A High-Frequency Isolated Four-Switch Single-Phase Quasi-Z-Source AC-AC Converter With Inherent Commutation and Step-Changed Frequency Operation

In this article, a high-frequency isolated single-phase quasi-Z-source ac-ac converter is proposed. This converter can generate a broad range of output voltage while also allowing the output frequency to be changed. The configuration is divided into two similar subcircuits in a way that only one unidirectional switch exists in each subcircuit, and complementary switches are removed. Therefore, the proposed converter has inherent commutation without the necessity to apply any delays or, safe commutation strategies. Two switches on the output side are responsible for changing the frequency. So, voltage regulation and changeable frequency are obtained with only four unidirectional switches and a simple switching strategy. Electrical isolation is also acquired via employing a compact-sized high-frequency transformer. All the aforementioned features result in the proposed converter's small size, compact structure, low cost, high reliability, and high power density. A comprehensive analysis of the circuit operation principles is discussed. Then, a 100 V rms /50 Hz laboratory prototype is implemented to indicate the accuracy of theoretical results.