Compared with line commutated converter（LCC）

the main problem of flexible high voltage direct current（HVDC） system based on modular multilevel converter（MMC） is the DC fault clearance schemes.At present

academic and industrial circles have proposed a variety of flexible HVDC systems with DC fault clearance capability.In order to better understand the advantages and disadvantages of these flexible HVDC systems

it is necessary to analyze their DC fault clearance characteristics.For the four typical flexible HVDC systems with DC fault clearance capability

the paper analyzes and compares their DC fault ride-through performances.Firstly

this paper summarizes four typical DC fault clearance configurations including the DC circuit breaker（DCCB）

the hybrid MMC with full bridge submodules and half bridge submodules（FHMMC）

the LCC-MMC hybrid configuration with diode groups installed in the DC line close to the converters（LCC-D-MMC） and the hybrid topology with an LCC and an MMC in series-connection.Then

the basic structure

control mode and fault clearance schemes of the four configurations based flexible HVDC systems are discussed.Finally

a three-terminal simulation model is built to compare the DC fault clearance characteristics of the four flexible HVDC systems.The simulation result shows that the DCCB can isolate DC faults quickly and selectively

and the DCCB based flexible HVDC system performs the best DC fault clearance characteristics.Considering the cost efficiency and operation flexibility

the LCC-MMC hybrid topology has certain value of practic al applic ation in engineering.