This article presents a control strategy for a modular multilevel converter (MMC) to prevent commutation failure of a line-commutated converter (LCC), forming a three-terminal hybrid HVDC transmission system, where one LCC sending end is connected to the large generation and two receiving ends (LCC inverter and MMC) are located near the load center. This configuration, one of the potential options, has been proposed to strengthen Korea electric power transmission system through the optimized use of existing assets…