A power electronic based transformer for feeding sensitive loads

In this paper a modular power electronic transformer (PET) for feeding sensitive loads is presented. The proposed PET can be directly connected to the medium voltage levels and provide a low-voltage and highly-stable interface with the consumer applications. At the input side, cascaded H-bridge rectifier serves as an active-front-end (AFE) rectifier to ensure sinusoidal input current, while converting AC input voltage to distinct DC buses. The isolated DC/DC converters are connected to the individual DC buses and reduce the AC voltage level through series-input and parallel-output configuration of the H-bridge cells. The proposed PET can compensate both the active and reactive powers, and remove the power quality disturbances such as sag, swell, under voltage, over voltage and voltage flicker. In comparison to the conventional transformers, it has low weight, compact volume, extended functionality, and eliminates the necessity for toxic dielectric coolants. The proposed topology and the principle of operation are explained and the validity of the design is verified using the simulation and experimental results.