Travelling wave-based fault detection and location in a real low-voltage DC microgrid

Abstract

This paper discusses a device-level implementation of a travelling wave (TW) protection device (PD) designed for a real low-voltage DC microgrid. The TWPD fault detection and location algorithm is executed on a commercial digital signal processor (DSP) board, involving signal sampling at 1 MHz via the DSP board's analog-to-digital converter (ADC). The analogue input card measures positive pole, negative pole and pole-to-pole voltages at the TWPD location. Upon a successful fault detection using a second-order high-pass filter, the voltage data is normalised and multi-resolution analysis (MRA) is performed on a 128-sample buffer around the TW arrival time. MRA employs the discrete wavelet transform (DWT) to capture high-frequency voltage patterns, and then the Parseval's energy theorem quantifies these TW characteristics by computing the energy of reconstructed wavelet coefficients. These energy values per decomposed frequency band are the basis for training a random forest classifier that predicts fault location and type. The TWPD is fully implemented and connected to a real DC microgrid in Albuquerque, NM, USA, for validation, and results are shown for field tests verifying the performance under faults.