Um método baseado na transformada de Stockwell para detecção de ilhamento em sistemas fotovoltaicos conectados à rede em baixa tensão.

Abstract

A method for islanding detection in photovoltaic systems connected to the low power grid is proposed. The method applies the Stockwell transform to extract time-frequency characteristics of the amplitude of the component of negative sequence of voltage signals at the common coupling point. From simple detection logic, with the use of adaptive thresholds, the proposed method is capable of distinguish the island from other events. The performance of method was evaluated by circuit simulation, considering scenarios proposed by Standard ABNT NBR IEC 62116:2012. In addition, the method was evaluated in scenarios with the operation of multiple sources of distributed photovoltaic generation at the time of islanding. In islanding events proposed by Standard, it was obtained an accuracy of 100% with an average detection time of 64.9 ms in scenarios with, and without, noise. In multi-inverter cases, a hit rate of 65% was obtained. In the end, the method presented an accuracy of 94, 40% of the data base.