Novel Three-Phase Electronic Transformer

Electronic transformers enable galvanic isolation and voltage level adaption at high frequency, and thus the magnetic core volume and weight can be reduced substantially compared to traditional transformers operating at the grid frequency. This article introduces a novel phase-modular single-stage three-phase electronic transformer (3 Phi-ET) which advantageously enables the use of standard power transistors with unipolar voltage blocking capability. The output frequency is identical to the grid input frequency and the bidirectional power flow can be adjusted by means of a simple dual active bridge (DAB)-type modulation which results in inherently sinusoidal grid currents. The 3 Phi-ET is thoroughly described and experimental waveforms with a 6 kW prototype system operated in a 400 V (rms, line-line) three-phase grid provide a proof of concept and verify the theoretical considerations.