A Pilot Differential Protection Scheme Based on Dominant Frequency Band for the Outgoing Lines of Inverter-Interfaced Renewable Energy Generator Station

Abstract

The reliability of conventional Pilot Differential Protection (PDP) may decrease when applied to outgoing lines that integrate Inverter-interfaced Renewable Energy Generator (IIREG) into the grid. Therefore, it is necessary to develop new principles of the PDP according to the fault characteristics of the IIREG station. This paper begins by analyzing the transient differential current characteristics under internal and external faults of outgoing lines. The theoretical analysis reveals notable differences in the Dominant Frequency Band (DFB) energy of the differential current between internal and external faults. Additionally, factors influencing the DFB of differential current energy, such as fault resistance and inner current loop control of inverters, are examined. Furthermore, Variational Mode Decomposition (VMD), optimized by the Northern Goshawk Optimization algorithm, was employed to extract modes from different frequency bands in the differential current. Finally, the Frequency-domain Energy (FDE) of the modes is computed using Fast Fourier Transform (FFT), and the DFB is obtained. A criterion for PDP based on the FDE of the DFB is presented. Simulation experiments confirm that the proposed scheme can operate correctly under various fault types and locations, demonstrating strong resilience to fault resistance and disturbances.

Keywords

• Inverter-interfaced renewable energy generator
• fault characteristics
• pilot differential protection
• dominant frequency band
• frequency-domain energy