An inverter system comprising an inverter and an expansion unit, wherein the inverter comprises a common DC link, an inverter bridge connected to the common DC link, at least one voltage converter (12a, 12b) and at least two direct current inputs (11a, 11b) coupled to the common DC link, wherein the extension unit comprises a further DC link and a further voltage converter, wherein between at least one of the direct current inputs (11a, 11b) and the common DC link of the inverter the at least one voltage converter (12a, 12b) of the inverter is connected, and wherein the voltage converter (12a, 12b) comprises two outputs (125a, 126a, 125b, 126b), of which one output (125a, 125b) is connected to the common DC link of the inverter and a further output (126a, 126b) is connected via the further voltage converter of the extension unit to the further DC link of the extension unit, wherein the voltage converter (12a, 12b) of the inverter comprises an inductance (121a, 121b) and a diode (123a, 123b) connected to the inductance (121a, 121b), the cathode of which diode forms the output (125a, 125b) of the voltage converter (12a, 12b), characterized in that the voltage converter (12a, 12b) comprises a further diode (124a, 124b) or an actively controllable semiconductor switch, which, like the diode (123a, 123b), is connected to the respective inductance (121a, 121b), wherein the voltage converter (12a, 12b) is expanded by the further diode (124a, 124b) or the actively controllable semiconductor switch with regards to the further output (126a, 126b), wherein the further voltage converter of the expansion unit is formed as a bidirectional converter and is connected on the side opposite the further DC link of the expansion unit to the common DC link of the inverter via a switch and a diode or via a switch and an actively controllable semiconductor switch in order to enable a power flow from the further DC link into the common DC link. wherein between at least one of the direct current inputs (11a, 11b) and the common DC link of the inverter the at least one voltage converter (12a, 12b) of the inverter is connected, and wherein the voltage converter (12a, 12b) comprises two outputs (125a, 126a, 125b, 126b), of which one output (125a, 125b) is connected to the common DC link of the inverter and a further output (126a, 126b) is connected via the further voltage converter of the extension unit to the further DC link of the extension unit, wherein the voltage converter (12a, 12b) of the inverter comprises an inductance (121a, 121b) and a diode (123a, 123b) connected to the inductance (121a, 121b), the cathode of which diode forms the output (125a, 125b) of the voltage converter (12a, 12b), characterized in that the voltage converter (12a, 12b) comprises a further diode (124a, 124b) or an actively controllable semiconductor switch, which, like the diode (123a, 123b), is connected to the respective inductance (121a, 121b), wherein the voltage converter (12a, 12b) is expanded by the further diode (124a, 124b) or the actively controllable semiconductor switch with regards to the further output (126a, 126b), wherein the further voltage converter of the expansion unit is formed as a bidirectional converter and is connected on the side opposite the further DC link of the expansion unit to the common DC link of the inverter via a switch and a diode or via a switch and an actively controllable semiconductor switch in order to enable a power flow from the further DC link into the common DC link.