A novel linear regression density peak clustering-based transmission line protection for line-commuted converter-voltage source converter hybrid high voltage direct current system

Line-commuted converter (LCC)–voltage source converter (VSC) hybrid high voltage direct current (HVDC) transmission system is an innovative technology, the existing LCC and VSC protection require setting, and it is difficult to be directly applied in the LCC–VSC hybrid HVDC, which is a serious problem in practical engineering. A novel linear regression density peak clustering (LRDPC) approach is introduced for transmission line protection. LRDPC employs Least Squares linear regression to compute the fault current slope, followed by density peak clustering for fault type identification. The proposed protection structure is straightforward and setting-less, eliminating the need for fault pole selection elements and classification thresholds. Validation on the Kun-Liu-Long LCC–VSC HVDC RTDS system demonstrates the method's effectiveness in identifying diverse faults under varying conditions, including fault types, locations, resistances, and signal-to-noise ratios. Notably, it remains robust against fault impedance (600 Ω) and noise interference (20 dB).