Supporting Capacity Expansion Planning in REMix by Detailed AC-Optimal Power Flow Experiments for Voltage Stability Modelling

Abstract

This thesis addresses the critical challenge of maintaining voltage stability in power systems with high renewable energy penetration during capacity expansion planning (CEP) in the Renewable Energy Mix (REMix) optimization framework. Given the intermittent nature of renewable energy sources and their impact on grid stability, this study proposes a comprehensive methodology that integrates voltage stability considerations, specifically the Voltage Collapse Proximity Indicator (VCPI), into the CEP process using the REMix energy system model. This work uses MATLAB as a supporting modelling software for running detailed AC optimal power flow. The research conducted in this thesis demonstrates the feasibility and effectiveness of incorporating VCPI to ensure voltage stability across the power network. The research employs a systematic model generation expansion planning approach using the IEEE RTS 24-bus system. Comparative analysis of observed scenarios with and without VCPI integration reveals that including additional voltage stability constraints leads to more reliable and cost-effective expansion planning, emphasizing the critical role of the voltage stability index in enhancing grid resilience and reducing power losses. Furthermore, this work extends the scope of typical REMix applications by introducing the concept of a voltage security-constrained optimal power flow algorithm, offering insights into optimizing power systems design and operation in the context of growing renewable energy integration. The particle swarm optimization (PSO) algorithm used to solve the optimal power flow (OPF) is part of the supporting tool. The findings highlight the potential for significant operational cost savings and improved system reliability through informed CEP decisions considering voltage stability. This thesis contributes to the body of knowledge by bridging the gap in existing REMix applications, offering a novel approach to ensuring voltage stability in renewable-rich power networks, thereby supporting the transition towards sustainable and stable electricity systems. The thesis concludes by suggesting future research directions, including integrating VCPI into linearized optimal power flow models in REMix for larger-scale applications and exploring alternative optimization solvers to enhance model compatibility and efficiency. This work underscores the importance of incorporating voltage stability considerations in CEP, paving the way for more sustainable and resilient power systems in the high renewable energy integration era.