A power circuit, a converter structure and a wind power generation system thereof are disclosed. The power circuit includes a first converter having an AC input side and a DC output side, a second converter having a DC input side and an AC output side, and a DC bus storage unit electrically connected to the DC output side of the first converter and the DC input side of the second converter. A level number, a switching valve type and/or a circuit connection of the first converter are different from those of the second converter.