The Performance of a Digital Interconnection Protection for Grid-Connected WECSs

Abstract

This paper develops and experimentally tests the performance of a digital interconnection protection for grid-connected wind energy conversion systems (WECSs). The developed protection is constructed by two frequency frames to process voltages and currents measured at the point-of-common-coupling (PCC). The first frequency frame is set to process the $d-q$ -axis components of the instantaneous $3\phi$ apparent powers ( $s_{d}$ and $s_{q}$ ) determined at PCC. This processing of $s_{d}$ and $s_{q}$ aims to extract their high-frequency subband contents in order to detect the islanding condition. The second frequency frame is set to extract the high-frequency contents (magnitudes and phases) present in the $3\phi$ currents flowing through PCC. These high-frequency contents provide signature information for detecting faults occurring on either side of PCC. The multiframe digital interconnection protection is implemented for performance evaluation on two different WECSs operated in grid connection. Performance results show accurate and reliable detection and identification of the islanding condition and faults occurring on either side of PCC. In addition, performance results show that the multiframe digital interconnection protection has minor sensitivity to the type, structure, ratings, and levels of power delivery to the host grid.