A DC Line Fault Isolation and Reclosing Strategy Based on DC Circuit Breakers

Abstract

The invention discloses a DC line fault isolation and reclosing strategy in a flexible direct current transmission system with a direct current circuit breaker as the main and a converter as the auxiliary. Its characteristics are: after a DC line fault, the blocking signal of the converter is isolated, the fault is disconnected by tripping the DC circuit breaker, and after a preset delay, the DC circuit breaker is reclosed to restore the DC system. If the reclosing of the DC circuit breaker is unsuccessful, the converter will be blocked immediately. The advantage of this strategy is that after a fault, the DC circuit breaker cuts off the fault current quickly without immediately blocking the converter, and only blocks the converter after the reclosing of the DC circuit breaker fails and is judged to be a permanent fault. Since most DC overhead line faults are instantaneous faults, the DC system can achieve rapid recovery after the fault and reduce the loss of power transmission, while the impact of the AC system due to the blockage of the converter and the possibility of successive blockage of the converter It is also greatly reduced, and the stability of the AC-DC system is enhanced.

Description

technical field [0001] The invention relates to a strategy for a DC line fault isolation and reclosing recovery system in a flexible direct current transmission system, which is based on a direct current circuit breaker and supplemented by a converter, and belongs to the field of flexible direct current transmission. Background technique [0002] The flexible DC transmission technology based on voltage source converter is the main direction of HVDC development because of its unique advantages in solving the problems of grid connection and consumption of new energy. However, the technologies related to flexible DC transmission are still relatively weak, one of which is the rapid removal of DC line faults. Due to the rapid development of faults in the DC system itself, the DC current has no zero-crossing point, so the duration of the arc at the DC fault point is longer than that of the AC arc with the same initial amplitude; It can still form a freewheeling path, so it is ver...

AI Technical Summary

Problems solved by technology

This will impact the AC system at the sending end, and the connected converter stations may be blocked one after another. It may also cause a large load adjustment of the AC system at the receiving end, which will increase the impact range of the DC line fault and bring great impact to system safety. risk, the recovery time of the DC system becomes longer, and the reliability of power transmission of the system decreases

And in fact, more than 90% of the instantaneous faults of the DC line can resume normal operation through the reclosing and restarting process similar to the AC system after the fault, and there is no need to continuously block the DC system

Images