Dual submodule for a modular multilevel converter and modular multilevel converter including the same

A dual submodule for a modular multilevel converter being electrically coupled to a power supply network, comprising:

• a first submodule interconnected to a second submodule, each submodule comprising:
• an asymmetrical half-bridge circuit having a first bridge branch and a second bridge branch, each bridge branch (i) being arranged in parallel to the other of the first and second bridge branch between a first and a second terminal connection of the submodule;
• (ii) being formed from a first diode and a single series circuit of a power semiconductor switch having an antiparallel free-wheeling diode allocated to it;
• and (iii) comprising an AC terminal located between the first diode and the single series circuit;
• and
• a capacitor connected in parallel to the asymmetrical half-bridge circuit between the first and the second terminal connections of each submodule;
• wherein, the AC terminal of the first bridge branch of the first submodule forms a first connection point with the AC terminal of the first bridge branch of the second submodule, and the AC terminal of the second bridge branch of the first submodule forms a second connection point with the AC terminal of the second bridge branch of the second submodule, the direct connections between the AC terminals being in parallel to each other and forming the dual submodule;
• and wherein in the event of a short-circuit within the converter, the power semiconductor switches of the second bridge branches are switched off, and a current being powered by the power supply network (i) flows from an output terminal to the capacitor of the first submodule and (ii) splits into two separate paths, one path being via the free-wheeling diode of the first bridge branch of the first submodule to the first connection point, and continuing to the capacitor of the second submodule via the free-wheeling diode of the first bridge branch of the second submodule, and the second path being via the first diode of the second bridge branch of the first submodule to the second connection point, and continuing to the capacitor of the second submodule via the first diode of the second bridge branch of the second submodule.