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. <EOS>