An Efficient Dual-Output Bipolar Buck-Boost AC-AC Converter With Flexible Operation Range

Three-phase flexible ac-link (FACL) converter configuration enables the production of three-phase ac voltages with decoupled magnitude and phase using single-phase ac–ac converters. However, traditional FACL converter require six discrete ac–ac converters. Building upon the recently introduced FACL configuration that utilizes only three dual-output converters, this article proposes a new and efficient single-input, dual-output bipolar ac–ac converter for applications in the new FACL topology. It can provide independent control of buck and boost voltage transfer ratios, and both outputs are completely independent of each other, capable of producing the same or opposite phase outputs with independent control of their magnitudes. Moreover, all devices experience significantly smaller (and identical) voltage stresses and current stresses. The proposed converter avoids the use of bidirectional ac switches, thus simplifying the commutation process of traditional ac–ac converters. The input and output currents are continuous, avoiding harmonic pollution in the input supply and saving additional filters. Furthermore, the proposed converter has reversible operation and can provide bidirectional power flow. An in-depth analysis of the proposed converter is provided based on the proposed switch modulation strategies for various operation scenarios. Detailed comparisons with existing counterpart converters prove its better circuit performance with smaller component stresses and ripples and improved input/output power quality. Finally, experimental results prove the feasibility of the proposed converter.