A highly efficient isolated single‐phase variable frequency AC–AC converter with flexible buck‐boost factor, inherent safe commutation, and continuous current

Abstract

This paper proposes an isolated single-phase flexible buck-boost ac–ac converter with an adjustable output frequency and optimized semiconductors count. One power switch only operates with a high switching frequency in each half-cycle of the input voltage, and others operate with a low switching frequency equal to the output frequency. Thanks to this feature, the converter provides high efficiency, 95.5% in step-down mode and 91.5% in step-up mode. The galvanic isolation between the input and output sides is also regarded for the proposed topology by employing two coupled inductors. The converter has an inherent safe commutation by utilizing a simple modulation strategy. Thus, additional snubber circuits and complex commutation strategies are no longer required. The proposed converter does not require any input filter as it operates with the continuous input current. This paper presents the operating principle of the proposed topology in detail. For this purpose, a 200-W experimental prototype has been designed to examine the performance of the suggested converter for different operating modes and output frequencies. Results confirm the theory and operation of the proposed topology.