Modular multilevel converter and power electronic transformer

A power electronic transformer, wherein comprising:

• an MMC, including:
• a low-frequency AC to DC conversion module, including at least three branch circuits connected in parallel between output ends, each branch circuit of the at least three branch circuits being formed of multiple IGBT half-bridge circuits connected in series, and an electric coupling point of two adjacent IGBT half-bridge circuits, in a middle position of the branch circuit, being connected to a voltage input end,
• a DC to high-frequency AC conversion module, connected between the output ends, the DC to high-frequency AC conversion module being formed of multiple IGBT half-bridge circuits connected in series, the DC to high-frequency AC conversion module including multiple sets of output ends, each set of output ends including a first output end and a second output end, the first output end being connected to an electric coupling point between two adjacent IGBT half-bridge circuits of the multiple IGBT half-bridge circuits, and the second output end being connected to an electric coupling point between another two adjacent IGBT half-bridge circuits of the multiple IGBT half-bridge circuits;
• multiple high-frequency transforming modules, each high-frequency transforming module, of the multiple high-frequency transforming modules, being connected to a corresponding first output end and a corresponding second output end;
• and
• multiple high-frequency AC to low-frequency AC conversion modules, each high-frequency AC to low-frequency AC conversion module, of the multiple high-frequency AC to low-frequency AC conversion modules, being connected to a corresponding high-frequency transforming module of the of the multiple high-frequency transforming modules.