A VSC-Based Isolated Matrix-Type AC/DC Converter Without Bidirectional Power Switches

In this article, a three-phase voltage-source converter (VSC)-based isolated matrix-type ac/dc converter is proposed for wind energy conversion system. The line-frequency transformer is replaced by the high-frequency transformer (HFT), and there is no need for the intermediate electrolytic capacitors used in conventional two-stage power conversion system. Moreover, the bidirectional switches used for conventional matrix converter are eliminated in the proposed topology. Consequently, the complicated four-step commutation scheme is avoided and the additional conduction loss caused by serial connection of power switches can be eliminated. The proposed isolated matrix-type ac/dc can be regarded as the dual VSC circuit, where two VSCs alternately work during each switching cycle. Hence, the voltage vectors-based space vector modulation can be employed and the control schemes for nonisolated VSCs can be used for the proposed converter. For safe operation, the commutation strategy is proposed for the leakage-inductor current of HFT. Both simulations and experiments are conducted to verify the performance of the proposed converter.