First-Fault Detection in DC Distribution With IT Grounding Based on Sliding Discrete Fourier-Transform

Since dc distribution minimizes the number of power conversion stages, it lowers the overall cost, power losses, and weight of a power system. Critical systems use IT grounding because it is tolerant to the first-fault. Hence, this is an attractive option for hybrid electric aircraft (HEA), which combines gas engines with electric motors driven by power electronic converters. This letter proposes an accurate implementation for the procedure of first-fault detection with IT grounding. The ac component injection along with the sliding discrete Fourier transform (SDFT) is used to estimate the fault impedance. The procedure is very accurate due to the heavy filtering of the implicit moving average filter. Further computation savings are obtained by using the double look-up tables, and the Goertzel algorithm for the SDFT. Results are validated by simulations and experiments.