A novel three-phase switched multi-winding power electronic transformer

In this paper, a novel topology for a three-phase high-frequency power electronic transformer is proposed. In each phase, there are two mutually-coupled primary windings and one secondary winding. On the high-voltage side of the transformer, only two controlled switches are required to create a three-phase high frequency ac link. This is a significant reduction in the required number of controlled high voltage semiconductor switches as compared to the present state-of-the-art, leading to simplicity, reliability and reduced system cost. A 3×3 matrix converter is used on the low-voltage side of the transformer. The matrix converter is modulated with the proposed space vector PWM to achieve the following features simultaneously: 1) grid power factor control, 2) load voltage of adjustable amplitude and frequency and 3) elimination of common-mode voltage at the load terminals. The simulation results of a 2 MVA system demonstrating the abovementioned capabilities of the proposed topology are presented.