一种具有固有换流能力且极性切换开关数量减少的改进型隔离Z源AC-AC变换器

ABSTRACT In this paper, a modified isolated Z‐source AC–AC converter with inherent commutation and reduced polarity changer switches is proposed. This converter enables flexible output voltage adjustment, determined by two degrees of freedom — namely, the high‐frequency transformer turns ratio ( n ) and the duty cycle ( D ). Its circuit structure comprises four unidirectional switches — two high‐frequency switches responsible for adjusting the output voltage amplitude and two low‐frequency polarity changer switches to provide output states in inverting and non‐inverting configurations relative to the input. One of the advantages of the proposed converter is its ability to resolve the commutation challenge without the need for snubber circuits, dedicated safe commutation techniques with intentional dead‐times implementation. In addition, it provides inherent commutation advantages without requiring the circuit to be separated into positive and negative switching units or incorporating series diodes at the input side. As a result, the converter maintains a simplified switching pattern and control while reducing the total number of circuit components. Additionally, all magnetic components remain active throughout each half‐cycle. The converter also maintains a continuous input current waveform and allows step‐changes in output frequency. Moreover, since only one high‐frequency switch operates per half‐cycle, switching losses are minimised, leading to improved overall efficiency compared to conventional converters. In terms of switch voltage and current stress, switching device power and power density, the proposed converter is cost‐effective and lightweight. After explaining the operating principle, a laboratory prototype with 110 Vrms is developed and evaluated under three frequencies — 25, 50 and 100 Hz — to validate the theoretical relationships.