Fractional-Order Virtual Impedance-Based Low-Frequency Current Ripple Mitigation for a Differential Boost Inverter

Differential boost inverter (DBI), which consists of two identical dc–dc boost converters, has been widely used in dc–ac conversion systems for low-voltage dc supplies such as fuel cells and batteries. However, a serious concern is the presence of significant low-frequency current ripple (LFCR) in the source current, which leads to system instability, reduced system efficiency, and a shortened lifetime of the new energy source. The DBI can be operated in dual mode, offering both differential mode (DM) and common mode (CM) functionality. Hence, the DBI is decoupled as a dc–dc converter and an inverter. The ac output voltage is well regulated under DM. Under CM, a control strategy based on fractional-order virtual impedance (FOVI) is proposed to reduce LFCR in this article. Where a fractional-order bandpass filter (FOBPF) is used for better dynamic performance, and a fractional-order notch filter (FONF) is introduced to further reduce LFCR and improve the system stability. Further, damping resistors are inserted to solve the resonance issue of DBI. The detailed design process of key parameters is given, and the performance of fractional-order filters is also deeply discussed. Finally, a 250 W prototype is constructed and tested to validate the effectiveness of the proposed FOVI-based control method.