Low-Frequency Input Current Ripple Reduction Based on Load Current Feedforward in a Two-Stage Single-Phase Inverter

A large amount of ripple at twice the output frequency will emerge in the input current due to the pulsating output power in a two-stage single-phase inverter. To reduce the low-frequency input current ripple, a control strategy is presented in this paper based on the front-end dc-dc converter load current feedforward. It intends to control the dc bus voltage to swing properly at twice the output frequency, making the dc bus capacitor supply nearly all the pulsating power. The implementation method is illustrated, and the operation performance analysis as well as the key parameter design principle is provided. Introducing the proposed feedforward path is able to significantly suppress the input current ripple with little impacts on the original system stability, steady-state tracking accuracy, and dynamic response. Finally, experimental results performed on a buck-type stand-alone two-stage single-phase inverter prototype verify the validity of proposed method and the correctness of analysis.