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Full-Process Operation, Control, and Experiments of Modular High-Frequency-Link DC Transformer Based on Dual Active Bridge for Flexible MVDC Distribution: A Practical Tutorial

DC transformer (DCT) will be the key device for medium-voltage dc (MVDC) power distribution system. This paper gives a practical tutorial on full-process operation, control, and experiments for application of DCT based on dual active bridge in flexible MVDC distribution system. The operation of DCT for MVDC distribution is designed to three modes: MVDC, low-voltage dc (LVDC), and power control modes. Three optimal modulation methods during startup, steady, and transient processes are proposed which can reduce current impact in practice. A full-process control strategy during operation state is proposed to achieve flexible control and fast management of voltage and power in MVDC distribution system, especially an optimal balance control during block process is proposed to reduce power losses. On this basis, a fault-handling solution is proposed to improve reliability of DCT in practice, and a hardware design method is proposed to enhance flexibility and modularity. Finally, an industrial prototype is built, and comprehensive experiments verify the validity and effectiveness of the proposed solution. The practical application of DCT in MVDC distribution are expected, and the exploration of this study could provide valuable references for the practical DCT design.