Active Power Decoupling for Reduced-Switch Current-Fed Switched Inverter with Enhanced Gain

The recently developed Reduced-Switch Current-Fed Switched Inverter (RSCFSI) is attributed with key features such as continuous input current, greater ac output voltage, simultaneous operation with ac and dc loads, shoot-through immunity, and so on. The low-frequency (LF) oscillation study of RSCFSI reveals that they are also plagued by both fundamental and second-harmonic oscillations. To address this LF oscillation problem, an active power decoupling (APD) approach for RSCFSI is found in the literature, in which an ancillary capacitor is added to the RSCFSI and the ac output filter inductor is split into two without increasing the total inductance. As a result, the dc-link capacitor needed is substantially lowered without the use of any additional switches. However, the dc-ac voltage gain is remarkably reduced compared to that of RSCFSI. As a solution, this paper provides an alternative APD approach, in which the dc-ac voltage gain range is enhanced, and the voltage stresses on switches and passive components are diminished. A closed-loop control scheme is also elucidated, which assimilates output voltage regulation as well as LF oscillation mitigation. The paper also exhibits an experimental verification of the benefits of the proposed APD approach.