Pole-to-pole short-circuit fault is the most serious DC fault

thus the research on the transient operation characteristics of the offshore wind power generation integration system with modular multilevel converter high voltage direct current（MMC-HVDC） in this scenario is of great significance to breaker configuration and control scheme design of the system. In this paper

firstly

the mechanism of the short-circuit current in converter station was analyzed when direct current circuit breaker（DCCB） was not activated

and a calculation method of the AC and DC short-circuit current on the wind farm side and grid side converter station was proposed. Secondly

the transient characteristics of the voltage and current on the AC and DC sides of the converter station under DCCB control were studied

and the impact of wind farm operation conditions and current-limiting reactance parameters on its transient characteristics were taken into consideration. Finally

the electromagnetic transient model of the whole system was built on the PSCAD/EMTDC simulation platform

and the transient characteristics of the voltage and current in the converter station with or without DCCB control under pole-to-pole short-circuit fault were analyzed by simulation. Research indicates that the proposed short-circuit current calculation method has good accuracy. In addition

the recovery rate of wind farm AC and DC voltage is positively correlated with its active power output after DCCB is activated. The research work provides a theoretical basis for the electrical design and circuit breaker selection of the system

and also lays the foundation for the control scheme during the recovery stage of the system.