A Single-Stage Matrix-Based Isolated Three-Phase AC-DC Converter With Novel Current Commutation

An isolated single-stage three-phase ac-dc converter is proposed for aircraft system in this paper. The proposed converter uses the matrix (3x1) topology to directly convert threephase line frequency ac voltages into high-frequency ac voltage, and therefore facilitates the use of high-frequency transformer for galvanic isolation leading to more compact and lighter weight of the power electronic converter. A space vector modulationbased switching scheme is proposed and digitally implemented for superior input power quality and improved power conversion efficiency. A current doubler rectifier (CDR) circuit is used at the output side, which essentially reduces the leakage inductance of the high-frequency transformer by decreasing the primary to secondary turns ratio. Moreover, an active softswitched lossless snubber circuit is proposed to overcome the high voltage spikes produced due to the leakage inductance of the high-frequency transformer. A novel approach of adding a series capacitor in the primary winding of the high-frequency transformer for the soft and uninterrupted commutation of the high-frequency ac current is presented. The modes of operation of the proposed converter with the CDR circuit are analyzed in detail. Subsequently, the design equations for the proposed converter are derived. Simulation and experimental results are presented for a 500-W prototype converter suitable for aircraft systems.