An isolated high-gain impedance source-based single-phase AC-AC converter with safe commutation and variable output frequency

Conventional AC-AC converters have some critical disadvantages, such as inappropriate input and output power quality features, employing snubber circuits to suppress the voltage stress on high-frequency switches without a safe commutation method that increases the converter size and cost, confined voltage gain, and using huge passive components. This paper proposes an isolated high-gain single-phase AC-AC converter with variable output frequency, extended voltage gain, and a safe commutation strategy. Ten semiconductors are only employed for the proposed topology that only two switches and two diodes are operated with high-frequency PWM signals. This new topology has noteworthy specifications like continuous input and output current, voltage isolation, extended inverting and non-inverting buck-boost modes, and frequency regulation. The high voltage gain has been achieved with small values for passive components in the impedance source section, reducing the volume and cost of the converter. The impedance source-based section of the converter comprises one input inductor, two coupled inductors, and two capacitors in each converter leg. A safe commutation strategy has been designed and applied to the converter to mitigate the voltage and current stresses without extra snubber circuits. The number of semiconductors that simultaneously conduct in each state of the converter has been reduced. So, the conduction loss of the converter diminished. The achieved efficiency equals 95.5% and 93.5% in step-down and step-up modes, respectively, validated by an accurate power loss model and experimental analysis. An experimental prototype has been designed to confirm the performance of the suggested converter. Results confirm the theory and operation of the proposed converter.