Feed-Forward Control Strategy for Cascade H-bridge High-Voltage Inverter based on Active Front-end Rectifier

In an active front-end rectifier based on cascaded H-bridge high-voltage inverter, the DC link voltage of the submodule often fluctuates due to load uncertainties, and the instantaneous output power pulsates at twice the frequency, which reduces system stability. In this work, the mathematical model of a back-to-back converter, comprised by a cascaded H-bridge (CHB) inverter and an active front-end (AFE) rectifier, is built. Based on the current reference of rectifier, the instantaneous active power balancing between AFE rectifier and CHB converter is seen as control objective. Then, an instantaneous active power feed-forward control is employed to mitigate the fluctuation of DC link voltage. Additionally, an extended state observer (ESO)-based load current estimation method is proposed to accurately estimate output current. Finally, the feasibility of proposed control strategy is verified by simulations.