An Isolated Resonant AC-Link Three-Phase AC-AC Converter Using a Single HF Transformer

An isolated three-phase ac-ac converter with a high frequency (HF) ac link, soft switching operation, high input power factor, and bidirectional power flow is introduced. The galvanic isolation is attained by a single HF transformer, which is substantially smaller than the line-frequency transformers. Moreover, the magnetizing inductance of this transformer and two small ac capacitors form the convertor's HF ac link; no bulky short-life electrolytic capacitor is used. The magnetizing inductance is the main component for transferring power, and the link capacitors provide partial resonance to achieve zero voltage switching for the power switches in all operating modes. The basic operation of the topology is composed of 16 modes and is described. The detailed analysis of the proposed topology is carried out to reveal further the converter's behavior in different operating conditions. The simulation and experimental results are also provided to demonstrate the effectiveness of the proposed power converter.