The line commutated converter-modular multilevel converter(LCC-MMC)hybrid DC system has good application prospects for combining the technical and economic advantages of two kinds of converters. The capacitive filtering device installed on the passive network can smooth the AC voltage waveform

provide voltage support

etc. Firstly

a mathematical model of the modular multilevel converter(MMC)containing the capacitive filtering device is developed through theory deduction

and the decoupling control strategy of the MMC is proposed based on the dq theory. For the problem of power transmission interruption during AC fault at the sending end of line commutated converter(LCC)

the system fault response characteristic is analyzed by proceeding from the control mechanism of LCC and MMC. Then an additional control strategy for the sending-end AC fault ride-through is put forward. In order to verify the effectiveness of the control strategies

a LCC-MMC hybrid DC transmission model is established in PSCAD/EMTDC. The feasibility and effectiveness of the proposed control strategies are verified by the simulation of the voltage/ frequency variation at the receiving end and the AC fault at the sending end.