Modelagem e desempenho de recursos baseados em inversores seguidores de rede diante de curtos-circuitos na linha de interconexão

Abstract

This work evaluates the influence of different phase-locked loop (PLL) structures on the response of grid-following inverter-based resources (IBRs) under faults on the interconnection line, considering the voltage support requirements established by the Brazilian Transmission System Operator (TSO). A representative 100 MVA wind power plant was modeled in four configurations: 50 units of 2 MVA, 20 of 5 MVA, 5 of 20 MVA, and an equivalent aggregated model. Three PLL topologies were analyzed — Synchronous Reference Frame (SRF), Quadrature Signal Generator with Second-Order Generalized Integrator (QSG-SOGI), and Multiple SRF (MSRF) — under three-phase, two-phase, and single-phase grounded faults applied at the midpoint of the interconnection line, with resistances defined according to technical standards. The results show that PLL performance directly affects the IBR response to faults, with distinct behaviors depending on the fault type, due to the nonlinear nature of the controllers and the presence of harmonics and waveform distortions. The SRF-PLL showed greater sensitivity to these distortions, resulting in pronounced oscillations in the estimated voltage, abrupt variations in reactive power injection, and higher harmonic content in the injected currents, especially during two-phase faults. In contrast, QSG-SOGI and MSRF PLLs demonstrated greater robustness, providing more stable estimates and more reliable control system behavior. The short-time window analysis — particularly within the first 20 ms after the fault — revealed that estimation errors in the SRF-PLL can compromise the performance of protection functions, highlighting the importance of knowing the PLL topology used. Simulations also indicated that equivalent IBR models with the same nominal power present similar transient responses when using the same PLL structure, regardless of the number or size of the units. This confirms the effectiveness of using aggregated models or units with higher ratings as a strategy to reduce computational burden without compromising the accuracy of dynamic simulations during fault transients. Based on this conclusion, new fault studies were carried out, varying the fault location and grounding resistance. The three-phase fault was found to be the most critical, with more severe effects when it occurred closer to the local terminal. The two-phase and single-phase faults exhibited a moderate increase in current as the fault moved closer to the terminal, and the single-phase fault showed more pronounced oscillatory behavior. It is concluded that the appropriate selection of the PLL topology, together with representative modeling of IBRs, is essential to ensure compliance with grid codes, protection reliability, and the operational stability of systems with high renewable penetration.