A Single-Phase Symmetric-Bipolar Buck-Boost AC-AC Converter With Continuous Input-Output Current

This article presents a novel single-phase, nonisolated buck-boost AC-AC converter featuring lower active and passive components compared with the existing designs. The proposed topology offers symmetric in-phase and antiphase buck-boost voltage operations, as well as a step-changed output voltage frequency, making it suitable for a broad range of applications, such as dynamic voltage restorers (DVR). The offered converter features only two magnetic elements, one on the input side and another on the output side, which ensure continuous input and output currents and lower total harmonic distortions (THD) in both input and output currents compared with the existing designs. The proposed AC-AC converter lacks coupled inductors, eliminating the need for RC snubbers on power switches. Additionally, it inherently achieves safe commutation by avoiding bidirectional AC switches and discarding dead- or overlap times from the commutation strategy. Comparative assessments indicate that the proposed topology performs better than its counterpart circuits in terms of switching device power (SDP) index, volumetric indexes of capacitors and magnetic components, efficiency, and input and output THD currents. The experimental results demonstrate an efficiency of 95.6% and a THD of less than 2.5%.