Faults occurring in receiving-end alternate current(AC)grid of multi-infeed high-voltage direct current(HVDC)system may result in simultaneous commutation failures and short-time huge power shortage

which are great threats to the stability of power grid. Due to the strong support abilities in reactive power

synchronous condenser has received more and more attention in restraining commutation failures of multi-infeed DC systems and speeding up the transient recovery process after faults. From the angle of interplay between multi-infeed DC systems

the superiority of synchronous condenser in restraining commutation failures is analyzed

and then the best dynamic reactive power compensation node level are determined by combining with concepts of multi-infeed interaction factor(MIIF)

multi-infeed effective short circuit ratio(MESCR)and relative-transient-voltage-drop-area index(RTVDAI). Finally

a reliable and applicable method for the site selection of synchronous condenser responding to commutation failures in multi-infeed HVDC system is proposed

and the simulation is carried out on the basis of typical operation mode of East China power grid.