A method for operating a power electronic converter device for an electrical power conversion system, the power electronic converter device comprising a converter circuit including an input side with input terminals, an output side with at least one AC output terminal, a first converter with semiconductor devices connected to the input terminals and at least one second converter connected between an AC output of the first converter and the AC output terminal, said second converter comprising at last one floating cell with a DC intermediate circuit and semiconductor devices; wherein the first converter and the second converter are switched with a switching pattern comprising first switching instants for the semiconductor devices of the first converter and second switching instants for the semiconductor devices of the second converter, such that the two converters (20, 22) generate voltages (42, 44) with stepwise voltage changes and an output voltage of the power electronic converter device results from the superposition of the voltages (42, 44) of the two converters (20, 22); wherein the first switching instants of the switching pattern are selected, such that the voltage of the first converter provides a fundamental voltage component of the output voltage; characterized in that the switching instants of the switching pattern are selected, such that, if the step size of a first switching instant of the first converter exceeds a step size limit, a compensating switching instant for the second converter is included in the switching pattern, which compensating switching instant results in a voltage of the second converter, which reduces the step size at the output voltage compared with the step size at the voltage of the first converter; wherein the switching pattern comprises switching instants for the second converter, which are neighboring the compensating switching instant and which directions and switching times are selected, such that the voltage of the second converter leaves the fundamental voltage component of the voltage of the first converter unchanged and such that the second converter does not generate a fundamental component of the output voltage. the power electronic converter device comprising a converter circuit including an input side with input terminals, an output side with at least one AC output terminal, a first converter with semiconductor devices connected to the input terminals and at least one second converter connected between an AC output of the first converter and the AC output terminal, said second converter comprising at last one floating cell with a DC intermediate circuit and semiconductor devices; wherein the first converter and the second converter are switched with a switching pattern comprising first switching instants for the semiconductor devices of the first converter and second switching instants for the semiconductor devices of the second converter, such that the two converters (20, 22) generate voltages (42, 44) with stepwise voltage changes and an output voltage of the power electronic converter device results from the superposition of the voltages (42, 44) of the two converters (20, 22); wherein the first switching instants of the switching pattern are selected, such that the voltage of the first converter provides a fundamental voltage component of the output voltage; characterized in that the switching instants of the switching pattern are selected, such that, if the step size of a first switching instant of the first converter exceeds a step size limit, a compensating switching instant for the second converter is included in the switching pattern, which compensating switching instant results in a voltage of the second converter, which reduces the step size at the output voltage compared with the step size at the voltage of the first converter; wherein the switching pattern comprises switching instants for the second converter, which are neighboring the compensating switching instant and which directions and switching times are selected, such that the voltage of the second converter leaves the fundamental voltage component of the voltage of the first converter unchanged and such that the second converter does not generate a fundamental component of the output voltage.