A Modified Single-Phase Quasi-Z-Source AC–AC Converter

Minh-Khai Nguyen, Student Member, IEEE, Young-Cheol Lim, Member, IEEE, and Yong-Jae Kim, Member, IEEE

IEEE TRANSACTIONS ON POWER ELECTRONICS, VOL. 27, NO. 1, JANUARY 2012

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Abstract—A modified single-phase quasi-Z-source ac–ac converter is proposed in this paper. The proposed converter has the main features in that the output voltage can be bucked or boosted and be both in-phase and out-of-phase with the input voltage. The input voltage and output voltage share the same ground, the size of a converter is reduced, and it operates in a continuous current mode. A safe-commutation strategy for the modified single-phase quasi-Z-source ac–ac converter is used instead of a snubber circuit. The operating principles and a steady-state analysis are presented. A laboratory prototype, tested using a resistive load, a passive load, and a nonlinear load, was constructed that used an input voltage of 70 Vrms/60 Hz in order to verify the performance of the modified single-phase quasi-Z-source ac–ac converter. The experimental results verified that the converter has a lower input current total harmonic distortion, a higher input power factor, and a higher efficiency in comparison to a conventional single-phase Z-source ac–acconverter. In addition, the experimental results show that the use of the safe-commutation strategy is a significant improvement, as it makes it possible to avoid voltage spikes on the switches.

Index Terms—Buck–boost capability, pulsewidth modulation (PWM), quasi-Z-source converter, reversing and maintaining phase angle, safe-commutation, single-phase ac–ac converter, total harmonic distortion (THD).