Abstract: Traditional half-bridge-submodule-based modular multilevel converter (MMC) has a single AC port and lacks of DC polarity reversal ability with the structure. It cannot be connected to the LCC-HVDC (line commutated converter- high-voltage DC) directly. A novel MMC with dual AC ports is proposed in this paper by adding a middle arm cell with full-bridge submodules in each phase leg. Full-bridge submodules are adopted in the upper and lower arm cells to achieve the DC polarity reversal ability and free power transfer with LCC-HVDC. The proposed MMC can provide DC voltage polarity reversal by one AC port while maintaining the output of the other AC port. Detailed topology and working principles are introduced firstly. An output control strategy is designed based on the mathematical modeling. The circulating current suppression strategy is proposed based on the essential component analysis of the circulating current. A DC polarity reversal strategy is proposed, thus the DC voltage polarity reversal is realized by controlling one AC port and the output of the other AC port maintains unchanged. Simulation results validate the correctness of the proposed approach.