Research on a Dual Active Bridge Based Power Electronics Transformer using Nanocrystalline and Silicon Carbide

A power electronics transformer (PET) based on dual active bridge (DAB) with input series and output parallel (ISOP) cascaded topology is studied in this paper. Fe-based nanocrystalline alloys transformer cores and Silicon Carbide (SiC) power MOSFETs are adopted to improve the power density and efficiency. Mathematical derivation of the input voltage distribution is deduced with the conclusion that the voltage equalization cannot be achieved autonomously. A feedback control method is proposed to balance the input voltage. The measurement of the dynamic B-H loops of the nanocrystalline core under the excitation of square wave and sinusoidal wave is conducted. The high frequency isolation transformer (HFIT) is designed based on the loss performance calculated using the dynamic B-H loop and Ohm's law. The optimized operating flux density is around +/- 0.68 T at 20 kHz, which is much higher than the empirical value around +/- 0.3 T to take full advantage of the nanocrystalline core. Finally, a 13.2 kVA prototype is built to verify the above analysis and design.