Low-Frequency Harmonics Reduction for Differential Boost Inverter With Nonlinear Loads Based on Fractional-Order Impedance

A single-phase differential boost inverter is designed to facilitate both dc/dc and dc/ac conversions, offering a cost-efficient substitute for two-stage single-phase inverters. While existing control methods for differential boost inverters exhibit satisfactory performance under linear loads and grid-connected conditions, they fall short when dealing with nonlinear loads. The output voltage of the inverter becomes distorted and is characterized by a prominent presence of odd harmonics when powering nonlinear loads. Furthermore, the input current is plagued by substantial even-order harmonics, compromising the system's efficiency and stability. The differential boost inverter can be decoupled into a dc/dc boost converter (differential mode) and a dc/ac inverter (common mode). In this study, a control strategy based on fractional-order impedance (FOI) is introduced for the differential mode. This strategy significantly reduces the output impedance of the differential inverter, enabling precise regulation of the output voltage and minimizing total harmonic distortion. Moreover, the proposed FOI control method effectively suppresses low-frequency harmonic currents (LFHCs) in the common mode by elevating the dc port impedance to a relatively high value. In conclusion, the proposed approach enables the boost inverter to function efficiently with both linear and nonlinear loads while effectively mitigating LFHCs. Experimental results are presented to substantiate the efficacy of the proposed control method.