Abstract: The VSC-HVDC protection method based on double-terminal information has the advantages of no setting threshold, strong resistance to transition resistance, full length of protection line, and high reliability. It can make up for the defects of single-terminal information protection. In order to realize the full range of fault detection for DC grid lines and realize the coordination between backup protection and main protection, a dual-terminal protection method based on fault component instantaneous power phase plane was proposed. Firstly, a multi-terminal flexible DC grid model was established, the short-circuit fault current and voltage were deduced by loop analysis method, and the instantaneous power of fault component was calculated. Then, the sum and difference characteristics of the instantaneous power of the positive and negative fault components under different fault types were analyzed, and the phase plane was constructed by the power difference and power sum, respectively, to realize fault area identification and fault pole selection. At the same time, by introducing low voltage criterion, the instantaneous power of fault component was recalculated to eliminate the problem of protection dead zone at the line outlet. The protection method has good selectivity, can protect the whole length of the line, and has good resistance to transition resistance.