Frequency Stability in Low Inertia Power Systems with High Renewable Generation Integration

Abstract

The pursuit of a more sustainable and environmentally conscious future has led to the progressive integration of non-synchronous Renewable Energy Sources (RESs) into power systems worldwide. However, integrating these non-synchronous RESs, such as wind and solar power, presents significant technical challenges due to their different operational characteristics compared to conventional synchronous generators. Non-synchronous RESs generate electricity through power electronic inverters rather than directly synchronizing with the grid frequency. Unlike traditional generators, they do not have large rotating masses that provide inertia, which is crucial for stabilizing grid frequency. Consequently, the absence of inherent inertia in non-synchronous RESs makes managing grid stability more challenging, especially as their share in the energy mix increases. The Kingdom of Saudi Arabia (KSA), in alignment with this global endeavour, has embarked on an ambitious journey to incorporate substantial amounts of non-synchronous RESs into its national grid. This thesis is dedicated to examining the general and regional consequences of this transition, particularly focusing on how high integration of non-synchronous RESs impacts the frequency stability of the KSA's national grid. Five studies are conducted to address various aspects of this complex interaction. The initial study lays the groundwork by developing future energy scenarios (Low Progression, Medium Progression, and High Progression) for 2025 and 2030, providing a foundational framework for subsequent analyses. Building upon this foundation, the second study estimates future power system inertia to evaluate long-term dynamic frequency response under high inverter-fed RESs. This inertia estimation methodology forms the basis for assessing long-term dynamic frequency response under high inverter fed RESs, revealing insights into the system's resilience and stability. Another challenge that this research is addressing, is the impact of renewable energy sources on the stability of the KSA power system at the regional level. To comprehensively evaluate this impact, an adaptive dynamic model of the KSA national grid is developed and validated in the professional power factory platform, considering regional operation area characteristics. This detailed model enables a thorough evaluation of how RESs integration affects stability across different regions of the system. iii In study four, a comprehensive analysis of the KSA system frequency stability in 2025 and 2030 under predesigned future energy scenarios was conducted, emphasizing the regional impact of RESs integration on frequency stability. This study provided vital insights into the frequency response dynamics of the power system under different scenarios, highlighting areas of vulnerability and potential challenges arising from high levels of RESs penetration. Finally, building upon the findings of study four, a methodology for selecting the optimal sizing of utility-scale Battery Energy Storage System (BESS) is developed to enhance frequency response, particularly in areas identified as having weak stability. The findings underscore the importance of integrating BESS into future energy planning strategies to ensure the reliable operation of power systems amidst increasing penetration of RESs. These studies collectively contribute to a deeper understanding of the challenges and opportunities associated with RESs integration, offering valuable insights for future energy planning and system operation. This research framework not only offers a holistic view of RESs integration challenges but also facilitates the development of strategic solutions. The findings emphasize the critical role of accurate scenario planning, inertia estimation, regional analysis, and BESS optimization in achieving a resilient and stable power system amidst the growing influence of non-synchronous renewable energy sources.