During the initial operation of Xinsong-Dongfang ultra-high voltage direct current(UHVDC)project

the delayed operation of sending generators results in insufficient capacity of island short-circuit and risks such as overvoltage and low-order resonance. In order to ensure the safety of devices when the UHVDC project passively jumps into island operation

this paper proposes a blocking strategy for Xinsong-Dongfang UHVDC project jumped into island operation

i. e.

add the automatic blocking function for island operation in the DC station control system

and adopt a low-power anti-false criterion of AC tie-line to effectively prevent the strategy from malfunctioning in the grid-connected mode. A strategy as follows can effectively reduce the overvoltage of the island UHVDC blocking and ensure the safety of related equipment: firstly

cut off all the filters; secondly

delay the UHVDC blocking; thirdly

the stability control system cut all generators in island operation mode. Field application shows that all AC filters can be cut within 300 ms after the UHVDC project jumps into island operation

and the UHVDC blocking is initiated after a delay time of 30 ms

then the stability control system delays after bipolar blocking

while all the island generators are accurately cut. The blocking logic and the stability control strategy are correct

and the overvoltage and frequency meet the requirement of the specification.