DC transformer based on centralized multi-winding high-frequency transformer, and control method

The invention discloses a DC transformer based on a centralized multi-winding high-frequency transformer, and a control method of the direct-current transformer. The transformer comprises M DC transformer units with input ends connected in series and output ends connected in parallel, wherein the medium-voltage DC side input ports of the M DC transformer units are connected in series to form a medium-voltage DC side port of the DC transformer, and low-voltage DC side output ports of the M DC transformer units are connected in parallel to form a low-voltage DC side port of the DC transformer. The multi-winding high-frequency transformers among the DC transformer units are mutually independent; each DC transformer unit comprises N submodules, the inputs of which are connected in series and the outputs of which are connected in parallel, wherein N is greater than or equal to 3; the input filter capacitors Cini of the submodules are connected in series to form a medium-voltage DC side input port of the unit, and the output filter capacitors Coi are connected in parallel to form a low-voltage DC side output port of the unit. According to the transformer, the bidirectional transmission of power between the medium-voltage DC side and the low-voltage DC side can be realized by controlling a phase shift angle between primary and secondary side bridge arms of the transformer in each sub-module, and zero-voltage switching-on of all switch tubes is realized.