Low-frequency suppression strategy based on predictive control model for modular multilevel converters

Modular multilevel converters (MMCs) have attracted a great deal of research attention in medium-voltage motor drive applications. However, the excessive fundamental-frequency submodule (SM) capacitor voltage ripple at low speeds or during start-up poses a major technological challenge. This paper develops a new control strategy for SM capacitor voltage ripple suppression based on model predictive control (MPC). The system mathematical model with common-mode voltage (CMV) and the SM capacitor voltage ripple suppression models are established. Then, a cost function of the system is established, and the control system is designed. When compared to existing strategies, the modulation process, PI regulation process, and high frequency injection control are avoided due to the MPC strategy. The performance of the proposed approach is verified through MATLAB simulations and experiments on a MMC system.