Influence of Negative-Sequence Control under Converter-Interface-based Generation in Distance Protection Relays

The growing adoption of renewable energy sources (RES) poses new challenges for protection relays. Traditional protection schemes are designed based on the dynamic characteristics of synchronous machines (SMs) as generation sources, while the dynamic behavior of RES, particularly influenced by converter-interface technology, is not adequately taken into account. As a result, certain distance protection algorithms for transmission lines face difficulties due to the impact of converter-interface generation on the level of negative-sequence current. Then, the start signal fails to pick-up the impedance measurement due to the low level of negative-sequence current since the minimum operating current have not reached. Therefore, this paper suggests using Wavelet transform analysis to extract the impedance measurement sequence with minimal negative-sequence current contribution. To confirm the effectiveness of this selection method, an imbalance and a fault scenario are simulated in a grid configuration based on the IEEE nine-bus standard test system, utilizing only grid-forming power converters. The simulation is conducted in MATLAB/Simulink.