Comprehensive Control Strategy And Robust Operation For Input Series Output Parallel Power Electronics Transformers In Mvdc Grids

In medium-voltage dc grids, power electronics transformers (PETs) play an important role in interconnecting grids with different voltage levels and directing power flow between grids. This paper presents a comprehensive control strategy for input series output parallel PETs, including control design for submodules consisting of boost and dual active bridge, balancing control between submodules, soft startup and operations after submodule faults. Through the control strategy, the PET is capable of regulating either the voltage or the power on the low voltage side, and it can operate safely and robustly during large transients in startup and submodule failures. The proposed control strategy is validated using PLECS simulation and verified experimentally with a scaled-down laboratory prototype.