Flux and winding current balancing control for a medium-frequency six-winding transformer

Solid state transformers normally include a transformer whose operating frequency is well above the usual grid frequencies. These transformers are supplied by power electronic inverters such as an H-bridge. The average value of transformer supply voltage can drift to a non-zero value which may lead to saturation of the magnetic core. This paper presents an active control method to prevent saturation of a multi-winding medium-frequency transformer. The control method comprises two control loops: the first balances the flux of the transformer and the other balances the currents in different windings. Simulation results which show the feasibility of the proposed control method are shown.