This paper investigates a hybrid multi-terminal Ultra-High Voltage Direct Current (UHVDC) transmission system, the rectifier adopts LCC and two inverters adopt hybrid MMC. Considering the lack of practical experience in such hybrid UHVDC system, many technical problems remain to be solved. This paper mainly studies the AC fault and DC fault ride-through strategy, which are two crucial threats to the safe operation of hybrid multi-terminal UHVDC system. According to the particularity of hybrid multi-terminal UHVDC, a fault ride-though control strategy is proposed. Simulation and real-time experiment results have demonstrated the feasibility and validity of the proposed strategy. The study results can provide an indispensable technical support for the application of LCC-MMC hybrid multi-terminal UHVDC project.

hybrid multi-terminal UHVDC system, hybrid MMC, fault ride-though strategy.