Theory and application of distribution electronic power transformer

Three-phase and 4-wire Distribution Electronic Power Transformer's (DEPT's) operation principle is analyzed in this paper. Based on the analysis, the control scheme is established. In this control scheme, the input stage is controlled as a three-phase balanced current source and makes the primary current sinusoidal and power factor easily adjusted. While the output stage is controlled as a three-phase balanced voltage source and keep the load voltage sinusoidal and nominal. In order to meet the requirement of the single phase or unbalanced loads, each phase is an independent voltage source. With the proposed control strategy, the characteristics of DEPT are studied by simulations. And further detailed simulations are carried out to validate the power quality control function of DEPT. The results show that DEPT has very good static and dynamic performances, and it can not only realize the functions of conventional power transformer, but also can prevent from voltage sags, swells, flickers and harmonics infecting the loads while avoid loads impacting the primary system. (C) 2006 Elsevier B.V. All rights reserved.