Expanding the CCM boundary of a current-fed switched inverter

摘要

Current-Fed Switched Inverter (CFSI) is widely used due to its higher gain and inherent shoot-through protection. To account for the pulsating power output of the single phase CFSI, the passive storage elements (inductor and capacitor) of its boost stage contains a second harmonic component. As a result, the peak-to-peak ripple in the inductor current increases. This increased ripple forces the CFSI to have Discontinuous Conduction Mode (DCM) during light load condition. This distorts the AC output voltage of the CFSI. To avoid DCM, the peak-to-peak ripple in inductor current must be reduced. This paper presents a control based approach, in which second harmonic component of the inductor current is suppressed. This expands the boundary range of Continuous Conduction Mode (CCM) in a CFSI and improves its light load range. The proposed control scheme is validated for CFSI using a 500 W prototype, and it shows that the peak to peak ripple in the inductor current is reduced from 6.04 A to 2.76 A for a resistive load. This results the CCM boundary is extended by 54.3 % for a DC input of 35 V and AC output of 61 V (RMS).