Driving of a phase module branch of a multilevel converter

A method for charging and/or discharging energy storage devices of a multilevel converter including at least one phase module branch with a series circuit of submodules each having at least one power semiconductor circuit for turning on or off an energy storage device connected in parallel with the power semiconductor circuit and a submodule sensor for detecting an energy storage actual value, the method comprising the following steps:

• upon obtaining an energy change state, determining if turned-on energy storage devices of a phase module branch can be charged or discharged;
• selecting the next energy storage device to be switched in each phase module branch with a predetermined logic in dependence on the energy change state;
• forming a sum of all turned-on energy storage actual values to obtain an energy storage summation actual value;
• determining a difference between a predetermined phase module branch energy desired value and the energy storage summation actual value to obtain an energy difference value;
• and
• defining a switching instant of the selected energy storage device if a magnitude of the energy difference value or a magnitude of a quantity derived from the energy difference value exceeds a magnitude of a switching threshold value.