Ground fault protection for DC filter high-voltage capacitors utilizing two-dimensional current reconstruction

As a crucial electrical component in a high voltage direct current (HVDC) system, the DC filter effectively eliminates the specific harmonics generated by line-commutated converters. However, the conventional protection methods employed for DC filters have certain inherent limitations, including poor selectivity and low sensitivity. To address these issues, this study proposes an earth fault protection method for high-voltage capacitors of DC filters, based on two-dimensional current reconstruction. The reconstruction of currents on both the high-voltage and low-voltage sides was performed for various fault types that affect high-voltage capacitors. Subsequently, the distribution characteristics of the reconstructed currents were analyzed and utilized to establish a novel protection scheme for high-voltage capacitors. The effectiveness of the proposed protection scheme was validated using a ± 800 kV UHVDC system constructed in PSCAD/EMTDC. The simulations demonstrate that the proposed protection method exhibits high reliability and sensitivity, and it is resilient to fault resistance up to 200 Ω , fault location, measurement errors, and variations in the DC filter structure. Additionally, it enables accurate fault detection even at a remarkably low sampling rate of 2 kHz. • A ground fault protection for DC filter high-voltage capacitors utilizing two-dimensional current reconstruction is proposed. • The proposed protection method demonstrates high reliability and sensitivity. • The proposed protection scheme enables accurate fault detection even at a remarkably low sampling rate of 2 kHz.