of solid-state transformer (SST) to electric vehicle (EV) fast
charging system, which can realize a large volume reduction
from the traditional system based on line frequency transformer
(LFT). For a 6.6 kV–800 V / 200-kW AC to DC SST, sizes of
passive components are analyzed and an oscillating power control
(OPC) is discussed to decrease the DC-link capacitance and the
volume of the capacitors in the SST. An optimization based on
the model of medium frequency transformer (MFT) to find the
minimal total volume of MFTs with a given core is performed.
As one of the system level parameters, the number of cascade
and resulting unit power capacity are treated as a parameter for
the optimization. The results indicate that increasing unit power
capacity for the given core shape results in total volume reduction
without major power loss increase.