Dynamic Analysis of the August 15th, 2023 Partial Blackout in the Brazilian Interconnected Power System

August 15, 2023 exposed significant weaknesses in the modeling and dynamic performance of inverter-based resources (IBR). The event was triggered by the improper opening of a 500 kV transmission line which, although operating within established limits, resulted in a voltage collapse in the Northeast region. The sequence of cascading outages culminated in the loss of synchronism between subsystems and the interruption of more than 23 GW of load, severely affecting electricity supply nationwide.

The analysis conducted by the Independent System Operator (ISO) revealed that simulation models overestimated the dynamic reactive power support capability of wind and photovoltaic power plants. The discrepancy between simulated and actual responses was decisive in the severity of the event. Based on PMU records and digital fault recorders (DFR) data, it was possible to adjust the models and more accurately reproduce the observed dynamics.

In response, structural and operational actions were adopted, including the revision of technical requirements for IBR, reinforcement of validation and commissioning processes, reformulation of the integration process for these resources, requests for EMT models, and enhancement of system observability. This paper documents the observed phenomena, lessons learned, and measures implemented to strengthen the operational security of the BIPS under the new paradigm of high IBR penetration.