Control strategy of shunt active power filter based on modular multilevel converter

The paper presents a new control strategy of modular multilevel converter(MMC) for shunt active power filter application. Compared with the H bridge cascaded topology, MMC has common DC bus, which makes it more flexible and adaptive. In order to eliminate harmonic, this paper introduces the repetitive controller into the inner current loop decoupling control in the rotating coordinate system. MMC sub-module capacitor voltage classification balancing control strategy is proposed in this paper, including the phase to phase voltage balance control strategy and independent capacitor voltage balancing control, to reduce module capacitor voltage fluctuation and maintain DC voltage. The proportional resonant(PR) controller, and the negative sequence double frequency coordinate transformation and decoupling control is implemented to suppress the circulation. The effectiveness and feasibility of the proposed control strategy are verified by the simulation performed based on PACAD.