The hybrid cascaded HVDC system employs a line commutated converter (LCC) as the rectifier and an LCC in series with multiple paralleled modular multilevel converters (MMCs) as the inverter. MMC arms are susceptible to overcurrent following a severe AC fault at the receiving end

however

its fundamental mechanism has not been totally revealed. Therefore

this article explores the overcurrent characteristics on MMC arms

in terms of both the DC and AC components. Apart from the DC overcurrent component induced by the commutation failure (CF) of the inverter LCC

the AC overcurrent component is also significant. It dramatically depends on the coupling effects among the AC systems of the inverter side. Further

corresponding suppression strategies are proposed

which are applicable to different receiving-end AC fault scenarios. Eventually

the time-domain simulation results from PSCAD/EMTDC validate the effectiveness of the proposed overcurrent suppression control. It is also demonstrated that the presented methods can not only suppress overcurrent for MMC arms

but also reduce the imbalanced power between two sides

as well as improve the dynamic performances of the entire system.