Control of HVDC transmission system based on MMC with three-level flying capacitor submodule

High voltage direct current (HVDC) transmission systems have proven to be a cost effective solution for very-long distance transmission requirement. Among the different HVDC technologies, the modular multilevel converter (MMC) based HVDC systems have become quite popular. It has the special features like transformer-less operation, completely modular design and a common DC-bus. Due to the above features, the MMC has become the most viable solution for the HVDC transmission applications. In this paper, a modulation and control strategy is proposed for the MMC-3L-FC based HVDC transmission system. The proposed control strategy manages the active and reactive power along with the total DC-line voltage, and also it will ensure the balancing of the submodule capacitors voltage.