Power supply system for a polyphase arc furnace with an indirect converter between a mains connection and a furnace transformer

A method for providing power to a polyphase arc furnace, comprising:

• connecting a primary of at least one furnace transformer via an indirect converter to a polyphase mains system and connecting a secondary of the at least one furnace transformer to the polyphase arc furnace, wherein the indirect converter has at least one rectifier on the mains side, at least one inverter on the transformer side, and a link circuit between the rectifier and the inverter,
• connecting each phase of the polyphase mains system to the link circuit via two converter elements of the rectifier, and
• connecting each primary phase of the furnace transformer to the link circuit via two converter elements of the inverter, wherein each converter element of the two converter elements of the rectifier and the two converter elements of the inverter consists of a multistage series circuit of submodules,
• providing for each submodule of the submodules an energy storage capacitor and self-commutated semiconductor switches, and
• switching the self-commutated semiconductor switches in each submodule independently of the self-commutated semiconductor switches in other submodules in a same converter element and in other converter elements, such that the energy storage capacitor in a respective submodule is bridged or active by means of the self-commutated semiconductor switches in the respective submodule, depending on their switching state.