance, inverter control dynamics, and Point of Interconnection (POI) characteristics, are analysed to evaluate grid performance under varying RES penetration levels. The study highlights that weak grids, characterized by low short-circuit ratios, are prone to voltage instability, impacting power quality and reliability. To mitigate these issues, an advanced Energy Management System (EMS) is proposed to optimize Battery Energy Storage System (BESS) operation for voltage regulation and reactive power support. The EMS addresses the challenges posed by diminishing grid strength, battery degradation, RES intermittency, and load uncertainties. The research further examines frequency stability in low-inertia grids, where the replacement of traditional synchronous generators with inverter-based RESs reduces rotational inertia, leading to faster frequency deviations and higher Rates of Change of Frequency (RoCoF) during disturbances. A frequency stability assessment framework is introduced, incorporating statistical analyses, Monte Carlo simulations, and dynamic studies. To enhance frequency stability, the thesis proposes optimized BESS deployment for virtual inertia provision and frequency regulation. A dynamic virtual inertia control strategy is developed to adaptively adjust BESS inertia contributions in real time, ensuring stability under varying RES penetration levels and dynamic operating conditions. The findings of this research provide valuable insights into addressing voltage and frequency stability challenges in renewable energy-dominated grids. By presenting a comprehensive framework and innovative control strategies, this work equips grid operators with practical tools to enhance system reliability and resilience. The strategic deployment of BESS, combined with advanced EMS and virtual inertia control mechanisms, ensures adaptability to the evolving energy landscape. These contributions lay a robust foundation for future research on integrating RESs, energy storage systems, and advanced control technologies into modern power systems.