A convenient form to connect single-phase cells to multi-pulse transformers in unbalanced systems

This paper shows that the proper connection of single-phase-input/single-phase-output power cells to a multi-pulse transformer to form a 7-levels voltage waveform has an important impact on the overall performance of the topology. Particularly, if the topology is used in systems that are connected to an unbalanced AC network and/or feeds an unbalanced load. The topology in combination with the proposed arrange of the power cells and the multi-pulse transformer becomes best suitable for applications where the quality of the voltage and current waveforms are of main concern. In fact, the topology minimizes the problems produced by unbalanced loads even though the single-phase nature of both the input and output of the power cells. Moreover, the proposed arrange acts as a buffer for the AC mains voltage unbalances as they do not have any effect on the load voltages. The paper includes the comparison between a reported alternative to arrange the cells with the proposed approach. Particularly, the voltages and currents are shown for both an unbalanced AC mains and an unbalanced load. Unbalance and distortion factors are included to quantify the advantages of the proposed arrange.