Implementing and testing d − q WPT-based digital protection for micro-grid systems

This paper introduces an implementation procedure and performance testings of a wavelet packet transform (WPT)-based digital protection for micro-grid systems. This digital protection is structured for detecting and classifying faults based on the values of the WPT coefficients of the high frequency sub-bands present in the d − q-axis current components. The WPT coefficients are determined using the Daubechies db4 wavelet basis functions, which are found optimal for analyzing transient disturbances likely to occur in power systems and electric machines. The proposed digital protection is implemented for experimental performance testing on a test micro-grid system that is constructed as a laboratory scale of an actual micro-grid system located in Fermeuse, Newfoundland, Canada. Several transient disturbances occurring in different parts of the test micro-grid system are experimentally investigated. Performance results demonstrate significant capabilities of the d − q WPT-based digital protection for accurate and reliable detection and classification of fault conditions, along with fast response to classified faults.