Dual Harmonic Injection for Reducing the Submodule Capacitor Voltage Ripples of Hybrid MMC

Reducing the capacitor voltage ripples of half-bridge submodules (HBSM) and full-bridge (FBSM) in a hybrid modular multilevel converter (MMC) is expected to reduce capacitance, volume, costs. To address this issue, article proposes dual harmonic injection method which injects second circulating current third-order into conventional MMC control. First, mathematical model proposed control established analyzed. Then, general strategy determining amplitude phase angle each component suppress fluctuations fundamental- double-frequency instantaneous power. The can achieve optimal power fluctuation suppression under various operating conditions, also has advantage reducing difference between HB FB SMs. correctness effectiveness are verified simulations PSCAD/EMTDC.