1011 / 2019-05-13 09:50:10

Analysis of Differential Protection on AC Line after VSC-HVDC Project Accessed

VSC-HVDC; fault ride-through; Differential protection; starting element

VSC-HVDC can improve the stability of AC grid, but the electronic equipment also changes the AC fault characteristics, so it is necessary to re-verify the AC line protection connected with DC system. Based on the different operation modes of VSC-HVDC, the fault characteristics on DC side are analyzed: The magnitude of positive and negative sequence fault current is greatly influenced by DC control strategy and the negative sequence fault current is completely suppressed, but the zero sequence fault current characteristics are not affected. Aiming at the fault characteristics, an optimization strategy of starting elements is proposed, which is based on AC strong fault side commanding VSC-HVDC weak fault side and voltage reduction criterion. Meanwhile, the influence range of VSC-HVDC access on fault characteristics of AC lines is given. Finally, a simulation model is built in PASCAD/EMTDC software and the effectiveness of the proposed optimization strategy is verified.