Module of a modular multilevel converter

A module of a modular multilevel converter, the module comprising:

• a first module terminal, a second module terminal, a first electrical conductor, a second electrical conductor, a third electrical conductor, a power semiconductor circuit and an electrical energy storage unit;
• said power semiconductor circuit having a first electronic switching element and a second electronic switching element, a first diode connected antiparallel with said first electronic switching element and a second diode connected antiparallel with said second electronic switching element;
• said power semiconductor circuit being connected to said energy storage unit by said first electrical conductor and said second electrical conductor;
• said first module terminal being connected to said third electrical conductor;
• a first thyristor and a second thyristor connected between said third electrical conductor and said second electrical conductor, said first thyristor and said second thyristor forming an antiparallel circuit;
• said first thyristor being integrated in a semiconductor wafer, or said first thyristor and said second thyristor being integrated in a semiconductor wafer;
• at least one of said first electrical conductor, said second electrical conductor or said third electrical conductor having a flat outer surface, said semiconductor wafer being disk-shaped, said first thyristor having semiconductor material disposed in said disk-shaped semiconductor wafer, and said disk-shaped semiconductor wafer being disposed in parallel with at least one said flat outer surface.

A method for discharging an electrical energy storage unit in a module of a modular multilevel converter, the method comprising:

• providing the module with a first module terminal, a second module terminal, a first electrical conductor, a second electrical conductor, a third electrical conductor, a power semiconductor circuit and an electrical energy storage unit;
• providing the power semiconductor circuit with a first electronic switching element and a second electronic switching element, a first diode connected antiparallel with the first electronic switching element and a second diode connected antiparallel with the second electronic switching element;
• using the first electrical conductor and the second electrical conductor to connect the power semiconductor circuit to the energy storage unit;
• connecting the first module terminal to the third electrical conductor;
• connecting a first thyristor and a second thyristor between the third electrical conductor and the second electrical conductor, the first thyristor and the second thyristor forming an antiparallel circuit;
• inducing a current switching on the first thyristor in semiconductor material due to a magnetic field changing over time, the magnetic field arising due to a discharge current of the energy storage unit flowing through at least one of the first electrical conductor or the second electrical conductor and permeating the semiconductor material of the first thyristor;
• immediately discharging the energy storage unit upon a fault arising in the module, resulting in the discharge current of the energy storage unit beginning to flow;
• and
• short-circuiting the first module terminal and the second module terminal by the switched-on first thyristor.