Mechanism analysis of DC bias increasing risk of commutation failure

Abstract

The relation among DC bias, zero-crossing shifting resulting from voltage distortion and commutation failure is analyzed in this paper. It is pointed out that magnetizing current of converter transformer distorts when DC biasing, which not only may cause distortion of AC bus voltage, but increase risk of commutation failure. Based on PSCAD / EMTDC simulation software, China Southern Power Grid AC-DC Parallel Transmission System is established. By means of this model, the above hypothesis is verified with simulation tests. The correctness of theoretical analysis is proved with simulation results.