Nonlinear load supplied with electric power by means of a power supply device, - wherein the nonlinear load is in the form of an arc furnace having an upstream furnace transformer, - wherein the power supply device has a plurality of converter units, - wherein the converter units each have a plurality of main modules, - wherein the main modules each have an input connection that is connected to a respective phase of a polyphase grid system operated at an operating frequency (f), - wherein the converter units each have a common star point that is connected firstly to a respective output of the main modules of the respective converter unit and secondly via an output connection of the respective converter unit to the primary side of the furnace transformer, - wherein the main modules each have a series circuit comprising a coupling inductance and a plurality of submodules, - wherein the submodules each have a submodule input and a submodule output and, between the respective submodule input and the respective submodule output, a bridge circuit having four self-commutated semiconductor switches and a bridge path in which a respective storage capacitor is arranged, and - wherein the semiconductor switches of the submodules are each switchable independently of the semiconductor switches of the other submodules of the same main module and of the other main modules, - wherein voltages applied to the secondary side of the furnace transformer and currents flowing on the secondary side of the furnace transformer are detected, - wherein the voltages and currents detected on the secondary side of the furnace transformer are taken as a basis for using electrode control to perform position control for electrodes of the arc furnace and - wherein the electrode control ascertains nominal current values (I1*) and/or nominal voltage values for the converter units. - wherein the nonlinear load is in the form of an arc furnace having an upstream furnace transformer, - wherein the power supply device has a plurality of converter units, - wherein the converter units each have a plurality of main modules, - wherein the main modules each have an input connection that is connected to a respective phase of a polyphase grid system operated at an operating frequency (f), - wherein the converter units each have a common star point that is connected firstly to a respective output of the main modules of the respective converter unit and secondly via an output connection of the respective converter unit to the primary side of the furnace transformer, - wherein the main modules each have a series circuit comprising a coupling inductance and a plurality of submodules, - wherein the submodules each have a submodule input and a submodule output and, between the respective submodule input and the respective submodule output, a bridge circuit having four self-commutated semiconductor switches and a bridge path in which a respective storage capacitor is arranged, and - wherein the semiconductor switches of the submodules are each switchable independently of the semiconductor switches of the other submodules of the same main module and of the other main modules, - wherein voltages applied to the secondary side of the furnace transformer and currents flowing on the secondary side of the furnace transformer are detected, - wherein the voltages and currents detected on the secondary side of the furnace transformer are taken as a basis for using electrode control to perform position control for electrodes of the arc furnace and - wherein the electrode control ascertains nominal current values (I1*) and/or nominal voltage values for the converter units.