Extra-high voltage flexible direct current power self-circulation system and use method thereof

The invention relates to an extra-high voltage flexible direct current power self-circulation system and a use method thereof. The system comprises a first valve group, a second valve group, a polar line, a valve group connecting line, a neutral line and a grounding electrode, the high-voltage end of the triangular winding of the first valve group is connected with an off-station power transmission line through a first isolating switch, a polar line and a second isolating switch in sequence; the low-voltage end of the first valve group triangular winding is connected with one end of a valve group connecting wire through a third isolating switch; the high-voltage end of the second valve group triangular winding is connected with the other end of the valve group connecting line through a fifth isolating switch, the low-voltage end of the second valve group triangular winding is connected with a grounding electrode through a sixth isolating switch, a neutral line and a seventh isolating switch in sequence, and t