Control Approach to Enhance the Performance of a Current-Fed Switched Inverter

Current-fed switched inverter (CFSI), a derivative of Z-source inverter, has the advantages of lower component count, single-stage conversion, high gain, and inherent shootthrough protection. But due to the limitation of modulation index, CFSI is forced to operate at higher dc-link voltage. As a result, voltage stress across the switches and capacitors increases. To mitigate this problem, a new pulsewidth modulation (PWM) technique is proposed. With the proposed scheme, CFSI can be operated at a lower dc-link voltage by increasing the modulation index. But operating at lower dc-link voltage increases peakto-peak ripple in the inductor current and leads to condition of early discontinuous conduction mode. Therefore, this paper also implemented a variable duty cycle (VDC) scheme, which reduces the peak-to-peak ripple in the input inductor current and increases the continuous conduction mode (CCM) operating range of CFSI. The proposed PWM scheme along with VDC scheme is validated for CFSI, which helps to: 1) reduce the voltage stress form 280 to 180 V; 2) reduce the input current ripple from 53.33% to 15.15%; 3) enlarge CCM range from 56% to 82%; and 4) improve the efficiency by 3.5%.