When a DC fault occurs in a line commutated converter (LCC)-based HVDC system

the fault current is usually cleared by a phase-shift blocking strategy. During the phase-shifting blocking period

the rectifier-side LCC will operate in the inverter state and there is a risk of commutation failure

which affects the fast and reliable removal of fault current. The paper investigates the commutation failure mechanism and fault transient characteristics of LCC rectifier stations during phase-shifting. First

the commutation failure mechanism of the LCC rectifier station during this period is analyzed. Based on the analysis above

the influences of the phase shift angle on fault characteristics and the changes in fault current during phase switching are taken into account

and a method for analyzing fault characteristics during phase shifting in LCC rectifier stations is proposed. Finally

a hybrid DC transmission system model with an LCC converter on the rectifier side is constructed on the PSCAD/EMTDC simulation platform. Through simulation examples under different phase shift conditions and fault distances

the accuracy of the theoretical analysis and the precision of the fault characteristic analysis during phase shifting are verified.