Impact of Synchronous Compensators on the Robustness in Short-Circuit Conditions of Transmission Systems with High Share of RES

Transmission systems are nowadays characterized by a high share of power coming from Distributed Generation (DG) units exploiting Renewable Energy Sources (RES). Compared to traditional synchronous generators, converter-interfaced DG units are less suitable to regulate reactive power, lack rotating inertia, and are less robust towards the sustain of bus voltage during faults. Synchronous Compensators (SyCs) have been consolidated equipment, primarily used to regulate voltage and to add rotating inertia, but are currently rediscovered due to the differentiated impacts they can bring in networks with a high share of RES. This paper analyzes a specific impact of SyCs in terms of the robustness of the network in short-circuit conditions, considering that SyCs are intrinsically prone to operate in low-voltage ride-through conditions. This paper focuses on a real case study that considers a RES-dominated portion of the Italian transmission system, investigating the utility of different SyC installations and configurations within a comparative framework, using robustness indices tailored for this purpose.