After a short-circuit fault in a half-bridge MMC-HVDC DC line

it is difficult to balance the contradiction between DC limiting and bridge arm over-current only by exploiting the current limiting potential of the MMC. To address this problem

this paper proposes a hybrid fault current limiting (FCL) method to balance the DC current limiting and the bridge arm over-current by sequentially putting in control current limiting (CCL) with a reduced number of sub-modules and series adaptive series bridge arm damping module-based device current limiting (DCL) after a fault. The mechanism of CCL is analyzed theoretically

and it is noted that insulated gate bipolar translator (IGBT) blocking cannot be avoided

particularly when connected to a strong AC system

due to different FCL effects in the CCL under extreme fault conditions. From the constraints of bridge arm overcurrent

the parameter boundaries of the CCL are deduced

and the starting moments of the DCL are given. Adaptive series connection of different numbers of bridge arm damping modules according to the change of bridge arm current achieves a better current limiting effect at the minimum cost. The test results show that compared with other hybrid FCL methods

the proposed current limiting method can reduce the peak bridge arm current by up to 30.71%

with the peak current lower than the IGBT safety boundary.