Abstract
The modular multilevel DC–DC transformer (MMDCT) provides a reliable solution to overcome the challenges of conventional dual-active-bridge converters in terms of power semiconductors ratings and dv/dt stress on transformer coupling windings. An alternative modulation method, quasi-square-wave, was proposed to reduce the cell capacitance of modular multilevel bridges. However the application of quasi-square-wave modulation is found to result in underdamped switching transients and losses when resetting energy stored in arm inductance. This paper presents a detailed transient analysis of MMDCT arm insertion based on an equivalent circuit, which contributes to a more accurate component sizing and gives voltage estimation for individual half-bridge submodules. Additionally, a revised switching sequence is proposed to recover this inductor energy and lower the oscillation-related losses. Simulated and experimental results from a scaled test rig of MMDCT are implemented and validate the proposed component sizing and switching sequence, indicating that the converter efficiency can be improved under revised switching sequence. Finally, a silicon carbide based, high-frequency MMDCT is proposed and simulated.
Original language | English |
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Pages (from-to) | 1943-1959 |
Number of pages | 17 |
Journal | IET Power Electronics |
Volume | 17 |
Issue number | 14 |
Early online date | 29 Jul 2024 |
DOIs | |
Publication status | Published - 4 Nov 2024 |
Keywords / Materials (for Non-textual outputs)
- DC transformers
- DC–DC power convertors
- HVDC power convertors
- HVDC power transmission
- power conversion