Research on protection adaptability and optimization scheme of VSC/LCC DC parallel hybrid system.

With the continuous development of high-voltage direct current (HVDC) technology and the relative concentration of power load and power, the HVDC parallel hybrid system will inevitably appear again. Because conventional DC transmission (LCC HVDC) and flexible DC transmission (VSC HVDC) in existing hybrid multi-infeed HVDC systems operate independently and are not coordinated with each other, and there is a gap in the research on the protection coordination relationship between VSC/LCC parallel hybrid systems and their near-area AC systems, it is necessary to study them systematically. This paper studies the protection coordination relationship between the VSC/LCC DC parallel hybrid system and its near area AC system, simulates and analyzes the typical faults of the hybrid multi-feed DC system, and puts forward a protection optimization scheme suitable for the VSC/LCC DC parallel hybrid system, which improves the safe and stable operation ability of the power grid, eliminates the hidden dangers of subsequent operation and maintenance, and provides a reference basis for further research. [ABSTRACT FROM AUTHOR]