Synchronous Condensers and Grid-Forming Control for the Integration of Inverter-Based Resources in Weak Grids

Abstract

Power systems with a higher share of inverter-based resources (IBR) exhibit reduced system strength and inertia, which are otherwise provided by synchronous generators (SG). This is because IBRs do not have the rotational inertia of SGs, and they do not contribute to short-circuit fault currents as much as SGs do. The lack of strength and inertia increases the risk of instability during contingencies, e.g., short-circuit faults. This dissertation investigates and proposes methodologies to enhance the stability of IBRs by leveraging synchronous condensers (SC) and grid-forming control. First, it presents an optimization model to find the optimal location and size of SCs, aiming to minimize the total cost of SCs and maintain the strength (measured by short-circuit ratio [SCR]) above a desired value at the point of connection of all IBRs. Second, it develops a robust exciter controller for SCs to maintain terminal voltage stability under large disturbances in weak grids. Third, it proposes a method to identify the most effective subset of IBRs to operate in grid-forming mode, accounting for the dynamic interactions between SGs and IBRs, to improve voltage and frequency stability. These contributions collectively support the reliable and cost-effective integration of IBRs into future power systems.