A high-frequency transformer-based buck-boost AC-AC converter with high efficiency and wide range conversion ratio for DVR application

This paper proposes an isolated single-phase impedance-source ac-ac converter with a wide voltage conversion ratio and a safe commutation strategy. The new topology has noteworthy features like continuous input current, galvanic isolation, and non-inverting and inverting buck-boost modes with a wide voltage coverage. Also, only one switch operates with high-frequency PWM signals, reducing the semiconductor switching loss. The galvanic isolation has been achieved by employing a high-frequency transformer (HFT), eliminating low-frequency transformers (LFT) from the topology. A safe commutation strategy has been designed and applied to the converter to mitigate the voltage and current spikes on power switches, which eliminates additional snubber circuits. A prototype has been designed to validate the suggested converter performance in stand-alone and DVR applications. The peak obtained efficiency equals 96.1% and 94.9% in inverting and non-inverting step-down and step-up modes, respectively, validated by an accurate power loss model and experimental results. Experimental results confirm the theory and operation of the proposed converter.