Patent ID: 8400796

Claim:
Device for converting a DC voltage into an AC voltage and vice versa comprising a control system to control the voltage conversion and comprising at least one phase leg with a first voltage source connected in series between a first DC terminal and a first AC terminal and with a second voltage source connected in series between the first AC terminal and a second DC terminal, where each of the voltage sources comprises at least a first and a second submodule in series-connection, each submodule comprising at least two power electronic switches connected in parallel with at least one capacitor, characterized in that the control system comprises a central control unit and as many subunits as submodules, where the central control unit transmits to each subunit a reference AC voltage and a switching carrier signal and where each subunit controls the switching of the power electronic switches of one of the submodules according to a PWM pattern so that each time the switching carrier signal crosses the reference AC voltage a change in the state of the corresponding submodule from, a state one to a state two or vice versa is initiated, where in state two the voltage across the capacitor, and in state one a zero voltage is applied to output terminals of the corresponding submodule, wherein the central control unit transmits the same reference AC voltage and the same switching carrier signal to all subunits belonging to the same voltage source.