A new circulating current suppressing control strategy for modular multilevel converters

Abstract

The modular multi-level converter (MMC) is considered as the state of the art converter among multilevel topologies. The harmonic suppression of circulating current is the inherent problem needed to be solved. In this paper, a new control strategy is proposed. The strategy includes the double fundamental frequency, negative sequence rotating coordinate transformation and the four fundamental frequency, positive sequence rotating coordinate transformation, besides, the PIR controller is used to improve the harmonic characteristic. Through this control strategy, the second- and the fourth-order harmonics are suppressed, and the source of higher-order harmonics generation are prevented. Simulation results based on MATLAB verify the effectiveness of the proposed control strategy.