Cascade Control Strategies for Power Electronic Transformers

Power Electronic Transformers (PETs), integrating voltage conversion, electrical isolation, and power quality regulation, have been widely applied in smart grids, renewable energy systems, and rail transit. The emergence of wide-bandgap semiconductors, exemplified by SiC and GaN, together with advances in digital control methods, has accelerated progress in this field. PETs have gradually begun to replace traditional transformers, playing a significant role in flexible ACDC hybrid grids. This paper systematically reviews the control strategies of PETs from three perspectives: modulation techniques, voltage and power balancing control strategies, and port control technologies. Finally, the paper summarizes the current technical challenges faced by PETs and discusses future development trends.