Converter system for an electric supply network, comprising - a first and at least one second converter apparatus, each of the converter apparatuses comprising - a voltage source for providing an electric voltage (U G), - an inverter device for providing an AC voltage (U 1, U 2, U 3) from the electric voltage (U G) provided by the voltage source, and - a transformer device for transforming the AC voltage (U 1, U 2, U 3) provided by the inverter and applied to a primary coil into a transformed AC voltage (UT 1, U T2, U T3) which is applied to a secondary coil, - the secondary coils of the first and the at least one second converter apparatus being electrically connected in series, - and a medium voltage formed by the series circuit of the secondary coils being applied to an output (A1, A2, A3) of the converter system, characterized in that - the inverter device of the first converter apparatus has a measuring unit for measuring the AC voltage provided using the inverter device of the at least one second converter apparatus and - the inverter device of the first converter apparatus is designed to adapt the AC voltage (U1, U2, U3) provided using the inverter device of the first converter apparatus in such a manner that the medium voltage has a sinusoidal profile and - the measuring unit of the inverter device of the first converter apparatus is used to measure the amplitude and/or the phase of the AC voltage (U 1, U 2, U 3) provided using the inverter device of the second converter apparatus, and - if the signal waveform of the AC voltage (U 1, U 2, U 3) deviates from a sinusoidal profile, the amplitude and/or phase of the AC voltage (U 1, U 2, U 3) provided using the inverter device of the first converter apparatus is/are adapted in such a manner that a sum voltage of the transformed AC voltages (U T1, U T2, U T3) from the converter apparatuses has a sinusoidal profile. - a first and at least one second converter apparatus, each of the converter apparatuses comprising - a voltage source for providing an electric voltage (U G), - an inverter device for providing an AC voltage (U 1, U 2, U 3) from the electric voltage (U G) provided by the voltage source, and - a transformer device for transforming the AC voltage (U 1, U 2, U 3) provided by the inverter and applied to a primary coil into a transformed AC voltage (UT 1, U T2, U T3) which is applied to a secondary coil, - the secondary coils of the first and the at least one second converter apparatus being electrically connected in series, - and a medium voltage formed by the series circuit of the secondary coils being applied to an output (A1, A2, A3) of the converter system, - the inverter device of the first converter apparatus has a measuring unit for measuring the AC voltage provided using the inverter device of the at least one second converter apparatus and - the inverter device of the first converter apparatus is designed to adapt the AC voltage (U1, U2, U3) provided using the inverter device of the first converter apparatus in such a manner that the medium voltage has a sinusoidal profile and - the measuring unit of the inverter device of the first converter apparatus is used to measure the amplitude and/or the phase of the AC voltage (U 1, U 2, U 3) provided using the inverter device of the second converter apparatus, and - if the signal waveform of the AC voltage (U 1, U 2, U 3) deviates from a sinusoidal profile, the amplitude and/or phase of the AC voltage (U 1, U 2, U 3) provided using the inverter device of the first converter apparatus is/are adapted in such a manner that a sum voltage of the transformed AC voltages (U T1, U T2, U T3) from the converter apparatuses has a sinusoidal profile.