A LCC and MMC hybrid HVDC topology with DC line fault clearance capability

•A LCC and MMC hybrid HVDC topology suitable for bulk power transmission is proposed.•The start-up process of the topology is implemented in two stages.•The LCC blocks itself to ride through dc faults.•High power diodes are installed in the overhead line near MMCs to clear dc faults.•A hybrid three terminal HVDC system is modeled in PSCAD/EMTDC.

This paper proposes a LCC and MMC hybrid HVDC topology with dc line fault clearance capability suitable for bulk power transmission, in which the rectifier adopts a line commutated converter (LCC) and the inverters adopt two modular multilevel converters (MMCs). Resiliency to dc line faults can be achieved by alpha-retard of the LCC and the high power diodes installed in the overhead line close to the inverters. The start-up process is implemented in two stages. A hybrid HVDC system is modeled in PSCAD/EMTDC to demonstrate the effectiveness of the control system and the start-up scheme. Moreover, simulation results of a dc line fault confirm the feasibility that the fault current paths can be blocked by alpha-retard of the LCC and the installed high power diodes, and the whole system is able to restart after clearance of the transient dc line fault.