High-power medium-voltage three-phase ac–dc buck–boost converter for wind energy conversion systems

•This paper proposes topologies A,B and C of acdc buck–boost converters for MV applications, with ‘A’ and ‘C’ have been identified as promising.•Topologies ‘A’ and ‘C’ facilitate scalability to higher and lower MV applications, with ‘C’ uses a novel parallel charging of inductors.•The theoretical principles that underpin the operation of the proposed topologies are established and verified using simulations and experiments. This paper proposes three topologies of single-stage three-phase ac–dc buck–boost converters suitable for medium-voltage and high-power wind energy conversion systems (WECS). The proposed converters draw sinusoidal input currents with nearly unity power factor from wind generators over wide range of ac voltages and frequencies. The proposed converters reduce the voltage and current stresses on the self-commutated switching device compared to existing solutions; thus, promising for new generation of relatively cheap WECSs. The proposed converters operate in Discontinuous Condition Mode (DCM), with their ac terminals connected to three-phase generator with open ended windings, or to ac supply using three single-phase transformers with isolated windings at converter side. The validity of the proposed converters and its detailed theoretical analysis and discussions are confirmed using PSCAD/EMTDC simulations, and further corroborated by experimentations, considering different operating conditions.