Optimization Strategies for the Mitigation of the Impact of Inverter-based Resources on Transmission and Distribution Networks

This Ph.D. Thesis investigates the integration of Inverter-based Resources (IBRs) into modern power systems, focusing on challenges related to frequency and voltage support in the context of high Renewable Energy Sources (RESs) penetration. Innovative methodologies are developed to optimize the operation of IBRs in transmission and distribution networks, with a particular emphasis on the Italian scenario, thanks to the activities carried out in partnership with the Italian transmission system operator, Terna, and the Italian National Agency for New Technologies, ENEA. At transmission level, novel algorithms are introduced to determine the optimal techno-economic mix of Synthetic Inertia (SI) providing resources, including Photovoltaic (PV) power plants, Wind Turbines (WT) and Battery Energy Storage Systems (BESSs), and of Synchronous Compensators (SCs) able to limit the Rate of Change of Frequency (RoCoF) of a transmission network within the limits prescribed by grid codes. Moreover, methodologies for the optimal allocation of inertia-providing resources among the market zones are provided. The procedures are validated through simulations in DIgSILENT PowerFactory and are widely applied over the whole 2030 Italian transmission network scenario. Analyses to evaluate the impact of IBRs and HVDC on system Primary Regulating Energy (PRE) are developed and applied to Sicilia and Sardegna market zones, that will represent critical areas in the 2030 Italian transmission network scenario. At distribution level, two Energy Management Systems (EMSs) are designed for polygenerative Microgrids (MGs) and MGs members of Renewable Energy Communities (RECs). The EMSs optimize active and reactive power flows, while minimizing energy costs and enhancing electric mobility integration, such as vehicle-to-grid and vehicle-to-building technologies. The impact of Distributed Energy Resources (DERs) on local voltage is assessed, along with the role of MGs in improving energy sharing within RECs. Two case studies are considered: a school complex MG and an industrial MG, member of a REC. The analysis shows the enhanced local energy sharing and the improved grid stability. The findings of this Ph.D. Thesis provide valuable insights for grid operators and policymakers in designing and operating future power systems with high penetration of IBRs, ensuring grid reliability while promoting the integration of DERs and RESs